Ranging measurements in wireless communication systems

1. A method for performing ranging measurements in a wireless network, the method comprising:

receiving, at a first communication device during a service period (SP) for a ranging measurement signal exchange between the first communication device and one or more second communication devices, respective first null data packets (NDPs) from the one or more second communication devices, the respective first NDPs omitting data portions;

transmitting, from the first communication device during the SP, respective second NDPs to the one or more second communication devices after the reception of the respective first NDPs, the respective second NDPs omitting data portions; and

one or both of

i) transmitting, from the first communication device during the SP, respective first ranging measurement feedback packets to the one or more second communication devices, the respective first ranging measurement feedback packet transmitted to a particular second communication device including at least a) an indication corresponding to a time t 2 at which the respective first NDP was received from the particular second communication device and b) an indication corresponding to a time t 3 at which the respective second NDP was transmitted to the particular second communication device to allow the particular second communication device to determine a time-of-flight between the first communication device and the particular second communication device, and

ii) receiving, at the first communication device during the SP, respective second ranging measurement feedback packets from the one or more second communication devices, the respective second ranging measurement feedback packet from a particular second communication device including at least a) an indication corresponding to a time t 1 at which the respective first NDP was transmitted by the particular second communication device, and b) an indication corresponding to a time t 4 at which the respective second NDP was received by the particular second communication device to allow the first communication device to determine a time-of-flight between the first communication device and the particular second communication device;

transmitting, by the first communication device at a beginning of the SP, a polling data unit to the one or more second communication devices to prompt the one or more second communication devices to be ready to transmit the respective first NDPs to the first communication device and to transmit respective poll response frames to the first communication device a short interframe space (SIFS) time period after reception of the polling data unit;

transmitting, from the first communication device, a trigger frame to the one or more second communication devices a SIFS time period after reception of the respective poll response frames to cause simultaneous transmission of the respective first NDPs, wherein the respective first NDPs are transmitted by the one or more second communication devices a SIFS time period after reception of the trigger frame; and

transmitting the respective first ranging measurement feedback packets to the one or more second communication devices, wherein transmitting the respective first ranging measurement feedback packets comprises transmitting the respective first ranging measurement feedback packets a SIFS time period after transmitting the respective second NDPs.

2. The method of claim 1 , further comprising

generating, at the first communication device, an NDP announcement (NDPA) frame to announce transmission of the respective second NDPs to the one or more second communication devices, and

prior to transmitting the respective second NDPs from the first communication device to the one or more second communication devices, transmitting, from the first communication device, the NDPA frame to the one or more second communication devices a SIFS time period after reception of the first NDPs;

wherein transmitting the respective second NDPs comprises transmitting the respective second NDPs a SIFS time period after transmitting the NDPA frame.

3. The method of claim 2 , wherein generating the NDPA frame comprises generating the NDPA frame to include a sounding dialog token field to indicate that the NDPA frame is for ranging measurement and not for channel sounding in a beamforming procedure.

4. The method of claim 2 , wherein generating the NDPA frame comprises generating the NDPA frame to include a disambiguation field set to indicate that the NDPA frame conforms to a first communication protocol and does not conform to a second communication protocol different from the first communication protocol.

5. The method of claim 1 , wherein

the one or more second communication devices comprise a single second communication device, and

the method further comprises, prior to receiving the first NDP from the single second communication device, receiving an NDPA frame from the single second communication frame, the NDPA frame announcing transmission of the first NDP from the second communication device to the first communication device.

6. The method of claim 1 , wherein the method comprises both i) transmitting the respective first ranging measurement feedback packets to the one or more second communication device and ii) receiving the respective second ranging measurement feedback packets from the one or more second communication devices, wherein the respective second ranging measurement feedback packets are transmitted by the one or more second communication devices a predetermined time interval after reception of the respective first ranging measurement feedback packets by the one or more second communication devices.

7. The method of claim 6 , wherein the predetermined time interval corresponds to a short interframe space (SIFS) time period.

