Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1998-04-24
2001-09-25
Kizuo, Hassan (Department: 3662)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S345000, 37
Reexamination Certificate
active
06295302
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to digital communications networks such as the Integrated Services Digital Network (ISDN) and digital radio systems and, more particularly, to the alternate transmission of speech and data communications in such networks and systems.
2. Description of the Related Art
The related art described herein consists of that related primarily to radio communication because it is in that field that the majority of work has been done regarding the alternating transmission of speech and data. However, the present invention is equally applicable to any terminals which have an associated coder or decoder that may be selectively bypassed under control of the system of the present invention.
Traditionally, both wireline and radio communication networks have been used for the transmission of speech information from one point in the network to another. Recent advances in computer and communications technologies indicate that the dominant use of both radio and wireline communication networks in the future may be for data communications, not voice. The recent proliferation of so-called “multimedia” applications and services frequently calls for the combined usage of both speech and data in a single user application. The implementation of such applications within the mobile radio network requires that subscribers be able to transmit both speech and data either simultaneously or alternately.
The increasing demand for such multimedia services within digital cellular radio systems requires fast and flexible transmission of both speech and data within the network. While many of these potential applications do not require a full simultaneous transmission of speech and data at the same time, they can function very efficiently if speech and data can alternate between one another very quickly and flexibly within the system.
For example, a mobile user might desire a feature such as voice controlled automatic call routing. This service is implemented by having the subscriber phone a routing server connected within the fixed network and then inform the server, by means of voice recognition, to reroute all incoming calls from the subscriber's regular number to a certain specified alternate number. This service requires the transmission of both data, for the control commands to the server, and voice parameters for the spoken commands. Another possible application requiring the alternate transmission of speech and data is the use of voice enabled e-mail in which a user dials into a server which is connected within the fixed network and functions as a e-mail box. The user issues commands to the server via data transmissions to cause the server to display on the user's terminal a list of received e-mails and enable the user to scroll up and down that list and then request the server to read a selected one of those e-mails by voice synthesis. In this application, the user alternatively sends digital control commands and speech vectors between the user's terminal and the server. Still other “multimedia” applications are file transfer of digital data over the same connection while a user is talking to speech recognition software within the server, and the implementation of video conferencing over a single connection.
Many prior art references have contemplated the multiplexing of speech and data in a single communication channel. For example, in U.S. Pat. No. 4,813,040 entitled “Method and Apparatus for Transmitting Digital Data and Real-Time Digitized Voice Information Over Communication Channels” issued Mar. 14, 1989 to Futato, data are inserted into the silence periods of voice communications on a communication channel. Similarly, in PCT published application no. W096/13916 entitled “Communications Method and Apparatus With Transmission of a Second Signal During Absence of a First One” the system transmits both a principal signal (voice) and a data signal. When the principal signal is present or contains information it is transmitted; however, when the principal signal is absent or does not contain a significant amount of information, data are transmitted through the channel. Neither of these systems contemplate solutions to the problems of alternate voice and data transmissions over a link including digital radio.
In digital radio systems such as TDMA digital cellular systems, digital speech content and digital data content are handled differently in the system. When the user speaks into a subscriber terminal of a digital radio system, the voice is encoded into speech parameters which are, in the full rate (FR) coding scheme of the Global System for Mobile communication (GSM), transmitted at 260 bits per 20 millisecond frame. This is a data rate of 13 K bits per second. When these encoded speech parameters reach the fixed network, they are conventionally converted by a speech decoder into normal 8K digital speech samples and transmitted at the rate of 64 K bits per second. In contrast, data are generally transmitted in the fixed network in accordance with somewhat different standards because of the inherently different characteristics between voice and data communications.
It is important for speech to undergo very few delays during transmission so that the other party receives it within a time frame which simulates normal conversation. The nature of digital speech is also such that errors in the digital representations of the speech are quite tolerable. Speech is redundant and the listener is also redundant so that communication is satisfactory and readily understandable even though a number of errors may occur in the transmission of the digital speech representations from one location to another. Data, on the other hand, is very intolerant of errors. Thus, it must be encoded with error correction coding and other techniques to ensure a high degree of accuracy in the transmission of the data from one point to another within a communication network. On the other hand, the delays in the transmission of data from one point to another are very tolerable in the case of data circuits. It does not usually matter that the data is delayed or buffered at various points in the transmission circuitry while the data is moving from one place to another within the network.
Because of these very different ways of handling speech and data in the communication network, it is infrequent that both can be efficiently transmitted in the same communication circuit. For example, in the multimedia facilities currently provided within the GSM cellular network, the speech portions of a circuit are handled by one set of infrastructure and the data portion of such circuits are handled by a different data path infrastructure. This results in a lack of synchronization of the two paths which make it difficult to implement services involving both. Thus, it is very difficult to combine in a single application, the alternate transmission of speech and data between two separate nodes in the network, especially one which includes a digital radio link.
The current GSM standards provide a variety of different service and traffic channels such as the three speech traffic channels full rate (FR), half rate (HR) and enhanced full rate (EFR), as well as many different types of data traffic channels. While GSM recommendations exist which describe solutions for simultaneous or alternative transmission of speech and data within one call, the practical realization of multimedia services suffers in many different aspects from insufficient specifications to insufficient realizations and insufficient support of the proposals by network operators.
For example, some of the drawbacks to existing suggested solutions include the fact that existing data services are not suitable for speech transmission due to long delays while current speech services are not transparent to data. In addition, “mode modification” between these two types of services are much too slow and cumbersome for practical implementation. Current solutions like USSD for GSM can carry slow speed data in par
Danne Anders
Hellwig Karl
Elallam Ahmed
Jenkens & Gilchrist P.C.
Kizuo Hassan
Telefonaktiebolaget L M Ericsson (publ)
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