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High-Speed Uplink Packet Access (HSUPA) is a data access protocol for mobile phone networks with extremely high upload speeds up to 5.76 Mbit/s . Similar to HSDPA (High-Speed Downlink Packet Access), HSUPA is considered 3.75G. The specifications for HSUPA are still under development ( July 2005 ) and will be included in Universal Mobile Telecommunications System Release 6. It will be published on www.3GPP.org . TECHNOLOGY HSUPA is expected to use an uplink ''enhanced dedicated channel'' (E-DCH) on which it will employ link adaptation methods similar to those employed by HSDPA, namely:
Similarly to HSDPA there will be a ''packet scheduler'', but it will operate on a ''request-grant'' principle where the UE s request a permission to send data and the schedular decides when and how many UEs will be allowed to do so. A request for transmission will contain data about the state of the transmission buffer and the queue at the UE and its available power margin. In addition to scheduled transmissions the standards also forsee a self-initiated transmission mode from the UEs - this mode can for example be used for VoIP services for which even the reduced TTI and the Node-B based scheduler will not be able to provide the very short delay time and constant bandwidth required. The standard foresees two basic scheduling methods: Long term grants are issued to several terminals which can then send their data simultaneously. The grants are increased or decreased according to the current load of the cell and the requirements of the terminals. Short term grants on the other hand are an alternative scheduling method to allow multiplexing terminals in the time domain instead of the code domain as is done for the long term scheduling. In order to allow multiplexing uplink transmissions of several terminals in both code and time domain the scrambling and channelisation codes are not shared between differents terminals like this is done in HSDPA on a shared downlink channel. Since in the uplink the DPDCH and DPCCH are code-multiplexed and transmitted simultaneously in time, the ratio of their transmit powers is important for the achievable pay-load bit rates. When a larger part of the UE's power is assigned to DPDCH, the payload bit rate achievable on that channel increases. Conversely, less power is left for DPCCH and transmission of signalling on that channel becomes less reliable. In UMTS Release'99 the ratio between the power of DPDCH and DPCCH was set to a constant. In HSUPA this ratio will be controlled by the Node-B. In HSUPA, unlike in HSDPA, soft and softer handovers will be allowed for packet transmissions. The control of UE's transmit power in soft/softer handover on E-DCH will be slightly different from that specified in Release'99 for DCH, namely: the main serving Node-B will be able to issue both ''power-up'' and ''power-down'' commands but all other Node-Bs participating in the handover will be able to issue only ''power-down'' commands. A power-down command will always have precedence over a power-up command. Another difference with HSDPA is that HSUPA will not use of the modulated signal, which requires transmitter amplifiers with greater linear range in their Amplitude Response (also called Dynamic Range ). Such amplifiers are less energy efficient – to produce the same output power they ''on average'' draw larger current, which in the case of a mobile would come from its battery and reduce its Talk Time . This would not be acceptable for HSUPA since the subscribers expect from any new technology to offer longer talk times. Hence it was decided for HSUPA to keep the presently standard UMTS modulation ( QPSK ), which has lower peak-to-average ratio. In HSDPA and other Downlink technologies the transmitter is at the Base Station and its power supply is not limited in time, but more importantly the dynamic range of its amplifier is inherently greater, which made the choice of higher-order modulations more attractive. DEPLOYMENT In Austria , T-Mobile is planning to introduce HSUPA in 2007 or 2008 . In Italy , Telecom Italia is planning to introduce HSUPA in 2007 . SEE ALSO EXTERNAL LINKS
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