JP2014175799A - Radio communication system and radio device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio communication system that is able to obtain excellent throughput even in the case where it uses a channel with transmission restriction in a radio communication system that performs communication by selecting a single-wave channel from a frequency group including a plurality of channels.SOLUTION: A radio communication system is made up of a plurality of radio devices, a packet used for radio communication comprises a preamble region which is repeated multiple times, a single synchronization region, and a single data region. The radio communication system is characterized by comprising: a transmitting unit of one radio device for transmitting a packet; a receiving unit of another radio device for receiving the packet by switching a reception-waiting channel at a period Tlonger than a period Tthat takes to transmit a set of preamble regions; and a control unit of the other radio device that fixes the reception-waiting channel of the receiving unit to a channel at which a preamble region was received and identified.

Description

  The present invention relates to a radio communication system and a radio apparatus, and is suitable for application to a radio communication system that performs communication by selecting one wave channel from a frequency group including a plurality of channels.

  Conventionally, in a wireless communication system including wireless devices used for telecontrol, telemetering, data transmission, etc., frequency bands and outputs that can be used for communication are defined by standards. Further, the center frequency and bandwidth for actual use are also defined as channels.

Some wireless communication systems select one wave from a frequency group including a plurality of channels as channels used for communication between wireless devices.
FIG. 7 shows the operating state of the wireless device in such a wireless communication system. In the wireless communication system of FIG. 7, the frequency group includes three channels of f ₁₀ , f ₁₁ , and f ₁₂ .

  In such a wireless communication system, the receiving wireless device searches for a synchronization code in a packet to be communicated when waiting for reception, and takes the packet data when the synchronization code is found. After the capturing is completed, the reception-side wireless device outputs a response signal (Ack: Acknowledgment), and the transmission-side wireless device retransmits the signal until it receives Ack.

When the retransmission to not receive Ack is, the wireless device on the transmitting side had transmitted the packet switched channels in a frequency group at intervals T ₁₀ is the sum of the time of transmission time and Ack wait packets. Wireless device on the receiving side has to change the channel of the reception waiting at different timings T ₁₁ is also the transmitting side.
Than the interval T ₁₀ the wireless device switches the channel for transmitting the time packet, the wireless device that receives the signal was as towards the interval T ₁₁ for switching the channel is long.

When Figure 7, the wireless device on the transmission side starts the transmission of packets at time t _10. Wireless devices and wireless devices sending and receiving also switch the channel, the channel match at time t _11, the communication is established, transmits the Ack from the receiving side.

  Also, as in the wireless communication system disclosed in Patent Document 1, what is called a multi-hop method in which one or more wireless devices are relayed and a packet is transmitted from a wireless device that is a transmission source to a wireless device that is a destination. is there.

  In the wireless communication system disclosed in Patent Document 1, a transmission source wireless device and a destination wireless device are determined, but a wireless device relaying in the middle is not determined. For this reason, when a plurality of wireless devices are ready for transmission, the performance of the wireless communication system is improved by performing a cooperative operation so that transmission is not performed at the same timing.

  With cooperative operation, when a plurality of wireless devices that are relay stations receive the same packet, a wait time until transfer is set for each wireless device of the relay station so that transmission (transfer) is not performed at the same timing. Is. The length of the wait time is set based on whether or not the wireless device serving as the relay station has transferred when receiving the previous packet, starting from the completion of packet reception.

JP 2010-114852 A

  Various frequency bands can be used in a wireless communication system depending on the standard. However, depending on the frequency band, a transmission restriction that provides a certain transmission pause time after transmitting a signal such as a packet is defined as an operation condition.

FIG. 8 is a diagram illustrating an operation state of the wireless device in the wireless communication system when there is a transmission restriction. Similar to the wireless communication system of FIG. 7, the frequency group includes three-wave channels of f ₁₀ , f ₁₁ , and f ₁₂ .

If there is a transmission suspension time longer than the Ack wait time, setting the transmission time of the packet on the transmission side and the switching time of the channel on the reception side in the same way as when there is no transmission restriction, until communication is established The number of retransmissions increases. Channel at time t ₁₂ when starting the transmission of the packet at time t ₁₀ as in FIG 7 are matched. As described above, the throughput may be significantly reduced due to the transmission pause time on the transmission side.

