G. Giambene

Handover and dynamic channel allocation techniques in mobile cellular networks

This paper deals with an efficient dynamic channel allocation (DCA) technique applicable to terrestrial mobile cellular networks. A channel (or resource) is a fixed frequency bandwidth (FDMA), a specific time-slot within a frame (TDMA), or a particular code (CDMA), depending on the multiple access technique used. A cost function has been defined by which the optimum channel to be assigned on demand can be selected. In addition, a suitable mobility model has been derived to determine the effects of handovers on network performance. The performance of the proposed DCA technique has been derived by computer simulations in terms of call blocking and handover failure probabilities. Comparisons with the classical fixed channel allocation (FCA) technique and other dynamic allocation algorithms recently proposed in the literature have been carried out to validate the proposed technique. >

Efficient dynamic channel allocation techniques with handover queuing for mobile satellite networks

Efficient dynamic channel allocation techniques with handover queuing suitable for applications in mobile satellite cellular networks, are discussed. The channel assignment on demand is performed on the basis of the evaluation of a suitable cost function. Geostationary and low Earth orbit (LEO) satellites have been considered. In order to highlight the better performance of the dynamic techniques proposed, a performance comparison with a classical fixed channel allocation (FCA) has been carried out, as regards the probability that a newly arriving call is not completely served. It has also been shown that a higher traffic density, with respect to GEO systems, is manageable by means of LEO satellites. >

Handover queuing strategies with dynamic and fixed channel allocation techniques in low Earth orbit mobile satellite systems

This paper deals with the performance evaluation of various resource management strategies that are suitable for low Earth orbit mobile satellite systems (LEO-MSSs). A user mobility model has been proposed and its statistical parameters have been derived. Both fixed channel allocation (FCA) and dynamic channel allocation (DCA) techniques have been considered. Moreover, in order to reduce the handover failure probability, we have assumed that interbeam handover requests which do not immediately obtain service can be queued. In particular, two different queuing disciplines have been compared: (a) the first input first output (FIFO) scheme and (b) a new technique called last useful instant (LUI) which is based on the knowledge of the maximum time within which the handover procedure must be accomplished. Implementation aspects for the LUI technique in a LEO-MSS have been discussed also in comparison with the measurement-based priority scheme (MBPS), previously proposed in the literature on this subject. The efficiency of the LUI queuing scheme as regards the FIFO technique has been investigated by simulations for both DCA and FCA techniques. An analytical approach has been also presented in order to allow the performance evaluation of the FCA scheme with different handover queuing disciplines.

Performance analysis for a guaranteed handover service in an LEO constellation with a "satellite-fixed cell" system

It is anticipated that the satellite component of the future universal mobile telecommunications system (UMTS) will be based (partly or totally) on non-geostationary (nonGEO) constellations of satellites to serve mixed populations of users, each category being treated through different contracts stipulating different quality of service (QoS). In particular, we envisage a high-quality premium service which guarantees the success of each handover procedure, called guaranteed handover (GH) service, and a low-cost lower quality service called regular service, where handover failures are accepted provided that the probability of a call being unsuccessful does not exceed a given value. This paper proposes a strategy which eliminates forced call terminations due to handover failures, thus allowing the GH service. This procedure applies to low Earth orbit (LEO) constellations using the satellite-fixed cell technique. An analytical model has been derived to calculate QoS parameters for a mixed population of GH and regular users. Providing both GH service to some users and regular service to other users requires an increased satellite capacity with respect to the case where all the users are served with the regular service; this capacity increase has been evaluated as a function of the percentage of GH users, the traffic load per cell, and the considered satellite mobility environment. The GH approach has been validated through the comparison with another scheme which envisages the queuing of handover requests for privileged users.

Characterization of user mobility in low earth orbit mobile satellite systems

Future mobile communication networks will provide a global coverage by means of constellations with nongeosynchronous satellites. Multi‐spot‐beam antennas on satellites will allow a cellular coverage all over the Earth. Due to the unstationarity of satellites a call may require many cell changes during its lifetime. These passages will be managed by inter‐beam handover procedures. This paper deals with the modeling of the user cell change process during call lifetime in Low Earth Orbit‐Mobile Satellite Systems (LEO‐MSSs). The analytical derivations presented in this study can be also applied to different mobility models provided that basic assumptions are fulfilled. This paper evaluates the impact of user mobility on the blocking performance of channel allocation techniques. Moreover, the handover arrival process towards a cell has been characterized by using a usual statistical parameter for stationary point processes. Finally, a performance analysis has been carried out on the basis of the classic teletraffic theory for telephone systems.

Different queuing policies for handover requests in low Earth orbit mobile satellite systems

In this paper, a mobility model suitable for low Earth orbit mobile satellite systems (LEO-MSSs) has been presented, and its statistical parameters have been derived in order to evaluate the impact of the mobility on the performance of the fixed channel allocation (FCA) strategy. Moreover, we have foreseen that interbeam handover requests, which do not immediately find service, can be queued to reduce the handover failure rate. Two different queuing disciplines have been assumed: (1) the first-input-first-output (FIFO) scheme and (2) an idealized strategy that requires knowledge of the last useful instant (LUI) within which the handover procedure must be completed in order to rank the queued handover requests. An analytical approach has been developed to compare these queuing techniques, and its results have been validated through simulations.

Performance analysis of an improved PRMA protocol for low Earth orbit-mobile satellite systems

Future mobile communication systems will be characterized by the integration of several networks at the system level. Therefore, the satellite component and the terrestrial one will use as far as possible the same protocols. Accordingly, this paper investigates the possibility of using the packet-reservation multiple-access (PRMA) technique as a medium access control protocol for low-Earth orbit-mobile satellite systems (LEO-MSSs). A modified version of the PRMA protocol, named PRMA with hindering states (PRMA-HSs), is also proposed in order to attain better performance.

An efficient technique for dynamically allocating channels in satellite cellular networks

This paper proposes an improved technique for dynamically allocating channels in mobile satellite cellular networks. Channel assignment on demand is performed on the basis of the evaluation of a cost-function. When the cell of a new call arrival does not have available channels, a single channel reconfiguration in an interfering cell is attempted in order to accept a new call. Handover requests that do not receive immediate service can be queued for a maximum time. The scenario envisaged is low Earth orbit-mobile satellite systems (LEO-MSSs). A performance comparison with other dynamic channel allocations has been carried out in order to highlight the higher efficiency of the dynamic technique proposed.

Performance analysis of a dynamic channel allocation technique for terrestrial and satellite mobile cellular networks

The paper deals with an efficient dynamic channel allocation (DCA) technique suitable for applications in both terrestrial and satellite cellular networks. A cost function is defined to allow an optimum selection of the channel to be allocated on demand. The performance of the novel DCA technique in terms of blocking probability has been derived by simulations. The obtained results are compared with those achieved by a fixed channel allocation (FCA) technique to show a better behaviour.<<ETX>>

A dynamic channel allocation technique based on Hopfield neural networks

The interest in global spectrum allocation techniques is growing with the always increasing spectrum demand for mobile communications. This paper deals with a dynamic channel allocation (DCA) technique based on an energy function whose minimization can be performed by a Hopfield neural network. The performance of the proposed DCA technique is derived by computer simulations. Comparisons with a classical FCA technique and a previously proposed DCA technique are given to highlight the better performance of our DCA technique.<<ETX>>