WO2013088281A1

WO2013088281A1 - Sound ranging system

Info

Publication number: WO2013088281A1
Application number: PCT/IB2012/056475
Authority: WO
Inventors: Paul Richard Simons; Stephen Michael Pitchers
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2011-12-16
Filing date: 2012-11-16
Publication date: 2013-06-20

Abstract

A ranging system having a transmitter (23) and a receiver (26) is proposed enabling a protocol (27) for acoustic ranging that greatly simplifies the control mechanism of acoustic ranging. Instead of using a separate communication channel to control the ranging or positioning application, the sound probe (28) used to make the range measurement is adapted to carry an implicit command to the receiver. More advanced control is also disclosed by using the sound to carry control data as part of the sound probe, further reducing additional control requirements.

Description

Sound ranging system

FIELD OF THE INVENTION

The invention relates to a transmitter device and a receiver device in a ranging system for sound ranging between the transmitter device at a first position and the receiver device at a second position. The invention further relates to a method for ranging and a computer program for ranging.

The invention relates to the field of measuring distances or relative position by sound signals travelling from a transmitter to a receiver. A distance between a sound transmitter at a first spatial position and receiver at a second spatial position may be derived from the time difference between transmitting and arrival of a sound signal from the transmitter to a receiver site. If a pulse is emitted from the transmitter, it will arrive at a different time at a spatially separated receiver site due to the distance of the receiver from the transmitter. It is noted that in this document pulse, sound signal or sound probe means any suitable sound that enables accurate arrival time detection or using a correlation method; a wide variety of non-pulse- like sounds are suitable for producing an impulse-like correlator result.

If the receiver knows the absolute time at which the pulse was transmitted, the distance can be easily calculated from the time of flight (TOF) measurement. For time-of- flight measurements it is required that the clock signals of the receiver are synchronized with the clock signal of the transmitter such that the receiver knows when the transmitter transmitted the event later received by the receiver.

Alternatively, the receiver responds to a received sound signal, and transmits a sound response. The transmitter may receive the sound response, and determines the time difference between its transmitted sound signal and the received response. It is now not required that the clock signals are synchronized, provided that the delay between receiving the first sound and transmitting the response is known.

BACKGROUND OF THE INVENTION

The document US 7,729,204 describes acoustic ranging, which involves determining a distance between a first device and at least one other device using time differences between one or more acoustic signals. A first device emits a first acoustic signal and then receives the first acoustic signal at a first time. The first device also receives a second acoustic signal at a second time, with the second acoustic signal having been emitted by a second device. The first device ascertains a first time difference that reflects a difference between the first time and the second time. Responsive to the ascertained first time difference, the first device determines a distance between the first device and the second device.

For controlling the ranging process, e.g. sending the sound signals and responses, transferring timing or synchronization data, defining or initiating the process of ranging, the devices may use a wired or wireless communication channel, for example WiFi or Bluetooth.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a ranging system that is less complicated.

For this purpose, according to a first aspect of the invention, in the ranging system as described in the opening paragraph, the transmitter device comprises a transmitter controller for controlling a ranging transmitter process in dependence of ranging control data, and a transmitter unit for transmitting a transmitter sound signal at a transmitter instant; and the receiver device comprises a receiver controller for controlling a ranging receiver process, and a receiver unit for receiving the transmitter sound signal at a receiver instant. In the system the transmitter unit is arranged for including the ranging control data in the transmitter sound signal, and the receiver unit is arranged for retrieving the ranging control data from the transmitter sound signal; and the receiver controller is arranged for controlling the ranging receiver process in dependence of the ranging control data.

For this purpose the invention further provides a method of transmitting for use in a ranging system comprising a transmitter and a receiver for sound ranging between the transmitter at a first position and the receiver at a second position, the method comprising controlling a ranging transmitter process in dependence of ranging control data, and transmitting a transmitter sound signal at a transmitter instant; and the receiver comprising a receiver controller for controlling a ranging receiver process, and a receiver unit for receiving the transmitter sound signal at a receiver instant, wherein the method comprises including the ranging control data in the transmitter sound signal, and the receiver unit is arranged for retrieving the ranging control data from the transmitter sound signal; and the receiver controller is arranged for controlling the ranging receiver process in dependence of the ranging control data.

