Channel and delay estimation for base-station–based cooperative communications in frequency-selective fading channels

Hongjun Xu, Laneil Padayachee
2011 South African Journal of Science  
How to cite this article: Xu H, Padayachee L. Channel and delay estimation for base-station-based cooperative communications in frequency-selective fading channels. S Afr J Sci. Space-time block coding is a technique used to achieve spatial diversity in both synchronous multiple-input multiple-output and synchronous cooperative communication systems in frequency-flat fading channels. 1 However, cooperative communication is generally asynchronous, not synchronous. This is because different
more » ... have different locations, and the transmitted signals from different relays may arrive at different times. In asynchronous cooperative communication systems, when the relays use orthogonal space-time block codes (STBC) to forward the received data from source to destination, the code structure at the receiver is not orthogonal. 2 The system can only achieve a diversity order of 1. Therefore, new transmission schemes based on STBC are required, and the estimation of the relative delays between different paths at the destination is needed. 2 New transmission schemes based on STBC have been studied, but these studies did not take into account delay estimation. 2, 3, 4, 5 In this paper, we focus on channel and delay estimation for asynchronous cooperative communication systems. A typical example of asynchronous cooperative communication systems is a base-station-based cooperative communication in macrocell downlink networks, proposed by Skjevling et al. 6 Tourki and Deneire 7 proposed a channel and delay estimation algorithm that achieved a lower Cramér-Rao bound (CRB) in Skjevling et al.'s system. But Tourki and Deneire's system was derived only for positive delays, that is, when Transmitter one's data always arrives at the receiver before Transmitter two's data. 7 Recently, Xu and Padayachee 8 extended Tourki and Deneire's scheme to accommodate negative delays (i.e. when Transmitter two's data arrives at the receiver before Transmitter one's data). However, Xu and Padayachee's scheme 8 works only in frequency-flat fading channels. The main motivation of this paper was to extend the scheme described in Xu and Padayachee 8 to work in frequency-selective fading channels. Extending the scheme to accommodate transmission in frequency-selective channels is pivotal because current and future broadband wireless communication systems aim to have high data rates, which gives rise to frequency-selective propagation effects. A typical example is that of a mobile communicating with a base station. As a result of the reflections of buildings, hills, cars and other obstacles, there are multiple delayed receptions of the transmitted signals at the receiver. This causes frequency-selective propagation effects. Mheidat et al. 9 have already discussed cooperative communication over frequencyselective channels, but their scheme assumed perfect channel knowledge at the receiver, as well as perfect synchronisation. Simeone and Spagnolini 10 discussed channel estimation in S Afr J Sci 2011; 107(7/8) Research Article
doi:10.4102/sajs.v107i7/8.414 fatcat:nx6mphcinnazhngojbxsqls6ku