JP4085557B2 - Optical wireless transmission method and system, optical wireless transmitter and optical wireless receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical wireless transmission method and system, an optical wireless transmitter, and an optical wireless receiver.
[0002]
[Prior art]
IEEE 1394. The b standard is a serial bus standard for connecting a personal computer or a consumer device to a peripheral device, and a wired medium such as a stranded wire or an optical fiber is defined as the transmission medium.
[0003]
FIG. 10 shows IEEE1394. It is a figure which shows the transmission form of the serial bus signal prescribed | regulated to b standard.
[0004]
In this serial bus signal, data such as video and audio is transmitted by packet, while a bus management signal synchronized with the clock of the packet is inserted between packets. In addition, IEEE 1394. The b standard stipulates that while one is transmitting a packet, the other transmits a bus management signal.
[0005]
By the way, IEEE1394. While studies are being made to expand the b standard, an optical wireless transmission method using wireless connection is proposed because of the ease of connection, and application to high-speed wireless LAN is expected.
[0006]
FIG. 11 shows IEEE1394. 1 is a configuration diagram of a one-to-one narrow beam bidirectional communication apparatus that performs one-to-one transmission in a transmission format based on the b standard.
[0007]
The light receiving units 101 and 201 and the light emitting units 102 and 202 provided in the devices 100 and 200 shown in FIG. For this reason, when transmitting and receiving light with these devices facing each other, optical isolation (separation) between wireless transmission paths is ensured, and full-duplex communication can be performed. That is, between the apparatuses shown in FIG. 11 to which the conventional optical wireless transmission method is applied, wireless transmission is performed substantially equivalent to bidirectional communication using two optical fibers, although wireless transmission is performed.
[0008]
[Problems to be solved by the invention]
However, in the above-described conventional optical wireless transmission method, when performing wireless transmission of light using a wide directivity signal, it is not possible to sufficiently secure isolation between the transmitted light and the received light. The following problems occur:
[0009]
In other words, because it is full-duplex communication, it must send a bus management signal even in a section in which a packet from a communication partner is received. Interference, and reception errors are likely to occur. In particular, when the communication partner is located far away, the level of the received light becomes low, and this tendency becomes prominent, making it difficult to establish communication (link) with the partner device.
[0010]
For example, IrDA (Infrared Data Association) is defined as a transmission method in an environment where isolation cannot be ensured in this way, but this is for half-duplex communication, and a reduction in communication speed cannot be denied. .
[0011]
Accordingly, the present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide an optical wireless transmission method capable of wirelessly transmitting an optical signal even when sufficient isolation between the transmitted light and the received light cannot be ensured. The present invention provides an optical wireless transmission device and an optical wireless reception device.
[0012]
[Means for Solving the Problems]
In order to solve the above problem, an optical wireless transmission method according to claim 1 of the present invention provides: Using two devices having a light emitting element for transmitting an optical signal and a light receiving element disposed close to the light emitting element to receive the optical signal, the optical signal transmitted from the light emitting element of one device is used as the other device. By receiving with the light receiving element of IEEE1394. Light in an optical wireless transmission system in which communication based on the b standard is performed and the communication state is maintained by a no-information signal received by the light receiving element of the one device A wireless transmission method, The light emitting element of the other device is connected to the light receiving element of the one device. The informationless signal is transmitted intermittently.
[0013]
In the present invention, when a communication state is maintained by a signal in a section that does not include information, that is, a no-information signal, the no-information signal is intermittently transmitted to maintain the communication state. Since interference between signals is prevented, optical signals can be transmitted wirelessly even in an environment where sufficient isolation of optical signals cannot be ensured.
[0015]
Claims of the invention 2 The optical wireless transmission system according to Using two devices having a light emitting element for transmitting an optical signal and a light receiving element disposed close to the light emitting element to receive the optical signal, the optical signal transmitted from the light emitting element of one device is used as the other device. By receiving with the light receiving element of IEEE1394. Communication based on the b standard An optical wireless transmission system, The one device is Comprising intermittent transmission means for intermittently transmitting a no-information signal; The other device is A communication state maintaining means for maintaining a communication state by the non-information signal transmitted intermittently is provided.
[0016]
Claims of the invention 3 The optical wireless transmission device according to Using two devices having a light emitting element for transmitting an optical signal and a light receiving element disposed close to the light emitting element to receive the optical signal, the optical signal transmitted from the light emitting element of one device is used as the other device. By receiving with the light receiving element of IEEE1394. The optical wireless transmission device is applied to the other device in the optical wireless transmission system that performs communication based on the b standard and maintains the communication state by an information-free signal received by the light receiving element of the one device. And An intermittent transmission means for intermittently transmitting the no-information signal is provided.
[0017]
Claims of the invention 4 An optical wireless transmission device according to claim 3 In the optical wireless transmission device described above, the intermittent transmission unit randomly transmits the informationless signal transmitted intermittently.
