JP2004032475A - Half duplex optical communication slave unit device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the communication performance of a system by reducing the number of times of suppressing by efficiently suppressing to a terminal in an optical communication system. <P>SOLUTION: If there is a data transmission from a terminal when a temporary storage means for temporarily storing is fully occupied until transmission data from the terminal 4 is transmitted to a master unit 1, a slave unit 3 suppresses the data transmission of the terminal by a continued suppressing signal during a period until the temporary storage means becomes free. If the slave unit is occupied in the temporary storage means, the data transmission of the terminal is suppressed by the continued suppressing signal irrespective of the presence or absence of the data transmission from the terminal. When the data optically transmitted by itself is returned to the other slave unit by the master unit or the data transmission exists from the terminal, the data transmission of the terminal is suppressed by the continued suppressing signal irrespective of the presence or absence of the data transmission from the terminal. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a half-duplex optical communication slave device in a system for performing half-duplex optical communication between a plurality of half-duplex optical communication slave devices to which terminals are individually connected and one half-duplex optical communication master device. About.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, when a LAN (Local Area Network) is constructed by mutually connecting a plurality of information processing devices such as personal computers, the information processing devices are often connected by a wire such as a coaxial cable or an optical cable. . Wired connection is advantageous in that there are few data errors due to external noise because the equipment can be securely connected, but the wiring work is complicated and requires work for each layout change. There is.
[0003]
In recent years, there has been an increasing demand for data transmission by interconnecting personal computers such as laptops, books and palmtops and portable information processing devices such as electronic notebooks. On the other hand, these portable information processing devices are originally intended to be moved and used, and it is extremely rare that the portable information processing device is moved while being wired. Therefore, when data transmission is performed by connecting these portable information processing devices to each other, a connector must be connected and disconnected every time the portable information processing device is moved, and such connection work is very troublesome. In addition, if the connector is repeatedly inserted and removed, there is a possibility that mechanical damage to a connection portion such as the connector may occur. For these reasons, when transmitting and receiving data between various types of information processing equipment, not limited to the stationary type and the portable type, there is a demand to reduce the number of wired connections by making all or part of the transmission path wireless. There is.
[0004]
Here, as a method of wireless transmission, there are a method using radio waves as a transmission medium and a method using light as a transmission medium. High-speed data transmission can be achieved using any of these radio wave and optical transmission media.However, in the case of radio waves, there are no legal restrictions due to legal restrictions and issues of confidentiality. It is advantageous to use wireless transmission using light that easily ensures the transmission property as a transmission medium. Also, since Ethernet (registered trademark) LAN, which is the most widely used wired LAN, has a transmission speed of, for example, 10 Mbps, it is desirable that the transmission speed of the wireless transmission path be at least 10 Mbps.
[0005]
For this reason, the present applicant discloses in Japanese Patent Application Laid-Open No. 8-56198 "a method and an apparatus for canceling the return light of optical wireless communication" which realizes a transmission speed of 10 Mbps by using light as a transmission medium. . The technology described in this publication realizes full-duplex communication by optical wireless between a base unit mounted on a ceiling and a slave unit installed in a room. A method is adopted in which a signal can be subtracted to remove an adverse effect due to reflected light. That is, in optical wireless transmission, light is transmitted to free space and light from free space is received.For example, the transmission signal light transmitted by itself is transmitted by an object located near the other device. There is a problem in that the signal is reflected and input to the light receiving unit, and a communication signal from the other party cannot be accurately taken out. However, in the technology described in the publication, a part of the transmission signal is branched, By adjusting the level and phase of this signal and adding it to the received signal, the signal due to the return light is canceled.
[0006]
On the other hand, in recent years, higher transmission speeds have been desired, and further higher transmission speeds have been demanded in the optical wireless communication system as described above. However, considering optical wireless communication having a transmission speed of, for example, 100 Mbps, the signal becomes a 125 Mbps transmission signal due to the necessity of 4B / 5B conversion or the like. When this signal is considered in terms of phase, the 1-bit length is 8 ns. The time for the light to travel 1 m is 3.3 ns. From this, if the reflection path is different by 1 m (a difference of 50 cm in distance to the reflection object), 360 * 3.3 / 8 = 148.5 degrees is also different. In other words, in order to cancel the reflected light whose phase is greatly shifted by the distance to such a reflection object, it is necessary to adjust not only the amplitude but also the phase that changes greatly, so that an extremely complicated circuit is required. It becomes. Further, even if these methods are used, the cancellation can only be improved within a limited range. Therefore, it is advisable to use a half-duplex communication system instead of a full-duplex communication system to realize a 1: N optical wireless communication device with high-speed transmission such as 100 Mbps.
[0007]
From these facts, the present applicant has realized “optical wireless communication device and optical wireless communication system” that realizes 100 Mbps transmission in JP-A-2002-51053. In this method, as shown in FIG. 1, the base unit 1 notifies the subordinate units 3 (3a, 3b, 3c) of the use status of the optical line as an optical line availability notification signal, and the sub unit 3 detects this signal. The child device 3 performs a transmission permission application process (such as ID exchange) with the parent device 1 every time a frame is transmitted, and after obtaining the transmission permission from the parent device 1, the child device 3 transmits to the parent device 1. Is started, that is, the problem of reflected light described above is avoided by so-called half-duplex communication.
[0008]
That is, as shown in FIG. 2, when the optical line is vacant, the master unit 1 sends an optical line idle notification signal EP (IDLE burst) for notifying the slave unit 3 under its control to the plurality of slave units 3. Send to. For example, the slave 3a to which the terminal 4a is connected detects the broadcast signal sent from the master 1 using a carrier sense circuit, and if there is a frame F1 sent from the terminal 4a, After receiving the line vacancy signal EP, the transmission request signal RQ is transmitted to the base unit 1, and the frame F1 received from the terminal 4a after receiving the permission signal AK from the base unit 1 is transmitted to the base unit 1. Send. Further, upon receiving the frame F2 from the trunk 2, the master 1 stops transmitting the optical line empty notification signal EP to the slave 3, and optically transmits the frame F2 received from the trunk 2 to the slave 3.
