Wireless communication system

Abstract

To reduce power consumption required for carrier sense.SOLUTION: A transmitter periodically and repeatedly transmits data. The number of times the transmitter repeatedly transmits data is equal to or greater than a value obtained by dividing the length of the data transmission cycle by the length of a data transmission time. A receiver periodically and repeatedly performs carrier sense. The length of the cycle in which the receiver performs carrier sensing is longer than the length of the data transmission cycle and shorter than the sum of the length of the data transmission cycle and the length of the data transmission time.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a wireless communication system.

Background Art

[0002] Conventionally, in a wireless communication system including a transmitter and a receiver, carrier sense is performed so that the receiver can confirm whether the transmitter is performing wireless transmission (see, for example, Patent Document 1). FIG. 4 is a diagram showing a general method of this carrier sense.

[0003] The transmitter shown in the figure periodically repeats data transmission. The data transmission period of this transmitter is represented by Tt in the figure, and the data transmission time is represented by e. The transmission period Tt is set longer than the transmission time e.

[0004] On the other hand, the receiver shown in the figure periodically repeats carrier sense. The carrier sense period of this receiver is represented by Tr in the figure. This carrier sense period Tr is set to satisfy the condition Tr < e in order to prevent detection omission of wireless transmission. That is, the carrier sense period Tr is set to be shorter than the transmission time e. By increasing this carrier sense period Tr within the range that satisfies the condition (that is, by reducing the number of times of carrier sense), the power consumption required for carrier sense can be reduced.

[0005] The receiver repeatedly performs carrier sense and, when detecting wireless transmission as shown in FIG. 4, receives data after (Tt - e) seconds.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention has been made against the background of such technology, and The purpose is to reduce power consumption. [Means for solving the problem]

[0008] In order to solve the above problems, the wireless communication system of the present invention is a wireless communication system comprising a transmitter and a receiver, wherein the transmitter periodically and repeatedly transmits data, the number of times the data is repeatedly transmitted is equal to or greater than a value obtained by dividing the length of the data transmission cycle by the length of the data transmission time, and the receiver periodically and repeatedly performs carrier sense, the length of the cycle for performing carrier sense is longer than the length of the data transmission cycle and shorter than the sum of the length of the data transmission cycle and the length of the data transmission time. Effect of the Invention

[0009] According to the present invention, it is possible to reduce the power consumption required for carrier sensing. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 shows a configuration of a wireless communication system 1. [Diagram 2] FIG. 1 shows a communication method of the wireless communication system 1. [Diagram 3] FIG. 13 is an explanatory diagram of a communication method according to a modified example. [Figure 4] A diagram showing the general method of carrier sensing DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 1. Embodiment A wireless communication system 1 according to an embodiment of the present invention will be described with reference to Fig. 1 and Fig. 2. Fig. 1, which will be referred to in this description, is a diagram showing a configuration of the wireless communication system 1, and Fig. 2 is a diagram showing a communication method of the wireless communication system 1.

[0012] 1, the wireless communication system 1 is composed of a transmitter 11 and a receiver 12. The transmitter 11 and the receiver 12 constituting this wireless communication system 1 are, for example, a wireless fire detector, a wireless flashlight (an alarm device for notifying the hearing impaired of the occurrence of a fire), or a wireless repeater.

[0013] The transmitter 11 periodically and repeatedly transmits data as shown in Fig. 2. The transmission period of the transmitter 11 is represented by Tt in the figure, and the transmission time is represented by e. The transmission period Tt is set to be longer than the transmission time e.

[0014] The transmitter 11 repeatedly transmits data n times or more to prevent the receiver 12 from missing the detection of wireless transmission. The number of times n that the data is transmitted is set to satisfy the condition n≧(Tt / e). In other words, the number of times n that the data is transmitted is set to be equal to or greater than the value obtained by dividing the length of the data transmission cycle Tt by the data transmission time e.

