Parent station device, child station device, and wireless communication system

Abstract

To provide a master station device, a slave station device, and a radio communication system capable of improving transmission efficiency of a fronthaul.SOLUTION: A radio communication system includes a radio base station comprising a master station device and a slave station device. The master station device comprises: a master station signal processing section for outputting a subcarrier modulation signal; and an FH transmission section for mapping an I component and a Q component of the subcarrier modulation signal to an optical signal to be transmitted to a fronthaul (FH). The slave station device comprises: an FH reception section for receiving the optical signal via the fronthaul; and a slave station signal processing section for identifying the subcarrier modulation signal on the basis of the I component and the Q component of the subcarrier modulation signal mapped to the optical signal.SELECTED DRAWING: Figure 3A

Description

Technical Field

[0001] The present disclosure relates to a master station device, a slave station device, and a wireless communication system.

Background Art

[0002] In a wireless communication system, in order to flexibly construct an area where wireless communication with a user equipment (UE) is possible, a configuration is adopted in which a radio base station is divided into a master station device and a slave station device, and the slave station device is arranged at a position different from that of the master station device.

[0003] For example, a master station device connected to a core network has a baseband signal processing function of a radio base station, and one or more slave station devices are connected to the master station device. The slave station device performs wireless processing such as analog conversion and performs wireless communication with the UE.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Non-Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in existing wireless communication systems (for example, wireless base stations), there is room for improvement in the transmission efficiency between the master station device and the slave station device (front-haul).

[0007] Non-limiting embodiments of the present disclosure contribute to providing a master station device, a slave station device, and a wireless communication system capable of improving the transmission efficiency of the front-haul.

Means for Solving the Problems

[0008] The master station device according to an embodiment of the present disclosure includes a processing unit that outputs a subcarrier modulation signal, and a transmission unit that maps the I component and the Q component of the subcarrier modulation signal to an optical signal transmitted to the front-haul.

[0009] The slave station device according to an embodiment of the present disclosure includes a receiving unit that receives an optical signal via a fronthaul, and a processing unit that identifies the subcarrier modulation signal based on the I component and the Q component of the subcarrier modulation signal mapped in the optical signal.

[0010] A wireless communication system according to an embodiment of the present disclosure includes a master station device and a slave station device. The master station device includes a processing unit that outputs a subcarrier modulation signal, and a transmitting unit that maps the I component and the Q component of the subcarrier modulation signal to an optical signal transmitted to the fronthaul. The slave station device includes a receiving unit that receives the optical signal via the fronthaul, and a processing unit that identifies the subcarrier modulation signal based on the I component and the Q component of the subcarrier modulation signal mapped in the optical signal.

[0011] These general or specific aspects may be implemented in a system, apparatus, method, integrated circuit, computer program, or recording medium, or may be implemented in any combination of a system, apparatus, method, integrated circuit, computer program, and recording medium.

Advantages of the Invention

[0012] According to an embodiment of the present disclosure, the transmission efficiency of the fronthaul can be improved.

[0013] Further advantages and effects in an embodiment of the present disclosure will be apparent from the specification and the drawings. Such advantages and / or effects are provided by some embodiments and the features described in the specification and the drawings, respectively, but not all are necessarily provided in order to obtain one or more of the same features.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 7A

Figure 7B

Figure 8

Figure 9A

Figure 9B

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments will be described with appropriate reference to the drawings. Note that detailed descriptions that are more than necessary may be omitted. For example, detailed descriptions of well-known matters and duplicate descriptions of substantially the same configurations may be omitted. This is to avoid making the following description unnecessarily redundant and to facilitate understanding by those skilled in the art.

[0016] Note that the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0017] <Findings Leading to the Present Disclosure> <In existing technologies (for example, Patent Document 1), the parent station device may be referred to as a BBU (baseband unit), and the child station device may be referred to as an RRH (remote radio head). For the connection between the parent station device and the child station device, for example, a wired transmission means (or a wired interface) such as a coaxial cable, a UTP (unshielded twisted pair) cable, an STP (Shielded twisted pair) cable, or an optical fiber cable is used. Such a connection between the parent station device and the child station device may be referred to as a "front-haul connection" or simply "front-haul".>

[0018] <For example, a network configuration called C-RAN (Centralized - Radio Access Network) is known, in which the parent station device is arranged in an aggregation station building that performs centralized control of the system, and the child station device is arranged in a distributed station building close to the antenna site. In C-RAN, centralized control can be performed in the aggregation station building, and interference can be avoided by performing cooperative operations in a plurality of different distributed station buildings.>

[0019] <In regulations regarding the communication method of front-haul (FH) (for example, Non-Patent Document 6), the parent station device is referred to as a REC (radio equipment controller), and the child station device is referred to as an RE (radio equipment). Also, in Non-Patent Document 1 that defines O-RAN (Open-Radio Access Network), the parent station device is referred to as an O-DU (O-RAN Distributed Unit), and the child station device is referred to as an O-RU (O-RAN Radio Unit).>

[0020] <For example, Patent Document 1 discloses a method for realizing a C-RAN configuration by connecting a plurality of child station devices (for example, RRHs) to a parent station device (for example, BBU) using a PON (Passive Optical Network).>

[0021] In optical transmission such as PON, digital coherent transmission is used (see Non-Patent Document 1). The use of digital coherent transmission is also considered in a C-RAN configuration. FIG. 1 is a diagram showing an example of the processing of digital coherent transmission.

[0022] FIG. 1 shows an example of the configuration of an FH transmission unit 300 corresponding to the transmission-side configuration of digital coherent transmission in FH and an FH reception unit 400 corresponding to the reception-side configuration.

[0023] As shown in FIG. 1, the symbols of 64QAM modulation output from the RE mapping unit 2100 of the master station apparatus are quantized by the Quantization unit 2101. For example, each of the I (In-phase) component and the Q (Quadrature-phase) component of the symbol of 64QAM modulation is quantized with 16 bits. Note that the I component and the Q component of the modulation symbol may be referred to as an I sample and a Q sample, respectively.

