Voice over 802.11, 802.16 and 3G/WCDMA

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Voice over 802.11, 802.16 and 3G/WCDMA

• D93944005 ???
• R94922068 ???
• R94922017 ???

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Outline

• IEEE 802.11
• IEEE 802.16(WiMAX)
• 3G/WCDMA

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Agenda

• 802.11 MAC layer QoS
• 802.11e MAC layer QoS
• 802.11e EDCA performance analysis

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Reference

• Analysis of IEEE 802.11e for QoS Support in
  Wireless LANs, IEEE Wireless Communication,
  Dec. 2003
• Performance Analysis of IEEE 802.11e
  Contention-Based Channel Access, IEEE
  Communication, vol. 22, NO. 10, Dec.2004
• Performance Analysis and Enhancements for IEEE
  802.11e Wireless Networks, IEEE Network,
  July/August 2005

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802.11 with QoS (PCF DCF)

• Support for time-bound services
• Coordinated by Point Coordinator (PC)
• Typically the AP
• A superframe
• Beacon
• Contention Free Period (CFP)
• Contention Period (CP)

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Contention Period (CP)
CTS
ACK
AP
RTS
DATA
Station 1
RTS
Station 2
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Contention Free Period (CFP)
B
Data andCF-Poll
Data andCF-Poll
CF end
AP
Data
Station 1
DATA
Station 2
Contention Free Period (CFP)
Contention Period (CP)
Contention Period (CP)
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Problems in the 802.11 MAC

• Time-bounded application (ex VoIP)
• Bandwidth, delay, and jitter is considered
• PCF problems
• Unpredictable Beacon delay
• Result in frame delay
• Variable transmission time
• Delay and jitter can not be guaranteed
• DCF problems
• All frames contention channel with the same
  priority
• No QoS label in MAC frame

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QoS Support Mechanisms of 802.11e

• Medium access mechanisms
• HCCA Solve PCF problem in 802.11 PCF
• Unpredictable Beacon delay
• Transmission exceed next beacon arrival is not
  allowed
• Variable transmission time
• TXOPlimit to bound transmission time
• EDCA Solve DCF problem in 802.11 DCF
• All frames contention channel with the same
  priority
• Four access categories with different QoS priority

CFP (polling)
CP (contention)
CFP (polling)
superframe
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HCCA
QoS CF-POLL
QoS CF-POLL
CF-end
Ask for Admitted_time Used_time
A
B
AP
TXOP
Station A
TXOP
Station B
Contention Free Period (CFP)
Contention Period (CP)
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EDCA four access categories
802.11e station
Voice
Video
Best Effort
Background
Backoff AIFSAC_VO CWminAC_VO CWmaxAC_VO
Backoff AIFSAC_VI CWminAC_VI CWmaxAC_VI
Backoff AIFSAC_BE CWminAC_BE CWmaxAC_BE
Backoff AIFSAC_BK CWminAC_BK CWmaxAC_BK
Contention to transmit
Transmission
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EDCA control

• AIFS, CWmin and CWmax can be decided by AP

AIFSAC_BK
Background
AIFSAC_BE
Best Effort
AIFSAC_VI
Video
AIFSAC_VO
ACK
RTS
DATA
Voice
CTS
DIFS
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EDCA channel access procedure
random backoff 3 slots
random backoff 5 slots
AIFS0
AIFS0
RTS
DATA
Freeze
Station A
CTS
ACK
AP
random backoff 3 slots
Remaining Backoff 2 slots
AIFS3
AIFS3
Freeze counter, set NAV
RTS
Station B
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EDCA performance analysis

• Analytical model for EDCA
• Some assumptions
• Fixed number of station (M)
• Each station has multiple access categories
• Each access category always has a packet to
  transmit.
• Ideal channel environment without errors

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(No Transcript)
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One step transition

• ( j , k , d )
• j j-th trying to transmit packet
• j -2 represent packet is now transmitting
• j -1 represent the state before the first
  transmission
• k backoff counter (range 0,Wj)
• d (1) remaining frozen time (2) remaining
  time for transmission (3) remaining time for
  collision period

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Delay
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Beacon delay

