Muhammed Salamah

On the vertical handoff decision for wireless overlay networks

The evolution of mobile multimedia services outlines a trend towards the coexistence of wireless overlay networks. These networks have overlaid coverage areas and are composed of a hierarchical structure ranging from in-room to in-building, campus, metropolitan, and wide-areas. For these networks to work as a seamless inter-working, optimal mobility management has to be implemented. Beside the traditional horizontal handoffs between cells of the same network, vertical handoffs between different networks have more impact on system performances. One of the important challenges for seamless vertical mobility is to maintain a user active connectivity while the user is changing its point of attachment. In this paper we are addressing one aspect of the mobility management, namely the vertical handoff decision problem in wireless overlay networks, in this study, an algorithm is proposed to avoid the unnecessary vertical handoffs for such networks under different circumstances. Simulation results on the key parameters such as grade of service (GoS) and system utilization prove that the proposed strategy can provide powerful support for QoS in wireless overlay networks

Dynamically adaptive channel reservation scheme for cellular networks

In personal communications networks (PCN) supporting network-wide handoffs, new and handoff requests compete for connection resources in both mobile and backbone networks. Forced call terminations due to handoff call blocking are generally more objectionable than new call blocking. In general, most of the previously proposed schemes for radio channel allocation in cellular networks reduce handoff call blocking probability substantially at the expense of increasing the new call blocking probability by giving higher priority to handoff calls over new calls in admission control. This reduces the total admitted traffic and results in inefficient utilization of wireless channels. The tradeoff between the new and handoff calls blocking probabilities should be defined on importance basis. In this paper, we propose a performance metric equation that makes a trade off between the two probabilities depending on the network preferences. Using this equation, we study the performance of various proposed channel reservation schemes. Also in this paper, a new dynamically adaptive channel reservation scheme (DACRS) is developed and compared with other schemes proposed in the literature. The DACRS assigns handoff-reserved channels to new calls depending on the locality principle in which the base station with the help of location estimation algorithms in the mobile location center predicts the position of the mobile terminal. Eventually, the DACRS is designed to improve channel utilization while satisfying the QoS of the calls. As will be shown analytically and through simulation, the DACRS outperforms current reservation schemes and results in more statistical gain, and powerful channel utilization.

An efficient approach for trilateration in 3D positioning

Trilateration is a common operation to find the object location using its distances or range measurements to three other known points or stations. Traditionally, this problem has been solved either by algebraic or numerical methods. These methods involve long and complex geometric computations which are usually implemented in software. An approach that avoids this complexity is proposed here. Simulation results show improvements of the proposed approach in terms of computational cost and implementation simplicity over the conventional methods used. In addition, the proposed approach is based on vector rotations and uses only simple add and shift operations and therefore can be easily implemented in the hardware (or firmware) of the mobile object.

Analytical modeling of a time-threshold based bandwidth allocation scheme for cellular networks

In this paper, we developed an analytical model of a time-threshold based bandwidth allocation scheme for voice calls in cellular networks. The main idea in this scheme is based on monitoring the elapsed real time of handoff calls and according to a time-threshold parameter; a handoff call is either prioritized or treated as a new call. The scheme is modeled using a two-dimensional Markov chain and numerical analysis is presented to estimate blocking probabilities of new calls, dropping probabilities of handoff calls and system utilization. The scheme is also simulated under different network conditions. It is observed that analytical results closely match the simulation results. The results show that the proposed scheme yields a considerable performance enhancement when compared with other schemes.

General approach to simple algorithms for 2-D positioning techniques in cellular networks

Finding the location of an object is one of the important features of autonomous and the 3G/4G wireless communication systems. Many valuable location based services can be enabled by this feature. Position 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. In this paper, we propose a general approach to design new hardware-oriented algorithms that use only simple add and shift operations in the computation and therefore can be easily implemented in hardware or firmware. In addition to their implementation simplicity, the proposed algorithms outperform the conventional ones in terms of the required number of operations for a specific accuracy level.

An Adaptive Multi-Guard Channel Scheme for Multi-Class Traffic in Cellular Networks

In this paper, an adaptive channel reservation scheme for multi-class traffic is proposed to ensure the quality of service for multimedia wireless cellular networks. Although different numbers of guard channels are reserved for the handoff calls of different traffic classes, new calls can access these channels with a certain probability determined by the mobility of calls and channel occupancy. We develop a generalized analytical model to investigate the performance of the proposed scheme. Compared with the traditional well-known FSS scheme, the analytical results show that our scheme achieves better results on the handoff dropping probability, new call blocking probability, and grade of service (GoS).

Performance Analysis of a Time-Threshold Based Bandwidth Allocation Scheme for Data Calls in Cellular Networks

In this paper, we developed an analytical model of a time-threshold based bandwidth allocation scheme for data calls in cellular networks. The scheme is based on monitoring the elapsed real time of handoff calls and according to a time threshold parameter, handoff calls are either prioritized or treated as new calls. The scheme is modeled using a onedimensional markov chain and numerical analysis is presented to estimate blocking probabilities of new calls, dropping probabilities of handoff calls and system utilization. The scheme is simulated under different network conditions. It is observed that analytical results closely match the simulation results. The results show that the proposed scheme yields a considerable enhancement in terms of performance/cost ratio when compared with the conventional schemes.

A fast hardware-oriented algorithm for cellular mobiles positioning

Finding the location of a cellular mobile phone is one of the important features of the 3G wireless communication systems. Many valuable location based services can be enabled by this new feature. All location determination techniques which are based on cellular system signals and global positioning system (GPS) use standard trigonometric complex computation methods that are usually implemented in software. In this paper, we propose a new algorithm that uses only simple add and s hift operations in the computation and therefore can be implemented in hardware. Our results show improvements of our algorithm in computation time, implementation simplicity and location accuracy over the traditional used method.

FBLLB: a fuzzy-based traffic policing mechanism for ATM networks

The statistical multiplexing of sources with diverse traffic characteristics in ATM networks necessitates the use of some policing mechanisms, especially sources with bursty traffic characteristics. Because of the statistical nature of burstiness, the policing of these sources is difficult and the known policing mechanisms cannot control them effectively. Even the leaky bucket control mechanism, which is the most widely and only implemented one has some drawbacks. Although the buffered learning leaky bucket (BLLB) shows nice improvements over the leaky bucket, yet the harshness of its decision might slow down the increase in the performance. In this paper a fuzzy approach for the BLLB aiming to overcome the uncertainty of the sources is proposed. This will relax the limits that BLLB suffered from. Simulation results show that the proposed fuzzy buffered learning leaky bucket (FBLLB) can achieve superior system utilization compared to the leaky bucket and BLLB. It results in high learning speed, and a simple design procedure, while increasing the level of QoS.

BLLB: a novel traffic policing mechanism for ATM networks

The statistical multiplexing of sources with diverse traffic characteristics in ATM networks necessitates the use of some policing mechanisms, especially sources with bursty traffic characteristics because of the statistical nature of burstiness, the policing of these sources is difficult and the known policing mechanisms cannot control them effectively. Even the leaky bucket control mechanism, which is the most widely and only implemented one has some drawbacks. In this paper anew policing mechanism that we named as Buffered Learning Leaky Bucket (BLLB) is developed and compared with the leaky bucket and other recent mechanisms. As will be shown by the simulation results, the new BLLB mechanism results in more statistical gain, guarantee of the QoS, and smart decisions for contract-non-violating sources.