[0024] The quantized bit sequence output from the Quantization unit is encoded, such as error correction, by the Encoding unit 3001. By being encoded by the Encoding unit 3001, the bit sequence with redundancy added is mapped to the symbols of 256QAM modulation by the Modulation unit 3002.

[0025] The electro-optical (E / O) conversion unit 3003 performs optical transmission processing (e.g., upsampling, waveform shaping, pre-equalization, conversion to an optical signal) on the mapped symbols and transmits the signal after the optical transmission processing. The FH reception unit 400 for optical transmission performs processing corresponding to the processing of the FH transmission unit 300 and outputs a received bit sequence. For example, the optoelectronic (O / E) conversion unit 4001 performs optical reception processing, the demodulation unit 4002 performs demodulation corresponding to the modulation unit 3002, and the decoding unit 4003 performs decoding corresponding to the encoding unit 3001. The received bit sequence is dequantized by the dequantization unit 5001, and a 64QAM-modulated symbol mapped by the RE mapping unit 2100 is obtained.

[0026] In a C-RAN configuration, as the number of remote units increases, the communication volume of FH (e.g., data traffic volume) also increases, and the communication bandwidth of FH becomes congested.

[0027] For example, Patent Document 2 discloses a method of reducing the data traffic of FH by changing the functional division between the central office device and the remote unit as an example of a countermeasure against the bandwidth congestion of FH. Patent Document 2 shows a configuration in which the remote unit is equipped with a buffer, PDCP, RLC, MAC, encoding, modulation, resource mapping, IFFT, up-conversion, and amplification, and the central office device is equipped with a bearer termination. Generally, as the processing approaches transmission, the header and / or redundancy increases, so the data volume becomes large. By arranging more functions in the remote unit than in the central office device, the data traffic from the central office device to the remote unit can be reduced.

[0028] As described in Patent Document 3, by arranging many functions in the slave station device, the FH band can be reduced by reducing the FH data traffic. However, in a C-RAN configuration, it is desirable that the MAC and High-PHY functions be in the master station device in order to cooperatively control a plurality of different slave station devices. Also, when the MAC and High-PHY functions are arranged on the slave station device side to perform cooperative control between the slave station devices, the signaling of control signals between the slave station devices may increase.

[0029] Therefore, in one embodiment of the present disclosure, for example, a fronthaul transmission method for reducing the bandwidth shortage of FH is provided using an interface as defined in Non-Patent Document 1.

[0030] [Embodiment 1] FIG. 2 is a diagram showing a first example of the configuration of a wireless communication system according to Embodiment 1. As illustrated in FIG. 2, the wireless communication system includes, for example, a radio base station 1 and a UE 2 which is an example of a terminal device. The number of radio base stations 1 and UEs 2 may each be two or more.

[0031] The UE 2 communicates wirelessly connected to the radio base station 1. The wireless communication between the UE 2 and the radio base station 1 includes at least one of uplink (UL) communication and downlink (DL) communication. Hereinafter, an example of the configuration and operation focusing on the DL of the radio base station 1 will be described. An example focusing on the UL will be described later with reference to FIGS. 5, 6A, and 6B).

[0032] The wireless base station 1 includes, for example, a parent station device 11 and a child station device 12 interconnected by FH13. The parent station device 11 may be referred to as, for example, a BBU, a CBBU (centralized baseband unit), a REC, a Central site, or a CU (central unit). The child station device 12 may be referred to as, for example, an RRH, an RE, a Distributed site, or a DU (distributed unit). Note that one parent station device 11 can also be connected to two or more child station devices 12. Also, one child station device 12 can also be connected to two or more UEs 2.

[0033] In the following description, an example is shown in which the parent station device has a parent station signal processing unit and an FH transmission unit, but the present disclosure is not limited thereto. For example, a configuration including the parent station signal processing unit and not including the FH transmission unit may be referred to as the parent station device. For example, the FH transmission unit may be referred to as the parent station transmission device. Also, in the following description, an example is shown in which the child station device has a child station signal processing unit and an FH reception unit, but the present disclosure is not limited thereto. For example, a configuration including the child station signal processing unit and not including the FH reception unit may be referred to as the child station device. For example, the FH reception unit may be referred to as the child station reception device.

[0034] Exemplarily, wired transmission means (or wired interface) such as a UTP cable, an STP cable, or an optical fiber cable may be applied to FH13. The wired interface may be an interface compliant with standards or technologies such as CPRI (common public radio interface), eCPRI (evolved CPRI), OBSAI (open base station architecture initiative), RoE (radio over Ethernet), or RoF (radio over fiber). Note that "Ethernet" is a registered trademark.

[0035] <Parent station device 11> As illustrated in FIG. 2, the parent station apparatus 11 includes, for example, a parent station signal processing unit 20 and a FH transmission unit 30, and the slave station apparatus 12 includes a FH reception unit 40 and a slave station signal processing unit 50. FIG. 3A shows an example of the configuration (DL) of the parent station signal processing unit 20 and the FH transmission unit 30, and FIG. 3B shows an example of the configuration (DL) of the FH reception unit 40 and the slave station signal processing unit 50.

[0036] (Parent station signal processing unit 20) As illustrated in FIG. 3A, the parent station signal processing unit 20 includes, for example, an SDAP (service data adaptation protocol) unit 201, a PDCP (packet data convergence protocol) unit 202, an RLC (radio link control) unit 203, and a MAC unit 204. Further, the parent station signal processing unit 20 includes, for example, an encoding unit 205, a scrambling unit 206, a modulation unit 207, a layer mapping unit 208, a precoding unit 209, and a RE (resource element) mapping unit 210.

[0037] These functional units 201 to 210, together with the functional units 501 and 502 in the slave station signal processing unit 50 described later with reference to FIG. 3B, are a non-limiting example of a plurality of base station functional units provided in the radio base station 1. Note that the encoding unit 205, the scrambling unit 206, the modulation unit 207, the layer mapping unit 208, the precoding unit 209, and the RE mapping unit 210 form, for example, a high physical layer (High-PHY) block 2001.

