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In this paper we derive general expressions for the performance of hierarchical multilevel quadrature amplitude modulation constellations (M-QAM), over flat Rayleigh fading environments with imperfect channel estimation. Cases of diversity reception with identical channels and with dissimilar channels, employing maximal ratio combining (MRC) are considered. Since hierarchical constellations are usually...
This paper presents a framework for the performance analysis of queueing networks under active queue management scheme. The analysis is based on a queue-by-queue decomposition technique where each queue is modelled as a GGeo/GGeo/1/{N1, N2} queue with single server, R (R = 2) distinct traffic classes, N1 as the buffer threshold and N2 as full buffer capacity under first-come-first-serve (FCFS) service...
In this paper, we propose a novel MAC protocol with the patterned preamble technique to improve performance in terms of low power, channel utilization, and delay in wireless sensor networks. B-MAC is one of typical MAC protocols for wireless sensor networks using the duty cycle in order to achieve low-power operation. Since it works in an asynchronous fashion, B-MAC employs extended preamble and preamble...
With the wide application of Web services, its performance has caused the extensive concern and becomes one of the key factors of determining whether it is widely applied further. Based on the idea of differentiating Web services, the paper presents a SLA-based Web services performance guarantee model to improve Web services runtime environment, and expatiates on the key techniques of realizing the...
File transfer, web download, and many other applications are primarily interested in minimal delay achievable for their messages. In this paper, we investigate allocating the bottleneck link capacity to transmit messages efficiently but fairly. While SRPT (Shortest Remaining Processing Time) is an optimally efficient algorithm that minimizes average delay of messages, large messages might starve under...
Wireless spectrum is a scare resource, while media streaming usually requires high end-to-end bandwidth. Media streaming in wireless ad hoc networks is therefore a particularly challenging problem, especially for the case of streaming to multiple receivers. In this paper, we design linear optimization models for computing a high-bandwidth routing strategy for media multicast in wireless networks,...
The linear information flow (LIF) algorithm and its relatives are the most efficient centralized algorithms known for finding network encoding equations for multicast communication. This paper examines the performance of the LIFE (linear information flow on edges) algorithm on a "real" network, through the use of a simulation model. We present results on the algorithm's ability to encode...
In this paper we propose an algorithm to adjust the transmission bit-rate of variable-bit-rate (VBR) MPEG video data by using a combination of transcoding and bit-rate smoothing algorithm. The algorithm works by smoothing out the bit-rate of high variance MPEG video data and when necessary transcodes some video frames in order to keep the video transmission bit-rate below a determined threshold value...
Because of its accuracy, signature matching is considered an important technique in anti-virus/worm applications. Among some famous pattern matching algorithms, the Aho-Corasick (AC) algorithm can match multiple patterns simultaneously and guarantee deterministic performance under all circumstances and thus is widely adopted in various systems, especially when worst-case performance such as wire speed...
Signaling protocols for GMPLS networks have been standardized and implemented in switch controllers. Most switch vendors allow for signaling messages to be carried over in-band signaling channels as well as through out-of-band networks. In this paper, we compare these two signaling transport options. In carrying out this analysis, we allow for both software-implemented signaling protocol processors,...
To handle more phone and personal computer users in such a natural disaster as terribly strong earthquake, a traffic control has been previously proposed by limiting the individual call holding time. This traffic control mechanism leads to our T-limited service. By T-limited service, we mean that the service time is limited to a threshold T. The call whose service time reaches T is assumed to be lost...
This paper proposes a network-layer protocol for wireless sensor networks based on the IEEE 802.15.4 standard. Our protocol is devised to provide reliable data gathering in latency-constrained applications, and exploits both the flexibility of the IEEE 802.15.4 MAC layer and features of data aggregation techniques, such as implicit acknowledgment of reception. The proposed protocol acts as a routing...
Autonomous localization of nodes in wireless sensor networks is essential to minimize the complex self organization task and consequently enhancing the overall network lifetime. Recently, precise localization algorithms are impeded by multi path propagation of signals originated by reflections at walls or other objects in the environment. However, the localization error can be reduced by applying...
Considerable research efforts in the networking community are focused on defining a new Internet architecture that not only solves some of the problems of the current design, but also meets future needs. Our work focuses on the issue of how to provide suitable abstractions for communication between end-systems. This is a particularly important aspect of the network architecture as it is exposed to...
In the past decade cluster computing platforms have been widely applied to support a variety of scientific and commercial applications, many of which are parallel in nature. However, scheduling parallel applications on large scale clusters is technically challenging due to significant communication latencies and high energy consumption. As such, shortening schedule length and conserving energy consumption...
In this paper, we present a collision free MAC protocol for wireless ad-hoc networks with multiple input multiple output (MIMO) links. The proposed MAC protocol provides proportional service differentiation to various classes of traffic based on their respective bandwidth demands. It exploits the spatial multiplexing and interference suppression capability of MIMO links in order to activate multiple...
Sequencer, privilege-based, and communication history algorithms are popular approaches to implement total ordering, where communication history algorithms are most suitable for parallel computing systems, because they provide best performance under heavy work load. Unfortunately, post-transmission delay of communication history algorithms is most apparent when a system is idle. In this paper, we...
The network lifetime is a key design factor of mobile ad-hoc networks (MANETs). To prolong the lifetime of MANETs, one is forced to attain the tradeoff of minimizing the energy consumption and load balancing. In MANETs, energy waste resulting from retransmission due to high frame error rate (FER) of wireless channel is significant. In this paper, we propose a novel protocol termed error-aware candidate...
In this paper, we investigate the reliable data transport problem in underwater sensor networks. Underwater sensor networks are significantly different from terrestrial sensor networks in two aspects: acoustic channels are used for communication and most sensor nodes are mobile due to water current. These distinctions feature underwater sensor networks with low bandwidth capacity, large propagation...
Distributed hash tables (DHTs) are a class of decentralized distributed systems that can efficiently search for objects desired by the user. However, a lot of communication traffic comes from multi-word searches. A lot of work has been done to reduce this traffic by using bloom filters, which are space-efficient probabilistic data structures. There are two kinds of bloom filters: fixed-size and variable-size...
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