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1.
Centralized CDMA networks with unslotted Aloha randomaccess mode are considered. Users communicate with a central node by sharing a finite number of signature sequences assigned to the receivers at the central node. Two methods for sharing preamble codes are considered. In one method a common preamble code is used by all receivers, and in the other method a distinct code is assigned for each receiver. A unified analysis framework for evaluating the performance of centralized FHCDMA networks is developed. Closed form expressions for packet decoding error probabilities are derived. Numerical results show that common preamble codes can support only low traffic levels. However, by appropriately selecting the design parameters, acceptable levels of packet loss probabilities are achievable with the receiverbased preambles. 相似文献
2.
ZHANG Zu-fan DU Hui-ping JIANG Ze Chongqing University of Posts Telecommunications Chongqing China University of Electronic Science Technology of China Chengdu China 《中国邮电高校学报(英文版)》2006,13(4):29-33
1 Introduction The calling dwell time characteristic is critical for the user network planning and deployment, e.g., global system for mobile communications (GSM), as well as the next generation wireless multimedia networks, such as, the currently standar… 相似文献
3.
Sivalingam Krishna M. Chen Jyh‐Cheng Agrawal Prathima Srivastava Mani B. 《Wireless Networks》2000,6(1):73-87
This paper describes the design and analysis of a low‐power medium access control (MAC) protocol for wireless/mobile ATM networks.
The protocol – denoted EC‐MAC (energy conserving medium access control) – is designed to support different traffic types with
quality‐of‐service (QoS) provisions. The network is based on the infrastructure model where a base station (BS) serves all
the mobiles currently in its cell. A reservation‐based approach is proposed, with appropriate scheduling of the requests from
the mobiles. This strategy is utilized to accomplish the dual goals of reduced energy consumption and quality of service provision
over wireless links. A priority round robin with dynamic reservation update and error compensation scheduling algorithm is
used to schedule the transmission requests of the mobiles. Discrete‐event simulation has been used to study the performance
of the protocol. A comparison of energy consumption of the EC‐MAC to a number of other protocols is provided. This comparison
indicates the EC‐MAC has, in general, better energy consumption characteristics. Performance analysis of the proposed protocol
with respect to different quality‐of‐service parameters using video, audio and data traffic models is provided.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
ATM is the future networking technology in the area of broadband networks. Using fiber optical cabling offers high bandwidth
and low error rates. It is supposed to support different kinds of services, e.g., file transfer, videoconferencing, and speech
transmissions. To support seamless end-to-end quality of service in a mobile environment a suitable extension to the fixed
network part is necessary. In a wireless ATM environment the medium access protocol takes a prominent position. It is responsible
for an efficient and fair media access on the shared radio resource. Due to the limited available bandwidth and the much higher
error rates on the radio link special provisions must be provided. The compliance of traffic contracts for connections with
different quality of services is the aim of our proposed protocol. This is the base of true end-to-end services with quality
of service assurance in wireless ATM.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
5.
Daneshrad Babak Cimini Leonard J. Carloni Manny Sollenberger Nelson 《Mobile Networks and Applications》1997,2(4):305-314
An elegant means by which highspeed burst wireless transmission can be accomplished with small amounts of overhead is through a novel technique referred to as clusteredOFDM (Cimini et al., 1996). By using OFDM modulation with a long symbol interval, clusteredOFDM overcomes the complex and costly equalization requirements associated with single carrier systems. Moreover, the need for highly linear power amplifiers typically required in OFDM systems is alleviated through the use of multiple transmit antennas combined with nonlinear coding. The clustering technique also leads to a natural implementation of transmit diversity. This paper reports on preliminary results on the performance of a clusteredOFDM system as well as the design and implementation of a clusteredOFDM transmitter. The prototype transmitter can deliver 7.5 Mbps, and it is expected that this data rate could be easily tripled with existing technology in a second generation system. The paper also describes the architectural tradeoffs made in order to reduce the hardware complexity of the boards as well as some experimental results showing the operation of the transmitter. 相似文献
6.
Effective energy management in heterogeneous wireless sensor networks is more challenging issue compared to homogeneous wireless sensor networks. Much of the existing research focuses on homogeneous wireless sensor networks. The energy conservation schemes for the homogeneous wireless sensor networks do not perform efficiently when applied to heterogeneous wireless sensor networks. The proposed algorithm in this paper exploits the redundancy properties of the wireless sensor networks and also changes the inter cluster communication pattern depending on the energy condition of the high energy nodes during the life cycle of the heterogeneous wireless sensor networks. Performance studies indicate that the proposed algorithm effectively solves the problem of load balancing across the network and is more energy efficient compared to multi hop versions of the standard low energy adaptive clustering hierarchy protocol. 相似文献
7.
