CN117223233A - Optical front end for use in optical wireless communications - Google Patents

Abstract

The invention relates to an optical front end, OFE, (400) for optical wireless communication, OWC, comprising: an optical receiver having at least a photodetector (102 a) and a transimpedance amplifier, and a two-dimensional array of optical transmitters (103 a) and one or more drivers, wherein each optical transmitter has a separate transmitter field of view, the two-dimensional array being arranged to create a combined transmitter field of view that is larger than the separate transmitter field of view, the plurality of optical transmitters being arranged such that the optical axes of the plurality of optical transmitters are evenly distributed within the combined transmitter field of view.

Description

Optical front end for use in optical wireless communications

Technical Field

The present invention relates to the field of optical front ends for Optical Wireless Communications (OWCs), which may find use in OWC transceiver systems, which may be deployed in, for example, a vehicle-to-vehicle (V2V) network or a vehicle-to-infrastructure (V2I) network.

Background

Optical wireless communication enables mobile devices to be connected to each other wirelessly using optical communication. In contrast to radio frequency communications, OWCs use a spectrum that can achieve unprecedented data transmission speeds and bandwidths to achieve this. Furthermore, it can be used in areas that are prone to electromagnetic interference and is based on line-of-sight links (line-of-sight links) in view of the directionality of light-based communications. The optical communication may utilize the visible spectrum or the infrared spectrum. The advantage of using infrared spectrum is that it is not immediately perceivable by humans. In contrast, visible light may not be annoying when integrated into functional light, but may be considered annoying when used for lateral communication, for example when used between vehicles during the day. In this case, the use of infrared rays may be preferable.

Based on the modulation, data may be embedded in the optical output and any suitable optical sensor and corresponding demodulator may be used to detect information in the optical communication signal. The photodetector may be a dedicated photocell (point detector), or an array of photocells such as a camera.

The data may be modulated using a variety of modulation techniques ranging from simple pulse amplitude modulation to orthogonal frequency division multiplexing modulation. The latter has recently received considerable attention and various techniques can be used to cope with the fact that light, as opposed to electrical signals, requires unipolar modulation. As a result, techniques such as ACO-OFDM and flip OFDM (FlipOFDM) have been designed to avoid having to add an offset to the light output.

Achieving high data throughput and/or long distances in point-to-point OWC systems while maintaining wide-angle coverage is a challenge. This is not only because of the increased power requirements for the transmitter, but also because it is not always possible to increase the transmission power in the optical system above a certain level due to eye safety requirements.

To solve this problem, it is known to deploy an electromechanical system for performing beam-steering (beam-steering). In such a system, the output beam direction is adapted under automated motor control. An alternative is known instead to use mechanical actuators in combination with mirrors for beam steering. However, systems using mechanical components are expensive and prone to reliability problems, particularly in some common use cases of beam steering systems (such as vehicle-to-vehicle communications).

Disclosure of Invention

The present invention proposes an alternative way of mechanical beam control that does not use moving mechanical or electromechanical parts, but rather uses multiple narrow angle transmitters and wide angle receivers to perform beam selection.

According to a first aspect of the present invention, there is provided an optical front end OFE for optical wireless communication OWC, the OFE comprising: an optical receiver having at least a photodetector facing in a detection direction and a transimpedance amplifier TIA for amplifying a signal from the at least one photodetector; and a two-dimensional array of optical transmitters and corresponding drivers, wherein each optical transmitter has an individual transmitter field of view, the two-dimensional array being arranged to create a combined transmitter field of view that is greater than the individual transmitter field of view, and wherein the number of optical transmitters along a first direction is greater than the number of optical transmitters along a second direction and the combined transmitter field of view in the first direction is greater than the combined transmitter field of view in the second direction, the first direction being orthogonal to the second direction, the optical transmitters being arranged such that optical axes of the optical transmitters are evenly distributed within the combined transmitter field of view, wherein: (1) Positioned along a surface curved about a first axis and curved about a second axis, the first axis and the second axis being orthogonal to each other, the first axis being perpendicular to the first direction, the second axis being perpendicular to the second direction; (2) Positioned with at least one point on the planar surface, each optical transmitter being angled to face a different direction; or (3) positioned on a flat surface and equipped with corresponding optical waveguides for directional outcoupling.

