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.
1. 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 method for device detection wherein 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, comprising:
sending, from the probing device, a probe request packet directed to the listening device that also reserves the medium for a medium reservation period, wherein the medium reservation period 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 a probe response packet and less than an amount of time needed for the probing device to transmit a data packet to the listening device in a data session;
sending, from the listening device, the probe response packet in response to the probe request packet, wherein the probe response packet is sent during the medium reservation period;
detecting, at the probing device, the existence of the listening device based on the probe response packet; and
at a time after detecting the existence of the listening device, initiating a connection between the listening device and the probe device using at least one parameter determined as a result of the detecting.
2. The method of claim 1 , wherein sending the probe response packet bypasses medium arbitration.
3. The method of claim 1 , wherein the communication system is a wireless network that uses at least one of 802.11a, 802.11b, 802.11e, 802.11g and 802.11n frame formatting.
4. The method of claim 1 , wherein the probe request packet is a data packet and the probe response packet sent from the listening device is arranged as a valid acknowledgement (ACK) packet, valid according to the protocol of the communication system, responsive to the data packet sent from the probing device.
5. The method of claim 1 , wherein the probe request packet is a Ready-to-Send (RTS) packet and the probe response packet is a Clear-to-Send (CTS) packet, and wherein the probing device and the listening device are configured to process RTS/CTS packets independent of whether a connection already exists between the probing device and the listening device.
6. The method of claim 1 , further comprising selecting channels on which to send, wherein the selection on what channels to scan and in which order is based on knowledge of channels on which device detection was previously successful.
7. The method of claim 1 , further comprising selecting channels on which to send, wherein the selection on what channels to scan and in which order is based on information that was communicated to the probing device during a previous connection.
8. The method of claim 1 , wherein the listening device, upon receiving a request for connection from or after establishing a connection with a first probing device, enters a higher activity scan state to speed up connection with additional probing devices that may be trying to connect.
9. The method of claim 8 , wherein the higher activity scan state comprises extending a power-on time.
10. The method of claim 8 , wherein the higher activity scan state comprises increasing a frequency of a wake-up schedule.
11. The method of claim 1 , wherein the probe request packet is a Ready-to-Send (RTS) packet, the probe response packet is a Clear-to-Send (CTS) packet, and wherein the initiating device reserves the medium with the RTS packet for one or more packet exchanges following a RTS/CTS-based device detection.
12. The method of claim 1 , wherein the probing device is an initiating device in a state wherein the initiating device has information, data and/or signals to be exchanged with a destination device.
13. The method of claim 1 , wherein the listening device is an initiating device in a state wherein the initiating device has information, data and/or signals to be exchanged with a destination device.
14. The method of claim 1 , wherein the sending of the probe request packet is done using a first set of signaling parameters and received by the listening device using a second set of signaling parameters different than the first set of signaling parameters, wherein the listening device can detect at least a part of the probe request packet.
15. The method of claim 14 , wherein the signaling parameters include frequency band, modulation type and/or channel number.
16. The method of claim 14 , further comprising, following device detection, an exchange of at least some of the signaling parameters, thereby allowing the probing device and the listening device to coordinate usage of a common set of signaling parameters.
17. The method of claim 14 , further comprising:
sending probe request packets using a plurality of signaling parameters;
listening, at the probing device, for responses from the listening device to which the probe request packets are directed;
upon receiving a plurality of responses, determining a best quality of response;
determining, from the plurality of signaling parameters used, the signaling parameters corresponding to the best response; and
signaling the listening device further using those corresponding signaling parameters.
18. The method of claim 17 , wherein determining a best quality of response comprises determining a strongest signal strength of the response.
19. The method of claim 1 , wherein the at least one parameter comprises one or more of a time slot selection, a frequency selection, a channel selection and/or a code selection.
20. The method of claim 1 , wherein the initiating of the connection occurs following the detecting by bypassing at least one medium access procedure.
21. 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 method for device detection wherein 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, comprising:
sending, from the probing device, a probe request packet directed to the listening device that also reserves the medium;
reserving, from the probing device, the medium, for a medium reservation period, wherein the medium reservation period 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 a probe response packet and less than an amount of time needed for the probing device to transmit a data packet to the listening device in a data session;
sending, from the listening device, the probe response packet in response to the probe request packet, wherein the probe response packet is sent during the medium reservation period;
detecting, at the probing device, the existence of the listening device based on the probe response packet; and
at a time after detecting the existence of the listening device, initiating a connection between the listening device and the probe device using at least one parameter determined as a result of the detecting.
22. The method of claim 21 , wherein the medium reservation exactly equals the duration of the transmission of the probe response packet and applicable response time.
23. The method of claim 21 , wherein the medium reservation equals the duration of the transmission of the probe response packet and applicable response time, within a predetermined tolerance.
24. The method of claim 21 , wherein the medium reservation covers less than all of the duration of the transmission of the probe response packet and applicable response time.
25. The method of claim 21 , wherein the listening device reserves the medium for one or more additional packets following the probe response packet.
26. The method of claim 21 , wherein the probe request packet is an Ready-to-Send (RTS) packet and the probe response packet is a Clear-to-Send (CTS) packet.
27. The method of claim 21 , wherein the probe request packet is not a Ready-to-Send (RTS) packet and the probe response packet is not a Clear-to-Send (CTS) packet, and the probe response packet is sent over the medium without medium arbitration.
28. The method of claim 21 , wherein the at least one parameter comprises one or more of a time slot selection, a frequency selection, a channel selection and/or a code selection.
29. The method of claim 21 , wherein the initiating of the connection occurs following the detecting by bypassing at least one medium procedure.
30. In a communication system wherein a plurality of electronic devices connect and disconnect from communication over a medium, a method for device detection wherein a probing device attempts to detect presence of a listening device, the method comprising:
determining, at the probing device, a plurality of scan steps, wherein each scan step uses sending parameters selected from a plurality of sending parameters valid for the communication system and the medium, and at least two scan steps in the plurality of scan steps will use different sending parameters;
selecting an initial scan step, wherein the sending parameters for the initial scan step are determined from stored values representing at least one aspect of prior interactions between, and specific to scan steps performed between, the probing device and the listening device, the sending parameters including at least a network identifier of the listening device as determined in a prior pairing between the probing device and the listening device; and
sending, from the probing device, a plurality of probe request packets directed to the listening device, wherein each of the probe request packets is sent in a scan step using sending parameters for that scan step and wherein the plurality of probe request packets begins with an initial probe packet sent using sending parameters for the initial scan step, and wherein the probe request packets also reserve a medium reservation period that includes an amount of time following the sending of the probe request packets 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 data packet to the listening device in a data session.
31. The method of claim 30 , wherein the sending parameters include one or more of time slot selection, frequency selection, channel selection and/or code selection.
32. The method of claim 30 , wherein the communication system is a wireless network that uses at least one of 802.11a, 802.11b, 802.11e, 802.11g and 802.11n frame formatting.
33. The method of claim 30 , wherein the sending parameters for the initial scan step are determined from a previous pairing operation.
34. The method of claim 30 , wherein the sending parameters include address information of the probe device and the listening device.
35. The method of claim 30 , wherein the sending parameters include identification of the communication system that comprises the probe device and the listening device.