JP2009171373A - Wireless communication network, wireless base station apparatus, and communication method in wireless communication network - Google Patents

Abstract

【Task】
In the radio base station apparatus divided into the BB unit and the RF unit, the RF unit is shared regardless of the radio system. In addition, the base station apparatus can be reduced in size.
[Means for Solving the Problems]
In a radio base station having a configuration in which a baseband unit that modulates / demodulates a digital baseband signal and a high-frequency radio unit that performs transmission / reception of a high-frequency radio signal and conversion into a digital baseband signal are connected by a transmission path A digital baseband signal having a sampling frequency specific to a radio communication system of a radio communication system is converted into a common baseband signal having a common sampling frequency, and signal transmission / reception between the radio frequency radio unit and the baseband unit is performed on a common base Perform by band signal.
[Selection] Figure 2

Description

  The present invention relates to a radio communication technique, and more particularly, to a configuration of a radio base station apparatus, a configuration of a radio communication network, and a radio communication method.

  Currently, wireless communication systems range from third-generation mobile phone systems such as W-CDMA and CDMA-2000 to LTE (Long Term Evolution), UMB (Ultra Mobile Broadband), WiMAX, etc. Is moving to next-generation systems such as fourth-generation mobile phone systems. In the 3.9th generation and 4th generation mobile phone systems, a specification study for realizing a communication speed of several hundred Mbps is being promoted, and the data rate is being increased. With the increase in data rate and the adoption of a multi-antenna system, in the next-generation mobile phone system, the base station apparatus is inevitable to be larger and more complicated than the current system.

On the other hand, communication traffic is increasingly concentrated in urban areas, and communication carriers have a problem of having to efficiently arrange base stations in a limited space for installing base station devices.
One of the technologies that allow more flexible design and construction of base station devices is CPRI (Common Public Radio Interface). CPRI separates the baseband unit (BB unit) that has the digital baseband signal processing function in the base station device from the radio signal processing unit (RF unit) that is responsible for the high-frequency radio signal processing function. Is an interface technology that connects the optical fiber and the like with optical fibers. By separating the base station device into a BB unit and an RF unit, and connecting the cables with optical fiber or the like between the units, the installation conditions of the base station device can be relaxed and a more flexible base station arrangement can be realized.

  The CPRI is an interface standard for transmitting digital baseband signals using optical fibers or metallic cables targeting W-CDMA, UMTS, and the like. Wireless standards such as W-CDMA and UMTS use a chip rate of 3.84 MHz, so the CPRI frame structure is based on a 3.84 MHz basic frame. One basic frame is divided into 16 words. Control data is stored in the first word, and digital sample data is stored in the remaining 15 words. The CPRI standard defines line bit rates from 614.4 Mbps to 3.072 Gbps, and the size of each word in the basic frame is 1 to 5 bytes according to each line bit rate. Using this basic frame as a basic frame, 256 basic frames have one hyperframe, and 150 hyperframes have a node B frame.

  As described above, the CPRI interface is a standard originally targeted for W-CDMA, UMTS, etc., and is based on a 3.84 MHz basic frame. Therefore, W-CDMA and UMTS systems have a high compatibility with the CPRI interface because the basic frame period and chip data period correspond 1: 1. However, since systems such as CDMA-2000 and WiMAX have different basic frame periods, the ratio between the CPRI chip data period and the CDMA-2000 or WiMAX basic frame period becomes a fractional ratio. As a result, the chip data and the basic frame cannot be synchronized, and CDMA-2000 and WiMAX have low compatibility with the CPRI interface, and some processing for rate matching is required to transmit using the CPRI interface.