Advantageously, the structuring of the two-dimensional array makes the OFE particularly suitable for OWCs in V2V and/or V2I environments.

Typically, the optical transmitter will be a Light Emitting Diode (LED) or a Vertical Cavity Surface Emitting Laser (VCSEL). While the photodetector may be a photodiode such as a silicon photon multiplier (SiPM) or an Avalanche Photodiode (APD).

The optical transmitters as described below will typically be mounted on a substrate or PCB, where in some implementations they may all be mounted on the same PCB. In this case, the transmitters may be mounted on the same PCB at an angle (to achieve their respective output emission directions), or they may be provided with optical components such as waveguides and lens structures to couple light out in the desired directions. Alternatively, each transmitter may be mounted on a separate smaller PCB that is placed at an angle (to achieve beam steering) from the main PCB.

The receiver field of view is greater than or equal to the combined transmitter field of view. This feature will facilitate two-way communication because it is more symmetrical.

In a preferred option of the first aspect, each of the transmitters has a separate driver so that each of the transmitters can be controlled separately. This allows simultaneous embedding of unique transmitter codes, which can be used for alignment purposes. Conversely, if a lower cost solution is desired, the transmission of the unique identifier/code/attribute may be time multiplexed using one or a subset of optical transmitters at the expense of a slower alignment process.

According to a first aspect, the OFE comprises at least one optical receiver mounted on a planar substrate with its optical axis aligned with the optical axis of the combined transmitter field of view. In this way, two OWC transceiver systems that include such optical front ends may use their respective receivers to align their transmitters.

According to a first aspect, the array of optical transmitters is arranged in a matrix along two orthogonal directions. Although the optical transmitters may represent planar orthogonal arrays, alternatively, different rows of transmitters may be offset so as to create a hexagonal structure instead of a square structure. The advantage of a hexagonal array structure as the coverage area can be achieved with reduced overlap (the advantage of a hexagonal array structure is that the coverage can be achieved with reduced overlap).

According to a first aspect, the number of transmitters along the first direction is greater than the number of transmitters along the second direction. This is advantageous because it allows the combined transmission field of view to be different in the vertical and horizontal directions while still using the same optical transmitter.

As discussed in one alternative according to the first aspect, the plurality of optical transmitters are positioned along a surface curved about a first axis and curved about a second axis, the first axis and the second axis being orthogonal to each other, the first axis being perpendicular to the first direction and the second axis being perpendicular to the second direction. This arrangement allows for a reduction in dead space between the fields of view of adjacent transmitters in the vicinity of the OFE. In this regard, it is noted that the overlap between transmitters will typically increase with distance from the OFE, as the emission pattern of the light source generally diverges with distance. Ideally, the overlap is selected such that the combined fields of view do not have any dead zone in the foreseen operating area.

Using the alternative option of the first aspect, the plurality of optical transmitters are positioned on a substantially planar surface, but wherein the optical transmitters are angularly adjusted corresponding to the curvature at their locations on the surface curved about the first axis and curved about the second axis, and wherein the optical transmitters are adjacent so as to cause little obstruction, or are spaced apart so as not to cause obstruction.

In a further alternative of the first aspect, a plurality of optical transmitters are placed on a planar substrate and are equipped with corresponding optical outcoupling means for manipulating the respective outputs. Such an implementation may allow for a simpler, more traditional PCB assembly process, thereby saving costs.

In a further option of the first aspect, the combined transmitter field of view is in the range of 30 degrees to 90 degrees in the first direction and in the range of 10 degrees to 60 degrees in the second direction. Such an implementation is suitable for use in vehicles used on conventional road networks, where the likelihood of a communication partner moving in a horizontal direction is higher than the likelihood of a communication partner moving in a vertical direction.

