Communication Systems

Abstract

To suppress signal interference when signals are transmitted and received with a plurality of communication methods.SOLUTION: A communication system transmits and receives signals between a first communication device and a second communication device with a first communication method requiring carrier sense and a second communication method requiring carrier sense. When the first communication device starts signal reception with the first communication method, the first communication device transmits a dummy signal with the second communication method, and the second communication device that has received the dummy signal with the second communication method does not start signal transmission with the second communication method to the first communication device.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The technology disclosed in this specification relates to communication technology. [Background technology]

[0002] In communication systems that realize multiplexing by carrier sense, such as wireless LAN (Local Area Network), a "hidden terminal problem" is known in which multiple slave devices that are unable to sense (detect) that each other are transmitting signals transmit signals simultaneously, causing the signals to collide at the master station (i.e., the signals interfere), preventing the master station from receiving the signals.

[0003] The IEEE802.11 standard, which is a representative standard for wireless LAN, takes measures to avoid signal interference by setting up transmission-prohibited zones using control signals. However, while this measure works as a mechanism to avoid signal interference when a common communication method is used, it does not work when different communication methods are used in the same frequency band, and signal transmissions from multiple child devices end up interfering with each other.

[0004] In response to this, for example, Patent Document 1 discloses a method for avoiding signal interference when a cellular system uses the same frequency band as a wireless LAN simultaneously as a different communication method, by incorporating a control signal compatible with the wireless LAN into the later cellular system and adding the control signal to the transmission signal of the cellular system. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2015 / 141292 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the method shown in Patent Document 1, if other slave units are unable to receive the above-mentioned control signal due to reasons such as differences in the signal strength that can be received depending on the communication method, there is a possibility that the signals will interfere with each other if multiple slave units transmit signals simultaneously.

[0007] When a communication device that transmits a signal takes measures to avoid signal interference and employs a method such as incorporating a control signal into the signal to be transmitted, as shown in Patent Document 1, the control signal does not function in the communication device of the other party that cannot receive the transmission signal with the control signal incorporated, and the communication device starts transmitting the signal. This may cause signal interference in the parent unit.

[0008] The technology disclosed in this specification has been made in consideration of the problems described above, and is a technology for suppressing signal interference when signals are transmitted and received using multiple communication methods. [Means for solving the problem]

[0009] A communication system that is a first aspect of the technology disclosed in the present specification is a communication system that includes at least a first communication device and a second communication device as multiple communication devices, and transmits and receives signals between the first communication device and the second communication device using a first communication method that is a communication method that requires carrier sense and a second communication method that is a communication method different from the first communication method and requires carrier sense, and when the first communication device starts receiving a signal using the first communication method, the first communication device transmits a dummy signal using the second communication method, and the second communication device that receives the dummy signal using the second communication method does not start transmitting a signal using the second communication method to the first communication device. Effect of the Invention

[0010] According to at least a first aspect of the technology disclosed in the present specification, when signals are transmitted and received using a plurality of communication methods, when signal reception begins using one communication method, a dummy signal is transmitted in the other communication method, thereby controlling so that signal transmission does not begin using the other communication method, thereby suppressing interference between signals.

[0011] Furthermore, objects, features, aspects and advantages associated with the technology disclosed herein will become more apparent from the detailed description set forth below and the accompanying drawings. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of a communication system according to an embodiment. [Diagram 2] 2 is a diagram illustrating an example of the configuration of a communication device corresponding to a terminal 1. FIG. [Diagram 3] 2 is a diagram illustrating an example of the configuration of a communication device corresponding to a terminal 2. FIG. [Figure 4] 2 is a diagram illustrating an example of the configuration of a communication device corresponding to a terminal 3. FIG. [Diagram 5] 4 is a timing chart showing communication timings of each terminal of the communication system according to the embodiment; [Figure 6] FIG. 1 is a diagram illustrating an example of a configuration of a communication system according to an embodiment. [Figure 7] 10 is a flowchart for determining whether or not a dummy signal needs to be transmitted in the communication system according to the embodiment. [Figure 8] FIG. 1 is a diagram illustrating an example of a configuration of a communication system according to an embodiment. [Figure 9] 10 is a flowchart for determining a transmission timing of a dummy signal in a communication system according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the embodiments will be described with reference to the accompanying drawings. In the following embodiments, detailed features are shown for the purpose of explaining the technology, but they are merely examples and are not necessarily all essential features for enabling the embodiments to be implemented.

[0014] The drawings are schematic, and for the convenience of explanation, the configuration may be omitted or simplified as appropriate. The size and positional relationship of the configurations shown in different drawings are not necessarily described accurately, and may be changed as appropriate. Hatching may be added to drawings such as plan views that are not cross-sectional views, in order to make it easier to understand the contents of the embodiment.

