Method and apparatus for providing a private communication system in a public switched telephone network

Abstract

A private communication network through which a plurality of member users communicate using the public switched telephone network (PSTN) is disclosed herein. Each member user utilizes either a modified land line telephone directly connected to PSTN, or uses a modified mobile telephone operatively coupled to the PSTN through a wireless communication system. The private communication network includes network call manager having a telephone network interface for establishing a telephone connection with each of a plurality of telephone lines of the PSTN. Each of the plurality of telephone lines is associated with one of the plurality of member users. The network call manager further includes a switch matrix, coupled to the telephone network interface, for providing an information signal received from an active member user over a selected telephone line to the remaining non-active member users. A network call manager controller identifies the active member user the basis of push-to-talk (PTT) request signals received from the member users'telephones over the plurality of telephone lines. The telephone set of each member user will typically be capable of both standard telephone operation as well as of PTT operation over the private communication network. The security of the PTT private network may be enhanced by configuring each telephone set for encryption of all such reverse link transmissions, as well as for corresponding decryption of the forward link information from the active member user.

Description

CROSS-REFERENCE TO RELATED APPLCATION[0001]This application is a reissue of application Ser. No. 08 / 595,566, filed Feb. 1, 1996, now Pat. No. 5,912,882.BACKGROUND OF THE INVENTION[0002]I. Field of the Invention[0003]The present invention relates generally to multiparty communication systems, and, more particularly, to a point-to-multipoint private communication network directly incorporated within a cellular or land line telephone system.[0004]II. Description of the Related Art[0005]Mobile cellular telephone service has been in use for some time, and traditionally has been characterized by a central site transmitting with high power to a limited number of mobile or portable units in a large geographic area. In early cellular systems only a limited number of radio channels were available, thus limiting the number of radiotelephone conversations within an entire metropolitan area to the number of channels available.[0006]Modern cellular radiotelephone systems have a comparatively larg...

AI Technical Summary

Benefits of technology

[0017]The telephone set of each member user will typically be capable of both standard telephone operation, and of PTT operation over the private communication network. When configured for PTT operation, each telephone set receives and digitally processes input voice or data information from a member user. The resultant vocoder data packets, as well as any PTT request signals initiated by the member user, are then supplied to a modem for reverse link transmission via the PSTN to the telephone network interface of the network call manager. The security of the PTT private network may be enhanced by configuring each telephone set for encryption of all such reverse link transmissions, as well as for corresponding decryption of the forward link information from the active member user.

Problems solved by technology

In early cellular systems only a limited number of radio channels were available, thus limiting the number of radiotelephone conversations within an entire metropolitan area to the number of channels available.

This results from the incapability of cellular systems to establish “point-to-multipoint” communication networks among a set of member users.

However, the infeasibility of providing repeater stations over a large geographic area limits the extent to which the set of member users may be geographically dispersed.

Although both cellular and conventional land line telephone systems are capable of facilitating communication between widely separated users, closed “PTT-type” communication networks have not hitherto been incorporated within either type of system.

This may be due in part to the absence of a convenient mechanism for automatically joining an identified set of users into such a closed network.

Moreover, even if such a mechanism were available, both types of systems are easily compromised by unauthorized third parties and are thus unsuitable for secure communication.

The conference calling capability provided by both cellular and land line carriers is also an unsuitable surrogate for a PTT-type communication network.

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