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11
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.
Integer ForcingandForward Transceiver Design for MIMO MultiPair TwoWay Relaying
, 2014
"... In this paper, we propose a new transmission scheme, named as Integer ForcingandForward (IFF), for communications among multipair multipleantenna users in which each pair exchanges their messages with the help of a single multi antennas relay in the multipleaccess and broadcast phases. The prop ..."
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In this paper, we propose a new transmission scheme, named as Integer ForcingandForward (IFF), for communications among multipair multipleantenna users in which each pair exchanges their messages with the help of a single multi antennas relay in the multipleaccess and broadcast phases. The proposed scheme utilizes computeandforward (CMF) strategy and Integer Forcing Linear Receiver (IFLR) at relay, which uses equations, i.e., linear integercombinations of messages, to harness the intrapair interference. Accordingly, we propose the design of mean squared error (MSE) based transceiver, including precoder and projection matrices for the relay and users, assuming that the perfect channel state information (CSI) is available. In this regards, in the multipleaccess phase, we introduce two new MSE criteria for the related precoding and filter designs, i.e., the sum of the equations ’ MSE (SumEquation MSE) and the maximum of the equations ’ MSE (MaxEquation MSE), to exploit the equations in the relay. Moreover, in the broadcast phase, we use the two traditional MSE criteria, i.e. the sum of the users ’ mean squred errors (Sum MSE) and the maximum of the users ’ mean squared errors (Max MSE), to design the related precoding and filters for recovering relay’s equations in the users. Then, we consider a more practical scenario with imperfect CSI. For this case, IFLR receiver is modified, and another transceiver design is proposed, which take into account the effect of channels estimation error. We evaluate the performance of our proposed strategy and compare the results with the conventional amplifyandforward (AF) and decodeandforward (DF) strategies for the same scenario. The results
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.
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.
Cloud ComputeandForward With Relay Cooperation
, 2015
"... We study a cloud network with M distributed receiving antennas and L users, which transmit their messages towards a centralized decoder (CD), whereM ≥ L. We consider that the cloud network applies the ComputeandForward (C&F) protocol, where L antennas/relays are selected to decode integer equ ..."
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We study a cloud network with M distributed receiving antennas and L users, which transmit their messages towards a centralized decoder (CD), whereM ≥ L. We consider that the cloud network applies the ComputeandForward (C&F) protocol, where L antennas/relays are selected to decode integer equations of the transmitted messages. In this work, we focus on the best relay selection and the optimization of the PhysicalLayer Network Coding (PNC) at the relays, aiming at the throughput maximization of the network. Existing literature optimizes PNC with respect to the maximization of the minimum rate among users. The proposed strategy maximizes the sum rate of the users allowing nonsymmetric rates, while the optimal solution is explored with the aid of the Pareto frontier. The problem of relay selection is matched to a coalition formation game, where the relays and the CD cooperate to maximize their profit. Efficient
ComputeandForward with Relay Selection: A Cooperative Game
, 2014
"... Motivated by the cooperative game theory, we propose an efficient physical layer network coding technique for computeandforward (C&F) relaying systems, which jointly optimizes the sum and the minimum transmission rate, while minimizing the total transmitting power. Specifically, we show that ..."
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Motivated by the cooperative game theory, we propose an efficient physical layer network coding technique for computeandforward (C&F) relaying systems, which jointly optimizes the sum and the minimum transmission rate, while minimizing the total transmitting power. Specifically, we show that relay selection in C&F networks leads to an increase of both rates. We also propose an algorithmic approach for the rates’ further optimization and we illustrate that its implementation can offer the same or even greater gain than adding an extra relay. Furthermore, the tradeoff between the minimum and the sum rate is explained by utilizing the concept of Pareto frontier. Simulations and numerical results show that a combination of relay selection and the proposed algorithms offers a considerable increase in the sum rate for the same transmitting power, without reducing the system’s Quality of Service.
1ComputeandForward on a MultiUser MultiRelay Channel
"... In this paper, we consider a system in which multiple users communicate with a destination with the help of multiple halfduplex relays. Based on the computeandforward scheme, each relay, instead of decoding the users ’ messages, decodes an integervalued linear combination that relates the transm ..."
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In this paper, we consider a system in which multiple users communicate with a destination with the help of multiple halfduplex relays. Based on the computeandforward scheme, each relay, instead of decoding the users ’ messages, decodes an integervalued linear combination that relates the transmitted messages. Then, it forwards the linear combination towards the destination. Given these linear combinations, the destination may or may not recover the transmitted messages since the linear combinations are not always full rank. Therefore, we propose an algorithm where we optimize the precoding factor at the users such that the probability that the equations are full rank is increased and that the transmission rate is maximized. We show, through some numerical examples, the effectiveness of our algorithm and the advantage of performing precoding allocation at the users. Also, we show that this scheme can outperform standard relaying techniques in certain regimes.
Distributed ComputeandForward Based Relaying Strategies in MultiUser MultiRelay Networks
, 2014
"... The computeandforward (CMF) relaying technique, proposed by Nazer et al., provides a substantially higher network coding throughput in multiuser cooperative networks, compared to the other conventional relaying techniques. The improvement is due to exploiting the multiuser interference rather than ..."
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The computeandforward (CMF) relaying technique, proposed by Nazer et al., provides a substantially higher network coding throughput in multiuser cooperative networks, compared to the other conventional relaying techniques. The improvement is due to exploiting the multiuser interference rather than avoiding it. However, a major drawback of this strategy is that the equations decoded by different relays are not necessarily linearly independent, and hence a rank failure may occur at the destination; which results in a substantial reduction of the system rate as well as the diversity order. In this paper, we propose three practical distributed schemes to deal with the problem in a multiuser multirelay network without central coordinator, in which the relays have not any prior information about each other. In first scheme, a new relaying strategy based on CMF, named incremental computeandforward (ICMF), is proposed that requires cooperation among relays. Second, a novel simple strategy, called amplifyforward and compute (AFC), is introduced in which the equations are recovered in the destination rather than in the relays. Finally, the two schemes ICMF and AFC strategies are combined to present hybrid computeamplify and forward (HCAF) relaying scheme, which improves the performance of the ICMF considerably. We evaluate the performance of our proposed strategies and compare the results with those of the conventional CMF strategy and also the well known Decode and Forward (DF) strategy. The results indicate the substantial superiority of the proposed schemes, specially at the higher number of users and also relays.