Private cellular system

• US 4,771,448 A
• Filed: 04/10/1987
• Issued: 09/13/1988
• Est. Priority Date: 11/18/1986
• Status: Expired due to Term

• Current Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Original Assignee: Northern Telecom Limited (Nortel Networks Corporation)
• Inventors: Fatica, Bambino, Koohgoli, Mahshad
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/036,730
• Time in Patent Office: 522 Days
• Field of Search: 379/61, 379/63, 379/60, 379/59, 379/58, 455/33
• US Class Current: 455/450
• CPC Class Codes: H04W 16/04 Traffic adaptive resource partitioning
• CPC Class Codes: H04W 16/16 for PBS [Private Base Station] arrangements
• CPC Class Codes: H04W 84/16 WPBX [Wireless Private Branch Exchange]
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A cellular mobile radio communication (e.g. telephone) system (hereinafter referred to as a private cellular system, PCS) that does not have the constraint of being a well defined, pre-planned system. The present invention differs from previous systems largely by the fact that it does not have to be well planned in advance. A user can simply install a base station virtually wherever he desires. Each base station is "intelligent" and produces a dynamic allocation. This of course means that if one were to install such a system, for example in an office building, no studies would be required. One would simply install a series of base stations.

Claims

1. A private cellular system for providing a wireless communication service, said system characterized by:

at least one base station for connection to a telephone switching means, said base station capable of transmitting and receiving simultaneously on a plurality of frequencies;

a plurality of portable terminal units for communicating with said base station, each said portable terminal unit capable of receiving on at least a first frequency while simultaneously transmitting on a second frequency;

each said portable terminal unit capable of scanning at least some of the plurality of frequencies on which said base station can transmit and said portable terminal unit can simultaneously receive two of said frequencies on which said base station can transmit;

said portable terminal unit includes means to initiate a call by;

(a) monitoring a common wireless signalling channel for communication between said portable terminal units and at least one base station;

(b) sending a request for service message to said base station, when said common wireless signalling channel is deemed idle;

(c) receiving offer messages destined for said terminal unit and sent by contending base stations;

(d) evaluating each said offer message and accepting the offer message that meets the criteria of (i) the information channel offered by the base station is idle in the terminal unit'"'"'s vicinity and (ii) the offer message has the best weighting of the signal strength of the terminal unit'"'"'s signal as received by the base station, the received signal strength by the terminal unit, and any priority level given by the base station via the offer message;

(e) acknowledging acceptance of one offer message by sending an acknowledge message to said base stations, said acknowledge message including the indentification of the base station whose offer has been accepted; and

(f) turning on a corresponding up-link information channel, in response to the detection of a wireless carrier signal on the selected down-link information channel.

2. The private cellular system of claim 1 wherein said portable terminal unit further includes means to process, and means to act on, messages received on one of said frequencies on which said base station can transmit.

3. The private cellular system of claim 1 wherein said communication service is a telephone service.

4. The private cellular system of claim 1 wherein said common wireless signalling channel, said down-link information channel, and said corresponding up-link information channel are all in the radio-frequency spectrum.

5. The private cellular system of claim 2 wherein each said base station further includes means to:

(a) receive a request for service message from said portable terminal units;

(b) evaluate each said request for service to ensure that it has been properly received, to ensure that there is a wireless information channel available, and that there is at least one land information channel available to said telephone switching means;

(c) selectively send an offer to provide service message in response to the evaluation performed in step b;

(d) receive an acknowledgement of acceptance of said offer message by a terminal unit whereby said base station turns on the down-link wireless information channel in response to the reception of said acknowledgement, otherwise said base station times out and returns to the idle state; and

(e) receive a corresponding up-link wireless information channel and in response to the reception of said up-link wireless information channel, to connect said terminal unit to said telephone switching means.

6. A method of operating a private cellular system for providing a wireless communication service using a plurality of base stations and a plurality of portable terminal units, said method characterized by:

(a) monitoring at each portable terminal unit the idle status of a common wireless signalling channel used for communication between said portable terminal units and said base stations;

(b) selectively transmitting a request for access to an information channel between one said portable terminal unit and said base stations in response to said signalling channel being idle;

(c) at each said base station that receives said request for access to an information channel (i) checking to see if the request was received properly, (ii) checking to ensure that there is at least one wireless information channel to offer, and (iii) checking to ensure that there is at least one land information channel available for use;

(d) each base station that received said request and at which all three conditions of step c are met, selecting one wireless information channel to be offered to said portable terminal unit and transmitting, to said portable unit, an offer to provide service message, said message comprising the identification of the portable terminal unit to which the offer is directed, the offered channel identification, an indication of the received signal strength at that base station, and a priority code indicative of the load status of said base station;

(e) said portable terminal unit evaluating each valid offer message and accepting the one that satisfies the conditions of (i) the offered information channel is idle in the portable unit'"'"'s area, and (ii) the offer message having the best weighting of the signal strength as received by the base station, the received signal strength at the portable terminal unit, and the priority code;

(f) the portable terminal unit acknowledging acceptance of one offer message by sending, via said wireless signalling channel, an acknowledge message containing the identification of the base station whose offer is being accepted;

(g) the base station whose offer has been accepted, responding by turning on the carrier on the offered down-link wireless information channel; and

(h) the portable terminal unit responding to the reception of the down-link carrier by turning on the corresponding up-link carrier.

