This paper develops efficient Compute-and-forward (CMF) schemes in multi-user multi-relay networks. To solve the rank failure problem in CMF setups and to achieve full diversity of the network, we introduce two novel CMF methods, namely, extended CMF and successive CMF. The former, having low complexity, is based on recovering multiple equations at relays. The latter utilizes successive interference cancellation (SIC) to enhance the system performance compared to the state-of-the-art schemes. Both methods can be utilized in a network with different number of users, relays, and relay antennas, with negligible feedback channels or signaling overhead. We derive new concise formulations and explicit framework for the successive CMF method as well as an approach to reduce its computational complexity. Our theoretical analysis and computer simulations demonstrate the superior performance of our proposed CMF methods over the conventional schemes. Furthermore, based on our simulation results, the successive CMF method yields additional signal-to-noise ratio gains and shows considerable robustness against channel estimation error, compared to the extended CMF method.
In the relay based telecommunications with $K$ relays between the source and destination, $K+1$ time or frequency slots are required for a single frame transmission. However, without the relays, only one time or frequency slot is used for a single frame transmission. Therefore, despite the benefits of relaying systems, this type of communications is not efficient from the spectral efficiency viewpoint. One solution to reduce this issue might be the full-duplex (FD) relays. An old technique which is reconsidered recently to improve the spectral efficiency of telecommunication systems. However, …
Cooperative Strategies for the Half-Duplex Gaussian Parallel Relay Channel: Simultaneous Relaying versus Successive Relaying
研究了在加性高斯白噪声环境下,两个半双工并联继电器组成的网络的通信问题。两个协议,即,提出了与两种可能的中继排序相关联的\emph{Simultaneous}和\emph{Successive}中继。同时中继协议基于\emph{Dynamic Decode and Forward (DDF)}方案。对于连续中继协议:(i)考虑基于\emph{Dirty Paper Coding (DPC)}的\emph{Non-Cooperative}方案,以及(ii)考虑基于\emph{Block Markov Encoding (BME)}的\emph{Cooperative}方案。此外,与\emph{Cooperative}方案相比,在一个中继器处采用BME而在另一个中继器处采用DPC的复合方案总是实现更好的速率。还提出了一种\emph{"Simultaneous-Successive Relaying based on Dirty paper coding scheme" (SSRD)}。中继的最佳顺序,从而在低和高的信号噪声比(SNR)的情况下,半双工高斯并行中继信道的容量推导。在低信噪比的情况下,它揭示了在一定的条件下的信道系数,基于DDF的同时中继的可达速率的割集界的比值趋于1。另一方面,当信噪比趋于无穷大时,证明了基于DPC的连续中继渐近地达到网络的容量。
The key advantage of successive relaying (SR) networks is their ability to mimic the full-duplex (FD) operation with half-duplex (HD) relays. However, the main challenge that comes with such schemes is the associated inter-relay interference (IRI). In this work, we propose a reconfigurable intelligent surface (RIS)-enhanced SR network, where one RIS is deployed near each of the two relay nodes to provide spatial suppression of IRI, and to maximize the gain of desired signals. The resultant max-min optimization problem with joint phase-shift design for both RISs is first tackled via the semidef…
We study a cooperative network with a buffer-aided multi-antenna source, multiple half-duplex (HD) buffer-aided relays and a single destination. Such a setup could represent a cellular downlink scenario, in which the source can be a more powerful wireless device with a buffer and multiple antennas, while a set of intermediate less powerful devices are used as relays to reach the destination. The main target is to recover the multiplexing loss of the network by having the source and a relay to simultaneously transmit their information to another relay and the destination, respectively. Successi…
Successive relaying can improve the transmission rate by allowing the source and relays to transmit messages simultaneously, but it may cause severe inter-relay interference (IRI). IRI cancellation schemes have been proposed to mitigate IRI. However, interference cancellation methods have a high risk of error propagation, resulting in a severe transmission rate loss in finite blocklength regimes. Thus, jointly decoding for successive relaying with finite-blocklength coding (FBC) remains a challenge. In this paper, we present an optimized channel-aware ordered successive relaying protocol with …
Signal Space Alignment for an Encryption Message and Successive Network Code Decoding on the MIMO K-way Relay Channel
本文研究了多输入多输出(MIMO)高斯无线网络的$K$ -用户和一个中间中继$M$天线的网络信息流问题。在该网络中,每个用户打算向所有其他用户传送多播消息,同时经由中间中继从其他用户接收$K-1$独立消息。该网络信息流被称为MIMO高斯$K$路中继信道。对于这个通道,我们表明,$\frac{K}{2}$自由度是可以实现的,如果$M=K-1$。为了证明这一点,我们提出了一个编码和解码策略的灵感来自密码学理论。所提出的编码和解码策略涉及用于多址接入阶段(MAC)的\textit{signal space alignment for an encryption message}和用于广播(BC)阶段的\textit{zero forcing with successive network code decoding}。\emph{signal space alignment for an encryption message}的思想是所有用户合作地选择预编码向量来发送消息,使得中继器可以接收具有特殊结构\textit{network code chain structure}的适当加密消息。在BC阶段期间,\emph{zero forcing combined with successive network code decoding}使所有用户能够解密来自中继的加密消息,尽管事实上他们…
