Chapter 3 SIMULATION OF UHF- RFID WIRELESS ...shodhganga.inflibnet.ac.in/bitstream/10603/42466/11/11...The system is simulated using Matlab software. 3.2. Repeater: In wireless communication

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Chapter 3

SIMULATION OF UHF- RFID WIRELESS REPEATER USING MATLAB

3.1. INTRODUCTION:

Presently we are using GPS (K. Brown and Peter Brown, 2005; Robert

MacCurdy 2009; Patrick E. Clark et al., 2005) and GSM for tracking an

object. The given solutions for tracking that are very expensive. Nowadays

RFID is used in Logistics management, Library management and Farm

management (Sewon Oh et.al, 2005; Raj Bridgelall, 2008; Urachada Ketprom

et al., 2007). But it is having severe coverage/ read range problem (Clinton S.

Hartmann and Lewis T. Claiborne, 2007).

In passive RFID technology, tags won’t have battery to transmit data. Each tag

gets energy signal from reader unit. Due to free space loss and passive antenna

efficiency the tag gets very low energy signal for its operation. So, the tag

cannot communicate over larger distance. H-E. Nilsson, et.al. 2007 have

developed a printed patch antenna for robust RFID tags to improve efficiency

of read range. But it is useful for short range of coverage extension only and

cannot give better coverage for large areas. To solve this wireless repeater

approach is proposed. The main component in repeater is signal booster; this

will improve RFID signal strength and can give better reading range.

Here we proposed wireless repeater with switch to control selection of antenna

of particular area which yields better tracking of tag. In the previous research,

wireless repeater was proposed as a simple energizer for LF application. It is

used to energize the tag and not to boost received signal (Afshin Partovi and

Micheale Sears, 2008; Ben J.Wild 2010). In our work we propose wireless

repeater for UHF range with switches to control the repeater and antenna for

tracking information. The selection of repeater and particular antenna is

controlled by switch. The repeater signal booster section amplifies weak RFID

signal transmitted from the tag, thereby it can reach long distance. The system

is simulated using Matlab software.

3.2. Repeater:

In wireless communication engineering, the part of repeaters is very important.

It helps better signal reception and for good decision making. It is basically an

amplifier which amplifies the RFID signal. In RFID system the reader sends

command/energy signal towards tags. This signal energises internal circuitry

of RFID tag from incoming signal and retransmits it towards the repeater. This

signal is so weak in strength and should not be able to reach reader in the long

distance. It reduces the c

booster to increase the strength. It will enhance the reading range of the

system.

3.3. Cell Structure

In mobile communication we are using hexagonal cellular architecture for

better frequency resource management and coverage. The same principle is

adopted here for antenna installation as discussed in previous chapter. Every

antenna is considered as base st

compact and efficient in coverage. It is given in figure 3.1.

3.4. Antenna Networking

It is the technique of connecting more number of antennas with each reader to

improve its efficiency in tracking range. Here we are using star network



is simulated using Matlab software.

Repeater:




energy signal towards tags. This signal energises internal circuitry



distance. It reduces the coverage of RFID system. So we introduce signal


Cell Structure:




antenna is considered as base station of the cell. This structure is more

compact and efficient in coverage. It is given in figure 3.1.

Figure 3.1: Cellular Structure

Antenna Networking:



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energy signal towards tags. This signal energises internal circuitry



overage of RFID system. So we introduce signal





ation of the cell. This structure is more



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topology based structure to connect antennas with the repeater ports. The

repeater will be placed at the centre cell for better performance and less loss. It

gives most efficient and suitable shortest path to our design.

3.5. General Block Diagram:

The general block diagram of our proposed system is given figure 3.2.

Initially RFID reader transmits energy signal to the RFID tag. Then the tag

transmits the ID data to the reader through antenna, switch (MUX/DEMUX)

and wireless repeater. Here wireless repeater plays major role in amplifying

the weak signal from tag. UHF passive tags are simulated in this work. In

general maximum coverage is 10 to 15 Meters operating at 865 MHz range.

