Impact of Channel Estimation Errors and Power Allocation on Analog Network Coding and Routing in Two-Way Relaying

Abstract

In this paper, we study two important transmission strategies in full-duplex two-way relaying in the presence of channel estimation errors. In analog network coding (ANC), the relay transmits the combined signals that were received from both sources, with the aim of achieving better spectral efficiency. However, due to imperfect channel-state information (CSI), sources cannot perfectly cancel their own data in the relayed signal. We derive an achievable information rate for ANC in imperfect-CSI conditions and show how the ANC performance can significantly be degraded as a result. Moreover, we derive cut-set bounds with channel estimation errors for traditional routing (TR), in which time sharing is used at the relay. Although it has been previously shown that ANC outperforms TR when the CSI is perfect, we find that it may not maintain its superiority in imperfect-CSI case at low signal-to-noise ratio (SNR) conditions. Next, we propose practical power allocation techniques that can be used in the sources and relay for both ANC and TR. The proposed power allocation schemes are relatively simple to compute and rely only on long-term channel statistics. Nevertheless, they are shown to be effective and close to optimal solutions for a wide range of SNRs, to different positions of the relay, and for both perfect-and imperfect-CSI conditions. By using the proposed power allocation techniques, it is possible to bring back advantages of ANC over TR for a wide range of SNRs in imperfect-CSI conditions.

Impact of loop-back interference and channel estimation errors on full-duplex relay networks

“…Under this condition, it is not possible to determine the optimal number of pilots in a closed form and for this reason, we assume that only one pilot symbol is sent from each node and the pilot and data symbol powers are equal. Similar assumptions are supposed in [10]. In mathematical formulation, we utilize a, b, and r as subscripts to be mapped to the nodes A, B and R, respectively.…”

“…It is assumed that the receivers utilize the (LMMSE) for channel estimation and model each channel as h kj ¼ĥ kj þh kj whereĥ kj represents the channel estimate, andh kj is zero-mean estimation error with variance of r 2 h kj given in [10] bŷ…”

“…Since the noise and signal terms are uncorrelated, Z anc ðiÞ can be replaced by a worst-case Gaussian noise [10,25] with the same variance. Thus, the achievable rate for A-B transmission over a known channel estimates can be calculated by the following formulation R ab anc ðĥÞ ¼…”

“…Most previous works assume perfect cancellation of loop-back interference [9][10][11][12]. However, since loop-back interference cannot be completely mitigated in practice, this ideal assumption overestimated the benefits of FD relaying.…”

Energy efficiency optimization of one-way and two-way DF relaying considering circuit power

“…In [22,23], authors maximize the sum-rate of a network with minimum power consumption in a DF twoway relaying network. In [24], authors propose a practical power allocation technique in a two-way AF (TWAF) relaying network for a wide range of signal-to-noise ratio (SNR) conditions. However, the circuitry power is not considered in the PCM of the mentioned two-way relaying systems.…”