Examples of techniques for transmitting digital baseband signals of wireless systems other than W-CDMA and UMTS using the CPRI interface include those shown in Patent Document 1 and Non-Patent Document 1, for example.
Patent Document 1 is a technique that enables digital baseband signals in the CDMA-2000 standard to be transmitted using a CPRI interface. The chip rate in the CDMA-2000 standard is 1.2288 MHz, and the ratio of the basic frame transmission rate 3.84 MHz in the CPRI interface to the chip rate in the CDMA-2000 standard is 25/8. In order to absorb this difference in rate, Patent Document 1 transmits one CDMA chip data in three basic frames, and one CDMA chip data (8 × 3 = 24 basic frames). Insert a null basic frame. As a result, rate matching between the CDMA chip rate and the CPRI interface transmission rate is performed.
Non-Patent Document 1 (CPRI Specification V3.0 p32-p37) relates to a technique for applying a CPRI interface to WiMAX. Non-Patent Document 1 describes several methods for mapping WiMAX digital sample data to the transmission rate of the CPRI interface. In either method, rate matching is performed by inserting surplus data called stuffing bits into the CPRI frame.

JP 2007-189675 A CPRI Specification V3.0 p32-p37 (http://www.cpri.info/)

  In order to perform rate matching between the sampling rate of the digital baseband signal and the transmission rate of the CPRI interface by the processes as described in Patent Document 1 and Non-Patent Document 1, the radio base station apparatus Null data insertion processing and null data deletion processing on the receiving side are required. This increases the circuit scale of the radio base station apparatus.

  Since the sample data received by the RF unit has a different sampling rate for each wireless system, it is necessary to prepare RF units having different specifications for each system. If the RF unit can be applied to a plurality of wireless communication systems, it is necessary to provide the RF unit with a configuration for supporting a plurality of wireless systems, which increases the circuit scale of the RF unit. End up.

An object of the present invention is to reduce the amount of processing in the RF unit and to reduce the device scale of the RF unit.
An object of the present invention is to share the RF unit regardless of the radio system in the radio base station apparatus divided into the BB unit and the RF unit.
Another object of the present invention is to improve the signal quality by efficiently using the transmission band of the interface between the BB unit and the RF unit.

  The present invention has been made to solve the above-described problems, and includes a first wireless communication system that performs wireless communication by a first wireless communication method, and wireless communication by a wireless communication method that is different from the first wireless communication method. Includes at least one second wireless communication system that transmits IP packets received from the IP network to the wireless terminals of the first and second wireless communication systems, and transmits data received from the wireless terminals to the IP network. A wireless base station apparatus of the first and second wireless communication systems receives a IP packet and performs modulation / demodulation of a digital baseband signal, and transmission / reception of a high-frequency wireless signal And a high-frequency radio unit that converts to a digital baseband signal are connected by a transmission line. The digital baseband signal having a sampling frequency specific to the wireless communication system of the first and second wireless communication systems is converted into a common baseband signal having a common sampling frequency that does not depend on the wireless communication system. In both wireless communication systems, transmission / reception of signals between the high-frequency wireless unit and the baseband unit is performed using the common baseband signal.

According to the present invention, it is not necessary to insert and delete surplus sample data and to perform filtering processing in the RF unit, and the apparatus scale of the RF unit can be reduced.
Further, according to the present invention, the sampling rate of the digital sample data at the output section of the BB unit can be made a common sampling rate independent of the wireless system, and the RF unit can be made common regardless of the wireless system. Can do.
Further, according to the present invention, the oversampling process is performed in accordance with the transmission band of the interface between the BB unit and the RF unit, so that the SN ratio can be improved while improving the transmission efficiency.

  Hereinafter, the present invention will be described using examples.

FIG. 1 is a network configuration diagram in an embodiment of the present invention.
As shown in FIG. 1, in one embodiment of the present invention, the entire network is composed of an IP network 100, BB units 200, 300, common RF units 400, 401, 402, 403, and user terminals 500, 501. Is done. In the present invention, the radio base station is separated into a baseband unit (BB unit) having a digital baseband signal processing function in the base station device and a radio signal processing unit (RF unit) having a high-frequency radio signal processing function. Composed. The CPRI interface is used between the BB unit and the RF unit, and they are cabled by optical fiber. The BB unit and the RF unit may be installed several kilometers to several tens of kilometers apart. The radio base station shown here shows a case where a mobile radio communication system represented by cellular communication is taken as an example.

