tailieunhanh - Wcdma for umts radio access for third genergation mobile communacations phần 8

Tối ưu hóa sự thống trị khu vực là rất quan trọng cho sự can thiệp và mềm mại bàn giao diện tích và khả năng chuyển giao mềm kiểm soát. Mềm được cải thiện / mềm hơn bàn giao và thực hiện can thiệp được tự động nhìn thấy trong cải thiện năng lực mạng lưới. | 11 High-speed Downlink Packet Access Antti Toskala Harri Holma Troels Kolding Preben Mogensen Klaus Pedersen and Karri Ranta-aho This chapter presents High-speed Downlink Packet Access HSDPA for WCDMA - the key new feature included in the Release 5 specifications. The HSDPA concept has been designed to increase downlink packet data throughput by means of fast physical layer L1 retransmission and transmission combining as well as fast link adaptation controlled by the Node B Base Transceiver Station BTS . This chapter is organised as follows First HSDPA key aspects are presented and a comparison to Release 99 downlink packet access possibilities is made. Next the impact of HSDPA on the terminal uplink user equipment UE capability classes is summarised and an HSDPA performance analysis is presented including a comparison to Release 99 packet data capabilities as well as performance in the case of a shared carrier between HSDPA and non-HSDPA traffic. The chapter is concluded with a short discussion of evolution possibilities of HSDPA including a description of the on-going work on uplink improvements in 3GPP. Release 99 WCDMA Downlink Packet Data Capabilities Various methods for packet data transmission in WCDMA downlink already exist in Release 99. As described in Chapter 10 the three different channels in Release 99 Release 4 WCDMA specifications that can be used for downlink packet data are Dedicated Channel DCH Downlink-shared Channel DSCH Forward Access Channel FACH . The DCH can be used basically for any type of service and it has a fixed spreading factor SF in the downlink. Thus it reserves the code space capacity according to the peak data WCDMA for UMTS third edition. Edited by Harri Holma and Antti Toskala 2004 John Wiley Sons Ltd ISBN 0-470-87096-6 308 WCDMA for UMTS rate for the connection. For example with Adaptive Multirate AMR speech service and packet data the DCH capacity reserved is equal to the sum of the highest rate used for the AMR speech .