  In addition, since the multi-hop wireless communication system disclosed in Patent Document 1 provides a wait time for transfer, there is a problem that a decrease in throughput becomes more noticeable as the number of wireless devices to be relayed increases.

  Furthermore, since the cooperative operation used in the multi-hop method starts the wait time based on the packet reception completion time, it will be fully effective if multiple wireless devices do not complete reception with one packet transmission. could not. However, as in the past, when the transmission time of a packet on a certain channel becomes relatively shorter than the reception waiting time per channel, it is difficult for a plurality of wireless devices to receive the packet by one transmission. If the cooperative operation is not realized, a large number of wireless devices communicate with each other, which may increase the traffic and deteriorate the quality of the wireless communication system.

  An object of the present invention is to solve such a problem and to obtain a good throughput even in a radio communication system with transmission limitation.

  In order to achieve the above object, the wireless communication system according to claim 1 is a radio formed by a plurality of wireless devices that perform wireless communication by selecting one wave channel from a frequency group including a plurality of channels. In a communication system, a wireless device includes a transmission unit, a reception unit, and a control unit, and a packet for wireless communication includes a preamble region, a single synchronization region, and a single data region that are repeated a plurality of times, and transmits one packet. The transmission unit of the wireless device, the reception unit of the other wireless device that performs packet reception by switching the channel waiting for reception in a period longer than the period required for one transmission of the front area, and the channel in which the front area was able to determine reception The control unit of the other radio apparatus that fixes the reception waiting channel of the receiving unit is provided.

  The wireless communication system according to claim 2 is the wireless communication system according to claim 1, wherein a pre-packet area of the packet includes a preamble for notifying start of communication and a first synchronization code for starting capturing of the subsequent packet. The packet synchronization area includes a second synchronization code for determining the start of the data area of the packet.

  The wireless device according to claim 3 is a wireless device that performs wireless communication by selecting one wave channel from a frequency group including a plurality of channels. A synchronization area and a single data area are provided, and a transmission unit for transmitting packets is provided.

  According to a fourth aspect of the present invention, in the wireless device according to the third aspect, the pre-packet area of the packet includes a preamble for notifying the start of communication and a first synchronization code for starting the subsequent packet capture. The synchronization area is provided with a second synchronization code for determining the start of the data area of the packet.

  The wireless device according to claim 5 is a wireless device that performs wireless communication by selecting one wave channel from a frequency group including a plurality of channels. A receiving unit that has a synchronization area and a single data area, and that receives a packet by switching a channel waiting for reception in a period longer than the period required for one transmission of the preamble area. A control unit for fixing the reception waiting channel of the receiving unit is provided.

  The wireless device according to claim 6 is the wireless device according to claim 5, wherein the pre-packet area of the packet includes a preamble for notifying start of communication and a first synchronization code for starting capturing of the subsequent packet, The synchronization area is provided with a second synchronization code for determining the start of the data area of the packet.

  The communication method according to claim 7 is a communication method of a wireless communication system formed by a wireless device that performs wireless communication by selecting one wave channel from a frequency group including a plurality of channels, and the preamble repeated a plurality of times. A step of transmitting a packet having a region, a single synchronization region, and a single data region, and a step of receiving a packet by switching a channel waiting for reception in a period longer than a period required for transmission of one preceding region And a step of fixing the reception channel with a channel whose reception area has been determined to be received.

  The communication method according to claim 8 is the communication method according to claim 7, wherein the preamble area of the packet includes a preamble for notifying the start of communication and a first synchronization code for starting the capture of the packet after this, The synchronization area is provided with a second synchronization code for determining the start of the data area of the packet.

By adopting a configuration in which the pre-transmission area of a packet to be transmitted is repeated a plurality of times, it is possible to prevent a decrease in throughput even when a frequency band with a transmission limit is used for communication.
In addition to increasing the length of the packet at the end and repeating the prefix area, it is possible to determine whether the receiving wireless device has received a packet or has received noise.

  In addition, when using the multi-hop method, it is possible to prevent a decrease in throughput and effectively realize cooperative operation.

It is a block diagram of a radio | wireless apparatus. It is a figure which shows a packet structure. It is the figure which showed the operation state of the radio | wireless apparatus in the radio | wireless communications system of this invention. It is a figure showing the flowchart of operation | movement of the radio | wireless apparatus of the receiving side of this invention. It is the figure which showed the concept of the radio communication system of a multihop system. It is the figure which showed the operation state of the radio | wireless apparatus of the radio | wireless communications system of the multihop system of this invention. It is the figure which showed the operation state of the radio | wireless apparatus in the conventional radio | wireless communications system. It is the figure which showed the operation state of the radio | wireless apparatus in a radio | wireless communications system in case there exists the conventional transmission restriction.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings.

