JP2004193987A - Wireless packet communication method and wireless packet communication device - Google Patents

Abstract

An object of the present invention is to minimize the waste of frequency resources when a collision occurs without depending on a limited modulation / demodulation method, and realize a highly efficient throughput.
A wireless packet signal is transmitted from one antenna, a signal is received by one antenna, and a transmission signal of a local station is transmitted from a received signal using a propagation coefficient h between a transmission antenna and a reception antenna. The signal component after removing the component is obtained, the reception level of the signal component is determined, and when the reception level is equal to or higher than the threshold, the transmission of the wireless packet signal is stopped. Continue sending until transmission is completed. In addition, when a measured value of the propagation coefficient h is obtained from the transmission signal component and the received signal of the own station during the transmission of the wireless packet, and the collision is not detected, the propagation coefficient is updated with the measured value and the collision is detected. Does not update the propagation coefficient.
[Selection] Fig. 2

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wireless packet communication method and a communication device. In particular, the present invention relates to a wireless packet communication method and a communication device in which a plurality of wireless stations such as wireless LANs share the same channel by autonomous distributed control.
[0002]
[Prior art]
(Prior art 1)
In a wireless LAN based on IEEE 802.11, CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) is adopted as a method for controlling transmission of wireless packets (for example, see Non-Patent Document 1).
[0003]
In this system, a wireless station observes a wireless channel (carrier sense) prior to transmission, and after confirming that another wireless station is not transmitting, transmits a packet. When another wireless station is transmitting, the packet is transmitted after confirming that no other wireless station is transmitting for a random time after the transmission of the wireless station is completed.
[0004]
In order to transmit after observing the usage status of the other station in the wireless channel, collision can be avoided if the other station is already transmitting a packet. Sharing by a plurality of wireless stations can be realized.
[0005]
(Prior art 2)
FIG. 10 shows the configuration of the invention of Patent Document 1 “Communication system and transmitter and receiver used for the communication system”. The present invention presupposes spread spectrum communication in which a modulated signal is multiplied by a spread code. If the spread code (sequence) of spread spectrum communication is known, a signal spread using the spread code is extracted or The signal from other terminals can be transmitted to the transmission line by receiving the signal at the same time as sending the signal and removing the signal transmitted by itself that is present in the received signal. It is determined whether or not it has been transmitted, that is, a collision is determined.
[0006]
In the collision detection processing system, the signal is received simultaneously while the own station is transmitting the signal, and after despreading processing in spread spectrum communication, the signal removing section removes the signal transmitted by itself present in the received signal and generates a collision. The determination unit determines whether a signal from another terminal is being transmitted to the transmission path.
[0007]
[Non-patent document 1]
Edited by Masanobu Fujioka and Takeshi Hattori, 2002.6.10, "Wireless Broadband Textbook", P255-P300, Chapter 7, IDG Japan Co., Ltd. [Patent Document 1]
JP-A-9-64884
[Problems to be solved by the invention]
In the prior art 1, when a plurality of wireless stations happen to transmit packets at the same time, a collision between the packets may occur. The destination wireless station cannot normally receive the colliding packet.
[0009]
However, in the prior art 1, since the wireless station does not have a function of detecting a collision, the wireless station continues to transmit a packet until the transmission is completed despite the collision. Continuing to transmit packets while in a collision state wastes radio frequency resources, causing a problem of lowering throughput.
[0010]
In the prior art 2, a collision detection function utilizing the property that "if a spread code (sequence) is known, a signal spread using the spread code can be extracted or removed if the spread code (sequence) is known" is used. Has been realized. However, since spread spectrum communication is premised, there is a problem that it cannot be applied to a wireless packet communication system that does not employ spread spectrum communication as a modulation / demodulation method.
[0011]
The present invention has been made in such a background, and minimizes waste of frequency resources at the time of collision occurrence without depending on limited modulation / demodulation schemes such as spread spectrum communication. An object of the present invention is to provide a wireless packet communication method and a communication device capable of realizing an efficient throughput.
