JP3823851B2 - Optical wireless communication system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical wireless communication system that performs half-duplex optical wireless communication between an optical wireless hub and an optical wireless node, and more particularly to optical axis adjustment of an optical wireless node with respect to the optical wireless hub.
[0002]
[Prior art]
In general, an optical wireless node (optical wireless communication terminal) connected to an information terminal (including a switching hub) such as a PC or WS performs optical axis alignment with an optical wireless hub (optical wireless collection and distribution device) attached to the ceiling. In order to perform accurately, automatic optical axis alignment using servo is performed on pilot light transmitted from an optical wireless hub as shown in FIG.
[0003]
10 and 11 show the configuration of a conventional optical wireless node and its optical axis adjustment processing, respectively. The optical wireless node 10a includes a reception unit 11, a communication data processing unit 12, an optical communication procedure processing unit 13, an optical transmission unit 14, an optical reception unit 15, a transmission unit 16, a pilot light extraction unit 17b, an optical axis alignment control unit 18a, and a servo. Means 19 are provided. Here, the optical receiving means 15 (and the optical transmitting means 14) rotate in the range of horizontal (pan) angle = 0 to 360 degrees, tilt (tilt) angle = vertical direction (0 degrees) to 70 degrees, and optical wireless. The pilot light of the hub 20 (see FIG. 1) is searched for, and the optical axis is adjusted to an accuracy of 5 degrees or less. In order to adjust from such a wide range to a narrow optical axis, first, “coarse adjustment” for checking the presence or absence of pilot light is performed (steps S1 to S4), and then the strongest of the pilot light from the rough range where the pilot light exists “Fine adjustment” to match the direction is performed (steps S5 and S6).
[0004]
In the “coarse adjustment” stage, as shown in FIG. 12, in order to quickly operate the entire service range of the optical wireless node 10a, the direction of the light receiving means 15 is changed at every constant rough angle to receive the light intensity of the pilot light. Observe. Here, the pilot light emitted from the optical wireless hub 20 blinks at a constant frequency that is larger than the frequency of the optical wireless communication so as not to interfere with the original optical wireless communication. When the optical wireless node 10a confirms the pilot light exceeding the threshold at the “coarse adjustment” stage, the optical wireless node 10a proceeds to the “fine adjustment” stage. The optical receiver 15 of the optical wireless node 10a is composed of PDs divided into 2 × 2 cells so that the reception intensity of the 2 × 2 cells is equal, that is, the pilot light is 2 × 2 cells. Orient the center. Furthermore, the optical wireless link is established by correcting the direction by an arbitrary amount from the direction of the pilot light to a communicable direction and further performing test communication (steps S7 and S8).
[0005]
[Problems to be solved by the invention]
However, in the optical axis alignment method using the pilot light, the optical axis alignment in the direction of the pilot light does not succeed due to disturbance light that is difficult to distinguish from the pilot light, and it is not possible to shift to actual communication. There is a point. That is, an inverter type fluorescent lamp is also installed on the ceiling where the optical wireless hub 20 that emits pilot light is installed. When the blinking frequency of the inverter type fluorescent lamp is close to the pilot light, the optical axis in the direction of the pilot light. Matching will never succeed. Furthermore, since the blinking frequency of the inverter type fluorescent lamp differs depending on the manufacturer, it is difficult to determine the blinking frequency of pilot light that can be used in all cases and to design the pilot light extraction means 17b.
[0006]
The present invention provides an optical wireless communication system that can perform optical axis alignment surely and quickly even in an environment with disturbance light close to the blinking frequency of pilot light, in view of the problems of the conventional example. With the goal.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention selects coarse adjustment or fine adjustment according to the reception state of the optical communication signal and pilot light from the optical wireless hub, and performs the optical axis adjustment processing with the selected adjustment accuracy. It is what I did.
