Matthias Schulist

Link level performance results for a WCDMA random access scheme with preamble power ramping and fast acquisition indication

Advanced packet-access based services play a key role in third-generation mobile communication systems. Thus, flexible and power-efficient random and packet access schemes with low access delay are identified as an important feature. This paper describes the random access proposal adopted for WCDMA, the third-generation system jointly specified by several standardization bodies within the 3rd-Generation Partnership Project (3GPP). Link level performance results for this method with preamble power ramping and fast acquisition indication are presented.

WCDMA multi-cell link-level performance

This paper presents a multi-cell simulation approach with which the impact of selected link-level aspects on cellular system performance can be investigated. The investigations are carried out for downlink dedicated physical channels (DL-DPCH) of third-generation wideband CDMA (3G WCDMA), specified by the 3GPP standardization body. The simulator incorporates user equipment (UE) that suffers from intra-cell interference of the connected base station (BS) as well as inter-cell interference originating from explicitly, i.e. chip-exact, modeled surrounding BSs. The employed multi-cell environment, based on a radio geometry concept; is described. Coded error performance is shown for various mobile radio channel scenarios, radio geometries and different models for the interference. The question whether inter-cell interference of surrounding BSs can be modeled alternatively by additive white Gaussian noise (AWGN) is addressed. It turns out that in all cases the chip-exact modelling of adjacent BSs is necessary in order to obtain realistic performance results. This holds especially the more the UE moves towards the cell border and beyond. Comparisons with simulations employing the AWGN model for inter-cell interference show that those results are too optimistic at low speeds. Moreover, it is shown that a performance analysis based solely on uncoded (raw) bit error rate is not sufficient, but must be complemented by decoded bit and block error rate figures.

Acknowledgment of 3GPP WCDMA random and packet access applying space-time transmit-diversity

Advanced packet-access based services are now widely considered to play the key role in 3/sup rd/ generation (3G) mobile communication systems. The FDD-mode (commonly denoted as WCDMA) standardized by the 3/sup rd/ Generation Partnership Project (3GPP) provides a variety of logical, transport and physical channels to assist efficient packet based transmission. Random access channel (RACH) and common packet channel (CPCH) are reverse link (packet) channels that are shared among several users. So-called acquisition indicator channels (AICH) are used with RACH and CPCH on the physical layer to assist fast acknowledgment of (packet) access grants or rejections. Space-time transmit diversity (STTD) is the WCDMA concept for performance improvement of forward link, nonpower-controlled, physical channels like AICH. This paper describes the RACH and CPCH concept with emphasis of the AICH. It introduces the STTD concept for AICH and shows link layer performance results with and without applying STTD.