BY AXXO

TZU TA’ readers (Guatemala).

Nothing much this time. Post 4G and 3.5G in my articles, I’m going to end it here on 3.75G.

3.75G, also known as High-Speed Uplink Packet Access (HSUPA), is a 3G mobile telephony protocol in the HSPA family with up-link speeds up to 5.76 Mbit/s. The name HSUPA was created by Nokia. The 3GPP does not support the name ‘HSUPA’, but instead uses the name Enhanced Uplink (EUL).

The specifications for HSUPA are included in Universal Mobile Telecommunications System Release 6 standard published by 3GPP. - “The technical purpose of the Enhanced Uplink feature is to improve the performance of uplink dedicated transport channels, i.e. to increase capacity and throughput and reduce delay.”

DESCRIPTION

HSUPA uses an uplink enhanced dedicated channel (E-DCH) on which it will employ link adaptation methods similar to those employed by HSDPA, namely:
Higher-order modulation

• Shorter Transmission Time Interval enabling faster link adaptation;
• HARQ (Hybrid Automatic Repeat-reQuest) with incremental redundancy making retransmissions more effective.

Similarly to HSDPA, HSUPA uses a packet scheduler, but it operates on a request-grant principle where the UEs request a permission to send data and the scheduler decides when and how many UEs will be allowed to do so. A request for transmission contains data about the state of the transmission buffer and the queue at the UE and its available power margin. However, unlike HSDPA, uplink transmissions are not orthogonal to each other.

In addition to this scheduled mode of transmission the standards also allows a self-initiated transmission mode from the UEs, denoted non-scheduled. The non-scheduled 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.

Each MAC-d flow (i.e. QoS flow) is configured to use either scheduled or non-scheduled modes; the UE adjusts the data rate for scheduled and non-scheduled flows independently. The maximum data rate of each non-scheduled flow is configured at call setup, and typically not changed frequently. The power used by the scheduled flows is controlled dynamically by the Node B through absolute grant (consisting of an actual value) and relative grant (consisting of a single up/down bit) messages.

At Layer 1, HSUPA introduces new physical channels E-AGCH (Enhanced-Absolute Grant CHannel), E-RGCH (Enhanced-Relative Grant CHannel), F-DPCH (Fractional - Dedicated Physical CHannel), E-HICH (E-DCH Hybrid ARQ Indicator CHannel), E-DPCCH (E-DCH Dedicated Physical Control CHannel) and E-DPDCH (E-DCH Dedicated Physical Data CHannel).

E-DPDCH is used to carry the E-DCH Transport Channel; and E-DPCCH is used to carry the control information associated with the E-DCH.

DIFFERENCES

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

HSUPA connects the advantages of UMTS - a wide network coverage in the final development and an application for use while on the move (eg, 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.

Next week, we start afresh. I have something forming in my head. Let’s see.

Till then, baaya mam.