JP5241611B2 - Mobile communication system, base station apparatus, mobile station apparatus, and connection request detection method - Google Patents

Description

  The present invention relates to a mobile communication system, a base station apparatus, a mobile station apparatus, and a connection request detection method, and more particularly to detection of a connection request in a multicarrier transmission scheme.

  A multicarrier transmission method represented by an OFDMA (Orthogonal Frequency Division Multiple Access) method is a communication method in which transmission data (data for one channel) is distributed and transmitted to a plurality of carriers having different frequencies. is there. In this transmission method, since the band of each carrier is narrow, it is difficult to be affected by frequency selective fading due to multipath or the like.

  Since a base station that performs multiple access with a plurality of mobile stations using such a multi-carrier transmission system communicates with each mobile station using a plurality of carriers having different frequencies, automatic gain control (Automatic Gain Control) is performed for each channel. AGC) cannot be performed, and automatic gain control is collectively performed for all carriers defined in the reception band.

  However, in such a base station, since the reception dynamic range depends on the reception dynamic range of the A / D converter, the reception level is low if there is a large difference in the reception levels of signals received from a plurality of mobile stations. There was a problem that the signal might not be detected.

  For example, as shown in FIG. 7, the reception level of the signal received from the mobile station 14-1 far from the base station (located in the weak electric field area) is relatively close to the base station (located in the strong electric field area). The above problem occurs when the difference between the reception level of the mobile station 14-2 received from the mobile station is larger than the dynamic range of the A / D converter. In this case, the adjusted reception level (input level to the A / D converter) of the signal received from the mobile station 14-2 is within the dynamic range of the A / D converter (below the upper limit value of the dynamic range). Since the reception level is adjusted collectively for all carriers, the reception level after adjustment of the signal received from the mobile station 14-1 becomes less than the lower limit value of the dynamic range of the A / D converter, and the mobile station Only 14-1 cannot communicate with the base station.

  In this regard, Patent Document 1 describes that the frequency characteristics of the reception band are inclined based on the reception strength of the signals received from a plurality of communication partner apparatuses, and the frequency characteristics inclination and the signals received from the plurality of communication partner apparatuses. A wireless communication apparatus is disclosed that addresses the above problem by reassigning communication channels based on the received strength of the communication.

JP 2008-245232 A

  However, although the technique disclosed in Patent Document 1 can cope with the above problem that occurs after the mobile station connects to the base station, the above problem that occurs when the mobile station connects to the base station is considered. Absent.

  For this reason, other mobile stations located in the strong electric field area have the same timing as when the mobile station located in the weak electric field area transmits a connection request (one of the control signals transmitted through the control channel) to the base station. When a communication signal is transmitted to the base station, AGC is performed based on the reception level of the communication signal received from another mobile station, so the reception level of the connection request is out of the dynamic range of the A / D converter, The base station may not be able to detect a connection request from a mobile station.

  The present invention has been made in view of the above problem, and adopts a multi-carrier transmission scheme, and can improve the connection success rate of a mobile station device, a mobile communication system, a base station device, a mobile station device, and An object is to provide a connection request detection method.

  In order to solve the above problems, a mobile communication system according to the present invention employs a multi-carrier transmission scheme, and a mobile station apparatus and a base station apparatus via any one of a plurality of channels defined in a predetermined band. Is a mobile communication system that performs wireless communication, and the mobile station apparatus detects a connection request transmitted to the base station apparatus with a predetermined number of carriers via a control channel defined in the band. Detecting and estimating means for estimating whether or not the connection request has been detected, and transmitting the connection request to the base station apparatus with a smaller number of carriers than the predetermined number of carriers when the connection request is estimated not to be detected by the base station apparatus The base station apparatus detects a connection request transmitted from the mobile station apparatus via the control channel, and is detected by the detection means. When the connection request is transmitted with the number of carriers smaller than the predetermined number of carriers, the transmission level of the communication signal is reduced with respect to another mobile station apparatus that has transmitted the communication signal received together with the connection request. Instructing means for instructing, wherein the transmitting means retransmits the connection request with the predetermined number of carriers after transmitting the connection request with the number of carriers smaller than the predetermined number of carriers.

  In the present invention, when it is estimated that a connection request transmitted with a predetermined number of carriers is not detected by the base station device, the mobile station device issues a narrowband connection request to the base station device with a number of carriers smaller than the predetermined number of carriers. Send. A narrow-band connection request is easily detected by the base station apparatus because the transmission level per carrier is high. When a narrowband connection request is detected by the base station apparatus, the base station apparatus reduces the transmission level of the communication signal to other mobile station apparatuses that have transmitted the communication signal received together with the connection request. As a result, the difference in reception level between signals (signals whose reception levels are collectively adjusted) in the base station apparatus becomes small, so when the mobile station apparatus retransmits a connection request with a predetermined number of carriers (per carrier) If the transmission level is returned to the original level), this connection request is likely to be detected by the base station apparatus. For this reason, according to the present invention, it is possible to improve the connection success rate of the mobile station apparatus to the base station apparatus adopting the multicarrier transmission scheme.

