Performance of TCP/UDP under Ad Hoc IEEE802.11

TCP is the De facto standard for connection oriented transport layer protocol, while UDP is the De facto standard for transport layer protocol, which is used with real time traffic for audio and video. Although there have been many attempts to measure and analyze the performance of the TCP protocol in wireless networks, very few research was done on the UDP or the interaction between TCP and UDP traffic over the wireless link. In this paper, we tudy the performance of TCP and UDP over IEEE802.11 ad hoc network. We used two topologies, a string and a mesh topology. Our work indicates that IEEE802.11 as a ad-hoc network is not very suitable for bulk transfer using TCP. It also indicates that it is much better for real-time audio. Although one has to be careful here since real-time audio does require much less bandwidth than the wireless link bandwidth. Careful and detailed studies are needed to further clarify that issue.Comment: 9 pages, 5 figures, ICT 2003 (10th International Conference on Telecommunication

Complexities of Layouts in Three-Dimensional VLSI Circuits

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryNational Science Foundation / DMC 85-19649Joint Services Electronics Program / N00014-84-C-0149Egyptian Educational and Cultural Bureau scholarshi

A Hierarchical Multistage Interconnection Network

Multistage interconnection networks are used in many applications ranging from connecting processors to memory modules in a parallel processing system, to high-speed network switches and routers. One of the major drawbacks in multistage networks is the lack of proximity concept. All nodes are at the same distance from any other node. In this paper, we propose a new hierarchical Multistage Network (HMN) based on the multi-stage Omega network. The new network requires less hardware (silicon area) than the Omega network, and enjoys the same ease of routing as the Omega network. Since the HMN is hierarchical in nature, not all the nodes are at the same distance from any other node. The distance between two nodes that belong to the same cluster are less than two nodes in two different clusters. That makes the HMN suitable for applications where there are preference among the nodes. We also introduce simple and efficient algorithm for routing in the HMN and we compare the performance of the HMN to the Omega network

Systematic design of computational arrays

In this thesis we discuss some aspects of the design of a system of systolic arrays, from the VLSI layout level to the system level. First, we discuss 3-D VLSI layout, where tighter lower and upper bounds for the volume and maximum wire length for the layout of the different families of graphs in a 3-D environment were developed. Except in two cases, all the bounds for the volume are optimal. The first case is the one-active-layer layout of the planar graphs, the other is the unrestricted layout for graphs with separators N\sp{\rm q}, q = 2/3. A cost model for reflecting the real cost of the layout, instead of taking the volume as a measure of cost, was also developed. In Chapter 3, we develop a methodology for designing a systolic array starting from recurrence equations. The idea of Control Flow Systolic Arrays to handle uniform, as well as nonuniform recurrence equations, is developed. This methodology is basically a search for a heuristic solution in the space of all the possible solutions. Because of the unlimited search space, the search process must be guided for the search to be completed in a reasonable amount of time. Chapter 4 introduces the idea of converting the data between two systolic arrays that were directly interfaced, instead of using a common memory which would be a bottleneck for the whole system. The minimum number of buffers required to convert the data between two given distributions was also calculated, a general purpose converter was also proposed