Adaptive Provision of CSI Feedback in OFDMA Systems

We address the problem of channel state information (CSI) feedback for scheduling the downlink (DL) data transmissions in a cellular system based on orthogonal frequency division multiple access (OFDMA). In order to benefit from multi-user diversity, the scheduler needs to know each user´s CSI for each subchannel and time frame. However, this feedback information can become very high when the number of subchannels and/or users increase. Therefore, we have designed an adaptive feedback encoding method which can optimize the amount of feedback according to the variable amount of CSI requested by the base station (BS). The amount of useful CSI depends not only on the number of users, but also on the scheduling made at the BS. The simulation results show that with our adaptive encoding scheme, the performance of maximum CSI and proportional fair scheduling (PFS) with full CSI can be approached with a considerably reduced amount of feedback