Design PHY/MAC Cross-layer protocols for IEEE 802.11 and 802.16 WLAN and WMAN.

1. Wireless Network Research 王蒞君教授 Explore the potential advantages of multi-user multi-input multi-output (MU-MIMO) systems from network aspect. Design the cross-layer network architecture for Cognitive Radio (CR) network. Analyze the UWB systems under IEEE 802.15.3a/4a channel model with RAKE receiver. UWB MU- MIMO CR WLAN/ WiMax Mesh Network MC-DS CDMA Investigate Radio Resource Management Techniques of Multi-Carrier Direct Sequence Code Division Multiple Access (MC-DS-CDMA) and High Speed Downlink Packet Access (HSDPA). Design PHY/MAC Cross-layer protocols for IEEE 802.11 and 802.16 WLAN and WMAN. A scalable multi-channel ring-based Wireless Mesh Network (WMN) is proposed to optimize the tradeoff among delay, throughput, and coverage. Wireless Network Lab, NCTU, Taiwan

2. Multi-Hop Cooperative Relay Network: Objective • Investigating the impacts of cooperative relay on handoff, capacity, and coverage from cooperative diversity and information mixing perspectives. Wireless Network Lab, NCTU, Taiwan

3. Cooperative Diversity • Virtual antenna arrays. • Macro-diversity gain to combat shadowing. • Micro-diversity in the presence of fading. Wireless Network Lab, NCTU, Taiwan

4.         Information Mixing (Network Coding) • Traditional multi-hop relaying • Information exchange between A and B needs 4 transmissions. • Information mixing multi-hop relaying • Only 3 transmissions are needed. Wireless Network Lab, NCTU, Taiwan

5. Multi-Hop Cooperative Relay Network: Subjects • Cooperative Diversity in Wireless Networks (偉賢) • Handoff in Relay-based WiMax networks with directional antennas (政敏) • Soft handoff in Relay-based WiMax networks (文山) • Capacity analysis in WiMax multi-hop relay networks (建華) • Network coding for cooperative relay network (tbd) Wireless Network Lab, NCTU, Taiwan

6. Multi-Hop Cooperative Relay Network • Sponsor: MoE ATU Program • Contact: Jane-Hua Huang • Current Results: • Jane-Hwa Huang, Li-Chun Wang and Chung-Ju Chang, “Capacity and QoS for A Scalable Ring-based Wireless Mesh Network,” to appear in IEEE J. Select. Areas Commun., Special issue on wireless mesh network. • Jane-Hwa Huang, Li-Chun Wang and Chung-Ju Chang, “Wireless Mesh Networks for Intelligent Transportation Systems,” IEEE SMC 2006. Wireless Network Lab, NCTU, Taiwan

7. Cognitive Radio • Overview: • A CR ad hoc network is a dynamically reconfigurable wireless network with no fixed infrastructure or central administration. • Nodes in these networks move arbitrary, and the radio spectrum which they occupy may change frequently. • Sponsor: NSC • Contact: Chung-Wei Wang Wireless Network Lab, NCTU, Taiwan

8. Cognitive Radio - Subject • Clustering Architecture for CR Networks (中瑋) • Spectrum Opportunity Identification Technique for CR Systems • A Game Theoretic Framework for Interference Avoidance in cooperative CR networks (中瑋) • CR MAC for MIMO network (盈志) • Coexistence of ad hoc and infrastructure networks (銘賓) • Coverage and Capacity of Wireless CR Mesh Networks (建華) • Cross-layer Analysis for Multicasting Information in CR Networks (tbd) Wireless Network Lab, NCTU, Taiwan

9. Spectrum Opportunity Identification Technique for CR Systems • One fundamental issue for the CR system is how to rapidly establish a temporary communication link on the spectrum of the exiting users. • We investigate the feasibility issue of establishing both an infrastructure-based link and an ad hoc link using the same spectrum simultaneously in an overlapped area. Wireless Network Lab, NCTU, Taiwan

10. CR Network Cluster Relay Clustering Architecture for CR Networks • In a building, CR devices self-organize into several cluster networks. • We proposed cluster head election and member assignment algorithms to form clusters. Wireless Network Lab, NCTU, Taiwan

11. Coverage and Capacity of Wireless CR Mesh Networks • We propose a scalable multi-channel multi-hop wireless mesh network. • Without the legacy IEEE 802.11 MAC protocol, a simple frequency planning is applied to effectively utilize the available multiple channels. • An optimization problem is formulated to maximize the coverage and capacity subject to the QoS requirement. Wireless Network Lab, NCTU, Taiwan

