Document Number:IEEE 802.16.1mp-00/14

Title:Media Access Control Layer Proposal for the 802.16.1 Air Interface Specification

Date Submitted:2000-04-14

Source:Glen Sater Voice: 480-441-8893Motorola Inc. Fax: 480-675-21168220 E. Roosevelt Street, M/D R1106 E-mail: g.sater@motorola.comScottsdale, AZ 85257

Co-ContributorsSee following page.

Venue:802.16 Session #7, May 1-5, 2000, Gaithersburg, MD, USA.

Base Document:IEEE 802.16mc-00/14 (/http://www.ieee802.org/16/mac/contrib/802161mc-00_14.pdf)

Purpose:This presentation is intended to provide an overview of the submission IEEE 802.16.1mc-00/14, “Media Access Control LayerProposal for the 802.16 Air Interface Specification”.

Notice:This document has been prepared to assist the IEEE 802.16. It is offered as a basis for discussion and is not binding on thecontributing individual(s) or organization(s). The material in this document is subject to change in form and content after furtherstudy. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.

Release:The contributor acknowledges and accepts that this contribution may be made public by 802.16.

IEEE Patent Policy:

The contributors are is familiar with the IEEE Patent Policy, which is set forth in the IEEE-SA Standards Board Bylaws<http://standards.ieee.org/guides/bylaws> and includes the statement: “IEEE standards may include the known use of patent(s),including patent applications, if there is technical justification in the opinion of the standards-developing committee and provided theIEEE receives assurance from the patent holder that it will license applicants under reasonable terms and conditions for the purpose ofimplementing the standard.”

May 1-5, 2000 IEEE 802.16.1mp-00/14 2

IEEE 802.16.1 MAC Proposal

Glen Sater and Karl Stambaugh

Arun Arunachalam and George Stamatelos

Jeff Foerster

Scott Marin and Bill Myers

Leland Langston and Wayne Hunter

Phil Guillemette

Chet Shiralli and Menashe Shahar

George Fishel

Ray Sanders

Moshe Ran

Andrew Sundelin

Mark Vogel and Jack Fijolek

Yonatan Manor

Motorola

Nortel Networks

Newbridge

SpectraPoint

Crosspan, A Raytheon Company

SpaceBridge Networks Corporation

Vyyo

Communications Consulting Services

CircuitPath Networks Systems

TelesciCOM

iSKY

3Com

Oren Semiconductors

May 1-5, 2000 Gaithersburg, NM

May 1-5, 2000 IEEE 802.16.1mp-00/14 3

Presentation Overview

Changes since last Proposal

Overview

PHY Layer Support

Conclusions

May 1-5, 2000 IEEE 802.16.1mp-00/14 4

AdditionalBurst Profile

Pairs

CPE TxFast Power

Control

DownstreamFragmentation

OptionalConcatenation

Header

GenericPDU

Format

MAC Proposal Evolution

IEEE 802.16Functional

Requirements

VendorSuppliedMarket

Requirements

DynamicChannelChange

Messages

PHYDecoupling

Session #5MAC

Session #7MAC

DownstreamAdaptive

ModulationSupport

ATMClassifiers

PHY DuplexingMode

Support

ATM

DOCSISMAC

Components

May 1-5, 2000 IEEE 802.16.1mp-00/14 5

Differences Since Session #6

• Defined a SAP Identifier for Generic PDU Formats– Allows for coordination of different convergence layers

– Independent of ATM and 802.3/Ethernet support

• Added Support for Downstream Adaptive Modulation– Integrated into the Ranging Process

– Defines modulation change request and acknowledgement

– Ensures CPE operates at optimum modulation

• TDD and H-FDD PHY are supported– Existing MAP message is used for both TDD and H-FDD

– Additional IUC defined to support H-FDD

– Existing MAP message can support framing• Works in conjunction with the scheduler

May 1-5, 2000 IEEE 802.16.1mp-00/14 6

IEEE 802.16.1 MAC Proposal

MAC Protocol Overview

May 1-5, 2000 IEEE 802.16.1mp-00/14 7

Overview

• Point to multi-point MAC protocol

• Upstream– Time divided into continuous stream of mini-slots

– Contention-based access for latency tolerant applications

– Reservation-based access for low-latency applications

– Polling-based access for variable-rate applications

– Message formats allow efficient scheduling of different message types

• Supports fragmentation, concatenation, and payload headersuppression

• MAC User Data Formats– Variable-length MAC PDU

– ATM cell MAC PDU

– Generic User Data PDU

May 1-5, 2000 IEEE 802.16.1mp-00/14 8

Overview (continued)

