Media Access Control Layer Proposal for the 802.16.1 Air ... · Access Control Layer Proposal for...
Transcript of Media Access Control Layer Proposal for the 802.16.1 Air ... · Access Control Layer Proposal for...
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: [email protected], 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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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)
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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
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IEEE 802.16.1 MAC Proposal
Additional PHY Layer Support
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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
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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
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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
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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)
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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
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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
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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
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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
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IEEE 802.16.1 MAC Proposal
Conclusions and Summary
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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
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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