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![Processing gain and Spreading
• Spread spectrum systems reduce the effect of interference due to processing gain
• Processing gainisgenerallydefined as follows:
– G[dB]=10*log10(W/R), where ’W’ is the chip rate and ’R’ is the user bit rate
• The number of userstakes negative effect onthe processing gain. The lossis defined as:
– Lp = 10*log10k, where ’k’ is the amount of users
• Processing gainwhenthe processing loss is takeninto account is
– Gtot=10*log10(W/kR)
• Highbit rate means lower processing gainand higher power OR smaller coverage
• The processing gainis different for different services over 3G mobile network(voice, web browsing, videophone) due to different bit rates
– Thus, the coverage area and capacity might be different for different services depending on the radio network planning issues](https://image.slidesharecdn.com/wcdmasystems003-150602040852-lva1-app6891/85/Wcdma-systems-003-24-320.jpg)
![HSDPA - general principle
• Fast scheduling is done directly in Node-B based on feedback information from UE and knowledge of current traffic state.
Channel quality
(CQI, Ack/Nack, TPC)
Data
Users may be time and/or code multiplexed
New base station functions
• HARQ retransmissions
• Modulation/coding selection
• Packet data scheduling (short TTI)
New base station functions
• HARQ retransmissions
• Modulation/coding selection
• Packet data scheduling (short TTI)
UE
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T im e [ n u m b e r o f T T Is ]
Q P S K 1 / 4
Q P S K 2 / 4
Q P S K 3 / 4
1 6 Q A M 2 / 4
1 6 Q A M 3 / 4
InstantaneousEsNo[dB]](https://image.slidesharecdn.com/wcdmasystems003-150602040852-lva1-app6891/85/Wcdma-systems-003-56-320.jpg)
Uploaded byKaushal Kumar
Wcdma systems 003
This document discusses WCDMA, HSPA, and advanced receivers. It provides an overview of key concepts such as code multiplexing, spreading, and the introduction to Wideband Code Division Multiple Access (WCDMA). It also discusses WCDMA performance enhancements including High Speed Packet Access (HSDPA/HSUPA) and advanced features for HSDPA. Finally, it covers the evolution of WCDMA standards and current WCDMA markets.
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Wcdma systems 003
- 1. WCDMA, HSPA andadvanced receivers
- 2. Readings related tothe subject • General readings – WCDMA for UMTS– HarriHolma, AnttiToskala – HSDPA/HSUPA for UMTS –Harri Holma, Antti Toskala • Network planning oriented – Radio NetworkPlanning and Optimisationfor UMTS– Janna Laiho, Achim Wacker, Tomás Novosad – UMTS Radio Network Planning, Optimizationand QoS Management For PracticalEngineering Tasks –Jukka Lempiäinen, Matti Manninen
- 3. Outline • Background • Keyconcepts – Code multiplexing – Spreading • Introduction to Wideband Code Division Multiple Access (WCDMA) • WCDMA Performance Enhancements – High Speed Packet Access (HSDPA/HSUPA) – Advanced featuresfor HSDPA
- 4. Background •Why new radioaccess system •FrequencyAllocations •Standardization •WCDMA background and evolution •Evolution of Mobile standards •Current WCDMA markets
- 5. Why new radioaccess system • Need for universal standard (Universal Mobile Telecommunication System) • Support for packet data services – IP data incore network – Wireless IP • New services in mobile multimedia need faster data transmission and flexible utilization of the spectrum • FDMA and TDMA are not efficient enough – TDMA wastestime resources – FDMA wastes frequencyresources • CDMA can exploit the whole bandwidth constantly • Wideband CDMA was selected for a radio access system for UMTS (1997) – (Actuallythe superiorityof OFDMwas not fullyunderstood bythen)
- 6. Frequency allocations forUMTS • Frequency plans of Europe, Japan and Korea are harmonized • US plan is incompatible, the spectrum reserved for 3G elsewhere is currently used for the US 2G standards • IMT-2000 band in Europe: – FDD 2x60MHz Expected air interfaces and spectrums, source: “WCDMA for UMTS”
- 7. Standardization • WCDMA wasstudied in various research programs in the industry and universities • WCDMA was chosen besides ETSI also in other forums like ARIB (Japan) as 3G technology in late 1997/early 1998. • During 1998 parallel work proceeded in ETSI and ARIB (mainly), with commonalities but also differences – Work was also on-going in USA and Korea