  Also, in one aspect of the present invention, the base station apparatus, based on the reception level of the connection request detected by the detection means and the number of carriers used for transmission of the connection request, Predicts a reception level of a connection request transmitted by the predetermined number of carriers, and determines a reduction amount of a transmission level instructed to the other mobile station apparatus based on the predicted reception level of the connection request The instruction means instructs the other mobile station apparatus to reduce the transmission level of the communication signal by the reduction amount determined by the reduction amount determination means.

  According to this aspect, based on the reception level (predicted reception level) of the connection request transmitted from the mobile station apparatus with the predetermined number of carriers, the base station apparatus determines the transmission level reduction amount instructed to the other mobile station apparatus Therefore, the connection success rate of the mobile station device can be improved.

  Moreover, in one aspect of the present invention, the reduction amount determination means is further based on the reception level of the communication signal received together with the connection request detected by the detection means, the reception dynamic range of the base station apparatus, A reduction amount of the transmission level instructed to the other mobile station apparatus is determined.

  For example, the base station apparatus receives a peak value of a reception level (predicted reception level) of a connection request transmitted from a mobile station apparatus with a predetermined number of carriers and a peak value of a reception level of a communication signal transmitted from another mobile station apparatus The transmission level reduction amount instructed to the other mobile station apparatus may be determined so that the difference between the two and the reception dynamic range of the base station apparatus is equal to or less than the reception dynamic range. In this way, it is possible to further improve the connection success rate of the mobile station apparatus while suppressing the amount of transmission level reduction instructed to other mobile station apparatuses.

  In one aspect of the present invention, the reduction amount determination means determines a reduction amount of a transmission level instructed to the other mobile station apparatus, further based on a reception level of a connection request detected by the detection means. .

  For example, the base station apparatus receives a connection request reception level (predicted reception level) transmitted from the mobile station apparatus with a predetermined number of carriers and a narrowband connection request transmitted with a number of carriers smaller than the predetermined number of carriers from the mobile station apparatus. The difference between the received signal level and the received signal level may be a transmission level reduction amount instructed to another mobile station apparatus. Even in this case, the connection success rate of the mobile station apparatus can be further improved.

  In one aspect of the present invention, the mobile station apparatus controls the transmission level of the connection request based on a reception level of a control signal transmitted from the base station apparatus via the control channel. And the detection estimation means determines that the connection request is received when the connection request from the base station apparatus is not received in response to the connection request and the reception level of the control signal is not less than a predetermined value. It is estimated that the station apparatus did not detect it.

  According to this aspect, the mobile station apparatus can estimate more accurately whether or not the connection request transmitted with the predetermined number of carriers via the control channel is detected by the base station apparatus.

  In the aspect of the invention, the instruction unit further instructs the mobile station apparatus to retransmit a connection request with the predetermined number of carriers, and the transmission unit retransmits from the base station apparatus. According to the instruction, the connection request is retransmitted with the predetermined number of carriers.

  According to this aspect, the mobile station apparatus can retransmit the connection request with the predetermined number of carriers after the base station apparatus instructs another mobile station apparatus to reduce the transmission level of the communication signal.

  In one embodiment of the present invention, the transmission with the predetermined number of carriers is multicarrier transmission, and the transmission with a smaller number of carriers than the predetermined number of carriers is single carrier transmission.

  In one aspect of the present invention, the reception dynamic range of the base station device is a dynamic range of an A / D converter included in the base station device.

  In one embodiment of the present invention, the multicarrier transmission scheme is an orthogonal frequency division multiple access scheme.

  According to this aspect, it is possible to improve the connection success rate of the mobile station apparatus to the base station apparatus adopting the orthogonal frequency division multiple access scheme.

  A base station apparatus according to the present invention is a base station apparatus that adopts a multicarrier transmission scheme and performs radio communication with a mobile station apparatus via any of a plurality of channels defined within a predetermined band. Detecting means for detecting a connection request transmitted from the mobile station device via a control channel defined in the band, and the connection request detected by the detecting means is transmitted with a number of carriers smaller than a predetermined number of carriers. If there is a communication signal, an instruction means for instructing another mobile station apparatus that has transmitted the communication signal received together with the connection request to reduce the transmission level of the communication signal is included.

  A mobile station apparatus according to the present invention is a mobile station apparatus that adopts a multi-carrier transmission scheme and performs radio communication with a base station apparatus via any of a plurality of channels defined within a predetermined band. Detecting and estimating means for estimating whether or not a connection request transmitted to the base station apparatus with a predetermined number of carriers via a control channel defined in the band is detected by the base station apparatus; and Transmitting means for transmitting a connection request to the base station apparatus with a carrier number smaller than the predetermined carrier number when it is estimated that the base station apparatus has not detected the base station apparatus, and the transmitting means is based on the predetermined carrier number After transmitting a connection request with a small number of carriers, the connection request is retransmitted with the predetermined number of carriers.

