??????? Wireless System Lab (ED900/913B)

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???????Wireless System Lab (ED900/913B)

• Li-Chun Wang (???)
• Department of Communications Engineering
• National Chiao Tung University
• Hsinchu,Taiwan
• lichun_at_cc.nctu.edu.tw
• http//cmbsd.cm.nctu.edu.tw/lichun

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3C Tradeoff in Wireless

• The 3C (Capacity, Cost, Cwality) Tradeoff
• The more things changes, the more remain the same
  (Alphonse Karr, 1808)

High Capacity
Good Quality
Low Cost
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What is the fundamental issue for wireless
communications?

• Spectrum Efficiency

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Missions

• ???????????????????
• ??? Cross-Layer Design??????????????????????????
  ?? ?
• ???????
• ????, ?????
• Think Big ! Think Different ! Think Simple!

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????

• 19821986 ?????? ????? ??
• 19861988 ?????? ????? ??
• 19921995 ????????? ??
• Georgia Institute of Technology, Master of
  Science
• 19951996 ????????? ??
• Georgia Institute of Technology, Ph. D.
• ???? Channel Modeling and Architecture Design
  for Cellular-Based Personal Communications

6
????

• 1990/071992/08 ????????
• ?????,?????
• 1995/011995/06 Nortel, BNR, Dallas, TX, Co-Op
• 1996/072000/01 ATT Labs-Research, Holmdel, NJ
• Wireless Communication Research
  Department, Senior Member of Technical
  Staff
• 2000/022000/08 ????????? ????
• 2000/08?? ????????? ???
• 2002/01?? NCTU Cisco Academy Training
  Center, Cisco Certified Academy Instructor

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????-??????

• ???????????????(Cross-layer Link Adaptation and
  Protocol Design)??????? (Radio Resource
  Management)??
• MIMO????
• MIMO ????????(Ultra-Wide Band, UWB)
• Wireless Mesh Network
• Cross-Layer Link Adaptation Techniques
• Advanced CDMA?????????
• Cooperative Cognitive Radio

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Professional Services

• Journal/Special Issue Editor
• Associate Editor, IEEE Transaction on Wireless
  Communications, 2001 2005
• Associate Editor, International Journal of Sensor
  Networks (2005 now)
• Associate Editor, International Journal on
  Wireless Mobile Computing (2005 now)
• Guest Editor, Special Issue on  Radio Resource
  Management and Protocol Engineering in Future
  IEEE Broadband Networks for IEEE Wireless
  Communications Magazine, 2006
• Guest Editor, Special Issue on "Mobile Computing
  and Networking of IEEE Journal on Selected Areas
  in Communications, Vol. 23, No. 6, June 2005.

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Honors

• 1997 IEEE Vehicular Technology Society Jack
  Neubauer Memorial Award for the Best Paper of the
  Year on the Subject of Vehicular Technology
  Systems.
• ?????
• ??? (95????)
• ?????????
• 96????????
• ???????? (to be official on 97)
• ?????
• ??? (96????)
• ????????
• ?? (93???)
• ??????????
• ???  (92???)
• ????????

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???????

• ???????
• ????MIMO Scheduling ????Soft Coverage ??,??MIMO
  Scheduling ????????????????,?????Multiuser MIMO
  Systems???????
• ??????MIMO?UWB??????Performance Tradeoff Analysis
  Model,???????????????????
• ?????
• ???????????????????ICC?Globecom?Flagship
  International Conference?
• ???????Tutorial Course,IEEE VTC 2003 Spring ,
  IEEE VTC 2007 Spring and Fall, IEEE PIMRC?
• ??????????????,???? Caltech ?University of
  Florida?WINLAB ?Bell Labs ???????????????,????????
  ??????????????, ????????????

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People

• ??????
• ???????(report on 2008) ?
• ??
• ???????????????? Samer Talat?
• ??
• ??????????????????????? Diego Ballesteros ?
• ??
• ????????????

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Current Research

• Cognitive Radio(?????)
• Sponsor ???(2005.82008.7)
• Subjects
• Cognitive MAC Protocol (???)
• Concurrent Transmission MAC Protocol (???)
• QoS-based Cognitive Scheduling (Samer Talat)
• Ultra-Wide Band (UWB)
• Sponsor ??? (2004.82007.7)
• Subject
• MIMO-UWB
• MIMO Ad Hoc Channels
• Space-Time-Frequency Coding (???)

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Current Research

• Intelligent Transport System
• Sponsor ??????? (2006.32009.2)
• Subject
• Vehicular Network (???)
• Wireless Mesh Network (???)
• Network-Coordination for Multi-Cell OFDM System
• Sponsor ??? (2007.1 2007.12)
• Joint base station coordination and user
  scheduling (???)

