【資料名稱】：WCDMA HSDPA Technical Description (Relea

【資料作者】：ERICSSON

【資料日期】：020321

【資料語言】：英文

【資料格式】：PDF

【資料目錄和簡介】：

For release 5, the WCDMA specification is extended with a new downlink transport channel,the High Speed
Downlink Shared Channel (HS-DSCH). HS-DSCH provides enhanced support for interactive, background, and, to
some extent, streaming radio-access-bearer (RAB) services in the downlink direction. More specifically, compared to
release 99/4, HS-DSCH allows for
?Higher capacity
?Reduced delay
?Significantly higher peak data rates
HS-DSCH transmission is based on Shared-Channel transmission, similar to release 99/4 Downlink Shared Channel
(DSCH). However, HS-DSCH transmission supports several new features, not supported for DSCH.
?HS-DSCH supports the use of higher-order modulation. This allows for higher peak data rates and higher
capacity.
?HS-DSCH supportsfast link adaptation andfast channel-dependent scheduling. This means that the
instantaneous radio-channel conditions can be taken into account in the selection of transmission parameters as
well as in the scheduling decision and allows for higher capacity.
?HS-DSCH supports fast Hybrid ARQ with soft combining. This reduces the number of retransmissions as well
as the time between retransmissions and allows for higher capacity and a substantial reduction in delay. The
use of Hybrid ARQ with soft combining also adds robustness to the link adaptation.
To support these features with minimum impact on the existing radio-interface protocol architecture, a new MAC
sub-layer, MAC-hs, is introduced for HS-DSCH transmission. To reduce the retransmission delay for Hybrid ARQ
and allow for as up-to-date channel-quality estimates as possible for the link adaptation and channel-dependent
scheduling, MAC-hs is located in the Node B. For the same reasons, HS-DSCH uses a shorter TTI (2 ms) compared
to release 99/4 transport channels.
This document gives a detailed description of the HS-DSCH transport channel and associated functions and
procedures. Although HS-DSCH is specified for both UTRA/FDD (WCDMA) and UTRA/TDD, only the FDD mode
is treated in this document. The document describesthe basic ideas behind HS-DSCH and the solutions chosen for
the 3GPP specifications as of March 2002. As the specifications are subject to updates and refinements, it is not
recommended to use this description as a basis for implementation.
The document is structured as follows: Section 2 gives a background to the general principles behind HS-DSCH.
Section 3 introduces the general architecture. Section 4 represents the main part of the document and discusses the
details of HS-DSCH, starting with layers 1 and 2 in the Node B and continuing with configuration, mobility, and a
summary of the data and control flows.