JP3350066B2 - Signal collision detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distributed control wireless LAN.
The present invention relates to a collision detection method for signals such as packets in (LOCAL AREANETWORK).

[0002]

2. Description of the Related Art A LAN using a coaxial cable is often used for an information transmission system in a premises or the like. By the way, when a layout change or the like occurs from the initial installation state of the LAN, it takes time and cost to re-install the LAN, so that a wireless LAN is strongly required.

Further, LAN access control is broadly classified into centralized control and distributed control. In the centralized control, when one centralized control device goes down, the whole communication system goes down, and it must be said that the reliability of the communication system is low. Further, in the centralized control, even a small system requires a centralized control device. As the system becomes smaller, the cost becomes disadvantageous. For these reasons, LAN standardization is based on distributed control.

There are the following systems for distributed control of a wireless LAN.

[0005] The first is a system called peer-to-peer distributed control, and FIG. 6 shows a schematic configuration thereof.

[0006] As shown in the figure, there is no master station in the network, and terminals 1 directly communicate with each other by transmitting and receiving radio waves from an antenna 2. This system is completely decentralized both physically and in terms of access control.

The second is a system called distributed control via access points, and FIG. 7 shows a schematic configuration thereof. The access point 3 is a so-called repeater, receives a radio wave transmitted from the terminal 1 via the antenna 4, demodulates the radio wave, and converts the demodulated signal into a signal having a frequency different from the frequency of the radio wave transmitted from the terminal 1. The carrier is modulated and emitted from the antenna 4 as a radio wave.

[0008] In the distributed control via access points, for example, if the access point 3 goes down, all communication between the terminals 1 becomes impossible. In the equal distribution control of the wireless LAN shown in FIG. 6, since the same frequency band is used for transmission and reception, a certain terminal receives a radio wave arriving from another terminal while transmitting a signal, and normally demodulates it as data. It is impossible to reproduce or recognize the presence of the signal. For this reason, if a packet collision occurs during packet transmission, the collision cannot be detected, and CSMA / CD (CARRIER SENSE MULTIP) which is a protocol used in a normal office LAN is used.
LEACCESS WITH COLLISION DETECTION cannot be used. Therefore, CS that does not need simultaneous transmission and reception knowing that the throughput performance during high traffic is degraded
We have to adopt MA (CARRIER SENSE MULTIPLE ACCESS) protocol.

Next, a conventional signal collision detection method used in a wired system will be described.

In a system for directly transmitting a baseband signal, a change in the DC level of the signal is detected. However, such a method cannot be applied to a wireless LAN that does not transmit a DC component. A broadband network using one coaxial cable by frequency division multiplexing as a wired network that performs modulation transmission similarly to a wireless LAN is known.

There is a system based on the signal collision detection system used in the broadband network.

Beat signal level detection method This method is basically a method for detecting that the signal level becomes abnormal due to two signals that have collided. Usually, in such a broadband network, FSK (FREQ
UENCY SHIFT KEYING) or MSK (MINIMUM SHIFT
KEYING), etc., but the signals modulated by these two signals are added when two different signals are added, that is, when a signal collision occurs, different deviation parts of the two signals are added. A beat signal is generated by the superposition. By detecting this beat signal, it is determined whether or not a signal collision has occurred.

In this method, in order to increase the reliability of signal collision detection, when signals collide, it is required that the signals have the same level. Therefore, as shown in FIG. 8, a headend 5 is provided in a wired broadband network to perform frequency conversion and level control. In the figure, reference numeral 6 denotes a branching device, 7 denotes a terminal, and 8 denotes a bidirectional amplifier. However, this method cannot be applied to a wireless network in which terminals in a certain area transmit signals completely omnidirectionally. Because in such a wireless network, the loss of the transmission system depends on the positional relationship between the terminals, and it is impossible in principle to control any terminal to keep the signal reception level from all other terminals constant. It is.

