Anonymous collection of broadband directional transmissions
A method for communication includes simultaneously transmitting over a wireless network from a first station to a second station at least first and second request-to-send (RTS) frames in different, respective first and second frequency channels. The first station receives first and second clear-to-send (CTS) frames transmitted in the first and second frequency channels, respectively, by the second station over the wireless network in response to the first and second RTS frames. At least one property associated with the first station is estimated by processing information extracted from both the first and second received CTS frames.
1 . A method for communication, comprising:
simultaneously transmitting over a wireless network from a first station to a second station at least first and second request-to-send (RTS) frames in different, respective first and second frequency channel;
receiving at the first station first and second clear-to-send (CTS) frames transmitted in the first and second frequency channels, respectively, by the second station over the wireless network in response to the first and second RTS frames, wherein the first and second CTS frames are coherent with one another due to being generated using a common frequency synthesizer in the second station; and
estimating at least one property associated with the first station by processing information extracted from both the first and second received CTS frames, while treating the first and second CTS frames as parts of a single, broadband transmission due to a coherence of the first and second CTS frames.
2 . The method according to claim 1 , wherein the first and second frequency channels occupy mutually adjacent frequency bands.
3 . The method according to claim 1 , wherein transmitting at least the first and second RTS frames comprises transmitting four RTS frames, including the first and second RTS frames, in four respective frequency channels, and wherein estimating the at least one property comprises processing up to four CTS frames received in response to the four RTS frames.
4 . The method according to claim 1 , wherein simultaneously transmitting at least the first and second RTS frames comprises detecting a beacon transmitted over the wireless network by the second station in the first frequency channel, and transmitting at least the first and second RTS frames in response to the beacon.
5 . The method according to claim 4 , wherein detecting the beacon comprises identifying, at the first station, a signal transmitted by the second station using a single-carrier modulation scheme as the beacon, and wherein transmitting at least the first and second RTS frames comprises modulating the RTS frames using a multi-carrier modulation scheme, whereby the CTS frames are also modulated using the multi-carrier modulation scheme.
6 . The method according to claim 5 , wherein the single-carrier modulation scheme is a complementary code keying (CCK) scheme, while the multi-carrier modulation scheme is an orthogonal frequency-division multiplexing (OFDM) scheme.
7 . The method according to claim 1 , wherein after receiving the first and second CTS frames, the first station does not transmit further frames to the second station for at least 100 ms.
8 . The method according to claim 1 , wherein the first station is a mobile station in a wireless local area network (WLAN), and the second station is a stationary access point (AP) in the WLAN.
9 . The method according to claim 8 , wherein transmitting the first and at least the second RTS frames and receiving the first and second CTS frames comprise transmitting and receiving the RTS and CTS frames to and from the AP without establishing an association between the mobile station and the AP.
10 . The method according to claim 1 , wherein estimating the at least one property comprises:
selecting at least a first frequency bin within the first frequency channel and at least a second frequency bin within the second frequency channel;
extracting at least first and second signals from at least the first and second frequency bins, respectively; and
computing the at least one property based on at least the first and second signals.
11 . The method according to claim 1 , wherein estimating the at least one property comprises processing the first and second CTS frames to find an angle of transmission from the second station to the first station.
12 . The method according to claim 1 , wherein estimating the at least one property comprises processing the first and second CTS frames to extract channel state information (CSI), and computing a value of the at least one property using the extracted CSI.
13 . The method according to claim 1 , wherein estimating the at least one property comprises processing the first and second CTS frames to find a location of the first station.
14 . The method according to claim 1 , wherein estimating the at least one property comprises processing the first and second CTS frames to find a velocity of the first station.
15 . The method according to claim 1 , wherein the method further comprises receiving the first and second CTS frames from the second station at a third station, which did not transmit the RTS frames, and estimating an angle of transmission from the second station to the third station based on the received CTS frames.
