Radio access method and radio communication system

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a random access control method when a plurality of radio stations share one radio frequency for communication, and a response packet from a data packet receiving station to a transmitting station does not conflict with other stations. The present invention relates to a wireless access method capable of packet transmission using preferential transmission timing and a wireless communication system adopting this method.

【0002】

[Conventional technology]

As a conventional wireless access method in which the priority station access time to be the subject of the present invention is set, an access method in a wireless LAN (local area network) system specified by the IEEE802 committee is typical. This regulation is described in detail in "IEEE P802.11, Draft Standard for Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specification, P802.11 D6.1,9 May 1997". The "priority station access time" referred to here is a timing at which packet transmission can be preferentially performed without competing with other stations. In addition, this regulation will be described below as the "802.11 standard".

【0003】

FIG. 1 is a first explanatory diagram showing packet transmission by the wireless access method specified in the 802.11 standard over time. The figure shows a case where four radio stations (radio stations # 1 to radio station # 4) share the same frequency and communicate with each other while avoiding packet collisions, and time elapses to the right. It is supposed to go. Further, as packets transmitted from these radio stations, two types are shown: a data packet and a response packet in which the radio station receiving the data packet notifies the transmitting side of the reception status.

【0004】

First, time t₁When radio station # 1 sends a data packet 11 addressed to radio station # 3, the time t when the transmission is completed₃After the priority station access time S1, the radio station # 3 can return the response packet 21 for the data packet 11 to the radio station # 1. Now, tentatively, the time t while radio station # 4 is transmitting data packet 11₂If you wish to transmit the data packet 12 to, you must confirm that the radio frequency is not used for the radio station random access time (= priority station access time + random time) after the transmission of the data packet 11 is completed (= priority station access time + random time). These times will be described in detail later with reference to FIG. 3). However, here, the response packet 21 is the time t after the priority station access time S1.₄Since it was sent to, radio station # 4 will refrain from sending data packet 12. After that, the radio station # 4 completes the transmission of the response packet 21 (time t).₅), Time t after radio station random access time T1₆Sends data packet 12 addressed to radio station # 2 to.

【0005】

Next, radio station # 2 is at time t₇I wanted to send the data packet 13 in, but since the data packet 12 was received, the time t at the time when the transmission was completed₈From time t after priority station access time S2₉Sends response packet 22 to radio station # 4. After that, the radio station # 2 is set to the time t when the transmission is completed.₁₀Check that the radio frequency is unused only during the radio station random access time T2 from the time t₁₁Starts transmitting data packet 13 addressed to radio station # 1. By the method described above, even if a plurality of radio stations share one radio frequency, wireless access is enabled so that transmission packets do not collide with each other and response packets can be reliably returned.

【0006】

On the other hand, FIG. 2 is a second explanatory diagram showing packet transmission by the wireless access method specified in the 802.11 standard over time. The figure shows a case where the transmitting station #S and the receiving station #R share the same radio frequency for communication, and it is assumed that time elapses to the right. In addition, there are two types of packets to be transmitted: a fragment that is transmitted by dividing a large data packet into a plurality of wireless packets, and a response packet in which the receiving station #R that receives these fragments notifies the transmitting side of the reception status. It is shown.

【0007】

As shown in Fig. 2, in the "802.11 standard", when transmitting a series of fragments, these fragments and response packets can be transmitted alternately at priority station access time (S1 to S6) intervals. The radio station random access time (T1, T2) before data packet transmission described in 1 is not required. In other words, the intervals between fragments 31 to 34 and response packets 41 to 43 are all priority station access times S1 to S6, and a series of fragments can be preferentially transmitted without being interrupted by data packet transmission from other radio stations. , Efficient wireless access can be realized.

【0008】

Next, FIG. 3 is a diagram illustrating the relationship between the priority station access time and the radio station random access time described above. In the figure, the priority station access time S is the time during which the receiving station #R, which has received the data packet 11 from the transmitting station #S, can return the response packet 21, and as shown in the figure, the three system times. Is defined as the sum of the reception processing time d1, the response packet creation time d2, and the transmission processing time d3.