[0038] The SDAP unit 201 receives, for example, signals (such as user data) sent from an upper-layer core network (such as EPC or 5GC). "EPC" is an abbreviation for "evolved packet core", and 5GC is an abbreviation for "5th generation (5G) core network". 5G represents the 5th generation radio access technology (RAT), and may also be denoted as NR (new radio). Also, 5GC may be denoted as NGC (next generation core network).

[0039] The SDAP unit 201, for example, performs mapping between QoS flows and radio bearers, attaches an SDAP header to signals (such as packets) sent from an upper-layer core network, and outputs the result to the PDCP unit 202.

[0040] The PDCP unit 202 performs processes such as encryption of user data and header compression on the output of the SDAP unit 201, and outputs a PDCP PDU (protocol data unit) to the RLC unit 203.

[0041] The RLC unit 203 performs processes such as error detection and retransmission control by ARQ (automatic repeat request) on the output of the PDCP unit 202, and outputs an RLC PDU.

[0042] The MAC unit 204 performs, for example, retransmission control by HARQ (hybrid automatic repeat request), determines the UE2 to which a communication opportunity is allocated by scheduling, and determines the MCS (modulation and coding scheme) in radio transmission, generates a MAC PDU from the RLC PDU, and outputs a transport block. CQI (channel quality indicator) fed back from the UE2 may be used for the determination of the MCS.

[0043] The MAC unit 204 outputs control information such as the information of the determined MCS and the information of the resources (e.g., resource elements (REs)) used for wireless transmission to the subsequent High-PHY block 2001.

[0044] In the High-PHY block 2001, the encoding unit 205 adds a CRC (cyclic redundancy check) code to the transport block input from the MAC unit 204, for example, and divides it into code blocks. Also, the encoding unit 205 performs encoding of the code blocks and rate matching corresponding to the MCS, for example.

[0045] The scrambling unit 206 performs a scrambling process on the output of the encoding unit 205, for example.

[0046] The modulation unit 207 modulates the output of the scrambling unit 206 by a modulation method such as QPSK (quadrature phase shift keying), 16QAM (quadrature amplitude modulation), 64QAM, or 256QAM, for example.

[0047] The layer mapping unit 208 maps the output of the modulation unit 207 to a plurality of layers, for example.

[0048] The precoding unit 209 performs precoding on the output of the layer mapping unit 208, for example.

[0049] The RE mapping unit 210 maps, for example, the output of the precoding unit 209 to a predetermined radio resource (e.g., RE). One RE is, for example, a radio resource area of one subcarrier and one symbol. One or more REs may constitute a resource block (RB). One or more RBs are interchangeable with other terms such as a physical resource block (PRB), a sub-carrier group (SCG), a resource element group (REG), a PRB pair, and an RB pair.

[0050] Note that since the layer mapping unit 208 and the precoding unit 209 are used for MIMO (multiple-input and multiple-output) transmission, they may be omitted when MIMO transmission is not applied.

[0051] (FH transmission unit 30) On the other hand, as illustrated in FIG. 3A, the FH transmission unit 30 includes, for example, a normalization unit 301, a direct IQ mapping unit 302, and an electro-optical (E / O) conversion unit 303.

[0052] The normalization unit 301 normalizes the output signal (e.g., subcarrier signal) output from the RE mapping unit 210. For example, the normalization unit 301 sets a normalization level so as to keep the output signal within the range of the amplitude level of the symbol arrangement used for mapping in the direct IQ mapping unit 302 described later, and normalizes the output signal based on the normalization level. Note that when the amplitude level of the output signal of the RE mapping unit 210 and the amplitude level of the symbol mapping in the direct IQ mapping unit 302 are aligned, the normalization unit 301 may not be provided in the FH transmission unit 30.

[0053] The direct IQ mapping unit 302 sets the normalized subcarrier signal output from the normalization unit 301 as symbols for optical transmission. In other words, the direct IQ mapping unit 302 processes the normalized subcarrier signal as it is as symbols for optical transmission. An example of the processing of the direct IQ mapping unit 302 will be described later.

[0054] The electro-optical conversion unit 303, for example, electro-optically converts the signal (symbol) output from the direct IQ mapping unit 302 and transmits the obtained optical signal to FH13.

[0055] The normalization unit 301, the direct IQ mapping unit 302, and the electro-optical conversion unit 303 form a non-limiting example of a transmission unit that transmits signals to FH13.

[0056] Note that the FH transmitter 30 may control signal transmission in FH based on the control information notified from the master station signal processing unit 20. Also, the FH receiver 40 described later may control signal reception in FH based on the control information notified from the master station signal processing unit 20 via the FH transmitter 30. The control information notified from the master station signal processing unit 20 includes, for example, information regarding the transmission method of FH.

[0057] The method of notifying the control information is not limited. For example, the control information may be notified using the header area defined in O-RAN (see Non-Patent Document 1). For example, in the area called the Common Header Fields in the header area, an area for notifying the transmission method of FH may be added. The added area may include information indicating the presence or absence of error correction for FH (for example, 1-bit size) and information indicating the transmission mode to be used among the defined transmission modes (for example, multiple bits).

[0058] As an example of a method for notifying control information, the method for transmitting the FH may be extended and notified in an existing area of the Common Header Fields. For example, the method for transmitting the FH may be indicated using information that defines the method for transmitting a payload called payloadVersion.

[0059] As an example of a method for notifying control information, an area for notifying the FH transmission method may be added to an area called Section header fields. Alternatively, the header area may be extended and a new area may be added, or an area for notifying the FH transmission method may be added to the reserve area. In the added area, information indicating the presence or absence of error correction for the FH (for example, having a size of 1 bit) and information indicating the transmission mode to be used among the defined transmission modes (for example, having a plurality of bits) may be included.

[0060] As an example of a method for notifying control information, an area for notifying the FH transmission method may be added to the PRB fields. For example, a new area may be added to the PRB fields, or the existing udCompParam may be extended to notify the FH transmission method.

[0061] <Slave device 12> Next, an example of the configuration (DL) of the slave device 12 will be described with reference to FIG. 3B.

[0062] (FH receiving unit 40) As illustrated in FIG. 3B, in the slave device 12, the FH receiving unit 40 includes, for example, an optoelectronic (O / E) conversion unit 401, an equalization unit 402, and a soft decision unit 403.