  The network shown in FIG. 1 shows an example in which the network is composed of two different wireless systems. In FIG. 1, a UMB system and an LTE system are exemplified as two different wireless communication systems, but the present invention is not limited to this, and the types of wireless communication systems are also limited to two. It is not a thing. In addition, FIG. 1 shows an example in which two common RF units are connected to one BB unit in each of the UMB and LTE systems. However, the number of RF units connected to the BB unit is shown. However, the present invention is not limited to this.

First, the flow of signals in the downlink will be described using the UMB system as an example.
An IP packet is transmitted from the IP network 100 to the user terminal 500. This IP packet is transmitted to the radio base station where the corresponding user terminal exists, and is received by the BB unit 200 of the radio base station. This IP packet is modulated into a digital baseband signal suitable for the UMB system by the BB unit, and a digital baseband signal having a sampling rate in the UMB system is generated. The digital baseband signal generated here is further converted into a common sampling rate that does not depend on the wireless communication system. Then, CPRI framing is performed at a common sampling rate that does not depend on the wireless communication system, and is transmitted to the RF unit 400 via the CPRI interface.

  The RF unit receives a digital baseband signal transmitted at a common sampling rate that does not depend on the wireless communication system. In the RF unit, the received digital baseband signal is subjected to DA conversion processing, up-conversion processing to a high-frequency signal, amplification processing, and the like, and transmitted to the corresponding user terminal through the antenna.

Next, the signal flow in the uplink will be described.
Uplink data transmitted from the user terminal 500 is input as a high-frequency radio signal to the RF unit 400 via an antenna. In the RF unit, contrary to the downlink, down-conversion processing and AD conversion processing from high-frequency signals to baseband signals with a common sampling rate that does not depend on the wireless communication system are performed, and common sampling that does not depend on the wireless communication system A rate digital baseband signal is generated. A digital baseband signal having a common sampling rate that does not depend on the wireless communication system generated by the RF unit is transmitted to the BB unit 200 via the CPRI interface, and the UMB is obtained from the common sampling rate that does not depend on the wireless communication system by the BB unit. The system performs rate conversion processing to a baseband signal and digital baseband demodulation processing, is carried on an IP packet, and is transmitted to an IP network.
The flow of data on the network is common to all wireless communication systems regardless of the LTE system and the UMB system.

  In the present invention, the BB units 200 and 300 in each wireless system are dedicated BB units that differ for each wireless system, but the RF units 400, 401, 402, and 403 are common regardless of the wireless system. .

Next, the configuration of the radio base station will be described.
FIG. 2 shows the configuration of a radio base station in one embodiment of the present invention.
The radio base station according to an embodiment of the present invention includes a BB unit 201 and a common RF unit 400 that does not depend on a radio communication system. The CPRI interface is used for the interface between the BB unit and the RF unit, and the cables are connected by optical fibers. Although FIG. 2 shows only one BB unit and one RF unit for easy understanding, as described in FIG. 1, a plurality of RF units can be connected to the BB unit.

  The common RF unit 400 that does not depend on the wireless communication system is a small device installed on the roof of a building, for example. The common RF unit includes an O / E, an E / O conversion unit 410, a D / A conversion unit 420, an A / D conversion unit 430, a high output amplification unit 440, and a low noise amplification unit 450. The O / E and E / O converter 410 terminates the optical interface with the BB unit 201, and performs conversion from an optical signal to an electrical signal and from an electrical signal to an optical signal. The CPRI interface framing and deframing processes are also performed here. The D / A converter 420 performs conversion from a digital baseband signal to an analog baseband signal and up-conversion processing to a radio frequency. The high output amplifier 440 amplifies the high frequency radio signal from the D / A converter and sends it to the antenna. The low noise amplification unit 450 amplifies the uplink high frequency radio signal received by the antenna and sends it to the A / D conversion unit. The A / D converter 430 performs down-conversion from the received high-frequency radio signal to an analog baseband signal and conversion from the analog baseband signal to a digital baseband signal.

