Radio

Introduction

1. 1GENERAL

With the increasing denial of time and space the RFID technology is gaining momentum day by day. RFID is a source of identification of individuals and unique products. The budding technology RFID proves to threaten even the cloning technique, through the chip insertion. New ways of improving the existing RFID technology are being found and implemented. This advancement of RFID technology is looked beyond the security purposes.

1. 2 PRESENT SCENARIO

Radio frequency identification (RFID) is a general term that is used to describe a system that transmits the identity (in the form of unique serial number) of an object wirelessly, using radio waves. RFID technologies are grouped under the more generic Automatic Identification and Data Capture (AIDC). The RFID technology is used only in security, tagging goods, inventory purposes. Since the RFID technology is not well established in India, the introduction of new methodology in the field of RFID will indeed enhance the use of RFID technology in various areas of science and technology.

3 PROBLEM

An individual should be allocated to maintain registers in all places and appointment of staffs for coordinating with students in all occasions. The ID card can be duplicated even thought it has some other advancement which will be used in rare occasions.

1. 4 SOLUTION

The best solution to the above problem is to develop a single RFID tag that can be used inside the college campus. Each and every RFID tag holds a particular number and it is integrated with the id cards of each and every individuals.

The RFID tag reader can be fixed anywhere in campus and it is used to collect the information about the tag location. The collected data can be sent to centralized server to handle that information. Another added advantage is that the ID cards can’t be duplicated. This has several advantages and it is a time saving one for the institution, students and staff members.

1. 5 HARDWARE AND SOFTWARE REQUIRED

The hardware required is:

1. Personal computer.
2. RS 232.
3. Reader.
4. Power supply unit.
5. IR transmitter and receiver pair.
6. Buzzer.
7. LCD.
8. Tags.

The software required is:

The RFID system is used to identify individual objects or things in the environment which can be monitored through use of wireless technology. RFID is a generic term for technologies that use radio waves to remotely store and retrieve data.

In other words, it is a combined term with RF and ID where RF means a wireless communication technology and ID means identification information of tag. So it is said that RFID is theoretically a wireless networking technology to transmit identification information stored at an electronic memory space.

2. 2 COMPONENTS OF RFID SYSTEM:

An RFID device (transponder or tag), that contains data about an item. ? An antenna used to transmit the RF signals between the reader and the RFID devices. An RF transceiver that generates the RF signals. A reader that receives RF transmissions from an RFID device and passes the data to the host system for processing.

The tag contains circuit to both rectify DC power from the incoming RF signal as well as to detect and extract the information modulated on the signal. The antenna load is a controlled resistance that changes the impedance of the dipole, enabling the backscatter. The tag IC is mounted on a carrier known as a strap and subsequently bonded to the antenna to form the fully assembled tag.

The chip itself is very small, enabled by modem CMOS technology. The mounting of the die on a carrier has been made very inexpensive and capable of large volume by either flip-flop or by other innovative technique such as the Alien Technologies Fluidic self Assembly process. : Basic Tag IC Architecture

2. 4 Components of a tag The major components of the tag are

• Microchip.
• Antenna.

2. 4. 1 Microchip

Microchip is electronic equipment consisting of a small crystal of silicon semiconductor fabricated to carry out a number of electronic functions in an integrated circuit.

The microchip used in a HF tag is a contact less read/ write passive RFID device that is optimized for 13. 56 MHz RF carrier signal. The device needs an external LC resonant circuit for wireless communication with the interrogator. The device is powered remotely by rectifying an RF signal that is transmitted from the interrogator and transmits or updates its contents from memory-based on commands from interrogator.

2. 4. 2 Antenna

The antenna emits the radio signal to activate the tag and reading and writing data to it.

Antennas are the conduits between the tag and the transceiver, which controls the system data acquisition and communication. Antennas are available in a variety of shapes and sizes; they can be built in a door frame to receive tag data from persons or things. The electromagnetic field produced by an antenna can be constantly present when multiple tags are expected continuously. If constant interrogation is not required, the field can be activated by the sensor device.

2. 5 rfid readers RFID reader is like any other device that can be connected to a PC Or might be in built like an external or internal modem.

The RFID reader can be powered by a power source using an adapter ”Reader” or ”Interrogator”, a device that is able to locate and activate tags so that the information that has been programmed onto the tag is transmitted back to the reader and subsequently to interface computing systems. The information that is received by the reader is then passed to the backend computing system to initiate the events, transactions, workflows, etc. Not only do reader locate activate and receive transmissions from RFID tags, a reader has the ability of sending data back to read/write capable tag in order to append or replace data.

Readers exist that can also scan bar codes in environments where both bar codes and RFID are used.

2. 6 COMPONENTS OF A READER

• The reader has the following main components:
• Transmitter and Receiver
• Microprocessor
• Memory

TRANSMITTER

The reader’s transmitter is used to transmit AC power and the clock cycle via antennas to the tags in its read zone.

This is part of the transceiver unit, the component responsible for sending the reader signal to the surrounding environment and receiving tag responses back via the reader antennas. The antenna ports of reader are connecting to its transceiver component. One reader antenna can be attached to each such antenna port. Receiver receives analog signals from the tag via the reader antenna. It then sends the signals to reader microprocessor, where it is converted to its equivalent digital form.

2. 6. 2 MICROPROCESSOR

This component is responsible for implementing the reader protocol to communicate with compatible tags.

It performs decoding and error checking of the analog signal from the receiver. In addition, the microprocessor might contain custom logic for doing low level filtering and processing of read tag data.

2. 6. 3 MEMORY

Memory is used for storing data such as the reader configuration parameters and list of tag reads. Depending on the memory size, however, a limit applies as to how many such tag reads can be stored at one time. If the connection remains down for an extended period with the reader reading tags during this downtime, this limit might be exceeded an part of the stored data lost.

2. 6. 4 I/O channels

Readers do not have to be turned on for reading tags at all time. A sensor of some sort, such as a motion or light sensor, detects the presence of tagged objects in the readers read zone. This sensor can then set the reader on to read this tag. Similarly, this component also allows the reader to provide local output depending on some condition via an annunciators or an actuator.

2. 6. 6 CONTROLLER

A controller is an entity that allows an external entity, either a human or a computer program, to communicate with and control a reader’s function and to control annunciators and actuators associated with the reader.

6. 7 COMMUNICATION INTERFACE

The communication interface component provides the communication instructions to a reader that allows it to interact with external entities, via a controller to transfers its stored data and to accept commands and send back the corresponding responses.

2. 6. 8 POWER

This component supplies power to the reader component. The power sources generally provided to this component through a power cord connected to an appropriate external electrical outlet.

2. 7 COMMUNICATION BETWEEN A READER AND A TAG

Depending on the tag type, the communication between the reader and a tag can be one of the following:

• Modulated backscatter
• Transmitter type
• Transponder type

The area between a reader antenna and one full wave length of the RF wave emitted by the antenna is called near field. The area beyond one full wavelength of the RF wave emitted from a reader antenna is called far field. Passive rfid systems operating in LF and HF use near field communication, whereas those in UHF and microwave frequencies use far field communication.

The signal strength in near field communication attenuates as the cube of the distance from the reader antenna. In far field, it attenuates as square of the distance from the reader antenna.

2. 7. 1 MODULATED BACK SCATTER

Modulated backscatter communication applies to passive as well as to semi active tags. In This type of communication, the reader sends out a continuous wave (CW) RF signal containing ac power and clock signal to the tag at carrier frequency. Through physical coupling, the antennas supplies power to the microchip. About 1. 2v are generally necessary to energize the tag microchip for reading microchips.

For writing, the microchip usually needs to draw about 2. 2v from the reader signal. The microchip now modulates or breaks up the input signal in to a sequence of on and off patterns that represents its data and transmits it back. When the reader receives this modulated signal, it decodes the pattern and obtains the data. Thus, in modulated backscatter communication, the reader always “talks” first, followed by the tag. A tag using this scheme cannot communicate at all in the absence of a reader because it depends totally on the reader’s power to transmit its data.

2. 7. 2 TRANSMITTER TYPE

This type of communication applies to active tags only. In this type of communication, the tag broadcasts its message to the environment in regular intervals irrespective of the presence or absence of a reader. Therefore, in this type of communication, the tag always “talks” first rather than the reader.

3. 4. 3 TRANSPONDER TYPE

In this type of communication, the tag goes to a “sleep” or in to dormant stage in the absence of interrogation from a reader.

In this stage, the tag might periodically send a message to check any reader is listening to it. When a reader receives such a query message, it can instruct the tag to “wake up” or end the dormant stage. When the tag receives this command from the reader, it exits its current state and starts to act as a transmitter tag again.

3. 1 INTRODUCTION

The hardware includes the following components:

• Atmega162 (micro controller).
• Power supply.
• In system programming.
• Buzzer. Liquid crystal display.

The fast-access Register File contains 32 x 8-bit general purpose working registers with a single clock cycle access time. This allows single-cycle Arithmetic Logic Unit (ALU) operation. In a typical ALU operation, two operands are output from the Register File, the operation is executed, and the result is stored back in the Register File – in one clock cycle. Six of the 32 registers can be used as three 16-bit indirect addresses register pointers for Data Space addressing – enabling efficient address calculations. One of these address pointers can also be used as an address pointer for look up tables in Flash Program memory.

Most AVR instructions have a single 16-bit word format. Every program memory address contains a 16 or 32-bit instruction. [pic] Figure 3. 2: BLOCK Diagram of the AVR Architecture Program Flash memory space is divided in two sections, the Boot Program section and the Application Program section. Both sections have dedicated Lock bits for write and read/write protection. The SPM instruction that writes into the Application Flash memory section must reside in the Boot Program section. During interrupts and subroutine calls, the return address Program Counter (PC) is stored on the Stack.