[0012]
[Means for Solving the Problems]
A first aspect of the present invention is a wireless packet communication method performed in a wireless packet network including a plurality of wireless stations each having a plurality of antennas, and the feature of the present invention is that the wireless station has at least A radio packet signal is transmitted from one antenna, a signal is received by at least one antenna, and a propagation coefficient h between the antenna transmitting the radio packet signal and the antenna receiving the signal is used. The signal component R obtained by removing the transmission signal component X of the own station from the received signal Y is represented by R = Y−h × X
The reception level of the signal component R is determined, and when the reception level is equal to or higher than the threshold value, it is determined that the radio packet signal has collided with a signal transmitted by another radio station, and the transmission of the radio packet signal is performed. It stops, and if it is less than the threshold, the transmission is continued until the transmission of the wireless packet signal is completed.
[0013]
That is, in order to solve the problem of the related art, according to the present invention, during transmission of a wireless packet signal, a signal including the wireless packet signal is received. By removing the transmission signal component of the own station from the received signal, it is determined whether or not another wireless station is transmitting a wireless packet signal that may cause a collision with the wireless packet signal of the own station. . Accordingly, if it is determined that the other wireless station is transmitting a wireless packet signal that may cause a collision with the wireless packet signal of the own station, the wireless station stops transmitting the wireless packet signal of the own station, thereby invalidating the wireless packet signal. Thus, transmission of a wireless packet signal can be avoided, whereby waste of radio frequency resources can be avoided, and highly efficient throughput can be realized.
[0014]
In order to remove the wireless packet signal of the own station from the received signal including the wireless packet signal of the own station, the antenna transmitting the wireless packet signal by the own station and the signal transmitted by the own station during the transmission of the wireless packet signal. Can be removed by obtaining a propagation coefficient between the antenna and the receiving antenna and subtracting a value obtained by multiplying the transmission signal component of the own station by the propagation coefficient from the received signal.
[0015]
Conventionally, the transmission signal component of the own station could be removed from the received signal only in a limited modulation / demodulation method such as spread spectrum communication. However, the present invention does not limit the modulation / demodulation method. There is a remarkable feature in that the transmission signal component of the own station can be removed from the inside.
[0016]
Further, during transmission of the radio packet, an actual measurement value H of the propagation coefficient h is calculated from the transmission signal component X of the own station and the reception signal Y as H = Y / X.
It is desirable to update the propagation coefficient h with the actual measurement value H when a collision is not detected, and not to update the propagation coefficient h when a collision is detected.
[0017]
That is, in the present invention, the propagation coefficient between the antennas is measured in parallel with the collision detection during the wireless packet transmission, and the propagation coefficient can be updated with the measured value when no collision is detected. The propagation coefficient can be updated in accordance with the change in the propagation environment, the accuracy of removing the own-station transmission signal component from the received signal can be improved, and the accuracy of collision detection can be improved. It is possible to avoid waste of radio frequency resources due to continuous transmission, and to realize highly efficient throughput.
[0018]
A second aspect of the present invention is a wireless packet communication device including a plurality of antennas, each of which is characterized in that a propagation coefficient memory for storing a propagation coefficient h between antennas, A signal component R obtained by receiving a signal from at least one antenna during transmission of a radio packet signal from one antenna and removing the transmission signal component X of the own station from the reception signal Y using the propagation coefficient h is represented by R = Y−h × X
A collision detecting means for judging that the radio packet signal has collided with a signal transmitted by another radio station when the reception level of the signal component R is equal to or higher than a threshold, and a transmission start of the radio packet signal. And the wireless packet transmitting means for stopping the transmission of the wireless packet signal when a collision is detected.
[0019]
Further, during transmission of the radio packet, an actual measurement value H of the propagation coefficient h is calculated from the transmission signal component X of the own station and the reception signal Y as H = Y / X.