Eddie C. Shek Son K. Dao Yongguang Zhang Darrel J. Van Buer Giovanni Giuffrida 《Mobile Networks and Applications》2000,5(4):273-284
The need for rapid deployment and user mobility suggest the use of a hybrid satellitewireless network infrastructure for important situation awareness and emergency response applications. An Intelligent Information Dissemination Service (IIDS) has been developed to support the dissemination and maintenance of extended situation awareness throughout such a network information infrastructure in a seamless manner. One of the goals of IIDS is to transparently handle the mismatches in characteristics of satellite and terrestrial wireless networks, allow effective utilization of available bandwidth, and support timely delivery of highly relevant information. IIDS achieves the above by implementing user profile aggregation that incrementally aggregates users into communities sharing common interests to enable multicastbased information dissemination. Based on the user grouping, semantic profile matching customizes information streams based on matching user group interest profiles. By taking into account expected changes in user profiles, profileoriented data dissemination achieves predictive push and caching that anticipates future user needs and minimizes latency of data request by making data available before they are explicitly requested. Finally, bandwidthaware filtering adapts information streams to resource bandwidth availability to gracefully hide the bandwidth mismatch between the satellite and wireless links in the hybrid network infrastructure. The IIDS software has been deployed on the Digital Wireless Battlefield Network (DWBN) that integrates commercial offtheshelf satellite and wireless products into a heterogeneous satellite/wireless hybrid network for supporting wireless mobile multimedia services. 相似文献
8.
Antenna diversity is an important technique to combat fading and reduce cochannel interference (CCI). In this paper, we present an analytical approach to derive bit error rate (BER) for Optimum Combining (OC) and Maximal Ratio Combining (MRC) in the presence of CCI. The paper has two parts. In the first part, the analysis of BER for OC with two cochannel interferers and MRC with an arbitrary number of interferers is presented for Marray antenna systems under the assumption that the channels of users are independent of each other. In the second part, the analysis of BER for OC and MRC in the presence of one dominant cochannel interferer is presented for dual antenna systems by assuming that the channels of the desired user or cochannel interferer are correlated. For DPSK signal, an exact BER expression is derived. The work presented here also yields an upper bound for BPSK or QAM signal based on the results of Foschini and Salz (1983). 相似文献
9.
We propose a framework for quality‐of‐service (QoS) provisioning for multimedia services in next generation wireless access
networks. This framework aims at providing a differentiated treatment to multimedia traffic flows at the link layer, which
can be broadly classified as real‐time (or delay‐sensitive) and non‐real‐time (or delay‐tolerant). Various novel schemes are
proposed to support the differential treatment and guarantee QoS. These schemes include bandwidth compaction, channel reservation
and degradation, with the help of which a call admission and control algorithm is developed. The performance of the proposed
framework is captured through analytical modeling and simulation experiments. Analytically, the average carried traffic and
the worst case buffer requirements for real‐time and non‐real‐time calls are estimated. Simulation results show up to 21%
improvement in the admission probability of real‐time calls and up to 17% improvement in the admission probability of non‐real‐time
calls, when various call control techniques like bandwidth compaction are employed. Using our channel reservation technique,
we observe a 12% improvement in the call admission probability compared to another scheme proposed in the literature.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.
In this paper we evaluate several routing protocols for mobile, wireless, ad hoc networks via packetlevel simulations. The ad hoc networks are multihop wireless networks with dynamically changing network connectivity owing to mobility. The protocol suite includes several routing protocols specifically designed for ad hoc routing, as well as more traditional protocols, such as link state and distance vector, used for dynamic networks. Performance is evaluated with respect to fraction of packets delivered, endtoend delay, and routing load for a given traffic and mobility model. Both small (30 nodes) and medium sized (60 nodes) networks are used. It is observed that the new generation of ondemand routing protocols use much lower routing load, especially with small number of peertopeer conversations. However, the traditional link state and distance vector protocols provide, in general, better packet delivery and endtoend delay performance. 相似文献
11.
