Method for efficient packet framing in a communication network

Abstract

Techniques to reduce the transmission overheads in a communication system are disclosed. In an embodiment, a method described herein relates to the elimination of redundant padding to realize an integer number of FEC code-words during the FEC-encoding process of transmission as well as the reduction/elimination of redundant padding to realize an integer number of transmission symbols during the subcarrier modulation mapping process of transmitting OFDM/ACMT/DMT symbols. The techniques are described in the context of a communication system based on the MoCA specification. Furthermore, techniques for channel-profiling, channel-estimation and bandwidth request/grant signaling that facilitate the realization of the method of reduction of transmission overheads in a MoCA system are also described.

1 . A method for generating a Forward Error Correction (FEC) encoded frame for use in communicating data between nodes over a network, the method comprising:
 identifying a set of FEC code-words having different sizes, the set of FEC code-words including a largest size FEC code-word;   encoding as much of a payload as possible into one or more FEC code-words of the largest size FEC code-word; and   encoding a remainder portion of the payload into a last FEC code-word, the last FEC code-word being the smallest possible FEC code-word of the set of FEC code-words;   wherein the combination of the one or more largest size FEC code-words and the last FEC code-word forms a shortened FEC encoded frame.   
     
     
         2 . The method of  claim 1  further comprises adding an FEC pad to the payload, wherein the size of the FEC pad is selected so that the remainder portion of the payload and the FEC pad fill the last FEC code-word. 
     
     
         3 . The method of  claim 2  further comprising removing the FEC pad to generate a shortened last FEC code-word and using the shortened last FEC code-word to form the shortened FEC encoded frame. 
     
     
         4 . The method of  claim 1  wherein the set of FEC code-words comprises FEC code-words of sizes (32, 40), (36, 44), (64, 74), (128, 140), and (192, 208) bytes. 
     
     
         5 . The method of  claim 1  further comprising:
 reducing the adaptive constellation multi-tone (ACMT) pad overhead required to ACMT modulate a data frame to form an ACMT-modulated frame, the reduction of said ACMT-pad resulting in a shortened ACMT modulated frame, said method comprising the steps of:   determining a number of ACMT symbols that reduces the medium-occupancy of the associated ACMT modulated frame; and   determining a reduced ACMT pad to be appended to the data frame, the resultant ACMT padded data frame, when modulated, resulting in the number of ACMT symbols, the resultant ACMT symbols being of sizes that reduce medium occupancy, the aggregate of the ACMT modulated symbols being referred to as a shortened ACMT modulated frame.   
     
     
         6 . The method of  claim 1  further comprising generating a shortened adaptive constellation multi-tone (ACMT) modulated frame from the shortened FEC encoded frame, wherein generating the shortened ACMT modulated frame comprises:
 establishing a set of ACMT modulation symbols having different sizes, the set of ACMT modulation symbols including a largest size ACMT modulation symbol;   encoding as much of the shortened FEC encoded frame as possible into one or more ACMT modulation symbols of the largest size ACMT modulation symbol; and   encoding a remainder portion of the shortened FEC encoded frame into a tail ACMT modulation symbol, the tail ACMT modulation symbol being the smallest possible ACMT modulation symbol of the set of ACMT modulation symbols;   wherein the combination of the one or more largest size ACMT modulation symbols and the tail ACMT modulation symbol form the shortened ACMT modulated frame.   
     
     
         7 . The method of  claim 6  further comprising adding an ACMT pad to the shortened FEC encoded frame, wherein the size of the ACMT pad is selected so that the remainder portion of the shortened FEC encoded frame and the ACMT pad fill the tail ACMT modulation symbol. 
     
     
         8 . The method of  claim 6  wherein the set of ACMT modulation symbols comprises ACMT modulation symbols of 32, 64, 128, and 256 tones. 
     
     
         9 . A method for generating an adaptive constellation multi-tone (ACMT) modulated frame for use in communicating data between nodes over a network, the method comprising:
 establishing a set of ACMT modulation symbols having different sizes, the set of ACMT modulation symbols including a largest size ACMT modulation symbol;   encoding as much of a payload as possible into one or more ACMT modulation symbols of the largest size ACMT modulation symbol; and   encoding a remainder portion of the payload into a tail ACMT modulation symbol, the tail ACMT modulation symbol being the smallest possible ACMT modulation symbol of the set of ACMT modulation symbols;   wherein the combination of the one or more largest size ACMT modulation symbols and the tail ACMT modulation symbol form a shortened ACMT modulated frame.   
     
     
         10 . The method of  claim 9  further comprising adding an ACMT pad to the payload, wherein the size of the ACMT pad is selected so that the remainder portion of the payload and the ACMT pad fill the tail ACMT modulation symbol. 
     
     
         11 . The method of  claim 9  wherein the set of ACMT modulation symbols comprises ACMT modulation symbols of 32, 64, 128, and 256 tones. 
     
     
         12 . The method of  claim 9  further comprising determining a number of ACMT modulation symbols that reduces the medium-occupancy of the associated ACMT modulated frame. 
     
     
         13 . A method for decoding a Forward Error Correction (FEC) encoded frame that is used in communicating data between nodes over a network, the method comprising:
 inserting an FEC pad of a predetermined content and size in between the data and parity of a shortened last FEC code-word of a shortened FEC encoded frame, resulting in an FEC encoded frame;   decoding the FEC encoded frame to determine an FEC padded data frame; and   discarding the FEC pad to recover an underlying data frame.   
     
     
         14 . A method for determining a modulation profile for use in communicating data between nodes over a network, the method comprising:
 transmitting a legacy modulation profiling sequence from a transmitter to a receiver;   using the received modulation profiling sequence to determine the signal to noise ratio of legacy tone positions; and   determining the signal-to-noise ratio at the tone positions of a shortened adaptive constellation multi-tone (ACMT) modulation symbol by interpolation of the signal-to-noise ratios of the legacy tone-positions.   
     
     
         15 . The method of  claim 14  further comprising communicating the determined modulation profile of the reduced-size ACMT symbol from the transmitter to the transmitter. 
     
     
         16 . A method determining a modulation profile for use in communicating data between nodes over a network, the method comprising:
 determining a modulation profile for a shortened adaptive constellation multi-tone (ACMT) modulation symbol from a modulation profile of a legacy ACMT modulation symbol, the determination including applying a common and pre-determined set of rules to the modulation profile of the legacy ACMT symbol to determine the modulation profile of the shortened ACMT modulation symbol.   
     
     
         17 . The method of  claim 16  wherein the bit-loading capacity of a tone of a shortened ACMT modulation symbol is determined as the minimum of the bit-loading capacities of adjacent tones of the legacy ACMT modulation symbol. 
     
     
         18 . The method of  claim 16  further comprising communicating a preamble type in use by a transmitter, the modulation profile used by the transmitter in transmitting a shortened ACMT modulated frame, the cyclic-prefix in use by the transmitter for every ACMT symbol, the duration of the transmission, and the ACMT-pad used by the transmitter in its transmission. 
     
     
         19 . The method of  claim 16  further comprising determining channel estimates at tone positions of the shortened ACMT symbol based on channel estimates at tone positions of legacy ACMT modulation symbols as determined from a legacy preamble by determining the size of the shortened ACMT modulation symbol prior to receiving it and interpolating the channel estimates at the tone positions of the legacy ACMT modulation symbol to determine the channel estimates at the tone positions of the shortened ACMT modulation symbol.