  In addition, the connection request detection method according to the present invention employs a multi-carrier transmission scheme, and the mobile station apparatus and the base station apparatus perform wireless communication via any one of a plurality of channels defined within a predetermined band. A connection request detection method in a mobile communication system, wherein the mobile station apparatus detects a connection request transmitted to the base station apparatus by a predetermined number of carriers via a control channel defined in the band. A step of estimating whether or not the connection request has been detected by the base station apparatus, the mobile station apparatus connects to the base station apparatus with a carrier number smaller than the predetermined carrier number. Transmitting a request; detecting a connection request transmitted from the mobile station apparatus via the control channel; and detecting the detected connection. When the request is transmitted with a number of carriers smaller than the predetermined number of carriers, the base station apparatus transmits a communication signal to another mobile station apparatus that has transmitted the communication signal received together with the connection request. Instructing to reduce the level and retransmitting the connection request with the predetermined number of carriers after the mobile station apparatus transmits the connection request with the number of carriers smaller than the predetermined number of carriers. Features.

It is a figure which shows the structure of the mobile communication system which concerns on embodiment of this invention. It is a figure which shows the channel structure in the mobile communication system which concerns on this embodiment. It is a functional block diagram of the base station which concerns on this embodiment. It is a functional block diagram of the mobile station which concerns on this embodiment. It is a figure which shows an example of the relationship between the reception level of the connection request | requirement transmitted by multicarrier, and the dynamic range of ADC. It is a figure which shows an example of the relationship between the reception level of the connection request | requirement transmitted by single carrier, and the dynamic range of ADC. It is a figure which shows the relative fall of the dynamic range of ADC accompanying the reduction of the transmission level of a communication signal. It is a figure which shows an example of the relationship between the reception level of the connection request | requirement transmitted by multicarrier, and the dynamic range of ADC reduced relatively. It is a flowchart which shows an example of the transmission process of the connection request which concerns on this embodiment. It is a figure which shows an example of the relationship between the reception level of the signal received from a mobile station, and the dynamic range of ADC.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a mobile communication system 10 according to an embodiment of the present invention. As shown in FIG. 1, the mobile communication system 10 includes a base station 12 and a plurality of mobile stations 14 (only mobile stations 14-1 and 14-2 are shown here). The base station 12 employs an OFDMA system and a TDMA / TDD (Time Division Multiple Access / Time Division Duplex) system, and a plurality of movements located in the cell 16 of the own station. Multiple access with the station 14 can be made.

  FIG. 2 is a diagram showing a channel configuration in the mobile communication system 10. As shown in FIG. 2, in the mobile communication system 10, a TDMA frame (5 ms) is divided into an uplink subframe (2.5 ms) and a downlink subframe (2.5 ms), and each subframe has four times each. It is equally divided into slots (slot 1 to slot 4). In addition, a plurality of (here, nine) OFDMA subchannels are defined in a predetermined radio frequency band (here, the bandwidth is 8.1 MHz). Note that the minimum unit (bandwidth 900 kHz, time width 625 μs) assigned to communication between the base station 12 and the mobile station 14 is called a PRU (Physical Resource Unit), and one of eight time slots and a plurality of subchannels Belonging to either.

  In the mobile communication system 10, a specific subchannel (here, subchannel 1) is defined for a control channel (Control Channel: CCH), and the other subchannels (here, subchannels 2 to 9) are communication channels. It is defined for (Traffic Channel: TCH).

  The mobile station 14 issues a connection request to the base station 12 when it is estimated that the connection request transmitted by the predetermined number (plurality) of subcarriers (multicarrier transmission) via the control channel is not detected by the base station 12. Transmit on a single subcarrier (single carrier transmission). Since the connection request transmitted by single carrier has a high transmission level per subcarrier, it is more easily detected by the base station 12 than the connection request transmitted by multicarrier.

  When the base station 12 detects the connection request transmitted by the single carrier, the base station 12 transmits the communication signal transmission level to the other mobile stations 14 that have transmitted the communication signal received together with the connection request. Reduce. Thereby, the reception level difference of the signals (signals whose reception levels are collectively adjusted) between the mobile stations 14 in the base station 12 is reduced. For example, RSSI (Received Signal Strength Indication) is used as the reception level.

  Therefore, when the mobile station 14 transmits the connection request again by multicarrier transmission, the transmission level per subcarrier returns to the original level, but the possibility that the connection request is detected by the base station 12 is the connection that was previously transmitted by multicarrier transmission. Higher than that of the request. That is, the success rate of connection of the mobile station 14 to the base station 12 is improved.

  Next, the configuration of the base station 12 and the mobile station 14 for realizing the above process will be described more specifically.

  FIG. 3 is a functional block diagram of the base station 12. As illustrated in FIG. 3, the base station 12 includes an antenna 100, a reception unit 110, a reception signal processing unit 120, a control unit 130, a transmission signal processing unit 140, and a transmission unit 150.

  The antenna 100 receives a radio signal and outputs the received radio signal to the receiving unit 110. Further, the antenna 100 transmits the radio signal supplied from the transmission unit 150 to the mobile station 14.

  The receiving unit 110 includes a band-pass filter 111, a low noise amplifier 112, a mixer 113, a band-pass filter 115, a variable gain amplifier 114, an ADC (A / D converter) 116, and a reception gain control unit 117.

