JP2011259198A - Radio node device of multi-hop radio system and intervention compensation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio node device of a multi-hop radio system which enables it to use the same radio frequency channel without reducing the throughput in a relay transmission, and an intervention compensation method.SOLUTION: A radio node device of a multi-hop radio system which has multiple radio node devices using the same radio frequency channel to relay data signals comprises an intervention compensation path which generates as an intervention replica signal a data signal addressed to its own device which is multiplied by a propagation path parameter from the radio node device that is an intervention source to its own device, detects the timing by which a reception signal receives intervention, subtracts the intervention replica signal from the reception signal by the timing, and outputs the reception signal without the intervention.

Description

  The present invention relates to a wireless node device and an interference in a multihop wireless system that compensates for interference between wireless node devices and improves throughput in a multihop wireless system in which each wireless node device relays using the same radio frequency channel. The compensation method.

  FIG. 7 shows a configuration example of a multi-hop wireless system. Here, a case where there are four wireless node devices is shown.

  In FIG. 7, the relay path is in the order of the wireless node device 1, the wireless node device 2, the wireless node device 3, and the wireless node device 4. In each relay transmission, the radio frequency channel is the same, and each radio node device hops by shifting the transmission timing.

  Here, as shown in FIG. 8, it is assumed that data is continuously hopped from the wireless node device 1 to the wireless node device 4. The wireless packet P1 is transmitted from the wireless node device 1 to the wireless node device 2, the wireless packet P1 ′ is transmitted from the wireless node device 2 to the wireless node device 3, and finally the wireless packet is transmitted from the wireless node device 3 to the wireless node device 4. The packet P1 ″ is transmitted. Subsequently, when the wireless node device 2 receives the wireless packet P2 transmitted by the wireless node device 1, the wireless packet P1 ″ transmitted to the wireless node device 4 by the wireless node device 3 is transmitted. Interference with the radio packet P2. The cause is that the radio node device 3 transmits to the radio node device 4 because the radio wave reception strength from the radio node device 1 is not sufficient and it cannot be determined that the radio frequency channel is used. Because it happens.

NTT Technology Journal 2009.12 “Research and development of wireless network coding technology to realize highly efficient multi-hop wireless systems”

  In the conventional multi-hop wireless system, when the same radio frequency channel is used for relay transmission, the wireless node device 1 and the wireless node device 3 cannot control the transmission timing with each other in the above-described example. Will occur. That is, when the number of hops is 3 or more, interference between radio node devices occurs, and thus the number of hops is limited.

  In order to avoid this interference, using different radio frequency channels for each relay means that two radio repeaters are mounted on an intermediate radio node device. This increases the device scale and deteriorates the frequency utilization efficiency. Alternatively, before each wireless node device transmits data, it transmits / receives an RTS / CTS (request to send / clear to send) signal for reserving the use of the radio frequency channel, thereby interfering with the same radio frequency channel. It is possible to avoid each other, but a decrease in throughput is unavoidable.

  In addition, the method of applying interference compensation in the conventional wireless relay is premised on bidirectional relay, in which an intermediate node relays as it is and cancels interference at an interference source node, and the configuration is limited. (Non-Patent Document 1).

  According to the present invention, interference between radio node devices can be removed by an interference compensation circuit provided in the radio node device, and thus the same radio frequency channel can be used for relay transmission without reducing throughput. An object of the present invention is to provide a wireless node device and an interference compensation method for a multihop wireless system.

  According to a first aspect of the present invention, there is provided a wireless node device of a multi-hop wireless system in which a plurality of wireless node devices relay data signals using the same wireless frequency channel. Multiplication of propagation path parameters from the device to its own device is generated as an interference replica signal, the timing at which the received signal receives interference is detected, the interference replica signal is subtracted from the received signal at that timing, and the interference is removed. An interference compensation circuit for outputting a signal is provided.

  The interference compensation circuit includes: a propagation path estimation circuit that estimates a propagation path parameter from a wireless node device serving as an interference source to the own apparatus from a received signal; a data storage circuit that accumulates a data signal obtained by demodulating the received signal addressed to the own apparatus; A modulation circuit that modulates the data signal stored in the data storage circuit, a multiplication circuit that multiplies the modulation signal output from the modulation circuit by a propagation path parameter to generate an interference replica signal, and a timing at which the received signal receives interference. An interference detection circuit that detects and outputs an interference detection signal, and a subtraction circuit that subtracts the interference replica signal from the reception signal at the timing of the interference detection signal and outputs the reception signal from which interference has been removed.