• Unpredictable beacon delays
• Result in frame delay transmitted in CFP

CTS
RTS
DATA
DATA
BACK
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TXOP

• A time duration
• During TXOP a station is allowed to transmit a
  burst of data frames
• TXOPlimit maximum value of a TXOP

BACK
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Agenda

• Introduce to IEEE 802.16
• Uplink request/grant scheduling algorithm for
  real-time service
• Unsolicited grant service
• Real-time polling service
• Proposed algorithm
• NUMERICAL ANALYSIS Simulation results

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Reference

• IEEE Standard 802.16 A Technical Overview of the
  WirelessMAN Air Interface of BWA
• A Quality of Service Architecture for IEEE 802.16
  Standards
• An Efficient Uplink Scheduling Algorithm Based on
  Voice Activity for VoIP Services in IEEE
  802.16d/e System

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Overview

• Standard for wireless metropolitan area networks
  (WirelessMAN)
• Goal Provide high-speed Internet access to home
  and business subscribers, without wires.
• Base stations (BS) can handle thousands of
  subscriber stations (SS)
• Supports
• A variety of services such as IP, voice over IP,
  and streaming video
• ATM packet based protocols
• Applications with different QoS requirements.

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Wireless Metropolitan Area Networks (MANs)
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IEEE 802.16 MAC layer(1/2)
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IEEE 802.16 MAC layer(2/2)

• The Service-Specific Convergence Sublayer (CS)
  provides any transformation or mapping of
  external network data, received through the CS
  service access point (SAP).
• The MAC CPS provides the core MAC functionality
  of system access, bandwidth allocation,
  connection establishment, and connection
  maintenance.
• The MAC security sublayer providing
  authentication, secure key exchange, and
  encryption.

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The Downlink and Uplink subframe
Ranging
Contention
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Uplink request/grant scheduling

• Uplink request/grant scheduling is performed by
  the BS with the intent of providing each
  subordinate SS with bandwidth for uplink
  transmissions or opportunities to request
  bandwidth.
• By specifying a scheduling service type and its
  associated QoS parameters, the BS scheduler can
  anticipate the throughput and latency needs of
  the uplink traffic and provide polls and/or
  grants at the appropriate times.

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Voice traffic Model
ON
OFF

• Assume that using a voice codec with a voice
  activity detector (VAD) or silence detector (SD),
  the SS can know whether its state is on or off by
  using a VAD or SD in the higher layer.

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Unsolicited grant service(1/2)

• The UGS is designed to support real-time service
  flows that generate fixed size data packets
  periodically.
• The BS periodically assigns fixed size grants to
  the SS.

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Unsolicited grant service(2/2)

• Advantage
• These grant size and period are negotiated in the
  initialization.
• It can minimize a MAC overhead and uplink access
  delay
• Disadvantage
• It causes a waste of uplink resource because of
  silence duration.

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Real-time polling service(1/2)

• The rtPS is designed to support real-time service
  flows that generate variable size data packets
  periodically.
• The BS assigns uplink resources which are
  sufficient for unicast bandwidth request to the SS

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Real-time polling service(2/2)

• Advantage
• It has more optimum data transport efficiency
  than the UGS algorithm.
• Disadvantage
• It has more MAC overhead and more access delay
  than the UGS algorithm.

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Other

• The non-real time polling service is designed to
  support delay-tolerant data streams consisting of
  variable-sized data packets for which a minimum
  data rate is required.
• The Basic Effort (BE) service is designed to
  support data streams for which no minimum service
  level is required and therefore may be handled on
  a space-available basis.

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Using Rule
UGS VoIP without silence mode Fixed-size grants on a real-time periodic
rtPS MPEG, VoIP with silence mode Periodic unicast request opportunities
nrtPS FTP Timely unicast request opportunities Contention request opportuniities
BE WWW, E-mail, instant message Contention request opportuniities
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Proposed Algorithm(1/3)

• In our proposed algorithm, the BS has to know the
  voice state transitions of the SSs.
• This higher layer information can be known in the
  MAC layer by using primitives of Convergence
  Sublayer.
• the SS has to inform the BS of its voice state
  transitions, it requires a method for relaying
  its voice status information.
• We define this reserved bit as a Grant-Me (GM)
  bit. When the voice state of the SS is on, the
  SS sets the GM bit to 1, otherwise it sets the
  GM bit to 0.