- 8. Standardization • At endof 1998 different standardization organizations got together and created 3GPP, 3rd Generation Partnership Project. – 5 Founding members: ETSI, ARIB+TTC (Japan), TTA (Korea), T1P1 (USA) – CWTS (China) joined later. • Different companies are members through their respective standardization organization. E T S I M e m b e r s E T S I A R I B M e m b e r s A R I B T T A M e m b e r s T T A T 1 P 1 M e m b e r s T 1 P 1 T T C M e m b e r s T T C C W T S M e m b e r s C W T S 3 G P P
- 9. WCDMA Background andEvolution • First major milestone wasRelease ‘99, 12/99 – Full set of specifications by 3GPP – Targeted mainly on access part of the network • Release 4, 03/01 – Core network was extended – markets jumped over Rel 4 • Release 5, 03/02 – High Speed Downlink Packet Access (HSDPA) • Release 6, end of 04/beginning of 05 – High Speed Uplink Packet Access (HSUPA) • Release 7, 06/07 – Continuous Packet connectivity (improvement for e.g. VoIP), advanced features for HSDPA (MIMO, higher order modulation)
- 10. WCDMA Background andEvolution 2000 2002 2004 2006 2007200520032001 3GPP Rel -99 12/99 3GPP Rel 4 03/01 3GPP Rel 5 (HSDPA) 03/02 3GPP Rel 6 (HSUPA) 2H/04 3GPP Rel 7 HSPA+ 06/07 Further Releases Japan Europe (pre-commercial) Europe (commercial) HSDPA (commercial) HSUPA (commercial)
- 11. Evolution of Mobilestandards EDGE GPRS GSM HSCSD cdmaOne (IS-95) WCDMA FDD HSDPA/ HSUPA cdma2000 TD-SCDMA TDD LCR cdma2000 1XEV - DO cdma2000 1XEV - DV TD-CDMA TDD HCR HSDPA/ HSUPA LTE
- 12. Current WCDMA markets •Graph of the technologiesadopted bythe wireless users worldwide: • Over 3.5 billionwireless users worldwide • GSM+WCDMA share currentlyover 88 % (www.umts-forum.org) • CDMA share isdecreasing every year GSM (80.9%) CDMA (12%) WCDMA (4.6%) iDEN (0.9%) PDC(0.8%) US TDMA (0.8%)
- 13. Current WCDMA markets •Over 200 millionWCDMA subscribers globally(04/08) (www.umts-forum.org) – 10 % HSDPA/HSUPA users • Number of subscribers isconstantlyincreasing Millionsubscribers
- 14. Key concepts •CDMA •Spread Spectrum •DirectSequence spreading •Spreading and Processing gain
- 15. Multiple Access Schemes •FrequencyDivision Multiple Access(FDMA), different frequencies for different users – example Nordic Mobile Terminal (NMT) systems • Time DivisionMultiple Access (TDMA), same frequencybut different timeslots for different users, – example Global System for Mobile Communication (GSM) – GSM also uses FDMA • Code Division Multiple Access(CDMA), same frequencyand time but users are separated from each other with orthogonalcodes Code Frequency Time 1 2 N … TDMAFDMA CDMA
- 16. Spread Spectrum • Meansthat the transmission bandwidth is much larger than the information bandwidth i.e. transmitted signal is spread to a wider bandwidth – Bandwidthis not dependent onthe informationsignal • Benefits – More secure communication – Reducesthe impact of interference (and jamming) due toprocessing gain • Classification – Direct Sequence (spreading with pseudo noise (PN) sequence) – Frequency hopping (rapidly changing frequency) – Time Hopping (large frequency, short transmission bursts) • Direct Sequence is currently commercially most viable
- 17. Spread Spectrum • Wheredoes spread spectrum come from – First publications, late 40s – First applications: Militaryfrom the 50s – Rake receiver patent 1956 – Cellular applicationsproposed late 70s – Investigations for cellular use 80s – IS-95 standard 1993 (2G) – 1997/1998 3G technologychoice – 2001/2002 Commerciallaunchof WCDMA technology
- 18. Direct Sequence • Indirect sequence (DS) user bits are coded with unique binary sequence i.e. with spreading/channelization code – The bits of the channelizationcode are called chips – Chip rate (W) is typicallymuchhigher than bit rate (R) – Codes need to be insome respect orthogonalto eachother (cocktail partyeffect) • Length of a channelization code – defineshow manychips are used tospread a single informationbit and thus determines the end bit rate – Shorter code equals to higher bit rate but better Signal to Interference and Noise Ratio (SINR) is required • Also the shorter the code, the fewer number of codes are available – Different bit rates have different geographical areascovered based on the interference levels
- 19. Direct Sequence • Transmission(Tx) side with DS – Information signal is multiplied with channelizationcode => spread signal • Receiving (Rx) side with DS – Spread signal ismultiplied withchannelizationcode – Multiplied signal (spread signalx code) isthenintegrated (i.e.summed together) • If the integration results in adequately high (or low) values, the signal is meant for the receiver
