Implementation of rake receiver in HSDPA with multi-code operation

Abstract

In the standardized air interface for 3rd generation mobile communication systems, WCDMA Release 5, a concept called High Speed Downlink Packet Access (HSDPA) is introduced. It is a packet-based data service with data transmission rates up to 8-10 Mbps (20 Mbps for MIMO systems) over a 5MHz. WCDMA downlink. HSDPA enables faster transmissions from Node-B to mobile users using a shared, high capacity channel called the High Speed Downlink Shared Channel (HS-DSCH) that is designed for best effort services. HSDPA is based on direct-sequence (DS) CDMA technology. A rake receiver is used to minimize the distortions of the signals in a DS-CDMA system. A signal transmitted through the wireless channel may be severely distorted due to co-channel interference, multiple access interference, thermal noise, and multipath fading. The most severe distortion comes from fading, which changes the bit error rate (BER) from an exponential to a linear curve. Rake receiver employs multipath diversity techniques to combat these distortions. It is the receiver of choice because it allocates one rake finger to each multipath, thus maximizing the amount of received signal energy. In this thesis work, we investigate and implement the rake receiver with multi-code functionality in the HSDPA system to evaluate the performance of the system. We analyze the performance through different simulation scenarios. Consequently, we observed that multi channelization codes enhance the data rate and system performance/throughput significantly. We developed a simulation tool in C-language in this work.