Error Control Code Combining Techniques in Cluster-based 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

1. The information source reaches the first relay
   cluster.
2. The nodes in the relay cluster share their
   information for diversity gain. Then they relay
   the information to the next cluster.
3. 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