JP2013098909A - Channel assignment method and base station device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a channel assignment method and a base station device capable of effectively using frequency resources of a radio system in the base station device having filters and assigning a plurality of channels to a plurality of mobile station devices.SOLUTION: A channel assignment method comprises the steps of: acquiring a reflected wave from a filter provided in a base station device (S11); if the intensity of the reflected wave corresponding to a band of a channel is higher than or equal to a threshold value (S14), preferentially assigning a mobile station device corresponding to the intensity of the reference signal of the mobile station device to the channel among a plurality of mobile station devices (S16); and controlling a modulation class of the channel according to the intensity of the reflected wave corresponding to the band of the channel (S15).

Description

  The present invention relates to a channel allocation method and a base station apparatus.

  A mobile communication base station apparatus or the like has a problem that interference with a base station apparatus of another adjacent wireless system occurs (for example, Patent Document 1), and a filter such as an external filter is used to remove spurious as a countermeasure against interference. There is a case. For example, since the filter is used when the spurious removal requirement is stricter than that of the mass production type base station device, the characteristics of the filter become very steep. A filter is used when the frequency band used is adjacent to another system without a guard band.

JP2008-172443

  However, a base station apparatus that includes a filter at the antenna terminal affects the frequency characteristics of the transmission band of the local station, and degrades modulation accuracy and decreases transmission output. Since the frequency band in which the modulation accuracy is degraded is used for communication in the same manner as the frequency band in which the modulation accuracy is not degraded, the throughput of the wireless system is lowered. In addition, the frequency band in which the transmission output is reduced is used for communication as it is as in the case where the frequency band is not deteriorated, so that the communication area of the wireless system is narrowed. As described above, in the related art, in the radio base station provided with the filter, the frequency resources of the radio system cannot be effectively used.

  Accordingly, an object of the present invention made in view of the above problems is to provide a channel allocation method and a base station apparatus that can effectively use frequency resources of a radio system in a base station apparatus provided with a filter. is there.

In order to solve the above problems, a channel allocation method according to the present invention includes:
A channel allocation method in a base station apparatus that allocates a plurality of channels to a plurality of mobile station apparatuses,
Obtaining a reflected wave by a filter provided in the base station device;
When the intensity of the reflected wave corresponding to the band of the channel is equal to or greater than a threshold, the mobile station apparatus is preferentially assigned to the channel according to the intensity of the reference signal of the mobile station apparatus among the plurality of mobile station apparatuses Steps,
It is characterized by including.

The channel allocation method according to the present invention includes:
In the assigning step, when the intensity of the reflected wave corresponding to a channel band is equal to or greater than a threshold value, the mobile station apparatus that is closer to the base station apparatus among the plurality of mobile station apparatuses is prioritized. The channel is assigned to the channel.

The channel allocation method according to the present invention further includes:
The method includes controlling the modulation class of the channel according to the intensity of the reflected wave corresponding to the band of the channel.

The base station apparatus according to the present invention is
A base station apparatus that allocates a plurality of channels to a plurality of mobile station apparatuses,
Filters,
A reflected wave acquisition unit for acquiring a reflected wave by the filter;
When the intensity of the reflected wave corresponding to the band of the channel is equal to or greater than a threshold, the mobile station apparatus is preferentially assigned to the channel according to the intensity of the reference signal of the mobile station apparatus among the plurality of mobile station apparatuses. A control unit to be assigned,
It is characterized by having.

The base station apparatus according to the present invention is
The control unit further includes:
When the intensity of the reflected wave corresponding to the band of the channel is greater than or equal to a threshold value, the mobile station devices that are closer to the base station device among the plurality of mobile station devices are preferentially assigned to the channel It is characterized by that.

The base station apparatus according to the present invention is
The control unit further includes:
The modulation class of the channel is controlled in accordance with the intensity of the reflected wave corresponding to the band of the channel.

