Coverage Enhancement in TDD-OFDMA Downlink by Using Simple-Relays with Resource Allocation and Throughput Guarantee Scheduler

Young Min KI  Dae Wook BYUN  Dong Ku KIM  

IEICE TRANSACTIONS on Communications   Vol.E90-B   No.12   pp.3704-3707
Publication Date: 2007/12/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e90-b.12.3704
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Wireless Communication Technologies
802.16 TDD-OFDMA,  simple-relay aided resource allocation (SRARA),  throughput guarantee scheduling (TGS),  

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Simple-relay aided resource allocation (SRARA) schemes are incorporated with throughput guarantee scheduling (TGS) in IEEE 802.16 type time division duplex--orthogonal frequency division multiple access (TDD-OFDMA) downlink in order to enhance service coverage, where the amount of resources at each relay is limited due to either its available power which is much smaller than base station (BS) power or the required overhead. The performance of SRARA schemes is evaluated with both proportional fair (PF) and TGS schedulers at 64 kbps and 128 kbps user throughput requirements when total RS power is set to 500 mW or 1 W. For SRARA with RSs of relatively lower power (500 mW), schemes that put total power into only one subchannel offer larger coverage than when both subchnnels are used with equal power allocation, while the RS with evenly power-allocated two subchannels could provide larger coverage gain for a relatively higher power (1 W). Depending upon the target throughputs it is shown which of the relay scheme or scheduler design would play more important role in improving coverage. In a lower target (64 kbps), more improvement comes from relay scheme rather than scheduler design. For a relatively higher level (128 kbps), it comes from scheduler design rather than relay due to the fact that simple relay can't help using strictly limited amount of resources.