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- 22. Processing gain andSpreading Frequency Despread narrowband signal Spread wideband signal W R Powerdensity(Watts/Hz)Powerdensity(Watts/Hz) Frequency Transmitted signal before spreading Received signal before despreading Interference for the part we are interested in
- 23. Processing gain andSpreading Frequency Powerdensity(Watts/Hz)Powerdensity(Watts/Hz) Frequency Received signal after despreading but before filtering Received signal after despreading and after filtering Transmitted signal Interference
- 24. Processing gain andSpreading • Spread spectrum systems reduce the effect of interference due to processing gain • Processing gainisgenerallydefined as follows: – G[dB]=10*log10(W/R), where ’W’ is the chip rate and ’R’ is the user bit rate • The number of userstakes negative effect onthe processing gain. The lossis defined as: – Lp = 10*log10k, where ’k’ is the amount of users • Processing gainwhenthe processing loss is takeninto account is – Gtot=10*log10(W/kR) • Highbit rate means lower processing gainand higher power OR smaller coverage • The processing gainis different for different services over 3G mobile network(voice, web browsing, videophone) due to different bit rates – Thus, the coverage area and capacity might be different for different services depending on the radio network planning issues
- 25. Processing gain andSpreading • Processing gain is what gives CDMA systems the robustness against self-interference that is necessary in order to reuse the available 5 MHz carrier frequency over geographically close distances. • Examples: Speech service with a bit rate of 12.2 kbps – processing gain 10 log10(3.84e6/12.2e3) = 25 dB – For speechservice the required SINR istypicallyinthe order of 5.0 dB, sothe required wideband signal-to-interference ratio (alsocalled “carrier- to-interference ratio, C/I) is therefore “5.0 dB minusthe processing” = -20.0 dB. – In other words, the signal power can be 20 dB under the interference or thermalnoise power, and the WCDMA receiver canstilldetect the signal. – Notice: inGSM, a good qualityspeechconnectionrequires C/I= 9–12 dB.
- 26. Introduction to WidebandCode Division Multiple Access (WCDMA) •Overview •Codes inWCDMA •QoS support •NetworkArchitecture •Radio propagationand fading •RAKE receiver •Power Control inWCDMA •Diversity •Capacityand coverage
- 27. WCDMA System • WCDMAis the most common radio interface for UMTS systems • Wide bandwidth, 3.84 Mcps (Megachips per second) – Maps to 5 MHz due to pulse shaping and smallguard bandsbetweenthe carriers • Users share the same 5 MHz frequency band and time – ULand DL have separate 5 MHz frequencybands • High bit rates – WithRelease ’99 theoretically 2 Mbps bothUL and DL – 384 kbps highest implemented • Fast power control (PC) => Reduces the impact of channel fading and minimizes the interference
- 28. WCDMA System • Softhandover – Improves coverage, decreases interference • Robust and low complexityRAKEreceiver – Introduces multipath diversity • Variable spreading factor – Support for flexible bit rates • Multiplexing of different services ona single physical connection – Simultaneous support of services with different QoS requirements: • real-time – E.g. voice,video telephony • streaming – streaming videoand audio • interactive – web-browsing • background – e-mail download
- 29. Codes in WCDMA •ChannelizationCodes (=short code) – Codes from different branches of the code tree are orthogonal – Length is dependent on the spreading factor – Used for • channel separation from the single source in downlink • separation of dataandcontrol channelsfrom each other in the uplink – Same channelization codes in every cell / mobiles and therefore the additional scrambling code is needed • Scrambling codes (=long code) – Very long (38400 chips = 10 ms =1 radio frame), many codes available – Does not spread the signal – Uplink: to separate different mobiles – Downlink: to separate different cells – The correlation between two codes (two mobiles/NodeBs) is low • Not fully orthogonal
- 30. Codes in WCDMA •For instance, the relationbetweendownlinkphysical layer bit rates and codes Spreading Factor (SF) Channel symbol rate (ksps) Channel bit rate (kbps) DPDCH channel bit rate range (kbps) Maximum user data rate with ½- rate coding (approx.) 512 7.5 15 3–6 1–3 kbps 256 15 30 12–24 6–12 kbps 128 30 60 42–51 20–24 kbps 64 60 120 90 45 kbps 32 120 240 210 105 kbps 16 240 480 432 215 kbps 8 480 960 912 456 kbps 4 960 1920 1872 936 kbps 4, with 3 parallel codes 2880 5760 5616 2.3 Mbps Half rate speech Full rate speech 144 kbps 384 kbps 2 Mbps Symbol_rate = Chip_rate/SF Bit_rate = Symbol_rate*2 Control channel (DPCCH) overhead User bit rate with coding = Channel_bit_rate/2
