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Survey on High Speed Downlink Packet Access (HSDPA) Technology

Survey on High Speed Downlink Packet Access (HSDPA) Technology . Chaoyi Chen April. 17, 2007. Agenda. HSDPA introduction Improvements HSDPA Evolution Key technologies High Speed Channel extension HS-DSCH HS-SCCH/HS-DPCCH Adaptive Modulation and Coding (AMC)

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Survey on High Speed Downlink Packet Access (HSDPA) Technology

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  1. Survey on High Speed Downlink Packet Access (HSDPA) Technology Chaoyi Chen April. 17, 2007 HSDPA Technology

  2. Agenda • HSDPA introduction • Improvements • HSDPA Evolution • Key technologies • High Speed Channel extension • HS-DSCH • HS-SCCH/HS-DPCCH • Adaptive Modulation and Coding (AMC) • Adaptive Modulation: QPSK/16QAM • Adaptive Coding • Fast packet scheduling at the Node B • Scheduler algorithms • Hybrid Automatic Repeat Request (HARQ) • References HSDPA Technology

  3. Cellular Networks evolution HSDPA Introduction • Urged by the need for high data rate applications (e.g. rich multimedia), especially for the downlink. • A combination of technologies that provides a smooth evolutionary path for UMTS-based networks allowing for higher data transfer speeds. • Part of the UMTS release 5 and actually an evolution of WCDMA technology. HSDPA Technology

  4. UMTS Network Architecture HSDPA Technology

  5. HSDPA Introduction (cont.) • Small changes to existing architectures – cost effective • Upgrades mainly happens in Access Network (NodeB and RNC) • No Core Network Impacts • New handset terminals will be required to support HSDPA HSDPA Technology

  6. HSDPA Improvements • Higher downlink peak data rate (14.4Mbps), also accompanies an higher uplink data rate (384Kbps) • Reduce latency, improving the round trip time for applications – 70ms in HSDPA • Increase network capacity – at least twice as many subscribers per cell should be supported with HSDPA HSDPA Technology

  7. HSDPA Evolution • First Phase (our focus today) • Specified in 3GPP release 5 • Aim to achieve peak data rates of 14.4Mbps • Technologies include AMC, HARQ, hs-DSCH etc. • Second Phase • Specified in the upcoming 3GPP release 7, part of HSPA Evolved (HSDPA+HSUPA) • Aim to achieve peak data rates of 42 Mbps • Technologies include beamforming and MIMO • HSOPA (High Speed OFDM Packet Access ) • Specified in 3GPP release 8 • Aim to achieve data rates of up 200Mbps for DL and 100Mbps for UL • Technologies include OFDMA modulation HSDPA Technology

  8. HSDPA Key Technologies • High Speed Channel extension • Adaptive Modulation and Coding (AMC) • Fast packet scheduling at the Node B • Hybrid Automatic Repeat Request (HARQ) HSDPA Technology

  9. High Speed Channel Extension • In UMTS Release99, DCH is the basic channel for voice and data transmission (each user assigned one DCH), along with FACH and DSCH • HSDPA Channels: • New transport channel – HS-DSCH (each HS-DSCH can be used by multiple users) • New control channel – HS-SCCH and HS-DPCCH • HS-SCCH: DL Transfer Information • HS-DPCCH: UL ACK/NACK, CQI • New physical channel – HS-PDSCH • This is the physical channel mapped to the HS-DSCH transport channel that carries actual user data HSDPA Technology

  10. HS Channel Extension (cont.) HS-DPCCH: CQI • In UMTS Release5, HS channel doesn’t totally replace DCH • Always operated with DCH running in parallel • CS data still run on DCH instead of HS-DSCH HS-SCCH: DL Transfer Information HS-DSCH: Data transmission HS-DPCCH: ACK/NACK HS Channels HSDPA Technology

  11. HSDPA Key Technologies • High Speed Channel extension • Adaptive Modulation and Coding (AMC) • Fast packet scheduling at the Node B • Hybrid Automatic Repeat Request (HARQ) HSDPA Technology

