JP6018030B2 - Wireless communication system, remote base station, and wireless communication method - Google Patents

Description

  The present invention relates to a radio communication system, a remote base station, and a radio communication method.

  Various wireless systems such as LTE, WiMAX (registered trademark), IEEE802.11a / b / g / n, and Bluetooth (registered trademark) are implemented in portable devices such as smartphones and mobile routers. Depending on the usage form, there may be cases where multiple methods are used simultaneously. Non-Patent Document 1 shows that characteristic degradation occurs due to sensitivity suppression when the use frequency band is adjacent or harmonics.

  FIG. 4 is a diagram showing transmission / reception timings when carrier sense according to the prior art is applied. FIG. 4 shows transmission / reception timings when two wireless LANs are mounted in the same housing and operated on adjacent channels. As shown in FIG. 4, in method B, after ACK reception (time t1-time t2) is performed, time t2 becomes idle start time 1 and shifts to an idle state. And it becomes busy in the transmission section (time t3-t4) of the scheme A, the time t4 when the transmission section of the scheme A ends becomes the idle start time 2, and the idle state continues. This idle state continues until the idle time exceeds a specified value. In system B, transmission is started with the time point (time t7) when the idle duration time ends as the transmission start time. On the other hand, method A performs ACK reception (time t5-time t6) after the transmission section (time t3-time t4) ends, and when the ACK reception ends (time t6) becomes the idle start time and enters the idle state. Transition.

  As described above, in the wireless LAN, transmission permission / inhibition is determined based on the carrier sense idle / busy determination and the idle duration (see, for example, Non-Patent Document 2).

  In the case of 2.4 GHz band (ISM band), the maximum power leaked to the adjacent channel at the time of transmission is −16 dBm / MHz, which is a rule for unnecessary emission. When the isolation between channels is 46 dB or less, the leakage power in the adjacent channel of the transmission channel is equal to or higher than the carrier sense level, so that the carrier sense determination of the own channel is busy during transmission of the adjacent channel. Therefore, every time an adjacent channel transmits, the carrier sense determination changes from idle to busy, and the continuation of idle time is interrupted. The interruption of the idle time may delay the transmission start time and cause a deterioration in throughput. Also, when the adjacent channel receives during transmission on the own channel, sensitivity suppression occurs due to the influence of leakage power, and the reception characteristics of the adjacent channel deteriorate.

Z. Hu, Z. Chen, IK. Fu, P. Dayal, S. Kumar, "Interference Avoidance for In-Device Coexistence in 3GPP LTE-Advanced," IEEE Comm. Mag., Nov., pp. 60-67, 2012 Supervised by Morikura and Kubota, “802.11 High-Speed Wireless LAN Textbook”, Impress R & D, pp. 80-84, 2006.

  Non-Patent Document 1 proposes a method of selecting a frequency channel that can sufficiently secure isolation, a method of adjusting a plurality of methods in a time division manner, and the like so as not to cause characteristic deterioration due to sensitivity suppression. However, there is a problem in that it may not be possible to select a frequency channel that can sufficiently secure isolation depending on the combination of methods. In addition, the time division adjustment method has a problem that it may be difficult to apply when a plurality of systems based on autonomous distributed control such as a wireless LAN are operated simultaneously.

  The present invention has been made in view of such circumstances, and when multiple wireless systems based on autonomous distributed control such as a wireless LAN are simultaneously operated, sensitivity suppression can be reduced and throughput degradation can be suppressed. An object is to provide a wireless communication system, a remote base station, and a wireless communication method.

One aspect of the present invention is a wireless communication system in which a remote base station that performs wireless communication with a wireless terminal is connected to a centralized control station that controls the operation of the remote base station, and a plurality of wireless systems operate in the remote base station. The centralized control station includes a busy determination acquisition unit that acquires information indicating that the channel state in each of the wireless systems is busy from the remote base station, and each of the wireless systems in the remote base station. When the received signal when the channel state is busy is a signal of the wireless communication system and is not addressed to the own station, the time when a predetermined time has elapsed from the end of the received signal is acquired as the idle start time . comprising an idle start time acquiring unit, an idle start time notifying means for notifying the idle start time to said remote base station, the far The base station, a channel measuring section that measures reception power of the channel in each of the radio system, said each wireless system, if the received power of the channel is the transmission time of another wireless system in threshold below or local station to determine the state of the channel and idle state, the determining means busy state of the channel otherwise, if the determination means determines that the busy state, the information indicating that A busy determination notifying unit for notifying a central control station, and a transmission control unit for controlling transmission of a radio signal based on the idle start time notified from the central control station for each of the radio systems , A wireless communication system .

