Abstract
Channel estimation protocols for wireless two-hop networks with amplify-and-forward (AF) relays are compared. We consider multiuser relaying networks, where the gain factors are chosen such that the signals from all relays add up coherently at the destinations. While the destinations require channel knowledge in order to decode, our focus lies on the channel estimates that are used to calculate the relay gains. Since knowledge of the compound two-hop channels is generally not sufficient to do this, the protocols considered here measure all single-hop coefficients in the network. We start from the observation that the direction in which the channels are measured determines (1) the number of channel uses required to estimate all coefficient and (2) the need for global carrier phase reference. Four protocols are identified that differ in the direction in which the first-hop and the second-hop channels are measured. We derive a sensible measure for the accuracy of the channel estimates in the presence of additive noise and phase noise and compare the protocols based on this measure. Finally, we provide a quantitative performance comparison for a simple single-user application example. It is important to note that the results can be used to compare the channel estimation protocols for any two-hop network configuration and gain allocation scheme.
Highlights
Cooperative networks offer diversity, multiplexing, and array gains as in MIMO systems but in a distributed fashion
We derive a sensible measure for the accuracy of the channel estimates in the presence of additive noise and phase noise and compare the protocols based on this measure
We investigate an alternative measure that is very simple. Since both protocols deliver the same estimates for the first-hop channels, we compare them based on the quality of the second-hop channel estimates
Summary
Cooperative networks offer diversity, multiplexing, and array gains as in MIMO systems but in a distributed fashion. The quality of these estimates obviously has an impact on the accuracy with which the gain factors can be computed This in turn determines the degree to which the signals from the relays combine coherently at EURASIP Journal on Wireless Communications and Networking the destinations and immediately affect the system performance. The authors of [21] consider a very simple special case of this problem They investigate the accuracy of a channel estimation protocol (corresponding to protocol B1 in this work) for a two-hop network with a single sourcedestination pair and multiple AF relays. Vectors with entries that are taken from a normal and a complex normal distribution with mean 0 and variance σ2 are denoted by x ∼ N (0, σ2I) and x ∼ CN (0, σ2I), respectively
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
