I-HSPA overview - HSPA Basics

Transcription

1 I-HSPA overview - HSPA Basics Nokia Siemens Networks 1 (13)

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3 Table of Contents: 1 Introduction HSDPA 1/ HSDPA 2/ HSDPA 3/ HSDPA 4/ Exercise HSUPA 1/ HSUPA 2/ Exercise HSPA Evolution Nokia Siemens Networks 3 (13)

4 1 Introduction I-HSPA can take full benefit of existing high speed downlink packet access (HSDPA) and high speed uplink packet access (HSUPA). In this section, we will familiarise ourselves with these two important technologies. HSDPA and HSUPA are together generally referred to as high speed packet access (HSPA). HSDPA increases the peak data rate in the downlink direction from 384 kbit/s to up to the theoretical maximum of 14.4 Mbit/s and is especially designed to handle bursty packet traffic in the downlink in an efficient and flexible manner. HSUPA specifies a similar kind of functionality in the uplink as HSDPA specifies in the downlink. HSUPA makes it possible to achieve up to 5.76 Mbit/s data rates in the uplink. The introduction of HSDPA and HSUPA mainly affects network elements in the radio access network (RAN), such as the radio network controller (RNC), base transceiver station (BTS), and user equipment (UE). Nokia Siemens Networks 4 (13)

5 2 HSDPA 1/4 The basic features of HSDPA are: Dynamic link adaptation Fast packet scheduling Fast retransmission. Dynamic link adaptation means that the modulation scheme and coding rate, as well as the number of parallel codes in downlink, are dynamically changed according to the channel quality information (CQI) received from the UE. Fast packet scheduling enables link adaptation, retransmission and priority choices in the BTS based on the information from the UE and RNC. The round-robin scheduling principle and the proportional fair resource scheduler types can be used as the packet scheduler. It is also possible that the packet scheduler is shared between cells in a cell group. The data retransmissions are primarily handled in HSDPA by the BTS in the physical layer, and based on a process called Hybrid Automatic Repeat request (HARQ). RLC layer and TCP layer retransmissions may also still be used, if required. Nokia Siemens Networks 5 (13)

6 3 HSDPA 2/4 HSDPA introduces one new transport channel and three new physical channels. There must also exist an associated Dedicated Channel (DCH) for each user connection to be used in parallel with the HSDPA channels. The new transport channel is called High-speed Downlink Shared Channel (HS- DSCH). The three physical channels are: The High Speed Physical Downlink Shared Channel (HS-PDSCH) in the downlink. The High Speed Shared Control Channel (HS-SCCH) in the downlink. The High Speed Dedicated Physical Control Channel (HS-DPCCH) in the uplink. The actual user data is carried over the HS-DSCH that is mapped to the corresponding HS-PDSCH. Unlike a DCH, the HS-PDSCH does not use fast power control and neither are soft handovers supported. The HS-SCCH is always used together with the HS-PDSCH in the downlink. It carries the control information necessary for the UE to decode and demodulate the data that is sent over the HS-PDSCH in the current transmission time interval. The HS-DPCCH carries control information from the user equipment to the BTS such as acknowledge information and the Channel Quality Indicator (CQI) values. Nokia Siemens Networks 6 (13)

7 4 HSDPA 3/4 The HS-PDSCH is shared between all active HSDPA users in the cell. This means that the users are multiplexed in the time domain. Thus, each 2 ms transmission time interval (TTI) or time slot is reserved for a single user. The HS-PDSCH can utilise up to 15 HS-PDSCH codes simultaneously for a single user, provided the BTS and UE can handle this number of codes. If code multiplexing is supported in the BTS, up to three users can be served simultaneously in a single transmission time interval. Obviously, the combined number of HS-PDSCH codes cannot exceed the maximum limit of 15 codes also in this case. Nokia Siemens Networks 7 (13)

8 5 HSDPA 4/4 HSDPA makes it possible to achieve high data bit rates. The theoretical maximum data rate is 14.4 Mbit/s based on the 3GPP release 5 specification. The maximum data rate can be achieved only if: all 15 HS-PDSCH codes are used the modulation used is 16 QAM the coding rate is three input bits to four output bits, usually written as 3/4 it is possible to use almost the whole downlink capacity for this connection (leaving very little capacity for other traffic) Nokia Siemens Networks 8 (13)

9 6 Exercise Nokia Siemens Networks 9 (13)

10 7 HSUPA 1/2 High Speed Uplink Packet Access (HSUPA) meets the HSDPA packet access capabilities in the uplink by introducing two new techniques: Fast hybrid automatic repeat request (HARQ) retransmissions in the physical layer between the UE and BTS, and fast packet scheduling performed in the BTS instead of the RNC. In the uplink, the HSUPA packet data is carried in a new transport channel called Enhanced Dedicated Channel (E-DCH) and there are two related physical channels: The E-DCH Dedicated Physical Data Channel (E-DPDCH), which carries one transport block of user data The E-DCH Dedicated Physical Control Channel (E-DPCCH), which carries physical layer related control information. There are also three new physical channels in the downlink: The E-DCH Absolute Grant Channel (E-AGCH) The E-DCH Relative Grant Channel (E-RGCH) The E-DCH Hybrid ARQ Indication Channel (E-HICH). Unlike the HS-DSCH in the downlink in HSDPA, the E-DCH in HSUPA supports intra-bts softer handovers and even inter-bts soft handovers. Nokia Siemens Networks 10 (13)

11 8 HSUPA 2/2 Based on 3GPP simulation information, HSUPA increases the system capacity by 50% - 70%, reduces end user packet delay by 20 % - 55% and increases the user packet data throughput by 50 %. The theoretical maximum data rate in HSUPA is 5.76 Mbit/s. Nokia Siemens Networks 11 (13)

12 9 Exercise Nokia Siemens Networks 12 (13)

13 10 HSPA Evolution HSPA evolution consists of several radio related enhancements in 3GPP releases 7 and 8 which will include: Multiple Input / Multiple Output (MIMO), which means improving system capacity and spectral efficiency by deploying multiple antennas at both the UE and the BTS. Downlink higher order modulation using 64QAM for HSDPA Uplink higher order modulation using 16QAM for HSUPA Nokia Siemens Networks 13 (13)