Receiver

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 the data transmission time. Meanwhile, a receiver periodically and repeatedly performs carrier sense. The length of the cycle during which the receiver performs 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.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 transmits data periodically and repeatedly. 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 performs carrier sense periodically and repeatedly. The carrier sense period of this receiver is represented by Tr in the figure. This carrier sense period Tr is set so as 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 carrier senses), the power consumption required for carrier sense can be reduced.

[0005] When the receiver repeatedly performs carrier sense and detects wireless transmission as shown in FIG. 4, it 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 has as its object to reduce the power consumption required for carrier sensing. [Means for solving the problem]

[0008] In order to solve the above problem, 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 the 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 the carrier sense being 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. [Effects of the Invention]

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

[0010] [Figure 1] FIG. 1 shows a configuration of a wireless communication system 1. [Figure 2] FIG. 1 shows a communication method of a wireless communication system 1. [Figure 3] FIG. 10 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 INVENTION

[0011] 1. Embodiment A wireless communication system 1 according to one 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 the 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 that make up this wireless communication system 1 are, for example, a wireless fire detector, a wireless flashlight (an alarm device for notifying the hearing impaired of a fire), or a wireless repeater.

[0013] The transmitter 11 periodically 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 or more times to prevent the receiver 12 from missing any wireless transmissions. The number of times n the data is transmitted is set to satisfy the condition n≧(Tt / e). In other words, the number of times n 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] Meanwhile, the receiver 12 periodically and repeatedly performs carrier sensing, as shown in Fig. 2. The carrier sensing cycle of this receiver 12 is represented by Tr in the figure. This carrier sensing cycle Tr is set to satisfy the condition Tr<(Tt+e) to prevent wireless transmissions from being missed. That is, the length of the carrier sensing 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 sensing 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 radio 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 with 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 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 performs carrier sensing. The carrier sensing cycle of this receiver 12 is represented by Tr. This receiver 12 repeatedly performs carrier sensing, 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 defines the worst-case condition for advancing the timing to start 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 minimum data transmission time emin. In addition, the transmitter 11 repeatedly transmits data n or more times so that the receiver 12 can reliably receive the data. The number of times n that the data is transmitted is set to satisfy the condition n≧(Ttmin / emin). That is, the number of times n that the data is transmitted 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 the carrier sense period Tr to satisfy the condition Tr<(Ttmin+emin), the receiver 12 can reliably receive data within n transmissions when the transmission period of the transmitter 11 is the minimum transmission period Ttmin.

[0025] Furthermore, 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, time e' shown in Figure 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 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. TIFF0007769084000001.tif6170

[0027] In this equation 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, so the condition emin>(n-1)×ΔTterr is derived from the above equation 1.

[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. 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. Carrier sense is performed periodically and repeatedly. a state in which data can be received from the transmitter after a time period obtained by subtracting a length of a data transmission time from a length of a data transmission cycle of the transmitter has elapsed from the time when wireless transmission is detected in the carrier sense; 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. A receiver characterized by:

2. a state in which data can be received from the transmitter after a time period obtained by subtracting a maximum transmission time of the data from a transmission cycle of the data has elapsed from the time when the wireless transmission is detected in the carrier sense; The length of the cycle for performing the carrier sense is longer than the length of the maximum data transmission cycle and shorter than the sum of the length of the minimum data transmission cycle and the minimum data transmission time. Receiver according to claim 1, characterized in that:

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