In order to provide more comprehensive services, a concept of integrated heterogeneous wireless and mobile network (IHWMN) is introduced by combing different types of wireless and mobile networks (WMNs). However, it imposes great challenges such as resource management schemes to support multiple traffic in IHWMNs. In this paper, we propose two resource management schemes for IHWMNs. The first scheme is called traffic-based resource management scheme (TRMS) which allocates the resource based on traffic type, call type, bandwidth availability, and bandwidth provision. In the second scheme which is called Q-learning-based resource management scheme (QRMS), the resource management scheme is formulated as a Markov decision process (MDP) and Q-learning approach is applied to conduct the resource allocation. The system performance of both proposed schemes are evaluated and compared by using extensive simulations.

With the advent of multimedia applications over wireless local area networks (WLANs), the IEEE 802.11e standard was proposed to incorporate quality of service (QoS) parameters in the medium access control (MAC) layer. It has been found through previous research work that the throughput of transport control protocol (TCP) is less when compared to that of User Datagram Protocol (UDP) in the IEEE 802.11e. This is because the TCP ACK (acknowledgement) packets are queued up at the access points (APs), as the TCP ACK packets are not prioritized. In this paper, we explore the performance of TCP traffic and also propose a new prioritized TCP ACK scheme. The proposed scheme improves the overall throughput of TCP in the IEEE 802.11e while maintaining the QoS requirements of the IEEE 802.11e. The scheme has been verified through simulation.

Abstract In ad hoc networks, CSMA/CA is a widely used MAC layer protocol. There has been considerable work on the performance evaluation of this protocol. But most work is confined to saturation performance of single‐hop ad hoc networks. In this paper, we employ a linear feedback model to evaluate the performance for CSMA/CA according to the Poisson distributed traffic in both single‐hop and multi‐hop ad hoc networks. To the best of our knowledge, this is the first attempt to analytically evaluate the performance for CSMA/CA protocol under a general assumption about the traffic. This paper also gives analytical results, showing the impact of RTS/CTS. Although RTS/CTS do add the overhead to the system, they become essential when either the hidden terminal problem is dominant, or the traffic is heavy, or the packet length is very large. This paper also shows that the performance degrades dramatically in multi‐hop ad hoc networks when the number of competing nodes increases, which implies that the scalability is still a major problem in ad hoc networks. To validate our analytical results, we have done extensive simulations, and it is observed that the simulation results match the analytical results very well. Copyright © 2006 John Wiley & Sons, Ltd.

The wide area wireless network (IEEE 802.16 WMAN) supports integrated services such as constant bit rate voice, variable bit rate video, high speed FTP and low speed www data. Efficient resource management in such network is a real challenge because of QoS requirements of integrated services and the error prone nature of the radio channel. In this paper, we mainly focus on the efficient packet transmission mechanism in such network. We propose an efficient channel prediction scheme which combines the handshake probing and prediction together to probe the channel state before transmission. Based on the maximum tolerant BER of different services, channel state is classified into three different states and an adaptive packet transmission scheme for all services under different channel states is introduced. The performance of the proposed schemes are evaluated and the results verified by using extensive simulations.

Handoff in the IEEE 802.11 wireless LANs (WLANs) occurs whenever the mobile station (STA) changes its association from one access point (AP) to another owing to poor link quality. In a WLAN, small coverage areas of APs create frequent handoffs. Previous studies have shown that the typical handoff latency is high enough to hamper the service quality of multimedia streams like VoIP (voice over IP). In this paper, a novel scheme to reduce the handoff latency is proposed by using inter-AP communication to receive the probe response(s). Another adaptive scheme to enhance the quality of service (QoS) for multimedia streams during handoff is presented which builds upon the first scheme and adaptively distributes the total handoff latency. Through extensive simulations, we prove that our adaptive scheme decreases handoff latency significantly and achieves both fast and smooth hand-off that multimedia applications entail.

IEEE 802.11 is the most important standard for wireless local area networks (WLANs). In the IEEE 802.11 WLANs, distributed coordination function (DCF) is a fundamental medium access control (MAC) protocol, whose performance has been studied analytically in the literature. However, there is no research work that takes into account different incoming traffic load, network size, hidden terminal problem, and the influence of transmission error at the same time. In this paper, a refined model is presented to evaluate the impact of these factors on the performance of the IEEE 802.11 DCF MAC protocol. In the analysis, the channel is modeled by a finite-state Markov (FSM) chain. In each channel state, the operation of the IEEE 802.11 DCF MAC protocol is modeled by an embedded Markov chain. Using these two Markov chains, the average throughput of the IEEE 802.11 DCF MAC protocol can be very accurately calculated. The results show that the performance of DCF strongly depends on the network size, the incoming traffic load, and the bit error rate (BER). This paper also shows that the performance degrades dramatically in multi-hop ad hoc networks due to hidden terminal problem.

