JP4091022B2 - Wireless communication terminal - Google Patents

Description

  The present invention relates to a wireless communication terminal used in an ad hoc network.

  With the development of the information society, the number of communication means that can be used in familiar situations has increased dramatically. In conventional wireless communication, there are base stations that control and manage the entire communication, such as mobile phones and wireless LANs, and many of them communicate with base stations in the form of wireless terminals. Wireless communication terminals that communicate with each other in an equal relationship include, for example, fixed wireless for trunk communication, amateur wireless, and low-power wireless using a transceiver. The fixed radio for main line communication is one in which base stations communicate with each other on a one-to-one basis. On the other hand, communication by amateur radio or transceiver is often used on a one-to-one basis, but these radio waves can be picked up by anyone who has a terminal and is basically there. N-to-n communication that anyone can participate in. These are used by dividing the same frequency band according to human judgment, or by dividing the space without permission because the range of effective radio waves is limited when the power is low.

  In this way, a network that does not have a fixed base station, center, or the like and is appropriately assembled on the spot among a plurality of terminals gathered on the spot is called an ad hoc network (see Non-Patent Document 1).

  The above is a primitive method in which control is performed with human hands and heads, but there is also a system in which an ad hoc network is automatically formed by an IC built in a wireless terminal by creating a protocol. For example, Bluetooth (registered trademark) has an ability to form an ad hoc network.

  These wireless communication terminals have a built-in IC for MAC (Media Access Protocol), start communication according to a procedure corresponding to the protocol, and end the communication. In many of such ad hoc communication protocols, a parent terminal is determined within a group of terminals that perform communication in a network, and the parent terminal determines various parameters and controls communication.

By the way, most of such ad hoc networks are formed by wireless communication terminals that are easily used in small areas such as offices and homes. In advanced information devices such as personal computers, the user pays attention to power management, so communication is rarely lost due to a sudden power shutdown. However, when an ad hoc wireless communication terminal is built in a household electrical appliance used at home, the user treats it as a household electrical appliance, so the power supply is suddenly stopped without following the correct procedure for shutting down the power supply. It is possible to make it. When such an unexpected power cut-off occurs, the incorporated wireless communication terminal stops without following the correct communication termination procedure. In general, a wireless terminal used for mobile communication creates a protocol on the assumption that the communication environment is unexpectedly disabled due to deterioration of the radio wave environment or movement of the terminal. In other words, the protocol describes how to deal with a case where communication with a certain terminal cannot be performed suddenly. Therefore, it is almost impossible that communication between terminals other than the terminal becomes impossible due to sudden disappearance of the terminal and cannot be recovered.
Johnson, DB, “Routing in ad hoc networks of mobile hosts”, Mobile Computing Systems and Applications, 1994. Proceedings., Workshop on, 8-9 Dec. 1994, Pages: 158-163

  As described above, when one of the terminals disappears in wireless communication, a protocol that assumes such a state is usually implemented, so that a big problem does not often occur. However, some confusion is inevitable due to the sudden disappearance of the terminal. The degree of confusion depends on what role the terminal played in the network. If it is a simple terminal, the communication partner only needs to be troubled. However, in the ad hoc network, if the terminal that has assumed the role of the parent suddenly disappears, the entire ad hoc network will be temporarily confused. Naturally, since the procedure for recovering from confusion is described in the protocol, recovery may be performed according to the procedure.

  However, recent wireless communication is highly functional, and temporary confusion, for example, streaming video data, may cause unacceptable degradation of communication quality. If there is a power failure of the streaming device itself, the user will also be praised, but the video will be displayed to the user due to the power failure of the parent device that does not seem to be directly related to the communicating device. It's hard to convince me to stop or disturb for a few seconds. Furthermore, in the case of an ad hoc network, the parent is not determined by the user, but in most cases, it is determined arbitrarily by negotiation between terminals. Which is the parent cannot be determined by the user, and thus the power may be turned off without knowing it.

  On the other hand, since ad hoc networks are disassembled when assembled on the spot, a plurality of ad hoc networks of the same standard may be in the same place for the same time. When the number of such networks increases, the limited wireless channels used for wireless communication cannot be supported while maintaining the independence of all ad hoc networks.

