System and method for power line communication

Abstract

A communication system for a power line is described. A transmission system of the communication system divides the time axis into a number of time slots synchronized such that one time slot can start about a zero crossing of the power line signal. These time slots are referred to as channels and are numbered from 1 to n. A modulation method is described to is narrow band continuous phase FSK, where a number m of modulating frequencies are used, arranged such that an integral number of full cycles fit into each channel time slot for all m frequencies. The system transmits during only a subset of the available time slots (channels) concentrated near the zero crossing of the power line waveform where the noise is typically minimal.

1 .- 19 . (canceled) 
     
     
         20 . A method, comprising:
 receiving data transmitted in an AC power line signal in a first transmission period from a transmitter, the transmitted data being modulated initially into a first set of time slots dividing the first transmission period;   determining whether the data is received properly;   transmitting an indication of the determination to the transmitter; and   when the transmitted indication indicates that the data was not received properly, subsequently receiving data transmitted in the AC power line signal in a second transmission period according to a modulation scheme in a second set of time slots dividing the second transmission period, the modulation scheme encoding at least one data bit into a greater number of time slots than would occur according to the initial modulation.   
     
     
         21 . The method of  claim 20 , wherein the first and second sets of time slots include similar time slots in different transmission periods. 
     
     
         22 . The method of  claim 20 , wherein the first and second sets of time slots include every available time slot within each transmission period. 
     
     
         23 . The method of  claim 20 , wherein the first and second sets of time slots include different time slots in different transmission periods. 
     
     
         24 . The method of  claim 20 , wherein a binary frequency shift keying modulation is used in the initial modulation and the modulation scheme. 
     
     
         25 . The method of  claim 20 , wherein the first and the second sets of time slots are centered around different zero-crossings of the AC power line signal. 
     
     
         26 . The method of  claim 20 , wherein one bit of the data is initially modulated in each time slot of the first set of time slots. 
     
     
         27 . The method of  claim 26 , wherein the modulation scheme includes redundantly encoding the at least one bit of the data over a plurality of the second subset of time slots. 
     
     
         28 . The method of  claim 27 , wherein the modulation scheme includes redundantly encoding the at least one bit of the data over a plurality of the second set of time slots centered around a same zero-crossing of the AC power line signal. 
     
     
         29 . The method of  claim 27 , wherein the modulation scheme includes redundantly encoding the at least one bit of the data over a plurality of the second set of time slots centered around different zero-crossings of the AC power line signal. 
     
     
         30 . The method of  claim 20 , wherein the modulation scheme includes redundantly encoding the at least one bit of data using frequency diversity. 
     
     
         31 . The method of  claim 30 , wherein the redundantly encoded data is encoded in at least one time slot in a plurality of second transmission periods at a different frequency in each of the second transmission periods, each of the second transmission periods having time slots centered around respective zero-crossings of the AC power line signal. 
     
     
         32 . The method of  claim 20 , wherein a cyclic redundancy check polynomial is used to determine a properly reception of data. 
     
     
         33 . The method of  claim 32 , wherein the indication is transmitted through a positive acknowledgment protocol. 
     
     
         34 . The method of  claim 20 , further comprising iteratively receiving data transmitted in additional sets of time slots with increasing redundancy in response to successive indications that the data was not received properly at each iteration. 
     
     
         35 . A circuit comprising:
 a connection to an AC power line signal;   a decoding module for decoding data modulated into a first set of time slots dividing a first transmission period of the AC power line signal; and   a processing device for determining whether the initially modulated data was properly received at a receiver and transmitting an indication of the determination to a transmitter, wherein the decoding module subsequently decodes data determined to be improperly received from a second set of time slots in a second transmission period and wherein at least one bit of the improperly received data is modulated into a greater number of time slots in the second set of time slots than in the first set of time slots.   
     
     
         36 . The circuit of  claim 35 , wherein the processing device is a microcontroller and the decoding module is part of the microcontroller. 
     
     
         37 . A method, comprising:
 initially receiving first data transmitted over a plurality of time slots dividing a time period in a power line signal,   identifying at least one time slot from the plurality of time slots likely to yield least noise based on the received first data;   notifying a transmitter of the identified at least one time slot; and   subsequently receiving second data from the transmitter over the identified at least one time slot.   
     
     
         38 . The method of  claim 37 , wherein the first data is different from the second data. 
     
     
         39 . The method of  claim 37 , wherein the first data is the same as the second data. 
     
     
         40 . The method of  claim 37 , wherein each time period includes a zero-crossing of the power line signal. 
     
     
         41 . The method of  claim 37 , wherein at least one time period includes a plurality of zero-crossings of the power line signal. 
     
     
         42 . The method of  claim 37 , further comprising:
 initially receiving the first data over a plurality of frequencies in the plurality of time slots;   identifying at least one of the frequencies likely to yield least noise; and   notifying the transmitter of the identified at least one frequency;   subsequently receiving the second data over the identified at least one frequency.   
     
     
         43 . The method of  claim 42 , further comprising:
 initially receiving the first data over a plurality of phases in the plurality of time slots;   identifying at least one of the phases likely to yield least noise; and   notifying the transmitter of the identified at least one phase; and   subsequently receiving the second data over the identified at least one phase.