Nour KADI, Khaldoun Al AGHA 21 st Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications 1

 Introduction  Previous work  The drawback of LT codes  Switched Code ◦ Analysis of Switched Distribution  Simulation  Conclusions 2

 A wireless ad hoc network is a decentralized type of wireless network. ◦ wireless Sensor networks (WSN) wireless Sensor networks  Each node participates in routing by forwarding data for other nodes, and so the determination of which nodes forward data is made dynamically based on the network connectivity. 3

 Overcoming problems associated with resource scarcity and unreliable channels has been a challenge for data broadcasting protocols in ad-hoc networks.  The network coding combined with network broadcasting can reduce the bandwidth and power consumption and increase the throughput.  Rateless codes achieve a reliable broadcast transmission. 4

5 b1b1 b2b2 b1b1 b1b1 b1b1 b2b2 b2b2 b2b2 b2b2 b1b1

6 (for channel coding)

7 (For network coding)

Linear Network Coding [4] LT Code Encoding & Decoding complexity Low complexity Intermediate nodes Decode & re-encode received information Just forward the encoded packets Result Save the network resource and increase the throughput Consume lot of network resource 8 [4]D. S. Lun, M. M´edard, R. Koetter, and M. Effros, “On coding for reliable communication over packet networks,” CoRR, vol. abs/cs/ , 2005.

 To achieve reliable broadcasting and efficient bandwidth utilization ： ◦ Using LT-code guarantees the simple complexity of the proposed coding scheme. ◦ Using network coding increases the throughput and saves the network resources.  We introduce a coding scheme that efficiently broadcasts the source packets. 9

 Combines LT-code with network coding, by enabling intermediate nodes to perform coding. 10

 The RSD is designed to decode plenty of symbols only when it receives sufficiently large number of encoded packets.  Hence, using LT- code in its original form increases significantly the end-to-end packet delay. 11

 We present a degree distribution that increases the symbol recovery probability at any time during the decoding process, while keeping the overhead as small as possible. 12

 The sender switches from the first distribution to the other according to the number of encoded packets which have been sent. 13 [6] S. Agarwal, A. Hagedorn, and A. Trachtenberg, “Adaptive rateless coding under partial information,” in Information Theory and Applications Workshop, 2008, 2008, pp. 5–11.

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Codeword with coding candidate {1, 3, 4}, and degree = Definition 1. (codeword and degree):

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 Lemma 3. To recover the last symbol, it is more useful to use Soliton Distribution. 19

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 Definition 6. Let’s consider an incremental decoder S. If the decoder S receives r codewords, then it decodes them in an ascending order according to their degree d. First step, it decodes the packets with d = 1. Then, using the packets which are recovered from the first step, it decodes the packets with d = 2. For a step i, it decodes the packets with d = i by using the packets which are recovered from steps 1,2,...,i-1. If a packet of degree d couldn’t be decoded at step i = d, then it will be ignored in the next steps. 21

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 To adapt LT code to the case where some input symbols are already known at the destination. ◦ Generate high degree with higher probability 24 k : total number of input symbols l : the number of input symbols already known at the destination.

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 Comparison with 2 other LT-code based schemes. ◦ Original LT code ◦ Forward & Re-code [4] (for line network)  Adapt LT-code with RSD to network coding  Comparison with a random linear network coding schemes. ◦ Probabilistic NC [8]  Random linear network coding with a probabilistic approach 26 [4] P. Pakzad, C. Fragouli, and A. Shokrollahi, “Coding schemes for line networks,” CoRR, vol. abs/cs/ , [8] C. Fragouli, J. Widmer, and J.-Y. L. Boudec, “Efficient broadcasting using network coding,” IEEE/ACM Trans. Netw, vol. 16, no. 2, pp. 450–463, 2008.

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28 The deliver ratio is the number of delivered packets at the destination over the total number of the source packets.

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 Considered the broadcast traffic in ad-hoc wireless networks, We have presented a novel rateless code which outperforms LT code as it allows intermediate nodes to process the received packets.  The proposed distribution increases the decoding probability of any received symbol.  The simulation shows that our scheme reduces the number of transmissions and increases the packet delivery ratio. 30