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Proposed Algorithm(2/3)

• Operation of theBS
• GM bit is 0
• The BS assigns the minimum grant size to the SS.
• GM bit is changed, 1 into 0, the BS once
  assigns maximum grant size to the SS whose voice
  state is off
• GM bit is 1
• The BS assigns the maximum grant size to the SS.
• GM bit is changed, 0 into 1, the BS
• once assigns minimum grant size to the SS whose
  voice state is on.

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Proposed Algorithm(3/3)

• Advantage
• It causes a little waste of uplink resources,
  which could be negligible.
• It doesnt modify IEEE 802.16 BWA

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NUMERICAL ANALYSIS
each state denotes the number of the voice users
in the on-state.

• TVC the voice codec frame duration
• LVC information bit per voice codec frame
• LHU compressed RTP/UDP/IP header size

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SIMULATION RESULTS
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3G packet scheduling
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Reference

• Jin Yuan Sun, Lian Zhao and Alagan Anpalagan, A
  Unified Framework for Adaptively Scheduling
  Hybrid Voice/Data Traffic in 3G Cellular CDMA
  Downlinks, IEEE International Conference on
  Wireless Networks, Communications and Mobile
  Computing, 2005, p751-756.
• J. Laiho, A. Wacker, and T. Novosad, Radio
  Network Planning and Optimisation for UMTS,
  Wiley, 2002.

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PCS system Architecture
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UMTS QoS(1/2)

• Congestion control
• Admission control enter sys or not
• Load control drop or distribute
• Packet scheduling
• QoS
• Admission control enter sys or not
• Packet scheduling

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UMTS QoS(2/2)

• Packet scheduling
• Time division, code division
• WCDMA
• Traffic classes
• Conversational class
• Streaming class
• Interactive class
• Background class

Delay sensitive
Real time
Nonreal time
Non-delay sensitive
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Example Packet scheduling

• A Unified Framework for Adaptively Scheduling
  Hybrid Voice/Data Traffic in 3G Cellular CDMA
  Downlinks

voice
data
voice
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Example Packet scheduling

• Motivation
• Existing scheduling algorithms fall into one of
  four categories
• (a) scheduling only one class without
  coordinating multi-classes
• (b) coordinating multi-classes with no
  scheduling for single
• classes
• (c) scheduling individual classes with
  completely distinct
• schemes, resulting in
  implementation complexity at
• base stations
• (d) scheduling individual classes with
  absolutely the same
• scheme, failing to exploit
  distinguishing performance
• optimizing manners of the two
  classes.
• We want Simple performance optimization
• for multi-classes

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• address
• consistency of the framework
• distinctions of voice and data scheduling
  processes
• method
• adaptive priority profile is designed in the
  scheduling algorithm based on
• queuing delay
• required transmission power
• available transmission rate

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• result
• system performance enhancement as a whole while
  retaining separate performance features without
  degradation.

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CDMA characteristics

• Interference control is important
• Specially in uplink
• Power control
• Smaller Rate, smaller powerl
• Downlink
• smaller power, higher downlink capacity
• Power control is an important issue.

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Scheduling framework(1/2)
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Scheduling framework(2/2)

• Unified voice/data scheduling framework
• Discrepancy of voice/data scheduling within
  framework

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better channel
AP Higher, better
sort
first
the largest AP first
after
sort
Voice/data different a,b,c
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data
sort
normal
moderate
urgent
Delay0
0 lt Delay lt D
D lt Delay
APb/power
APadelay b/power
APadelay b/rate
Different state, different calculation
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voice
sort
normal
urgent
0 lt Delay lt V
V lt Delay
APb/power
APadelay b/power
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Comparison conclusion
--QoS services WiMAX(802.16) voice
--Voice data Simple performance
optimization for
multi-classes --On-off traffic efficient
resource usage --HSDPA(High speed downlink
packet access) HSUPA --Cross layer mechanism
routing, phy CDMA packet scheduling
queue delay, power control, rate
control 802.16, 802.11 no CDMA