For this purpose the invention further provides a method of receiving for use in a ranging system comprising a transmitter and a receiver for sound ranging between the transmitter at a first position and the receiver at a second position, the transmitter comprising a transmitter controller for controlling a ranging transmitter process in dependence of ranging control data, and a transmitter unit for transmitting a transmitter sound signal at a transmitter instant; and the method comprising controlling a ranging receiver process, and receiving the transmitter sound signal at a receiver instant, wherein the transmitter unit is arranged for including the ranging control data in the transmitter sound signal, and the method comprises retrieving the ranging control data from the transmitter sound signal; and controlling the ranging receiver process in dependence of the ranging control data.

For this purpose the invention further provides a computer program for use in the ranging system, which program comprises computer program code means operative to cause a processor to perform the above methods. The computer program may be embodied on a computer readable medium.

In the sound ranging system at the transmitter side and/or receiver side the ranging process is controlled based on control data such as protocols, commands and parameters. Such control includes that sounds are selected or defined as such, or modulated or composited, or are detected or transmitted, in dependence of the ranging control data.

The measures have the following effect. The transmitter sound signal is used in determining the distance between the devices at the first and second position based on the travel time of the sound signal. The transmitter includes, in the ranging transmitter sound signal, also the ranging control data, e.g. by modulation of the sound signal. The receiver, which has to detect the sound signal in the ranging system, derives, from the received sound signal, also the control data, which informs the receiver on the ranging process to be executed, or parameters or further data for performing the ranging function. Advantageously, the traditional communication channel is not required, as communication of any necessary control data for the ranging process is transferred by the measuring sound signal itself.

The invention is also based on the following recognition. Although ranging by sound signals as such is known, in traditional ranging systems communication between devices was commonly present. However the inventors have seen that, in particular in low- cost ranging systems, even the small additional cost of having a Bluetooth unit in the system is limiting the range of applications. By enabling the communication between devices via the ranging sound signals, i.e. adapting the transmitter sound signal and/or the receiver response, provides a low cost, but sufficient communication channel for controlling the ranging process.

Optionally, the ranging control data comprises an instruction, and the transmitter unit is arranged for including the instruction in the transmitter sound signal.

Optionally, the ranging control data comprises an instruction and the receiver unit is arranged for retrieving the instruction from the transmitter sound signal. This has the advantage that the transmitter is enabled to instruct the receiver to engage a specific function in the ranging receiver process, e.g. send a specific type of response.

Optionally, the instruction comprises at least one of

- a command that instructs the receiver controller to perform a step in the ranging receiver process;

- a command that instructs the receiver controller to send a receiver sound signal of a predetermined type;

- a command that instructs the receiver controller to refrain from sending a receiver sound signal;

- a command that instructs the receiver controller to engage a predetermined ranging protocol;

- a command that instructs the receiver controller to select a type of ranging sound. The respective commands have the advantage that the transmitter is enabled to have the receiver to perform a specific function.

Optionally, the transmitter unit is arranged for including a first sound pulse and a second sound pulse in the transmitter sound signal, and the interval between the first sound pulse and the second sound pulse encodes the ranging control data. It is noted that the receiver has to detect and determine the arrival time of the transmitter sound signal anyhow. Hence encoding control data in a time interval has the advantage that the receiver can easily determine said time interval, and derive the ranging control data.

Optionally, the interval between the first sound pulse and the second sound pulse is indicative of a response delay interval between receiving a further sound signal by the device and responding to the further sound signal by transmitting the transmitter sound signal. The further sound signal, when originating from the receiver device, and the transmitter sound signal enable a two-way ranging system. The receiver device is aware of the time of sending the further sound signal, and the period to receiving the transmitter sound signal in response. By detecting the interval between the first sound pulse and the second sound pulse the delay interval in the transmitter device is also known to the receiver. Hence two way ranging is enabled without requiring separate communication or predetermined values regarding the delay interval.

Optionally, the sound ranging comprises two-way ranging and the device comprises both a transmitter unit and a receiver unit. In any of the above embodiments the ranging system may involve devices that can act both as receiver and transmitter. The combination advantageously enables two-way communication of the ranging control data.