[0018]
Claims of the invention 5 An optical wireless transmission device according to claim 3 Or claims 4 In the optical wireless transmission device described above, the intermittent transmission unit is configured to be capable of adjusting an on / off ratio of the non-information signal transmitted intermittently.
[0019]
Claims of the invention 6 An optical wireless transmission device according to claim 3 To claims Any of 5 In the described optical wireless transmission device, the intermittent transmission unit stops transmission of the informationless signal transmitted intermittently according to a communication state.
[0020]
Claims of the invention 7 An optical wireless transmission device according to claim 3 To claims Any of 6 In the optical wireless transmission device described above, the intermittent transmission unit converts the subsequent portion of the control signal repeatedly input into the informationless signal transmitted intermittently in connection with the communication. .
[0021]
Claims of the invention 8 The optical wireless receiver according to Using two devices having a light emitting element for transmitting an optical signal and a light receiving element disposed close to the light emitting element to receive the optical signal, the optical signal transmitted from the light emitting element of one device is used as the other device. By receiving with the light receiving element of IEEE1394. an optical wireless receiver applied to the other device in an optical wireless transmission system that performs communication based on the b standard and the light emitting element of the one device intermittently transmits a no-information signal, It is characterized by comprising a communication state maintaining means for maintaining a communication state by an intermittent no-information signal.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an optical wireless transmission method and system, an optical wireless transmitter, and an optical wireless receiver according to the present invention will be described below with reference to the drawings.
[0025]
FIG. 1A is a block configuration diagram of an optical module to which the present invention according to the first embodiment is applied.
[0026]
In this optical module, the preamble adding circuit 1, the intermittent signal generating circuit 2, and the drive circuit 3 constitute an optical signal transmitting means.
[0027]
The preamble adding circuit 1 is an IEEE1394. A serial bus signal (electrical signal) based on the b standard is used as an input signal, and a collision avoidance signal (referred to as a preamble in the following description) having a predetermined width is added to the head of a packet included in this signal. It should be noted that the IEEE1394. An optical fiber connector specified by the b standard may be attached to receive an optical signal, and an electrical signal obtained by photoelectric conversion of the optical signal may be used as an input signal. In addition, meaningless information (hereinafter referred to as “postamble”) may be added after the packet.
[0028]
The intermittent signal generation circuit 2 is a circuit that converts a signal (hereinafter referred to as a no-information signal) in a section that does not include information in the input signal into an intermittent signal, and generates an intermittent signal (electric signal). A circuit for generating a clock to be included in the intermittent signal is incorporated. Further, the intermittent signal generation circuit 2 can control the transmission timing of each intermittent signal.
[0029]
The drive circuit 3 emits an infrared ray (transmission light) by causing the light emitting element 3a provided in the drive circuit 3 to emit light according to the ON / OFF timing of the signal from the intermittent signal generation circuit 2.
[0030]
On the other hand, the light receiving circuit 4, the AGC amplifier 5, the clock recovery circuit 6 and the signal processing circuit 7 constitute an optical signal receiving means.
[0031]
The light receiving circuit 4 photoelectrically converts an optical signal received by the light receiving element 4a provided in the light receiving circuit 4 and outputs an electrical signal. The AGC amplifier 5 appropriately amplifies the electric signal and outputs it to the clock recovery circuit 6.
[0032]
The clock recovery circuit 6 separates and extracts a clock component from the input electrical signal (this process is called clock recovery) and outputs it as a recovered clock. The clock recovery circuit 6 binarizes the input electrical signal and outputs it to the signal processing circuit 7 as a data signal.
[0033]
The signal processing circuit 7 converts the intermittent signal included in the input data signal into a continuous signal, further removes the preamble, and IEEE1394. Output as a serial bus signal (output signal) specified in the b standard.
[0034]
FIG. 1B is a diagram illustrating a mounting example of this optical module.
[0035]
As shown in this figure, the optical module of this embodiment is provided in each of a personal computer and a digital video camera having a transmission function based on the IEEE 1394 standard. These are arranged so as to face each other, and an optical signal is wirelessly transmitted between both optical modules.
[0036]
Next, the operation of the present embodiment will be described with reference to FIG.
[0037]
FIG. 2 is a timing chart of intermittent signals transmitted and received between the optical modules A and B each having the configuration shown in FIG. That is, the optical module A and B constitute an optical wireless transmission system.
[0038]
The intermittent signal generation circuit 2 operates at the same timing as in FIG. 2 during a period in which bidirectional data communication cannot be performed (for example, when no link is established) and a period of no information signal due to a distance from the communication partner. Then, an intermittent signal (electric signal) is generated, and this signal is output to the drive circuit 3.
