At&t Bell Laboratories

At+t Corp.

Michel L Hearn

Douglas A Spencer

Charles Y Farwell

Kelvin K Ho

Richard M Heidebrecht

David M Kissel

Michael J English

Richard Alan Windhausen

Kenneth Wayne Strom

John S Thompson

Kenneth Frank Smolik

Alan S Mulberg

Richard D Miller

Paul E Miller

Kenneth Yiu-Kwong Ho

Michael A Smith

Brian D Bolliger

Talmage P Bursh, Jr

LaJeana N Roberts

Jerome J Zelenski

Jeffrey A Williams

Marc K Dennison

A port system interfaces digital PBX's to any transmission facility having DSX-1 communications ports via a microprocessor controlled PBX port board connected between PBX switch fabric and a first DSX-1 communications port. A channel service unit (CSU) module coupled directly to the port board for communications with DS1 transmission lines defines a second DSX-1 communications port which is coupled to the first DSX-1 communications port. The CSU module also includes a T1 transceiver and line interface circuitry for coupling the CSU module to a DS1 transmission line. The combination of the port board and CSU module provide full functionality of conventional CSU's while the port board alone permits direct coupling of transmission facilities utilizing a DSX-1 communications port. For remote maintenance, a microprocessor of the port board is coupled to a control processor of a PBX for control of the port board microprocessor via the PBX control processor. Wiring test circuitry is provided in the CSU module to detect faults in the wiring between a CSU module and a DS1 transmission line. The CSU module includes a transmitter transformer having a center-tapped secondary winding and a receiver transformer having a center-tapped primary winding. A current limited current source is selectively connected between the center taps of the transmitter and receiver transformers such that, when connected, one or more transformers in a CSU/DS1 interface circuit which is faulty will saturate leading to failure of transmission tests and hence proper detection of the fault.

Port system for interfacing digital PBX to digital transmission facility

A CDMA cellular radio-telephone system (FIG. 2) has switching systems (201) synchronized to public telephone network (100) timing signals (600), and radio telephones (203) and cell base stations (202) synchronized to a different clock (1000). Transmission delays between the cell base stations and the telephone network are variable. Switching systems include digital communications interfaces (264) to the telephone system, whose connections to the telephone system are synchronized to the telephone system, and whose connections to the cells are nominally also synchronized to the telephone system but whose processor (602) operates for each call within predefined windows (1302, 1402) of phase relationships to the operation of the cell that is handling the call, and occasionally adjusts (FIGS. 13-16) its phase relationships to the operation of the telephone system to achieve and maintain its operation within the predefined windows. Packet-switched communications (350) between the cells and the switching systems absorb the phase relationship fluctuations and the timing adjustments in inter-packet intervals. Circuit-switched signal communications between the switching systems and the telephone system absorb the timing adjustments by means of vocoder (604)-implemented slips--bit insertions or deletions--in the communications traffic bit stream.

Adaptive synchronization arrangement

A wireless-access communications system, such as a CDMA cellular radio-telephone system (FIG. 2), comprises a packet-switched communications network (202, 207, 201) that interconnects cells (base stations; 202) with each other and with the public telephone network (100). Traffic of individual calls is packetized, and packet-bearing frames (300 in FIG. 7) of a plurality of calls are then statistically multiplexed and frame-relayed through the network to yield the high capacity, efficiency, and speed of traffic transport and handoff required for a CDMA cellular system. At each call processing unit (264 in FIG. 5), individual calls are handled by individual service circuits (602 and 612) which perform speech-processing functions such as coding and decoding, tone insertion, and echo cancellation, and packet-to-circuit-switched-PCM traffic conversion. Processors (602) adapt call processing unit timing to compensate for asynchrony between cells and call processing units and variations in call path transmission delays. Cell-to-cell communications, fixed call path addressing, and packetized control message transfers ensure that the same service circuit handles a call through even multiple soft handoffs (FIGS. 27-29) and efficiently communicates simultaneously with all cells involved in the handoff without involvement of system control entities and negative effect on system call-handling capacity. Both coded (packet-switched) and uncoded (circuit-switched) radio-telephone traffic are accommodated side-by-side. Wherever possible, existing and proven technology and component units are used to achieve low cost and high reliability.

Wireless access telephone-to-telephone network interface architecture

A CDMA cellular radio-telephone system (FIG. 2) has switching systems (201) synchronized to public telephone network (100) timing signals (600), and radio telephones (203) and cell base stations (202) synchronized to different clock (1000). Transmission delays between the cell base stations and the telephone network are variable. Switching systems include digital communications interfaces (264) to the telephone system, whose connections to the telephone system are synchronized to the telephone system, and whose connections to the cells are nominally also synchronized to the telephone system but whose processor (602) operates for each call within predefined windows (1302, 1402) of phase relationships to the operation of the cell that is handling the call, and occasionally adjusts (FIGS. 13-16) its phase relationships to the operation of the telephone system to achieve and maintain its operation within the predefined windows. Packet-switched communications (350) between the cells and the switching systems absorb the phase relationship fluctuations and the timing adjustments in inter-packet intervals. Circuit-switched digital communications between the switching systems and the telephone system absorb the timing adjustments by means of vocoder (604)-implemented slips--bit insertions or deletions--in the communications traffic bit stream.

Growing community of inventors

Broomfield, CO, United States of America

Michel L Hearn