Abstract: A transceiver device having a forward error correction decoder providing at least one forward error correction metric and a data integrity monitor providing at least one automatic retry query metric to a data processor or CPU. The data processor or CPU is responsive to the forward error correction metric and the automatic retry query metric and has outputs providing a forward error correction value and an automatic retry query value to the forward error correction/data encoder and decoder.

Abstract: A technique is disclosed for allowing a seamless handover between base stations in a TDMA controller as a telephone handset is transported from one base station's area to another. The disclosed circuitry enables the TDMA controller to assess the quality of the handover before switching to the new base station. When it is determined that a handover operation is to commence, transmissions are made in the original slot time and a handover slot time within the same frame. Also during the same frame, data is received at two separate slot times. Only when it is determined that the data received in the handover slot time contains no transmission errors is the handover completed by then only transmitting on the handover slot transmit time and receiving on the handover slot receive time. In the preferred embodiment, it is determined whether the received data contains no transmission errors by detecting the CRC codes, the signal strength, and the existence of any invalid words.

Abstract: A multi-tasking, dynamically controlled micro-sequencer for use in a TDMA communication system is described. Rather than the output of the sequencer being solely a linear sequence of instructions in a microcode RAM, the output of the sequencer is augmented by an output of finite state machines (FSMs) providing a sequence of control codes. The FSMs provide control signals for building a slot in accordance with a specific protocol. The sequencer core provides enabling signals to the FSMs to enable the proper FSM depending upon the mode of the transceiver. A conditional logic block is included in the sequencer core which detects special operation codes (opcodes) for each slot to cause the microcode sequence to jump to a certain routine if a condition is met or not met.

Abstract: An audio error mitigation technique for a TDMA communication system is disclosed. An audio error is assumed if any one of the following criteria is met: a detection of a CRC error in the control data or audio data within a slot; the received signal strength is below a certain threshold; or, the detection of an invalid code word, such as an all zero nibble. If either of the criteria is met, and the slot contains audio data, an error mitigation routine is performed. In one embodiment, the error mitigation routine replaces the faulty burst with the previous non-faulty burst. In another mitigation routine, any dv/dt spikes in the faulty burst are detected and smoothed by averaging nearby samples. In one embodiment, both mitigation routines are selectable in the TDMA system.

Abstract: A multi-tasking, dynamically controlled micro-sequencer for use in a TDMA communication system is described. Rather than the output of the sequencer being solely a linear sequence of instructions in a microcode RAM, the output of the sequencer is augmented by the output of finite state machines (FSMs) providing a sequence of control codes. The FSMs provide control signals for building a slot in accordance with a specific protocol. The sequencer core provides enabling signals to the FSMs to enable the proper FSM depending upon the mode of the transceiver. A conditional logic block is included in the sequencer core which detects special operation codes (opcodes) for each slot to cause the microcode sequence to jump to a certain routine if a condition is met or not met.

Abstract: A TDMA communication system having a selectable synchronization code receive window is described. To eliminate any false detections of a synchronization code, a selectable window is created during which the synchronization code is expected to appear. The size of the window is reduced once the synchronization code is detected. In one embodiment, the size of the window is based on the elapsed time since the last synchronization of the TDMA system.

Abstract: A synchronization method for synchronizing a plurality of base stations in a TDMA communication system is disclosed. The synchronization topology may be via dedicated hardwire, via any DSL from the PSTN, or via an ad-hoc RF synchronization technique. Slots containing data are arranged in frames and these frames are transmitted to the base stations, and received from the base stations, by wireless telephone handsets. Each of the slots in a frame have a guard field comprising a plurality of guard bits. The base stations derive frame sync pulses via the received Unique Word correlation detect. These derived frame sync pulses are ultimately synchronized with frame sync signals received from the master base station.

Abstract: A method and apparatus increases spectrum efficiency in a wireless communication system having base stations which may be positioned to operate within range of one another. The method and apparatus eliminates the requirement for a base station to periodically transmit to maintain synchronization with an associated handset (504). The handset effectively assumes the role of a base station when making a call (508). The handset will synchronize with other handset traffic or another base station which is within range (506). The handset will then page the base station (510). Eliminating the requirement that the base station repeatedly transmit a signal to maintain sync with a handset significantly increases the available spectrum allocation for providing communication. Reversing the role of a handset also enables handset-to-handset communication independent of the base station (808).