[0039]
At this time, the intermittent signal generation circuit 2 includes, for example, an on / off signal with a repetition period of 61.44 MHz in each intermittent signal constituting the intermittent signal, and generates each intermittent signal at random timing. That is, IEEE1394. In the b standard, the data transfer rate is stipulated as m × 122.88 Mbps (m is an integer) by the encoding technique. For example, when an on / off signal having a “1010... This is because a 61.44 MHz clock component whose repetition frequency is ½ of the transfer rate is required.
[0040]
The intermittent signal generation circuit 2 repeats this 61.44 MHz on / off pattern for 16 cycles to generate an intermittent signal having a pulse width of about 0.130 μs, and then 240 cycle times ± n × 0.260 [μs] (however, A random intermittent signal is sequentially generated with a time interval of (n is a random integer from 0 to 7). The signal output from the intermittent signal generation circuit 2 may be, for example, a signal including an arbitrary frequency or a fixed pattern data signal instead of the 61.44 MHz signal.
[0041]
Then, the drive circuit 3 converts the intermittent signal (electric signal) into an optical signal and sends the intermittent signal to the optical module B as shown in the upper part of FIG.
[0042]
In contrast, as shown in the lower part of FIG. 2, a random intermittent signal (optical signal) is also sent from the optical module B.
[0043]
The light receiving circuit 4 of the optical module A photoelectrically converts the optical signal (received light) from the optical module B, the AGC amplifier 5 amplifies this signal, and the amplified electrical signal is input to the clock recovery circuit 6. . Since the intermittent signal is continuously transmitted during the link non-establishment and the no-information signal period during the link establishment, the AGC amplifier 5 can stabilize the gain using this signal.
[0044]
The clock recovery circuit 6 maintains the communication state between the optical modules AB by separating and extracting the clock included in the received signal and generating a recovered clock. For this reason, when a packet occurs in the input signal or when a packet occurs in the received light, it is possible to perform quick processing.
[0045]
When the link is not established, no packet (data) is included in the received light, and therefore no data signal is output from the clock recovery circuit 6 to the signal processing circuit 7.
[0046]
As described above, in this embodiment, an intermittent signal is included in the transmission light, and the communication state is maintained using the intermittent signal in the reception light, so that transmission to the reception light is maintained while maintaining the communication state. Light interference can be prevented.
[0047]
Next, processing at the time of packet transmission in the first embodiment will be described with reference to FIG.
[0048]
When a packet is generated in the input signal to the optical module B, the preamble adding circuit 1 adds a collision avoidance signal (preamble) having a predetermined length to the packet as shown in the lower part of FIG. Output to the generation circuit 2. Then, the intermittent signal generation circuit 2 stops outputting the intermittent signal, and outputs the packet with the preamble added to the drive circuit 3.
[0049]
The drive circuit 3 converts this signal into transmission light and sends it out. Then, the optical module B starts transmitting the intermittent signal again after a predetermined time has elapsed after the end of packet transmission.
[0050]
On the other hand, as shown in the upper part of FIG. 3, the communication partner optical module (optical module A) receives an optical signal longer than the width of each intermittent signal (in the case of FIG. 3, the preamble corresponds to this optical signal). Then, this is recognized separately from the intermittent signal, and transmission of its own intermittent signal is stopped until reception and processing of the packet following this preamble are completed.
[0051]
Therefore, according to the present invention relating to the first embodiment, the intermittent signal generation circuit 2 is provided as the intermittent transmission means, and the reception means uses the intermittent signal in the received light, that is, the intermittently transmitted no information signal. Thus, by providing the clock recovery circuit 6 as a communication state maintaining means for maintaining the communication state, it is possible to prevent the interference of the transmitted light with the received light while maintaining the communication state. Even if sufficient isolation from the received light cannot be ensured, the optical signal can be transmitted wirelessly.
[0052]
Further, by making the transmission timing random, it is possible to avoid as much as possible collisions between the intermittent signals in the transmission light and the reception light.
[0053]
The intermittent transmission means can be configured such that the transmission timing of each intermittent signal is different from the reception timing of each idle signal in the received light. By performing such transmission timing control, collision between idle signals can be actively avoided, and the stability of the communication state can be further increased.
[0054]
Moreover, since the intermittent transmission means stops the transmission of the intermittent signal according to the communication status, it is possible to prevent unnecessary transmission of the intermittent signal.
[0055]
In particular, since a preamble adding circuit 1 for adding a collision avoidance signal to a packet in the transmission light is provided, and when a collision avoidance signal in the reception light is received, the transmission of its own intermittent signal is stopped. Interference can be prevented and packets in the received light can be reliably received.
[0056]
As shown in FIG. 3, by making the width of the preamble added to the packet longer than the width of each intermittent signal, the signal destruction due to the intermittent signal remains only within the preamble as shown by the arrow y1, and the packet The contents (data) itself can be prevented from being destroyed.
[0057]
Also, in the unlikely event that the intermittent signals in the transmission light and the reception light collide with each other, there is a possibility that the operation of the clock recovery circuit 6 may be adversely affected. For example, the processing of the reception light during its own transmission is stopped. Therefore, this can be prevented. Further, the output signal may be switched to another electric signal as appropriate.
