Lucent Technologies Inc.

At&t Ipm Corp.

William J Nealon

Heidi Anne Rajan

Guido Bertocci

Walter Tomkoski

Hon-Chi Yu

Siegfried F Rehwinkel

A cordless telephone system achieves synchronism for each one of multiple portable units to the same communication channel for communicating with a common base unit. The cordless system uses a dual channel process to allow both the freedom to dynamically change channels as needed to avoid interference while simultaneously providing a capability to resynchronize any portable unit with the base unit on a selected active channel. This is achieved through the use of a fixed service channel and an active channel which changes as needed. If a channel change is made during a call, after the call is completed, the base unit returns to the previous active channel and broadcasts a message to the multiple portable units indicative of the new active channel. Also, any portable unit that attempts to communicate with the base unit on the wrong channel and fails to get a response will transmit a message on the fixed service channel requesting the current active channel from the base unit. Responsive to this request, the base unit provides information indicative of the active channel over the service channel. Once equipped with the current active channel information, the portable unit is able to reach and establish communications with the base unit.

Apparatus and method for synchronizing a cordless telephone base unit

A cordless telephone arranged for operation in a frequency hopping system includes an arrangement which achieves optimum utilization of multiple cordless telephone portable units by permitting these units to access a common base unit and also access each other. The portable units are configured for subsequent operation with the base unit and each other during a registration process by having the base unit select from a plurality of communication channels available in the frequency hopping system a different starting channel for each one of the portable units. The portable units are thereby advantageously selectably addressable by the base unit and by each other. Any one of the registered portable units, for example, is capable of selectively paging and communicating with any other one of the registered portable units over selected ones of the plurality of communication channels. Once a base unit establishes a communication link with a portable unit, or a portable unit establishes a communication link with another portable unit, using set-up channels designated for such purpose, both units move away from these channels. Another two units, two unoccupied or free portable units, for example, may then advantageously also use these set-up channels for establishing another communication link.

Cordless telephone arranged for operating with multiple portable units

A cordless telephone system includes an arrangement wherein multiple portable units operate with a common base unit using the same security code without conflict or confusion. When a portable unit attempts to establish a radio link with the base unit, for example, this originating portable unit generates a random number which is retained by this unit and also transmitted to the base unit. This random number is substituted for the common stored security code, then shared by the base unit and all of the portable units, for creating a temporary unique security code that is known only to the base unit and the originating portable unit. Interference from other portable units attempting to gain access to the base unit while the originating portable unit is actively communicating with the base unit is thereby advantageously prevented.

Cordless telephone base unit arranged for operating with multiple

A cordless telephone arranged for operation in a frequency hopping system includes multiple portable units configured for operation with a base unit and with each other by having the base unit pseudo randomly select from a plurality of communication channels available in the frequency hopping system a different starting channel for each one of the portable units. Each portable unit then provides initial communications with the base unit over the selected starting channel of the portable unit. For maintaining communications during a frequency hopping cycle between a portable unit and the base unit, the portable unit and base unit both generate a set of communication channels from the starting channel assigned to the portable unit for subsequent use in communicating over the radio frequency link. Each of the portable units is configured for operation with the base unit and with each other during a registration procedure. Information indicative of the starting channel for each portable unit and also a security code is transmitted to each of the portable units from the base unit during this registration procedure and on a predetermined communication channel at a radiated energy level well below the level normally used for normal communications.

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Neptune City, NJ, United States of America

William J Nealon