Iterative Soft-decision Interference Cancellation Using Selective Variance for Multiple Antenna System

Abstract

Multiple antenna technique is one of the key technologies in modern wireless communication systems to increase transmission rate In rich scattering environment there is no clear line-of-sight (LOS) path between transmitter and receiver The signals in these environments are reflected scattered or diffracted among multiple paths before being received at the receiver which may interfere other receiving antennas and causing multiple antenna interference In order to limit the impact of multiple antenna interference on system performance an iterative soft-decision interference cancellation (ISIC) method was presented to mitigate interference by using a combination of a successive interference cancellation and a turbo decoder However error propagation is a source of performance degradation in the ISIC scheme In this thesis a modified ISIC scheme is proposed to reduce the probability of error propagation with an adjustable cancellation order in each iteration The cancellation order is decided by ascending variance values from the previous iteration To increase system convergence speed an accumulated max-log-MAP algorithm is presented to accumulate soft information over iterations Furthermore a low-complexity iterative QR decomposition method is proposed to reduce the effort of changing the cancellation order In the complexity analysis the overall execution time is reduced by about 35% in a 4×4 system using 4 iterations Compared to the ISIC scheme the modified scheme can obtain 0 9dB performance gain in a 4×4 system with 4 iterations

Date of Award	2015 Aug 21
Original language	English
Supervisor	Ming-Der Shieh (Supervisor)