[0015] In the following description, the same components are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed descriptions thereof may be omitted to avoid duplication.

[0016] Furthermore, in the description in this specification, when a certain component is described as "comprising," "including," or "having," unless otherwise specified, this is not an exclusive expression that excludes the presence of other components.

[0017] Furthermore, even if ordinal numbers such as "first" or "second" are used in the description of this specification, these terms are used for convenience to facilitate understanding of the contents of the embodiments, and the contents of the embodiments are not limited to the orders that may result from these ordinal numbers.

[0018] <First embodiment> A communication system according to this embodiment will be described below.

[0019] <Communication system configuration> 1 is a diagram illustrating an example of the configuration of a communication system according to the present embodiment. As illustrated in FIG. 1, the communication system includes a terminal 1, a terminal 2, and a terminal 3.

[0020] Terminal 1 is a communication device that transmits and receives data using two communication methods: communication method A that supports carrier sensing (i.e., requires carrier sensing) and communication method B that also supports carrier sensing. Terminal 2 is a communication device that communicates with terminal 1 using communication method A. Terminal 3 is a communication device that communicates with terminal 1 using communication method B.

[0021] Terminal 2 may or may not support communication method B, but terminal 3 supports only communication method B and is therefore unable to receive signals transmitted by terminal 2 using communication method A.

[0022] Fig. 2 is a diagram illustrating an example of the configuration of a communication device 101 corresponding to the terminal 1. As illustrated in Fig. 2, the communication device 101 includes a modulation / demodulation unit 102, which is a modulation / demodulation circuit capable of modulation and demodulation corresponding to the communication method A and the communication method B, and a signal processing unit 103 that can communicate with the modulation / demodulation unit 102 via a communication path 104 and processes a signal received by the communication device 101. An example of the signal processing unit 103 is a microcontroller (micro controller unit, i.e., MCU) that performs signal calculations and recording.

[0023] Fig. 3 is a diagram illustrating an example of the configuration of a communication device 201 corresponding to a terminal 2. As illustrated in Fig. 3, the communication device 201 includes a modulation / demodulation unit 202 capable of modulation and demodulation corresponding to only communication method A or to communication methods A and B, and a signal processing unit 203 capable of communicating with the modulation / demodulation unit 202 via a communication path 204 and processing a signal received by the communication device 201. An example of the signal processing unit 203 is an MCU.

[0024] Fig. 4 is a diagram illustrating an example of the configuration of a communication device 301 corresponding to the terminal 3. As illustrated in Fig. 4, the communication device 301 includes a modulation / demodulation unit 302 capable of modulation and demodulation corresponding only to the communication method B, and a signal processing unit 303 capable of communicating with the modulation / demodulation unit 302 via a communication path 304 and processing a signal received by the communication device 301. An example of the signal processing unit 303 is an MCU.

[0025] <About the operation of the communication system> Next, the operation of the communication system according to this embodiment will be described. Fig. 5 is a timing chart showing the communication timing of each terminal of the communication system according to this embodiment. Note that this timing chart applies when the signal of communication method A received by terminal 1 is equal to or lower than the carrier sense level, and does not apply when the signal of communication method A received by terminal 1 is higher than the carrier sense level.

[0026] First, in step ST21, the terminal 2 starts transmitting a preamble in the communication method A. Specifically, the signal processing unit 203 in FIG.

[0027] Then, in the terminal 1, in step ST22, the preamble transmitted by the communication method A is detected. Specifically, the modem unit 102 in FIG. 2 demodulates the received signal, and further inputs the signal to the signal processing unit 103 via the communication path 104.

[0028] Then, in step ST23, the terminal 1 stops receiving the preamble in the communication method A. Specifically, the signal processing unit 103 in FIG.

[0029] Furthermore, in step ST24, transmission of a preamble as a dummy signal is started in communication method B. Specifically, the signal processing unit 103 in FIG.

[0030] In the terminal 3, in step ST25, by receiving the preamble in communication method B, the carrier sense function is used to prevent the transmission of a signal. Specifically, the modem unit 302 in Fig. 4 demodulates the received signal, and further inputs the signal to the signal processing unit 303 via the communication path 304, thereby controlling not to transmit the signal.

[0031] After that, in step ST26, the terminal 1 stops transmitting the preamble in the communication method B. Specifically, the signal processing unit 103 in FIG.

[0032] Then, in step ST27, the terminal 1 resumes receiving the preamble in the communication method A. Specifically, the signal processing unit 103 in FIG.

