MobileComm Technologies India Pvt. Ltd. Dallas . Atlanta . Washington . LA . Sao Paulo . New Delhi . Toronto . Muscat. SydneyHSDPA BASIC
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HSPA Motivations
3G Enables Wider Options of Services
3G Enables Advanced Data Services
HSPA for Higher Speed
Data Rate Demand for higher peak data rates Delay Lower latency Capacity Better capacity and throughput Better spectrum efficiency Finer resource granularity Coverage Better coverage for higher data rateWhat are the requirements for HSPA?
UMTS Data Rate Evolution
Uplink Peak Data Rate (Typical Deployment)Downlink Peak Data Rate (Typical Deployment)GSM9.6 kbps9.6 kbpsGPRS20 kbps40 kbpsEDGE60 kbps120 kbpsWCDMA Release 99 64 kbps 384 kbpsHSDPA - Release 5 384 kbps10 Mbps*HSUPA - Release 61.4 Mbps (early deployment)10 Mbps
Applications Benefiting from HSPA
Voice-over-IP (VoIP)- Low latency, Quality of Service (QoS) control, fine resource granularity and improved capacityVideo Telephony (in Packet Switched domain)- Low latency, Quality of Service (QoS) control, high data rates and improved coverage and capacityGamingLow latency, fast resource allocation
Video Share / Picture Share- High Uplink data rates and improved coverage and capacityFile Uploading (large files)- High Uplink data rates and improved coverage and capacity
UMTS Evolution / 3GPP ReleasesYear19992001matured GSM/GPRS CN+ UTRAN+ WCDMA Air Interfaceup to 384 kbps (2 Mbps) Bearer independent CS CN CAMEL Phase 4 UTRA FDD repeater low chip rate TDD mode HSDPA (14 Mbps) IMS Phase 1 W-AMR enhanced Location Services 1800/1900 MHz HSUPA (5.76 Mbps) IMS Phase 2 WLAN-Interworking MBMS Push-services2002/032005
HSPA Motivation and General Principle
Improved performance and spectral efficiency in DL and UL by introducing a shared channel principle:Significant enhancement with peak rates up to 14.4 Mbps in DL, and 2 Mbps in ULHuge capacity increase per site; no site pre-planning necessaryImproved end user experience: reduced delay/latency, high response time
HSDPA Basic
What is High Speed Downlink Packet Access (HSDPA)Smooth Upgrade Short time to market with existing sites
HSDPAWhat is HSDPA?A UMTS packet air interface3.6 Mbps up to theoretical 14.4 Mbps peak/userAdd-on solution on top of 3GPP R99/R4 architectureHSDPA terminals co-exist with R99 terminalsNo modification to the Core Network & Traffic Classes
Difference between HSDPA and WCDMA today?More Content for High End Users (5x faster and lower latency of 150 ms)More Data Users per Cell (because it is ~10x more spectrally efficient)
Adaptive Modulation and Coding (AMC) - Depending on UE channel conditions (CQI) - QPSK, 16QAM - Coding rate (1/4 - 3/4) - Data rate adapted on 2 ms time basis Fast Retransmission - Hybrid Automatic Repeat reQuest (HARQ) - UE soft-combines data - Reduced RTT Fast Packet Scheduling (PS) Scheduling of users on 2 ms time basis New radio channels included for HSDPA - DL: HS-(P)DSCH, HS-SCCH - UL: HS-DPCCH It is important to note that downlink HSDPA is a shared data channel - End user throughput depends on the number of the other users on the same HSDPA cell - Capacity planning and dimensioning of HSDPA is different to non-real time (NRT) DCH bearer Introduction HSDPA Basics
HSDPA Basic Principles
Dynamic Power Allocation
Dedicated channels (power controlled)Common channelsPower usage with dedicated channelstUnused powerPower3GPP Release 993GPP Release 5 Dedicated channels (power controlled)Common channelsPower usage with dedicated channelstUsed for HSDPAPower
Shared Channel Transmission Up to 15 codes (SF16) can be allocated and shared between the users. It also depends on what the UE can support. A set of radio resources dynamically shared among multiple users, primarily in the time domain.
