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Showing papers in "Wireless Networks in 2001"


Journal ArticleDOI
TL;DR: The first distributed algorithms for routing that do not require duplication of packets or memory at the nodes and yet guarantee that a packet is delivered to its destination are described.
Abstract: We consider routing problems in ad hoc wireless networks modeled as unit graphs in which nodes are points in the plane and two nodes can communicate if the distance between them is less than some fixed unit. We describe the first distributed algorithms for routing that do not require duplication of packets or memory at the nodes and yet guarantee that a packet is delivered to its destination. These algorithms can be extended to yield algorithms for broadcasting and geocasting that do not require packet duplication. A by product of our results is a simple distributed protocol for extracting a planar subgraph of a unit graph. We also present simulation results on the performance of our algorithms.

1,234 citations


Journal ArticleDOI
TL;DR: A comprehensive summary of recent work addressing energy efficient and low-power design within all layers of the wireless network protocol stack of wireless networks is presented.
Abstract: Wireless networking has witnessed an explosion of interest from consumers in recent years for its applications in mobile and personal communications. As wireless networks become an integral component of the modern communication infrastructure, energy efficiency will be an important design consideration due to the limited battery life of mobile terminals. Power conservation techniques are commonly used in the hardware design of such systems. Since the network interface is a significant consumer of power, considerable research has been devoted to low-power design of the entire network protocol stack of wireless networks in an effort to enhance energy efficiency. This paper presents a comprehensive summary of recent work addressing energy efficient and low-power design within all layers of the wireless network protocol stack.

958 citations


Journal ArticleDOI
TL;DR: An analytic model is used to study the channel capacity – i.e., maximum throughput – when using the basic access (two-way handshaking) method in the IEEE 802.11 MAC protocol, suggesting guidelines on when and how W can be adjusted to suit measured traffic, thus making the protocol adaptive.
Abstract: The IEEE 80211 MAC protocol provides shared access to a wireless channel This paper uses an analytic model to study the channel capacity - ie, maximum throughput - when using the basic access (two-way handshaking) method in this protocol It provides closed-form approximations for the probability of collision p, the maximum throughput S and the limit on the number of stations in a wireless cell The analysis also shows that: p does not depend on the packet length, the latency in crossing the MAC and physical layers, the acknowledgment timeout, the interframe spaces and the slot size; p and S (and other performance measures) depend on the minimum window size W and the number of stations n only through a gap g D W=n 1/ - consequently, halving W is like doubling n ;t he maximum contention window size has minimal effect onp and S; the choice of W that maximizes S is proportional to the square root of the packet length; S is maximum when transmission rate (including collisions) equals the reciprocal of transmission time, and this happens when channel wastage due to collisions balances idle bandwidth caused by backoffs The results suggest guidelines on when and howW can be adjusted to suit measured traffic, thus making the protocol adaptive

540 citations


Journal ArticleDOI
TL;DR: A new single channel, time division multiple access (TDMA)-based broadcast scheduling protocol, termed the Five-Phase Reservation Protocol (FPRP), is presented for mobile ad hoc networks and shows that the protocol works very well in all three aspects.
Abstract: A new single channel, time division multiple access (TDMA)-based broadcast scheduling protocol, termed the Five-Phase Reservation Protocol (FPRP), is presented for mobile ad hoc networks. The protocol jointly and simultaneously performs the tasks of channel access and node broadcast scheduling. The protocol allows nodes to make reservations within TDMA broadcast schedules. It employs a contention-based mechanism with which nodes compete with each other to acquire TDMA slots. The FPRP is free of the "hidden terminal" problem, and is designed such that reservations can be made quickly and efficiently with negligible probability of conflict. It is fully-distributed and parallel (a reservation is made through a localized conversation between nodes in a 2-hop neighborhood), and is thus scalable. A "multihop ALOHA" policy is developed to support the FPRP. This policy uses a multihop, pseudo-Bayesian algorithm to calculate contention probabilities and enable faster convergence of the reservation procedure. The performance of the protocol, measured in terms of scheduling quality, scheduling overhead and robustness in the presence of nodal mobility, has been studied via simulations. The results showed that the protocol works very well in all three aspects. Some future work and applications are also discussed.

