Selecting the data rate of a wireless network link according to a measure of error vector magnitude

1. An apparatus for inclusion in a node of a wireless network, the apparatus comprising:

a receiver to receive data from a remote node, including an analog-to-digital converter producing samples of signals received at the node from the remote node, said received signals in the form of packets of data;

a demodulator coupled to the receiver to demodulate samples of the signals received at the receiver to produce demodulated signals, the samples at decision points; and

an error vector magnitude calculator coupled to the receiver to determine a measure of the signal quality of the decision point samples of the received signal; and

a transmitter to transmit data for transmission to the remote node, the transmitter having a settable data rate, the data rate set according to a data rate signal accepted by the transmitter; and

a data rate setting processor coupled to the error vector magnitude calculator and to the transmitter and producing the data rate signal for the transmitter, the data rate signal set such the data rate for transmission to a particular remote node is dependent on the measure of the signal quality produced by the error vector magnitude calculator from signals received from the particular remote node,

such that the error vector magnitude measure determined by the error vector magnitude calculator can be used to select a data rate for communicating between the node and the remote node,

wherein the measure of signal quality is a measure of the error vector magnitude of the received packet, and

wherein the data rate processor includes a memory to store for each remote node from which data was received the measure of the error vector magnitude of the last packet received from the remote node, and a running average the measure of the error vector magnitude of the last number of packets received from the remote node.

2. An apparatus for inclusion in a node of a wireless network the apparatus comprising:

a receiver to receive data from a remote node, including an analog-to-digital converter producing samples of signals received at the node from the remote node, said received signals in the form of packets of data;

a demodulator coupled to the receiver to demodulate samples of the signals received at the receiver to produce demodulated signals, the samples at decision points; and

an error vector magnitude calculator coupled to the receiver to determine a measure of the signal quality of the decision point samples of the received signal; and

a transmitter to transmit data for transmission to the remote node, the transmitter having a settable data rate, the data rate set according to a data rate signal accepted by the transmitter; and

a data rate setting processor coupled to the error vector magnitude calculator and to the transmitter and producing the data rate signal for the transmitter, the data rate signal set such the data rate for transmission to a particular remote node is dependent on the measure of the signal quality produced by the error vector magnitude calculator from signals received from the particular remote node;

such th at the error vector magnitude measure determined by the error vector magnitude calculator can be used to select a data rate for communicating between the node and the remote node,

wherein the measure of signal quality is a measure of the error vector magnitude of the received packet, and

wherein the data rate processor includes a memory to store for each remote node from which data was received the measure of error vector magnitude of the last packet received from the remote node, and a memory to store a table of maximum error vector magnitude measure for each data rate such that data rate signal for transmitting to a particular remote node is determined by a table lookup of the table for the error vector magnitude measure of the last packet received from the particular remote node.

3. An apparatus for inclusion in a node of a wireless network, the apparatus comprising:

a receiver to receive data from a remote node, including an analog-to-digital converter producing samples of signals received at the node from the remote node, said received signals in the form of packets of data;

a demodulator coupled to the receiver to demodulate samples of the signals received at the receiver to produce demodulated signals, the samples at decision points; and

an error vector magnitude calculator coupled to the receiver to determine a measure of the signal quality of the decision point samples of the received signal,

such that the error vector magnitude measure determined by the error vector magnitude calculator can be used to select a data rate for communicating between the node and the remote node,

wherein the determining of the measure of the error vector magnitude of the received packet includes determining a function of the average of the squared Euclidian distance on the I,Q plane between decision-point samples of the signal received and the nearest ideal constellation points to the decision points samples.

4. An apparatus for inclusion in a node of a wireless network, the apparatus comprising:

a receiver to receive data from a remote node, including an analog-to-digital converter producing samples of signals received at the node from the remote node, said received signals in the form of packets of data;

a demodulator coupled to the receiver to demodulate samples of the signals received at the receiver to produce demodulated signals, the samples at decision points; and

an error vector magnitude calculator coupled to the receiver to determine a measure of the signal quality of the decision point samples of the received signal,

such that the error vector magnitude measure determined by the error vector magnitude calculator can be used to select a data rate for communicating between the node and the remote node,

wherein the error vector magnitude calculator is coupled to the demodulator and wherein determining of the measure of the error vector magnitude of the received packet includes determining a function of the average of the squared Euclidian distance on the I,Q plane between decision-point samples of the signal received and the correct ideal constellation points for the signal as determined by demodulating the signal.