  In preparation for such cases, most ad hoc protocols use the same channel in a time-sharing manner to support multiple ad hoc networks. In that case, a parent-child relationship is formed between a plurality of ad hoc networks, and one of them becomes a parent network to manage the channel. In such a case, the parent terminal of the parent network is very large. If a power failure occurs in the parent terminal of the parent network, not only the parent network but all other child networks are temporarily confused. .

  The present invention has been made in view of such circumstances, and provides a wireless communication terminal capable of minimizing confusion when a power failure occurs in a wireless communication terminal serving as a parent terminal The purpose is to do.

  In order to solve such a problem, a first aspect of the present invention is a wireless communication terminal for connecting to an ad hoc network, in which a message storage area, an energy storage unit, and the wireless communication terminal are connected to an ad hoc network. After becoming a parent terminal, a means for creating the latest shutdown message and storing it in the message storage area, a disconnection detecting means for detecting disconnection of the main power supplied to the wireless communication terminal, and the disconnection detecting means, In response to detecting that the power supply from the main power supply has been cut off unexpectedly, the shutdown message stored in the message storage area is transmitted using the energy stored in the energy storage unit. And a message sending means.

  According to the first aspect described above, when an ad hoc network becomes a parent, the terminal is always provided with an area for creating and storing the latest shutdown message as the parent. And it has a mechanism for storing energy, such as a capacitor with an appropriate capacity, and even if the main power supply is cut off due to unplugging the power plug, the amount necessary to properly send the shutdown message is stored . Further, the terminal is provided with a disconnection detection function for detecting that the main power supply is unexpectedly disconnected. When the disconnection detection function detects the disconnection of the main power supply, the shutdown message is transmitted using the energy (voltage, current, etc.) stored in the energy storage unit. That is, a procedure for sending a shutdown message at the same time as driving a part necessary for sending a shutdown message with the voltage and current stored in the energy storage unit.

  The shutdown message as a parent is a message to notify the network when the terminal quits its role as the parent terminal. The specific contents differ depending on each protocol, but the terminal leaves the parent and, in some cases, terminates the operation of the terminal itself, the nomination of the parent terminal, or the ad hoc network changes the parent / child. If it is made, the nomination of the next parent network is entered. By transmitting this to the network, a terminal other than the parent or a terminal of the child network can detect that the parent shuts down. Further, depending on the content of the shutdown message, it is possible to detect which terminal (or which network) takes over after that. Therefore, unlike the prior art, there is no blank time until it is determined that it is certain that there is no parent after the absence of the parent, and confusion between them is avoided. Furthermore, if a terminal (or network) that succeeds the terminal is designated, if the terminal (or network) can succeed it, the state of the network can be quickly recovered by becoming the parent.

  According to a second aspect of the present invention, the message sending unit includes an analog unit that converts the encoded data into a prescribed radio wave form, and the analog unit includes: The power storage unit supplies power only to a part necessary for sending out the shutdown message.

  According to the second aspect, the energy storage unit operates to drive only the minimum necessary part when sending the shutdown message, and does not supply power to the other parts. In order to take out the shutdown message from the message storage area and send it out, it is necessary to use the analog part of the transmitter in the terminal. The transmission unit includes a digital unit that performs a data encoding process and an analog unit that converts the data into an appropriate radio wave form. If the shutdown message to be stored is as close to the final form as possible, the digital unit will be unnecessary when sending the shutdown message. Only the analog part can receive the energy supply. Since it is difficult to save an analog signal in the same form as a radio wave with the current technology, it is necessary to survive an analog part for converting it into a radio wave form and transmitting it. However, the power supply is stopped in the analog part that is not necessary for sending the shutdown message. Further, a portion that can be stopped by fixing the parameter, for example, a power control unit of the power control unit is also stopped.

  Next, in a third aspect of the present invention, the wireless communication terminal further includes means for detecting a timing at which signal transmission is permitted to the wireless communication terminal, and the disconnection detecting means detects the power supply disconnection. Until the timing is reached, control for stopping the start of the shutdown message transmission process in the analog portion is performed.