  12. Adaptive Modulation and Coding • DL block size, modulation type and number of codes are dynamically changed according to the channel condition • Adaptive modulation: • 16QAM is added in addition to QPSK (variable rate and power) • Optional support for 64QAM based on 3GPP TS 25.855 • Adaptive coding: • Coding rate of ¼ and ¾ and are added in addition of 1/3 • 5, 10 or 15 multi-codes: • The HS-DSCH channel uses a constant spreading factor of 16 for code multiplexing • A maximum of 15 parallel codes can be allocated to one user or split across several users HSDPA Technology

  13. AMC (cont.) • Node B determines different combination, based on Channel Quality Indicator (CQI), which is reported by UE every 2ms (TTI). • CQI is not the only determinant factor, QoS, UE capability and user priority are also taken into account. HSDPA Technology

  14. HSDPA Key Technologies • High Speed Channel extension • Adaptive Modulation and Coding (AMC) • Fast packet scheduling at the Node B • Hybrid Automatic Repeat Request (HARQ) HSDPA Technology

  15. Fast Scheduling in Node B • The scheduler is a key element of HSDPA that determines the overall behavior of the system • Each user device periodically (500 times per second) transmits an indication of the downlink channel quality • For each TTI of 2ms (previous shortest 10 ms in UMTS): • Determines which terminals the HS-DSCH should be transmitted to • AMC decision • The scheduler is now located at the Node B instead of RNC – more quickly track the UE channel condition and make AMC decision HSDPA Technology

  16. Fast Scheduling in Node B (cont.) • Scheduler algorithms (types of scheduler can be configured by operator per Node B): • Round Robin (RR) • FIFO scheme • High degree of fairness/Low overall system throughput • Maximum Carrier to Interference (C/I) • Schedules users with the highest C/I during the current TTI (select UEs with highest CQI) • No effort to maintain fairness/Highest system throughput • Proportional Fair (PF) • Tradeoff between RR and max C/I • Selects UEs with highest ratio of instantaneous over average rate max{Ri(t)/R(t)} (Ri(t) denotes the amount of data that can be transmitted to the UE i according to the most recent CQI) HSDPA Technology

  17. HSDPA Key Technologies • High Speed Channel extension • Adaptive Modulation and Coding (AMC) • Fast packet scheduling at the Node B • Hybrid Automatic Repeat Request (HARQ) HSDPA Technology

  18. Hybrid ARQ • ARQ • a mechanism which allows the receiver to request retransmissions of erroneous received packets • HARQ • a combination of ARQ and error correcting code • HSDPA HARQ • combines retransmission with the original transmission – “incremental redundancy” (increase UE complexity) • retransmission blocks can be constructed with different coding rate, not just the same as original blocks HSDPA Technology

  19. HARQ (cont.) • The functionality is moved from RNC to Node B, thus reduce the delay, faster the retransmission and fast response with the channel condition • HARQ retransmission protocol is implemented in MAC layer instead of RLC layer – further decrease delay Radio interface protocol stack HSDPA Technology

  20. References • [1] 3GPP TS 25.855 High Speed Downlink Packet Access (HSDPA); Overall UTRAN description. • [2] 3GPP TS 25.876 Multiple-Input Multiple-Output Antenna Processing for HSDPA. • [3] 3GPP TS 25.877 High Speed Downlink Packet Access (HSDPA) - Iub/Iur Protocol Aspects. • [4] 3GPP TS 25.890 High Speed Downlink Packet Access (HSDPA); User Equipment (UE) radio transmission and reception (FDD). • [5] QUALCOMM CDMA Technologies white paper, “HSDPA for Improved Downlink Data Transfer”, October 2004. • [6] M. Chatterjee, G.D. Mandyam, S.K. Das. “Fast ARQ in High Speed Downlink Packet Access for WCDMA Systems,” Proc. Of European Wireless, pp 451-457, Feb. 2002. • [7] Hari Holma and Antti Toscala, “WCDMA for UMTS,” edited at Wiley & Sons, Ltd, 2002. HSDPA Technology

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