394 citations


Journal ArticleDOI
TL;DR: A new reservation protocol, MRSVP, is described for supporting integrated services in a network with mobile hosts for supporting real-time services to mobile users in an Integrated Services Packet Network.
Abstract: This paper describes a reservation protocol to provide real-time services to mobile users in an Integrated Services Packet Network. Mobility of hosts has significant impact on the quality of service provided to a real-time application. The currently proposed network system architecture and mechanisms to provide real-time services to fixed hosts are inadequate to accommodate the mobile hosts which can frequently change their point of attachments to the fixed network. Mobile hosts may experience wide variations of quality of service due to mobility. To reduce the impacts of mobility on QoS guarantees, a mobile host needs to make advance resource reservations at multiple locations it may possibly visit during the lifetime of the connection. The currently proposed reservation protocol in the Internet, RSVP, is not adequate to make such reservations for mobile hosts. In this paper, we describe a new reservation protocol, MRSVP, for supporting integrated services in a network with mobile hosts.

316 citations


Journal ArticleDOI
TL;DR: It is demonstrated that even flooding is insufficient for reliable multicast in ad hoc networks when mobility is very high, and traditional multicast approaches are not appropriate.
Abstract: Ad hoc networks are gaining popularity as a result of advances in smaller, more versatile and powerful mobile computing devices. The distinguishing feature of these networks is the universal mobility of all hosts. This requires re-engineering of basic network services including reliable multicast communication. This paper considers the special case of highly mobile fast-moving ad hoc networks and argues that, for such networks, traditional multicast approaches are not appropriate. Flooding is suggested as a possible alternative for reliable multicast and simulation results are used to illustrate its effects. The experimental results also demonstrate a rather interesting outcome that even flooding is insufficient for reliable multicast in ad hoc networks when mobility is very high. Some alternative, more persistent variations of flooding are sketched out.

251 citations


Journal ArticleDOI
TL;DR: It is proved that the control packet overhead scales linearly with node speed and as N3/2 with increasing number of nodes and these results indicate that the protocol is well suited to relatively large ad hoc networks where nodes travel at high speed.
Abstract: In this paper we present a scalable routing protocol for ad hoc networks. The protocol is based on a geographic location management strategy that keeps the overhead of routing packets relatively small. Nodes are assigned home regions and all nodes within a home region know the approximate location of the registered nodes. As nodes travel, they send location update messages to their home regions and this information is used to route data packets. In this paper, we derive theoretical performance results for the protocol and prove that the control packet overhead scales linearly with node speed and N3/2 with increasing number of nodes. These results indicate that our protocol is well suited to relatively large ad hoc networks where nodes travel at high speed. Finally, we use simulations to validate our analytical model.

247 citations


Journal ArticleDOI
TL;DR: Using analytical models, it is demonstrated that the leader-based protocol exhibits higher throughput in comparison to two other protocols which use traditional delayed feedback-based probabilistic methods.
Abstract: Multicast is an efficient paradigm for transmitting data from a sender to a group of receivers. In this paper, we focus on multicast in single channel multi-access wireless local area networks (LANs) comprising several small cells. In such a system, a receiver cannot correctly receive a packet if two or more packets are sent to it at the same time, because the ackets "collide". Therefore, one has to ensure that only one node sends at a time. We look at two important issues.First, we consider the problem of the sender acquiring the multi-access channel for multicast transmission. Second, for reliable multicast in each cell of the wireless LAN, we examine ARQ-based approaches. The second issue is important because the wireless link error rates can be very high. We present a new approach to overcome the problem of feedback collision in single channel multi-access wireless LANs, both for the purpose of acquiring the channel and for reliability. Our approach involves the election of one of the multicast group members (receivers) as a "leader" or representative for the purpose of sending feedback to the sender. For reliable multicast, on erroneous reception of a packet, the leader does not send an acknowledgment, prompting a retransmission. On erroneous reception of the packet at receivers other than the leader, our protocol allows negative acknowledgments from these receivers to collide with the acknowledgment from the leader,thus destroying the acknowledgment and prompting the sender to retransmit the packet. Using analytical models, we demonstrate that the leader-based protocol exhibits higher throughput in comparison to two other protocols which use traditional delayed feedback-based probabilistic methods. Last, we present a simple scheme for leader election.

