Wireless Multimedia Networks Research Articles

A More Realistic Thinning Scheme for Call Admission Control in Multimedia Wireless Networks

A call admission control scheme named thinning scheme, which smoothly throttles the admission rates of calls according to their priorities and aims to provide multiple prioritized traffic with a desired quality of service, is investigated under more general conditions. Using the theory of multidimensional Markov birth-death process, analytical formulas for call blocking probabilities are derived.

Tiered bandwidth reservation scheme for multimedia wireless networks

AbstractIt is important to provide quality of service (QoS) guarantees if we want to support multimedia applications over wireless networks. In this paper, considering the features of tiering in sectored cellular networks, we propose a novel scheme for bandwidth reservation to approach QoS provisioning. By predicting the movement of each connection, the reserving of bandwidth is only required in needful neighboring cells instead of in all neighboring cells. In addition, an admission control mechanism incorporated with bandwidth borrowing assists in distributing scarce wireless bandwidth in more adaptive way. Through mathematical analysis, we proof the advantages of tier‐based approach and the bound for the selection of tiered boundary. The simulation results also verify that our scheme can achieve superior performance than traditional schemes regarding no bandwidth reserving, fixed bandwidth reserving, and bandwidth borrowing in sectored cellular networks when performance metrics are measured in terms of the connection dropping probability (CDP), connection blocking probability (CBP), and bandwidth utilization (BU). Copyright © 2008 John Wiley & Sons, Ltd.

A New QoS Provisioning Method for Adaptive Multimedia in Wireless Networks

Future wireless networks are designed to support adaptive multimedia by controlling individual ongoing flows to increase or decrease their bandwidths in response to changes in traffic load. There is growing interest in quality-of-service (QoS) provisioning under this adaptive multimedia framework, in which a bandwidth adaptation algorithm needs to be used in conjunction with the call admission control algorithm. This paper presents a novel method for QoS provisioning via average reward reinforcement learning in conjunction with stochastic approximation, which can maximize the network revenue subject to several predetermined QoS constraints. Unlike other model-based algorithms (e.g., linear programming), our scheme does not require explicit state transition probabilities, and therefore, the assumptions behind the underlying system model are more realistic than those in previous schemes. In addition, when we consider the status of neighboring cells, the proposed scheme can dynamically adapt to changes in traffic condition. Moreover, the algorithm can control the bandwidth adaptation frequency effectively by accounting for the cost of bandwidth switching in the model. The effectiveness of the proposed approach is demonstrated using simulation results in adaptive multimedia wireless networks.

A Theoretical Framework for Quality‐Aware Cross‐Layer Optimized Wireless Multimedia Communications

Although cross‐layer has been thought as one of the most effective and efficient ways for multimedia communications over wireless networks and a plethora of research has been done in this area, there is still lacking of a rigorous mathematical model to gain in‐depth understanding of cross‐layer design tradeoffs, spanning from application layer to physical layer. As a result, many existing cross‐layer designs enhance the performance of certain layers at the price of either introducing side effects to the overall system performance or violating the syntax and semantics of the layered network architecture. Therefore, lacking of a rigorous theoretical study makes existing cross‐layer designs rely on heuristic approaches which are unable to guarantee sound results efficiently and consistently. In this paper, we attempt to fill this gap and develop a new methodological foundation for cross‐layer design in wireless multimedia communications. We first introduce a delay‐distortion‐driven cross‐layer optimization framework which can be solved as a large‐scale dynamic programming problem. Then, we present new approximate dynamic programming based on significance measure and sensitivity analysis for high‐dimensional nonlinear cross‐layer optimization in support of real‐time multimedia applications. The major contribution of this paper is to present the first rigorous theoretical modeling for integrated cross‐layer control and optimization in wireless multimedia communications, providing design insights into multimedia communications over current wireless networks and throwing light on design optimization of the next‐generation wireless multimedia systems and networks.