[0063] The optoelectronic conversion unit 401 receives, for example, an optical signal transmitted as FH13 and converts it into an electrical signal.

[0064] The equalization unit 402 performs equalization processing corresponding to the characteristics of the transmission path of FH13 on the electrical signal output from the optoelectronic conversion unit 401.

[0065] The soft decision unit 403 performs a soft decision process on the equalized signal output from the equalization unit 402. For example, the soft decision unit 403 determines the amplitude level of the I component and the amplitude level of the Q component of the equalized signal.

[0066] The optoelectronic conversion unit 401, the equalization unit 402, and the soft decision unit 403 form a non-limiting example of a receiving unit that receives signals from FH13.

[0067] (Slave station signal processing unit 50) As illustrated in FIG. 3B, the slave station signal processing unit 50 includes, for example, a beamforming unit 501, an IFFT (inverse fast Fourier transform) + CP (cyclic prefix) unit 502, a D / A (digital to analog) conversion unit 503, and a radio (RF) unit 504.

[0068] The beamforming unit 501 and the IFFT + CP unit 502 form, for example, a lower physical layer (Low-PHY) block 5001.

[0069] The beamforming unit 501 performs beamforming processing on the output of the FH receiving unit 40, for example. Note that the beamforming unit 501 may be omitted if beamforming is not performed in the slave station device 12. Alternatively, the beamforming process may be performed in the master station device 11.

[0070] The IFFT + CP unit 502 performs IFFT and CP insertion on the output of the beamforming unit 501, for example.

[0071] The D / A conversion unit 503 converts the output of the IFFT + CP unit 502 from a digital signal to an analog signal, for example.

[0072] The RF unit 504 performs transmission RF processing such as up-conversion processing to a radio frequency and amplification processing on the output of the D / A conversion unit 503, for example. The radio signal generated by the transmission RF processing is radiated into space (for example, transmitted to the UE2) via an antenna (not shown) provided in the RF unit 504, for example.

[0073] <Example of direct IQ mapping and soft decision processing> FIG. 4 is a diagram showing an example of direct IQ mapping and soft decision processing. In FIG. 4, a configuration example focusing on the RE mapping unit 210 illustrated in FIG. 3A, the FH transmission unit 30 illustrated in FIG. 3A, and the FH reception unit 40 illustrated in FIG. 3B is shown together with an example of expression in the complex plane (IQ plane) of a signal.

[0074] In FIG. 4, a symbol S (an example of a sub-carrier signal) mapped to a radio resource is shown in the RE mapping unit 210. In FIG. 4, exemplarily, a multi-value modulation (for example, 64QAM modulation) is performed in the modulation unit 207, and a symbol S subjected to pre-coding in the pre-coding unit 209 is shown. Note that i sample indicates the I component (in-phase component) of the symbol S, and q sample indicates the Q component (orthogonal component) of the symbol S.

[0075] The direct IQ mapping unit 302 directly sets (or may be referred to as "mapping") the sub-carrier signal output from the RE mapping unit 210 and normalized in the normalization unit 301 to the symbol for optical transmission.

[0076] For example, as illustrated in FIG. 4, for the symbol (which may also be referred to as a sub-carrier symbol) S of the sub-carrier signal output from the RE mapping unit 210, its I component and Q component are respectively set to the I component and Q component of the symbol in optical transmission. Note that the sub-carrier signal may also be referred to as a sub-carrier modulation signal.

[0077] In other words, the symbol S is mapped to a symbol having its I and Q components in the optical domain, for example. The symbol S after mapping is electro-optically converted and transmitted to the FH receiver 40 via the FH13.

[0078] Thus, in the case of "direct IQ mapping" in which the I and Q components of the symbol S are respectively mapped directly to the I and Q components of the symbol for optical transmission, it may be understood that there are no candidate points for multi-valued modulation in optical transmission (for example, the candidate points of 256QAM in FIG. 1). In other words, in "direct IQ mapping", it does not depend on the number of multi-values in optical transmission. The symbol S output from the RE mapping unit 210 is transmitted in the FH13 in the same manner as in analog RoF and / or coherent transmission.

[0079] Note that in the present embodiment, the term "direct IQ mapping" does not mean that no other processing intervenes in the process of mapping a symbol in the electrical domain to a symbol in the optical domain. For example, processing such as the normalization described above may intervene in the process of the mapping process.

[0080] Also, the symbol S may not be encoded (for example, error correction encoding) before being transmitted to the FH13. Errors that may occur in the FH transmission may be corrected by error correction processing for the wireless section (for example, the section between the radio base station 1 and the UE2).

[0081] For example, according to the error correction capability in the wireless section, the error correction capability required for the optical signal in the FH13, which is the optical transmission section, can be relaxed. Therefore, even if the transmission error rate in the FH13 may increase due to the application of "direct IQ mapping", the communication quality between the radio base station 1 and the UE2 is easily guaranteed by the error correction processing in the wireless section. Therefore, error correction can be made unnecessary in optical transmission using "direct IQ mapping".

[0082] The optically transmitted symbol S is received by the FH receiver 40 via FH13. Note that the optical transmission symbol S may be affected by the influence of the transmission path (e.g., the influence of noise) in FH13, for example. In the FH receiver 40, the received symbol is subjected to optical-electric conversion and equalization processing in the optoelectronic conversion unit 401 and the equalization unit 402, respectively, and then soft decision is performed in the soft decision unit 403.

[0083] For example, as shown in FIG. 4, the soft decision unit 403 determines that the received symbol Sr is a subcarrier signal transmitted from the FH transmitter 30. The soft decision unit 403 determines, for example, the I component and the Q component of the received symbol Sr.

[0084] In this case, since the I component and the Q component of the received symbol Sr are directly determined as the I component and the Q component of the subcarrier signal, it is not necessary to perform hard decision on the received symbol Sr based on the signal point arrangement of the multi-valued modulation, so there is no influence of signal misjudgment.

[0085] Note that in the example of FIG. 4, the case where precoding is performed is shown, but precoding may not be performed. Similar to the case where the precoding illustrated in FIG. 4 is performed, when precoding is not performed, the I component and the Q component of the symbol S of the subcarrier signal output from the RE mapping unit 210 are set as the I component and the Q component of the symbol in optical transmission, respectively.