  FIG. 1A is a block diagram of a wireless device. The wireless device 1 includes a transmission unit 2, a reception unit 3, a control unit 4, and an interface unit 5. In addition, an antenna 6, a power supply unit 7, and an external device 8 are provided outside the casing of the wireless device 1.

  The transmission unit 2 and the reception unit 3 are configured as a single integrated circuit (IC) including a modulation unit, a power amplification unit, a high frequency amplification unit, and a demodulation unit. The transmission unit 2 and the reception unit 3 may be configured separately. Moreover, the transmission part 2 and the reception part 3 may be comprised by the combination of the element of a single function.

  The control part 4 is comprised centering on the central processing unit (CPU: Central Processing Unit). A ROM (Read Only Memory) and a RAM (Random Access Memory) (not shown) are provided around the CPU. A control program for controlling the control unit 4 is stored in the ROM. The RAM is a temporary storage area necessary for executing the program. The control unit 4 also controls a channel for transmitting a packet and a channel for waiting for reception. The control unit 4 performs control according to the contents of the fetched packet.

  The interface unit 5 is configured to connect to the external device 8. The control unit 4, the ROM, the RAM, and the interface unit 5 may be configured individually or as a single microcomputer.

The antenna 6 is used for packet transmission and reception. Although it is provided outside the casing of the wireless device 1 in the figure, it may be provided inside the casing.
The power supply unit 7 supplies power to the transmission unit, the reception unit, and the control unit. Although the power supply unit is provided outside the casing of the wireless device in the drawing, the power supply unit may be configured inside the casing as a dry battery, a lithium ion battery, or the like.

  An information device may be used as the external device 8. Information equipment includes various sensors such as fire alarms, automatic meter readings such as gas, water, and electricity, various actuators such as valve controllers, and alarm transmitters. Furthermore, a printer that collects and uses information from a plurality of wireless devices in one place by a wireless communication system may be used as an external device.

  FIG. 1B is a diagram illustrating a configuration of the wireless device 10 when the wireless device is used only as a relay station in the wireless communication system without connecting to an external device. The configuration is the same as that of the wireless device 1 in FIG. 1A except that the interface unit and the external device are not provided. The same components as those in FIG. 1A are denoted by the same reference numerals and description thereof is omitted. The control unit 11 is the same as the control unit 4 in FIG. 1A except that the connection with the interface unit is lost.

FIG. 2 is a diagram illustrating a packet structure of the embodiment.
The packet 20 of the present invention refers to the content communicated between wireless devices. The packet 20 includes a front area 21, a synchronization area 22, and a data area 23.

The front area 21 includes a preamble 24 and a first synchronization code 25.
The preamble 24 is a code that notifies the receiving side of the start of communication. The first synchronization code 25 is a code that adjusts the sampling timing of the transmission side and the reception side to synchronize, and can take in the packet 20 after synchronization. When the receiving-side radio apparatus receives the preamble 24 and the first synchronization code 25, it starts fetching packets after the first synchronization code.

By repeating the introductory area 21 a plurality of times, the packet length is increased.
In particular, it is possible to lengthen the packet length by repeating only the preamble 24, but the present invention is more effectively implemented by repeating the first synchronization code 25 together with the preamble 24 so that the preamble 24 and noise can be distinguished. it can.

  The synchronization area 22 includes a second synchronization code 26. The second synchronization code 26 is a code for determining the start of the data area 23. The wireless device on the receiving side discards the data in the received packet 20 until the second synchronization code 26 is received, and takes in the data area 23.

  The data area 23 includes a control data area 27 in which control data such as the type of the packet 20 is described, an identification area 28 indicating the ID of a transmission source or destination wireless device, a message area 29 for inserting a message, and information is accurately transmitted. It is divided into a check area 30 in which CRC (Cyclic Redundancy Check), BCC (Block Check Code) and the like for checking whether or not the check has been completed are stored. In particular, the contents and length of the identification area 28 and the message area 29 differ depending on the type of the packet 20.

