Method and apparatus for performing forward error correction in an orthogonal frequency division multiplexed communication network
View Patent ↗According to some embodiments of the disclosed method and apparatus, systems and methods are provided that utilize extra payload capacity present in a symbol pad of a PHY payload to decrease the coding rate of an FEC coding scheme without increasing the symbol rate or decreasing the PHY rate of a corresponding data transmission. If a symbol pad length that would result from encoding a MAC frame using a default coding scheme would be at least as great as a parity length of the default coding scheme, and a new coding scheme maintaining the same parity length but having a reduced information bit length may be determined and used to encode the MAC frame. Owing the reduced information bit length, the new coding scheme has a reduced coding rate, but maintains the same number of OFDM symbols as the default coding scheme.
1. A method for a transmitting network device to encode data for transmission on a network link to a receiving network device, comprising:
obtaining a media access control (MAC) frame scheduled for a physical layer (PHY) payload transmission and having a MAC frame length, wherein the PHY payload comprises a number of symbols;
obtaining a default forward error correction (FEC) coding scheme for the network link, the default FEC coding scheme having a default parity length;
calculating a payload capacity value for the PHY payload using characteristics of the default coding scheme;
if the payload capacity value is at least as great as the default parity length, determining a new FEC coding scheme that maintains the number of orthogonal frequency division multiplexing (OFDM) symbols and is configured such that a symbol pad length for the PHY payload using the new FEC coding scheme is less than a default symbol pad length for the PHY payload using the default FEC coding scheme; and
encoding the MAC frame using the new FEC coding scheme.
2. The method of claim 1 , wherein a new encoded output block of the new FEC coding scheme has a parity length equal to the default parity length, and an information bit length less than the default information bit length.
3. The method of claim 1 , wherein the MAC frame length is known to the receiving device before transmission;
wherein the payload capacity value comprises the default symbol pad length; and
wherein the new FEC coding scheme is configured such that the reduced symbol pad length is less than or equal to the default parity length.
4. The method of claim 3 , wherein the step of determining the new FEC coding scheme comprises:
computing a default number of FEC encoded output blocks to encode the MAC frame using the default FEC coding scheme;
determining an additional encoded output block number equal to an integer that is less than the default symbol pad length divided by the default parity length; and
determining the new FEC such that the new FEC coding scheme encodes the MAC frame using a number of encoded output blocks equal to the default number of FEC encoded output blocks plus the additional encoded output block number.
5. The method of claim 1 , wherein the MAC frame length is not known to the receiving device before transmission;
wherein the payload capacity value comprises a bit length of a remainder value, wherein the remainder value comprises a difference equal to a total number of bits in the PHY payload minus a minimum number of default encoded output blocks multiplied by the default encoded output block length; and
wherein the new FEC coding scheme is configured such that the number of encoded output blocks of the new FEC coding scheme used to encode the MAC frame is one greater than the number of encoded output blocks of the default FEC coding scheme that would be used to encode the MAC frame.
6. A method for a receiving network device to decode data transmitted on a network link from a transmitted network device, comprising:
obtaining an encoded media access control (MAC) frame modulated onto a physical layer (PHY) payload comprising a number of orthogonal frequency division multiplexing (OFDM) symbols;
obtaining a default forward error correction (FEC) coding scheme for the network link, the default FEC coding scheme having a default parity length;
calculating a payload capacity value for the PHY payload using characteristics of the default coding scheme;
if the payload capacity value is at least as great as the default parity length, determining a new FEC coding scheme that maintains the number of OFDM symbols and is configured such that a symbol pad length for the PHY payload using the new FEC coding scheme is less than a default symbol pad length for the PHY payload using the default FEC coding scheme; and
decoding the encoded MAC frame using the new FEC coding scheme.
7. The method of claim 6 , wherein a new encoded output block of the new FEC coding scheme has a parity length equal to the default parity length, and an information bit length less than the default information bit length.
8. The method of claim 6 , wherein an uncoded MAC frame length of the encoded MAC frame is known to the receiving device before transmission;
wherein the payload capacity value comprises the default symbol pad length; and
wherein the new FEC coding scheme is configured such that the reduced symbol pad length is less than or equal to the default parity length.
9. The method of claim 8 , wherein the step of determining the new FEC coding scheme comprises:
computing a default number of FEC encoded output blocks to encode a bit stream having a length equal to the uncoded MAC frame length using the default FEC coding scheme;
determining an additional encoded output block number less than or equal to the greatest integer that is less than the default symbol pad length divided by the default parity length; and
determining the new FEC coding scheme such that the new FEC coding scheme is capable of encoding the bit stream using a number of encoded output blocks equal to the default number of FEC encoded output blocks plus the additional encoded output block number.
10. The method of claim 6 , wherein the MAC frame length is not known to the receiving device before transmission;
wherein the payload capacity value comprises a bit length of a remainder value, wherein the remainder value comprises a difference equal to a total number of bits in the PHY payload minus a minimum number of default encoded output blocks multiplied by the default encoded output block length; and
wherein the new FEC coding scheme is configured such that the number of's of the new FEC coding scheme used to decode the MAC frame is one greater than the number of encoded output blocks of the default FEC coding scheme that would be required to decode the MAC frame.
