415324
Mobility information for resource management in wireless ATM networks
User mobility poses a significant technical challenge to network resource management in wireless ATM (Asynchronous Transfer Mode) networks. In order to guarantee quality of service (QoS) to mobile users and to achieve a high efficiency in network resource management, the information of mobile users' handoff at a future moment is essential for statistical multiplexing. This paper develops a novel fuzzy logic inference system to estimate the user mobility information for a wireless ATM network which uses a direct sequence code division multiple access (DS/CDMA) protocol. The estimation is based on measured pilot signal strengths from a number of the nearest base stations by the mobile user. Numerical results are presented to demonstrate the performance of the proposed technique under various path losses and channel shadowing conditions. The proposed technique can achieve simplicity, accuracy and low cost.
41776046
A Node Cooperative ARQ Scheme for Wireless Ad-Hoc Networks
We propose a Node Cooperative Automatic Repeat reQuest (ARQ) scheme for wireless ad-hoc networks to combat the effects of channel fading on the performance of link layer retransmission scheme. The proposed scheme is inspired by the idea of cooperative diversity. Simulation results are given to demonstrate the significant throughput gain, even when the quality of channel between the communicating nodes is poor.
768133
Performance analysis of TCP-friendly AIMD algorithms for multimedia applications
In this paper, the performance of TCP-friendly generic AIMD (Additive Increase and Multiplicative Decrease) algorithms for Web-based playback and multirate multimedia applications is investigated. The necessary and sufficient TCP-friendly condition is derived, and the effectiveness and responsiveness of AIMD are studied. Due to practical implications, a Dynamic TCP-friendly AIMD (DTAIMD) algorithm is proposed. Extensive simulation results are given to verify the derived necessary and sufficient condition, and to demonstrate the performance of the proposed DTAIMD algorithm.
40278707
Modeling and Analysis of WAP Performance over Wireless Links
In this paper, an analytical model for studying the performance behavior of wireless application protocol (WAP) over wireless links is proposed. A Rayleigh fading channel model is used to characterize the behavior of the wireless channel. Mathematical expressions that represent the performance of WAP as a function of the protocol and the channel parameters are derived. Computer simulation results are presented to validate the analytical results. It is shown that WAP performs better in a bursty error environment than in a random error environment. The goodput of WAP can be improved by increasing the WAP packet group size, but the significance of the improvement depends on the underlying channel condition.
449557
Power allocation and scheduling for MAC layer design in UWB networks
This paper proposes a practical joint power allocation and scheduling scheme for medium access control (MAC) layer design in ultra-wideband (UWB) networks. The scheme increases system spectral efficiency and reduces power consumption by fully considering the properties of the UWB, such as its capacity in supporting parallel transmission and providing accurate positioning, and its stringent constraint on computational complexity. Practical implementations of the proposed scheme are achieved by introducing a margin based power allocation scheme and an exclusive region based scheduling scheme. The margin based power allocation scheme is carried out based on each link's own information, and is simple to implement, while the exclusive region based scheduling scheme takes into account the interaction among different links. Simulation results show that the proposed power allocation and scheduling schemes exhibit good performance in terms of the average number of slots per frame and the power consumption reduction
7313627
Voice capacity analysis of WLAN with unbalanced traffic
An analytical model to study the performance of wireless local area networks (WLANs) supporting asymmetric nonpersistent traffic using the IEEE 802.11 distributed coordination function mode for medium access control (MAC) is developed. Given the parameters of the MAC protocol and voice codecs, the voice capacity of an infrastructure-based WLAN, in terms of the maximum number of voice connections that can be supported with satisfactory user-perceived quality, is obtained. In addition, voice capacity analysis reveals how the overheads from different layers, codec rate, and voice packetization interval affect voice traffic performance in WLANs, which provides an important guideline for network planning and management. The analytical results can be used for effective call admission control to guarantee the quality of voice connections. Extensive simulations have been performed to validate the analytical results
36146131
A parallel algorithm for multiple edge updates of minimum spanning trees
The authors present a parallel algorithm for the multiple edge update problem on a minimum spanning tree. This problem is defined as follows: given a minimum spanning tree T(V,E/sub T/) of an undirected graph G(V,E), where mod V mod =n and E/sub T/ is the set of tree edges, recompute a new minimum spanning tree when (1) adding K new edges, (2) changing the weights of existent K edges, or (3) deleting a vertex of degree K in the tree, where 1<or=K<n. Their algorithm requires O(logKlogn) time and O(n/sup 2//lognlogK) processors on a SIMD CREW PRAM model. If the weights of the current tree edges are not allowed to increase, then their algorithm runs in the same time bound, but only using O(max(n,nK/lognlogK)) processors. Their algorithm is optimal for dense graphs, if no intermediate results are available from computing the original MST.<<ETX>>
44902657
The 4-Star Graph is not a Subgraph of Any Hypercube
Abstract We prove that it is impossible to precisely embed any star graph S n ( n ⩾4) into a hypercube.
17618182
Locality approximation using time
Reuse distance (i.e. LRU stack distance) precisely characterizes program locality and has been a basic tool for memory system research since the 1970s. However, the high cost of measuring has restricted its practical uses in performance debugging, locality analysis and optimizations of long-running applications.In this work, we improve the efficiency by exploring the connection between time and locality. We propose a statistical model that converts cheaply obtained time distance to the more costly reuse distance. Compared to the state-of-the-art technique, this approach reduces measuring time by a factor of 17, and approximates cache line reuses with over 99% accuracy and the cache miss rate with less than 0.4% average error for 12 SPEC 2000 integer and floating-point benchmarks. By exploiting the strong correlations between time and locality, this work makes precise locality as easy to obtain as data access frequency, and opens new opportunities for program optimizations.
205000553
Scheduling on a Hypercube
Abstract We present a Θ(n2) worst-case-time algorithm to determine the minimum finishing time for a preemptive schedule of n independent jobs on a hypercube of fixed dimension.
14429022
Mining long-term search history to improve search accuracy
Long-term search history contains rich information about a user's search preferences, which can be used as search context to improve retrieval performance. In this paper, we study statistical language modeling based methods to mine contextual information from long-term search history and exploit it for a more accurate estimate of the query language model. Experiments on real web search data show that the algorithms are effective in improving search accuracy for both fresh and recurring queries. The best performance is achieved when using clickthrough data of past searches that are related to the current query.