Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-09-16
2002-03-12
Vo, Nguyen T. (Department: 2682)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S435100
Reexamination Certificate
active
06356762
ABSTRACT:
FIELD OF INVENTION
The invention concerns a method for the operation of a radio system and a system to execute the method.
DESCRIPTION OF RELATED ART
Due to their difference in application, different technical norms with regard to transmitter frequencies, transmission journals, working ranges etc. were developed originally for mobile radio systems on the one hand and for radio systems for the purpose of wireless telephony on the other hand. This led to the fact that in most cases there is no compatibility between mobile radio systems, as they are for example used for automobile telephony, and the so-called CT systems (CT=cordless telephone), i.e. small-scale radio systems for wireless telephony.
Not always, but frequently, mobile radio systems (e.g. GSM systems) are cellular systems with a coverage area that is structured in a cell-like fashion. In each cell the mobile stations communicate via an air interface with a fixed base station. The base station can be connected with other cells of the same mobile radio system and/or other telecommunication system via suitable communication links (e.g. hard-wire telecommunication systems, beam links, radio links, etc.). Typical ranges of mobile radio systems (i.e. cell radii for cellular systems) are between a few km and about 60 km. In the case of cellular mobile radio systems, frequency allocation occurs usually based on active cell planning.
In contrast, CT systems usually comprise one or several fixed stations/parts which are hooked to the connection of a hard-wire fixed system, and one or several portable, wireless handsets or wireless telephones (portable parts) which can communicate with the fixed part via a radio interface. Typical ranges are between 50 m and several 100 m. Frequency allocation generally occurs with a dynamic, automatic procedure for frequencies that happen to be free at that time.
On the user side, there is a large need for a mobile telecommunication device, e.g. in the form of a hand mobile telephone which can be used both as a wireless telephone in one or several (small-scale) CT systems and as a mobile station for one or several (large-scale) mobile radio systems. Such a telecommunication device, which can be used in at least two different radio systems, is called a DMT (Dual Mode Terminal). Ideally the user of a DMT can always be reached at the same phone number, regardless which of the different radio systems he used to communicate with. This, however, depends heavily on the network support for such a service.
Several suggestions were submitted for the combined operation of large-scale mobile radio systems and small-scale radio systems. There are, for example, suggestions for the combination of a mobile radio system, according to the GSM standard, with a radio system operated in accordance with a standard developed for CT systems, particularly DECT.
For the production of relatively simple and inexpensive DMTs for the combined operation in a mobile radio system and a CT system, it is desirable that most of the components, such as antenna, receiver, transmitter etc., can be used for both the mobile radio system and the CT system. For this reason a more recent suggestion plans for the combination of a GSM mobile radio system with a CT system, which is operated according to a GSM norm modified for wireless telephony. A portion of the modification for this so-called GSM-CTS (CTS means “Cordless Telecommunication System”) affects the GSM system control channels. The base station of a “normal” GSM mobile radio system continuously transmits system-relevant data via special system control channels like identification of the base station, frequencies and channels used by the base station and possibly neighboring cells, etc. Much of this data is only required for the operation of a mobile radio system, but not for the operation of a CT system. To reduce the channel load, the so-called HBS (Home Base Station=fixed part or fixed station of a CT system operated according to GSM-CTS) therefore only emits system-relevant data required for CT operation instead of all GSM system control channels on a so-called beacon channel. Among other things, on the beacon channel an identification signal is transmitted continuously, based on which the DMTs can determine whether they are still in the coverage area of the HBS.
Mobile radio systems and wireless telephones have become more widespread over the last few years. Apart from speech transmission, newer systems also offer telefax and/or data transmission (e.g. computer communication). Although the frequency area made available for mobile radio systems and/or CT systems is relatively large by existing standards, capacity limits are already being met due to the wide-spread availability of these systems. We should therefore strive to use the limited resources of available frequency channels sparingly and use them efficiently.
For simplicity reasons, the terms “frequency” or “carrier frequency” are used in the following even if not only one, but actually a pair of so-called duplex frequencies or duplex carrier frequencies are used, e.g. to send from a base station to a mobile station (down-link) or vice versa (up-link). In the following, “channel” means the resource that is required to transmit signals or user data via the air interface. In the GSM, for example, a channel consists of a combination of a certain carrier frequency and a certain time slot. A mobile telecommunication terminal is a telecommunication terminal (telephone, telefax machine, data transfer modem etc.) which sends and/or receives electromagnetic waves via an air interface for communication purposes. A mobile telecommunication terminal that can be used for at least two different radio systems is called a DMT (Dual Mode Terminal). A fixed station/fixed part is generally a typical fixed radio station, in the particular case of the CT system it is its fixed part. However, in the example of a car phone equipped for tandem operation the fixed part is not really fixed because the fixed station in this case consists of a part of the device that is fastened (fixed) in the car. The coverage area of a radio station is the area in which a mobile telecommunication terminal can communicate with the radio station via the air interface.
SUMMARY OF THE INVENTION
The invention is based on the task of making a method available for the operation of a radio system that ensures efficient utilization of a limited resource of available channels in a limited frequency range.
According to the invention, a method for the operation of a radio system includes muting a fixed station of the radio system when no operable mobile telecommunication terminal is located within the station's coverage area. Muting by definition defines that no electromagnetic signals are sent via the transmitter, in particular this defines that no system-relevant data is sent via a beacon channel or a system control channel and no signals are sent for data or speech transmission i.e. that the transmitter of the fixed station is entirely muted. Preferably, a mobile telecommunication terminal that is capable to communicate with one or several other radio systems frequently monitors the busying of the channels by other radio systems. When this telecommunication terminal initially only sends on free channels itself and secondly informs the fixed station repeatedly of free and available channels on which it can transmit, then this would largely prevent that other radio systems with access to the same frequencies interfere with the radio system operated according to the method invented. In addition, other independent systems of the same type as well are not disturbed at all or only minimally. If there is no operable mobile telecommunication terminal any longer in the coverage area of the radio system's fixed station, then no frequencies or channels are used by the radio system because the fixed station is being muted; the limited frequency bands are kept available for efficient utilization that is free from interferences.
In contrast to the invention
Ascom Business Systems AG
Mehrpour Melody
Vo Nguyen T.
LandOfFree
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