Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-05-21
2001-10-30
Trost, William (Department: 2683)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S458000, C455S466000
Reexamination Certificate
active
06311060
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to communicating data via a cellular network control channel of a cellular mobile radiotelephone system and more particularly relates to a method and apparatus for triggering the registration of the location of a mobile cellular communications device.
BACKGROUND OF THE INVENTION
In recent years, the communications industry has shown a growing interest in various types of wireless communications systems for communicating voice and/or data between numerous remote sites and a central location. It is well recognized that the use of a dedicated telephone facility for a conventional telephone system is not a convenient or economical option for all communications applications. For example, individuals who must be away from their base of operations have a need to conveniently and efficiently communicate with their base. Likewise, for many industrial applications, a central data collection site has a need for acquiring information from a variety of remotely located monitoring devices that collect data about the operation or performance of equipment. To overcome the limitations of a conventional telephone system, a two-way wireless communications link is often necessary to permit a response to a communication initiated from another location. In an attempt to solve the problem of supplying a response to an initial communication, the industry has offered various wireless communications systems, such as mobile radiotelephones.
One form of two-way communications is a cellular mobile radiotelephone (CMR) system, which is connected to the extensive public switched telephone network (PSTN) and permits communications between a mobile radiotelephone user and anyone with a conventional telephone (or another radiotelephone). Typical CMR systems are characterized by dividing a radio coverage area into smaller coverage areas or “cells” using low power transmitters and coverage-restricted receivers. As shown in U.S. Pat. Nos. 3,906,166 and 4,268,722, the limited coverage area enables the radio channels used in one cell to be reused in another cell. As a cellular mobile radiotelephone within one cell moves across the boundary of the cell and into an adjacent cell, control circuitry associated with the cells detects that the signal strength of the radiotelephone in the just-entered cell is stronger, and communications with the radiotelephone are “handed-off” to the just-entered cell. Thus, a CMR system can supply two-way communications for an array of cells, thereby supplying communications for a much wider area than conventional two-way radios.
A radiotelephone can “roam” between CMR systems and still place calls as well as remain accessible to receive calls from other callers. This is accomplished by means of a roaming system. Usually, a radiotelephone has a “home” CMR system in which the radiotelephone's Mobile Identification Number (MIN) and billing account are initially established. Because many CMR systems are capable of communicating information between themselves, the roaming system permits a home CMR system to contact a roaming radiotelephone by sharing information with a “foreign” CMR system. A CMR system can contact a radiotelephone and inform it about an incoming call by transmitting a Mobile Station Control Message to the radiotelephone within the cell in which the radiotelephone resides.
The most common of these Mobile Station Control Messages is commonly referred to as a “page”, which is carried within a Mobile Station Control Message over a cellular network control channel. By monitoring the cellular network control channel, a radiotelephone within the CMR system can receive and analyze each page that is transmitted by the CMR system. Among other information, a page includes the MIN of the radiotelephone to which a connection is sought. The radiotelephone responds to a page that contains the MIN assigned to the radiotelephone. To avoid paging radiotelephones in every CMR system when a call is attempted, many CMR systems keep track of which radiotelephones are in the CMR system's coverage area.
Generally, a radiotelephone will monitor a cellular network control channel which transmits Mobile Station Control Messages including information such as the CMR system's System Parameter Overhead Message (SPOM) and the Global Action Overhead Message (GAOM). When the radiotelephone roams from its home CMR system and into a foreign CMR system, it will lose contact with the home CMR system's cellular network control channel, which is referred to as “losing synch.” When a radiotelephone loses synch, it will scan the range of available radiotelephone frequencies for a new cellular network control channel. Where the radiotelephone has roamed into the coverage area of a foreign CMR system, the new cellular network control channel will be transmitting a control message that identifies the foreign CMR system. One way the control message can be used to distinguish the transmitting CMR system from other CMR systems is by including a unique System Identification Number (SID) with the control message's data. The monitoring radiotelephone will then recognize that the SID contained in the current control message is different from the SID of the control message that was previously received and will transmit an autonomous registration signal.
The autonomous registration signal tells the foreign CMR system that the radiotelephone is roaming and identifies the radiotelephone's home system. After contacting the radiotelephone's home CMR system and verifying that the roaming radiotelephone is a valid user of the home CMR system, the foreign CMR system will enable the radiotelephone to operate in the foreign CMR system as if the radiotelephone were in its home CMR system. Thus, the roaming radiotelephone can place and receive calls. Because the radiotelephone is registered as a user in the foreign CMR system, pages corresponding to calls being made to the radiotelephone need only be broadcast in the CMR system where the radiotelephone is registered.
A conventional CMR system operates on a 50 MHz range of frequencies in the 800 MHz and 2,000 MHz frequency bands. The frequency range is divided into channels which can transmit either control data or voice data. The control data is used to setup incoming and outgoing radiotelephone calls. The channels which carry such control data are the cellular network control channels, which are also described as “control channels.”When a radiotelephone user attempts to place a call, the radiotelephone transmits control data over the control channel to the CMR system. This control data will be transmitted in the form of a “call origination signal” which alerts the CMR system to the user's desire to place a call. The CMR system responds by transmitting control data to the radiotelephone via the control channel to assign another channel (a voice channel) that can be used to transmit voice data (i.e., the callers' conversation). A conventional CMR system typically has 42 control channels that are divided into two sets of 21 control channels. Separate radiotelephone carriers (designated as Carrier A or Carrier B) can provide radiotelephone service support for the individual sets of control channels. For the purposes of this discussion, a radiotelephone will be referred to as being tuned to either “System A” or “System B”, depending on the set of control channels that the radiotelephone is using to communicate.
A conventional CMR system has both cellular network control channels and cellular network voice channels. Generally, the control channels permit the transmission of the information used by the CMR system to complete a call placed by a radiotelephone or placed to a radiotelephone. The voice channels, on the other hand, are used to transmit the voice communications of the calling party and the called party, as well as a limited occasional amount of data related to the established voice communications (e.g., a power level change order). A conventional CMR system utilizes the control ch
Britain David J.
Comer Edward I.
Evans Thomas F.
Cellemetry LLC
Gesesse Tilahun
Kilpatrick & Stockton LLP
Trost William
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