High-Speed Downlink Packet Access
From Free net encyclopedia
Template:Table Mobile phone standards High-Speed Downlink Packet Access (HSDPA) is a new mobile telephony protocol and is sometimes referred to as a 3.5G (or "3½G") technology. In this respect it extends WCDMA in the same way that EV-DO extends CDMA2000. HSDPA provides a smooth evolutionary path for Universal Mobile Telecommunications System (UMTS) networks allowing for higher data capacity. It is an evolution of the W-CDMA standard, designed to increase the available data rate by a factor of 5 or more. HSDPA defines a new W-CDMA channel, the high-speed downlink shared channel (HS-DSCH) that operates in a different way from existing W-CDMA channels, but is only used for downlink communication to the mobile.
The HS-DSCH channel does away with two basic features of other WCDMA channels - the variable spreading factor and fast power control - and instead uses Adaptive Modulation and Coding (AMC), fast scheduling at the Node B (Base Station) and fast retransmissions to deliver the improved downlink performance. The concept of incremental redundancy is used, where retransmissions contain different codings of the user data, relative to the orignal transmission. When a corrupted packet is received, the user device saves it, and combines it with subsequent retransmissions, to formulate an error-free packet as quickly and efficiently as possible. Even if the retransmitted packet(s) is itself corrupted, the combination of the sum of the errored transmissions can yield an error-free packet.
The HS-DSCH downlink channel is shared between users using channel-dependent scheduling to take advantage of favourable channel conditions to make best use of available radio conditions. Each user device periodically transmits (as many as 500 times per second) an indication of the downlink signal quality. The Node B uses this information received from all user devices to decide which users will be sent data on the next 2 ms frame and, for each user, how much data should be attempted. More data can be sent to users which report high downlink signal quality.
The amount of the channelisation code tree, and thus network bandwidth, allocated to HSDPA users is determined by the network. The allocation is "semi-static" in that it can be modified while the network is operating, but not on a frame-by-frame basis. This allocation represents a tradeoff between bandwidth allocated for HSDPA users, versus that for voice and non-HSDPA data users. The allocation is in units of channelisation codes for Spreading Factor 16, of which 16 exist, and of which up to 15 can be allocated to HSDPA.
When the Node B decides which users will receive data on the next 2 ms frame, it also determines which channelisation code(s) will be employed for each user, and this information is sent to the user devices over one or more HSDPA "scheduling channels" (these scheduling channels are not part of the HSDPA allocation previously mentioned, but are allocated separately). Thus, for a given 2 ms frame, data may be sent to a number of users simultaneously, using different channelisation code. The maximum number of users to receive data on a given 2 ms frame is determined by the number of allocated channelisation codes. This differs from CDMA 1xEV-DO, where data is sent to only one user at a time.
Although 3G is not available in most countries, this protocol does have a chance to become the follow up to 3G where WCDMA is deployed. Its success as a GSM-replacement, vis-à-vis other contenders like CDMA2000 1x or CDMA2000 1xEV-DO and cellular datacommunication standards like WiMAX (IEEE 802.16) is still unclear, especially considering that KDDI's CDMA2000 is generally considered as being much more successful and smooth than DoCoMo's and Vodafone's UMTS/W-CDMA introduction in Japan, which are much slower than initially hoped.
Deployment
Cingular began to deploy UMTS with expansion to HSDPA in eighteen markets on 1 December 2005. By year end 2006, Cingular will have UMTS service in the top 100 markets in the United States.
Cingular announced availability of HSDPA at speeds of 400-700 kbit/s in 16 cities on 6 December 2005, under the brand name "BroadbandConnect". Cingular faces competitive pressure from operators such as Verizon Wireless and Sprint who use a competing 3G technology, 1xEV-DO, and who have already deployed a similar high speed data service.
In Czech Republic, T-Mobile UMTS TDD with HSDPA from IPWireless as "4G Internet" from 1 October 2005.
In Japan, KDDI has been commercially deploying 3.5G services based on a nationwide 1xEV-DO network since December 2003. Docomo has recently announced (2005) that it will introduce HSDPA from 2006.
In Germany, T-Mobile officially introduced its HSDPA service at the CeBIT 2006 (9 March - 15 March 2006).
In Italy, TIM, Vodafone and 3 will introduce their HSDPA service in mid 2006.
In Sweden, 3 will introduce HSDPA service in Spring 2006.
In the Netherlands, T-Mobile will introduce HSDPA service mid 2006, according to their technical support callcenter.
In Austria, T-Mobile started HSDPA deployments in fall of 2005 and will open the network upgrade for public use in March 2006. Mobilkom Austria launched HSDPA on January 23 2006.
In Canada, Rogers Wireless has announced (13 February 2006) that it will complete the HSDPA trials with Ericsson in March 2006 and its commercial launch will take place as early as Fall 2006.
In South Korea, SK Telecom has announced that it will commercialize HSDPA service by April 2006. KTF will commercialize HSDPA by June 2006.
In the United Kingdom, O2 has announced (20 October 2005) deployment of HSDPA on the Isle of Man on 1 November 2005. Vodafone has announced it will launch services in mid-April 2006.
In South Africa, Vodacom, MTN HSDPA will be commercially available from 2 April 2006 on the Vodacom Network and has been available from 22 March 2006 on the MTN Network.
In the Philippines, Globe Telecom used its 3G and HSDPA facilities during the 23rd SEA Games.
In Australia, Telstra announced plans on the 15 November 2005 for the rollout of a new national 3G/WCDMA network with HSDPA which is expected to be operational by the end of 2006. In 2007 it is expected to reach 98% of the Australian population.
In Switzerland, Swisscom has announded (22 February, 2006), that they will provide coverage in Berne, Geneva and Zurich by mid-2006. Swisscom also announced a 5 in 1 card HSDPA/UMTS/EDGE/GPRS and WLAN and two Notebooks by Fujitsu and Acer that have the technology built-in.
In Israel, Partner has announced (March 8, 2006) deployment of 3.5G, and will offer phones and computers with built-in HSDPA capability.
In Portugal, Optimus Telecomunicações, S.A., Telecomunicações Móveis Nacionais, SA and Vodafone have announced the release of a HSDPA product for the beginning of April, 2006.
In Spain Movistar and Amena started tests at Barcelona in coincidence of the 3GSM World Congress, February 2006, and Vodafone has started tests in the city of Salamanca on March, 2006.
In Finland, telecom operator Elisa Oyj launched (6 April, 2006) the first commercial High Speed Downlink Packet Access (HSDPA) network in the Nordic Countries. The solution, provided by Nokia, is implemented in the whole of Elisa's 3G network in Finland.
In Malaysia, MAXIS Communications Bhd announced in April 2006 that it has full integrated HSPDA into its 3G network and anticipates HSPDA service by the end of 2006.
See also
External links
- HSDPA Info and resources
- HSDPA in Africa
- HSDPA Wireless Internet News
- HSDPA Test Equipmentcs:High-Speed Downlink Packet Access
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