[0058]
Next, a second embodiment will be described with reference to FIGS.
[0059]
FIG. 4 is a diagram showing a block configuration of the optical module according to the second embodiment. In addition to the configuration of the first embodiment, a reclock circuit 8 and a carrier sense circuit 9 are provided.
[0060]
The reclocking circuit 8 in FIG. 4 is connected to the input side of the preamble adding circuit 1. The reclock circuit 8 generates a clock signal having a repetition frequency of about 1 MHz and outputs it to the preamble adding circuit 1. In addition, the reclocking circuit 8 is supplied with the recovered clock (frequency 122.88 MHz) from the clock recovery circuit 6 and can output a clock signal synchronized therewith instead of the above-mentioned clock signal of about 1 MHz. It has become. Hereinafter, for simplification of description, the frequency is described as 1 MHz, but the frequency can be arbitrarily set as necessary.
[0061]
In order to generate a clock signal synchronized with the reproduction clock in the reclock circuit 8, a method using fifo (11) or a method of dividing the reproduction clock and supplying it to the physical layer IC according to the IEEE 1394 standard. Etc. may be used.
[0062]
In addition, the carrier sense circuit 9 gives an instruction as to whether or not to output the clock signal to the preamble adding circuit 1 to the reclock circuit 8.
[0063]
The carrier sense circuit 9 is a circuit for detecting an optical signal from a communication partner optical module, and is connected between the AGC amplifier 5 and the clock recovery circuit 6. The carrier sense circuit 9 detects the level of the signal output from the AGC amplifier 5 and gives an instruction regarding the clock output to the reclock circuit 8 described above according to the detected level. Further, the drive circuit 3 is configured to issue a gain switching instruction. The signal output from the intermittent signal generation circuit 2 passes through the carrier sense circuit 9 and is supplied to the drive circuit 3.
[0064]
Next, the operation of the optical module in the second embodiment will be described.
[0065]
FIG. 5 is a timing chart of intermittent signals when a link is not established.
[0066]
When the link is not established in this embodiment, the intermittent signal generation circuit 2 lowers the ratio of the transmission period to the average period of each intermittent signal (referred to as the on / off ratio) than when the link is established.
[0067]
For example, as shown in FIG. 5, for an ON period of 0.1 mS (transmission period of each intermittent signal), the average period is 100 mS and the on / off ratio is 1: 1000. Each intermittent signal itself is a burst signal that repeats on / off operations 100 times at a frequency of 1 MHz.
[0068]
The intermittent signal generation circuit 2 sequentially transmits intermittent signals at time intervals of 100 ± n × 0.1 [ms] (n is a random integer between 0 and 499). The intermittent signal when the link is not established is called a burst signal.
[0069]
Thus, by setting the on / off ratio of the intermittent signal when the link is not established to be larger than that when the link is established, it is possible to save power in the optical module.
[0070]
Next, with reference to FIG. 6 and FIG. 7, a process at the time of link establishment in the second embodiment will be described.
[0071]
FIG. 6 is a timing chart relating to processing from when the link is not established to when the link is established.
[0072]
First, a burst signal from one optical module is received by the counterpart optical module. In FIG. 6, the burst signal transmitted from the optical module A is received by the optical module B. The AGC amplifier 5 amplifies the burst signal, and the carrier sense circuit 9 determines the level of the amplified signal.
[0073]
Here, when it is determined that the signal level is equal to or higher than the predetermined level, the presence of the optical module A is detected by the optical module B. At this time, the optical module B recognizes itself as a master.
[0074]
When the presence of the optical module A is detected, in the optical module B, the carrier sense circuit 9 instructs the drive circuit 3 to switch the gain so that the level of the transmitted light is double that when the link is not established. The In accordance with this instruction, the drive circuit 3 transmits a burst signal having a frequency of 1 MHz for a predetermined time with the transmission light level set to twice that when the link is not established.
[0075]
When the optical module A receives the burst signal from the optical module B, it stops transmitting the optical signal and recognizes itself as a slave. In this way, a link between the optical modules A and B is established.
[0076]
When the link is established, in the master optical module B, the carrier sense circuit 9 instructs the reclock circuit 8 to stop outputting the clock signal to the preamble adding circuit 1. The intermittent signal generation circuit 2 outputs an intermittent signal (electric signal) including a clock generated in its own circuit at a constant cycle. Therefore, an optical signal is transmitted at the same timing. The on / off ratio of the intermittent signal at this time is set smaller than that when the link is not established, and the signal level is maintained at twice.
[0077]
On the other hand, when the slave optical module A receives the intermittent signal from the master optical module B, the slave optical module A similarly transmits an intermittent signal with a constant period and a phase difference of 180 degrees. For this reason, the collision of intermittent signals can be avoided.