Further preferred embodiments of the device and method according to the invention are given in the appended claims, disclosure of which is incorporated herein by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from and elucidated further with reference to the embodiments described by way of example in the following description and with reference to the accompanying drawings, in which

Figure 1 shows one way time-of- flight measurement,

Figure 2 shows a system for ranging and two way time-of- flight measurement, Figure 3 shows a ranging system having multiple transmitters and receivers, Figure 4 shows a layout of a lighting installation,

Figure 5 shows a ranging system for extended two-way ranging. The figures are purely diagrammatic and not drawn to scale. In the Figures, elements which correspond to elements already described have the same reference numerals. DETAILED DESCRIPTION OF EMBODIMENTS

Figure 1 shows one way time-of- flight measurement. The prior art system has a transmitter 11 and a receiver 12, and a controller 13 that controls a ranging process via a communication channel between transmitter and receiver. A ranging sound signal 14 is transmitted by the transmitter at a transmitter instant (Tx), and later received by the receiver at a receiver instant (Rx). A basic ranging process 15 is schematically shown to involve a transmission time Tl of the transmitter ranging sound at the transmitter side (left), which signal arrives at the receiver side (right) at a receiving time T2. The process is controlled via the controller 13 which communicates to the transmitter and the receiver. The distance between transmitter and receiver is derived from the travel time (Td) by

Td = (T2 - Tl). The travel time Td is to be multiplied by the speed of sound.

Acoustic ranging is a relatively simple and highly accurate ranging technology which can yield measurements of approximately 5 cm accuracy. It is recently being investigated as a technology to enable the commissioning of acoustically equipped lighting, by integrating microphones and loudspeakers into the lighting infrastructure.

Automatic commissioning systems use determined distances between the transmitter(s) and the receiver(s) from the ranging measurements in accordance with the present invention to assign identifiers to the receivers and transmitters in accordance with the geometrical information. This obviates a cumbersome process of identifying the positions of the items associated with the receivers and the items associated with the transmitters by hand to fit, for example, an existing division of a floor into rooms such that the control of the light in a particular room can be controlled taking care which controller is actually controlling which light. By having determined the relation between the position of a particular receiver and the controller controlling the associated item it is known to the controller system which controllers should control which items such that the desired output is obtained. For example, the items may be light sources such a TLs or any other lamps, or may be loudspeakers conveying particular messages or a particular genre of music intended for a particular room, or may be a heater/cooler or flow regulator for influencing a temperature in a particular room. Such devices may further include a sensor such as a proximity sensor detecting the presence of a person in a room, a light sensor or a heat sensor. Once automatic commissioning is complete a large network of acoustic technology is available to the infrastructure for other applications.

For example, US7, 623,413 describes a time-of- flight ranging system. Range measurements can be made by calculating the time-of- flight between the transmission and receiving of a signal sent over a medium and multiplying by the speed of flight over that medium. However, this is only possible to achieve accurately when the transmitter and receiver share the same clock, or the clocks are accurately synchronized.

Figure 2 shows a system for ranging and two way time-of- flight measurement. The system has a first device 20, e.g. a mobile device, that has a transmitter unit 21, a receiver unit 22, and a controller 23 that controls a transmitter ranging process. The system further has a second device 29, e.g. a reference device, that has a transmitter unit 24, a receiver unit 25, and a controller 26 that controls a receiver ranging process. It is noted that in the system both the first device and the second device may act as transmitter and/or receiver, and may control the respective process at their end of the ranging system.

The transmitter unit 21,24 typically includes a loudspeaker or other sound transducer, and a sound signal generator to provide a ranging sound signal 28, also called sound probe. Furthermore, the proposed transmitter device includes a modulator to encode control data in the ranging sound signal. By said encoding the ranging control data is transferred via the ranging sound signal 28 to the receiver. The ranging control data may be an instruction, and the transmitter unit is arranged for including the instruction in the transmitter sound signal.