【0009】

Here, the reception processing time d1 means the time required for the receiver in the receiving station #R to perform processing such as demodulation and error correction to assemble the original data packet after receiving the data packet 11. The response packet creation time d2 means the time required to confirm the validity of the assembled data packet and create a response packet for the data packet. Further, the transmission processing time d3 means the time required to modulate the created response packet and start transmission on the radio frequency from the transmitter in the receiving station #R. In this way, the priority station access time S is determined by the processing capacity of the radio station, and is defined as the minimum time required from the reception of the data packet to the transmission of the response packet.

【0010】

On the other hand, in the station #T other than the transmitting station #S and the receiving station #R, after confirming the completion of the transmission of the data packet 11, the radio frequency over the radio station random access time T before starting the transmission of the data packet 12. Must be checked for unused. Here, the radio station random access time T is the priority station access time S and the random time r (0 <r the maximum value r defined in the system) set by the user._max) Is given as the sum. As a result, as shown in the figure, the other station #T cannot start transmitting the data packet 12, and can avoid a collision with the response packet 21. After that, the other station #T can try to transmit the data packet 12 by newly setting the radio station random access time T after confirming the completion of the transmission of the response packet 21.

【0011】

[Problems to be Solved by the Invention]

When a plurality of radio stations share a radio frequency and use it, the frequency utilization efficiency can be maximized by transmitting all the radio packets without any time gap. However, in order to avoid radio packet collisions between arbitrary radio stations, a considerable amount of radio frequency monitoring time before transmission is required. Regarding the section of "conventional technology", the shortest radio packet interval in the "802.11 standard" is the priority station access time S (see FIG. 3). Further, when transmitting a normal data packet, the radio station random access time T is obtained by adding the random time r to the priority station access time S, and these time intervals affect the frequency utilization efficiency.

【0012】

By the way, as shown in FIG. 3, the priority station access time S is determined by the processing capacity of the radio station, which is a fixed time interval that cannot be easily shortened. Further, the reception processing time d1, which is one of the components of the priority station access time S, will be further increased if an advanced error correction method or the like is adopted to ensure reception quality. Further, the radio station random access time T, which is another time interval, must exceed at least the priority station access time S, and as a result, it is set as a value depending on the priority station access time S. .. As described above, in the conventional method, since the priority is given only to the response packet corresponding to the data packet immediately after the data packet, the frequency is used by the priority station access time S which cannot be shortened due to the capacity of the radio station. There is a problem that efficiency is dominated and system capacity is limited.

【0013】

Further, in a situation where the response packet 22 must be transmitted first even though there is a desire to transmit the data packet 13 as in the radio station # 2 described in FIG. 1, the transmission of the data packet 13 cannot be started before the transmission of the data packet 13 can be started. Since the transmission of the response packet 22 is completed after the priority station access time S2 elapses and the interval of the radio station random access time T2 is waited for, there is a problem that the transmission delay becomes large.

【0014】

Furthermore, even if a system with improved transmission speed on the radio frequency is adopted and data packets can be transmitted in a short time, the priority station access time S is constant regardless of the transmission speed as long as the conventional method is applied. Therefore, there is a problem that the ratio between the radio packet length and the radio packet interval becomes rather large. Therefore, there is a problem that the frequency utilization efficiency cannot be improved when transmitting an efficient series of fragments as described in FIG.

【0015】

The present invention has been made in view of the above points, and an object thereof cannot be shortened in terms of the capability of a radio station because priority is given immediately after a data packet only to a response packet corresponding to the data packet. An object of the present invention is to provide a wireless access method and a wireless communication system that solve the conventional problem that the frequency utilization efficiency is controlled by the priority station access time and the system capacity is limited.

