Exchange of ranging data

1 . A first radio device comprising:

at least one processor; and

at least one memory including a computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the first radio device to perform:

causing wireless transmission of one or more first advertising messages at one or more advertising radio frequencies using a Bluetooth Low Energy connectionless mode of the first radio device;

receiving, using the Bluetooth Low Energy connectionless mode, for at least one of the one or more first advertising messages, a first SCAN_REQ protocol data unit, PDU, requesting a transmission of a first scan response from a second radio device, wherein the second radio device is a device which received said at least one of the one or more first advertising message;

transmitting, for each of one or more first SCAN_REQ PDUs, a first SCAN_RSP PDU to the second radio device using the Bluetooth Low Energy connectionless mode;

performing, based on one or more received first SCAN_REQ PDUs, bi-directional channel sounding with the second radio device at one or more sounding radio frequencies;

receiving, from the second radio device, at least one first message comprising information on one or more second channel sounding measurements performed by the second radio device at the one or more sounding radio frequencies; and

transmitting, to the second radio device, at least one second message comprising information on one or more first channel sounding measurements performed by the first radio device at the one or more sounding radio frequencies.

2 . The first radio device according to claim 1 , wherein the performing of the channel sounding comprises:

causing synchronizing, before performing any channel sounding measurements, the first radio device with the second radio device.

3 . The first radio device according to claim 1 , wherein the performing of the channel sounding comprises performing for each radio frequency of the one or more sounding radio frequencies:

transmitting, to the second radio device, at least one first sounding signal at a radio frequency of the one or more sounding radio frequencies; and

measuring at least one second sounding signal transmitted by the second radio device at said radio frequency of the one or more sounding radio frequencies.

4 . The first radio device according to claim 1 , wherein the one or more sounding radio frequencies comprise a plurality of sounding radio frequencies, the one or more first channel sounding measurements comprise a plurality of first channel sounding measurement and the one or more second channel sounding measurements comprise a plurality of second channel sounding measurements and the means are further configured to perform:

estimating a distance between the first and second radio devices based on the information on the plurality of first channel sounding measurements and the plurality of second channel sounding measurements, wherein the information on the plurality of first and second channel sounding measurements comprises at least information on phase measurements at the plurality of sounding radio frequencies and the estimating of the distance is performed using a multi-carrier phase ranging method with round trip timing estimation.

5 . The first radio device according to claim 1 , wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the first radio device perform:

scanning for advertising messages from radio devices within a scanning range of the Bluetooth Low Energy connectionless mode at one or more advertising radio frequencies;

during the scanning, receiving one or more second advertising messages transmitted by a third radio device;

transmitting, for each of the one or more second advertising message, a second SCAN_REQ PDU requesting a transmission of a second SCAN_RSP PDU to the third radio device using the Bluetooth Low Energy connectionless mode;

receiving, from the third radio device, one or more second SCAN_RSP PDUs using the Bluetooth Low Energy connectionless mode;

performing bi-directional channel sounding with the third radio device at one or more sounding radio frequencies based on the one or more second SCAN_RSP PDUs;

transmitting, to the third radio device, a third message comprising information on one or more fourth channel sounding measurements performed by the first radio device based on sounding signals received from the third radio device at the one or more sounding radio frequencies; and

receiving, from the third radio device, a fourth message comprising information on one or more third channel sounding measurements performed by the third radio device at the one or more sounding radio frequencies.

6 . A second radio device comprising:

at least one processor; and

at least one memory including a computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the second radio device to perform:

scanning for advertising messages from radio devices within a scanning range of a Bluetooth Low Energy connectionless mode of the second radio device at one or more advertising radio frequencies;

during the scanning, receiving one or more first advertising messages transmitted by a first radio device;

transmitting, for each of the one or more first advertising message, a first SCAN_REQ PDU requesting a transmission of a first SCAN_RSP PDU to the first radio device using the Bluetooth Low Energy connectionless mode;

receiving, from the first radio device, one or more first SCAN_RSP PDUs using the Bluetooth Low Energy connectionless mode;

performing bi-directional channel sounding with the first radio device at the one or more sounding radio frequencies based on the one or more first SCAN_RSP PDUs;

transmitting, to the first radio device, at least one first message comprising information on one or more second channel sounding measurements performed by the second radio device at the one or more sounding radio frequencies; and

receiving, from the first radio device, at least one second message comprising information on one or more first channel sounding measurements performed by the first radio device at the one or more sounding radio frequencies.

7 . The second radio device according to claim 6 , wherein the performing of the channel sounding comprises:

causing synchronizing, before performing any channel sounding measurements, the second radio device with the first radio device.

8 . The second radio device according to claim 6 , wherein the performing of the channel sounding comprises performing for each radio frequency of the one or more sounding radio frequencies in sequence:

measuring at least one first sounding signal transmitted by the first radio device at a radio frequency of the one or more sounding radio frequencies; and

transmitting, to the first radio device, at least one first sounding signal at said radio frequency.