- 31. QoS Support • KeyFactors: – Simultaneous support of services with different QoS requirements: • up to 210 Transport Format Combinations, selectable individually for every radio frame (10 ms) • going towards IP core networks greatly increases the usage of simultaneous applications requiring different quality, e.g. real time vs. non-real time – Optimized usage of different transport channels for supporting different QoS
- 32. QoS support Example: Downlink Shared Channel Downlink Dedicated Channels USER 1 .... 10ms USER 2 USER 3 USER 1 USER 1 USER 4 Data Rate 2 Mbps Code 5 Code 4 Code 3 Code 2 Code 1USER 1 USER 2 USER 3 USER 4 USER 2 Time
- 33. UMTS Terrestrial RadioAccess Network (UTRAN) Architecture • New Radio Access network needed mainly due to new radio access technology • Core Network (CN) is based on GSM/GPRS • Radio Network Controller (RNC) corresponds roughly to the Base Station Controller (BSC) in GSM • Node B corresponds roughly to the Base Station in GSM – Term “Node B”is a relic from the first 3GPP releases RNC NodeB NodeB NodeB UE CN RNC UE Uu interface Iub interface Iur interface UTRAN
- 34. UMTS Terrestrial RadioAccess Network (UTRAN) Architecture • Radio network controller (RNC) – Ownsand controls the radio resources inits domain – Radio resource management (RRM) tasks include e.g. the following • Mapping of QoS Parameters into the air interface • Air interface scheduling • Handover control • Outer loop power control • Call Admission Control • Setting of initial powers and SIR targets • Radio resource reservation • Code allocation • Load Control
- 35. UMTS Terrestrial RadioAccess Network (UTRAN) Architecture • Node B – Mainfunctiontoconvert the data flow betweenUu and Iub interfaces – Some RRM tasks: • Measurements • Inner loop power control
- 36. Radio propagation andfading • A transmitted radio signal goes through several changes while traveling via air interface to the receiver – reflections, diffractions, phase shifts and attenuation • Due to length difference of the signal paths, multipath components of the signal arrive at different times to the receiver and can be combined either destructively or constructively – Depends onthe phases of the multipathcomponents
- 37. Radio propagation andfading • Example of the fast fading channel of a function of time • Opposite phases of two random multipath components arriving at the same time cancel each other out – Resultsina fade • Coherent phases are combined constructively
- 38. • Every multipathcomponent arriving at the receiver more than one chip time (0.26 μs) apart can be distinguished by the RAKE receiver – 0.26 μs corresponds to 78 m inpath lengthdifference • RAKE assigns a “finger” to each received component (tap) and alters their phases based on a channel estimate so that the components can be combined constructively Finger #1 Finger #2 Finger #3 RAKE receiver Transmitted symbol Received symbol at each time slot Phase modified using the channel estimate Combined symbol
- 39. Power Control inWCDMA • The purpose of power control (PC) is to ensure that each user receives and transmits just enough energy to have service but to prevent: – Blocking of distant users (near-far-effect) – Exceeding reasonable interference levels UE1 UE2 UE3 UE1 UE2 UE3 UE1 UE2 UE3 Without PC received power levels would be unequal With ideal PC received power levels are equal
- 40. Power Control inWCDMA 1. Open loop power control • Onlyfor the initial power setting of the MS • Based on distance attenuationestimationfrom the downlinkpilot signal 1. Inner loop transmitter power control (CL TPC) at a rate of 1500 Hz • Mitigates fading processes (fast and slow fading) • Tx power is adjusted up/down to reachSIR target • BothinULand DL • Usesqualitytargets in MS /BS 1. Outer loop PC at the rate of 100 Hz • Sets the qualitytarget used bythe inner loop PC • Compensates the changes inthe propagationconditions • Adjusts the qualitytarget • BothinULand DL
- 41. Power Control inWCDMA • Inner loop power control in the uplink – Outer loop PC (running inthe radio network controller, RNC) definesSIR target for the BS. – If the measured SIR at BS is lower thanthe SIR-target, the MSis commanded to increases its transmit power. Otherwise MS is commanded todecrease its power – Power controldynamics at the MS is 70 dB
