Sub-band feedback for beamforming on downlink multiple user MIMO configurations
View Patent ↗A method in a communication network includes an access point, using a multiple input multiple output antenna configuration, sending out a sounding packet to a plurality of client stations. The client stations determine a channel estimation of the sounding packet, but only a channel estimation of a portion of the entire sounding packet to avoid processing the entire packet. The resulting partial estimation is sent to the access point for using in transmit beamforming. In other examples, the client station sends a reverse link sounding packet over a portion a channel having a bandwidth less than the sounding packet, and from this the access point determines partial channel estimations and transmit beamforming conditions.
1. A method in a communication network, the method comprising:
(i) receiving, at a client device, a sounding packet from an access point device over a wireless downlink communication channel having a plurality of 20 MHz-wide subchannels, the sounding packet having a packet bandwidth that spans the plurality of 20 MHz-wide subchannels;
(ii) at the client device, identifying a subchannel block of the sounding packet, wherein the subchannel block spans only a subset of the plurality of 20 MHz-wide subchannels, and the subchannel block has a subchannel block contiguous bandwidth that is a) at least 20 MHz and b) smaller than the packet bandwidth of the sounding packet;
(iii) performing a channel estimation (a) on the subchannel block, but (b) not on any other 20 MHz-wide subchannels of the plurality of 20 MHz-wide subchannels, to determine a partial channel estimation of the downlink communication channel; and
(iv) communicating, to the access point in a feedback frame, the partial channel estimation of the downlink communication channel so that the access point can determine a steering matrix from the partial channel estimation for application to only a portion, in frequency, of an information carrying data packet, transmitted by the access point, when the information carrying data packet has a bandwidth larger than the subchannel block, wherein the feedback frame includes an indication of a bandwidth of the subchannel block to which the partial channel estimation corresponds, wherein the portion of the information carrying data packet corresponds in frequency to the subchannel block.
2. The method of claim 1 , wherein the sounding packet is a null data packet (NDP) sounding packet containing (i) an announcement frame and (ii) a very high throughput control frame.
3. The method of claim 1 , wherein the (i)-(iv) are performed for each of a plurality of client stations.
4. The method of claim 1 , wherein performing the channel estimation on the subchannel block comprises determining, at the client device, a compressed steering matrix from the subchannel block.
5. The method of claim 1 , wherein performing the channel estimation on the subchannel block comprises determining, at the client device, an uncompressed steering matrix from the subchannel block.
6. The method of claim 1 , wherein performing the channel estimation on the subchannel block comprises determining, at the client device, channel state information from the subchannel block.
7. The method of claim 1 , wherein the sounding packet is an IEEE 802.11ac sounding packet.
8. The method of claim 7 , wherein the packet bandwidth of the sounding packet is 40 MHz, 80 MHz, or 160 MHz.
9. The method of claim 1 , wherein the plurality of 20 MHz-wide subchannels comprises a 20 MHz-wide control channel and at least one 20 MHz-wide extension channel, wherein identifying the subchannel block of the sounding packet comprises identifying a subchannel block that includes at least the 20 MHz-wide control channel.
10. The method of claim 1 , wherein identifying the subchannel block of the sounding packet comprises identifying any combination of at least two contiguous 20 MHz-wide subchannels in the plurality of 20 MHz-wide subchannels as the subchannel block.
11. The method of claim 1 , further comprising:
determining, at the access point, the steering matrix from the partial channel estimation; and
applying, at the access point, the steering matrix in transmitting the information carrying data packet to the client device on the downlink channel.
12. The method of claim 11 , wherein applying the steering matrix in transmitting the information carrying data packet comprises:
applying the steering matrix to the full information carrying data packet, when the information carrying data packet has a bandwidth that is the same as the packet bandwidth.
