Post on 05-Jan-2016
description
Quality of Service Schedulingfor 802.16
Broadband Wireless Access Systems
Sih-Han Chen Department of Computer Science and Information EngineeringNational Taipei University of Technology2006.11.21
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Outline Overview IEEE 802.16 IEEE 802.16 MAC and QoS Proposed QoS strategy Simulation result Summary and Reference
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Wireless TechnologiesBandwidth
1 Gbps
100 Mbps
10 Mbps
1 Mbps
PAN LAN MAN WAN<1m 10m 100m Up to 50Km Up to 80Km
802.15.1Bluetooth
Wi-Fi802.11a/g
Wi-Fi802.11b
802.15.3High Speed
WirelessPAN
Wi-MAX802.16
(802.16-2004 & 802.16e)
4G
3G
2.5G
IEEE 802.15 IEEE 802.11 IEEE 802.16 3GPP
PAN: Personal area networksMAN: Metropolitan area networks
LAN: Local area networks Wide area networks
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IEEE 802.16 Operation Mode
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IEEE 802.16 TDD frame structure
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DL-MAP and UL-MAP
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Downlink Subframe
Broadcast
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Uplink Subframe
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Outline Overview IEEE 802.16 IEEE 802.16 MAC and QoS Proposed QoS strategy Simulation result Summary and Reference
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IEEE Std 802.16 MAC Protocol Layering
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Service Specific Convergence Sublayer
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MAC Convergence Sublayer Functions:
Classification processing of higher-layer PDUs
Delivery to proper MAC SAP Receives CS PDUs from peer
Two sublayers specified: ATM convergence sublayer Packet convergence sublayer
Service Specific Convergence Sublayer
(CS)
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ATM Convergence Sublayer ATM cells mapped to MAC frames Differentiates Virtual Path switched / Virtual
Channel switched ATM connections Assigns channel ID (CID) Can perform Payload Header Suppression
(PHS)
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Packet Convergence Sublayer Used for all packet-based protocols,
such as IPv4, IPv6, Ethernet, and VLAN Similar functions as ATM convergence
sublayer, including PHS
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MAC Common Part Sublayer Defines multiple-access
mechanism Functions :
connection establishment connection maintenance Call admission control bandwidth request bandwidth allocation
MAC Common Part Sublayer
(MPC)
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Security Sublayer Two component protocols
Encapsulation protocol for data encryption
Privacy key management (PKM)
describes how the BS distributes keys to client SS
Security Sublayer
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Media Acces Control (MAC) Connection orienteded
Service Flow(SF) Connection ID (CID)
Channel access: UL-MAP
Defines uplink channel access Defines uplink data burst profiles
DL-MAP Defines downlink data burst profiles
UL-MAP and DL-MAP are both transmitted in the beginning of each downlink subframe (FDD and TDD).
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Bandwidth Request SSs may request bandwidth in 3 ways:
Use the ”contention request opportunities” interval upon being polled by the BS (unicast, multicast or broadcast poll)
Send a standalone MAC message called ”BW request” in an already granted slot
Piggyback a BW request message on a data packet
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Bandwidth Allocation BS grants/allocates bandwidth in one of
two modes Grant Per Subscriber Station (GPSS) Grant Per Connection (GPC)
Decision based on requested BW, QoS parameters and available resources
Grants are realized through the UL-MAP
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Service Classes Unsolicited Grant Services (UGS):
Constant Bit Rate (CBR) services, T1/E1 emulation, and Voice Over IP (VoIP)
Real-Time Polling Services (rtPS): real-time services variable size data packets MPEG video or VoIP with silence suppression.