A novel routing algorithm, namely dynamic XY (DyXY) routing, is proposed for NoCs to provide adaptive routing and ensure deadlock-free and livelock-free routing at the same time.A new router architecture is developed to support the routing algorithm.Analytical models based on queuing theory are developed for DyXY routing for a two-dimensional mesh NoC architecture,and analytical results match very well with the simulation results.It is observed that DyXY routing can achieve better performance compared with static XY routing and odd-even routing.

IEEE 802.11 is the most important standard for wireless local area networks (WLANs). In the IEEE 802.11 WLANs, distributed coordination function (DCF) is a fundamental medium access control (MAC) protocol, whose performance has been studied analytically in the literature. However, there is no research work that takes into account various incoming traffic load, network size, and the influence of transmission error at the same time. In this paper, a refined model is presented to evaluate the performance of DCF in a time-varying wireless channel. In this study, the wireless channel is modeled by a finite-state Markov (FSM) chain. In each channel state, the operation of the IEEE 802.11 DCF is modeled by an embedded Markov chain. Using these two Markov chains, the throughput of the IEEE 802.11 DCF can be very accurately calculated. The results show that the performance of DCF strongly depends on the network size, the incoming traffic loads, and the bit error rate (BER).

In an overlay wireless network, a mobile user can connect to different radio access networks if it is equipped with appropriate network interfaces. When the mobile user changes its connection between different radio access networks, a vertical handoff occurs. Most existing vertical handoff decision strategies are designed to meet individual needs that may not achieve a good system performance. In this paper, we propose and analyze a novel vertical hand-off decision strategy that considers the performance of the whole system. The performance comparison of the proposed vertical handoff decision strategy and existing strategy shows that the proposed strategy is better in the blocking probability of vertical handoff calls

High user mobility in an ad hoc network causes frequent link breaks when a pair of communicating nodes moves out of transmission range of each other. This causes several unnecessary retransmissions between them at MAC layer unless the link is declared dead. Such retransmissions result in inefficient network resource utilization and bad QoS support. This paper proposes three enhancements for a MAC layer protocol with associated changes at network layer routing protocol. Enhancements suggested, use current ongoing transmission information contained in handshake packets, used for data transmission at MAC, piggybacked with transmitting node's mobility-location information. A higher overall performance is achieved with suggested implementation of routing protocol over MAC layer protocol in terms of throughput, power utilization and better QoS

In this paper, we propose two novel schemes, which prevent starvation of low priority traffic in the IEEE 802.11e MAC layer protocol, and at the same time ensure proper service differentiation and QoS to high priority traffic. A study of the starvation of low priority traffic in the IEEE 802.11e MAC layer protocol is presented. We also study the effectiveness of dynamic MAC parameters in achieving better performance in the IEEE 802.11e EDCF. The extensive simulation results show that the proposed schemes outperform the IEEE 802.11e EDCF and at the same time prevent starvation of low priority traffic. The proposed schemes are evaluated in a MANET through simulations to assess the impact of mobility on the performance of the proposed schemes

In this paper, we use a discrete Markov chain model to analyze the throughput of CSMA/CA protocol in a wireless local area network (WLAN) considering the capture phenomenon, which means the packet with the strongest power may capture the receiver even in the presence of other overlapping packets. The model of capture effect over the theoretical throughput of CSMA/CA protocol in the presence of Rayleigh fading, shadowing, and path loss are obtained and compared with the model without capture effect

Next generation wireless networks are expected to support multi-class variable bandwidth real-time multimedia applications. High user mobility and inherent instability of wireless channels makes quality of service (QoS) provisioning a challenging issue in wireless networks. In this paper, we propose a novel resource management scheme, FATP, for QoS provisioning in wireless networks for adaptive multimedia calls. We improve handoff call dropping probabilities and reduce bandwidth fluctuations a call suffers by making the call time adaptable to bandwidth changes. Simulation results show that our scheme maintains low handoff call dropping probabilities and significantly reduces bandwidth variations at the end users.

In a multiple service wireless and mobile system, different numbers of channels (or bandwidth) are assigned to different services according to their QoS requirements. Real-time services have the lowest delay tolerance, while they might not need very large bandwidth. Non-real-time services can improve their performance if they are given more bandwidth and they are also not as sensitive to delay as the real-time services. Many channel allocation and resource management schemes have been carried out for wireless system with differentiated services. However, the link status of channel has not been considered very well in those schemes. Many of them just assume that all channels are homogeneous and their status will not charge throughout the service durations. This is not true in real world. In this paper, we take into account the physical channel status in our preemptive priority channel allocation scheme. Transmission rate changes dynamically according to variational channel status as a result of shadowing and fading. Our scheme uses the transmission rate of each channel as one important fact in choosing the channel candidate to be preempted. When the channel originally having a poor transmission rate is assigned to a new user, its link status is very likely to gain some improvements. Therefore, both the user QoS and the system utilization get a boost using this scheme. We evaluate the system performance in terms of blocking probabilities, forced termination probabilities, and average number of user in the system.