[0009]
Similarly, when the frame F1 is transmitted from the slave 3a to the slave 3b in the same wireless zone as shown in FIG. 3, when the master 1 finishes receiving the frame F1 sent from the slave 3a, The frame F1 is transmitted back to the optical line side.
[0010]
Further, in the conventional example, as shown in FIGS. 4 and 5, the slave unit 3a transmits the frame F1 from the terminal 4a to the optical line or receives the return frame F1 from the terminal 4a. When the frame F2 is transmitted, a suppression signal (DMY signal) for suppressing reception of transmission data is transmitted to the terminal 4a, the transmission of the terminal 4a is suppressed, and transmission stop and retransmission processing to the terminal 4a are performed. Prompt to enter. By such a method, a 1: N (master unit: slave unit) optical half-duplex communication system is realized.
[0011]
[Problems to be solved by the invention]
However, such a method requires a half-duplex transmission process (transmission application, transmission permission) exchanged when the slave 3 transmits a frame to the master 1, an optical preamble for synchronizing reception, and the like. However, there is an overhead in communication, and it is important how the communication performance is exhibited. Further, in such a system, as described above (FIGS. 4 and 5), when the slave 3a cannot receive the next frame F2 sent from the terminal 4a (cannot perform optical transmission), the terminal 4a is suppressed. Then, the terminal 4a is prompted to retransmit the data. Of course, if the slave unit 3 can be equipped with a sufficient temporary storage device (memory), the occurrence of such a case can be reduced. However, considering the circuit scale (space and power consumption) and cost, how small the capacity is It is important to realize this with a memory. Therefore, if the system is realized with the minimum necessary memory, the case where the above-mentioned slave unit 3 suppresses the terminal 4 increases in many cases, which adversely affects the communication performance.
[0012]
This is because, considering Ethernet (R) as a typical example to which the present system is applied, the control of the collision retransmission time greatly increases the time until the next retransmission if the number of collisions is overlapped. It can be imagined that it is better to avoid the occurrence of many collisions at once in terms of communication performance. Further, according to the standard of the Ethernet (R), the number of consecutive collisions is limited to 16 times, and when there is more collision, the frame disappears, and a higher layer (application level) on the network protocol. In such a situation, a significant loss of performance occurs.
[0013]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a half-duplex optical communication device capable of efficiently suppressing a terminal, reducing the number of times of suppression, and improving the communication performance of the system.
[0014]
[Means for Solving the Problems]
To achieve the above object, the present invention suppresses data transmission of a terminal by a continuous suppression signal (signal for suppressing reception of transmission data).
[0015]
That is, according to the present invention, a terminal for exchanging data is connected, and a half-duplex optical communication slave device that transmits and receives the data to and from the half-duplex optical communication master device by half-duplex optical communication. hand,
Temporary storage means for receiving transmission data for transmission to the half-duplex optical communication master device from the terminal and temporarily storing the transmission data,
When there is no free area for storing the transmission data in the temporary storage means, reception of transmission data from the terminal is continued until a free area for storing the transmission data is secured in the temporary storage means. Suppression means,
A half-duplex optical communication device is provided.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of a main part of an optical wireless communication system including a handset 3 which is an optical wireless communication handset device according to an embodiment of the present invention. The optical wireless system according to the present embodiment is a system connected to a trunk network (simply called trunk) 2 such as Ethernet (registered trademark) (Ethernet (R)) for transmitting and receiving data by frame (packet) transmission. As shown in FIG. 1, an optical wireless communication device 1 (hereinafter, referred to as a parent device 1) as a parent device and a child are connected between a main line 2 and a terminal (for example, a personal computer) 4 (4a, 4b, 4c). The connection is made using half-duplex optical communication by an optical wireless communication device 3 (3a, 3b, 3c) (hereinafter referred to as a slave device 3) as a device. The terminal 4 includes a relay device such as a network interface card (NIC) or a hub (HUB), in addition to a personal computer or the like.
[0017]
FIG. 2 shows the basic communication timing between the base unit 1 connected to the trunk line 2 as shown in FIG. 1 and the slave unit 3a connected to the terminal 4a. In this figure, basic timing for transmitting frame F1 generated by terminal 4a from slave unit 3a to master unit 1 and for sending frame F2 sent from trunk line 2 to master unit 1 to slave unit 3a Is shown. First, in this figure, the master unit 1 transmits an optical line idle signal EP for notifying that the optical line is idle to all the slave units 3 (line idle section indicated by (1) in the figure). All the slaves 3 detect the optical line idle signal from the master 1.
[0018]
For example, when the slave 3a receives the frame F1 sent from the terminal 4a at the timing of T2, when the reception of the optical line free signal EP from the master 1 detected at T1 ends, the slave 3a As in the middle T3, an optical preamble (optical P) is added to the optical line transmission application signal RQ requesting the use of the optical line, and optical transmission is performed. The master unit 1 that has received the optical line transmission application signal RQ transmits an optical line for permitting use of the optical line to the slave unit 3a as indicated by T4 in the figure when the optical line is available. The optical transmission is performed by adding the optical preamble (optical P) to the permission signal AK, and waits for the transmission of the frame F1 from the slave unit 3a.
[0019]
When receiving the optical line transmission permission signal AK from the base unit 1, the slave unit 3a adds an optical preamble (light P) to the frame F1 received from the terminal 4a as indicated by T5 in FIG. To transmit light. At this time, the frame F1 from the terminal 4a is temporarily secured in a storage device such as a FIFO by the slave unit 3a, and is delayed until the transmission application processing is completed. Master device 1 that has received frame F1 from slave device 3a transmits the frame F1 to trunk line 2 (section indicated by (2) in the figure).
[0020]
Next, the master unit 1 that has received the frame F2 from the trunk line 2 at the timing of T9 adds the optical preamble and transmits the frame F2 to the slave unit 3a at the timing of T10. The slave 3a that has received the frame F2 transmits the frame F2 to the terminal 4a at the timing of T11 (section indicated by (3) in the figure).