【0016】

[Means for solving problems]

In order to solve the above problems, in the invention according to claim 1, when a plurality of radio stations share one radio frequency for packet data communication, the radio station that intends to transmit a packet is with another station. The packet can be transmitted after confirming that the radio frequency is not used over the priority station access time that can preferentially transmit the packet without conflict and the random time selected from the preset range, and the transmitting station can transmit the packet. In a wireless access method in which a receiving station that has received a data packet from the above can preferentially transmit a response packet notifying the completion of reception of the data packet to the transmitting station with the passage of the priority station access time. When the receiving station returns the response packet, (1a) if the receiving station already has a data packet waiting to be transmitted, (1b) the priority station access time and the random time are described as described above. It monitors whether the radio frequency remains unused, and (1c) if the radio frequency remains unused, the transmission waiting data packet is transmitted, and the priority station access time after the transmission is completed. After that, the response packet is returned, and (2a) if the data packet waiting to be transmitted does not exist at the receiving station, (2b) after receiving the data packet, the priority station access time and the range are within the range. over the maximum time, the radio frequency is monitored either left unused, (2c) the radio frequency is unused Mamadea return the lever immediately the response packet, (3) the ( When the radio frequency is used during the monitoring in 1b) or (2b), after the transmission of the subsequent data packet transmitted from the radio station other than the own station is completed and the priority station access time elapses. It is characterized in that the response packet is returned.

【0017】

Further, in the invention of claim 2, in the invention of claim 1, the confirmation that the radio frequency is not used is that the reception level measured while monitoring the radio frequency is predetermined. It is characterized by not exceeding the specified tolerance level. Further, in the invention of claim 3, in the invention of claim 1, confirmation that the radio frequency is unused means that the radio packet received while monitoring the radio frequency is normally received. It is characterized by doing what it couldn't do.

【0018】

Further, the invention according to claim 4 is a radio communication system in which a plurality of radio stations share one radio frequency for packet data communication, and the radio station that intends to transmit a packet does not compete with other stations. The packet can be transmitted after confirming that the radio frequency is not used over the priority station access time that can preferentially transmit the packet and the random time selected from the preset range, and the data packet can be transmitted from the transmitting station. When returning a response packet notifying the completion of reception of the data packet to the transmitting station, the radio station receiving the data packet can preferentially transmit the data packet with the lapse of the priority station access time. Is a confirmation means for confirming whether or not a data packet waiting to be transmitted already exists in the radio station at the time of returning the response packet to the received data packet, and the transmission according to the presence or absence of the data packet waiting to be transmitted. If there is a waiting data packet, the unused of the radio frequency is monitored over the priority station access time and the random time, and if the waiting data packet does not exist, the time when the data packet is received is received. Therefore, if the monitoring means for monitoring the unused of the radio frequency over the priority station access time and the maximum time within the range, and the radio frequency is used according to the monitoring result by the monitoring means. If it is confirmed that the subsequent data packet transmitted from a radio station other than the own station has been transmitted, and the response packet is returned after the priority station access time has elapsed, the radio frequency remains unused. If the transmission-waiting data packet exists depending on the presence or absence of the transmission-waiting data packet, the transmission-waiting data packet is transmitted and the response packet is returned after the priority station access time has elapsed from the completion of the transmission. It is characterized by including a return means for immediately returning the response packet if the data packet waiting for transmission does not exist.

【0019】

Further, the invention according to claim 5 is the invention according to claim 4, wherein the monitoring means includes a measuring means for measuring a reception level while monitoring the radio frequency, a measurement result of the reception level, and a priori. It is characterized by having a determination means for comparing a predetermined allowable level and determining that the radio frequency is unused if the measurement result of the reception level does not exceed the allowable level. The invention according to claim 6 is the invention according to claim 4, wherein the monitoring means is a determination means for determining the normality of a radio packet received while monitoring the radio frequency, and the reception. It is characterized in that it has a determination means for determining that the radio frequency is unused if the normality of the radio packet is not confirmed.

【0020】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Here, in the present invention, as described in detail below, the priority station access time is shortened to the equivalent of the transmission processing time, whereby the expected value of the radio station random access time including the random time is also shortened as compared with the conventional case. I am trying to do it. In the following, the details of the procedure of the wireless access method according to the present invention will be explained first with reference to FIG. 4, and then the explanation will be given according to the actual examples shown in FIGS. 5 to 6 while comparing with FIGS. 1 to 2 described above. I will do it.

