IEEE 802 16 Overview Sunmyeng Kim Wireless Networks

IEEE 802. 16 Overview Sunmyeng Kim Wireless Networks Lab. University of Florida 1

Outline Introduction Physical Layer MAC Layer Traffic Service 2

Introduction Wireless Metropolitan Area Networks (MAN) Offering Broadband Wireless Access Last mile wireless broadband connectivity Base stations (BS) can handle thousands of subscriber stations (SS) Range up to 50 km. Provide high speed connectivity that supports data, voice and video 3

IEEE 802. 16 Standards History 802. 16 (Dec 2001) • Fixed wireless broadband 10 – 66 GHz: Line-ofsight only, Point-to-Multi-Point applications 802. 16 c (2002) 802. 16 Amendment Wi. MAX System Profiles 10 - 66 GHz 802. 16 a (Jan 2003) 802. 16 REVd (802. 16 -2004) (Oct 2004) 802. 16 e (802. 16 -2005) (Dec 2005) • Extension for 2 -11 GHz: Targeted for non-line -of-sight, Point-to-Multi-Point applications like “last mile” broadband access • Adds Wi. MAX System Profiles for 2 -11 GHz • MAC/PHY Enhancements to support subscribers moving at vehicular speeds 4

Channel Characteristics 10 -66 GHz n LOS is required n Multipath is negligible n Rain attenuation is a major issue n Single-carrier PHY 2 -11 GHz n NLOS n Multipath n Single and multi-carrier PHYs 5

IEEE 802. 16 Architecture 6

Physical Layer Wireless. MAN-SCa Wireless. MAN-OFDMA Wireless. HUMAN SC: Single Carrier OFDM: Orthogonal Frequency Division Multiplexing OFDMA: Orthogonal Frequency Division Multiple Access HUMAN: High-speed Unlicensed Metropolitan Area Networks 7

Physical Layer Allows use of two different duplexing schemes: n Frequency Division Duplexing (FDD) • Downlink & Uplink on separate channels • Static asymmetry • Support for both full and half duplex stations n Time Division Duplexing (TDD) • Downlink & Uplink time share the same channel • Dynamic asymmetry 8

TDD Frame Structure 9

Adaptive Modulation-Coding Scheme Modulation: BPSK/QPSK/16 QAM/64 QAM Coding: Reed solomon code, space time code Dynamically assigned according to link conditions n Burst profiles can be modified on a frame-by-frame basis for each SS. 10

Air Interface Additional MAC Requirements Designation Applicability Wireless. MAN-SC 10– 66 GHz Wireless. MAN-SCa Below 11 GHz licensed bands AAS, ARQ, STC Wireless. MANOFDM Below 11 GHz licensed bands AAS, ARQ, Mesh, STC Wireless. MANOFDMA Below 11 GHz licensed bands AAS, ARQ, STC Wireless. HUMAN Below 11 GHz license-exempt bands DFS: dynamic frequency selection ARQ: automatic repeat request DFS Options AAS, ARQ, Mesh, STC AAS: adaptive antenna system STC: space time coding 11

Frame Structure >= propagation delay + processing time 12

Management Messages DL-MAP n Defines downlink data burst profiles UL-MAP n Defines uplink data burst profiles DL-MAP and UL-MAP are both transmitted at the beginning of each downlink subframe (FDD and TDD) Downlink Channel Descriptor (DCD) n Characteristics of a downlink physical channel Uplink Channel Descriptor (UCD) n Characteristics of an uplink physical channel DCD and UCD are both transmitted at a periodic interval after ULMAP 13

DL MAP Message Type PHY Synchronization Field n Frame Duration Code n Frame Number DCD Count Base Station ID DL-MAP IEs MSG Type PHY Sync DCD Count BS ID Burst Descriptors n CID n DIUC n Start. PS – starting point of the burst n Downlink Interval Usage Code (DIUC) 14

DCD Message Type Downlink Channel ID MSG Type Channel ID DCD Count n Identifier of the downlink channel Configuration Change Count n Incremented by one (modulo 256) Downlink Burst Profiles n Modulation type n FEC Code Type n DIUC mandatory exit threshold n DIUC minimum entry threshold DIUC Descriptors 15

Burst Profile Threshold Usage CINR: carrier-to-interference-and-noise ratio 16

TDD Downlink Subframe Structure Preamble TDM Portion Broadcast DIUC=0 TDM DIUC a TDM DIUC b TDM DIUC c Preamble Tx/Rx Transition Gap DL-MAP UL-MAP 17

FDD Downlink Subframe Structure • TDM (Time Division Multiplexing) • TDMA (Time Division Multiple Access) 18