The bit comparison / collation method with the signal collision enhancement channel stores the transmitted data, receives and demodulates the transmitted data at the same time, and the packet transmitting terminal compares the transmitted data with the demodulated data. Then, a bit error is detected. If a signal collision occurs, at least a signal having a weaker signal strength has a difference in address or the like, and it is possible to determine a signal collision by detecting the discrepancy. Also, at this stage, at most, only the packet transmitting terminal can know the collision, so that the packet transmitting terminal that has detected the signal collision detects the collision of the signal due to the bit discrepancy. Transmits a randomly modulated collision detection signal. The signal collision enhancement channel uses an auxiliary band of a frequency band different from the signal transmission band, and is a type of out-band signaling. The packet sending terminal that has not detected a bit error and the other receiving-only terminal check for the presence of a collision detection signal on the signal collision enhancement channel.
If it is recognized that a collision detection signal exists in the signal collision enhancement channel, it is recognized that a signal collision has occurred. However, this method requires a function of simultaneously receiving while transmitting, and the distributed control via access point shown in FIG. 7 can be applied, for example, by changing the frequency at the access point 3 and performing echo back.
The feasibility of the peer-to-peer distributed control method shown in FIG. Because the strongest signal source for a packet sending terminal is a signal transmitted from itself, it is theoretically impossible to receive and demodulate a signal of the same frequency sent from another terminal. is there.

FIG. 9 is a diagram schematically showing the configuration of a high-frequency transmission / reception unit of the wireless device.

When considering a wireless LAN using the 2.5 GHz band in this wireless device, the modulator 9 is located at a distance of 1 m.
The reception level of the signal modulated and transmitted by the transmitter is about 40 dB lower than the transmission level of its own signal. Even if the return loss of the omnidirectional antenna 10 is set to 15 dB, the signal transmitted by the demodulator 11 itself is higher than the received signal level by 25 dB, and the two-phase PSK,
The phase PSK or the like cannot recognize signals from other terminals. Reference numeral 12 denotes a circulator as a directional coupler.

Wired random pulse method In this method, two pulses are transmitted at random time intervals before each packet transmission.
The received signal is monitored for a predetermined time, and if it is recognized that there are three or more pulses, it is determined that a pulse has been transmitted from another terminal and a collision has occurred.

FIG. 10 is a diagram showing the operation of this system in time series.

As shown in the figure, if there is a packet transmission request of the upper layer at the point A in the figure, the presence or absence of a signal on the transmission medium is checked at the point B. If there is no signal, two pulses P1 and P2 are transmitted at random intervals during the random pulse transmission period T1. Then, the number of pulses is counted in the pulse number check period T2. T3 indicates the total time of the maximum propagation delay time of the network and the processing delay time of the terminal. Then, the number of pulses is counted, and if a pulse equal to or greater than the number of pulses transmitted by itself is not detected, the packet PT is transmitted. This method always requires a pulse number check period corresponding to the maximum propagation delay of the network prior to packet transmission, and the throughput is reduced accordingly.

[0020]

As described above, in a conventional wireless LAN, if a packet collision occurs during packet transmission, the collision cannot be detected, and thus the conventional wireless LAN is used in a normal office LAN. CSMA / CD, which is a protocol, cannot be used, and a CSMA-based protocol that does not require simultaneous transmission / reception has to be adopted, knowing that the throughput performance during high traffic is degraded.

The present invention has been devised to solve such a problem, and has been developed in a distributed control wireless LAN in CSMA.
It is an object of the present invention to provide a signal collision detection method that enables / CD.

[0022]

In order to achieve the above-mentioned object, a first invention is a signal collision detection method in a network for transferring communication data between a plurality of wireless terminals using a predetermined band. A communication data existence determining step of determining whether or not communication data already exists in the predetermined band before a communication data transmission terminal of the plurality of wireless terminals requests transmission of communication data; When the communication data presence determination step determines that communication data does not exist, the terminal requesting communication data is transmitted to the predetermined band, and the pulse interval is random within a predetermined first period. A test signal transmitting step of transmitting a test signal composed of a number of pulse trains; and a terminal requesting transmission of communication data within a predetermined second period including the first period. A signal collision determination step of determining that there is a signal collision when a pulse other than the transmitted pulse is received, and a second invention is to set a predetermined band between a plurality of wireless terminals. A signal collision detection method in a network for transferring communication data using a communication device, wherein a terminal requesting transmission of communication data among the plurality of wireless terminals has already communicated in the predetermined band prior to transmission of communication data. A communication data presence determination step of determining whether data exists; and the terminal requesting transmission of communication data when the communication data presence determination step determines that no communication data exists. A test for transmitting a test signal composed of a random number of burst signals whose intervals are random within a predetermined first period and whose sum of signal lengths is a predetermined value And a terminal that requests transmission of communication data within a predetermined second period including the first period determines that there is a signal collision when a terminal other than the signal transmitted by the terminal is received. The third invention is a signal collision detection method in a network for transferring communication data between a plurality of wireless terminals using a predetermined band. A communication data existence determining step of determining whether or not communication data already exists in the predetermined band before a communication data transmission terminal of the plurality of wireless terminals transmits communication data; When it is determined in the communication data presence determination step that communication data does not exist, the terminal requesting transmission of communication data to the predetermined band has a random pulse interval within a predetermined first period. A test signal transmitting step of transmitting a test signal composed of a predetermined number of pulse trains, and a terminal that has not requested transmission of communication data within a predetermined second period including the first period is the predetermined signal period. A signal collision determination step of determining that there has been a signal collision when a pulse exceeding the number is detected, and a fourth invention uses a predetermined band between a plurality of wireless terminals. A signal collision detection method in a network for transferring communication data, wherein a terminal requesting transmission of communication data among the plurality of wireless terminals has already received communication data in the predetermined band prior to transmission of communication data. A communication data presence determination step of determining whether or not the communication data exists; and if the communication data presence determination step determines that communication data does not exist, the communication data is transmitted to the predetermined band. A test signal transmission step in which the terminal requesting transmission transmits a test signal composed of a random number of burst signals whose sum of signal lengths is a predetermined value within a predetermined first period; and A terminal which has not requested transmission of communication data within a predetermined second period including a period determines that a signal collision has occurred when the sum of the signal lengths of the burst signals exceeds the predetermined value. And a collision determination step.

