Line Topology Estimation of Indoor power Lines Using Multipoint Single Ended Loop Testing

Quality of broadband connectivity over a residential power line is dependent on its topology; which is very different from twisted pair copper used in telephony. In this paper methods to estimate the topology of a power line are investigated. A two step procedure comprising of a set of correlation time domain Reflectometry (CTDR) measurements based on Single Ended Loop Testing (SELT) and an initial topology estimate as a first step, followed by a comparison with frequency domain Reflectometry (FDR) measurement as a second step to finally ascertain the power line topology. A set of codes with complementary autocorrelation property is used for probing the line. The number of bridge taps (BTs) in a power line is large and spaced closely; hence multiple applications of CTDR from different sockets are carried out to understand tap positions close to the measuring socket. An analysis of the measurements from multiple CTDR applications is then used to generate a first estimate of the complete power line topology. In the second step a FDR signature of the loop is computed and compared with the frequency domain Reflectometry (FDR) measurement in a mean squared sense to validate the findings. The CTDR and FDR use existing functional blocks of any DSL modem and do not need any additional equipment for measurement. This method is tested for a wide range of power line topologies with multiple bridge taps. The transfer characteristic of the estimated power line loop topology is derived using transmission matrix method and the channel capacity estimated.