HSDSCH

HS-DSCH, or High-Speed Downlink Shared Channel, is a downlink data channel used in UMTS networks to deliver high-speed user data in HSDPA (High-Speed Downlink Packet Access). It is designed to increase downlink throughput by allowing shared transmission of data to multiple users, managed by the network’s NodeB.

In operation, HS-DSCH data is scheduled and carried on the HS-PDSCH (High-Speed Downlink Physical Channel). Control information necessary for decoding, such as user assignment, modulation and coding scheme, and timing, is transmitted on the HS-SCCH (High-Speed Shared Control Channel). The data path employs adaptive modulation and coding, turbo codes, and often hybrid automatic repeat request (HARQ) with incremental redundancy to improve reliability and efficiency. The system multiplexes data for multiple users within the same downlink resources, enhancing spectral efficiency.

Technical characteristics and options include support for higher-order modulation and various coding rates depending on channel quality, enabling significant increases in downlink throughput over standard UMTS downlinks. The exact throughput depends on bandwidth, radio conditions, and scheduling decisions, with performance improving as modulation order and code rate are optimized for the link.

History and standards: HS-DSCH was introduced as part of 3GPP HSDPA starting in Release 5, with subsequent enhancements in later releases to extend capabilities and efficiency. It remains a foundational element of HSPA and its evolution, including enhancements in newer generations and configurations.

See also: HSDPA, HS-SCCH, HS-PDSCH, UMTS, NodeB, HARQ.