FIG. 3 is a diagram showing an operating state of the wireless device in the wireless communication system of the present invention. FIG. 4 is a flowchart showing the operation of the radio apparatus on the receiving side.
In this embodiment, a radio apparatus using a frequency group including three-wave channels f ₁ , f ₂ , and f ₃ is used. The frequency group used in the wireless communication system of the present invention only needs to include two or more channels so that the channels can be switched.

Further, the radio apparatus of this embodiment has the same configuration as the radio apparatus having the configuration shown in FIG. 1, and the packet structure is the same as that of the packet shown in FIG.
In FIG. 3, the packet is transmitted on the channel f ₁ during the period from time t ₁ to time t ₄ . More time taken for the transmission of preamble region one time is T _2, is transmitted 10 times repeatedly during the period from time t ₁ to t _3.

The reception operation of the wireless device will be described with reference to FIG.
The receiving-side radio apparatus sets a predetermined channel and waits for reception (ST100 or ST103 or ST106). If the reception area can receive the pre-order area (ST101, Yes or ST104, Yes or ST107, Yes), the channel is fixed and the packet is captured (ST109). In the case of FIG. 3, the packet starts to be transmitted at channel f ₁ at time t ₁ , the receiving side switches the reception waiting channel at a waiting time T ₁ per channel, and the channel waiting for reception becomes f ₁ at time t ₂ . The sending side and receiving side channels match to receive the prefix area.

When the synchronization area is received (ST110, Yes), the front area until the second synchronization code is received is discarded (ST111), and the data area is taken in (ST112). When the capture of the data area is completed, Ack is transmitted as a response signal (ST113), and the reception process is terminated. For Figure 3, the received packet is complete at time t _4.
In addition, after completion of the reception process, the channel waiting for reception may be released. Further, the wireless device returns to the state of waiting may be switched to the channel of waiting in the waiting time T ₁ of the per channel one wave again.

Without receiving a preamble area (ST 101, No, or ST 104, No, or ST 107, No) when the predetermined time _{T 1} is passed (ST 102, Yes or ST105, Yes or ST 108, Yes), the receiving side of the wireless device receives The waiting channel is switched.

Since that is a long packet length to be transmitted in the present embodiment, the waiting time T ₁ of the per channel one wave on the receiving side of the wireless device can be shortened as compared with the prior art. Specifically, the waiting time T ₁ per channel of the receiving-side radio apparatus may be switched over a time longer than the time T ₂ required for transmission for one preamble area so as to satisfy the condition of (Equation ₁ ). .
Also, the throughput is improved as close to the time T ₂ the waiting time T ₁ of the per channel one wave on the receiving side of the wireless device to transmit the preamble area one time.

Also, parameters of the number m of channels included in the frequency group to be used, the number n of repetitions of the preamble area, the waiting time T ₁ per channel of the reception-side wireless device, and the time T ₂ required for transmission for _one preamble area May be appropriately changed so as to satisfy the conditions of (Equation 2) and (Equation 3) in addition to (Equation 1).

  By satisfying the conditions of (Equation 1), (Equation 2), and (Equation 3), it is possible to receive the preamble area once in all reception waiting channels by transmitting one packet.

  FIG. 5 is a diagram showing the concept of a multi-hop wireless communication system. The wireless communication system includes a wireless device 40 to a wireless device 46. In FIG. 5, the number of wireless devices constituting the wireless communication system is seven, but any number of wireless devices may be included in the wireless communication system of the present invention. Each wireless device will be described as having the same configuration as the wireless device in FIG. 1, but each wireless device may have a different configuration within a feasible range. In addition, each wireless device may exist at a fixed position or move.

The structure of the packet transmitted in the wireless communication system is the same as the packet shown in FIG.
In this embodiment, a radio apparatus using a frequency group including three-wave channels f ₁ , f ₂ , and f ₃ is used. The frequency group used in the wireless communication system of the present invention only needs to include two or more channels so that the channels can be switched.

  FIG. 6 is a diagram illustrating a communication state of each wireless device in a multi-hop wireless communication system. The description will be made on the assumption that the wireless device 40 shown in FIG. 5 transmits a packet and the wireless device 41 and the wireless device 42 are in a reception waiting state.

The wireless device 40 starts transmitting the packet on the channel f ₁ at time t5. Find wireless device 41 and the wireless device 42 and the preamble 24 of the preamble area 21 while switching the reception standby channel respectively at time T ₃ the first synchronization code 25.
The packet to be transmitted by the wireless device 40 takes time for transmission of preamble region one time T _4, is repeated eight times prelude region until the time t _7.