Utilisation analysis and comparison for multimedia wireless networks

In this paper, we consider a homogeneous wireless multimedia system with both priority and non-priority calls. The resources of the system are either as the nominal channels assigned evenly to each of the coved cells or reserved in the control centre exclusively for priority calls. Different classes of calls may request different bandwidths for a satisfactory connection. We investigate how the utilisation depends on the channel allocation schemes and whether a buffer space affects the performance of the system in terms of the utilisation of the system. Our observation is expected to provide technical guidance for the design of channel allocation of multimedia wireless systems.

Hierarchical Markov chain analysis of an adaptive bandwidth reservation algorithm in wireless communication systems

Admission control for handoff drops is a key resource management technique in wireless multimedia networks. While several adaptive schemes have been studied in the literature, little effort has been made for their analysis due to difficulty in mathematical modeling. Our main contribution is the proposal of a methodology for analyzing the Markov chain that is created when modeling a simple adaptive bandwidth reservation mechanism. For this purpose, we decompose the Markov chain into two levels: intra-domain for the analysis of equilibrium states and inter-domain for the analysis of transient states. This hierarchical decomposition provides an exact solution with significantly reduced computational complexity.

Reliable bandwidth estimation for handoff calls in wireless networks

The aim of handoff is to enable a mobile terminal (MT) to seamlessly move between cells while maintaining the negotiated Quality of Service (QoS) of its active connections. This can be achieved by providing sufficient resources (e.g., bandwidths) when the MT crosses the boundary of cells (the geographic area within which while MTs can communicate with each other to ensure continuity of connections when the MT users move from one cell to another). Handoff technique is especially important in application of wireless multimedia networks. A pressing problem is the need to reduce the probability of drops while maintaining an ongoing session during the handoff operation of mobile terminals (MTs). In general, the blocking of new calls is regarded as more acceptable than the risk of inducing handoff failures. Numerous schemes have been proposed to provide a satisfactory QoS for handoff calls. This paper uses a stochastic method to develop a novel approach for calculating the reserved bandwidth requirements of handoff calls. Significantly, in the proposed method, the reserved bandwidth requirements are estimated by taking the MT’s speed into consideration; the direction of travel of the MT is ignored. The main contribution in this paper is concentrated on estimation of the bandwidth requirement for handoff calls in wireless networks. Unlike traditional method, which dividing bandwidth by using arrival rate. We propose a generic method of bandwidth estimation for handoff calls according to the residence duration which have the advantages both on resource cost reducing and accuracy in bandwidth estimations with ignoring the direction of the MT movement.

An HMM prediction and throttling-based call admission control scheme for wireless multimedia networks

With the increase in data transmission for wireless networks, multimedia services are gaining popularity in next-generation cellular networks. If the appropriate information exists for Call admission control (CAC) schemes, the terms of quality of service (QoS), such as call dropping probability (CDP), and call blocking probability (CBP) will be kept as low as possible, and higher system utilization can be achieved. Unfortunately, it is difficult to obtain such information owing to user indeterminate mobility. In this paper, the proposed scheme reduces the CDP with a statistical method, called Hidden Markov Models (HMM), that is suitable for solving a dynamic situation has been introduced and applied to the CAC scheme. The prediction of user mobility can be modeled and solved as an optimal-state sequence problem for the HMM. The proposed CAC method that adopts the prediction result of user mobility can reserve appropriate bandwidths for a handoff call in advance, thus, the CDP will be kept below a lower level. Moreover, the throttle flag that indicates the usage of bandwidth in each cell is proposed to prevent the new call request from being dropped in the adjacent cells if handoff is needed, and then the CDP will be further lowered. Besides, the CBP will also be kept relatively low since the proposed method can reserve the suitable bandwidths in the appropriate cells but not reserve stationary ones which are always adopted by traditional CAC methods for each cell. The simulation results show that the proposed method can meet CDP and CBP requirements, and the system utilization can also be improved.