In the present invention, the processing content of the BB unit differs for each wireless communication system. First, the case of the UMB system will be described as an example.
The BB unit 201 includes an external line interface unit 211, a baseband modulation / demodulation unit 221, a rate conversion unit 231, and an O / E / E / O conversion unit 241, and transmits / receives IP packets to / from the IP network and digital baseband. Modulation / demodulation processing and transmission / reception of digital sample data to / from the RF unit.

  First, the external line interface unit 211 has a function of terminating the received IP packet from the IP network in the downlink and transmitting the IP packet to the IP network in the uplink.

  The baseband modulation / demodulation unit 221 performs general baseband modulation / demodulation processing in wireless communication such as channel coding and decoding, digital modulation / demodulation such as QPSK, and OFDM modulation / demodulation, and the digital baseband signal subjected to I / Q mapping. Perform input / output.

The digital baseband signals input / output here are digital baseband signals having different sampling rates depending on the radio system.
In the case of the UMB system, since the subcarrier interval is 9.6 kHz and the service bandwidth is 10 MHz, the number of FFT points is 1024 (of which the number of effective subcarriers is 960 points), so the sampling rate is 9.8304 Msps (1000). In addition, when the service bandwidth is 5 MHz, the number of FFT points is 512 points (of which the number of effective subcarriers is 480 points), and the sampling rate is 4.9152 Msps.
On the other hand, in the LTE system, the subcarrier interval is 15 kHz, and the number of FFT points is 1024 points (of which the number of effective subcarriers is 601 points) at the service bandwidth of 10 MHz, so the sampling rate is 15.36 Msps ( 1001). In the service bandwidth of 5 MHz, the number of FFT points is 512 points (including 301 effective subcarriers), and the sampling rate is 7.86 Msps.
Thus, in the case of the UMB system, the sampling rate is an integer multiple of the base clock frequency of 1.2288 MHz, and in the case of the LTE system, the sampling rate is an integer multiple of the base clock frequency of 3.84 MHz.

  Therefore, in the present invention, the rate conversion unit 231 is inserted in the output stage of the baseband modulation / demodulation unit 221, and sampling rate conversion processing is performed. In this sampling rate conversion process, the sampling rate of the digital baseband signal output from the BB unit is a common sampling rate that does not depend on the wireless system, and is a sampling rate that has a high affinity with the CPRI interface. Rate conversion is performed (1002). In other words, differences between wireless communication systems are absorbed by the BB unit so that the subsequent processing can be made common without depending on the system. In the BB unit, also for the uplink, conversion is performed from a digital baseband signal having a common sampling rate that does not depend on the wireless communication system transmitted from the CPRI interface to a sampling rate corresponding to each wireless system.

The O / E and E / O conversion unit 241 performs framing processing of the digital baseband signal sent from the rate conversion unit 231 to the CPRI interface, converts the electrical signal into an optical signal, and transmits the optical signal to the RF unit via an optical fiber. .
Also, for the uplink, the digital baseband signal transmitted through the optical fiber from the RF unit is terminated, the optical signal is converted into an electrical signal, and the CPRI interface deframing processing is performed, and then to the rate conversion unit 231. Transfer digital baseband signals.

Next, the processing flow of the present invention will be described.
3 and 4 are diagrams for explaining the processing flow in one embodiment of the present invention.
Here, FIG. 3 shows a radio base station in the UMB system, and FIG. 4 shows a radio base station in the LTE system. In the present invention, the BB units 200 and 300 in FIGS. 3 and 4 are dedicated to different radio systems. On the other hand, the RF unit 400 does not depend on the radio system, and is common to the radio base station of the UMB system shown in FIG. 3 and the radio base station of the LTE system shown in FIG. 3 and 4, the BB unit and the RF unit are cable-connected by an optical fiber using a CPRI interface.