8. The method of claim 1 , wherein the transmissions of the polling data unit, the poll response frames, the trigger frame, the first NDPs, the second NDPs, and the first ranging measurement feedback packets occur during a same transmission opportunity (TXOP).

9. An apparatus, comprising:

a network interface device associated with a first communication device, wherein the network interface device includes one or more integrated circuits (ICs) configured to:

receive, during a service period (SP) for a ranging measurement signal exchange between the first communication device and one or more second communication devices, respective first null data packets (NDPs) from respective one or more second communication devices,

transmit, during the SP, respective second NDPs to the respective one or more second communication devices after the reception of the respective first NDPs, and

one or both of

i) transmit, during the SP, respective first ranging measurement feedback packets to the one or more second communication devices, the respective first ranging measurement feedback packet transmitted to a particular second communication device including at least a) an indication corresponding to a time t 2 at which the respective first NDP was received from the particular second communication device and b) an indication corresponding to a time t 3 at which the respective second NDP was transmitted to the particular second communication device to allow the particular second communication device to determine a time-of-flight between the first communication device and the particular second communication device, and

ii) receive, during the SP, respective second ranging measurement feedback packets from the one or more second communication devices, the respective second ranging measurement feedback packet from a particular second communication device including at least a) an indication corresponding to a time t 1 at which the respective first NDP was transmitted by the particular second communication device, and b) an indication corresponding to a time t 4 at which the respective second NDP was received by the particular second communication device to allow the first communication device to determine a time-of-flight between the first communication device and the particular second communication device; and

wherein the one or more ICs are further configured to, at a beginning of the SP:

transmit a polling data unit to the one or more second communication devices to prompt the one or more second communication devices to be ready to transmit the respective first NDPs to the first communication device and to transmit respective poll response frames to the first communication device a short interframe space (S IFS) time period after reception of the polling data unit;

transmit a trigger frame to the one or more second communication devices a SIFS time period after reception of the respective poll response frames to cause simultaneous transmission of the respective first NDPs, wherein the respective first NDPs are transmitted by the one or more second communication devices a SIFS time period after reception of the trigger frame; and

transmit the respective first ranging measurement feedback packets to the one or more second communication devices, wherein transmitting the respective first ranging measurement feedback packets comprises transmitting the respective first ranging measurement feedback packets a SIFS time period after transmitting the respective second NDPs.

10. The apparatus of claim 9 , wherein the one or more ICs are further configured to

generate an NDP announcement (NDPA) frame to announce transmission of the respective second NDPs to the one or more second communication devices,

prior to transmitting the respective second NDPs to the one or more second communication devices, transmit the NDPA frame to the one or more second communication devices a SIFS time period after reception of the first NDPs, and

transmit the respective second NDPs a SIFS time period after transmitting the NDPA frame.

11. The apparatus of claim 10 , wherein the one or more ICs are configured to generate the NDPA frame to include a sounding dialog token field to indicate that the NDPA frame is for ranging measurement and not for channel sounding in a beamforming procedure.

12. The apparatus of claim 10 , wherein the one or more ICs are configured to generate the NDPA frame to include a disambiguation field set to indicate that the NDPA frame conforms to a first communication protocol and does not conform to a second communication protocol different from the first communication protocol.

13. The apparatus of claim 9 , wherein

the one or more second communication devices comprise a single second communication device, and

the one or more ICs are further configured to, prior to receiving the first NDP from the single second communication device, receive an NDPA frame from the single second communication frame, the NDPA frame announcing transmission of the first NDP from the second communication device to the first communication device.

14. The apparatus of claim 9 , wherein the one or more ICs are configured to, during the SP, both i) transmit the respective first ranging measurement feedback packets to the one or more second communication device and ii) receive the respective second ranging measurement feedback packets from the one or more second communication devices, wherein the respective second ranging measurement feedback packets are transmitted by the one or more second communication devices a predetermined time interval after reception of the respective first ranging measurement feedback packets by the one or more second communication devices.

15. The apparatus of claim 14 , wherein the predetermined time interval corresponds to a short interframe space (SIFS) time period.