According to a second aspect, there is provided an OWC transceiver system for optical wireless communication OWC for use with a further OWC transceiver system, the OWC transceiver system comprising: the optical front end OFE according to the first aspect, wherein the OFE comprises a separate driver for each of the plurality of optical transmitters; a baseband unit configured to modulate outgoing data for transmission by the OFE and demodulate incoming data from the output of the transimpedance amplifier of the OFE; and a controller configured to control which of the plurality of optical transmitters is used to transmit outgoing data based on a result of the alignment.

Such OWC transceiver systems may be single units or "distributed" systems comprising several discrete modules or parts, which may be installed and/or integrated in a vehicle, respectively, for example for V2V or V2I communication. Also, the OWC transceiver may be integrated in a stationary device connected to a backbone network for interfacing with the vehicle.

In an advantageous option of the second aspect, the controller is arranged to perform an alignment operation with a further OWC transceiver system, wherein the controller is configured to: generating a unique directional beacon comprising identifying attributes/information for each of a plurality of optical transmitters; controlling each of a plurality of transmitters to transmit their respective directional beacons; in the output of the TIA, receiving feedback from the communication partner regarding detection of a unique attribute of the optical transmitter of the OWC transceiver system in the beacon of the OWC transceiver system; and based on the feedback, selecting an appropriate subset from the plurality of optical transmitters for transmitting outgoing data to the further OWC transceiver system.

More preferably, the directional beacon is a low frequency CDMA beacon transmitted out-of-band from the output data, allowing the optical transmitter to transmit the directional beacon and the output data simultaneously; and the detection feedback from the communication partners is a beacon transmitted by the communication partner with an inverted version of the CDMA sequence transmitted with a corresponding one of the optical transmitters received by the communication partner.

In this way, a controller performing beacon transmission using out-of-band signaling may use the same signaling mechanism to temporarily signal the potential communication partner with the out-of-band channel the CDMA sequence received by the OWC transceiver in the communication partner's directional beacon. As a result, when communicating with a similar device, the communication partner can select a channel on which to output its data for communication purposes based on the provided signaling.

According to a third aspect, there is provided a vehicle comprising: a vehicle-mounted network; a first OWC transceiver system comprising a forward OFE according to the first aspect, the optical axis of the forward OFE facing the forward direction of movement of the vehicle, wherein the in-vehicle network is connected to the first OWC transceiver.

In one option of the third aspect, the vehicle further comprises: a second OWC transceiver system comprising a backward OFE according to the first aspect, the optical axis of the backward OFE facing in a direction opposite to the forward direction of movement of the vehicle, wherein the on-board network is connected to the second OWC transceiver.

In a further option of the third aspect, the vehicle is one of a car, bus, train, boat or truck.

Drawings

In the drawings, like reference numerals generally refer to the same parts throughout the different views. Moreover, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.

FIGS. 1A and 1B illustrate corresponding elements of a system including two communication point-to-point optical wireless transceiver systems;

FIGS. 2A and 2B illustrate the alignment of two point-to-point optical wireless transceiver systems;

FIG. 3A shows a perspective view of an optical front-end unit;

fig. 3B and 3C show top and side views, respectively, of an optical front-end unit;

fig. 4A and 4B show top and side views of a further optical front-end unit;

FIGS. 5A, 5B and 5C show schematic cross-sectional views of an array of transmitters of an optical front-end unit; and

fig. 6 shows a proposed transceiver with multiple out-of-band transmitters.

Detailed Description

Fig. 1A and 1B depict one OWC transceiver, respectively, arranged to communicate with each other using a point-to-point optical link. Each of the optical wireless systems may be connected to a local network (e.g., an in-vehicle network) or other communication port (104, 204). Each of the OWC transceivers further includes a baseband unit configured to modulate and demodulate incoming and outgoing data signals in a bi-directional manner between the communication port and an optical transmitter (103, 202) and an optical receiver (102, 203) of the respective optical front-end unit of the OWC transceiver.