7. A method of operating a private cellular system for providing a wireless communication service using a plurality of base stations connected to at least one telephone switching means, and a plurality of portable terminal units, said method at each said base station characterized by:

(a) monitoring a wireless information channel to detect requests for access to an information channel, as sent by said portable terminal units;

(b) in response to reception of a request for access to an information channel, performing the steps of (i) checking to see if the request was received properly, (ii) checking to ensure that there is at least one wireless information channel to offer; and

(iii) checking to ensure that there is at least one land information channel available for use;

(c) if all three conditions of step c are met, selecting one wireless information channel to be offered to said portable terminal unit and transmitting, to said portable terminal unit, an offer to provide service message, said message comprising the identification of the portable terminal unit to which the offer is directed, the offered channel identification, an indication of the received signal strength at that base station, and a priority code indicative of the load status of said base station; and

(d) said base station, upon notification of acceptance of said offer, responding by turning on the carrier on the offered down-link wireless information channel, and if said offer is not accepted, said base station timing out and returning to the idle state.

8. The method of claim 7 further including the step of registration, whereby each base station receives periodically, registration messages from the portable terminal units and stores a list of the identification of those portable terminal units at said base station.

9. A method of operating a private cellular system for providing a wireless communication service using a plurality of base stations connected to at least one telephone switching means, and a plurality of portable terminal units, said method at each said portable terminal unit characterized by:

(a) monitoring the idle status of a common wireless signalling channel used for communication between said portable terminal units and said base stations;

(b) selectively transmitting a request for access to an information channel between said portable terminal unit and one said base station in response to said signalling channel being idle;

(c) monitoring said common wireless signalling channel for offer to provide service messages from said base stations, and evaluating each valid offer message and accepting the one that satisfies the conditions of (i) the offered information channel is idle in the portable unit'"'"'s area, and (ii) the offer message having the best weighting of the signal strength as received by the base station, the received signal strength at the portable terminal unit, and a priority code; and

(d) acknowledging acceptance of one offer message by sending, via said wireless signalling channel, an acknowledge message containing the identification of the base station whose offer is being accepted.

10. A base station for use in the operation of a private cellular system for providing a wireless communication service using a plurality of base stations connected to at least one telephone switching means, and a plurality of portable terminal units, said base station characterized by:

(a) first means for monitoring a wireless information channel to detect requests for access to an information channel, as sent by said portable terminal units;

(b) second means, responsive to reception of a request for access to an information channel for performing the steps of (i) checking to see if the request was received properly, (ii) checking to ensure that there is at least one wireless information channel to offer; and

(iii) checking to ensure that there is at least one land information channel available for use;

(c) third means, responsive to the output of said second means, for selecting one wireless information channel to be offered to said portable terminal unit and for transmitting, to said portable terminal unit, an offer to provide service message, said message comprising the identification of the portable terminal unit to which the offer is directed, the offered channel identification, an indication of the received signal strength at that base station, and a priority code indicative of the load status of said base station; and

(d) fourth means, responsive to notification of acceptance of said offer, for turning on the carrier on the offered down-link wireless information channel, and if said offer is not accepted, for timing out and returning said base station to the idle state.

11. A portable terminal unit for use in the operation of a private cellular system for providing a wireless communication service using a plurality of base stations connected to at least one telephone switching means, and a plurality of portable terminal units, said portable terminal unit characterized by:

(a) first means for monitoring the idle status of a common wireless signalling channel used for communication between said portable terminal units and said base stations;

(b) second means for selectively transmitting a request for access to an information channel between said portable terminal unit and one said base station in response to said signalling channel being idle;

(c) third means for monitoring said common wireless signalling channel for offer to provide service messages from said base stations, and for evaluating each valid offer message and for accepting the one that satisfies the conditions of (i) the offered information channel is idle in the portable unit'"'"'s area, and (ii) the offer message having the best weighting of the signal strength as received by the base station, the received signal strength at the portable terminal unit, and a priority code; and

(d) a fourth means for acknowledging acceptance of one offer message by sending, via said wireless signalling channel, an acknowledge message containing the identification of the base station whose offer is being accepted.