A novel multiple access scheme over multi-packet reception channels for wireless multimedia networks

Recent advances in signal processing techniques have enabled wireless networks to have multi-packet reception (MPR) capability at the physical layer, where it is possible to receive more than one packets when concurrent transmissions occur. In this paper, we propose a novel multi-reservation multiple access (MRMA) scheme for future wireless multimedia networks based on such an MPR channel model. MRMA can fully exploit the channel's MPR capacity while fulfilling the quality of service requirements of different multimedia traffic. Similar to many existing reservation protocols, MRMA guarantees (i) bounded access delay for real-time traffic by dropping packets not transmitted within the required delay bound, and (ii) satisfaction of the required packet loss ratio when applied in conjunction with a connection admission control method to limit the number of admitted traffic streams. MRMA further incorporates a priority control mechanism to differentiate guaranteed and best-effort services for real-time voice/video and connectionless data, respectively. Analytical and simulation results are presented to illustrate the effectiveness of MRMA in service differentiation and increasing the number of admitted traffic streams

Mobility model used for QoS management for wireless multimedia networks

A radio service and more particularly for multimedia services, the availability of the resources often fluctuates, according to the load, mobility of users and variation of the transmission quality. The fluctuation is a major problem for radio network operators to adapt the use of the resources considering the mobility of the users. The allocation of the bandwidth of various types of traffic is done only at fresh call arrival or for a handover. The mobility of the users has an important influence on the configuration of the network. Such intercellular handover modifies the distribution of the traffic in the system and generates additional signalling load. In this study, we consider the mobility of the users in the dimensioning network and four traffic models (voice, video, www and ftp). This mobility model allows us to determine at the cell level as well as at the entire system level, for QoS parameters, threshold values beyond which a call can be blocked.

Optimized bandwidth allocation with fairness and service differentiation in multimedia wireless networks

AbstractIn this article we present an optimal Markov Decision‐based Call Admission Control (MD‐CAC) policy for the multimedia services that characterize the next generation of wireless cellular networks. A Markov decision process (MDP) is used to represent the CAC policy. The MD‐CAC is formulated as a linear programming problem with the objectives of maximizing the system utilization while ensuring class differentiation and providing quantitative fairness guarantees among different classes of users. Through simulation, we show that the MD‐CAC policy potentially achieves the optimal decisions. Hence our proposed MD‐CAC policy satisfies its design goals in terms of call‐class‐differentiation, fairness and system utilization. Copyright © 2006 John Wiley & Sons, Ltd.

Flow-level QoS for a dynamic load of rate adaptive sessions sharing a bottleneck link

We consider the flow-level quality of service (QoS) seen by a dynamic load of rate adaptive sessions sharing a bottleneck link based on fair share bandwidth allocation. This is of interest both in considering wired networks supporting rate adaptive multimedia sessions and wireless networks supporting voice with rate adaptation to realize graceful degradation during congested periods. Two QoS metrics are considered: the time-average instantaneous utility of the allocated bandwidth, and the time-average of transition penalties associated with the changes in allocation seen by a flow. We present a simple model for rate adaptation, where (heterogeneous) flows can vary their rates within (different) ranges, and present closed-form results for these perceived flow-level QoS metrics. We then prove asymptotic results for large capacity systems exhibiting the salient features of rate adaptation in a dynamic network. Finally, we provide a concrete example, showing how the QoS seen by sessions with different degrees of adaptivity would vary under a natural fair bandwidth allocation policy.