209 citations


Journal ArticleDOI
TL;DR: Efficient approximation algorithms for the distance-2 coloring problem for various geometric graphs including those that naturally model a large class of packet radio networks, including (r,s)-civilized graphs, planar graphs, graphs with bounded genus, etc.
Abstract: We consider the frequency assignment (broadcast scheduling) problem for packet radio networks. Such networks are naturally modeled by graphs with a certain geometric structure. The problem of broadcast scheduling can be cast as a variant of the vertex coloring problem (called the distance-2 coloring problem) on the graph that models a given packet radio network. We present efficient approximation algorithms for the distance-2 coloring problem for various geometric graphs including those that naturally model a large class of packet radio networks. The class of graphs considered include (r, s)-civilized graphs, planar graphs, graphs with bounded genus, etc.

190 citations


Journal ArticleDOI
TL;DR: Experimental results indicate that adaptation to mobility can improve performance over that of similar non-adaptive algorithms when nodes are mobile.
Abstract: A fault-tolerant distributed mutual exclusion algorithm that adjusts to node mobility is presented, along with proof of correctness and simulation results. The algorithm requires nodes to communicate with only their current neighbors, making it well-suited to the ad hoc environment. Experimental results indicate that adaptation to mobility can improve performance over that of similar non-adaptive algorithms when nodes are mobile.

146 citations


Journal ArticleDOI
TL;DR: An adaptive service comprising bandwidth utility functions, which capture the adaptive nature of mobile applications in terms of the range of bandwidth over which they prefer to operate, and adaptation scripts, which enable adaptive mobile applications to program the per-flow adaptation time scale and bandwidth granularity realizing application-specific adaptive services are proposed.
Abstract: This paper assesses the state-of-the-art in Quality-of-Service (QoS) adaptive wireless networks and proposes new adaptation techniques that better suit application specific needs. The contribution of the paper is as follows: we propose an adaptive service comprising (i) bandwidth utility functions, which capture the adaptive nature of mobile applications in terms of the range of bandwidth over which they prefer to operate; and (ii) adaptation scripts, which enable adaptive mobile applications to program the per-flow adaptation time scale and bandwidth granularity realizing application-specific adaptive services. To maintain adaptive services in wireless packet access networks, we propose a split level adaptation control framework that operates at the network and application levels. Network level control employs a periodic probing mechanism between mobile devices and network gateways in support of utility based max---min fair resource allocation. Application level control is managed by a set of distributed adaptation handlers that operate at mobile devices realizing application-specific adaptation strategies.

Journal ArticleDOI
TL;DR: It is demonstrated that the hyper-Erlang model provides a very general model for users' mobility and may provide a viable approximation to fat-tailed distribution which leads to the self-similar traffic.
Abstract: This paper presents the study of the hyper-Erlang distribution model and its applications in wireless networks and mobile computing systems. We demonstrate that the hyper-Erlang model provides a very general model for users' mobility and may provide a viable approximation to fat-tailed distribution which leads to the self-similar traffic. The significant difference from the traditional approach in the self-similarity study is that we want to provide an approximation model which preserves the Markovian property of the resulting queueing systems. We also illustrate that the hyper-Erlang distribution is a natural model for the characterization of the systems with mixed types of traffics. As an application, we apply the hyper-Erlang distribution to model the cell residence time (for users' mobility) and demonstrate the effect on channel holding time. This research may open a new avenue for traffic modeling and performance evaluation for future wireless networks and mobile computing systems, over which multiple types of services (voice, data or multimedia) will be supported.

Journal ArticleDOI
TL;DR: Three new paging schemes, reverse, semi-reverse and uniform, are introduced to provide a simple way of partitioning the service areas and decrease the paging costs based on each mobile terminal's location probability distribution.
Abstract: In this paper new paging schemes are presented for locating mobile users in wireless networks. Paging costs and delay bounds are considered since paging costs are associated with bandwidth utilization and delay bounds influence call setup time. In general, location tracking schemes require intensive computation to search for a mobile terminal in current PCS networks. To reduce the paging costs, three new paging schemes, reverse, semi-reverse and uniform, are introduced to provide a simple way of partitioning the service areas and decrease the paging costs based on each mobile terminal's location probability distribution. Numerical results demonstrate that our approaches significantly reduce the paging costs for various probability distributions such as uniform, truncated discrete Gaussian, and irregular distributions.