In order for the system to establish stable communications with maximum throughput, the transmitter (103) of a unit and its opposing receiver (203) on other units need to be aligned. If the transmitter and receiver have different fields of view (also called opening angles), it is sufficient for a good connection that the cone or beam pattern has a large amount of overlap. In general, the more overlap the better the connection.

In the case of a narrow angle transmitter and a wide angle receiver, the transmitter beam must at least partially overlap with the receiver beam near the receiver source, as shown in fig. 2A.

This allows some freedom of movement between the systems, as perfect alignment is not necessary. The disadvantage is that for these wide angle receivers the effective receiver sensor area is larger, thus increasing noise, resulting in lower performance for the same received power. This can be partially compensated by adding multiple identical photodetectors (e.g., photodiodes, silicon photomultipliers, or avalanche photodiodes).

However, the movement of the transceiver and thus the coverage area is still limited. Here we propose that each transceiver system has multiple narrow angle transmitters (a narrow angle transmitter consisting of separate optical transmitters, lenses and amplifiers, each pointing in a different direction) and a single planar wide angle receiver. All transmitters will be connectable to a single baseband output signal, wherein one or more of these transmitters may be activated at the moment the output signal is provided by the best aligned transmitter beam (or combination of best aligned transmitter beams).

Fig. 2B illustrates such an architecture for use in a point-to-point system, where different IDs indicate transmitter beams pointing in different directions. In this example, transmitter unit 1103 selects beam ID2 as the strongest beam, while transmitter unit 2202 selects beam ID3 due to the orientation.

Both receivers 102, 203 have a receive optical angle equal to or greater than the combined transmit angle at which all of the transmitter beams are together. The solid cone of the receiver field of view is wider than the solid cone of the combined transmitter field of view.

To avoid a significant drop in throughput when the unit is precisely aligned between two transmitter beams, all subsequent transmitter beams will need to have some overlap (in this simple example, ID1 overlaps ID2, ID2 overlaps ID3, etc., but there may also be more overlap when the transmitters are oriented in 3D space). The farther the transceiver system is, the larger the overlap area between the two beams becomes, and therefore, there will be an optimal distance range between the systems in which this solution is feasible: beyond a certain distance, the overlap between the two ID transmit beams is so large that the choice of transmitters may become less useful, however, the choice of a single beam at this time means that the transmit power can remain optimized for near eye safety.

It is worth noting that below the minimum distance there will no longer be a subsequent overlap, creating dead zones. In the latter case, however, the relatively wide-angle receiver field of view may still allow communication despite the absence of a continuing cone. In practical systems, such as for V2V communications, the minimum distance may be configured such that continuous communications are possible in a real-world scenario between similar vehicles or assuming a known placement of the OWC transceivers. In practice, this may be very close in traffic congestion, in the range of 1 to 5 meters, or at normal safe driving distance, depending on the type of vehicle.

Fig. 3A illustrates an exemplary mechanical assembly of a perspective view of the optical front-end unit 400, and fig. 3B and 3C illustrate corresponding top and side views, respectively, of the optical front-end unit 400. In an exemplary mechanical arrangement of the OFE unit, a common transmitter board 103 is provided that includes a number of individual transmitters 103a..n, each of which is mounted on separate boards that are mechanically assembled at an angle to form an overall greater coverage angle on both the horizontal and vertical axes. The receiver board 102 is assembled flat and is composed of one or more wide-angle photodetectors 102a and an electronic circuit that all point in the same direction.

The optical front-end unit 400 comprises a common transmitter board 103 comprising a number of individual transmitters 103a..n, each of which is mounted on separate boards that are mechanically assembled at an angle to form an overall larger coverage angle in horizontal and vertical directions. The driver(s) for the respective optical transmitters are not shown. The receiver board 102 is assembled flat, and it is composed of one or more wide-angle photodetectors 102a all pointing in the same direction. The receiver board may include receiver circuitry (not shown).