Crossband Flexible UWB Multiple Access for High-Rate Multipiconet WPANs

Emerging indoor technologies including wireless multimedia and personal area networks (WPANs) entail high-rate systems capable of supporting multiple users (piconets) with variable rates. These requirements motivate the design of multiband (MB) ultra-wideband (UWB) radios for their simplicity in handling pronounced frequency selectivity, agility in coping with interference, scalability in providing multirate operation, and their potentially low cost. Relative to baseband UWB radios, MB-UWB systems have gained popularity in the IEEE standards for short-range wireless links. However, multiple-access (MA) schemes must be designed carefully to harness the diversity benefits provided by the MB-UWB propagation, in a spectrally efficient manner. To this end, we introduce a crossband flexible UWB MA scheme for multipiconet WPANs. The resultant design that we term FLEX-UWB offers resilience to multiuser interference, can conveniently accommodate various spreading alternatives, enables full multipath diversity, and can effect scalable spectral efficiency (from low to medium and high data rates). Simulations confirm the merits of FLEX-UWB radios in comparison with various alternatives

Space-time narrowband interference suppression with receive diversity for DS-UWB systems

As the consumer demand for higher capacity, faster service, and more secure wireless connections increases, new enhanced technologies have to find their place in the overcrowded and scarce radio frequency (RF) spectrum. Ultra-wideband (UWB) technology can offer a promising solution to the RF spectrum drought by allowing new services to coexist with current narrowband systems. On the other hand, this coexistence brings the narrowband interference (NBI) problem for UWB systems due to their very low power spectral densities. To meet increasing requirements for low cost, low power, flexible, and reliable wireless multimedia networks, an adaptive NBI suppressing method employing space-time adaptive processing (STAP) with receive diversity is discussed and experimentally investigated for direct-sequence (DS) UWB systems. Analytical results show that, in wireless home environments, the investigated scheme is capable of significantly improving the performance in combating NBI, compared with the conventional temporal approach. The effect of receive diversity is also examined via the Monte-Carlo simulations

A Borrowing-Based Call Admission Control Policy for Mobile Multimedia Wireless Networks

Providing multimedia services with a quality-of-service guarantee in mobile wireless networks presents more challenges due to user's mobility and limited bandwidth resource. In order to provide seamless multimedia services in the next-generation wireless networks, efficient call admission control algorithm must be developed. A novel borrowing-based call admission control policy is proposed in this paper as a solution to support quality-of-service guarantees in the mobile multimedia wireless networks. Based on the existing network conditions, the proposed scheme makes an adaptive decision for bandwidth allocation and call admission by employing attribute-measurement mechanism, dynamic time interval reservation strategy, and service-based borrowing strategy in each base station. We use the dynamically adaptive approaches to reduce the connection-blocking probability and connection-dropping probability, and to increase the bandwidth utilization, while the quality-of-service guarantees can be maintained at a comfortable level for mobile multimedia wireless networks. Extensive simulation results show that our proposed scheme outperforms the previously proposed scheme in terms of connection-blocking probability, connection-dropping probability, and bandwidth utilization, while providing highly satisfying degree of quality-of-service in mobile, communication systems.

A conservative approach to adaptive call admission control for QoS provisioning in multimedia wireless networks

In this paper, we propose a framework called conservative and adaptive quality of service (CAQoS) to perform the quality of service (QoS) provisioning on both real-time and non real-time traffic in the wireless network. Unlike most conventional schemes which gradually scale-down the bandwidth rates of ongoing connections to accommodate new connection/handoff requests, CAQoS introduces an early scaling-down of bandwidth for new connections based on designated provisioning model. The objectives of CAQoS are to minimize the need for frequent bandwidth reallocation and to achieve lower call blocking and handoff dropping rates, while maximizing the overall bandwidth utilization. The performance of CAQoS system is evaluated through simulations of a realistic wireless cellular-based environment. Simulation results showed that CAQoS met our objectives and outperformed the conventional schemes.