【0021】

FIG. 4 is a flowchart showing a detailed procedure of the wireless access method according to the present invention (corresponding to claims 1 and 4). First, when the receiving station that has received the data packet addressed to its own station (step SP1) returns the response packet corresponding to the data packet, whether or not the data packet waiting to be transmitted already exists in the receiving station. Determine if (step SP2). If there is a data packet waiting to be transmitted (the judgment result of the same step is "Y"), the random time r is set to (0 <rmaximum value r defined in the system)._max) Is set within the range (step SP3). On the other hand, if there are no data packets waiting to be transmitted (the judgment result of step SP2 is "N"), the maximum value r defined in the system as the random time r._maxSet to (step SP12).

【0022】

After this, it monitors whether the radio frequency is used until the radio station random access time obtained by adding the priority station access time to the set random time expires (that is, there is a data packet waiting to be transmitted). If it is, the loop of steps SP4 to SP5, if it does not exist, the loop of steps SP13 to SP14). Then, when there is a data packet waiting to be transmitted, if the random access time of the radio station expires while the radio frequency is unused (the judgment result of step SP5 is "Y"), the data packet waiting to be transmitted is transmitted (step SP6). After that, when the priority station access time has elapsed, the response packet for the originally received data packet (step SP1) is continuously transmitted (step SP8).

【0023】

On the other hand, if there is no data packet waiting to be transmitted and the random access time of the radio station expires while the radio frequency is unused (the judgment result of step SP14 is "Y"), the response packet is immediately transmitted (step). SP15). On the other hand, when the transmission of the succeeding data packet from another station is confirmed during the monitoring of the radio frequency (step SP9), the transmission of the succeeding data packet is waited for to be completed regardless of the presence or absence of the data packet waiting to be transmitted. The response packet is transmitted after the priority station access time has elapsed (step SP10) (step SP11). Therefore, in this case, even if there is a data packet waiting to be transmitted, the transmission of the response packet is prioritized.

【0024】

As a method of monitoring whether or not a radio frequency is used (steps SP4 and SP13), a method of using the measurement result of the reception level (corresponding to claims 2 and 5) and a method of using the correctness of the received packet (corresponding to claims 2 and 5). (Corresponding to claims 3 and 6). The former is generally called the carrier sense method, which is a method of comparing the measurement results of a predetermined allowable level and the reception level and determining that the radio frequency is used when the measurement result becomes larger. is there. This carrier sense is also an indispensable function in the wireless access method described in the section of "conventional technology", and is not a function newly required for carrying out the present invention.

【0025】

On the other hand, the latter is a method based on whether or not the received packet is normal regardless of the reception level, and when normal reception can be confirmed, it is determined that the radio frequency has been used. Normally, the validity of the received packet can be confirmed by calculating on the receiving side using the error detection bit added on the transmitting side. The use of such an error detection bit is indispensable when implementing a retransmission protocol for error recovery, and is realized by diverting the current method rather than a function newly required for implementing the present invention. be able to.

【0026】

[Example]

Next, the wireless access procedure according to the present invention will be described with reference to the flowchart of FIG. 4 with reference to the examples shown in FIGS. 5 to 6. FIG. 5 is a first explanatory diagram showing packet transmission by the wireless access method of the present invention over time. Here, the notation and packet communication conditions in the figure are basically the same as those in FIG. 1, but the radio station random access times P1 to P3 and the priority station access times Q1 to Q2 are newly set by the present invention. It differs in that it is a time interval.

【0027】

First, time t₂₁Data packet 11 transmitted by radio station # 1 to time t₂₃Radio station # 3 receives up to (step SP1). In this case, since there are no packets waiting to be transmitted at radio station # 3 (the judgment result of step SP2 is "N"), the maximum value r that can take a random time for transmitting the response packet 21._maxIs set (step SP12), and whether or not the radio frequency is used is monitored only during the "set random time + priority station access time" (steps SP13 to SP14).

