JP5247354B2 - Base station equipment - Google Patents

Description

  The present invention relates to a base station apparatus that performs communication by an orthogonal frequency division multiplexing system or an orthogonal frequency division multiple access system.

  In PHS (Personal Handy-phone System), next-generation PHS with high communication speed will be commercialized soon, but base stations for next-generation PHS are not installed all over the country. Since the expansion will be developed mainly in the department, the existing PHS will not disappear rapidly, and the existing PHS will be operated in the form of coexisting with the next-generation PHS for the time being.

  The next-generation PHS performs communication using an OFDMA (Orthogonal Frequency Division Multiplexing Access) method. In the OFDMA scheme, a plurality of subcarriers called subcarriers centered on a predetermined frequency are used, and subcarriers of adjacent frequencies are conveyed orthogonally to each other. The problem with the OFDMA scheme is that even if subcarriers of a certain predetermined frequency are not used, the aftermath of adjacent subcarriers may be affected. This aftermath is called “sidelobe”.

As a technique for reducing the side lobe, there is ECP (Extended Cyclic Prefix) processing using a window function. In OFDMA, the side lobe in the band becomes large due to the effect of the discontinuity between symbols, so by applying a window function to the discontinuous part between the symbols described above and changing it smoothly, A side lobe is reduced (for example, refer patent document 1). However, the side lobe can be reduced as the number of samples of the signal to be processed with the window function is increased. However, the data rate is lowered and the SNR (Signal to Noise Ratio) is deteriorated, so the number of samples is appropriately adjusted. It is preferable.
JP 2008-136055 A

  However, when the existing PHS and next-generation PHS coexist in a communication area such as an urban area, and the number of existing PHS terminals in communication within the area cannot afford the allowable range, When an existing PHS terminal that is going to communicate from now on calls, if the side lobe of the signal that the next-generation PHS base station is communicating with the next-generation PHS is not properly processed, the bandwidth used by the next-generation PHS is not available. In spite of this, the carrier for call cannot be assigned to the band used in the next generation PHS, so that the frequency band cannot be used efficiently. This will be described in detail below.

  FIG. 8 is a diagram illustrating an allocation status of carriers (subcarriers) in the existing PHS band and the next-generation PHS band. When the existing PHS terminal that is communicating in the area where the existing PHS and the next-generation PHS coexist cannot be allocated any more, the existing PHS terminal that is going to communicate in the area is called When the next-generation PHS base station does not sufficiently reduce the side lobes of signals in the OFDM frequency band (the portion surrounded by diagonal lines), the side lobes are large as shown in FIG. A call carrier is not allocated even though there is a vacant band used for PHS.

  Accordingly, the present invention has been made to solve the conventional problems, and wireless communication using an orthogonal frequency division multiplex system or an orthogonal frequency division multiplex connection system and wireless systems using other systems within the band of the wireless communication. An object of the present invention is to provide a base station apparatus that can efficiently use a frequency band and improve the communication quality as much as possible when communication is performed in the same frequency band.

  The base station apparatus according to the present invention is different from the first radio communication system in the same frequency band of the first radio communication system and the first radio communication system by the orthogonal frequency division multiplexing system or the orthogonal frequency division multiple access system. In a base station apparatus of a wireless communication system that performs two wireless communication, a side lobe control unit that controls a side lobe of a wireless communication signal using a window function with respect to a sample extracted from transmission data by the first wireless communication method A carrier sense unit that identifies a frequency of a carrier in use in the second wireless communication; and a sample number determination unit that determines the number of samples from the frequency of the carrier in use identified by the carrier sense unit; The side lobe control unit includes the window for the sample according to the number of samples determined by the sample number determination unit. And a configuration using a number.

  With this configuration, when there is no room in the carrier band of the second wireless communication, the side frequency is controlled by increasing the number of samples used in the window function, so that the orthogonal frequency division multiplex system or the orthogonal frequency division multiplex connection system is used. If the frequency band is used efficiently and the second wireless communication carrier band has room, the side lobe is controlled by reducing the number of samples used in the window function. The communication quality can be as good as possible.

  Further, the base station apparatus of the present invention is configured so that the number of samples decreases as the number of samples of the carrier used by the sample number determination unit specified by the carrier sense unit increases. The structure which determines the number of is provided.

  With this configuration, the number of samples is determined so that the number of samples decreases as the number of carrier frequencies in use increases, so when controlling the side lobes by reducing the number of samples used in the window function. The communication quality can be made as good as possible.