[0015] On the other hand, the receiver 12 periodically and repeatedly performs carrier sensing as shown in Fig. 2. The carrier sense cycle of the receiver 12 is represented by Tr in the figure. This carrier sense cycle Tr is set to satisfy the condition Tr<(Tt+e) to prevent wireless transmission from being missed. That is, the length of the carrier sense cycle Tr is set to be shorter than the sum of the length of the data transmission cycle Tt and the length of the data transmission time e. For example, this carrier sense cycle Tr is set to be longer than the length of the data transmission cycle Tt and shorter than the sum of the length of the data transmission cycle Tt and the length of the data transmission time e.

[0016] The receiver 12 repeatedly performs carrier sensing, and when it detects a wireless transmission as shown in FIG. 2, it receives the data after (Tt-e) seconds.

[0017] As described above, by setting the number of data transmission times n to satisfy the condition n≧(Tt / e) and setting the carrier sense period Tr to satisfy the condition Tr<(Tt+e), the receiver 12 can surely receive the data within n times of transmission.

[0018] In this embodiment, in order to realize reliable data reception, the carrier sense period Tr is set to satisfy the condition Tr<(Tt+e). On the other hand, in the above background art, in order to realize reliable data reception, the carrier sense period Tr is set to satisfy the condition Tr<e. Comparing these two conditions, the carrier sense period can be made longer by Tt in this embodiment than in the background art. Therefore, according to this embodiment, the power consumption required for carrier sense can be reduced as compared with the background art.

[0019] 2. Modification The above embodiment is premised on the fact that the data transmission period Tt is always constant. However, the data transmission period Tt may vary for each data transmission. Specifically, at the timing of a certain data transmission, the data transmission period Tt may be longer than a predetermined period, or at the timing of another data transmission, the data transmission period Tt may be shorter than a predetermined period. When the data transmission period Tt varies in this way, the number of transmission times n and the carrier sense period Tr required for reliable data reception change, and there is a possibility that the receiver 12 cannot surely receive the data. Therefore, in this modification, a communication method in which the receiver 12 can surely receive the data even when the data transmission period Tt varies will be described with reference to FIG. 3. FIG. 3 referred to in this description is a diagram for explaining such a communication method.

[0020] The upper part of the figure shows a case where the transmitter 11 repeatedly transmits data at the minimum transmission period. The minimum transmission period in this upper case is represented by Ttmin, and the minimum transmission time is represented by emin. The minimum transmission period Ttmin is set to be longer than the minimum transmission time emin.

[0021] The middle part of the figure shows a case where the transmitter 11 repeatedly transmits data at the maximum transmission period. In this middle case, the maximum transmission period is represented by Ttmax, and the minimum transmission time is represented by emin. The maximum transmission period Ttmax is set longer than the minimum transmission time emin.

[0022] The lower part of the figure shows the receiving operation of the receiver 12. The receiver 12 shown in the lower part periodically and repeatedly executes carrier sense. The carrier sense cycle of this receiver 12 is represented by Tr. This receiver 12 repeatedly executes carrier sense, and when it detects a wireless transmission as shown in the figure, it receives data after (Tt-emax) seconds. Here, emax represents the maximum wireless transmission time, and specifies the worst-case condition for advancing the timing for starting the data reception operation.

[0023] The carrier sense cycle Tr of the receiver 12 is set to satisfy the condition Tr<(Ttmin+emin) so that data can be reliably received when the transmission cycle of the transmitter 11 is the minimum transmission cycle Ttmin. That is, the length of the carrier sense cycle Tr is set to be shorter than the sum of the length of the minimum data transmission cycle Ttmin and the length of the minimum data transmission time emin. For example, the carrier sense cycle Tr is set to be longer than the length of the maximum data transmission cycle Ttmax and shorter than the sum of the length of the minimum data transmission cycle Ttmin and the length of the minimum data transmission time emin. In addition, the transmitter 11 repeatedly transmits data n times or more so that the receiver 12 can reliably receive the data. The number of times n of data transmission is set to satisfy the condition n≧(Ttmin / emin). That is, the number of times n of data transmission is set to be greater than or equal to the value obtained by dividing the length of the minimum data transmission cycle Ttmin by the minimum data transmission time emin.

