Elements of Cross-Layer System & Network Design for QoS-Enabled Wi-Max Networks

Metanoia, Inc.
Critical Systems Thinking™

Elements of Cross-Layer System
and Network Design for QoS-
Enabled Wi-Max Networks
Dr. Abhay Karandikar
Dr. Vishal Sharma
IIT Bombay
Metanoia, Inc.
http://www.ee.iitb/ac/in/~abhay
http://www.metanoia-inc.com
© Copyright 2006-07
All Rights Reserved

Metanoia, Inc.

Workshop Overview

 IEEE 802.16 standards – an introduction

 PHY and MAC: Key design QoS design aspects

 Scheduling services & design implications

 System architectures for QoS

 Cross-layer based scheduling techniques for QoS

 Implementation issues in algorithms and protocols

 Future of WiMax and applicability to military communications

©Copyright 2006-07
All Rights Reserved Milcom’07, 29-31 October 2007, Orlando, FL 2

Metanoia, Inc.

Wi-MAX System Architecture

Metanoia, Inc.
IEEE 802.16 Wireless MAN Critical Systems Thinking™

Standard: Background
 Developed by IEEE 802.16. WG
 Technologies/protocols for air-interface of BWA systems
 Specifies PHY and MAC layer

1999 2000 2001 2002 2003 2004 2005 2006

IEEE Std. 802.16-2001
IEEE Std. 802.16-2004

IEEE Std. 802.16e

 Evolutionary standard …
 Originally -- stationary, enterprise-class deployments (2001)
 Enhanced for residential-class applications (2003)
 Extended for mobile + fixed terminals (2002-2005)

©Copyright 2006-07

Metanoia, Inc.

802.16 Wireless MAN Standard
 PHY layer – primary arbiter of physical environment in which
technology can operate

 MAC layer – essence of standard – supports …
 Differentiated QoS – specifies scheduling behavior, not algos.
 Many demanding enterprise-class or consumer-class apps.

 “Metropolitan”  target scale, not geography
 Size of city, but could be rural or urban

 Ensures spectrum efficiency – via techniques we see later

©Copyright 2006-07

Metanoia, Inc.
IEEE 802.16 MAN Critical Systems Thinking™

Market Applications and Deployment
Wi-Fi Backhaul
Mall/Coffee
Shop Hotspot Mobile
Station (MS) Industrial
Enterprise

DSL/Cable
Alternative Multi-tenant
Base Station
Customers (condo)
(BS)

Mesh Node
Residential
Customer

Enterprise
Core Network Customer

Company
Base Station
Wired Fiber Extension for
warehouse Backhaul
(BS) Core Infrastructure
©Copyright 2006-07

Metanoia, Inc.
A Word on QoS Architecture: Critical Systems Thinking™

Basic Elements
Signaling
From provisioning
system

Connection
Service Admission Control
definitions/Rules (CAC)

Management Control Plane
Plane

Metering

Incoming data
Packet Shaping/
Marking Scheduling
Classification Policing

Data Plane
©Copyright 2006-07

Metanoia, Inc.

802.16 High-Level System Operation

SS1

SS2

BS

SS3

SS4
©Copyright 2006-07

Metanoia, Inc.

1

SS1 1 2 3 4

2

SS2

3
BS

SS3 4

SS4
©Copyright 2006-07

Metanoia, Inc.

1

Requests

SS1
BS computes non-
2
conflicting schedule

SS2 Grants

3
UL Control
BS UL Data Part Start

DL UL
SS3
1 3 2

Frame
©Copyright 2006-07 SS4

Metanoia, Inc.

 Fixed BS (one), distributed SS’s (many)
 Time-slotted operation
 Time adjusted such that receptions at BS arrive in sync.

 Initial ranging for each SS
 Multiple access to share radio medium
 Bandwidth requests SSs  BS in UL
 BS computes non-conflicting schedule
 Based on nature of requests, # of SS’s, channel state

 Grants BS  SSs in DL
 At appointed time, SS’s transmit to BS

©Copyright 2006-07

Metanoia, Inc.
System and Protocol Architecture: Critical Systems Thinking™

Components

System Architecture Protocol Architecture
 Topologies supported  Layered reference model
 Framing + slot structure  Convergence sublayer (CS)
 Duplexing  Common Part Sublayer (CPS)
 Multiplexing – discussed in detail

 Multiple access technique  Security sublayer (SS) – not
focus of this talk
 B/w request/grant mechanism
 ARQ protocol
 MAC
 Adaptive PHY

©Copyright 2006-07

Metanoia, Inc.

