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
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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)
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
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
Simulation results: Transport throughput
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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!