Journal ArticleDOI
TL;DR: An authenticated link-level ad hoc routing protocol is designed and integrated with the Portland State University implementation of Mobile-IP and replaces ARP, and may be integrated with higher-level multi-hopAd hoc routing protocols.
Abstract: We have designed an authenticated link-level ad hoc routing protocol and integrated it with the Portland State University implementation of Mobile-IP. The routing protocol addresses link security issues. In our protocol, mobile nodes, as well as agents, broadcast ICMP router discovery packets. The router discovery packets are authenticated and bind the sender's MAC and IP addresses. Problems caused by tying IP subnet schemes to routing on radio links are eliminated. Security problems associated with ARP spoofing are also reduced. This link-level protocol is integrated with Mobile-IP on links where increased security is needed. The protocol replaces ARP, and may be integrated with higher-level multi-hop ad hoc routing protocols.

Journal ArticleDOI
TL;DR: An efficient multicast routing protocol based on IEFT mobile IP in wireless mobile networks that reduces data delivery path length and decreases the amount of duplicate copies of multicast datagrams is proposed.
Abstract: Providing multicast service to mobile hosts in wireless mobile networking environments is difficult due to frequent changes of mobile host location and group membership If a conventional multicast routing protocol is used in wireless mobile networks, several problems may be experienced since existing multicast routing protocols assume static hosts when they construct the multicast delivery tree To overcome the problems, several multicast routing protocols for mobile hosts have been proposed Although the protocols solve several problems inherent in multicast routing proposals for static hosts, they still have problems such as non-optimal delivery path, datagram duplication, overheads resulting from frequent reconstruction of a multicast tree, etc In this paper, we summarize these problems of multicast routing protocols and propose an efficient multicast routing protocol based on IEFT mobile IP in wireless mobile networks The proposed protocol introduces a multicast agent, where a mobile host receives a tunneled multicast datagram from a multicast agent located in a network close to it or directly from the multicast router in the current network While receiving a tunneled multicast datagram from a remote multicast agent, the local multicast agent may start multicast join process, which makes the multicast delivery route optimal The proposed protocol reduces data delivery path length and decreases the amount of duplicate copies of multicast datagrams We examined and compared the performance of the proposed protocol and existing protocols by simulation under various environments and we got an improved performance over the existing proposals

Journal ArticleDOI
TL;DR: Experimental results indicate that the SWiMNet parallel simulation model yields good speedup, and significantly reduces the execution time compared to a sequential implementation, and an analytical study of the model is found to be consistent with the analytical study.
Abstract: We present a framework, called SWiMNet, for parallel simulation of wireless and mobile PCS networks, which allows realistic and detailed modeling of mobility, call traffic, and PCS network deployment. SWiMNet is based upon event precomputation and a combination of optimistic and conservative synchronization mechanisms. Event precomputation is the result of model independence within the global PCS network. Low percentage of blocked calls typical for PCS networks is exploited in the channel allocation simulation of precomputed events by means of an optimistic approach.Various experiments were conducted to study the performance and scalability of SWiMNet using a realistic mobility model and executed on a cluster of workstations. Experimental results indicate that our parallel simulation model yields good speedup, and significantly reduces the execution time compared to a sequential implementation. Finally, an analytical study of our PCS simulation model is also presented and compared with the experimental results. Our model is found to be consistent with the analytical study.

Journal ArticleDOI
TL;DR: Two additional approximate analytical models are developed and it is found that all are in close agreement with the original “single isolated cell, Poisson handoff arrival model,” which requires the least states.
Abstract: Handoffs in cellular communication systems cause interactions among cells that can be modeled using multi-dimensional birth–death process approaches and the concept of system state However, exact numerical calculation of traffic performance characteristics is hindered by unmanageably large system state spaces even for systems of modest size Previous analytical models get around the difficulty by isolating a cell of interestand invoking a Poisson process assumption for handoff arrivals to the cell Interactions among cells are characterized by relating the mean handoff and departure rates from cells The current paper seeks to explore the interactions in more detail Two additional approximate analytical models are developed for this purpose Each of these is more complicated than the simple Poisson process model, but is analytically tractable – at least for small system sizes One model isolates a cluster of cells (rather than just the cell of interest) from the system and invokes a Poisson process assumption for cells on the cluster periphery Performance is calculated for the central cell The second model also isolates a cluster of cells surrounding the cell of interest, but uses an equivalent two-state Markov Modulated Poisson Process (MMPP) to characterize handoff arrival processes to the cell of interest from each of the neighboring cells Poisson handoff arrivals to cells on the cluster periphery are assumed This approach has fewer states than the cluster approach Finally we present the exact solution for a regional coverage area consisting of a single seven-cell cluster Teletraffic performance characteristics are computed for each modeling technique and are compared It was found that all are in close agreement with the original “single isolated cell, Poisson handoff arrival model,” which requires the least states