[0023]

According to the signal collision detection method of the present invention, a terminal which intends to transmit a packet first checks whether or not there is a transmission from another terminal (the presence or absence of a received signal). If a signal from another terminal is detected, transmission of the packet is waited until the end of the packet. If a signal from another terminal is not detected, the operation shifts to a packet transmission operation.

When the operation shifts to the packet sending operation, a certain period T1
A test signal composed of a plurality of predetermined pulse-like signals having random time intervals or one or more burst signals whose sum of burst lengths is a constant value is transmitted.

The terminal which has transmitted the test signal has a certain period T
If a signal is detected during a period in which the terminal does not transmit a test signal within a certain period T2 including the number 1, it is determined that a signal collision has occurred.

A terminal that has not transmitted a test signal determines that a signal collision has occurred when a test signal exceeding a predetermined number of pulses or a total burst length is received within a predetermined time T2.

By doing so, it becomes possible to realize CSMA / CD in a wireless LAN.

[0028]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of a radio terminal to which the signal collision detection system of the present invention is applied.

As shown in FIG. 1, this terminal comprises a high-frequency unit as a physical layer and a data processing unit as a MAC (MEDIA ACCESS CONTROL) layer. Further, the high-frequency part includes an omnidirectional antenna 100 and a circulator 10.
1, a receiving system 200, and a transmitting system 300.

The receiving system 200 includes a switch 201 for turning on / off a high-frequency signal from the circulator by a carrier switch signal, a high-frequency amplifier 202 with an AGC (AUTOMATIC GAIN CONTROL) for amplifying the high-frequency signal passing through the switch 201, and a local oscillator. 203, a mixer 204 that mixes a high-frequency signal oscillated by the local oscillator 203 and a high-frequency signal output from the high-frequency amplifier 202 to output an intermediate frequency signal, and limits a band of the high-frequency signal output from the mixer 204. Bandpass filter 205
, An intermediate frequency amplifier 206 that amplifies the intermediate frequency signal output from the bandpass filter 205, a demodulator 207 that demodulates baseband data from the output of the intermediate frequency amplifier 206, and detects and smoothes the output of the intermediate frequency amplifier 206 And a carrier detector 208 for detecting the presence or absence of a carrier. The gain of the high frequency amplifier 202 is controlled by the AGC signal from the intermediate frequency amplifier 206.

The transmission system 300 is a modulator 301 for FSK-modulating data from a data processing unit which is a MAC sublayer.
A local oscillator 302, a mixer 303 for mixing a high-frequency signal output from the local oscillator 302 and a modulated high-frequency signal output from the modulator 301 and converting the mixed signal into a high-frequency signal having a predetermined transmission frequency. Bandpass filter 304 for limiting the band of the output high-frequency signal
And a power amplifier 305 that amplifies the power of the high-frequency signal output from the band-pass filter 304. The modulator 301 is turned on / off by a carrier switch signal from the MAC sublayer. The carrier switch signal is subjected to signal processing by an inverter 401 and a delay 402, and on / off control of the switch SW is performed.