[0033] After that, in step ST28, the terminal 2 starts transmitting a sync word in the communication method A. Specifically, the signal processing unit 203 in FIG.

[0034] Then, in step ST29, terminal 1 receives the sync word by communication method A, and continues receiving signals such as the payload. Specifically, the modem unit 102 in Fig. 2 demodulates the received signal, and further inputs the signal to the signal processing unit 103 via the communication path 104. The preamble transmission period in communication method A in terminal 2 is determined taking into consideration the preamble transmission period as a dummy signal in communication method B in terminal 1.

[0035] In this embodiment, a communication method such as Gaussian frequency-shift keying (i.e., GFSK) is assumed, and a case has been described in which terminal 1 starts transmitting a preamble in communication method B upon detecting a preamble in communication method A. However, similar processing can also be performed in a Short Training Field (STF) in a communication method such as orthogonal frequency division multiplexing (i.e., OFDM).

[0036] As described above, even in an environment where terminal 3 cannot detect the signal of communication method A transmitted by terminal 2, terminal 3 can detect the signal of communication method B transmitted by terminal 1 and appropriately prohibit terminal 3 from starting to transmit the signal of communication method B to terminal 1, thereby reducing the probability that the signal of communication method B transmitted by terminal 3 and the signal of communication method A transmitted by terminal 2 will interfere with each other at terminal 1.

[0037] <Second embodiment> A communication system according to the present embodiment will be described. In the following description, components similar to those described in the above embodiment are illustrated with the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0038] <Communication system configuration> In the first embodiment, it is assumed that the terminal 1 always transmits a preamble as a dummy signal. However, if a transmission time for the preamble as a dummy signal is secured, the throughput of the entire communication system may decrease.

[0039] On the other hand, Fig. 1 shows a case where a terminal 3 that communicates with terminal 1 using communication method B is provided, but as shown in Fig. 6, a communication system may be configured only by terminal 1, which is a communication device that transmits and receives using two communication methods, communication method A corresponding to carrier sense and communication method B corresponding to carrier sense, and terminal 2, which is a communication device that communicates with terminal 1 using communication method A. Fig. 6 is a diagram that shows a schematic example of the configuration of a communication system according to this embodiment.

[0040] In this case, no interference will occur between terminal 1 and terminal 2 even if a preamble as a dummy signal is not transmitted. Therefore, in preparation for possible signal interference, terminal 1 is provided with a function for monitoring the signal reception status in communication method B and determining whether or not it is necessary to transmit a preamble as a dummy signal.

[0041] <About the operation of the communication system> Next, the operation of the communication system according to this embodiment will be described below. Fig. 7 is a flow chart showing the operation of the communication system according to this embodiment for determining whether or not a dummy signal needs to be transmitted.

[0042] When the terminal 1 determines whether or not a dummy signal is necessary (step ST41), in step ST42, the terminal 1 determines whether or not reception has occurred in communication method B within a certain period of time.

[0043] Then, if reception occurs via communication method B within a certain period of time, that is, if the result corresponds to "YES" branching from step ST42 shown in Fig. 7, the process proceeds to step ST43 shown in Fig. 7. On the other hand, if reception does not occur via communication method B within a certain period of time, that is, if the result corresponds to "NO" branching from step ST42 shown in Fig. 7, the process proceeds to step ST44 shown in Fig. 7.

[0044] In step ST43, it is necessary to transmit a dummy signal from terminal 1. Therefore, terminal 1 notifies terminal 2 that it is necessary to determine the transmission period of the preamble in communication method A, taking into consideration the transmission period of the dummy signal in communication method B. Then, the process proceeds to step ST45, and ends.

[0045] In step ST44, there is no need to transmit a dummy signal from terminal 1. Therefore, terminal 1 notifies terminal 2 that it may determine the transmission period of the preamble in communication method A without considering the transmission period of the dummy signal in communication method B. Then, the process proceeds to step ST45 and ends.

[0046] As described above, by configuring terminal 1 not to transmit a dummy signal when there is no terminal communicating using communication method B, the throughput of the entire communication system can be improved when no interference is occurring.

[0047] <Third embodiment> A communication system according to the present embodiment will be described. In the following description, components similar to those described in the above embodiment are denoted by the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0048] <Communication system configuration> In the first embodiment, the case where the terminal 1 is the only communication device that communicates with the terminal 2 using the communication method A has been shown, but as shown in the example of Fig. 8, in addition to the terminal 1 that is a communication device that transmits and receives using two types of communication methods, the communication method A corresponding to carrier sense and the communication method B corresponding to carrier sense, the terminal 2 that is a communication device that communicates with the terminal 1 using the communication method A, and the terminal 3 that is a communication device that communicates with the terminal 1 using the communication method B, a terminal 4 that is a communication device that transmits and receives using two types of communication methods, the communication method A corresponding to carrier sense and the communication method B corresponding to carrier sense, and that communicates with the terminal 2 using the communication method A, may also be included. Fig. 8 is a diagram that shows an example of the configuration of a communication system according to this embodiment.

