JP2001127745A - Radio packet receiving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that it is difficult to set a pattern decision threshold used to decide a synchronous word to cope with troubles of misdecision making and overlooking of the synchronous word due to noise. SOLUTION: The pattern decision threshold used by a decision unit 6 to decide the synchronous word is varied by a threshold control circuit 3 according to a receive signal level detected by a level detector 2 to totally reduce both the probability that a random pattern is misdecided as the synchronous word when a packet signal is not received and the probability that the synchronous word is overlooked when the packet signal is received.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless packet communication technique for performing packet communication using a wireless line, and more particularly to a technique suitable for reliably determining a synchronization word contained in a received wireless packet. The present invention relates to a wireless packet receiving device.

[0002]

2. Description of the Related Art In radio packet communication, a signal is transmitted only when data transmission is necessary, and signal transmission is stopped in other cases, so that a plurality of transmission stations can use a line efficiently. In this case, since the receiving side cannot predict when the transmitting station will transmit a signal, a "synchronous word" consisting of a specific bit string pattern is arranged in a part of the packet, and the bit string received and demodulated in the wireless packet receiving apparatus. It is common to detect the pattern of the synchronizing word from, and specify the presence of the signal transmitted from the transmitting side and the exact position of the data in the received bit string.

FIG. 2 is an explanatory diagram showing an example of a format of a radio packet signal. In FIG. 2, 10 is a preamble, 11 is a synchronization word, and 12 is data. A preamble 10 is a non-modulated signal, and a signal modulated with a predetermined bit pattern is used as the synchronization word 11.
FIG. 6 shows a conventional wireless packet receiving apparatus for receiving a wireless packet signal having such a configuration.

FIG. 6 is a block diagram showing a configuration example of a conventional wireless packet receiving apparatus. The wireless packet signal is subjected to removal of unnecessary band components and frequency conversion to a frequency band suitable for subsequent processing by the receiver 61. The level detector 62 detects the level of the received signal from the output of the receiver 61. The detection result is input to the demodulator control circuit 68.

The demodulator control circuit 68 includes a level detector 62
Is controlled so that the demodulator 64 operates for a certain period of time from the time when the detection result exceeds a predetermined signal level threshold value. Demodulator 64 demodulates digital data (demodulated data) from the received signal.

During the operation of the demodulator 64, the pattern comparator 65 compares the bit string of the demodulated data output from the demodulator 64 with the bit string of a preset synchronizing word pattern, Output the number of bits).

The output of the pattern comparator 65, that is, the number of matching bits and a predetermined pattern determination threshold value are input to a determining unit 66, and the determining unit 66 determines whether the number of matching bits is a predetermined pattern. It is determined that a packet has arrived when it becomes larger than the threshold value. The result of the determination by the determiner 66 is input to the output control circuit 67, and subsequent data is output from the output control circuit 67 to the outside from the time when it is determined that the packet has arrived.

On the other hand, if the decision of the arrival of the packet is not made by the decision unit 66 within a predetermined time, the demodulator control circuit 68 stops the operation of the demodulator 64 and the received signal level is again changed to the signal level. Wait until the threshold is exceeded.

The operation principle similar to that of such a wireless packet receiving apparatus is described in, for example, "Hamao et al .:" Performance evaluation of DS / SS receiver using double-gate SAW convolver ", IEICE research. Technical report, SST93-5
2, pp1-6 ".

[0010] In the radio packet receiving apparatus, the signal level threshold value must be set smaller than the assumed minimum received signal level. Therefore, if the assumed received signal level is small and the signal level threshold is set smaller, the noise level will be lower than the signal level threshold even though no packet signal is received. The probability of exceeding is increased.

In this case, since the demodulator 64 operates in a state where only the noise is input instead of the original packet signal, the input of the pattern comparator 65 has a completely random pattern. Since this random pattern becomes a pattern similar to the synchronization word with a certain probability, it is necessary to set the pattern determination threshold value to be considerably large in order to prevent the random pattern from being erroneously determined as the synchronization word.

However, even when a packet signal is received, a bit error due to noise occurs in the demodulation result. Therefore, when the pattern determination threshold value is increased, the probability that the original synchronization word determination fails and is overlooked increases. Become.

In the prior art, when such a packet signal is not received, it is difficult to sufficiently suppress both the probability of erroneously determining a random pattern as a synchronization word and the probability of missing the original synchronization word. .

If the random pattern is erroneously determined as a synchronizing word, meaningless data is output to the outside, and even if an original packet signal arrives during that time, the correct start position of the data cannot be determined. Will be discarded. On the other hand, if the original synchronizing word is missed, the data following it is naturally discarded. As described above, it is difficult for the conventional wireless packet receiving device to efficiently receive a packet signal.

