High Speed Uplink Packet Access (HSUPA) is a UMTS / WCDMA uplink evolution technology currently being standardised in 3rd Generation Partnership Project (3GPP); HSUPA is expected to be standardised by the 3GPP in UMTS Release 6.
The new HSUPA mobile telecommunications technology is directly related to HSDPA and the two are complimentary to one another. It seems that HSDPA is the more advanced of the two technologies, but when they can function side-by-side the resulting system will benefit with major data transfer speed enhancements for receiving or sending.
Both procedures resemble each other technically and, by the employment of special modulation procedures, allow a better use of the net infrastructure. The power spectrum of the UMTS network may be enhanced at relatively small expenditure. Improved intensive data services can then be offered. Thus HSUPA opens further areas for innovations and new business possibilities.
HSDPA and HSUPA both offer high voice and data performance and together will enable the success of mass-market mobile IP multimedia. HSUPA enhances the uplink speed of UMTS / WCDMA networks and is the next step after HSDPA.
HSUPA will enhance advanced person-to-person data applications with higher and symmetric data rates, like mobile e-mail and real-time person-to-person gaming. Traditional business applications along with many consumer applications will benefit from enhanced uplink speed. HSUPA will initially boost the UMTS / WCDMA uplink up to 1.4Mbps and in later releases up to 5.8Mbps.
HSUPA - THE TECHNOLOGY OF 3.75G AND 4G
HSUPA is a data access protocol for mobile phone networks which is considered to be 3.75G or sometimes 4G. One of its earliest deployments will be in Austria where T-Mobile is planning to introduce the technology in 2007 or 2008. UbiNetics, a US company specialising in WCDMA and HSDPA terminal and test and measurement technology, has added support for HSUPA to its highly regarded TM500 Test Mobile product (function added in mid-2005). This will help the roll out of HSUPA 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 including:
- Higher-order modulation in addition to the existing Quadrature Phase Shift Keying (QPSK) - a phase modulation algorithm - and 16-QAM (Quadtrative Amplitude Modulation) (four amplitudes and four phases) might be used enabling higher data rates under favourable radio conditions (i.e. over less noisy channels)
- Shorter TTI (Transmission Time Interval) enabling faster link adaptation
- HARQ (Hybrid ARQ (Automatic Repeat reQuest)) with incremental redundancy making retransmissions more effective
Similarly to HSDPA, there will be a packet schedular, but it will operate on a request-grant principle where the UE (User Equipment) requests permission to send packets and the scheduler 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, the queue at the UE and its available power margin.
In addition to scheduled transmissions a provision may be made for self-initiated transmissions from the UE - this can 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 required.
ENHANCEMENTS OF HSUPA OVER HSDPA
While the transmissions from the different UEs connected to the same Node-B will be sequential in time, like on a shared channel, the scrambling and channelisation codes will not be shared between them as is done in HSDPA on a shared downlink channel.
Because in the uplink the DPDCH (Dedicated Physical Data Channel) and DPCCH (Dedicated Physical Control Channel) are code-multiplexed and transmitted simultaneously in time, the ratio of their transmit powers is important for the achievable payload bit rates. The greater part of the UE's power is assigned to DPDCH the higher the pay-load bit rate achievable on that channel but the less power is left for DPCCH and the less reliable the signalling in the link. 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 the 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.
ADVANTAGES AND INTRODUCTION OF HSUPA
HSUPA connects the advantages of UMTS - a wide network coverage in the final development and an application for use while on the move (e.g., driving vehicles). The system will have the advantages of radio-based local networks and WLAN in providing inexpensive broadband Internet. HSUPA should also be relatively inexpensive, because it is based on software. No new infrastructure needs to be developed or installed by the mobile network providers. Their network equipment need only be updated with new software.