11. A network device comprising a non-transitory machine-readable storage medium, the computer readable medium having a computer executable code embodied therein for enabling the network device to encode data for transmission on a network link to a receiving network device, the encoding comprising:
obtaining a media access control (MAC) frame scheduled for in a physical layer (PHY) payload transmission and having a MAC frame length, wherein the PHY payload comprises a number of orthogonal frequency division multiplexing (OFDM) symbols;
obtaining a default forward error correction (FEC) coding scheme for the network link, the default FEC coding scheme having a default parity length;
calculating a payload capacity value for the PHY payload using characteristics of the default coding scheme;
if the payload capacity value is at least as great as the default parity length, determining a new FEC coding scheme that maintains the number of OFDM symbols and is configured such that a symbol pad length for the PHY payload using the new FEC coding scheme is less than a default symbol pad length for the PHY payload using the default FEC coding scheme; and
encoding the MAC frame using the new FEC coding scheme.
12. The apparatus of claim 11 , wherein a new encoded output block of the new FEC coding scheme has a parity length equal to the default parity length, and an information hit length less than the default information hit length.
13. The apparatus of claim 1 wherein the MAC frame length is known to the receiving device before transmission;
wherein the payload capacity value comprises the default symbol pad length; and
wherein the new FEC coding scheme is configured such that the reduced symbol pad length is less than or equal to the default parity length.
14. The apparatus of claim 13 , wherein the step of determining the new FEC coding scheme comprises:
computing a default number of FEC encoded output blocks to encode the MAC frame using the default FEC coding scheme;
determining an additional encoded output block number equal to an integer that is less than the default symbol pad length divided by the default parity length; and
determining the new FEC such that the new FEC coding scheme encodes the MAC frame using a number of encoded output blocks equal to the default number of FEC encoded output blocks plus the additional encoded output block number.
15. The apparatus of claim 14 , wherein the MAC frame length is not known to the receiving device before transmission;
wherein the payload capacity value comprises a bit length of a remainder value, wherein the remainder value comprises a difference equal to a total number of bits in the PHY payload minus a minimum number of default encoded output blocks multiplied by the default encoded output block length; and
wherein the new FEC coding scheme is configured such that the number of encoded output blocks of the new FEC coding scheme used to encode the MAC frame is one greater than the number of encoded output blocks of the default FEC coding scheme that would be used to encode the MAC frame.
16. A network device comprising a non-transitory machine-readable storage medium, the computer readable medium having a computer executable code embodied therein for enabling the network device to decode data transmitted on a network link from a transmitted network device, the decoding comprising:
obtaining an encoded media access control (MAC) frame modulated onto a physical layer (PHY) payload comprising a number of orthogonal frequency division multiplexing (OFDM) symbols;
obtaining a default forward error correction (FEC) coding scheme for the network link, the default FEC coding scheme having a default parity length;
calculating a payload capacity value for the PHY payload using characteristics of the default coding scheme;
if the payload capacity value is at least as great as the default parity length, determining a new FEC coding scheme that maintains the number of OFDM symbols and is configured such that a symbol pad length for the PHY payload using the new FEC coding scheme is less than a default symbol pad length for the PHY payload using the default FEC coding scheme; and
decoding the encoded MAC frame using the new FEC coding scheme.
17. The apparatus of claim 16 , wherein a new encoded output block of the new FEC coding scheme has a parity length equal to the default parity length, and an information bit length less than the default information hit length.
18. The apparatus of claim 16 , wherein an uncoded MAC frame length of the encoded MAC frame is known to the receiving device before;
wherein the payload capacity value comprises the default symbol pad length; and
wherein the new FEC coding scheme is configured such that the reduced symbol pad length is less than or equal to the default parity length.
19. The apparatus of claim 18 , wherein the step of determining the new FEC coding scheme comprises:
computing a default number of FEC encoded output blocks to encode a bit stream having a length equal to the uncoded MAC frame length using the default FEC coding scheme;
determining an additional encoded output block number less than or equal to the greatest integer that is less than the default symbol pad length divided by the default parity length; and
determining the new FEC coding scheme such that the new FEC coding scheme is capable of encoding the bit stream using a number of encoded output blocks equal to the default number of FEC encoded output blocks plus the additional encoded output block number.
20. The apparatus of claim 16 , wherein the MAC frame length is not known to the receiving device before transmission;
wherein the payload capacity value comprises a bit length of a remainder value, wherein the remainder value comprises a difference equal to a total number of bits in the PHY payload minus a minimum number of default encoded output blocks multiplied by the default encoded output block length; and wherein the new FEC coding scheme is configured such that the number of encoded output blocks of the new FEC coding scheme used to decode the MAC frame is one greater than the number of encoded output blocks of the default FEC coding scheme that would be required to decode the MAC frame.