ZBP: A Zone-Based Broadcasting Protocol for Wireless Sensor Networks

Wireless Sensor Networks (WSNs) have been widely used in motoring and collecting interests of environment information. Packet flooding or broadcasting is an essential function for establishing a communication path from sink node to a region of sensor nodes. However, flooding operation consumes power and bandwidth resources and raises the packet collision and contention problems, which reduce the success rate of packet transmissions and consume energy. This article proposes an efficient broadcasting protocol to reduce the number of sensor nodes that forward the query request, hence improves the packet delivery rate and saves bandwidth and power consumptions. Sensor node that received the query request will dynamically transfers the coordinate system according to the zone-ID of source node and determines whether it would forward the request or not in a distributed manner. Compared with the CBM and traditional flooding operation, experimental results show that the proposed zone-based broadcasting protocol decreases the bandwidth and power consumptions, reduces the packet collisions, and achieves high success rate of packet broadcasting.Chih-Yung Chang received the Ph.D. degree in Computer Science and Information Engineering from National Central University, Taiwan, in 1995. He joined the faculty of the Department of Computer and Information Science at Aletheia University, Taiwan, as an Assistant Professor in 1997. He was the Chair of the Department of Computer and Information Science, Aletheia University, from August 2000 to July 2002. He is currently an Associate Professor of Department of Computer Science and Information Engineering at Tamkang University, Taiwan. Dr. Chang served as an Associate Guest Editor of Journal of Internet Technology (JIT), Special Issue on “Wireless Ad Hoc and Sensor Networks” (2004) and a member of Editorial Board of Tamsui Oxford Journal of Mathematical Sciences (2001–2005). He was an Area Chair of IEEE AINA′2005, Vice Chair of IEEE WisCom2005, Track Chair (Learning Technology in Education Track) of IEEE ITRE′2005, Program Co-Chair of MNSA′2005, Workshop Co-Chair of INA′2005, MSEAT′2003, MSEAT′2004, Publication Chair of MSEAT′2005, and the Program Committee Member of ICPP′2004, USW′2005, WASN′2005, and the 11th Mobile Computing Workshop. Dr. Chang is a member of the IEEE Computer Society and IEICE society. His current research interests include wireless sensor networks, mobile learning, Bluetooth radio systems, Ad Hoc wireless networks, and mobile computing.Kuei-Ping Shih received the B.S. degree in Mathematics from Fu-Jen Catholic University, Taiwan, Republic of China, in June 1991 and the Ph.D. degree in Computer Science and Information Engineering from National Central University, Taiwan, Republic of China, in June 1998. After two years of military obligation, he joined the faculty of the Department of Computer Science and Information Engineering, Tamkang University, Taiwan, Republic of China, as an assistant professor in 2000. Dr. Shih served as a Program Area Chair in the IEEE International Conference on Advanced Information Networking and Applications (AINA), 2005, and as a Technical Track Chair in the IEEE International Conference on Information Technology: Research and Education (ITRE), 2005. Dr. Shih’s current research interests include wireless networks, sensor networks, mobile computing, and network protocols design.Dr. Shih is a member of the IEEE Computer and Communication Societies and Phi Tau Phi Scholastic Honor Society.Shih-Chieh Lee received the B.S. degree in Computer Science and Information Engineering from Tamkang University, Taiwan, in 1997. Since 2003 he has been a Ph.D. Students in Department of Computer Science and Information Engineering, Tamkang University. His research interests are wireless sensor networks, Ad Hoc wireless networks, and mobile/wireless computing.     

A traffic-aware scheduling for bluetooth scatternets

Bluetooth is a low cost, low power, short-range radio technology used for wireless personal area networks (PANS). Bluetooth scatternet is a set of piconets interconnected via bridge devices. Good interpiconet schedulings are necessary for bridge devices to switch among piconets they participate in. This paper proposes an interpiconet scheduling algorithm named "Traffic-Aware Scatternet Scheduling" (TASS), for bridges in Bluetooth scatternets. According to masters' traffic information, TASS can adaptively switch the bridge to high traffic load masters, and increase the usage of the bridge. In addition, TASS can reduce the number of failed "unsniffs" and the overhead of "bridge switch wastes" to further increase overall system performance. Simulation results show that TASS outperforms existing interpiconet scheduling in both network throughput and adaptability for various traffic loads.     