The Stack is effectively allocated in the general data SRAM, and consequently the Stack size is only limited by the total SRAM size and the usage of the SRAM. All user programs must initialize the SP in the reset routine (before subroutines or interrupts are executed).

The ALU operations are divided into three main categories – arithmetic, logical, and bit-functions.

3. 3. 3 Status Register

The Status Register contains information about the result of the most recently executed arithmetic instruction. This information can be used for altering program flow in order to perform conditional operations. Status Register format Bit 7 – I: Global Interrupt Enable: The Global Interrupt Enable bit must be set for the interrupts to be enabled. The individual interrupt enable control is then performed in separate control registers.

If the Global Interrupt Enable Register is cleared, none of the interrupts are enabled independent of the individual interrupt enable settings. The I-bit is cleared by hardware after an interrupt has occurred, and is set by the RETI instruction to enable subsequent interrupts. Bit 6 – T: Bit Copy Storage: The Bit Copy instructions BLD (Bit Load) and BST (Bit Store) use the T bit as source or destination for the operated bit. Bit 5 – H: Half Carry Flag: The Half Carry Flag H indicates a half carry in some arithmetic operations.

Half Carry is useful in BCD arithmetic. Bit 4 – S: Sign Bit, S = N. V: The S-bit is always an exclusive or between the Negative Flag N and the Two’s Complement Overflow Flag V. Bit 3 – V: Two’s Complement Overflow Flag: The Two’s Complement Overflow Flag V supports two’s complement arithmetic. Bit 2 – N: Negative Flag: The Negative Flag N indicates a negative result in an arithmetic or logic operation. Bit 1 – Z: Zero Flag: The Zero Flag Z indicates a zero result in an arithmetic or logic operation. Bit 0 – C: Carry Flag:

The Carry Flag C indicates a carry in an arithmetic or logic operation.

3. 3. 4 Stack Pointer

The Stack is mainly used for storing temporary data, for storing local variables and for storing return addresses after interrupts and subroutine calls. The Stack Pointer Register always points to the top of the Stack. The Stack Pointer points to the data SRAM Stack area where the Subroutine and Interrupt Stacks are located. This Stack space in the data SRAM must be defined by the program before any subroutine calls are executed or interrupts are enabled. Stack Pointer FORMAT pic] The Stack Pointer is incremented by one when data is popped from the Stack with the POP instruction, and it is incremented by two when data is popped from the Stack with return from subroutine RET or return from interrupt RETI. The AVR Stack Pointer is implemented as two 8-bit registers in the I/O space. The number of bits actually used is implementation dependent.

3. 3. 5 Reset and Interrupt Handling

The AVR provides several different interrupt sources. These interrupts and the separate Reset Vector each have a separate program vector in the program memory space.

All interrupts are assigned individual enable bits which must be written logic one together with the Global Interrupt Enable bit in the Status Register in order to enable the interrupt. There are basically two types of interrupts. The first type is triggered by an event that sets the Interrupt Flag. For these interrupts, the Program Counter is vectored to the actual Interrupt Vector in order to execute the interrupt handling routine, and hardware clears the corresponding Interrupt Flag. Interrupt Flags can also be cleared by writing a logic one to the flag bit position(s) to be cleared.

If an interrupt condition occurs while the corresponding interrupt enable bit is cleared, the Interrupt Flag will be set and remembered until the interrupt is enabled, or the flag is cleared by software. The second type of interrupts will trigger as long as the interrupt condition is present. These interrupts do not necessarily have Interrupt Flags. If the interrupt condition disappears before the interrupt is enabled, the interrupt will not be triggered.

3. 3. 6 In-System Reprogrammable

Flash Program Memory The ATmega162 contains 16K bytes On-chip In-System Reprogrammable Flash memory for program storage.

Since all AVR instructions are 16 or 32 bits wide, the Flash is organized as 8K x 16. For software security, the Flash Program memory space is divided into two sections, Boot Program section and Application Program section.  Programmable Memory Map The Flash memory has an endurance of at least 10,000 write/erase cycles. The ATmega162 Program Counter (PC) is 13 bits wide, thus addressing the 8K program memory locations.

3. 4 EEPROM

Data Memory The ATmega162 contains 512 bytes of data EEPROM memory. It is organized as a separate data space, in which single bytes can be read and written.

The EEPROM

has an endurance of at least 100,000 write/erase cycles. The access between the EEPROM and the CPU is described in the following, specifying the EEPROM Address Registers, the EEPROM Data Register, and the EEPROM Control Register.

3. 4. 1 EEPROM

Read/Write Access The EEPROM Access Registers are accessible in the I/O space. A self timing function, however, lets the user software detect when the next byte can be written. If the user code contains instructions that write the EEPROM, some precautions must be taken. In heavily filtered power supplies, VCC is likely to rise or fall slowly on Power-up/down.

This causes the device for some period of time to run at a voltage lower than specified as minimum for the clock frequency used. In order to prevent unintentional EEPROM writes, a specific write procedure must be followed. The EEPROM Address Register [pic] Bits 15. 9 – Res: Reserved Bits These bits are reserved bits in the ATmega162 and will always read as zero. Bits 8. 0 – EEAR8. 0: EEPROM Address The EEPROM Address Registers – EEARH and EEARL specify the EEPROM address in the 512 bytes EEPROM space. The EEPROM data bytes are addressed linearly between 0 and 511. The initial value of EEAR is undefined.

Writing EERIE to one enables the EEPROM Ready Interrupt if the I bit in SREG is set. Writing EERIE to zero disables the interrupt. The EEPROM Ready interrupt generates a constant interrupt when EEWE is cleared. Bit 2 – EEMWE: EEPROM Master Write Enable The EEMWE bit determines whether setting EEWE to one cause the EEPROM to be written. When EEMWE is set, setting EEWE within four clock cycles will write data to the EEPROM at the selected address. If EEMWE is zero, setting EEWE will have no effect. When EEMWE has been written to one by software, hardware clears the bit to zero after four clock cycles.

See the description of the EEWE bit for an EEPROM write procedure. Bit 1 – EEWE: EEPROM Write Enable The EEPROM Write Enable signal EEWE is the write strobe to the EEPROM. When address and data are correctly set up, the EEWE bit must be written to one to write the value into the EEPROM. The EEMWE bit must be written to one before a logical one is written to EEWE; otherwise no EEPROM write takes place. The following procedure should be followed when writing the EEPROM (the order of steps 3 and 4 is not essential):

1.  Wait until EEWE becomes zero.
2. Wait until SPMEN in SPMCR becomes zero.
3. Write new EEPROM address to EEAR (optional).
4. Write new EEPROM data to EEDR (optional).
5. Write a logical one to the EEMWE bit while writing a zero to EEWE in EECR.
6. Within four clock cycles after setting EEMWE, write a logical one to EEWE. The EEPROM can not be programmed during a CPU write to the Flash memory.

The software must check that the Flash programming is completed before initiating a new EEPROM write. Step 2 is only relevant if the software contains a Boot Loader allowing the CPU to program the Flash.

If the Flash is never being updated by the CPU, step 2 can be omitted. Caution: An interrupt between step 5 and step 6 will make the write cycle fail, since the EEPROM Master Write Enable will time-out. If an interrupt routine accessing the EEPROM is interrupting another EEPROM access, the EEAR or EEDR Register will be modified, causing the interrupted EEPROM access to fail. It is recommended to have the Global Interrupt Flag cleared during all the steps to avoid these problems. When the write access time has elapsed, the EEWE bit is cleared by hardware.

The user software can poll this bit and wait for a zero before writing the next byte. When EEWE has been set, the CPU is halted for two cycles before the next instruction is executed. Bit 0 – EERE: EEPROM Read Enable The EEPROM Read Enable Signal EERE is the read strobe to the EEPROM. When the correct address is set up in the EEAR Register, the EERE bit must be written to a logic one to trigger the EEPROM read. The EEPROM read access takes one instruction, and the requested data is available immediately. When the EEPROM is read, the CPU is halted for four cycles before the next instruction is executed.

The user should poll the EEWE bit before starting the read operation. If a write operation is in progress, it is neither possible to read the EEPROM, nor to change the EEAR Register.

3. 5 Timing

External memory devices have various timing requirements. It is important to consider the timing specification of the external memory device before selecting the wait-state. The most important parameters are the access time for the external memory in conjunction with the set-up requirement of the ATmega162.  External Data Memory Cycles without Wait-state.

3. 6 Crystal Oscillator

XTAL1 and XTAL2 are input and output, respectively, of an inverting amplifier which can be configured for use as an On-chip Oscillator. Either a quartz crystal or a ceramic resonator may be used. C1 and C2 should always be equal for both crystals and resonators. The optimal value of the capacitors depends on the crystal or resonator in use, the amount of stray capacitance, and the electromagnetic noise of the environment. The Oscillator can operate in four different modes, each optimized for a specific frequency range.

The Low-frequency Crystal Oscillator must be selected by setting the CKSEL Fuses to “0100”, “0101”, “0110” or “0111”. The crystal should be connected as shown in Figure. If CKSEL equals “0110” or “0111”, the internal capacitors on XTAL1 and XTAL2 are enabled, thereby removing the need for external capacitors. The internal capacitors have a nominal value of 10 pF. When this Oscillator is selected, start-up times are determined by the SUT Fuses (real time-out from Reset) and CKSEL0 (number of clock cycles) as shown in below tables Start-up DELAYS from Reset when Low-frequency Crystal Oscillator is selected .