  The interference compensation circuit is configured to generate an interference replica signal using a propagation path parameter obtained by a demodulation circuit that demodulates a received signal, instead of the propagation path estimation circuit.

  The modulation circuit of the interference compensation circuit is configured to perform modulation processing in accordance with the modulation scheme of the transmission section determined using the MAC address by the demodulation circuit that demodulates the received signal.

  According to a second aspect of the present invention, in the interference compensation method for a multi-hop wireless system in which a plurality of wireless node devices relay data signals using the same radio frequency channel, the interference compensation circuit of the wireless node device includes data addressed to itself. A signal multiplied by the propagation path parameter from the wireless node device that is the interference source to its own device is generated as an interference replica signal, the timing at which the received signal receives interference is detected, and the interference replica signal is detected from the received signal at that timing. The received signal from which interference is removed is output by subtraction.

  In the interference compensation method of the second invention, the interference compensation circuit estimates a propagation path parameter from the wireless node device serving as the interference source to the own apparatus from the received signal, and generates an interference replica signal using the estimated propagation path parameter. To do.

  In the interference compensation method of the second invention, the interference compensation circuit generates an interference replica signal using the propagation path parameter obtained by the demodulation circuit that demodulates the received signal.

  In the interference compensation method of the second invention, the interference compensation circuit performs a modulation process in accordance with the modulation scheme of the transmission section determined using the MAC address in the demodulation circuit that demodulates the received signal.

  According to the present invention, interference between radio node apparatuses can be removed by an interference compensation circuit provided in the radio node apparatus, and relay transmission can be performed using the same radio frequency channel without reducing throughput. It becomes possible.

It is a figure which shows the structural example of the radio | wireless node apparatus of this invention. 2 is a diagram illustrating a first configuration example of an interference compensation circuit 9. FIG. 3 is a time chart showing an operation example of an interference compensation circuit 9; 6 is a diagram illustrating a second configuration example of the interference compensation circuit 9. FIG. It is a figure explaining the calculation example of the propagation path parameter H. FIG. 6 is a diagram illustrating a third configuration example of the interference compensation circuit 9. FIG. It is a figure which shows the 4-hop example of a multihop radio | wireless system. It is a figure which shows the case of the interference of a multihop radio | wireless system.

  FIG. 1 shows a configuration example of a wireless node device of the present invention. The present invention is characterized in that an interference compensation function is provided in a wireless node device affected by interference. Here, a case will be described as an example where interference between the wireless packet P2 and the wireless packet P1 ″ is removed in the wireless node device 2 shown in FIG.

  In FIG. 1, a received signal of the wireless node device 2 is input to a receiving circuit 7 via a shared transmission / reception antenna 5 and a transmission / reception changeover switch 6, and is converted from an RF signal to a baseband signal. The output of the receiving circuit 7 is input to the demodulating circuit 8 and the interference compensating circuit 9, and demodulated data is output from the demodulating circuit 8. The output of the demodulation circuit 8 is input to the switching circuit 11 and the interference compensation circuit 9. The interference compensation circuit 9 detects interference from the output of the reception circuit 7, outputs an interference switching signal D according to the presence or absence of interference detection to the switching circuit 11, and receives a reception signal when the interference signal is included in the reception signal. The interference signal is removed from the signal and output to the demodulation circuit 10. The switching circuit 11 selects the output of the demodulation circuit 8 when the interference signal is not included in the received signal according to the interference switching signal D, and removes the interference signal by the interference compensation circuit 9 when the interference signal is included. The output of the demodulation circuit 10 that demodulates the received signal is selected.

  With the above configuration, when the received signal is not subject to interference, the output of the demodulation circuit 8 is directly output as demodulated data via the switching circuit 11. On the other hand, when the received signal receives interference, the interference signal in the received signal is removed by the interference compensation circuit 9, and the demodulated data subjected to interference compensation is output from the demodulation circuit 10 via the switching circuit 11.

