Adaptive Subframe Partitioning and Efficient Packet Scheduling in OFDMA Cellular System with Fixed Decode-and-Forward Relays

Liping WANG
Yusheng JI
Fuqiang LIU

IEICE TRANSACTIONS on Communications   Vol.E92-B    No.3    pp.755-765
Publication Date: 2009/03/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E92.B.755
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Ad Hoc and Mesh Networking for Next Generation Access Systems)
OFDMA relay system,  resource allocation,  packet scheduling,  throughput,  fairness,  

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The integration of multihop relays with orthogonal frequency-division multiple access (OFDMA) cellular infrastructures can meet the growing demands for better coverage and higher throughput. Resource allocation in the OFDMA two-hop relay system is more complex than that in the conventional single-hop OFDMA system. With time division between transmissions from the base station (BS) and those from relay stations (RSs), fixed partitioning of the BS subframe and RS subframes can not adapt to various traffic demands. Moreover, single-hop scheduling algorithms can not be used directly in the two-hop system. Therefore, we propose a semi-distributed algorithm called ASP to adjust the length of every subframe adaptively, and suggest two ways to extend single-hop scheduling algorithms into multihop scenarios: link-based and end-to-end approaches. Simulation results indicate that the ASP algorithm increases system utilization and fairness. The max carrier-to-interference ratio (Max C/I) and proportional fairness (PF) scheduling algorithms extended using the end-to-end approach obtain higher throughput than those using the link-based approach, but at the expense of more overhead for information exchange between the BS and RSs. The resource allocation scheme using ASP and end-to-end PF scheduling achieves a tradeoff between system throughput maximization and fairness.