  In the following embodiment, a case where the service bandwidth is 10 MHz will be described as an example. When the service bandwidth is 10 MHz, the sampling rate of the digital baseband signal in the UMB system is 9.8304 Msps, and the sampling rate of the digital baseband signal in the LTE system is 15.36 Msps.

First, a radio base station in the UMB system of FIG. 3 will be described.
First, downlink processing will be described.
In the downlink, a digital baseband signal of 9.8304 Msps is input from the baseband modem unit 220. The digital baseband signal is converted by the rate converter 230 in the BB unit by 25/16 times the sampling rate. As a result, the sampling rate is 15.36 Msps, and an integer multiple digital baseband signal of 3.84 MHz that has high affinity with the CPRI interface is generated. Here, digital baseband signal filtering can be performed simultaneously with rate conversion. By filtering the digital baseband signal at the same time as the rate conversion, it is possible to eliminate the filtering processing that has been performed in the conventional RF unit. Therefore, by adopting the configuration of the present embodiment, it is possible to reduce the size of the RF unit. Furthermore, in the present embodiment, the rate conversion unit 230 performs processing to increase the sampling rate by 25/16 times, so that the Nyquist frequency is widened and the S / N ratio of the digital baseband signal is improved.
In the uplink, it is assumed that the sampling rate transmitted through the CPRI interface is 15.36 Msps as in the downlink. A digital baseband signal of 9.8304 Msps is generated by performing 16/25 times sampling rate conversion on the digital baseband signal as opposed to the downlink, and this is input to the baseband modem 220.

Next, a radio base station in the LTE system will be described with reference to FIG.
The LTE system is a system based on 3.84 MHz like W-CDMA and UMTS. Therefore, it has a high affinity with the CPRI interface originally, and the sampling rate of digital baseband signal in the 10MHz bandwidth is 15.36Msps.
Accordingly, in the downlink, the digital baseband signal input from the baseband modulation / demodulation unit 320 is subjected to a sampling rate conversion of 1/1 times by the rate conversion unit 330 and is transmitted as it is through the CPRI interface.
Similarly for the uplink, a 15.36 Msps digital baseband signal transmitted through the CPRI interface is subjected to a sampling rate conversion of 1/1 times by the rate conversion unit 330 and input to the baseband modulation / demodulation unit 320.

Next, detailed contents of the rate conversion units 230 and 330 will be described with reference to FIGS.
As a specific example of the rate conversion processing in this embodiment, FIG. 5 shows an example of a digital low-pass filter type and FIG. 6 shows an example of a DFT (Discrete Fourier Transform) type, which will be described below. Here, as an example, a rate conversion unit used for the BB unit for the UMB system shown in FIG. 3 is shown.

First, the digital low-pass filter type rate conversion process will be described.
FIG. 5 is an example of a digital low-pass filter type rate converter in an embodiment of the present invention.
An FIR filter is used as a digital low-pass filter. The configuration of the rate conversion unit 600 includes oversampling units 610 and 660, FIR filter units 630 and 640, and downsampling units 620 and 650.
First, in the downlink, the sampling rate of the digital baseband signal input to the rate converter 600 is 9.8304 Msps. The oversampling processing unit 610 performs oversampling on the sample data by performing a 25-fold complement process. Since the signal subjected to oversampling processing includes aliasing noise components, low-pass filtering is performed by a 2000-tap FIR filter 630 to remove the aliasing noise components. Finally, the signal is thinned by 1/16 times in the down-sampling unit 650 and down-sampled to generate a 15.36 Msps signal.
Next, in the uplink, processing opposite to that in the downlink is performed. First, a 15.36 Msps digital baseband signal input from the CPRI interface is subjected to oversampling by performing a 16-fold complementation process in the oversampling processing unit 660. Since the oversampled signal here also includes aliasing noise components as well as the signals after downlink oversampling, low-pass filter processing is performed with a 2000 tap FIR filter to remove aliasing noise components. . Finally, the signal is subjected to 1/25 times thinning processing by the down-sampling unit 620 and down-sampled to generate a 9.8304 Msps signal.