Statement-Level Communication-Free Partitioning Techniques for Parallelizing Compilers

This paper addresses the problem of communication-free partition of iteration spaces and data spaces along hyperplanes. To finding more possible communication-free hyperplane partitions, we treat statements within a loop body as separate schedulable units. Instead of using the information about data dependence distance or direction vectors, our technique explicitly formulates array references as transformations from statement-iteration spaces to data spaces. Based on these transformations, the necessary and sufficient conditions for communication-free partition along hyperplanes to be feasible have been proposed. This approach can be applied to all programs with an imperfectly nested loop or sequences of imperfectly nested loops, whose array references are affine functions of outer loop indices or loop invariant variables. The proposed approach is more practical than existing methods in finding the data and computation distribution patterns that can cause the processor to execute fully-parallel on multicomputers without any interprocessor communication.     

On avoiding RTS collisions for IEEE 802.11-based wireless ad hoc networks

The paper proposes an RCA (RTS collision avoidance) MAC protocol to reduce RTS collisions for IEEE 802.11-based mobile ad hoc networks (MANETs). RTS/CTS exchanging is used for the resolution of the hidden terminal problem. However, the paper shows that, even the backoff counters of two stations are different, RTS frames are also collided to each other due to the hidden terminal problem. The situation would be getting worse in high traffic load or in a dense network. RTS collisions not only result in the following CTS or ACK collisions, but also induce false blocking problem, even dead locks of transmissions. To address the above problems, an RCA MAC protocol is proposed to reduce RTS collisions. The RCA protocol utilizes a narrow band, called the tone channel, to announce the RTS transmission in advance in order to preclude the RTS transmissions of two-hop neighbors. To reduce the channel and hardware overhead, an improvement to the RCA protocol is also devised, which only uses a single channel and one transceiver to reduce RTS collisions. The RCA protocol provides a type of fast collision detection and decreases the probability of RTS collisions, which is benefit for RTS/CTS exchange scheme. Meanwhile, the RCA protocol can reduce the retransmission cost and have lower control overhead than that of IEEE 802.11 DCF. In addition, simulation results verify the advantages of the RCA protocol in comparison with IEEE 802.11 DCF.     

A location-aware multicasting protocol for Bluetooth Location Networks

Bluetooth Location Network (BLN) is a Bluetooth radio network that is composed of some mobile Bluetooth devices and static Bluetooth units, and is established at the system initialization to form a spontaneous network topology. In a BLN, a multicast service is defined as the periodical delivering of messages from a Service Server to a set of mobile devices which are the multicast members predefined by the Service Server. Several multicast protocols have been proposed for the Ad-Hoc networks, but they create an inefficient multicast tree for the BLN due to the existing differences in the radio characteristics between Ad-Hoc and Bluetooth radio networks. The present paper analyzes these differences and proposes a novel multicasting protocol for constructing an efficient multicast tree in a BLN. The proposed protocol constructs a multicast tree with good features which include the shortest path, a higher degree of path sharing, and fewer forwarding nodes. Simulation results reveal that the proposed multicast protocol outperforms the existing multicast protocols in the BLN.     

An efficient scheduling algorithm for radio resource reuse in IEEE 802.16j multi-hop relay networks

The IEEE 802.16j standard for WiMAX introduced the concept of relay station in order to increase the service area and decrease the deployment cost of the network. In this paper, we have proposed an efficient scheduling scheme for IEEE 802.16j networks, which maximizes the number of connections that are scheduled in a particular time slot. The proposed scheme schedules the connections based on their priority, which is decided by the quality of service (QoS) requirement of the connections. A selected connection can be scheduled in the current timeslot only if it is not having interference with any of the already scheduled connections. Our algorithm considers scheduling of lower priority connections even if any higher priority connection is not scheduled due to interference. Thus, the delay for lower priority connections is reduced without increasing the delay for higher priority connections. In addition, our algorithm achieves higher frame utilization and higher system throughput by reducing the length of the schedule.