6-1©2006 Raj JainCSE574sWashington University in St. LouisWireless Metropolitan Wireless Metropolitan Area Networks Area Networks (WMANs)(WMANs)Raj JainProfessor of CSE Washington University in Saint LouisSaint Louis, MO [email protected] slides are available on-line at:http://www.cse.wustl.edu/~jain/cse574-06/6-2©2006 Raj JainCSE574sWashington University in St. Louis IEEE 802.16 - WiMAX LMDS, MMDS IEEE 802.20 – Mobile Broadband Wireless Access IEEE 802.21 – Handover IEEE 802.22 – Wireless Regional Area NetworksOverviewOverview6-3©2006 Raj JainCSE574sWashington University in St. LouisBroadband Wireless AccessBroadband Wireless AccessRuralAreasNon Line of SightPoint to MultipointPoint to PointBackhaulTelco CoreCongestedAreasMTU6-4©2006 Raj JainCSE574sWashington University in St. LouisIEEE 802.16: Key FeaturesIEEE 802.16: Key Features Broadband Wireless Access Up to 50 km. Up to 70 Mbps. Data rate vs Distance trade off using adaptive modulation. 64QAM to BPSK Offers non-line of site (NLOS) operation 1.5 to 28 MHz channels Hundreds of simultaneous sessions per channel Delivers >1 Mbps per user Both Licensed and license-exempt spectrum QoS for voice, video, and T1/E1, continuous and bursty traffic Support Point-to-multipoint and Mesh network models6-5©2006 Raj JainCSE574sWashington University in St. LouisWiMAXWiMAX A vendor organization for ensuring interoperability A WiMAX certified product will work with other WiMAX certified products Plugfests started November 2005 3rdWiMAX plug fest in France, March 2006. WiMAX forum lists certified base stations and subscriber stations from Aperto Networks, Redline Communications, and SEQUANS Communications More to come:¾ Outdoor subscriber stations similar to satellite dish by 2006 ≈$350¾ Indoor subscriber stations by 2006-2007 ≈ $250¾ Portable modems for laptops by 2007-2008 ≈ $1006-6©2006 Raj JainCSE574sWashington University in St. LouisDuplexing OptionsDuplexing Options Duplex = Bi-Directional Communication Full-Duplex = Both directions at the same timeThis is known as Frequency division duplexing (FDD) Half-duplex = One direction at a timeThis is known as Time division duplex (TDD) Half-Duplex FDD (HFDD): Two frequencies. But either transmitter or receiver is on.Base SubscriberBase SubscriberBase SubscriberFrequency 1Frequency 2Base SubscriberFreq1 Freq2 Freq1 Freq2 Freq16-7©2006 Raj JainCSE574sWashington University in St. LouisOFDMAOFDMA Orthogonal Frequency Division Multiple Access A large number of subcarriers, e.g., 2048 Each user has a subset of subcarriers OFDMA is a form of FDMAU1 U2 U36-8©2006 Raj JainCSE574sWashington University in St. LouisIEEE 802.16 PHYsIEEE 802.16 PHYsFunction LOS Freq. BandCarrier DuplexingWirelessMAN SC Pt-to-pt LOS 10-66 GHzSingle TDD, FDDWirelessMAN SCaPt-to-pt LOS 2-11 GHzLicensedSingle TDD, FDDWirelessMAN OFDMPt-to-mpt NLOS 2-11 GHzLicensed256 TDD, FDDWirelessMANOFDMA (16e)Pt-to-mpt NLOS 2-11 GHzLicensed2048 TDD, FDDWirelessHUMAN(High-speed Unlicensed)Pt-to-mpt NLOS 2-11 GHzLicense Exempt1/256/ 2048TDDDynamic Freq. Sel.6-9©2006 Raj JainCSE574sWashington University in St. LouisIEEE 802.16 PHY: Other FeaturesIEEE 802.16 PHY: Other Features Adaptive Modulation and Coding Space Time Block Codes (STBC) Adaptive Antenna System6-10©2006 Raj JainCSE574sWashington University in St. LouisSpace Time Block Codes (STBC)Space Time Block Codes (STBC) Invented 1998 by Vahid Tarokh. Transmit multiple redundant copies of the data from multiple antennas Precisely coordinate distribution of symbols in space and time. Receiver combines multiple copies of the received signals optimally to overcome multipath. Example: Two antennas:S1 S2-S2* S1*SpaceTimeAntenna 1 Antenna 2Slot 1Slot 2S1* is complex conjugate of S1 ⇒ columns are orthogonal6-11©2006 Raj JainCSE574sWashington University in St. LouisAdaptive Antenna System (AAS)Adaptive Antenna System (AAS) Multiple antennas are used to transmit a subset of OFDM subcarriers each Example: 4 Antennas. 192 data subcarriers plus 8 pilot subcarriers are divided into 4 groups of 50 subcarriers each. Each of the four antennas transmits one group. Receivers perform channel estimation on each beam Receivers feedback the channel information to transmitter Transmitters adjust the beam forming accordingly IEEE 802.16 has MAC messages and burst format required for AAS. Allows mixing non-AAS and AAS subscribers.BaseStationSubscriberStation6-12©2006 Raj JainCSE574sWashington University in St. Louis802.16 Frame Structure802.16 Frame StructureTDD = Time Division DuplexingDL = Downlink (Base to subscriber)FCH = Frame control header:Preamble FCH Burst 1 Burst nBurst1BurstmPreamble UL BurstDL Subframe UL Subframe DL Subframe UL SubframeTDD……FDD = Freq Div DuplexingUL = UplinkContention forInitial RangingContention forBandwidth Req.Burst2Burst Profile, Down-link map, Uplink map, DL channel descriptor, etc.6-13©2006 Raj JainCSE574sWashington University in St. Louis802.16 AAS Zone Structure802.16 AAS Zone StructurePreamble FCH Burst 1 Burst n AAS ZoneSlot for IR Slot for BR Burst 1 Burst mNon-AAS AAS ZoneNon-AAS AAS ZoneAAS ZoneFDDTDDDL SubframeUL SubframeDL Subframe UL Subframe6-14©2006 Raj JainCSE574sWashington University in St. LouisIEEE 802.16 Protocol StructureIEEE 802.16 Protocol Structure CS: Maps packets and ATM cells CPS: ¾ Fragmentation and reassembly of large MAC SDUs¾ Packing and unpacking of several small MAC SDUs¾ QoS control, Scheduling and retransmission of MAC PDUs¾ Bandwidth request¾ Automatic repeat request (ARQ) using sliding windows Service Specific Convergence Sublayer (CS)MAC Common Part Sublayer (CPS)Security SublayerPhysical Layer (PHY)PHYMAC6-15©2006 Raj JainCSE574sWashington University in St. LouisIEEE 802.16 IEEE 802.16 ––QoS ClassesQoS ClassesConnection oriented: one or more unidirectional connections between subscriber and baseFour Service Classes:1. Unsolicited Grant Service (UGS): CBR traffic like voice2. Real-Time Polling Services (rtPS): rtVBR like MPEG video3. Non-Real-Time Polling Service (nrtPS): nrtVBR, e.g., FTP4. Best Effort (BE)6-16©2006 Raj JainCSE574sWashington University in St. LouisScheduling and Link AdaptationScheduling and Link Adaptation Scheduling: ¾ Base schedules usage of the air link among the subscribers ¾ Packet schedulers at the
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