TDD Frame Structure -- Details
Frames

j-3 j-2 j-1 j j+1 j+2 j+3 j+4

Preamble DL-subframe UL-subframe SS transition
gap
TDM portion
Frame Adaptive SS1
DIUC a DIDU b DIDU Initial main Request
Control sched
data data n data -tainance contention
Section data

DL-MAP UL-MAP DCD UCD

Collision Collision
Initial Data Access Burst
Request Gap End of
Ranging Grant IEs Bandwidth
IEs IE MAP IE
IE request

Unicast Unicast Multicast Broadcast
Poll to Poll to Conten- Contention
SSi SSj tion IE IE
©Copyright 2006-07

Metanoia, Inc.

MAC and PHY: Key QoS
Design Aspects

Metanoia, Inc.

MAC Key Aspects
 Centralized scheduling & multiple access
 Access overhead ~ zero
 Nearly no wasted bandwidth

 Data encapsulation
 Small headers -- minimize per-PDU overhead

 Packing
 Multiple SDU’s/PDU for apps. with small pkts. (VoIP, TCP) - efficiency

 Fragmentation
 Split large SDU’s across PDU’s for real-time adaptation to channel
©Copyright 2006-07

Metanoia, Inc.

802.16 MAC Layer − Basics
 Functions
 Protocol for accessing medium
 Radio resource and radio-link control
 Security

 MAC instance identified by unique 48-bit address
 SS can have multiple MAC addresses (with multiple I/Fs)

 Full MAC address used only during
 Initial registration
 Authentication

 Not carried in every 802.16 MPDU

©Copyright 2006-07

Metanoia, Inc.

MAC Design Features Supporting QoS
 RLC (radio link control) pulled into MAC
 Enables tighter control of cross-layer scheduling

 Connection-oriented MAC
 Gives notion of connection ID
 Allows management + housekeeping per connection

 MAC headers for efficient transport of
 Control/signaling information
 Bandwidth requests

 Efficient transportation of MAC PDUs
 Via packing/fragmentation ops.

©Copyright 2006-07

Metanoia, Inc.

ARQ + H-ARQ Key Aspects
 Process for handling MPDU errors
 Error detection via CRC/FEC or checksum

 Retransmission (ReTX) strategy
 Selective-Repeat (SR) and Go-Back-N (GBN) variant

 ReTX unit – block-based
 Block size ranging from 1 to 2040 bytes

 Compact bitmap-based feedback – for multiple blocks

 Cross-layer protocol: involves both PHY and MAC
 Negotiated during SS initialization; for OFDMA PHY only

 Stop-and-wait with immediate/synchronous feedback

©Copyright 2006-07

Metanoia, Inc.

802.16 Protocol Reference Model
CS SAP

Service-Specific Service-Specific
Convergence Sublayer Convergence Sublayers

MAC SAP
MAC MAC Common Part
MAC Common Part
Sublayer Sublayer
Network
Security Sublayer Mgt. Sys.
Security Sublayer

PHY SAP

PHY Physical Layer PHY Layer
(PHY)

Data/Control Plane Management Plane
©Copyright 2006-07

Metanoia, Inc.

Convergence Sub-layer (CS) : Architecture
1 4’
Data PDU arrives Deliver payload protocol
(payload protocol) PDU to higher layer

CS SAP CS SAP CS SAP
ATM-CS IP-CS Ethernet CS

2
Map PDU to
Svc. Flow 3’ Restore compressed
protocol headers
3 Compress redundant MAC SAP
hdrs., add PDU hdr. 2’ Receive MSDU
MAC Common Part
Sublayer
4 Deliver processed
pkt. to MAC SAP
MAC Security Sublayer
Classification &
mapping of IP QoS
PHY SAP 1’
to 802.16 Qos 5
Scheduling and Reception and
transmission decoding
©Copyright 2006-07

Metanoia, Inc.
Protocol Architecture: Critical Systems Thinking™

Common Part Sub-layer (CPS)
 Supports multiple MAC CSs MAC SDU’s
Medium Access,
 Performs core MAC functions, Connection Management,
QoS (scheduling, CAC)
independent of CS
MAC SAP
 Oblivious to internals of MAC
MAC Common Part
CS PDU
Sublayer

 Transforms MSDUs from CS
MAC Security Sublayer
into MPDUs
 Via various operations, some PHY SAP
of which we see later Encapsulation of MAC
payload, privacy key mgt.
protocol
 Responsible for media MAC PDU’s
access, connection mgt, QoS

©Copyright 2006-07

Metanoia, Inc.