C1,0 = [1]C2,1 = [1-1]C2,0 = [11]C4,0 = [1111]C4,1 = [11-1-1]C4,2 = [1-11-1]C4,3 = [1-1-11]C8,0 = [11111111]C8,1 = [1111-1-1-1-1]C8,2 = [11-1-111-1-1]C8,3 = [11-1-1-1-111]C8,4 = [1-11-11-11-1]C8,5 = [1-11-1-11-11]C8,6 = [1-1-111-1-11]C8,7 = [1-1-11-111-1]C16,0 = [.........]C16,1 = [.........]C16,15 = [........]C16,14 = [........]C16,13 = [........]C16,12 = [........]C16,11 = [........]C16,10 = [........]C16,9 = [.........]C16,8 = [.........]C16,7= [.........]C16,6 = [.........]C16,5 = [.........]C16,4 = [.........]C16,3 = [.........]C16,2 = [.........]SF = 1248SF = 16256512...Multi Code OperationShared Channel Transmission
CQI Channel Quality IndicatorUE sends CQI info in the UL to aid rate adaptation and scheduling
CQI (1-30) provides the Node B with a measure of the UE's perceived channel quality and the UE receiver performance
The CQI report estimates the number of bits that can be transmitted to the UE using a certain assumed power with a block error rate of 10%
Node BCQI (Report periodically)
Fast Link Adaptation
Rate controlAdjusts data rate based on the Radio conditions (CQI)Fast Adaptation : 2 ms TTI basisAdaptive Modulation (QPSK and 16 QAM) and CodingUse available power
Fast Hybrid ARQ with Soft CombiningHARQFor Fast retransmissions
Fast Hybrid ARQ with Soft CombiningDuring retransmission, the UW employs soft combining.1st Decoding in UE2nd Decoding in UEFinal Picture
HSPA BasicsFast Scheduling in the Time domain (1):Transmission Time Interval (TTI) of 2ms assigned to usersA short TTI reduces round-trip time and improves the tracking of channelvariationsthe length of HSDPA sub-frame (TTI) is 3 slots (7680 chips) Fast Schedulingin the Node-BFast Channel-dependent Scheduling
Slot #0
Slot#1
Slot #2
T
slot
= 2560 chips, M*10*2
k
bits (k=4)
Data
N
data
1
bits
1 HS
-
PDSCH subframe: T
f
= 2 ms
HSPA BasicsFast Scheduling in the Time domain (2):Transmission is based on:Channel QualityUE CapabilitiesCurrent load in the cell (available resources / buffer status)Traffic Priority classes / QoS classesUE Feedback (ACK/NACK)Fast Scheduling in the code DomainUp to 15 codes in parallel per TTIFast Schedulingin the Node-BFast Channel-dependent Scheduling
Queue Selection AlgorithmsRound Robin RR:Assigns sub-frames in rotation User at cell edge served as frequently as user at cell centre
Doesnt account for UEs channel conditions Low total throughput in cell
If no data have to be transferred to certain UE then sub-frame assigned to next UEProportional Fair PF:Takes into account multipath fading conditions experienced by UEImproved total throughput in cell compared to RR
Sub-frames assigned according scheduling metricRatio instantaneous data rate / average data rate experienced in the pastUser at cell edge served less frequently as user at cell centre
HSPA BasicsHigh Order modulation: 16QAMCode Multiplexing: up to 15 codes in parallelUser can be code and time multiplexed (TTI= 2ms)
CodesTTI = 2msUser 1User 2User 3Time and Code multiplexing in HSDPAFixed Spreading Factor, SF=16-> 3.84Mcps/16 = 240 K symbols/s-> @ 16QAM -> 240 x 4 = 960 kbps-> @ code rate = 3/4 -> 720 kbps720 kbps bit rate can be achieved per code -> 10.8 Mbps over 15 codesAdaptive Modulation & Coding (AMC)
AIRCOM International 2006Adaptive Modulation & Coding (AMC)16 QAM allows twice the data rate to a user compared to QPSK
Currently all R99 channels use QPSK
16 QAM will only be possible for users within a limited radius of the NodeB (
