Mostafa Nofal

An effective approach for authentication of mobile users

In the next generation of mobile communication system users will be allowed to have a universal wireless access to multiple services. This implies the exchange of secret information with the home domain via the radio link. As the radio path is more susceptible to eavesdropping. A new set of inter-domain security mechanisms is needed to secure this information especially in the absence of a single central certification authority. Accordingly, the current paper presents a new protocol for authentication of mobile users. The main features of the proposed protocol include the use of mutual authentication between the communicating entities, KrpytoKnight, and public key cryptography. These features will provide a high security level for the whole system.

A novel cellular structure for stratospheric platform mobile communications

A novel cellular structure is proposed for the ambitious stratospheric platform mobile communications. The innovated structure adopts a multibeam scanning antenna array to create ring-shaped cells instead of the classical honey cells. This helps in avoiding the impact of positional instability especially the rotational motion of the platform around its vertical axis. Furthermore the transmitted power is reduced as well as the handover and location updating rates. The adaptation of the cell area for traffic balancing is easier than using the traditional hexagonal one. The geometry of the ring cell is analyzed in order to investigate the main parameters affecting the system performance such as the beam visiting time and the beam-scanning rate.

GEOMETRICAL CORRECTION FOR CELL DEPLOYMENT IN STRATOSPHERIC CELLULAR SYSTEMS

In this paper, cellular communications from Stratospheric platforms (SPs) is studied, and the coverage footprint analysis and design is demonstrated. In the analysis, two coverage schemes are introduced; ∞at-earth and real-earth models and cell footprint are determined in each case. The ∞at-earth provides simple footprint equations describing the cell dimensions especially for the cells of higher elevation angles while more accurate coverage equations, which well determine the geometry of the cells of lower elevation angles, can be obtained from the real-earth scheme. The design of a cellular system using the proposed coverage models is then introduced through a procedure that determines the cells locations and dimensions on the ground according to the teletra-c information. The procedure takes into considerations the cell broadening when going outwardly from the central cell to the outer lower elevation cells and constructs a cellular layout that has the most proper cells overlap and uniform coverage edges, which helps the linking between difierent SPs coverage areas.

Optimization of Beams Directions for High Altitude Platforms Cellular Communications Design

Cellular communications using high altitude platforms will predominate the existing conventional terrestrial or satellite cellular systems but requires some optimization especially in the, radio coverage cellular design. In this paper either spot-beam antennas or antenna phased arrays are used in the radio coverage which is optimized in directing their beams to satisfy mostly uniform cellular layout with minimal coverage problems such as coverage gaps between cells or excessive cells overlap

Performance and feasibility of different switched-beam antennas for the stratospheric platform mobile communications covering newly developing regions

Extending the mobile radio service to the newly developing regions is necessary for accelerating their economic and social progress. The cost and flexible deployment of such communication systems are the key issues. The emerging technology of stratospheric platform mobile communications is devised for covering such regions. Introducing smart antenna technology with this kind of communication systems provides additional improvements. The paper suggests several switched-beam smart antenna techniques in order to increase the user location accuracy especially in emergency situations, reduce power consumption, efficiently use the radio spectrum and reduce the errors resulting from the positional instability of the platform. In addition, the performance and feasibility of such approaches in terms of the hardware and processing requirements are addressed. The study dictates the adoption of beam-splitting approach as a superior one due to its compromise between the hardware and processing requirements.

Base station selection algorithms in microcellular mobile radio networks

Base station (BS) selection algorithms that dynamically adapt to teletraffic variations in the microcellular environment are introduced. Though overlapping areas usually exist between BS coverage, we redirect teletraffic away from heavily loaded cells. We present three algorithms. The first is the directed retry with handover priority algorithm that recognises blocking of a call and searches for alternative BSs. The second is the BS load equalization algorithm that directs new calls initiated in the overlapping area to be made to the BS with most available channels. The third is the rearrangement upon blocking algorithm that clears a connection from the current saturated BS in order to allow the mobile station in trouble to be served. The performance of these algorithms is evaluated using event driven computer simulations in addition to an analytical queueing model. It is found that in situations where radio coverage of adjacent cells is overlapped, the proposed algorithms yield higher system capacity.

A Novel Technique to improve the Performance of Wireless Sensor Network using Adaptive Antennas and High-Altitude Platform Communications

this paper, the performance of Wireless Sensor Networks (WSN) is improved using adaptive antenna technique and High-Altitude Platforms Systems (HAP). An adaptive concentric circular array (ACCA) is proposed to improve the communications link between sink and sensor nodes. The system is first demonstrated for several scenarios including different cell sizes at a HAP height of 20 km and the quality of link in terms of the ratio of bit energy to noise power is demonstrated where it shows the capability and reliability of building HAP-WSN despite of the long distance between ground sensors and HAP sink. The proposed ACCA technique provides a power gain profile that both increases the power to and from sensor nodes as well as it reduces the out-of cell radiation to other HAP-WSN areas.

SUPPORTING DISTRESS SIGNALS OVER LOW EARTH ORBIT MOBILE SATELLITE SYSTEMS FOR EMERGENCY INFORMATION ACQUISITION

Low earth orbit (LEO) satellite systems allow a broad range of services to be provided using small, lightweight, cellular-like portable telephones. Exploiting LEO satellites to support distress signals for aircrafts, ships and international travelers is explored in the current paper. A multi-service priority-oriented algorithm is proposed for handling voice, data and emergency signals over LEO satellites. The emergency signal is privileged with service priority so that rescue operation can be carried out as soon as possible. The priority mechanism includes channel reservation as well as joining a queue if no free channel is available as long as the request is roaming in the handover area. In addition, a simplified but efficient approach is suggested for locating the object of an imminent danger situation. As LEO satellites are non-geostationary, the visible period of each spot-beam is small. Consequently, a teletraffic model, that accommodates the mobility of spot-beams as well as the resulting handover rate, is developed in order to gauge the performance of the proposed algorithm. Numerical results for access denying and service-dropping rates are presented for nominal system parameters.

An integrated space/terrestrial cellular architecture with different priority schemes for global mobile communications

A multiple hierarchical cellular structure is proposed to handle the teletraffic load resulting from different user densities. In the lowest hierarchical level, microcells serve the highest teletraffic density, while overlaying macrocells serve both calls from areas that are difficult to be covered by microcells, as well as overflow traffic from microcells. At the highest hierarchical level, nongeostationary satellites focus their spotbeams to serve satellite-only users sparsely distributed and act as teletraffic relief for the terrestrial segment At each hierarchical level, different priority schemes are used to privilege handoff requests. A reserved channel scheme (RCS) is applied in the microcell layer, both RCS and a sub-rating scheme (SRS) are used in the macrocell layer, while in the spotbeam cell layer, RCS, SRS and a queuing priority scheme (QPS) are implemented. An analytical teletraffic model is developed to evaluate the proposed architecture. Numerical results are presented and discussed for the probabilities of new call blocking, handoff failure, forced termination and probability.

A robust protocol for authentication of mobile users

In the next generation of mobile communication system users will be allowed to have a universal wireless access to multiple services. This implies the exchange of secret information with the home domain via the radio link as the radio path is more susceptible to eavesdropping. A new set of inter-domain security mechanism is needed to secure this information especially in the absence of a single central certification authority. Accordingly, the paper presents a new protocol for authentication of mobile users. The main features of the proposed protocol include the use of mutual authentication between the communicating entities, KrpytoKnight, and public key cryptography. These features will provide a high security level for the whole system.