  In the base station apparatus of the present invention, the first wireless communication system is a PHS communication system with an orthogonal frequency division multiple access system, and the second wireless communication system is a PHS communication system without an orthogonal frequency division multiple access system. It has a configuration that is a communication system.

  The base station apparatus according to the present invention is different from the first wireless communication method in the frequency band of the first wireless communication method and the first wireless communication method by the orthogonal frequency division multiplexing method or the orthogonal frequency division multiple access method. In a base station control method for controlling a base station apparatus constituting a wireless communication system in which a wireless communication system is performed, a carrier sense step in which the base station apparatus specifies a frequency of a carrier in use in the second wireless communication system And a sample number determining step for determining the number of samples extracted from transmission data by the first wireless communication system from the frequency of the carrier in use specified in the carrier sense step, and the sample number determining step Wireless communication of the first wireless communication method using the window function for the samples according to the number of samples obtained And a step of controlling the issue of side-lobe.

  By this method, when there is no vacant band in the carrier band of the second wireless communication, the side frequency is controlled by increasing the number of samples used in the window function, so that the orthogonal frequency division multiplex system or the orthogonal frequency division multiplex connection system is used. If the frequency band is used efficiently and the second wireless communication carrier band has room, the side lobe is controlled by reducing the number of samples used in the window function. The communication quality can be as good as possible.

  The present invention effectively reduces the frequency band when wireless communication using an orthogonal frequency division multiplexing system or an orthogonal frequency division multiple access system and wireless communication using another system within the same frequency band of the wireless communication are performed. The present invention provides a base station apparatus that can be used and can improve communication quality as much as possible.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration diagram of a radio communication system according to an embodiment of the present invention. The wireless communication system shown in FIG. 1 includes the existing PHS base station apparatus 9 and the next generation PHS in an area where the next generation PHS (first wireless communication system) and the existing PHS (second wireless communication system) coexist. A base station apparatus 10 exists.

  The wireless communication system shown in FIG. 1 includes an existing PHS base station apparatus 9 and a next-generation PHS base station apparatus 10, and communicates with the next-generation PHS base station apparatus 10 and the existing PHS base station apparatus 9. It has an existing PHS terminal 21 that communicates with. The next generation PHS base station apparatus 10 and the next generation PHS terminal 20 communicate by OFDM or OFDMA.

  FIG. 2 shows a block diagram of the next generation PHS base station apparatus according to the embodiment of the present invention. As illustrated in FIG. 2, the next-generation PHS base station apparatus 10 includes a wireless communication unit 11, a control unit 12, and a network interface 13.

  The wireless communication unit 11 transmits and receives a wireless signal from an antenna for communicating with the next-generation PHS terminal 20, and performs processing such as signal modulation and demodulation. The wireless communication unit 11 includes an encoding / modulation unit 14, a transmission unit 15, a reception unit 16, and a decoding / demodulation unit 17.

  FIG. 3 is a block diagram of the encoding and modulation unit according to the embodiment of the present invention.

  The code modulation unit 14 includes an error correction coding unit 30, an interleaver 31, a serial / parallel conversion unit 32, a digital modulation unit 33, an IFFT (Inverse Fast Fourier Transform) unit 34, a GI (Guard Interval) addition unit 35, and an ECP ( An extended cyclic prefix) processing unit 36 (side lobe control unit) is provided. For details, refer to Japanese Patent Application Laid-Open No. 2008-136055.

  The error correction coding unit 30 is, for example, an FEC (Forward Error Correction) encoder, and based on the coding rate instructed by the control unit 12, redundant information is added to the bit string of the control signal or data signal input from the control unit 12. Is added to the interleaver 31. The interleaver 31 performs an interleaving process on the bit string to which the error correction code is added by the error correction encoding unit 30. The serial / parallel conversion unit 32 divides the bit string after the interleaving process in units of bits for each subcarrier included in the subchannel instructed by the control unit 12 and outputs the result to each digital modulation unit 33.

  The digital modulation unit 33 is provided in the same number as the subcarriers, digitally modulates the bit data divided for each subcarrier using the subcarrier corresponding to the bit data, and outputs the modulation signal to the IFFT unit 34. . Each digital modulation unit 33 performs digital modulation using a modulation method instructed by the control unit 12, for example, BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), 64QAM, or the like. I do. The IFFT unit 34 generates an OFDM signal by performing inverse Fourier transform and orthogonal multiplexing on the modulation signal input from each digital modulation unit 33, and outputs the OFDM signal to the GI addition unit 35. The GI adding unit 35 adds a guard interval (GI) to the OFDM signal input from the IFFT unit 34 and outputs the result to the ECP processing unit 36.