- 42. Power Control inWCDMA • Inner loop power control in downlink: – Outer loop PC (running inthe MS) defines SIR target for the MS – If the measured SIR at the MS is lower thanthe SIR-target, the BSis commanded to increasesits transmit power for that MS. Otherwise, BS iscommanded to decrease its power. – Power controlrate 1500 Hz – Power controldynamics is dependent onthe service – There’sno near-far problem inDL due toone-to-manyscenario. However, it is desirable toprovide a marginal amount of additionalpower tomobile stations at the cell edge, astheysuffer from increased other-cell interference.
- 43. Power Control inWCDMA • Example of inner loop power control behavior: • With higher velocities channel fading is more rapid and 1500 Hz power control may not be sufficient
- 44. Power Control inWCDMA • Inner loop power controltries to keep the received SIR as close to the target SIR aspossible. • However, the constant SIR alone does not actually guarantee the required frame error rate (FER) which canbe considered as the qualitycriteria of the link/service. – There’s no unique SIR that automatically gives a certain FER – FER is a function of SIR, but also depends on mobility and propagation environment. • Therefore, the frame reliabilityinformationhas to be delivered toouter loop control, whichcantune the SIR target if necessary.
- 45. Diversity • Transmitting onasingle pathonlycanlead to seriousperformance degradationdue tofading • As fading is independent betweendifferent times and spacesit is reasonable to use the available diversityof them todecrease the probability of a deep fade – The more there are paths to choose from, the less likely it is that all of them have a poor energy level • There existsdifferenttypes of diversitywhichcan be used to improve the quality, e.g.: – Multipath • RAKE receiver exploitstaps arrivingat different times – Macro • Different Node Bs sendthe same information – Site Selection Transmit Diversity (SSTD) • Maintain alist of available base stationsand choose the best one, from which the transmission isreceivedandtell the others not totransmit
- 46. Diversity – Time • Sameinformation is transmitted in different times – Receive antenna • Transmission is received with multiple antennas • Power gain and diversity gain – Transmit antenna • Transmission is sent with multiple antennas
- 47. WCDMA Handovers • WCDMAhandovers can be categorized into three different types • Intra-frequency handover – WCDMA handover withinthe same frequencyand system. Soft, softer and hard handover supported • Inter-frequency handover – Handover betweendifferent frequencies (carriers) but within the same system – E.g. from one WCDMA operator to another – Onlyhard handover supported • Inter-system handover – Handover betweenWCDMA and another system, e.g.from WCDMA to GSM – Onlyhard handover supported
- 48. WCDMA Handovers • Softhandover – Handover betweendifferent Node Bs – Several Node Bstransmit the same signalto the UE whichcombines the transmissions • Advantages: lower Tx power needed for each Node B and UE – lower interference, battery saving for UE • Disadvantage: resources (code, power) need to be reserved for the UE in each Node B – Excess soft handovers limit the capacity – No interruptionindata transmission – Needs RNC duplicating frame transmissions to two Node Bs
- 49. WCDMA Handovers • Softerhandover – Handover betweentwo sectors of the same Node B • Special case of a soft handover • No need for duplicate frames • Hard handover – The source isreleased first and then new one is added – Short interruption indata flow
- 50. WCDMA Handovers • Someterminology – Active set (AS), represents the Node Bs to whichthe UEis in soft handover – Neighbor set (NS), representsthe links that UE monitorsbut whichare not already in active set Received signal strength BS1 BS2 Threshold_1 Triggering time_1 Threshold_2 Triggering time_2 BS2 from the NS reaches the threshold to be added to the AS BS2 is still after the triggering time above threshold and thus added to the AS BS1 from the AS reaches the threshold to be dropped from the AS BS1 dropped from the AS
- 51. Capacity and coverage •In WCDMA coverage and capacity are tight together: – When the load increases, the interference levels increases, too, and therefore also increased transmit powers are needed inorder to keep constant quality. – Due to finite power resources, the more users Node B servesthe less power it has for eachUE coverage willdecrease • This leads to cell breathing: the coverage area changes as the load of the cell changes. • Therefore, the coverage and the capacity have to be planned simultaneously • Radio resource management (RRM) is needed in WCDMA to effectively control cell breathing.
