Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-08-14
2001-03-20
Bost, Dwayne (Department: 2744)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S436000, C455S449000, C455S450000, C455S453000, C370S328000, C370S331000
Reexamination Certificate
active
06205336
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates in general to the mobile communications field and, in particular, to a method and system for improving utilization of network resources with handovers in a cellular communication system.
2. Description of Related Art
A hierarchical (layered) cell structure can be used as one approach to obtain higher network capacities in mobile radiotelephone systems. For example, Hierarchical Cell Structures (HCSs) are being used in Personal Digital Cellular (PDC) System radio networks in Japan, so that cells of different sizes can be used to cover the same geographical areas. Using such a hierarchical cell structuring approach, the PDC networks' radio channel frequencies can be re-used to a much greater extent than with conventional cell structures, which results in higher capacity (traffic load). In that regard, a hierarchically structured network can employ a handover procedure to order a mobile station (MS) to move from one radio channel frequency to another in the same cell or a different cell.
A problem that arises with such cell structuring approaches is that certain, special communication resources provided by the radio networks are not necessarily maintained and made available in cells at all levels, especially in those networks where higher capacities are desired. An example of such a resource typically not made available in lower level cells is a full-rate traffic channel, or a circuit-switched data transmission service. In radio networks utilizing a HCS, the operators typically configure the networks to provide these resources in the higher level, broader coverage cells (e.g., layer
3
or “umbrella” cells in a three-layered HCS network). As such, in existing mobile systems, an MS accesses the “best” (e.g., higher carrier-to-interference or carrier-to-adjacent ratio) available cell in the radio network. The network then assigns a traffic channel (TCH) to the MS in a cell on the lowest possible level. Consequently, when an active MS requests a service that requires the use of a specific resource (e.g., full-rate traffic channel, or circuit-switched data transmission service), and if that resource is not available in the cell handling the ongoing call, the requested service will not be provided for that call. Therefore, the network will most likely disconnect that call. However, as described in detail below, the present invention successfully resolves this problem and other related problems.
SUMMARY OF THE INVENTION
In accordance with a preferred embodiment of the present invention, in a HCS network, when an active MS requests a service that requires the use of a network resource not available in the cell handling the ongoing call (or, alternatively, during call set up), the network checks for cells on the higher levels to determine if the required resource is available. If the resource is available in a higher level cell, the “call” is handed over to that cell and the resource is allocated to the call. The call can be maintained in the higher level cell until the resource is no longer needed, or a “better” cell capable of providing the required resource is found.
An important technical advantage of the present invention is that a network operator can create a radio network plan based on the capacities of different communication resources.
Another important technical advantage of the present invention is that network resource utilization is increased significantly over conventional approaches.
Yet another important technical advantage of the present invention is that the flexible resource utilization allows more calls to be set up in the lower layer cells, which allows mobile stations to transmit at lower power levels and thus save battery power.
Still another important technical advantage of the present invention is that the flexible resource utilization that allows more calls to be set up in the lower layer cells, also reduces the total interference level in the network.
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Yi-Bing Lin, Li-Fang Chang, and Anthony Noerpel Bellcore, “Modeling Hierarchical Microcell/Macrocell PCS Architecture”, Communications—Gateway to Globalization, Proceedings of the International Conference on Communications, Seattle, Jun. 18-22, 1995, vol. 1, Jun. 18, 1995, pp. 405-409, XP000533019, IEEE.
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Johansson Lars Folke
Östrup Nils Peter
Palm Lars Håkan
Schultz Per Johan
Bost Dwayne
Davis Temica M.
Jenkens & Gilchrist a Professional Corporation
Telefonaktiebolaget LM Ericsson (publ)
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