AIRCOM International 20062msTTI 0TTI 1TTI 2TTI 3TTI 4TTI 5etcTimeNumber of allocated codes50Adaptive Modulation & Coding (AMC)
AIRCOM International 2006
AIRCOM International 2006Coding is used to protect the user data bits from errorsHSDPA has a very flexible coding scheme which can vary every 2ms and between each user This allows a much more varied distribution of data rates within a cellHigher rates in very good radio conditions near the NodeBHigher rates compared to R99 on cell edgeAdaptive Modulation & Coding (AMC)
AIRCOM International 2006
AIRCOM International 2006UE Support for AMCMaximum data rate possible to a single user depends heavily on the UE they are usingThere are 12 categories defined in the standards for different levels of HSDPA support
CategoryCodesInter-TTIModulationData rate153QPSK/16QAM1.2 Mbps253QPSK/16QAM1.2 Mbps352QPSK/16QAM1.8 Mbps452QPSK/16QAM1.8 Mbps551QPSK/16QAM3.6 Mbps651QPSK/16QAM3.6 Mbps7101QPSK/16QAM7.2 Mbps8101QPSK/16QAM7.2 Mbps9151QPSK/16QAM10.2 Mbps10151QPSK/16QAM14.4 Mbps1152QPSK only0.9 Mbps1251QPSK only1.8 Mbps
The big picture for HSDPAAdditional capacitySoftware upgradeAdditional capacityCore NetworkHLRRNCNode BBackhaulAdditional backhaul bandwidth to support higher data ratesIncreased processing power (HW)RF power allocation to HSDPA (min,max)Management of new device categories & signalling ch.Software upgrade Extended QoS field for HSDPA devices (for data rates >8 Mbps)
HSPA BasicsSummary of HSDPA key benefitsThroughputs of :Up to 3.6 Mbps with QPSKUp to 14 Mbps with 16QAMAdapted to variable-throughput flowsQuicker response timeMix of HSDPA and dedicated traffic possible on same carrierCost effectiveHigh Speed Downlink Packet AccessAdapted to burstytraffic (statisticalMultiplexing benefit)
Fabricio Martinez
AIRCOM International 2006HSDPA LimitationsHSDPA does not respond for the following needsHigh uplink speed (uploading, video calls, video conferences, browsing, online gaming, E-commerce)Large capacity (Limited number of users)Limited coverage (WCDMA has lower coverage than GSM in rural areas WCDMA infrastructure is not profitable)
POSSIBLE SOLUTIONS: HSUPA significantly improved uplinkWiMAX significantly improved capacityCDMA2000 increased coverage
Fabricio Martinez
AIRCOM International 2006
HSDPA Channels
Physical Channel OverviewHS-PDSCHHigh-Speed Physical DL Shared ChannelHS-SCCHHigh Speed Shared Control Channelassociated DCHDedicated Channel (Rel. 99)HS-DPCCHHigh Speed Dedicated Physical Control ChannelNode BMAC-hsF-DPCHFractional Dedicated Physical Channel (Rel. 6/7)
HS-PDSCHSF= 1SF= 2SF= 4SF= 8SF=16Example: Allocated for HS-DSCHallocated for other channelsHS-PDSCH: High-Speed Physical Downlink Shared Channel Transfer of actual HSDPA data 5 - 15 code channels QPSK or 16QAM modulation 2 ms TTIs Fixed SF16
HS-SCCHHS-SCCH: High-Speed Shared Control ChannelL1 Control Data for UE; informs the UE how to decode the next HS-PDSCH frame e.g. UE Identity, Channelisation Code Set, Modulation Scheme, TBS, H-ARQ process informationFixed SF128transmitted 2 slots in advance to HS-PDSCHsNSN implementation with slow power control: shares DL power with the HS-PDSCHmore than 1 HS-SCCH required when Code Multiplexing is usedUp to 4 HS-SCCHs CodesTBS: Transport Block SizeSF16HS-PDSCHTimeUser 1User 2User 3User 4Subframe2 ms51015