The receiver detects the ranging sound signal 28 and derives the ranging control data. The receiver unit 22,25 typically has a microphone, and a sound analysis processor for determining the time of arrival of the ranging sound signal, and further includes a demodulator for deriving the encoded ranging control data, such as a command or control parameter for the ranging protocol to be engaged. The ranging control data may comprise an instruction, and the receiver unit is arranged for retrieving the instruction from the transmitter sound signal. The sound analysis processor for the receiver unit 22,25 may be embodied in the controller 23,26, or may be combined with the sound generator of transmitter unit 21,24, or clock data or sample numbers may be synchronized between separate processors for transmitter and receiver units.

Optionally, the instruction comprises transferred via the sound ranging signal embodies a selected command. A few examples are as follows. The instruction may be a command that instructs the receiver controller to perform a step in the ranging receiver process. The step may be just initializing a protocol, or any specific step in a protocol, or may just be to enter the device in a specific operational state, e.g. power up to receive further ranging sound signals of a specific nature. Also, a command may instruct the receiver controller to send a receiver sound signal of a predetermined type. The type of response signal may be specific for the receiver, e.g. include a device type indicator or a device identifier. The command may instruct the receiver controller to refrain from sending a receiver sound signal, such as an indicator that the signal is a response which implies that no response is to be sent. A different command may instruct the receiver controller to engage a predetermined ranging protocol, e.g. the device may support a set of protocols for different applications or environments, and a master device may order all devices to selects one of the predetermined protocols. The command may instruct the receiver controller to select a type of ranging sound, e.g. a particular response frequency or response channel may be selected, or a specific modulation type or signal strength.

In a two-way ranging process 27 a first ranging sound signal is transmitted by the first transmitter 21 at a transmitter instant, and later received by the receiver 25 at the receiver side. After a known, or determinable, delay T_B a further ranging sound signal is transmitted by the second transmitter 24 at time instant T3 and received in the first receiver 22 at time instant T4. The total time period T_A between the transmittal of the first ranging sound signal at Tl and receiving the second ranging sound signal at T4 is known to the first device.

The distance between transmitter and receiver is derived from the travel time

(Td) by Td = (T_A - T_B) / 2. The travel time Td is to be multiplied by the speed of sound to calculate the distance.

Using two-way ranging measurements is a technique used to measure distances between two devices with unsynchronized clocks as shown in Figure 2. Three-way ranging measurements can further be employed to increase accuracy of the range, which compensates for drift in time between different clocks of two devices.

There are various wireless communication protocols commonly used for radio communications. These protocols define sophisticated interactions to transfer data between separate devices and to control the flow of data to reduce collisions and to maximize the efficiency of communication. The standard procedure for making acoustic range

measurements is to send control signals over wired or radio communication to coordinate the measurements and collection of data. Below is described a proposed method where sound protocols are used to coordinate the whole measurement process.

In the sound ranging system various sound ranging signals are transmitted, also called sound probes, which typically are logarithmic sweeps for optimizing signal/noise ratio, to make range measurements between a loudspeaker and a microphone. Over a large area, the audible range will be restricted to nearby devices. In order to make two-way, three- way or many- way measurements it is important to differentiate between the signals so that the receiver can understand the nature of any received signal, and engages the required ranging protocol. For example separate control signals would traditionally be required to understand if a received sound was the first or second of a two-way measurement. Such a first signal requires a response, but hearing the second signal does not, which is called a hidden node problem. If traditional sound probes were used, a device that was out of range of the initial sound probe but in range of a (responding) sound probe would respond to the second probe is if it were a request. This would lead to a lot of unwanted sound signals, unless an additional control mechanism were used.

The proposed ranging system includes control data in the ranging sound signals. Hence the receiving end is enabled to differentiate between the types of sounds. The need for additional radio or wired control protocols to coordinate the measurement process is reduced. Furthermore, in more complex protocols additional data can be encoded in the sound to coordinate the measurements.

Figure 3 shows a ranging system having multiple transmitters and receivers.

Multiple devices 30 are shown, each device having a transmitter unit and/or a receiver unit, and a respective ranging process controller. In the system of Figure 3, a transmitted sound is heard by multiple nearby devices (as indicated by the Transmit circle 31). However, when they respond with a sound probe (Received circle 32), other devices that didn't hear the original probe, i.e. outside the transmit circle, but inside the received circle, will hear a sound probe and issue a responding probe, causing a cascade of unwanted sound probes. Without being able to control the ranging process and the types of sounds, additional communication needs to be provided.