5. A method of setting a data rate for a node of a wireless network the data rate for sending data to a remote node, the method comprising:

receiving a packet from the remote node; and

determining a measure of signal quality for the received packet,

such that the determined signal quality can be used to select a data rate for communicating between the node and the remote node,

wherein the determined measure of signal quality is a measure of the error vector magnitude of the received packet, and

wherein the determining of the measure of the error vector magnitude of the received packet includes determining the average of the squared Euclidian distance on the I,Q plane between decision-point samples of the signal received and the nearest ideal constellation points to the decision point samples.

6. A method of setting a data rate for a node of a wireless network, the data rate for sending data to a remote node, the method comprising:

receiving a packet from the remote node; and

determining a measure of signal quality for the received packet,

such that the determined signal quality can be used to select a data rate for communicating between the node and the remote node,

wherein the determined measure of signal quality is a measure of the error vector magnitude of the received packet, and

wherein the determining of the measure of the error vector magnitude of the received packet includes determining the average of the squared Euclidian distance on the I,Q plane between decision-point samples of the signal received and the correct ideal constellation points for the signal as determined by demodulating the signal.

7. A method of setting a data rate for a node of a wireless network, the data rate for sending data to a remote node, the method comprising:

receiving a packet from the remote node; and

determining a measure of signal quality for the received packet;

such that the determined signal quality can be used to select a data rate for communicating between the node and the remote node,

wherein the determined measure of signal quality is a measure of the error vector magnitude of the received packet,

wherein the method further comprises:

storing for each remote node from which data was received the measure of error vector magnitude of the last packet received from the remote node, and

wherein selecting the data rate for transmitting to a particular remote node uses a table lookup of a table of maximum error vector magnitude measure for each data rate, the table lookup using the error vector magnitude measure of the last packet received from the particular remote node.

8. A method of setting a data rate for a node of a wireless network, the data rate for sending data to a remote node, the method comprising:

receiving a packet from the remote node;

determining a measure of signal quality for the received packet; and

storing for each remote node from which data was received the measure of signal quality of the last packet received from the remote node,

such that the determined signal quality can be used to select a data rate for communicating between the node and the remote node;

wherein the determined measure of signal quality is a measure of the error vector magnitude of the received packet, and

the method further comprising:

storing for each remote node from which data was received the measure of error vector magnitude of the last packet received from the remote node;

storing for each remote node from which data was received a measure of the average error vector magnitude of the last number N of packets received from the remote node;

ascertaining whether to decrease the data rate for transmitting to a particular remote node according to the stored last packet's error vector magnitude; and

ascertaining whether to increase the data rate for transmitting to a particular remote node according to the stored measure of the average error vector magnitude of the last N packets.

9. An apparatus for setting the data rate for a node of a wireless network, the data rate for sending data to a remote node, the apparatus included in the node and comprising:

means for receiving a packet from the remote node; and

means for determining a measure of signal quality for the received packet,

such that the determined sisal quality can be used to select a data rate for communicating between the node and the remote node,

wherein the measure of signal quality is a measure of the error vector magnitude of the received packet, and

wherein the means for determining the measure of the error vector magnitude of the received packet includes means for determining the average of the squared Euclidian distance on the I,Q plane between decision-point samples of the signal received and the nearest ideal constellation points to the decision points samples.

10. An apparatus for setting the data rate for a node of a wireless network, the data rate for sending data to a remote node, the apparatus included in the node and comprising:

means for receiving a packet from the remote node; and

means for determining a measure of signal quality for the received packet,

such that the determined signal quality can be used to select a data rate for communicating between the node and the remote node,

wherein the measure of signal quality is a measure of the error vector magnitude of the received packet, and

wherein the means for determining the measure of the error vector magnitude of the received packet includes means for determining the average of the squared Euclidian distance on the I,Q plane between decision-point samples of the signal received and the correct ideal constellation points for the signal as determined by demodulating the signal.