Multiplex communications – Communication over free space – Message addressed to multiple destinations
Patent
1996-12-06
1999-03-02
Olms, Douglas W.
Multiplex communications
Communication over free space
Message addressed to multiple destinations
370329, 370347, 455517, 455561, H04J 300
Patent
active
058780335
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a process for transmitting messages from an infrastructure of a radio communication network to mobile stations, as well as the equipment for implementing this process.
The invention applies to the broadcasting, by a base station of the infrastructure, of service messages destined a priori for all the mobile stations situated within the zone of coverage of the base station, each mobile station being able to decide whether or not to receive these service messages. The relevant broadcasting channels can in particular be channels for monitoring radio links if the service messages convey signals for setting up and managing the communications, channels for broadcasting service messages of which the users are intended to be made aware, or else mixed channels on which both these types of service messages will be broadcast.
To illustrate the problems raised by the broadcasting of such messages, in what follows we consider the example of the GSM ("Groupe Special Mobiles") European cellular digital radio communication system, for which there is a message broadcasting service, termed "SMS-CB" standing for "Short Message Service Cell Broadcast". When this service is provided, a particular radio channel is used in each cell and a message is broadcast roughly every two seconds on this channel. A mobile station equipped for this service reads the messages on this channel and displays them on a screen. Typically, the messages are rebroadcast cyclically.
The applications of this service are diverse. Those exploiting the network may use it for information relating to other services, as for example the tariff zones. It may also be used by external service providers, for example to broadcast travel information or weather forecasts.
The service messages are made up of 88 bytes sent in four successive blocks of equal length, the first of which contains four bytes for identifying the message, including 2 bytes, namely 16 bits, which consist of a message category cue. Each block can be received independently by the mobile stations, in the sense that reception of a block may be correct whether the other blocks have or have not been correctly received, and that the mobile station can decide whether or not to receive each individual block.
In the current state of the public specifications for the system, the mobile stations have to receive at least the first blocks of all the messages, failing prior information as to their contents, even if the user is only interested in certain of these messages. This tends to shorten the electrical endurance of the mobile stations, each reception consuming energy. Now, the endurance of portable mobile stations, which are light in weight and therefore have a small battery, is a point of importance to users.
To remedy this drawback, studies are in progress into reducing the number of receptions required, by sending information in advance. The objective is to provide indications in advance enabling the mobile station to know whether or not it is interested in a given message. Cases in which it is not interested are for example messages of a category of no interest to the user (the latter may program his apparatus to, for example, indicate to it that he is not interested in travel information). Another case is that of messages already received. Thus, the messages are rebroadcast regularly, there being many which are not modified for hours or days.
It has in particular been proposed to broadcast, on the same radio channel, schedule messages each giving information about a number of service messages which will be broadcast consecutively after the schedule message. The period for which the service messages catalogued in the schedule message are broadcast is called the schedule period. The information contained in the schedule message includes the categories of the various messages to be broadcast during the schedule period, so that a mobile station which has been programmed to ignore certain categories of message, may refrain from receiving the
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Hom Shick
Nortel Marta Cellular
Olms Douglas W.
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