One aspect of the present invention is the above wireless communication system, the remote base station, for each of the radio system, the threshold value when the transmission time of another wireless system in its own station of the other wireless system further Ru comprising a threshold setting means for setting a larger value than the leakage power.

One aspect of the present invention, transmits a said wireless communication system, the remote base station, information on each of the radio system, to obtain the reception time are decided beforehand other wireless system in the own station as a transmission inhibited period further comprising prohibition period information acquisition unit, the transmission control unit, for each of the radio system, controls the transmission of the radio signal so as not to overlap the transmission time of the transmission prohibition section and the wireless system.

One aspect of the present invention is a wireless communication system in which a remote base station that performs wireless communication with a wireless terminal is connected to a centralized control station that controls the operation of the remote base station, and a plurality of wireless systems operate in the remote base station. a remote base station, said a wireless system channel measurement section that measures reception power of the channel in each of said each radio system, the transmission time of another wireless system received power is at the threshold or less or the local station of the channel If the determination means determines that the channel state is idle , otherwise determines that the channel state is busy, and indicates that the determination means determines that the channel is busy a busy judgment notifying means for notifying the information to the central control station, for each of the radio system, notified from the central control station, before If the received signal when the channel condition of is busy is not addressed to signal a is and the centralized control station of a wireless communication system, the acquired idle start time as the last of a predetermined time has elapsed time of the received signal A remote base station comprising transmission control means for controlling transmission of a radio signal on the basis thereof.

One aspect of the present invention is the remote base station, and for each of the radio systems, the threshold value is larger than the leakage power of the other radio system when the transmission time of the other radio system is the local station. further Ru comprising a threshold setting means for setting the.

One aspect of the present invention is a wireless communication system in which a remote base station that performs wireless communication with a wireless terminal is connected to a centralized control station that controls the operation of the remote base station, and a plurality of wireless systems operate in the remote base station. a wireless communication method for performing, before Symbol remote base station, a channel measurement step of measuring the received power of a channel in each of the radio system, the remote base station, for each of the radio system, the reception power of the channel and transmitting the state of the channel is determined that the idle state when it is time, determination step of determining the state of the channel busy otherwise of other wireless systems in threshold below or local station, the remote base station, when it is determined that the busy state by said determining step, busy judgment notify scripts that notifies information indicating that the central control station And-up, the centralized control station, the busy judgment acquiring step state of the channel to acquire information indicating a busy state of each said from remote base station radio system, the centralized control station, the remote base For each of the wireless systems in the station, when the received signal when the channel state is busy is a signal of the wireless communication system and is not addressed to the local station, the time when a predetermined time has elapsed from the end of the received signal An idle start time acquisition step for acquiring as an idle start time, an idle start time notification step for the central control station to notify the remote base station of the idle start time, and the remote base station for each of the radio systems for controls the transmission of the radio signal based on the idle start time notified from the central control station It is a wireless communication method characterized by having a signal control step.

  According to the present invention, it is possible to suppress the interruption of the idle duration time due to the influence of the leakage power and the delay of the transmission start time, and it is possible to reduce the throughput degradation.

It is a block diagram which shows the structure of one Embodiment of this invention. It is a figure which shows the transmission / reception timing in the radio | wireless communications system shown in FIG. It is a figure which shows the transmission / reception timing in the radio | wireless communications system shown in FIG. It is a figure which shows the transmission / reception timing at the time of applying the carrier sense by a prior art.

