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

2. 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

3. HSDPA Technology 3 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. Cellular Networks evolution

4. HSDPA Technology 4 UMTS Network Architecture

5. 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

6. 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

7. 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

8. 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)

9. 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

10. HSDPA Technology 10 HS Channel Extension (cont.) 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-DPCCH: CQI HS-SCCH: DL Transfer Information HS-DSCH: Data transmission HS-DPCCH: ACK/NACK HS Channels

11. 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)

12. 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

13. 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.

14. 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)

15. 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 decisionNode B instead of RNC

16. 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)

17. 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)

18. 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

19. 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

20. 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.