Watchdog Timer

If the Watchdog Timer is not needed in the application, this module should be turned off. If the Watchdog Timer is enabled, it will be enabled in all sleep modes, and hence, always consume power. In the deeper sleep modes, this will contribute significantly to the total current consumption.

4. 1 INTRODUCTION

This project describes about the efficient used of RFID technology around us, it also describes about the use of both hardware and software. In addition we also focus on monitoring every individual inside the campus.

4. 2 Basic setup

The basic external setup for the project is shown in figure 8. 1. The HF reader is connected to microcontroller through RS-232 cable and the IR pairs are connected to the port pins of microcontroller. The microcontroller is then connected to the host computer (server) through RS-232 cable. The detailed explanation of the blocks are given below

For interrupt driven USART operation, the Global Interrupt Flag should be cleared (and interrupts globally disabled) when doing the initialization. The TXC Flag can be used to check that the Transmitter has completed all transfers, and the RXC Flag can be used to check that there are no unread data in the receive buffer.

4. 5 SENSOR

Sensors are the devices that are used to convert the physical parameter into signal that can be measured electrically and it can be easily given as an input to the microcontroller. The effectual sensor should have the following properties namely,

Sensor should be sensitive to measured property.  It should be insensitive to any other property.  It should not influence any other property. An IR sensor is used. It uses IR LED as an IR transmitter, which emits IR rays in the wavelength of 940 nm and a phototransistor is used as IR receiver, which detects IR rays and the output comes in collector. If the receiver is receiving IR rays the output will be low otherwise output is high. The output of the receiver is given to the comparator chip LM393, which compares the receiver output with the prefixed voltage signal.

The output of the comparator is given to microcontroller.

4. 3 CIRCUIT DIAGRAM OF IR SENSOR

4. 5. 1 IR TRANSMITTER LED, a special type of semiconductor diode that has a pn junction acts as a transmitter. The wavelength and the color of the light depend on the band gap energy of the material forming pn junction. The materials used for a LED have a direct band gap energy corresponding to near IR, but Germanium and silicon are indirect band gap materials resulting in a non – radiative recombination. Hence does not emit light.

The advantages of LED over incandescent sources are:  Less costly Long life p . Insensitive to vibration and shocks.

4. 5. 2 IR RECEIVER A phototransistor is used to detect the IR rays from the LED. It is a bi polar junction that is encased in a transparent case so that light can reach the base collector junction. The phototransistor works like a photodiode with a very high very high sensitivity for light, because the electrons that are generated by photons in the base collector junction are injected to base and amplified like a transistor. It has a slower response time than photodiode.

4. 4 BLOCK DIAGRAM OF IR SENSOR

4. 5. 3COMPARATOR

The comparator is a circuit which compares a signal voltage applied at one input of an op-amp with a known reference voltage at the other input. For an inverting comparator the reference voltage is applied to the (+) input and input is given to the (-) terminal. The common mode voltage range includes ground, and the differential input voltage equals power supply voltage.

4. 5: PIN CONFIGURATION OF LM

4. 6 BUZZER It is a transducer which converts electrical signal to sound signal. Piezoelectricity is the ability of certain crystals to produce a voltage when subjected to mechanical stress. The effect is reversible (i. . ) crystals when subjected to external applied voltage can change shape by a small amount and the effect is of nanometers.

Once the basics of Visual Basic are understood then one becomes productive.

5. 2 About Visual Basic The “Visual” part refers to the method used to create the graphical user interface (GUI), Rather than writing numerous lines of code to describe the appearance and location of interface elements, simply add pre built objects into place on screen. The “Basic” part refers to the BASIC (Beginners All-Purpose Symbolic Instruction Code) language, a language used by more programmers. Visual Basic has evolved from the original BASIC languages and now contains several hundred statements, functions, and keywords, many of which relate directly to the Windows GUI.

Beginners can create useful applications by learning just a few of the keywords, yet the power of the language allows professionals to accomplish anything that can be accomplished using any other Windows programming language. The Visual Basic programming language is not unique to Visual Basic. The Visual Basic programming system, Applications Edition included in Microsoft Excel, Microsoft Access, and many other Windows applications uses the same language. The Visual Basic Scripting Edition (VB Script) is a widely used scripting language and a subset of the Visual Basic language. The investment one makes in learning Visual Basic will carry over to many other areas.

Whether the goal is to create a small utility for an individual, a work group a large enterprise-wide system, or even distributed applications pning the globe via the Internet, Visual Basic has the required tools.

5. 3 ADVANTAGES

Data Access features allow you to create databases, front-end applications, and scalable server-side components for most popular database formats, including Microsoft SQL Server and other enterprise-level databases.  ActiveXTM Technologies allow you use the functionality provided by other applications, such as Microsoft Word Processor, Microsoft Excel spreadsheet, and other Windows applications.

Even applications can be automated and objects can be created using the Professional or Enterprise editions of Visual Basic.  Internet capabilities make it easy to provide access to documents and applications across the Internet or intranet from within the application, or to create Internet server applications.  The finished application is a true. exe file that uses a Visual Basic Virtual Machine that you can freely distribute.

5. 4 Program description

The front end is visual basic and this programming concept is chosen because it is more users friendly. The information or the status about the persons is displayed and the same can be stored in a database so that it can be accessed later. [pic] Figure 5. : output and database creation, checking form Chapter 6 conclusion RFID technology is a budding technology that is fast growing world wide. RFID proves to be cutting edge technology through its applications. This project moves a step ahead in RFID’s application and presents a new dimension to view through. This project proves to be entirely different and innovative of RFID technology with the existing components. Such an introduction of a new methodology in the RFID technology enhances its use and improves the present knowledge. The project “INTELLIGENT campus using RFID” will sure make a great difference in the present industrial applications of RFID.

It will provide the ultimate solution for the problems that exists in various cases. This is a prototype of the proposed idea wherein the entire reason behind it is to provide a fully compact, covering larger distance.

6. 1 PROCESS EXPLANATION

The various processes that take place during the working of the project are as follows: The RFID tag is a passive, high frequency device in which some unique data’s can be stared in the form of serial numbers known as ELECTRONIC PRODUCT CODE (EPC). Whenever the RFID tag comes in the field of a particular reader, the reader detects the tag and sends the detected information about the EPC to the microcontroller.

The received information will be fed into the microcontroller which compares the epc number to specific information’s about group of individuals. If the received information is already in the list, it will allow the user to enter inside the campus and also maintains a database for storing this information. The reader refreshes its data continuously checks after certain amount of time interval and when the RFID reader detects the absence of a tag it will remove the tag details from the list. The database can be created with the help of visual basic programming.

Two IR transmitter – receiver pairs are used for the purpose of monitoring whether the person is entering the room or leaving the room. The IR rays interfering sequence is fed to the microcontroller and it is used for detecting the status of the person having that particular tag. The details or the status are also saved into database using visual basic coding. The databases can be shared in the network and it can be used for finding or monitoring each and every individual belonging to that campus.

6. 2 FUTURE ENHANCEMENTS

The project could further be developed and enhanced in an effective way by suitable polarization RFID reader antennas and increasing the frequency range so that it would not only provide the solution for monitoring persons in a smaller area as mentioned in this model. The security can also be increased by replacing IR devices by some bio-metric ideas

Investing aggressively in creating sustainable competitive advantage is a company’s single most dependable contributor to above-average profitability. The objective of competitive strategy is to overcome rival companies by doing a significantly better job of providing what buyers are looking for. We can distinguish among 3 different competitive strategies, each one being applied to a certain share of the radio industry.

Overall Cost Leadership A low-cost leader’s basis for competitive advantage is lower overall costs than competitors. Successful low-cost leaders are exceptionally good at finding ways to drive costs out of their businesses. Outperforming rivals in controlling the factors that drive costs is a very demanding managerial exercise. Success in achieving cost advantages over rivals comes from exploring all avenues for reducing costs and pressing for continuous cost reductions across all aspects of the company’s operations year after. A low-cost provider’s product offering must always contain enough attributes to be attractive to prospective buyers-low price, by itself, is not always appealing to buyers.

This first distinction is often found in the local radio landscape. Having not huge founds to invest, especially at the beginning of the business, many small radio companies tend to save money from buying infrastructures, or investing in the creation of new and original programs. Speaking clearly, they do not offer a various program schedule, preferring just to be present in the market with a simple and sometimes very “poor” service. Furthermore, many companies do not spend money in the purchase of territorial tunings, so that they can not reach a significative share of the listeners.

In markets where rivals compete mainly on price, low cost relative to competitors is the only competitive advantage that matters. Personally, I believe this competitive strategy is not effective in the radio sector. But we have to consider other aspects that influence the landscape. For example in the radio market, the fidelization, the habits of the costumers play a central role. This is why in a local market this competitive strategy can sometimes be applied.

Differentiation The essence of a differentiation strategy is to be unique in ways that are valuable to customers and that can be sustained. Easy-to-copy differentiating features cannot produce sustainable competitive advantage. A differentiator’s basis for competitive advantage is a radio offering whose attributes differ significantly from the offerings of rivals or a set of capabilities for delivering customer value that rivals don’t have or can’t quite match.

Speaking radio, the differentiation strategy is the strongest one. Why should someone listen to my radio station? Not considering the fidelization factor, that plays an important role, people listen and choose a specific radio because it is able to entertain, to be a good companion during the day. And this is possible through a various program schedule that offers not only the kind of music the costumer is looking for, but as an added value in the services. All the radio have more or less a generic program, usually made of music, information, maybe horoscope and so on.

