Bell Telephone Laboratories

At&t Bell Laboratories

Lucent Technologies Inc.

Alcatel-lucent USA Inc.

American Telephone & Telegraph Co., At&t Bell Laboratories

Ronald J Canniff

Alan Howard Matten

Ronald A Spanke

Alex Lawrence Wierzbicki

John J Stanaway, Jr

Peng Zhang

Meyer Joseph Zola

Philip C Chao

Mark Thomas Manfred

Charles E Stroud

Calvin Aaron

Harvey P Siy

Ali N Jablway

Thomas Lloyd Hiller

Michael R Kosek

Gordon K Lin

Mike A Derrenberger

A method and apparatus are provided for determining the quality of a speech transmission, including temporal clipping, delay and jitter, using a carefully constructed test signal () and digital signal processing techniques. The test signal that is to be transmitted through a speech transmission system () is created (). Then the test signal is transmitted through the speech transmission system such that the speech transmission system creates an output signal that corresponds to the input signal, as modified by the speech transmission system (). The test signal includes multiple segments () of speech signals interleaved with periods of silence. The periods of silence vary in duration according to a predefined pattern. Each segment of speech signals includes multiple predefined speech samples or symbols () interleaved with a plurality of silence gaps. The speech samples have a common period of duration, but the silence gaps do not. The output signal from the speech transmission system is preferably recorded () and analyzed to determine its quality, including temporal clipping (). This analysis preferably includes comparing the output signal with a reference signal derived from the test signal using a cross correlation function. A processor () coupled to memory () records and analyzes the output signal.

Method and apparatus for measuring the quality of speech transmissions that use speech compression

An enhanced Time Slot Interchange (TSI) facility, in addition to serving synchronous channels of communication, decomposes and composes asynchronous data cells to provide real-time communication among and between both synchronous and asynchronous channels served by a network access switch. An asynchronous cell comprises a 5 byte header and a 48 byte payload. The payload comprises voice samples from a temporarily defined set of DSO facilities and/or data from a variety of data facilities. Time slots of the TSI are temporarily assigned to the payload bytes of each incoming asynchronous cell; the payload bytes are stored in memory locations corresponding to those time slots; and the stored data is read out during time slots assigned to the destination channels of communication. The TSI comprises three data rams to accommodate for frame to frame jitter in the time of arrival of payload samples. Asynchronous cells are composed by transferring stored voice samples and data bytes to an asynchronous link during the times slots which are currently assigned to bytes of the composed cell payload. The header for outgoing asynchronous cells is inserted by a message handler.

Communication switch

This tone detector which is suited for dual tone multifrequency (DTMF) digit detection, separates the pairs of tones into a low frequency and high frequency group in which the other frequency group is attenuated by filtering. The amplitude of the low and high frequency groups serve as separate variable threshold reference signals. Individual tones are bandpass filtered with their corresponding outputs converted into an amplitude signal. The amplitude of the individually bandpass filtered tone signals are compared against the corresponding low or high frequency variable threshold signal for a determination of whether a tone is present. Preferably, additional validation steps are applied to the preliminary tone decisions to provide improved digit detection accuracy, especially in the presence of other signals such as speech.

Tone detector with improved performance in the presence of speech

A transmission scheme serially propagates time slot data to a plurality of TSI modules with time slot data contained in one TSI frame being serially transmitted from module to module in a daisy-chain technique. A dedicated outbound transmission bus transmits the frame of data from one module to a dedicated inbound transmission bus of another module. The outbound and inbound data buses are connected by separate buses on a backplane which is coupled to each of the TSI modules. Preferably, the TSI modules do not transmit selected ones of the stored data to end destinations until the last TSI module has received the frame of data so that all modules can begin the transmission in time synchronization. Maximum transfer data rates can be achieved since undesired transmission line characteristics or disruptions are minimized by the use of dedicated input and output transfer buses between the modules. Additional modules can be added without disrupting the transmission data rate between existing modules, thereby permitting a growable TSI facility without adversely impacting the data transmission rate between modules.