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New Project

• Cooperative Cognitive Radio Network
• Sponsor ???(2007.82010.7)
• Subject
• Cooperative Sensing and Robust Topology Control
  techniques
• Cooperative Cognitive MAC Protocol
• Multiplexing-based Cooperative Multi-hop systems

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Multiuser Scheduling for MIMO Wireless Networks
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Background on MIMO Techniques

• Independent parallel transmit and receive antenna
  pair
• MIMO antenna techniques
• boost channel capacity
• enhance link reliability
• reject strong interference

Nt
Nr
Tx
Rx


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Major Challenges for MIMO Techniques

• Difficulties to simultaneously leverage the
  benefits of diversity and multiplexing
• e.g. diversity-multiplexing tradeoff (huge
  capacity gain
• may come at a price of reduced link reliability)
• implementation complexity

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Diversity-Multiplexing Tradeoff

• Diversity -gt improve link reliability by
  replicas
• Multuplexing -gt enhance data rate by multiplexing

Tx
Rx
a
a
a
a
a
a
Tx
Rx
a
ab
ba
ba
ba
b
subchannel interference canceling is required
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Background on Scheduling Techniques

• Through periodically selecting the best user to
  serve, the system performance is improved by
  exploiting multiuser diversity or cooperative
  diversity.
• Ordered Statistics is the fundamental
  mathematical techniques for analyzing the
  scheduling wireless systems.

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A Multiuser MIMO Scheduling System

• Perfect SNR estimation and noiseless feedback
• Hk hij(k) , each hij(k) is subject to
  Nakagami fading
• The BS selects the target user with highest
  effective SNR

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Effect of SWNSF Scheduling on ?min
SWNSF scheduling enhances the output SNR of the
weakest subchannel
?3 gt ?2 gt?1
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Effect of SWNSF Scheduling on Coverage
MS
MS
MIMO RR Scheduling
MIMO SWNSF Scheduling (soft coverage depends
on K)
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Coverage Extension Capacity Improvement
number of users
number of antennas
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Publications

• Scheduling for MIMO Systems
• Chiung-Jang Chen and Li-Chun Wang, A Unified
  Capacity Analysis for Wireless Systems with Joint
  Multiuser Scheduling and Antenna Diversity in
  Nakagami Fading Channels, IEEE Trans. on
  Communications, vol. 54, No. 3,  pp. 469478,
  Mar. 2006.
• Chiung-Jang Chen and Li-Chun Wang, "Enhancing
  Coverage and Capacity for Multiuser MIMO Systems
  by Utilizing Scheduling, " IEEE Trans. on
  Wireless Communications, Vol. 5, No. 5, pp.
  1148-1157, May 2006.
• Chiung-Jang Chen and Li-Chun Wang, "Impacts of
  Radio Channel Characteristics, Heterogenous
  Traffic Intensity and Near-Far Effect on Rate
  Adaptive Scheduling Algorithms," IEEE Trans. on
  Vehicular Technology, Vol. 55, No. 5, pp.
  15441554, Sep. 2006
• Chiung-Jang Chen and Li-Chun Wang, Performance
  Analysis of Scheduling in Multiuser MIMO Systems
  with Zero-Forcing Receivers, IEEE Journal of
  Selected Area in Communication, July 2007 .
• Li-Chun Wang and Chu-Jung Yeh, Comparison of
  Scalar Feedback Mechanisms in MIMO Scheduling
  Systems, Wireless Personal Mulitmedia (WPMC),
  pp. 1172-1176, Sep. 2005.
• Li-Chun Wang and Chu-Jung Yeh,On the Performance
  of Zero-Forcing Beamforming for MIMO Broadcast
  Systems, 2007 IEEE AP-S International Symposium
  on Antennas and Propagation in Honolulu, Hawaii,
  USA, June 2007

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• MIMO Ultra-Wideband
• Li-Chun Wang, Wei-Cheng Liu, and Kuan-Jiin Shieh,
  On the performance of using multiple transmit
  and receive antennas in pulse based
  ultra-wideband systems, IEEE Transactions on
  Wireless Communications, vol. 4, no. 6, pp.
  2738-2750, Nov. 2005.
• Wei-Cheng Liu and Li-Chun Wang, Performance
  analysis of pulse based ultra-wideband systems in
  the highly frequency selective fading channel
  with cluster property, VTC2006-Spring.
• Wireless Mesh Network
• Jane-Hwa Huang, Li-Chun Wang, and Chung-Ju Chang,
  Coverage and Capacity of A Wireless Mesh
  Network, IEEE International Conference on
  Wireless Networks, Communications and Mobile
  Computing, pp. 458463, June 2005.
• Jane-Hwa Huang, Li-Chun Wang, and Chung-Ju Chang,
  Deployment Strategies of Access Points for
  Outdoor Wireless Local Area Networks, IEEE VTC
  2005, pp. 29492953, May 2005.
• Jane-Hwa Huang, Li-Chun Wang, and Chung-Ju Chang,
  Coverage Enhancement for a Multi-channel
  Ring-based Wireless Mesh Network with Guaranteed
  Throughput and Delay, IEEE ICC 2006.

