Location aware communication system using visible light transmission
A visible light communication system identifies the location of a mobile device using light intensities corrected by mobile device orientation. This location can be used to generate a dynamic cluster of visible light transmitters about the mobile device providing improved “handoff” between transmitters and reduced shadowing.
1. A location-aware communication system for mobile devices comprising:
(a) a plurality of light transmission units spatially dispersed in an area through which a mobile device may move, the light transmission units outputting a light signal into the area including an identifier for each given light transmission unit;
(b) a mobile device including:
(i) a light sensor for receiving light from a set of the light transmission units and processing that light to extract the identifier of the light transmission units of the set and an intensity of the light signal;
(ii) an orientation sensing system sensing an orientation of the mobile device; and
(c) a location server communicating with the mobile device;
wherein the mobile device and location server execute stored programs held in non-transitory medium to:
(i) for each given light transmission unit of the set, determine an intensity of the light signal received at the mobile device by the light sensor,
(ii) identify at least one possible location of the mobile device with respect to the given light transmission unit of the set based on a relationship between intensity of the light signal and location of the mobile device corrected for orientation of the mobile device;
(iii) use the at least one possible location of the mobile device to determine a single location of the mobile device with respect to the light transmission units of the set;
wherein the orientation sensing system includes a sensor sensing at least one of roll and pitch of the mobile device with respect to gravity,
wherein the orientation sensing system includes sensors sensing yaw of the device with respect to a predefined azimuth heading,
wherein the correction of the intensity of the light signal at the mobile device uses predetermined relationships between light dispersion from the given light transmission unit as a function of angle and light sensitivity of the mobile device's light sensor unit as a function of angle and a determination of a degree of alignment between the light transmission unit and the light sensor unit based on the orientation of the mobile device.
2. The location-aware system of claim 1 wherein step (iii) uses the at least one possible location of the mobile device for multiple given light transmission units to determine a single location of the mobile device with respect to the light transmission units of the set.
3. The location-aware system of claim 1 wherein step (iii) finds an intersection of possible locations determined among different given light transmission units to determine the single location among an intersection of the possible locations.
4. The location-aware system of claim 1 wherein the mobile device further includes at least one movement sensor and wherein step (iii) calculates movement since a last determined single location and wherein step (iii) determines the single location by combining the at least one possible location and the movement since the last determined signal location.
5. The location-aware system of claim 4 wherein step (iii) finds an intersection of possible locations determined among different given light transmission units to determine the single location among an intersection of the possible locations.
6. The location-aware system of claim 1 wherein the light sensor is a single photosensing element providing an identification of the at least one possible location with respect to the given light transmission unit to receive a light intensity signal from only a single light sensor.
7. The location-aware system of claim 1 wherein the light signal is visible light and the light transmission units operate to provide ambient light to the area.
8. The location-aware system of claim 1 wherein the mobile device and the location server both further include a wireless transceiver for communicating therebetween and wherein data needed to determine the location of the mobile device is communicated from the mobile device to the location server using the wireless transceivers.
9. A location-aware communication system for mobile devices comprising:
(a) a plurality of light transmission units spatially dispersed in an area through which a mobile device may move, the light transmission units outputting a light signal into the area including an identifier for each given light transmission unit;
(b) a mobile device including:
(i) a light sensor for receiving light from a set of the light transmission units and processing that light to extract the identifier of the light transmission units of the set and an intensity of the light signal;
(ii) an orientation sensing system sensing an orientation of the mobile device; and
(c) a location server communicating with the mobile device;
wherein the mobile device and location server execute stored programs held in non-transitory medium to:
(i) for each given light transmission unit of the set, determine an intensity of the light signal received at the mobile device by the light sensor;
(ii) identify at least one possible location of the mobile device with respect to the given light transmission unit of the set based on a relationship between intensity of the light signal and location of the mobile device corrected for orientation of the mobile device;
(iii) use the at least one possible location of the mobile device to determine a single location of the mobile device with respect to the light transmission units of the set,
wherein the location server communicates with the light transmission units over a network to control the light transmission units and the single location of the mobile device is used to dynamically define the set of light transmission units to move with the mobile device as the mobile device moves.
10. The location-aware system of claim 9 wherein the selected light transmission units of the set of light transmission units are selected to surround the mobile device to reduce shadowing on the mobile device by a mobile device user.
11. The location-aware system of claim 9 wherein the network is a powerline communication network communicating data together with power over power lines communicating with the light transmission units.
12. The location-aware system of claim 9 wherein the location server further communicates data to be transmitted synchronously from each of the light transmission units of the set of light transmission units.