Non-Real-Time Polling Services (nrtPS): Used for delay tolerant traffic requiring some minimum data rate FTP
Best Effort Services (BE) : Used for streams with no rate guarantees. WEB , HTTP
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QoS mechanisms Classification
Mapping from MAC SDU fields (e.g destination IP address or TOS field to CID and SFID
Call admission Control Scheduling
Downlink scheduling module Uplink scheduling module
No algorithms defined in standard
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IEEE 802.16 QoS Architecture
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Call Admission Control in IEEE 802.16 Admission control
To ensure required QoS is guaranteed while admit a new connection
Assessment of admission connection Usually use traffic descriptor and effective bandwidth
But… Traffic descriptors may not reflect the real traffic Traffic descriptors is very simple (peak rate, avg. rate, etc…) Users may overestimate their requirements QoS is uneasy to guarantee
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Outline Overview IEEE 802.16 IEEE 802.16 MAC and QoS Proposed QoS strategy Simulation result Summary and Reference
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Hierarchical and Distributed QoS Architecture
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Scheduling Algorithm at BS Define two types of queue
Type (I) queue Type (I I) queue
Admission Control
Scheduling Algorithm
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At BS Scheduling for Type I queue Type I queue Use for
UGS Dedicated request opportunities for rtps and nrtp
s
Guarantee grants to be scheduled without interrupt
First-in First-out (FIFO) , is employed
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At BS Scheduling for Type II queue Type II queue Use for
rtPS , nrtPS , and BE
To Guarantee Minimum bandwidth for each service flow Fairness to distributing excess bandwidth
To propose a fair queuing algorithm
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Type II QueueBandwidth Allocation
Grant Per Connection (GPC) BiMIN : the minimum reserved bandwidth
for connection i BRi : bandwidth currently demanded by th
e connection
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Call Admission Control (CAC) The sum of minimum reserved bandwidth
for all the connection should not exceed the available bandwidth B
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Fairness to distributing excess bandwidth
i queue connection of weightthe :
i queue connection to allcated bandwidth excess of amount the :
bandwidth excess the :
bandwidth available total the :
wbBB
i
EX
i
EX
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A Extended Issue It also can be wasted when :
Certain of connections don’t need so much bandwidth
Solution : It allows the empty connection queue to contribut
e its unused portion to the next round of excess bandwidth allocation
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Scheduling Algorithm at SS WHY ?
Due to the large Round Trip Delay (RTD) Possible collision occurred in the uplink channel
So…BS has only limited or even outdated information about each uplink connection
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At SS Priority of scheduling service
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At SS UGS Queue Scheduling Properties
Critical delay Critical delay jitter
Firstly guarantee the bandwidth
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At SS rpPS Queue Scheduling Properties
Should meet tight delay bound Each packet of rtPS should be mark a deline
t : arrival time tolerated delay : Maximum Latency for each service flow
Schedule base on the deadline stamp
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At SS nrtPS Queue Scheduling Properties
Target at maintaining throughput Each packed with a virtual time stamp When a new packer arrives in , the virtual time
must be calculated at first
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Virtual Time Stamp
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At SS BE Queue Scheduling Properties
There is no QoS guarantee required
A simple FIFO mechanisms is applied
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Outline Overview IEEE 802.16 IEEE 802.16 MAC and QoS Proposed QoS strategy Simulation result Summary and Reference
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Simulation Environment Used NS2 PMP MAC opera
tion TDD-OFDM One BS and 20
SSs
SS UGS rtPS nrtPS BE
First 1 1 1 1
Second 1 1 1 1
Third 2
Fourth 2
Fifth 2
Other v
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PHY layer parameters
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The End-to-End Delay
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The End-to-End Delay (for UGS_1)
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Compare Delay of rtPS_1 service
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For rtPSDifferent number of background SS
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Throughput of nrtPS
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Outline Overview IEEE 802.16 IEEE 802.16 MAC and QoS Proposed QoS strategy Simulation result Summary and Reference
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Summary Introduced a hierarchical distributed QoS At BS
Guarantee the minimum bandwidth Fairness distributing excess bandwidth
At SS Flexible QoS support four service flow Reduce the delay of real-time application Guarantee the throughput of non-real-time applicati
on
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References[1] Sun, J.; Yanling Yao; Hongfei Zhu,“Quality of Service Sched
uling for 802.16 Broadband Wireless Access Systems” Vehicular Technology Conference, 2006. VTC 2006-Spring. IEEE 63rd Volume 3, 2006 Page(s):1221 - 1225
[2] Jayaparvathy, R.; Sureshkumar, G.; Kanakasabapathy, P., “Performance evaluation of scheduling schemes for fixed broadband wireless access systems”,2005 13th IEEE International Conference on Volume 2, 16-18 Nov. 2005 Page(s):6 pp.
[3] IEEE 802.16 Standard (2004), "IEEE Standard For Local and Metropolitan Area Networks - Part 16:Air Interface for Fixed Broadband Wireless Access Systems".
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OFDM Frame Structure with TDD:PMP mode
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Service Specific Convergence Sublayer
The service specific convergence sublayer (CS) provides any transformation or mapping of external network data, received through the CS service access point (SAP)
Object : classifying external network service data units (SDU) and associating them to the proper service flow identified by the connection identifier (CID)
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IEEE 802.16 Scope :
Specifies the air interface, MAC (Medium Access Control), PHY(Physical layer)
Purpose : Enable rapid worldwide deployment of cost-effective
broadband wireless access products Facilitate competition in broadband access by providi
ng alternatives to wireline broadband access Main advantage :
Fast deployment, dynamic sharing of radio resources and low cost
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IEEE 802.16 Deployment