Near outage limit joint network coding and decoding for the Semi-Orthogonal Multiple-Access Relay Channel

In this paper, we investigate the benefit of Joint Network Channel Coding (JNCC) for a new class of Multiple Access Relay Channel (MARC), defined as follows: (1) Independent sources communicate with a single destination in the presence of a relay; (2) The relay is half-duplex and applies a Selective Decode and Forward (SDF) strategy, i.e, it forwards only a deterministic function of the error-free decoded messages; (3) The sources are allowed to transmit simultaneously during both the listening phase and the transmission phase of the relay. We refer this model to as Non-Orthogonal MARC (NOMARC), which better leverages the broadcast nature of the radio channel than its more conservative orthogonal counterpart, i.e., Orthogonal MARC (OMARC). This paper aims at measuring the advantage brought by NOMARC/JNCC over OMARC/JNCC from both an information-theoretic and a practical code design perspectives.

We propose to use joint network-channel coding based on turbo codes for the multiple-access relay channel. Such a system can be used for the cooperative uplink for two mobile stations to a base station with the help of a relay. We compare the proposed system with a distributed turbo code for the relay channel and with a system which uses separate network-channel coding for the multiple-access relay channel. Simulation results confirm that the systems with network coding for the multiple-access relay channel gain cooperative diversity compared to the system with the distributed turbo code for the relay channel. Moreover, the results show that joint network-channel coding outperforms separate network-channel coding. The reason for this is that the redundancy which is contained in the transmission of the relay can be exploited more efficiently with joint network-channel coding

In this paper, we study state‐dependent multiple‐access relay channel (MARC). (i) Inner and outer bounds are derived for two‐user state‐dependent discrete memoryless MARC in which channel state information is known non‐causally at the relay (informed relay). The inner bound is obtained by using decode and forward strategy and a combination of binning scheme and codeword splitting. Also, by applying Fano's inequality, we obtain an outer bound for state‐dependent MARC with channel state at the relay. (ii) Furthermore, we extend the results of discrete alphabet to Gaussian case as a discrete time and continuous alphabet model. Our general Gaussian results subsume previous special ones and specifically gives a general version for the Costa's theorem. (iii) We show numerically that the achievable rate region of Gaussian MARC with cognition of the relay about interference is larger than the achievable rate region of Gaussian MARC without any knowledge about interference. Also, by numerical examples, we investigate the capacity‐achieving case in high signal to noise ratios at the relay. Copyright © 2014 John Wiley & Sons, Ltd.

This paper proposes a novel joint network- channel coding (JNCC) system based on improved distributed turbo coded (DTC) scheme for multiple-access relay channel, using decode-and-forward protocol. The diversity of improved DTC scheme is that the two parity streams of the two RSC encoders of UE are converted into one stream by puncturing. In addition, we adopt the punctured parity streams of Convolutional Turbo Code (CTC) at the relay and BS, which takes advantage of the feature of two inputs for the decoded information bits from two mobile stations. Here, CTC acts as a network coding as well as channel coding between relay and BS. The performance of this communication system depends on the twice decoding at the BS according to the side information and CTC punctured parity information. The simulation results show that performance of proposed scheme overperforms the reference network-coding scheme which separates channel decoding from network coding, and has 0.8dB improvement at a bit error rate (BER) of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> in AWGN channel than the reference scheme.

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We consider a general multiple-antenna network with multiple sources, multiple destinations, and multiple relays in terms of the diversity–multiplexing tradeoff (DMT). We examine several subcases of this most general problem taking into account the processing capability of the relays (half-duplex or full-duplex), and the network geometry (clustered or nonclustered). We first study the multiple-antenna relay channel with a full-duplex relay to understand the effect of increased degrees of freedom in the direct link. We find DMT upper bounds and investigate the achievable performance of decode-and-forward (DF), and compress-and-forward (CF) protocols. Our results suggest that while DF is DMT optimal when all terminals have one antenna each, it may not maintain its good performance when the degrees of freedom in the direct link are increased, whereas CF continues to perform optimally. We also study the multiple-antenna relay channel with a half-duplex relay. We show that the half-duplex DMT behavior can significantly be different from the full-duplex case. We find that CF is DMT optimal for half-duplex relaying as well, and is the first protocol known to achieve the half-duplex relay DMT. We next study the multiple-access relay channel (MARC) DMT. Finally, we investigate a system with a single source–destination pair and multiple relays, each node with a single antenna, and show that even under the ideal assumption of full-duplex relays and a clustered network, this virtual multiple-input multiple-output (MIMO) system can never fully mimic a real MIMO DMT. For cooperative systems with multiple sources and multiple destinations the same limitation remains in effect. </para>

