Telecommunications – Receiver or analog modulated signal frequency converter – Measuring or testing of receiver
Reexamination Certificate
2000-07-11
2004-05-25
Trost, William (Department: 2683)
Telecommunications
Receiver or analog modulated signal frequency converter
Measuring or testing of receiver
C455S226200, C455S226400, C455S414100, C455S452200
Reexamination Certificate
active
06741843
ABSTRACT:
The present invention relates to a method and arrangement for measuring and indicating the field strength of a signal received by a mobile station operating in a cellular network. The invention also relates to a mobile station in a cellular telephone system, comprising means for sending and receiving signals, means for measuring the field strength of a signal, and means for reading data into a storage means in the mobile station. The invention also relates to a cellular radio system that comprises switching centers, base station controllers, base stations and mobile stations, and in which the base stations are provided with means for generating messages and for sending said messages to mobile stations, and the mobile stations are equipped so as to operate on a certain service level and receive said messages.
In cellular telephone systems the conditions of the locations of the different mobile stations in a cell are different with respect to the location of the base station. Some mobile stations are located near the base station without interfering obstructions between them. On the other hand, a mobile station may be located on the outskirts of a cell, or there may be an obstacle between it and the base station that attenuates the signal, or signals of other mobile stations may interfere with the operation of the mobile station. Mobile stations located in poor conditions have to use high transmission power so that their signals be on an acceptable level as they arrive in the base station. If the conditions are good, on the other hand, a high transmission power unnecessarily drains the battery of the mobile station and, at the same time, the mobile station's signal unnecessarily interferes with the signals of the other mobile stations in the same cell. The transmission power applied by the mobile station can be controlled by the base station if the service provider so wishes, see e.g. Michelle Mouly & Marie-Bernadette Pautet: The GSM System for Mobile Communications, chapter 6.1.5.1. In the GSM system, for example, the transmission power of a mobile station, like that of a base station, can be changed by about 30 dB in 2-dB steps at intervals of 60 ms. The control information is based on data obtained from a received signal level measurement carried out by the base station and mobile station.
The mobile station measures and indicates the received field strength. The measured field strength can be displayed to the user as a graphic indication on the mobile station. On the basis of the measurement result the mobile station decides whether or not the measured field strength meets the requirements for the connection. The prior-art field strength measurement indication was developed during the early stages of GSM (Global System for Mobile communications) standards when all that were used were mainly the basic services, such as speech transmission and slow data transmission. At the moment, however, there are additional services available that can be utilized in a GSM cellular network. These include e.g. fast data transmission at 14.4 kbps, general packet radio service (GPRS), and high speed circuit switched data (HSCSD) services. For example, the error correcting coding used on the faster 14.4 kbps channel had to be reduced so that a greater amount of data can be transferred on the channel. Along with increased data transmission rates it has been necessary to tighten up the field strength requirement on the connection so that errors occurring in the signal on the transmission path can be reduced to such an extent that the channel coding in use is able to correct the errors. The mobile station, however, measures and indicates the field strength as an absolute value just like before. Points P
1
and P
2
in
FIG. 1
show, by way of example, the field strength indicated by the mobile station in accordance with
FIGS. 2
a
and
2
b.
In
FIGS. 2
a
and
2
b
the field strength is shown on the display unit of the mobile station
20
using e.g. a vertical piecewise-continuous line
22
,
23
above the symbol depicting an antenna
21
. If, for example, the vertical line on the display unit
20
of the mobile station shows five indicator blocks
22
, like in
FIG. 2
b,
the field strength is optimal for GSM use. If the display shows only one indicator block
23
, like in
FIG. 2
a,
the field strength value is near the lower limit of operation, but the link is still acceptable. If there are no field strength indicating blocks at all above the antenna symbol
21
or the antenna symbol is missing, the field strength is insufficient for communication and no link can be established.
When using absolute field strength indication, it is possible to have a situation in which the field strength indication
23
indicates sufficient field strength but in reality the communication link will not function as desired with the service selected by the user. In the case of
FIG. 1
, two different operating ranges can be drawn, by way of example, around the base transceiver station (BTS) such that the outer circle
11
meets the GSM basic operation requirements at 9.6 kbps. However, the other GSM service shown in
FIG. 1
, fast data transmission at 14.4 kbps, can only be accomplished inside the inner circle
12
, say, at point P
2
, since the channel coding used on a fast transmission link cannot correct all errors generated on the transmission path when the mobile station is located at point P
1
. In the situation depicted by
FIG. 1
, it is difficult for the user, while at point P
1
, to understand why the fast data transmission will not work although the prior-art field strength indicator in the mobile station indicates that the field strength is sufficient for transmission, as shown in
FIG. 2
a.
At point P
2
the prior-art absolute field strength indication is in accordance with
FIG. 2
b,
and at P
2
the both services will work because the channel coding used on the faster transmission channel is able to correct the errors possibly generated on the transmission channel.
To remove the problem, various improvements have been proposed in order to enhance the services provided by the GSM system. U.S. Pat. No. 5,732,328 discloses a method in which the mobile station is controlled so as to change its transmission power in accordance with the information class of the signal itself, such as speech, data, or video, for instance. According to experience, the error tolerances of these different information classes are different. For example, normal speech transmission tolerates interference and even momentary disconnections better than pure data transmission. Statistically, then, the transmission power of the mobile station can be controlled according to the information contents of its signal. Data transmission, for example, needs higher transmission power than speech transmission.
The transmission power of a mobile station may also be controlled according to a method disclosed in U.S. Pat. No. 5,710,981 without direct control from the base station. The signal received by the mobile station described in said patent publication is degraded by means of a circuit in the mobile station in a controlled manner until it reaches a level where the quality of the signal is unacceptable. Since the mobile station has received information about the transmission power of the base station, it can now make a calculation of the transmission path losses and, based on that, the transmission power of the mobile station itself can be set as desired with respect to power consumption, signal quality and interference caused.
However, the basic problem remains. The mobile station measures and, if necessary, indicates the absolute value of the measured field strength. The field strength can be adjusted in the methods described above by changing the transmission power of the mobile station when necessary. However, the need for additional power is different for the different value-added services offered in the cellular network in question and, therefore, one single absolute measurement value will not provide sufficient data to form a
Kalliokulju Juha
Ruuska Satu
Ewart James D
Nokia Mobile Phones Ltd.
Trost William
LandOfFree
Method and arrangement for service-based indication and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and arrangement for service-based indication and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and arrangement for service-based indication and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3186102