Journal ArticleDOI
TL;DR: This paper shows that the presence of such links can jeopardize the performance of the existing distance vector routing algorithms, and presents modifications to distance vector based routing algorithms to make them work in ad hoc networks with unidirectional links.
Abstract: Most of the routing algorithms for ad hoc networks assume that all wireless links are bidirectional. In reality, some links may be unidirectional. In this paper we show that the presence of such links can jeopardize the performance of the existing distance vector routing algorithms. We also present modifications to distance vector based routing algorithms to make them work in ad hoc networks with unidirectional links. For a network of n nodes, neighbors exchange n x n matrices to propagate routing information. This results in loop-free routes.

Journal ArticleDOI
TL;DR: The Hybrid Control Scheme yields the best performance, particularly during periods when load differs from the expected level, and the simple Reservation Scheme performs remarkably well, often superior to more complex schemes that have been proposed.
Abstract: This paper evaluates call admission control algorithms for a cellular or microcellular system. Algorithms are evaluated based on two Quality of Service (QoS) metrics: the new call blocking probability, which is the probability that a new call is denied access to the system, and the forced-termination probability, which is the probability that a call that has been admitted will be terminated prior to the call's completion. Three novel algorithms are presented: the Weighted Sum Scheme, the Probability Index Scheme, and the Hybrid Control Scheme. The weighted sum scheme uses the weighted sum of the number of calls underway in various cells when making the admission decision. The probability index scheme computes a probability index, which reflects the forced-termination probability of a new call arrival, and admits those calls with low probability indexes. The hybrid control scheme combines these two approaches. These novel algorithms are compared with three known algorithms: the Reservation Scheme in which a specific number of channels are reserved in each cell for handoffs, the Linear Weighting Scheme in which the admission decision depends on the total number of calls underway in a group of cells, and the Distributed Admission Control Scheme in which the admission decision depends on the projected overload probabilities in the cell at which the new call arrives and adjacent cells. We show that the Hybrid Control Scheme yields the best performance, particularly during periods when load differs from the expected level. We also show that the simple Reservation Scheme performs remarkably well, often superior to more complex schemes that have been proposed.

Journal ArticleDOI
TL;DR: An enhancement for IEEE 802.11 standard that improves the WLAN support for multimedia applications by using a chaining mechanism in which each packet resends in its turn the SuperPoll message appended to its packet.
Abstract: Design of Wireless Local Area Networks (WLANs) needs to take into consideration the limited bandwidth available in the ISM band along with the noisy characteristics of the wireless environment and hidden terminal effects. In this paper we propose an enhancement for IEEE 802.11 standard that improves the WLAN support for multimedia applications. In the IEEE 802.11 PCF polling based protocol designed for multimedia applications support, the Point Coordinator (PC) polls each station in the Basic Service Area (BSA) individually. In the proposed SuperPoll approach the PC broadcasts at the beginning of the contention free period a SuperPoll, i.e., a message that includes the list of stations that will be polled during the current period. To improve the reliability of the polling based approach in a noisy environment, we propose to use a chaining mechanism in which each packet resends in its turn the SuperPoll message appended to its packet. We provide performance measurements of the proposed method in terms of channel efficiency and channel access time for multimedia applications that use the contention free period of IEEE 802.11 PCF. We notice that for noisy channels, the proposed method provides a dramatic throughput increase and delay decrease when compared with the Single Poll mechanism used in IEEE 802.11 PCF, thus providing better support for multimedia applications.