A strategic management of what you want to present to the public is to say and offer something unique, both in the schedule and in the way people can listen your station. For example in the latest month we have the possibility to listen to digital radio, and only few stations jet are transmitting digitally. Or again the possibility to listen a radio through the Net, so that if a person is in another country can receive its Italian favourite radio just being connected to Internet. A firm whose differentiation strategy delivers only modest extra value but clearly signals that extra value may command a higher price than a firm that actually delivers higher value but signals it poorly. Any differentiating element that works well tends to draw imitators.

Examples of radios with differentiation strategies are “RTL 102.5”, “Radio Dimensione Suono”, “Radio Deejay”, “Radio 105”. Focusing The most successful best-cost producers have competencies and capabilities to simultaneously manage unit costs down and product calibre up. The most powerful competitive strategy of all is relentlessly striving to become a lower-and-lower-cost provider of a higher-and-higher-calibre product. The closer a firm can get to the ultimate of being the industry’s absolute lowest-cost provider and, simultaneously, the provider of the industry’s overall best product, the less vulnerable it becomes to rivals’ actions.

Even though a focuser may be small, it still may have substantial competitive strength because of the attractiveness of its product offering and its strong expertise and capabilities in meeting the needs and expectations of niche members. In a landscape composed by so many players that everyday compete to gain the bigger market share, focusing becomes the most used competitive strategy. We can speak of focusing both from geographical areas and by targeting the audience. The first choices a radio manager makes is which territory he wants to reach (so they buy tunings in the specified areas), and within this territory which target he wants to acquire.

If you study the monthly report made by Audiradio, where are registered all the radios and their performances in terms of audience, you will see that a first distinction is made by areas, then for each radio is reported its performances, how many listeners it has reached and which kind of listeners. Male, female, professional people, employees, housekeepers, the age and so on. Almost every radio has previously studied its target so that he can offer a schedule and music in line with the needs of the listeners. So we have those stations that focus on a specific kind of (Italian, international, pop, jazz, classic, and so on), those radio that want just to inform, those radio that want also to interact with listeners, and so on.

An example of a private radio that has focused on a specific niche is “Radio Sole 24 Ore”, with a listening target and a program just for professionals. The Radio Industry Life Cycle When studying a market it’s very important to know at which stage of its life cycle is the industry. Then you can set the stage for the volume by reviewing research across four stages of the industry life cycle: fragmentation, shakeout, maturity and decline. The figure summarizes the basic industry life cycle model.

The introduction surveys research findings on how firms influence the industry life cycle on the one hand, and exploit the life cycle to enhance their performance on the other hand. At this stage it’s also important to consider how institutional, economic, and social contexts affect firms’ influence on and exploitation of industry life cycles. The four main sections of the volume track the stages of the life cycle. Each section includes new research and commentary by leading scholars from strategic management, economics and organization theory.

The radio industry is an old market, the first private radio channels were born around 1975, when competition with public channels started. Since then there has been a continuous evolution in the market, speaking both of technologies and of the quality of the service, such as marketing studies oriented to create an always better relation with the costumers. The actual stage of the industry is the Maturity Stage. The mature phase of industry evolution occurs when technological advances associated with the shakeout begin to yield only incremental operational and service improvements, changing the basis of competition to favor industry leaders emphasizing the efficiencies enabled by the dominant model.

In the phases of introduction of new technologies we can also argue that the industry has the features of an industry at a Shakeout Stage. The shakeout phase of industry evolution occurs when a dominant model emerges, permitting efficiencies to be realized, and industry volume to rise quickly. A view to the future  Digital techniques, the automation of the systems and the direct employment of services such as selfservices for journalists-productors of radio programs, should allow in the future to generally cut costs of production on programs. By improving the diffusion of such techniques the costs of investments in the radio landscape is supposed to decrease.

On the other hand, costs regarding copyrights and journalistic labour costs have different trends and less changing. The landscape suggests that more or less the next ten years will be a period of many and fast changes and challenges in technologies and in the market.The services in the radio with big covering bands are now not rewarding, specially for the creation of new programs. Frequency bands are all full and this causes significant problems of interference of different tunings.

Today we assist to a general decrease in international tuning problems (such as jamming), but we notice also a parallel increase of small and big companies of radio services and diffusion in big areas, that’s why short waves can satisfy always less Italian listeners (due to interferences, difficulty in the transmission of the band and the harshness of the audio band, that is more or less 3 – 4 KHz).

Listeners of FM (frequency modulation) from cars have great problems in receiving a good signal, especially when they are moving from an area to another one, even if in the last months it has been developed a new technique that should avoid this phenomena (the RDS system for cars). On the other hand, many listeners are used to a music quality of CDs and Mini Disks, that is obviously higher. The new digital transmission should be a solution. Systems of diffusion that able to give strong, stable and loyal radio transmission should represent a generic reality in the next years. Experts forecast many improvements, both in short and in long term.

CONCLUSIONS

The development of this project should have been able to show you the general asset of the radio industry in Italy, not only from a technical point of view but also considering the forces that influence its structure, such as competition, development in technologies, different strategies that are used in the market. Italians in the last years have found again their old love for this media, that has been for a long period replaced by television. People need always more to develop imagination, to be creative, there is a general require for romanticism and thinking. In such a frenetic landscape, with so few time to dedicate to ourselves, radio appears as the best mean to develop this need.

Please answer the following questions, you can upload your answers In a MS Word flee, or Word file. Answer all the questions, and upload the answers back before Sunday March 31, 2013 (before 11: 55 pm):

1. Differentiate between guided media and unguided media
2. What are three important characteristics of a periodic signal
3. Define fundamental frequency
4. What Is attenuation?
5. Describe the components of optical fiber cable.
6. Indicate some significant differences between broadcast radio and microwave.
7. What Is the difference between diffraction and scattering?
8. Last and briefly define important factors that can be used in evaluating or comparing the various digital-to- digital encoding techniques.
9. What function does a modem perform?
10. What Is JAM? Differentiate between guided media and unguided media Gulled media Is that where we use any path for communication like cables (coaxial, fiber optic, twisted pair) etc. Unguided media is also called wireless where not any physical path is used for transmission. What are three important characteristics of a periodic signal?

Period (or frequency), amplitude and phase. All periodic signals can be broken down into other signals… Cost commonly Selene/coolness waves, but there are others too. These components will each have their own frequency, amplitude and phase that combine into the original signal. The strange part of the question is the phase. A signal on its own does not have a phase unless you provide some reference signal to compare it to. Generally, this comparison signal Is Implied by the context of your particular situation.

When you decompose a periodic signal into components, however, it is almost always implied that the phase of each component is in reference to the fundamental component (So the fundamental has phase O. Hill the others have phases referenced to that). This is done specifically so that each component will combine to create the original signal. Define fundamental frequency. What Is attenuation? The fundamental frequency, often referred to simply as the fundamental, is defined as the lowest frequency of a periodic waveform.

In terms of a superposition of sinusoids The fundamental frequency Is the lowest frequency sinusoidal in the sum. In some contexts, the fundamental is usually abbreviated as of (or IF), indicating the lowest frequency counting from zero. In other contexts, it is more common to abbreviate It as FL, the first harmonic. The second harmonic Is then if = off, etc. In this context, the zeros harmonic would be O Hz’s. )All sinusoidal and many non-sinusoidal waveforms are periodic, which Is to say they repeat exactly over time. Describes the signal completely.

We can show a waveform is periodic by finding some period T for which the following equation is true: Reduction of signal strength during transmission. Attenuation is the opposite of amplification, and is normal when a signal is sent from one point to another. Describe the components of optical fiber cable. An optical fiber is a flexible, transparent fiber made of glass (silica) or plastic, slightly hickey than a human hair. It functions as a waveguide, or “light pipe”, to transmit light between the two ends of the fiber.

The field of applied science and engineering concerned with the design and application of optical fibers is known as fiber optics. Optical fibers are widely used in fiber-optic communications, which permits transmission over longer distances and at higher bandwidths (data rates) than other forms of communication. Fibers are used instead of metal wires because signals travel along them with less loss and are also immune to electromagnetic interference. Fibers are also used for illumination, and are wrapped in bundles so that they may be used to carry images, thus allowing viewing in confined spaces.

Specially designed fibers are used for a variety of other applications, including sensors and fiber lasers. Indicate some significant differences between broadcast radio and microwave. FL Radio is about 50 Kilohertz to 400 Kilohertz. AM Broadcast Band Radio is about 500 Kilohertz to 1600 Kilohertz. And microwave begins around 2000 Mesh and goes up thru. Some frequency ranges like 26,000 Mesh in allocated bands, depending upon the type of service you’re operating. What is the difference between diffraction and scattering?

Diffraction is a phenomenon observed only in waves, but scattering is a phenomenon observed in both waves and particles. Diffraction is a property of propagation of waves, whereas scattering is a property of wave interactions. Diffraction can be taken as evidence for the wave nature of light. Some forms of scattering (Compton scattering) can be taken as evidence for the particle nature of light. List and briefly define important factors that can be used in evaluating or comparing the various digital-to-digital encoding techniques. Digital signals don’t have large ranges, nor do they reflect constant activity.

Digital signals have very few values. Each signal is unique from a previous digital value and unique from one to come. In effect, a digital signal is a snapshot of a condition and does not represent continual movement In comparing analog and digital signals, advantages lie on either end of the spectrum. Analog signals suffer far less from attenuation over long distances. This rather makes sense. Since digital data can only be a 1 or O, what happens when a signal becomes so weak that it is hard to distinguish between each state? Sometimes we Just can’t.

