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UBC Theses and Dissertations

On random access control for multipacket reception S-ALOHA in wireless cellular networks Seo, Jun-Bae


Studies on slotted ALOHA (S-ALOHA) systems have a long research history and been quite mature in the literature. However, this thesis revisits S-ALOHA systems by considering multipacket reception (MPR) channels, because previous studies are no longer applicable to MPR capable S-ALOHA systems due to the new random access channels (RACHs) of contemporary wireless cellular network standards. Particularly, it is dubious to apply the contention resolution algorithms (CRAs) developed so far for S-ALOHA systems to MPR S-ALOHA systems without any modification. Accordingly, this thesis proposes cross-layer CRAs and investigates the performance of some existing CRAs in MPR S-ALOHA systems in order to maximize the system throughput in tandem with stabilizing the system. Cross-layer CRAs proposed are based on estimating the system backlog information, which is obtained from multiple access interference (MAI) in the physical layer of Code Division Multiple Access (CDMA) MPR channel. Then, the proposed algorithms broadcast a retransmission probability in order to maximize the system throughput. The performance and the stability of the proposed algorithms are examined under various radio channel conditions. Compared to the proposed algorithms based on the system backlog information, the existing uniform backoff (UB) and exponential backoff (EB) algorithms are blind to such information. In order to understand the behaviour of these algorithms in MPR S-ALOHA, they are investigated with respect to various performance metrics and stability conditions. Additionally, the power ramping (PR) scheme is examined together with UB algorithm, in order to see whether it shows power capture effect in MPR S-ALOHA systems during a random access. Furthermore, the queueing performance of the MPR S-ALOHA system is investigated with an uplink traffic of the Markov Modulated Bernoulli Process (MMBP), when UB algorithm with retry limit is employed. It is also examined whether MPR S-ALOHA would be feasible for reserving a channel for a delay sensitive traffic. As a practical example, Semi-Persistent Scheduling (SPS) with initial random access in Long Term Evolution (LTE) is examined over MPR S-ALOHA, in which a traffic channel reservation for Voice-over IP (VoIP) is made at the onset of the ON period by a random access.

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Attribution 3.0 Unported