Multi-user lattice coding for the multiple-access relay channel (original) (raw)

On the design of a novel joint network-channel coding scheme for the multiple access relay channel

IEEE Journal on Selected Areas in Communications, 2013

This paper proposes a novel joint non-binary network-channel code for the Time-Division Decode-and-Forward Multiple Access Relay Channel (TD-DF-MARC), where the relay linearly combines-over a non-binary finite field-the coded sequences from the source nodes. A method based on an EXIT chart analysis is derived for selecting the best coefficients of the linear combination. Moreover, it is shown that for different setups of the system, different coefficients should be chosen in order to improve the performance. This conclusion contrasts with previous works where a random selection was considered. Monte Carlo simulations show that the proposed scheme outperforms, in terms of its gap to the outage probabilities, the previously published joint networkchannel coding approaches. Besides, this gain is achieved by using very short-length codewords, which makes the scheme particularly attractive for low-latency applications.

Network coding for the Multiple Access Relay channel using lattices

2010 3rd International Symposium on Applied Sciences in Biomedical and Communication Technologies (ISABEL 2010), 2010

We 1 consider the problem of two transmitters would like to communicate with a destination with the help of a halfduplex relay. In this work, we are presenting the advantages of using nested lattices for the AWGN channels. The sources map their messages using lattice code and then broadcast them to the relay and the destination. The relay receives two independent symbols at the same channel. The relay either combines the two symbols using lattice modulo and then decode or decode the two symbols separately also using modulo lattice, then forwards the new symbol to the destination. The destination tries to recover the two messages using different decoding strategies. One of the strategies is to recover two linear equations in function of the two received symbols with integer coefficients then, solve these equations to recover the two messages. The integer coefficients need to be optimally selected to reduce the noise at the receivers. The other strategy is to use successive decoding at the relay and the destination. This strategy outperforms the first when two integer coefficients are zero. The strategies are discussed and compared with the traditional DF (Decode and Forward). The simulation results show the advantages of using lattice codes and the improvement in rates for certain regimes.

Cooperative lattice coding and decoding in half-duplex channels

IEEE Journal on Selected Areas in Communications, 2007

We propose novel lattice coding/decoding schemes for half-duplex outage-limited cooperative channels. These schemes are inspired by the cooperation protocols of Azarian et al. and enjoy an excellent performance-complexity tradeoff. More specifically, for the relay channel, we first use our lattice coding framework to generalize Yang and Belfiore implementation of the non-orthogonal amplify and forward cooperation protocol. This generalization is shown to offer significant performance gains while keeping the decoding complexity manageable. We then devise a novel variant of the dynamic decode and forward protocol, along with a lattice-coded implementation, which enjoys a near-optimal diversity-multiplexing tradeoff with a low encoding/decoding complexity. Finally, for the cooperative multiple-access channel, we present a lattice-coded implementation of the non-orthogonal amplify and forward protocol and demonstrate its excellent performance-complexity tradeoff. Throughout the paper, we establish the performance gains of our proposed protocols via a comprehensive simulation study.

Coding Schemes for the Two-Way Relay Channels

In modern transmission networks, relay plays an important role for cooperative strategies. Several relaying strategies, such as decode-forward, compress-forward and amplify-forward, have been proposed for relay channels and networks. However, the capacity for the general relay channel and network is still unknown. In this thesis, we propose several relay schemes for different relay models.

Multiple-access relaying with network coding: iterative network/channel decoding with imperfect CSI

EURASIP Journal on Advances in Signal Processing, 2013

In this paper, we study the performance of the four-node multiple-access relay channel with binary Network Coding (NC) in various Rayleigh fading scenarios. In particular, two relay protocols, decode-and-forward (DF) and demodulate-and-forward (DMF) are considered. In the first case, channel decoding is performed at the relay before NC and forwarding. In the second case, only demodulation is performed at the relay. The contributions of the paper are as follows: (1) two joint network/channel decoding (JNCD) algorithms, which take into account possible decoding error at the relay, are developed in both DF and DMF relay protocols; (2) both perfect channel state information (CSI) and imperfect CSI at receivers are studied. In addition, we propose a practical method to forward the relays error characterization to the destination (quantization of the BER). This results in a fully practical scheme. (3) We show by simulation that the number of pilot symbols only affects the coding gain but not the diversity order, and that quantization accuracy affects both coding gain and diversity order. Moreover, when compared with the recent results using DMF protocol, our proposed DF protocol algorithm shows an improvement of 4 dB in fully interleaved Rayleigh fading channels and 0.7 dB in block Rayleigh fading channels.

