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WUSTL CSE 574S - Wireless Metropolitan Area Networks (WMANs)

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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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WUSTL CSE 574S - Wireless Metropolitan Area Networks (WMANs)

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