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High-Speed Downlink Packet Access [HSDPA]

High-Speed Downlink Packet Access (HSDPA) is a 3G, third generation mobile telephony communications protocol in the High-Speed Packet Access [HSPA] family.

HSPA allows networks based on Universal Mobile Telecommunications System [UMTS] to have higher data transfer speeds and capacity.

Current HSDPA deployments support down-link speeds of 1.8, 3.6, 7.2 and 14.4 Mbit/s. Further speed increases of 42 Mbit/s downlink will occur when networks are upgraded to Evolved HSPA.

The High-Speed Downlink Shared Channel (HS-DSCH) lacks two basic features of other W-CDMA channels:

Variable spreading factor
Fast power control

Instead, it delivers the improved downlink performance using:

Adaptive modulation and coding [AMC]
Fast packet scheduling at the base station
Fast retransmissions from the base station - known as hybrid automatic repeat-request [HARQ].

Deployment

As of May 25, 2007, 102 HSDPA networks have commercially launched mobile broadband services in 55 countries.

40 HSDPA networks support 3.6 Mbit/s peak downlink data throughput.
A few are delivering 7.2 Mbit/s peak data downlink, leveraging new higher-speed devices coming into the market.
One network has been declared as “14.4 Mbit/s (peak) ready” and several others will have this capability by end 2007.

The first commercial HSUPA uplink network is launched, with several more set to follow in 2007.

This protocol is a relatively simple upgrade where UMTS is already deployed.

CDMA-EVDO networks took an early lead on performance, but more recent trends have favored HSDPA.

Australia - Telstra announced that its CDMA-EVDO network would be replaced with a HSDPA network [NextG], offering high speed internet, mobile television and traditional telephony and video calling.
Canada - Rogers Wireless deployed HSDPA system 850/1900 April 1, 2007.
South Korea - currently the only country boasting nationwide HSDPA

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