Compute-and-Forward on a Multiaccess Relay Channel: Coding and Sum-Rate Optimization

2012

We consider a system in which two users communicate with a destination with the help of a halfduplex relay. Based on the compute-and-forward scheme, we develop and evaluate the performance of coding strategies that are of network coding spirit. In this framework, instead of decoding the users' information messages, the destination decodes two integer-valued linear combinations that relate the transmitted codewords. Two decoding schemes are considered. In the first one, the relay computes one of the linear combinations and then forwards it to the destination. The destination computes the other linear combination based on the direct transmissions. In the second one, accounting for the side information available at the destination through the direct links, the relay compresses what it gets using Wyner-Ziv compression and conveys it to the destination. The destination then computes the two linear combinations, locally. For both coding schemes, we discuss the design criteria, and derive the allowed symmetric-rate. Next, we address the power allocation and the selection of the integer-valued coefficients to maximize the offered symmetric-rate; an iterative coordinate descent method is proposed.

Compute-and-forward on a multiaccess relay channel: Coding and symmetric-rate optimization

Network coding with diversity and outdated channel state information

Journal of Modern Transportation, 2012

Physical-layer network coding (PNC) has the potential to significantly improve the throughput of wireless networks where the channels can be modeled as additive white Gaussian noise (AWGN) channel. As extending to multiple channels, this technique requires both amplitude and phase compensation at each transmitter and will lead to inefficient systems yielding no diversity even with perfect channel state information (CSI). In order to avoid these limitations, we apply network coding with diversity (NCD) to achieve a form of selection diversity and extend NCD to cooperative multiple access channels in this paper. However, in practical wireless communication systems, the CSI could become outdated due to the difference between the CSI used in the relay selection and data transmission phases. Hence, the selected relay may not be the best one during data transmission phase due to the dynamic change in the wireless channels. Therefore, we first explore the relation between the present and past CSIs. Exploiting this relationship, the NCD scheme with outdated CSI is investigated based on the past CSI. To evaluate the performance of this scheme, an information-theoretic metric, namely the outage capacity, is studied under this condition.

Coding and Decoding for the Dynamic Decode and Forward Relay Protocol

We study the Dynamic Decode and Forward (DDF) protocol for a single half-duplex relay, singleantenna channel with quasi-static fading. The DDF protocol is well-known and has been analyzed in terms of the Diversity-Multiplexing Tradeoff (DMT) in the infinite block length limit. We characterize the finite block length DMT and give new explicit code constructions. The finite block length analysis illuminates a few key aspects that have been neglected in the previous literature: 1) we show that one dominating cause of degradation with respect to the infinite block length regime is the event of decoding error at the relay; 2) we explicitly take into account the fact that the destination does not generally know a priori the relay decision time at which the relay switches from listening to transmit mode. Both the above problems can be tackled by a careful design of the decoding algorithm. In particular, we introduce a decision rejection criterion at the relay based on Forney's decision rule (a variant of the Neyman-Pearson rule), such that the relay triggers transmission only when its decision is reliable. Also, we show that a receiver based on the Generalized Likelihood Ratio Test rule that jointly decodes the relay decision time and the information message achieves the optimal DMT. Our results show that no cyclic redundancy check (CRC) for error detection or additional protocol overhead to communicate the decision time are needed for DDF. Finally, we investigate the use of minimum mean squared error generalized decision feedback equalizer (MMSE-GDFE) lattice decoding at both the relay and the destination, and show that it provides near optimal performance at moderate complexity.

Decode-forward and compute-forward coding schemes for the two-way relay channel

2011 IEEE Information Theory Workshop, 2011

We consider the full-duplex two-way relay channel with direct link between two users and propose two coding schemes: a partial decode-forward scheme, and a combined decode-forward and compute-forward scheme. Both schemes use rate-splitting and superposition coding at each user and generate codewords for each node independently. When applied to the Gaussian channel, partial decode-forward can strictly increase the rate region over decode-forward, which is opposite to the one-way relay channel. The combined scheme uses superposition coding of both Gaussian and lattice codes to allow the relay to decode the Gaussian parts and compute the lattice parts. This scheme can also achieve new rates and outperform both decode-forward and compute-forward separately. These schemes are steps towards understanding the optimal coding.

Multi-user lattice coding for the multiple-access relay channel (original) (raw)

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