Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2001-05-14
2004-08-10
Vo, Nguyen T. (Department: 2685)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S062000, C455S063100, C455S067110
Reexamination Certificate
active
06775547
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention is related to communication networks and in particular to transmission quality measurements of communication signals between distributed components of a communication network.
2. State of the Art
In distributed wireless communication systems jointly using the same frequency bands or channels, the channel actually allocated to a base station for communication with respective remote stations has to be selected. Such a channel selection can be accomplished at the instant a communication connection between a base station and a remote station is set up (e.g. DECT-systems), centralized for all base station covering a certain geographical area (e.g. GSM-systems), or at arbitrary times (e.g. HIPERLAN/2).
In the latter case, which is addressed by the present invention, the channel selection, i.e. the allocation of certain frequencies of a jointly used frequency band, is performed de-centralized and autonomously at each base station. As a result, a selected channel is not allocated to individual communication links for a base station above allocated for a base station which uses the selected channel and the frequencies contained therein, respectively, for several communication links established with this base station.
Such selections and allocations of channels and frequencies, respectively, are often controlled by methods for a so-called adaptive channel selection (ACS). ACS-methods are based on measurements of received signal strength (RSS) levels on available channels for a base station. The RSS-measurements could be performed both in the up-link (i.e. the communication link from the base station to a remote station) and in the down-link (i.e. the communication link from a remote station to the base station). The result of a RSS-measurement is indicative of signal interference for signals transmitted between the base station and respective remote stations. In particular, down-link signal interference is caused by two or more remote stations communicating with same base station within a channel commonly used, while up-link signal interference on signals transmitted by a base station can result from signal interference of signals transmitted by base stations via a commonly used channel.
On the basis of RSS-measurements being indicative of the transmission quality of available channels, the channel selection/allocation for a base station is performed. In order to select/allocate the channel having an optimum transmission quality, the above ACS-methods have to react quickly on changed/modified operational conditions within a communication network. Therefore, the actual communication situation and especially signal interference associated therewith are monitored by means of RSS-measurements. In order to obtain the actual signal interference situation, conventionally, the RSS-measurements are performed continuously. Usually, measurement periods for RSS-measurement are predefined fixed time periods both for allocated and available channels. As used in the following, a measurement period is the time between two successive measurements.
Depending on the number of allocated/available channels and the number of remote stations assigned to a base station, this can result in a large number of measurements. Since RS-measurements for down-links are usually performed by remote stations, the large number of RSS-measurements lead to an increased need of additional power resources, which is especially disadvantageous for (mobile) remote stations using batteries. Further, an increased channel transmission capacity must be provided for measurement requests and measurement reports between base stations and remote stations. Moreover, an increased load can occur for handling measurement requests, reports and results at a base station, requiring an increased processing time and capacity.
Moreover, RSS-measurements should compensate for signal fluctuations due to varying propagation losses and varying transmission power for base and remote stations, in order to provide reliable results. On one hand, this can accomplished by a large number of measurements for continuously monitoring the current interference situation, also leading to the above-mentioned problems. On the other hand, temporary fluctuations of RSS-measurements can be compensated by linear filtering. In case RSS-measurement fluctuations do not occur temporarily but persistently, the linear filtering follows the RSS-measurements with a certain delay time leading to an delayed/impaired channel selection.
3. Object of the Invention
Principally, the object of the present invention is to solve the above-mentioned problems of known communication networks. In particular, the object of the present invention is to provide a method and a system for measuring the transmission quality in a communication network requiring a reduced number of measurements (e.g. RSS-measurements).
SUMMARY OF THE INVENTION
4. Principle Underlying the Invention
In order to reduce transmission quality measurements in a communication network, the present invention is based on the principle both to adaptively control transmission quality measurements with respect to operational conditions/situations in a communication network and/or to perform transmission quality measurements providing a long term transmission quality estimation for a communication network.
5. Solution According to the Invention
In particular the invention provides a method for measuring the transmission quality between a base station and at least one remote station in a communication network having at least one channel for transferring signals between the base station and the at least one remote station. The method comprises measuring a transmission quality for signal transmissions via the at least one channel, and defining a transmission quality measurement period for the at least one channel in relation to the measured transmission quality.
Preferably, the measuring of the transmission quality includes measuring of a transmission quality for a channel allocated to the base station for communicating with the at least one remote station and/or measuring of a transmission quality for at least one channel available for the base station for communicating with the at least one remote station.
Here, it is possible to define a transmission quality measurement period for the allocated channel in relation to a ratio of the transmission quality value of the allocated channel and at least one of the transmission quality value of the at least one available channel.
Moreover, the defining of the transmission quality measurement period include defining a transmission quality measurement period for each of the at least one available channel in relation to a ratio of the transmission quality value for the allocated channel and the transmission quality value for a respective one of the at least one available channel.
As a result, the ratio for the transmission quality measurement period for the allocated channel can be a ratio of the transmission quality value of the allocated channel and the maximum transmission quality value of the transmission quality value for the at least one available channel.
In order to select an optimal channel for the base station, the transmission quality measurement period for the allocated channel and the transmission quality measurement period for the at least one available channel are compared, whereby the allocated channel can be replaced by allocating one of the at least one available channel having a larger transmission quality measurement period compared to the allocated channel.
Further, the invention provides a method for measuring the transmission quality between a base station and at least one remote station in a communication network as defined above, wherein the method comprises determining the number of remote stations associated to the base station, and defining a transmission quality measurement period for the at least one channel in relation to the number of the remote stations for measuring the transmission quality
Huschke Joerg
Torsner Johan
Zimmerman Gerd
Le Nhan T.
Telefonaktiebolaget LM Ericsson (publ)
Vo Nguyen T.
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