FDD Bandwidth Allocation 19

UL MAP Message Type Uplink Channel ID UCD Count Allocation Start Time MSG Type Channel ID UCD Count Allocation Start Time n Start time of the uplink allocation UL-MAP IEs n CID n UIUC n Offset • start time of the burst relative to the Allocation Start Time n Uplink Interval Usage Code (UIUC) Burst Descriptors 20

UCD Message Type Configuration Change Count n Incremented by one (modulo 256) Ranging Backoff Start / End Request Backoff Start / End Uplink Burst Profiles n Modulation type n FEC Code Type n Preamble Length MSG Type UCD Count RNG Backoff Start RNG Backoff End Req Backoff Start Req Backoff End UIUC Descriptors n Uplink Interval Usage Code (UIUC) 21

General Uplink Subframe Structure 22

Ranging Maintains the Qo. S of link between SS and BS Uplink ranging n Initial ranging • Correct transmission parameters acquirement – time offset, Tx power level • Collisions may occur in this interval n Periodic ranging • On time transmission parameters adjustment Downlink ranging n Downlink burst profile n SS measures the CINR and compares the average value against the threshold values n SS requests a change to a new burst profile • In granted uplink bandwidth or Initial ranging interval 23

Architecture BS SS Connection Request Connection Response Traffic Admission Control Connection Classfier Polling Bandwidth Request UGS rt. PS nrt. PS Scheduler Uplink Bandwidth Allocation Scheduling BE UL-MAP Data Packets 24

Connection – New SS 802. 16 is connection oriented Each SS has universal 48 bit MAC address Unidirectional logical link between BS and SS MAC n For each direction, 3 management connections established • Basic, Primary, and Secondary n A connection identified by a 16 -bit CID 25

Connection – New Flow Service Flow n Service Flow ID: An SFID is assigned to each existing service flow. n Characterize Qo. S parameters (latency, jitter, and throughput assurance) n CID: Mapping to an SFID Multiple connection can be established for multiple service flows Higher layer sessions can share the same connection Connections share the air link 26

Traffic Types Traffic Category UGS Unsolicited grant service rt. PS Real-time polling service Applications • Constant bit rate • Periodic interval • Vo. IP • Variable bit rate • Periodic interval • Video Ert. PS Extended Real-time polling service • UGS + rt. PS • Vo. IP with Activity Detection IEEE 802. 16 e nrt. PS Non-real-time polling service • Variable bit rate • File Transfer Protocol (FTP) BE Best effort service • Fixed size bandwidth • Data Transfer, Web Browsing Qo. S Parameters • Maximum Sustained Rate • Maximum Latency Tolerance • Jitter Tolerance • Minimum Reserved Rate • Maximum Sustained Rate • Traffic Priority 27

Bandwidth Request/Grant (1) Polling n BS allocates the SSs bandwidth to send bandwidth requests n Unicast: SS is polled individually over basic CID n Multicast and broadcast: • Bandwidth allocation to multicast/broadcast CID • SSs perform contention resolution for bandwidth request n PM (poll-me) bit: • Used by the SS to request a bandwidth poll for non. UGS services • Only works for active UGS connections • Set the PM bit in a MAC packet to indicate the BS to poll 28

Bandwidth Request/Grant (2) Requests n BW stealing: SS uses a part of its granted bandwidth to send a request n Piggyback: SS uses a piggyback field in the header Grants n BS grants bandwidth to the SS’s basic CID (not individual CID) n SS may re-distribute bandwidth among its connections 29

Polling (1) Unicast BS Poll (UL-MAP) Allocation (UL-MAP) 1. 2. 3. 4. SS Request Data BS allocates BW for the SS in the uplink subframe. SS uses the allocated BW to send a BW request. BS allocates the requested BW for the SS (if available). SS uses allocated BW to send data. 30

Polling (2) Multicast/Broadcast BS Poll (UL-MAP) Allocation (UL-MAP) 1. 2. 3. 4. 5. SS Request (Contention) Data BS allocates BW for contention among SSs in the uplink subframe. SSs contends for the allocated BW to send a BW request. BS allocates the requested BW for the successful SSs. SS uses allocated BW to send data. If a SS does not receive BW for data, it contends again. 31

Summary of Bandwidth Request 32

Contention Resolution (1) Collisions may occur during Ranging/Bandwidth request intervals A truncated binary exponential backoff • Ranging Backoff Start / End • Request Backoff Start / End n The SS shall randomly select a number within its backoff window. n This value indicates the number of contention transmission opportunities that the SS shall defer before transmitting n If the contention transmission fails, the SS increases its backoff window by a factor of two. 33

Contention Resolution (2) Example n Start: 3, End: 8 n CWmin = 23 -1=7 n CWmax=28 -1=255 n Backoff counter = rand [0, CW]×transmission opportunity where, CWmin <= CWmax 34

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