Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-06-19
2001-04-17
Le, Thanh Cong (Department: 2745)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S422100, C455S424000, C455S432300, C455S067150, C455S067700
Reexamination Certificate
active
06219544
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to maintenance of quality in a mobile telephone network and especially to measurement of radio path quality and coordinates of a measuring point at an arbitrary point of the network.
FIG. 1
shows those parts of a mobile station system which are substantial for the invention. A mobile station MS communicates by radio with a base station BTS. One or several base stations BTS form together with a base station controller BSC a base station subsystem BSS, which again is connected to a mobile telephone network PLMN. The quality of the services produced by the network is monitored in a network management subsystem NMS and, to be precise, in an operation and maintenance centre OMC therein. The broken lines in
FIG. 1
represent interfaces crossed by signals. Signals between the mobile station MS and the base station BTS propagate over air interface. The base station subsystem BSS communicates with the network subsystem over A interface. The management subsystem NMS communicates with the rest of the network over operation and maintenance interface O&M.
Signals do not always propagate straight between an antenna ANT of a base station BTS and a mobile station MS. The propagation of signals is interfered e.g. by attenuations caused by terrain form and buildings, reflections from even surfaces, such as walls of buildings. When signals arriving along different paths are summed in a receiver, it can be observed that the signal strength as a function of the distance of the receiver reaches several minimum points at distances of almost one wavelength from each other. The phenomenon is called Rayleigh fading, i.e. multipath fading. See e.g. Mouly-Pautet: “The GSM System for Mobile Communications”, FIG. 4.19 with explanation. Other interfering factors are for instance narrow-band interferences from other mobile stations MS and broadband interferences from electric systems of cars or from lightnings, for instance. In addition, rain attenuates radio signals.
For monitoring the signal quality in a mobile telephone network, the following parameters among others are used: signal strength, bit error ratio BER and propagation time, on the basis of which a timing advance is formed. Within the scope of this application, these parameters associated with signal quality are combined to a concept ‘signal quality’ SQ. In the exemplifying GSM system, both the mobile station and the base station measure the above three parameters. The mobile station measures the signal strength in that base station where it is locked and, in addition to that, in adjacent base stations.
In general, parameters associated with signal quality are functions of location and also of time. One problem with mapping shadow regions conists of precision requirements with respect to location determination. Due to multipath fading, particularly, the signal strength varies considerably along a distance as small as one wavelength (about 30 cm). It is known to provide important measuring points of the network with special measuring telephones, which give the network feedback concerning signal quality. A problem with such fixed measuring telephones is that they can measure network parameters only at predetermined fixed points. For example, fixed telephones are not capable of measuring how a handover succeeds.
PCT Publication WO 93/15569 (PCT/US93/00579, Franza et al.) discloses a partial solution to the above problems. However, this solution involves certain problems. Firstly, the equipment is big and it is suggested to be located in a delivery van, for instance. This leads to the problem that radio path quality values of a network can be measured only at places which are accessible by a car or a delivery van. Indoor spaces of buildings, public vehicles, subway tunnels, pedestrian streets, recreational areas and water areas etc. are areas where no measurements can be performed by means of the system according to said WO Application. Another problem, which is not solved by the system according to this PCT Application, consists in combining measurement results from an uplink transmission path and a downlink transmission path. On page 8 of said WO Published Application, it says that “The data accumulated by the computer in the base station and the computer on the mobile platform may be stored and later combined”. This later combining is problematic per se, because it requires additional calculation. The results from the uplink transmission path of a predetermined measuring device have to be combined with the results from the downlink transmission path of the same measuring device. This combining also causes delays in the maintenance of the network. If the measurement results from the uplink transmission path are poor, the user of the measuring device does not know that and cannot concentrate measurements on problematic places. Still another problem caused by a later combining is that it is not possible until after the combining to make a final decision on whether some measuring event involves something abnormal due to which the measurement result should be stored for a later analysis.
BRIEF DESCRIPTION OF THE INVENTION
Accordingly, it is an object of the present invention to measure parameters associated with radio path signal quality in a mobile telephone network and co-ordinates of corresponding measuring points and to transmit them to the operation and maintenance centre of the network at an arbitrary point of the network from a measurement station moving at an arbitrary speed. It shall be as simple as possible to combine the measurement results from a downlink transmission path and an uplink transmission path so that storage of data for an unnecessarily long time could be avoided.
The objects of the invention are achieved by methods and systems, which are characterized in what is set forth in the characterizing portions of the independent claims. The preferred embodiments of the invention appear from the independent claims.
The invention is based on an exact measurement of location of a mobile station, preferably by means of satellite positioning, and on using an intelligent controller connected to the system. According to the invention, quality parameters of the mobile telephone network are measured and these parameters are transmitted immediately to the mobile station network, where the measurement results from an downlink transmission path are combined with the measurement results from an uplink transmission path. In addition, coordinates of the measurement site are determined as exactly as possible. It is thus possible to conclude almost without delays, whether the measurement result is within the limits of predetermined standard values or not. While measurement results can be utilized for network planning in an arrangement according to the prior art, an arrangement according to the invention allows a utilization of measurement results for real time monitoring and maintenance of the network.
By combining the measurements of the uplink transmission path and the downlink transmission path immediately, even such an advantage is achieved that the information generated in this way can be utilized for the location control of a mobile measurement station. For instance, the measurement station can be commanded directly to remeasure a predetermined location or an information of a poor measurement result can be transmitted to it, in which case it can decide on a new measurement independently. On problematic sites, measurements can also be performed at different frequencies.
By combining the measurement results of the downlink transmission path and the uplink transmission path immediately, they can be used by the mobile telephone network, for instance by its operation and maintenance centre OMC, and a decision concerning permanent storage of the measurement results can be made as soon as possible, whereby unnecessary storage of unessential information and waste of memory space attached thereto are avoided. Thanks to an intelligent controller, storage of unessential information can be reduced and, on
Cong Le Thanh
Nokia Telecommunications Oy
Pillsbury Madison & Sutro LLP
Woldetatios Yemane
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