Here we are proposing cellular architecture for implementing base station

antenna. It gives greater performance in coverage for larger areas. The read

error probability and antenna cabling issue is solved in this method. The

physical area is divided by hexagonal cells and repeater antenna is placed in

this cell. For the given physical area number of cells, number of antennas and

number of readers are calculated by following procedures.

Number of cells (Cn) = Farm Area( Fa) / 2.59 D2

D is radius of hexagon.

Area of the hexagon = 2.59 R2

If we consider each antenna to cover 10 meters radius,

Test antenna range = 10 meters;

D = 10 meters; If Fa = 10000 Sq. meters,

Cn = 100X100/2.59 X 100

No of Hexagon Cells = 38.7

No of Antennas per repeater ( Na) = 8

No of repeater = 39/8 = 5;

No of reader = 1

So, we need Approximately1reader and 5 repeaters to cover 10000 Sq.

Meters area. Proper division of land area and antenna placement will lead

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good results. Rough and tough uneven areas we have to choose special

directional antennas for better results

Figure 3.2: Repeater model

3.6. Design of Repeater:

Elements of repeaters are transmitting and receive purpose antennas, low

noise and power amplifiers. Based on the distance and frequency range power

loss is calculated. Amplifier gain is selected based on the loss in the particular

site. Free-space path loss is proportional to the square of the distance between

the transmitter and receiver, and also proportional to the square of the

frequency of the radio signal.

The equation for Free Space Path Loss is

FSPL = (4πd/λ)2

FSPL = (4πdf/c)2

M

U

X

/

D

E

MU

X

M

U

X

/

D

E

MU

X Encoder/Decoder

RF AMPLIFIER

RFID Reader

RFID

RFID

RFID tag

Where:

• is the signal wavelength (in metres),

hertz), is the distance from the transmitter (in metres),

of light in a vacuum, 2.99792458 × 10

This equation is only accurate in the far field where sp

assumed; it does not hold close to the transmitter.

Free-space path loss in decibels

A convenient way to express FSPL is in terms of dB:

FSPL (dB) = 10 log

= 20 log10

= 20 log

FSPL (dB) = 20 log

For typical radio applications, it is common to find

MHz and in km, in which case the FSPL equation becomes

FSPL (dB) = 20 log

In our design we have to consider free space loss at tag to repeater and

repeater to reader link. So, we have to design a power amplifier to compensate

this loss for collect the data from repeater link.

3.7. Multiplexer Switch Unit:

Here we are using MUX/DEMUX for switching RF signal between

reader and tag. At any particular time of interval one port will be activated to

collect data. Antenna networking is used instead of more readers

reduce cost of the network. The switching

is the signal wavelength (in metres), is the signal frequency (in

is the distance from the transmitter (in metres),

of light in a vacuum, 2.99792458 × 108 metres per second.

This equation is only accurate in the far field where spherical spreading can be

assumed; it does not hold close to the transmitter.

space path loss in decibels

A convenient way to express FSPL is in terms of dB:

FSPL (dB) = 10 log10 ((4πdf/c)2)

10 (4πdf/c)

= 20 log10 (d) + log10 (f) + log10 (4π/c)

FSPL (dB) = 20 log10 (d) + log10 (f) – 147.55; Where the units are as before.

For typical radio applications, it is common to find measured in units of

in km, in which case the FSPL equation becomes

= 20 log10 (d) + log10 (f) + 32.45



this loss for collect the data from repeater link.

Multiplexer Switch Unit:



Antenna networking is used instead of more readers

reduce cost of the network. The switching control signal will be sent to the

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is the signal frequency (in

is the distance from the transmitter (in metres), is the speed

metres per second.

herical spreading can be

147.55; Where the units are as before.

measured in units of

in km, in which case the FSPL equation becomes





Antenna networking is used instead of more readers. It will

control signal will be sent to the

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repeater from reader and based on that it will activate specific ports for

communication. In our design we have explained forward control path and

return signal path from repeater antenna port. The signal path from tag to

reader through repeater is very important in decision making for RFID data

retrieval. We have taken 10000 square meter area as an example and here we

need 39 output ports to connect an antenna and 5 repeaters with 8Ch switch.