The base station apparatus according to the present invention is
A base station apparatus that allocates a plurality of channels to a plurality of mobile station apparatuses,
A control unit that preferentially assigns the mobile station apparatus to the channel according to the communication quality status of the band corresponding to the channel and the strength of the reference signal of the mobile station apparatus among the plurality of mobile station apparatuses;
It is characterized by having.

  The channel allocation method and the base station apparatus according to the present invention can effectively use frequency resources of a radio system in a base station apparatus provided with a filter.

It is a block diagram showing the structure of the base station apparatus which concerns on one Embodiment of this invention. It is a conceptual diagram showing the relationship between the main signal and reflected wave which concern on one Embodiment of this invention. It is a figure showing the relationship between the reflected wave and each channel which concern on one Embodiment of this invention. It is a flowchart which shows operation | movement of the base station apparatus which concerns on one Embodiment of this invention.

  Embodiments of the present invention will be described below.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a base station apparatus according to an embodiment of the present invention. The base station apparatus 1 which concerns on one Embodiment of this invention is provided with the external filter 2 and the antenna 3 as schematic structure. The external filter 2 is provided for removing spurious as a countermeasure against interference with base station apparatuses of other adjacent wireless systems, and performs filtering of transmission waves transmitted from the antenna 3.

  Next, a detailed configuration of the base station apparatus 1 will be described. The base station apparatus 1 includes an OFDM signal generation apparatus 11, an equalizer 12, a digital-analog converter (DAC) 13, a DAC 14, a low-pass filter (LPF) 15, an LPF 16, an IQ modulator 17, and a local oscillator ( LO) 18, amplifier (AMP) 19, power amplifier (PA) 20, isolator (ISO) 21, bandpass filter (BPF) 22, circulator 23, BPF 24, and mixer (MIX) 25 LO 26, AMP 27, IQ demodulator 28, LPF 29, LPF 30, analog-digital converter (ADC) 31, ADC 32, FFT unit 33, and control unit 34.

  The OFDM signal generation device 11 inputs transmission data to the equalizer 12. The equalizer 12 outputs, to the DAC 13 and the DAC 14, an I-channel baseband signal and a Q-channel baseband signal, which are corrected for each channel based on a digital signal related to a reflected wave from the FFT unit 33 described later.

  The DAC 13 and the DAC 14 convert the baseband signals of the I channel and the Q channel, respectively, into analog signals. The LPF 15 and the LPF 16 remove harmonics of the analog signal output from the DAC 13 and the DAC 14.

  The IQ modulator 17 receives the analog signal and the local oscillation frequency signal output from the LO 18 and orthogonally modulates the analog signal into a high-frequency signal in a radio frequency band. The AMP 19 and PA 20 amplify the high frequency signal.

  The ISO 21 outputs the input signal only in a predetermined direction. Specifically, the high frequency signal output from the PA 20 is received and output to the BPF 22. The BPF 22 filters unwanted waves and outputs a main signal to the circulator 23.

  The circulator 23 outputs the main signal from the BPF 22 to the external filter 2. The circulator 23 outputs the reflected wave from the external filter 2 to the BPF 24.

  A directional coupler may be used in place of the circulator 23. Similarly, when the directional coupler is used, the input signal from the BPF 22 is output to the external filter 2, while the reflected wave from the external filter 2 is output to the BPF 24.

  The BPF 24 receives the reflected wave from the external filter 2 and filters unnecessary waves. In addition, as a reflected wave, when the high frequency signal output from the circulator 23 attenuate | damped about the unused band with the external filter 2, it generate | occur | produces in this band.

  The MIX 25 synthesizes the reflected wave and the local oscillation frequency signal from the IO 26. The AMP 27 amplifies the synthesized reflected wave. The amplified reflected wave is demodulated by the IQ demodulator 28.

  The LPF 29 and LPF 30 remove harmonic components of the demodulated reflected wave, and the ADC 31 and ADC 32 convert the reflected wave from an analog signal to a digital signal.