[0086] As described above, in the parent station apparatus 11 in the configuration of DL of the first embodiment, a parent station signal processing unit 20 (an example of a processing unit) that outputs a subcarrier modulation signal, and an I component and a Q component of the subcarrier modulation signal are mapped to an optical signal to be transmitted to the FH. And an FH transmission unit 30 (an example of a transmission unit). Further, the slave station apparatus 12 in the configuration of DL of the first embodiment includes an FH reception unit 40 (an example of a reception unit) that receives an optical signal via the FH, and an I component and a Q component of the subcarrier modulation signal mapped in the optical signal. And a slave station signal processing unit 50 (an example of a processing unit) that identifies the subcarrier modulation signal. With this configuration, as illustrated in FIG. 4, in order to map the subcarrier signal output from the RE mapping unit 210 to an optical signal, for example, quantization and encoding of the signal can be made unnecessary. Therefore, for example, an increase in redundant bits associated with the application of quantization and encoding can be suppressed, and the transmission efficiency can be improved.

[0087] Also, in the example of FIG. 4, since soft decision is performed in the FH reception unit 40, for example, errors in symbol decision that may occur can be suppressed as compared with the case of using hard decision of symbols.

[0088] Although FIGS. 3A and 3B show an example of the DL configuration, a configuration similar to the DL configuration may be applied to the UL. Hereinafter, an example of the UL configuration will be shown.

[0089] FIG. 5 is a diagram showing a second example of the configuration of the wireless communication system according to the first embodiment. As illustrated in FIG. 5, when paying attention to the UL communication from the UE2 to the radio base station 1, the radio base station 1 includes, in the slave station apparatus 12, for example, a slave station signal processing unit 60 and an FH transmission unit 70, and in the master station apparatus 11, for example, an FH reception unit 80 and a master station signal processing unit 90.

[0090] FIG. 6A shows an example of the configuration of the slave station apparatus 12 (the slave station signal processing unit 60 and the FH transmission unit 70) focusing on the UL, and FIG. 6B shows an example of the configuration of the master station apparatus 11 (the FH reception unit 80 and the master station signal processing unit 90) focusing on the UL.

[0091] <Slave station apparatus 12> First, referring to FIG. 6A, an example of the configuration of the slave station signal processing unit 60 and the FH transmission unit 70 in the slave station device 12 will be described. Note that, as in FIG. 2, it is possible to connect two or more slave station devices 12 to one master station device 11, and it is possible to connect one slave station device 12 to two or more UEs 2.

[0092] (Slave station signal processing unit 60) As illustrated in FIG. 6A, the slave station signal processing unit 60 includes, for example, an RF unit 601, an A / D (analog to digital) conversion unit 602, a CP removal + FFT (first Fourier transform) unit 603, and a beamforming unit 604.

[0093] The RF unit 601 has, for example, an antenna, receives the UL radio signal transmitted from the UE 2 with the antenna, and performs reception RF processing such as down-conversion processing and low-noise amplification processing on the received radio signal.

[0094] The A / D conversion unit 602 converts, for example, the output (analog signal) of the RF unit 601 into a digital signal.

[0095] The CP removal + FFT unit 603 and the beamforming unit 604 form, for example, a lower physical layer (Low-PHY) block 6001.

[0096] The CP removal + FFT unit 603 performs, for example, FFT and CP removal on the output of the A / D conversion unit 602.

[0097] The beamforming unit 604 performs, for example, reception beam forming processing on the output of the CP removal + FFT unit 603. Note that the beamforming unit 604 may be omitted when beamforming is not performed in the slave station device 12.

[0098] (FH transmission unit 70) On the one hand, as illustrated in FIG. 6A, the FH transmitter 70 includes, for example, a normalization unit 701, a direct IQ mapping unit 702, and an electro-optical (E / O) conversion unit 703.

[0099] Each functional unit 701 to 703 of the FH transmitter 70 related to UL may be regarded as equivalent to each functional unit 301 to 303 of the FH transmitter 30 related to DL (see FIG. 3A), respectively.

[0100] For example, the normalization unit 701 normalizes the signal output from the slave station signal processing unit 60. For example, the normalization unit 701 sets a normalization level so as to keep the signal within the range of the amplitude level of the symbol arrangement used for mapping in the direct IQ mapping unit 702 described later, and normalizes the output signal based on the normalization level. Note that when the amplitude level of the output signal of the slave station signal processing unit 60 is the same as the amplitude level of the symbol mapping in the direct IQ mapping unit 702, the normalization unit 701 may not be included in the FH transmitter 70.

[0101] Similar to the direct IQ mapping unit 302, the direct IQ mapping unit 702 sets the normalized subcarrier signal output from the normalization unit 701 as the symbol for optical transmission. In other words, the direct IQ mapping unit 702 processes the normalized subcarrier signal as the symbol for optical transmission as it is.

[0102] The electro-optical conversion unit 703, for example, electro-optically converts the signal (symbol) output from the direct IQ mapping unit 702 and transmits the obtained optical signal to FH13.

[0103] <Master station device 11> Next, with reference to FIG. 6B, an example of the configuration of the FH receiver 80 and the master station signal processing unit 90 in the master station device 11 will be described.

[0104] (FH receiver 80) As illustrated in FIG. 6B, the FH receiver 80 includes, for example, an optoelectronic conversion unit 801, an equalization unit 802, and a soft decision unit 803.

[0105] Each functional unit 801 to 803 of the FH receiver 80 related to UL may be regarded as equivalent to each functional unit 401 to 403 of the FH receiver 40 related to DL (see FIG. 3B), respectively.

[0106] For example, the optoelectronic conversion unit 801 receives the optical signal transmitted by FH13 and converts it into an electrical signal.

[0107] The equalization unit 802 performs equalization processing corresponding to the characteristics of the transmission path of FH13 on the electrical signal output from the optoelectronic conversion unit 801.