Channel-Aware Earliest Deadline Due Fair Scheduling for Wireless Multimedia Networks

Providing delay guarantees to time-sensitive traffic in wireless multimedia networks is a challenging issue. This is due to the time-varying link capacities and the variety of real-time applications expected to be handled by such networks. We propose and evaluate the performance of a channel-aware scheduling discipline and a set of policies that are capable of providing such delay guarantees in TDM-based wireless networks. First, we introduce the Channel-Dependent Earliest-Due-Date (CD-EDD) discipline. In this discipline, the expiration time of the head of line packets of users' queues is taken into consideration in conjunction with the current channel states of users in the scheduling decision. This scheme attempts to guarantee the targeted delay bounds in addition to exploiting multiuser diversity to make best utilization of the variable capacity of the channel. We also propose the violation-fair policy that can be integrated with the CD-EDD discipline and two other well-known scheduling disciplines [1, 2]. In this policy, we attempt to ensure that the number of packets dropped due to deadline violation is fairly distributed among the users. The proposed schemes can provide statistical guarantees on delays, achieve high throughput, and exhibit good fairness performance with respect to throughput and deadline violations. We provide extensive simulation results to study the performance the proposed schemes and compare them with two of the best known scheduling disciplines [1, 2] in the literature.

Analysis and Characterization of Intercarrier and Interblock Interferences for Wireless Mobile OFDM Systems

OFDM has been applied in a wide variety of wireless communications in recent years since it has the advantage over the conventional single-carrier modulation schemes when enduring the frequency-selective fading. However, intercarrier-interference (ICI) and interblock interference (IBI) due to the Doppler effect, carrier frequency drift of local oscillators and multipath fading limit the capability of OFDM systems. In this paper, a new generalized mathematical model for intercarrier and interblock interferences is derived for wireless mobile OFDM systems, in which Doppler frequency drift, local carrier frequency offset, multipath fading, and cyclic prefix coding are all present in reality. Such a new ICI/IBI model can be applied for OFDM performance evaluation in different environments. This new formulation of IBI and ICI provides a generalized framework which includes special ICI models appearing in the previous literature. Besides, the derived OFDM performance evaluation analysis in this paper can greatly benefit OFDM designers for wireless multimedia networks and digital video broadcasting technologies.

QoS provisioning for multimedia wireless networks

As we move towards IP-based multimedia wireless networks with voice, video and data convergence, quality of service (QoS) provisioning will become an increasingly challenging task. One implication is that greater emphasis on managing the call admission and overall network resources will be needed. This paper presents a conservative and adaptive quality of service (CAQoS) framework for provisioning the QoS for both real-time and non-real-time traffic in a multimedia wireless network. Unlike most conventional schemes, which gradually scale down the bandwidth of ongoing connections to accommodate new connection/hand-off requests, CAQoS introduces an early scaling-down of bandwidth for new connections based on a designated provisioning model. The performance of a CAQoS system is evaluated through simulations of a realistic wireless environment. Simulation results show that CAQoS meets our design goals and outperforms conventional schemes.

Dynamic rate-based borrowing scheme for QoS provisioning in high speed multimedia wireless cellular networks

The provisioning of QoS in wireless networks carrying multimedia traffic imposes a big challenge to network designers and traffic engineers. Guaranteeing QoS in wireless networks is a complicated task due to the unique characteristics of wireless networks such as user mobility, limited link capacity, frequent link failure, scarcity of bandwidth, channel fading, and inability to predict the availability of resources in the network. In this paper, we investigate multiple QoS schemes in multimedia wireless networks. A modification to an existing scheme, rate-based borrowing scheme, where the concept of borrowing bandwidth from existing connections to accept both new and handoffs connections is proposed. Unlike Rate-Based Borrowing Scheme (RBBS) and Statistical Scheme (SBS), Dynamic Rate-Based Borrowing Scheme (DRBBS) exploits the positive feature of fair borrowing bandwidth and avoids pre-allocation of resources. This is based on the concept of borrowing from existing connections. Extensive simulation experiments have been performed using a simulation package designed for the purpose of this research. Using the call dropping/blocking probabilities and bandwidth utilization as a performance metrics, the proposed scheme, DRBBS outperforms the previously known schemes in terms of the aforementioned performance metrics. Fair borrowing from ongoing connections shows a decrease in the rate of calls dropping probabilities and a decrease in the calls blocking probabilities, while avoiding pre-allocation of resources offers a significant improvement in the bandwidth utilization.