The current system proposes a protocol in which ranging sound signals from a sound source, typically a loudspeaker, which when heard by a receiver unit, typically a microphone, include control data, such as an instruction to control the ranging process.

A basic sound ranging process is to select a specific request-response protocol, such that the sound for request is acoustically different from the sound for response. The control data to encode the difference could be in terms of the frequency, amplitude or length of sound. It is essential that the two sounds can be distinguished when received at the microphone to retrieve the inferred command to engage the respective sound ranging protocol, i.e. the respective transmitter and/or receiver part of that protocol.

When the microphone receives the sound it can be identified and used to control the action required at the receiver. If the receiver hears sound signal that infers a request command, it is required to make a response sound. If the receiver hears a response, the included control data indicates a command to engage the protocol part of receiver that receives a response. Hence, if the device did not send the original request it can ignore the message, but if it sent the original request it can measure the time intervals between sending and receiving to make range measurements. Further embodiments are also enabled by encoding additional data into the sound message to include essential information required to make suitable range

measurements, for example to encode the identity of the device emitting the sound into each sound probe, or the identity of a specific device that is required to send a response.

Figure 4 shows a layout of a lighting installation. In the lighting installation lights and switches and sensors are distributed over the area of a building and are connected to control boxes. A number of ellipses 41 in the figure show the different groups of lights that are to be managed by each control box.

In this example, the control boxes contain signal processing hardware to modulate the sound for the loudspeakers and also process the received sound from the microphones. The lights, switches and sensors are wired to a particular port on the control box so that they can be addressed separately.

In an embodiment the lights, switches and sensors have embedded loudspeakers and microphones. In order to make acoustic ranging measurements the lighting installation uses embedded loudspeakers to make sounds. These sounds are received by microphones on other nearby lights, sensors and switches.

For sounds that are received by microphones that share a same control box as the emitting loudspeaker a time difference calculation can be simply deduced as shown in Figure 1. However, the sound is also heard by many other microphones in other devices, whose control box does not share the same clock as the control box of the emitting microphone. Control signals may be exchanged via the sound signals to exchange clock control data. However, distance calculation based on one-way ranging and unsynchronized clocks will contain a large error. This can be resolved by making a second range

measurement in the reverse direction as shown in Figure 2.

Optionally, for a two-way ranging system, it is proposed to differentiate the two different types of sounds used for ranging: Request and Response. In this example a range measurement from a mobile device 20 to a known reference device 29 is performed. The mobile device issues a request sound from its loudspeaker. When the sound is received by the microphone of the reference device the ranging sound is analyzed and the included control data is detected. If the ranging sound is determined to be a response sound the device knows not to respond and need take no further action. However, if the sound is determined to include a request command, the receiving node sends a response sound. Optionally, in order to establish the time-of- flight, the receiving device may be instructed or required by a selected protocol, to communicate the delay time interval, indicated in Figure 2 as T_B, back to the mobile device.

In an embodiment control data to be transmitted is encoded by modulating the ranging sound signal according to the control data. For example, when the above reference device responds, it may encode the time interval T_B into its response. When it is decoded at the mobile sufficient data is available to determine the two-way time-of- flight. The control data can be conveyed using any suitable audio data communication protocol. An example is sound modulation according to Dual-tone multi-frequency signaling (DTMF), which is known from telecommunication signaling over analog telephone lines in the voice- frequency band between telephone handsets and other communications devices and the switching center. DTMF is standardized by ITU-T Recommendation Q.23.

It order to encode T_B into its response, the reference device must be capable of predicting the time of transmission of the second probe signal. In general this will be the the combination of hardware and control algorithms is expected to be adequately deterministic. Otherwise, the reference device could detect, calculate or measure the delay time T_B and send a separate data packet as an additional sound signal, following the response used for the ranging measurements. For example, the reference device might record both the received ranging sound signal and its own response signal, and determine the time interval in that recording, e.g. by counting the intermediate number of sound samples between request and response. The time interval so measured may be encoded as control data in a separate audio ranging signal.