  The band pass filter 111 is a filter having a pass bandwidth of 8.1 MHz that attenuates frequency components outside the reception band of the radio signal input from the antenna 100 and passes only frequency components within the reception band. The low noise amplifier 112 amplifies the radio signal passing through the band pass filter 111 and outputs the amplified signal to the mixer 113. The mixer 113 down-converts the radio signal input from the low noise amplifier 112 into a baseband signal and outputs the baseband signal to the variable gain amplifier 114.

  The variable gain amplifier 114 is an amplifier that changes the gain according to the gain control signal input from the reception gain control unit 117, and amplifies the baseband signal input from the mixer 113 and outputs the amplified signal to the band pass filter 115. That is, the reception level of the signal received from the mobile station 14 is collectively adjusted by the variable gain amplifier 114 over the entire band (bandwidth 8.1 MHz) before being input to the ADC 116.

  The bandpass filter 115 is a filter having a passband width of 8.1 MHz that attenuates unnecessary frequency components (spurious) of the baseband signal input from the variable gain amplifier 114 and passes only a desired frequency component.

  The ADC 116 converts an analog baseband signal passing through the band pass filter 115 into a digital signal, and outputs the digital signal to the reception signal processing unit 120.

  The reception gain control unit 117 controls the gain of the variable gain amplifier 114 based on the reception level detected by the reception signal processing unit 120 described later (the reception level of the signal received by each subchannel), that is, automatic gain. Take control. Specifically, the reception gain control unit 117 is a variable gain so that the maximum value of the reception level of the signal received from the mobile station 14 falls within the dynamic range of the ADC 116 (below the upper limit value of the dynamic range of the ADC 116). The gain of the amplifier 114 is determined, and a gain control signal for setting the gain of the variable gain amplifier 114 to the gain determined here is output to the variable gain amplifier 114.

  The received signal processing unit 120 is configured by, for example, a DSP (Digital Signal Processor), and removes guard intervals, primary demodulation (FFT), communication with respect to the digital signal input from the ADC 116 of the receiving unit 110. Complex symbol string combination based on channel assignment status, secondary demodulation (digital demodulation), error correction, and the like are performed, and received data from each mobile station 14 is acquired. Then, the reception signal processing unit 120 outputs the acquired reception data to the control unit 130 or an upper layer (not shown).

  Received signal processing section 120 connects the subcarrier components of the complex symbol sequence obtained by the primary demodulation (FFT) for each subchannel, and detects the reception level of the signal received on each subchannel. Reception signal processing section 120 then sequentially outputs the detected reception level to reception gain control section 117 and control section 130. The reception level detected by reception signal processing section 120 is the reception level after adjustment by variable gain amplifier 114 of reception section 110.

  The control unit 130 includes, for example, a CPU (Central Processing Unit) and a program that controls the operation of the CPU, and controls each unit of the base station 12. The control unit 130 includes a connection request detection unit 131, a transmission level reduction amount determination unit 132, and an instruction unit 133, and performs processing related to detection of a connection request transmitted from the mobile station 14.

  The connection request detection unit 131 receives the reception level detected by the reception signal processing unit 120 at the reception timing of the control signal (for example, the arrival timing once every 20 frames) (reception of signals received in each subchannel). Based on the level), a connection request transmitted from the mobile station 14 (here, mobile station 14-1) is detected via the control channel. The connection request detection unit 131 transmits the detected connection request using a predetermined number of subcarriers (multicarrier transmission) or transmits the connection request using a single subcarrier (single carrier transmission). Determine if there is. Note that the connection request detection unit 131 detects a connection request in which the reception level after adjustment by the variable gain amplifier 114 is less than the lower limit value of the dynamic range of the ADC 116, such as a connection request A1 illustrated in FIG. 5A. I can't.

  When the connection request detected by the connection request detection unit 131 is a multi-carrier transmission, the control unit 130 determines that the detected connection request is a regular connection request and transmits the regular connection request. The transmission signal processing unit 140 and the transmission unit 150 are controlled so as to return a connection response designating the communication channel to the mobile station 14-1.

  On the other hand, when the connection request detected by the connection request detection unit 131 is a single carrier transmission as in the connection request A2 shown in FIG. It is determined that the request is a “connection request transmitted from the mobile station 14-1 located in the weak electric field area for which an increase is required”. In this case, the control unit 130 transmits another communication station 14 (in this case, a mobile station) that has transmitted the communication signal received in the same time slot as the connection request so that the reception gain of the variable gain amplifier 114 increases at the reception timing of the connection request. The transmission level of the communication signal is reduced with respect to the station 14-2. Specifically, the transmission level reduction amount determination unit 132 and the instruction unit 133 perform the following processing.

  When the connection request detected by the connection request detection unit 131 is a single-carrier transmission as in the connection request A2 shown in FIG. 5B, the transmission level reduction amount determination unit 132 determines the reception level of the connection request. Based on the number of subcarriers used in the transmission of the connection request (here, one), the reception level (hereinafter referred to as the normal connection request) that the mobile station 14-1 performs multicarrier transmission using a predetermined number of subcarriers (Referred to as “predicted reception level”) (see predicted connection request A3 ′ in FIG. 5B). Then, the transmission level reduction amount determination unit 132 determines the transmission level reduction amount instructed to the mobile station 14-2 based on the predicted reception level.