[0021]
Further, for simplicity of description, here, base unit 1 transmits frame F1 to trunk line 2 (T7) and base unit 1 transmits frame F2 to terminal 4a (T11). -The case where there is no collision between the trunk line 2 and between the slave unit 3a and the terminal 4a is described. However, when a collision occurs, the master unit 1 and the slave unit 3a perform retransmission processing (retransmission processing function is performed). Otherwise, frame loss occurs at the physical layer level.) That is, both the master unit 1 and the slave unit 3 are provided with a storage device for that purpose, and the retransmission capability (possible number of times) depends on the capacity of the storage device.
[0022]
Further, when the slave unit 3a receives the frame F1 from the terminal 4a and the transmission request is not accepted (cannot be made) to the master unit 1, the suppression signal is transmitted to the terminal 4a to stop the transmission from the terminal 4a. This is a case where the slave unit 3 does not have a sufficient storage device for storing the frame from the terminal 4. If the slave unit 3 has a sufficient storage device, the capacity of the storage device is reduced. Needless to say, it is not necessary to suppress the terminal 4 as long as it is allowed.
[0023]
In this system, one master unit 1 also has a role of relaying communication between a plurality of slave units 3, and in such a case, a frame transmitted from a certain slave unit 3 Is transmitted to the optical line side. This will be described with reference to FIG. FIG. 3 shows a basic case in which a frame F1 generated by terminal 4a is transmitted from slave unit 3a to master unit 1, and master unit 1 transmits the frame F1 by returning it to trunk line 2 and slave unit 3b on the optical line side. This shows the target timing.
[0024]
First, in this figure, the base unit 1 transmits an optical line empty signal EP indicating that the optical line is free to all the slave units 3 (section indicated by (1) in the figure). All the slaves 3 detect an optical line free signal from the master. The slave 3a receives the frame F1 sent from the terminal 4a at the timing of T2, and when the reception of the optical line free signal EP from the master 1 detected at Tl ends, the slave 3a transmits the frame T3 to the master 1 in FIG. As described above, an optical preamble (optical P) is added to an optical line transmission application signal RQ requesting the use of an optical line, and optical transmission is performed. The master unit 1 that has received the optical line transmission application signal RQ transmits an optical line for permitting use of the optical line to the slave unit 3a as indicated by T4 in the figure when the optical line is available. The optical transmission is performed by adding the optical preamble (optical P) to the permission signal AK, and waits for the transmission of the frame F1 from the slave unit 3a.
[0025]
When receiving the optical line transmission permission signal AK from the base unit 1, the slave unit 3a adds an optical preamble (light P) to the frame F1 received from the terminal 4a as indicated by T5 in FIG. To transmit light. At this time, the frame F1 from the terminal 4a is temporarily secured in a storage device such as a FIFO by the slave unit 3a, and is delayed until the transmission application process can be followed. Master device 1 that has received frame F1 from slave device 3a transmits the frame F1 to trunk line 2 (section indicated by (2) in the figure).
[0026]
When transmitting the frame F1 to the trunk line 2, when the base unit 1 determines from the address information of the frame F1 that the frame F1 needs to be transmitted also to the optical line side, the base unit 1 After the reception of the frame F1 from the device 3a, the frame F1 is looped back at the timing of T8 and transmitted to the optical line side (of course, the master device 1 needs a memory for performing the looping transmission). . The frame F1 transmitted back by the master unit 1 is received by the slave units 3a and 3b under its control. At this time, the slave unit 3a discards the frame F1, and the slave unit 3b transmits the frame F1 to the terminal 4b at the timing of T9 (section indicated by (3) in the figure).
[0027]
In the present system, communication between the slave unit 3 and the master unit 1 and between the slave unit 3 using the master unit 1 as a relay unit are realized by the basic procedure as described above. , A procedure such as an application for transmission to the base unit 1 is required, so that a large delay occurs before the handset 3 transmits a frame to the base unit 1. For this reason, if there is not enough room in the temporary storage device of the child device 3, a case may occur in which the next frame from the terminal 4 cannot be received, and the child device 3 suppresses the terminal 4 side and transmits the signal from the terminal 4. Need to be controlled in a timely manner. Further, since this system requires half-duplex communication, the terminal 4 cannot transmit the next frame when the base unit 1 loops back the frame from the slave unit 3 and transmits the frame to the optical line. Therefore, the slave unit 3 has to suppress the terminal 4 until the line is free.
[0028]
The above will be described with reference to FIGS. FIG. 4 shows the procedure for the line free signal EP, transmission application RQ, and transmission permission AK indicated by T1 to T4 between the slave unit 3a and the master unit 1 for the frame F1 generated by the terminal 4a. 5 shows the suppression timing from the slave unit 3a to the terminal 4a when the terminal 4a transmits the next frame F2 when the frame F1 is transmitted to the master unit 1 at the timing of T6. As shown in this figure, when the slave 3a is optically transmitting the frame F1 from the terminal 4a at the timing of T6 and the next frame F2-1 is transmitted from the terminal 4a, the slave 3a is set at the timing of T8. Transmits the suppression signal DMY to the terminal side.
[0029]
As a result, the terminal 4a stops the transmission of the frame F2-1 being transmitted, and retransmits the frame again as the frame F2-2 with a certain time interval Tf-gap1. In this figure, even when this retransmission frame F2-2 is transmitted from the terminal 4a, since the child device 3a has not yet optically transmitted the previous frame F1, the child device 3a again transmits the suppression signal at the timing of T9. DMY is transmitted to the terminal 4a side to urge the terminal 4a to retransmit.
[0030]
The terminal 4a urged to retransmit by the slave 3a transmits a frame again as a frame F2-3 at a certain time interval Tf-gap2. Here, at the same time that the slave 3a has finished transmitting the previous frame F1, the line free signal EP from the master 1 can be confirmed, and the frame F2-3 is transmitted from the slave 3a to the master 1 at the same time. It will be transmitted to the optical line following the procedure.