  The FFT unit 33 performs Fourier transform on the digital signal related to the reflected wave and inputs the digital signal to the equalizer 12 and the control unit 34.

  The control unit 34 controls transmission wave channel assignment based on the reflected wave digital signal. Further, the control unit 34 controls channel assignment of transmission waves based on the reference signal from the mobile station apparatus.

  FIG. 2 is a conceptual diagram showing the relationship between the external filter 2 and the reflected wave. FIG. 2A shows the waveform of the main signal input to the external filter 2. FIGS. 2B and 2C show the case where the characteristic of the external filter 2 is expressed by the waveform of the filter characteristic A and the case where the characteristic of the external filter 2 is expressed by the waveform of the filter characteristic B, respectively. At this time, waveforms of signals (hereinafter referred to as “output signals”) output from the external filter 2 to the antenna 3 are as shown in FIG. 2D and FIG. That is, the waveform of the output signal is a waveform in which a signal in a part of the band is deteriorated by the filter 2 in the waveform of the main signal. In addition, as shown in FIGS. 2 (f) and 2 (g), each reflected wave is generated with a signal intensity corresponding to the degree of degradation in the degraded band of the main signal waveform. From the above, it is possible to estimate the degraded band of the main signal based on the reflected wave.

  FIG. 3 is a diagram illustrating the relationship between the reflected wave and each channel. In this example, description will be made assuming that there are a total of 12 channels from channel 1 to channel 12, but the number of channels is not limited to this. Each channel is assigned a band obtained by dividing the frequency of the transmission band into twelve.

  Here, it is assumed that the reflected wave from the external filter 2 is represented by a waveform 41. In this case, in the band of channel 5 to channel 12, the signal intensity of the reflected wave is less than a predetermined threshold (threshold A). Therefore, it can be estimated that the main signal is hardly deteriorated in the band of channel 5 to channel 12.

  In the band of channel 3 and channel 4, the signal intensity of the reflected wave is equal to or higher than the threshold A, but is lower than a predetermined threshold (threshold B) higher than the threshold A. Therefore, it can be estimated that the main signal is degraded in the band of channel 3 and channel 4 as compared with the band of channel 5 to channel 12.

  Further, the signal strength of the reflected wave in the band of channel 1 and channel 2 is equal to or higher than the threshold value B. Therefore, it can be estimated that the main signal is degraded in the band of channel 1 and channel 2 as compared with channel 3 to channel 12.

  Regarding the waveform of the reflected wave, if the reflected wave is an OFDM signal, the test signal scattered in time and frequency is used, and the intensity of the test signal is statistically aggregated to obtain the waveform of the reflected wave. presume. In the case of a CDMA signal or a PHS signal, the spectrum spread uses the entire transmission band. Therefore, it is only necessary to simply detect the waveform of the reflected wave without having to add up the special test signal intensity.

  Next, the operation of the base station apparatus 1 according to the present invention will be described with reference to the flowchart shown in FIG. In general, the base station apparatus 1 performs control so that a channel with a lower degree of degradation shown in FIG. 3 can be modulated with a modulation class having a higher rate, and a channel is allocated to a mobile station apparatus existing in the vicinity. To do.

  First, the base station apparatus 1 transmits a transmission wave (step S10). Specifically, the OFDM signal generation device 11 of the base station device 1 generates transmission data. The baseband signal output from the equalizer 12 based on the transmission data is converted into an analog signal by the DAC 13 and the DAC 14, the harmonics are removed by the LPF 15 and the LPF 16, and then orthogonally modulated by the IQ modulator 17. Thereafter, after being amplified by the AMP 19 and the PA 20, unnecessary waves are filtered by the BPF 22 via the ISO 21, and transmitted as a transmission wave from the antenna 3 via the circulator 23 and the external filter 2.

