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.
Highlights
Cooperative telecommunication systems can effectively be used to combat fading by exploiting the broadcast nature of the wireless medium [1,2,3,4,5,6]
This degradation is almost completely mitigated using the code-aided approach, yielding essentially the same frame error rate (FER) performance as the reference system. These results prove that the proposed two-way relaying QF system is suitable to be used in real-life systems, because efficient estimation of the unknown channel parameters can be achieved
In order to keep the relay complexity low, all parameters are estimated at the destination, requiring no additional operations from the relay
Summary
Cooperative telecommunication systems can effectively be used to combat fading by exploiting the broadcast nature of the wireless medium [1,2,3,4,5,6]. The relay is required to have multiple antenna’s, raising its hardware cost Both [12] and [13] assume that there is no direct link between the two user terminals, making it impossible to exploit cooperative diversity. These hardware requirements can limit the usefulness of existing two-way relaying strategies in applications requiring a low relay complexity, such as sensor networks and battery powered devices. A quantization scheme that does not necessitate the storage of analog values is proposed, where the relay separately quantizes the signals received in the first and second slot and properly combines the quantized values This involves the following operations, which do not require any channel knowledge at the relay
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