Performance of a reference symbol assisted multi-stage successive interference cancelling receiver with quadriphase spreading

Abstract

The performance of a multi-stage successive interference cancelling receiver using reference symbols to obtain channel estimates in a CDMA system is investigated with quadriphase spreading. The focus is on the reverse link of a system with binary antipodal modulation and coherent detection. The results show that for a hexagonal cell geometry with path loss exponent of 4 and without any forward error correction coding, the capacity of the system is between 1.17 and 1.67 times that of the IS-95 system. Further investigation with non-idealized cell geometries and other path loss exponents shows substantial capacity improvement over that of conventional non-interference cancelling receivers. The sensitivity of the system to power control and synchronization errors is also investigated. The results also show that relaxing the power control reduces the capacity. The capacity increase over systems with interference cancelling receivers and biphase spreading is between 1.4 and 2.0 times. Chip synchronization errors of the order to be expected in a properly designed conventional CDMA system have minimal effect on performance.