[0108] The soft decision unit 803 performs soft decision processing on the signal after the equalization processing output from the equalization unit 802. For example, the soft decision unit 803 determines the amplitude level of the I component and the amplitude level of the Q component of the signal after the equalization processing.

[0109] (Base station signal processing unit 90) On the other hand, as illustrated in FIG. 6B for example, the base station signal processing unit 90 includes an RE demapping unit 901, a layer demapping unit 902, a demodulation unit 903, a descrambling unit 904, and a decoding unit 905. These functional units 901 to 905 form, for example, a high physical layer (High-PHY) block 9001.

[0110] Also, the base station signal processing unit 90 includes, for example, a MAC unit 906, an RLC unit 907, a PDCP unit 908, and an SDAP unit 909.

[0111] The RE demapping unit 901 demaps the UL signal mapped to the radio resources (for example, RE).

[0112] The layer demapping unit 902 demaps the UL signals mapped for each layer in the output of the RE demapping unit 901, for example. Note that since the layer demapping unit 902 is used for MIMO transmission, it may be omitted when MIMO transmission is not applied.

[0113] The demodulation unit 903 demodulates the output of the layer demapping unit 902 by a demodulation method corresponding to a modulation method such as QPSK, 16QAM, 64QAM, or 256QAM, for example.

[0114] The descrambling unit 904 performs a descrambling process for descrambling, for example, the output of the demodulation unit 903.

[0115] The decoding unit 905 decodes the output of the descrambling unit 904, for example.

[0116] The MAC unit 906 generates an RLC PDU from the MAC PDU of the UL signal and outputs it to the RLC unit 907, for example.

[0117] The RLC unit 907 performs processes such as error detection and retransmission control by ARQ, for example, on the output of the MAC unit 906 and outputs a PDCP PDU.

[0118] The PDCP unit 908 performs processes such as decoding of encrypted user data and header decompression on the output of the RLC unit 907 and outputs an SDAP PDU to the SDAP unit 909.

[0119] The SDAP unit 909 performs mapping between a QoS flow and a radio bearer, removes the SDAP header from the output of the PDCP unit 908, and transmits it to the upper core network.

[0120] Note that the FH receiving unit 80 may control signal reception in FH based on the control information notified from the master station signal processing unit 90. Further, the FH transmitting unit 70 may control signal transmission in FH based on the control information notified from the master station signal processing unit 90. Note that an example of the control information notified from the master station signal processing unit 90 may be the same as the control information notified from the master station signal processing unit 20 described above for DL.

[0121] As described above, the slave station device 12 in the UL configuration of the first embodiment includes a slave station signal processing unit 60 that outputs a subcarrier modulation signal, and an FH transmitting unit 70 that maps the I component and Q component of the subcarrier modulation signal to an optical signal transmitted to FH. Further, the master station device 11 in the UL configuration of the first embodiment includes an FH receiving unit 80 that receives an optical signal via FH, and a master station signal processing unit 90 that identifies a subcarrier modulation signal based on the I component and Q component of the subcarrier modulation signal mapped in the optical signal. With such a configuration in UL, the same or similar operational effects as the DL configurations shown in FIGS. 3A and 3B can be obtained.

[0122] [Second Embodiment] Next, a configuration example of the DL of the second embodiment will be described with reference to FIGS. 7A and 7B. In FIGS. 7A and 7B, the same components as those in FIGS. 3A and 3B may be given the same reference numerals and the description may be omitted. In the second embodiment, the configurations of the FH transmitting unit and the FH receiving unit are different from those in the first embodiment. Note that the system configuration example may be the same as that in FIG. 2. Also, it is the same as in the first embodiment that two or more slave station devices 12 can be connected to one master station device 11, and one slave station device 12 can be connected to two or more UEs 2.

[0123] In the second embodiment, as illustrated in FIG. 7A, the FH transmitting unit 30A includes, for example, a normalization unit 301, an IQ symbol candidate detection unit 304, and an electro-optical (E / O) conversion unit 303.

[0124] The IQ symbol candidate detection unit 304 detects candidates for symbols to be mapped in optical transmission, based on, for example, the normalized subcarrier signal output from the normalization unit 301. For example, when multi-value modulation (e.g., 256QAM modulation) is used in optical transmission, the IQ symbol candidate detection unit 304 determines, among a number (e.g., 256) of candidate signal points corresponding to the order of multi-value modulation in the signal point arrangement on the IQ plane, a candidate signal point whose relationship with the signal point indicated by the I component and Q component of the subcarrier signal is a predetermined relationship, as the signal point (e.g., symbol) in optical transmission. For example, the predetermined relationship is the relationship of being the closest on the IQ plane. When using this predetermined relationship, the signal point in optical transmission may be the candidate signal point closest to the signal point indicated by the I component and Q component of the subcarrier signal among the number of candidate signal points corresponding to the order of multi-value modulation. Note that an example of the processing of the IQ symbol candidate detection unit 304 will be described later.

[0125] In Embodiment 2, as illustrated in FIG. 7B, the FH reception unit 40A may include, for example, an optoelectronic (O / E) conversion unit 401, an equalization unit 402, and a symbol decision unit 404.

[0126] The symbol decision unit 404 determines, for example, the symbol of the signal after the equalization process output from the equalization unit 402. For example, when 256QAM modulation is used in optical transmission, the symbol decision unit 404 determines a candidate signal point whose relationship with the signal indicated by the I component and Q component after the equalization process is a predetermined relationship, among the candidate signal points of 256QAM. The predetermined relationship is, for example, the same as that of the IQ symbol candidate detection unit 304.

[0127] <Example of IQ Symbol Candidate Detection and Symbol Decision> FIG. 8 is a diagram showing an example of IQ symbol candidate detection and symbol decision. FIG. 8 shows a configuration example focusing on the RE mapping unit 210 illustrated in FIG. 7A, the FH transmission unit 30A illustrated in FIG. 7A, and the FH reception unit 40A illustrated in FIG. 7B, together with an example of the representation of the signal on the IQ plane.

[0128] In FIG. 8, in the RE mapping unit 210, a symbol S (an example of a subcarrier signal) mapped to a radio resource is shown. In FIG. 4, exemplarily, a symbol S that has been 64QAM modulated in the modulation unit 207 and precoded in the precoding unit 209 is shown. Note that i sample indicates the I component of the symbol S, and q sample indicates the Q component of the symbol S.

