Frequency Selective Hybrid Precoding in Millimeter Wave OFDMA Systems

Hybrid precoding, a combination of analog and digital precoding, is an attempt to reach a compromise between complexity and performance. By exploiting more than one radio frequency chain, hybrid precoding enables a millimeter wave (mmWave) system to take advantage of both spatial multiplexing and beamforming gain. A major challenge with hybrid precoding is its configuration in wideband systems because the analog beamforming weights should be the same across the entire band. This limitation is a harsh condition in OFDMA systems where multiple users with different preferable beam patterns need to be allocated at the same time.

 

To mitigate this problem, WNCG graduate student Sungwoo Park and WNCG Professor Robert W. Heath Jr. propose an algorithm to jointly optimize the wideband analog beamformers and the per-subcarrier digital precoders. They compare an upper bound with their solution and show that their optimized approach achieves good performance in terms of beamforming gain in the sense that it minimizes the loss caused by allocating multiple users to different subcarriers with a limited number of radio frequency chains.

 

This work was presented at IEEE Globecom 2015 conference.

 

This work was supported by a gift from Huawei Technologies Co. Ltd.