9 . The second radio device according to claim 6 , wherein the one or more sounding radio frequencies comprise a plurality of sounding radio frequencies, the one or more first channel sounding measurements comprise a plurality of first channel sounding measurement and the one or more second channel sounding measurements comprise a plurality of second channel sounding measurements, and the at least one memory and the computer program code are configured to, with the at least one processor, cause the second radio device further to perform:

estimating a distance between the first and second radio devices based on estimated round trip times based on the information on the plurality of first and second channel sounding measurements, wherein the information on the plurality of first and second channel sounding measurements comprises at least information on phase measurements at the plurality of sounding radio frequencies and the estimating of the distance is performed using a multi-carrier phase ranging method with round trip timing estimation.

10 . A method comprising:

causing wireless transmission of one or more first advertising messages at one or more advertising radio frequencies using a Bluetooth Low Energy connectionless mode of a first radio device;

receiving, using the Bluetooth Low Energy connectionless mode, for at least one of the one or more first advertising messages, a first SCAN_REQ PDU requesting a transmission of a first SCAN_RSP PDU from a second radio device, wherein the second radio device is a device which received said at least one of the one or more first advertising message

transmitting, for each of one or more first SCAN_REQ PDUs, a first SCAN_RSP PDU to the second radio device using the Bluetooth Low Energy connectionless mode;

performing, based on one or more received first SCAN_REQ PDUs, bi-directional channel sounding with the second radio device at one or more sounding radio frequencies;

receiving, from the second radio device, at least one first message comprising information on one or more second channel sounding measurements performed by the second radio device at the one or more sounding radio frequencies; and

transmitting, to the second radio device, at least one second message comprising information on one or more first channel sounding measurements performed by the first radio device at the one or more sounding radio frequencies.

11 . A method comprising:

scanning for advertising messages from radio devices within a scanning range of a Bluetooth Low Energy connectionless mode of a second radio device at one or more advertising radio frequencies;

during the scanning, receiving one or more first advertising messages transmitted by a first radio device;

transmitting, for each of the one or more first advertising message, a first SCAN_REQ PDU requesting a transmission of a first SCAN_RSP PDU to the first radio device using the Bluetooth Low Energy connectionless mode;

receiving, from the first radio device, one or more first SCAN_RSP PDUs using the Bluetooth Low Energy connectionless mode;

performing bi-directional channel sounding with the first radio device at one or more sounding radio frequencies based on the one or more first SCAN_RSP PDUs;

transmitting, to the first radio device, at least one first message comprising information on one or more second channel sounding measurements performed by the second radio device at the one or more sounding radio frequencies; and

receiving, from the first radio device, at least one second message comprising information on one or more first channel sounding measurements performed by the first radio device at the one or more sounding radio frequencies.

12 . A non-transitory computer readable medium having stored thereon instructions that, when executed by a computer, cause the computer to perform at least the following:

causing wireless transmission of one or more first advertising messages at one or more advertising radio frequencies using a Bluetooth Low Energy connectionless mode of a first radio device;

receiving, using the Bluetooth Low Energy connectionless mode, for at least one of the one or more first advertising messages, a first SCAN_REQ PDU requesting a transmission of a first SCAN_RSP PDU from a second radio device, wherein the second radio device is a device which received said at least one of the one or more first advertising message;

transmitting, for each of one or more first SCAN_REQ PDUs, a first SCAN_RSP PDU to the second radio device using the Bluetooth Low Energy connectionless mode;

performing, based on one or more received first SCAN_REQ PDUs, bi-directional channel sounding with the second radio device at one or more sounding radio frequencies;

receiving, from the second radio device, at least one first message comprising information on one or more second channel sounding measurements performed by the second radio device at the one or more sounding radio frequencies; and

transmitting, to the second radio device, at least one second message comprising information on one or more first channel sounding measurements performed by the first radio device at the one or more sounding radio frequencies.

13 . A non-transitory computer readable medium having stored thereon instructions that, when executed by a computer, cause the computer to perform at least the following:

scanning for advertising messages from radio devices within a scanning range of a Bluetooth Low Energy connectionless mode of a second radio device at one or more advertising radio frequencies;

during the scanning, receiving one or more first advertising messages transmitted by a first radio device;

transmitting, for each of the one or more first advertising message, a first SCAN_REQ PDU requesting a transmission of a first SCAN_RSP PDU to the first radio device using the Bluetooth Low Energy connectionless mode;

receiving, from the first radio device, one or more first SCAN_RSP PDUs using the Bluetooth Low Energy connectionless mode;

performing bi-directional channel sounding with the first radio device at one or more sounding radio frequencies based on the one or more first SCAN_RSP PDUs;

transmitting, to the first radio device, at least one first message comprising information on one or more second channel sounding measurements performed by the second radio device at the one or more sounding radio frequencies; and

receiving, from the first radio device, at least one second message comprising information on one or more first channel sounding measurements performed by the first radio device at the one or more sounding radio frequencies.