Simultaneous uplink transmission in a wireless network

1. A method for use in a communication system including (i) an access point having a plurality of antennas, and (ii) a plurality of communication devices, wherein a multiple-input, multiple output (MIMO) communication channel corresponds to the plurality of antennas of the access point and respective antennas of the plurality of communication devices, the method comprising:

generating, at the access point, a synchronization data unit to be transmitted by the access point to the plurality of communication devices, wherein the synchronization data unit (i) is for scheduling subsequent simultaneous transmission of a plurality of data units by communication devices among the plurality of communication devices, and (ii) specifies respective sets of spatial streams, among a plurality of spatial streams, that respective communication devices among the plurality of communication devices are to use when transmitting respective data units among the plurality of data units;

receiving, at the access point, a signal via the plurality of antennas, wherein the signal corresponds to the plurality of data units transmitted simultaneously from the respective communication devices among the plurality of communication devices via the respective sets of sets of spatial streams;

generating an estimate of the MIMO communication channel using i) a plurality of training fields included in a first portion of the signal and ii) a matrix that indicates a mapping of the plurality of training fields over the plurality of spatial streams, wherein respective submatrices of the matrix correspond to the respective communication devices; and

decoding data in a second portion of the signal using the estimate of the MIMO communication channel, wherein the data in the second portion of the signal corresponds to data included in the plurality of data units.

2. The method of claim 1 , further comprising generating, at the access point, respective acknowledgement data units for respective data units among the plurality of data units.

3. The method of claim 1 , further comprising generating a single acknowledgement data unit that indicates data units among the plurality of data units that were successfully decoded.

4. The method of claim 1 , wherein generating the synchronization data unit comprises generating the synchronization data unit to indicate at least one of:

a duration of a time period during which the plurality of communication devices can simultaneously transmit the plurality of data units;

a maximum length of a data unit that can be transmitted by the plurality of communication devices in response to the synchronization data unit; and

a time interval between the transmission of the synchronization data unit and the transmission of the plurality of data units.

5. The method of claim 1 , wherein generating the synchronization data unit comprises generating the synchronization data unit to indicate respective modulation and coding schemes (MCSs) that respective communication devices among the plurality of communication devices are to use when transmitting respective data units among the plurality of data units.

6. The method of claim 1 , wherein generating the synchronization data unit comprises generating the synchronization data unit to indicate respective amounts of bandwidth allocated to respective communication devices among the plurality of communication devices for transmitting respective data units among the plurality of data units.

7. The method of claim 1 , further comprising scheduling a time period during which the plurality of communication devices are to simultaneously transmit the plurality of data units;

wherein generating the synchronization data unit comprises generating the synchronization data unit to specify the scheduled time period.

8. An apparatus for use in a communication system including (i) an access point having a plurality of antennas, and (ii) a plurality of communication devices, wherein a multiple-input, multiple output (MIMO) communication channel corresponds to the plurality of antennas of the access point and respective antennas of the plurality of communication devices, the apparatus comprising:

a network interface device having one or more integrated circuits configured to

generate a synchronization data unit to be transmitted by the access point to the plurality of communication devices, wherein the synchronization data unit (i) is for scheduling subsequent simultaneous transmission of a plurality of data units by communication devices among the plurality of communication devices, and (ii) specifies respective sets of spatial streams, among a plurality of spatial streams, that respective communication devices among the plurality of communication devices are to use when transmitting respective data units among the plurality of data units,

generate an estimate of the MIMO communication channel using i) plurality of training fields included in a first portion of a signal and ii) a matrix that indicates a mapping of the plurality of training fields over the plurality of spatial streams, wherein respective submatrices of the matrix correspond to the respective communication devices, and wherein the signal is received via the plurality of antennas and corresponds to the plurality of data units transmitted simultaneously from the respective communication devices among the plurality of communication devices via the respective sets of sets of spatial streams, and

decode data in a second portion of the signal using the estimate of the MIMO communication channel, wherein the data in the second portion of the signal corresponds to data included in the plurality of data units.

9. The apparatus of claim 8 , wherein the one or more integrated circuit devices are configured to generate respective acknowledgement data units for respective data units among the plurality of data units.

10. The apparatus of claim 8 , wherein the one or more integrated circuit devices are configured to generate a single acknowledgement data unit that indicates data units among the plurality of data units that were successfully decoded.

11. The apparatus of claim 8 , wherein the one or more integrated circuit devices are configured to generate the synchronization data unit to indicate at least one of:

a duration of a time period during which the plurality of communication devices can simultaneously transmit the plurality of data units;

a maximum length of a data unit that can be transmitted by the plurality of communication devices in response to the synchronization data unit; and

a time interval between the transmission of the synchronization data unit and the transmission of the plurality of data units.

12. The apparatus of claim 8 , wherein the one or more integrated circuit devices are configured to generate the synchronization data unit to indicate respective modulation and coding schemes (MCSs) that respective communication devices among the plurality of communication devices are to use when transmitting respective data units among the plurality of data units.

13. The apparatus of claim 8 , wherein the one or more integrated circuit devices are configured to generate the synchronization data unit to indicate respective amounts of bandwidth allocated to respective communication devices among the plurality of communication devices for transmitting respective data units among the plurality of data units.

14. The apparatus of claim 8 , wherein the one or more integrated circuit devices are configured to:

schedule a time period during which the plurality of communication devices are to simultaneously transmit the plurality of data units, and

generate the synchronization data unit to specify the scheduled time period.

15. The apparatus of claim 8 , wherein the network interface device comprises:

a physical layer processor device implemented on the one or more integrated circuits; and

a media access control processor device implemented on the one or more integrated circuits.

16. The apparatus of claim 8 , wherein the network interface device comprises a plurality of transceivers implemented on the one or more integrated circuits.

17. The apparatus of claim 16 , further comprising the plurality of antennas, wherein the plurality of antennas are coupled to the plurality of transceivers.

18. The apparatus of claim 8 , wherein the network interface device comprises a processor that executes machine readable instructions, wherein the processor is implemented on the one or more integrated circuits.