  Specifically, the transmission level reduction amount determination unit 132 is based on the predicted reception level, the reception level of the communication signal received together with the connection request detected by the connection request detection unit 131, and the dynamic range of the ADC 116. The transmission level reduction amount instructed to the mobile station 14-2 may be determined. For example, as illustrated in FIG. 5B, the transmission level reduction amount determination unit 132 determines the peak value of the predicted reception level (see predicted connection request A3 ′) and the peak reception level of the communication signal transmitted from the mobile station 14-2. The transmission level reduction amount ΔP instructed to the mobile station 14-2 may be determined so that the difference (peak difference) between the value and the communication signal B 1 is equal to or less than the dynamic range of the ADC 116.

  When the mobile station 14-2 reduces the transmission level of the communication signal by the reduction amount ΔP determined in this way, the reception level at the base station 12 of the communication signal transmitted from the mobile station 14-2 decreases as shown in FIG. 5C. (See communication signal B2), the reception gain control unit 117 increases the gain of the variable gain amplifier 114, and the dynamic range of the ADC 116 is relative to the reception level of the connection request transmitted from the mobile station 14-1. descend.

  As a result, as shown in FIG. 5D, even if the mobile station 14-1 transmits the connection request to the base station 12 by multicarrier (see connection request A3), the connection request after being adjusted by the variable gain amplifier 114 The received level falls within the dynamic range of the ADC 116. For this reason, the connection request detection unit 131 can detect a regular connection request from the mobile station 14-1.

  Further, the transmission level reduction amount determination unit 132 determines the transmission level reduction amount instructed to the mobile station 14-2 based on the predicted reception level and the reception level of the connection request detected by the connection request detection unit 131. You may decide. For example, the transmission level reduction amount determination unit 132 instructs the mobile station 14-2 of the difference between the peak value of the predicted reception level and the peak value of the reception level of the connection request detected by the connection request detection unit 131. The transmission level reduction amount ΔP may be used. In this way, even if the mobile station 14-1 transmits the connection request to the base station 12 by multicarrier transmission, the reception level of the connection request after being adjusted by the variable gain amplifier 114 falls within the dynamic range of the ADC 116. Therefore, the connection request detection unit 131 can detect a regular connection request transmitted from the mobile station 14-1.

  The instruction unit 133 instructs the mobile station 14-2 to reduce the transmission level of the communication signal by the reduction amount determined by the transmission level reduction amount determination unit 132. That is, the instruction unit 133 generates an instruction message specifying the reduction amount determined by the transmission level reduction amount determination unit 132, and transmits the instruction message to the mobile station 14-2. The transmission unit 150 is controlled. In addition, instead of the amount of reduction of the transmission level, the instruction unit 133 may specify the increase number of subcarriers necessary for reducing the transmission level by the amount of reduction in the instruction message.

  Further, the instruction unit 133 instructs the mobile station 14-1 to retransmit the connection request with a predetermined number of subcarriers (multi-carrier transmission of the connection request again). That is, the instruction unit 133 generates an instruction message instructing retransmission of the connection request, and controls the transmission signal processing unit 140 and the transmission unit 150 to transmit the instruction message to the mobile station 14-1.

  The transmission signal processing unit 140 is configured by, for example, a DSP, and performs error correction coding, primary modulation (digital modulation), and communication channel allocation status on a digital signal input from the control unit 130 or an upper layer (not shown). Based on the division of the complex symbol sequence based thereon, secondary modulation (IFFT: Inverse Fast Fourier Transform), addition of a guard interval, and the like, the obtained digital signal (OFDM signal) is output to the transmitter 150.

  The transmission unit 150 includes a DAC (D / A converter) 151, a band pass filter 152, an amplifier 153, a mixer 154, a power amplifier 155, and a band pass filter 156.

  The DAC 151 converts the digital signal input from the transmission signal processing unit 140 into an analog baseband signal, and outputs the baseband signal to the band pass filter 152. The bandpass filter 152 is a filter having a passband width of 8.1 MHz that attenuates unnecessary frequency components (spurious) of the baseband signal input from the DAC 151 and passes only a desired frequency component.

  The amplifier 153 amplifies the baseband signal passing through the band pass filter 152 and outputs the amplified baseband signal to the mixer 154. The mixer 154 up-converts the baseband signal input from the amplifier 153 into a radio signal and outputs the radio signal to the power amplifier 155.

  The power amplifier 155 amplifies the radio signal input from the mixer 154 to the transmission output level and outputs it to the band pass filter 156. The band pass filter 156 is a filter having a pass bandwidth of 8.1 MHz that attenuates the frequency component outside the transmission band of the radio signal input from the power amplifier 155 and passes only the frequency component within the transmission band. A radio signal passing through the band pass filter 156 is supplied to the antenna 100.