[0129] The IQ symbol candidate detection unit 204 detects a candidate for the symbol to be mapped in optical transmission from among the candidate signal points based on the subcarrier signal output from the RE mapping unit 210 and normalized in the normalization unit 301. In FIG. 8, as an example, multilevel modulation (e.g., 256QAM modulation) is used in optical transmission. As illustrated in FIG. 8, when the symbol S is output from the RE mapping unit 210, the symbol T that is closest to the symbol S among the candidate signal points of 256QAM is set as the symbol for optical transmission. The symbol T is electro-optically converted and transmitted to the FH reception unit 40A via FH13.

[0130] Also, the symbol T may not be encoded (e.g., error correction encoding) for FH transmission before being transmitted to FH13. Errors that may occur in FH transmission may be corrected by error correction processing for the radio section (e.g., the section between the radio base station 1 and the UE2).

[0131] For example, according to the error correction capability in the radio section, the required error correction capability for the optical signal in FH13, which is the optical transmission section, can be relaxed. Therefore, even if the transmission error rate in FH13 increases due to no encoding for FH transmission, the communication quality between the radio base station 1 and the UE2 can be easily guaranteed by error correction processing in the radio section.

[0132] The optically transmitted symbol T is received by the FH receiving unit 40A via FH13. Note that the optically transmitted symbol T can be affected by the influence of the transmission path (e.g., the influence of noise) in FH13, for example. In the FH receiving unit 40A, the received symbol is subjected to optical - electrical conversion and equalization processing in the photoelectric conversion unit 401 and the equalization unit 402, respectively, and then the symbol is determined in the symbol determination unit 404.

[0133] For example, as shown in FIG. 8, among the candidate signal points of 256QAM, it is determined that the symbol Tx closest to the received symbol Tr is the symbol (e.g., sub - carrier modulation signal) transmitted from the FH transmitting unit 30A.

[0134] Note that in the example of FIG. 8, the case where precoding is performed is shown, but precoding may not be performed. Similar to the case where the precoding exemplified in FIG. 8 is performed, even when precoding is not performed, the symbol in optical transmission is determined based on the I - component and Q - component of the symbol S of the sub - carrier signal output from the RE mapping unit 210.

[0135] As described above, in the parent station apparatus 11 in the DL configuration of the second embodiment, a parent station signal processing unit 20 (an example of a processing unit) that outputs a sub - carrier modulation signal, and an FH transmitting unit 30A (an example of a transmitting unit) that maps the I - component and Q - component of the sub - carrier modulation signal to an optical signal transmitted to the FH are provided. Also, in the child station apparatus 12 in the DL configuration of the second embodiment, an FH receiving unit 40A (an example of a receiving unit) that receives an optical signal via FH, and a child station signal processing unit 50 (an example of a processing unit) that identifies the sub - carrier modulation signal based on the I - component and Q - component of the sub - carrier modulation signal mapped in the optical signal are provided. With this configuration, as exemplified in FIG. 8, in order to map the sub - carrier signal output from the RE mapping unit 210 to an optical signal, for example, quantization and coding of the signal can be made unnecessary. Therefore, for example, an increase in redundant bits associated with the application of quantization and coding can be suppressed, and the transmission efficiency can be improved.

[0136] Also, in the second embodiment, as illustrated in FIG. 8, symbol determination is performed based on the signal point arrangement used for optical transmission, so that noise resistance can be improved.

[0137] Also, in the second embodiment, symbol mapping and symbol determination of optical transmission are performed based on the signal point arrangement used for optical transmission, so that a system can be configured using existing optical transmission transmitting and receiving devices.

[0138] Also, in the example of FIG. 8, in the FH receiving unit 40A, since hard determination of symbols is performed, the symbols transmitted from the FH transmitting unit 30A can be restored.

[0139] Note that although FIGS. 7A and 7B show examples of the DL configuration, a configuration similar to the DL configuration may be applied to the UL. Hereinafter, an example of the UL configuration will be shown.

[0140] The example of the UL system configuration in the second embodiment may be the same as the configuration example shown in FIG. 5 of the first embodiment. Also, the fact that two or more slave station devices 12 can be connected to one master station device 11 and the fact that one slave station device 12 can be connected to two or more UEs 2 are the same as in the first embodiment.

[0141] FIG. 9A shows an example of the configuration of the slave station device 12 (slave station signal processing unit 60 and FH transmitting unit 70A) focusing on the UL, and FIG. 9B shows an example of the configuration of the master station device 11 (FH receiving unit 80A and master station signal processing unit 90) focusing on the UL. Note that in FIGS. 9A and 9B, for the same configurations as in FIGS. 6A and 6B, the same reference numerals may be given and the description may be omitted.

[0142] In the second embodiment, as illustrated in FIG. 9A, the FH transmitting unit 70A includes, for example, a normalization unit 701, an IQ symbol candidate detection unit 704, and an electro-optical (E / O) conversion unit 703.

[0143] The IQ symbol candidate detection unit 704 detects the symbol for optical transmission from among the candidates based on the normalized sub-carrier signal output from the normalization unit 701. For example, when 256QAM modulation is used in optical transmission, the IQ symbol candidate detection unit 704 determines, as the transmission symbol, the candidate point closest to the sub-carrier signal in the signal point arrangement on the IQ plane indicating the candidate points of 256QAM.

[0144] In Embodiment 2, as illustrated in FIG. 9B, the FH receiving unit 80A includes, for example, a photoelectric conversion unit 801, an equalization unit 802, and a symbol decision unit 804.

[0145] The symbol decision unit 804 determines the symbol of the signal after the equalization process output from the equalization unit 802. For example, when 256QAM modulation is used in optical transmission, the symbol decision unit 804 determines that the candidate point closest to the sub-carrier signal in the signal point arrangement on the IQ plane indicating the candidate points of 256QAM is the received symbol.