  In ad hoc networks, when multiple terminals perform transmission in time division, there are many forms in which the position within each frame that can be transmitted by each terminal is determined, so the main power supply of the parent terminal stops unexpectedly and a shutdown message Even if the frame position is not allowed to be transmitted to the parent terminal even if it is sent, it will not be received due to interference with the transmission of other terminals, or it is not ready to receive to other terminals, It may not be received or may not be regarded as a correct transmission and ignored by the receiving terminal. Therefore, according to the third aspect of the present invention described above, transmission is performed after waiting for transmission of the shutdown message to the correct transmission frame position. The main power-off detection function includes a counter, and the frame timing is always taught. When power-off is detected, the main power-off detection function counts down to the next transmittable frame position. When the analog unit receives a power-off notification from the disconnection detection function, it first stops the power supply except for the essential part, and starts sleeping for the essential part. When the counter indicates that the next transmittable frame position has been approached, the break detection function wakes up the analog portion from sleep. When the counter indicates that the next transmittable frame position is reached, the shutdown message is taken out from the storage unit, sent to the analog unit, and radiated as a radio wave.

  By doing in this way, it becomes possible to transmit a shutdown message at a correct timing that can be transmitted with a finite amount of energy provided in the energy storage unit.

  Next, a fourth aspect of the present invention is characterized in that a capacitor is used as the energy storage unit.

  If a large amount of energy is stored in the energy storage unit, it is possible to continue operating the entire terminal until a shutdown message is sent using, for example, a battery, and thus it is also possible to end by following the proper shutdown procedure. . However, increasing the energy stored in the energy storage unit is not desirable because the entire terminal becomes larger. Therefore, by making the energy storage unit as small as possible by using the present invention, it is possible to prevent the terminal from being enlarged due to the function of the present invention.

  As described above, according to the present invention, a shutdown message can be sent even when the main power supply of the terminal that became the parent of the ad hoc network is unexpectedly disconnected. As a result, the parent terminal suddenly leaves the network. By doing so, it is possible to minimize the confusion of the ad hoc network.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing the first embodiment. The figure shows only the main parts related to the present invention inside the terminal 1 for ad hoc wireless communication. In the figure, lines related to power supply are indicated by bold lines, lines related to transmission of control signals are indicated by broken lines, and lines related to movement of signals and messages are indicated by solid lines.

  A main power supply line 4 from a main power supply (not shown) supplied from a device or the like to which the terminal 1 is connected is branched, and the transmission unit 2 and the energy storage unit 5, which are the main parts of transmission processing in communication, are disconnected. Input to the detector 3.

  The transmission unit 2 includes a digital unit 8 and an analog unit 9, and performs transmission processing. The power source input to the transmission unit 2 is used for normal transmission processing.

  The energy storage unit 5 is obtained by adding a simple control mechanism for sending energy in a necessary direction when necessary to a simple energy storage mechanism such as a capacitor.

  The power-off detector 3 monitors whether the main power is not cut off. The power-off detection unit 3 may be driven by the main power supply or may be driven by the energy storage unit 5. In the case of being driven from a normal main power supply, a mechanism is provided that immediately switches to the supply from the energy storage unit 5 when a main power supply disconnection is detected. When the energy storage unit 5 supplies power, the energy storage unit 5 is configured to always replenish the released energy from the main power source.

  The data input to the transmission unit 2 is subjected to encoding processing according to the wireless system such as packetization, encoding, and interleaving in the digital unit 8 and is sent to the analog unit 9. The analog unit 9 puts this on a carrier and radiates it from the antenna 10 by appropriately amplifying and band filtering. When a D / A converter is inserted between the analog unit 9 and the digital unit 8, the D / A converter is included in the analog unit 9. The analog unit 9 includes a clock generation unit (not shown). Alternatively, the clock generation unit is in another part and the analog unit receives the clock supply from it, and when the power is turned off, a clock holding mechanism for holding the clock until the worst shutdown message is transmitted is provided. The analog part includes.

