ECE710: Wireless Communication Networksbbcr.uwaterloo.ca/~x27liang/710.pdf · • Started in 1997...
Transcript of ECE710: Wireless Communication Networksbbcr.uwaterloo.ca/~x27liang/710.pdf · • Started in 1997...
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ECE710:
Wireless Communication Networks — Broadband Wireless Access Technology
Lin CaiBroadband Communications Research (BBCR) Group
June 8, 2010
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Wireless communication networks
Internet
Vehicle Networks
Wireless HotspotsSatellite Communication
Network
Medical sensor
TV
PC/PDA
Broadband Home Network
WiMAX/cellular Networks
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UWB
Whom is this tutorial for?
• Someone who– is interested in
knowing the research issues in last mile wireless broadband access technology
– expects to learn the objectives and specifications of IEEE 802 family
4G
WiFi
WiMAX
Mesh
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Agenda
• Introduction• Local/Personal Area Networking Technology
– Overview– WLAN PHY & MAC– UWB and mmWave WPAN
• WiMAX and Resource Management– WiMAX PHY & MAC– Resource Management
• Summary
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Wireless Network Classification
• Network scale or scope
Distance Location Network Abbre.
<2m Wireless Body area network WBAN
<10m Room WPAN
10-100m(1km) Building WLAN
1-10km city Wireless Metropolitan area network WMAN
100-100km country Wireless Wide area network WWAN
Wireless Personal area network
Wireless Local area network
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Global Wireless Standards
BAN
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Scope of 802 Standards
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Agenda
• Introduction• Local/Personal Area Networking Technology
– WLAN PHY & MAC– UWB and mmWave WPAN
• WiMAX and Resource Management– WiMAX PHY & MAC– Resource Management
• Summary
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Part I: WLAN/WPAN
• WLAN and WPAN:– wireless networks suitable for local short-distance
networking and compatible with existing LANs
• Benefits: open technology, easy deployment, expandability, cost efficiency, convenient, mobility, etc.
• Challenges: transmission range, reliability, data rate, QoS, security, etc.
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Historical perspective of WLAN standards
• WLAN Standards:– HiperLAN: European Telecommunications Standards
Institute (ETSI)– Wi-Fi: IEEE 802.11 Worldwide Standard Group
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Historical perspective of WPAN projects
• Started in 1997 as ‘ad hoc’ group within IEEE Portable Applications Standards Committee (PASC)
• In March 1998 a Study Group was formed within 802.11, and in March 1999, IEEE 802.15 Working Group for WPANs established
• In 2003, IEEE 802.15.3 specifies a MAC and PHY standard for high-rate WPANs– 3a: high speed UWB PHY – 3b: amendment– 3c: Millimeter Wave alternative PHY
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Part I: WLAN/WPAN--- WLAN Technology
• WLAN technology– Architecture– WLAN PHY & MAC protocols– Performance study – Other Issues
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WLAN Architecture
Infrastructure Mode Independent Mode (Ad Hoc)
Station
Station
Station
Station
Station
Station
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WLAN Architecture (Cont’d)
StationStation
Station
Station
BSS
Station
Station
Station
BSS
Distribution System
LAN (802.X)
Portal
Basic Service Set (BSS):
-Group of stations using the same radio frequency
Portal:
-Bridge to other networks
Distribution System:
-interconnection network to from one logical network, extended service set (ESS) based on several BSSs.
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WLAN PHY and MAC Layers
[5]
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DIFS
BO
DIFS DIFS
Busy
BO
t
Station1
Station2
Station3
Station4
BO
BO
Busy
BOr
BOr
BO Busy
Busy
BOrBO
DIFS
Station5
: Packet arrival; BO: Elapsed backoff time; BOr: Residual backoff time; : Collision occurs.
IEEE 802.11 MAC - Distributed Coordination Function (DCF)
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IEEE 802.11 MAC -Point Coordination Function (PCF)
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IEEE 802.11e MAC -Enhanced DCF (EDCF)
Traffic differentiation(TC); Transmission Opportunity( TXOP); PF
{AIFS ,CWmin, Cwmax}
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IEEE 802.11e MAC -Hybrid Coordination Function
Differences between hybrid coordinator (HC) and point coordinator (PC):HC can poll QSTAs in both CP and CFPHC grants a polled TXOP to one QSTA, which restricts the duration of the QSTA’s access to the medium.
