Abstract: A mobile telephone able to save power in response to the position of the mobile telephone is disclosed. Location circuitry within the mobile telephone enables the establishment of one or more deep-sleep locations associated with a mobile telephone. When the location circuitry determines that the current location of the mobile telephone is within a selected distance of one of the deep-sleep locations, the mobile telephone operates according to a low power mode of operation wherein only a timer enabling periodic updates of the mobile telephone's position is active. If the location circuitry determines that the mobile telephone is not within a selected distance of one of the predetermined locations, the mobile telephone operates in a standby mode which utilizes more power than the deep-sleep mode but still conserves battery power and enables the mobile telephone to receive calls.

Abstract: An antenna operable in two disparate frequency bands is disclosed as including a first quadrifilar helix having four conductive elements arranged helically to define a cylinder of substantially constant radius, where the first quadrifilar helix is formed of two bifilar helices arranged orthogonally and excited in phase quadrature. A quadrature feed network is connected to the first quadrifilar helix, wherein one end of a coupling element thereof is connected to a first end of each conductive element. The quadrature feed network also includes a first feedpoint for operation of the antenna with circular polarization in a first frequency band and a second feedpoint for operation of the antenna with linear polarization in a second frequency band.

Abstract: A telecommunications system and method for minimizing interruptions to voice transmissions due to the transmission of overriding control signals is disclosed. Since FACCH and other control signals replace or block-out speech data, the quality of speech transmissions deteriorates the longer the control transmission. Through modifications to the FACCH protocol, lengthy sequential FACCH or other control transmissions are divided into a plurality of discrete control segments, which are transmitted non-sequentially throughout a speech transmission, and queued at the receiving end. After receipt of all of the control segments, the original control message is reconstructed and forwarded for processing.

Abstract: A system for generating a pseudo-random bit sequence which may be used in enciphering digital data prior to transmission or storage of the data. The bit sequence is generated by expanding a plurality of secret key bits in a manner suitable for implementation with a conventional microprocessor arithmetic logic unit (ALU). The system of the present invention may be used, for example, to secure voice or data communications between a base station and a mobile station in a digital cellular communications system.

Abstract: A system for the authentication of mobile stations and base stations in a cellular communications network. The system includes an algorithm which generates not only a key dependent response to a random challenge, but also a temporary conversation key or call variable which may be used to encipher traffic in the network. To protect against clones in the network, the algorithm uses a rolling key which contains historical information. A bilateral authentication procedure may be used to update the rolling key and to generate a new conversation key.

Abstract: A system for the synchronization of encryption and decryption in a duplex cellular radio system in which an encrypted call may be switched from one cell to another. At the instant of handoff, a rapid first resynchronization means temporarily seizes the voice channel in one direction only and transmits synchronization information in such one direction. The first resynchronization means ceases to transmit the synchronization information and releases such one direction of the voice channel as soon as an indicator of successful resynchronization is detected in the other direction. Transmission of speech traffic in such one direction is then resumed after such detection of successful resynchronization.

Abstract: In a phase locked loop having a variable divider, a dual modulus counter is used to provide the variable divider with selection signals. The variable divider is capable of providing an overall division ratio in increments of one over a contiguous range of values. The dual modulus counter includes a counter, a comparator and logic gates which generate selection signals that allow the variable divider to divide an input signal by at least division ratios R1 and R2. A phase locked loop utilizing the dual modulus counter is particularly well suited for use in a digital frequency synthesizer.

Abstract: A system for the synchronization of encryption devices in a digital cellular communications system. Each of the encryption devices includes a multi-bit counter and generates a pseudo-random keystream which is combined with the data to be encrypted. The keystream is a function of the multi-bit counter value which is periodically incremented in response to a series of clock pulses. To allow proper decryption of the encrypted data, the system of the present invention provides continuous or very frequent updates of the transmitter counter value which may be used to reset the receiver counter and to resynchronize the system without the necessity of reinitialization and repetition of the intervening clock pulses.