• Service Flows– Provides mechanism to manage upstream and downstream QoS

– Integral to bandwidth allocation process (using mini-slots)

– Multiple service flows per SS• each can have a different set of QoS parameters

• Upstream controlled by variety of scheduling services– Best Effort

– Polling

– Unsolicited Grant

• QoS Parameters used in conjunction with scheduling services– Provides ability to bound delay and jitter

– Specifies bandwidth

• Scheduling algorithms not defined by the MAC

May 1-5, 2000 IEEE 802.16.1mp-00/14 9

Overview (continued)

• Full set of MAC management messages– Network access, entry, and ranging

– Upstream bandwidth allocation

– Dynamic connection creation/modification/deletion

• PHY Support– Upstream Adaptive Burst Profiles

– Downstream Adaptive Modulation

– FDD carrier-based adaptive modulation

– FDD, H-FDD, and TDD with CPE-based adaptive modulation

– Implicit framing

• Security– CPE Authentication

– User data PDU encryption

May 1-5, 2000 IEEE 802.16.1mp-00/14 10

MAC Proposal Comparison Overview

Request/grant/

piggyback

Extended header

Contention

Resolution

Adaptive

Polling

Header

compression

ATM

Packets

DS0

compression

TDM

FDD DL-MapTDD

E+ and D+ aresimilar

E+ only

D+ only

TC framing

Registration

TDM, Frame

Fragmentation

ARQ

H-FDD

Concatenation

Security

Concat. hdr

Session #7 D+MAC Extensions

D+ Deleted

May 1-5, 2000 IEEE 802.16.1mp-00/14 11

PHYSICAL

Protocol Stack

• Flexible Protocol Stack– Directly supports IP

– Supports ATM and Services over ATM

– Generic Convergence Process for special cases

DATA LINK

NETWORK

TRANSPORT

SESSION

PRESENTATION

APPLICATION

Physical Media Dependent802.16PHY

802.16MAC

Transmission Convergence

Security (optional)

MAC

802 LLC

IP

ATM

AAL1

GenericConvergence

Process

CES

AAL5

FrameRelay

Vendor Specific

May 1-5, 2000 IEEE 802.16.1mp-00/14 12

PDU Formats

• 802.3/Ethernet– Direct, native support for IP-based protocols

– Fast, efficient

– No convergence process required

• ATM with Adaptation Layers– Chosen to support leased-line services

– Existing standards by the ITU and ATM Forum• DS1, E1, Frame Relay, …

• No need to develop new convergence process

• Uses proven technologies

May 1-5, 2000 IEEE 802.16.1mp-00/14 13

MAC HEADER

FC(1 byte)

MAC_PARM(1 byte)

LEN(2 byte)

EHDR(0~255 Bytes)

HCS(2 byte)

SAP ID(1 byte)

DATA PDU

Generic PDU Format

• Service Access Point ID– Uniquely identifies different convergence

layers using the generic PDU format

– IDs are assigned by an external authority asvendors/protocols are added

May 1-5, 2000 IEEE 802.16.1mp-00/14 14

Generic PDU

Vendor AProtocol X

Vendor BProtocol X

Vendor CProtocol Y

SAP_ID=1 SAP_ID=2 SAP_ID=3

Generic PDU

Vendor AProtocol X

Vendor BProtocol X

Vendor CProtocol Y

SAP_ID=1 SAP_ID=2 SAP_ID=3

802.16.1 MAC

SAP ID Usage

Convergence Sub-Layer Processes Convergence Sub-Layer Processes

SAP ID is used by the generic SAP to deliver generic PDUsto the appropriate sub-layer process

May 1-5, 2000 IEEE 802.16.1mp-00/14 15

Bearer Services - Service Flows

• Key to providing different services

• Establish a “virtual circuit” for each service (using a SID)