  FIG. 4 is a functional block diagram of the mobile station 14. As shown in FIG. 4, the mobile station 14 includes an antenna 200, a reception unit 210, a reception signal processing unit 220, a control unit 230, a transmission signal processing unit 240, and a transmission unit 250.

  The antenna 200 receives a radio signal and outputs the received radio signal to the receiving unit 210. Further, the antenna 200 transmits the radio signal supplied from the transmission unit 250 to the base station 12.

  The receiving unit 210 includes a band pass filter 211, a low noise amplifier 212, a mixer 213, a band pass filter 215, an amplifier 214, and an ADC 216.

  The bandpass filter 211 is a filter having a passband width of 8.1 MHz that attenuates frequency components outside the reception band of the radio signal input from the antenna 200 and passes only frequency components within the reception band. The low noise amplifier 212 amplifies the radio signal passing through the band pass filter 211 and outputs the amplified signal to the mixer 213. The mixer 213 down-converts the radio signal input from the low noise amplifier 212 into a baseband signal, and outputs the baseband signal to the amplifier 214.

  The amplifier 214 amplifies the baseband signal input from the mixer 213 and outputs it to the band pass filter 215. The bandpass filter 215 is a filter having a passband width of 8.1 MHz that attenuates unnecessary frequency components (spurious) of the baseband signal input from the amplifier 214 and passes only a desired frequency component.

  The ADC 216 converts the analog baseband signal passing through the band pass filter 215 into a digital signal, and outputs the digital signal to the reception signal processing unit 220.

  The reception signal processing unit 220 is configured by, for example, a DSP, and removes guard intervals, primary demodulation (FFT), secondary demodulation (digital demodulation), and error correction for a digital signal input from the ADC 216 of the reception unit 210. Etc., and receive data from the base station 12 is acquired. Then, the reception signal processing unit 220 outputs the acquired reception data to the control unit 230 or an upper layer (not shown).

  Received signal processing section 220 connects the subcarrier components of the complex symbol sequence obtained by the primary demodulation (FFT) for each subchannel, and detects the reception level of the signal received on each subchannel. Then, reception signal processing section 220 sequentially outputs the detected reception level to transmission gain control section 257 and control section 230.

  The control unit 230 includes, for example, a CPU and a program that controls the operation of the CPU, and controls each unit of the mobile station 14. The control unit 230 includes a connection request detection estimation unit 231 and a carrier number control unit 232, and performs processing related to transmission of a connection request to the base station 12.

  The connection request detection estimation unit 231 estimates whether or not the connection request transmitted to the base station 12 (multicarrier transmission) with a predetermined number of subcarriers via the control channel is detected by the base station 12. For example, the connection request detection estimation unit 231 may estimate that the connection request has not been detected by the base station 12 when a connection response from the base station 12 to the connection request is not received.

  In the present embodiment, the transmission unit 250 controls the transmission level of the connection request based on the reception level of the notification signal transmitted from the base station 12 via the control channel. For this reason, the connection request detection estimation unit 231 determines that the reception level of the notification signal transmitted from the base station 12 is equal to or higher than a predetermined value (that is, the distance between the base station 12 and the mobile station 14 is relatively short). ) When a connection response from the base station 12 to the connection request is not received, it may be estimated that the connection request has not been detected by the base station 12. In this way, it is possible to more accurately estimate the case where the connection request is not detected by the base station 12 because it is out of the reception dynamic range of the base station 12.

  The carrier number control unit 232 controls the number of subcarriers used by the transmission unit 250 to transmit a connection request. Specifically, when it is estimated that the connection request transmitted by multicarrier transmission by the connection request detection estimation unit 231 is not detected by the base station 12, the carrier number control unit 232 uses the number of subcarriers used for transmission of the connection request. Is reduced from a predetermined number to one. By doing so, the transmission level per subcarrier increases, and it becomes easy for the base station 12 to detect a connection request. Conversely, when an instruction message instructing retransmission of a connection request is received from the base station 12 in response to a connection request transmitted by a single carrier, the carrier number control unit 232 determines the number of subcarriers used for transmission of the connection request. From one to a predetermined number.

  The transmission signal processing unit 240 is configured by, for example, a DSP, and performs error correction coding, primary modulation (digital modulation), secondary modulation (IFFT) on a digital signal input from the control unit 230 or an upper layer (not shown). , Adding a guard interval, etc., and outputting the obtained digital signal (OFDM signal) to the transmitter 250.

  The transmission unit 250 includes a DAC (D / A converter) 251, a band pass filter 252, a variable gain amplifier 253, a mixer 254, a power amplifier 255, and a band pass filter 256.

  The DAC 251 converts the digital signal input from the transmission signal processing unit 240 into an analog baseband signal, and outputs the baseband signal to the band pass filter 252. The bandpass filter 252 is a filter having a passband width of 8.1 MHz that attenuates unnecessary frequency components (spurious) of the baseband signal input from the DAC 251 and passes only a desired frequency component.

  The variable gain amplifier 253 is an amplifier that changes the gain according to the gain control signal input from the transmission gain control unit 257, amplifies the baseband signal that passes through the band pass filter 252, and outputs the amplified signal to the mixer 254. The mixer 254 up-converts the baseband signal input from the variable gain amplifier 253 into a radio signal and outputs the radio signal to the power amplifier 255.