3.8. Antenna Installation:

Antenna selection and installation is an important task in communication

engineering. Here we are using star networking topology to connect the

antennas. Every antenna is connected to its repeater and selection of the port is

controlled by main reader. An Antenna is installed at the center of the base

station. Here we have in this case we have designed 39 hexagon cells and

therefore 39 base stations. So, we have to use 39 antennas. We must find out

shortest path to connect antenna and network center for less wire loss.

3.9. Mapping of Tracking Data :

Mapping is identifying physical locations using graphical representation.

Here the physical areas are structured by hexagonal cells. Every cell is

represented by specific ID which gives its exact location. Actually the antenna

selection control signal is sent from the reader. So, we can easily visualize the

tags and location. Here we are using predetermined location mapping, that is

antenna and base station is controlled by repeater control signal transmitted by

reader. It can be used for identifying the present location of the tag. This

method is most economic for tracking the object.

3.10. Implementation:

We have used hexagonal cell structure for placing antenna tower. It is very

efficient method for calculating number of antennas and readers for area

mapping. It gives perfect solution for complete coverage. That is visibility will

be more compared with other mapping methods. Using wi

this hexagonal structure we can cover large physical area with less number of

RFID readers. In the above mentioned calculation totally 1 reader,

and 39 antenna ports are needed to cover 10000 Sq.

economical and closed loop algorithm is used to track the objects. In this work

we tried to solve reading range issue with switch controlled wireless repeater

and antenna networking. The

and Matlab model is represented by 3.4.

Here we are using passive RFID because of battery replacement and cost. For

long range, life and low cost application UHF tags are more suitable. Mobile

communication technology uses

management. Here also we tried the same approach to fix reading point

antennas for successive read rate. Every cell will have one antenna as a base

station. It will identify the tag and based on the control signal infor

particular port the location map is updated. Suppose the control signal is 1,

then the first antenna of repeater will be activated and others will be off. If we

read any tag in this time slot, means that it is transmitted from location

corresponds to reader 1, cell 1. By this data we can locate particular object and

its present location.


be more compared with other mapping methods. Using wireless repeater and


RFID readers. In the above mentioned calculation totally 1 reader,

antenna ports are needed to cover 10000 Sq. meter areas. It is very



and antenna networking. The block diagram is given by figure 3.

and Matlab model is represented by 3.4.

Figure 3.3: Block Diagram



communication technology uses cellular structure for base station



station. It will identify the tag and based on the control signal infor




s to reader 1, cell 1. By this data we can locate particular object and

its present location.

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reless repeater and


RFID readers. In the above mentioned calculation totally 1 reader, 5 repeater

eter areas. It is very



is given by figure 3.2, figure 3.3



cellular structure for base station



station. It will identify the tag and based on the control signal information of




s to reader 1, cell 1. By this data we can locate particular object and

Figure 3.4: Simulation model in MatlabFigure 3.4: Simulation model in Matlab

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Figure 3.5: Simulation result window snapshot

3.1. Conclusion

We have simulated 8 cells. One reader was used to cover whole area. We used

one multiplexer and one repeater. The location is mapped based on the port

control signal and corresponding tag data was displayed. Here we have tested

for 8 different tags which a

was displayed for individual cases. Power spectrum and BER is calculated and

displayed in figure 3.5 and figure 3.6.


Figure 3.6: BER

Conclusion:




for 8 different tags which are placed in 8 different cells. The mapping chart


displayed in figure 3.5 and figure 3.6.

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re placed in 8 different cells. The mapping chart


Documents

Chapter 3 SIMULATION OF UHF- RFID WIRELESS ...shodhganga.inflibnet.ac.in/bitstream/10603/42466/11/11...The system is simulated using Matlab software. 3.2. Repeater: In wireless communication