That is, according to the present invention, meet the row earthenware pots optical wireless communication system half-duplex optical wireless communications between the optical wireless hub and the pan direction and the tilt direction to be rotatable at a predetermined angle unit light wireless nodes,
The optical wireless hub is:
Optical transmission means for transmitting an optical communication signal and pilot light to the optical wireless node;
The optical wireless node is:
Said optical communication signal and the pilot light sent from the optical wireless hub to receive a reception detecting means for detecting the reception duration of the optical communication signal and detects the reception intensity of the pilot beam,
Coarse adjustment processing means for executing optical axis coarse adjustment processing of the optical wireless node in units of relatively coarse angles with respect to the received spot light of the pilot light;
Fine adjustment processing means for performing optical axis fine adjustment processing of the optical wireless node in a relatively narrow angle unit with respect to the center within the range of the spot light,
In the reception detection means, when the optical communication signal is not detected and the reception intensity of the pilot light is a predetermined threshold value or less, the coarse adjustment processing means is selected, while the optical communication signal is not detected, And when the reception intensity of the pilot light is larger than the threshold, or when the optical communication signal is detected and the reception duration is less than a predetermined time, the fine adjustment processing means is selected, and this Optical axis adjustment control means for executing optical axis adjustment processing by the selected means,
An optical wireless communication system is provided.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing an optical wireless hub of an embodiment of the optical wireless communication system according to the present invention, FIG. 2 is a block diagram showing an optical wireless node of an embodiment of the optical wireless communication system according to the present invention, and FIG. 2 is a block diagram showing in detail the communication light determining means in FIG. 2, FIG. 4 is an explanatory diagram showing communication signals and their determination processing in the communication light determining means in FIG. 3, and FIG. 5 is an optical axis alignment determining / controlling means in FIG. FIG. 6 is a flowchart for explaining in detail the optical axis alignment determination process of FIG. 5.
[0009]
The optical wireless hub 20 shown in FIG. 1 includes an optical receiver 21, a communication data processor 22, an optical communication procedure processor 23, a transmitter 24, a receiver 25, an optical transmitter 26, a pilot light generator 27, and a pilot optical transmitter. Means 28 are provided. The optical receiving means 21 includes a light receiving element such as a PD (photo detector) that receives an optical wireless signal transmitted from the optical wireless node 10 shown in FIG. 2, and a photoelectric element that converts the optical signal received by the light receiving element into an electrical signal. And a conversion unit.
[0010]
The communication data processing means 22 extracts the communication data from the optical wireless node 10 and transfers it in an appropriate direction of the optical space direction or the trunk line direction. The optical communication procedure processing means 23 extracts a communication signal from the optical wireless node 10 from the optical signal received by the optical receiving means 21, and performs control for optical wireless communication. The transmission unit 24 outputs a signal (communication data or a collision notification signal) to be transmitted to the main line or the like, and the reception unit 25 is connected to the main line or the like and receives the communication data. The optical transmission means 26 converts a communication signal (optical communication procedure signal or communication data) to be transmitted to the optical space into an optical signal, and transmits the optical signal to the optical wireless node 10 by a light emitting means such as a light emitting diode. The pilot light generating means 27 and the pilot light transmitting means 28 generate pilot light for the optical wireless node 10 to be connected to the optical wireless hub 20 by optical communication to perform optical axis alignment, and radiate it into space. .
[0011]
2 includes a receiving unit 11, a communication data processing unit 12, an optical communication procedure processing unit 13, an optical transmitting unit 14, an optical receiving unit 15, a transmitting unit 16, a communication light determining unit 17a, and a pilot light extracting unit. Means 17b, optical axis alignment determination / control means 18, and servo means 19 are provided.
[0012]
The receiving means 11 has an interface function for receiving data transmitted from an external device (not shown) such as a personal computer or a (PC) workstation (WS) connected to the optical wireless node 10. The communication data processing means 12 performs procedural processing to transmit the data received by the receiving means 11 to the optical wireless hub 20 shown in FIG. The optical communication procedure processing means 13 performs a procedure process for performing an optical wireless communication procedure with the optical wireless hub 20.