PHY Key Aspects
 WirelessMAN-SC  Modulation
 10-66 GHz operations  BPSK
 LOS necessary  QPSK
 QAM

 WirelessMAN-SCa
 2-11 GHz operation  Physical slot-WirelessMAN-SC
 Simpler Tx, complex Rx due  4 QAM symbols
to multipath

 OFDM
 2-11 GHz operation
 NLOS transmission

©Copyright 2006-07

Metanoia, Inc.
PHY Modulation and Coding Critical Systems Thinking™

Schemes for 802.16d

Rate ID Modulation Coding Information Information Peak data rate
rate bits/symbol bits/OFDM symbol in 5MHz (Mb/s)
0 BPSK 1/2 0.5 88 1.89
1 QPSK 1/2 1 184 3.95
2 QPSK 3/4 0.5 280 6.00
3 16QAM 1/2 2 376 8.06
4 16QAM 3/4 3 568 12.18
5 64QAM 2/3 4 760 16.30
6 64QAM 3/4 4.5 856 18.36
Source: [GWA05]

©Copyright 2006-07

Metanoia, Inc.

Scheduling Services and
Design Implications

Metanoia, Inc.

Enforcing QoS Requirements -- Options
 Applications: voice, video, data, multi-media, gaming
 Widely varying QoS needs

Quality-of-Service

Prioritized QoS Parameterized QoS
 Network treats traffic based on  Network guarantees a set of QoS
relative priority parameters for traffic
 E.g. Diffserv approach  E.g. ATM approach

©Copyright 2006-07

Metanoia, Inc.

Quality of Service (QoS) Parameters
 Bit level
 Minimum BER Requires Effective
 Packet level Link level
Scheduling
 Throughput
Algorithms
 Delay
 Jitter
 Packet Loss
 Call level
 Blocking probability
 Dropping probability
 Application level
 End-to-End Throughput / response time
 Peak signal-to-noise ratio

©Copyright 2006-07

Metanoia, Inc.

QoS in Access Networks
 # flows limited  per-flow QoS possible

 Adverse channel environment, b/w scarcity
⇒ Wireless access is the bottleneck

 Connection-oriented services with guaranteed perf. will help
ensure end-to-end QoS

©Copyright 2006-07

Metanoia, Inc.

Wireless QoS: What’s Different?
 Variable capacity networks

 High probability of error

 Variable airtime for transmitting data
 Depends on AMC, FEC, link quality

 Fairness is an issue

©Copyright 2006-07

Metanoia, Inc.

Differentiated QoS: What is needed?
 Flexible PHY and MAC framing

 Centrally-controlled MAC

 Sophisticated AMC, FEC, retransmission schemes

 Ability to give QoS on DL and UL

 Symmetric operation – high throughput in both UL/DL

 Efficient scaling with sufficient per-subscriber throughput

©Copyright 2006-07

Metanoia, Inc.

Wi-MAX QoS Classes

Low

M
TD 1
/E
T1
Unsolicited Grant Service eo
id

Delay Tolerance
V
(UGS) g IP
in o
am , V
re V
St I PT
Real Time Polling Service ng
si P
(rtPS) w T
ro d F
B e
eb pe
W hS
Non Real Time Polling Service ig
H
(nrtPS) ai
l
m
E P
FT
Best Effort
(BE) High

©Copyright 2006-07

Metanoia, Inc.
QoS Classes in 802.16 and Critical Systems Thinking™

Characterizing Parameters
Type Service Flow Parameters
- Max. sustainable traffic rate
- Max. latency
UGS
- Tolerated jitter
- Request/transmission policy
- Min. reserved traffic rate
Unsolicited Grant Service
- Max. sustainable traffic rate
(UGS) rt-PS
- Max. latency
Real-Time Polling Service - Min. reserved rate
(rtPS) - Max. sustainable rate
nrt-PS
- Priority
Non Real-Time Polling Service - Max. sustainable traffic rate
(nrtPS) BE - Priority

Best Effort
(BE)

©Copyright 2006-07

Metanoia, Inc.

Mapping Applications to 802.16 QoS
Enterprise Enterprise Provider IP QoS 802.16 Traffic
Applications (100s) Service Classes Service Classes PHBs Types
(8-11) (3-5) (5-8) (4)
VoIP

VoD
Voice
H.323, SIP
Video EF
OSPF, RIP, BGP, Real-time
SNMP, NFS
UGS
Signaling
AF3, CS6,
SAP, Oracle, BEA
Control CS3 rt-PS
Control
SNA Critical AF2, CS2
Critical Data nrt-PS
Messaging AF1
Bulk
Bulk Data
Email BE
Best Effort BE BE
FTP/HTTP
Scavenger
Data apps., Intranet
Web
KaZaa, Quake,
recreational video
©Copyright 2006-07

Metanoia, Inc.