[0049] In this case, if terminal 1 receives a signal (preamble) transmitted by terminal 2 to terminal 4 using communication method A before terminal 4 receives it, and terminal 1 starts transmitting a preamble as a dummy signal using communication method B, the transmission of the preamble as a dummy signal from terminal 1 using communication method B and the transmission of a signal (preamble) from terminal 2 using communication method A will interfere with each other at terminal 4. To avoid this, in this embodiment, terminal 1 monitors the reception status of the signal using communication method A and determines the transmission timing of the preamble as a dummy signal.

[0050] <About the operation of the communication system> Next, an operation of the communication system according to the present embodiment will be described below. Fig. 9 is a flow chart showing the operation of the communication system according to the present embodiment for determining the transmission timing of the dummy signal.

[0051] When the terminal 1 determines the transmission timing of the dummy signal (step ST61), in step ST62, the terminal 1 searches for whether or not there is a terminal capable of communicating with the communication method A within a certain period of time in the vicinity. Specifically, the modem unit 102 in Fig. 2 is maintained in a state in which it is capable of receiving a signal transmitted by the communication method A for a certain period of time, and determines whether or not a signal transmitted by the communication method A is received.

[0052] Then, if there is a terminal capable of communication by the communication method A in the vicinity within a certain time, that is, if it corresponds to "YES" branching from step ST62 shown in Fig. 9, the process proceeds to step ST63 shown in Fig. 9. On the other hand, if there is no terminal capable of communication by the communication method A in the vicinity within a certain time, that is, if it corresponds to "NO" branching from step ST62 shown in Fig. 9, the process proceeds to step ST64 shown in Fig. 9.

[0053] In step ST63, the terminal 1 stores information on the following operations. Specifically, after the terminal 1 detects a preamble in communication method A, it stops receiving the preamble in communication method A. Furthermore, after a random time has elapsed, the terminal 1 transmits a preamble as a dummy signal in communication method B. Then, the process proceeds to step ST65 and ends.

[0054] Here, the random time is a time of any length that can be set by the user, etc. The random time is, for example, a time for preventing a dummy signal from terminal 1 from being received by terminal 4 at the timing when a signal transmitted from terminal 2 to terminal 4 is received by terminal 4 (i.e., a time for shifting the timing when the dummy signal is received), and can be a time that is determined in advance depending on the positional relationship between the terminals, etc. The random time may be a fixed time, or may be a variable time that is arbitrarily set each time step ST63 is performed.

[0055] In step ST64, the terminal 1 stores information on the following operations. Specifically, after the terminal 1 detects a preamble in communication method A, it stops receiving the preamble in communication method A. Furthermore, without waiting for the random time to elapse, the terminal 1 transmits a preamble as a dummy signal in communication method B. Then, the process proceeds to step ST65 and ends.

[0056] The above operations may be performed in terminal 4, or in both terminal 1 and terminal 4.

[0057] In this embodiment, a case has been described in which terminal 1 and terminal 4 do not cooperate and wait for a random time to elapse before transmitting a preamble as a dummy signal using communication method B. However, it is also possible for terminal 1 and terminal 4 to cooperate with each other, with one transmitting a preamble as a dummy signal using communication method B and the other not transmitting a preamble as a dummy signal.

[0058] As described above, when there are multiple terminals capable of communicating using communication method A and communication method B, signal interference can be suppressed by changing (delaying) the transmission timing of the preamble as a dummy signal.

[0059] In addition, when the transmission timing of the dummy signal is delayed by a random time, as shown in the example of the first embodiment, the preamble transmission period in the communication method A in the terminal 2 is determined taking into account that the preamble transmission period becomes longer by the random time.

[0060] A possible application example of the above-described embodiment is an M2M (machine-to-machine) network in which a plurality of communication methods with different reception sensitivity points are mixed, in which a communication method with a lower reception sensitivity point than communication method B is adopted as communication method A for the purpose of long-distance transmission, and a communication device that transmits and receives signals only using communication method B cannot detect the presence of signal transmission and reception using communication method A. According to the above-described embodiment, in such a network, it is possible to avoid the hidden terminal problem and continue communication.

