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ComputeandForward TwoWay Relaying
 IET Commun
"... In this paper, a new twoway relaying scheme based on computeandforward (CMF) framework and relay selection strategies is proposed, which provides a higher throughput than the conventional twoway relaying schemes. Two cases of relays with or without feedback transmission capability are considered ..."
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In this paper, a new twoway relaying scheme based on computeandforward (CMF) framework and relay selection strategies is proposed, which provides a higher throughput than the conventional twoway relaying schemes. Two cases of relays with or without feedback transmission capability are considered. An upper bound on the computation rate of each relay is derived, and based on that, a lower bound on the outage probability of the system is presented assuming block Rayleigh fading channels. Numerical results show that while the average sum rate of the system without feedback, named as Max ComputeandForward (MCMF), reaches the derived upper bound only in low SNRs, that of the system with feedback, named as Aligned ComputeandForward (ACMF) reaches the bound in all SNRs. However, both schemes approach the derived lower bound on the outage probability in all SNRs. For the ACMF, another power assignment based on applying the constraint on the total powers of both users rather than on the power of each separately, is introduced. The result shows that the ACMF performs better under the new constraint. Moreover, the numerical results show that the outage performance, average sum rate, and symbol error rate of the proposed schemes are significantly better than those of twostep and threestep decodeandforward (DF) and amplifyandforward (AF) strategies for the examples considered. Index Terms compute and forward, max computeandforward, aligned computeandforward, feedback, twoway relaying, relay selection, outage probability, average sum rate, symbol error rate. I
IntegerForcing Linear Receiver Design over MIMO Channels
, 2012
"... Motivated by recently presented integerforcing linear receiver architecture, we propose algorithms to design optimal integerforcing coefficient matrix such that the total achievable rate is maximized. ..."
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Motivated by recently presented integerforcing linear receiver architecture, we propose algorithms to design optimal integerforcing coefficient matrix such that the total achievable rate is maximized.
Power Adaptive Network Coding for a NonOrthogonal MultipleAccess Relay Channel
"... Abstract—In this paper we propose a novel power adaptive network coding (PANC) for a nonorthogonal multipleaccess relay channel (MARC), where two sources transmit their information simultaneously to the destination with the help of a relay. In contrast to the conventional XORbased network coding ..."
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Abstract—In this paper we propose a novel power adaptive network coding (PANC) for a nonorthogonal multipleaccess relay channel (MARC), where two sources transmit their information simultaneously to the destination with the help of a relay. In contrast to the conventional XORbased network coding (CXNC), the relay in PANC generates network coded symbols by considering the coefficients of the sourcetorelay channels, and forwards each symbol with a preoptimized power level. Specifically, by defining a symbol pair as two symbols from the two sources, we first derive the expression of symbol pair error rate (SPER) for the system. Noting that deriving the exact SPER are complex due to the irregularity of the decision regions caused by random channel coefficients, we propose a coordinate transform (CT) method on the received constellation to simplify the derivations of the SPER. Next, we obtain the optimal power level by decomposing it as a multiplication of a power scaling factor and a power adaptation factor. We prove that with the power scaling factor at the relay, our PANC scheme can achieve a full diversity gain, i.e., an order of two diversity gain, while the CXNC can achieve only an order of one diversity gain. In addition, we optimize the power adaptation factor at the relay to minimize the SPER at the destination by considering of the relationship between SPER and minimum Euclidean distance of the received constellation, resulting in an improved coding gain. Simulation results show that (1) the SPER derived based on our CT method can well approximate the exact SPER with a much lower complexity; (2) the PANC scheme with power adaptation optimizations and power scaling factor design can achieve a full diversity, and obtain a much higher coding gain than other network coding schemes. Index Terms—Network coding, power optimization, multiple access relay channel, error probability. I.
Author manuscript, published in " " Practical Physical Layer Network Coding in MultiSources Relay Channels via the ComputeandForward
, 2013
"... Abstract—Recent years have witnessed the development of the ComputeandForward (CF) as a successful solution to perform noiseless linear Physical Layer Network Coding (PLNC). Research outcomes shed considerable light on the promising gain of this strategy from informationtheoretic perspective. Wha ..."
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Abstract—Recent years have witnessed the development of the ComputeandForward (CF) as a successful solution to perform noiseless linear Physical Layer Network Coding (PLNC). Research outcomes shed considerable light on the promising gain of this strategy from informationtheoretic perspective. What misses is to design practical PLNC schemes based on the ComputeandForward and to evaluate their endtoend performance in real communication scenarios. In this work we try to fill the gap between theory and practice: we investigate endtoend communication over a MultiSources Relay Channel where the CF is used at intermediate nodes. We figure out practical constraints that deserve special attention in real endtoend communication design and propose reliable solutions that enable to meet the promised potential of the CF. In order to confirm our theoretical analysis, we evaluate performance of the proposed schemes at the destination in terms of both average achievable rate and error rates under practical low complexity nested lattice encoding.
LowComplexity PHYLayer Network Coding for TwoWay ComputeandForward Relaying
"... Abstract—We present a novel lowcomplexity technique that obtains the PhysicalLayer Network Coding (PNC) equation coefficient vectors for the twoway relay channel when ComputeandForward is employed. The proposed method is based on precomputed lookup tables that are used for all channel realiza ..."
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Abstract—We present a novel lowcomplexity technique that obtains the PhysicalLayer Network Coding (PNC) equation coefficient vectors for the twoway relay channel when ComputeandForward is employed. The proposed method is based on precomputed lookup tables that are used for all channel realizations. It is shown that the size of the lookup tables can be made small by taking into account the statistics of the channel coefficients as well as power and performance specifications. Moreover, a lowcomplexity algorithm is developed for efficient realtime selection of the equation coefficient vectors using the instantaneous channel coefficients and the lookup tables. Although the method may at times exclude some candidate vectors from the search space, simulation results indicate that the effect on the achievable computation rate at the relay is very small. Hence, significant complexity reduction is achieved, while the computation rate remains extremely close to the optimal value. Index Terms—twoway relay channel, computeandforward, PHYlayer network coding I.