Hewlett Packard Enterprise Development LP

Dongho Kim

Souvik Sen

A method of determining the location of a mobile computing device includes measuring a first time of flight (ToF) value and a first value of received energy of direct path (EDP) (P) of a number of acknowledgement (ACK) packets received in response to a number of first probe packets sent to a first mobile device. The method calculates a preliminary distance value (d) using a ToF-based distance equation, selects an ACK packet with a distance closest to dfrom the number of ACK packets, calculates an initial path loss exponent (&#x3b3;) of the selected ACK packet sample using dand P. With the access point, the method also includes measuring a second Pfor a second number of ACK packets received in response to a number of second probe packets sent to the first mobile device, calculates a supplemental distance value using an EDP-based distance equation and the &#x3b3;, and determines the location of the mobile device using multilateration and the supplemental distance value.

Determining the location of a mobile computing device

In an example, a method for correcting time-of-flight measurements includes receiving a plurality of time-of-flight measurements and determining whether the time-of-flight measurements relate to a strong signal client, a weak signal client, or a preferred signal client. If the time-of-flight measurements relate to a strong signal client or a weak signal client, the method determines whether the time-of-flight measurements constitute two distinct distributions. If the time-of-flight measurements constitute two distinct distributions, a mean value for each distribution is determined. If the mean values differ by a predetermined time delay attributable to automatic gain control processing, the time-of-flight measurements corresponding to the distribution having the lower mean value are used. If the mean values differ by less than the predetermined time delay attributable to automatic gain control processing, the time-of-flight measurements corresponding to both distributions are used.

Correcting time-of-flight measurements

Described herein are techniques for determining a location of a disconnected device. In an example, a method includes instructing a first access point to sniff a wireless channel for probe request packets from disconnected devices, and instructing the first access point to send a distance-probing packet to a disconnected device after receiving a probe request packet from the disconnected device. The method further includes receiving, from the first access point, a MAC address of the disconnected device determined from the received probe request packet. After receiving the MAC address from the first access point, a group of access points is instructed to send distance-probing packets to the disconnected device. The method further includes receiving, from the first access point and the group of access points, time-of-flight measurements associated with the disconnected device. A location of the disconnected device can be determined using the time-of-flight measurements.

Determining a location of a disconnected device

Described herein are techniques for determining a location of a device. In an example, a group of access points may be selected. Time-of-flight (ToF) measurements relative to the device may be received from each of the access points in the group. A respective distance of the device from each access point may be determined using the ToF measurements and a baseToF value. Location coordinates of the device and a new baseToF value may be determined based on the determined distances and the location coordinates of each access point in the group.

Determining a location of a device

Example implementations relate to an access point. One example apparatus includes a transceiver and a processor. The processor is to instruct the transceiver to transmit a first wake up message to a client device at a first transmission rate via a wireless network. The processor, in response to receiving a sleep message from the client device via the transceiver, is to instruct the transceiver to transmit a second wake up message to the client device at a second transmission rate that is greater than the first transmission rate.

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Palo Alto, CA, United States of America

Dongho Kim