Journal ArticleDOI
TL;DR: It is shown that the routing protocol can cope with high mobility and deliver packets to the destinations successfully and be intoduced to distribute the routing overhead uniformly among the mobile base stations.
Abstract: In this paper, a new hierarchical multihop routing algorithm and its performance evaluation is presented for fully dynamic wireless networks. The routing algorithm operates on a virtual topology obtained by partitioning the routing information for mobile terminals and mobile base stations into a hierarchical, distributed database. Based on the virtual topology, each mobile base station stores a fraction of the routing information to balance the complexity of the location-update and the path-finding operations. Mobility of the network entities changes the load distribution and causes processing and memory bottlenecks in some parts of the network. However, since the network routing elements are also mobile, their movement can be used to distribute the load. Thus, new load balancing schemes are introduced to distribute the routing overhead uniformly among the mobile base stations. The performance of the hierarchical multihop routing algorithm is investigated through simulations. It is shown that the routing protocol can cope with high mobility and deliver packets to the destinations successfully.

Journal ArticleDOI
TL;DR: This paper introduces a novel adaptive bandwidth allocation scheme which estimates dynamically the changing traffic parameters through local on-line estimation, and proposes the use of a probabilistic control policy, which achieves a high channel utilization, and leads to an effective and stable control.
Abstract: The next generation of mobile wireless networks has to provide the quality-of-service (QoS) for a variety of applications. One of the key generic QoS parameters is the call dropping probability, which has to be maintained at a predefined level independent of the traffic condition. In the presence of bursty data and the emerging multimedia traffic, an adaptive and dynamic bandwidth allocation is essential in ensuring this QoS. The paradox, however, is that all existing dynamic bandwidth allocation schemes require the prior knowledge of all traffic parameters or/and user mobility parameters. In addition, most proposals require extensive status information exchange among cells in order to dynamically readjust the control parameters, thus making them difficult to be used in actual deployment. In this paper, we introduce a novel adaptive bandwidth allocation scheme which estimates dynamically the changing traffic parameters through local on-line estimation. Such estimations are restricted to each individual cell, thus completely eliminating the signaling overhead for information exchange among cells. Furthermore, we propose the use of a probabilistic control policy, which achieves a high channel utilization, and leads to an effective and stable control. Through simulations, we show that our proposed adaptive bandwidth allocation scheme can guarantee the predetermined call dropping probability under changing traffic conditions while at the same time achieving a high channel utilization.

Journal ArticleDOI
TL;DR: The impact of the accuracy of the wireless channel model on the accuracyof the results and on the execution time of large-scale network models is described and means to reduce the runtime execution when deploying such detailed propagation models are introduced.
Abstract: Accurate simulation of wireless networks requires realistic models of the channel propagation medium. The widely used free space model is computationally efficient but ignores many attenuation components which affect wireless signal propagation. This paper describes the impact of the accuracy of the wireless channel model on the accuracy of the results and on the execution time of large-scale network models. It then introduces means to reduce the runtime execution when deploying such detailed propagation models.

Journal ArticleDOI
TL;DR: The use of overlapping coverage areas and dynamic load balancing as a means to increase network survivability by providing mobiles with multiple access points to the fixed infrastructure is proposed and the simulation approach to survivability analysis is described which combines empirical spatial information, network models, and fault models for more realistic analysis of real service areas.
Abstract: The development of robust, survivable wireless access networks requires that the performance of network architectures and protocols be studied under normal as well as faulty conditions where consideration is given to faults occurring within the network as well as within the physical environment User location, mobility, and usage patterns and the quality of the received radio signal are impacted by terrain, man-made structures, population distribution, and the existing transportation system The work presented herein has two thrusts One, we propose the use of overlapping coverage areas and dynamic load balancing as a means to increase network survivability by providing mobiles with multiple access points to the fixed infrastructure Two, we describe our simulation approach to survivability analysis which combines empirical spatial information, network models, and fault models for more realistic analysis of real service areas We use our simulation approach to compare the survivability of our load balancing protocols to a reference scheme within two diverse geographic regions We view survivability as a cost-performance tradeoff using handover activity as a cost metric and blocking probabilities as performance metrics Our results illustrate this tradeoff for the protocols studied and demonstrate the extent to which the physical environment and faults therein affect the conclusions that are drawn