- 52. Capacity and coverage •Received power of one user as a function of users per cell • Due to finite maximum Tx power of the UE coverage is usually limited by the uplink • Node B does not have this problem – There is enough Tx power to transmit veryfar to a single user if necessary – However, downlinkTx power isdivided betweenall users and thus capacityis limited bythe downlink
- 53. WCDMA evolution •HighSpeed DownlinkPacketAccess (HSDPA) •HighSpeed Uplink Packet Access(HSUPA) •Advanced receivers withHSDPA •Advanced HSDPA scheduling •Femto cells withHSDPA
- 54. High Speed DownlinkPacket Access (HSDPA) • The High Speed Downlink Packet Access (HSDPA) concept was added to Release 5 to support higher downlink data rates • It is mainly intended for non-real time traffic, but can also be used for traffic with tighter delay requirements. • Peak data rates up to 10 Mbit/s (theoretical data rate 14.4 Mbit/s) • Reduced retransmission delays • Improved QoS control (Node B based packet scheduler) • Spectrally and code efficient solution
- 55. HSDPA features • Agreedfeatures in Release 5 – Adaptive Modulation and Coding (AMC) • QPSK or 16QAM – Multicode operation • Support of 1-15 code channels (SF=16) – Short frame size (TTI = 2 ms) – Fast retransmissions using Hybrid Automatic Repeat Request (HARQ) • Chase Combining • Incremental Redundancy – Fast packet scheduling at Node B • E.g.Round robin, Proportionalfair • Features agreed in Release 7 – Higher order modulation (64QAM) – Multiple Input Multiple Output (MIMO)
- 56. HSDPA - generalprinciple • Fast scheduling is done directly in Node-B based on feedback information from UE and knowledge of current traffic state. Channel quality (CQI, Ack/Nack, TPC) Data Users may be time and/or code multiplexed New base station functions • HARQ retransmissions • Modulation/coding selection • Packet data scheduling (short TTI) New base station functions • HARQ retransmissions • Modulation/coding selection • Packet data scheduling (short TTI) UE 0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 - 2 0 2 4 6 8 1 0 1 2 1 4 1 6 T im e [ n u m b e r o f T T Is ] Q P S K 1 / 4 Q P S K 2 / 4 Q P S K 3 / 4 1 6 Q A M 2 / 4 1 6 Q A M 3 / 4 InstantaneousEsNo[dB]
- 57. HSDPA functionality • Schedulingresponsibility has been moved from RNC to Node B • Due to this and the short TTI length (2 ms) the scheduling is dynamic and fast • Support for several parallel transmissions – When packet A issent it starts to wait for anacknowledgement from the receiver, during which other packets canbe sent via a parallel SA W (stop-and-wait) channels Pkt A Pkt B Pkt C Pkt D Pkt E Pkt F Ack B
- 58. HSDPA functionality • UEinforms the Node B regularly of its channel quality by CQI messages (Channel Quality Indicator)
- 59. HSDPA functionality • NodeB can use channel state information for several purposes – In transport format (TFRC) selection • Modulation and coding scheme – Scheduling decisions • Non-blind scheduling algorithms can be utilized – HS-SCCH power control
- 60. HSDPA channels • Userdata is sent on High Speed Downlink Shared Channel (HS-DSCH) • Control information is sent on High Speed Common Control Channel (HS-SCCH) • HS-SCCH is sent two slot before HS-DSCH to inform the scheduled UE of the transport format of the incoming transmission on HS-DSCH
- 61. High Speed UplinkPacket Access (HSUPA) • Peak data rates increased to significantly higher than 2 Mbps; Theoretically reaching 5.8 Mbps • Packet data throughput increased, though not as high throughput as with HSDPA • Reduced delay from retransmissions. • Solutions – Layer1 hybrid ARQ – NodeB based scheduling for uplink – Frame sizes 2ms & 10 ms • Schedule in 3GPP – Part of Release 6 – First specifications version completed 12/04 – In 3GPP specs with the name Enhanced uplink DCH (E-DCH)