[0031]
On the other hand, FIG. 5 shows the procedure of the line free signal EP, transmission application RQ, and transmission permission AK indicated by T1 to T4 between the child device 3a and the parent device 1 for the frame F1 generated by the terminal 4a. When the frame F1 is transmitted from the device 3a to the master device 1 at the timing of T6, and the frame F1 is transmitted back to the optical line at the timing of T8 by the master device 1, the next frame F2 is transmitted from the terminal 4a. 4 shows the suppression timing from the slave unit 3a to the terminal 4a in the case where it comes. As shown in the figure, when the next frame F2-1 is transmitted from the terminal 4a while the frame F1 transmitted by the child device 3a is being transmitted back by the parent device 1, the child device 3a starts the terminal at the timing of T8. The suppression signal DMY is transmitted to the 4a side. As a result, the terminal 4a stops transmitting the frame F2-1 being transmitted, and retransmits the frame again as the frame F2-2 with a certain time interval of Tf-gap1.
[0032]
In this figure, when the retransmission frame F2 is transmitted from the terminal 4a, since the slave 3a has not yet received the return frame F1, the slave 3a transmits the suppression signal DMY again at the timing of T9. 4a, and prompts the terminal 4a to retransmit. The terminal 4 urged by the slave 3a to retransmit transmits a frame again as a frame F2-3 at a certain time interval Tf-gap2. Here, at the same time that the slave unit 3a has finally completed the reception of the return frame F1 and at the same time has confirmed the line free signal EP from the master unit 1, the frame F2-3 is transmitted from the slave unit 3a to the master unit 1 Is transmitted to the optical line by following the transmission procedure described above.
[0033]
As described above, when the handset 3 cannot receive the transmission frame from the terminal 4, the handset 3 transmits the suppression signal DMY to the terminal 4, and urges the stop of the frame being transmitted and the retransmission thereof to thereby reduce the transmission frame. Preventing loss. However, as shown in FIG. 4 and FIG. 5, the terminal 4 that has received the suppression signal DMY from the slave 3 often tries to retransmit the frame immediately after the stop of the frame and the suppression signal DMY is interrupted. In particular, retransmission after receiving the first suppression is transmitted with a minimum inter-frame gap Tf-gap1. However, in the cases shown in FIGS. 4 and 5, even if a retransmission frame is transmitted from the terminal at this timing, it cannot be received yet, and the suppression is performed again.
[0034]
However, according to the Ethernet (R) standard, there is a tendency that the interval of retransmission increases as the number of retransmissions increases, and if the same frame is suppressed many times, the inter-frame gap Tf-gap until retransmission is extremely wide. turn into. This can easily be expected that if such a state occurs frequently, an unnecessary load is imposed on the communication performance. Further, in Ethernet (R), the upper limit of the number of retransmissions is 16 times, and when the number of retransmissions is more than 16, frames are lost once at the physical layer level. (Of course, only when the upper layer has a retransmission function). For this reason, if suppression is performed more than necessary, a case may occur in which the number of retransmissions exceeds 16 times. As a result, frame loss occurs at the physical layer level, resulting in extremely lower communication performance.
[0035]
Therefore, the present invention realizes appropriate control of the line without unnecessary unnecessary suppression when the terminal 4 needs to be suppressed from the slave unit 3. Hereinafter, the timing of the execution example will be described with reference to FIGS.
[0036]
FIG. 6 shows an improvement (the present invention) for the case shown in FIG. As shown in FIG. 6, for the frame F1 generated by the terminal 4a, the procedure of the line free signal EP, transmission application RQ, and transmission permission AK indicated by T1 to T4 is performed between the slave 3a and the master 1, In the case where the frame F1 is transmitted from the child device 3a to the parent device 1 at the timing of T6, the suppression timing from the child device 3a to the terminal 4a when the next frame F2 is transmitted from the terminal 4a is shown. ing.
[0037]
As shown in this figure, when the slave 3a is optically transmitting the frame F1 from the terminal 4a at the timing of T6, when the next frame F2-1 is transmitted from the terminal 4a, the slave 3a The suppression signal DMY is transmitted to the terminal 4a at the timing. This causes the terminal 4a to stop transmitting the frame F2-1 being transmitted. Further, the slave unit 3a continuously transmits the suppression signal DMY to the terminal 4a while optically transmitting the frame F1 received earlier (or until detecting the next line free signal EP). The transmission is continued to the terminal 4a side. As a result, the terminal 4a secures Tf-gap1 and transmits the frame F2 to the slave unit 3a as the retransmission frame F2-2 after the termination of the suppression signal from the slave unit 3a (end of transmission of the frame F1). .
[0038]
FIG. 7 shows an example of the improvement (the present invention) to the case shown in FIG. 4 as in FIG. This is because the slave unit 3 receives a frame from the terminal 4 and transmits the frame to the optical line, and once the reception of the frame from the terminal 4 is completed, once transmits the suppression signal to the terminal 4 and transmits it to the optical line side. Until the middle frame ends, the terminal 4 is kept suppressed.
[0039]
That is, with respect to the frame F1 generated by the terminal 4a, the child device 3a takes steps of the line free signal EP, transmission request RQ, and transmission permission AK indicated by T1 to T4 between the child device 3a and the When the frame F1 is transmitted to the device 1 at the timing of T6, the slave device 3a waits until the optical transmission of the frame F1 ends (or until the next line free signal EP is detected, regardless of the presence or absence of the frame from the terminal 4a). ), The slave unit 3a keeps transmitting the suppression signal DMY to the terminal 4a at the timing of T8 to prevent careless transmission from the terminal 4a. As a result, the terminal 4a secures Tf-gap1 and transmits the frame F2 to the slave unit 3a as the retransmission frame F2-1 after the termination of the suppression signal from the slave unit 3a (end of transmission of the frame F1). .
[0040]
Next, FIG. 8 shows an improvement (the present invention) with respect to the case shown in FIG. FIG. 8 shows the procedure of the line free signal EP, transmission application RQ, and transmission permission AK indicated by T1 to T4 between the slave unit 3a and the master unit 1 for the frame F1 generated by the terminal 4a. When the frame F1 is transmitted from the terminal 3a to the master unit 1 at the timing of T6, and the frame F1 is transmitted back to the optical line at the timing T8 by the master unit 1, the next frame F2 is transmitted from the terminal 4a. In this case, the suppression timing from the slave unit 3a to the terminal 4a is shown.