  When the terminal 1 becomes the parent terminal of the ad hoc network, the latest shutdown message is always stored in the shutdown message storage area 6. Specifically, the content of the shutdown message is received from the data input 7, and all necessary processing is performed by the digital unit 8 and then stored in the storage area 6. For example, if the entrance of the analog unit 9 is a D / A converter, a shutdown message in a state where only D / A conversion is performed is stored. Re-save each time the shutdown message changes due to changes in the network or terminal configuration. If a time stamp or serial number is required for the transmission packet, a value at the next transmission timing is stored for each frame and stored.

  In FIG. 1, the shutdown message storage area 6 operates by receiving power supply from the energy storage unit 5. Of course, it is also possible to normally receive the supply from the main power supply and supply it from the energy storage unit 5 after disconnecting. Alternatively, a memory such as a flash memory that does not require a power supply for holding data is used, and a data writing unit (digital unit 8 in the present invention) or a data reading unit (analog unit 9, depending on the configuration, the power interruption detection unit 3). ) You can turn on the power. The shutdown message storage area 6 is desirably independent of other memories in the terminal at least in terms of power system. If possible, it should be an area independent of other memories.

  When the main power supply is cut in this state, the power cut detection unit 3 first detects it. When the power-off detection unit 3 is mainly supplied with power from the main power source, the power-off detection unit 3 switches to power supply from the energy storage unit 5. When the structure of the energy storage unit 5 does not normally release energy, but only when the power is turned off, the power-off detection unit 3 instructs the energy storage unit 5 to start releasing the energy. It is desirable to create a mechanism with a simple analog electric circuit so that the discharge instruction is issued at the same time as the power-off detection. If the energy storage unit 5 is a capacitor to which a diode for determining the emission direction is added, the capacitor is released without any need. In the case where the energy storage unit 5 is a capacitor, the voltage decreases unless energy is released and supplemented. Therefore, when the energy storage unit is configured in such a manner that a simple control circuit is attached to the capacitor, the part that is driven by the energy storage unit 5 when the power is turned off operates even if the power supply voltage is somewhat lowered. It is configured or stored at a slightly higher voltage when energy is stored in the energy storage unit 5. In either case, a configuration in which a slight change in the power supply voltage can be allowed in the driven portion is provided.

  Further, if the terminal 1 needs both positive and negative power supplies, and both are also required when sending a shutdown message, the energy storage unit 5 shall correspond to both. When the current direction is determined by a diode or the like, two positive and negative capacitors are built in each.

  The power-off detection unit 3 that has detected the power-off notifies the analog unit 9 to switch the power supply system from the main power source to the energy storage unit 5 and to disconnect the parts other than those essential for the shutdown message. Switching the system and separating the necessary part may be performed by an independent mechanism, and the circuit is configured in advance so that the wiring of the power supply line from the energy storage unit 5 is not connected to other than the essential part. The power supply system may be switched. The analog part that survives, that is, the part that is essential for sending the shutdown message, has a minimum configuration, for example, the part that controls the parameter such as power control determines the parameter at the time of power off beforehand or remembers it as a fixed value, It is good to separate the part which calculates a parameter, instruct | indicates, and applies a feedback to a parameter.

  In addition, even when the power is cut off, the digital unit 8 may output a signal slightly with the energy remaining in the circuit or the peripheral circuit. In this case, since the output data may no longer be correct due to the influence of the power supply voltage decrease, the analog unit 9 may block the signal input from the digital unit 8 when the power-off is notified. The simplest method is to switch the input of the analog unit 9 from the output of the digital unit 8 to the output of a shutdown message.

  The power-off detector 3 sends a shutdown message from the shutdown message storage area 6 to the analog unit 9. Alternatively, when the analog unit 9 is notified of power-off, the shutdown message is retrieved from the shutdown message storage area 6. The analog part 9 that has survived is converted into an appropriate radio wave shape, sent to the antenna 10, and radiated as a radio wave.

  By doing so, a shutdown message can be sent even if the power is cut off, and the remaining network disruption can be quickly collected.

  Of course, a shutdown message may be issued using this mechanism when the power is unexpectedly cut off even when the terminal is not the parent terminal.