The depicted optical front-end has a 4x3 optical transmitter configuration, resulting in a slightly wider horizontal field of view (35 degrees) than the vertical field of view (25 degrees). This is practical for vehicle-to-vehicle communications in view of the nature of traffic flow and the limitations of commercial vehicle climbing/downhill capabilities.

The optical transmitter in turn may generate a wider field of view, for example with a VCSEL with appropriate optics, or with an LED.

Fig. 4A and 4B depict, in order, a top view and a side view of another exemplary mechanical assembly of a perspective view of an optical front-end unit 400. In this case the optical front-end has a 6x2 optical transmitter configuration, so the horizontal field of view is more pronounced, i.e. in the range of 50-55 degrees, and the vertical field of view is 15-17 degrees.

As will be clear to the ordinarily skilled artisan, the corresponding field of view will depend on the device optics mounted on the associated LED/VCSEL.

Fig. 5A shows a section along the horizontal axis of the top view of fig. 5A. From this figure it will be clear that the optical transmitter is placed on a curved surface, which in this cross-section is a flat curved surface, but in the case of a full three-dimensional surface curved around a first axis and curved around a second axis, the first axis and the second axis are orthogonal to each other, the first axis being perpendicular to the first direction and the second axis being perpendicular to the second direction.

By placing the emitters on a surface as shown in FIG. 5A, dead space between the emitters can be significantly reduced. However, as shown in fig. 5B, alternative placements are contemplated. As shown in fig. 5B, the transmitter may alternatively be placed with at least one point on a flat surface. In this case, it may be necessary to space some of the emitters apart in order to prevent emissions from one of the emitters from being blocked. In this way, a separate field of view for each transmitter may be utilized. Strictly speaking, this is not necessary, as in case of occlusion, this section of the combined transmission field of view will then be covered by the neighboring device, whereas occlusion may lead to abrupt changes in signal quality when moving.

Further improvements are possible by placing the transmitters on a flat surface and providing an optical waveguide with out-coupling, which allows all transmitters to be mounted on a flat substrate, as shown in fig. 5C. Such an implementation may allow for a simpler, more traditional PCB assembly process, thereby saving costs.

A more detailed illustration of the electronics/optics of the proposed transceiver system is shown in fig. 6.

The transceiver systems depicted herein may be used to perform beam selection in conjunction with similar types of transceiver systems (as discussed with respect to fig. 2B). In a preferred embodiment, the transceiver may transmit an out-of-band low frequency CDMA beacon for beam selection. When using a specific CDMA modulation as described in co-pending european patent application EP21163846.5 (attorney docket 2021P80042 EP), which is incorporated herein by reference, a CDMA beacon may be generated using dedicated hardware or alternatively using a controller.

In CDMA, binary bits are represented by (-1, +1). The message of length N' is extended by a code of length N (chip sequence) by multiplying each bit message of the full sequence. This generates a transfer message of length n' xN. Each of the optical wireless transmitters is encoded using a different chip sequence that is statistically uncorrelated.

The chip time is constant and it is the same for all chip sequences. When the coded sequences are mixed in the overlapping region, the receiver can decode the original message of all transmitters simultaneously by cross-correlating the received signal with the same N-chip sequence used to code the message. This will produce peaks in the correlation when the portion of the signal matches the chip sequence. To simplify the system, for this particular case of beacon transmission, we can use different chip sequences to encode a single bit, resulting in a message of length N.

By using a different CDMA chip sequence for each optical transmitter beam (the beams partially overlap), the receiving unit pointing to the area between the two beams will thus be in a position to detect the signal strength of each respective beam and thus may allow the receiving device to select the strongest beam. CDMA beacons may be multiplexed with lower power (approximately 10-100 times lower) than the main high-speed signal. As a result, the use of CDMA allows all transmitters to continuously transmit CDMA beacons, while only the selected high-speed transmitter with the best orientation is connected to the output signal from baseband unit 101.