[0041]
As shown in this figure, when the base unit 1 is transmitting the frame F1 from the slave unit 3a back to the optical line at the timing of T8, when the next frame F2-1 is transmitted from the terminal 4a, the slave unit 3a transmits the suppression signal DMY to the terminal 4a at the timing of T9. This causes the terminal 4a to stop transmitting the frame F2-1 being transmitted. Further, the slave unit 3a sends this terminal 4a to the terminal 4a while the frame F1 previously sent to the master unit 1 is transmitted back from the master unit 1 (or until the next line free signal EP is detected). Continuously transmitted. As a result, the terminal 4a secures Tf-gap1 and transmits the frame F2 to the slave unit 3a as the retransmission frame F2-2 after the termination of the suppression signal from the slave unit 3a (end of the reception of the return frame F1). Become.
[0042]
FIG. 9 shows an example of the improvement (the present invention) to the case shown in FIG. 5 as in FIG. This is because, when the slave 3 receives a frame from the terminal 4 and transmits the frame to the optical line, and the frame is returned by the master 1 and optically transmitted, the slave 3 transmits a suppression signal to the terminal 4. Then, the terminal 4 is kept suppressed until the reception of the return frame is completed.
[0043]
That is, with respect to the frame F1 generated by the terminal 4a, the child device 3a takes steps of the line free signal EP, transmission request RQ, and transmission permission AK indicated by T1 to T4 between the child device 3a and the When the frame F1 is transmitted to the device 1 at the timing of T6 and the frame F1 is optically transmitted by the master device 1 at the timing T8, the slave device 3a transmits the optical signal of the folded frame F1 regardless of the presence or absence of the frame from the terminal 4a. During reception (or until the detection of the next free line signal EP), the slave unit 3a transmits the suppression signal DMY to the terminal 4a at the timing of T9 to prevent inadvertent transmission from the terminal 4a. I do. As a result, the terminal 4a secures Tf-gap1 and transmits the next frame F2 to the slave unit 3a as the retransmission frame F2-1 after the termination of the suppression signal from the slave unit 3a (end of reception of the folded frame F1). Will be.
[0044]
FIG. 10 shows an example of an improvement method (the present invention) obtained by combining the methods shown in FIGS. 7 and 9 with each other. This is because the slave unit 3 receives a frame from the terminal 4 and transmits the frame to the optical line, and once the reception of the frame from the terminal 4 is completed, once transmits the suppression signal to the terminal 4 and transmits it to the optical line side. Until the middle frame ends, the terminal 4 is kept suppressed. After that, when the frame is looped back from the base unit 1, the suppression signal to the terminal 4 is continuously transmitted until the reception of the loop-back frame is completed.
[0045]
That is, with respect to the frame F1 generated by the terminal 4a, the child device 3a takes steps of the line free signal EP, transmission request RQ, and transmission permission AK indicated by T1 to T4 between the child device 3a and the When the frame F1 is transmitted to the device 1 at the timing of T6, the slave 3a transmits the terminal 4a at the timing of T8 until the optical transmission of the frame F1 ends, regardless of the presence or absence of the next frame from the terminal 4a. If the suppression signal DMY is transmitted to the terminal 4a, and after the transmission of the frame F1 is completed, the return frame F1 is transmitted from the master unit 1, the suppression signal DMY to the terminal 4a is directly received and the reception of the return frame F1 is performed. The transmission is continued until the processing is completed, thereby preventing careless transmission from the terminal 4a. As a result, the terminal 4a secures Tf-gap1 and transmits the next frame F2 to the slave unit 3a as the retransmission frame F2-1 after the termination of the suppression signal DMY from the slave unit 3a (end of transmission of the frame F1). Will be.
[0046]
Next, FIGS. 11 and 12 show examples of specific configurations of the master unit 1 and the slave unit 3 of the optical wireless communication system for realizing half-duplex communication between the slave unit 3 and the master unit 1 as described above. Show. In master unit 1 shown in FIG. 11, control means (hereinafter, "means" is referred to as "unit") 13 controls the entire operation of master unit 1, controls communication with main line 2, and sets slave unit 3. And half-duplex optical communication control between them, and the transmission destination of frames received from the trunk line 1 and the optical line side is also managed in this portion. In addition, the base unit 1 outputs light over a wide range and transmits each signal as an optical signal as a configuration for performing wireless wireless communication with the slave unit 3 using light. And an optical line receiving unit 11 for receiving the light and receiving the optical signal as an electric digital signal.
[0047]
The optical signal received by the optical line receiving unit 11 is input as an electrical digital signal to the optical line frame receiving unit 8, the optical line frame detecting unit 9, and the optical line transmission application signal detecting unit 10. The optical line frame receiving unit 8 secures a frame to be transmitted to the trunk line 2 until the transmission timing to the trunk line 2 according to the detection result of the optical line frame detecting unit 9 for the signal input from the optical line receiving unit 11, and Is output to the output signal switching unit 6 according to the control of.
[0048]
The optical line frame detecting section 9 detects a frame from the input signal from the optical line receiving section 11 and instructs the optical line frame receiving section 8 on the received frame. The optical line transmission application signal detection unit 10 detects an optical line transmission application signal sent from any slave unit 3 under the control from the signal input from the optical line reception unit 11, and transmits the detection to the control unit 13, The information of the detected transmission application signal (such as an ID indicating from which slave unit 3 the application is applied) is transmitted to the optical line transmission permission signal generator 37. The optical line transmission permission signal generation unit 37 controls the optical line transmission permission signal to the slave unit 3 which has transmitted the transmission application signal using the application information (ID or the like) detected and extracted by the optical line transmission application signal detection unit 10. The signal is transmitted to the optical transmission signal switching unit 18 according to the instruction of the unit 13.
[0049]
The suppression pseudo signal generation unit 7 on the wire line side generates a suppression pseudo signal when it becomes necessary to suppress the signal from the trunk line 2 according to the instruction of the control unit 13 and suppresses the suppression pseudo signal on the switching unit 6 on the wire output signal side. Transmit a pseudo signal. The wired output signal switching unit 6 receives the frame from the optical line frame receiving unit 8 and the suppression pseudo signal from the suppression pseudo signal generation unit 7 for the wired line, and appropriately switches each signal at any time according to the instruction of the control unit 13 to change the wired line. Transmit to transmitting section 5. The wired line transmitting unit 5 outputs the signal from the wired output signal switching unit 6 to the trunk 2 as a trunk output signal.
