Low-complexity quantize-and-forward cooperative communication using two-way relaying
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Low-complexity quantize-and-forward cooperative communication using two-way relaying Iancu Avram* , Nico Aerts and Marc Moeneclaey
Abstract Cooperative communication is used as an effective measure against fading in wireless communication systems. In a classical one-way cooperative system, the relay needs as many orthogonal channels as the number of terminal it assists, yielding a poor spectral efficiency. Efficiency is improved in two-way relaying systems, where a relay simultaneously assists two terminals using only one timeslot. In the current contribution, a two-way quantize-and-forward (QF) protocol is presented. Because of the coarse quantization, the proposed protocol has a low complexity at the relay and can be used with half-duplex devices, making it very suitable for low-complexity applications like sensor networks. Additionally, channel parameter estimation is discussed. By estimating all channel parameters at the destination terminals, relay complexity is kept low. Using Monte Carlo simulations, it is shown that the proposed QF protocol achieves a good frame error rate (FER) performance as compared to two-way amplify-and-forward (AF) and one-way relaying systems. It is further shown that, using the proposed estimation algorithm, the FER degradation arising from the channel parameter estimation is negligible when compared to an (unrealistic) system in which all parameters are assumed to be known. Keywords: Cooperative communication; Two-way relaying; Estimation; Sensor networks; Diversity
1 Introduction Cooperative telecommunication systems can effectively be used to combat fading by exploiting the broadcast nature of the wireless medium [1-6]. In a classical cooperative communication system, only unilateral communication is considered: one transmitting terminal communicates to one receiving terminal with the help of a relaying terminal. Many practical applications however require bilateral communication, in which two terminals both send and receive information to/from each other. Using a classical (one-way) cooperative system in this situation would yield a poor spectral efficiency, as this would require four orthogonal channels, i.e., the two transmitting terminals need one channel each, and the relay transmits over two channels that the data received from the first and second terminal, respectively. The spectral efficiency can be improved using a two-way relaying system, *Correspondence: [email protected] Department of Telecommunications and Information Processing (TELIN, UGent), St-Pietersnieuwstraat 41, 9000 Ghent, Belgium
in which the relay uses a single channel to simultaneously assist in the information transfer from the first to the second terminal and from the second to the first terminal. As for one-way cooperative systems, a variety of forwarding protocols have been developed for two-way systems, including, but not limited to, network coding [7,8], amplify-and-forward (AF) [9], decode-and-forward (DF) [9,10], and compress-and-forward (CF) [11]. While many
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