Expandable time slot interchanger

An arrangement where a plurality of digital signal processors cooperate in the performance of a digital signal processing function. The processors are interconnected by means of a synchronous network which provides time division multiplexed communication links between processors for communicating intermediate processing results therebetween. The synchronous network includes a plurality of port circuits each associated with one of the processors. The network generates timing signals defining frames of time slots and defining superframes comprising N frames. Each port circuit can control the transmission of digital data from a memory of its associated processor during M1 time slots of each superframe. Each port circuit can also control the writing of digital data to its associated processor during M2 time slots of each superframe. The value of N, the number of frames per superframe, is programmable. The values of M1 and M2 are also programmable for each port circuit.

Digital signal processor synchronous network

A method and apparatus for generating accurate digital representations of one or more sine waves. A digital signal processor is used to generate the sample digital values, spaced at period T, of a sine wave of frequency F, F&lt;1/2T, using recursive methods. The magnitude of the generated sample values is stabilized and controlled by normalizing the recursively generated samples from time to time, but not necessarily after each recursive calculation. Methods are described for generating values based on the values of two previously generated samples using the recursion formula: y(n)=y(n-1)2 cos.omega.-y(n-2) where .omega.=2.pi.FT and y(n), y(n-1) and y(n-2) represent three consecutive sample values. The normalizing factor, used for multiplying a recursively generated sample value to stabilize the amplitude, associated with this calculation is ##EQU1## where A is the desired amplitude. Methods are also described for generating two sine waves of the same frequency but displaced in phase, and for generating frequency and phase-shift keyed sine waves. Advantageously, these methods and apparatus minimize the resources required for performing the generation of the sine waves.

Method and apparatus for generating digital signals representing

An arrangement for selectively connecting a first or a second frequency synchronous timing signal to an outgoing conductor is disclosed. When a transition from the first to the second timing signal occurs, the first timing signal is inhibited from being transmitting on the outgoing conductor and the logical AND of the second timing signal and a delayed version of the second timing signal is transmitted on the outgoing conductor for approximately one period of the timing signals. Thereafter, the second clock signal is transmitted on the outgoing conductor. Arrangements are also disclosed for switching from the second timing signal to the first timing signal.

Timing signal distribution arrangement

A dual tone multifrequency and dial pulse receiver that receives 8000 digital data words per second, each of the data words including eight PCM bits representing the analog signal transmitted from a subscriber set and also including a line status bit indicating the DC status of the line. The receiver includes a time-shared processor which processes the PCM bits of 4000 words per second to detect tone-pairs and which also processes the line status bit of 4000 words per second to detect valid dial pulse sequences. The time-shared processor stores one of a first plurality of code words in a register when a tone-pair is detected and stores one of a second plurality of code words in the register when a valid dial pulse sequence is detected. Advantageously, the receiver can detect either dual tone multifrequency or dial pulse signaling from a subscriber even though the type of signaling to be used by the subscriber is not known a priori.

Dual tone multifrequency and dial pulse receiver

A digital concentrator system for use with a plurality of digital carrier systems in the telephone subscriber loop plant is disclosed. The concentrator system comprises a central office terminal (100), a remote terminal (102), and an interconnecting digital carrier path (108). In the transmit direction at each terminal (110,112), a plurality of multiplexed encoded signal streams are demultiplexed and the encoded signals stored. A selected number of encoded signals are retrieved and multiplexed for transmission to a distant terminal (112,110) as a concentrated pulse stream (123,175). In the receive direction at each terminal (110,112), the encoded signals in the multiplexed concentrated stream (125,177) are demultiplexed and stored. The stored encoded signals are retrieved and the original number of encoded signal streams are derived for transmission to the carrier terminal (100,102). Supervisory and control communication between the two concentrator terminals (100,112) is achieved by way of data messages on a derived data link. Operation between the transmit and receive directions at each terminal is asynchronous and controlled by a microcomputer (124,160). Signaling and class of service information are collected directly from the carrier terminals.

