Nada Chendeb Taher

A complete and accurate analytical model for 802.11e EDCA under saturation conditions

Extensive research addressing IEEE 802.11 Distributed Coordination Function (DCF) and 802.11e Enhanced Distributed Channel Access (EDCA) performance analysis, by means of analytical models, exists in the literature. It started mainly with the famous Bianchis model and still continues today as several aspects have not been yet covered. Indeed, the ultimate goal is to obtain the model that provides the most accurate prediction of the performance metrics such as throughputs and delays. Unfortunately, the currently proposed models, even if there are numerous, do not reach this accuracy and are still not sufficiently complete, in the sense that they omit some important EDCA features. In this paper, we propose a complete analytical model for EDCA under saturation conditions. Based on the proposed model, saturated throughput and access delay of each EDCA Access category are given. Simulation is also performed to demonstrate that the proposed model has better accuracy than others.

Towards a better support of Machine Type Communication in LTE-networks: Analysis of random access mechanisms

Machine Type Communication (MTC) is an essential service for next generation cellular networks. Because of the massive number of communicating devices, MTC poses great challenges for Radio Access Network (RAN). This is mainly caused by the overloading problem that has been aggressively addressed by 3GPP as an essential working item. Because of this overloading problem, classical Human to Human (H2H) communications may be negatively affected. In this paper we first introduce the MTC and its challenges with a focus on its use in the healthcare domain. The Random Access procedure (RACH) used in Long Term Evolution (LTE) cellular networks will be then explained in order to address the issue of RACH overload coming from massive number of MTC devices. To resolve RAN overload, 3GPP and others have proposed several RAN solutions. We evaluate and compare these solutions and conclude finally with their advantages and weaknesses in order to select the best solution for an operator.

Towards voice/video application support in 802.11e WLANs: A model-based admission control algorithm

Supporting emergent voice/video applications in all wireless technologies is a requirement in the Next Generation Network (NGN) where Wireless Local Area Networks (WLANs) is a main component. For this type of applications, QoS needs to be fully maintained in order to assure user satisfaction. Actually, QoS control in 802.11e WLANs to support real time voice/video services remains an open problem. All the solutions that only aim to enhance the performance of the Enhanced Distributed Channel Access (EDCA) mechanism cannot resolve the performance degradation problem once the channel becomes saturated. Hence, an efficient admission control scheme in EDCA is the key to guarantee the QoS required by voice/video services in WLANs. In this paper, we propose a model-based admission control algorithm that is located within the QoS Access Point (QAP). An accurate analytical model is used to predict the QoS metrics that can be achieved once a new flow is introduced in the WLAN. Based on this prediction and on the QoS constraints of already admitted (active) flows as well as of the new flow, the QAP takes the appropriate decision for the new flow. The proposed admission control scheme is fully compatible with the legacy 802.11e EDCA MAC protocol. It is validated numerically and through simulations using several realistic usage scenarios.

An Accurate Analytical Model for 802.11e EDCA under Different Traffic Conditions with Contention-Free Bursting

Extensive research addressing IEEE 802.11e enhanced distributed channel access (EDCA) performance analysis, by means of analytical models, exist in the literature. Unfortunately, the currently proposed models, even though numerous, do not reach this accuracy due to the great number of simplifications that have been done. Particularly, none of these models considers the 802.11e contention free burst (CFB) mode which allows a given station to transmit a burst of frames without contention during a given transmission opportunity limit (TXOPLimit) time interval. Despite its influence on the global performance, TXOPLimit is ignored in almost all existing models. To fill in this gap, we develop in this paper a new and complete analytical model that (i) reflects the correct functioning of EDCA, (ii) includes all the 802.11e EDCA differentiation parameters, (iii) takes into account all the features of the protocol, and (iv) can be applied to all network conditions, going from nonsaturation to saturation conditions. Additionally, this model is developed in order to be used in admission control procedure, so it was designed to have a low complexity and an acceptable response time. The proposed model is validated by means of both calculations and extensive simulations.

An efficient model-based admission control algorithm to support voice and video services in 802.11e WLANs

QoS control and resource management in 802.11e WLANs to support real time and multimedia services remains an open problem. All the solutions that only aim to enhance the performance of the Enhanced Distributed Channel Access (EDCA) mechanism cannot resolve the performance degradation problem once the channel becomes saturated. Hence, an efficient admission control scheme in EDCA is a key to guarantee the QoS required by real-time and multimedia services. In this paper, we propose a model-based admission control algorithm that is located within the QoS Access Point (QAP). An accurate analytical model is used to predict the QoS metrics that can be achieved once a new flow is introduced in the WLAN. Based on this prediction and on the QoS constraints of already active flows as well as the new flow, the QAP takes its decision of admitting or rejecting the new flow. The proposed admission control scheme is completely compatible with the legacy 802.11e EDCA MAC protocol. It is validated numerically and through simulations using several realistic evaluation scenarios.