A Buffer-aided Successive Opportunistic Relay Selection Scheme with Power Adaptation and Inter-Relay Interference Cancellation for Cooperative Diversity Systems
In this paper, we adopt the relay selection (RS) protocol proposed by Bletsas, Khisti, Reed and Lippman (2006) with Enhanced Dynamic Decode-and-Forward (EDDF) and network coding (NC) system in a two-hop two-way multi-relay network. All nodes are single-input single-output (SISO) and half-duplex, i.e., they cannot transmit and receive data simultaneously. The outage probability is analyzed and we show comparisons of outage probability with various scenarios under Rayleigh fading channel. Our results show that the relay selection with EDDF and network coding (RS-EDDF&NC) scheme has the best perf…
A new coding scheme for general N-node relay networks is presented for unicast, multicast, and broadcast. The proposed distributed decode-forward scheme combines and generalizes Marton coding for single-hop broadcast channels and the Cover-El Gamal partial decode-forward coding scheme for 3-node relay channels. The key idea of the scheme is to precode all the codewords of the entire network at the source by multicoding over multiple blocks. This encoding step allows these codewords to carry partial information of the messages implicitly without complicated rate splitting and routing. This part…
This paper investigates a wireless-powered cooperative communication network consisting of a source, a destination and a multi-antenna decode-and-forward relay. We consider the relay as a wireless-powered node that has no external power supply; but it is equipped with an energy harvesting (EH) unit and a rechargeable battery such that it can harvest and accumulate energy from radio-frequency signals broadcast by the source. By fully incorporating the EH feature of the relay, we develop an opportunistic relaying protocol, termed accumulate-then-forward (ATF), for the considered WPCCN. We then a…
The "weak" relay-eavesdropper channel was first studied by Lai and El Gamal, whose achievable scheme introduced noise forwarding (NF) and used backward decoding. We suggest a novel sliding window decoding scheme with a two block decoding delay, where the relay uses compress-forward with Wyner-Ziv (WZ) binning but does not use NF. Wireless engineers will welcome the reduced decoding delay. Sliding window decoding mandates multiblock equivocation calculations; dispensing with NF enables it. We identify nine regimes and develop a case-by-case choice of relay channel codebook and WZ bin sizes to m…
In this paper, we consider a full-duplex (FD) amplify-and-forward (AF) relay system and optimize its power allocation and relay location to minimize the system symbol error rate (SER). We first derive the asymptotic expressions of the outage probability and SER performance by taking into account the residual self interference (RSI) in FD systems. We then formulate the optimization problem based on the minimal SER criterion. Analytical and numerical results show that optimized relay location and power allocation can greatly improve system SER performance, and the performance floor caused by the…
In this letter, signal-to-noise ratio (SNR) performance is analyzed for orthogonal frequency division multiplexing (OFDM) based amplify-and-forward (AF) relay systems in the presence of carrier frequency offset (CFO) for fading channels. The SNR expression is derived under one-relay-node scenario, and is further extended to multiple-relay-node scenario. Analytical results show that the SNR is quite sensitive to CFO and the sensitivity of the SNR to CFO is mainly determined by the power of the corresponding link channel and gain factor.
Spectrum Sharing-based Multi-hop Decode-and-Forward Relay Networks under Interference Constraints: Performance Analysis and Relay Position Optimization
In this paper, we consider relay-assisted simultaneous wireless information and power transfer (SWIPT) for two-hop cooperative transmission, where a half-duplex multi-antenna relay adopts decode-and-forward (DF) relaying strategy for information forwarding. The relay is assumed to be energy-free and needs to harvest energy from the source node. By embedding power splitting (PS) at each relay antenna to coordinate the received energy and information, joint problem of determining PS ratios and power allocation at the multi-antenna relay node is formulated to maximize the end-to-end achievable ra…