(Second Embodiment)
As another configuration, a configuration as shown in FIG. 2 is also possible. 2 is significantly different from FIG. 1 in that the energy storage unit 11 is inserted into the main power supply system. That is, the energy storage unit 11 is a bypass capacitor of the main power supply, and the terminal 1 is constantly supplied with power through this. The energy storage unit 11 is protected by a diode or the like so that current does not flow backward in the direction of the main power supply when the main power supply is cut off. A power system switching unit 12 is connected to the output of the energy storage unit 11, and the output is switched between normal times and when the power is cut off.

  In normal times, the output of the energy storage unit 11 is connected to a terminal wired so as to reach all parts of the terminal 1. The main power supply is branched and input from the front of the energy storage unit 11 to the power-off detector 3 so that it can be detected immediately when the main power is cut off.

  The power system switching unit 12 is controlled by the power-off detection unit 3, and when the power-off is detected, the output of the energy storage unit 11 is switched to the system at the time of power-off. The system when the power is cut off supplies power only to the minimum part necessary for sending a shutdown message. Therefore, as in the case of FIG. 1, the operation of the analog unit 8 receiving the power-off notification and disconnecting an unnecessary part from the power source is unnecessary. This is because the power-off detection unit 3 is effectively operated by the power system switching unit 12. Is achieved by controlling. Other operations are the same as those in FIG. 1, and the shutdown message is taken out from the storage area 6 and transmitted using the surviving portion of the analog portion 9, that is, the portion essential for transmitting the shutdown message. Note that the portion of blocking the input from the digital unit 8 so as not to receive illegal data from the digital unit 8 is not achieved by the operation of the power system switching unit 12, and therefore the analog unit 9 as in FIG. Do.

(Third embodiment)
FIG. 3 shows an embodiment including a mechanism for sending a shutdown message after the next transmission timing when the timing in the frame transmitted by the parent terminal is predetermined. Although the configuration shown in FIG. 2 is used as a matter of course, a similar mechanism may be added to the configuration shown in FIG. FIG. 4 shows the configuration of the power-off detection unit 3 in that case.

  In FIG. 4, the power cut-off detection unit 3 mainly includes a cut-off detection circuit 16 that detects cut-off of the main power, a control unit 17, and a counter 15. The disconnection detection circuit 16 may be configured by an analog circuit as simple as possible, and it is preferable to detect the disconnection of the main power supply and notify the control unit 17 of it. The control unit 17 is a part that performs the main operation of the power-off detection unit 3, and performs notifications and instructions to other parts at an appropriate timing. The counter 15 is originally built in the control unit 17, but is shown separately in the figure for easy explanation.

  Frame timing is supplied to the power-off detector 3 through a supply line indicated by reference numeral 14. This is supplied from the receiving unit (not shown) in the normal state or from the frame timing generating unit (not shown) because it should have generated the frame timing after it became the parent. Yes. In addition, the terminal has a clock generation unit (not shown), and even if it is included in the analog unit or there is a clock generation unit in another part of the terminal, a shutdown message is sent after the power is turned off. The analog unit 9 has a mechanism capable of holding the clock until the transmission is completed.

  The power-off detection unit 3 receives a clock from the analog unit 9, and receives a frame timing to count in the frame. Of course, the frame length (clock count of one frame) is known in advance. When the frame length is a fixed value and known, the value is stored in advance. In the case of a variable value, it is taught every time it changes from a part that knows the other frame length, such as the digital part 8 or the MAC control part (not shown). Also, the frame position that can be transmitted next as a parent terminal is taught from other parts such as the digital part 8 or the MAC control part, and the value of the corresponding counter is known.

  In order to know the next frame timing, the power-off detector 3 has a counter 15 therein, and when the frame timing is supplied, starts counting down with the frame length as an initial value. This should always be done regardless of the occurrence of power interruption. When the power is not turned off, nothing is done basically just by repeating the counting in the frame. The time when the countdown ends and the time when the next frame timing is supplied should be the same. However, if there is a discrepancy, it is preferable to prioritize the frame timing, reset the counter to the initial value according to the frame timing, and perform the next countdown.

