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IEEE 802.16

IEEE 802.16. Preliminaries. IEEE 802.16 defines the WirelessMAN air interface specification for wireless metropolitan area networks (MANs) It will facilitate broadband wireless access Designed for point-to-multipoint broadband access applications using roof-top or tower-mounted antennas

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IEEE 802.16

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  1. IEEE 802.16

  2. Preliminaries • IEEE 802.16 defines the WirelessMAN air interface specification for wireless metropolitan area networks (MANs) • It will facilitate broadband wireless access • Designed for point-to-multipoint broadband access applications using roof-top or tower-mounted antennas • Addresses the need for very high bit rates • Types: • 802.16.1: air interface for 10-60 GHz • 802.16.2: Coexistence of broadband wireless access system • Air interface for licensed frequencies: 2-11 GHz

  3. Services • Digital audio/video multicast • Digital telephony • ATM • Internet Protocol • Bridged LAN • Back-haul

  4. Physical Layer • 10-16 GHz: • Line of sight propagation • The BS transmits a TDM signal with individual subscriber stations (SSs) allocated time slots serially • Access in uplink direction is by TDMA • Both TDD and FDD are used for uplink/downlink • 2-11 GHz (802.16a): • Includes both licensed and unlicensed spectra • Non line-of-sight (NLOS) operations • Use of OFDM

  5. MAC • Service Specific Convergence Sublayer: interfaces to higher layers • ATM convergence sublayer • Packet convergence sublayer • Common Part Sublayer • Privacy Sublayer • Protocol based on privacy key management (PKM) built around the concept of security associations

  6. Common Part Sublayer • A central BS handles multiple independent sectors • On the downlink, data to SSs are multiplexed in TDM fashion. The uplink is shared between SSs in TDMA fashion • MAC is connection oriented – provides a mechanism for requesting bandwidth, associating QoS and traffic parameters, transporting and routing data to the appropriate convergence sublayer, and other actions • Connections are referenced with 16-bit connection identifiers (CIDs)

  7. Connections • Upon entering the network, the SS is assigned three management connections in each direction • Basic connection: used for transfer of short, time-critical MAC and radio link control messages • Primary connection: used to transfer longer, more delay-tolerant messages such as those used for authentication and connection set-up • Secondary connection: used for transfer of standards-based management messages such DHCP, TFTP, and SNMP • SSs are allocated unidirectional transport connections for contracted services • Additional connections are reserved for other operations, such as contention-based access, broadcast, multicast, etc.

  8. Radio Link Control • RLC begins with periodic BS broadcast of burst profiles that have been chosen for the uplink and downlink • Downlink Interval Usage Code (DIUC) • Uplink Interval Usage Code (UIUC) • During initial ranging, the SS also requests to be served in the downlink via a particular burst profile by transmitting its DIUC • After initial determination of uplink/downlink burst profiles, RLC continues to monitor and control burst profiles

  9. Uplink Scheduling Services • Each connection in the uplink direction is mapped to a scheduling service • Each scheduling service is associated with a set of rules imposed on the BS scheduler

  10. Types of Services • Unsolicited Grant Service (UGS): for services that generate fixed units of data periodically • The BS schedules regularly grants of size negotiated at connection set-up • Real-time Polling Service: for services that are dynamic in nature, but offers periodic dedicated request opportunities to meet real-time requirements • Well-suited for VoIP, streaming audio/video • Non-RT Service: almost identical to RT polling service except that connections may utilize random access transmit opportunities for sending bandwidth requests • Best effort service: No guarantees

  11. Channel Acquisition • Upon installation, an SS begins scanning its frequency list to find an operating channel. • It may be programmed to register with a specified BS, referring to a programmable BS ID broadcast by each • After deciding on which channel to attempt connection, the SS tries to synchronize to the downlink transmission by detection periodic frame preambles • Other steps: • Initial ranging and negotiation of SS capabilities • SS authentication and registration • IP connectivity (obtains IP address through DHCP)

  12. Connection Setup • IEEE 802.16 uses the concept of service flows to define unidirectional transport of packets on either downlink or uplink • To utilize the network resources most effectively, IEEE 802.16 adopts a 2-phase activation model in which resources assigned to a particular admitted service flow may not be actually committed until the service flow is activated • Each admitted or active service flow is mapped to a MAC connection with a unique CID • Service flows are pre-provisioned, and setup of the service flows is initiated by the BS during SS initialization • Dynamic service establishment and dynamic service changes are also supported

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