  Next, the base station apparatus 1 acquires a reflected wave (step S11). Specifically, the reflected wave from the external filter 2 is acquired, and the unnecessary wave is filtered by the BPF 24 via the circulator 23. Thereafter, the signal is combined with the local oscillation frequency signal from the IO 26 in the MIX 25 and amplified by the AMP 27. The amplified reflected wave is demodulated by the IQ demodulator 28, the harmonics are removed by the LPF 29 and the LPF 30, and then converted into a digital signal by the ADC 31 and the ADC 32, and Fourier-transformed by the FFT unit 33, and the equalizer 12 and the control unit 34. Hereinafter, in this example, it is assumed that the reflected wave shown in the waveform 41 in FIG. 3 is obtained.

  Next, the control part 34 determines whether the external filter 2 is provided based on a reflected wave (step S12). Specifically, the control unit 34 determines that the external filter 2 is not provided when there is no reflected wave, and determines that the external filter is provided when there is a reaction wave. If it is determined that there is no external filter, the process ends.

  When it is determined that there is an external filter, the control unit 34 performs channel allocation control based on the intensity of the reflected wave (band communication quality status) corresponding to the band of each channel. First, the control unit 34 sets a variable N in which a channel serial number is stored as 1 as an initial setting (step S13). N is an integer value ranging from 1 to Nmax, and Nmax represents the number of channels. In the example shown in FIG. 3, since the number of channels is 12, N takes an integer value from 1 to 12. That is, the subsequent steps are repeated for each channel from channel 1 to channel 12.

  Subsequently, the control unit 34 determines whether or not the reflected wave corresponding to the band of the channel N is less than the threshold value A (step S14). If it is less than the threshold A, the process proceeds to step S15. Specifically, since channels 5 to 12 are less than the threshold value A, the process proceeds to step S15 in determining these channels.

  Subsequently, the control unit 34 selects a modulation class corresponding to the channel N (N = 5 to 12 in this case) (step S15). For this channel, since there is almost no reflected wave, the flatness, group delay characteristics, and transmission output are negligible, so any modulation class from high-rate modulation class to low-rate modulation class can be ignored. Can also be used. Specifically, the control unit 34 selects any one of QPSK, 16QAM, and 64QAM and performs control so as to modulate the channel. That is, the control unit 34 controls channel 5 to channel 12 to modulate based on these modulation classes.

  Subsequently, the control unit 34 assigns the channel N to communication with the mobile station device (step S16). The control unit 34 determines a mobile station device to be assigned according to the strength of the reference signal transmitted by the mobile station device. Specifically, a mobile station apparatus whose reference signal intensity is less than a predetermined threshold (threshold C) is preferentially assigned. Note that “priority” means that, when there are a plurality of candidate mobile station apparatuses to be assigned to the channel, the channel is assigned to a mobile station apparatus having a reference signal strength (reception strength) less than a threshold C. . The strength of the reference signal decreases as the distance between the mobile station device and the base station device 1 increases. The longer the distance between the mobile station apparatus and the base station apparatus 1, the more the transmission output is required, and the greater the influence of a reduction in throughput and narrowing of the communication area due to the deteriorated channel. Therefore, according to the reference signal, a channel with a low degree of degradation is preferentially assigned to a mobile station device located at a long distance from the base station device 1 to effectively use frequency resources of the radio system. In step S16, a mobile station apparatus having a reference signal strength equal to or higher than a predetermined threshold (threshold D) may be preferentially assigned.

  Subsequently, the control unit 34 increments the value of N and determines whether or not the value of N exceeds Nmax (step S16). If Nmax is not exceeded, the process returns to step S12, and after repeating for all the channels, proceeds to the next step.

  If the reflected wave corresponding to channel N is greater than or equal to the threshold A in step S14, the process proceeds to step S18. Specifically, since channel 1 to channel 4 are equal to or greater than threshold A, the process proceeds to step S18 in determining these channels.

