High Speed Packet Access

High Speed Packet Access (HSPA) is a collection of two mobile telephony protocols High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), that extend and improve the performance of existing WCDMA protocols. A further standard, Evolved HSPA (also known as HSPA+), is soon to be released.

Overview

HSDPA and HSUPA provide increased performance by using improved modulation schemes and by refining the protocols by which handsets and base stations communicate. These improvements lead to a better utilization of the existing radio bandwidth provided by WCDMA.

HSPA improves the end-user experience by increasing peak data rates up to 14 Mbit/s in the downlink and 5.8 Mbit/s in the uplink. It also reduces latency and provides up to five times more system capacity in the downlink and up to twice as much system capacity in the uplink, reducing the production cost per bit compared to original WCDMA protocols. HSPA increases peak data rates and capacity in several ways:

* Shared-channel transmission, which results in efficient use of available code and power resources in WCDMA
* A shorter Transmission Time Interval (TTI), which reduces round-trip time and improves the tracking of fast channel variations
* Link adaptation, which maximizes channel usage and enables the base station to operate close to maximum cell power
* Fast scheduling, which prioritizes users with the most favorable channel conditions
* Fast retransmission and soft-combining, which further increase capacity
* 16QAM (Quadrature Amplitude Modulation), which yields higher bit-rates

HSPA has been commercially deployed by over 200 operators in more than 80 countries.

Many HSPA rollouts can be achieved by a software upgrade to existing 3G networks, giving HSPA a headstart over WiMax, which requires dedicated network infrastructure. Rich variety of HSPA enabled terminals, more than 1000 available today together with ease of use gives rising sales of HSPA-enabled mobiles and are helping to drive the HSPA.

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 channel 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 (ARQ).

The upgrade to HSDPA is often just a software update for most WCDMA networks, and as of JuneApril 2008, the Global mobile Suppliers Association (GSA) reported that 90.88 percent of all WCDMA networks are upgraded to HSDPA. With HSDPA mobile broadband becomes a reality and users can download files, read mails and browse web pages with the same end user experience as of fixed broadband.

Majority of deployments provide up to 7.2 Mbit/s in the down-link and 14 Mbit/s will be available as soon as the devices are available in the market.

Voice calls are usually prioritized over data transfer. The Australian provider, Telstra uses up to 14.4 Mbit/s nationwide. The Croatian VIPnet network supports the speed of 7.2 Mbit/s in down-link as does Rogers Wireless in Canada. In South Korea, a nationwide 7.2 Mbit/s coverage is now established by SK Telecom and KTF. In Hong Kong, PCCW and Smartone-Vodafone also provide 7.2 Mbit/s coverage. In Portugal all the mobile phone operators support 7.2 Mbit/s HSDPA, and the Sri-Lankan companies Airtel Pvt Ltd and Mobitel Pvt Ltd also provide 7.2 Mbit/s in the Asian region.

See full list of HSDPA networks committed and in service.

High Speed Uplink Packet Access (HSUPA)

The second major step in the WCDMA upgrade process is to upgrade the uplink, which is introduced in 3GPP Release 6. Upgrading to HSUPA is often only a software update. Enhanced Uplink adds a new transport channel to WCDMA, called Enhanced Dedicated Channel (E-DCH). An enhanced uplink creates opportunities for a number of new applications including VoIP, uploading pictures and sending large e-mails. The enhanced uplink increases the data rate (up to 5.8 Mbit/s), and the capacity, and also reduces latency. The enhanced uplink features several improvements similar to those of HSDPA, such as multi code transmission, short Transmission Time Interval (TTI), fast scheduling and fast hybrid Automatic Repeat reQuest (ARQ).

In Singapore, Starhub announced a 1.9 Mbit/s HSUPA Service as part of its new MaxMobile plan in 1 August 2007. In Finland, Elisa announced on 30 August 2007 1.4 Mbit/s HSUPA to most large cities with plans to add the service to its whole 3G network within months. 3 Italia and Ericsson announced on 16 July 2008 the successful tests of HSUPA 5.8 Mbit/s in the live network of 3 Italia.

Evolved High Speed Packet Access (HSPA+)

Evolved HSPA (also known as: HSPA Evolution, HSPA+, I-HSPA or Internet HSPA) is an upcoming wireless broadband standard defined in 3GPP release 7 and 8 of the WCDMA specification. Evolved HSPA provides data rates up to 42 Mbit/s in the downlink and 11 Mbit/s in the uplink (per 5MHz carrier) with multiple input, multiple output (MIMO) technologies and higher order modulation.

Dual-Cell HSDPA (DC-HSDPA)

Dual-Cell HSDPA, part of 3GPP Release 8, is the natural evolution of HSPA by means of carrier aggregation. An HSPA+ network can theoretically support up to 28Mbit/s and 42Mbit/s with a single 5MHz carrier for Rel7 (MIMO) and Rel8 (Higher Order Modulation + MIMO), in good channel condition with low correlation between transmit antennas. Alternatively DC-HSPA can be used from Release 8 where the MAC scheduler can allocate two HSPA carrier in parallel and double the bandwidth from 5MHz to 10MHz. Besides the throughput gain from double the bandwidth, some diversity and joint scheduling gains can also be expected. This can particularly improve the QoS for end users in poor environment conditions that can not gain from MIMO and Higher Modulation only. From Release 9 onwards it will be possible to use DC-HSDPA in combination with MIMO used on both carrier. The support of MIMO in combination with DC-HSDPA will allow operators deploying Release 7 MIMO to benefit from the DC-HSDPA functionality as defined in Release 8.

Dual-Cell HSUPA (DC-HSUPA)

Similar enhancements as introduced with DC-HSDPA in the downlink for UMTS Release 8 are being standardized for UMTS Release 9 in the uplink called Dual-Cell HSUPA. DC-HSUPA will have similar limitations, for instance that the carriers have to belong to the same Node-B and have to be adjacent. Furthermore, it is assumed that at least 2 carriers are configured simultaneously in the downlink and have the same duplex distance to the uplink. The dual carrier transmission will only be applied to HSUPA UL physical channels and DPCCH. The standardisation of Release 9 is expected to be completed in December 2009.

Multi-carrier HSPA (MC-HSPA)

While the aggregation of more than two carriers has been studied the 3GPP specification does not yet allow this option. Nevertheless it seems likely that such option will be added at a later state of the technology.

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