  Hereinafter, a wireless communication system according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment. In this figure, the central control station 100 and remote base stations 200-1 to 200-n are connected via a core network 300. The centralized control station 100 includes a network interface 101, a demodulation unit 102 (method A), an upper layer 103 (method A), a modulation unit 104 (method A), a control unit 105, and an upper layer 106 (method B). And a modulation unit 107 (method B) and a demodulation unit 108 (method B).

  The remote base station 200-1 includes an antenna 201, a switch 202 (scheme A), a reception unit 203 (scheme A), a transmission unit 204 (scheme A), a carrier sense unit 205 (scheme A), and a control unit. 207, a network interface 206, an antenna 208, a switch 209 (scheme B), a reception unit 210 (scheme B), a transmission unit 211 (scheme B), and a carrier sense unit 212 (scheme B). The configurations of the remote base station 200-2 and the remote base station 200-n shown in FIG. 1 are the same as those of the remote base station 200-1 shown in FIG.

  Next, a basic operation when a single radio system is operating in the remote base station 200-1 shown in FIG. 1 will be described. Since the operations of the remote base station 200-2 and the remote base station 200-n shown in FIG. 1 are the same as those of the remote base station 200-1 shown in FIG. 1, detailed description thereof is omitted here.

  The uplink signal of the wireless terminal connected to the remote base station 200-1 is received by the antenna 201 and input to the receiving unit 203 via the switch 202. The receiving unit 203 performs level adjustment, frequency conversion, waveform shaping, A / D conversion, and the like on an input signal that is equal to or higher than a predetermined threshold level, and outputs the result to the network interface 206. The network interface 206 forms frames such as a header part, a data part, and a CRC based on the input signal, and transmits the frames to the centralized control station 100 via the core network 300.

  The network interface 101 of the centralized control station 100 extracts the data part from the received frame and outputs it to the demodulator 102. The demodulator 102 demodulates the baseband signal and outputs it to the upper layer 103. The upper layer 103 converts the frame into a MAC / IP layer frame, refers to the destination address and address table in the header, and outputs to the network interface 101 when transmitting to a wireless terminal or server connected to another network. To do. The network interface 101 refers to the address table, performs address conversion, and transmits the result to the core network 300.

  When data addressed to a wireless terminal connected to the remote base station 200-1 via the core network 300 is input to the centralized control station 100, the network interface 101 refers to the frame destination address and the address table, and 103. Upper layer 103 selects a desired remote base station (here, remote base station 200-1) from the destination address and address table, converts it to a PHY layer signal, and outputs it to modulation section 104. Modulation section 104 converts the PHY layer data string into a radio transmission signal and outputs the signal to network interface 101.

  The network interface 101 forms a frame such as a header part, a data part, and a CRC based on the input signal and transmits the frame to the core network 300. The data portion of the frame input to the remote base station 200-1 via the core network 300 is extracted by the network interface 206 and output to the transmitter 204. The transmission unit 204 performs D / A conversion, level adjustment, frequency conversion, filtering, and the like, and transmits the result as a radio signal from the antenna 201 via the switch 202.

  The transmission time is adjusted by the control unit 207 of the remote base station 200-1 and the control unit 105 of the centralized control station 100 in cooperation. For example, in method A of remote base station 200-1, reception time other than transmission time becomes reception time, and a part of the input signal of reception unit 203 is branched and input to carrier sense unit 205. The carrier sense unit 205 measures power at a desired frequency by FFT, square detection, or the like, and determines idle / busy based on threshold determination. In the case of busy determination, the control unit 207 is notified. The control unit 207 instructs the transmission unit 204 to stop transmission on the occasion of the busy determination notification, and controls the central control station 100 via the network interface 206, the core network 300, and the network interface 101 on the result of the busy determination. Notification to the unit 105.

  Further, in the case of busy determination, the demodulation unit 102 performs correlation processing such as preamble detection on the signal at the time of busy determination to determine whether the signal is a wireless LAN signal. When the signal is a wireless LAN signal, the demodulation unit 102 outputs the signal to the upper layer 103 in order to determine whether the signal is addressed to the own station. The upper layer 103 refers to the destination address and the address table, and when the signal is not addressed to its own station, the control unit 105 determines that the idle time starts after the EIFS (Extended IFS) interval elapses from the end of the received signal. Notify The control unit 105 notifies the control unit 207 of the idle start time via the network interface 101, the core network 300, and the network interface 206. The control unit 207 counts the idle time from the notified idle start time, and if the prescribed idle time continues and transmission data is stored in the transmission buffer in the transmission unit 204, instructs the transmission unit 204 to perform transmission. .

