Cooperative Timing Acquisition for Distributed

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Cooperative Timing Acquisition for Distributed Antenna Systems: A Preliminary Study Chaojin Qing, Youxi Tang, Shihai Shao, and Xia Lei National Key Laboratory of Science and Technology on Communications, University of Electronic Science and Technology of China, 610054 Chengdu, China Email: { qingchj, tangyx, ssh, leixia } @uestc.edu.cn Abstract —This paper investigates the cooperative timing ac- quisition (CTA) for distributed antenna systems (DAS). As a preliminary study, the path loss and additive white Gaussian noise (AWGN) channel are considered without assuming multi- path fading and shadowing. In the DAS coverage region, two remote antennas (RA) are assumed at base station (BS) for receiving the signal transmitted from the mobile station (MS) with a single antenna. Under the constraint that is derived from the known locations of the two RAs, a maximum-likelihood (ML)- based CTA method is proposed. By the analysis and simulation, it is shown that the probability of correct acquisition for each RA can be improved by the cooperation of the two RAs. I. INTRODUCTION Recent studies have identified that distributed antenna sys- tems (DAS) have many advantages, such as decreased outage probability [1], reduced transmitted power [2] and increased system capacity [2]–[4]. In general, timing acquisition for DAS should be processed before synchronization tracking, channel estimation and data detection, etc, it is a critical task in DAS. Meanwhile, the transmit diversity and receive diversity can be exploited by employing cooperative transmission and cooperative reception [5]–[7], respectively. Using multiple remote antennas (RA), many prior studies for exploring spatial diversity, which utilize cooperative transmission or cooperative reception, are mainly based on the basic assumption that time and frequency are perfect synchronization [5]–[7]. However, the timing acquisition by cooperative processing using multi- ple RAs has rarely been considered for DAS. Inaccuracies in timing synchronization can degrade the performance of communication systems. The performance improvement of timing acquisition by cooperative processing of multiple receive antennas is an interesting topic. In tradi- tional co-located antenna systems (CAS), the base station (BS) antennas are centralized at the same location, the transmitted signals arrive at the different receive antennas simultaneously, hence cooperative processing of multiple receive antennas can be used to enhance the acquisition performance by receiver diversity [8]–[10]. In DAS, receive antennas are sparsely placed, the timing acquisition for receivers is mainly focus independent timing acquisition (ITA) [11]–[13], i.e., none cooperative processing is employed between RAs. Considering two RAs at the BS and one mobile station (MS) with single antenna, this paper mainly focuses on cooperative timing acquisition (CTA) for DAS. With the constraint derived from the location information of the two RAs, we propose fiber or coax cable MS 1 RA 2 RA D BS } Region 1 d 2 + , 111 ,, xyz + , 222 Fig. 1. System model. In the DAS coverage region
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This note was uploaded on 10/01/2010 for the course ELEC 6111 taught by Professor Brown during the Spring '10 term at E. Illinois.

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Cooperative Timing Acquisition for Distributed - This full...

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