Multicasting has become an important part of current networking technologies. To accommodate the multicasting traffic, switches in ATM (Asynchronous Transfer Mode) networks need to be able to support multicasting. In multicast ATM switches, usually there are many cells contending for the same output port resources at the same time. This may lead to serious performance degradation. In the past, many special output port components are proposed to solve this problem. However, most of these approaches alleviate the output port overflowing problem without considering the output port congestion or the internal routing blocking problem. Especially when the switch fabric is based on the banyan-like network, these two problems will seriously degrade the switch performance. In this paper, we propose a pre-scheduling mechanism to precede the multicast switch. This mechanism will completely eliminate the problems mentioned above. Two architectures are designed to implement this mechanism. Analysis and simulations show that our design performs quite well.

Multicasting functionality is an important criterion in judging the powerfulness and extendibility of ATM switches. Recently many multicast ATM switches have been proposed. They are mostly modified from unicasting switches. For such switches to support multicasting, they often need some additional components, e. g. , copy network, and numerous modifications on the original unicasting network. Although the multicasting is supported, the method is often inefficient and the architecture is complicated and costly. In this paper, we propose a new multicast ATM switch. In the proposed architecture, the nonblocking unicast network will not be modified. All that need is a simple external nonblocking multicast module. The external nonblocking multicast module will not delay the original nonblocking unicast network module, and the cost in hardware complexity for the external nonblocking multicasting module will be O(NK log K), where N is the switch size and K is the number of broadcast buses used in the multicast module.

With the advances of micro-electronic and wireless communication technology, deploying a large number of low cost, small-sized sensor nodes over a vast area for environment monitoring is becoming more practical. Setting up gradients for delivering queries or data reports by flooding the sensor networks consumes a great deal of energy especially for large scale sensor networks. In this paper, we propose an energy conserving observer-initiated data dissemination protocol, called Grid Map Data Query Protocol (GMDQP), for multiple mobile sinks on a large scale sensor network. It conserves communication energy by employing a grid map data query technique to avoid full network events or queries flooding. A data source only announces the existence of data within a local area and a sink collects data by sending query message in a grid map. Nodes at cross point of grid check and query the data. It conserves energy by avoiding full network flooding in setting up data forwarding path. Simulations show that the proposed architecture is quite energy efficient.

Video on demand is regarded as one of the most important applications in future broadband networks. Although several trial runs in various parts of the world do not bring instant success, its inherent requirements for bandwidth and bounded delay make it a suitable candidate for studying various networks and protocols in real-time applications. Recently, the Hybrid Fiber Coaxial (HFC) networks emerged as network architecture for bringing broadband services to the home. The co-axial cable network uses a tree-like architecture and requires complex protocols for synchronizing and sharing uplink communications among many users. This paper proposes that a dual bus network may be a simpler and cost effective alternative. We implement an interactive VOD (IVOD) system as an example to demonstrate its simplicity and suitability as a community network. The system uses client/server architecture with guaranteed bandwidth and bounded delays. Simulations are conducted to test the network load and response time for different number of users. The results indicate its feasibility and the delay time can be further reduced by releasing bandwidth during the pause operation.

Recently, wireless networks have become a major sector in the telecommunication industry. More and more applications seek to become wireless. However, a major obstacle in adapting wired applications to wireless is the quality of service problem. Although the wireless bandwidth is improving at a fast pace, it still is not enough for modern multimedia applications. Even if we solve the bandwidth problem, the mobility of users also poses challenges for QoS provision. If the user moves randomly, how and where can resources be reserved in advance for roaming users to move smoothly and seamlessly? In this paper, we propose a method for predictive resource reservation in wireless networks. Resources reserved but not used will seriously affect the system performance. Therefore, we also have mechanisms to release the reserved resources when it is not used within a time limit and allow resources to be used temporarily by another mobile user. We compare the performance of our method with those of fixed allocation scheme and shadow cluster scheme. The results indicate its effectiveness and feasibility.

A set of spanning trees of a graphs G are called completely independent spanning trees (CISTs for short) if for every pair of vertices x, y∈V(G), the paths joining x and y in any two trees have neither vertex nor edge in common, except x and y. Constructing CISTs has applications on interconnection networks such as fault-tolerant routing and secure message transmission. In this paper, we investigate the problem of constructing two CISTs in the balanced hypercube BHn, which is a hypercube-variant network and is superior to hypercube due to having a smaller diameter. As a result, the diameter of CISTs we constructed equals to 9 for BH2 and 6n-2 for BHn when n≥3.

IEEE 802. 11 is a standard for wireless LANs. The basic access method in its MAC layer protocol is the distributed coordination function (DCF) for the ad hoc networks. It is based on the mechanism of carrier sense multiple access with collision avoidance (CSMA/CA). DCF is used to support asynchronous data transmission. However, frames in DCF do not have priorities, making it unsuitable for real-time applications. With a little bad luck, a station might have to wait arbitrarily long to send a frame. In this paper, we propose a method to modify the CSMA/CA protocol such that station priorities can be supported. The method is simple, efficient and easy to implement in comparison to point coordination function (PCF), another access method in IEEE 802. 11 based on access points (base stations). Simulations are conducted to analyze the proposed scheme. The results show that DCF is able to carry the prioritized traffic with the proposed scheme.