FIG. 2 shows a first configuration example of the interference compensation circuit 9.
In FIG. 2, the interference compensation circuit 9 includes a propagation path estimation circuit 12, a data storage circuit 13, a modulation circuit 14, a multiplication circuit 15, a subtraction circuit 16, an interference detection circuit 17, and a delay circuit 18. The output of the reception circuit 7 is input to the propagation path estimation circuit 12, the interference detection circuit 17 and the subtraction circuit 16, and first, by the demodulation operation of the training signal having a known pattern added to the reception signal by the propagation path estimation circuit 12, A propagation path parameter H is calculated. In the case of the wireless node device 2 illustrated in FIG. 8, propagation path parameters of both the wireless node device 1 and the wireless node device 3 that are counterparts are calculated. Demodulated data output from the demodulation circuit 8 is input to the data storage circuit 13 and stored for each wireless packet.

  Here, as shown in FIG. 8, a case where the wireless packet P1 ″ transmitted from the wireless node device 3 to the wireless node device 4 interferes with the wireless packet P2 transmitted from the wireless node device 1 to the wireless node device 2. In this case, the wireless packet P1 ″ has already been received as the wireless packet P1 in the wireless node device 2, and the demodulated data can be stored in the data storage circuit 13. The multiplication circuit 15 multiplies the signal P1 obtained by modulating the demodulated data stored in the data storage circuit 13 by the modulation circuit 14 and the propagation path parameter H estimated by the propagation path estimation circuit 12 from the wireless node device 3 to the wireless node device 2. The signal R1 is the same as the signal received by the wireless node device 2 in the wireless packet P1 ″. The output R1 (= P1 ″) of the multiplication circuit 15 can be used for interference removal as an interference replica signal.

  When the wireless node device 2 receives the wireless packet P2 from the wireless node device 1, the interference detection is performed on the output of the receiving circuit 7 in order to detect the timing of receiving the interference wireless packet P1 "from the wireless node device 3. The interference detection is performed by inputting the signal to the circuit 17. The interference detection circuit 17 monitors a time variation of a known pattern in the wireless packet, for example, a pilot channel of the OFDM signal, and detects the timing at which all the patterns are suddenly disturbed. The interference detection circuit 17 outputs the interference detection signal D to the delay circuit 18 and the switching circuit 11 of Fig. 1 at the timing when the interference is detected, and the delay circuit 18 outputs the output R1 of the multiplication circuit 15 to the interference detection signal D. Is output to the subtracting circuit 16. A signal matching the interference timing is defined as an interference replica signal R1 '.

  The subtraction circuit 16 performs interference removal by subtracting the interference replica signal R1 ′ from the radio packet P2. At this time, as shown in FIG. 3, the timing of the interference signal R1 "and the cancellation replica signal R1 'in the radio packet P2 is the same. When the interference detection circuit 17 detects interference during reception of the radio packet P2, Then, the output of the subtracting circuit 16 is demodulated by the demodulating circuit 10 and output as demodulated data of the radio packet P2. On the other hand, when no interference signal is detected, the output of the demodulating circuit 8 is output as demodulated data.

The radio packet P2 input to the subtraction circuit 16 is subjected to delay adjustment corresponding to the interference detection time in the interference detection circuit 17, but in this embodiment and the following embodiments, a delay circuit for this delay adjustment is used. Is omitted.
Further, the output of the demodulation circuit 10 may be input to the data storage circuit 13 of the interference compensation circuit 9, and an interference replica signal for the next interference compensation may be generated based on the demodulation data subjected to interference compensation.

  FIG. 4 shows a second configuration example of the interference compensation circuit 9. The interference compensation circuit 9 of this configuration example has a configuration in which the propagation path estimation circuit 12 in the interference compensation circuit 9 of the first configuration example shown in FIG.

  In general wireless communication, channel estimation is performed using a training signal at the head of a wireless packet, and transmission data is demodulated using a calculated propagation path parameter H. FIG. 5 shows an example of calculating propagation path parameters. In general wireless communication, a training signal at a reference amplitude phase point is arranged at the head of a wireless packet to be transmitted, and a propagation path parameter H is calculated based on the amount of amplitude phase that the training signal has shifted in the propagation process. This process is called channel estimation. In the demodulation process of the data signal, the transmission signal is estimated by back-calculating the propagation path parameter H calculated for the received signal. In normal wireless communication, channel estimation is usually performed, and in this embodiment, such a case is assumed.