Out-of-band (OOB) transmitted beacons preferably use the same optical transmitters and receivers as the primary optical signal. For the receiver 102, one or more photodiodes 108 receive a signal that contains both the high-speed communication signal and the out-of-band signal (CDMA beacon), which is then amplified with one or more TIAs 107 and then summed if needed. Then, the high-speed signal follows a path to the input of the baseband unit 101, and the main channel signal is demodulated in the baseband unit 101. To decode the OOB signal, a low pass filter 211 is placed after the first amplification and further amplified with an additional low bandwidth TIA212 if needed. Thereafter, the signal is fed to a controller 209, where the signal is converted using an ADC (which may be internal or external) in order to achieve digital signal processing.

For each of the selectable directional beam transmitters 103a … n, the controller generates an OOBCDMA beacon that is amplified 111 and coupled to the light source 109, possibly along with a high speed signal. To activate the selected high speed beam transmitter, the controller needs to connect the path from baseband to the high frequency amplifier 110 by means of the switch 112 and change the DC current of the light source 113.

When CDMA is being used, it is possible that the high speed signal requires a much higher DC bias than the beacon, for which reason a DC control block 113 is provided. Each of the optical wireless transmitter blocks in turn generates a different OOBCDMA-based ID, with each transmitter pointing in a different direction, as shown in fig. 2B.

However, in order for one of the transceiver systems to select an output beam to establish communication, a beacon being continuously transmitted by the first system 100 to the second system 200 needs to be transmitted back to the first system 100 to inform the system which is the better-aligned transmitter at that time (and vice versa from the second system to the first system). Thus, the communication needs to be bi-directional but fast enough because some applications, such as vehicle-to-vehicle communication, require fast response/reaction times.

The proposed first mechanism allowing fast beam selection may be performed by the controller and transceiver system as follows:

1. the first system 100 begins transmitting CDMA beacons in succession, wherein each transmitter includes a separate ID for each orientation.

2. The first system 100 begins to continuously receive (preferably in parallel) the out-of-band signal (e.g., when emerging from the second system 200) and performs cross-correlation with all possible CDMA chip sequences; i.e. all possible IDs are tested.

3. The second system 200 starts to perform the same steps 1 and 2.

4. If the cross-correlation of the first system 100 detects a high positive peak, the OOB transmitter briefly switches to retransmit the corresponding received beacon simultaneously through all transmitters, but with the CDMA sequence reversed. When associated with a CDMA sequence at the receiver, this will produce a negative peak with the same amplitude at the receiver receiving the inverted signal. After a short time, the first system 100 returns to step 1.

5. If the cross-correlation of the first system 100 detects a high negative peak, this means that it is receiving a reply from the second system 200. In accordance therewith, it connects the output of the baseband unit 101 to a high speed signal path (switch 112) for the transmitter corresponding to the detected ID of the inverted chip sequence.

6. The second system 200 performs the same steps 4 and 5 in parallel as the first system 100.

By using the invention in co-pending european patent application EP21163846.5 an alternative mechanism is proposed in which the information of the received beacon can be embedded in the continuously transmitted beacon of step 1:

1. the first system 100 transmits a different CDMA beacon (ID) for each directional beam transmitter in succession.

2. The first system 100 receives the out-of-band signal continuously (in parallel) and performs cross-correlation with all possible CDMA chip sequences (possible IDs) of its communication partners.

3. The second system 200 preferably performs the same steps 1 and 2 simultaneously.

4. The first system 100 performs cross-correlation to detect more than one high positive peak of the same beacon and then it calculates the interval between two consecutive peaks, which should always be N-chips. Then, it:

a. all the different beacons transmitted in step 1 are modified by adding an additional interval to each beacon. The length of the interval will be: increment_detected_id (increment_num_detected_id).

b. The path is connected to a high speed signal on the transmitter corresponding to the ID that was decoded based on the calculated extra space between two consecutive cross-correlation peaks.

