Method and apparatus for transmitting data in a communication system

An apparatus for use in a communication system, the communication system comprising a transmitter and a plurality of receiver devices, each receiver of the plurality of receiver devices being connected to the transmitter via a respective communication channel, the apparatus comprising:

• one or more processors configured to:
• i) precode the data for transmission on the respective communication channels, thereby to provide first precoded data;
• ii) using the first precoded data, for each of the respective communication channels, compute a number of bits to be allocated to that channel;
• iii) determine that the bit allocation does not achieve a maximum bit limit on one or more of the respective communication channels;
• iv) responsive thereto, rank the respective communication channels in an order dependent on their potential channel capacities;
• v) discard for use as a direct channel, one or more of the respective communication channels based on the ranking;
• vi) precode the data for transmission on the respective communication channels such that the one or more discarded channels are not used as a direct channel, thereby to provide second precoded data;
• and
• vii) cause the transmitter to transmit the second precoded data on the respective communication channels.

A method of transmitting data in a communication system comprising a transmitter and a plurality of receiver devices, each receiver device of the plurality of receiver devices being connected to the transmitter via a respective communication channel, the method comprising:

• i) precoding the data for transmission on the respective communication channels, thereby to provide first precoded data;
• ii) using the first precoded data, for each of the respective communication channels, computing a number of bits to be allocated to that respective communication channel, wherein the computing comprises maximizing:
• Σi,kbik
• subject to:
• 0≤bik≤bmax,∀i,k
• E[pik]≤PSDk,∀i,
• where:
• i is an index for the respective communication channels;
• j is an index for the respective communication channels;
• k is a frequency index for one or more different tones;
• bik is a number of bits to be loaded onto an ith channel for a kth tone;
• bmax is a maximum bit limit;
• pik is an instantaneous value of power after precoding for transmission on the ith channel for the kth tone;
• and
• PSDk is a transmission power mask for tone k;
• iii) determining that the bit allocation does not satisfy one or more predetermined criteria;
• iv) ranking the respective communication channels in an order based on one or more channel properties;
• v) discarding for use as a direct channel, one or more of the respective communication channels based on the ranking;
• vi) precoding the data for transmission on the respective communication channels such that the one or more discarded channels are not used as a direct channel, thereby to provide second precoded data;
• and
• vii) transmitting, by the transmitter, the second precoded data on the respective communication channels.