System Architectures for QoS

Metanoia, Inc.
System-Level View of QoS in 802.16 Critical Systems Thinking™

Networks: Building Blocks
@ Subscriber Station (SS) @ Base Station (BS)
 SS UL scheduler  BS UL grant scheduler
 Request generator  UL/DL MAP generators
 Contention resolution module  DL/UL data schedulers
 UL traffic classifier  UL channel monitor
 DL channel monitor  BS periodic grant generator
 Contention ratio calculator (CRC)
 Contention slot allocator (CSA)
 Frame partitioner
 Frame generator

©Copyright 2006-07

Metanoia, Inc.
Representative Subscriber Station Critical Systems Thinking™

(SS) QoS Architecture
Bandwidth
Queue Requests
Information UL B/w Request
Generator
Request Retry
Size Signal
Class 1 CRM

Grant
Size
UL Traffic

Class 2
Classifier

Uplink Data
SS UL Data (to BS)
UL
Class 3 Scheduler
Traffic

Grant
Class n Size

Uplink Multi-class Downlink
Data Queues Downlink Data
(to clients)

©Copyright 2006-07

Metanoia, Inc.
Representative Base Station (BS) Critical Systems Thinking™

QoS Architecture
To network

DSA_REQ UL Data UL data
Uplink
Traffic Shaper
Admission
Control B/w requests Channel
sense
DSA_RSP
Channel
BS Periodic B/w Monitor
Grant Generator
Queue info. Request
BS Upstream Grants
status
Scheduler
UL B/w Request CRC
Queue Status UL Subframe UL MAP Contention
start Generator ratio
Frame Partitioner CSA
DL Subframe Slots allocated
DL Data queue start Downlink
status Frame Generator
Outgoing
Class 1
frame to SSs
Classifier

Class 2
Shaper
Traffic

Traffic

Generator
DL MAP
BS DL Data
Class 3 Scheduler

Class n DL Scheduler
DL data from Periodic Poll
network DL Data Queues Generator
©Copyright 2006-07

Metanoia, Inc.

Cross-Layer Based
Scheduling Techniques for
QoS

© Copyright 2006
All Rights Reserved

Metanoia, Inc.

At the start …

© Copyright 2006
All Rights Reserved

Metanoia, Inc.

A Layered View of Networks
Application

Transport View the physical layer as
a “reliable bit pipe”
Network

MAC

PHY

 Network engineer’s viewpoint
 Allocate the resources of the reliable bit-pipe efficiently

 Communication engineers viewpoint
 Build better pipes
 Higher reliability, better spectral efficiency

©Copyright 2006-07

Scheduling in Wireline Networks
Metanoia, Inc.

(Network Layer)
 Frame-based scheduling
 Time split into frames
 Max. amount of traffic that session may transmit during the
frame is reserved
 e.g., Round Robin, Deficit Round Robin

S

©Copyright 2006-07

Scheduling in Wireline Networks
Metanoia, Inc.

(Network Layer)
 Sorted-priority scheduling
 Global parameter p associated with each user
 Updated on packet arrival and departure
 Packet time-stamped with a value = f(p)
 Packets sorted based on their timestamps

4 3

7 5 S 1 2 3 4 5 6 7

6 2 1

©Copyright 2006-07

Metanoia, Inc.

Cross-Layer Design
 Wireless channel characterized by …
 Signal strength variation (fading) over time, frequency, space
 Interference
 Limited battery life at hosts

 Physical layer no longer viewable as fixed-rate bit pipe

 Resource allocation must account for channel quality
 Adaptive MAC
 Adaptive PHY – modulation and coding

Significant performance gains in wireless networks
by Cross-Layer Design
©Copyright 2006-07

Metanoia, Inc.

Scheduling in Wi-Max
 Determines
 Transmission opportunities
Sub
Channel
 Appropriate burst profile
 Transmission Opportunities o n
si Time slot
 TDMA is
m ne
 Timeslots ns o
T ra Z
 OFDM PHY
Scheduling Axes
 DL – (Time slots)
 UL – (Time slots within individual sub-channels)

 OFDMA
 DL/UL opportunities -- time slots within sub-channels

 MIMO
 Normal zone
 Transmit diversity zone
 AAS zone
©Copyright 2006-07

Metanoia, Inc.

Wireless Channel Fading
 Large-scale
 Signal-strength variation due to path loss

 Medium-scale
 Caused by shadowing due to obstructions
 Buildings, hills, rain, and foliage

 Small-scale
 Due to multipath between transmitter and receiver
 Constructive/destructive interference by signals from multiple
paths

©Copyright 2006-07

Metanoia, Inc.