5. The second system 200 performs the same step 4 in parallel as the first system 100.

With this approach, the reaction time can be faster because the system is transmitting continuously in the same state, with each transmitter transmitting a different beacon, and the received beacons being encoded back into the extra interval of all beacons.

A further improvement to the system may be to connect more than one high speed transmitter path simultaneously, which may be used to increase throughput by link aggregation or to perform smooth handoff when switching between different beams.

While the above implementations use CDMA as the out-of-band signaling method, other out-of-band signaling methods are contemplated. A simple alternative is the following: wherein the first transceiver system is arranged to have different frequencies f for n wireless optical transmitters facing n orientations _1,1 ..f _1,n Transmits different predetermined output beacons in the form of scattered pilot tones, and wherein the frequency f _1,1 ..f _1,n Outside the frequency band used for the primary transmission.

In the above example, a second transceiver system similar to the first method presented herein above detects the presence of a corresponding sine wave by simple bandpass filtering and pilot tone detection (e.g., using fourier analysis). When pilot tones are detected and the second transceiver system is similar to the examples described herein above, the second transceiver system may temporarily transmit from a different frequency f in addition _2,1 ..f _2,n Selected different sinusoids in a set of (1), where f _2,x For reflecting the signal f _1,x Is received. After a brief interlude of providing feedback on all optical transmitters, the second transceiver system itself may continue to transmit with frequency f _1,1 ..f _1,n For each of its respective wireless transceivers of n wireless optical transmitters facing n orientations.

Similar to the case described herein above, both the first and second transceiver systems may thus each inform the other system which of their transmitters is most suitable and receive feedback from the other system allowing selection of their own transmitter.

In summary, to assist in output beam selection for potential/current communication partners, each of the transceiver systems includes in its respective beacon information uniquely identifying the transmitter, information perceptible to the similar transceiver system, which allows the similar transceiver system to detect the unique identification information and temporarily switch from transmitting its own unique identification transmitter information with the beacon to communicate feedback by transmitting the received unique identification transmitter information with the beacon in a form discernable by the transceiver system, thereby allowing the transceiver system to select the appropriate transceiver system.

Also in this case, it is possible to activate more than one high speed transmitter path simultaneously, which can be used to increase throughput by link aggregation or to perform smooth handoff when switching between different beams.

It will be clear to a person skilled in the art that code, frequency or other uniquely identifying transmitter information should be available at both communication partners and may for example be standardized or set during the commissioning period, using a predefined convention, allowing the communication partners to perform beam selection tasks.

The term "controller" is used generically herein to describe various means for involving the operation of one or more network devices or coordinators, as well as other functions. The controller may be implemented in a variety of ways (e.g., such as with dedicated hardware) to perform the various functions discussed herein. A "processor" is one example of a controller that employs one or more microprocessors that may be programmed with software (e.g., microcode) to perform the various functions discussed herein. A controller may or may not be implemented using a processor, and may also be implemented as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions. Examples of controller components that may be employed in various embodiments of the present disclosure include, but are not limited to: conventional microprocessors, application Specific Integrated Circuits (ASICs), and Field Programmable Gate Arrays (FPGAs).

In various implementations, the processor or controller may be associated with one or more storage media (collectively referred to herein as "memory," e.g., volatile and non-volatile computer memory, such as RAM, PROM, EPROM and EEPROM, compact disks, optical disks, and the like). In some implementations, a storage medium may be used for one or more programs that, when executed on one or more processors and/or controllers, perform at least some of the functions discussed herein. The various storage media may be fixed within the processor or controller or may be removable such that one or more programs stored thereon may be loaded into the processor or controller to implement various aspects of the present invention discussed herein. The term "program" or "computer program" is used herein in a generic sense to refer to any type of computer code (e.g., software or microcode) that can be employed to program one or more processors or controllers.

The term "network" as used herein refers to any interconnection of two or more devices (including controllers or processors) that facilitates the transfer of information (e.g., for device control, data storage, data exchange, etc.) between any two or more devices and/or between multiple devices coupled to the network.