  On the other hand, when the signal is addressed to the own station, the upper layer 103 notifies the control unit 105 of an ACK response, confirms the transmission source address, forms an ACK frame, and outputs the ACK frame to the modulation unit 104. The control unit 105 notifies the control unit 207 that the ACK response is preferentially transmitted to the control unit 207 via the network interface 101, the core network 300, and the network interface 206. The modulation unit 104 performs modulation, frequency conversion, waveform shaping, and the like on the ACK frame and inputs the ACK frame to the network interface 101. In the network interface 101, a frame such as a header part, a data part, and a CRC is formed and transmitted to the remote base station 200-1 via the core network 300.

  The network interface 206 extracts the ACK part from the frame and inputs it to the transmission unit 204. The transmission unit 204 in the transmission stop state temporarily performs frequency conversion, waveform shaping, D / A conversion, etc. on the ACK on the occasion of an ACK transmission instruction from the control unit 207, and converts it to other transmission data via the switch 202. On the other hand, ACK is transmitted with the highest priority. When the upper layer 103 determines that the signal is not a wireless LAN, the control unit 105 discards the data, causes the idle start time to go back to the idle start time immediately before the busy determination and restarts the idle time detection. Notice. The control unit 105 notifies the control unit 207 via the network interface 101, the core network 300, and the network interface 206 that the idle start time goes back and the level detection of the received signal is resumed.

  The control unit 207 recounts the elapsed idle time from the retroactive idle start time and restarts the busy / idle determination. If the continuation of the idle time exceeds the specified value and there is transmission data in the transmission buffer, the transmission unit 204 is instructed to transmit. The transmission unit 204 performs frequency conversion, waveform shaping, D / A conversion, and the like on the data in the transmission buffer in response to an instruction from the control unit 207, and transmits a radio signal from the antenna 201 via the switch 202.

  Next, with reference to FIG. 2, the operation of transmission / reception timing control when a plurality of wireless systems (for example, system A and system B) are operating simultaneously will be described. FIG. 2 is a diagram illustrating transmission / reception timings when the scheme A starts from transmission standby and the scheme B starts from ACK reception. When method A is transmitted during the time when method B receives ACK, ACK reception may be hindered by sensitivity suppression due to leakage power of method A. Therefore, the control unit 207 requests the transmission unit 204 of the scheme A that affects the reception of the ACK of the scheme B to provide a transmission prohibited section (time t1−time t2).

  In addition, when leakage electric power straddles a some system, it requests | requires that the transmission prohibition area should be provided with respect to the transmission part of all the object systems. The control unit 207 determines the transmission time (time t3−time t4) of the method A in consideration of the transmission prohibition period of the method A and the idle duration that is equal to or greater than the specified value of the method B. When carrier sense is performed as usual in the carrier sense unit 212 of method B at the time (time t3 to time t4) transmitted by method A, no signal is actually received due to the influence of leakage power. Nevertheless, it is determined to be busy.

  This busy determination is an erroneous determination, and in order to correct this to a correct idle determination, the control unit 207 determines the threshold value of the carrier sense unit 212 of the method B during the transmission time of the method A (time t3−time t4). Is set higher than the leakage power, or a mask interval (time t3−time t4) in which busy determination is changed to idle determination is provided. Thus, even if the transmission time (time t3—time t4) of method A overlaps in the idle time interval (time t2—time t7) of method B, the continuation of the idle time is not interrupted in the carrier sense unit 212 of method B. . In this way, by suppressing the erroneous determination of the carrier sense due to the transmission of another method, the delay of the transmission start time due to the interruption of the idle time is suppressed, and the deterioration of the throughput can be reduced.