When the collision detecting means does not detect a collision, the propagation coefficient h of the propagation coefficient memory is updated with the actually measured value H. When the collision detecting means detects a collision, the propagation coefficient memory is updated. It is desirable to provide a propagation coefficient updating unit that does not perform updating.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an example of a network configuration used in the embodiment of the present invention. It consists of three radio stations, each radio station having two antennas. Wireless packet communication is performed between the wireless stations.
[0021]
FIG. 2 shows a flowchart of the wireless packet communication method according to the present embodiment. An antenna transmitting a wireless packet signal is called a transmitting antenna, and an antenna receiving a signal without transmitting a wireless packet signal is called a receiving antenna. When the wireless station starts transmitting a wireless packet signal from the transmitting antenna (step 1), the receiving antenna receives the signal for a predetermined time T (step 2), and uses the propagation coefficient between the transmitting antenna and the receiving antenna to convert the received signal from the received signal. The own station transmission signal component is removed (step 3). Specifically, assuming that a propagation coefficient is h, a transmission signal of a transmission antenna is X, and a reception signal of a reception antenna is Y,
R = Y-h × X
To extract a signal component R from which the own-station transmission signal component is removed.
[0022]
Next, the signal power of R is compared with a predetermined threshold (Step 4). If the signal power is equal to or larger than the threshold, collision detection is determined and transmission is stopped (Step 5). If less than the threshold, transmission is continued. Thus, the transmission of the wireless packet signal is completed (step 6).
[0023]
FIG. 3 shows a time chart of the wireless packet communication method according to the present embodiment. FIG. 3A shows a case where there is no simultaneously transmitting wireless station other than the own station, that is, a case where there is no collision. FIG. 3B shows a case where a wireless station other than the own station happens to be simultaneously transmitting, that is, a case where a collision occurs. Here, while X is the transmission signal of the own station, X 'indicates the transmission signal of the other station. When a collision occurs, the signal level of the signal component R becomes higher than when there is no collision, so that the collision can be detected by measuring the reception power of the signal component R. In the example of FIG. 3, a monitoring time T is provided, and the signal component R is monitored only for the time T from the start of transmission.
[0024]
Note that the propagation coefficient h may be set in advance to, for example, a value measured at the time of shipment from a factory in an environment where a collision cannot occur. In addition, the radio station performs carrier sense before starting transmission of a transmission signal from the transmission antenna, starts transmission if no carrier is detected, and retransmits after waiting for a random delay time if a carrier is detected. You may. Alternatively, the wireless station may wait for a random delay time after resuming transmission after collision detection and retransmit.
[0025]
Further, the radio station may have two or more antennas, and the antennas may not be fixedly assigned to transmission and reception. That is, it is only necessary to be able to receive a signal with at least one antenna for a certain period during transmission of the own station. Good. FIG. 4 shows a time chart when MIMO is applied. X1 indicates transmission from antenna # 1, and X2 indicates transmission from antenna # 2. In MIMO, in order for a destination wireless station to separate spatially multiplexed data signals transmitted simultaneously from a plurality of antennas, the wireless station sequentially transmits a channel estimation signal from each antenna at the head of a packet. At this time, it is possible to perform signal reception with an antenna that does not transmit the channel estimation signal and detect collision. If no collision is detected, MIMO spatial multiplexing transmission is performed, and if collision is detected, transmission is stopped.
[0026]
FIG. 5 shows a flowchart of an embodiment of a wireless packet communication method for updating a propagation coefficient. The difference from the flowchart of FIG. That is, when the wireless station starts transmitting a wireless packet signal from the transmitting antenna (step 1), the receiving antenna receives the signal for a predetermined time T (step 2), and receives the signal using the propagation coefficient between the transmitting antenna and the receiving antenna. The own station transmission signal component is removed from the signal (step 3). Specifically, assuming that a propagation coefficient is h, a transmission signal of a transmission antenna is X, and a reception signal of a reception antenna is Y,
R = Y-h × X
To extract a signal component R from which the own-station transmission signal component is removed.
