High Speed Downlink Packet Access (HSDPA)
The first step required to upgrade WCDMA to HSPA is to improve the downlink by introducing HSDPA. The improved downlink provides up to 14 Mbit/s with significantly reduced latency. The improvement in speed and latency reduces the cost per bit and enhances support for high-performance packet data applications.
HSDPA is based on shared channel transmission and its key features are shared channel and multi-code transmission, higher-order modulation, short Transmission Time Interval (TTI), fast link adaptation and scheduling along with fast Hybrid Automatic Repeat reQuest (HARQ).
The upgrade to HSDPA is often just a software update for most WCDMA networks, and as of May 2008 90 percent of WCDMA networks have been upgraded to HSDPA.
Voice calls are usually prioritized over data transfer.
Singapore's three network providers M1, StarHub and SingTel provide up to 28 Mbit/s throughout the entire island. The Australian provider Telstra provides up to 14.4 Mbit/s nationwide and up to 42Mbit/s in selected areas. The Croatian VIPnet network supports a downlink speed of 7.2 Mbit/s, as does Rogers Wireless in Canada which also supports 21 Mbit/s in the Toronto area. In South Korea, a nationwide 7.2 Mbit/s coverage is now established by SK Telecom and KTF. In Hong Kong, PCCW, CSL and Hutchinson 3 provide 21 Mbit/s coverage and, BPL, MTS and Tata DoCoMo provide speed of 21.1 Mbit/s nationwide while Reliance ADAE provides speeds up to 28.8 Mbit/s nationwide. Sri Lankan companies like Mobitel, Etisalat provides upto 42Mbit/s and Dialog, Airtel and Hutch provides 7.2 Mbit/s. In Brazil, the four biggest network providers offer up to 1 Mbit/s downlink speeds.
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