In the idle state, the carrier switch signal is off, and the switch 201 is on for signal reception. In this case, the antenna 10
The signal received at 0 is guided to the high-frequency amplifier 202 via the circulator 101 and the switch 201. The high-frequency amplifier 202 is operated in a range where no carrier is erroneously detected due to noise when there is no signal. The high-frequency signal output from the high-frequency amplifier 202 is supplied to the local oscillator 20
3 and converted to an intermediate frequency. After this,
The band-pass filter 205 passes only a predetermined band, and the intermediate frequency amplifier 206 performs intermediate frequency amplification.
An AGC signal is sent from the intermediate frequency amplifier 206 to the high frequency amplifier 202, and the gain of the high frequency amplifier 202 is feedback-controlled based on the AGC signal. With such control, the output level of the intermediate frequency amplifier 206 becomes constant. The signal output from the intermediate frequency amplifier 206 is demodulated by the demodulator 207 and the demodulated data is
The data is sent to the data processing unit which is the C sublayer. On the other hand, the signal output from the intermediate frequency amplifier 206 is also sent to the carrier detector 208, and the presence or absence of a carrier is detected.

The MAC sub-layer, which has received a packet transmission request from the upper layer, checks the presence or absence of a carrier from the high-frequency unit which is the physical layer. If there is no carrier, a test signal is transmitted.

Although FIG. 1 shows a configuration based on the heterodyne system, a homodyne system may be used.

FIG. 2 is a diagram showing an example of the configuration of the test signal.

The pulse P1 is transmitted at the head point C of the test signal transmission period T1. The second pulse P2 is sent out after the elapse of the randomly selected bit period r1. The transmission of the pulse is performed by turning on the carrier switch signal in the MAC sublayer. At that time, the switch 201 is turned off to prevent a strong signal from being guided to the high frequency amplifier 202 of the receiving system 200. In addition,
The carrier switch signal for controlling the switch 201 must be delayed by the delay of the transmission system 300 such as the modulator 301. In addition, unnecessary vibration occurs before and after a burst signal output as a high-frequency signal due to band limitation in the modulator 301 and the like, so the switch 201 must be turned off accordingly. This switch 201
Is not always necessary when the circulator 101 is complete, there is no reflected wave from the antenna 100, and there is no unnecessary vibration. Further, a limiter for blocking the input of a signal having a level higher than a predetermined level may be provided instead of the switch 201.

FIG. 3 is a timing chart showing transmission and reception of a test signal.

As shown in the figure, the first pulse P01 of the test signal transmitted from another terminal is transmitted to the antenna 1 at substantially the same timing as the pulse P00 itself is transmitted.
Suppose we arrive at 00. Since the switch 201 is off while receiving the pulse P01, no carrier is detected.
However, if the timing of the second pulse P10 of the test signal is different from the timing of the input pulse P11, this terminal uses P11
, And it is possible to detect signal collision. The time interval Tr0 between the pulse P00 and the pulse P01 and the time interval Tr1 between the pulse P01 and the pulse P11 are determined at random. In the above description, the pulse P00 is transmitted at the beginning of the test signal transmission period T2, and the test signal is two pulses. However, two or more pulses may be transmitted, and the first pulse is not always the first pulse. Is also good. However, in order to shorten the signal collision detection time, it is better that the first pulse is at the beginning of the test signal transmission period T2.

The longer the test signal transmission period T2, the greater the number of combinations of pulses transmitted at random intervals.
The combination of the pulses also changes according to the number of the pulses. In general, if the number of time slots for pulse transmission during the test signal transmission period T2 is n and the number of pulses is m, the combination of pulse positions is _n C _m . For example, n
= 33, a combination of m = 16 if 10 ^nine becomes possible. If the unnecessary signal before and after the high frequency burst signal is sufficiently short and the off time of the control signal of the switch 201 (the output of the delay 402) is almost the same as the on time of the carrier switch signal, the two terminals transmitting the test signal will As long as the combination of pulse positions is different, signal collision detection becomes possible. In the case where the parameter is as described above, the probability of overlooking signal collision detection is 10 ⁻⁹ , and practically sufficient characteristics are realized.

In the above-described embodiment, the high-frequency amplifier 202 of the receiving system 200 is provided with the AGC function.
The AGC function may not be provided as long as the distortion characteristic and the cross modulation characteristic of 00 are good.

The pulse number check period T1 depends on the size of the operating area.