• Service Flows are unique– across CPEs

– across Subscribers

CPE 1

BS

T1

T1

100BaseT

T1 Data

T1 Data

IP Data

T1 PDUs scheduled atconstant intervals

Management PDUs

IP PDUs schedule as best effort

Upstream RF Channel

CPE 2

May 1-5, 2000 IEEE 802.16.1mp-00/14 16

Bearer Services - Scheduling and QoS

Application Service Class MACPDU Type

MACScheduling

CircuitEmulation

CBR ATM/AAL1 Unsolicited GrantService

Web Browsing UBR 802.3/Ethernet Best Effort

VoIP CBR 802.3/Ethernet UGS withActivity Detection

CBR ATM/AAL5 Unsolicited GrantService

Frame Relay

VBR ATM/AAL5 Real Time Polling

StreamingVideo

VBR 802.3/Ethernet Real Time Polling

Supports different types of services using the scheduling and QoSparameters

May 1-5, 2000 IEEE 802.16.1mp-00/14 17

Distributed Scheduling (E+ Approach)

• CPE active participant in scheduling– CPE knows QoS requirements and reorders input queue

PDUs for output queue

– BS and CPE must coordinate to guarantee QoS

– QoS will fail if either CPE or BS makes mistake

• Complex CPE implementation

PDU

Scheduler

InputQueue

OutputQueue

Upstream Burst

MAC Control

May 1-5, 2000 IEEE 802.16.1mp-00/14 18

Centralized Scheduling (D+ Approach)

• CPE passive participant in scheduling– CPE does not even need to know QoS req’ts

– CPE simply puts packet in proper FIFO queue

– BS alone guarantees QoS

– Easier to have interoperable implementations

• Simple & inexpensive CPE implementation

PDU

Classifier

Output QueuesMAP

Upstream Burst

May 1-5, 2000 IEEE 802.16.1mp-00/14 19

Bearer Services - Service Flows

• Three-tiered Service Flow approach– Provisioned - known to both BS and CPE

– Admitted - Resources reserved but not used

– Active - Resources committed

• Why provision without use?– To allow quick establishment of service flows

• Why have an admitted state?– To allow resources to be temporarily allocated

to other services (but resumption is guaranteed)

May 1-5, 2000 IEEE 802.16.1mp-00/14 20

Bearer Services - Service Flows (cont.)

• Two-Phase Activation Model– Conserve network resources until end-to-end

connection has been established

– Fast policy checks and admission control

Provisioned Admitted Active

CPENetworkEntry

DS0 (off-hook) Active Service Flow

DS0 (On-hold) - Temporarily release resource

DS0 (Off-hold) - ReacquireResources

May 1-5, 2000 IEEE 802.16.1mp-00/14 21

IEEE 802.16.1 MAC Proposal

Additional PHY Layer Support

May 1-5, 2000 IEEE 802.16.1mp-00/14 22

Upstream Burst Profiles

• Different Services require different FEC– Examples:

• UDP packets get lower FEC

• ATM carrying CES get higher FEC

– Implemented with 3 pairs of data grants• Scheduler can apply as needed

• Feature can not be leveraged if differentservices are carried in the same burst

• Also supports different modulation types

May 1-5, 2000 IEEE 802.16.1mp-00/14 23

Downstream Adaptive Modulation

• CPE Modulation change identified by PHY preamble

• BS must schedule downstream appropriately– QPSK broadcast data first, followed by 16-QAM and 64-QAM

– No MAC-specific messaging required to identify transitions

FRAMESTART

QPSK P16 16-QAM P64 64-QAM

FDD Example

FRAMESTART

QPSKBroadcast

P16CPE

1

H-FDD Example

1 frame

P16CPE

2P4

CPE3

P64CPE

4

1 frame

May 1-5, 2000 IEEE 802.16.1mp-00/14 24

Adaptive Modulation and RangingBS CPE

Detects need to changedownstream modulationby monitoring C/(I+N)

Verifies CPE capabilityand makes necessaryscheduler and PHYchanges

Ranging Opportunity

RNG-REQ (New Modulation)

RNG-RSP (ACK Modulation)

