Implementation of base station receiver for CDMA wireless local loop system

Abstract

The wireless local loop (WLL) system has been deployed as a new application for wireless communication with fixed subscriber units which impose a fixed to fixed propagation and no handoffs compared to the wireless mobile communication systems. The design of the WLL system is much simpler than that of a mobile system because no handoff occurs in a fixed-to-fixed link. This paper describes the hardware design and implementation of base station receiver for code division multiple access (CDMA) WLL system proposed by Electronics and Telecommunications Research Institute (ETRI). This base station demodulator module of the WLL system is implemented by hardware chips, such as a digital signal processor (DSP), erasable programmable logic device (EPLD), and a field programmable gate array (FPGA). Timing simulation of the implemented system is operated using the ALTERA MAXPLUS tool. The basic hardware modules of the base station receiver consist of two searchers for antenna diversity and four fingers for multipath combining. We verify the operation of the code acquisition and time tracking loop on the call test. The reconstructed speech shows a good quality in the reverse link.