Next, DFT type rate conversion processing will be described.
FIG. 6 is an example of a DFT type rate converter in an embodiment of the present invention.
The configuration of the DFT rate conversion unit includes a cyclic prefix deletion unit (hereinafter referred to as CP deletion unit) 710 and 780, a DFT processing unit 730 and 760, an IDFT processing unit 740 and 750, and a cyclic prefix insertion unit (hereinafter referred to as CP insertion unit) 720. 770.
First, the downlink will be described. The signal input to rate conversion section 700 is an OFDM symbol of a time domain signal including a cyclic prefix with a sampling rate of 9.8304 Msps. Cyclic Prefix is a copy of the latter half of the original OFDM symbol and connected to the first half of the OFDM symbol in order to reduce the effect of multipath. CP deleting section 710 deletes the Cyclic Prefix portion from the OFDM symbol input to rate converting section 700 and extracts 1024 original OFDM symbols. The DFT processing unit 730 performs DFT conversion on the 1024 OFDM symbols from the CP deletion unit and converts them to frequency domain signals. By inserting 0 into the high-frequency region outside the original signal band for the DFT-processed 1024-point frequency domain signal, the IDFT processing unit 750 performs 1600-point IDFT conversion. , It converts again to a time domain signal. The sampling rate of the time domain signal here is 15.36 Msps because the signal is multiplied by 1600/1024 with respect to the 9.8304 Msps signal. Further, CP insertion section 770 copies the latter half of the OFDM symbol to the first half as a Cyclic Prefix to generate an OFDM symbol of 15.36 Msps.
Next, in the uplink, the CP deletion unit 780 first deletes the cyclic prefix from the OFDM symbol having the sampling rate of 15.36 Msps including the cyclic prefix input from the CPRI interface, and takes out 1600 OFDM symbols. The DFT processing unit 760 performs DFT conversion on the 1600 OFDM symbols and converts them to frequency domain signals. Next, only 1024 points in the low frequency domain are extracted from the 1600 frequency domain signals, and IDFT processing unit 740 performs 1024 IDFT conversions to convert the signals again into time domain signals. The sampling rate of the time domain signal here is 9.8304 Msps because it is a signal multiplied by 1024/1600 with respect to the 15.36 Msps signal. Further, CP insertion section 720 copies the latter half of the OFDM symbol as a cyclic prefix to the first half to generate a 9.8304 Msps OFDM symbol.

  As described above, by adopting the configuration of the radio base station according to the present embodiment, it is possible to use a common interface such as the CPRI interface even in different radio systems, and to share the RF unit. Furthermore, the rate conversion unit in the BB unit can simultaneously perform the filtering process of the baseband signal, and the apparatus can be reduced in size by simplifying the process in the RF unit. Furthermore, the SN ratio of the baseband signal can be improved by expanding the Nyquist frequency by oversampling processing in the BB unit. Furthermore, since unnecessary data such as stuffing bits and null data need not be inserted, the transmission band between the BB unit and the RF unit can be used efficiently.

It is a network block diagram in one Example of this invention. It is a figure explaining the structure of the wireless base station in one Example of this invention. It is a figure explaining the processing flow in one Example of this invention. It is a figure explaining the processing flow in one Example of this invention. It is a block diagram of the digital low pass filter type | mold rate conversion part in one Example of this invention. It is a block diagram of the DFT type | mold rate conversion part in one Example of this invention.

Explanation of symbols

100: IP networks 200, 201, 300: BB units 210, 211, 310: External line interface units 220, 221, 320: Baseband modulation / demodulation units 230, 231, 331: Rate conversion units 240, 241, 340: In BB units E / O, O / E converter 400, 401, 402, 403: RF unit 410: E / O in RF unit, O / E converter 420: D / A converter 430: A / D converter 440: High Output amplifier 450: Low noise amplifier 500, 501: User terminal 600: Digital low-pass filter type rate converter 610, 660: Oversampling unit 620, 650: Downsampling unit 630, 640: FIR filter unit 700: DFT type rate Conversion unit 710, 780: CP deletion unit 720, 770: CP insertion unit 730, 760: DFT processing unit 740, 750: IDFT processing 1000: UMB system digital baseband signal 1001: LTE system digital baseband signal 1002: rate converted digital baseband signal