  The power amplifier 255 amplifies the radio signal input from the mixer 254 to the transmission output level and outputs the amplified signal to the band pass filter 256. The band pass filter 256 is a filter having a pass bandwidth of 8.1 MHz that attenuates the frequency component outside the transmission band of the radio signal input from the power amplifier 255 and passes only the frequency component within the transmission band. A radio signal passing through the band pass filter 256 is supplied to the antenna 200.

  The transmission gain control unit 257 controls the gain of the variable gain amplifier 253 based on the reception level detected by the reception signal processing unit 220 (the reception level of the signal received by each subchannel). Specifically, the transmission gain control unit 257 determines the gain of the variable gain amplifier 253 based on the reception level of the broadcast signal transmitted from the base station 12 via the control channel, and sets the gain of the variable gain amplifier 253. A gain control signal for setting the gain determined here is output to variable gain amplifier 253. Thereby, the transmission level of the connection request is controlled based on the reception level of the notification signal.

  Next, the operation of the mobile station 14 will be described. FIG. 6 is a flowchart showing an example of connection request transmission processing in the mobile station 14.

  As shown in FIG. 6, the mobile station 14 periodically receives a broadcast signal transmitted from the base station 12 via the control channel (S300). When communication with the base station 12 is started, the mobile station 14 transmits a regular connection request to the base station 12 via the control channel (S302).

  Thereafter, the mobile station 14 estimates whether or not the connection request transmitted by multicarrier is detected by the base station 12 (S304). For example, if the reception level of the notification signal received in S300 is equal to or higher than a predetermined value and the connection response from the base station 12 to the connection request transmitted in S302 is not received, the mobile station 14 receives the connection request. Is not detected by the base station 12.

  Here, when it is estimated that the connection request is not detected by the base station 12 (S304: N), the mobile station 14 sends a single connection request to the base station 12 in order to increase the transmission level per subcarrier. Carrier transmission is performed (S306). Thereafter, when an instruction message instructing retransmission of the connection request is received from the base station 12 in response to the connection request transmitted by the single carrier (S308: Y), the mobile station 14 issues a regular connection request to the base station 12. Multi-carrier transmission is performed again (S310). This instruction message means that the reception gain of the base station 12 is increased (the reception dynamic range of the base station 12 is relatively decreased) by causing the other mobile stations 14 to reduce the transmission level of the communication signal. ing. Thereby, the possibility that the regular connection request transmitted from the mobile station 14 is detected by the base station 12 increases.

  On the other hand, when it is estimated that a connection request is detected by the base station 12 in S304 (S304: Y), or when an instruction message instructing retransmission of the connection request is not received from the base station 12 in S308 (S308: N) The process is terminated without further transmission of the connection request.

  According to the mobile communication system 10 described above, the success rate of connection of the mobile station 14 to the base station 12 adopting the OFDMA scheme can be improved.

  In addition, this invention is not limited to the said embodiment, The following modifications can also be considered.

  For example, in the above embodiment, when it is estimated that a normal connection request transmitted by a predetermined number of subcarriers (multicarrier transmission) has not been detected by the base station 12, the connection request is transmitted by a single subcarrier. Although an example of (single carrier transmission) has been shown, instead of single carrier transmission, a connection request may be transmitted by multicarrier with the number of subcarriers rather than a predetermined number.

  In the above embodiment, the example in which the reception dynamic range of the base station is equal to the dynamic range of the A / D converter is shown. However, the reception dynamic range of the base station is a circuit element (A / D converter installed in the reception system). May be determined in whole or in part.

  Furthermore, the present invention is widely applicable not only to mobile communication systems that employ OFDMA and TDMA / TDD but also to mobile communication systems that employ multi-carrier transmission.

  10 mobile communication systems, 12 base stations, 14 mobile stations, 16 cells, 100, 200 antennas, 110, 210 receivers, 111, 115, 152, 156, 211, 215, 252, 256 band pass filters, 112, 212 low Noise amplifier, 113, 154, 213, 254 mixer, 114, 253 variable gain amplifier, 116, 216 ADC (A / D converter), 117 reception gain control unit, 120, 220 reception signal processing unit, 130, 230 control unit, 131 connection request detection unit, 132 transmission level reduction amount determination unit, 133 instruction unit, 140, 240 transmission signal processing unit, 150, 250 transmission unit, 151, 251 DAC (D / A converter), 153, 214 amplifier, 155 255 Power amplifier, 231 Connection request detection estimation unit, 232 Carrier number control unit, 257 Transmission gain control unit.