[0013]
The optical transmission unit 14 is responsive to the communication signal for performing the optical communication procedure generated by the optical communication procedure processing unit 13 and the communication data to be transmitted to the optical wireless hub 20 processed by the communication data processing unit 12. The light emitting element is caused to emit light and converted into an optical signal, which is transmitted to the optical wireless hub 20. The optical receiving means 15 receives an optical signal transmitted from the optical wireless hub 20 by a light receiving element such as a PD (photo detector), photoelectrically converts it, and outputs it. Here, the optical transmission unit 14 and the optical reception unit 15 are configured to be able to pan and tilt in order to align the optical axis with the optical wireless hub 20. The transmission unit 16 transmits the communication data from the optical wireless hub 20 output from the optical reception unit 15 and processed by the communication data processing unit 12 to an external device such as a PC or WS connected to the own device.
[0014]
The pilot light extracting means 17b extracts the pilot light of the optical wireless hub 20 from the optical reception signal output from the optical receiving means 15, and the communication light determining means 17a is shown in detail in FIGS. The communication light of the optical wireless hub 20 is determined from the optical reception signal output by The optical axis alignment determination / control means 18 is between the pilot light extracted by the pilot light extraction means 17b, the communication light detection signal determined by the communication light determination means 17a, and the communication control block (12, 13). The optical axis alignment with the optical wireless hub 20 is controlled using the test communication request / result signal to be input / output. The servo unit 19 converts the pan / tilt servo mechanism control signal output from the optical axis alignment determination / control unit 18 into power, and changes the orientation of the optical transmission unit 14 and the optical reception unit 15.
[0015]
A network forming a star topology is formed between the plurality of optical wireless nodes 10 having the above-described configuration and the optical wireless hub 20, and communication is performed between the optical wireless nodes 10 via the optical wireless hub 20, Communication is performed between the trunk line and the optical wireless node 10.
[0016]
The communication light determination unit 17a will be described in detail with reference to FIGS. The optical reception signal output from the optical reception means 15 is detected by the detection circuit 101 and then integrated by the integration circuit 102. The output of the integration circuit 102 is binarized by the comparator 103 according to the reference value voltage, and the output of the comparator 103 is sent to the determination circuit 104 to determine the presence or absence of communication light. FIG. 4 shows the output of the comparator 103, and FIG. 4 (a) shows the case of no communication light (no signal). FIG. 4B shows a case where communication light is detected with an insufficient length (unstable), and FIG. 4C shows a case where communication light is detected with a sufficient length (stable). Show.
[0017]
The determination result of the determination circuit 104 is sent to the optical axis alignment determination / control unit 18 shown in FIG. 2, and the optical axis alignment determination / control unit 18 as shown in FIG. 5 and FIG. Based on the above, the optical axis alignment is determined and controlled. As the communication light at this time, data of optical wireless communication and an optical link signal for synchronizing the optical wireless node 10 are used.
[0018]
In FIG. 5, first, the position information of the servo means 19 is initialized at the time of activation or the like (step S11), and in the subsequent step S12, the optical axis alignment determination detailed in FIG. 6 is performed. In FIG. 6, first, the determination result of the determination circuit 104 is checked (step S21), and in the case of “no signal” as shown in FIG. 4A, it is checked whether or not the received light intensity of the pilot light> the threshold value. (Step S22). If the received light intensity is not greater than the threshold value, the process proceeds to step S23 to check whether or not the rough adjustment is completed. If completed, it is determined that the optical axis alignment has failed (step S24), and then the process returns to step S11. On the other hand, if coarse adjustment is not completed in step S23, the process proceeds to coarse adjustment servo processing (step S13).