Receives ACK of modulationchange and beginsmonitoringusing new threshold

New format is requestedby CPE

Generates periodicranging opportunitiesas part of normalactivities

Begin using the newmodulation type forthe CPE

May 1-5, 2000 IEEE 802.16.1mp-00/14 25

Ranging Message Extensions

• RNG-REQ– Added one TLV to indicate modulation type

• Optional (sent when needed)

• 1 = QPSK, 2 = 16-QAM, 4 = 64-QAM

• RNG-RSP– Added four TLVs (optional, sent when needed)

• Acknowledged modulation type (as above)

• 16-QAM Threshold in C/(N+I)

• 64-QAM Threshold in C/(N+I)

• Threshold Delta in C/(N+I)

May 1-5, 2000 IEEE 802.16.1mp-00/14 26

Threshold Usage

• CPE utilizes thresholds to determine whento request change to minimize overhead

C/(

N+

I) (

dB)

20

15

10

5

0

64-QAMRegion

16-QAMRegion

QPSKRegion

64-QAM Threshold + Threshold Delta

64-QAM Threshold - Threshold Delta

16-QAM Threshold + Threshold Delta

16-QAM Threshold - Threshold Delta

May 1-5, 2000 IEEE 802.16.1mp-00/14 27

DATA DATA

TDD Support

• MAP message defines– Starting mini-slot for this frame’s upstream burst

– ACK time for previous frames upstream burst• contention resolution

– All mini-slot offsets (upstream burst allocations) for CPE

– Receive time (implicitly by lack of upstream mapping)• CPE must listen to downstream when not mapped to upstream

MAP MAP

Tx/Rx Gap

DATADownstream

Upstream

1 frame

Rx/Tx Gap

ACK

FS FS

May 1-5, 2000 IEEE 802.16.1mp-00/14 28

CPE C

CPE D(FDD)

MAP Downstream

Upstream

1 frame

BROADCASTCPE B

(H-FDD)CPE A

(H-FDD)CPE C(FDD)

CPE A(H-FDD)

CPE B(H-FDD)

CPE C(FDD)

H-FDD Support

CPE B

CPE A

CPE D

256

192

128

64

0 64 128 192 256

Example MAP

SID Mini-Slot Offset• Same method as for TDD

• Downstream access scheduled by BS

• Upstream access handled by MAP

• Both H-FDD and FDD supported

May 1-5, 2000 IEEE 802.16.1mp-00/14 29

HD-FDD Scheduling

• PDU lengths don’t always allow “perfect” scheduling– Scheduler may use a Reserved IUC in the MAP for this time

– Forces all CPEs to listen to downstream

Downstream

Upstream

1 frame

CPE B (10)(H-FDD)

CPE A (8)(H-FDD)

CPE C (10)(FDD)

CPE A (4)(H-FDD)

CPE B (8)(H-FDD)

CPE C (6)(FDD)

0

Ranging Opportunity

Unallocated Upstream Mini-slots (Reserved IUC)

() indicates length of PDU

May 1-5, 2000 IEEE 802.16.1mp-00/14 30

Framing

• Framing implicitly defined by MAP at MAC layer– Frame Start (FS) marks start of PHY frame

– TDD• BS can be synchronized for coordination of multiple TDD

channels

• External timing trigger at BS can mark start of “frame”

• Up/Down bandwidth split is implicitly defined via MAP

• Management messages broadcast at regularintervals– SYNC, UCD and Ranging (Initial and Maintenance)

• Broadcast user data typically sent first– Required for TDD

May 1-5, 2000 IEEE 802.16.1mp-00/14 31

IEEE 802.16.1 MAC Proposal

Conclusions and Summary

May 1-5, 2000 IEEE 802.16.1mp-00/14 32

Conclusions

• Supports the functional requirements– Multiple classes of services

– Multiple services per subscriber

– Multiplexing allows statistical gains

• Uses proven technologies– Extensive implementation experience

– Extensive research• academic/commercial

– History of on-going change process tostrengthen the MAC technologies

May 1-5, 2000 IEEE 802.16.1mp-00/14 33

Conclusions (cont.)

• Robust and efficient solution

• Well defined– A complete solution

– SDL used to describe dynamic behavior

– No undefined convergence layers/processes

• Tailored for hardware implementation– Faster operation, simpler CPEs

• Complete PHY support– FDD with continuous or adaptive modulation

– H-FDD and TDD with adaptive modulation