An Ethernet Passive Optical Network over Coax, EPoC, PHY transmitter, comprising: a bit loading table (304, 908) containing respective symbol bit loading for each of a plurality of sub-carriers; a symbol mapper (302, 910) configured to receive a bit stream and, for each sub-carrier of the plurality of sub-carriers, to assign zero or more bits of the bit stream to the sub-carrier based on the respective symbol bit loading for the sub-carrier indicated in the bit loading table; and a plurality of multi-subcarrier modulators associated respectively with a plurality of channels, the plurality of channels formed by respective subsets of the plurality of sub-carriers, configured to modulate the plurality of channels respectively to generate a plurality of respective multi-subcarrier modulated signals, characterized in that to assign zero or more bits of the bit stream to the sub-carrier, the symbol mapper is further configured to: determine, by examining an X-bit of a sub-carrier from the bit loading table, whether or not the sub-carrier is used; if the sub-carrier is not used, assign zero bits of the bit stream to the sub-carrier; if the sub-carrier is used, determine, by examining an M-bit of the sub-carrier from the bit loading table, whether or not the sub-carrier is reserved for data; if the sub-carrier is reserved for data and the symbol bit loading of the sub-carrier is greater than zero, assign one or more bits of the bit stream to the sub-carrier based on a Subcarrier Bit Loading, SBL, field of the sub-carrier in the bit loading table; and if the sub-carrier is not reserved for data, assign zero bits of the bit stream to the sub-carrier. a bit loading table (304, 908) containing respective symbol bit loading for each of a plurality of sub-carriers; a symbol mapper (302, 910) configured to receive a bit stream and, for each sub-carrier of the plurality of sub-carriers, to assign zero or more bits of the bit stream to the sub-carrier based on the respective symbol bit loading for the sub-carrier indicated in the bit loading table; and a plurality of multi-subcarrier modulators associated respectively with a plurality of channels, the plurality of channels formed by respective subsets of the plurality of sub-carriers, configured to modulate the plurality of channels respectively to generate a plurality of respective multi-subcarrier modulated signals, characterized in that to assign zero or more bits of the bit stream to the sub-carrier, the symbol mapper is further configured to: determine, by examining an X-bit of a sub-carrier from the bit loading table, whether or not the sub-carrier is used; if the sub-carrier is not used, assign zero bits of the bit stream to the sub-carrier; if the sub-carrier is used, determine, by examining an M-bit of the sub-carrier from the bit loading table, whether or not the sub-carrier is reserved for data; if the sub-carrier is reserved for data and the symbol bit loading of the sub-carrier is greater than zero, assign one or more bits of the bit stream to the sub-carrier based on a Subcarrier Bit Loading, SBL, field of the sub-carrier in the bit loading table; and if the sub-carrier is not reserved for data, assign zero bits of the bit stream to the sub-carrier. determine, by examining an X-bit of a sub-carrier from the bit loading table, whether or not the sub-carrier is used; if the sub-carrier is not used, assign zero bits of the bit stream to the sub-carrier; if the sub-carrier is used, determine, by examining an M-bit of the sub-carrier from the bit loading table, whether or not the sub-carrier is reserved for data; if the sub-carrier is reserved for data and the symbol bit loading of the sub-carrier is greater than zero, assign one or more bits of the bit stream to the sub-carrier based on a Subcarrier Bit Loading, SBL, field of the sub-carrier in the bit loading table; and if the sub-carrier is not reserved for data, assign zero bits of the bit stream to the sub-carrier.