Wireless device 41 receives the preamble and the first synchronization code channels f ₁ of the transmission channel f _1, waits to receive the packets at time t ₅ coincides, by fixing the channel waiting to f _1, packet uptake To do. The wireless device 42 also receives the preamble and the synchronization code at time t _{6 because} the transmission channel f ₁ of the packet matches the channel f ₁ waiting for reception, fixes the channel waiting for reception to f ₁ , and captures the packet. Do it.

When receiving the second synchronization code in the synchronization area, the radio apparatus 41 and the radio apparatus 42 take in the data area of the packet and complete the reception. In this case, the time t ₈ the completion of reception of the wireless device 41 and the wireless device 42 is coincident. Since the reception completion times of the packets coincide with each other in a plurality of wireless devices, cooperative operation is realized.

  In this embodiment, the length of the packet to be transmitted is increased, so that many wireless devices within the communicable range can receive the packet with one transmission, and the cooperative operation is realized as originally assumed. Can do.

DESCRIPTION OF SYMBOLS 1, 10 ... Wireless apparatus 2 ... Transmission part 3 ... Reception part 4, 11 ... Control part 20 ... Packet 21 ... Preliminary area 22 ... Synchronization area 23 ... Data area 24 ... Preamble 25 ... First synchronization code 26 ... Second synchronization code

Claims (8)

In a wireless communication system formed by a plurality of wireless devices that perform wireless communication by selecting one wave channel from a frequency group including a plurality of channels,
The wireless device includes a transmission unit, a reception unit, and a control unit,
A packet for wireless communication has a preamble area, a single synchronization area, and a single data area that are repeated multiple times.
A transmitting unit of one wireless device that transmits the packet;
A receiving unit of the other wireless device that performs reception of the packet by switching a channel waiting for reception in a period longer than a period of time required for transmission of the preamble area once;
A wireless communication system, comprising: a control unit of the other wireless device that fixes a reception waiting channel of the reception unit with a channel in which reception of the front-end area can be determined. The wireless communication system according to claim 1, wherein
The preamble area of the packet comprises a preamble for notifying the start of communication and a first synchronization code for starting the subsequent packet capture,
The wireless communication system, wherein the synchronization region of the packet includes a second synchronization code for determining the start of the data region of the packet. In a radio apparatus that performs radio communication by selecting one wave channel from a frequency group including a plurality of channels,
A packet for wireless communication has a preamble area, a single synchronization area, and a single data area that are repeated multiple times.
A radio apparatus comprising a transmitter for transmitting the packet. The wireless device according to claim 3, wherein
The preamble area of the packet comprises a preamble for notifying the start of communication and a first synchronization code for starting the subsequent packet capture,
The radio apparatus according to claim 1, wherein the synchronization area of the packet includes a second synchronization code for determining a start of the data area of the packet. In a radio apparatus that performs radio communication by selecting one wave channel from a frequency group including a plurality of channels,
A packet for wireless communication has a preamble area, a single synchronization area, and a single data area that are repeated multiple times.
A receiver that receives the packet by switching a channel waiting for reception in a period longer than a period required for transmission of the pre-transmission area once;
A radio apparatus comprising: a control unit that fixes a reception waiting channel of the reception unit with a channel in which the reception area can be received. The wireless device according to claim 5, wherein
The preamble area of the packet comprises a preamble for notifying the start of communication and a first synchronization code for starting the subsequent packet capture,
The radio apparatus according to claim 1, wherein the synchronization area of the packet includes a second synchronization code for determining a start of the data area of the packet. In a communication method of a wireless communication system formed by a wireless device that performs wireless communication by selecting one wave channel from a frequency group including a plurality of channels,
Sending a packet with a preamble region, a single synchronization region, and a single data region repeated multiple times;
Receiving the packet by switching a channel waiting for reception in a period longer than a period required for transmission of the pre-transmission area once;
A communication method comprising the step of fixing a reception channel with a channel for which the reception area has been determined to be received. The communication method according to claim 7,
The preamble area of the packet comprises a preamble for notifying the start of communication and a first synchronization code for starting the subsequent packet capture,
The communication method according to claim 1, wherein the synchronization area of the packet includes a second synchronization code for determining the start of the data area of the packet.

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