  Furthermore, in method A, when the reception time is fixed in advance, such as ACK reception after data transmission or CTS after RTS (the control unit 207 knows the transmission time of all methods, the ACK reception completion time, etc.) ), The control unit 207 notifies the transmission unit 211 of the method B as the transmission prohibition period of the section (time t5-time t6) and continues the idle time by the mask section (time t3-time t4) of the system B. In consideration of whether or not there is no overlap between the transmission time (time t7-time t8) of the system B that starts after the idle time of the specified time and the transmission prohibited section (time t5-time t6) It is determined from the magnitude relationship between the time t7) and the end time of the transmission prohibited section (time t6) and the magnitude relationship between the transmission end time (time t8) and the start time of the transmission prohibited section (time t5).

  If it is determined that they overlap (time t6> time t7 and time t5 <time t8), the end time (time t6) of the transmission prohibited section is set to the transmission start time of method B so that the transmission time and the transmission prohibited section do not overlap. To the transmission unit 211 of method B.

  On the other hand, as shown in FIG. 3, when it is determined that the transmission-prohibited section (time t5-time t6) and the transmission time (time t7-time t8) do not overlap (time t6 <time t7 or time t5> time t8). Notifies the transmission unit 211 of the method B of the transmission start time (time t7) as the transmission start time of the method B. FIG. 3 is a diagram illustrating transmission / reception timings when method A starts from transmission standby and method B starts from ACK reception. Thus, by setting the transmission prohibition section, sensitivity suppression can be reduced, and deterioration of reception characteristics can be reduced.

  As described above, the remote base station apparatus of the wireless communication system in which the remote base station apparatus is connected to the centralized control station apparatus via the network and the remote base station apparatus performs wireless communication using a plurality of channels is It is determined whether the state is busy or idle every time, and includes a carrier sense unit that measures the duration in the idle state, and a control unit that sets the transmission time of each channel. When notifying the carrier sense part of the other channel as a mask period the time zone for transmission, the carrier sense part determines the idle state in the notified mask period when measuring the duration of the idle state, Alternatively, the threshold for determining the busy state is increased and the duration is measured.

  In this way, when multiple wireless systems are installed in the same housing and operate simultaneously using multiple adjacent channels, etc., where carrier detection misjudgment due to the influence of leakage power and reception characteristics deteriorate due to sensitivity suppression By adjusting the transmission / reception timing while grasping the transmission start / end times, it is possible to reduce the deterioration of transmission opportunities due to erroneous carrier sense determination and the deterioration of reception characteristics due to sensitivity suppression.

  According to this configuration, the transmission time can be determined as the idle time by grasping the transmission time of the other method, and the transmission prohibition time is provided by grasping the reception time of the other method. By setting the transmission times in consideration of the continuation of transmission and the transmission prohibition time, transmission can be performed while reducing erroneous determination of sensitivity suppression and carrier sense, and throughput deterioration can be suppressed.

  The remote base station and central control station in the above-described embodiment may be realized by a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system serving as a server or a client in that case may be included and a program held for a certain period of time. Further, the program may be for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in the computer system. It may be realized using hardware such as PLD (Programmable Logic Device) or FPGA (Field Programmable Gate Array).

  As mentioned above, although embodiment of this invention has been described with reference to drawings, the said embodiment is only the illustration of this invention, and it is clear that this invention is not limited to the said embodiment. is there. Therefore, additions, omissions, substitutions, and other modifications of the components may be made without departing from the technical idea and scope of the present invention.

  When a plurality of systems based on autonomous distributed control such as a wireless LAN are operated simultaneously, it can be applied to an application in which it is indispensable to reduce sensitivity suppression and suppress throughput degradation.