[0015]

The problem to be solved in the prior art is that it is used for the determination of the synchronizing word so as to cope with both the erroneous judgment and the oversight of the synchronizing word due to noise. It is difficult to set a pattern determination threshold.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a probability that a random pattern composed of noise is erroneously determined as a synchronizing word when a packet signal is not received, and that the synchronizing word is missed when a packet signal is received. An object of the present invention is to provide a wireless packet receiving device that can reduce both of the probabilities in total and enable efficient wireless packet communication.

[0017]

In order to achieve the above object, a wireless packet receiving apparatus according to the present invention comprises a level detector for detecting a pattern determination threshold value used for determining a synchronization word by a level detector. Change in response to the For example,
If the signal level is large, the probability that a packet signal has arrived is high, and the probability that it has not arrived is low.In this case, the pattern determination threshold is reduced, and synchronization is performed even if the number of matching bits is small. Thus, the probability that a synchronization word is missed when a packet signal is received is suppressed.

The smaller the detected signal level, the higher the possibility that the packet signal has not arrived. Therefore, the smaller the signal level, the larger the pattern determination threshold value, and If the number is not large, it is determined not to be a synchronization word, and the probability of erroneously determining a random pattern as a synchronization word when a packet signal is not received is suppressed.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration example according to the present invention of a wireless packet receiving device of the present invention. FIG. 2 is an explanatory diagram showing a format of a packet signal received by the wireless packet receiving device in FIG.
FIG. 4 is an explanatory diagram showing an example of controlling a pattern determination threshold based on a received signal level by the wireless packet receiving device in FIG. 1.

As shown in FIG. 2, the radio packet signal is
It consists of a preamble 10, a synchronization word 11, and data 12,
A preamble 10 is a non-modulated signal, and a signal modulated with a predetermined bit pattern is used as the synchronization word 11.

The wireless packet receiving apparatus shown in FIG.
A level detector 2, a threshold control circuit 3, a demodulator 4, a pattern comparator 5, a determiner 6, and an output control circuit 7 are provided. The component is removed and frequency conversion to a frequency band suitable for subsequent processing is performed.

The level of the received signal is detected from the output of the receiver 1 by the level detector 2. Further, the threshold control circuit 3 refers to the detection result of the level detector 2 and outputs a pattern determination threshold to the determiner 6.

The threshold value control circuit 3 sets the pattern determination threshold value to be small when the received signal level is large and large when the received signal level is small, as shown in FIG. Control so that

The output of the receiver 1 is also input to the demodulator 4,
The demodulator 4 outputs digital data (demodulated data). The pattern comparator 5 compares the bit string (here, 16 bits) of the demodulated data output from the demodulator 4 with the bit string (16 bits) of the preset sync word pattern, and determines the number of matched bits (16 bits). Is output.

The output of the pattern comparator 5 is input to the decision unit 6, and when the number of matching bits becomes larger than the pattern decision threshold from the threshold control circuit 3, the decision unit 8 determines that a packet has arrived. judge. This determination result is input to the output control circuit 7, and the output control circuit 7 outputs subsequent data to the outside from the time when it is determined that the packet has arrived.

As described above, the wireless packet receiving apparatus according to the present embodiment changes the pattern determination threshold value used for determining the synchronization word in accordance with the received signal level detected by the level detector 2.

For example, when the signal level detected by the level detector 2 is relatively large, the probability that the packet signal has arrived is high and the probability that the packet signal has not arrived is low. Even if the number of matching bits output from the pattern comparator 5 is small, the decision threshold
Is determined to be a synchronization word.

Thus, the probability of missing the synchronization word when receiving a packet signal is suppressed. In this case, the probability that the random pattern is erroneously determined as the synchronizing word increases, but the probability that the packet signal has not arrived is low and the influence is small.

If the signal level is small, it is highly likely that no packet signal has arrived. In this case, the pattern determination threshold value is increased, and the coincidence output from the pattern comparator 5 is increased. If the number of bits is not sufficiently large, the determination unit 6 does not determine a synchronization word.

Thus, the probability of erroneously determining a random pattern as a synchronization word when a packet signal is not received is suppressed. In this case, the probability of missing the original synchronization word increases, but the received signal level is small, so that the probability that a packet signal has arrived is low and the effect is small.

Hereinafter, such probabilities will be described using mathematical expressions. Let the detected received signal level be "A",
At this time, the probability that a packet signal has arrived is represented by “Pp
(A), the probability of not having arrived is “1-Pp
(A) ". Also, the pattern determination threshold is set to “ε”.
It is assumed that the probability of overlooking a packet signal arriving is “Pm (ε)”, and the probability of erroneously determining a synchronizing word even if the packet signal has not arrived is “Pf (ε)”.

