Error Control Code Combining Techniques in Clusterbased Cooperative Wireless Networks

1
Error Control Code Combining Techniques in
Cluster-based Cooperative Wireless Networks
Su Yi Babak Azimi-Sadjad Shivkumar
Kalyanaraman Vijaynarayan Subramanian Presenter
Jayasri Akella
2
Outline

• Introduction and Related work
• Performance Analysis for Link Layer Cooperation
• Simulations
• Conclusions and Future Work

3
Introduction

• Objective to improve the overall channel
  quality/ throughput for each transmitter/receiver
  pair
• Method link layer cooperation scheme for
  multi-hop wireless networks and sensor networks
• Advantage extract diversity gain out of the
  redundancy inherently present in all broadcast
  network transmission

4
Previous Work Physical Layer Cooperation

• The information source reaches the first relay
  cluster.
• The nodes in the relay cluster share their
  information for diversity gain. Then they relay
  the information to the next cluster.
• The next cluster has a reliable channel with the
  destination node, hence there is no need of
  physical layer cooperation. A single node can
  relay the information to the final destination
  node.

5
Link Layer Cooperation

• Stage 1 Cluster head decides if cooperation is
  necessary
• Stage 2 FEC and Code combining among cluster
  nodes
• Stage 3 Use ARQ or transmit diversity if else
  fail

6
Code Combining Procedure
7
Code Combining Technique

• Combine L repeated packets encoded with a code of
  rate R
• Thus obtain a lower rate R/L and more powerful
• Viterbi (maximum-likelihood) decoding
• The decoding function
• An alternate way is
• where weight for the i th channel

8
Code Combining with Convolutional Codes An
Example

• A (3,1,2) code with an information sequence h 3

001
S
S
3
3
1
1
0
0
1

0
0
1
1
1
0
0

S
S
S
1
1
1
1
1
1
0
0
0
1
1
1



S
S
S
2
2
2
0
0
1
1
1
1

0


1
1
1
1
1
1
1
1
1
1
1
000
000
000
000
000
S
S
S
S
S
S
0
0
0
0
0
0
r ( 000 , 000 , 001 ,
000 , 000)
9
Code Combining with Convolutional Codes An
Example

• A (3,1,2) code with an information sequence h 3
• Cooperative nodes L3
• Weight for each channel is w1, w2, w3

• If w1w2w3, the all zero path is chosen.
• If w11, w22, w33, then the highlighted path
  is chosen.

001 001 001
S
S
3
3
1
0
1
1
0
0
0

1

0
0
1
1

1
0
0

1
0
0
0
1


0
0
1
1
1
1
0
1
0
0

1
1
S
S
S
1
1
1
0
1
1
1

0
0
0
1
1
1
1

1


1
1
1
0
0
0
0
1
1
1



1
1
1
0
0
0
1
1
1
1
w1 w2 w3
1
S
S
S
2
2
2
1
1
1

0
1
1
0
1
1
1

1
1
1
1
1

1
1

0
1
0


0
1
1
1
1
1
1
1
1
1

1

1

0
1
0
1
0
1
1
1
1
1
1
1
1
1
1

0
1
1
1
1
000 000 000
000 000 000
000 000 000
000 000 000
000 000 000
S
S
S
S
S
S
0
0
0
0
0
0
r ( 000 001 111 , 000 100 101 , 001 010
001 , 000 000 000 , 000 000 000)
10
Code Combining with Convolutional Codes in a
Uniform Channel Condition

• Bit-error prob of the non-combined code
• Bit-error prob of the L-repeated code
• p BER for wireless channel
• - coefficient of power term in
  B(X), the bit weight enumerating function (WEF)
  of the convolutional code
• - minimum free distance

11
Code Combining with Different Channel Conditions

• Bit-error prob of the L-repeated code
• where
• is the coefficient in the generating
  function of r.v. S
• S is a weighted sum of the received sequence

12
Simulations

• A simple network topology

L 4
50 or 100 m
250 m
Cluster head
Sender
13
Link Layer Decoding Performance
Decoded bit-error rate Pb vs. number of
cooperative nodes L. PL is the amount of power
deduction of the intra-cluster transmission upon
the inter-cluster transmission.
Decoded bit-error rate Pb vs. number of
cooperative nodes L with different cluster
radius. Smaller cluster radius has a better
performance.
14
Energy Consumption
Aggregate energy consumption vs. number of
cooperative nodes or packet repeats L. A decoded
bit-error rate Pb10-7 is fixed.
SNR vs. number of cooperative nodes L. With a
fixed objective Pb, the required SNR decreases
with the increase of the cluster size L.
15
Conclusion and Future Work

• Cooperation architecture is effective in
  improving the link performance and reducing the
  energy consumption
• Less power leads to less interference among
  nodes, thus can improve the capacity of the
  wireless networks.
• Future work on designs which explicitly exploit
  physical layer, data link layer, and network
  layer cooperation among nodes
• These designs include
• cooperation-intended cluster-based routing
• medium access issues in the intra-cluster
  communications
• network performance from all aspects
• more information theoretic analysis of the coding
  technique and network capacity.

16
Thank you!

• For more information yis_at_rpi.edu