【0028】

On the other hand, in radio station # 4, time t₂₂0 <rmaximum value r defined in the system for transmission of data packet 12 to radio station # 2 that occurred in_maxRandom time r is selected within the range of, and the priority station access time is added to this to obtain the radio station random access time P1. Next, radio station # 4 is at time t₂₃After monitoring the radio frequency only during the radio station random access time P1 and confirming that the radio frequency is unused, time t₂₄Starts transmission of data packet 12 at. As a result, radio station # 3 detects that the radio frequency has been used (determination result of step SP13 is N), and confirms subsequent data packets from other stations (step SP9). Next, radio station # 3 is the time t when the transmission of data packet 12 is completed.₂₅Time t when the priority station access time Q1 has elapsed (step SP10) based on₂₆The transmission of the response packet 21 to the radio station # 1 is started from (step SP11).

【0029】

Here, the priority station access time Q1 can be defined in a short time corresponding to the transmission processing time d3 (Fig. 3), and as a result, the expected value of the radio station random access time including the priority station access time is also short. It will be something like that. Therefore, the frequency can be effectively used as compared with the case where the conventional priority station access time S (that is, the sum of the reception processing time d1, the response packet creation time d2, and the transmission processing time d3) is used.

【0030】

On the other hand, in the radio station # 2 that received the data packet 12 (step SP1), the time t₂₇The request for transmission of the data packet 13 occurs at. After that, radio station # 2 can return the response packet 22, but at that point, there is a data packet waiting to be transmitted (the judgment result of step SP2 is "Y"). Therefore, radio station # 2 sets the radio station random access time P2 (step SP3), and waits for the transmission of the response packet 21 to be completed.₂₈After waiting until, start monitoring whether the radio frequency is used (steps SP4 to SP5). In this case as well, the radio frequency is not used until the expiration of the random access time P2 of the radio station (the judgment result of step SP5 is "Y"), so that the radio station # 2 is set to the time t.₂₉The data packet 13 waiting to be transmitted is transmitted at (step SP6), and then the transmission is completed at time t.₃₁Time t when only the priority station access time Q2 has passed since (step SP7)₃₂In, the response packet 22 is transmitted to the radio station # 4 (step SP8).

【0031】

Also, at radio station # 4, time t₃₀Since the desire to transmit the data packet 14 has occurred in, 0 <r the maximum value r defined in the system, as in the case of the radio station random access time P1._maxSet the radio station random access time from the random time r and priority station access time selected within the range of, and time t₃₁The radio frequency is monitored over the random access time of this radio station. However, in this case, as mentioned above, radio station # 2 is at time t.₃₂Since the transmission of the response packet 22 is started from, the radio station # 4 temporarily gives up the transmission of the data packet 14 so as not to interrupt between the data packet 13 and the response packet 22. Then time t₃₃When the transmission of the response packet 22 is completed in, radio station # 4 sets the radio station random access time P3 again, and the time t₃₃After monitoring the radio frequency only during this radio station random access time P3 and confirming that it remains unused, time t₃₄The transmission of the data packet 14 is started at. As described above, according to the present invention, since the data packet and the response packet can be continuously transmitted from the same radio station, it is possible to suppress the transmission delay of the data packet and realize the reliable return of the response packet. It becomes.

【0032】

By the way, in the above explanation, if time t₂₄The maximum value r set earlier by radio station # 3 without transmitting data packet 12 at_max+ If the time corresponding to the priority station access time (step SP12) has elapsed (the judgment result of step SP14 is "Y"), the radio station # 3 immediately returns the response packet 21 to the radio station # 1 (step). SP15). Further, in the above description, if the subsequent data packet is transmitted by another station during the radio station random access time P2 in which the radio station # 2 is monitoring the radio frequency (the judgment result of step SP4 is ". N "), radio station # 2 confirms this subsequent data packet (step SP9), and when the priority station access time elapses after the transmission is completed (step SP10), the response packet 22 is transmitted (step SP11). ) Will be done.

