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Abstract

Nowadays, with the rapid development of wireless network, people’s demandfor data services becomes higher and higher than before. The larger amount of dataand the faster speed of data transmission put forward a higher request on thewireless communication technology. But wireless channel fading and coverageproblem still exist, which means in many cases, the data transmission may failwithout the help of relay coordination. In2000, R.Ahlswede first put forward theconcept of network coding, which means using a relay to deal with forward data bycoding processing, and then the efficiency of data exchange is improved effectively.In2006, Zhang and others from The Chinese University of Hong Kong, developedphysical layer network coding based on the network coding, in which the concept ofnetwork coding was applied to the physical layer and by the artful use ofsuperposition characteristic of wireless channel itself, they increased the throughputof the system.This paper first introduces the origin and development of network coding,including three kinds of traditional relay cooperating mode and discusses theirstrengths and weaknesses respectively. Then, detailed instructions on the model ofnetwork coding and common network transmission mode are shown. It can be seenthat, in the comparison of network transmission mode, the physical layer networkcoding has significant improvement to the traditional transmission mode and straightforward network, even a100%improvement to the traditional transmission mode.Because of the differences between wire and wireless environment in signaltransmission, physical layer network coding also differs in signal processing in adifferent environment. This paper makes the instructions for the differences betweenthe former and the latter, proposes scheme on physical layer network coding forwireless communications. Low density parity check code (LDPC), is a channelcoding which can approach the Shannon capacity limit, with the merits of lineartime complexity as decoding, long code performance even exceeds the Turbo code,which makes the research of low density check code have become the hotspot in thechannel coding and is more and more used in the real system.In this paper, a joint design of physical layer network coding and channelcoding will be proposed, by using channel coding error correction function as muchas possible to improve system performance. Because of the excellent performance ofthe LDPC code, it is chosen as the channel coding. Finally, putting forward jointdesign system model with low-order and high-order modulation respectively, andthen joint decoding scheme of mapping and decoding algorithm is deduced in detail. Under low modulation circumstance, the throughput of the system is significantlyenhanced and performance degradation remains at a very low level. Under the highmodulation circumstance, system further improves the channel capacity in the caseof guaranteed throughput. The simulation results show that joint desigen of physicallayer network coding and LDPC can effectively improve the efficiency of relaycoordination system in collaboration, throughput and performance of the channelcapacity compared with conventional relay scheme.

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CLC: > Industrial Technology > Radio electronics, telecommunications technology > Communicate > Communication theory > Information Theory > Channel coding theory
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Joint Design of Physical Layer Network Coding and LDPC

Abstract

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