Ridha Ouni

Dynamic slot assignment protocol for QoS support on TDMA-based mobile networks

An efficient bandwidth allocation scheme in wireless networks should not only guarantee successful data transmission without collisions but also enhance the channel spatial reuse to maximize the system throughput. The design of high-performance wireless Local Area Network (LAN) technologies making use of TDMA/FDD MAC (Time Division Multiple Access/Frequency Division Duplex Medium Access Control) is a very active area of research and development. Several protocols have been proposed in the literature as TDMA-based bandwidth allocation schemes. However, they do not have a convenient generic parameters or suitable frame repartition for dynamic adjustment. In this work, we undertake the design and performance evaluation of a QoS (Quality of Service)-aware scheme built on top of the underlying signaling and bandwidth allocation mechanisms provided by most wireless LANs standards. The main contribution of this study is the new guarantee-based dynamic adjustment algorithm used in MAC level to provide the required QoS for all traffic types in wireless medium especially Wireless ATM (Asynchronous Transfer Mode). Performance evaluation of this approach consists of improving the bandwidth utilization, supporting different QoS requirements and reducing call reject probability and packet latency. Highlights The compensation algorithm employs non-guaranteed slots for dynamic bandwidth allocation. The compensation of time slots increases the throughput and decreases the blocking probability. Rewarding released slots for MT transmitting with lower QoS improves resource utilization rate. Processing handoff requests with high priority decreases the call blocking probability.

A new geometric approach to mobile position in wireless LAN reducing complex computations

Positions estimation from Time of Arrival (TOA), Time Difference of Arrival (TDOA), and Angle of Arrival (AOA) measurements are the commonly used techniques. These approaches use the location parameters received from different sources and they are based on intersections of circles, hyperbolas, and lines, respectively. The location is determined using standard complex computation methods that are usually implemented in software and needed relatively long execution time. An important factor in achieving this is to minimize and simplify the instructions that the mobile station (MS) has to execute in the location determination process. Finding an effective location estimation technique to facilitate processing data is the main focuses in this paper. Therefore, in the wireless propagation environment the Received Signal Strength (RSS) information from three base stations (BSs) are recorded and processed and they can provide an overlapping coverage area of interest. Then an easy geometric technique is applied in order to effectively calculate the location of the desired MS.

TCP flow control technique for an interworking interface: hardware implementation

Abstract Current TCP flow control depends on packet losses to find the workload that a network can support. A variety of situations, including lossy wireless networks, asymmetric networks and web traffic workload, violates many of the assumptions made by TCP, causing degraded end-to-end performances. To improve the performance of TCP over heterogeneous networks (Ethernet and ATM interconnection), we propose a new technique, which we call Vegas–Snoop+, based on Vegas and Snoop protocols. Two modified service elements take part on the Vegas–Snoop+ technique. First, Vegas service element manages the connection parameters to achieve better throughput. Second, Snoop service element isolates the Ethernet senders from the characteristics of the ATM link. The objective in this paper is to win from advantages of Vegas and Snoop protocols, as well as to search an interconnection interface for networks interoperability. Actually, the development of two new integrated circuits (the BCM5680 (switch) and the BCM5401 (PHY)) orientate researchers to implement, at higher layer of the OSI model, flow control mechanisms to ensure reliability. Vegas–Snoop+ is an implementation of TCP, which gives in this way a solution for traffic management and congestion control improving good throughput with more reliability.

Reducing Wi-Fi handover delay using a new positioning process

Mobility has now a crucial requirement for wireless communication. Handover is one of the major tasks that are used to support continuous transmission for a mobile terminal into different radio coverage area. Optimizing the existing handover protocol requires integrating new functionalities. This work focuses on presenting and optimizing handover algorithm. We analyze handover time in wireless local area networks based on the IEEE 802.11b MAC protocol. In fact, scan phase is the main contributor to the handover time. Then, we propose a handover model which replaces a scan phase by a positioning process. This model is able to select the suitable access point (AP) based on the shortest distance far from the mobile terminal (MT). Proposed Handover allows a mobile user to reacting quickly to decide about to which access point to connect. Simulation results show that the proposed model provides gains in term of delays and Handover success in various scenarios

Wireless propagation channel modeling for optimized Handoff algorithms in wireless LANs

