Multiple-input multiple-output system and method
A multiple-input multiple-output (MIMO) system can transmit on multiple antennas simultaneously and receive on multiple antennas simultaneously. Unfortunately, because a legacy 802.11a/g device is not able to decode multiple data streams, such a legacy device may “stomp” on a MIMO packet by transmitting before the transmission of the MIMO packet is complete. Therefore, MIMO systems and methods are provided herein to allow legacy devices to decode the length of a MIMO packet and to restrain from transmitting during that period. These MIMO systems and methods are optimized for efficient transmission of MIMO packets.
1. A method of improving transmission of a multiple-input multiple-output (MIMO) signal, the method comprising:
assessing a quality of a channel using a first packet received by an intended receiver from a transmitter of the MIMO signal;
generating channel corrected pilots based at least in part on one or more correction values for the channel, wherein the one or more correction values are computed based at least in part on antenna gain control and channel inversion and are fed back as inputs to the antenna gain control; and
sending a second packet from the intended receiver to the transmitter, the second packet including feedback information for improving transmission of the MIMO signal by the transmitter, the feedback information derived from a first plurality of data streams previously transmitted substantially simultaneously, wherein the feedback information comprises channel information including a pilot error vector magnitude (EVM) computed from the channel corrected pilots and known clean pilots.
2. The method of claim 1 , wherein the second packet includes a clear to send (CTS) packet.
3. The method of claim 1 , wherein the second packet includes an acknowledge (ACK) packet.
4. The method of claim 1 , wherein the channel information comprises channel estimates.
5. The method of claim 1 , wherein the channel information comprises a recommended transmit scheme for the transmitter of the multiple-input multiple-output (MIMO) signal.
6. The method of claim 1 , wherein the feedback information includes a data rate to be used by the transmitter.
7. The method of claim 1 , wherein the feedback information includes an indicator for at least one of a minimum data rate, a maximum data rate, a higher data rate, and a lower data rate to be used by the transmitter.
8. The method of claim 1 , wherein the transmitter selects a data rate to use for each of the number of data streams transmitted from the transmitter in response to the feedback information.
9. The method of claim 1 , wherein the transmitter selects sub-carriers to use for each of the number of data streams transmitted from the transmitter in response to the feedback information.
10. The method of claim 1 , wherein the transmitter selects transmit antennas used to transmit each of the number of data streams from the transmitter in response to the feedback information.
11. The method of claim 1 , wherein the transmitter selects transmit power for transmit antennas used to transmit each of the number of data streams from the transmitter in response to the feedback information.
12. An apparatus for wireless communication, comprising:
a processor;
a memory in electronic communication with the processor, the memory embodying instructions, the instructions being executable by the processor to cause the apparatus to:
assess a quality of a channel using a first packet received from a transmitter of the MIMO signal;
generate channel corrected pilots based at least in part on one or more correction values for the channel, wherein the one or more correction values are computed based at least in part on antenna gain control and channel inversion and are fed back as inputs to the antenna gain control; and
send a second packet to the transmitter, the second packet including feedback information for improving transmission of the MIMO signal by the transmitter, the feedback information derived from a first plurality of data streams previously transmitted substantially simultaneously, wherein the feedback information comprises channel information including a pilot error vector magnitude (EVM) computed from the channel corrected pilots and known clean pilots.
13. The apparatus of claim 12 , wherein the second packet comprises a clear to send (CTS) packet.
14. The apparatus of claim 12 , wherein the second packet comprises an acknowledge (ACK) packet.
15. The apparatus of claim 12 , wherein the channel information comprises channel estimates.
16. The apparatus of claim 12 , wherein the channel information comprises a recommended transmit scheme for the transmitter of the multiple-input multiple-output (MIMO) signal.
17. The apparatus of claim 12 , wherein the feedback information includes a data rate to be used by the transmitter.
18. The apparatus of claim 12 , wherein the feedback information includes an indicator for at least one of a minimum data rate, a maximum data rate, a higher data rate, and a lower data rate to be used by the transmitter.
19. The apparatus of claim 12 , wherein the transmitter selects a data rate to use for each of the number of data streams transmitted from the transmitter in response to the feedback information.
20. A computer program product comprising a non-transitory computer-readable medium storing instructions executable by a processor to cause a device including the non-transitory computer-readable medium and the processor to:
assess a quality of a channel using a first packet received by an intended receiver of the device from a transmitter of the MIMO signal;
generate channel corrected pilots based at least in part on one or more correction values for the channel, wherein the one or more correction values are computed based at least in part on antenna gain control and channel inversion and are fed back as inputs to the antenna gain control; and
send a second packet from the intended receiver to the transmitter, the second packet including feedback information for improving transmission of the MIMO signal by the transmitter, the feedback information derived from a first plurality of data streams previously transmitted substantially simultaneously, wherein the feedback information comprises channel information including a pilot error vector magnitude (EVM) computed from the channel corrected pilots and known clean pilots.
21. The method of claim 1 , further comprising:
receiving, by the intended receiver, a number of data streams transmitted substantially simultaneously by the transmitter of the MIMO signal, wherein the transmitter of the MIMO signal selects the number of data streams based at least in part on the sent pilot EVM.
22. The apparatus of claim 12 , wherein the memory embodying further instructions, the further instructions being executable by the processor to cause the apparatus to:
receive a number of data streams transmitted substantially simultaneously by the transmitter of the MIMO signal, wherein the transmitter of the MIMO signal selects the number of data streams based at least in part on the sent pilot EVM.
23. The computer program product of claim 20 , wherein the non-transitory computer-readable medium storing further instructions executable by a processor to cause a device including the non-transitory computer-readable medium and the processor to:
receive, by the intended receiver, a number of data streams transmitted substantially simultaneously by the transmitter of the MIMO signal, wherein the transmitter of the MIMO signal selects the number of data streams based at least in part on the sent pilot EVM.