Analog devices, on the other hand, are equipped to handle the infinite values between 1 and O. Digital devices are a lot less sophisticated, meaning that they are fairly easy to manufacture and cost-effective. In addition, bandwidths than analog systems do. What function does a modem perform? The function of a modem is Modulation and Demodulation mean to turn data into a format that can be transmitted via an audio link such as a phone line. A modem at the other side of the connection answers the phone and converts the audio back into sable data.

This is why if you lift a phone while the modem is in use there appears to be random noise on the line, this noise is the data in audio What JAM? JAM stands for Quadrate Amplitude Modulation. It’s a modulation scheme that transmits data by changing the amplitude of two carrier waves. The two carrier waves are out of phase with each other by 90 degrees. Digital Cable uses JAM to transmit the majority of their signals. Two major JAM schemes are GAMMA and GAMMA. GAMMA contains data throughput around 28 Mbps, where GAMMA has data throughput of 38. 8 Mbps.

Chapter 2- Communication System

Telecommunication systems have now made it possible to pass on with virtually anyone at any clip. Early telegraph and telephone system used Cu wire to transport signal over the earth’ surface and across oceans and high frequence ( HF ) wireless, besides normally called shortwave wireless, made possible inter-continental telephone links.Every communicating system has its ain frequence scope, system, capacity, application execution cost.

On the footing of transmittal system there are two types of communicating system

• Wired communicating system

• Wireless communicating system

2.2 Multiple Access Technique

A limited sum of bandwidth is allocated for radio services. A radio system is required to incorporate as many users as possible by efficaciously sharing the limited bandwidth. Therefore, in communicating, the term multiple entree can non be defined as a agency of leting multiple users to at the same time portion the finite bandwidth with least possible debasement in the public presentation of the system.

There are four multiple entree methods –

a ) Frequency Division Multiple Access ( FDMA )

B ) Time Division Multiple Access ( TDMA )

degree Celsius ) Code Division Multiple Access ( CDMA )

vitamin D ) Space Division Multiple Access ( SDMA )

1. Frequency Division Multiple Accesses ( FDMA )

FDMA is one of the oldest multiple entree techniques for cellular systems when uninterrupted transmittal is required for parallel services. In this bandwidth is divided into a figure of channels and distributed among users with a finite part of bandwidth for lasting usage, as illustrated in figure 2.2. The channels are assigned merely when there is a demand of the users. Therefore when a channel is non in usage it consequences in a otiose resource.

Fig 2.2Channel Use by FDMA

FDMA channels have narrow bandwidth of about 30 KHz, and therefore they are normally implemented in narrow set system. Since the user has his part of bandwidth all the clip, FDMA does non necessitate clocking control, which makes it simple. Even though no two users use the same frequence set at the same clip, guard sets are introduced between sets to minimise channel intervention. Guard sets are fresh frequence slots which separates neighbouring channels. This leads to a wastage of bandwidth. In a non-continuous transmittal bandwidth goes wasted since it is non being utilized for a part of the clip.

2. Time Division Multiple Access ( TDMA )

In digital systems, uninterrupted transmittal is non required as the users do non use the allotted bandwidth all the clip. In such systems, TDMA is a O.K.ing technique compared to FDMA. Global Systems for Mobile communications i.e GSM uses the TDMA technique. In TDMA, bandwidth is available to the user but merely for a finite period of clip. In most instances the bandwidth is divided into fewer channels compared to FDMA and the users are allotted clip slots during which they have the full channel bandwidth at their disposal. This is illustrated in figure 2.3.

Fig 2.3Channel Uses by TDMA

TDMA requires careful clip synchronism since users portion the bandwidth in the frequence sphere. As the figure of channels are less, channel intervention is about negligible, hence the guard clip between the channels is significantly smaller. Guard clip is spacing clip between the TDMA. In cellular communications, whenever a user moves from one cell to other there is a opportunity that user could see a call loss if there are no free clip slots. TDMA uses different clip slots for transmittal every bit good as response.

3. Code Division Multiple Access

In CDMA, all the users occupy the same bandwidth, though they are all assigned separate codifications, which distinguishes them from each other as shown in figure 2.4. CDMA systems utilize a spread spectrum technique in which a spreading signal, is uncorrelated to the signal and has a larger bandwidth, is used to distribute the narrow set signal. Direct Sequence Spread Spectrum i.e DS-SS is most normally used for codification division multiple surplus. In Direct sequence spread spectrum, the message signal is multiplied by a Pseudo Random Noise Code, which has a noise like belongingss. Each user has its ain codification which is extraneous to the codification of every other users. In order to feel the user, the receiving system is required to cognize the codeword used by the sender. contrasting TDMA, CDMA does non necessitate clip synchronism between the users.

Fig 2.4Channel Uses by CDMA

2.4 CDMA

2.4.1 History

Code Division Multiple Access ( CDMA ) is a new construct in wireless communications. It has achieved widespread credence by cellular system operators, that will dramatically increase both their system capacity and the service quality. CDMA is a signifier of spread-spectrum, that have been used in military applications for old ages. The rule of spread spectrum is the usage of noise-like moving ridges and, as the name connote bandwidths much larger than that required for simple point to indicate communicating at the same information rate. foremost there were two motive: To defy enemy attempts to throng the communications ( anti-jam, or AJ ) , or to conceal the fact that communicating was even taking topographic point, from clip to clip called low chance of intercept. It has a history that goes back to the early yearss of World War second. The usage of CDMA for nomadic wireless applications is new. It was planned theoretically in the late fourty’s. profitable applications became promising because of two evolutionary developments. One was the handiness of really low cost, high denseness digital ICs, which cut down the size and cost of the endorser Stationss to an adequately low value.

Introduction to CDMA

CDMA is a multiple entree technique that allows multiple users to convey independent information within the same bandwidth at the same time. Each user is assigned a pseudo-random codification that is either extraneous to the codifications of all the other users or the codification possesses appropriate cross-correlation belongingss that minimize the multiple entree intervention ( MAI ) . This codification is superimposed on an information signal therefore, doing the signal emerges to be noise like to other users. Merely the intended receiving system has a reproduction of the same codification and uses it to pull out the information signal. This so allows the sharing of the same spectrum by multiple users without doing inordinate MAI. It besides ensures message privateness, since merely the intended user is able to “decode” the signal. This codification is besides known as a spreading codification, since it spreads the bandwidth of the original informations signal into a much higher bandwidth before transmittal.

2.4.2 CDMA Classification Tree

Fig 2.6Classification Tree of the assorted types of CDMA Techniques

Advantages of CDMA

One of the chief advantages of CDMA is that call dropouts occur merely when the phone is at least twice every bit far from the base station. It is used in the pastoral countries where GSM make non acquire to work decently. Another advantage is capacity means it has a really high spectral capacity so that it can suit more users.

Disadvantages of CDMA

One major job in CDMA engineering is channel pollution, where signals from excessively different cell sites are present in the subscriber’s phone but none of them is foremost. When this state of affairs arises the characteristic of the audio signal degrades. Another disadvantage is when compared to GSM it lacks international roaming capablenesss.

2.5 Spread Spectrum

Spread spectrum are the methods in which energy generated at a individual frequence is spread over a broad set of frequences. The basic spread spectrum technique is shown in Figure 2.7. This is done to accomplish transmittal that is robust against the channel damages, and to be able to defy natural interventions or thronging besides to forestall hostile sensing. These techniques were developed by military counsel systems. The technique is said to be spread spectrum if transmittal bandwidth is much greater than minimal bandwidth needed to convey the information.The system achieves spread spectrum if it fulfills the undermentioned demands:

1. Signal occupies bandwidth much larger of the minimal bandwidth necessary to direct information.
2. Spreading is done with the aid of distributing codification signal which is independent of the informations.
3. At the receiving system, de-spreading is done by the correlativity of the received dispersed signal with a synchronised reproduction of the distributing signal used to distribute the information.

Spread signal bandwidth
Undesired signal
informations signal
recovered informations

Spreading code signal Spreading codification signal

Fig 2.7Model of Basic Spread Spectrum Technique

The chief parametric quantity in dispersed spectrum systems is the treating addition: Is the ratio of transmittal and information bandwidth:Gp =, which is fundamentally the spreading factor.

The processing addition calculates the figure of users that can be allowed, the sum of multi-path effects and the trouble to throng a signal.

Spread spectrum can be classified as follows –

a ) Direct Sequence Spread Spectrum

B ) Frequency Hoping Spread Spectrum

degree Celsius ) Time Hopping Spread Spectrum

2.5.1 DS-CDMA

Direct Sequence is the best Dispersed Spectrum Technique. The DS-CDMA method provides a multiple of benefits in cellular systems including easiness in planing frequence channels and protection against intervention, such that a high procedure addition is used. In DS-CDMA each user has its ain spreading codification. The choice of good codification is of import because auto-correlation belongingss and length of the codification restricts system capacity. The codification can be divided into two categories-

1. Orthogonal codifications ( Walsh codifications )
2. Non-orthogonal codifications ( PN, Gold, Kasami codifications )

The informations signal is multiplied by a Pseudo Random Noise Code. A PN codification is a sequence of french friess its scope is -1 and 1 ( polar ) or 0 and 1 ( non-polar ) . This consequences in low cross-correlation values among the codifications and the trouble to throng or observe a information message.