This paper introduces a distributed channel assignment scheme (DCA) for wireless sensor networks. Recent developments in sensor technology, as seen in Berkeley's Mica2 Mote, Rockwell's WINS nodes and the IEEE 802.15.4 Zigbee, have enabled support for single-transceiver, multi-channel communication. DCA exploits this capability by assigning optimally minimum channels in a distributed manner in order to make subsequent communication free from both primary and secondary interference. The main contribution of this paper is solving the channel assignment problem, also named as the 2-hop coloring problem, in which repetition of colors occurs only if the nodes are separated by more than 2 hops. Our work achieves legal coloring under energy constrained conditions for sensor networks and significant performance improvements are shown when compared with similar existing schemes. Finally, we validate our approach through extensive analysis and simulation results.

In this paper, we propose an analytical model for novel multimedia wireless and mobile networks using smart antennas. In the proposed networks, several beams having the same physical channel (e.g., frequency in FDMA, time slot in TDMA, spreading code in CDMA, or any combination of them) are formed in a cell. System capacity is increased dramatically by reusing the channels in the same cell. In this paper, we consider two types of multimedia services, real-time services and non-real-time services. Quality of service (QoS) is guaranteed by reserving different numbers of channels for different types of handoff calls, respectively. The system is analyzed by a 4D Markov chain. The blocking probability of originating calls and blocking probability of handoff calls are obtained from our formulas. As we expect, system capacity and performance are highly improved by employing smart antennas.

Abstract End‐to‐end quality of service (QoS) control for multiple traffic in wired networks is carried out through Differentiated services (DiffServ). Edge routers in DiffServ domain classify incoming flows into different per‐hop behavior (PHB) groups and give a policy‐based QoS guarantee to these behavior aggregates. As Internet extends into the wireless and mobile section, different traffic flows should be treated differently not only in wired core network, but also in wireless resource allocations. In this paper, we propose a preemptive priority handoff and adaptive resource allocation scheme. DiffServ PHB groups are mapped into different wireless and mobile QoS classes. Traffic flows are categorized into these classes in order to allow the system to allocate different bandwidth and make resource reservation according to their priorities. Higher priority traffic flows are permitted to preempt lower priority flows in service. Lower ones, on the contrary, can expand their bandwidth into areas reserved for higher priority traffic flows for better resource utilization. We use both analytical model and simulation to evaluate the system performance in terms of blocking probabilities, forced termination probabilities, and delay. The forced termination probability of high priority traffic flows can be decreased significantly by introducing the preemptive priority scheme. Therefore, this scheme can be used in wireless part of the system along with DiffServ to give further guarantee for low delay, low jitter, and low loss services to high priority services. Copyright © 2005 John Wiley & Sons, Ltd.

We consider the medium access control (MAC) protocol design for nodes in a wireless LAN that use a wide-azimuth switched beam smart antenna system comprised of a multiple beam antenna array. The one-hop performance of carrier sense multiple access (CSMA) as well as slotted aloha for such a system is presented analytically and through simulation. The problem of synchronization of multiple beams in CSMA is investigated in our analysis. Our results show that, under heavy offered load conditions, CSMA is a good choice with nodes that have multiple-beam smart antennas, despite the performance loss due to the beam synchronization, providing a stable throughput that approaches unity and is invariant to fluctuations in the offered load. Slotted Aloha, on the other hand, is capable of higher peak throughput in a narrow range of offered loads as more switched beams are employed, but performance drastically reduces beyond optimum offered loads. We also introduce a method, expanded receive rule (ERR), whereby the tight synchronization among different beams of a receiver node in CSMA is relaxed, which is observed to provide better throughput. Finally, we also present performance results for a 4-way-handshake-type carrier sense mechanism using multiple beam antennas.

Abstract The IEEE 802.11e working group aims to enhance the current 802.11 medium access control (MAC) to support integrated data and voice (or video) communications. Till now, a draft of the IEEE 802.11e enhanced distributed coordination function (EDCF) has been proposed. In the literature, there is very limited analysis about EDCF since it is a new protocol, and most related work are only confined to simulation or saturation state. In this paper, we evaluate the performance of EDCF by dividing the traffic into two groups, namely real‐time packets and non‐real‐time packets, and use an analytical model to quantify the performance of both IFS priority and contention window (CW) priority in the EDCF. In our analysis, we assume that the traffic arrival is a Poisson process. We provide a queue model for EDCF. Since there are multiple stations contending for one channel in the system, the queue model for EDCF cannot be a regular M/G/1 model. We redefine the service time and the waiting time so that we can still use M/G/1 model in the analysis. To validate the accuracy of our analytical results, we have done extensive simulations and we observed that EDCF does provide service differentiation between different traffic categories. But due to the inherent contention characteristic of carrier sense multiple access with collision avoidance (CSMA/CA) MAC protocol, the delay cannot be guaranteed, even for the highest priority traffic. A lot more work needs to be done for the MAC protocol to effectively support service differentiation in the future. Copyright © 2004 John Wiley & Sons, Ltd.

