Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-11-04
2002-08-27
Ramakrishnaiah, Melur (Department: 2643)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S450000, C455S511000
Reexamination Certificate
active
06442392
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the method defined in the preamble of claim
1
for locating a mobile station. The invention also relates to a mobile station defined in the preamble of claim
10
for locating a mobile station. In addition, the invention relates to a base station defined in the preamble of claim
13
for locating a mobile station. Furthermore, the invention relates to the arrangement defined in the preamble of claim
16
for locating a mobile station. In addition to that, the invention relates to the location service centre defined in the preamble of claim
19
for locating a mobile station.
2. Description of the Related Art
Methods for determining the position of a mobile station are known previously, which methods are based on transferring radio signals between a mobile station and a mobile station network, and the measurement and signal processing thereof. Usually the mobile station network has a central controlling device, which controls the location process and the receivers participating in it. In these methods, location is usually based on two basic arrangements:
1. The mobile station operates as a receiver, and there are several transmitters in the mobile station network. The smallest number of transmitters depends on the location method. This arrangement is known as the mobile station based setting.
2. The mobile station operates as a transmitter, and there are several receivers in the mobile station network. The smallest number of receivers depends on the location method. This arrangement is known as the network based setting.
One such location method is a method based on the measurement of the angle of arrival (AOA) of the radio transmission, which uses direction finding (DF), in which method the mobile station transmits a radio signal to at least two base stations, which examine the angle of arrival of the signal and transmit the measurement results to the location service centre. Because of the inaccuracy of the AOA measurement, instead of defining an accurate angle, a sector from which the signal comes from is defined in this method. The mobile station is situated at the intersection of the arrival sectors. Two sectors are sufficient for the determination, but if there are more, the measurement becomes more accurate. The locations of the base stations are used as the basis of comparison for locating the mobile station. Another such location method is a method based on the transition time of a radio transmission. In this method, at least three base stations send a radio signal to a mobile station on the basis of the network, and the mobile station examines the observed time difference (OTD) of arrival of the signals, and, based on the mobile station, the mobile station transmits a radio signal to at least three base transceiver stations (BTS), which examine the observed time difference of arrival (TDOA) of the signals. In the location service centre (LSC), the arrival times are used to form at least two hyperbolas, at the intersection of which the mobile station is located. Because of the inaccuracy of the arrival times, the hyperbolas are expanded as wide bands, the intersection of which limits an area and not a certain point. The location of the hyperbolas is determined in relation to the location of the base stations.
A third such locating method is based on the radio transmission delay, which method uses the transition time between the mobile station and the base station. In this method, the mobile station and the base station exchange radio signals, the times of arrival (TOA) of which are examined. The transition time must be determined between the mobile station and at least three base stations. In mobile station systems based on Time Division Multiple Access (TDMA), it is necessary to know the transition time of the radio transmission between the mobile station and the base station in order to avoid the overlapping of the time intervals. On the basis of the transition time, the distance of the mobile station from the base station is determined as a location circle in which the radius corresponds to distance and in which the central point is at the base station. There must be at least three of the location circles. The intersection of these circles is the location of the mobile station. One such TOA location method is the Timing Advance (TA) method, which is planned to be used in the GSM system. In the GSM system, as is known, the to-and-from transmission time between the mobile station and the base station is measured. From this it is possible to calculate the distance between the mobile station and the base station.
There is also a system known as Timing Advance, in which the mobile station is forced to carry out consecutive connection switchings to the neighbouring base stations for determining its location.
Other such location methods are the Satellite-based Global Positioning System (GPS), using the identity of the serving cell and measuring the intensity of the signal received.
The known network-based methods have the drawback that heavy signalling is needed between the base stations and the service centre that carries out the location determination. In this method, the mobile station operates as a transmitter, and the network provides the receivers.
A further problem in the known network-based methods is the required coordination in the network. For example, the location service centre indicates to the receiving base stations which channels they should listen to according to the mobile station to be located, or in accordance with the basic settings of the base station, certain predetermined channels are listened to. The channels are indicated by means of time and frequency information, for example. In addition, the measurement results are transferred in the network, which adds to the load on the network.
Furthermore, some known methods based on transition time, such as TA, have the problem that a two-way connection must be established from the mobile station to many base stations before the location can be determined.
In addition, the known system has the drawback that the location process is slow.
The purpose of the invention is to provide a new method for locating a mobile station and to eliminate the above mentioned drawbacks.
BRIEF SUMMARY OF THE INVENTION
The method according to the invention is characterized in what is set forth in claim
1
. The mobile station according to the invention is characterized in what is set forth in claim
10
. The base station according to the invention is characterized in what is set forth in claim
13
. The arrangement according to the invention is characterized in what is set forth in claim
16
. The location service centre according to the invention is characterized in what is set forth in claim
19
. Preferred embodiments of the invention are presented in the dependent claims.
The invention relates to a method for determining the location of a mobile station by means of radio signals between the mobile station and the mobile station network. In the manner according to the invention, at least one separate location channel is formed between the mobile station and the network in addition to other channels, to which location channel the radio communications related to the measurement of the location of the mobile station is concentrated. All other radio communication related to the location of the mobile station is also preferably concentrated to this channel. Other channels here mean all the known channels used between the mobile station network and the mobile station, such as the channels for ordinary communications and signalling.
In one application of the method, two location channels are formed, of which the first location channel is used for radio communications from the mobile station to the network and the second for radio communications from the network to the mobile station. These are called the Location Access CHannel (LACH) and the Location Receipt CHannel (LRCH). The location access channel resembles the Random Access CHannel (RACH) in the
Rantalainen Timo
Ruutu Ville
Nokia Mobile Phones
Perman & Green LLP
Ramakrishnaiah Melur
LandOfFree
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