  It should be noted that the location where the frame timing is generated is shown in FIG. 4 as being different from the power-off detector 3. Of course, it does not matter, but when the terminal 1 becomes the parent of the ad hoc network and is in a position to supply the frame timing to the network itself, the frame timing is generated using the counter inside the power-off detection unit 3, and from here You may supply to each part in a terminal.

  In such a configuration, when the main power supply is unexpectedly disconnected, the disconnection detection circuit 16 detects this and notifies the control unit 17 of it. In response to this, the control unit 17 first instructs the power system switching unit 12 to switch the power system. At the same time, the remaining count up to the next transmittable position of the counter is confirmed. If the count remains enough (the part necessary for sending the shutdown message in the analog unit 9 has time to sleep once), the analog unit 9 is notified and the digital unit 8 needs to be disconnected. To make it sleep. Here, “sleeping” refers to stopping / reducing the supply of power while leaving the minimum necessary. If it is completely stopped, it may take a long time to wake up. Therefore, how much power is to be stopped is set by a trade-off between the time required for restart from sleep and the power saving.

  Thereafter, when the count to the next transmittable position is reduced and the remaining time is about the time required for the analog unit 9 to wake up from sleep, the analog unit 9 is notified and the analog unit 9 is woken up. When the counter 15 indicates the next transmittable time, the shutdown message is sent from the shutdown message storage area 6 via the analog unit 9.

  If the analog unit 9 does not have enough counts to sleep once it is detected that the main power supply is cut off, the analog unit 9 is not instructed to sleep. After switching the power supply system, the analog unit 9 is instructed to perform necessary operations, and when the counter 15 indicates that the next transmittable time is reached, the analog unit 9 is caused to send a shutdown message.

  In this way, even if the main power is cut off, the shutdown message can be sent to the frame at the correct timing, and the terminal 1 sends the shutdown message to the parent ad hoc network and then the network is I can leave.

  Although the embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment. For example, the content of the shutdown message is variously modified according to the ad hoc network standard.

The block diagram which shows the 1st Embodiment of this invention. The block diagram which shows the 2nd Embodiment of this invention. The block diagram which shows the 3rd Embodiment of this invention. The figure which shows the specific structure of the power-off detection part for sending out a shutdown message in the correct flame | frame position.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wireless communication terminal 2 ... Transmission part 3 ... Power-off detection part 4 ... Main power supply line 5, 11 ... Energy storage part 6 ... Shutdown message storage area 7 ... Data input supply line 8... Digital section 9... Analog section 10... Antenna 12... Power system switching section 13... Clock supply line 14. ... Disconnection detection circuit 17 ... Control unit

Claims (6)

A wireless communication terminal for connecting to an ad hoc network,
A message storage area;
An energy storage unit;
After the wireless communication terminal becomes a parent terminal of an ad hoc network, a latest shutdown message is created and stored in the message storage area;
Disconnection detecting means for detecting disconnection of the main power supplied to the wireless communication terminal;
The shutdown message stored in the message storage area is stored in the energy storage unit in response to detecting that the power supply from the main power supply has been cut off unexpectedly by the disconnection detection unit. A wireless communication terminal comprising: a message sending means for sending using energy.   The message sending unit includes an analog unit that converts the encoded data into a prescribed radio wave form, and the analog unit sends the shutdown message after the cutoff detecting unit detects a power supply cutoff. 2. The wireless communication terminal according to claim 1, wherein power is supplied from the energy storage unit only to a necessary portion. The wireless communication terminal further includes means for detecting a timing at which signal transmission is permitted, and the interruption detection means detects the power supply supply interruption until the timing is reached. The wireless communication terminal according to claim 1, wherein control for stopping the start of transmission processing of the shutdown message is performed. The wireless communication terminal according to claim 1, wherein a capacitor is used as the energy storage unit. The wireless communication terminal according to claim 1, wherein the shutdown message is a message indicating that the role of the parent terminal is stopped in the ad hoc network to which the terminal belongs. The wireless communication terminal according to claim 1, wherein the shutdown message is a message indicating a terminal that assumes the role of a parent terminal after the terminal stops the role of the parent terminal in the ad hoc network to which the terminal belongs.

Images