Figure 5 shows a ranging system for extended two-way ranging. The system is similar to the system shown in Figure 2, but provides an enhanced response signal. Thereto the Figure schematically shows an enhanced two-way ranging protocol 51. The known reference device sends a first pulse of the response sound signal on time T3. The first pulse has a delay time of T_B from the request received at T2. The transmitter unit 54 of the responding side device is extended to transmit, in the sound ranging signal, a second sound pulse transmitted at T5. The interval between the first sound pulse and the second sound pulse encodes ranging control data. Optionally the time difference between the first and second sound pulse encodes the control data representing the delay time T_B itself. For example, the time difference may be equal to the delay time T_B or it may have a

predetermined ratio to the delay time, or an offset to a reference delay interval. In a practical embodiment, having received the request probe and issued the response probe, the reference device issues an additional probe at a carefully controlled moment to indicate the magnitude of the T_B interval measurement. For example, the third probe (measurement) could be sent an exact delay of T_B after it sends the second probe (initial response). Using the same pulse for both the first and the second response probe has the advantage that, in the receiver unit of the mobile device where both probes arrive, the same detection process will be used which results in cancelling out any detection delay error. The mobile device will receive the first response probe T_A seconds after the request probe; and receive the third probe exactly T_B seconds after the second response probe. Where:

T_B = T₆ - T₄ = T₃ - T₂

Since T₆ and T₄ are both measureable at the mobile device it will therefore have all the control data required to calculate the time-of- flight between the mobile and the reference device. This is achieved by transferring the control data acoustically encoded by the ranging control signal.

The invention may be summarized as follows. A protocol for acoustic ranging is disclosed that greatly simplifies the control mechanism of acoustic ranging. Instead of using independent communication to control the ranging or positioning application, the sound probe used to make the range measurement is adapted to carry an implicit command to the receiver. More advanced control is also disclosed by using the sound to carry control data as part of the sound probe, further reducing additional control requirements.

The primary application for the proposed system is indoor ranging, which gives rise to automatic commissioning and indoor positioning of domestic devices. Other applications are also enabled, such as asset tracking, people tracking (e.g. firemen in a building), tracking children - keeping them within a safe distance of a reference point or away from a dangerous object or place, indoor guidance (airports, shopping malls etc), object location (find keys), automatic/autonomous robot movement and positioning, etc. For such applications, the proposed devices include a lighting device such as a luminaire or illumination assembly provided with sound ranging components, or a lighting control device such as a lighting control switch; a mobile computing device or a mobile telephone; a portable guidance device or object location device; an autonomous moving device such as a house cleaning robot; or a fixed reference device, such as a reference unit for enabling acoustic ranging in a room. Although the text may refer to a mobile device and/or a fixed reference device, the invention can just as easily be applied to all- fixed installations, and also to all-mobile installations or any combination of these. Moreover, encoding ranging control data may also be applied in one-way ranging systems to transfer control data from the transmitting side to the receiving end.

It is to be noted that the invention may be implemented in hardware and/or software, using programmable components. A method for implementing the invention has the steps corresponding to the ranging functions defined for the system as described with reference to Figure 2. The method may be embodied in software, which may be provided on a storage medium, e.g. a computer readable medium.

It will be appreciated that the above description for clarity has described embodiments of the invention with reference to different functional units and processors. However, it will be apparent that any suitable distribution of functionality between different functional units or processors may be used without deviating from the invention. For example, functionality illustrated to be performed by separate units, processors or controllers may be performed by the same processor or controllers. Hence, references to specific functional units are only to be seen as references to suitable means for providing the described functionality rather than indicative of a strict logical or physical structure or organization. The invention can be implemented in any suitable form including hardware, software, firmware or any combination of these.

It is noted, that in this document the word 'comprising' does not exclude the presence of other elements or steps than those listed and the word 'a' or 'an' preceding an element does not exclude the presence of a plurality of such elements, that any reference signs do not limit the scope of the claims, that the invention may be implemented by means of both hardware and software, and that several 'means' or 'units' may be represented by the same item of hardware or software, and a processor may fulfill the function of one or more units, possibly in cooperation with hardware elements. Further, the invention is not limited to the embodiments, and the invention lies in each and every novel feature or combination of features described above or recited in mutually different dependent claims.

