Method and arrangement to estimate tranmission channel characteristcs

#The present invention relates to a method to estimate a transmission channel characteristic as defined in the non-characteristic part of claim 1, a transmission channel characteristic estimating arrangement able to perform this method as defined in the non-characteristic part of claim 8, and a related remote terminal as defined in the non-characteristic part of claim 9.

#Such a method to estimate a transmission channel characteristic and related equipment are already known in the art, e.g. from the U.S. Pat. No. 4,105,995, entitled ‘Digitally Controlled Transmission Impairment Measurement Apparatus’. Typically, the operator needs knowledge of certain channel characteristics of a transmission channel between a central office and a remote terminal to be able to guarantee a certain service to a subscriber that has installed the remote terminal. The presence of line imperfections such as bridged taps, line attenuation, ageing effects, disturbers like radio frequency interference, and so on, has to be estimated by the operator before a certain quality of service can be guaranteed. To estimate all basic parameters necessary to characterise a transmission channel for its ability to carry data traffic, U.S. Pat. No. 4,105,995 describes a portable microprocessor controlled apparatus that measures specified parameters for a telephone channel. The known apparatus for channel characteristic estimation either consists of two units to be connected respectively to both ends of the transmission channel, or of a single unit to be connected to a single end of the transmission channel. The latter embodiment of the known channel characteristic estimating apparatus requires manual loop-back at the end of the transmission channel whereto the apparatus is not coupled. Summarising, U.S. Pat. No. 4,105,995 describes dedicated transmission channel test equipment enabling off-line measurement of channel characteristics. To apply the known technique, transmission of user data over the transmission channel has to be interrupted and test equipment has to be connected to the transmission channel either at one or at both sides of the channel.

#It is an object of the present invention to provide a method for estimation of a transmission channel characteristic and related equipment similar to the above described one, but which allows both on-line and off-line channel characteristic estimation without the necessity to connect dedicated test equipment to the transmission channel.

#According to the invention, this object is achieved by the method to estimate a transmission channel characteristic defined by claim 1, the transmission channel characteristic estimating arrangement defined by claim 8, and the remote terminal defined by claim 9.

#Indeed, the remote terminal itself collects all information required to estimate the transmission channel characteristic of interest and sends this information back to the central office wherein the information is matched with a simulation model of the transmission channel and remote terminal. The information collected by the remote terminal can be fed back in a multiplexed way simultaneously with user data so that the data traffic over the transmission channel does not have to be interrupted. The simulation model used in the central office for the matching process typically contains a number of parameters, e.g. the location along the transmission line of a bridged tap, corresponding to the transmission channel characteristics of interest. During the matching process, the values of these parameters are determined.

#It is to be noticed that the term ‘comprising’, used in the claims, should not be interpreted as being limitative to the means listed thereafter. Thus, the scope of the expression ‘a device comprising means A and B’ should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.