Line status detection in a digital concentrator system

A digital concentrator system for use with a plurality of digital carrier systems in the telephone subscriber loop plant is disclosed. The concentrator system comprises a central office terminal (100), a remote terminal (102), and an interconnecting digital carrier path (108). In the transmit direction at each terminal (110,112), a plurality of multiplexed encoded signal streams are demultiplexed and the encoded signals stored. A selected number of encoded signals are retrieved and multiplexed for transmission to a distant terminal (112,110) as a concentrated pulse stream (123,175). In the receive direction at each terminal (110,112), the encoded signals in the multiplexed concentrated stream (125,177) are demultiplexed and stored. The stored encoded signals are retrieved and the original number of encoded signal streams derived for transmission to the carrier terminal (100,102). Supervisory and control communication between the two concentrator terminals (110,112) is achieved by way of data messages on a derived data link. Operation between the transmit and receive directions at each terminal is asynchronous and controlled by a microcomputer (124,160).

Concentrator in a subscriber loop digital carrier system

A digital concentrator system for use with a plurality of digital carrier systems in the telephone subscriber loop plant is disclosed. The concentrator system comprises a central office terminal (110), a remote terminal (102), and an interconnecting digital carrier path (108). In the transmit direction at each terminal (110,112), a plurality of multiplexed encoded signal streams are demultiplexed and the encoded signals stored. A selected number of encoded signals are retrieved and multiplexed for transmission to a distant terminal (112,110) as a concentrated pulse stream (123,175). In the receive direction at each terminal (110,112), the encoded signals in the multiplexed concentrated stream (125,177) are demultiplexed and stored. The stored encoded signals are retrieved and the original number of encoded signal streams derived for transmission to the carrier terminal (100,102). Supervisory and control communication between the two concentrator terminals (110,112) is achieved by way of data messages on a derived data link. Operation between the transmit and receive directions at each terminal is asynchronous and controlled by a microcomputer (124,160). When all talking paths are in use through the concentrator system, a fast-busy encoded signal is multiplexed with other encoded signals and transmitted to the carrier terminal (100,102).

Generation of busy signals in a digital concentrator

A digital concentrator system for use with a plurality of digital carrier systems in the telephone subscriber loop plant is disclosed. The concentrator system comprises a central office terminal (100), a remote terminal (102), and an interconnecting digital carrier path (108). In the transmit direction at each terminal (110,112), a plurality of multiplexed encoded signal streams are demultiplexed and the encoded signals stored. A selected number of encoded signals are retrieved and multiplexed for transmission to a distant terminal (112,110) as a concentrated pulse stream (123,175). In the receive direction at each terminal (110,112), the encoded signals in the multiplexed concentrated stream (125,177) are demultiplexed and stored. The stored encoded signals are retrieved and the original number of encoded signal streams derived for transmission to the carrier terminal (100,102). Supervisory and control communication between the two concentrator terminals (110,112) is achieved by way of data messages on a derived data link. Operation between the transmit and receive directions at each terminal is asynchronous and controlled by a microcomputer (124,160). A PCM looping test for determining that a continuous path exists through the digital concentrator system is included.

Loopback test

A digital concentrator system for use with a plurality of digital carrier systems in the telephone subscriber loop plant is disclosed. The concentrator system comprises a central office terminal (100), a remote terminal (102), and an interconnecting digital carrier path (108). In the transmit direction at each terminal (110,112), a plurality of multiplexed encoded signal streams are demultiplexed and the encoded signals stored. A selected number of encoded signals are retrieved and multiplexed for transmission to a distant terminal (112,110) as a concentrated pulse stream (123,175). In the receive direction at each terminal (110,112), the encoded signals in the multiplexed concentrated stream (125,177) are demultiplexed and stored. The stored encoded signals are retrieved and the original number of encoded signal streams derived for transmission to the carrier terminal (100,102). Supervisory and control communication between the two concentrator terminals (110,112) is achieved by way of data messages on a derived data link. Operation between the transmit and receive directions at each terminal is asynchronous and controlled by a microcomputer (124,160). A method of synchronizing the carrier terminal with the concentrator terminal is included.

Digital concentrator terminal synchronization

A subscriber loop carrier system using digital multiplex techniques is disclosed in which remote subscriber loops include multiparty lines. Four party fully selective ringing signals are detected at the central office terminal of the system and converted to cyclic codes which are detected at the remote terminal with simple asynchronous circuits. The code generation and detection circuits are implemented with multiple output inverter circuits which provide simple logic structures for integrated circuit realization. Standard polarized ringing signals are applied to either conductor at the remote terminal of the system to ring the proper party.

Growing community of inventors

Naperville, IL, United States of America

Ronald J Canniff