[0050]
The wired line receiving unit 14 receives data from the trunk line 2 and transmits the received data to the wired line frame detecting unit 15 and the optical line transmission timing delay unit 16. The wired line frame detecting unit 15 detects a frame from the received data sent from the wired line receiving unit 14 and transmits the detection result to the control unit 13, and also sends a detection result to the optical line transmission timing delay unit 16. Submit the result. The optical line transmission timing delay unit 16 causes the frame to wait in a temporary storage device such as a FIFO or the like based on the frame detection result of the wired line frame detecting unit 15 from the signal sent from the wired line receiving unit 14, and receives an instruction from the control unit 13. The frame that has been waiting at the optical line transmission timing is transmitted to the optical line output switching unit 18.
[0051]
The optical preamble generator 17 generates a preamble signal to be added as a synchronization signal before the frame at the time of optical transmission of the frame according to the instruction of the controller 13 and transmits the preamble signal to the optical line output switching unit 18. The optical line vacancy notification signal generation unit 12 generates an optical line vacancy notification signal for notifying the subordinate unit 3 that is under control that the optical line is vacant when the optical line is vacant according to the instruction of the control unit 13. The signal is transmitted to the switching unit 18 on the line output signal side. The optical line output signal switching unit 18 includes an optical line transmission permission signal from the optical line transmission permission signal generating unit 37, an optical line idle notification signal from the optical line idle notification signal generating unit 12, an optical preamble from the optical preamble generating unit 17, and The data of the frame from the optical line transmission timing delay unit 16 is switched to the optical line transmitting unit 19 and transmitted according to an appropriate instruction from the control unit 13 as needed. The optical line transmitting unit 19 transmits the data appropriately switched and output by the optical line output signal switching unit 18 to the optical line as an optical signal.
[0052]
Next, an example of a specific configuration of the slave unit 3 will be described with reference to FIG. In the slave unit 3 shown in FIG. 12, the control unit 27 controls the entire operation of the slave unit 3, controls communication with the terminal 4, and controls half-duplex optical communication with the master unit 1. It is. Further, here, it manages the free space of its own reception storage device, determines whether a transmission frame from the terminal 4 can be received, and controls the suppression operation to the terminal 4 according to the determination. .
[0053]
The slave unit 3 has a configuration for performing wireless wireless communication with the master unit 1 by light, and includes an optical line transmitting unit 20 for outputting light to a narrow range and transmitting each signal as an optical signal. It has an optical line receiving unit 28 that receives light from the device 1 and receives optical signals as electrical digital signals. The wired line receiving unit 26 receives the signal from the terminal 4 and transmits the received data to the optical line transmission timing delay unit 24, the wired line frame detecting unit 25, and the wired line non-signal time measuring unit 36.
[0054]
The wired line no-signal time measuring unit 36 is in a state where a signal from the wired line is no signal (no frame comes) after the frame received by the wired line receiving unit 26 and detected by the wired line frame detecting unit 25 is finished. Is measured, and the measurement result is sent to the control unit 27. The wired line frame detecting unit 25 detects a frame to be transmitted to the optical line from the signal from the terminal 4 received by the wired line receiving unit 26, sends the detection result to the control unit 27, and similarly transmits the detection result to the optical line. It is sent to the transmission timing delay means 24. The optical line transmission timing delay unit 24 causes the frame to wait in a temporary storage device such as a FIFO according to the detection result of the wired line frame detecting unit 25 from the signal received by the wired line receiving unit 26, and according to the instruction of the control unit 27. The transmitted frame is transmitted to the optical line output signal switching unit 21.
[0055]
The optical line transmission application signal generating unit 23 generates an optical line transmission application signal when a frame is transmitted from the terminal 4 and transmission from the master unit 1 to the optical line is required in accordance with an instruction from the control unit 27. Then, an optical line transmission application signal is transmitted to the optical line output signal switching unit 21. The optical preamble generating unit 22 generates a preamble as a synchronization signal at the time of reception of the master unit 1 before transmitting the frame optically, and transmits the optical preamble to the optical line output signal switching unit 21 according to the instruction of the control unit 27.
[0056]
The optical line output signal switching unit 21 controls the frame from the optical line transmission timing delay unit 24, the optical line transmission application signal from the optical line transmission application signal generation unit 23, and the optical preamble signal from the optical preamble generation unit 22. Each signal is switched and transmitted to the optical line transmitting unit 20 according to an appropriate instruction from the unit 27 as needed. The optical line transmitting unit 20 includes a light emitting unit for optical transmission, and transmits each signal sent from the optical line output signal switching unit 21 to the master unit 1 as an optical signal. Light emission and light emission stop can be controlled.
[0057]
The optical line receiving unit 28 receives the optical signal sent from the base unit 1 and, as an electrical signal, a carrier sense unit 38, an optical line empty notification signal determining unit 30, an optical line transmission permission signal detecting unit 31, an optical line The frame detection unit 29 transmits the received signal to the wired line transmission timing delay unit 32. The carrier sense means 38 receives the transmission signal from the master unit 1 as an electric signal from the optical line light receiving unit 28, detects the transmission carrier from the master unit 1 from the signal, and uses the optical line vacancy notification signal determination means 30 to The vacancy notification signal is detected and sorted, and the result is sent to the control unit 27.
[0058]
The optical line transmission permission signal detecting unit 31 converts the received signal sent from the optical line reception unit 28 into an optical line transmission permission signal for permitting the base unit 1 to transmit its own slave unit 3 to transmit a frame to the optical line. The detection is sent to the control unit 27. The optical line frame detecting unit 29 detects an optical transmission frame transmitted by the master unit from the received signal transmitted from the optical line receiving unit 28, and transmits the result to the control unit 27, and simultaneously transmits the result to the wired line transmission timing delay unit 32. Send and instruct frame temporary waiting. The wired line transmission timing delay unit 32 temporarily suspends the detected frame from a received signal sent from the optical line receiving unit 28 in a temporary storage device such as a FIFO according to the frame detection result of the optical line frame detecting unit 29, and controls In accordance with a transmission instruction to the terminal 4 from the unit 27, the wired output signal switching unit 34 transmits the waiting frame.