FIG. 4 is a diagram showing a case where it takes a longest time to complete signal collision detection when terminal A and terminal B each transmit a pulse as a test signal.

As shown in the figure, the pulse P0A transmitted from the terminal A arrives at the terminal B after a lapse of the propagation delay time Tpd. It is assumed that the terminal B transmits the pulse P0B before the arrival of the pulse P0A can be recognized after a lapse of time τ1 during the processing operation after the arrival of the pulse P0A. The pulse P0B arrives at the terminal A after a lapse of the propagation delay time Tpd. At this time, if the terminal A transmits the pulse P1A at the same timing as the arrival of the pulse P0B, the terminal A cannot recognize the arrival of the pulse P0B. Further, the pulse P1A transmitted from the terminal A arrives at the terminal B after the propagation delay time Tpd elapses. After a lapse of the processing delay time τ2 (point D in the figure), the existence of the pulse P1A is recognized, and the terminal B knows that a signal collision has occurred. Assuming that the second pulse of the terminal B is transmitted in the last time slot of the test signal transmission period T0 by randomization, it arrives at the terminal A after a lapse of the propagation delay time Tpd from this point, and the processing time τ2 elapses. After that (point E in the figure), terminal A
Indicates that a signal collision has occurred. When it is detected that a signal collision has occurred, the terminal forgoes transmission of the packet.

As described above, the total time TA from when the terminal A transmits the test signal pulse to when the terminal A detects the signal collision is as follows.

TA = Tpd + τ1 + T0 + Tpd + τ2 = 2Tpd + T0 + τ1 + τ2 If the pulse width is 0.5 μsec and the number of time slots is 33, the test signal transmission period T0 is 16.5 μsec. 2Tpd is 0.67 μsec, assuming that the distance between terminals in the same area of the wireless LAN is 100 m.
A is about 17 μsec. If this is a wired LAN, the cable of the private network is about 6 km and the propagation delay time is 40 μm.
sec.

In the above example, the pulse is fixedly transmitted at the beginning of the test signal transmission period. However, if the position of the first pulse is also randomized, the collision detection time in the worst case scenario increases and the throughput decreases. The detection accuracy of the collision detection is increased. The longest time required for detection can be shortened by setting the interval between the transmission of the two pulses to be equal to or longer than 2Tpd + T0 + τ2 + pulse width so that the pulse P0B is not masked by the pulse P1A. Further, the terminal that detects the collision of signals can shorten the detection time even if it immediately transmits a jam signal.

In the above-described example, each terminal transmits a plurality of pulse signals as a test signal. However, each terminal transmits a burst signal having a constant total time during a test signal transmission period to cause a signal collision. The terminal may detect a signal collision by monitoring the burst signal length during the test signal transmission period. For example, as shown in FIG. 5, during a test signal transmission period, terminal A transmits a burst signal having a total signal length of 5 μsec as shown in FIG. 5A, and terminal B transmits a total signal length shown in FIG. When a burst signal of 5 μsec is transmitted, the total signal length is 8 μs as shown in FIG.
An ec burst signal is generated in the communication band. If the terminal requesting transmission recognizes that a signal exists during a period other than when the terminal itself is transmitting, it determines that a signal collision has occurred, and the terminal not requesting transmission has a total signal length of the burst signal. When it is recognized that the time exceeds 5 μsec, it may be determined that a signal collision has occurred.

The modulation of the test signal or the packet data may employ a spread spectrum method such as DS (direct sequence) or FH (frequency hopping), which is multiplied by pseudo noise. When such a method is adopted, the influence of radio waves transmitted from other sources is reduced, a diversity effect can be expected for multipath, and stable communication can be performed.

Therefore, in the above-described embodiment, the wireless LA
It is possible to detect packet collisions at N and to employ CSMA / CD with good throughput characteristics.

[0051]

According to the signal collision detection system of the present invention, first, a terminal which intends to transmit communication data checks whether there is a test signal from another terminal. If a signal from another terminal is not detected, the sum of a plurality of predetermined pulse-like signals or burst lengths having random time intervals within a fixed time T is set to a fixed value prior to transmission of communication data. A test signal is transmitted.

The terminal which has transmitted the test signal has a predetermined time T
If the terminal detects a signal during a period in which its own terminal does not transmit a test signal within a certain period including the above, it is determined that a signal collision has occurred.

A terminal which has not transmitted a test signal determines that a signal collision has occurred when a test signal exceeding a predetermined number of pulses or a total burst length is received within a predetermined time T.

