Multiuser Two-Way Relaying Schemes for UWB Communication

Abstract

In this paper we propose multiuser two-way relaying strategies for pairwise internode communication in a network consisting of ultra-wideband (UWB) transceivers with limited signal processing capability, via a central relay unit. We propose reducing the complexity associated with the design of filters at the relay by using pre/post-rake processing in conjunction with optimized filtering at the relay. Two relaying strategies relevant to multipath fading channels, namely detect-and-forward and filterand-forward with self-interference cancelation, are considered. For both methods, we start with a convex optimization problem formulation with closed-form solutions, then extend the design to the more general case which is a non-convex problem and use an alternating optimization algorithm to solve the design problems. Furthermore, for both design schemes widely linear design formulations are devised. The presented numerical results demonstrate the capability of the proposed design schemes in establishing a reliable communication link between nodes with limited signal processing power and in absence of a direct link.Index Terms-Detect-and-forward relaying, filter-and-forward relaying, intersymbol interference, multi-way relaying, multiuser interference, multiuser two-way relaying, pre-rake filtering, selfinterference cancelation, ultra-wideband (UWB), UWB relay communication.

Code-Multiplexing-Based One-Way Detect-and-Forward Relaying Schemes for Multiuser UWB MIMO Systems

“…In particular, T s = 512 ns, which guarantees absence of inter-symbol interference in both systems, so that the only impairment is represented by MAI. As expected, the coherent scheme in [32], which is based on (pre/post)-rake filtering, outperforms DMD-CEK (which requires much less channel information and is computationally less demanding) especially at low SNRs. However, it is worth noting that the performance gap tends to reduce as the SNR increases.…”

“…The bandwidth of the front-end filter is B = 1 GHz. Following [32], the statistics of the propagation channel are taken from the IEEE 802.15.4a model CM2 [48], [49], which corresponds to a residential non-line-of-sight (NLOS) environment. Its rms delay spread is about 13 ns [49].…”

“…Fig. 10 compares the performance of the DMD-CEK based relaying scheme and the Widely Linear DFT system proposed in [32,Section II.D]. The number of antennas is N a = 2 and the other parameters are the same as in Fig.…”

“…Rake-receivers and time-reversed transmissions (pre-rake filtering) are used in [31] for the design of single-user MIMO UWB one-way relaying systems, with multiple antennas at the source and destination nodes, and at the relay. Recently, in [32] post/pre-rake filtering have also been proposed for multiuser two-way schemes, in conjunction with filter-and-forward (FF) or DF relaying protocols. Source and destination nodes have a single antenna whereas multiple antennas are installed at the relay.…”

“…Each node of a pair is connected to the other node of that pair via the relay. Following the same line of reasoning as in [32] we consider a network with lowcomplexity nodes and a central transceiver unit (i.e. the relay) with a higher computational capacity.…”