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• Advanced CDMA Systems
• Li-Chun Wang and Chih-Wen Chang, On the
  Performance of Multicarrier DS-CDMA with
  Imperfect Power Control and Variable Spreading
  Factors, IEEE Journal on Selected Areas in
  Communications, Special issue on Advances in
  Multicarrier CDMA, Vol. 24, No. 6, pp. 1154-1166,
  June 2006.
• Li-Chun Wang and Chih-Wen Chang, Probability of
  false power control command in CDMA systems
  subject to measurement errors, IEEE
  Communications Letters, vol. 9, no. 4, pp.
  298-300, Apr. 2005.
• Ching-Yu Liao, Li-Chun Wang and Chung-Ju Chang,
  "Comparison of Downlink Power Allocation
  Mechanisms in Soft Handoff for the WCDMA System
  with Heterogeneous Cell Structures," ACM/Kluwer
  Wireless Network, pp. 593-605, Nov. 2005 (EI,
  SCI1.17)
• Chih-Min Chao, Yu-Chee Tseng, Li-Chun Wang,
  Reducing Internal and External Fragmentations of
  OVSF Codes in WCDMA Systems with Multiple
  Codes,  IEEE Trans. on Wireless Communications,
   Vol. 4,  No. 4,  pp. 15161526, July  2005
  (EI,SCI 1.232)

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• Advanced CDMA Systems
• Chih-Min Chao, Yu-Chee Tseng, Li-Chun Wang,
  Dynamic Bandwidth Allocation for Multimedia
  Traffic with Rate Guarantee and Fair Access in
  WCDMA Systems," IEEE Trans. on Mobile Computing,
  Vol. 4, No. 5, pp. 420429, Sep./Oct. 2005
• Li-Chun Wang, Shi-Yen Huang, and Yu-Chee Tseng,
  "Interference Analysis and Resource Allocation
  for TDD-CDMA Systems to Support Asymmetric
  Services by Using Directional Antennas," IEEE
  Trans. on Vehicular Technology, Vol. 54, No. 3,
  pp. 1056-1069, May 2005  
• Li-Chun Wang, Ming-Chi Chen and Yi-Cheng Chen, "A
  Cross-layer Cost-function Based Rate Adaptation
  Mechanism for the WCDMA System with Multi-class
  Services by Transport Format Selection," Wireless
  Communications and Mobile Computing (Wiley Inter
  Science), Vol. 5, No. 4,  pp. 397 406,  July
  2005.
• Li-Chun Wang and Chih-Wen Chang, An interference
  avoidance code assignment strategy for MC-DS-CDMA
  with TF-domain Spreading, accepted by IEEE
  International Conference on Communications 2006.

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• Fast HARQ for HSDPA
• Li-Chun Wang and Chih-Wen Chang, Gap Processing
  Time Analysis for Stall Avoidance Mechanisms for
  High Speed Downlink Packet Access with Parallel
  HARQ Schemes,  IEEE Trans. on Mobile Computing,
  Vol. 5, No. 11, pp. 1591 -1605, Nov. 2006.
• Li-Chun Wang, Chih-Wen Chang, and Chung-Ju Chang,
  On the Performance of Indicator-based Stall
  Avoidance for High-Speed Downlink Packet Access
  Systems,  IEEE Trans. on Vehicular Technology,
  Vol. 55, No. 2, pp. 691 703, March 2006.
• Cross-Layer Protocol Design for WLAN and Sensor
  Network
• L. C. Wang and C. H. Lee, A TCP-physical
  cross-layer congestion control mechanism for the
  multirate WCDMA system using explicit rate change
  notification," IEEE International Conference on
  Advanced Information Networking and Application,
  vol. 2, pp. 449-452, Mar 2005.
• Li-Chun Wang, Chung-Wei Wang, and Chuan-Ming Liu,
  Adaptive Contention Window-based Cluster Head
  Election Algorithms for Wireless Sensor
  Networks, appeared in the VTC'05 Fall.
• Li-Chun Wang, Hung-Hsi Chen, and Anderson Chen,
  Optimal Channel Search Time for Handoff in the
  IEEE 802.11 WLANs, to appear in VTC2006-Spring.
• Li-Chun Wang, Kuang-Nan Yen, and Anderson Chen,
  Joint Rate and Power Adaptation for Wireless
  Local Area Networks in Nakagami Fading Channels,
  to appear in IEEE WCNC, Apr. 2006