13. An apparatus comprising:
a transceiver configured to
receive a sounding packet from an access point, the sounding packet having a packet bandwidth that spans a downlink communication channel having a plurality of 20 MHz-wide subchannels;
a channel estimation circuit configured to
identify a subchannel block within the sounding packet, wherein the subchannel block spans only a subset of the plurality of 20 MHz-wide subchannels, and the subchannel block has a subchannel block contiguous bandwidth that is a) at least 20 MHz and b) smaller than the packet bandwidth of the sounding packet, and
perform channel estimation (i) on the subchannel block, but (ii) not on any other 20 MHz-wide subchannels of the plurality of 20 MHz-wide subchannels, to determine a partial channel estimation of a downlink communication channel;
wherein the transceiver is further configured to
communicate, to the access point in a feedback frame, the partial channel estimation of the downlink communication channel so that the access point can determine a steering matrix from the partial channel estimation for application to only a portion, in frequency, of an information carrying data packet when the information carrying data packet has a bandwidth larger than the subchannel block, wherein the feedback frame includes an indication of a bandwidth of the subchannel block to which the partial channel estimation corresponds, wherein the portion of the information carrying data packet corresponds in frequency to the subchannel block.
14. The apparatus of claim 13 , wherein the channel estimation circuit is configured to perform the channel estimation on the subchannel block by determining a compressed steering matrix from the subchannel block.
15. The apparatus of claim 13 , wherein the channel estimation circuit is configured to perform the channel estimation on the subchannel block by determining an uncompressed steering matrix from the subchannel block.
16. The apparatus of claim 13 , wherein the channel estimation circuit is configured to perform the channel estimation on the subchannel block by determining channel state information from the subchannel block.
17. The apparatus of claim 13 , wherein the plurality of 20 MHz-wide subchannels comprises a 20 MHz-wide control channel and at least one 20 MHz-wide extension channel, wherein the channel estimation circuit is configured to identify the subchannel block within the sounding packet by identifying a subchannel block that includes at least the 20 MHz-wide control channel.
18. The apparatus of claim 13 , wherein the plurality of 20 MHz-wide subchannels comprises a 20 MHz-wide control channel and at least one 20 MHz-wide extension channel, wherein the channel estimation circuit is configured to identify the subchannel block within the sounding packet by identifying any combination of at least two contiguous 20 MHz-wide subchannels in the plurality of 20 MHz-wide subchannels as the subchannel block.
19. An access point apparatus comprising:
a plurality of antennas;
a network interface device configured to transmit, via the plurality of antennas, a sounding packet over a wireless downlink communication channel that comprises a plurality of 20 MHz-wide subchannels, wherein the network interface device includes
a steering vector controller configured to receive, from a client device, a feedback frame that includes a partial channel estimation of a subchannel block corresponding to the wireless downlink communication channel between (i) the access point and (ii) the client device, wherein
the partial channel estimation corresponds to only a subset of the plurality of 20 MHz-wide subchannels,
the feedback frame does not include channel estimation information for any other 20 MHz-wide subchannels in the wireless downlink communication channel,
the subchannel block corresponds to only the subset of the 20 MHz-wide subchannels and has a contiguous bandwidth of at least 20 MHz, and
the steering vector controller is configured to use the partial channel estimation to identify a steering matrix for use in communicating on the wireless downlink communication channel between (i) the access point and (ii) the client device, and
a spatial steering controller configured to apply the identified steering matrix to only a portion, in frequency, of an information carrying packet, wherein the portion, in frequency, of the information carrying packet corresponds, in frequency, to the subchannel block.
20. The access point apparatus of claim 19 , wherein:
the plurality of 20 MHz-wide subchannels includes a 20 MHz-wide control channel; and
the subchannel block includes the 20 MHz-wide control channel.
21. The access point apparatus of claim 19 , wherein the steering vector controller is configured to receive channel state information as the partial channel estimation and from the channel state information determine the steering matrix.
22. The access point apparatus of claim 19 , wherein the steering vector controller is configured to receive a compressed steering matrix and/or an uncompressed steering matrix as the partial channel estimation to identifying the steering matrix.