Abstract: A method and structure for virtually eliminating any false detections of a synchronization code is described which creates a selectable window during which the synchronization code is expected to appear. A coincidental replication of the synchronization code outside the window does not trigger false synchronizations.

Abstract: A method provide delays during memory dialing by automatically inserting pause characters within the dialing sequence based upon the user's entry of the dialing sequence. The method establishes a time-out period (64) when storing dialing sequences, and adds a pause character (66) to the dialing sequence if the time-out has expired. The method also determines whether any digit keys have been selected (68) to be stored in the sequence. Finally, the method monitors the tip and ring line of a standard telephone line to detect a far end ringing signal (76) and insert a special pause character (78). The special pause character will provide a delay until a far end pickup is detected during automatic dialing.

Abstract: A method for transparently coupling an encrypted two-way RF communication unit (100) with an encrypted landline communication unit (104). An RF message comprised of a plurality of data frames (401,402, 403) is transmitted from the RF communication unit (100), wherein a plurality of the data frames include encrypted voice information (403). Some bits from the data frames (501,502) are selectively removed, without removing the encrypted voice information (503), to form reduced bit data frames, and the reduced bit data frames are transmitted via the landline to the landline communication unit (104).

Abstract: In a wireless communication system comprising a plurality of fixed communication units (FCUs) (102) and portable communication units (PCUs) (120), each comprising an encryption synchronization counter (ESC) (314, 414), the PCU and FCU having a digital transmission format (201), a method of maintaining encryption and decryption throughout a hand-off is shown, comprising the steps of:(a) loading (708) during a hand-off initiation a continuation value for a second FCU ESC; and(b) incrementing (709) synchronously the second FCU ESC and the PCU ESC, starting from the continuation value and beginning at the time of hand-off completion.

Abstract: In frequency-hopping spread-spectrum systems, it is necessary to maintain frequency and bit synchronization (sync) between the transmitter and receiver in order to maintain quality data recovery at the receiver. A protocol is described which includes a synthesizer lock field (109) to allow frequency sync, a clock sync field (123) to achieve quick clock sync, and a data sync field (125) to provide data sync. Other fields are provided in the protocol to allow both voice (141) and data (127) transmissions, inband signalling (139), and error correction (143). A method and apparatus, driven by a microprocessor (303) and ASIC (301) combination, are described that generate and transmit this protocol.

Abstract: In frequency-hopping spread-spectrum systems, it is necessary to maintain frequency and bit synchronization (sync) between the transmitter and receiver in order to maintain quality data recovery at the receiver. Two transmissions in adjacent hop-time intervals may overlap because of various time delays within the system. Collision bits (203 and 207) are used to realign the transmitted messages in time. The base station (103) manufactures (401) the collision bits (203 and 207) and transmits them to the communication unit (101), which echoes back (503) the bits on its next transmission. If the bits received at the base station do not match the bits sent (407), the base station (103) initiates (409) collision maintenance such that the communication unit (101) can adjust its DPLL (331) to realign its transmissions in time.

Abstract: In a secure communication system, a method for generating dummy traffic to forestall cryptanalytic attack by traffic analysis. Both the dummy traffic signal and certain characteristics of the dummy transmissions, such as duration and inter-transmission delay, are derived from the same source.

Abstract: A secure Telephone Terminal apparatus and method is disclosed which permits clear analog or coded digital message signals to operate on a non-secure telephone network having conventional equipment. This Telephone Terminal is utilized as a Remote Interface at the location of each predetermined telephone subscriber authorized to receive and transmit coded message signals. Included within the Telephone Terminal is a telephone line interface, a telephone interface, a signal converting stage, and a mode selector, or controller. By utilizing a duplexer in the telephone interface and telephone line interface, the controller utilizes separate inbound and outbound signal paths to determine if a coded message signal is about to be received and switches the mode accordingly. This permits either subscriber to select the coded mode regardless of which subscriber initially set up the call.

Abstract: A Gateway apparatus and method is disclosed which permits secure, end-to-end communications to exchange automatically between predetermined authorized subscribers operating on a radio network and a telephone network. The Gateway determines whether clear or coded message signals are to be routed from one network to another without utilizing an intervening decryption and encryption to accomplish the interconnection. The Gateway includes a radio network interface, a telephone network interface, a signal processor, and a supervisory controller. A Remote Interface at the location of the predetermined telephone subscriber is utilized to adapt a conventional telephone for clear and coded modes of operation. Moreover, an alternate embodiment is disclosed which permits two radio networks to be interconnected via the telephone network by utilizing two Gateways.