Small-Scale Fading

Signal
Strength

Time
Variation over frequency Variation over time
 Frequency selective  Fast
 Amp. gains, phase shifts vary with freq.  Coherence time Tc < Symbol period T
 Flat fading  Slow
 Multipath delay < Symbol period T
 Coherence time Tc >> Symbol period T
 Delay spread Td << Symbol period T
 Coherence b/w Wc >> Signal b/w W

©Copyright 2006-07

Metanoia, Inc.

Effects of Channel Fading
 BER: additive white Gaussian noise (AWGN) without fading
− K 2 ( SNR )
 Pe ≈ K1e

 Constants K1 and K2 depend on the modulation scheme

 BER: AWGN wireless channel with fading
−1
 Pe = K ( SNR )

 Non-fading channel  BER decays exponentially with SNR
 Fading channel  BER decays inversely with SNR

©Copyright 2006-07

Metanoia, Inc.

Fading Countermeasures

Diversity Type WiMAX CDMA

Multi Carrier Modulation
Frequency Rake Receiver
(OFDM)

Adaptive Modulation and
Time Coding
Coding (AMC)

Base Station
Spatial MIMO (Soft Handoff)
MIMO

©Copyright 2006-07

Metanoia, Inc.

Multiuser Diversity: A New Paradigm for
Scheduling

© Copyright 2006
All Rights Reserved

Metanoia, Inc.

SNR Fluctuations in a Multiuser System

User 1
User 2
SNR User 3

Time

©Copyright 2006-07

Multi-User Diversity and
Metanoia, Inc.

Opportunistic Scheduling
h1
BS
h2 SS1
S

Scheduler
hk
SS2

 Channel fades independently for each user so
… different users experience different channel gains
SSk
 High prob. that some user will have strong channel

 BS schedules the user with strongest (best) channel

 Hence … “Opportunistic Scheduling”

©Copyright 2006-07

Metanoia, Inc.

Opportunistic Scheduling in WiMAX
 Channel-quality measurements
 Each user performs RSSI and CINR measurements
 Reports to BS via REP-RSP messages

 BS changes data rate adaptively as a function of channel gain

 Adaptive modulation and coding

 Transmit at a high rate when the channel is good

 Higher constellation 64-QAM and ¾ rate convolutional coding

 Transmit at a lower rate when the channel is bad

 Lower constellation QPSK and ½ rate convolutional coding

©Copyright 2006-07

Metanoia, Inc.
DRR: A Practical Scheduling Critical Systems Thinking™

Algorithm
Round Robin Round Robin
Pointer Pointer

1 2
Deficit Deficit
Packet sent
Counter Counter

1 400 500 300 600 1 400 500 300

Balance

2 300 400 300 200 0 2 300 400 300 200 600

3 550 400 250 0 3 550 400 250 0

4 350 200 650 0 4 350 200 650 0

600 600

Quantum Quantum
Size Size
 FairnessDRR = 3*(FairnessWFQ)  Time complexity O(1)
Adapted from: [ShV96]
©Copyright 2006-07

Metanoia, Inc.
Opportunistic DRR (O-DRR): Critical Systems Thinking™

Fairness and Throughput:
 Fair among users
 Max. difference in allocated bandwidth < 10 % of average
 Fair among traffic classes
 Both class1 and class2 traffic get almost equal number of slots

 As k increases, fairness decreases (intuitively expected)

Source [RBS06a,b]
©Copyright 2006-07

Metanoia, Inc.

O-DRR: Delay Performance
 Meets delay guarantees of different classes of traffic
 Packets dropped only if delay is violated
 Packet drop < 8.5% for both classes of traffic
 For larger k, the dropping percentage is higher
 For worst case k=100, 91.5% of traffic meets its delay

©Copyright 2006-07
Source [RBS06b]

Metanoia, Inc.

Cross-Layer Scheduling in OFDMA

© Copyright 2006
All Rights Reserved

Metanoia, Inc.

OFDM Basics
 If coherence bandwidth Wc << signal bandwidth W
 Signal experiences frequency-selective fading

 Split transmission b/w into large number of sub-carriers
W
 Create N sub-carriers with bandwidth = WN
N
1 1
 Symbol time TN ≈ >> ≈ Tm (delay spread)
WN Wc
 No inter-symbol interference (ISI)

 Overlapping bands possible, if sub-carriers are orthogonal
©Copyright 2006-07

Metanoia, Inc.

OFDMA Explained
 OFDM: PHY layer technique

 OFDMA: multiple-access scheme User 1

1
 User occupies subset of sub- 1
carriers (traffic channels) User 2
2 2

 Sub-carriers assigned to a
2 User 3
3
particular user may change y
c 3
over time u en 3
r eq 3
F

Time
©Copyright 2006-07

Metanoia, Inc.

