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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

Survey on High Speed Downlink Packet Access (HSDPA) Technology

Chaoyi Chen

April. 17, 2007

HSDPA Technology

agenda
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

hsdpa introduction

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

hsdpa introduction cont
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

hsdpa improvements
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

hsdpa evolution
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

hsdpa key technologies
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

high speed channel extension
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

hs channel extension cont
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

hsdpa key technologies11
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

adaptive modulation and coding
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

amc cont
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

hsdpa key technologies14
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

fast scheduling in node b
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

fast scheduling in node b cont
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

hsdpa key technologies17
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

hybrid arq
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

harq cont
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

references
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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