Multi-Carrier Communication Systems Employing Variable Symbol Rates and Number of Carriers

摘要

A multi-carrier communication system such as an OFDM or DMT system has nodes which are allowed to dynamically change their receive and transmit symbol rates, and the number of carriers within their signals. Changing of the symbol rate is done by changing the clocking frequency of the nodes' iFFT and FFT processors, as well as their serializers and deserializers. The nodes have several ways of dynamically changing the number of earners used. The selection of symbol rate and number of earners can be optimized for a given channel based on explicit channel measurements, a priori knowledge of the channel, or past experience. Provision is made for accommodating legacy nodes that may have constraints in symbol rate or the number of carriers they can support. The receiver can determine the correct symbol rate and number of earners through a priori knowledge, a first exchange of packets in a base mode that all nodes can understand, or an indication in the header of the data packet which is transmitted in a base mode of operation that all nodes can understand.

主权项

1. An apparatus for communicating in a wireless multi-carrier system comprising:
a transmitter; and a controller unit coupled to the transmitter, wherein:
the controller unit is configured for setting in the transmitter an initial number of carriers and an initial symbol rate at which symbols are transmitted from the transmitter to a receiver;the transmitter is configured for transmitting a first group of symbols using the initial number of carriers and the initial symbol rate;the controller unit is further configured for changing in the transmitter the rate at which symbols are transmitted from the transmitter to the receiver from the initial symbol rate to a subsequent symbol rate that is different than the initial symbol rate by changing a frequency that is used to clock a serial to parallel converter, a divide by N counter coupled to an iFFT, and a parallel to serial converter by changing a multiplexer output, thereby selecting a different circuit capable of generating the subsequent symbol rate rather than a previous circuit capable of generating the initial symbol rate; andthe transmitter is further configured for transmitting a second group of symbols using the initial number of carriers and the subsequent symbol rate.