This paper presents the outage probability analysis of Joint Channel and Network Coding (JCNC) scheme in Multiple Access Relay Channel (MARC). In particular, the effect of using different interleaver patterns at different users is analysed. The motivation of this work is to show that despite its capability of achieving up to 2 dB gain in Packet Error Rate (PER), the corresponding outage probability improvement is only minimal (upper bounded at approximately 0.6 dB). This signifies that the improvement achieved by using different interleaver patterns is largely attributed by the ability of iteratively decodable codes to perform closer to the capacity limit compared to the conventional convolutional code with Soft Input Soft Output (SISO) decoder.

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This paper considers relay assisted transmission for multiuser networks when the relay has no access to the codebooks used by the transmitters. The relay is called oblivious for this reason. Of particular interest is the generalized compress-and-forward (GCF) strategy, where the destinations jointly decode the compression indices and the transmitted messages, and their optimality in this setting. The relay-to-destination links are assumed to be out-of-band with finite capacity. Two models are investigated: 1) the multiple access relay channel (MARC) and 2) the interference relay channel (IFRC). For the MARC with an oblivious relay, a new outerbound is derived and it is shown to be tight by means of achievability of the capacity region using GCF scheme. For the IFRC with an oblivious relay, a new strong interference condition is established, under which the capacity region is found by deriving a new outerbound and showing that it is achievable using GCF scheme. The result is further extended to establish the capacity region of M-user MARC with an oblivious relay, and multicast networks containing M sources and K destinations with an oblivious relay.

This paper aims at studying user association for uplink (UL) transmission in cooperative heterogeneous cellular networks, where small cell sum rate is limited by the backhaul (BH) capacity. The investigated architecture can be modeled as a multiple-access relay channel (MARC) channel where multiple users communicate with a final destination (the macro base station) with the help of a relay (the small cell base station). A network-coding-based MARC, which exploits both the direct and relayed transmissions, is introduced to deal with low-capacity BH. We assess the UL average system capacity for 1) the baseline association based on the strongest reference signal received power (RSRP) in downlink (DL) and 2) the optimized user association chosen to improve the overall network UL sum-rate. Our results show that the network-coding-based MARC scheme achieves significant gains with respect to the pure relaying strategy. We further show that the optimized user association provides significant gains in network UL sum-rate with respect to the RSRP association, for the same sum power constraint and without degrading DL performance, especially when the BH capacity is sufficiently large.

Low-density lattice codes (LDLCs) are known for their high decoding efficiency and near-capacity performance on point-to-point Gaussian channels. In this paper, we present a distributed LDLC-based cooperative relaying scheme for the multiple-access relay channel (MARC). The relay node decodes LDLC coded packets from two sources and forwards a network-coded combination to the destination. At the destination, a joint iterative decoding structure is designed to exploit the diversity gain as well as coding gain. For the LDLC-based network coding operation at the relay, we consider two alternative methods which offer a tradeoff between implementation complexity and performance, called superposition LDLC (S-LDLC) and modulo-addition LDLC (MA-LDLC). Simulation results show that the proposed scheme can provide more diversity gain and up to 6.2 dB coding gain when compared with non-cooperative LDLC coding and uncoded network-coded transmission.

