Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-12-31
2001-06-26
Urban, Edward F. (Department: 2683)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S444000
Reexamination Certificate
active
06253084
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process and a device for managing intercellular transfers of communications in a GSM-type cellular radio communication system.
2. Discussion of the Background
It applies in particular to the implementing of cellular radio communication systems in an urban environment in which the density of traffic requires a multitude of cells and consequently a reduction in their size.
In these systems, such as those described, for example in Patent Applications DE-A-4 414 428 and EP-A-0 589 278, the radio coverage of a territory is achieved by using macrocells also termed umbrella cells, each of which encompasses a set of adjoining microcells, each cell possessing a transmit and receive base station. The base station of an umbrella cell is generally arranged at a spot which is high up with respect to the surface of the ground, on the roof of a building for example, and its transmission power is defined so as to enable it to broadcast information in a circular zone whose radius may reach several kilometers. In a different way each transmit/receive base station of a microcell services a zone of small radius which may reach a few hundred meters, and their transmit/receive aerials are generally sited below the level of the roof of buildings, on public lampposts for example.
The umbrella cell makes it possible to absorb the excess traffic appearing in a micro-cell and to manage the gaps in coverage in the micro-cellular deployment. The microcells allow an increase in traffic in a given zone, and make it possible to compensate for coverage hindered by obstacles. However, the construction of microcells of small dimensions gives rise to a complexity in the processing of the transfers of communications between microcells since the more the size of the microcells is reduced, the more it becomes necessary to manage the transfers between cells ever more frequently, and this is all the more so the larger the speed of movement of the mobiles in communication within the cellular network thus formed. This difficulty incurs risks of congestion of the multicellular network which takes a considerable time to manage the signalling signals which accompany each transfer. This difficulty is encountered in particular in GSM mobile radio networks in which no distinction is made between the mobiles in communication, apart from their power class, thus making it difficult to track mobiles in communication so as to offload the communications of the fast mobiles onto the umbrella cell.
SUMMARY OF THE INVENTION
The purpose of the invention is to alleviate the aforesaid drawbacks.
For this purpose, the subject of the invention is a process for managing the intercellular transfer of communications from mobile stations in a cellular radio communication system comprising a specified number of microcells inside umbrella cells each respectively possessing a base station for allowing the routing of the communications, characterized in that it consists, when the station is under the control of a base station of a microcell, in counting the number of transfers H
0
performed between microcells by the mobile station during a specified observation interval T
0
, in calculating a rate of transfer H
0
/T
0
for performing the transfer of the communications to the umbrella station when the rate of transfer is greater than a specified threshold value, in maintaining the transfer of communications to the base station of the microcell when the rate of transfer is below the specified threshold value and in that it consists, when the mobile station is under the control of an umbrella cell, in using direction finding to measure a virtual speed of movement of the mobile station in relation to the base station of the umbrella cell in such a way as to perform a transfer of the communications to a base station of a microcell when the speed measured by the direction finding is below a specified threshold value.
REFERENCES:
patent: 5396645 (1995-03-01), Huff
patent: 5513380 (1996-04-01), Ivanov et al.
patent: 5623535 (1997-04-01), Leung et al.
patent: 5711005 (1998-01-01), Farrag
patent: 5752168 (1998-05-01), Monot et al.
patent: 5787348 (1998-07-01), Willey et al.
patent: 6075993 (2000-06-01), Kawamoto
"Thomson-CSF"
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Urban Edward F.
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