System and method for measuring signal to noise values in an adaptive wireless communication system
View Patent ↗The system and method optimizes a SNR calculation for a signal received during a downlink burst even in the absence of a node's preferred modulation. This system and method are used in communication systems that include a multi-modulation modem. An adaptation factor is selected whereby its use during portions of the downlink burst, which were not modulated using the preferred modulation, provides the SNR. The selected adaptation factor is used by an equalizer to perform channel inversion to the signal. The system and method can be used in, for example, an FDD or TDD communication system. Such communication systems can be, for example, symmetric, asymmetric, and/or adaptive in their operation.
1. A wireless communication system, comprising:
a base station configured to transmit a signal as a downlink burst, the downlink burst including a portion modulated with a modulation technique; and
a processor coupled to the base station and configured to receive, in an uplink transmission from a recipient node in response to a receipt of the downlink burst from the base station, a signal-to-noise ratio (SNR) measurement measured by the recipient node during the portion of the downlink burst, the portion addressed to one of a plurality of wireless nodes other than the recipient node, the processor further configured to determine, based on the received SNR measurement, whether a current preferred modulation technique of the recipient node should be changed for future downlink communication addressed to the recipient node.
2. The system of claim 1 , wherein the modulation technique that modulates the portion of the downlink burst is selected from a group consisting of quadrature amplitude modulation (“QAM”)-16, quadrature phase shift keying (“QPSK”) modulation, and QAM-64.
3. The system of claim 1 , wherein the portion is a first portion, the modulation technique that modulates the first portion is a first modulation technique, the downlink burst further includes a second portion modulated with a second modulation technique, and the first portion comprises a control header of the downlink burst.
4. The system of claim 3 , wherein the second portion is addressed to one of the plurality of wireless nodes other than the recipient node.
5. The system of claim 3 , wherein the first modulation technique is more robust than the second modulation technique.
6. The system of claim 1 , wherein the portion is a first portion, and the downlink burst includes a second portion modulated with a second modulation technique.
7. The system of claim 1 , wherein the downlink burst includes no portion addressed to the recipient node.
8. The system of claim 1 , wherein the processor is further configured to compare the received SNR measurement to a SNR range associated with the current preferred modulation technique, the SNR range including a bottom threshold and a top threshold, and the processor is configured to change the current preferred modulation technique to a more robust modulation technique if the received SNR measurement is lower than the bottom threshold and the processor is configured to change the current preferred modulation technique to a less robust modulation technique if the received SNR measurement is higher than the top threshold.
9. The system of claim 1 , wherein the portion is one of two portions of the downlink burst, each portion modulated with one of a plurality of available modulation techniques, the SNR measurement is one of two SNR measurements received from the recipient node corresponding to the two portions, respectively, and the processor is further configured to select, from the two SNR measurements, the SNR measurement to be used to determine whether to change the current preferred modulation technique.
10. The system of claim 9 , wherein the processor is configured to identify whether one of the two SNR measurements is a preferred SNR measurement corresponding to a portion modulated with the current preferred modulation technique associated with the recipient node, and, if so, to select the preferred SNR measurement to be used to determine whether to change the current preferred modulation technique.
11. An apparatus, comprising:
a modem configured to receive a downlink burst from a base station, the downlink burst including a portion modulated with a modulation technique, the portion addressed to one of a plurality of wireless nodes other than the apparatus; and
a processor module coupled to the modem and configured to measure a signal-to-noise ratio (SNR) measurement corresponding to the portion and determine, based on the SNR measurement, whether to change a current preferred modulation technique for receiving future downlink transmissions from the base station.
12. The apparatus of claim 11 , wherein the modulation technique that modulates the portion of the downlink burst is selected from a group consisting of: quadrature amplitude modulation (“QAM”)-16, QAM-64, and quadrature phase shift keying (“QPSK”) modulation.
13. The apparatus of claim 11 , wherein the portion is a first portion, the modulation technique that modulates the first portion is a first modulation technique, the downlink burst further includes a second portion modulated with a second modulation technique, and the first portion comprises a control header of the downlink burst.
14. The apparatus of claim 13 , wherein the second portion is addressed to one of the plurality of wireless nodes other than the apparatus.
15. The apparatus of claim 13 , wherein the first modulation technique is more robust than the second modulation technique.
16. The apparatus of claim 11 , wherein the portion is a first portion, and the downlink burst includes a second portion modulated with a second modulation technique.
17. The apparatus of claim 16 , wherein the downlink burst includes no portion addressed to the apparatus.
18. The apparatus of claim 11 , wherein the processor module is further configured to compare the SNR measurement to a SNR range associated with the current preferred modulation technique, the SNR range including a bottom threshold and a top threshold, the processor module is configured to change the current preferred modulation technique to a more robust modulation technique if the SNR measurement is lower than the bottom threshold and the processor module is configured to change the current preferred modulation technique to a less robust modulation technique if the SNR measurement is higher than the top threshold.
19. The apparatus of claim 11 , wherein the portion is one of two portions of the downlink burst, each portion modulated with one of a plurality of available modulation techniques, the SNR measurement is one of two SNR measurements measured by the apparatus corresponding to the two portions, respectively, and the processor module is further configured to select, from the two SNR measurements, the SNR measurement to be used to determine whether to change the current preferred modulation technique.
20. The apparatus of claim 19 , wherein the processor module is configured to identify whether one of the two SNR measurements is a preferred SNR measurement corresponding to a portion modulated with the current preferred modulation technique and to select the preferred SNR measurement if so identified.
21. A method, comprising:
receiving, by a wireless node from a base station, a downlink burst including a portion modulated with a modulation technique, the portion addressed to one of a plurality of wireless nodes other than the wireless node;
measuring, by the wireless node, a signal-to-noise ratio (SNR) measurement of the portion; and
using the SNR measurement, by the wireless node, to determine whether to change a current preferred modulation technique for receiving future transmissions from the base station.
22. The method of claim 21 , wherein the portion is a first portion, the modulation technique that modulates the first portion is a first modulation technique, the downlink burst further includes a second portion modulated with a second modulation technique, and the first portion comprises a control header of the downlink burst.
23. The method of claim 22 , wherein the second portion is addressed to one of the plurality of wireless nodes other than the wireless node.
24. The method of claim 22 , wherein the first modulation technique is more robust than the second modulation technique.
25. The method of claim 21 , wherein the downlink burst includes no portion addressed to the wireless node.
26. The method of claim 21 , wherein the using comprises comparing the SNR measurement to a SNR range associated with the current preferred modulation technique, the SNR range including a bottom threshold and a top threshold, and the method further comprises changing the current preferred modulation technique to a more robust modulation technique if the SNR measurement is lower than the bottom threshold and the method further comprises changing the current preferred modulation technique to a less robust modulation technique if the SNR measurement is higher than the top threshold.
27. The method of claim 21 , wherein the portion is one of two portions of the downlink burst, each portion modulated by the base station with one of a plurality of available modulation techniques, and wherein the measuring of the method comprises measuring two SNR measurements corresponding to the two portions, respectively, and the method further includes selecting, from the two SNR measurements, the SNR measurement to be used for determining whether to change the current preferred modulation technique.
28. The method of claim 27 , wherein the selecting of the SNR measurement to be used for determining whether to change the current preferred modulation technique includes identifying whether one of the two SNR measurements is a preferred SNR measurement corresponding to a portion modulated with the current preferred modulation technique, and, if so, selecting the preferred SNR measurement.