Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1998-06-08
2001-05-01
Vincent, David R. (Department: 2732)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C455S511000
Reexamination Certificate
active
06226278
ABSTRACT:
FIELD OF THE INVENTION
The field of the invention is that of cellular systems for radio communication with mobile stations, and particularly but not exclusively, systems designed to implement the public GSM radio communication standard.
The term GSM standard is used herein to mean the GSM 900 standard (“Global System for Mobile communications” operating in the 900 MHz band) or the DCS 1800 standard (“Digital Cellular System, operating in the 1800 MHz band).
More precisely, the invention relates to transmitting the pilot channel of each operator in a system for radio communication with mobile stations.
BACKGROUND OF THE INVENTION
In general, a cellular radio communication system enables one or more network operators to manage respective distinct networks. When there are several networks, a single zone can be covered by the networks of distinct operators.
Each network is constituted by geographical cells through which mobile stations travel. Each cell of a given network is associated with a base station via which those mobile stations which are to be found in the cell and which subscribe with the operator managing the given network make calls.
Within the coverage zone of its network, each operator transmits a pilot data channel supplying each mobile station with pilot data enabling it, specifically, to log-on to the network, once it has decoded various items of system data relating in particular to the identity of the operator supplying coverage, the services available, which carriers to use, etc.
The quality of network coverage from the point of view of the pilot data channel can be assessed on the basis of the following criteria, in particular:
the time required for a mobile station to log-on initially with the network;
the total spectrum required for a network;
compatibility with future changes to the network and/or to services;
the outgoing data rate; and
transmission times.
Traditionally, over its entire network, each operator reserves a plurality of radio carriers for transmitting its pilot data channel. Each cell has its own pilot data channel which is carried by a particular carrier known as the BCCH carrier, which carrier is transmitted at constant power by the base station associated with the cell.
To log-on initially with the operator of its network via one of the base stations of the network, a mobile station begins by scanning all of the radio carriers in the allocated spectrum in order to identify, amongst those carriers which are BCCH carriers, the carrier that it receives with the greatest power. It is assumed that the BCCH carrier received at greatest power is the carrier transmitted by the base station associated with the cell in which the mobile station is to be found. Thereafter the mobile station reads the pilot data (in particular the data that will enable it to access the network) as supplied by the pilot channel carried by the BCCH carrier.
In this way, in GSM, the mobile station may have to scan 125 existing carriers and to select the six carriers that are received with greatest power. Then it verifies that the first of the six selected carriers is a BCCH carrier by looking for pilot data of the kind transmitted by BCCH carriers only. If the first selected carrier is not a BCCH carrier, the mobile station moves onto the next selected station and repeats the same operation until it has found a BCCH carrier and the pilot data it carries.
Finally, on the basis of the pilot data read, it can request access on the random access channel (RACH) in order to log-on to the network of its operator.
That present technique for transmitting the pilot data channel of each operator suffers from several drawbacks.
Firstly, because of the need to scan through all possible carriers, the time required by a mobile station to access the network is relatively lengthy.
Another drawback is that each operator, independently of the other operators, must, both on a microcell basis and on a macrocell basis, decide on transmission levels and on reuse schemes within the various cells for the set of BCCH carriers that have been allocated thereto. Implementing this feature at operator level makes future changes difficult to implement.
Finally, coverage quality at the limits of cells is not satisfactory.
OBJECTS AND SUMMARY OF THE INVENTION
A particular object of the present invention is to mitigate these various drawbacks of the state of the art.
More precisely, one of the objects of the present invention is to provide a radio communication system in which transmission of the pilot data channel of each operator is optimized compared with the above-mentioned present solution.
Another object of the present invention is to provide such a technique for transmitting pilot data channels that makes it possible to reduce the time required by a mobile station to log-on with the network of its operator.
Another object of the invention is to provide such a technique for transmitting pilot data channels that makes it possible to simplify management of carrier allocation between the various carriers.
A further object of the present invention is to make it easier in the context of transmitting pilot data channels, to include new operators and/or new services in a given radio communication system.
Yet another object of the invention is to make it possible to improve radio coverage.
These various objects, and others that appear below, are achieved, according to the invention, by a system for radio communication with mobile stations, the system being of the type enabling a plurality of network operators each to manage a distinct network, each network being made up of geographical cells and having said mobile stations travelling therethrough,
each cell of a given network being associated with a respective base station through which it can communicate with those of said mobile stations that are to be found in said cell and that are subscribers with the operator managing said given cell,
each operator transmitting in its network a pilot data channel supplying each mobile station with pilot data enabling it, in particular, to log-on with said network,
the system comprising:
a super-network made up of geographical super-cells each associated with a super-basestation, each super-basestation having means for transmitting a data signal carrying the pilot data channel of the, or each, of the operators, and each mobile station comprising means for receiving and processing said data signal so as to extract therefrom the pilot data channel of the operator with which it is a subscriber; and
means for multiplexing the pilot data channels of the various operators on said data signal.
The general principle of the invention thus consists in implementing a separate network referred to as a “super-network” for transmitting the pilot data channel(s) on a common data signal.
Thus, for initial log-on with the network of its operator, a mobile station no longer needs to scan all of the radio frequencies of the allocated spectrum prior to being able to read the contents of the pilot data channel of its operator. All that is required of the mobile station, regardless of its position within the super-network, is to receive the data signal and to extract therefrom the pilot data channel of its operator.
In addition, each super-basestation transmits a data signal obtained by multiplexing pilot data channels from various operators.
Also, management of pilot data channel transmission can be centralized and thus optimized.
Furthermore, the arrival of a new operator is thus made easier to manage since all that is required is to add a new pilot data channel to the data signal already being transmitted by each super-cell.
It would be observed that with the invention, the pilot data channel of each operator is uniform per super-cell, whereas in the conventional configuration it is uniform per cell.
Advantageously, said pilot data supplied by the pilot data channel of each operator via a data signal transmitted by a given super-basestation belonging to the group, comprises:
data concerning the identity of said operator;
data concerning t
Balech Jean-Pierre
Bursztejn Jacques
Fratti Marco
Kumar Vinod
Alcatel
Sughrue Mion Zinn Macpeak & Seas, PLLC
Vincent David R.
LandOfFree
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