- 62. 5 codes QPSK ofcodes# Modulation 5 codes 16-QAM 10 codes 16-QAM 15 codes 16-QAM 15 codes 16-QAM 1.8 Mbps Max data rate 3.6 Mbps 7.2 Mbps 10.1 Mbps 14.4 Mbps 2 x SF4 2 ms 10 ms of codes# TTI 2 x SF2 10 ms 2 x SF2 2 ms 2 x SF2 + 2 x SF4 2 ms 1.46 Mbps Max data rate 2.0 Mbps 2.9 Mbps 5.76 Mbps Downlink HSDPA • Theoretical up to 14.4 Mbps • Initial capability1.8 – 3.6 Mbps Uplink HSUPA • Theoretical up to 5.76 Mbps • Initial capability1.46 Mbps HSPA Peak Data Rates
- 63. Performance of advancedHSDPA features
- 64. Advanced receivers withHSDPA • UE receiver experiences significant interference from different sources – In a reflective environment the signalinterferes itself – Neigboring base stationsignals interfere eachother – One solutionto decrease mainlyownbase stationsignal interference is touse anequalizer before despreading Own cell interference Other cell interference Own signal
- 65. Advanced receivers withHSDPA • In a frequency-selective channel there is a significant amount of interfering multipaths • Linear Minimum Mean Squared Error (LMMSE) equalizer can be used to make an estimate of the original transmitted chip sequence before despreading – The interfering multipathcomponentsare removed – The channelbecomes flat again
- 66. Advanced receivers withHSDPA • LMMSE equalizer (Equ in the figure) offers a very good performance for the user especially near the base station • Using antenna diversity (1x2) the throughput can be doubled compared to a single antenna • Both techniques increase the cost of a mobile unit
- 67. Advanced HSDPA scheduling •Node B has a limited amount of scheduling opportunities • The amount of data transmitted by the network must be maximized whilst offering the best possible quality of service to all users – The scheduling canbe improved byanadvanced algorithm
- 68. Advanced HSDPA scheduling •An improved scheduling algorithm (Proportional Fair, PF) offers significant gain over a conventional algorithm (Round Robin, RR) • PF has a very good price-quality ratio – User equipment needs no changes – Node B’sneed onlyminor changes
- 69. Femtocells • More andmore consumers want to use their mobile devices at home, even when there’s a fixed line available – Providing full or evenadequate mobile residentialcoverage is a significant challenge for operators – Mobile operators need to seize residential minutes from fixed line providers, and compete withfixed and emerging VoIPand WiFiservices => There is trend indiscussing verysmallindoor, home and campus NodeB layouts • Femtocells are cellular access points (for limited access group) that connect to a mobile operator’s network using residential DSL or cable broadband connections • Femtocells enable capacity equivalent to a full 3G network sector at very low transmit powers, dramatically increasing battery life of existing phones, without needing to introduce WiFi enabled handsets
- 70. Femtocells • The studyconsiders the system performance of an HSDPA network consisting of macro cells and very low transmit power (femto) cells • The impact of using 64QAM in addition to QPSK and 16QAM in order to benefit from the high SINR is studied • The network performance is investigated with different portions of users created in the buildings (0-100%)
- 71. Femtocells • Femtocells providemaximum of 15-17 % gainto networkthroughput alreadywithout dedicated indoor users • The gainis visible with high load inthe networkand comes directlyfrom the increased number of access points inthe network • Average load of a cell is decreased and users canbe scheduled more often Scheme Offered load Medium High Congested Rake 1x1 3 % 8 % 15 % Rake 1x2 -1 % 19 % 13 % Equ 1x1 -2 % 18 % 15 % Equ 1x2 -1 % 3 % 17 % Table: Network throughput gain of femto cells to macro users
- 72. Femtocells • When theamount of dedicated indoor users increase, the gain of femto cells explodes • Gain is in the range of hundreds of percents even with small portion of indoor users