Claims (12)

A mobile communication system that adopts a multi-carrier transmission scheme and performs wireless communication between a mobile station apparatus and a base station apparatus via any of a plurality of channels defined within a predetermined band,
The mobile station device
Detection estimation means for estimating whether or not a connection request transmitted to the base station apparatus with a predetermined number of carriers via the control channel defined in the band is detected by the base station apparatus;
When it is estimated that the connection request has not been detected by the base station apparatus, transmission means for transmitting a connection request to the base station apparatus with a smaller number of carriers than the predetermined number of carriers,
Including
The base station device
Detecting means for detecting a connection request transmitted from the mobile station apparatus via the control channel;
When the connection request detected by the detection means is transmitted with a number of carriers smaller than the predetermined number of carriers, the communication signal is transmitted to another mobile station apparatus that has transmitted the communication signal received together with the connection request. Instruction means for instructing to reduce the transmission level of
Including
The transmission means retransmits a connection request with the predetermined number of carriers after transmitting a connection request with a smaller number of carriers than the predetermined number of carriers.
A mobile communication system. The mobile communication system according to claim 1, wherein
The base station device
Based on the reception level of the connection request detected by the detection means and the number of carriers used for transmission of the connection request, the reception level of the connection request transmitted by the mobile station apparatus with the predetermined number of carriers is predicted. And a reduction amount determination means for determining a transmission level reduction amount for instructing the other mobile station apparatus based on the predicted reception level of the connection request.
Further including
The instruction means instructs the other mobile station apparatus to reduce the transmission level of the communication signal by a reduction amount determined by the reduction amount determination means;
A mobile communication system. The mobile communication system according to claim 2,
The reduction amount determining means instructs the other mobile station apparatus on the basis of the reception level of the communication signal received together with the connection request detected by the detecting means, and the reception dynamic range of the base station apparatus. Determine the amount of transmission level reduction,
A mobile communication system. The mobile communication system according to claim 2,
The reduction amount determining means determines a reduction amount of a transmission level instructed to the other mobile station apparatus based on the reception level of the connection request detected by the detection means;
A mobile communication system. The mobile communication system according to any one of claims 1 to 4,
The mobile station device
A transmission level control means for controlling a transmission level of the connection request based on a reception level of a control signal transmitted from the base station apparatus via the control channel;
Further including
The detection estimation means detects that the connection request is not detected by the base station apparatus when the reception level of the control signal is equal to or higher than a predetermined value and a connection response from the base station apparatus to the connection request is not received. Presumed that
A mobile communication system. The mobile communication system according to any one of claims 1 to 5,
The instruction means further instructs the mobile station device to retransmit a connection request with the predetermined number of carriers,
The transmission means retransmits a connection request with the predetermined number of carriers in accordance with a retransmission instruction from the base station device.
A mobile communication system. The mobile communication system according to any one of claims 1 to 6,
The transmission with the predetermined number of carriers is multi-carrier transmission,
Transmission with fewer carriers than the predetermined number of carriers is single carrier transmission.
A mobile communication system. The mobile communication system according to claim 3,
The reception dynamic range of the base station device is a dynamic range of an A / D converter included in the base station device.
A mobile communication system. The mobile communication system according to any one of claims 1 to 8,
The multi-carrier transmission scheme is an orthogonal frequency division multiple access scheme.
A mobile communication system. A base station device that adopts a multi-carrier transmission scheme and performs wireless communication with a mobile station device via any of a plurality of channels defined within a predetermined band,
Detecting means for detecting a connection request transmitted from the mobile station apparatus via a control channel defined in the band;
When the connection request detected by the detection means is transmitted with a carrier number smaller than a predetermined number of carriers, the communication signal is transmitted to another mobile station apparatus that has transmitted the communication signal received together with the connection request. Instruction means for instructing to reduce the transmission level;
A base station apparatus comprising: A mobile station apparatus that adopts a multi-carrier transmission scheme and performs radio communication with a base station apparatus via any of a plurality of channels defined within a predetermined band,
Detection estimation means for estimating whether or not a connection request transmitted to the base station apparatus with a predetermined number of carriers via the control channel defined in the band is detected by the base station apparatus;
When it is estimated that the connection request has not been detected by the base station apparatus, transmission means for transmitting a connection request to the base station apparatus with a smaller number of carriers than the predetermined number of carriers,
Including
The transmission means retransmits a connection request with the predetermined number of carriers after transmitting a connection request with a smaller number of carriers than the predetermined number of carriers.
A mobile station apparatus. A connection request detection method in a mobile communication system that adopts a multi-carrier transmission scheme and wirelessly communicates between a mobile station apparatus and a base station apparatus through any of a plurality of channels defined within a predetermined band,
Estimating whether a connection request transmitted from the mobile station apparatus to the base station apparatus with a predetermined number of carriers via a control channel defined in the band is detected by the base station apparatus;
When it is estimated that the connection request is not detected by the base station apparatus, the mobile station apparatus transmits a connection request to the base station apparatus with a number of carriers smaller than the predetermined number of carriers;
The base station device detecting a connection request transmitted from the mobile station device via the control channel;
When the detected connection request is transmitted with a number of carriers smaller than the predetermined number of carriers, the base station apparatus transmits to the other mobile station apparatus that has transmitted the communication signal received together with the connection request. Instructing to reduce the transmission level of the communication signal,
After the mobile station apparatus transmits a connection request with the number of carriers smaller than the predetermined number of carriers, and retransmits the connection request with the predetermined number of carriers;
A connection request detection method comprising:

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