Limited Feedback Schemes for Downlink OFDMA Based on Sub-Channel Groups

作者：Chen Jeying^*; Berry Randall A; Honig Michael L

来源：IEEE Journal on Selected Areas in Communications, 2008, 26(8): 1451-1461.

DOI：10.1109/JSAC.2008.081011

• Limited feedback
• multiuser
• OFDMA
• down-link
• channel grouping
• finite coherence time
• feedback overhead

In a downlink Orthogonal Frequency Division Multiple Access (OFDMA) system, optimally allocating sub-channels across mobile users can require excessive feedback of channel state information (CSI). We consider an OFDMA model in which the feedback overhead is explicitly taken into account, given a fixed feedback rate and finite coherence time. The tradeoff between feedback rate and sum capacity is studied for two limited feedback schemes: a sequential scheme in which the users send compressed feedback bits over consecutive time slots, and a contention scheme in which users send their feedback via a random access protocol. For both schemes each feedback bit indicates a request for a group containing multiple subchannels. We show that the sum capacity for both schemes with optimized sub-channel groups grows linearly with the number of sub-channels N, and that the associated constant increases as the log of the normalized feedback rate measured in bits per coherence time per sub-channel. We also compare the asymptotic (large N) performance of the two limited feedback schemes as a function of the feedback rate and load (users per sub-channel). The sequential scheme performs best with moderate to large feedback rates, or small loads, whereas the contention scheme performs best with small feedback rates or large loads.

• 出版日期2008-10
• 单位西北大学