On multipath detection in CDMA systems

This paper addresses the problem of multipath detection in CDMA systems. In conventional CDMA receivers, the detection of multipath components and RAKE finger management is normally based on the received signal energy per path. These energy-based schemes essentially overlook the interference component contaminating the total received power. Consequently, they exhibit poor detection capability especially at low signal-to-interference-plus-noise ratio (SINR). In this paper, we present a new scheme for multipath detection and RAKE finger assignment that takes into consideration the interference level in each resolved path individually. The proposed scheme utilizes information provided by the pseudo random code acquisition circuit to estimate the interference power per path. To account for the hardware limitations of the receiver, a low complexity version of the proposed scheme is designed and incorporated into the receiver structure. Analytical and simulation results show that the proposed scheme provides significant improvements in the detection probability of multipath components over the energy-based schemes. For instance, our results show that the proposed scheme can achieve the same detection probability of all multipath components as that of the energy-based scheme with a saving of at least 2 dB in E_b/N₀. In some cases, it is shown that the improvement can be as high as 3 dB.