Research On DPC Precoding In MIMO Roadcast Channels

Multiple-input multiple-output(MIMO) system is implemented with multiple transmit antennas and multiple receive antennas. It can obviously improve spectral efficiency. MIMO broadcast channel can increase information rate and improve communication quality simultaneously。The capacity region of the multi-user MIMO Gaussian broadcast channel can be achieved through dirty paper precoding.Theoretical analysis about MIMO broadcast channels is proposed in this paper, which shows that:(1)When the side information is casually known at the transmitter, by using high dimensional lattices and incorporating MMSE scaling, the capacity of dirty paper channel can be approached, but the complexity of the scheme is too high.(2)Tomlinson-Harashima precoding suffers modulo loss, power loss and shaping loss compared with ideal dirty paper coding.(3)The shaping loss can be greatly recovered by trellis precoding in the high SNR region.The design, encoding and decoding principles of trellis precoding in dirty paper channel is introduced and the performance is conducted by simulation. Analysis shows that when SNR is high, trellis precoding in dirty paper channels performs as well as trellis shaping in AWGN channels and its error propagation is not very serious. Simulation shows that, compared with ideal dirty paper coding, the performance of trellis coding in dirty paper channel is about 3.75 d B away at bit-error-rate for the transmission rate of. A scheme combining trellis precoding with QR decomposition of the channel matrix for 510-2 bits/ dimsuccessive dirty paper encoding is proposed in this paper, simulations shows that it suffers serious error propagation in MIMO broadcast channels. Compared with those without precoding, systems combining trellis precoding with random interleaving can obtain about 2.5d B gains in block fading channels.