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Cooperative Relaying(Matlab Prototype)

Green Group

2008-04-30

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Project Description

• We will implement the 3-node

communication system including Source,Relay, and Destination.

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Project Description

• Half duplex, Orthogonal System

• First time slot

• Next time slot

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Project Description

• Three different types of relaying protocols

• Amplify-and-forward

• Decode-and-forward• Detect-and-forward

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Matlab Prototype

• The Matlab prototype in our project

consists of two parts:

• First, the Matlab simulation of the three-node communication system

• Second, the Matlab simulation of the SISOsystem using fading channel on DSP

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Matlab Prototype

• We will provide results with the BER

performance, and some analyses of thoseresults.

• Also a comparison of BER performance of

3 different relaying protocols will be

provided.

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3-node communication system

• The basic idea is based on 2-node

communication system (SISO system).

• “Relay” works cooperatively with Source.• Spatial Diversity

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SISO system

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Transmitter

• M-sequence for training bits• Convolutional code

• QPSK• Upsampling by factor 8• Raised cosine pulse shape with rolling factor

0.22

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Transmitter

• Training sequence with a good ACF

property

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Transmitter

• 1/2 rate convolution channel encoding

T T Input BitSequence

Output BitSequence

Rc=2RbRb

X

Y2

Y1

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Frame structure

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Transmitter

• Symbol mapping :

QPSK with gray mapping

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Transmitter

• Pulse shaping

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Transmitter

• Pulse shaping

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Transmitter

• Upconversion

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Channel

• Baseband Rayleigh fading channel withDoppler frequency shift 0.5 Hz by using

Jake’s model

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Receiver

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Receiver

• Synchronization

Cross-correlation between the received

signal and a locally generated time-shifted replica of the training sequence.

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Receiver

• Channel estimation

Calculated based on Least-square

criteria by using the received signalduring the training sequence

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Receiver

•Channel estimation

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Receiver

• Three kinds of detectors

• ZF (Zero Forcing)

• MMSE (Minimum Mean Square Error)• ML (Maximum Likelihood)

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3-node communication system

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3-node communication system

• Relaying protocols

Amplify-and-forward

Decode-and-forwardDetect-and-forward

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3-node communication system

Amplify-and-forward

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3-node communication system

Decode-and-forward

• we decode the received signals at relayand transmit the fresh codeword using

the same code to destination.

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3-node communication system

Detect-and-forward

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3-node communication system

• Combining

• Maximum Ratio Combining (MRC)

• MRC is used for combining in the

decode-and-forward in our simulation.

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3-node communication system

• Combining

• Improved Maximum Ratio Combining 

(MRC)• This method is used in amplify-and-

forward relay.

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3-node communication system

• Combining

• Maximum Ratio Combining (MRC) and 

• Sub-optimalCombining(Linear MMSE)• Used for detect-and-forward 

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Simulation results in Matlab

• Signal Constellation

• (a)Amplify-and-forward (b)Decode-and-forward

• (c)Detect-and-forward (d)One link

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Simulation results in Matlab

• BER comparison

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SISO Simulation on DSP Board

• We simulate the SISO system using the

channel enumerated on DSP board.• The system works in the way that the

receiver always keeps listening to theincoming signal and measure the variance

of it.

• The receiver will detect the signal by using

the noise variance threshold.

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SISO Simulation on DSP Board

• Synchronization

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SISO Simulation on DSP Board

• BER performance