Comparison of Channel Estimation Protocols for Coherent AF Relaying Networks in the Presence of Additive Noise and LO Phase Noise
AuthorsStefan Berger and Armin Wittneben
ReferenceEURASIP Journal on Wireless Communications and Networking, June 2010.
AbstractIn this work 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.
KeywordsCooperative relaying, channel estimation, amplify-and-forward, phase synchronization
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