Multiplex communications – Wide area network – Packet switching
Patent
1990-11-26
1993-07-13
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
3701054, 3701101, 379 63, H04B 156, H04M 172
Patent
active
052280268
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to telecommunications systems, and has particular application to cordless telephones. Aspects of the invention are useful in so called "CT2" cordless telephone systems, and systems in accordance with the British Department of Trade and Industry specification MPT 1375. The May 1989 version of specification MPT 1375 is incorporated herein by reference.
BACKGROUND
In a cordless telephone system, it is necessary to provide a way of carrying the signal for the contents of communication, normally speech, in both directions between parts of the system which are not connected by a cord or wire. Additionally, it will normally be necessary to pass other signals between the parts, which are used to control the operation of the parts or carry other control messages separate from the content of the communication In some known radio telephone systems, the requirement for two way communication is achieved by providing two radio channels between the parts, each channel being used for communication in one respective direction. In an embodiment of the present invention, multiplexed signal structures are provided enabling a plurality of logical channels to be carried with communication in both directions, over a single signal communications channel. In the embodiment, the use of different multiplex structures at different times permits differences in the logical channel structure of the cordless communication at different stages of the creation and use of the cordless communications link.
In a conventional radio telephone system, an arrangement must be provided enabling a link to be set up so that parts can communicate with each other. When one of the parts is operating in a manner synchronised to some routine, it may be difficult for another part to establish a link with the first part if the second part is not itself synchronised to the same routine.
In an embodiment of the present invention, an arrangement is provided allowing for asynchronous initiation of a link between two parts, even when one of the parts is operating in a synchronous manner.
In a radio telecommunication system, the ability of a radio link to carry useful signals will tend to vary in accordance with external factors, such as interference and transmission past obstructions. Accordingly, it is advantageous to encode transmitted signals for error detection and correction and/or monitor the link quality to enable remedial steps such as breaking and re-establishing the link, possibly on a different radio channel, if the link quality becomes unacceptably low. In an embodiment of the present invention, an arrangement is provided in which two logical channels are multiplexed together, with signals of one logical channel being encoded to enable error detection, and detected errors in this logical channel being monitored and used as a measure of the extent to which the other channel is exposed to errors.
In a system for radio telecommunications, there will typically be a large number of communication devices capable of communicating in the system, some of which may be more sophisticated and have greater communication abilities than others. In order for two devices to communicate with each other, they must communicate in a manner which is within the capabilities of both devices. Thus, when a relatively sophisticated device communicates with an unsophisticated device, they must communicate in a manner within the capabilities of the unsophisticated device. However, it is inefficient to force the sophisticated device also to communicate in this particular manner when it is communicating with another sophisticated device capable of communicating in a different manner. In an embodiment of the present invention, devices conduct an operation (sometimes referred to as a "negotiation" operation) during the creation of a cordless telecommunications link, so as to adopt a way of communicating which is within the capabilities of both devices.
When two devices are communicating over a cordless telecommunications link,
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Albrow Richard
Barnes Nigel E.
Beesley Graham E.
Cant Chris
Crisp Malcolm
British Telecommunications public limited company
Ferranti Creditphone Limited
GEC Plessey Telecommunications Limited
Kizou H.
Mercury Communications Limited
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