  In this case, the control unit 34 determines whether or not the reflected wave corresponding to the channel N is less than the threshold value B (step S18). If it is less than the threshold B, the process proceeds to step S19. Specifically, since channel 3 and channel 4 are less than the threshold value B, in the determination of these channels, the process proceeds to step S19.

  Subsequently, the control unit 34 selects a modulation class corresponding to the channel N (N = 3, 4 here) (step S19). Since the reflected wave is slightly present for the channel, there are a decrease in flatness, a decrease in group delay characteristics, and a decrease in transmission output. Therefore, some modulation classes that can be selected are limited. Specifically, the control unit 34 selects either QPSK or 16QAM, and performs control to modulate the channel. That is, the control unit 34 controls channel 3 to channel 4 to modulate based on these modulation classes.

  Subsequently, the control unit 34 assigns the channel N to communication with the mobile station device (step S20). The control unit 34 determines the mobile station device to be assigned according to the strength of the reference signal transmitted by the mobile station device. Specifically, a mobile station apparatus whose reference signal intensity is equal to or higher than a predetermined threshold (threshold C) and lower than a predetermined threshold (threshold D) higher than the threshold C is preferentially assigned. Thereafter, the process proceeds to step S17.

  If the reflected wave corresponding to channel N is greater than or equal to threshold B in step S18, the process proceeds to step S21. Specifically, since the corresponding reflected waves of channel 1 and channel 2 are equal to or greater than the threshold value B, the process proceeds to step S21 in determining these channels.

  Subsequently, the control unit 34 selects a modulation class corresponding to the channel N (N = 1, 2 here) (step S21). With respect to the channel, the intensity of the reflected wave is larger than that of the other channels, so that the flatness, the group delay characteristic, and the transmission output are greatly reduced as compared with the other channels. Therefore, the modulation classes that can be selected are limited. Specifically, the control unit 34 performs control so that the channel is modulated by QPSK. That is, channel 1 and channel 2 are controlled to be modulated by QPSK.

  Subsequently, the control unit 34 assigns the channel N to communication with the mobile station device (step S22). The control unit 34 determines the mobile station apparatus to be assigned to the strength of the reference signal transmitted by the mobile station apparatus. Specifically, a mobile station apparatus whose reference signal intensity is equal to or higher than a predetermined threshold (threshold D) is preferentially assigned. A mobile station apparatus having a relatively short distance from the base station apparatus 1 is preferentially assigned to the channel. If the mobile station apparatus is located closer to the mobile station apparatus, the influence is small even if the transmission output is low due to the low rate modulation. Therefore, even if a deteriorated channel is assigned, the influence on the reduction of the throughput and the narrowing of the communication area is small. Thereafter, the process proceeds to step S17. In step S22, a mobile station apparatus whose reference signal strength is less than a predetermined threshold (threshold C) may be preferentially assigned.

  Thus, according to the present invention, when the intensity of the reflected wave corresponding to the band of each channel is equal to or greater than the threshold, the control unit 34 preferentially assigns the mobile station apparatus having the reference signal intensity equal to or greater than the threshold to the channel. In the base station apparatus provided with the external filter, the frequency resources of the radio system can be effectively used.

  Further, according to the present invention, since the control unit 34 controls the modulation class of the channel according to the intensity of the reflected wave corresponding to the band of each channel, the optimum modulation class is selected in the base station apparatus provided with the external filter. The frequency resources of the wireless system can be effectively used.

  Note that the channel allocation according to the intensity of the reflected wave is divided into three cases by the threshold A and the threshold B (that is, the reflected wave is divided into three cases of the threshold A less than the threshold A, the threshold A greater than the threshold B, and the threshold B greater than) However, the present invention is not limited to this, and more or less cases may be divided. In this case, it can be realized by increasing or decreasing the threshold value set as appropriate.

  Note that the choice of modulation class in step S15, step S19, and step S21 is not limited to this. As another modulation class, 128QAM or BPSK may be selected.