A usual manner to make a PN codification is by agencies of at least one displacement registry. The bit rate decides the rate at which distributing signals are transmitted. At the receiver terminal, spread signals are decoded with the aid of correlativity maps. Cross correlativity de-spreads the standard signals and retrieves the familial signal similar to the user’s original signal. The distributing sequences can orthogonal agencies ‘0’ transverse correlativity or random sequences with low cross-correlation belongingss.

Y ( T )
m ( T )

C ( T ) Cos ( wt )

Fig 2.8Direct Sequence Spread – Spectrum Modulation System

In the DS-CDMA technique, each spots of the users informations are multiplied with a codification in the transmitting terminal. The codification sequence used in conveying terminal performs the function of distributing codification.

The baseband theoretical account of a DS-CDMA system is shown in fig 2.8. Let m ( T ) denotes a binary information sequence, degree Celsius ( T ) denotes a codification sequence. The wave forms m ( T ) and c ( T ) denote polar representations in footings of two degrees as ±1. By multiplying the information spots by the codification, each information spot is divided into a little clip increases that are called french friess.

The baseband signal( T ) is filtered to restrict energy within the bandwidth, defined by the codification rate. The bearer transition normally used in dispersed spectrum is phase displacement identifying. Sing the figure we get:
( T ) = m ( T ) C ( T ) ………………………………………………………………… ( 3.2 )

The baseband signal( T ) is convoluted with the impulse response of the spectrum determining filter to give Y ( T ) : Y ( T ) =( T ) ? H ( T ) , where * denotes convolution………………

The set base on balls signal( T ) = [( T ) ? H ( T ) ] cosT ) …………………….. ( 3.4 )

m ( T )

Cos ( wt ) Clock

C ( T )

Fig 2.9Matched Filter Spread-Spectrum Receiver.

The standard Band base on balls signal( T ) is converted to an tantamount complex low base on balls signal A ( T ) by blending with a locally generated coherent bearer.

The complex low base on balls signal A ( T ) =( T ) cost……………………….. ( 3.5 )

The de-spread signal B ( T ) = A ( T ) [ C ( T ) ? H ( T ) ] ………………………… ( 3.6 )

The end product of the matched filter D ( T ) =( 3.7 ) .

The receiving system decodes the informations: D ( T ) & A ; gt ; 0 decode binary ‘1’ otherwise decode binary ‘0’.

-11 1 1 -1 -1 1 -1 -1 1 1 1 -1 -1 1 -1 -1 -1
user’s spot dispersed signal Despread signal Received spot

distributing sequence distributing sequence

Fig 2.10User Signal in DS-CDMA System

Let us believe the first spots of four users. By multiplying each spot with a PN codification, users spots are represented by seven french friess as shown above.

User 1 [ 1 ] : 1 C1: -1 -1 1 1 1 -1 1 = & A ; gt ; -1 -1 1 1 1 -1 1

User 2 [ 1 ] : -1 C2: 1 -1 -1 1 1 1 -1= & A ; gt ;-1 1 1 -1 -1 -1 1

User 3 [ 1 ] : 1 C3: -1 1 -1 -1 1 1 1 = & A ; gt ; -1 1 -1 -1 1 1 1

User 4 [ 1 ] : -1 C4: 1 -1 1 -1 -1 1 1

= & A ; gt ; -1 1 -1 1 1 -1 – 1

R [ 1 ] : -4 2 0 0 2 -2 2 ( received informations )

The received information consists of information of four users. To retrieve the original spots of users from the received informations, the received informations should multiplied with the codification sequence in the receiving system that is precisely same with that is used for distributing the original informations in sender agencies ( de-spreading ) . We assume that the receiving system operates in perfect synchrony with the sender. As a last measure, determination is made by comparing the consequences with a threshold value as shown below.

R [ 1 ] * C1= 4-2+2+2+2= 8 & A ; gt ; 0 = & A ; gt ; 1

R [ 1 ] * C2= -4-2+2-2-2= -8 & A ; lt ; 0 = & A ; gt ; -1

R [ 1 ] * C3= 4+2+2-2+2= 8 & A ; gt ; 0 = & A ; gt ; 1

R [ 1 ] * C4= -4-2-2-2+2= -8 & A ; lt ; 0 = & A ; gt ; -1

Advantages of DS-CDMA

• It has an intervention rejection belongings ; every user is identified with a specific codification sequence which is about extraneous to the other users codifications.
• The DS-CDMA besides excludes the demand of channel spliting therefore all users use the full channel bandwidth.
• Furthermore, it is stiff to multipath attenuation. Signals in DS-CDMA systems are indistinguishable strength full a broad bandwidth which can pull strings the multipath attenuation to modify the end product.

Properties of DS-CDMA.

• Multiple Access – If multiple users use the channel at the same clip, there will be multiple signals overlapping in clip and frequence. At the receiver terminal coherent demodulation is used to take the codification transition. This method concentrates the power of the desired user in the information bandwidth. If the cross-correlations between the codification of the desired user and the codifications of the interfering users are little, consistent sensing will merely set a little portion of the power of the interfering signals into the information bandwidth.

• Narrowband Interference- The coherent sensing at the receiving system involves a generation of the standard signal with a locally generated codification sequence. However, as we see at the sender, multiplying a narrowband signal with a wideband codification sequence spreads the spectrum of the narrowband signal so that its power in the information bandwidth decreases by a factor which is equal to the processing addition.

2.6 Problem Description

Main job with DS-SS is the so called Near –Far consequence. This is described by an illustration. In figure 2.12 this consequence is present when an interfering sender TX ( B ) is closer to the receiving system RX ( A ) than the intended TX ( A ) and, the correlativity between the standard signal from the interfering sender TX ( B ) and RX ( A ) can be higher than the correlativity between the standard signal from the intended sender TX ( A ) and RX ( A ) . The consequence is that proper informations sensing is non possible.

Transmitter Tx ( B )

Transmitter Tx ( A )

Fig 2.12Near Far Effect

Another job is hidden and exposed terminus in wireless Ad-hoc web.

Hidden terminusjob refers- The hit of package at the having node due to the coincident transmittal of those nodes that are non within the direct transmittal scope of the transmitter.

Exposed terminusjob refers- The inability of a node which is blocked due to nearby transmission node, to convey another node.

For Example if both node S1 and S2 transmit to node R1 at same clip their packages collide at node R1.This happens because both nodes S1 and S2 are hidden from each other as they are non within the direct transmittal scope of each other.

This is called concealed terminus job. On the other manus if a transmittal from node S1 to another node R1 is already in advancement, node S3 can non convey to node R2, as it concludes that its neighbour node S1 is in conveying node and hence it should non interface with the on-going transmittal. This job reduces the throughput of web when traffic burden is high.

Transmission scope of node S1 Transmission scope of node S2

Fig 2.13Hidden and Exposed Terminal Problems

2.7 Proposed Work

The Basic motivation of our undertaking was to analyze and develop an Efficient Mac based DS-CDMA protocol for work outing near far job. A CDMA communicating system requires an efficient design and testing of its subsystems of PN-sequence generator, spectrum spreading and de-spreading digital circuits and digital modulator and detector faculties which give high throughput.

Another issue is near far consequence.

2.7.1 Reason for proposed protocol

The Near far consequence is created in the uplink of DS-SS CDMA. When a combination of unfastened and closed-loop power control which ensures that each terminus generates the same signal power at the base station. The base station monitors the power of standard signal from each terminus and instructs distant terminuss to increase their signal powers and nearby terminuss to diminish theirs illustration below shows the power control entirely is non plenty to cut down the near–far job in DS SS CDMA ad-hoc Network. Example: – Letdenote the distance between nodes Ks and n. suppose A wants to pass on with B utilizing a given codification and C wants to pass on with D utilizing a different codification. Suppose that tap ? dCD, dCB & A ; lt ; & A ; lt ; tap, and dad & A ; lt ; & A ; lt ; dCD. Then, the MAI caused by C makes it impossible for B to have A transmittal. Similarly, the Multiple entree intervention caused by A makes it impossible for D to have C transmittal. It is of import to observe that the two transmittals can non take topographic point at the same time, irrespective of what transmittal powers are selected if an addition in power is made to battle the MAI at B, this increased power will destruct the response at D.

Fig 2.14Example shows the Power Control entirely is non plenty to cut down the Near–Far job in DS-SS CDMA Ad-hoc Network

The above Fig. unveils two types of jobs – .

1.Medium entree job: – The usage of two different distributing codifications to happen at the same clip is non possible for two transmittals, this job is referred to as medium entree job.

2. Power control job: – If the terminuss adjust their signal powers so two transmittals can take topographic point at the same clip so that the intervention caused by one transmittal is non big plenty to pulverize package response at other terminuss. This is referred as power control job.

So the cardinal solution to the close far job must hold both elements: power control and medium entree.

2.7.2 DESIGN GOAL FOR PROTOCOL

The Following are the specifications while planing a MAC protocol for Ad-hoc web:

1. The operation of the protocol should be widen and provide quality of service for existent clip traffic.
2. The protocol must be a non-synchronous, spread operation, every bit good as scalable for big webs. It must besides affect minimum exchange of information and must be suited for real-time execution.
3. The protocol must be scalable to big web. in this protocol should be minimise the consequence of hidden and exposed terminus job.
4. The protocol should hold agencies for adaptative informations rate control and it should hold power control mechanisms in order to expeditiously pull off the energy ingestion of node.
5. The receiving system circuitry should non be complex in the sense that it should non be required to supervise the whole codification set.

So we design the DS-SS CDMA system with MAC protocol utilizing VHDL.

