Clock domain translation for non-synchronized sensors
There is described a system for translating clock domain for non-synchronized sensors comprising a first sensor, a second sensor, and an upstream device. The first and second sensors receive a beacon from a tag. Each sensor transmits a report including a beacon receive time in a sensor clock domain. The upstream device receives the reports and translates beacon receive times from the sensor clock domain to an aggregator clock domain. The translation is based, at least in part, on beacon reception data of the sensors, report transmission data of the sensors, and report reception data of the upstream device. The upstream device determines a location of the tag based on a delta of the beacon receive times in the aggregator clock domain.
1. A system for translating clock domain for non- synchronized sensors comprising:
a first sensor configured to receive a beacon from a tag and transmit a first report including a first beacon receive time in a sensor clock domain;
a second sensor configured to receive the beacon and transmit a second report including a second beacon receive time in the sensor clock domain;
an upstream device configured to receive the first and second reports, the upstream device being effective to translate each of the first and second beacon receive times from the sensor clock domain to an aggregator clock domain by establishing a report ratio of a difference of a current report receive time and a previous report receive time in the aggregator clock domain to a difference of a current report transmit time and a previous report transmit time in the sensor clock domain, and applying the report ratio to a difference of the beacon receive time in the sensor clock domain and the previous report transmit time, as represented by the following equation:
B
a
=
R
x
p
+
(
B
s
-
T
x
p
)
R
x
c
-
R
x
p
T
x
c
-
T
x
p
-
P
D
,
wherein Txc represents the current report transmit time, Rxc represents current report receive time, Txp represents previous report transmit time, Rxp represents previous report receive time, Bs represents beacon receive time, Ba represents beacon receive time, and PD represents propagation delay,
wherein the upstream device determines a location of the tag based, at least in part, on a delta of the first and second beacon receive times in the aggregator clock domain.
2. The system as described in claim 1 , wherein the beacon transmitted by the tag includes a tag identification.
3. The system as described in claim 2 , wherein:
the first report includes a first report transmit time in the sensor clock domain; and
the second report includes a second report transmit time in the sensor clock domain.
4. The system as described in claim 1 , wherein:
the upstream device determines a first beacon receive time in the aggregator clock domain based, at least in part, on the first beacon receive time in the sensor clock domain, a first current report transmit time and a first previous report transit time in the sensor clock domain, and a first current report receive time and a first previous report receive time in the aggregator clock domain; and
the upstream device determines a second beacon receive time in the aggregator clock domain based, at least in part, on the second beacon receive time in the sensor clock domain, a second current report transmit time and a second previous report transit time in the sensor clock domain, and a second current report receive time and a second previous report receive time in the aggregator clock domain.
5. The system as described in claim 1 , wherein:
the tag and the plurality of sensors communicate via a first channel of a particular radio technology, and the plurality sensors and the upstream device communicate via a second channel of the particular radio technology.
6. The system as described in claim 5 , wherein the particular radio technology is based on ultrawide band wireless communications.
7. A method of translating clock domain for non-synchronized sensors comprising:
receiving, at first and second sensors, a beacon;
transmitting, at the first sensor, a first report including a first beacon receive time in a sensor clock domain in response to receiving the beacon;
transmitting, at the second sensor, a second report including a second beacon receive time in the sensor clock domain;
receiving, at an upstream device, the first and second reports;
translating, at the upstream device, each of the first and second beacon receive times from the sensor clock domain to an aggregator clock domain, wherein translating each of the first and second beacon receive times comprises:
establishing a report ratio of a difference of a current report receive time and a previous report receive time in the aggregator clock domain to a difference of a current report transmit time and a previous report transmit time in the sensor clock domain to; and
applying the report ratio to a difference of the beacon receive time in the sensor clock domain and the previous report transmit time, as represented by the following equation:
Ba
=
Rxp
+
(
Bs
-
Txp
)
Rxc
-
Rxp
Txc
-
Txp
-
PD
,
wherein Txc represents the current report transmit time, Rxc represents current report receive time, Txp represents previous report transmit time, Rxp represents previous report receive time, Bs represents beacon receive time, Ba represents beacon receive time, and PD represents propagation delay; and
determining, at the upstream device, a location of a tag based, at least in part, on a delta of the first and second beacon receive times in the aggregator clock domain.
8. The method as described in claim 7 , wherein the beacon received by the first and second sensors includes a tag identification.
9. The method as described in claim 8 , wherein:
the first report includes a first report transmit time in the sensor clock domain; and
the second report includes a second report transmit time in the sensor clock domain.
10. The method as described in claim 7 , wherein translating each of the first and second beacon receive times comprises:
determining the first beacon receive time in the aggregator clock domain based, at least in part, on the first beacon receive time in the sensor clock domain, a first current report transmit time and a first previous report transit time in the sensor clock domain, and a first current report receive time and a first previous report receive time in the aggregator clock domain; and
determining a second beacon receive time in the aggregator clock domain based, at least in part, on the second beacon receive time in the sensor clock domain, a second current report transmit time and a second previous report transit time in the sensor clock domain, and a second current report receive time and a second previous report receive time in the aggregator clock domain.
11. The method as described in claim 7 , wherein:
receiving, at the first and second sensors, the beacon includes receiving the beacon via a first channel of a particular radio technology; and
receiving, at the upstream device, the first and second reports includes receiving the first and second reports via a second channel of the particular radio technology.
12. The method as described in claim 11 , wherein the particular radio technology is based on ultrawide band wireless communications.