[0027]
Next, the signal power of R is compared with a predetermined threshold (step 4), and if the signal power is equal to or larger than the threshold, transmission is stopped (step 5). If it is less than the threshold, the measured value H of the propagation coefficient h is calculated as H = Y / X
And the propagation coefficient h is updated with the actually measured value H (step 7). The transmission is continued to complete the transmission of the wireless packet signal (step 6).
[0028]
That is, as shown in FIG. 6A, compared with the case where there is no obstacle around, as shown in FIG. 6B, in the case where there is an obstacle around, as shown in FIG. Due to the influence of reflection or the like, the propagation coefficient h changes (h ′) depending on the environment around the wireless station. Therefore, when no collision is detected, the accuracy of collision detection can be improved by updating the propagation coefficient.
[0029]
FIG. 7 shows a block diagram of the wireless packet communication device of this embodiment. Transmission data is input to the transmission circuit 1. The transmission circuit 1 generates a radio packet signal, sends it out from the transmission antenna 5, and notifies the removal circuit 2 of the transmission signal X. The elimination circuit 2 acquires the propagation coefficient h from the propagation coefficient memory 4 and calculates R = Y−h × X from the reception signal Y input from the reception antenna 6.
To extract a signal component R from which the own-station transmission signal component is removed, and input the signal component R to the collision detection circuit 3.
[0030]
The collision detection circuit 3 compares R with a predetermined threshold value, and if not less than the threshold value, determines that a collision has occurred and notifies the transmission circuit 1 of the collision. When receiving the collision notification, the transmission circuit 1 stops the transmission, and when not receiving the collision notification, continues the transmission and completes the transmission of the wireless packet signal.
[0031]
FIG. 8 shows a block diagram of a wireless packet communication device when the above-mentioned MIMO is applied. MIMO transmits transmission data sequences 1 and 2, respectively, and includes transmission circuits 1 and 11, and antennas 15 and 16 for that. The use of the antenna 16 is switched by the switch 7 between transmission and reception. That is, it is used as a transmitting antenna during transmission of a channel estimation signal or a data signal, and is used as a receiving antenna except during transmission of a channel estimation signal or a data signal.
[0032]
FIG. 9 shows a block diagram of a wireless packet communication device that updates a propagation coefficient. Transmission data is input to the transmission circuit 1. The transmission circuit 1 generates a radio packet signal, sends it out from the transmission antenna 5, and notifies the removal circuit 2 of the transmission signal X. The elimination circuit 2 acquires the propagation coefficient h from the propagation coefficient memory 4 and calculates R = Y−h / X from the reception signal Y input from the reception antenna 6.
To extract a signal component R from which the own-station transmission signal component is removed, and input the signal component R to the collision detection circuit 3. The collision detection circuit 3 compares R with a predetermined threshold value. If the threshold value is equal to or greater than the threshold value, the collision detection circuit 3 determines that the collision has occurred, and notifies the transmission circuit 1 of the collision. Make a notification. When receiving the collision notification, the transmission circuit 1 stops the transmission, and when not receiving the collision notification, continues the transmission and completes the transmission of the wireless packet signal. The propagation coefficient update circuit 8 calculates the actual measured value H of the propagation coefficient h from the reception signal Y input from the reception antenna 6 and the transmission signal X input from the transmission circuit 1 as H = Y / X
Is calculated as When a non-collision detection notification is received from the collision detection circuit 3, the propagation coefficient h stored in the propagation coefficient memory 4 is updated with the actually measured value H. As shown in FIG. 6, the propagation coefficient h changes in the environment around the wireless station. When a collision is not detected, the accuracy of collision detection can be improved by updating the propagation coefficient.