  DESCRIPTION OF SYMBOLS 100 ... Central control station, 101, 206 ... Network interface, 102, 108 ... Demodulation part, 103, 106 ... Upper layer, 104, 107 ... Modulation part, 105, 207 ... Control part, 200-1-n ... Remote base station , 201, 208 ... antenna, 202, 209 ... switch, 203, 210 ... reception unit, 204, 211 ... transmission unit, 205, 212 ... carrier sense unit, 300 ... core network

Claims (6)

A remote base station that performs wireless communication with a wireless terminal is connected to a centralized control station that controls the operation of the remote base station, and a wireless communication system in which a plurality of wireless systems operate in the remote base station,
The central control station is
Busy determination acquisition means for acquiring information indicating that the state of the channel in each of the wireless systems is busy from the remote base station;
About each of the radio system in the remote base station, when the received signal when the state of the channel is busy is not a signal a is and addressed to the mobile station of a wireless communication system, the last of a predetermined time of the received signal Idle start time acquisition means for acquiring the elapsed time as the idle start time ;
Idle start time notifying means for notifying the remote base station of the idle start time ,
The remote base station is
Channel measuring means for measuring the received power of the channel in each of the wireless systems;
Wherein each wireless system, the state of the channel is determined that the idle state when the transmission time of another wireless system in the received power is equal to or smaller than the threshold or the local station of the channel, otherwise of the channel state Determining means for determining that the state is busy ;
A busy determination notification means for notifying the centralized control station of information indicating that when the determination means determines that it is in a busy state ;
A wireless communication system comprising: a transmission control unit that controls transmission of a radio signal based on the idle start time notified from the central control station for each of the radio systems. The remote base station is
For each of the radio system, characterized in that the Ru further comprising threshold setting means for setting the threshold value when the transmission time of another wireless system to a value larger than the leakage power of the other radio system in the own station The wireless communication system according to claim 1. The remote base station is
The radio system about the respective further includes a transmission prohibition period information acquisition means for acquiring a transmission prohibition period previously determined to have received time other wireless system in the own station,
The transmission control means includes
The radio communication system according to claim 1 or 2 , wherein for each of the radio systems, radio signal transmission is controlled so that the transmission prohibited section and the radio system transmission time do not overlap. A remote base station in a wireless communication system in which a remote base station that performs wireless communication with a wireless terminal is connected to a centralized control station that controls the operation of the remote base station, and a plurality of wireless systems operate in the remote base station,
Channel measuring means for measuring the received power of the channel in each of the radio systems;
Wherein each wireless system, the state of the channel is determined that the idle state when the transmission time of another wireless system in the received power is equal to or smaller than the threshold or the local station of the channel, otherwise of the channel state Determining means for determining that the state is busy ;
A busy determination notification means for notifying the centralized control station of information indicating that when the determination means determines that it is in a busy state ;
For each of the radio systems , when the received signal notified from the central control station when the channel state is busy is a signal of a radio communication system and is not addressed to the central control station, the received signal A remote base station, comprising: a transmission control unit that controls transmission of a radio signal based on an idle start time acquired as a time when a predetermined time has elapsed from the end . Wherein for each radio system, further Ru comprising a threshold setting means for setting a larger value than the leakage power of the other wireless system with the threshold value when the transmission time of another wireless system in the own station <br / The remote base station according to claim 4, wherein: A wireless communication method performed by a wireless communication system in which a remote base station that performs wireless communication with a wireless terminal is connected to a centralized control station that controls the operation of the remote base station, and a plurality of wireless systems operate in the remote base station. ,
Before Symbol remote base station, a channel measurement step of measuring the received power of a channel in each of the radio system,
The remote base station determines, for each of the radio systems, the channel state as an idle state when the received power of the channel is equal to or less than a threshold value or the transmission time of another radio system in the own station , A determination step for determining that the state of the channel is busy ,
When the remote base station is determined to be busy in the determination step, a busy determination notification step of notifying the central control station of information indicating that ,
A busy determination acquisition step in which the centralized control station acquires information indicating that a channel state in each of the wireless systems is busy from the remote base station;
The centralized control station, for each of the radio systems in the remote base station, when the received signal when the channel state is busy is a signal of a wireless communication system and is not addressed to its own station, An idle start time acquisition step of acquiring a time at which a predetermined time has elapsed from the end as an idle start time;
The central control station, an idle start time notification step of notifying the remote base station of the idle start time;
A radio communication method, comprising: a transmission control step in which the remote base station controls transmission of a radio signal based on the idle start time notified from the central control station for each of the radio systems .

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