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Analog Network Coding in General SNR Regime: Performance of A Greedy Scheme
"... Abstract—The problem of maximum rate achievable with analog network coding for a unicast communication over a layered relay network with directed links is considered. A relay node performing analog network coding scales and forwards the signals received at its input. Recently this problem has been c ..."
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Abstract—The problem of maximum rate achievable with analog network coding for a unicast communication over a layered relay network with directed links is considered. A relay node performing analog network coding scales and forwards the signals received at its input. Recently this problem has been considered under certain assumptions on per node scaling factor and received SNR. Previously, we established a result that allows us to characterize the optimal performance of analog network coding in network scenarios beyond those that can be analyzed using the approaches based on such assumptions. The key contribution of this work is a scheme to greedily compute a lower bound to the optimal rate achievable with analog network coding in general layered networks. This scheme allows for exact computation of the optimal achievable rates in a wider class of layered networks than those that can be addressed using existing approaches. For the specific case of the Gaussian Nrelay diamond network, to the best of our knowledge, the proposed scheme provides the first exact characterization of the optimal rate achievable with analog network coding. For general layered networks, our scheme allows us to compute optimal rates within a “small ” gap from the cutset upper bound asymptotically in the source power. I.
Performance of Multihop Relaying System in Cognitive Radio Networks
"... This paper introduces multihop relay system where the benefits of spatial diversity are achieved from the concurrent reception of signals that have been transmitted by multiple terminals. Amplify and forward cooperative relays will be used in this system. It will be obvious that multihop system can ..."
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This paper introduces multihop relay system where the benefits of spatial diversity are achieved from the concurrent reception of signals that have been transmitted by multiple terminals. Amplify and forward cooperative relays will be used in this system. It will be obvious that multihop system can effectively mitigate the performance deterioration caused by fading, without imposing delay or bandwidth expansion. The channel models are compared through the simulations to prove that multihop system is better than single hop system where it gives low symbol error rate and therefore the performance will be improved. Maximum Ratio Combining will be used. Analysis of different hops system will be made. Different modulations will be applied. From simulation results it will be obvious that symbol error rate will be reduced when using multihop than single hop.
Analog Network Coding in Nonlinear Chains
"... The problem of characterizing the optimal rate achievable with analog network coding (ANC) for a unicast communication over general wireless relay networks is computationally hard. A relay node performing ANC scales and forwards its input signals. The sourcedestination channel in such communication ..."
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The problem of characterizing the optimal rate achievable with analog network coding (ANC) for a unicast communication over general wireless relay networks is computationally hard. A relay node performing ANC scales and forwards its input signals. The sourcedestination channel in such communication scenarios is, in general, an intersymbol interference (ISI) channel which leads to the singleletter characterization of the optimal rate in terms of an optimization problem with nonconvex, non closedform objective function and nonconvex constraints. For a special class of such networks, called layered networks, a few key results and insights are however available. To gain insights into the nature of the optimal solution and to construct lowcomplexity schemes to characterize the optimal rate for general wireless relay networks, we need (1) network topologies that are regular enough to be amenable for analysis, yet general enough to capture essential characteristics of general wireless relay networks, and (2) schemes to approximate the objective function in closedform without significantly compromising the performance. Towards these two goals, this work proposes (1) nonlinear chain networks, and (2) two approximation schemes. We show that their combination allows us to tightly characterize the optimal ANC rate with low computational complexity for a much larger class of general wireless relay networks than possible with existing schemes. I.
1Secure Transmission in Amplify and Forward Networks for Multiple Degraded Eavesdroppers
"... We have evaluated the optimal secrecy rate for AmplifyandForward (AF) relay networks with multiple eavesdroppers. Assuming i.i.d. Gaussian noise at the destination and the eavesdroppers, we have devised technique to calculate optimal scaling factor for relay nodes to obtain optimal secrecy rate u ..."
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We have evaluated the optimal secrecy rate for AmplifyandForward (AF) relay networks with multiple eavesdroppers. Assuming i.i.d. Gaussian noise at the destination and the eavesdroppers, we have devised technique to calculate optimal scaling factor for relay nodes to obtain optimal secrecy rate under both sum power constraint and individual power constraint. Initially, we have considered special channel conditions for both destination and eavesdroppers, which led us to analytical solution of the problem. Contrarily, the general scenario being a nonconvex optimization problem, not only lacks an analytical solution, but also is hard to solve. Therefore, we have proposed an efficiently solvable quadratic program (QP) which provides a suboptimal solution to the original problem. Then, we have devised an iterative scheme for calculating optimal scaling factor efficiently for both the sum power and individual power constraint scenario. Necessary figures are provided in result section to affirm the validity of our proposed solution. I.