Showing papers on "Handover published in 1986"

Comments on "Teletraffic model and performance analysis for cellular mobile radio telephone systems with prioritized and nonprioritized handoff procedures"

Abstract: A traffic model and analysis for cellular mobile radio telephone systems with handoff are described. Three schemes for call traffic handling are considered. One is nonprioritized and two are priority oriented. Fixed channel assignment is considered. In the nonprioritized scheme the base stations make no distinction between new call attempts and handoff attempts. Attempts which find all channels occupied are cleared. In the first priority scheme considered, a fixed number of channels in each cell are reserved exclusively for handoff calls. The second priority scheme employs a similar channel assignment strategy, but, additionally, the queueing of handoff attempts is allowed. Appropriate analytical models and criteria are developed and used to derive performance characteristics. These show, for example, blocking probability, forced termination probability, and fraction of new calls not completed, as functions of pertinent system parameters. General formulas are given and specific numerical results for nominal system parameters are presented.

Traffic Model and Performance Analysis for Cellular Mobile Radio Telphone Systems with Prioritized and Non-Prioritized Handoff Procedures.

Abstract: A traffic model and analysis for cellular mobile radio telephone systems with handoff are described. Three schemes for call traffic handling are considered. One is nonprioritized and two are priority oriented. Fixed channel assignment is considered. In the nonprioritized scheme the base stations make no distinction between new call attempts and handoff attempts. Attempts which find all channels occupied are cleared. In the first priority scheme considered, a fixed number of channels in each cell are reserved exclusively for handoff calls. The second priority scheme employs a similar channel assignment strategy, but, additionally, the queueing of handoff attempts is allowed. Appropriate analytical models and criteria are developed and used to derive performance characteristics. These show, for example, blocking probability, forced termination probability, and fraction of new calls not completed, as functions of pertinent system parameters. General formulas are given and specific numerical results for nominal system parameters are presented.

Handoff apparatus and method with interference reduction for a radio system

Abstract: A two way radio system employing power control of a remote station transmitter to produce a predetermined received signal level at a fixed site after handoff of the remote station from one radio channel to another is disclosed. A signal strength measurement is made on the in-use channel and a power level for the remote station transmitter is calculated from the measured signal strength, a predetermined nominal signal strength desired on the target radio channel, and a linear correlation of signal strength and remote station power level steps. The calculated remote station power level is then transmitted to the remote station as part of a handoff command.

Two-way radio communication system with max-minimum call assignment method

Abstract: An improved two-way radio communication system having a limited number of channels is disclosed which assigns calls in a max-minimum method, in a first embodiment according to the type of call and sector to be served. This disclosed first embodiment includes a method that ascertains the type of call, handoff or first assignment, and assigns a server with a given central controller to a channel frequency within the requestor sector that minimizes interference to present users. The method of the second embodiment controls requests for assignment to a limited number of channels to reduce adjacent channel interference to and from the requestor with respect to present users operating on a system by utilizing one or more thresholds to arrange channel assignments based upon progressively larger or smaller values of received signal strength.

Queueing and Traffic in Cellular Radio

Abstract: A Cellular Radio system is analyzed from the communications traffic point of view. A cell within a given system is modeled by a multi-server service facility with or without the possibility of queueing some type of customers. Two types of arrivals are distinguished, corresponding to handoff calls (calls already in progress that enter the cell) and originating calls (calls initiated inside the cell). The queueing system used assumes Poisson distributed arrivals with different rates for the two types of customers. We initially assume, as is usually done for telephone communications, an exponential distribution for the service times of the customers. Due to mobility of the subscribers that can travel through several cells in the system, the channel occupancy time is in general different from the total call duration. Using both a simulation of a cellular system and an analytic model we offer evidence that a memory-less distribution may not be too unrealistic for the channel occupancy time. We derive some traffic policies that give a higher level of protection to handoff calls, and their influence on the other class of customers as well as on the overall traffic is analyzed. The first policies proposed have the advantage of simplicity and provide an efficient way of reducing the blocking probability of handoff calls while only slightly increasing the blocking probability of originating calls. The price paid is, however, a small decrease in the total carried traffic. Some more evolved traffic policies are then introduced that still decrease the blocking probability of handoff calls without much penalizing originating calls whose access to the system will only be slightly delayed. These more evolved policies provide the additional advantage of increasing the total carried traffic, while still providing a higher level of protection to handoff calls.

Cellular intersystem handoff: Creating transparent boundaries

Abstract: Cellular systems are configured in such a way that a mobile subscriber who originates a call at any geographical point in the system will receive high quality, uninterrupted service while moving to any other geographical point within the system. However, with cellular systems operating in many cities in the U.S. and Canada, a new situation has arisen. Cellular service areas, which were once isolated, are now either adjacent to or overlapping other service areas. The need to provide high quality, uninterrrupted service while moving between cellular service areas has been under discussion for some time. An intersystem protocol for this application must not only satisfy the need of multivendor communications, but also take into account the diversity in cellular market sizes and applications. This paper approaches the issue of intersystem communications from two perspectives: 1. The services expected by a subscriber traveling between two systems are analyzed, and solutions to potential problems are discussed. 2. The characteristics of a protocol to provide these services are defined, and a protocol structure to accommodate these requirements is proposed.

Cellular telecommunications handoff between cellular systems

Abstract: Cellular systems obtain high spectrum efficiency by reusing frequency pairs within the system. This is accomplished through the use of a grid of low-power transceivers physically deployed throughout the system in groups of channels called cells. Since the coverage area of each cell is relatively small, it is often necessary to hand off a call in progress from one cell to another. Present cellular systems have the capability to hand off a call between cells controlled by that system, but do not have the capability to hand off a call to a cell controlled by another system. This capability will become more important as cellular systems proliferate and the need to provide continuous service across system borders increases. Today, the procedure used by cellular systems to accomplish handoff is not standardized, but rather reflects the design approach of each manufacturer. The basic principles are, however, common to all system designs. This paper describes a procedure which embraces the common principles of handoff, adapted for use between systems whose internal procedures differ. The procedure is intended to be as simple as is consistent with effective operation, and can be readily implemented in existing cellular systems. Three basic functions essential to a successful inter-system handoff are described in this paper. First, a simple, architecture independent method is described for requesting and returning location measurement information. Second, procedures are provided for negotiating a voice path between systems for use by a particular handoff event. Third, procedures are provided for coordinating the transfer of the subscriber's transceiver from the initial cell site to the final cell site.

Simulation of handover conditions for cellular radio systems

Abstract: A computer model has been used to study the effects of handover in a cellular radio system. Three parameters are used to represent the radio propagation conditions including fading, which can give rise to multiple handovers on a single crossing of the cell boundary. Means for reducing unnecessary handovers are discussed.