Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1997-11-12
2001-02-27
Vo, Nguyen (Department: 2682)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S522000, C455S557000
Reexamination Certificate
active
06195562
ABSTRACT:
FIELD OF THE INVENTION
This invention is aimed at limiting the maximum transmitted power used by a mobile communication means.
BACKGROUND OF THE INVENTION
In most countries there are regulations in force which place certain maximum limits on the power of electromagnetic radiation directed towards humans. These limits vary from country to country and will most probably be tightened in the future.
On the other hand, as the transmission speed in mobile communication means systems increases, the amount of energy radiated by mobile communication means also increases. For example, in networks based upon TDMA technology, data transmission speeds may in principle be increased by using several successive time slots in the same TDMA frame, in which case the mean transmitted power increases. The use of several successive time slots in the same frame is possible in the Universal Mobile Telecommunication System (UMTS) under development and in new Global System for Mobile communications (GSM) standards which are under development. In CMDA systems the transmitted power has to be raised in line with the data transmission speed if one wishes to keep the bit error rate constant. In both basic techniques the amount of energy radiated by the antenna increases as the data transmission speed increases, in which case the permitted limits may at some stage be exceeded.
The radiation power caused by a particular radio set and directed towards the user is typically measured on the basis of the least favourable operating situation, in the case of a cordless telephone with the antenna almost pressed against the user's head. If a radio set may be used in many ways demanding differing transmitted power, for example for voice transmission and for high-speed data transfer, all functions of the radio set have to adjust to the limits which follow from the least favourable operating situation.
For example in the current GSM system, the maximum power of a mobile communication means which is used during one time slot is 2 W, which means that the mean transmitted power is approximately 250 mW. According to new GSM standards which are being developed, a mobile communication means may use for the high-speed data transfer as many as all eight time slots in one frame, in which case the mean transmitted power is 2 W. This causes problems if the 250 mW which is satisfactory for voice calls has been set as the upper limit of radio power directed towards the user's head. In this situation the mobile communication means may not use maximum power levels, but must use instantaneous transmitted power lower than in a voice call, so that the limit of mean transmitted power is not exceeded. This again causes audibility problems, since the base stations in the mobile communication means network are designed to cope with the needs of a voice link.
SUMMARY OF THE INVENTION
The aim of this invention is to create a system which adjusts the power level used by a mobile communication means to the mode of usage of the mobile communication means. A further aim of the invention is to create a system with the aid of which a mobile communication means may utilize the maximum permitted transmitted power in any given situation. In addition, an aim of the invention is to create a system with the aid of which the user may, if he so desires, limit the maximum values of electromagnetic radiation directed towards his body.
These aims are achieved by incorporating in the mobile communication means a device for identification of the mode of usage, and by arranging for the transmitted power of the mobile communication means to be limited according to the mode of usage and the type of current connection or connections.
Characteristic of the system according to the invention is what is described in the characteristic part of the independent claims. Dependent claims describe further advantageous embodiments of the invention. The invention is further directed to a mobile communication means, which is characterized by that which is described in the characterizing part of the corresponding independent claim.
In the system according to the invention, the upper limit of transmitted power used by the mobile communication means is varied according to the mode of usage. A mobile communication means according to such a system meets the more stringent requirements placed upon sets which are to be used next to the user's head, but the same mobile communication means may still be employed for applications demanding greater transmitted power in a situation where the power limits imposed on the radio set are less strict.
When a mobile communication means is used in a situation typical of a telephone, the mean power transmitted by the mobile communication means is limited to the maximum value for a telephone permitted by regulations and test procedures. When a mobile communication means is used for example as a data transfer device in conjunction with a portable computer, the maximum permissible transmitted power may be increased in accordance with the requirements of the data transfer rate employed.
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Mobile Communications International, Issue 31, 1996, pp. 57-58.
Ojanpera Tero
Pirhonen Riku
Nokia Mobile Phones Ltd.
Perman & Green LLP
Vo Nguyen
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