Method and apparatus for scanning and device detection in a communication system
View Patent ↗In a communication system wherein a plurality of electronic devices connect and disconnect from communication over a medium and wherein the communication system has a protocol such that it is followed by the plurality of electronic devices when using the communication system, a probing device attempts to detect presence of a listening device and parameters associated with a connection to be set up between the probing device and the listening device by sending a probe request packet directed to the listening device and sending, from the listening device, a probe response packet in response to the probe request packet, wherein the listening device bypasses at least one step of the protocol when sending the probe response packet. The bypassed step might be medium arbitration, the communication system might be a wireless network fully or partially based on an 802.11x specification, or a wireless network that uses 802.11x frame formatting and/or modifications/extensions thereof.
1. A method comprising:
transmitting, from a probing device, a probe request packet directed to a listening device, the probing device configured to reserve a medium for a medium reservation period, the medium reservation period including an amount of time following the sending of the probe request packet that is greater than or equal to an amount of time needed to receive a probe response packet and less than an amount of time needed for the probing device to transmit a subsequent data packet to the listening device in a data session;
receiving, by the probing device from the listening device during the medium reservation period, a probe response packet in response to the probe request packet; and
determining, at the probing device, an existence of the listening device based on the probe response packet.
2. The method of claim 1 , further comprising:
maintaining, by the probing device, one or more parameters obtained during a previous connectivity state with the listening device; and
initiating a scan to locate a communication channel of the listening device using the one or more parameters.
3. The method of claim 2 , wherein the one or more parameters includes a communication channel that was previously used by the listening device.
4. The method of claim 3 , where the probing device determines a frequency of the channel by detecting unrelated traffic that is addressed to the listening device or is coming from the listening device.
5. The method of claim 1 , wherein the medium reservation period includes a delay that accounts for a response time of the listening device.
6. The method of claim 1 , wherein the medium reservation period is requested by the probing device before the probe request packet is sent to the listening device.
7. The method of claim 1 , wherein the probe request packet is a Ready-To-end (RTS) packet and the probe response packet is a Clear-To-Send (CTS) packet.
8. The method of claim 7 , wherein the probing device and the listening device are configured to process RTS or CTS packets independent of whether a connection exists between the probing device and the listening device.
9. The method of claim 7 , wherein the probing device reserves the medium with the RTS packet for one or more packet exchanges following RTS/CTS-based device detection.
10. The method of claim 1 , wherein the probe response packet is received over the medium without medium arbitration.
11. The method of claim 1 , wherein the probe request packet is a data packet and the probe response packet is an acknowledgement (ACK) packet.
12. The method of claim 1 , further comprising:
sending a second probe request packet on a first communication channel; and
listening for the probe response packet on a second communication channel.
13. The method of claim 1 , wherein the probing device powers down some or all of its circuitry for period of time if the probing device does not receive the probe response packet within a specified period of time.
14. A method comprising:
receiving, by a listening device, a probe request packet from a probing device; and
sending, by the listening device to the probing device during a medium reservation period, a probe response packet in response to the probe request packet, the probe response packet configured to enable the probing device to determine an existence of the listening device, wherein the medium reservation period is reserved by the probing device and includes an amount of time following the sending of the probe request packet that is greater than or equal to an amount of time needed to receive the probe response packet and less than an amount of time needed for the probing device to transmit a subsequent data packet to the listening device in a data session.
15. The method of claim 14 , wherein the listening device reserves the medium for one or more additional packets following receipt of the probe response packet by the probing device.
16. The method of claim 14 , wherein the listening device, upon receiving a request for connection from or after establishing a connection with the probing device, enters a higher activity scan state to speed up connection with additional probing devices that may be trying to connect.
17. The method of claim 16 , wherein the higher activity scan state comprises extending a power-on time.
18. The method of claim 16 , wherein the higher activity scan state comprises increasing a frequency of a wake-up schedule.
19. The method of claim 14 , where the listening device bypasses some or all medium access procedures when sending the probe response packet or data packets.
20. The method of claim 14 , wherein the listening device is configured to combine or align listening intervals to a time of information exchange with another device.