[0078]
The reclock circuit 8 of the slave optical module A uses the recovered clock extracted by the clock recovery circuit 6 of the optical module A as a clock for transmission. That is, synchronization between the optical modules is ensured by a common clock. For this reason, it is possible to increase the processing speed of clock recovery and further reduce jitter.
[0079]
FIG. 7 is a timing chart relating to processing during packet transmission.
[0080]
As shown in this figure, when a packet is input to the input signal in the master optical module A, as in the first embodiment, the optical module A stops sending intermittent signals and adds a preamble to the packet. And send it out. On the other hand, when receiving the preamble, the optical module B stops sending its own intermittent signal until sending of the subsequent packet is finished. In this way, it is possible to prevent interference with received light due to its own transmitted light.
[0081]
Note that the carrier sense circuit 9 of this embodiment ignores the detection result at the level described above when sending its own packet.
[0082]
Similarly to the first embodiment, the contents of the packet itself can be prevented from being destroyed by making the width of the preamble longer than the width of the intermittent signal.
[0083]
Therefore, according to the present invention relating to the second embodiment, the intermittent transmission means (intermittent signal generation circuit 2) can adjust the ratio of the transmission time width to the transmission period of each intermittent signal, that is, the on / off ratio. With this configuration, the power consumption of the optical module can be adjusted.
[0084]
In addition, by providing a transmission level adjusting means (carrier sense circuit 9) that adjusts the level of the transmitted light according to the communication status, the degree of interference of the own transmitted light with respect to the received light is adjusted according to the communication state. be able to.
[0085]
Further, by generating transmission light using a clock included in the reception light, wireless transmission between optical modules synchronized with a common clock can be performed.
[0086]
The above description is about packet transmission from the master to the slave, but packet transmission in the reverse direction is performed in exactly the same procedure.
[0087]
Next, a third embodiment of the present invention will be described.
[0088]
IEEE 1394. On the signal based on the b standard, a bus management signal for controlling a bus arbitration signal (arbitration signal) is transmitted in addition to a packet including data such as video and audio. Therefore, it becomes necessary to secure full-duplex communication.
[0089]
In addition, IEEE 1394. The bus management signals such as PARENT_NOTIFY and CHILD_NOTIFY are continuously transmitted and received even when communication is performed by performing nBmB code conversion (n and m are integers), respectively, in the bus state defined in the IEEE 1394-1995 standard, not limited to the b standard. It must be.
[0090]
However, even when this bus management signal is converted into transmission light and transmitted, it is considered that the bus management signal in the transmission light interferes with the reception light. Interference caused by management signals is prevented.
[0091]
FIG. 8 is a diagram illustrating a block configuration of an optical module according to the third embodiment.
[0092]
The bus management signal discriminating circuit 10 is a circuit that discriminates whether or not an input signal to the optical module is a bus management signal and gives the discrimination result to the reclocking circuit 8. The intermittent idle extraction circuit 11 is a circuit that receives a signal output from the AGC amplifier 5 via the carrier sense circuit 9 and monitors whether this is an intermittent signal. The intermittent idle extraction circuit 11 provides the monitoring result of whether or not the signal is an intermittent signal together with the input signal to the pre-state holding circuit 12 described later. The previous state holding circuit 12 is a hold circuit that holds the state of the input data signal, and outputs the held signal to the signal processing circuit 7. The configuration other than these circuits is the same as that of the second embodiment.
[0093]
First, the transmission process in the third embodiment will be described with reference to FIG.
[0094]
When the bus management signal discriminating circuit 10 detects one code of the PARENT_NOTIFY (hatched portion) which is a bus management signal, the preamble adding circuit 1 extracts the 10B code for the one code and adds a predetermined preamble thereto. To do. The intermittent signal generation circuit 2 adds an intermittent signal after the 10B code and outputs it to the drive circuit 3. The drive circuit 3 converts this signal into an optical signal and transmits transmission light. Thereafter, if there is no change in the state of the input signal, the intermittent signal is continuously transmitted.
[0095]
As described at the beginning, a postamble may be added in addition to the preamble.
[0096]
When the state of the input signal changes and the bus management signal discriminating circuit 10 detects one code of another bus management signal CHILD_NOTIFY, the 10B code (first bus management signal) for this one code is also the same as PARENT_NOTIFY. Signal processing is performed, and an intermittent signal is transmitted following the first management signal CHILD_NOTIFY.
[0097]
Next, reception processing in the third embodiment will be described.
[0098]
The intermittent idle extraction circuit 10 continuously determines whether or not the signal from the carrier sense circuit 9 is an intermittent signal, and supplies the result to the previous state holding circuit 12.
[0099]
As shown in FIG. 9, the previous state holding circuit 12 outputs the signal to the signal processing circuit 7 while holding the state of the bus management signal immediately before the intermittent signal. The signal processing circuit 7 processes the input signal and outputs it as an output signal, as in the first or second embodiment.