In this paper we investigate the performances of the EFCI‐based (Explicit Forward Congestion Indication) and ER‐based (Explicit
Rate) algorithms for the rate‐based flow control of the ABR (Available Bit Rate) traffic in an ATM network. We consider the
case of two switches in tandem. We present several definitions of a bottleneck, and provide conditions that determine whether
the first, the second or both queues are bottleneck. We show that it is not necessarily the queue with the slowest transmission
rate in which congestion actually occurs. We derive analytic formulas for the maximum queue length. We compare our results
to those obtained by approximating a network by a simpler one, containing only the bottleneck switch. We show that the maximum
queue lengths under the approximating approach may largely underestimate the ones obtained in the real network.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
12.
HUANG Ping TIAN Hui ZHANG Ming ZHANG Ping Wireless Technology Innovation Institute Beijing University of Posts Telecommunications Beijing China 《中国邮电高校学报(英文版)》2007,14(1):1-5
Wireless sensor networks are being widely researched and are expected to be used in several scenarios. On the leading edge of treads, on-demand, high-reliability, and low-latency routing protocol is desirable for indoor environment applications. This article proposes a routing scheme called robust multi-path routing that establishes and uses multiple node-disjoint routes. Providing multiple routes helps to reduce the route recovery process and control the message overhead. The performance comparison of this protocol with dynamic source routing (DSR) by OPNET simulations shows that this protocol is able to achieve a remarkable improvement in the packet delivery ratio and average end-to-end delay. 相似文献
13.
In a wireless sensor–actor network, an actor usually has to provide services as soon as the actor receives the event signals from the sensors. Therefore, the performance of a wireless sensor–actor network depends on the actor deployment. In many circumstances, actors may fail or go out to deal with events, and thus, the sensors covered by the missing actors could be not to be reachable in time. This introduces the necessity of actor redeployment. In this paper, we study the problems of redeploying actors to maximize the number of sensors able to be covered by actors and to maximize the decrease of the residual distances of sensors, respectively. Both problems are shown to be NP-complete. Additionally, we prove that the greedy algorithm for each problem has an approximation ratio of 2. Simulations show that the greedy algorithm for each problem performs well. 相似文献
14.
The FAMANCS protocol is introduced for wireless LANs and adhoc networks that are based on a single channel and asynchronous transmissions (i.e., no time slotting). FAMANCS (for floor acquisition multiple access with nonpersistent carrier sensing) guarantees that a single sender is able to send data packets free of collisions to a given receiver at any given time. FAMANCS is based on a threeway handshake between sender and receiver in which the sender uses nonpersistent carrier sensing to transmit a requesttosend (RTS) and the receiver sends a cleartosend (CTS) that lasts much longer than the RTS to serve as a busy tone that forces all hidden nodes to back off long enough to allow a collisionfree data packet to arrive at the receiver. It is shown that carrier sensing is needed to support collisionfree transmissions in the presence of hidden terminals when nodes transmit RTSs asynchronously. The throughput of FAMANCS is analyzed for singlechannel networks with and without hidden terminals; the analysis shows that FAMANCS performs better than ALOHA, CSMA, and all prior proposals based on collision avoidance dialogues (e.g., MACA, MACAW, and IEEE 802.11 DFWMAC) in the presence of hidden terminals. Simulation experiments are used to confirm the analytical results. 相似文献
15.
This paper compares five different schemes – called CHOI, NAG, AG, BHARG, and NCBF – for reserving bandwidths for handoffs
and admission control for new connection requests in QoS‐sensitive cellular networks. CHOI and NAG are to keep the handoff
dropping probability below a target value, AG is to guarantee no handoff drops through per‐connection bandwidth reservation,
and BHARG and NCBF use another type of per‐connection bandwidth reservation. CHOI predicts the bandwidth required to handle
handoffs by estimating possible handoffs from adjacent cells, then performs admission control for each newly‐requested connection.
On the other hand, NAG predicts the total required bandwidth in the current cell by estimating both incoming and outgoing
handoffs at each cell. AG requires the set of cells to be traversed by the mobile with a newly‐requested connection, and reserves
bandwidth for each connection in each of these cells. The last two schemes reserve bandwidth for each connection in the predicted
next cell of a mobile where the two schemes use different admission control policies. We adopt the history‐based mobility
estimation for the first two schemes. Using extensive simulations, the five schemes are compared quantitatively in terms of
(1) handoff dropping probability, connection‐blocking probability, and bandwidth utilization; (2) dependence on the design
parameters; (3) dependence on the accuracy of mobility estimation; and (4) complexity. The simulation results indicate that
CHOI is the most desirable in that it achieves good performance while requiring much less memory and computation than the
other four schemes.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
With the advent of multimedia over wireless local area networks, the IEEE 802.11e standard was proposed to incorporate Quality
of Service (QoS). It has been found that the throughput of Transmission Control Protocol (TCP) is less than that of User Datagram
Protocol (UDP) in the IEEE 802.11e. This is because the TCP acknowledgment packets are queued up at the access points. In
this paper, two types of TCP acknowledgment prioritizing schemes are proposed. The proposed schemes improve the overall throughput
of TCP while maintaining the QoS requirements. We also analyze the problem of starvation of lower priority traffic and its
effects on the performance of lower priority TCP traffic. The proposed dynamic scheme of TCP acknowledgment prioritization
aims at improving the throughput of the lower priority TCP traffic under heavy network load while maintaining the QoS requirements
of the higher priority traffic. The schemes have been verified through extensive simulation. 相似文献
17.