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IEEE 802.11n
• PHY Key features –Bandwidth extension
• Using double channel (40 MHz) to achieve higher data rate
–MIMO• Enhance the PHY data rate of 802.11
– 2X2: 108Mbps (54Mbps X2)– 4X4: 216Mbps (54Mbps X4)
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MIMO Technolgoy: Diversity vs Multiplexing
IEEE 802.11n - MIMO
[2]V. Tarokh, N. Seshadri, and A. R. Calderbank. Space–time codes for high data rate wireless communication: Performance criterion and code construction. IEEE transaction on Information Theory. Vol 44. Iss. 2. 1998.
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• MAC Enhancement:– Aggregation of multiple frames => improve transmission
efficiency– Bi-directional transmission– One single medium access for one High Throughput
PHY (HTP) burst transmission; frames can be sent to different destinations
– Block ACK that improves the channel efficiency by aggregating several acknowledgements into one frame
IEEE 802.11n (Cont’d)
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• Saturated Station Scenario– Bi-dimensional Markov model [3]
• Non-saturated Station Scenario– M/M/1 and M/G/1 Model [4]– G/G/1 Model [5,6]
[3] G. Bianchi. Performance analysis of the IEEE 802.11 distributed coordination function. IEEE J. Select. Areas Commun., 18(3):535-547, March 2000.
[4] C. H. Foh and M. Zukerman. Performance analysis of the IEEE 802.11 MAC protocol. In European Wireless, Feburary 2002.[5] O. Tickoo and B. Sikdar. Queueing analysis and delay mitigation in IEEE 802.11 random access MAC based wireless
networks. In Proc. IEEE Infocom’04, volume 2, pages 1404-1413, March 2004.[6] L.X. Cai, X. Shen, J.W. Mark, L. Cai and Y. Xiao, "Voice Capacity Analysis of WLAN with Unbalanced Traffic'', IEEE Trans.
on Vehicular Techn ology, Vol. 55, No. 3, pp. 752-761, 2006.
MAC performance analysis
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CN1
CN2
AP
CN3
CNN-1
MNN-1
MN2
MN1
………… MN
3
802.11 WLAN
Internet
A single hop WLAN; Ideal channel;
Conditional Collision Probability p is assumed constant;
Mean traffic arrival rate of MN i: frames per slot;
Mean frame service rate of MN i: frames per slot;
Traffic intensity/queue utilization ratio:
MAC performance analysis (Cont’d)
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The channel is busy due to the successful transmissions of the tagged node;The channel is busy due to the successful transmissions of the remaining nodes; The channel is busy due to the collisions;The channel is idle when the tagged node is in the backoff stage.
[6] L.X. Cai, X. Shen, J.W. Mark, L. Cai and Y. Xiao, "Voice Capacity Analysis of WLAN with Unbalanced Traffic'', IEEE Trans. on Vehicular Techn ology, Vol. 55, No. 3, pp. 752-761, 2006.
During the interval 1/ μ, one of the following events must occur[6]:
=
MAC performance analysis (Cont’d)
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Numerical results
Queue utilization ratio Voice capacity in IEEE 802.11b WLAN
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Number of Voice Connections
Que
ue U
tiliz
atio
n R
atio
AP-729-10ms(typical) MN-729-10ms(typical) AP-729-20msMN-729-20ms AP-729-30ms MN-729-30msAP-711-20ms(typical) MN-711-20ms(typical) AP-723-30ms(typical)MN-723-30ms(typical)
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Voice Capacity in IEEE 802.11n WLAN [7][7] Lin X. Cai et.al. Supporting voice and video in an IEEE 802.11n WLAN. Accepted in Wireness Networks
Numerical results (Cont’d)
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• Improve range: – farthest distance is 300 feet, and performance drops off rapidly
as an MN move farther from the access point
• Enhance data rate and throughput – 60GHz frequency bands (mmWave communication technology)– Higher throughput at a longer distance
• Provide QoS – Efficient Connection control and DiffServ mechanisms
• Security
Other issues in WLAN
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• IEEE 802.15.3– Standard for high-rate (20Mbit/s – Gbit/s) WPANs,
while still low-power/low-cost Short Range (at least 10m, up to 70m possible)
– 802.15-3a: UWB 400Mbit– 802.15-3c: mmWave 2-3Gbit
IEEE 802.11 WLAN vs IEEE 802.15 WPAN
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Part I: WLAN/WPAN--- WPAN Technology
• WPAN technology– Applications and design criteria– UWB and mmWave communication techniques– IEEE 802.15.3 MAC– Exclusive region based MAC protocol design and
capacity analysis
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Applications
Last-meter wireless access
– Support video streaming, broadband ad-hoc meeting,
high volume content distribution, etc.
