Shankar Prakriya

Performance of Two-Way Opportunistic Relaying With Analog Network Coding Over Nakagami-

In this paper, we evaluate the performance of an outage-optimal two-way opportunistic relaying (TWOR) scheme with analog network coding (ANC) over independent but not necessarily identically distributed (i.ni.d.) Nakagami-m fading channels. Considering arbitrary integer-valued fading parameters over the two hops, we derive an exact outage expression that is applicable for the entire range of signal-to-noise ratio (SNR). For better insights, we provide simple closed-form expressions at high SNR for bounds on the outage probability and on the ergodic sum-rate of the scheme. We show that the achievable diversity order is equal to the minimum of the per-hop fading parameters times the number of relaying candidates. Numerical and simulation results are presented to illustrate the theoretical analysis and the effects of the various Nakagami fading conditions on the overall system performance.

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In this letter, we evaluate the outage performance of analog network coding (ANC) protocol for a two-way half-duplex relaying system with asymmetric traffic requirements at end terminals. We derive a simple and generalized expression for overall system outage probability in a Rayleigh flat-fading environment. We also deduce the optimal relay location and power allocation in order to minimize the overall system outage. Numerical and simulation results highlight the effect of optimal relay positioning and power allocation under various traffic requirements.

Fading

In this paper, we investigate the performance of an analog network coding (ANC)-based two-way relay system that employs beamforming at the multi-antenna sources. Specifically, we analyze the overall system performance by deriving an exact expression for the overall symbol error rate (OSER) and an upper bound expression for the ergodic sum-rate (ESR) over independent and non-identically distributed Nakagami- m fading channels. We also derive closed-form representations of these expressions in the asymptotic high signal-to-noise ratio (SNR) regime to provide useful insights into the system behavior, and the optimal power allocation and relay location. Moreover, we address the joint optimization problem of power allocation and relay location to minimize the OSER and to maximize the ESR. Our results highlight the influence of key system/channel parameters on the overall system performance.

Performance of Analog Network Coding with Asymmetric Traffic Requirements

We consider a two-way relay system where multi-antenna sources employ beamforming to communicate bidirectionally via a single-antenna relay with analog network coding over Nakagami-m fading channels. We address the problem of both separate and joint optimization of power allocation and relay location in order to minimize the overall system outage probability. Our results demonstrate that separate optimization of relay location is more significant than that of power allocation to improve the overall system outage performance. We further emphasize that the joint optimization of power allocation and relay location can provide noticeable outage performance improvement over unbalanced per-hop fading conditions and/or nonidentical antenna configurations.

Performance Evaluation and Optimization for Two-Way Relaying With Multi-antenna Sources

In this letter, we analyze the performance of a zero forcing (ZF) crosstalk canceler/precoder in vectored VDSL2. We show that there is gap between the theoretical capacity and the performance of the ZF canceler/precoder at higher frequencies and/or large number of vectored users. Unlike bounds developed to date, the tight rate approximations presented in this paper are valid over all frequency bands, even when the number of vectored users is large. Numerical results confirm the tightness of the derived approximations.

Joint power and location optimization for analog network coding with multi-antenna sources

This paper evaluates the performance of an opportunistic scheduling scheme for a multiuser two-way relay network, wherein an analog network coding (ANC)-based relay assists the communication between multiple pairs of users. To ensure fairness for each user pair, we consider a scheduler based on maximizing the normalized minimum of the instantaneous signal-to-noise ratios (SNRs) at each user of the pair. Under a high SNR assumption, we derive upper and lower bound expressions for the outage probability and the average sum-rate in a Rayleigh fading environment and establish that a multiuser diversity of order equal to the number of user pairs is harnessed by the scheme. Numerical and simulation results are presented to confirm the performance gain of the proposed scheme.

Performance Analysis of Zero Forcing Crosstalk Canceler in Vectored VDSL2

We propose the use of an iterative receiver based on the Space Alternating Generalized Expectation maximization (SAGE) algorithm for crosstalk cancellation in upstream vectored VDSL. In the absence of alien crosstalk, we show that when initialized with the frequency-domain equalizer (FEQ) output, the far-end crosstalk (FEXT) can be cancelled with no more real-time complexity than the existing linear receivers. In addition, the suggested approach does not require offline computation of the channel inverse and thus reduces the receiver complexity. In the presence of alien crosstalk, there is a significant gap between the rate performance of the linear receivers as compared with the single-user bound (SUB). The proposed receiver is shown to successfully bridge this gap while requiring only a little extracomplexity. Computer simulations are presented to validate the analysis and confirm the performance of the proposed receiver.

Performance bounds for analog network coding based two-way relaying with multiuser selection diversity

In this letter, we analyze the physical layer secrecy performance of a two-hop cooperative cognitive underlay relay network with a decode and forward relay and a passive eavesdropper. Unlike other works to date, we assume combining of direct and relayed signals at the destination and the eavesdropper. A closed-form expression is derived for secrecy outage probability. We show that ignoring the direct channel leads to pessimistic estimate of secrecy outage. Furthermore, we propose a power backoff method that is shown to improve secrecy outage performance. Computer simulation results demonstrate the accuracy of derived expressions.

Iterative receiver based on SAGE algorithm for crosstalk cancellation in upstream vectored VDSL

We consider a two-way relaying (TWR) system over Rayleigh fading channels. An accurate closed form expression for its outage performance is derived assuming a fixed-gain relay. Unlike previous works that consider interference only at the relay or at the terminals, we assume interference at all three terminals of the system. Computer simulations demonstrate that the derived expressions are accurate at low and medium SNRs.

Secrecy Outage Performance of a Cooperative Cognitive Relay Network

We consider an end-to-end antenna selection (E2E-AS) scheme for a multiple-input multiple-output (MIMO) two-way relaying system with amplify-and-forward (AF) based relay terminal between two source terminals, each having multiple antennas. The proposed E2E-AS strategy involves selecting a single best antenna at each terminal of the system. Under a Rayleigh flat-fading environment, we present exact and asymptotic expressions of the overall system outage probability. We show that with single-antenna selection at each terminal, the underlying strategy achieves the same diversity order as the scheme using all the available antennas. We also highlight the impact of relay location and power allocation on the overall system outage performance. Finally, we provide numerical and simulation results to confirm the theoretical analysis and the performance of the proposed scheme.