Protocol for the application of cooperative MIMO based on clustering in sparse wireless sensor networks 总被引:1,自引:0,他引:1
WANG Qing-hua QU Yu-gui LIN Zhi-ting BAI Rong-gang Department of Electronic Engineering Information Science University of Science Technology of China Hefei ChinaZHAO Bao-hua PAN Quan-ke Department of Computer University of Science Technology of China Hefei China 《中国邮电高校学报(英文版)》2007,14(2):51-57
Wireless sensor networks (WSN) using cooperative multiple-input multiple-output (MIMO) communication are effective tools to collect data in several environments. However, how to apply cooperative MIMO in WSN remains a critical challenge, especially in sparse WSN. In this article, a novel clustering scheme is proposed for the application of cooperative MIMO in sparse WSN by extending the traditional low-energy adaptive clustering hierarchy (LEACH) protocol. This clustering scheme solves the problem that the cluster heads (CH) cannot find enough secondary cluster heads (SCH), which are used to cooperate and inform multiple-antenna transmitters with CHs. On the basis of this protocol, the overall energy consumption of the networks model is developed, and the optimal number of CHs is obtained. The simulation results show that this protocol is feasible for the sparse WSN. The simulation results also illustrate that this protocol provides significant energy efficiencies, even after allowing for additional overheads. 相似文献
18.
This paper proposes a scheme for fast and reliable handover that uses dynamic rerouting controlled by a call setup control
station (CCS) operating in mobile asynchronous transfer mode (ATM) networks. The CCS selects appropriate rerouted path and
crossover switch (COS), and remotely controls the new path's setup. This omits crossover switch discovery process, and makes
fast handover possible. The CCS can select the appropriate rerouted path because it directly and with little delay collects
information about the state of links such as traffic loads, quality-of-service (QoS) parameters, and disconnection or restoration
of links advertised from every ATM switch in its domain. This reduces blocking and congestion, and makes reliable handover
possible. The CCS accepts a handover request message for either backward or forward handover, and can remotely control the
new path's setup in the same manner for either handover. The scheme provides forward handover when the radio propagation conditions
deteriorate unpredictably. This paper also shows sequences of call origination, connection pre-establishment, and route-change
in our proposed scheme, and illustrates operation of the CCS and the ATM switches.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
19.
In recent years, IP networks have become increasingly complex and the range of network applications has widened. As a result,
the need for experimental evaluation of application performance has increased. We introduce a measurement‐based performance
evaluation method that combines a function to generate various patterns of application traffic with one to measure end‐to‐end
network performance at the application level. For our method, we also propose traffic models of various applications that
can represent the characteristics of these applications, for example, the burstiness of traffic. This method has already been
implemented as a benchmarking tool on UNIX operating systems.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
20.
In order to support diverse communication‐intensive real‐time and non‐real‐time data flows over a scarce, varying and shared
wireless channel with location‐dependent and bursty errors, we define a service model that has the following characteristics:
short‐term fairness among flows which perceive a clean channel, long‐term fairness for flows with bounded channel error, worst‐case
delay bounds for packets, short‐term throughput bounds for flows with clean channels and long‐term throughput bounds for all
flows with bounded channel error, expanded schedulable region, and support for both delay sensitive and error sensitive data
flows. We present the wireless fair service algorithm, and show through both analysis and simulation that it achieves the
requirements of the service model in typical wireless network environments. The key aspects of the algorithm are the following:
(a) an enhanced fair queueing based service scheme that supports decoupling of delay and bandwidth, (b) graceful service compensation
for lagging flows and graceful service degradation for leading flows, (c) support for real‐time delay sensitive flows as well
as non‐real‐time error sensitive flows, and (d) an implementation within the framework of the simple and robust CSMA/CA wireless
medium access protocol.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献