Low-density lattice codes (LDLCs) are known for their high decoding efficiency and near-capacity performance on point-to-point Gaussian channels. In this paper, we present a distributed LDLC-based cooperative relaying scheme for the multiple-access relay channel (MARC). The relay node decodes LDLC-coded packets from two sources and forwards a network-coded combination to the destination. At the destination, a joint iterative decoding structure is designed to exploit the diversity gain as well as coding gain. For the LDLC-based network coding operation at the relay, we consider two alternative methods which offer a tradeoff between implementation complexity and performance, called superposition LDLC (S-LDLC) and modulo-addition LDLC (MA-LDLC). Soft symbol relaying is considered as an alternative to hard decision relaying which is capable of reducing the effect of error propagation at the relay. Simulation results show that the proposed scheme can provide greater diversity gain and up to 6.2 dB coding gain when compared with noncooperative LDLC coding and uncoded network-coded transmission. The proposed scheme also achieves 2.5 dB gain over network-turbo-coded cooperation, for the same code rate and overall transmitted power. Also, soft symbol relaying is shown to provide approximately 2 dB gain over hard decision relaying when the source-relay link suffers from deep fading.

[Abstract]: We consider the zero-delay encoding of discrete-time analog information over the Multiple Access Relay Channel (MARC) using non-linear mapping functions. On the one hand, zero-delay non-linear mappings are capable to deal with the multiple access interference (MAI) caused by the simultaneous transmission of the information. On the other, the relaying operation is a Decode-and-Forward (DF) strategy where the decoded messages are merged into a single message using a specific continuous mapping depending on the correlation level of the source information. At the receiver, an approximated Minimum Mean Squared Error (MMSE) decoder is developed to obtain an estimate of the transmitted source symbols which exploits the information received from the relay node in combination with the messages received from the transmitters through the direct links. The resulting system provides better performance than the other alternative encoding strategies for the MARC with similar complexity and delay and also approaches the performance of theoretical strategies which require a significantly higher delay and computational cost.

In this paper, we introduce a generalization of the Multiple-Access-Relay-Channel (MARC) called Multiple-Access-Relay-Network (MARN). In the proposed network, there are many transmitters, many relays and one receiver. The MARC model was first introduced by Kramer and consists of many transmitters, one receiver and only one relay.We also define semi-deterministic MARN, in which the output of the link between each transmitter and each relay is a deterministic function of the transmitter's input. We first obtain an achievable rate region for MARN by considering Partial Decode-and-Forward (PDF) strategy at the relays. Then we show that in semi-deterministic MARN, the proposed achievable rate region yields the capacity region.We also prove that the region obtained using PDF strategy subsumes the region obtained by Kramer for MARC. In our coding scheme, each transmitter's message is partitioned into different parts. These parts are sent to all relays and also to the receiver. Each relay uses Partial Decode-and-Forward (PDF) strategy to decode its own share of each transmitter's message. It then forwards a copy of all decoded sequences to the receiver. In the proof, we take advantage of regular encoding/backward decoding strategy at the receiver, and also the proof of Mutiple-Access-Channel (MAC)'s capacity region is utilized to analyze the probability of error at relays and the receiver.

Focusing on densely deployed wireless sensor networks, this paper presents a novel method for joint source-channel-network coding of distributed correlated sources through multiple access relay channels. In such networks, the role of intermediate sensors as relay nodes permits to achieve enhanced end-to-end error performance and increased spatial diversity in presence of channel fading. This paper addresses this scenario for a two source, single relay architecture by proposing a novel coding approach based on concatenated Zigzag codes, whose low complexity is specially suitable for energy-constrained autonomous systems. Joint decoding and estimation of the parameters defining the correlation between sensors is iteratively performed at the receiver side. Simulation results show that the proposed joint coding scheme attains significant energy gains with respect to traditional routing techniques, specially at high signal to noise ratios.

Two energy and computationally efficient strategies are proposed for Multiple Access Relay Channel (MARC), where all links are suffering from block fading. By exploiting the error probabilities of the intra links, defined as the links between sources and relay, relay can still utilize the received frames, even though they may contain errors, and forward them rather than discard them. This makes efficient utilization of the information of those erroneous frames and thereby reduces the frame error rate (FER). Moreover, by applying differential encoding at sources following the recursive convolutional encoding, differential detection can be used at relay for recovering the received signals from the sources; with the use of differential detection, signals can be recovered without requiring heavy computational burden for channel estimation, and hence, as a whole the necessity of the use of very powerful limit-achieving codes can also be avoided. This leads to energy efficient relay strategies.