Vehicle communication networks
– Safety, entertainment, location-based services, etc.
Other applications
– Imaging, real time location sensing (RTLS), etc.
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Design criteria for high rate WPAN
• Very low power consumption and low complexity wireless connection within personal operating space
• Co-existence with other standard devices such as 802.11, Bluetooth etc.
• Cost effective implementation in ad hoc networks– Fast connection– Dynamic membership– Efficient data transmission
• QoS provision for a variety of traffic classes • WPAN mesh networking
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WPAN PHY: Ultra-wideband (UWB)
Ultra-wideband (UWB) communication system:
FCC: BW>500MHz or (fH-fL)/fC >20%
• Large bandwidth: 3.1-10.6 Ghz
• Low emission power: < -41.3 dBm/MHz
• Adaptive data rate, interference-limited multiple access,
ranging capability
Narrowband (30kHz)
Wideband CDMA (5 MHz)
UWB (Several GHz)
Frequency
Part 15 Limit
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WPAN PHY: Millimeter Wave (mmWave)
IEEE 802.15.3c:
57-64 GHz unlicensed band
Principle characteristics:
High, variable data rate
Severe path loss
Small size of RF unit
⇒Directional antenna
High rate and efficient operation in dense environment
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IEEE 802.15.3 MAC
Piconet Coordinator manages piconet
Starting a Piconet
DEV uses passive scanning to detect piconet
DEV chooses the channel and broadcasts its
beacon
Managing a Piconet
Assign DEVID to devices requesting to
associate to a piconet
Scheduling peer to peer transmission among
devices
DEV DEV
DEV
DEVWPAN
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IEEE 802.15.3 MAC
• Channel time is divided into superframe– Beacon
– Contains piconet synchronization parameter and IE (Information Element)s
– CAP (Contention Access Period) Optional – For command frames and non-stream data. Using CSMA/CA with
backoff scheme– CFP (Contention Free Period)
– For data stream. PNC assigns to DEV with each CTA (Channel Time Allocation)
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Distributed Reservation Protocol (DRP) for WPAN mesh networks
Distributed MAC without central controller
Reservation based DRP and random access based PCA
Disadvantages:
– Beacon period (BP)
synchronization
– Merging multiple BPs
– Beacon collision
(burst join)
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ER based MAC for UWB/mmWave WPANs
Narrow band collision model is no longer applicable in
UWB systems
Explore spatial capability to significantly improve
resource utilization
=> Exclusive Region (ER) [JSAC04] based MAC
protocol for appropriate concurrent transmissions
[JSAC04] B. Radunovic and J. Le Boudec. “Optimal Power Control, Scheduling, andRouting in UWB Networks”, IEEE J. Sele. A. in Comm., vol. 22, no, 7, pp. 1252-1270,Sept. 2004.
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ER based MAC design principle
Define an exclusive region around the receiver
Other senders outside of the ER can transmit
concurrently; otherwise, refrain their transmissions
Case 1: Omni-Omni Case2: Directional-Omni
Case 4: Directional-Directional
r0
r3r4
r8r6
r7
r5
r2r1
Case 3: Omni-Directional
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Central controller schedules concurrent transmissions
Key parameter: ER radius r
– Smaller r , higher spatial multiplexing
gain, higher interference;
– Vice versa.
Spatial multiplexing capacity of WPAN
To maximize the network spatial multiplexing capacity by fine
tuning ER size r [Cai_TWC10]
DEV
DEV
[Cai_TWC10] L. X. Cai, L. Cai, X. Shen, and J. W. Mark, “REX: a Randomized EXclusive region based scheduling scheme for mmWave WPANs with directional antenna,” IEEE Transactions on Wireless Communications, Jan. 2010.
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Numerical results: Spatial multiplexing gain
Omni-Omni Dir-Omni, Dir-Dir
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WPAN mesh networks
Asynchronous distributed MAC:
– No central controller with global user information
– Avoid the need of synchronization, which is difficult
and costly
CSMA/CA based asynchronous MAC:
Hidden/exposed terminal problem
Flow starvation and unfairness problems
Distributed Exclusive region (DEX) based MAC42
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Distributed MAC design
DEX: Distributed EXclusive region based MAC
– Use RTS/CTS exchange to reserve small ERs for each pair of sender and receiver
– Other flows can initiate their transmission if they are outside the ERs of ongoing transmissions
Key parameters: transmission rate R and ER radius r
[Cai_TWC10] L. X. Cai, L. Cai, X. Shen, J. W. Mark, and Q. Zhang, “MAC protocol design and optimization for multi-hop Ultra-wideband networks,” IEEE Transactions on Wireless Communications, in press.