[0059]
The suppression pseudo signal generation unit 33 on the wire line side generates a suppression pseudo signal when it is necessary to suppress transmission from the terminal 4 connected by wire according to an appropriate instruction from the control unit 27, and switches the wire output signal. Send to section 34. The wire output signal switching unit 34 receives the frame signal from the wire line transmission timing delay unit 32 and the suppression pseudo signal from the wire line suppression pseudo signal generation unit, and follows these frame signals as needed according to an appropriate instruction from the control unit 27. And the suppression signal are switched as needed, and transmitted to the wired line transmission unit 35. The wired line transmitting unit 35 transmits the signal transmitted from the wired output signal switching unit 34 to the wired line on the terminal 4 side.
[0060]
Next, the flow of processing when the above-described master unit 1 having the configuration of FIG. 11 and the slave unit 3 having the configuration of FIG. explain. First, in FIG. 13, the flow of processing in the base unit 1 from when the base unit 1 receives a frame transmitted through the trunk line 2 to when this frame is transmitted to the subordinate unit 3 (mainly the control unit 13 Is shown.
[0061]
In FIG. 13, first, the control unit 13 of the base unit 1 monitors whether or not optical communication is performed with the slave unit 3 as a process of step S1, and when the optical line is not used. Then, the optical line free notification signal is optically transmitted to the slave unit 3 under the control. Next, in step S2, a signal from the trunk line 2 is monitored, and if no frame is transmitted from the trunk line 2, the optical transmission control state is a frame waiting from the trunk line 2, and if a frame is received from the trunk line 2, In the next step 46, it is determined whether or not the frame needs to be transmitted to the optical line side.
[0062]
If it is determined that transmission to the optical side is necessary, the process proceeds to the next step S3, and it is checked whether or not the frame received from the trunk line 2 can be output to the optical line based on the state of the optical line. If the optical line is used by the slave unit 3 or the like, the process proceeds to step S8, where a suppression signal is transmitted to the trunk line 2. In the following step S9, it is confirmed that the frame transmission from the trunk line 2 has stopped, and in step S10, The suppression signal is stopped, and the process waits again in step S2 until a frame from the trunk line 2 is received.
[0063]
If the optical line is vacant in step S3, the process proceeds to step S4, where the frame from the trunk line 2 is kept in a temporary storage device such as a FIFO until the optical line transmission timing, and transmitted to the slave unit 3 in the next step S5. The optical line availability notification signal, which has been performed, is stopped, and in the next step S6, the slave unit 3 transmits an optical preamble for synchronizing at the time of reception before transmitting a frame, and then temporarily suspends in step S5. The transmitted frame is optically transmitted in step S7. When the transmission of the frame is completed, an optical line empty notification signal is sent to the slave unit 3 in step S45 to notify that the optical line has become idle, and the process waits until a frame is received from the trunk line 2 again in step S2.
[0064]
Next, in FIG. 14, there is an optical transmission application from the slave unit 3 under the control, the master unit 1 permits the request, and the master unit 1 receives the frame optically transmitted from the slave unit 3 and transmitted. 2 shows a flow of processing (mainly a flow of a control operation of the control unit 13) in the base unit 1 until the transmission to the trunk line 2. In FIG. 14, as a process of step S11, it is monitored whether or not there is an optical line transmission application signal from the slave unit 3 based on the detection result of the optical line transmission application signal detection unit 10, and If there is a transmission application signal, the process proceeds to step S12 to stop the optical line empty notification signal, and then proceeds to step S13 to transmit the optical line transmission incorporating the slave unit identification information (ID or the like) of the transmission signal received from the slave unit 3. The permission signal is transmitted to the optical line with an optical preamble added.
[0065]
When the transmission permission signal is transmitted, in step S14, a frame light transmission from the slave unit 3 is waited. If no frame arrives within a certain period of time, a timeout occurs in step S16, and then a frame from the trunk line 2 is transmitted in step S17. After confirming that it has not been received, an optical line empty notification signal is transmitted in step S18 to release the optical line to the slave unit 3 under the control again. If a frame has come from the trunk line 2 in step S17, an optical preamble is added and optical transmission is performed in step S19. Here, the optical transmission of the frame from the trunk line 2 is simply expressed in steps S17 and S19, but the optical transmission flow of the frame from the trunk line 2 operates according to the above-described flow of FIG.
[0066]
If the frame can be optically received from the slave unit 3 in step S14, the optically received frame is temporarily stored in the temporary storage device in step S47. Then, in step S15, the received frame is transmitted to the trunk line 2 in consideration of timing. Send. Next, in step S48, it is determined whether or not the received frame needs to be looped back to the optical line. If not, the process waits for the next frame again in step S14. If it is determined in step S48 that return transmission is necessary, it is determined (standby) whether or not reception of a transmission frame from the child device has been completed in the next step S49. 3 is transmitted back.
[0067]
Next, an operation of the slave unit 3 for realizing communication as described in the transmission timing images of FIGS. 6 and 8 will be described. First, in FIG. 15, the slave unit 3 receives a frame transmitted from the master unit 1 and transmits the frame to the terminal 4 connected via a wired line. 2 shows the flow of the control operation of the unit 27. In FIG. 15, first, in step S20, it is monitored whether or not a frame has been transmitted from the base unit 1, and if there is an optical transmission frame from the base unit 1, in step S51, the frame transmitted by itself is transmitted. Determine whether the frame is a folded frame.
[0068]
If the frame is not a loopback frame, the optically received frame is temporarily secured in the temporary storage device of the FIFO in step S21, and then, in step S22, it is checked whether a frame from the terminal 4 has come to the wired line. If a frame has been sent from the terminal 4, the process moves from step S52 to step S25, and once a suppression pseudo signal is sent to the wired side in order to suppress frame transmission from the terminal 4. Thereafter, returning to step S22, if the wired line is free, if the suppression pseudo signal is being transmitted at this time in step S23, it is stopped in this step 23, and in the next step S24, the frame held in step S21 is put on standby. Is transmitted to the wire line and transmitted to the terminal 4.