[0024] In this way, by setting the number of data transmissions n to satisfy the condition n≧(Ttmin / emin) and setting the carrier sense period Tr to satisfy the condition Tr<(Ttmin+emin), the receiver 12 can reliably receive data within the number of transmissions n when the transmission period of the transmitter 11 is the minimum transmission period Ttmin.

[0025] In order for the receiver 12 to reliably receive data within n transmissions when the transmission period of the transmitter 11 is the maximum transmission period Ttmax, the time e' shown in Fig. 3 is required. This time e' is the time during which the minimum transmission time emin overlaps when the transmission period is the maximum transmission period Ttmax and when the transmission period is the minimum transmission period Ttmin. In other words, it is the time during which data is transmitted whether the transmission period is the maximum transmission period Ttmax or the minimum transmission period Ttmin. If this time e' exists, the receiver 12 can reliably receive data within n transmissions when the transmission period is the maximum transmission period Ttmax.

[0026] The time e' is expressed by the following Equation 1. JPEG0007603532000001.jpg9165

[0027] In this formula 1, ΔTterr represents the maximum error in the transmission period. The maximum error in the transmission period represented by ΔTterr is defined as ΔTterr=Ttmax-Ttmin. In other words, the maximum error in the transmission period is the difference between the maximum transmission period Ttmax and the minimum transmission period Ttmin.

[0028] If the time e' becomes a negative number, this system will not be valid. Therefore, from the above formula 1, the condition emin>(n-1)×ΔTterr is derived.

[0029] If the minimum data transmission time emin and the number of data transmissions n satisfy this condition, the receiver 12 can reliably receive the data within the number of transmissions n, even if the transmission period of the transmitter 11 is the maximum transmission period Ttmax.

[0030] In the present modification described above, in order to achieve reliable data reception, the carrier sense period Tr is set so as to satisfy the condition Tr < (Ttmin + emin). On the other hand, in the above-described background art, in order to achieve reliable data reception, the carrier sense period Tr is set so as to satisfy the condition Tr < e. When comparing these two conditions, since both emin and e represent the transmission time and are common, the carrier sense period can be made longer by Ttmin in the present modification than in the background art. Therefore, according to the present modification, the power consumption required for carrier sense can be reduced as compared with the background art. In addition, according to the present modification, even if the transmission period of the transmitter 11 varies, the receiver 12 can surely receive data.

Explanation of Reference Numerals

[0031] 1... wireless communication system, 11... transmitter, 12... receiver

Claims

1. A wireless communication system comprising a transmitter and a receiver, The transmitter repeatedly transmits data periodically; the number of times the data is repeatedly transmitted is equal to or greater than a value obtained by dividing a length of a transmission cycle of the data by a length of a transmission time of the data, The receiver periodically and repeatedly performs carrier sensing; The length of the cycle for performing the carrier sense is longer than the length of the data transmission cycle and shorter than the sum of the length of the data transmission cycle and the length of the data transmission time.

1. A wireless communication system comprising:

2. the number of times the data is repeatedly transmitted is equal to or greater than a value obtained by dividing a length of a minimum transmission cycle of the data by a length of a minimum transmission time of the data, a length of a period for performing the carrier sense is longer than a length of a maximum transmission period of the data and shorter than a sum of a length of a minimum transmission period of the data and a minimum transmission time of the data; The number of times the data is repeatedly transmitted and the minimum transmission time of the data satisfy the condition expressed by the following formula: emin>(n-1)×ΔTterr In this formula, emin represents the minimum transmission time of the data, n represents the number of times the data is repeatedly transmitted, and ΔTterr represents the difference between the maximum transmission period and the minimum transmission period of the data.

2. The wireless communication system according to claim 1 .

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