  The ECP processing unit 36 includes a window function processing unit 36a and a symbol arrangement unit 36b. When the ECP processing start request is input from the control unit 12 and no ECP processing start request is input, a GI is added. The subsequent OFDM signal is output to the transmitter 15 without processing.

  The window function processing unit 36a applies a predetermined window function to the GI reducible region for each symbol included in the OFDM signal after GI addition based on the GI reducible region input from the control unit 12, and immediately after the GI. Extension data obtained by applying a predetermined window function to the window function target data extracted from the head part of the data part is added to the tail of the data part.

  Further, the window function processing unit 36a performs window function processing of the OFDM signal to be processed with the number of samples notified from the control unit 12.

  The symbol arrangement unit 36b arranges the symbols processed by the window function processing unit 36a in series so that the heads of the symbols do not overlap the data portions of adjacent symbols, and outputs the symbols to the transmission unit 15. The transmission unit 15 frequency-converts the OFDM signal input from the symbol arrangement unit 36b into an RF frequency band, and transmits it to the next-generation PHS terminal 20 as a transmission signal.

  On the other hand, the receiving unit 16 receives a signal transmitted from the next-generation PHS terminal 20 via an antenna. The decoding demodulator 17 extracts the received OFDM signal by frequency-converting the received signal received by the receiver 16 to the IF frequency band, removes the portion and GI that have been multiplied by the window function from the received OFDM signal, and performs FFT processing. Then, digital demodulation, parallel-serial conversion processing, deinterleaver processing, and error correction decoding processing are performed to reconstruct the bit string and output it to the control unit 12.

  The control unit 12 includes, for example, a CPU, a ROM, and a RAM that execute a program, and includes a carrier sense unit 18 and a sample number determination unit 19.

  The carrier sense unit 14 measures the frequency usage status of the existing PHS band and the noise level of the band via the wireless communication unit 11.

  The sample number determination unit 19 is processed by the window function processing unit 36a based on information on carriers that can be used in the existing PHS band (hereinafter referred to as usable carriers) obtained from the execution result of the carrier sense unit 14. The number of samples taken out from the OFDM signal is determined, and the determined number of samples is notified to the window function processing unit 36a. For example, the sample number determination unit 19 has correspondence data in which the number of usable carriers (hereinafter referred to as the number of usable carriers) corresponds to the number of samples, and obtains the number of samples from the correspondence data.

  For example, as shown in FIG. 4, the correspondence data is data such that the larger the number of usable carriers, the smaller the number of samples, and the smaller the number of usable carriers, the larger the number of samples. Note that when the number of samples to be processed by the window function is increased by the sample number determination unit 19, the side lobe is reduced, but the data rate and SNR are also increased. When the number of samples is decreased, the side lobe is reduced. It will not be reduced. For this reason, side lobes are allowed as the number of usable carriers increases, but as the number of usable carriers decreases, the side lobes are reduced to try to allocate carriers.

  The network interface 13 performs communication with the Internet or a telephone network. Data transmitted / received from the network interface 13 is transmitted / received to / from the next-generation PHS terminal 20 via the wireless communication unit 11.

  The operation of the next-generation PHS base station apparatus 10 configured as described above will be described with reference to the drawings. FIG. 5 is a flowchart showing processing of the next generation PHS base station apparatus 10.

  First, carrier sense is performed by the carrier sense unit 18, and the frequency allocation status of the existing PHS band is detected (S1). Next, the sample number determination unit 19 obtains the number of usable carriers from the carrier sense result, and determines the number of samples of the OFDM signal processed by the window function processing unit 36a from the corresponding data in FIG. 4 (S2). The determined number of samples is notified to the window function processing unit 36a and set (S3). In addition, the process of this flowchart of step S1-S3 is performed with a fixed period.

  For example, as shown in FIG. 6, since the carrier band of the existing PHS terminal 21 can be sufficiently allocated when there is only one carrier used (the number of usable carriers is large), the frequency for OFDM can be allocated. There are probably side lobes in the band. In addition, as shown in FIG. 7, when many carriers of the existing PHS terminal 21 are allocated, the carrier band of the existing PHS terminal 21 cannot be allocated, and the existing PHS terminal is used in the frequency band used in OFDM. In order to allocate 21 carriers, the next-generation PHS base station apparatus 10 sufficiently reduces the side lobes in the frequency band for OFDM.