[0061] <Effects of the above-described embodiment> Next, examples of effects produced by the above-described embodiments are shown. In the following description, the effects are described based on the specific configurations shown as examples in the above-described embodiments, but they may be replaced with other specific configurations shown as examples in the present specification as long as the same effects are produced. In other words, for convenience, only one of the corresponding specific configurations may be described as a representative below, but the representatively described specific configuration may be replaced with another corresponding specific configuration.

[0062] Furthermore, the replacement may be made across a number of embodiments, that is, configurations shown as examples in different embodiments may be combined to produce the same effect.

[0063] According to the embodiment described above, in the communication system, when a first communication device starts receiving a signal in a first communication method, the first communication device transmits a dummy signal in a second communication method. Here, the first communication device corresponds to, for example, terminal 1. The first communication method corresponds to, for example, communication method A. The second communication method corresponds to, for example, communication method B. The second communication device that receives the dummy signal in communication method B does not start transmitting a signal in communication method B to terminal 1. Here, the second communication device corresponds to, for example, terminal 3.

[0064] According to such a configuration, when transmitting and receiving signals using a plurality of communication methods, when signal reception starts using one communication method, a dummy signal is transmitted in the other communication method, and control is performed so that the signal transmission in the other communication method is not started, thereby suppressing interference between signals. Also, by having a communication device receiving a signal (e.g., terminal 1 in FIG. 1) transmit a dummy signal, rather than a communication device transmitting a signal (e.g., terminal 3 in FIG. 1), a communication device (e.g., terminal 3 in FIG. 1) that may transmit a signal to a communication device receiving a signal (e.g., terminal 1 in FIG. 1) at a reception level that may cause interference between signals does not start transmitting a signal due to a carrier sense function. Therefore, interference between signals in a communication system can be effectively suppressed.

[0065] Furthermore, according to the embodiment described above, if terminal 1 receives a signal in communication method B, it transmits a dummy signal when it starts receiving a signal in communication method A. Also, if terminal 1 does not receive a signal in communication method B, it does not transmit a dummy signal when it starts receiving a signal in communication method A. According to this configuration, by configuring terminal 1 not to transmit a dummy signal when there is no terminal communicating in communication method B, it is possible to improve the throughput of the entire communication system when no interference is occurring.

[0066] Furthermore, according to the embodiment described above, the communication system includes a plurality of communication devices capable of communicating in both communication method A and communication method B. Then, when terminal 1 starts receiving a signal in communication method A, terminal 1 transmits a dummy signal in communication method B with a predetermined delay. According to such a configuration, in a case such as that illustrated in FIG. 8 where there are a plurality of terminals capable of communicating in communication method A and communication method B, by changing (delaying) the transmission timing of the preamble as the dummy signal, the timing at which the dummy signal is received can be shifted from the timing at which another signal (for example, a signal transmitted from terminal 2 to terminal 2) is received, thereby suppressing interference of the dummy signal with signals of other communication methods.

[0067] <Modifications of the above-described embodiments> In the embodiments described above, the dimensions, shapes, relative positional relationships, and implementation conditions of each component may be described, but these are merely examples in all respects and are not limiting.

[0068] Therefore, countless modifications and equivalents not shown as examples are assumed within the scope of the technology disclosed in the present specification, including, for example, modifying, adding, or omitting at least one component, and further, extracting at least one component in at least one embodiment and combining it with a component in another embodiment.

[0069] Furthermore, the descriptions in this specification are incorporated by reference for all purposes related to the present technology, and none of them are admitted to be prior art. [Explanation of symbols]

[0070] 101 communication device, 201 communication device, 301 communication device, A communication method, B communication method.

Claims

1. A communication system including at least a first communication device and a second communication device as a plurality of communication devices, transmitting and receiving signals between the first communication device and the second communication device using a first communication method that is a communication method requiring carrier sense and a second communication method that is a communication method different from the first communication method and requires carrier sense, When the first communication device starts receiving a signal in the first communication method, the first communication device transmits a dummy signal in the second communication method; the second communication device that has received the dummy signal in the second communication method does not start transmitting a signal in the second communication method to the first communication device; Communication systems.

2. A communication system according to claim 1, When the first communication device receives a signal in the second communication method, the first communication device transmits the dummy signal when starting signal reception in the first communication method; When the first communication device is not receiving a signal in the second communication method, the first communication device does not transmit the dummy signal when starting signal reception in the first communication method. Communication systems.

3. A communication system according to claim 1 or 2, a plurality of communication devices capable of communicating in both the first communication method and the second communication method; When the first communication device starts receiving a signal in the first communication method, the first communication device transmits the dummy signal in the second communication method with a delay of a predetermined time. Communication systems.

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