OFDMA Explained
 OFDM: PHY layer technique

 OFDMA: multiple-access scheme

 User occupies subset of sub-
3
3 2
2 2
2
carriers (traffic channels) y
nc 1
1 3
3
q ue 3
3 1
1
F re
3
3 2
2
 Sub-carriers assigned to a
Time

particular user may change
over time

©Copyright 2006-07

Metanoia, Inc.

802.16 OFDMA Frame Structure

OFDM Symbol Number
0 1 3 5 7 9 ... ... N-1 0 ... ... ... M-1
1
FCH UL UL Burst
DL Burst
MAP #2 #1
(cont.)
Sub-channel Logical Number

UL Burst
S-1
#2
DL Burst
S
#4 UL Burst
Preamble

S+1 DL
DL Burst #3
MAP
#1
ACK UL Burst
CH #4
DL Burst DL Burst
#3 #5
UL Burst
DL Burst #5
UL #6

Ranging
MAP
DL Burst #7 Fast Feedback (CQICH)
Ns

Downlink Subframe Guard Uplink Subframe
©Copyright 2006-07

Metanoia, Inc.

Opportunistic OFDMA
 Total sum capacity is maximized …
… if throughput in each sub-carrier is maximized

 Schedule each sub-carrier to user with best channel gain

 Optimum power allocation
 Water-filling

 Proportional fairness can be extended to OFDMA
 Select users with largest ratio of instantaneous data rate to
average data rate
©Copyright 2006-07

Metanoia, Inc.

OFDMA Scheduling in IEEE 802.16
 Users allocated groups of sub-carriers (sub-channels)

 Smallest allocation unit – a slot
 Single sub-channel, spanning over 1 to 3 OFDM symbols

 Subscriber stations (SSs)
 Perform channel-quality measurements
 Send feedback to Base Station (BS)
 Fast feedback channel (CQICH) allocated
 MAC sub-header

 DL MAP

©Copyright 2006-07

Metanoia, Inc.

Implementation Issues in
Protocols and Algorithms

Metanoia, Inc.

System Design Issues
 End-to-end QoS is a must for growing multimedia applications

 Access network is the usual bottleneck – more so, if wireless!

 Provisioned & perceived QoS may differ markedly for wireless
 Must address fading and interference

 Wireless QoS thus requires:
 Connection-oriented service
 Implies a centralized coordinated MAC

 Cross-layer based resource allocation
 Adaptive MAC

 Adaptive PHY

©Copyright 2006-07

Metanoia, Inc.

Wi-Max Protocol Implementation Model
IP QoS

Mapping Layer
CS SAP
Service-Specific Service-Specific
Convergence Convergence Sublayers
Sublayer
MAC SAP
Mapping Layer
MAC MAC Common Part
Sublayer MAC Common Part
Sublayer Tuning Network
Layer Mgt. Sys.
Security Sublayer Security Sublayer
PHY SAP Mapping Layer

PHY Physical Layer
(PHY) PHY Layer

Data/Control Plane Management Plane
Realizes cross-
layer functions
©Copyright 2006-07

Metanoia, Inc.

Implications …
 WiMAX has many options and features
 Requires a mapping and tuning layer for translating provider
managed services finally to bit/packet-level QoS

 Mapping and tuning layer must integrate with service
provisioning platform
 Requires a unified implementation framework

©Copyright 2006-07

Metanoia, Inc.

802.16 Challenges in Practice
 Fluctuating channel
 Adaptive modulation based on link quality
 Link quality fluctuation between very high to very low SNR lead to wide
variation in data rates
 May affect pkt level performance
 TCP and BS scheduler
 Inappropriate scheduling may lead to time-outs
 BW grants need to take into account congestion window
 TCP over OFDM
 Interactions of TCP over OFDM and fading channel not yet fully
understood
 OFDMA
 Performance degrades due to Doppler spread

©Copyright 2006-07

Metanoia, Inc.

Future of WiMax and
Applicability to Military
Communications

Metanoia, Inc.
IEEE 802.16j Mobile Multi-hop Critical Systems Thinking™

Relay for Military Mesh Network
 Network Elements
 MMR BS
 Relay Station (RS)
 Fixed RS (FRS)

 Nomadic Relay Station (NRS)

 Typical military environment …
 RS pre-planned
 Antenna heights less than in a commercial env.
 Redundant routes between RS and MMR-BS
 Support for NRS

©Copyright 2006-07

Metanoia, Inc.

Features of 802.16e
 PHY Layers
 OFDMA 2048, 1024, 512 FFT modes
 STC, MIMO
 Extensions for H-ARQ

 MAC
 Handover support
 Power management

 Multi-zone frame structure
 Frame partitioned into multiple zones
 Different sub-channelization schemes supportable in each zone

©Copyright 2006-07

Metanoia, Inc.