Accordingly, when the received signal level "A" is detected, the probability that the original synchronizing word is overlooked or the random pattern is erroneously determined to be the same word is expressed by the following equation. Pp (A) · Pm (ε) + {1-Pp (A)} · Pf
(Ε)

The probability that a packet signal has arrived (“Pp
(A) ”) is not constant with respect to the received signal level“ A ”, so the pattern determination threshold“ ε ”that minimizes the probability of the above equation is determined by the received signal level“ A ”. different.

In this example, as shown in FIG. 3, the pattern determination threshold value “ε” is changed according to the received signal level “A”, so that the probability of the above equation is always minimized. Is possible.

FIG. 4 is a block diagram showing another example of the configuration of the wireless packet receiving apparatus of the present invention according to the present invention.
5 is an explanatory diagram showing an example of controlling a pattern determination threshold based on a received signal level by the wireless packet receiving device in FIG.

The radio packet receiving apparatus shown in FIG. 4 is provided with a demodulator control circuit 8 in the same configuration as that of the radio packet receiving apparatus in FIG. 1, and receives a packet signal in the format shown in FIG. In contrast to the processing based on the “number of matching bits” in the wireless packet receiving device in the above, the processing based on the “number of mismatching bits” is performed.

That is, in the wireless packet receiving apparatus of this embodiment, the receiver 1a removes unnecessary band components from the received signal and performs frequency conversion to a frequency band suitable for subsequent processing. Then, the level of the received signal is detected from the output of the receiver 1a by the level detector 2a. The result of the level detection of the received signal by the level detector 2a is input to the demodulator control circuit 8 together with the threshold control circuit 3a.

The threshold control circuit 3a refers to the detection result of the level detector 2a and outputs a pattern determination threshold to the determiner 6a. For example, as shown in FIG. 5, the pattern determination threshold value is controlled so as to be large when the received signal level is large and to be small when the received signal level is small.

The output of the receiver 1a is also input to the demodulator 4a, and the demodulator 4a outputs demodulated data. However, in this example, the demodulator 4a is
Under the control of the demodulator control circuit 8, and outputs demodulated data during the period when the demodulator 4a is operating.

The pattern comparator 5a is a bit string (here, 32 bits) of the demodulated data output from the demodulator 4a.
And a bit string (3
2 bits) and outputs the number of bits that do not match (the number of mismatching bits).

The output of the pattern comparator 5a is input to a decision unit 6a, and the decision unit 6a decides that a packet has arrived when the number of mismatched bits is smaller than the pattern decision threshold value given from the threshold value control circuit 3a. . The determiner 6a
Is output to the output control circuit 7a, and the output control circuit 7a outputs subsequent data to the outside from the time when it is determined that the packet has arrived.

If the level detector 2a does not determine that a packet has arrived within a certain period of time, the demodulator control circuit 8 stops the operation of the demodulator 4a and outputs the received signal detected by the level detector 2a. Until the level again exceeds the signal level threshold, the operation of the demodulator 4a is stopped and stopped.

As described above, in the wireless packet receiving apparatus of the present embodiment, similarly to the wireless packet receiving apparatus having the configuration shown in FIG. 1, the pattern detector threshold used for determining the synchronizing word is determined by the level detector 2a. It changes according to the received signal level to be detected, and suppresses the probability of overlooking the synchronization word when receiving a packet signal, and suppresses the probability that a random pattern is erroneously determined as a synchronization word when a packet signal is not received. By controlling the activation of the demodulator 4a in accordance with the received signal level, the operation of the demodulator 4a is performed when the received signal level is small and the probability that a packet signal has arrived is extremely small. And unnecessary power consumption can be suppressed.

As described above with reference to FIGS. 1 to 5, in the wireless packet receiving apparatus of this embodiment, the pattern determination threshold value used for determining the synchronizing word is determined by the level detectors 2 and 2a.
The probability of erroneously determining a random pattern as a synchronizing word when a packet signal is not received and the probability of overlooking the synchronizing word when receiving a packet signal are comprehensively changed by changing the received signal level detected by To
Enables efficient wireless packet communication.

That is, the larger the signal level of the received signal detected by the level detectors 2 and 2a, the more
Since the probability that a packet signal has arrived is high and the probability that it has not arrived is low, the wireless packet receiving apparatus in FIG. Even if the number of bits is small, it is determined that the word is a synchronizing word. Also, in the wireless packet receiving apparatus in FIG. At most, it is determined to be a synchronous word.
As a result, it is possible to suppress the probability of missing the synchronization word when receiving a packet signal.

