DIRTY PAPER CODE DESIGN FOR MULTIUSER MIMO BROADCAST CHANNEL

Abstract

Dirty paper code (DPC) can be used to presubtract interference non-causally known to the transmitter and to achieve capacity as if no interference is present at all. In this thesis, DPC based on nested trellis code is designed using Trellis coded quantizaion/trellis coded modulation (TCQ/TCM) scheme. Rate 1/2 convolutional code is cascaded with rate 2/3 Trellis coded modulation (TCM) to form DPC. TCM code acts as channel code to protect transmitted signal against channel noise where as cascading of both convolutional and TCM codes act as source code which implements vector quantization using Viterbi algorithm. Gain obtained from DPC can be increased using stronger source and channel codes which can be achieved by increasing number of states, because gain of both channel code and source code increases with states of encoder. DPC is the best candidate for precoding in multiuser multiple input multiple output (MU-MIMO) broadcast scenario. In MU-MIMO broadcast channel, signal transmitted to a user acts as interference for other users and this interference is non-causally available to base station because code for all users is encoded by same base station. So, in MU-MIMO broadcast channel interference to a user due to signal transmitted to another user can be nullify using DPC. This thesis implements DPC for MU-MIMO broadcast channel with base station containing multiple antennas and multiple receivers each equipped with single antenna.