Mobile Broadband Standardization
 Various standards (all based on OFDMA + MIMO)
 802.16e
 802.16m
 3GPP Long Term Evolution (LTE)
 3GPP UMB
 802.20

 IMT-Advanced
 May harmonize various projects
 Global low-cost 4G standard may emerge based on OFDMA

©Copyright 2006-07

Metanoia, Inc.

Thank You!
Questions?

Metanoia, Inc.

Glossary and References

Metanoia, Inc.

Glossary
AAS Adaptive Antenna Systems CID Connection Identifier
ABR Available Bit Rate CINR Carrier to Interference plus Noise Ratio
ACK Acknowledgement CLP Cell Loss Priority
ADSL Assymetrical Digital Subscriber Line CLR Cel Loss Ratio
AMC Adaptive Modulation and Coding CoS Class-of-Service
ARQ Automatic Repeat Request CPS Common Part Sublayer
ATM Asynchronous Transfer Mode CQICH Channel Quality Indicator Channel
AWGN Additive White Gaussian Noise CRA Contention Ratio Algorithm
BE Best Effort CRC Cyclic Redundancy Check
BER Bit Error Rate CRC Contention Ratio Calculator
BoD Bandwidth-on-Demand CS Convergence Sublayer
bps bits per second CSA Contention Slot Allocator
BPSK Binary Phase Shift Keying CSMA/CA Carrier Sense Multiple Access/Collision Avoidance
BS Base Station DA-FDRR Demand-Aware Fair Deficit Round Robin
BSN Block Sequence Number DC Direct Current
BWA Broadband Wireless Access DCD Downlink Channel Descriptor
CAC Connection Admission Control Diffserv Differentiated Services
CBR Constant Bit Rate DIUC Downlink Interval Usage Code

CDMA Code Division Multiple Access DL Downlink

CH Channel DOCSIS Data Over Cable Service Interface Specification

CI CRC Indicator
©Copyright 2006-07

Metanoia, Inc.

Glossary
DRR Deficit Round Robin H-FDD Half Frequency Division Duplex
DSL Digital Subscriber Line HT Header Type
EC Encryption Control HTTP Hyper-Text Transfer Protocol
EKS Encryption Key Sequence IFFT Inverse Fast Fourier Transform
EV-DO EVolution Data Optimized IFS Inter-Frame Spacing
FDD Frequency Division Duples Intserv Integrated Services
FDMA Frequency Division Multiple Access IP Internet Protocol
FEC Forward Error Correction ISI Inter-Symbol Interference
FFSH Fast-Feedback Allocation Sub-Header KHz Kilohertz
FFT Fast Fourier Transform LAN Local Area Network
FIFO First-In First-Out LEN Length
FSH Fragmentation Sub-Header LOS Line-of-Sight
FSN Fragment Sequence Number MAC Media Access Control
FTP File Transfer Protocol MAN Metopolitan Area Network
FUSC Full Usage of Sub-Channels MHz Megahertz
GBN Go-Back-N MIMO Multi-Input Multi-Output

GFR Generic Frame Rate MPDU MAC Protocol Data Unit

GMSH Grant Management Sub-Header MPLS Multi-Protocol Label Switching

GSM Global System for Mobile Communications MSDU MAC Service Data Unit

HARQ Hybrid ARQ NACK Negative Acknowledgement

HCS Header Check Sequence

©Copyright 2006-07

Metanoia, Inc.

Glossary
NFS Network File System QoS Quality-of-Service
NLOS Non Line-of-Sight QPSK Quadrature Phase Shift Keying
nrt-PS Non Real-Time Polling Service Rcv Receive
O-DRR Opportunistic Deficit Round Robin Rcvr Receiver
OFDM Orthogonal Frequency Division Multiplexing REQ Request
OFDMA Orthogonal Frequency Divison Multiple Access RNG Ranging
O-FUSC Optional-Full Usage of Sub-Channels RSP Response
O-PUSC Optional-Partial Usage of Sub-Channels RSSI Received Signal Strength Indicator
PAR Project Authorization Request Rsv Reserved
PCR Peak Cell Rate rt-PS Real-Time Polling Service
PDU Protocol Data Unit Rv Reserved
PER Packet Error Rate Rx Receiver
PHSI Payload Header Suppression Index SAP Service Access Point
PHSI Payload Header Suppression SC Single Carrier
PHY Physical Layer SCR Sustainable Cell Rate
PM Poll Me SDU Service Data Unit
PSH Packing Sub-Header SFID Service Flow ID
PTI Payload Type Indicator SI Slip Indicator
PUSC Partial Usage of Sub-Channels SINR Signal to Interference plus Noise Ratio
QAM Quadrature Amplitude Modulation SNMP Simple Network Management Protocol

©Copyright 2006-07

Metanoia, Inc.