The smaller the signal level of the received signal detected by the level detectors 2 and 2a, the higher the possibility that a packet signal has not arrived.
The smaller the signal level, the larger the pattern determination threshold is. In the wireless packet receiving device of the above, the synchronization word is not determined unless the number of matching bits is large. In the device, the smaller the signal level is, the smaller the pattern determination threshold is, and the smaller the number of mismatched bits is, the less it is determined that the pattern is not a synchronization word. This allows
When a packet signal is not received, the probability of erroneously determining a random pattern as a synchronizing word can be suppressed.

Further, the radio packet receiving apparatus shown in FIG. 4 controls the demodulator 4a to start and start the receiving operation only when the detected signal level is larger than the predetermined threshold value. , The received signal level is small,
When it is estimated that the probability that a packet signal has arrived is extremely small, the demodulator 4a can be stopped to suppress unnecessary power consumption.

The present invention is not limited to the examples described with reference to FIGS. 1 to 5, and can be variously modified without departing from the gist thereof. For example, in the wireless packet receiving apparatus shown in FIG. 1, a demodulator control circuit 8 may be provided to control the operation of the demodulator 4a, similarly to the wireless packet receiving apparatus shown in FIG.

Also, in the wireless packet receiving apparatus shown in FIG. 4, like the wireless packet receiving apparatus shown in FIG.
A configuration without the demodulator control circuit 8 may be adopted. Also,
In this example, as shown in FIGS. 3 and 5, the pattern determination threshold value is continuously changed according to the received signal level, but may be changed stepwise.

[0050]

According to the present invention, both the probability of erroneously determining a random pattern composed of noise as a synchronization word when a packet signal is not received and the probability of missing a synchronization word when a packet signal is received are comprehensively obtained. The wireless packet communication can be reduced and efficient wireless packet communication is possible. Further, when it is estimated that the reception signal level is small and the probability that a packet signal has arrived is extremely small, the demodulation operation can be stopped, so that unnecessary power consumption can be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration example according to the present invention of a wireless packet receiving apparatus of the present invention.

FIG. 2 is an explanatory diagram showing a format of a packet signal received by the wireless packet receiving device in FIG.

FIG. 3 is an explanatory diagram showing an example of controlling a pattern determination threshold based on a received signal level by the wireless packet receiving device in FIG. 1;

FIG. 4 is a block diagram showing another example of the configuration of the wireless packet receiving apparatus according to the present invention;

FIG. 5 is an explanatory diagram showing an example of control of a pattern determination threshold based on a received signal level by the wireless packet receiving device in FIG.

FIG. 6 is a block diagram illustrating a configuration example of a conventional wireless packet receiving device.

[Explanation of symbols]

1, 1a: receiver, 2, 2a: level detector, 3, 3
a: threshold control circuit, 4, 4a: demodulator, 5, 5a:
Pattern comparator, 6, 6a: decision unit, 7, 7a: output control circuit, 8: demodulator control circuit, 9: wireless packet signal,
10: preamble, 11: synchronization word, 12: data, 6
1: receiver, 62: level detector, 64: demodulator, 6
5: pattern comparator, 66: determiner, 67: output control circuit, 68: demodulator control circuit.

Continued on front page F term (reference) 5K014 AA01 EA08 GA03 5K033 AA07 CB03 CC01 DA17 5K047 AA12 BB01 BB15 HH31 HH53 MM11 5K067 AA23 BB21 CC08 DD25 GG09 HH21

Claims (3)

[Claims] 1. A wireless packet receiving apparatus for receiving a wireless packet signal, comprising: a level detecting means for detecting a signal level of the received signal; a demodulating means for demodulating digital data from the received signal; A pattern comparing means for comparing the determined synchronizing word pattern and outputting the number of matching bits (the number of matching bits); and Threshold value control means for reducing a threshold value used for the comparison, and determination means for determining the digital data as the synchronous word pattern when the number of matching bits exceeds the threshold value. Wireless packet receiver. 2. A wireless packet receiving apparatus for receiving a wireless packet signal, comprising: level detecting means for detecting a signal level of the received signal; demodulating means for demodulating digital data from the received signal; Pattern comparing means for comparing with a predetermined synchronization word pattern and outputting the number of mismatched bits (number of mismatched bits);
Threshold value control means for increasing a threshold value used for comparison with the number of mismatched bits as the signal level detected by the level detection means is larger, and if the number of mismatched bits is smaller than the threshold value, Determining means for determining the digital data as the synchronous word pattern. 3. The wireless packet receiving apparatus according to claim 1, wherein a signal level detected by said level detecting means is larger than a predetermined value. A wireless packet receiving apparatus comprising demodulator control means for activating the demodulation means.