HS-DPCCHUL HS-DPCCH: High-Speed Dedicated Physical Control ChannelMAC-hs Ack/Nack information (send when data received)Channel Quality Information (CQI reports send every 4ms, hardcoded period)Fixed SF 256HARQ-ACK(10 bit)1 Slot = 2560 chip2 Slots = 5120 chipSubframe # 0Subframe # iSubframe # N1 HS-DPCCH Subframe = 2ms CQI (20 bit)Channel Quality IndicationCQI values = 0 (N/A), 1 .. 30; steps: 1;1 indicating lowest, 30 highest air interface quality
HS-DPCCH & CQIUE observesP-CPICH (Ec/Io) CQI** UE internal (proprietary) processTB Size [bit]CQI value 0: N/A (Out of range) = Reference Power Adjustment (Power Offset) [dB]CQI used for: Link Adaptation decision Packet Scheduling decision
ACK/NACK used for: H-ARQ process Link Adaptation decision HS-SCCH power adaptationCQI TB Size # codes Modulation up to 15 HS PDSCHsP-CPICHHS DPCCH (ACK; CQI)HS SCCH
11371QPSK021731QPSK032331QPSK043171QPSK053771QPSK064611QPSK076502QPSK087922QPSK099312QPSK01012623QPSK01114833QPSK01217423QPSK01322794QPSK01425834QPSK01533195QPSK0163565516-QAM0174189516-QAM0184664516-QAM0195287516-QAM0205887516-QAM0216554516-QAM0227168516-QAM0239719716-QAM02411418816-QAM025144111016-QAM026144111216-QAM-127144111216-QAM-228144111216-QAM-329144111216-QAM-430144111216-QAM-5
Associated DCH (DL & UL)DL DPCH: Associated Dedicated Physical ChannelTransfer of L3 signalling messagesSpeech - AMRPower control commands for associated UL DPCH
UL DPCH: (DPDCH & DPCCH)Transfer of L3 signalling messagesTransfer of UL data 16 / 64 / 128 / 384 kbps, e.g. TCP acknowledgementsSpeech - AMR
DPDCH / DPCCH (time multiplexed)DPDCH: L3 signalling; AMRDPCCH: TPC for UL DPCH power controlDPDCH: L3 signalling, AMR; TCP ACKs; 16 / 64 / 128 348 kbpsDPCCH: TPC, Pilot, TFCI
Fractional DPCH: F-DPCH (DL)The Fractional DPCH (F-DPCH): was introduced in 3GPP Rel. 6 replaces the DL DPCCH when the DL DPDCH is not present, i.e. both application data and SRB are transferred using HSDPA includes Transmit Power Control (TPC) bits but excludes TFCI & Pilot bitsTFCI bits - no longer required as there is no DPDCHPilot bits - no longer required as TPC bits are used for SIR measurements increases efficiency by allowing up to 10 UE to share the same DL SF256 channelisation code time multiplexed one after another
Tx OffTPCSlot #i1 time slot 2560 chipsTx Off256 chips
HSPA mobilityHSDPASoft handover on associated DCH channels (signalling, UL data)Serving cell change for HSDPA data channelConnected only to one cell at a time
HS-SCCHHS-PDSCHDPCHDPCHServing HS-DSCH cellNotice that soft/softer handover is not supported for HS-SCCH/HS-PDSCH
* | HSPA BasicsComparison with R99 DCH and R5 HSDPA
Channel
DCH (R99)
HSDPA (R5)
Channel Type
Dedicated
Shared
Spreading Factor
Variable
Fixed (SF =16)
L1- H-ARQ
No
Yes
Multicode transmission
Possible
Yes
TTI length (ms)
40 / 20 / 10
2
Adaptive Modulation
No
Yes
Node B Scheduling
No
Yes
Fast Power Control
Yes
No
Soft Handover
Yes
No
Thank You
*HSDPAHSDPA stands for High Speed Downlink Packet Access. As the name suggests, this is a piece of UMTS functionality designed to deliver downlink packet data at very high data rates. It is a release 5 feature. It achieves its aim by using the following techniques:Use of shared channel concept Rather than constantly allocating and deallocating dedicated channels to individual users, users share a high bandwidth channel the HS-DSCH (High Speed Downlink Shared Channel). This allows the system to operate with a fat pipe
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