Glossary
SNR Signal to Noise Ratio VoIP Voice-over-IP
VPI Virtual Path Identifier
S-OFDMA Scalable Orthogonal Frequency Division Multiple Access
WDRR Wireless Deficit Round Robin
SR Selective Repeat
WG Working Group
SS Subscriber Station
Wi-Fi Wireless Hi-Fidelity
TC Traffic Category
WLAN Wireless LAN
TCP Transmission Control Protocol
TDD Time Division Duplex
TDMA Time Division Multiple Access
TFTP Trival File Transfer Protocol
TLV Type-Length-Value
Tx Transmitter or Transmit

UBR Unspecified Bit Rate
UCD Uplink Channel Descriptor
UF-DRR Uniformly Fair Deficit Round Robin
UGS Unsolicited Grant Service
UIUC Uplink Interval Usage Code
UL Uplink

VBR Variable Bit Rate
VCI Virtual Circuit Identifier
VOD Video-on-Demand

©Copyright 2006-07

Metanoia, Inc.

References and Readings (1)
 [FaL02] H. Fattah and C. Leung, “A Efficient Scheduling Algorithm for Packet
Cellular Networks,” in Proc. VTC, vol. 4, pp. 2419-2423, September 2002.
 [GWA05] A. Ghosh, G. R. Walter, J. G. Andrews, and R. Chen, “Broadband Wireless
Access withWiMax/8O2.16: Current Performance Benchmarks and Future Potential,”
IEEE Commun. Magazine, vol. 45, pp. 129-136, February 2005.
 [IEEE04] LAN/MAN Standards Committee, “IEEE Standards for Local and
Metropolitan Area Network: Part 16: Air Interface for Fixed Broadband Wireless
Access Systems,” IEEE Computer Society and IEEE Microwave Theory and
Techniques Society, May 2004.
 [IEEE05] LAN/MAN Standards Committee, “IEEE Standards for Local and
Metropolitan Area Network: Part 16: Air Interface for Fixed and Mobile Broadband
Wireless Access Systems (Amendments for Physical and Medium Access Control
Layers for Combined Fixed and Mobile Operation in Licensed Bands),” IEEE
Computer Society and IEEE Microwave Theory and Techniques Society, September
2005.
 [RBS06a] H. Rath, A. Bhorkar, and V. Sharma, “An Opportunistic Deficit Round
Robin (O-DRR) Uplink Scheduling Scheme for Wi-Max Networks,” Proc. IETE Int’l
Conf. on Next-Generation Networks (ICNGN’06), Mumbai, 9-11 February, 2006.

©Copyright 2006-07

Metanoia, Inc.

References and Readings (2)
 [RBS06b] H. Rath, A. Bhorkar, and V. Sharma, “An Opportunistic Uplink Scheduling
Scheme to Achieve Bandwidth Fairness and Delay for Multiclass Traffic in Wi-Max
(IEEE 802.16) Broadband Wireless Networks,” to appear IEEE Globecom’06, San
Francisco, CA, 27 Nov. – 1 Dec. 2006.
 [ShV96] M. Shreedhar and G. Varghese, “Efficient Fair Queueing Using Deficit
Round Robin,” IEEE/ACM Trans. on Networking, vol. 4, no. 3, pp. 375-385, June
1996.
 [SRK03] S. Shakkottai, T. S. Rappaport, and P. C. Karlsson, “Cross Layer Design for
Wireless Networks,” IEEE Commun. Magazine, vol. 41, no. 10, pp. 74-80, October
2003.
 [Vam06] N. Vamaney, “Scheduling in IEEE 802.16 Metropolitan Area Networks,” M.
Tech. Dissertation, Dept. of Electrical Engineering, IIT Bombay, September 2006.

©Copyright 2006-07

Elements of Cross-Layer System & Network Design for QoS-Enabled Wi-Max Networks

Recommandé

Recommandé

Contenu connexe

Tendances

Tendances (18)

Similaire à Elements of Cross-Layer System & Network Design for QoS-Enabled Wi-Max Networks

Similaire à Elements of Cross-Layer System & Network Design for QoS-Enabled Wi-Max Networks (20)

Plus de Vishal Sharma, Ph.D.

Plus de Vishal Sharma, Ph.D. (20)

Dernier

Dernier (20)

Elements of Cross-Layer System & Network Design for QoS-Enabled Wi-Max Networks

Notes de l'éditeur