Researches in MACS Lab macs.cs.cityu.hk/

1. Researches in MACS Labhttp://macs.cs.cityu.edu.hk/ Prof. Xiaohua Jia Dept of Computer Science City University of Hong Kong

2. On-going research projects • 可信移动互联网络的关键理论与应用研究 , NSF China Key Project (07– 10) • Minimum Latency Broadcast and Data Aggregation in Wireless Ad Hoc and Sensor Networks, HK UGC (07 – 09) • Energy Efficient Query Dissemination and Aggregation in Wireless Sensor Networks, HK UGC (06 – 07) • Virtual Backbone Construction in Multihop Ad Hoc Wireless Networks, HK UGC (05 – 07)

3. Wireless Sensor and Ad Hoc Networks Sensor surveillance systems Given the locations of sensors and targets, sensor initial energy, find a schedule for sensors to watch the targets in turn, such that the lifetime is maximized. “Maximizing Lifetime of Sensor Surveillance Systems”, IEEE/ACM Trans on Networking, Vol. 15, No. 2, Apr 07. "Maximal Lifetime Scheduling for Sensor Surveillance Systems with K Sensors to 1 Target", IEEE Trans on Parallel and Distributed Systems, Vol. 17, No. 12, Dec 06.

4. Wireless Sensor and Ad Hoc Networks Broadcast / multicast in ad hoc networks • Efficient flooding "A Distributed and Efficient Flooding Scheme Using 1-hop Information in Mobile Ad Hoc Networks," IEEE Trans on Parallel and Distributed Systems, Vol. 18, No. 5, May 2007. • Energy efficient routing “Energy efficient broadcast routing in ad hoc wireless networks”, IEEE Trans on Mobile Computing, Vol. 3, No. 2, Apr - Jun, 2004. • Minimum latency broadcast / multicast

5. Wireless Sensor and Ad Hoc Networks Real-time data aggregation • CSMA model (802.15.4) • TDMA model • Multi-channel

6. Wireless Mesh Networks (WMN)

7. Channel Assignment in WMNs Given a network physical topology (determined by transmission power of nodes) and limited # of channels, assign channels to the radios in each node, such that certain connectivity of the network is preserved and the network interference is minimized. Channel assignments can be: • static assignment • dynamic assignment • hybrid assignment

8. Topology Control in WMNs • Topology control in WMNs includes two steps: • Power adjustment • Channel assignment • Power adjustment • Define the physical topology of network • A link between two nodes if they are reachable via transmission power. • Channel assignment • Define the logical topology on the top of the physical topology • A link between two nodes if they are reachable and use a common channel. • Goals of topology control • Min interference (given connectivity requirement) • QoS guaranteed (end-end bandwidth, delay, etc) topology

9. Timeslot schedule in TDMA systems • Free timeslot matching on links • Interference (inter-flow / intra-flow)

10. Timeslot schedule in SR/SC systems Given traffic demand on each link, find a TDMA schedule that all traffic demands can be met and the TDMA cycle is minimized.

11. Channel assignment and timeslot schedule in MR/MC systems • Separate channel assignment from slot scheduling (channel static) • Joint channel assignment and slot scheduling (channel switchable at packet level) • Real-time traffic scheduling

12. Channel assignment and timeslot schedule in a tree

13. Multiple trees configuration in WMNs Given a set of mesh routers and multiple gateway nodes, configure a set of trees (via power-adjustment or channel-assignment), such that the total throughput of the trees is maximized. Issues to be considered: • Load balancing • Interference • Timeslot schedule

14. Online QoS routing & timeslot scheduling • QoS unicast • QoS multicast

15. Thanks!