【0033】

Next, FIG. 6 is a second explanatory diagram showing packet transmission by the wireless access method of the present invention over time. The notation and packet communication conditions in the figure are basically the same as in FIG. 2, except that the priority station access times Q1 to Q7 are the time intervals newly set by the present invention. As shown in the figure, in the case of the present invention as in the conventional case, when a series of fragments 31 to 35 are transmitted, these fragments and the response packets 41 to 43 are alternately transmitted at intervals of the priority station access time. Can be radio station random access time is not required. Therefore, the intervals between fragments 31 to 35 and response packets 41 to 43 are all priority station access times Q1 to Q7, and a series of fragments are preferentially processed without being interrupted by data packet transmission from other radio stations. Can be sent.

【0034】

Here, as described above, the priority station access times Q1 to Q7 in the present invention can be significantly shortened as compared with the conventional priority station access times S1 to S6 (see FIG. 2). Therefore, in the present invention, it is possible to perform fragment transfer with further improved frequency utilization efficiency as compared with the conventional system, and when the transmission speed on the radio frequency is improved or a system requiring advanced error correction processing. Also, the priority station access time can be maintained in a short time.

【0035】

As described in detail above, a feature of the present invention is that, immediately after receiving a data packet, the response packet corresponding to the data packet is not returned, but is returned immediately after the subsequent data packet. .. As a result, the priority station access time due to the capability of the radio station can be defined only by the transmission processing time. Therefore, the priority station access time can be significantly shortened as compared with the case where the reception processing time, the response packet creation time, and the transmission processing time are defined as the sum of the conventional cases. Therefore, even if the system adopts advanced error correction processing and the reception processing time is increased, it is necessary to realize efficient wireless access that maintains the frequency utilization efficiency without increasing the priority station access time. Can be done.

【0036】

[Effect of the invention]

As described above, according to the present invention, when a transmission-waiting data packet exists in the receiving station, the response packet is continuously transmitted when the priority station access time elapses after transmitting the transmission-waiting data packet. Since it can be transmitted, the response packet can be reliably returned, and the transmission delay of the data packet can be suppressed. In addition, when there is no data packet waiting to be transmitted, the response packet can be returned immediately if there is no subsequent data packet from another station, and even if there is a subsequent data packet, the priority station access time elapses after the transmission is completed. Since the response packet can be returned at that point, the response packet can be reliably returned. Further, immediately after receiving the data packet, instead of returning the response packet corresponding to the data packet, if the receiving station of the data packet has a data packet waiting to be transmitted or a subsequent data packet from another station, these data packets The response packet is returned after the transmission of is completed. Therefore, the priority station access time due to the capability of the radio station can be defined only by the transmission processing time, and has priority over the conventional case where it is defined by the sum of the reception processing time, the response packet creation time, and the transmission processing time. The station access time can be significantly reduced. Therefore, even in a wireless communication system in which the reception processing time increases due to the adoption of advanced error correction processing, it is necessary to provide wireless access that maintains frequency utilization efficiency without increasing the priority station access time. Can be done. On the other hand, according to the inventions of claims 2, 3, 5, and 6, whether or not a radio frequency is used can be realized by using only a function that also exists in conventional wireless access.

[Simple explanation of drawings]

[Figure 1]

It is 1st explanatory diagram which showed the packet transmission in the wireless access method by the prior art with the passage of time.

[Figure 2]

It is a 2nd explanatory diagram which showed the packet transmission in the wireless access method by the prior art with the passage of time.

[Fig. 3]

It is explanatory drawing which showed the relationship between the priority station access time and the radio station random access time in the radio access method by the prior art.

[Fig. 4]

It is a flowchart explaining the detailed procedure of the wireless access method by one Embodiment of this invention.

[Fig. 5]

It is 1st explanatory diagram which showed the packet transmission in the wireless access method by the same embodiment with the passage of time.

[Fig. 6]

It is a 2nd explanatory diagram which showed the packet transmission in the wireless access method by the same embodiment with the passage of time.

[Explanation of symbols]

#R receiver #S transmitter #T other stations # 1 ~ # 4 Radio stations d1 reception processing time d2 Response packet creation time d3 Transmission processing time P1, P2, T1, T2 radio station random access time Q1 ~ Q7, S, S1 ~ S6 Priority station access time r Random time set by another station T Radio station random access time of other stations 11 ~ 14 data packets 21,22,41 ~ 43 Response packets 31 ~ 35 Fragment