  As described above, the next-generation PHS base station apparatus 10 of the present embodiment controls the side lobes by increasing the number of samples used in the window function when there is no room in the carrier band of the existing PHS terminal 21. Thus, when a frequency band is efficiently used using a frequency based on OFDM or OFDMA, and there is a vacant margin in the carrier band of the existing PHS terminal 21, the number of samples used in the window function is reduced to reduce the side By controlling the lobe, the communication quality can be made as good as possible.

  Although the next-generation PHS base station apparatus 10 has been described as communicating with the next-generation PHS terminal 20, the next-generation PHS base station apparatus 10 is configured to communicate with both the next-generation PHS terminal 20 and the existing PHS terminal 21. Also good. Of course, the base station apparatus of the present invention is not limited to the next-generation PHS terminal 20, but may be any base station that uses a communication method based on ODFM or OFDMA.

  The present invention effectively reduces the frequency band when wireless communication using an orthogonal frequency division multiplexing system or an orthogonal frequency division multiple access system and wireless communication using another system within the same frequency band of the wireless communication are performed. It has the effect of improving the communication quality as much as possible, and is useful for a wide range of base station apparatuses using the next generation PHS and various communication methods.

It is a block diagram of the radio | wireless communications system which concerns on embodiment of this invention. It is a block diagram of the next generation PHS base station apparatus which concerns on embodiment of this invention. It is a block diagram of the encoding modulation part which concerns on embodiment of this invention. It is a figure which shows the correspondence relationship between the number of usable carriers and the number of samples. It is a flowchart which shows the process of the next generation PHS base station apparatus 10 which concerns on embodiment of this invention. It is a figure which shows the allocation condition of the carrier (subcarrier) of the zone | band of the existing PHS and the zone | band for OFDM when there are almost no carriers in use. It is a figure which shows the allocation condition of the carrier (subcarrier) of the band of the existing PHS and the band for OFDM when many carriers are allocated. It is a figure which shows the allocation condition of the band (subcarrier) of the band of the existing PHS and the next generation PHS.

Explanation of symbols

DESCRIPTION OF SYMBOLS 9 Existing PHS base station apparatus 10 Next generation PHS base station apparatus 11 Wireless communication part 12 Control part 13 Network interface 14 Carrier sense part 14 Encoding modulation part 15 Transmission part 16 Reception part 17 Decoding demodulation part 18 Carrier sense part 19 Determination of sample number Unit 20 Next-generation PHS terminal 21 Existing PHS terminal 30 Error correction coding unit 31 Interleaver 32 Serial parallel conversion unit 33 Digital modulation unit 34 IFFT unit 35 GI addition unit 36 ECP processing unit 36a Window function processing unit 36b Symbol allocation unit

Claims (3)

A radio in which a first radio communication scheme based on an orthogonal frequency division multiplex scheme or an orthogonal frequency division multiplex connection scheme and a second radio communication scheme different from the first radio communication scheme performed within the frequency band of the first radio communication scheme are performed. In a base station apparatus of a communication system,
A side lobe control unit that controls a side lobe of a wireless communication signal using a window function for a sample extracted from transmission data by the first wireless communication method;
Information on the number of usable carriers that can be used in the frequency band of the second wireless communication method, and the number of samples decreases as the number of usable carriers increases, and the number of samples increases as the number of usable carriers decreases. based on the correspondence data, and a sample number determining unit for determining the number of said sample,
The base station apparatus, wherein the side lobe control unit uses the window function for the samples according to the number of samples determined by the sample number determination unit. The first wireless communication system is a PHS communication system with an orthogonal frequency division multiple access system, and the second wireless communication system is a PHS communication system without an orthogonal frequency division multiple access system. Item 8. The base station apparatus according to Item 1 . A radio in which a first radio communication scheme based on an orthogonal frequency division multiplex scheme or an orthogonal frequency division multiplex connection scheme and a second radio communication scheme different from the first radio communication scheme performed within the frequency band of the first radio communication scheme are performed. In a base station control method for controlling a base station apparatus constituting a communication system,
Information on the number of usable carriers that the base station apparatus can use in the frequency band of the second wireless communication method and the number of samples decreases as the number of usable carriers increases, and the number of samples decreases as the number of usable carriers decreases. A number-of- samples determining step for determining the number of samples extracted from the transmission data according to the first wireless communication system , based on the corresponding data such that the number increases .
According to the number of samples determined by the sample number determining step, characterized by comprising the steps of: controlling the sidelobes of a radio communication signal of the first wireless communication system using a window function with respect to the sample Base station control method.