Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-03-26
2001-06-12
Trost, William G. (Department: 2681)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S466000, C455S550100
Reexamination Certificate
active
06246875
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to subscriber cellular mobile radiotelephones. More specifically, the present invention is related to methods for efficiently registering cellular subscriber stations by automatically downloading system data pertaining to preferred foreign cellular providers with which the cellular subscriber stations can communicate.
BACKGROUND ART
The modern analog cellular system for mobile wireless duplex voice transmission called “Advanced Mobile Phone Service” (AMPS), uses the FCC assigned carrier frequency range of 800 to 900 MHz. Automobile-mounted cellular units transmit voice signals to a cellular base station within a given cell at up to one watt of power. Battery powered, hand-held cellular units transmit voice signals to a cellular base station within a given cell using up to one quarter watt of transmission power.
Despite the relatively low power output of the hand-held subscriber station, sustained power use and resulting decreased battery life is a major problem. Since a battery in a standard subscriber terminal is expected to last approximately one month, additional power drainage resulting in loss of battery life imposes substantial hardship on any subscriber using a portable handset. This problem is one of the major issues confronting designers of cellular handsets and systems today.
Conventional cellular subscriber stations are capable of communicating on at least one of two independent sets of frequencies. However, a conventional cellular base system normally communicates on only one of these two sets of frequencies. Thus, a cellular base system may be referred to as an “A” system if it uses one set of frequencies or a “B” system if it uses the other set of frequencies. This dual-system approach to radiotelephony results from regulations which are intended, at least in part, to promote competition in providing radiotelephone services.
When “A” and “B” cellular systems are both located in a single geographic area, radiotelephone service customers may choose to subscribe to either the “A” or “B” system in accordance with which system provides the best value to the customer. “B” systems are often referred to as “wireline” carriers because “B” systems are typically operated by 'the companies that provide wireline telecommunication services where the “B” systems are located. “A” systems are often referred to as non-wireline carriers because they are operated by companies other than the companies that operate the competing “B” systems. These frequency allocations are not necessarily permanent.
Each frequency set in a given cellular service area is assigned to one and only one carrier. However, in different service areas the same frequency set may be assigned to different carriers (much as a television channel may be assigned to an affiliate of one network in one city and to an affiliate of another network in another city).
The home frequency set of a given telephone unit is the set of frequencies which the unit will ordinarily attempt to use. This will depend in large part on which carrier is subscribed to by the telephone unit's user: if the user is a subscriber of a nonwireline carrier, the user's home frequency set will be the “A” frequencies, and vice versa.
As is well-known to those of ordinary skill in this field, a frequency set typically includes paging channels and associated signalling or control channels, as well as voice channels. The paging and control channels are used for preliminary coded communications between a cellular telephone and a cell site or base station in setting up a telephone call, after which a voice channel is assigned for the telephone's use on that call.
Each cellular carrier broadcasts a unique System Identification Number (SID) on all paging channels of the frequency sets on which it provides service in a given service area. A suitably equipped cellular subscriber station can thus determine which carrier is providing service on a given paging channel by identifying the SID. Usually the SID contains three digits.
Identification of a home SID is not necessarily required to be able to place a cellular call. Many carriers have reciprocal billing arrangements with one another, meaning that a call can be placed on a frequency associated with a non-home cellular system. However, use of a non-home carrier in this manner to place a call may result in the imposition of a surcharge (e.g., a fixed surcharge or a higher per-unit rate).
Furthermore, if the non-home carrier does not have a reciprocal billing arrangement with the user's home carrier, as a practical matter the user may not be able to place a call at all. Even though the telephone unit is capable of establishing a connection via the carrier signal, the non-home carrier's switching equipment typically will not allow the user to do anything with the connection without a way to bill the user for his or her usage. Some carriers automatically switch calls of this kind to an operator who can take down a credit card number. However, absent a billing arrangement of some kind, no call can be completed.
When a customer subscribes to a cellular system (either an “A” or “B” system), that system becomes the subscriber/customer's home system. The company that operates a customer's home system collects billing information and bills the customer for the customer's use of the home system's radiotelephone services. Whenever a customer is operating his or her cellular subscriber stations on a system other than the customer's home system, the customer is engaging in an activity known as roaming. The cellular system upon which a roaming cellular subscriber station is operating is viewed as a foreign system.
Subscribers may receive cellular telecommunication services while roaming. However, the home cellular carrier and the foreign cellular carrier must cooperate with one another before roaming services are permitted. For example, the foreign system must transfer call record information to the home system, and the home system must bill for, collect funds for, and distribute funds back to the foreign system for the roaming telecommunication services. Accordingly, the customer must typically pay additional charges when the customer uses roaming services.
When the customer operates his or her cellular subscriber station in the area covered by the cellular subscriber's home system, no serious cellular base system selection choice needs to be made. The customer will almost always want to use the home system because the charges for home-system telecommunication services will be less. On the other hand, when the customer is roaming away from the home system, a choice of whether to operate a cellular subscriber station on an “A” or “B” foreign system must be made.
Conventional cellular subscriber station handsets employ any one of several different programmable selection processes in choosing a cellular system upon which to operate. For example, a cellular subscriber station may prefer an “A” system but accept a “B” system if an “A” system is not available. This is called an “A/B” selection process. Conversely, a cellular subscriber station may prefer a “B” system but accept an “A” system if a “B” system is not available. This is called a “B/A” selection process. Alternatively, a cellular subscriber station may select only “A” systems (“A”-Only) or only “B” systems (“B”-Only) regardless of whether a competing system is available. Furthermore, a cellular subscriber station may select only the home system so that roaming is prohibited. Other selection processes may be implemented as well. A cellular subscriber station will typically utilize a default selection process which is consistent with its home system. For example, if a cellular subscriber station's home system is an “A” system, then the cellular subscriber station will typically utilize the “A”-Only or “A/B” selection processes as a default selection process.
Conventional cellular subscriber station handsets permit alteration of the default selectio
Farris Robert D.
Seazholtz John W.
Bell Atlantic Network Services Inc.
Contee Joy K.
McDermott & Will & Emery
Trost William G.
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