16 . Apparatus for communication, comprising:
a transceiver, which is configured to transmit and receive signals over a wireless network; and
a processor, which is configured to drive the transceiver to transmit simultaneously to a station in the wireless network at least first and second request-to-send (RTS) frames in different, respective first and second frequency channels, to extract information from both first and second clear-to-send (CTS) frames received over the wireless network by the transceiver in the first and second frequency channels, respectively, in response to the first and second RTS frames, wherein the first and second CTS frames are coherent with one another due to being generated using a common frequency synthesizer in the station, and to process the extracted information in order to estimate at least one property associated with the apparatus, while treating the first and second CTS frames as parts of a single, broadband transmission due to a coherence of the first and second CTS frames.
17 . The apparatus according to claim 16 , wherein the first and second frequency channels occupy mutually adjacent frequency bands.
18 . The apparatus according to claim 16 , wherein the processor is configured to drive the transceiver to transmit four RTS frames, including the first and second RTS frames, in four respective frequency channels, and to extract and process the information from up to four CTS frames received in response to the four RTS frames.
19 . The apparatus according to claim 16 , wherein the transceiver is configured to detect a beacon transmitted over the wireless network by the station in the first frequency channel, and the processor is configured to drive the transceiver to transmit at least the first and second RTS frames in response to the beacon.
20 . The apparatus according to claim 19 , wherein the beacon is transmitted by the station using a single-carrier modulation scheme, and wherein the processor is configured to drive the transceiver to modulate at least the first and second RTS frames using a multi-carrier modulation scheme, whereby the CTS frames are also modulated using the multi-carrier modulation scheme.
21 . The apparatus according to claim 20 , wherein the single-carrier modulation scheme is a complementary code keying (CCK) scheme, while the multi-carrier modulation scheme is an orthogonal frequency-division multiplexing (OFDM) scheme.
22 . The apparatus according to claim 16 , wherein after receiving the first and second CTS frames, the processor does not transmit further frames to the station for at least 100 ms.
23 . The apparatus according to claim 16 , wherein the transceiver is configured for operation in a mobile station in a wireless local area network (WLAN), and the station is a stationary access point (AP) in the WLAN.
24 . The apparatus according to claim 23 , wherein the mobile station is configured to transmit the first and at least the second RTS frames and to receive the first and second CTS frames to and from the AP without establishing an association between the mobile station and the AP.
25 . The apparatus according to claim 16 , wherein the processor is configured to estimate the at least one property by selecting at least a first frequency bin within the first frequency channel and at least a second frequency bin within the second frequency channel, extracting at least first and second signals from at least the first and second frequency bins, respectively, and computing the at least one property based on at least the first and second signals.
26 . The apparatus according to claim 16 , wherein the processor is configured to process the first and second CTS frames to find an angle of transmission from the second station to the first station.
27 . The apparatus according to claim 16 , wherein the processor is configured to process the first and second CTS frames to extract channel state information (CSI), and to compute a value of the at least one property using the extracted CSI.
28 . The apparatus according to claim 16 , the processor is configured to process the first and second CTS frames to find a location of the apparatus.
29 . The apparatus according to claim 16 , the processor is configured to process the first and second CTS frames to find a velocity of the first station.
30 . A computer software product, comprising a non-transitory computer-readable medium in which program instructions are stored, which instructions, when read by a processor, cause the processor to drive a transceiver to transmit simultaneously to a station in a wireless network at least first and second request-to-send (RTS) frames in different, respective first and second frequency channels, to extract information from both first and second clear-to-send (CTS) frames received over the wireless network by the transceiver in the first and second frequency channels, respectively, wherein the first and second CTS frames are coherent with one another due to being generated using a common frequency synthesizer in the station, in response to the first and second RTS frames, and to process the extracted information in order to estimate at least one property associated with the transceiver, while treating the first and second CTS frames as parts of a single, broadband transmission due to a coherence of the first and second CTS frames.