Introduction:

Presents, wireless communicating engineering has been spread outing quickly. It is important part to human being as the distance between each other become shorter because of these radio engineerings, such as Radio Frequency, Microwave, Bluetooth, LAN and WIFI engineerings. Wireless communicating devices are indispensable to human being lives as people use to pass on with other by utilizing cordless phones and other radio devices. Besides that, wireless frequence devices are being applied in infirmary or a nursing place for monitoring of patients, and besides the radio mouse, keyboards for computing machine countries and robotics every bit good.

Since the radio communicating engineering is important and indispensable to human lives, so the wireless frequence technique has been chosen as the robot remote control in order to look into and use this engineering. The wireless frequence technique uses on this undertaking but non other radio engineerings because it has the suited transmittal scope and more dependable than other techniques. For illustration, infrared technique requires signal transmit in line with unobstructed between the sender and receiving system.

Radio frequence technique applies on this undertaking for conveying the signal sent by user from sender to robot ‘s receiving system in order to command the going waies of automaton, such as move frontward, rearward, left or right. The scope between RF sender and receiving system is based on the frequence of its faculty. Higher frequence RF faculty will hold farther transmittal scope and RF range from 100 kilohertzs to 1 GHz. It is propagating along the land or contemplation from the ionosphere so reaches the receiving system.

The wireless frequence controlled robot platform motions non merely command by RF remote control, but besides obstacle sensors. Two supersonic detectors are installed on the forepart and dorsum of automaton to move as obstruction sensors to avoid obstruction in the class set by the accountant. Furthermore, a PIC ( Peripheral Interface Controller ) is used to command the turning way of motors which the automaton wheels by determines RF and supersonic detector signals. When there is an obstruction in the class set of automaton, automaton will halt, so LED on automaton platform will illume on and the doorbell will makes a warning sound to bespeak accountant to alter the going way of automaton.

Aim:

The purpose of the undertaking is to plan a RF ( Radio Frequency ) Controlled Robot Platform which the going way of automaton is controlled by RF remote control within a peculiar scope without the usage of electrical music directors. Besides that, detectors will be installed to move as an obstruction sensor of this automaton to do certain it can avoid obstructions in the class set by the accountant. Furthermore, a micro accountant will be used to command and to implements the operation by analysis the signal receives from distant control and detectors. For this undertaking, it involves larning to utilize detectors, Peripheral Interface Controllers and larning its scheduling every bit good.

Background literature:

A PIC microcontroller is use to move as a control Centre of the automaton as it has computation, memory and I/O maps. By utilizing PIC, C scheduling or assembly linguistic communications accomplishments are required as microcontroller operations are based on the package programming to implement the undertakings. The PIC16F76  has been chosen as the microcontroller of this undertaking as it has several particular pins and characteristics that suits for this undertaking demands such as:

O PIC16F76 has a entire figure of 28 pins. It is made up of three I/O ports ( Port A, B and C ) which has a 22 I/O pins in sum.

O In I/O port A, there are five input channels of 8-bit Analog-to-Digital Module which allows transition of an parallel input signal to a corresponding 8-bit digital figure that is helpful in analysis the signal transmits from RF receiving system.

O Two PWM ( Pulse Width Modulation ) Capture/Compare pins those are good in control the velocity and on/off of the DC motor by puting PWM responsibility rhythm.

O SCL and SDA pins can pass on with supersonic straight.

An supersonic is a type of detector that uses to bring forth high frequence ( above 20 KHz ) sound wave pulsations and detects an object by construing the reverberations signal from its sound moving ridge pulsation. The sound moving ridge pulsations are going in one way, when it detects an object, the echoed signal will be reflected back to the transducer of the supersonic detector. The scope from detector to object is able to find by ciphering the continuance of clip between the minute the sound wave pulse detects the object and clip for the echoed signal to return back to detector. When detector detects an object, it will trip a signal and sends it to PIC.

Supersonic detector is good in observing liquids, seeable objects and irregularly molded objects. Therefore, it has been chosen to move as an obstruction sensor of this undertaking instead than other detectors. Besides that, supersonic detector has a higher sensing scope and the reflected signal does non affected by the surface and colour of objects. The supersonic detector SRF08  is a high public presentation supersonic scope finder with a scope from 3cm to 6m. The communicating between SRF08 with microcontroller is via I2C coach. The I2C coach consists of 2 active wires and a land. Bi-directional SDA and SCL are the active coachs. SDA is Serial Data line and SCL is Consecutive Clock line, both of them have a pull-up resistance to +5v someplace on I2C coach. SRF08 is ever a slave ne’er a coach maestro.

For the wireless frequence remote control, the wireless wave signal can go through around or through the object, such as wood, glass, walls and other stuffs. The advantages of utilizing wireless frequence remote control are, signal transmits range farther than infrared distant control and signal does non necessitate to be transmitted in line to receiver. The disadvantage of utilizing wireless moving ridges to convey signal is, signal will be affected by the presence electromagnetic intervention in the environment. A RF faculty [ 3 ] ( TWS-434 and RWS-434 ) has transmitter frequence 433.92 MHz when it end product is 8mW with a scope of about 200 pes for indoors and 400 pes for out-of-doorss. It is ability to accept both digital and additive inputs. Operating electromotive force is 1.5 to 12 volts-DC. For the RWS-434 receiving system, it is besides operates at the same frequence which is 433.92 MHz and a sensitiveness of 3uV. The receiving system has both additive and digital end products and runing electromotive force from 4.5 to 5.5 volts-DC supply.

Two DC Gear motors are installed on the automaton platform as the motor thrusts ( wheels of automaton ) . The EMG30motor is a DC motor with encoder. Encoder is used to tracking the figure of revolutions and the place of motor. The rated electromotive force of this motor is 12v. These are the characteristics of EMG30 DC motor:

• No burden velocity: 216 revolutions per minute
• No load current: 150 ma
• Rated torsion: 1.5 kg/cm
• Rated current: 530 m
• Rated velocity: 170 revolutions per minute
• Rated end product: 4.22 W

The motor shaft can be rotated in two waies that clockwise or counter-clockwise way. Therefore, the automaton moves frontward or rearward merely inversing the mutual opposition of the power supply of the DC motor. The turning operation makes by holding two wheels turning in different waies at the same time. This motor has Hall detectors every bit good. A hall detector varies its end product electromotive force in response to alterations in magnetic field, it used for placement and velocity sensing applications of this undertaking.

An H-bridge is a four shift elements device which enables a electromotive force to be applied across the motor or burden in merely one way. It is utilizing to move as a motor control circuit that allow DC motor to run forwards and backwards by providing the electromotive force to different switches. An H-bridge is built with four switches. When the switches S1 and S4 are closed, S2 and S3 are unfastened a positive electromotive force will be applied across the motor. The electromotive force will be in the reversed way by opening S1 and S4 switches, shuting S2 and S3 switches. The H-bridge is by and large used to change by reversal the mutual opposition of the motor, but it can be besides used to halt the motor or to allow the motor run freely. Switches S1 and S2 or S3 and S4 should non be closed at the same clip as it will do a short circuit on the input electromotive force. L298  is a high electromotive force and high current double full-bridge driver. The chief intent of L298 is to move as a motor accountant to command the rotate way of DC motor harmonizing to the end product electromotive force from PIC.

It is taken from mention of ”H-bridges: Theory and Practice ” , available from: hypertext transfer protocol: //www.mcmanis.com/chuck/robotics/tutorial/h-bridge/

Work done

In the past few hebdomads, a batch of consideration and research undertakings have been done. For illustration, the extension rule of wireless frequence, and besides the working rule of H-bridge motor control and PWM. Some tutorials that helpful and related to the PIC scheduling have been read as good. On the other manus, all the constituents of this undertaking have been decided after reading the datasheets of each constituent. At the same clip, automaton platform has been designed and sent to the mechanical ‘s workshop in order to cut metal home base into the designed form. Furthermore, the pin connexions between the PIC, detectors and motors have been decided after reading datasheets of constituents and PIC. So far, the advancement of this undertaking is on the measure of circuit conventional designing and larning the package scheduling of PIC undertakings.

• Pin 1: Seriess connected with a 10kI© resistance to +5v DC supply.
• Pins 2 & A ; 3: End product ports for LEDs.
• Pins 5 & A ; 7: to move as inputs from shaft encodes of motor.
• Pin 8: Connect to land.
• Pin 9 & A ; 10: Connect to a parallel crystal 4 MHz and two series 33 pF capacitances with land.
• Pins 12 & A ; 13: PWM outputs connect to the H-bridge.
• Pins 14 & A ; 15: I/O ports of I2C lines connect to the supersonic detectors.
• Pin 18: End product port for doorbell.
• Pins 25 & A ; 26: End product signals connect to H-bridge.
• Pins 21, 22, 23 and 24: Act as input ports from RF receiving system.

Advancement AND Plan:

Now, it is on the measure of larning package scheduling and circuit conventional designing undertakings, but it is a small spot delayed due to the clip disbursement on the undertaking less than undertaking program for past few hebdomads, since I was busy in making other faculty ‘s assignments and could non make up one’s mind the constituents on clip.

On the following semester, the clip disbursement on this undertaking will be more than the novice program in order to catch up the advancement that has been planned as undertaking program. These are the major undertakings that will transport out consequently on the undermentioned semester:

1. RF faculty proving.
2. Supersonic faculty testing.
3. DC motor testing.
4. PCB circuit design.
5. PCB etching and soldering of constituents.
6. Prototype theoretical account building.
7. Trial and seek run the automaton system to modify the scheduling of PIC.
8. Troubleshooting and debugging.
9. Test overall functionality.