Claims

CLAIMS:

1. Transmitter device for use in a ranging system further comprising a receiver device for sound ranging between the transmitter device at a first position and the receiver device at a second position,

the transmitter device comprising

a transmitter controller (23) for controlling a ranging transmitter process in dependence of ranging control data, and

a transmitter unit (21) for transmitting a transmitter sound signal (28) at a transmitter instant (Tl); and

the receiver device comprising

a receiver controller (26) for controlling a ranging receiver process, and a receiver unit (25) for receiving the transmitter sound signal at a receiver instant (T2), wherein

the transmitter unit is arranged for including the ranging control data in the transmitter sound signal, and

the receiver unit is arranged for retrieving the ranging control data from the transmitter sound signal; and

the receiver controller is arranged for controlling the ranging receiver process in dependence of the ranging control data.

2. Receiver device for use in a ranging system further comprising a transmitter device for sound ranging between the transmitter device at a first position and the receiver device at a second position,

the transmitter device comprising

the receiver device comprising

3. Device as claimed in claim 1, wherein the ranging control data comprises an instruction, and the transmitter unit is arranged for including the instruction in the transmitter sound signal.

4. Device as claimed in claim 2, wherein the ranging control data comprises an instruction and the receiver unit is arranged for retrieving the instruction from the transmitter sound signal.

5. Device as claimed in claim 3 or 4, wherein the instruction comprises at least one of

- a command that instructs the receiver controller to select a type of ranging sound.

6. Device as claimed in claim 1, wherein

the transmitter unit (54) is arranged for including a first sound pulse and a second sound pulse in the transmitter sound signal, and the interval between the first sound pulse and the second sound pulse encodes the ranging control data.

7. Device as claimed in claim 6, wherein

the interval between the first sound pulse and the second sound pulse is indicative of a response delay interval between receiving a further sound signal by the device and responding to the further sound signal by transmitting the transmitter sound signal.

8. Device as claimed in claim 1, 2, 6 or 7, wherein the sound ranging comprises two-way ranging and the device comprises both a transmitter unit and a receiver unit.

9. Device as claimed in claim 1 or 2, wherein the device comprises at least one of - a lighting device, or a lighting control device;

- a mobile computing device or a mobile telephone;

- a portable guidance device or object location device;

- an autonomous moving device;

- a fixed reference device.

10. Method of transmitting for use in a ranging system comprising a transmitter and a receiver for sound ranging between the transmitter at a first position and the receiver at a second position,

the method comprising

controlling a ranging transmitter process in dependence of ranging control data, and

transmitting a transmitter sound signal (28) at a transmitter instant (Tl); and the receiver comprising

a receiver controller for controlling a ranging receiver process, and a receiver unit for receiving the transmitter sound signal at a receiver instant

(T2), wherein

the method comprises including the ranging control data in the transmitter sound signal, and the receiver unit is arranged for retrieving the ranging control data from the transmitter sound signal; and

11. Method of receiving for use in a ranging system comprising a transmitter and a receiver for sound ranging between the transmitter at a first position and the receiver at a second position,

the transmitter comprising

a transmitter controller for controlling a ranging transmitter process in dependence of ranging control data, and

a transmitter unit for transmitting a transmitter sound signal (28) at a transmitter instant (Tl); and

the method comprising

controlling a ranging receiver process, and

receiving the transmitter sound signal at a receiver instant (T2), wherein the transmitter unit is arranged for including the ranging control data in the transmitter sound signal, and

the method comprises retrieving the ranging control data from the transmitter sound signal; and

controlling the ranging receiver process in dependence of the ranging control data.

12. Computer program for use in a ranging system comprising a transmitter and a receiver for sound ranging between the transmitter at a first position and the receiver at a second position, which program comprises computer program code means operative to cause a processor to perform the method as claimed in claim 10 or 11.

13. A computer program as claimed in claim 12 embodied on a computer readable medium.