  In step S16, step S20, and step S22, the base station apparatus 1 performs assignment control based on the reference signal from the mobile station apparatus, but is not limited thereto. In addition, the base station apparatus 1 may estimate a mobile station that is present in the vicinity based on GPS information from the mobile station apparatus, and may perform channel control. That is, in order for the base station apparatus 1 to preferentially allocate a channel to a mobile station apparatus that exists in the vicinity, the distance to the mobile station apparatus is estimated, and the mobile station apparatus that has a lower transmission output and may perform low rate modulation Any method may be used as long as it can be estimated.

  The external filter 2 may be a built-in filter built in the base station device 1. In the case of the built-in filter, it is considered that the modulation class setting for each channel is set in advance according to the characteristics of the built-in filter. However, even in this case, by applying the present invention, it is possible to set the optimum channel assignment and modulation class when the characteristics of the built-in filter change due to temperature change or aging change.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, the functions included in each member, each means, each step, etc. can be rearranged so as not to be logically contradictory, and a plurality of means, steps, etc. can be combined into one or divided. Is possible.

DESCRIPTION OF SYMBOLS 1 Base station apparatus 2 External filter 3 Antenna 11 OFDM signal generation apparatus 12 Equalizer 13, 14 Analog-digital converter (DAC)
15, 16 Low pass filter (LPF)
17 IQ modulator 18 Local oscillator (LO)
19 Amplifier (AMP)
20 Power amplifier (PA)
21 Isolator (ISO)
22 Bandpass filter (BPF)
23 Circulator 24 Band pass filter (BPF)
25 Mixer (MIX)
26 Local transmitter (LO)
27 Amplifier (AMP)
28 IQ demodulator 29, 30 Low-pass filter (LPF)
31, 32 Analog-to-digital converter (ADC)
33 FFT unit 34 Control unit 41 Waveform

Claims (7)

A channel allocation method in a base station apparatus that allocates a plurality of channels to a plurality of mobile station apparatuses,
Obtaining a reflected wave by a filter provided in the base station device;
When the intensity of the reflected wave corresponding to the band of the channel is equal to or greater than a threshold, the mobile station apparatus is preferentially assigned to the channel according to the intensity of the reference signal of the mobile station apparatus among the plurality of mobile station apparatuses Steps,
A channel allocation method comprising:   In the assigning step, when the intensity of the reflected wave corresponding to a channel band is equal to or greater than a threshold value, the mobile station apparatus that is closer to the base station apparatus among the plurality of mobile station apparatuses is prioritized. 2. The channel assignment method according to claim 1, wherein the channel assignment method is assigned to the channel. The channel allocation method further includes:
3. The channel assignment control method according to claim 1, further comprising a step of controlling a modulation class of the channel according to the intensity of the reflected wave corresponding to the band of the channel. A base station apparatus that allocates a plurality of channels to a plurality of mobile station apparatuses,
Filters,
A reflected wave acquisition unit for acquiring a reflected wave by the filter;
When the intensity of the reflected wave corresponding to the band of the channel is equal to or greater than a threshold, the mobile station apparatus is preferentially assigned to the channel according to the intensity of the reference signal of the mobile station apparatus among the plurality of mobile station apparatuses. A control unit to be assigned,
A base station apparatus comprising: The control unit further includes:
When the intensity of the reflected wave corresponding to the band of the channel is greater than or equal to a threshold value, the mobile station devices that are closer to the base station device among the plurality of mobile station devices are preferentially assigned to the channel The base station apparatus according to claim 4. The control unit further includes:
The base station apparatus according to claim 4 or 5, wherein a modulation class of the channel is controlled in accordance with the intensity of the reflected wave corresponding to the band of the channel. A base station apparatus that allocates a plurality of channels to a plurality of mobile station apparatuses,
A control unit that preferentially assigns the mobile station apparatus to the channel according to the communication quality status of the band corresponding to the channel and the strength of the reference signal of the mobile station apparatus among the plurality of mobile station apparatuses;
A base station apparatus comprising:

Images