[0100]
Therefore, according to the third embodiment, the intermittent signal generation circuit 2 and the bus management signal discriminating circuit 10 maintain the function of the control signal (bus management signal) included in the transmission light, and the subsequent part of the control signal. By using intermittent intermittent information signals, interference of the transmitted light with the received light can be prevented even during the transmission period of the predetermined control information in the transmitted light.
[0101]
In the third embodiment, only the first 10B code is extracted. However, the reliability of wireless transmission is improved by extracting two or more codes and including them in the transmission light. In addition, when the same bus management signal is repeatedly input as well as when the state of the input signal changes, the bus management signal is transmitted as transmission light at an arbitrary timing (for example, at a constant cycle). It may be.
[0102]
In the first to third embodiments, the electrical signal and the output signal input to the optical module are IEEE1394. Although described as being based on the b standard, the IEEE 1394-1995 standard or the IEEE 1394. a signal based on the IEEE standard IEEE 1394. By providing a conversion processing unit that converts the signal into a signal based on the b standard and outputs the signal to the transmission unit, and an inverse conversion processing unit that performs an inverse conversion for the conversion on the output signal output from the reception unit, It becomes possible to handle electrical signals based on the standard.
[0103]
Next, a fourth embodiment will be described.
[0104]
[Whole block configuration of wireless module]
FIG. 12 is an overall block diagram of the wireless module.
[0105]
The wireless module (WM) consists of a half-duplex controller, a selector: selector for switching signals between IEEE1394 and another protocol, and an optical analog transceiver. ing.
[0106]
The optical analog transceiver has an LED driver with a transfer speed of 125 Mbps, a receiver amplifier, and a comparator function. The serial data signal switched by the selector is used as an optical wireless communication signal. The selector switching determination is performed by a control unit that monitors the intermittent idle signal.
[0107]
[Optical packet]
FIG. 13 is a configuration diagram of an optical packet.
[0108]
The optical packet has a configuration in which a preamble, a flag, and a postamble are added so as to completely comply with the IEEE1394b standard.
[0109]
The length of the preamble depends on the clock recovery performance of the receiving side that recovers the clock from the serial data.
[0110]
However, since the length of the preamble directly affects the data delay, a certain restriction is provided so that the transmission delay time falls within a certain period predetermined for 1394.
[0111]
If it is necessary to increase the preamble length, it is necessary to increase the value of the gap count variable defined in 1394.
[0112]
Preamble, flag, and postamble are also added in units of 10B. The Preamble code pattern uses the “10101_01010” pattern with many [1] [0] transitions to encourage fast-attack clock recovery, and the FLAG is K28.5 (comma code) or p1394.b. Use an unused INVALID pattern. The receiver can extract the necessary DATA by detecting the FLAG immediately after the preamble, and can know the END of the DATA by the second FLAG.
[0113]
FIG. 14A is a diagram illustrating an example of transmission of a request code, and FIG. 14B is a diagram illustrating an example of isochronous and asynchronous data packets. It is embedded as one optical packet during the data period.
[0114]
FIG. 15 shows p1394. It is a figure which shows the packet example used as a Running Disparity countermeasure prescribed | regulated by b. If an error occurs due to RD mismatch, the data received immediately after the first FLAG is likely to be lost. Therefore, it is desirable to add the request code and control code sent last time as dummy data immediately after the first FLAG. Even if an RD error occurs, the lost data can be dummy data.
[0115]
[Intermittent IDLE]
After reset, optical link
Intermittent idle signals are inserted for optical link establishment after reset, confirmation of light shielding, and communication protocol negotiation.
[0116]
FIG. 16 is a block diagram of a half-duplex control logic unit for inserting an intermittent idle signal. When the intermittent idle signal is not detected, the mode is switched to another protocol, for example, IrDA mode.
[0117]
When an intermittent idle signal is not observed, it is possible to control to prompt a bus reset.
[0118]
[Half duplex protocol]
The adoption of the half-duplex protocol aims to avoid the influence of reflected light from surrounding obstacles in optical radio. When performing light emission / reception with a single wavelength / wide directional angle, the optical signal requires serial data that can reproduce the clock component on the receiving side, and therefore, the 8B / 10B code defined by IEEE1394.b is used. However, since p1394.b is a full-duplex communication that performs BOSS mode arbitration, in this paper, only the 8B / 10B coding technology is referred to in the function of the p1394.b PHY. This is hereinafter referred to as IR-MODE.
[0119]
In IEEE1394-1995 and p1394.a, most of the time is arbitration is full-duplex communication with the same request and control code repeated, and data transfer is only in one direction. Therefore, by deleting redundant control codes and request codes sent in full-duplex communication, communication is made free and half-duplex is realized by communicating alternately.
[0120]
When the intermittent IDLE is detected by the Negotiator, the B-PHY is operated in Ir-Mode. On the other hand, if the intermittent IDLE is not detected, the B-PHY can be operated in a full-duplex operation fully compliant with 1394.b and 1394.b communication can be used by another PMD. Negotiator also has support for initializing root contention.
