AEU - International Journal of Electronics and Communications
An efficient network coded ARQ for multisource multidestination relay networks over mixed flat fading channels
Introduction
Relay techniques are normally deployed to increase coverage between remote transmission and reception nodes as well as improve service quality and link capacity for local users [1], [2]. Recently spatial diversity gain methods have been considered in an attempt to extend relay transmission coverage and further improve transmission integrity [3], [4].
Basically, relays transmit packets through a store-and-forward mechanism, and thus do not increase the network throughput. In an attempt to improve throughput, network coding (NC) techniques have been investigated at the relays [5], [6], [7]. The basic concept of NC is that the relays perform algebraic linear/logic operations on received packets from multiple transmission sources in order to create a new combined packet, which is then forwarded to the destination nodes in the subsequent transmission. Various NC-based protocols have recently been proposed for some particular relay channel topologies such as relay-assisted bidirectional channels [8], broadcast channels [9], multicast channels [10] and unicast channels [11].
Automatic repeat request (ARQ) techniques permit information to be reliably delivered over multicast or broadcast networks. However, lost packets require to be retransmitted with ARQ protocols which may introduce significant packet latency since each packet is retransmitted individually. In addition, for ARQ, retransmissions are repeated until all packets are received correctly at each reception node. For multisource multidestination relay networks (MMRNs), in [12], the beamforming matrix was designed to minimize the sum transmit power at the relays subject to signal-to-interference constraints at the destinations to reliably support multiple parallel data streams. Also, in [13], stop-and-wait ARQ, go-back-N ARQ and the selective-repeat ARQ were investigated and compared to evaluate the maximum achievable throughput and the steady-state throughput of butterfly networks, a specific model of the MMRNs. However, the design of reliable transmissions over MMRNs that can achieve high network throughput efficiency and reduced retransmission packet latency has received little attention in the previous literature.
As an improved solution to these issues, we propose a new ARQ protocol based on NC for MMRNs. In this new protocol, the relay detects packets, combines information through NC, and transmits the lost packets from different sources to the destinations. Additionally, to achieve an optimal performance, multi-user detection (MUD) techniques [14] are implemented at both the relay and destinations. Thus along with MUD, lost packets can be combined and retransmitted to achieve an improved ARQ mechanism. The representation of lost packets in MMRNs may be categorized into two classification types: Type-I – packets that are successfully received at the relay but lost at the destinations, and, Type-II – packets that are lost at both the relay and destinations. Retransmission of Type-II packets is undertaken by the source, but the issue of how the relay retransmits Type-I packets with the lowest number of retransmissions requires to be addressed. To solve this retransmission problem, we propose a relay algorithm and also a source algorithm to enable retransmission of Type-I and Type-II packets, respectively. As an example of the protocol implementation, a two source, relay, two destination configuration is considered. Specifically, for this scenario, the proposed algorithm employed for retransmission at the relay is based on a combination of NC and packet detection from the two different sources.
A further contribution of this paper involves a performance comparison between our proposed NC-based ARQ protocol and other typical ARQ protocols for MMRNs. The other typical ARQ protocols considered are the direct transmission (DT)1 and the relaying transmission (RT)2 protocol. The performance comparison is achieved through deriving principally the complex analytical expressions of the transmission bandwidth for the new NC-based ARQ protocol and comparing it with the general analytical formulations for the other two protocols. The paper also extends the analytical performance analysis to include channel fading for the situations when the sources and destinations are located near to, or distant, from the relay. In these scenarios, it is approximated that the links from the sources to the relay, or the links from the relay to the destinations are line-of-sight (LOS) transmissions (close by, Rician fading), or non-line-of-sight (NLOS) transmissions (distant, Rayleigh fading).3 Accordingly, the considered fading channels are modelled as a mix of both Rayleigh and Rician fading, or are both Rayleigh or Rician fading.
It is shown through appropriate analytical and simulation examples, that our proposed ARQ protocol when applied to two-source two-destination single-relay network, significantly reduces the number of retransmissions for all fading situations, when compared with the DT and RT protocols.
The paper is organized as follows: Section 2 describes the system model and the different retransmission protocols of MMRNs; Section 3 derives the transmission bandwidths; Section 4 presents the numerical evaluation results and Section 5 concludes the paper.
Section snippets
MMRN system model and transmission protocols
Consider the MMRN displayed in Fig. 1 where data multicast from two sources and to two destinations and is assisted by one relay . Increasing the number of sources and destinations to the model is straightforward. The sources are able to send data packets which must be received without error after a number of transmissions and retransmissions. Basic ARQ is considered, where the sender simply waits for a positive or negative acknowledgement message from the receiver for every data
Transmission bandwidth analysis
In this section, the transmission bandwidths4 of the three protocols discussed above are derived for the scenarios of mixed Rayleigh and Rician flat fading channels for the MMRNs as described in Fig. 1.
When a channel is affected by fading, the signal received at any node when transmitted from any node , where , (), can
Numerical and simulation results
In this section, the transmission bandwidths of the different protocols are evaluated both from the analytical formulations above and also simulation models over mixed Rayleigh and Rician flat fading channels. Rayleigh flat fading channels are considered NLOS transmissions reflecting more distant locations, whilst Rician flat fading channels are considered LOS transmissions representing closer proximities. Four scenarios representing typical fading situations are now considered.
Conclusions
In this paper, a new improved and reliable retransmission scheme for multisource multidestination relay networks based on network coding has been proposed. It has been shown that the new protocol significantly reduces the number of retransmissions. The performance of the proposed retransmission scheme was investigated for the specific case with two sources and two destinations and shown to be superior in terms of transmission bandwidth improvement when compared with RT and DT protocols even
References (16)
IMT-advanced relay standards [WiMAX/LTE update]
IEEE Commun Mag
(2010)- et al.
Cooperative wireless networks: from radio to network protocol designs
IEEE Commun Mag
(2011) - et al.
User cooperation diversity—Part I. System description
IEEE Trans Commun
(2003) - et al.
Cooperative diversity in wireless networks: Efficient protocols and outage behavior
IEEE Trans Inf Theory
(2004) - et al.
Hot topic: physical-layer network coding.
- et al.
Embracing wireless interference: Analog network coding.
- et al.
Practical physical layer network coding for two-way relay channels: performance analysis and comparison
IEEE Trans Wireless Commun
(2010) - et al.
Error performance analysis of BPSK modulation in physical-layer network-coded bidirectional relay networks
IEEE Trans Commun
(2010)
Cited by (5)
Cross-layer topology design for network coding based wireless multicasting
2015, Computer NetworksCitation Excerpt :By performing algebraic linear/logic operations on received packets at the intermediate nodes with NC techniques, the bandwidth could be saved for a higher system throughput. Many NC-based protocols have been proposed and investigated for multicast channels (e.g. in [4,6]). In NC-based WMNs, topology design has significant impact on the system throughput [14–19].
Optimization of relay placement in wireless butterfly networks
2018, Studies in Computational IntelligenceOn the energy-delay tradeoff and relay positioning of wireless butterfly networks
2015, IEEE Transactions on Vehicular TechnologyCross-layer optimisation for topology design of wireless multicast networks via network coding
2014, Proceedings - Conference on Local Computer Networks, LCNQueueing analysis of retransmission schemes over fading wireless channels
2014, International Journal of Applied Engineering Research