[0069]
If it is determined in step S51 that the received frame from the base unit 1 is a loopback frame, the process proceeds to step S22 to monitor the wired line side. If a frame has been transmitted from the terminal 4, the process proceeds from step S52 to step S53. To start transmitting the suppression signal to the terminal 4. After that, in step S54, after waiting for the return frame being received, the suppression signal transmitted to the terminal 4 is stopped in step S55, and the process returns to step S20. Further, in this case, the simplification of the circuit can be realized by using the data obtained by returning the suppression signal to the start bit of the frame or destroying the address field (replacement with another data).
[0070]
FIG. 16 shows a processing flow (mainly performed by the control unit 27) of the slave 3 until the slave 3 transmits the frame transmitted from the terminal 4 to the master 1 via the optical line. Operation flow) is shown. In this figure, it monitors and waits for the transmission of a frame from the terminal 4 in step S26, and if a frame has been transmitted, determines in step S56 whether or not it itself is transmitting the previous frame (memory is free). Is determined, and if the previous frame is being transmitted, the child device 3 starts transmitting a suppression signal to the terminal 4 in step S57. Then, in step S58, the process stands by until the frame transmission during the optical transmission is transmitted. When the optical transmission is completed, the suppression signal to the terminal 4 is stopped in step S59, and the process again waits for the frame transmission from the terminal 4 in step S26.
[0071]
If the handset 3 is not transmitting the previous frame in step S56, it is stored in the temporary recording device in step S27. The child device 3 that has received the frame from the terminal 4 determines the availability of the optical line based on the optical line availability notification signal from the master device 1 in step S28. If the slave unit 3 cannot detect the optical line empty notification signal within a predetermined time after receiving the frame from the terminal 4, the slave unit 3 times out in step S35, and then in step S37, the slave unit 3 transmits a suppression signal to the terminal 4 side. Then, the stop of the frame transmitted from the terminal 4 is confirmed in step S38, and the suppression signal to the terminal is stopped in step S39.
[0072]
On the other hand, if a free optical line is detected within the prescribed period in step S28, the slave unit 3 transmits a transmission application signal to the optical line to the master unit 1 in step S29, and then in step S30 the master unit It waits for a transmission permission signal from 1. Here, if the permission signal from the base unit 1 is not obtained within a predetermined time, the timeout is performed in step S36, and the suppression signal is transmitted to the terminal 4 in steps S37, S38, and S39. If the transmission permission is successfully obtained from the base unit 1 in step S30, an optical preamble for synchronization is transmitted in step S31, and subsequently, the frame temporarily suspended in step S32 is transmitted to the optical line. Then, the process returns to step S26 to monitor the frame from the terminal 6 side.
[0073]
【The invention's effect】
As described above, the master unit requires a transmission procedure with the slave unit, the master unit performs data communication with a plurality of slave units, and the slave unit transmits data from a terminal or the like connected thereto. In a half-duplex optical transmission system in which it is necessary to suppress and control the line, if it is known that the slave unit cannot receive the transmission from the terminal, the slave unit is continuously suppressed during that period. The number of inadvertent suppressions (collisions) between terminals can be reduced, and the retransmission time from the terminals can be made more efficient. As a result, efficient transmission is realized, and a higher-performance 1: N optical wireless communication system can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram schematically illustrating a half-duplex optical communication system according to the present invention.
FIG. 2 is an explanatory diagram showing basic communication timing of the half-duplex optical communication system of FIG.
FIG. 3 is an explanatory diagram showing basic communication timing in the case of a half-duplex optical communication system of FIG. 1 with a loopback frame;
FIG. 4 is an explanatory diagram showing a basic communication timing of suppression on the wire side of the conventional half-duplex optical communication slave device (in the case of suppression during transmission).
FIG. 5 is an explanatory diagram showing the basic communication timing of wire side suppression of the conventional half-duplex optical communication handset device (in the case of suppression during reception of a loopback frame).
FIG. 6 is an explanatory diagram showing an example of basic communication timing (in the case of suppression during transmission) of suppression on the wire side of the half-duplex optical communication device of the present invention.
FIG. 7 is an explanatory diagram showing another example of the basic communication timing (in the case of suppression during transmission) of suppression on the wire side of the half-duplex optical communication slave device of the present invention.
FIG. 8 is an explanatory diagram showing an example of basic communication timing of suppression on the wire side of the half-duplex optical communication device of the present invention (in the case of suppression during reception of a loopback frame).
FIG. 9 is an explanatory diagram showing another example of the basic communication timing of suppression on the wire side of the half-duplex optical communication device of the present invention (in the case of suppression during reception of a loopback frame).
FIG. 10 is an explanatory diagram showing basic communication timing of suppression on the wire side of the half-duplex optical communication device of the present invention (in the case of suppression during transmission and return frame reception).
FIG. 11 is a block diagram showing a half-duplex optical communication master device of the present invention.
FIG. 12 is a block diagram showing a half-duplex optical communication slave device of the present invention.
FIG. 13 is a flowchart illustrating a process of transmitting an optical line frame and transmitting an optical line empty notification signal by the half-duplex optical communication master device of the present invention.
FIG. 14 is a flowchart for explaining an optical line frame receiving process of the half-duplex optical communication master device of the present invention.
FIG. 15 is a flowchart for explaining processing of optical line frame reception and wired transmission of the half-duplex optical communication slave device of the present invention.
FIG. 16 is a flowchart for explaining an optical line frame transmission process of the half-duplex optical communication slave device of the present invention.
[Explanation of symbols]
3 cordless handset
4 terminal
24 Optical line transmission timing delay unit
27 control means
33 Suppression pseudo signal generation means

Claims (1)

A terminal for exchanging data is connected, a half-duplex optical communication slave device that transmits and receives the data to and from the half-duplex optical communication master device by half-duplex optical communication,
Temporary storage means for receiving transmission data for transmission to the half-duplex optical communication master device from the terminal and temporarily storing the transmission data,
When there is no free area for storing the transmission data in the temporary storage means, reception of transmission data from the terminal is continued until a free area for storing the transmission data is secured in the temporary storage means. Suppression means,
A half-duplex optical communication handset device, comprising:

Images