[0019]
If "unstable" as shown in FIG. 4B in step S21 and if the received light intensity> threshold value in step S22, the process proceeds to step S25 to check whether fine adjustment is completed and complete. If so, it is determined that the optical axis alignment has failed (step S24), and then the process returns to step S11. On the other hand, if fine adjustment is not completed in step S25, the process proceeds to fine adjustment servo processing (step S14). If “stable” as shown in FIG. 4C in step S21, test transmission is performed (step S26), and then it is checked whether the test transmission is successful (step S27). If not successful, the process proceeds to step S25. If successful, on the other hand, the optical axis alignment is completed and a wireless link is established (step S28).
[0020]
Next, “rough adjustment servo processing” will be described. The coarse adjustment servo process is a process of scanning at high speed so as to roughly know the presence and direction of the optical wireless hub from the entire service range of the optical wireless node 10. For this reason, in the coarse adjustment servo process, the direction is changed at each roughly constant angle as shown in FIG. In the initial state of coarse adjustment, control is performed to return the direction to a specific direction (origin direction).
[0021]
Next, “fine servo processing” will be described. The fine adjustment servo processing is performed to accurately align the optical axis after the direction of the optical wireless hub 10 can be determined to some extent. For this reason, the direction of fine servo control is changed by a fine angle as shown in FIG. Further, it is determined every time whether the optical axis is aligned with the optical axis center of the pilot light, and when the optical axis alignment is successful, the direction is adjusted so that further communication is possible from there. This correction is a control for correcting that the directions of the pilot light transmitting means (pilot light source) 28 of the optical wireless hub 20 and the optical transmitting means 26 and the optical receiving means 21 are shifted. The value varies depending on the shape, the distance between the optical wireless node 20 and the optical wireless hub 10, and the inclination of the optical wireless node 20. This correction amount is used as a value that has been clarified in advance through experiments or the like.
[0022]
Next, “test communication” will be described. The optical wireless node 10 generates a test packet after confirming that the optical transmission line is free (in a state where transmission is possible), and optically transmits the test packet to the optical wireless hub 20. Here, the test packet is a packet unique to the present system that is effective only in the optical wireless space. When the optical wireless hub 20 or all the optical wireless nodes 10 receive the packet, the packet can be recognized as a test packet. Assume that the optical wireless devices 10 and 20 having the structure are processed by the optical wireless communication procedure processing means 13 and 23 so as not to flow this packet to the trunk network or PC.
[0023]
In addition, a unique value is assigned to each test packet so that the transmitted optical wireless node 10 can be identified as a test packet sent by itself. When the optical wireless hub 20 receives the test packet, it returns the optical packet to the optical wireless transmission path as it is (referred to as a response). When receiving the response, the optical wireless node 10 determines whether or not the own device can communicate with the optical wireless hub 20 by checking the contents of the packet when the test packet is transmitted immediately before. The optical wireless node 10 that has not transmitted (irrelevant) immediately before may discard this when it is determined as a test packet. If the collation results match, it can be determined that optical communication is possible (link establishment). However, if the collation results do not match or there is no response from the optical wireless hub, it is necessary to perform optical axis alignment again.
[0024]
In the optical wireless hub 20 of the above embodiment, as shown in FIG. 1, an optical transmission means 26 and a pilot optical transmission means 28 for transmitting actual optical communication data are separately provided. Instead, as shown in FIG. Alternatively, the pilot light may be transmitted by the optical transmission means 26. In this case, the pilot light is time-division multiplexed and transmitted at the time when the actual optical communication data is transmitted, and the blinking frequency of each signal is made different. In the optical wireless node 10 of the above embodiment, as shown in FIG. 2, the optical receiving means 15 is also used to receive actual optical communication data and pilot light, but instead, as shown in FIG. The pilot light receiving unit 17 c may be provided separately from the light receiving unit 15.
