7 WiMAX – EKSPANSI COVERAGE World Interoperability for Microwave AccessThere are two main applications of WiMAX:Fixed WiMAX (IEEE ) - Fixed WiMAX applications are point-to-multipoint enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL for homes and businesses.Mobile WiMAX (IEEE e-2005) - Mobile WiMAX offers the full mobility of cellular networks at true broadband speeds.
10 LTE – EKSPANSI DATA RATE LTE is the latest standard in the mobile network technology tree that previously realized the GSM/EDGE and UMTS/HSxPA networkCharacteristics :Significantly increase peak data rates, scaled linearly according to spectrum allocationimproving spectral efficiencylowering costsimproving servicesmaking use of new spectrum opportunitiesImproved quality of servicebetter integration with other open standardsLTE is the next step on a clearly-charted roadmap to so-called ‘4G’ mobile systems that starts with today’s 2G and 3G networks. Building on the technical foundations of the 3GPP family of cellular systems that embraces GSM, GPRS and EDGE as well as WCDMA and now HSPA (High Speed Packet Access), LTE offers a smooth evolutionary path to higher speeds and lower latency. Coupled with more efficient use of operators’ finite spectrum assets, LTE enables an even richer, more compelling mobile service environment.
11 LTE Network Architecture The LTE architecture consists of E-UTRAN (Evolved UMTS Terrestrial Radio Access Network) on the access side and EPC (Evolved Packet Core) on the core side.A typical LTE/SAE network will have two types of network elements.The first is the new enhanced base station, so called “Evolved NodeB (eNodeB)” per 3GPP standards. This enhanced BTS provides the LTE air interface and performs radio resource management for the evolved access system.The second is the new Access Gateway (AGW). The AGW provides termination of the LTE bearer. It also acts as a mobility anchor point for the user plane. It implements key logical functions including MME (Mobility Management Entity) for the Control Plane and for the User Plane. These functions may be split into separate physical nodes, depending on the vendor-specific implementation.
18 PROBLEMS OF WIRELESS CHANNEL Incoming signal consists of several paths with different time delays (multiple copies of the same signal)Signal Fluctuation leads to loss of SNRIntersymbol Interference leads to very slow data rate
20 FDM vs. OFDMConventional v/s Modern FDM technique
21 LTE-Downlink (OFDM) Improved spectral efficiency Reduce ISI effect by multipathAgainst frequency selective fadingfrequency selective fading在正交分頻多工系統中，原來的寬頻通道被分割成N 個子通道，透過使用串列至並行轉換器，將資料送至各個子載波上，由於資料區間被拉長為原本的N倍，所以這些子載波有著較低的傳輸速率，當子通道數目足夠多時，每個子載波可以視具有平坦的通道頻率響應，進而可以有效的對抗頻率選擇性衰減通道所造成的失真
22 LTE Uplink (SC-FDMA)SC-FDMA is a new single carrier multiple access technique which has similar structure and performance to OFDMAA salient advantage of SC-FDMA over OFDM is low to Peak to Average Power Ratio (PAPR) :Increasing battery life
24 Phased Array Antenna...Beam-steering using phase shifters at each radiating elementBeam direction32dEqui-phasewave front = [(2/)d sin]RadiatingelementsPhaseshiftersPowerdistribution
25 MIMO techniques<=> different propagation environment WLLMSCLOSUrban areaBSBSNLOSRural areaBSMSCmultiple antennas at MS
26 SDMA concept - expected up to 8 times capacity improvement - power classes concept (can be dynamicor static)- with ref. signal BF MSs can beseparated even when they have thesame angular position to BS !- for DoABF MSs angular distributionis important (macrocell)- network planning (frequency) is simpler,but larger cell size can require new planning,more smooth migration into existing network- more network management upgrade requiredPCH 1PCH 1PCH 1PCH 1
28 Comparison of FDMA, TDMA, and CDMA FDMACDMATDMAPowerFrequencyTimeCode
29 DS-CDMA Concepts– Freq domain Signal-to-interference ratio (SIR)Desired SIR will limit the capacityWrong code will not detect signalNon CDMA signal received at the Rx will be reduced by spreading and filtering jammer suppressionUser’s codeOther non-CDMA user
30 CDMA Rake Receiver GSM use equalizer at bit level processing r(t -1)c(t - )DespreaderDemodulator/DetectorD1D2D3r(t -2r(t -3)Multipath fading is unavoidable in wireless communicationsCDMA is wideband Frequency Selective channelIntersymbol Interference (ISI) can be better resolvedGSM use equalizer at bit level processingCDMA Rake chip level processingThe number of resolvable paths is much higher.Better performance !!
31 Problem of Power Control - CDMA The main problems of cellular is multipath propagation :Frequency selective channel due to delay spread propagation.Signal fluctuation due to mobilityCDMA is a spread spectrum multiple access technique that uses large bandwidth (1.25 MHz for narrowband and 5 MHz for wideband CDMA).Coherence Bandwidth for typical multipath channel is in the order of hundreeds KHz CDMA channelis always frequency selective.Need to solve for both problems.(b) Multipath fading problem2Pt1Pr1Pr2Pt2d1d2Signal fluctuationUser(a) Near-far distance problemDelay spread
32 Multi Carrier Technique (to solve for frequency selective channel) Carrier bandwidth Bu is divided into J subcarriers of bandwidth Bd so that Bd = Bu/J or Bu = JBdBy Choosing a large number of J, bandwidth of each sub carrier can be made lower than the channel coherence bandwidth to produce a frequency non selective channel .
33 Multiuser Detection Receiver Conventional receiver detects the signal using each user’s code individually.Multiuser detection /receiver (MUD) use all user’s signal to detect each user signal iteratively.In MUD, MAI is reduced for each iterationr(t -)c(t - )DespreaderDemodulatorInterference component will decrease by iterationOther user interference is subtracted using feedback
34 Performance Of multi user Detection Single User DetectionMulti User DetectionMULTI USER DETECTION IMPROVES DETECTION PERFORMANCE SIGNIFICANTLY
35 Penutup/DiskusiTeknik Multi-Carrier merupakan trend teknologi wireless access network yang bisa mengatasi Problem Kanal Wirelss dan Keterbatasan FrequensiTeknik Multi User Detection bisa menghilangkan/mengurangi interferensi, sehingga meningkatkan kapasitas.Kapasitas dan laju data Wireless Communication meningkat tajam dalam 10 tahun terakhir.