Journal ArticleDOI
TL;DR: This study introduces a Simulated Annealing (SA) based method to determine the design parameters of a multi-tier cellular network, for which the implementation cost is minimized.
Abstract: Wireless communications systems enable the end users to be mobile. The majority of the wireless communications networks are cellular networks. Several methods are developed to increase the performance of the cellular networks, which depends on the correct determination of the design parameters as well as the architecture of the system and the traffic requirements. In this study, we introduce a Simulated Annealing (SA) based method to determine the design parameters of a multi-tier cellular network, for which the implementation cost is minimized. The cellular system employs guard channels and allows calls to overflow to upper tiers. We conducted experiments with the SA-based technique on different example problems in two-tier cellular networks and obtained promising results.


Journal ArticleDOI
TL;DR: The results of these experiments show that the proposed model, where handoff rates are state-dependent, captures additional traffic due to mobility when compared to the traditional method of modeling handoffs using information about the average behavior.
Abstract: This paper proposes a model for configuring cellular networks to study the dynamics of mobility between a single cell and its adjacent cells. It differs from most models considered in the literature by explicitly incorporating the dependency between the handoff rate and the system state. Besides, the handoff rate is also a function of cell size and subscriber mobility. Extensive computational experiments were done to study the impact of various input parameters on specific performance measures. Several observations are made regarding the system performance and as to how they are affected by the complex interaction between subscriber mobility, cell size, number of channels and the mean call initiation rate. The results of these experiments show that the proposed model, where handoff rates are state-dependent, captures additional traffic due to mobility when compared to the traditional method of modeling handoffs using information about the average behavior. Finally, the economic impact of mobility on system configuration decisions is analyzed. Though an approximation, the above work provides interesting insights about the impact of mobility in configuring cellular networks.

Journal ArticleDOI
TL;DR: This work discusses how multi-fidelity algorithms can improve the latency and battery life of interactive mobile applications and allows the system to automatically discover sweet spots: sharp discontinuities in the fidelity-resource tradeoff space.
Abstract: We introduce the concept of multi-fidelity algorithms, which revises the classical notion of an algorithm. Instead of having a fixed output criterion and allowing the resource consumption to vary, we bound the resource consumption and allow the fidelity or output criterion to vary. We discuss how multi-fidelity algorithms can improve the latency and battery life of interactive mobile applications. An extension of this idea allows the system to automatically discover sweet spots: sharp discontinuities in the fidelity-resource tradeoff space.

Journal ArticleDOI
TL;DR: The results demonstrate that the adaptive-transmission protocol can improve the utility of a link and reduce energy consumption by adjusting the transmission parameters in response to changes in the side information.
Abstract: An energy-efficient adaptive-transmission protocol for mobile frequency-hop spread-spectrum wireless communication networks is described and evaluated. The purpose of the protocol is to permit each of the mobile terminals to adjust its transmitter power and code rate to match the characteristics of the time-varying communication links in the network. The proposed adaptive-transmission protocol bases its choice of transmission parameters on a very simple form of side information that is easy to obtain in a FH communication receiver. The performance of the adaptive-transmission protocol is evaluated for networks in which each communication link may have a time-varying propagation loss and intermittent partial-band interference. Our results demonstrate that the adaptive-transmission protocol can improve the utility of a link and reduce energy consumption by adjusting the transmission parameters in response to changes in the side information.

Journal ArticleDOI
TL;DR: In this article, the TCP decoupling approach is proposed to improve TCP connection's goodput over wireless networks, and the performance improvement can be analytically shown to be proportional to the maximum transmission unit of participating wireless links and the size of packet containing only a TCP/IP header.
Abstract: We propose using the TCP decoupling approach to improve a TCP connection's goodput over wireless networks. The performance improvement can be analytically shown to be proportional to $$\sqrt {{\text{MTU/HP\_Sz}}} $$ , where MTU is the maximum transmission unit of participating wireless links and HP_Sz is the size of a packet containing only a TCP/IP header. For example, on a WaveLAN [32] wireless network, where MTU is 1500 bytes and HP_Sz is 40 bytes, the achieved goodput improvement is about 350%. We present experimental results demonstrating that TCP decoupling outperforms TCP reno and TCP SACK. These results confirm the analysis of $$\sqrt {{\text{MTU/HP\_Sz}}} $$ performance improvement.