[0025]
【The invention's effect】
According to the present invention, during execution of optical axis alignment, it is possible to know this if it is possible to communicate even if it happens, and the optical axis alignment can be completed, so that waste of optical axis alignment time is saved. be able to. In addition, since optical wireless communication can be tested to check the communication status, the optical axis can be reliably aligned, and the optical axis can be aligned with communication light even in environments with disturbance light that is difficult to distinguish from pilot light. It is possible to know whether it is facing the power direction or whether communication is already possible, and there is an effect that more reliable optical axis alignment can be executed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an optical wireless hub of an embodiment of an optical wireless communication system according to the present invention.
FIG. 2 is a block diagram showing an optical wireless node of an embodiment of an optical wireless communication system according to the present invention.
FIG. 3 is a block diagram showing in detail a communication light determination unit in FIG. 2;
4 is an explanatory diagram showing a communication signal and its determination processing in the communication light determination means of FIG. 3. FIG.
5 is a flowchart for explaining processing of an optical axis alignment determination / control unit in FIG. 2;
6 is a flowchart for explaining in detail the optical axis alignment determination processing of FIG. 5;
7 is a block diagram showing a modification of the optical wireless hub in FIG. 1. FIG.
8 is a block diagram showing a modification of the optical wireless node in FIG. 1. FIG.
FIG. 9 is an explanatory diagram showing pilot light and its light reception level.
FIG. 10 is a block diagram showing a conventional optical wireless node.
FIG. 11 is a flowchart for explaining optical axis alignment processing of a conventional optical wireless node.
FIG. 12 is an explanatory diagram showing coarse adjustment processing and fine adjustment processing;
[Explanation of symbols]
10 optical wireless node 15 optical receiving means 17a communication light determining means 17b pilot light extracting means 18 optical axis alignment determining / controlling means 19 servo means 20 optical wireless hub 27 pilot light generating means 28 pilot light transmitting means

Claims (2)

Met row earthenware pots optical wireless communication system half-duplex optical wireless communications between the optical wireless hub and the pan direction and the tilt direction to be rotatable at a predetermined angle unit light wireless nodes,
The optical wireless hub is:
Optical transmission means for transmitting an optical communication signal and pilot light to the optical wireless node;
The optical wireless node is:
Said optical communication signal and the pilot light sent from the optical wireless hub to receive a reception detecting means for detecting the reception duration of the optical communication signal and detects the reception intensity of the pilot beam,
Coarse adjustment processing means for executing optical axis coarse adjustment processing of the optical wireless node in units of relatively coarse angles with respect to the received spot light of the pilot light;
Fine adjustment processing means for performing optical axis fine adjustment processing of the optical wireless node in a relatively narrow angle unit with respect to the center within the range of the spot light,
In the reception detection means, when the optical communication signal is not detected and the reception intensity of the pilot light is a predetermined threshold value or less, the coarse adjustment processing means is selected, while the optical communication signal is not detected, And when the reception intensity of the pilot light is larger than the threshold, or when the optical communication signal is detected and the reception duration is less than a predetermined time, the fine adjustment processing means is selected, and this Optical axis adjustment control means for executing optical axis adjustment processing by the selected means,
Optical wireless communication system that Yusuke. The optical wireless node is:
When an optical test signal including an identifier is transmitted to the optical wireless hub, a response signal is received from the optical wireless hub with respect to the optical test signal, and the identifier included in the response signal is an identifier of the optical wireless node In addition, it has a test means for executing an optical axis confirmation process for determining that the optical axis of the optical communication signal has been adjusted to a state capable of optical wireless communication,
The optical wireless hub is:
A response signal sending means for sending the received optical test signal as the response signal when the optical test signal transmitted from the optical wireless node is received;
The optical axis adjustment control unit of the optical wireless node selects the test unit when the optical communication signal is detected by the reception detection unit and the reception duration has passed a predetermined time. The optical wireless communication system according to claim 1, wherein the optical axis confirmation process is performed .

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