We propose an analytical model for integrated real-time and non-real-time services in a wireless mobile network with priority reservation and preemptive priority handoff schemes. We categorize the service calls into four different types, namely, real-time and non-real-time service originating calls, and real-time and non real-time handoff service request calls. Accordingly, the channels in each cell are divided into three parts: one is for real-time service calls only, the second is for non-real-time service calls only, and the last one is for overflow of handoff requests that cannot be served in the first two parts. In the third group, several channels are reserved exclusively for real-time service handoffs so that higher priority can be given to them. In addition, a realtime service handoff request has the right to preempt non-real-time service in the preemptive priority handoff scheme if no free channels are available, while the interrupted non-real-time service call returns to its handoff request queue. The system is modeled using a multidimensional Markov chain and a numerical analysis is presented to estimate blocking probabilities of originating calls, forced termination probability, and average transmission delay. This scheme is also simulated under different call holding time and cell dwell time distributions. It is observed that the simulation results closely match the analytical model. Our scheme significantly reduces the forced termination probability of real-time service calls. The probability of packet loss of non-real-time transmission is shown to be negligibly small, as a non-real-time service handoff request in waiting can be transferred from the queue of the current base station to another one.

This paper presents an efficient algorithm for near optimal channel assignment when different types of services are to be provided in the next generation integrated wireless and mobile networks. We specifically propose a preemptive priority scheme for an integrated wireless and mobile network by first dividing channels into three independent groups and classifying traffic into four different types. The proposed system is modeled by Markov chain model, and then such a model is used to obtain a set of relations that correlate performances with various system parameters. We have analytically determined the minimal number of channels required for each type of traffic that can satisfy a desired level of QoS (Quality of Service) requirements. We also investigate the impact of load ratio for different types of traffic on channel assignment. Finally, we discuss some limitations of our approach and indicate possible future work. We believe that the partitioning scheme proposed in this paper can become a starting point for analysis of future integrated wireless and mobile networks.

Wireless sensor networks are a new class of ad hoc networks that will find increasing deployment in coming years, as they enable reliable monitoring and analysis of unfamiliar and untested environments. The advances in technology have made it possible to have extremely small, low powered sensor devices equipped with programmable computing, multiple parameter sensing, and wireless communication capability. Because of their inherent limitations, the protocols designed for such sensor networks must efficiently use both limited bandwidth and battery energy. We develop an M/G/1 model to analytically determine the delay incurred in handling various types of queries using our enhanced APTEEN (Adaptive Periodic Threshold-sensitive Energy Efficient sensor Network protocol) protocol. Our protocol uses an enhanced TDMA schedule to efficiently incorporate query handling, with a queuing mechanism for heavy loads. It also provides the additional flexibility of querying the network through any node in the network. To verify our analytical results, we have simulated a temperature sensing application with a Poisson arrival rate for queries on the network simulator ns-2. As the simulation and analytical results match perfectly well, this can be said to be the first step towards analytically determining the delay characteristics of a wireless sensor network.

In this paper, we propose an analytical modeling for integrated wireless networks with priority reservation and preemptive priority procedures. In our scheme, calls are separated into four different classes: originating voice calls, originating data calls, voice and data handoff request calls. In the proposed scheme, there are queues for handoff request calls. Some number of channels in each cell are reserved exclusively for handoff request calls. Out of this number of channels, some are reserved exclusively for voice handoff requests. The remaining channels are shared by both originating and handoff request calls. Higher priority is given to voice handoff requests over data handoff requests and can preempt the service of ongoing data calls if on arrival it finds no free channels. A three-dimensional Markov chain model is used to determine system performance in terms of blocking probabilities of originating calls, forced termination probability of voice handoff requests calls, and average transmission delay of data calls.

Studies a queueing scheme of calls in cellular radio systems where priority is given to handoff calls by assigning several channels exclusively for them. The remaining channels are shared by both the originating and handoff calls. In this scheme both the originating and handoff calls make their own queues. A handoff call queues up if on arrival it finds no idle channels. An originating call also queues if on arrival it finds that the number of available channels is less than or equal to that of the reserved channels. Important performance measures of the system such as forced termination probability, and queue lengths are obtained. Solutions for some special systems such as ones with a queue only for the handoff calls and without queues for any calls were also investigated.>