[0121]
The transmission system detects the control code and request code, and monitors the output of the beta port operating in Ir-Mode. When the bus state changes, optical packet data is generated by adding a preamble, FLAG, and postamble. When there is optical packet data, it becomes optical transmission data by the analog unit, but if there is no data to be transmitted, an intermittent IDLE is transmitted.
[0122]
The receiving system includes a carrier sense circuit that determines whether data is received from a communication partner. A clock recovery unit generates a synchronous clock from the serial data. The data from which the preamble, postamble, and FLAG are removed is temporarily stored in the FIFO for resynchronization. The data stored in the FIFO is read until it becomes Empty, and the last received request code and control code are held and repeated. However, if it is a request code, the value obtained by switching the 10B code is repeated according to the value of Running Disparity.
[0123]
Until a new 10B code is received, the last received 10B code indicating the valid bus management state is held. And it behaves as if it is always receiving on the optical transmission line. No repeat code is sent to establish half-duplex control.
[0124]
FIG. 17 is a sequence diagram between wireless modules incorporating a one-to-one optical wireless module.
[0125]
If there is no change in the bus state, Intermittent IDLE is exchanged between the Optical Modules. CH1 is an optical wireless module for PHY_A. PHY_A and PHY_B function as p1394.b PHY in the optical wireless mode.
[0126]
CH2 is an optical wireless module for PHY_B. An optical connection is made between CH1 and CH2. Both CH1 and CH2 perform carrier sense before transmission.
[0127]
When PHY_A outputs "NONE_EVEN" request code, CH1 checks whether carrier sense is inactive.
[0128]
If the carrier sense is active, CH1 suspends the transmission of the optical packet until the carrier sense becomes active.
[0129]
In the case of no carrier sense, CH1 starts transmitting an optical packet including a NONE_EVEN code.
[0130]
When the NONE_EVEN code is correctly received on the CH2 side, the code is retained and repeatedly transmitted to PHY_B.
[0131]
Similarly, when PHY_B transmits a NONE_EVEN code and detects that CH2 is no-carrier sense, the NONE_EVEN code is transmitted from CH2 to PHY_A through CH1.
[0132]
If there is no change on the Tx data line of the p1394.b PHY block, the intermittent idle signal has been exchanged (transmitted in both directions) between the two modules. .
[0133]
Regardless of whether it is isochronous or asynchronous, signal transmission is performed according to this procedure.
[0134]
First, when “Legacy_Request” is transmitted from PHY_A, CH1 confirms that carrier sense is OFF, then creates an optical packet including legacy_request and transmits it to PHY_B via CH2. Subsequently, when the Grant signal is output from PHY_B, it is transmitted from CH2 to CH1 and then transmitted to PHY_A.
[0135]
PHY_A starts DATA transmission with DATA_PREFIX after receiving Grant. When CH1 receives DATA_PREFIX (control code) from PHY_A, CH1 stops transmitting the GRANT output to PHY_A and transmits NONE_EVEN indicating IDLE to PHY_A. This is because, when DATA_PREFIX is transmitted to PHY_B on the CH2 side, PHY_B outputs NONE_EVEN, but since CH1 is in the Data period, CH2 cannot transmit NONE_EVEN to CH1 over a long period of time. Not only CH1, but CH2 has the same function.
[0136]
In particular, during the DATA period, even if the bus state of the p1394.b PHY changes, it is difficult to properly notify the bus state if half duplex is used. Therefore, CH1 outputs in advance to PHY_A without receiving a NONE_EVEN code indicating IDLE from CH2.
[0137]
Thus, even when the PHY_B bus state changes during the DATA period, it is possible to transmit and receive DATA correctly.
[0138]
Therefore, according to the fourth embodiment, the following effects can be obtained.
[0139]
1) IEEE1394 optical transmission by the half-duplex method and light emission time can be reduced, so that a small and power-saving optical module that can be incorporated into a portable terminal can be configured.
[0140]
2) Since a plurality of protocols can be automatically switched by negotiation using an intermittent idle signal, the protocol of the communication partner can be selected without the user being aware of it.
[0141]
3) A transceiver IC for high-speed optical wireless can be developed, and a transceiver IC equipped with a 125Mbps LED driver and receiver can be developed.
[0142]
Further, the present invention can be applied not only in one-to-one communication as in the above-described embodiment, but also in an environment such as a wireless LAN.
[0143]
Further, values such as frequency, pulse width, or phase are not limited to the values in the above embodiment, and can be arbitrarily set as necessary.
[0144]
【The invention's effect】
As described above, according to the present invention, when the communication state is maintained by the no-information signal, the no-information signal is intermittently transmitted, thereby maintaining the communication state and transmitting itself to the received light. Since light interference can be prevented, wireless transmission of an optical signal can be performed even in an environment where sufficient isolation between transmission light and reception light cannot be ensured.