Claims (9)

1. An optical front end OFE for optical wireless communication OWC, the OFE comprising:

-an optical receiver (102) having at least a photo detector facing a detection direction and a transimpedance amplifier TIA for amplifying a signal from the at least one photo detector, and

a two-dimensional array of optical transmitters (103 a) and corresponding drivers, wherein each optical transmitter has a separate transmitter field of view,

the two-dimensional array being arranged to create a combined transmitter field of view that is larger than the individual transmitter fields of view, and wherein the number of optical transmitters along a first direction is larger than the number of optical transmitters along a second direction and the combined transmitter field of view in the first direction is larger than the combined transmitter field of view in the second direction, the first direction being orthogonal to the second direction, the optical transmitters being arranged such that the optical axes of the optical transmitters are evenly distributed within the combined transmitter field of view,

wherein the optical receiver is mounted on a flat substrate with its optical axis aligned with the optical axis of the combined transmitter field of view and the receiver field of view is greater than or equal to the combined transmitter field of view, and

wherein the optical transmitter:

-positioned along a surface curved about a first axis and curved about a second axis, the first axis and the second axis being orthogonal to each other, the first axis being perpendicular to the first direction, the second axis being perpendicular to the second direction;

-positioning with at least one point on a planar surface, each optical transmitter being angled to face a different direction; or alternatively

Positioned on a flat surface and equipped with corresponding optical waveguides for directional outcoupling.

2. The OFE of claim 1, wherein the array of optical transmitters are arranged in a matrix or in a hexagonal configuration in two orthogonal directions.

3. The OFE of claim 1 or 2, wherein the combined transmitter field of view is in a range of 30 degrees to 90 degrees in a first direction and in a range of 10 degrees to 60 degrees in a second direction.

4. An OWC transceiver system for optical wireless communication OWC, for use with a further OWC transceiver system, the OWC transceiver system comprising:

the optical front-end OFE according to any of the preceding claims, wherein the OFE comprises a separate driver for each of the plurality of optical transmitters,

a baseband unit configured to modulate outgoing data for transmission by the OFE and demodulate incoming data from the output of the transimpedance amplifier of the OFE,

-a controller configured to control which of the plurality of optical transmitters is used for transmitting outgoing data based on a result of the alignment operation.

5. An OWC transceiver according to claim 4, wherein the controller is arranged to perform an alignment operation with a further OWC transceiver system, wherein

The controller is configured to:

-generating a unique directional beacon comprising identification information for each of the plurality of optical transmitters;

-controlling each of the plurality of transmitters to transmit their respective directional beacons;

-receiving in the output of the TIA feedback from the communication partner transmitted by the communication partner regarding detection of a unique property of the optical transmitter of the OWC transceiver system in the beacon from the OWC transceiver system; and

-based on the feedback, selecting an appropriate subset from the plurality of optical transmitters for transmitting outgoing data to a further OWC transceiver system.

6. The OWC transceiver of claim 5, wherein:

the directional beacon is a low frequency, CDMA beacon transmitted out-of-band from the output data, allowing the optical transmitter to transmit the directional beacon and the output data simultaneously; and

-wherein the detection feedback from the communication partners is a beacon transmitted by the communication partners, the beacon having an inverted version of the CDMA sequence transmitted with a corresponding one of the optical transmitters received by the communication partners.

7. A vehicle arranged for optical communication, the vehicle comprising:

-a vehicle-mounted network,

-a first OWC transceiver comprising a forward OFE as claimed in claim 1, the optical axis of which is facing the forward direction of movement of the vehicle, wherein the on-board network is connected to the first OWC transceiver.

8. The vehicle of claim 7, the vehicle further comprising:

-a second OWC transceiver comprising a backward OFE as claimed in claim 1, the optical axis of the backward OFE facing opposite to the forward direction of movement of the vehicle, wherein the on-board network is connected to the second OWC transceiver.

9. The vehicle of claim 7 or 8, wherein the vehicle is one of a car, bus, train, boat, or truck.