Methods for coherent antenna switching in AOD positioning scheme
Devices and methods of estimating the AoD of a STA are generally described. The STA receives comparison symbols from a first AP antenna. The comparison symbols are received prior to and after switching of transmitter chains from a first set of antennas to a second set of antennas. AoD symbols are received immediately after the comparison symbols. A phase and amplitude correction is determined based on a phase and amplitude change between the comparison symbols and the second AoD symbol corrected based thereon. The AoD is subsequently estimated based on the symbol measurements.
1. An apparatus of a station (STA), the apparatus comprising:
processing circuitry arranged to:
decode at least one packet from an access point (AP) comprising antennas and transmit chains, the at least one packet comprising:
a header,
a pair of correction symbols on a first tone from a single antenna among the antennas before and after switching of the transmit chains, and
an angle of departure (AoD) symbol on a second tone from each of a different set of the antennas ; including the single antenna ; before and after the switching of the transmit chains;
determine from the header a position within the at least one packet of each of the correction and AoD symbols, if the header comprises the position within the at least one packet of each of the correction and AoD symbols;
estimate a phase change and an amplitude change based on the pair of correction symbols;
correct each AoD symbol after the switching of the transmit chains based on the phase and amplitude change to determine a corrected AoD symbol; and
estimate an AoD from the AoD symbols before the switching of the transmit chains and the corrected AoD symbols; and
a memory configured to store the phase and amplitude changes.
2. The apparatus of claim 1 , wherein the processing circuit is further configured to:
determine, based on the header, that at least one symbol position is present between the correction and AoD symbols before and after the switching of the transmit chains;
determine a power of a carrier wave of the first tone in the at least one symbol position, the carrier wave free from modulation of the correction symbol; and
determine a change in transmit power between the pair of correction symbols from the power of the carrier wave.
3. The apparatus of claim 1 , wherein the processing circuitry is further configured to:
determine, based on the header, that at least one symbol position is present between the correction and AoD symbols before and after the switching of the transmit chains; and
ignore a signal on the first tone in the at least one symbol position.
4. The apparatus of claim 1 , wherein:
the correction and AoD symbols before the of the transmit chains are independent, and
the correction and AoD symbols after the switching of the transmit chains are independent.
5. The apparatus of claim 1 , wherein the processing circuitry is further configured to:
determine, based on the header, that the correction and AoD symbols are in adjacent positions both before and after the switching of the transmit chains.
6. The apparatus of claim 1 , wherein the processing circuitry is further configured to:
determine, based on an announcement frame received prior to the at least one packet, the position within the at least one packet of each of the correction and AoD symbols.
7. The apparatus of claim 6 , wherein the processing circuitry is further configured to:
determine the position within the at least one packet of each of the correction and AoD symbols based further on the header.
8. The apparatus of claim 6 , wherein the processing circuitry is further configured to:
determine, from the announcement frame:
a number of correction and AoD symbols transmitted between each switching operation,
a number of intermediate symbols used for the switching operation,
a codebook that maps tones to respective physical angles,
calibration data for estimation of the correction and AoD symbols, and
beamshape patterns for estimation of the correction and AoD symbols.
9. The apparatus of claim 1 , wherein the sets of antennas have no more than the single antenna in common.
10. The apparatus of claim 1 , wherein:
the at least one packet is a single packet.
11. The apparatus of claim 1 , wherein:
the at least one packet comprises a pair of packets,
each packet comprises the header, one of the correction symbols, and an AoD symbol associated with the one of the correction symbols, and
one packet of the pair of packets comprises the AoD symbol before the switching of the transmit chains without the AoD symbol after the switching of the transmit chains and another packet of the pair of packets comprises the AoD symbol after the switching of the transmit chains without the AoD symbol before the switching of the transmit chains.
12. The apparatus of claim 1 , wherein whether the at least one packet is a single packet or multiple packets is dependent on an amount of buffering of the memory to use in a determination of the AoD.
13. The apparatus of claim 1 , wherein the processing circuitry is further configured to:
determine, from a codebook in an announcement frame, a limited set of tones across all available tones to be used to transmit the correction symbols, the limited set of tones dependent on the single antenna used to transmit the correction symbols.
14. The apparatus of claim 13 , wherein:
the codebook indicates that the correction symbols are to be received on every even tone when a first single antenna is used to transmit the correction symbols and on every odd tone when a second single antenna is used to transmit the correction symbols.
15. The apparatus of claim 13 , wherein:
the codebook indicates excluded tones that are excluded based on noise on the excluded tones.
16. The apparatus of claim 1 , wherein the processing circuitry is further configured to:
determine, based on the header, that the correction and AoD symbols are in non-adjacent positions both before and after the switching of the transmit chains.
17. An apparatus of an access point (AP), the apparatus comprising:
a plurality of antennas and transmit chains associated with the antennas; and
processing circuitry arranged to:
encode for transmission to a station (STA):
an announcement frame comprising:
a position of correction and angle of departure (AoD) symbols within a packet,
a number of correction and AoD symbols transmitted between each switching operation between the transmit chains,
a number of intermediate symbols used for the switching operation,
a codebook that maps tones to respective physical angles,
calibration data for estimation of the correction and AoD symbols, and
beamshape patterns for estimation of the correction and AoD symbols, and
the packet, the packet comprising:
a header that contains the position within the packet of each of the correction and AoD symbols,
a pair of the correction symbols on a first tone from a single antenna among the antennas before and after the switching operation, and
the AoD symbols on a second tone from each of a different set of the antennas, including the single antenna, before and after the switching operation; and
decode, from the STA based on the correction and AoD symbols, a phase change and an amplitude change caused by the switching operation.
18. The apparatus of claim 17 , wherein the antennas further transmit an unmodulated carrier wave on the first tone during the intermediate symbols.
19. A non-transitory computer-readable storage medium that stores instructions for execution by one or more processors of a station (STA), the one or more processors to configure the STA to:
receive, from an access point (AP), an announcement frame comprising:
a position of correction and angle of departure (AoD) symbols within a packet,
a number of correction and AoD symbols transmitted between each switching operation between transmit chains of the AP, and
a number of intermediate symbols used for the switching operation, receive the packet from the (STA), the packet comprising:
a header that contains the position within the packet of each of the correction and AoD symbols,
a pair of correction symbols on a first tone from a single antenna among antennas of the AP before and after switching of the transmit chains, and
an AoD symbol on a second tone from each of a different set of the antennas, including the single antenna, before and after the switching operation;
estimate a phase change and an amplitude change based on the pairs of correction symbols;
correct each AoD symbol after the switching of the transmit chains based on the phase and amplitude change to determine a corrected AoD symbol; and
estimate an AoD from the AoD symbols before the switching operation and the corrected AoD symbols.
20. The medium of claim 19 , wherein the one or more processors further configure the STA to:
determine a power of a carrier wave of the first tone during the intermediate symbols, the carrier wave free from modulation of the correction symbol; and
determine a change in transmit power between the pair of correction symbols from the power of the carrier wave.