[Brief description of the drawings]
FIG. 1 (a) is a block diagram of an optical module to which the present invention of the first embodiment is applied, and FIG. 1 (b) is a diagram showing an example of mounting of the optical module.
FIG. 2 is a timing chart of intermittent signals in the form shown in FIG.
3 is a timing chart for explaining processing at the time of packet transmission in the embodiment shown in FIG. 1; FIG.
FIG. 4 is a block configuration diagram of an optical module to which the present invention of the second embodiment is applied.
5 is a timing chart of intermittent signals when a link is not established in the embodiment shown in FIG.
6 is a timing chart relating to processing up to link establishment in the embodiment shown in FIG. 4;
7 is a timing chart relating to processing at the time of packet transmission in the form shown in FIG. 4; FIG.
FIG. 8 is a block diagram of an optical module to which the present invention of the third embodiment is applied.
FIG. 9 is a diagram for explaining a processing process of a bus management signal in the form shown in FIG. 8;
FIG. 10 shows IEEE1394. It is a figure which shows the transmission form of the signal prescribed | regulated by b standard.
FIG. 11 is an apparatus diagram to which a conventional optical wireless transmission method is applied.
FIG. 12 is an overall block configuration diagram of a wireless module.
FIG. 13 is a configuration diagram of an optical packet.
14A is a diagram illustrating an example of transmission of a request code, and FIG. 14B is a diagram illustrating an example of isochronous and asynchronous data packets.
FIG. 15: p1394. It is a figure which shows the packet example used as a Running Disparity countermeasure prescribed | regulated by b.
FIG. 16 is a block diagram of a half-duplex control logic unit for inserting an intermittent idle signal.
FIG. 17 is a sequence diagram between wireless modules incorporating a one-to-one optical wireless module.
[Explanation of symbols]
1 Preamble addition circuit
2 Intermittent signal generation circuit
3 Drive circuit
4 Light receiving circuit
5 AGC amplifier
6 Clock recovery circuit
7 Signal processing circuit
8 Reclocking circuit
9 Carrier sense circuit
10 Bus management signal discrimination circuit
11 Intermittent idle extraction circuit
12 Previous state holding circuit

Claims (8)

Using two devices having a light emitting element for transmitting an optical signal and a light receiving element disposed close to the light emitting element to receive the optical signal, the optical signal transmitted from the light emitting element of one device is used as the other device. By receiving with the light receiving element of IEEE1394. b is an optical wireless transmission method in an optical wireless transmission system in which communication based on the b standard is performed and the communication state is maintained by a no-information signal received by the light receiving element of the one device ,
An optical wireless transmission method, wherein the light emitting element of the other device intermittently transmits the no-information signal to the light receiving element of the one device . Using two devices having a light emitting element for transmitting an optical signal and a light receiving element disposed close to the light emitting element to receive the optical signal, the optical signal transmitted from the light emitting element of one device is used as the other device. By receiving with the light receiving element of IEEE1394. An optical wireless transmission system that performs communication based on the b standard ,
The one apparatus includes intermittent transmission means for intermittently transmitting a no-information signal,
The other apparatus includes a communication state maintaining means for maintaining a communication state by the intermittently transmitted no-information signal. Using two devices having a light emitting element for transmitting an optical signal and a light receiving element disposed close to the light emitting element to receive the optical signal, the optical signal transmitted from the light emitting element of one device is used as the other device. By receiving with the light receiving element of IEEE1394. The optical wireless transmission device is applied to the other device in the optical wireless transmission system that performs communication based on the b standard and maintains the communication state by an information-free signal received by the light receiving element of the one device. And
An optical wireless transmission device comprising intermittent transmission means for intermittently transmitting the non-information signal. 4. The optical wireless transmission apparatus according to claim 3 , wherein the intermittent transmission means transmits the informationless signal transmitted intermittently at random. The optical wireless transmission device according to claim 3 or 4 , wherein the intermittent transmission means is configured to be able to adjust an on / off ratio of the non-information signal transmitted intermittently. The intermittent transmission means, an optical wireless transmission device according to any one of claims 3 to 5, characterized in that stops in response to transmission of the non-information signals transmitted said intermittently in communication conditions. The intermittent transmission means relates to the communication, repeating successive portions of the control signal input of the claims 3 to 6, characterized in that into a no-information signal to be transmitted the intermittently The optical wireless transmission device according to any one of the above. Using two devices having a light emitting element for transmitting an optical signal and a light receiving element disposed close to the light emitting element to receive the optical signal, the optical signal transmitted from the light emitting element of one device is used as the other device. By receiving with the light receiving element of IEEE1394. an optical wireless receiver applied to the other device in the optical wireless transmission system that performs communication based on the b standard and the light emitting element of the one device intermittently transmits a no-information signal,
Optical wireless receiver characterized by comprising a communication state maintaining means for maintaining a communication state by the intermittent no-information signal.

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