In this paper, we present a time-series analysis technique which covers the basic concepts and mechanisms driving the wireless propagation channel. We also use a generated series for simulation study of Handoff performance showing the impact of multipath phenomena. Moreover, the extraction of the average signal has been used to reduce significantly the number of unnecessary Handoffs. The wireless propagation channel modeling is based on the linear model concept of the received power from the access point (AP). This concept has a crucial role in modeling new decentralized Handoff based on the ratio of expected and current signal slopes already provided by the linear model. Hence, a fuzzy-based solution is developed and a comparison with the analytical solution results is established. Until recently, Handoff mechanisms are implemented entirely in software, which increasingly becoming infeasible. Therefore, this work attempt to follow the top-down co-design approach providing hardware prototype which leads to reduce the power consumption and support high processing speed.

A NEW ENERGY-EFFICIENT NEIGHBOR DISCOVERY AND LOAD BALANCING PROTOCOL FOR MOBILE SENSOR NETWORKS

The wireless sensor networks (WSNs) are formed by a large number of sensor nodes working together to provide a specific duty. However, the low energy capacity assigned to each node prompts users to look at an important design challenge which is lifetime maximization. Especially the availability of nodes, the sensor coverage, and the connectivity have been included in discussions on network lifetime. Therefore, designing effective techniques that conserve scarce energy resources is a critical issue in WSNs. In this regard, we are interested in developing various mechanisms to save energy based on the constraints involved for energy consumption in WSNs. Three mechanisms are proposed to reduce the number of control packets responsible for path discovery, optimize diffusion area, and balance the load distribution in the network.

Traffic differentiation and scheduling for QoS support in vehicular sensor networks

The IEEE 802.15.4 is widely used next-generation standard protocol in many applications utilizing wireless sensor networks (WSNs) especially in vehicular sensor networks (VSNs). However, currently differentiation and scheduling mechanisms are not provided in IEEE 802.15.4 specification to improve the quality of service (QoS) for delay-sensitive and critical events. In this paper, multiple scheduling algorithms such as FIFO, Priority queue, WRR and DWRR are integrated in compliance with IEEE 802.15.4 to improve the throughput, enhance the bandwidth utilization rate and perform fast processing and delivery for urgent data traffic. we divide the standard traffic into various types of data on the basis of different QoS requirements such as real-time fixed data packets generation on periodic basis, real-time variable size data packets generation on periodic basis, non real-time variable size data packets and best effort. The mandatory QoS service flow parameters are defined for each type of traffic according to its time-criticality and delay sensitivity.

A NEW SCHEDULING PROTOCOL DESIGN BASED ON DEFICIT WEIGHTED ROUND ROBIN FOR QoS SUPPORT IN IP NETWORKS

We present a study of the effects of active queue management (AQM) on the average queue size in routers. In this work, three prominent AQM schemes are considered: packet classification, checking se...

Peformance evaluation of fuzzy controller for traffic stabilization

This paper proposes a useful algorithm approach to hybrid control systems combining fuzzy logic and predictable control techniques for network infrastructure. The given model employs two rules to Fuzzy logic rate prevention based on queue length and buffer frequency. The learning rule for this network must then be modified accordingly. The implementation of the fuzzy model was carried out in simulation phase. The simulation was tested with several scenarios. Obtained results proved favourable comparing to ideal models.

A new solution for micro-mobility management in 802.11 wireless LANs using FPGA

Seamless connectivity in wireless access networks is critical for time sensitive applications requiring Quality-of-Service guarantees with bounded data transmission delay. Currently, the latency inherent in the handoff process can preclude the successful delivery of such applications by introducing delays up to several seconds. As the mobile clients are moving from one access point to another, the convectional layer-2 handoff consumes more time in the channel-scanning process. We present a novel WLAN handoff architecture using a hardware method. This new handoff procedure reduces the discovery phase according two models extended from the basis model. There are two general methods to implement MAC functions in normal case. The first method is CPU-based. It uses software for protocol analysis and CPU, such as DSP, for process management. It is more flexible in design stage and easy to modify, but its disadvantages are processing speed too low and higher cost. The other method means that all functions are processed by hardware circuits. The advantage of this method is circuit reconfiguration and processing speed very high, but it needs long developed time. We purpose the last method to implement handoff functions in the MAC layer.