[0033]
【The invention's effect】
As described above, according to the present invention, it is possible to detect a collision without depending on the modulation and demodulation method by removing the transmission wave component of the own station using the propagation coefficient. , The transmission of the wireless packet can be stopped, and the waste of the radio frequency resources due to the continuous transmission of the packet in the state of the collision can be avoided, so that a highly efficient throughput can be realized.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a network configuration used in an embodiment of the present invention.
FIG. 2 is a flowchart of a wireless packet communication method according to the embodiment.
FIG. 3 is a flowchart of a wireless packet communication method according to the embodiment.
FIG. 4 is a flowchart of a wireless packet communication method when MIMO is applied according to the embodiment.
FIG. 5 is a flowchart of a wireless packet communication method for updating a propagation coefficient according to the embodiment;
FIG. 6 is a diagram for explaining a relationship between an environment around a wireless station and a propagation coefficient h.
FIG. 7 is a block configuration diagram of the wireless packet communication device according to the embodiment.
FIG. 8 is a block diagram of a wireless packet communication device when MIMO is applied according to the embodiment.
FIG. 9 is a block diagram of a wireless packet communication apparatus that updates a propagation coefficient according to the embodiment.
FIG. 10 is a block diagram of a spread spectrum communication apparatus.
[Explanation of symbols]
1, 11 Transmission circuit 2 Elimination circuit 3 Collision detection circuit 4 Propagation coefficient memory 5 Transmission antenna 6 Receiving antenna 7 Switch 8 Propagation coefficient updating circuit 15, 16 Antenna

Claims (4)

In a wireless packet communication method performed in a wireless packet network including a plurality of wireless stations each having a plurality of antennas,
The wireless station transmits a wireless packet signal from at least one antenna and receives a signal on at least one antenna;
Using the propagation coefficient h between the antenna transmitting the radio packet signal and the antenna receiving the signal, the signal component after removing the transmission signal component X of the own station from the received signal Y R is R = Y−h × X
The reception level of the signal component R is determined, and when the reception level is equal to or higher than the threshold value, it is determined that the radio packet signal has collided with a signal transmitted by another radio station, and the transmission of the radio packet signal is performed. A wireless packet communication method, wherein the wireless packet communication method stops and, if the value is less than a threshold, continues transmission until the transmission of the wireless packet signal is completed. During transmission of the wireless packet, an actual measurement value H of the propagation coefficient h is calculated from the transmission signal component X of the own station and the reception signal Y as H = Y / X.
2. The wireless packet communication method according to claim 1, wherein when no collision is detected, the propagation coefficient h is updated with the actually measured value H, and when a collision is detected, the propagation coefficient h is not updated. In a wireless packet communication device each having a plurality of antennas,
A propagation coefficient memory for storing a propagation coefficient h between antennas;
While the own station receives a signal with at least one antenna while transmitting a radio packet signal from at least one antenna, a signal component R obtained by removing the transmission signal component X of the own station from the received signal Y using the propagation coefficient h is represented by R = Yh × X
Removal means sought as
Collision detection means for determining that the radio packet signal has collided with a signal transmitted by another radio station when the reception level of the signal component R is equal to or higher than a threshold value;
Wireless packet communication means for notifying the removing means of the start of transmission of the wireless packet signal to the removing means, and wireless packet transmitting means for stopping the transmission of the wireless packet signal when the collision detecting means detects a collision. apparatus. During transmission of the wireless packet, an actual measurement value H of the propagation coefficient h is calculated from the transmission signal component X of the own station and the reception signal Y as H = Y / X.
When the collision detection means does not detect a collision, the propagation coefficient h of the propagation coefficient memory is updated with the actually measured value H. When the collision detection means detects a collision, the propagation coefficient memory is updated. 4. The wireless packet communication device according to claim 3, further comprising a propagation coefficient updating unit that does not perform updating.

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