By doing so, it becomes possible to realize CSMA / CD in a wireless communication network.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an embodiment of a wireless terminal to which a signal collision detection method according to the present invention is applied.

FIG. 2 is a diagram illustrating a configuration of an example of a test signal.

FIG. 3 is a timing chart showing transmission and reception of a test signal.

FIG. 4 is a diagram illustrating a case where a longest time is required to complete signal collision detection when terminal A and terminal B each transmit a pulse as a test signal.

FIG. 5 shows an example of a test signal in which the sum of burst signals is constant.

FIG. 6 is a diagram showing one schematic configuration of a system called peer-to-peer distributed control.

FIG. 7 is a diagram showing a schematic configuration of a system called distributed control via access points.

FIG. 8 is a diagram illustrating a configuration of a wired broadband network.

FIG. 9 is a diagram schematically illustrating a configuration of a high-frequency transmitting / receiving unit of the wireless device.

FIG. 10 is a diagram showing the operation of the wired random pulse system in a time-series manner.

[Explanation of symbols]

 Reference Signs List 100 antenna 101 circulator 200 reception system 201 switch 202 high-frequency amplifier 203 local oscillator 204 mixer 205 band-pass filter 206 intermediate frequency amplifier 207 demodulator 208 carrier detector 300 transmission system 301 modulation Instrument 302 local oscillator 303 mixer 304 bandpass filter 305 power amplifier 401 inverter 402 delay

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-27640 (JP, A) JP-A-1-135241 (JP, A) JP-A 64-3231 (JP, U)

Claims (4)

(57) [Claims] 1. A signal collision detection system in a network for transferring communication data between a plurality of wireless terminals using a predetermined band, wherein the terminal requests transmission of communication data among the plurality of wireless terminals. Prior to the transmission of communication data, a communication data presence determination step of determining whether communication data already exists in the predetermined band; and A test signal transmission step in which the terminal requesting transmission of communication data transmits a test signal composed of a predetermined number of pulse trains whose pulse intervals are random within a predetermined first period to the predetermined band, A terminal that requests transmission of communication data within a predetermined second period including the first period has a signal collision when receiving a pulse other than the pulse transmitted by itself. Signal collision detection scheme and a signal collision determination step of determining that the. 2. Using a predetermined band between a plurality of wireless terminals.
Signal collision detection in networks that transfer communication data
A out method, to request transmission of communication data of the plurality of wireless terminals
Before sending the communication data, the terminal
Communication data that determines whether communication data already exists
Communication data exists by the existence determination step and the communication data existence determination step.
Request transmission of communication data when it is determined not to
The terminal is moved to the predetermined band within a predetermined first period.
Is a random number of burst signals
Test signal whose total signal length is a predetermined value.
Outputting a test signal, and transmitting the communication data within a predetermined second period including the first period.
The terminal requesting data transmission sends a signal other than the signal transmitted by itself.
When a signal is received, it is determined that there is a signal collision.
A signal collision detection method comprising a signal collision determination step. 3. A signal collision detection method in a network for transferring communication data between a plurality of wireless terminals using a predetermined band, wherein the terminal requests transmission of communication data among the plurality of wireless terminals. Prior to the transmission of communication data, a communication data presence determination step of determining whether communication data already exists in the predetermined band; and To the predetermined band, a test signal transmission step in which the terminal requesting transmission of communication data transmits a test signal composed of a predetermined number of pulse trains whose pulse intervals are random within a predetermined first period, A terminal that has not requested transmission of communication data within a predetermined second period including the first period detects a signal collision when detecting a pulse exceeding the predetermined number. There was a determining signal collision determination process and the signal collision detection method comprising a. 4. A signal collision detection method in a network for transferring communication data between a plurality of wireless terminals using a predetermined band, wherein the terminal requests transmission of communication data among the plurality of wireless terminals. Prior to the transmission of communication data, a communication data presence determination step of determining whether communication data already exists in the predetermined band; and A test in which the terminal that requests transmission of communication data to the predetermined band transmits a test signal composed of a random number of burst signals whose sum of signal lengths is a predetermined value within a predetermined first period A signal transmitting step, wherein the terminal that has not requested transmission of communication data within a predetermined second period including the first period has a total sum of signal lengths of the burst signals equal to the predetermined value. Signal collision detection scheme and a and determining signal collision determination process was a collision of signals when exceeded.