Adaptive User Cooperation with HARQ for the Uplink of a Turbo-Coded System.
ABSTRACT Coded cooperation has been proposed to increase the diversity or cell coverage in the uplink of a cellular network. In the method, a relay transmits incremental redundancy (IR) of the source's codeword in cooperation stage. However, for a turbo coded system, IR is not always a best way especially when the first code segment is corrupted badly. Thus, we propose an adaptive cooperation method using different HARQ schemes by estimating the reliability of the first code segment. From simulation results, it is shown that the proposed method improves the performance irrespective of the SNR values of cooperating users.
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ABSTRACT: Mobile users' data rate and quality of service are limited by the fact that, within the duration of any given call, they experience severe variations in signal attenuation, thereby necessitating the use of some type of diversity. In this two-part paper, we propose a new form of spatial diversity, in which diversity gains are achieved via the cooperation of mobile users. Part I describes the user cooperation strategy, while Part II (see ibid., p.1939-48) focuses on implementation issues and performance analysis. Results show that, even though the interuser channel is noisy, cooperation leads not only to an increase in capacity for both users but also to a more robust system, where users' achievable rates are less susceptible to channel variations.IEEE Transactions on Communications 12/2003; · 1.75 Impact Factor
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ABSTRACT: For pt.I see ibid., p.1927-38. This is the second of a two-part paper on a new form of spatial diversity, where diversity gains are achieved through the cooperation of mobile users. Part I described the user cooperation concept and proposed a cooperation strategy for a conventional code-division multiple-access (CDMA) system. Part II investigates the cooperation concept further and considers practical issues related to its implementation. In particular, we investigate the optimal and suboptimal receiver design, and present performance analysis for the conventional CDMA implementation proposed in Part I. We also consider a high-rate CDMA implementation and a cooperation strategy when assumptions about the channel state information at the transmitters are relaxed. We illustrate that, under all scenarios studied, cooperation is beneficial in terms of increasing system throughput and cell coverage, as well as decreasing sensitivity to channel variations.IEEE Transactions on Communications 12/2003; · 1.75 Impact Factor
Conference Proceeding: Performance and modeling of WCDMA/HSDPA transmission/H-ARQ schemes[show abstract] [hide abstract]
ABSTRACT: As part of 3GPP Release'5 standardization work on WCDMA/UTRA, a new packet concept has been added to grant high speed downlink packet access (HSDPA). One of the central features of the HSDPA concept is advanced physical layer retransmission scheduling employing soft combining gain, incremental redundancy, and low retransmission delays. Since the average retransmission probability in HSDPA is typically on the order of 10-40%, the retransmission scheduling needs to be accurately simulated and modeled at both link and network level. Based on an extensive simulation campaign, this paper presents methods to map the link level performance of the HSDPA retransmission schemes into a low-complexity representation suitable for network level evaluation. The method accurately predicts the throughput and delay performance within a few percent.Vehicular Technology Conference, 2002. Proceedings. VTC 2002-Fall. 2002 IEEE 56th; 02/2002