12. Cross-layer Analysis for Multicasting Information in CR Networks • Multicasting is a more efficient way of supporting group communications than unicasting or broadcasting. • We want to establish a scalable and efficient multicast routing algorithm that is suitable for a CR ad hoc network. Wireless Network Lab, NCTU, Taiwan

13. Current Results: • [1] Li-Chun Wang, Chung-Wei Wang, and Chuan-Ming Liu, “Adaptive Contention Window-based Cluster Head Election Algorithms for Wireless Sensor Networks,” VTC'05 Fall, vol. 3, pp. 1819-1823, September 2005. • [2] Li-Chun Wang, and Anderson Chen, “On the Coexistence of Infrastructure-Based and Ad Hoc Connections for a Cognitive Radio System,” to be appeared in CrownCom 2006. Wireless Network Lab, NCTU, Taiwan

14. MIMO-UWB (1/2) • Objective: Performance analysis of the MB-OFDM MIMO-UWB system • Subject: • BER analysis and system design under the IEEE 802.15.4a UWB channel model using MB-OFDM and MIMO techniques • Sponsor: NSC • Contact: Wei-Cheng Liu Wireless Network Lab, NCTU, Taiwan

15. MIMO-UWB (2/2) • Current Results: • Li-Chun Wang and Wei-Cheng Liu, “Performance of Pulse Position Modulated Signals over the Ultra-Wideband Channel with Multiple Transmit and Receive Antennas,” IEEE Vehicular Technology Conference 2004 Fall, vol. 2, pp. 822-826, Sep. 26-29, 2004. • 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,” appeared in VTC2006-Spring. • Wei-Cheng Liu and Li-Chun Wang, “Performance Analysis of Pulse Based Ultra-Wideband Systems in the Highly Frequency Selective Fading Channel with Random Clusters and Rays,” submitted to IEEE Trans. Veh. Technol. • Wei-Cheng Liu and Li-Chun Wang, “BER Analysis of the IEEE 802.15.4a Channel Model with RAKE Receiver,” accepted by VTC2006-Fall. Wireless Network Lab, NCTU, Taiwan

16. Scheduling for MIMO OFDM (1/2) • Objective: • Subject: • Link reliability and coverage enhancement for multiplexing-based MIMO OFDMA systems by scheduling. (正偉) • Performance analysis of the zero-forcing beamforming for MIMO broadcast channel systems. (俥榮, Now) • Space-time scheduling for MIMO BC systems with co-channel interference. (俥榮, Next) • Space-time-frequency scheduling for MIMO-OFDM Wireless Network Lab, NCTU, Taiwan

17. Scheduling for MIMO OFDM (2/2) • Sponsor: NSC 2007~2010? • Contact: Chu-Jung Yeh • Current Results: • Comparison of transmit and receive zero-forcing scheduler for MIMO broadcast channels • Analyze the link outage and cell coverage for multiplexing-based MIMO OFDM systems. Wireless Network Lab, NCTU, Taiwan

18. Handoff in OFDMA-based Network • Objective: • MAC design and performance analysis for OFDMA-based inter/intra network handoff • Subject: • Enhanced MAC layer hard handoff for mobile WiMax （銘賓） • Soft handoff for mobile WiMax with relay station （文山） • Smart vertical handoff between WiFi and WiMax （鴻昕） • Sponsor: • Contact: Anderson Chen Wireless Network Lab, NCTU, Taiwan

19. Motivation • OFDMA PHY is considered a candidate access technique for the future wireless system to combat the severe multipath fading. • However, the future mobile terminal may equip multiple wireless interfaces to connect various wireless networks, e.g WiFi/WiMax. Wireless Network Lab, NCTU, Taiwan

20. Issues • Always best connect (ABC) becomes an important issue for the handoff in heterogeneous network. • Seamless handoff is one of the key issue for the ABC in the inter/intra network handoff. • Sub-channel allocation for the HHO/SHO/FBSS in OFDMA-based system is another challenging issue. • Which sub-channels should be reserved for the handoff MNs to increase the transmission success probability and thus expedite the re-entry process? Wireless Network Lab, NCTU, Taiwan

21. Current Results • Li-Chun Wang, Hung-Hsi Chen, Anderson Chen, Chung-Ju Chang, “Optimal channel search time for handoff in the IEEE 802.11 WLANs,” appeared in VTC 2006 Spring • Anderson Chen and Li-Chun Wang, “On the performance of re-entry process in OFDMA-based IEEE 802.16 WiMax,” to be appeared in WPMC 2006 Wireless Network Lab, NCTU, Taiwan