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Part of U.S. PATENT 3663762: MOBILE
COMMUNICATION SYSTEM
Inventor(s): Joel, Jr.; Amos Edward , South Orange, NJ
Applicant(s): Bell Telephone Laboratories, Incorporated, Murray
Hill, NJ
Issued/Filed Dates: May 16, 1972 / Dec. 21, 1970
Abstract:
A high capacity cellular mobile communication system arranged
to establish and maintain continuity of communication paths to
mobile stations passing from the coverage of one radio transmitter
into the coverage of another radio transmitter. A control center
determines mobile station locations and enables a switching center
to control dual access trunk circuitry to transfer an existing
mobile station communication path from a formerly occupied cell
to a new cell location. The switching center subsequently enables
the dual access trunk to release the call connection to the formerly
occupied cell.
Claims (Omitted)
BACKGROUND OF THE INVENTION
1. Field of the Invention This invention concerns mobile communication
systems. In particular, it relates to cellular mobile communication
systems wherein mobile stations may be located within a plurality
of cell transmission areas. In a still more particular aspect
this invention is related to communication systems wherein communication
paths may be established and continuity of communications maintained
between mobile stations and between mobile stations and fixed
stations regardless of the movement of the mobile stations between
various cell transmission areas.
2. Description of the Prior Art
The literal mobility of communication stations having the
ability to move from one location to another has presented problems
in prior arrangements which have attempted to furnish adequate
communication services to mobile station users. It has long been
a goal of mobile communication systems to supply facilities to
detect and provide communication service for roaming mobile stations
that may be located in different transmission service areas than
those to which they are normally assigned. It has further been
a goal to provide continuity of communication service between
mobile stations and between mobile stations and the telephone
direct distance dialing network regardless of the geographical
locations of mobile stations.
In the mobile radio art it is the practice for mobile stations
to be served by a radio base station which is in turn connected
to a switching central office. Communication is effected between
the base station and mobile stations by modulating radio carrier
waves with intelligence signals. The service zone of the base
station is, of course, limited to a certain geographical area,
the boundaries of which depend upon the power of the carrier
waves and the nature of the terrain.
Basically, the prior art procedure is to assign a plurality
of two-way radiant energy radio channels to each base station
and to provide each mobile station with radio equipment capable
of transmitting and receiving every channel assigned to the base
station. In addition, each mobile station permanently assigned
to a geographical area served by a base station is given a unique
termination identified by a directory number in a conventional
switching central office. The switching office is, in turn, connected
by transmission lines, hereinafter referred to as land lines,
to the base station in order that communication paths may be
established between mobile stations and between mobile stations
and fixed telephone stations of the telephone direct distance
dialing network.
With the growth of mobile communication service, it is necessary
to provide communication facilities with low blocking features
and more efficient channel utilization of the available radio
frequency spectrum. In a large serving area, for example, an
area surrounding a metropolitan center, the prior art procedure
has been to assign all available radio channel frequencies to
high power transmitters located at or near the center of the
area. Under this arrangement, an increase in the number of mobile
stations necessitates additional radio channels be added until
the number of channels is equal to the maximum number of available
frequencies. Thus, for a large area, the system is limited by
the total number of available radio channels that can be assigned
to the area.
A more efficient system may be
obtained by dividing a metropolitan center into a number of small
serving areas, hereinafter referred to as cell areas, each equipped
with low power base transmitters and receivers.
In such a system a given radio frequency spectrum assigned
to a first base station of one cell area may be assigned to a
second base station of another cell area provided that there
is sufficient separation between the two cells assigned the same
radio frequency spectrum to prevent interference. The reuse of
a radio frequency spectrum within a metropolitan center will
permit the reuse of available radio channels to serve more mobile
stations than heretofore possible with the present mobile communication
systems. In such a system the cell areas may be quite small and
mobile stations may traverse several cell areas during the course
of a single conversation thereby requiring that communication
paths established to mobile stations be transferred from one
base station to another without loss of conversation. A prior
art automatic mobile radio telephone switching system such as
disclosed by R. A. Chaney in U.S. Pat. No. 3,355,556, issued
Nov. 28, 1967, is arranged to provide full telephone service
features to mobile stations located in a specific cell area.
Although the Chaney patent is a substantial contribution to the
technology it does not provide continuity of automatic telephone
service to mobile stations moving between separate cell areas.
Accordingly a need exists in the art for a mobile communication
system capable of locating predetermined mobile stations in a
plurality of cell areas each served by a base station. A need
also exists for an arrangement to establish and maintain continuity
of communication paths extending between mobile stations and
between mobile stations and fixed stations as located mobile
stations move in and between different cell areas.
SUMMARY OF THE INVENTION
In the exemplary embodiment an electronic data processor is
incorporated into a mobile communications system comprising a
plurality of base stations each located in individual cell areas.
The system is arranged to locate mobile stations in any cell
area and to establish communication paths between located mobile
stations and between located mobile stations and fixed stations.
Apparatus is provided to establish and maintain a record of communication
links serving located mobile stations.
Additional apparatus is provided to periodically interrogate
predetermined cell areas to detect the movement of located mobile
stations into new cell areas. Apparatus is also provided to establish
and record identity of communication links to the new cell areas
and to reassign existing communication paths to new communication
links while maintaining continuity of communication service.
In accordance with one feature of my invention directional antenna
apparatus is provided in each cell area to locate mobile stations
within particular cell areas.
Another feature of my invention is the provision of a stored
program electronic data processor to assimilate location information,
assign communication links, and process service requests for
mobile stations located in a plurality of cell areas. Another
feature of my invention is the provision of switching apparatus
wherein communication paths may be established between located
mobile stations and between located mobile stations and fixed
stations connected to the telephone direct distance dialing network.
In accordance with still another feature of my invention dual
access switching apparatus is provided wherein communication
paths established over communication links to certain cell areas
may be switched onto communication links to other cell areas
while maintaining continuity of communications between roaming
mobile stations.
[The patent continues with dozens of pages]
Text and images of patents are available in many places. Among
them:
http://www.uspto.gov
http://www.delphion.com/
FROM US PATENT 3663762: MOBILE
COMMUNICATION SYSTEM
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