On the undermentioned semester, the clip disbursement on making this undertaking will be 18 hours per hebdomad.

The item agenda of this undertaking has been shown on the Gantt chart.

References

1. DEVENDRA K. MISRA, “ Radio-Frequency and Microwave Communication Circuits ” , Printed in the United States of America, By John Wiley & A ; Sons, Inc, 2001.
2. Newton C. Braga, “ Roboticss, Mechatronics, and Artificial Intelligence, Experimental Circuit Blocks for Designers ” , Printed in the United States of America, By Newnes Boston Oxford Auckland Johannesburg Melbourne New Delhi, 2002.
3. Richard J. Valentine, “ Motor Control Electronics Handbook ” , Printed in the United States of America, The McGraw-Hill Companies, Inc. , accessed by 30th October 2009, E-book, available from:
4. hypertext transfer protocol: //books.google.com/books? id=kLZL5hTsVIYC & A ; printsec=frontcover & A ; source=gbs_navlinks_s # v=onepage & A ; q= & A ; f=false
5. Jim Brown, “ Brief H-BRIDGE THEORY OF OPERATION ” , Written at April 1998, accessed by 1st November 2009, available from: hypertext transfer protocol: //www.dprg.org/tutorials/1998-04a/
6. Chuck McManis, “ H-bridges: Theory and Practice ” , accessed by 1st November 2009, available from: hypertext transfer protocol: //www.mcmanis.com/chuck/robotics/tutorial/h-bridge/
7. Milan Verle, “ PIC Microcontrollers ” , mikroElektronika ; 1st edition, Written at 2008, accessed by 25th November 2009, available from: hypertext transfer protocol: //www.mikroe.com/en/books/picmcubook/ch5/
8. Nebojsa Matic, “ Programing PIC Microcontroller in BASIC ” , mikroElektronika, Chapter 6 PWM Module, accessed by 1st December 2009, available from: hypertext transfer protocol: //www.mikroe.com/en/books/picbasicbook/06.htm # 6.5
9. Chuck McManis, “ H-bridges: Theory and Practice ” , accessed by 1st November 2009, available from: hypertext transfer protocol: //www.mcmanis.com/chuck/robotics/tutorial/h-bridge/
10. PIC16F7X Data Sheet28/40-Pin, 8-bit CMOS FLASH Microcontroller, By Microchip Technology, Inc. , 2002.hypertext transfer protocol: //ww1.microchip.com/downloads/en/DeviceDoc/30325b.pdf
11. SRF08 High Performance Ultrasonic Range Finder, By Acroname, Inc. , 1994-2009.hypertext transfer protocol: //www.acroname.com/robotics/parts/R145-SRF08.htmlhypertext transfer protocol: //www.robot-electronics.co.uk/htm/srf08tech.shtml
12. Radio Frequency Module ( TWS-434 and RWS-434 ) Data Sheet, By Rentron Electronic.hypertext transfer protocol: //www.rentron.com/Files/rf.pdf
13. DC Gear motor ( EMG 30 ) Data Sheet, By technonots.co.uk.

Week 2 Lab Report 1. Read through the lab instructions before executing the lab steps and creating the reports. 2. Follow all procedures in the lab instructions for the items you will need to include in your report. 3. After executing all steps contained in the lab instructions, submit a one Word document for each project containing your report to the Dropbox. Create your reports using the template starting on page 2 and submit it to the Week 2 Dropbox by the due date. Have fun while learning! Thanks Your NameJeret Burnett

NETW360, Professor’s Name Mario Kosseifi Current Date July 15, 2012 Lab #2 Part 1, Antennas Lab Report Case Project 3-1 Antenna Type Using the internet and other resources, research the different types of antennas that are included under the three main categories: omni-directional, semi-directional, and highly-directional. Draw or print an example of each type and summarize when it is used, what is its maximum transmission distance, and it’s advantages and disadvantages. Omni-Directional [pic] When it is used?

This antenna can be used for indoor and outdoor access points. It is an excellent solution for RV parks, Marinas, Resort Wi-Fi, and other general outdoor area where other wireless access is needed but unable to be achieved by the small antennas on a router. What is its maximum transmission distance? The range of this antenna is 3000 feet. However, a longer rage is possible with additional antennas on the receiving end. Advantages and disadvantages? The main advantage to this antenna is that you can receive wireless signal in areas that were not available before.

Everyone has heard of internet “Cafes”, but with this antenna you could make an internet “Cafe” literally in the middle of a campground. The disadvantage is that trees, building and hills can reduce the signal and in somecases can completely stop the signal from getting through. Also, to get this antenna high enough to cover some areas the length of the coax cable will reduce the signal; thus making the antenna less effective. Semi-Directional [pic] When it is used? Semi-directional antennas are ideally suited for short and medium range bridging.

If you want to connect two office buildings that are across the street from one another and need to share a network connection semi-directional would be a good choice. Or if you have a long narrow room where you need coverage throughout the whole room you can mount the antenna on an end wall. This is because the side-to side signal will not travel as far but the forward signal will travel quite far. What is its maximum transmission distance? Semi-directional range can vary greatly but is commonly used in situations that call for a range of a few hundred feet to two miles.

Advantages and disadvantages? The main advantage of a semi-directional antenna is that in some cases a semi-directional antenna can provide such a long range coverage that they eliminate the need for multiple access points. The main disadvantage is that if you need coverage over a large open area, such as a cubical office where the entire floor is open, a semi-directional antenna would not be the best choice because not every computer will receive coverage. Highly-Directional [pic] When it is used?

It’s main usage is for point-to-point communication links where wired or other directional wireless coverage is not possible. What is its maximum transmission distance? Highly-directional antennas can operate at a range of up to 35 miles. Advantages and disadvantages? The main advantage is if you need to transmit wireless signal over a very long range without the signal going all over. Such as a person that is quite wealthy, they may have their own private island and want internet connectivity, but does not want to go with satellite internet and wired connectivity is out of the question.

Another advantage is that if you are located in a building where wireless signal is very hard to get, a highly-directional signal may be the answer because since it is so focused in such a small narrow margin it may be able to basically blast through the wall. The main disadvantage is that the dish antenna is subject to damage from weather, especially if not mounted correctly. Highly directional antennas, for the most part, require a clear line-of-sight between ends. Your NameJeret Burnett NETW360, Professor’s Name Mario Kosseifi Current Date July 15, 2012 Lab #2 Part 2, RF Behavior Lab Report

Determining the behavior of an RF signal can be an aid when troubleshooting a WLAN that does not function properly. In this project you will use several online calculators to computer the RF behavior. 4. 30dBm 7. 8. 4 11. -81. 538 19. -5. 474469367710745 |Name |Power Output | |Cell Phone |. 6 W | |Cordless phone |10 mW | |Garage Door Opener |100 W |

Chapter 3 Mobile Radio Propagation: Large-Scale Path Loss 1. (a) Explain the advantages and disadvantages of the 2-ray ground reflection model in the analysis of path loss. (b) What insight does the 2-ray model provide about large-scale path loss that was disregarded when cellular systems used very large cells? 2 . In a 2-ray ground reflected model, assume that must be kept below 6. 261 radians for phase cancellation reasons. Assuming a receiver height of 2 m, and given a requirement that be less than 50 , what are the minimum allowable values for the T-R separation distance and the height of the transmitter antenna?

The carrier frequency is 900 MHz. 3. In the 2-ray path loss model with ? derive an appropriate expression far the location of the signal nulls at the receiver. 4 . Compare the received power for the exact expressions for the 2-ray ground reflection model. Assume the height of the transmitter is 40 m and the height of the receiver is 3m. The frequency is 1800 MHz, and unity gain antennas are used. Plot the received. 5. Referring to Figure P3. 3, compute d = d1, the first Fresnel zone distance between transmitter and receiver for a 2-ray ground reflected propagation path, in terms of and X.

This is the distance at which path loss begins to transition from d to d behavior. Assume 6 . If the received power at a reference distance d0 = I km is equal to 1 microwatt, find the received powers at distances of 2 km, 5 kin, 10 km, and 20 km from the same transmitter for the following path loss models: (a) Free space; (b) n = 3; (c) n = 4; (d) 2-ray ground reflection using the exact expression; (e) extended Hata model. Assume f=1800 MHz, ht = 40m, hr = 3m, Gt=Gr=0dB. Plot each of these models on the same graph over the range of 1 km to 20km. 7 .

Assume the received power at a reference distance d0 = 1 km is equal to 1 microwatt, and f=1800 MHz, ht = 40m, hr = 3m, Gt=Gr=0dB. Compute, compare, and plot the exact 2-ray ground reflection model with the approximate expression. At what T-R separations do the models agree and disagree? What are the ramifications of using the approximate expression instead of the exact expression in cellular system design? 8 . A transmitter provides 15W to an antenna having 12 dB gain. The receiver antenna has a gain of 3 dB and the receiver bandwidth is 30 kHz.

If the receiver system noise figure is 8 dB and the carrier frequency is 1800 MHz, find the maximum T-R separation that will ensure that a SNR of 20 dB is provided for 95% of the time. Assume n = 4, dB, and d0 = 1 km. 9. Assume a SNR of 25 dB is desired at the receiver. If a 900 MHz cellular transmitter has an EIRP of 100 W, and the AMPS receiver uses a 0 dB gain antenna and has a 10 dB noise figure, find the percentage of time that the desired SNR is achieved at a distance of 10 km from the transmitter. Assume n=4, dB, and d0 = 1 km.