Claims (9)

A wireless base station that transmits an IP packet received from an IP network to a wireless terminal and transmits data received from the wireless terminal to the IP network. The wireless base station receives the IP packet and modulates and demodulates a digital baseband signal. In a radio base station composed of a baseband unit and a high-frequency radio unit that performs transmission / reception of a high-frequency radio signal and conversion into a digital baseband signal, and the baseband unit and the high-frequency radio unit are connected by a transmission path,
The baseband unit includes a sampling rate conversion unit, wherein the sampling rate conversion unit converts the digital baseband signal into a common baseband signal having a common sampling frequency that does not depend on a wireless communication system,
A radio base station that performs transmission and reception of signals between the high-frequency radio unit and the baseband unit using the common baseband signal.   A CPRI (Common Public Radio Interface) interface is used as an interface between the baseband unit and the high-frequency radio unit, and the sampling rate of the common baseband signal is a sampling rate that is an integer multiple of 3.84 MHz. The radio base station according to claim 1.   The radio base station according to claim 1, wherein the sampling rate conversion unit uses a digital low-pass filter for sampling rate conversion processing.   The radio base station according to claim 1, wherein the sampling rate conversion unit uses a discrete Fourier transform filter for sampling rate conversion processing. A first wireless communication system that performs wireless communication by a first wireless communication method, and at least one second wireless communication system that performs wireless communication by a wireless communication method different from the first wireless communication method, A wireless communication network for transmitting IP packets received from an IP network to wireless terminals of the first and second wireless communication systems and transmitting data received from the wireless terminals to the IP network,
The radio base station apparatus of the first and second radio communication systems receives an IP packet, performs a baseband unit that modulates / demodulates a digital baseband signal, transmits / receives a radio frequency radio signal, and converts it into a digital baseband signal. A high-frequency radio unit to be connected by a transmission line,
The baseband unit includes a sampling rate conversion unit, and the sampling rate conversion unit outputs a digital baseband signal having a sampling frequency specific to the wireless communication system of the first and second wireless communication systems to the wireless communication system. Convert to a common baseband signal with a common sampling frequency,
In both the first and second wireless communication systems, a wireless communication network characterized in that transmission / reception of signals between the high-frequency wireless unit and the baseband unit is performed by the common baseband signal.   A CPRI (Common Public Radio Interface) interface is used as an interface between the baseband unit and the high-frequency radio unit, and the sampling rate of the common baseband signal is a sampling rate that is an integer multiple of 3.84 MHz. The wireless communication network according to claim 5.   6. The wireless communication network according to claim 5, wherein the sampling rate conversion unit uses a digital low-pass filter for sampling rate conversion processing.   The wireless communication network according to claim 5, wherein the sampling rate conversion unit uses a discrete Fourier transform filter for sampling rate conversion processing. A first wireless communication system that performs wireless communication by a first wireless communication method, and at least one second wireless communication system that performs wireless communication by a wireless communication method different from the first wireless communication method, A communication method in a wireless communication network for transmitting IP packets received from an IP network to wireless terminals of the first and second wireless communication systems and transmitting data received from the wireless terminals to the IP network,
The radio base station apparatus of the first and second radio communication systems receives an IP packet, performs a baseband unit that modulates / demodulates a digital baseband signal, transmits / receives a radio frequency radio signal, and converts it into a digital baseband signal. It is configured to be connected to a high-frequency radio unit to be performed by a transmission line,
The baseband unit converts a digital baseband signal having a sampling frequency specific to the wireless communication system of the first and second wireless communication systems into a common baseband signal having a common sampling frequency that does not depend on the wireless communication system. ,
A communication method in a wireless communication network, wherein both the first and second wireless communication systems perform transmission and reception of signals between the high-frequency wireless unit and the baseband unit using the common baseband signal.

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