Performance evaluation of user centric multihoming strategies in LTE/WiFi networks

This paper presents an analytical performance evaluation framework for 4G/WiFi multihoming techniques. Several multihoming flavors have been compared, with a focus on user centric allocation strategies. In these strategies the user splits his packets between two radio interfaces following a policy that depends on the amount of information he gets. First, the simplest policy is considered in which the user sends an amount of traffic on each interface proportional to the latters peak rate. Second, the optimal selfish policy is investigated in which the user has complete information about the traffic intensities. This latter policy has been proved to achieves a global optimum. The numerical results show that an optimized user centric policy achieves good gains for both the system capacity and the user throughput compared to a peak maximization strategy. The results also show that multihoming provides large performance gains for multi-homed users while degrading neither the capacity of the system nor the performance of single-homed users.

Cooperative dynamic eHealth service placement in Mobile Cloud Computing

In the area of mobile applications, emerging eHealth applications used in conjunction with wearable medical sensor devices and personal devices are being adopted increasingly by people with the aim to improve their lifestyle and health. eHealth providers, willing to provide remote eHealth management, are integrating Wireless Body Area Networks (WBANs) technology and Cloud Computing. Cloud computing has the benefit to eliminate the need of maintaining costly hardware, software and network infrastructures. This combination of Cloud Computing and Mobile Computing is known as Mobile Cloud Computing (MCC). It allows eHealth providers to deploy instantly and on demand their eHealth services to monitor peoples health status. In this paper, we propose a cooperative strategy between a mobile operator and a cloud provider for an efficient eHealth service placement in the cloud which take into account the network latency. We highlight the importance of mutual coordination between them to minimize the cost of deployed services while maintaining customers satisfaction.

Towards Efficient Automatic Scaling and Adaptive Cost-Optimized eHealth Services in Cloud

Cloud Computing is an emerging commercial model which allows organizations to eliminate the need to maintain costly hardware, software and network infrastructures. It also permits to avoid the high operational cost for operating and maintaining these infrastructures. Similarly, in the eHealth area, emerging eHealth applications used in conjunction with wearable medical sensor devices and personal devices are being adopted by more and more people with the aim to improve their lifestyle and health. eHealth organizations, willing to provide remote eHealth management, are integrating Wireless Body Area Networks (WBANs) technology and Cloud Computing technology. This integration allows eHealth organizations to deploy their eHealth services on demand and instantly to monitor patients health status. We propose in this paper, a solution for such organizations to efficiently deploy their eHealth services and adapt provisioned physical resources dynamically to satisfy the quality of health of potentially millions of subscribers

Analysis and enhancement of WiMAX scheduling for telemedicine support

WiMAX is a radio technology for transmitting data at high speed. The challenge for these networks is to ensure the Quality of Service (QoS) for different types of applications having different characteristics and requirements. Among these applications we note the telemedicine; where communication and information technology is used to help improving human life especially in regard to health. Medical information has an inherent characteristic that differs it from other type of information, which is the emergency level. WiMAX technology is considered as a good candidate for telemedicine services. It offers different classes of services and proposes scheduling the radio resources between users according to their application priority. But it leaves the manufacturers and service providers to develop scheduling algorithms based on the scope and depending on the services offered to their customers. In this context, we are interested in evaluating and improving the performance of WiMAX toward the support of telemedicine by proposing a new scheduling scheme which takes into consideration the emergency of the traffic and the QoS requirements in terms of delay and throughput. The evaluation of the existing scheduling algorithms and that of the new proposed one is done via simulations.

Towards using blockchain technology for eHealth data access management

eHealth is a technology that is growing in importance over time, varying from remote access to Medical Records, such as Electronic Health Records (EHR), or Electronic Medical Records (EMR), to real-time data exchange from different on-body sensors coming from different patients. With this huge amount of critical data being exchanged, problems and challenges arise. Privacy and confidentiality of this critical medical data are of high concern to the patients and authorized persons to use this data. On the other hand, scalability and interoperability are also important problems that should be considered in the final solution. This paper illustrates the specific problems and highlights the benefits of the blockchain technology for the deployment of a secure and a scalable solution for medical data exchange in order to have the best performance possible.