  In this configuration example, the propagation path parameter H of the propagation path calculated in the demodulation process in the demodulation circuit 8 is used for interference compensation. That is, the propagation path parameter H calculated when the wireless node device 3 transmits to the wireless node device 2 is stored in the memory circuit 19, and this is multiplied by the output of the wireless packet P 1 by the multiplication circuit 15. The interference replica signal R1 is used for interference removal.

  FIG. 6 shows a third configuration example of the interference compensation circuit 9. This configuration example is applied when there are a plurality of modulation schemes used in a multi-hop wireless system, and an adaptive modulation scheme for selecting an optimal modulation scheme depending on the state of the propagation path is used. That is, the demodulation circuit 8 of the wireless node device 2 discriminates the MAC address of the received signal and records in the memory circuit 20 the modulation method information M of the wireless packet transmitted from the wireless node device 3 to the wireless node device 4. To do. The modulation circuit 14 generates a modulation signal P1 based on this information M. Thereby, even when the modulation method is different for each section in the adaptive modulation method, the modulation method of the interference replica signal can be made the same as that of the interference signal.

1, 2, 3, 4 Wireless node device 5 Transmission / reception shared antenna 6 Transmission / reception changeover switch 7 Reception circuit 8, 10 Demodulation circuit 9 Interference compensation circuit 11 Switching circuit 12 Propagation path estimation circuit 13 Data storage circuit 14, 21 Modulation circuit 15 Multiplication circuit 16 Subtraction circuit 17 Interference detection circuit 18 Delay circuit 19, 20 Memory circuit 22 Transmission circuit

Claims (8)

In a wireless node device of a multi-hop wireless system in which a plurality of wireless node devices relay data signals using the same radio frequency channel,
A data signal addressed to the local device multiplied by the propagation path parameter from the wireless node device that is the interference source to the local device is generated as an interference replica signal, and the timing at which the received signal receives interference is detected and received at that timing. A radio node apparatus comprising: an interference compensation circuit that subtracts the interference replica signal from a signal and outputs a reception signal from which interference is removed. The radio node device according to claim 1,
The interference compensation circuit includes:
A propagation path estimation circuit for estimating a propagation path parameter from a wireless node device serving as an interference source to the own apparatus from the received signal;
A data storage circuit for storing a data signal obtained by demodulating a received signal addressed to the own device;
A modulation circuit for modulating the data signal stored in the data storage circuit;
A multiplier for multiplying the modulation signal output from the modulation circuit by the propagation path parameter to generate the interference replica signal;
An interference detection circuit for detecting a timing at which the received signal receives interference and outputting an interference detection signal;
A radio node device comprising: a subtraction circuit that subtracts the interference replica signal from the reception signal at the timing of the interference detection signal and outputs the reception signal from which interference has been removed. The wireless node device according to claim 2, wherein
The interference compensation circuit is configured to generate the interference replica signal using a propagation path parameter obtained by a demodulation circuit that demodulates the received signal instead of the propagation path estimation circuit. apparatus. The wireless node device according to claim 2, wherein
The radio node apparatus according to claim 1, wherein the modulation circuit of the interference compensation circuit is configured to perform a modulation process in accordance with a modulation scheme of a transmission section determined using a MAC address by a demodulation circuit that demodulates the received signal. In an interference compensation method for a multi-hop radio system in which a plurality of radio node devices relay data signals using the same radio frequency channel,
The interference compensation circuit of the wireless node device is:
Generate a data signal addressed to its own device multiplied by the propagation path parameter from the wireless node device as the interference source to its own device as an interference replica signal,
Detecting when the received signal is subject to interference;
An interference compensation method, wherein the interference replica signal is subtracted from the received signal at that timing, and the received signal from which interference is removed is output. The interference compensation method according to claim 5, wherein
The interference compensation circuit estimates a propagation path parameter from a wireless node device serving as an interference source to the own apparatus from the received signal, and generates the interference replica signal using the estimated propagation path parameter. Compensation method. The interference compensation method according to claim 5, wherein
The interference compensation circuit generates the interference replica signal using a propagation path parameter obtained by a demodulation circuit that demodulates the received signal. The interference compensation method according to claim 5, wherein
The interference compensation method, wherein the interference compensation circuit performs a modulation process in accordance with a modulation scheme of a transmission section determined using a MAC address by a demodulation circuit that demodulates the received signal.

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