US 7,933,344 B2 · OFDMA based on cognitive radio

Abstract

A multiuser scheme allowing for a number of users, sets of user, or carriers to share one or more channels is provided. In the invention, the available channel bandwidth is subdivided into a number of equal-bandwidth subchannels according to standard OFDM practice. The transmitter is informed by an application that it needs to transmit data a particular rate. The transmitter determines the minimum number of subchannels and maximum energy (or noise) threshold for each subchannel necessary to achieve that data rate and selects a set of subchannels matching those requirements. The subchannels need not be contiguous in the spectrum or belong to the same channel. Once the transmitter has selected the required number of subchannels, it begins transmitting simultaneously on those subchannels across the entire bandwidth used by those subchannels.

Claims19

Dependent claims

A method of wireless communication between two or more devices at a data rate, the method comprising:

a) receiving a request for communication at the data rate;
b) determining a minimum number of OFDM subchannels and energy threshold for each subchannel necessary to achieve the data rate;
and
c) selecting a set of the OFDM subchannels;
d) tuning a transmitter to one or more of the subchannels in the set;
and
e) performing energy detection on one or more subchannels from said set of OFDM subchannels;
and
f) dropping any subchannels from said set of OFDM subchannels whose energy level exceeds the threshold;
and
g) comparing the number of OFDM subchannels in the set after dropping in (f) to the determined minimum number of OFDM subchannels;
and
h) when the comparing in (g) indicates that the set contains less than the determined minimum number of OFDM subchannels, adding one or more subchannels to said set of OFDM subchannels;
and
i) repeating (f) through (h) until the comparing in (g) indicates that set contains the determined minimum number of OFDM subchannels;
and
j) transmitting on a channel consisting of the set of OFDM subchannels.

14 more elements

A wireless communication system for transmitting data, the system including a plurality of communication devices that share a plurality of OFDM subcarriers, each of the communication devices executing an application that defines a data rate for transmission, the system comprising:

in each of the plurality of communication devices:
a) a subchannel determining module to receive a request for communication at the data rate, and to determine a minimum number of OFDM subcarriers needed to achieve the data rate and an energy threshold for determining whether an OFDM subcarrier is available;
and
b) a signal-to-noise level detection module to detect the signal-to-noise level on each OFDM subcarrier, to determine whether an OFDM subcarrier is available by determining whether the signal-to-noise level of the OFDM subcarrier is below the energy threshold determined by the subchannel determining module, and to select a set of available OFDM subcarriers;
and
c) a transmitter that, when a number of subcarriers selected for the set by the signal-to-noise detection module meets the minimum number of OFDM subcarriers determined by the subchannel determining module, transmits data generated by the application over the set of subcarriers while a second transmitter in a second of the plurality of communication devices transmits on a second, disjoint set of subcarriers of the plurality of OFDM subcarriers,
wherein, in each of the plurality of communication devices, when the number of subcarriers selected for the set by the signal-to-noise detection module does not meet the minimum number of OFDM subcarriers determined by the subchannel determining module, provides an indication is provided to the application that the data rate is not achievable.

4 more elements

Dependencies are inferred from the claim text.

OFDMA based on cognitive radio

Life of this patent

OFDMA based on cognitive radio

Life of this patent

Abstract

Claims19