Researches in MACS Labhttp://macs.cs.cityu.edu.hk/

Prof. Xiaohua Jia

Dept of Computer Science

City University of Hong Kong

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)

Wireless Sensor and Ad Hoc Networks

Sensor surveillance systemsGiven the locations of sensors and targets, sensor

initial energy, find a schedule for sensors to find a schedule for sensors to watch the targets in turn, such that the lifetime watch the targets in turn, such that the lifetime is maximized.is maximized.

““Maximizing Lifetime of Sensor Surveillance Systems”, Maximizing Lifetime of Sensor Surveillance Systems”, IEEE/ACM Trans on NetworkingIEEE/ACM Trans on Networking, Vol. 15, No. 2, Apr 07., 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.

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

Wireless Sensor and Ad Hoc Networks

Real-time data aggregation CSMA model (802.15.4) TDMA model Multi-channel

Wireless Mesh Networks (WMN)

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

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

Timeslot schedule in TDMA systems

Free timeslot matching on links Interference (inter-flow / intra-flow)

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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.

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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

Channel assignment and timeslot schedule in a tree

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

Online QoS routing & timeslot scheduling

QoS unicast QoS multicast

Thanks!