How to decide the data transmission rate R to ensure
successful data transmissions [Cai_TWC10] ?
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Performance Analysis and Parameter Setting
Given ER radius r
maximum interference to a receiver
where
Considering the worst case scenario
of interference, we can determine the
transmission rate with guaranteed bit
error performance
)]()1([)3/(6 0 αςαςrPGI α −−−≤ −
.1∑∞
=k
xk=ς(x) r
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Performance study
• Given r and a saturated network in an area L*L, the upper bound of CT is(Circle packing problem)
• The lower bound of CT is(Circle covering problem)
• Optimal ER size that maximizes the expected network transport throughput
22 32Lmax CT r=
22 27min CT rL=
)1(log][ 22 I+NPd+ηWd
Dk=TRE
αα
r
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Hidden/Exposed Terminal and Fairness Problems
Hidden terminal problem:
– Reserve a relatively long TXOP -> less collisions
Exposed terminal problem:
– With smaller ERs, more flows transmit concurrently to
achieve a higher spatial multiplexing gain
Starvation and unfairness problems are mitigated
with the reduced contention level within the ER
4646
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Simulation results: Transport throughput
47
Transport throughput = Link throughput x Distance 47
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Compare Jain's Fairness Index
Simulation results: Fairness
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• WiMAX Overview– WiMAX objectives– WiMAX & IEEE 802.16
• WiMAX PHY & MAC • Resource Management
Part II: WiMAX*
* The WiMAX part of this talk are prepared by our bbcr former colleague Mehri Mehrjoo.
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WiMAX Overview
IEEE 802.16 is a standard for:
fixed and mobilebroadband Wireless systems
with a P2M and/or mesh technology
Objectives:
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IEEE 802.16: A standard forFixed and Mobile Application
Backhaul
Residential
Rural
Industrial
Business
Wired-line Network
Mobile users
Nomadic Application
802.16-2004
802.16e Hot spot
Last mile
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IEEE 802.16: A standard for Broadband Wireless Application
• Point-to-multipoint scenarios
Reference: http://www.wcai.com/pdf/2004/w_Krzywicki_John.pdf100 m
3-8 Km
2-8 Km NLOS
30-50 Km LOS
WiFi (80.11)
11-54 Mbps
2G, 2.5G, 3G
10-21 Kbps (2G)
30-130 Kbps (2.5G)
300-500 Kbps (3G)
802.16
1.5-70 Mbp
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Performance Comparison
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Where is WiMAX?
3G
WiMAX
WiFiLarge coverage
Full mobility
broadband
simplicity
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IEEE 802.16: A standard for PMP& mesh application
Mesh• SS to SS &/or BS communication
• Distributed &/or centralized coordination
• Only TDD is supported
PMP• No communication between SSs
• Centralized coordination
• Three channel access mechanisms:• Unsolicited bandwidth grants• Polling• Contention-based
P2P• BS to BS communications
• A fiber replacement
• Backhaul solutions
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IEEE 802.16 Family
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WiMAX & IEEE 802.16
Broadband Wireless product
IEEE 802.16: A standard for fixed and mobile broadband wireless systems with a point-to-multipoint design and/or mesh technology
WiMAX: Worldwide Interoperability for Microwave Access
WiMAX Forum WiMAX
WiMAX WiMAX
WiMA
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• WiMAX Overview– WiMAX objectives– WiMAX & IEEE 802.16
• WiMAX PHY & MAC • Resource Management
Part II: WiMAX
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WiMAX PHY Issues
• Spectrum• OFDM/OFDMA fundamentals• OFDMA sub-channelization• Antenna system• Power control & Adaptive modulation
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SpectrumLow frequency
Low energy
Long wavelength
High frequency
High energy
Short wavelength
WiM
AX
28-
29 U
n
WiM
AX
5.2
5-5.
85 U
n
802.
11 a
,e 5
.0 U
n
802.
