A bandwidth allocation strategy for a FDM multichannel modem

Implementing a frequency division multiplexing (FDM)-based modem for a multichannel application requires a bandwidth allocation strategy. That is, one must decide how to allocate total bandwidth to individual channels such that (a) the desired aggregate rate can be achieved and (b) the desired individual channel bit rates can be achieved. An optimal strategy for bandwidth allocation is proposed. The multitone channel result is used to specify a scheme to allocate four separate channels. The allocation strategy assigns to each subchannel a constellation that is equal in size to that of an equivalent single-band modem operating at the aggregate rate. In this manner, bandwidth is allocated proportional to the desired bit rate on a particular subchannel. Power allocation will be done to maintain a constant probability of error between all channels. This technique will allow the user to split total bandwidth to meet error performance objectives, provided that the desired aggregate rate does not exceed the maximum bit rate allowed by channel conditions