Abstract:

The effect on the received signal to interference plus noise ratio (SINR) of spatial division multiple access (SDMA) systems with zero-forcing beamforming due to the channel estimation error and feedback delay is investigated. To reduce the negative effect of channel estimation error, a dynamic adaptive modulation scheme is proposed. This scheme dynamically adjusts the SINR thresholds for different modulation orders according to the feedbacks information from the receiver until the all the data are received correctly. Without increasing the signaling load and modifying original system parameters (e.g., modulation order and threshold), it can be easily extended to the cross-layer design existing channel estimation error.

Key words: spatial division multiple access, zeroforcing beamforming, imperfect channel state information