11 b
,g 2
.4 U
n
CD
MA
2000
460,
800
,1.7
, 1.9
, 2.1
GSM
800
, 1.8
Lice
nsed
1 2 3 5 11 29 66GHz
WiM
AX
3.3
-3.8
Li
WiM
AX
2.5
-2.6
9 L
i
802.16a Licensed+ Un 802.16-2004 Licensed+ Un
Radio microwave IR visible UV X-Ray Gamma
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Spectrum (Cont’d)
Licensed Band advantages:
• Relatively high max power level• Better quality of service
Unlicensed Band advantages: • Fast rollout, more worldwide options• Low administrative/regulatory costs• Promote spectrum efficiency
Licensed Unlicensed
Unlicensed WiMAX applications:
• Point to point, or point to multipoint in scarcely populated environments
• Where interference in the unlicensed band can be controlled. Such as campuses, large enterprise
• Where cost is the major factor
Licensed WiMAX applications:
• large coverage• When controlling the interference is needed• When cost is not the primary issue (3G data
overlays will cost more and have worse performance)
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OFDM Fundamentals
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OFDMA
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• Power saving methods for portable and mobile user devices
• Sub-channelization is an optional feature in OFDM 256 that is generating a lot of interest from operators. It allows a subscriber station to concentrate its transmit power on a subset (sub-channel) of the total OFDM subcarriers, leading to link budget improvements in the uplink
WiMAX uses subchannelization
Sub-channelization
BS- downlink
SS- uplink without subchannelization
SS- uplink with subchannelization
Power level of sub-carrier
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Antenna Systems
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Adaptive Modulation
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MAC Issues
• Service scheduling• Admission control
& bandwidth request/grant
• Link Initiation• Ranging• Moblity• Power
Management• Fragmentation• Retransmission• Security
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Service Flows
• Unsolicited Grant Service (UGS)– Supports real-time service flows that generate fixed size data
packets on a periodic basis, such as T1/E1 and Voice over IP
• Real-time Polling Service (rtPS)– Supports real-time service flows that generate variable size data
packets on a periodic basis, such as MPEG video
• Non-real-time Polling Service (nrtPS)– Supports non real-time service flows that generate variable size
data packets on a regular basis, such as high bandwidth FTP.
• Best Effort (BE)– Supports data streams with no minimum service level
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Bandwidth Allocation and Request Mechanisms
• UGS : – The BS provides fixed size bandwidth at periodic intervals to the UGS.– The SS is prohibited from using any contention request opportunities.– The BS shall not provide any unicastrequest opportunities.
• rtPS– The BS provides periodic unicastrequest opportunities.– The SS is prohibited from using any contention request opportunities.
• nrtPS– The BS provides timely unicastrequest opportunities.– The SS is allowed to use contention request opportunities.
• BE– The SS is allowed to use contention request opportunities.
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Mandatory QoS Service Flow Parameters
• Radio resources have to be scheduled according to the QoS(Quality of Service) parameters.
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Downlink/Uplink Transmissions
• IEEE 802.16 supports both TDD and FDD.• TDD allows flexible allocation of BW between UL & DL. Downlink tx needs
higher throughput.• TDD transceiver design is cheaper and less complex.
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Mobility
• Real-time handoff: – portable applications with simple mobility provide adequate
handover performance for latency tolerant applications such as TCP , but not VoIP. Obviously considering full mobility as well as real-time multimedia scenarios makes a quite challenging hand over.
• Security & Authentication: – portable & mobile applications need enhanced security than
fixed wireless application. Re-authentication at a new place after movement needs a centralized authentication method.
• Power management:– sleep and idle modes
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• WiMAX Overview– WiMAX objectives– WiMAX & IEEE 802.16
• WiMAX PHY & MAC• Resource Management
Part II: WiMAX
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Resource Management
• Scheduling Heterogeneous traffic in OFDMA WiMAX
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Utility based Resource Management
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Problem Description
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Opportunistic Fair Scheduling
• Opportunistic fairscheduling is between the two extremes of pure opportunistic scheduling and fair scheduling.
• Proposed opportunistic fair scheduling jointly considers:
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Opportunistic Fair Scheduling
• To achieve all in one and reduce the complexity, we propose a modular scheduler design and use decomposition algorithms to exploit parallel processing and achieve a real-time scheduling scheme
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Opportunistic Fair Scheduling
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Numerical Results
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Numerical Results (Cont’d)
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Summary
PHY & MAC research issues in broadband
wireless access networks
IEEE 802.11WLAN
IEEE 802.15 WPAN
IEEE 802.16 WiMAX
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Final Comment
• WLAN, WPAN, and WiMAX are complementary wireless networks of each other, none of which will entirely replace the others
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Thank You!