[0146] As described above, the slave station device 12 in the UL configuration of the present Embodiment 2 includes a slave station signal processing unit 60 that outputs a sub-carrier modulation signal, and an FH transmission unit 70A that maps the I component and Q component of the sub-carrier modulation signal to an optical signal transmitted to the FH. Further, the master station device 11 in the UL configuration of the present Embodiment 2 includes an FH receiving unit 80A that receives an optical signal via the FH, and a master station signal processing unit 90 that identifies the sub-carrier modulation signal based on the I component and Q component of the sub-carrier modulation signal mapped in the optical signal. With such a UL configuration, the same or similar operational effects as those of the DL configurations shown in FIGS. 7A and 7B can be obtained.

[0147] Note that the configuration shown in Embodiment 1 and the configuration shown in Embodiment 2 may be used in combination.

[0148] For example, in the DL configuration, the FH transmission unit 30 shown in Embodiment 1 and the FH reception unit 40A shown in Embodiment 2 may be combined. In this case, the symbol mapped by the direct IQ mapping unit 302 of the FH transmission unit 30 is received by the FH reception unit 40A, and the symbol closest to the received symbol by the symbol determination unit 404 of the FH reception unit 40A is determined from among the candidate points.

[0149] For example, in the DL configuration, the FH transmission unit 30A shown in Embodiment 2 and the FH reception unit 40 shown in Embodiment 1 may be combined. In this case, the symbol mapped by the IQ symbol candidate detection unit 304 of the FH transmission unit 30A is received by the FH reception unit 40, and the symbol received by the soft determination unit 403 of the FH reception unit 40 is determined.

[0150] Also, in Embodiments 1 and 2, the DL configuration and the UL configuration are shown separately, but the DL configuration and the UL configuration may be configured as physically different devices, or may be realized within a physically same device.

[0151] Also, regarding the above-described Embodiments 1 and 2, in the master station device 11, the DL master station signal processing unit 20 and the UL master station signal processing unit 90 may be configured as physically different devices, or may be realized within a physically same device.

[0152] Similarly, in the master station device 11, the DL FH transmission unit 30 (or 30A) and the UL FH reception unit 80 (or 80A) may be configured as physically different devices, or may be realized within a physically same device. Also, the FH transmission unit 30 (or 30A) and the FH reception unit 80 (or 80A) may be integrated, for example, as a shared FH transceiver or FH communication device for DL and UL.

[0153] Similarly, with respect to the slave station device 12 as well, the DL FH receiver 40 (or 40A) and the UL FH transmitter 70 (or 70A) may be configured as physically different devices, or may be realized within the same physical device. Further, the FH receiver 40 (or 40A) and the FH transmitter 70 (or 70A) may be integrated, for example, as a shared FH transceiver or FH communication device for DL and UL.

[0154] Also, the DL slave station signal processing unit 50 and the UL slave station signal processing unit 60 may be configured as physically different devices, or may be realized within the same physical device.

[0155] Also, in the master station device 11, at least one of the DL master station signal processing unit 20 and the UL master station signal processing unit 90 may be configured by a logical slice.

[0156] Similarly, in the slave station device 12, at least one of the DL slave station signal processing unit 50 and the UL slave station signal processing unit 60 may be configured by a logical slice.

[0157] At least one of the master station device 11 and the slave station device 12 may be configured by a logical slice.

[0158] Also, in the above-described Embodiments 1 and 2, the description was made focusing on the one-to-one connection relationship between the master station device 11 and the slave station device 12, but the connection relationship between the master station device 11 and the slave station device 12 may be a one-to-many relationship.

[0159] In the above-described Embodiments 1 to 2, when the notation “··· unit” is used to mean a physical element, it may be replaced with other notations such as “··· circuitry”, “··· device”, “··· unit”, or “··· module”. On the other hand, when it means a logical element, the notation “··· unit” may be replaced with, for example, “slice” as described above.

[0160] For example, regarding DL, the master station signal processing unit 20 (see FIG. 3A) in Embodiment 1 and the master station signal processing unit 20 (see FIG. 7A) in Embodiment 2 may be provided in one master station apparatus 11. Also, regarding DL, the slave station signal processing unit 50 (see FIG. 3B) in Embodiment 1 and the slave station signal processing unit 50 (see FIG. 7B) in Embodiment 1 may be provided in one master station apparatus 11.

[0161] Similarly, regarding UL, the slave station signal processing unit 60 (see FIG. 6A) in Embodiment 1 and the slave station signal processing unit 60 (see FIG. 9A) in Embodiment 2 may be provided in one slave station apparatus 12. Also, regarding UL, the master station signal processing unit 90 (see FIG. 6B) in Embodiment 1 and the master station signal processing unit 90 (see FIG. 9B) in Embodiment 2 may be provided in one master station apparatus 11.

[0162] In addition, in Embodiments 1 and 2, the case where there is one function division point (in other words, the function division configuration is two, i.e., the master station apparatus 11 and the slave station apparatus 12) has been described, but the number of function division points may be two or more. For example, a plurality of base station functional units may be divided and arranged into three, i.e., CU, DU, and RU (radio unit), by two function division points.

[0163] Note that in the DL configurations of Embodiments 1 and 2, a subcarrier signal mapped to radio resources (e.g., RE) arranged on the frequency axis is transmitted by FH, and in the slave station apparatus, an OFDM signal is obtained by performing IFFT processing on the subcarrier signal. In other words, in the DL configurations of Embodiments 1 and 2, in the function division between the master station apparatus and the slave station apparatus, the function of performing mapping to RE is included in the master station apparatus, and the function of performing IFFT processing is included in the slave station apparatus. According to the configuration example based on this function division, the influence of out-of-band radiation due to noise superimposed in FH can be reduced by IFFT processing.

[0164] Also, in the UL configurations of Embodiments 1 and 2, in the slave station device, by performing FFT processing on the OFDM signal, a subcarrier signal is obtained, and the subcarrier signal is transmitted by FH. In the master station device, demapping processing of the transmitted subcarrier signal is executed. In other words, in the UL configurations of Embodiments 1 and 2, in the functional division between the master station device and the slave station device, the function of performing demapping processing is included in the master station device, and the function of performing FFT processing is included in the slave station device. According to the configuration example based on this functional division, the influence of out-of-band radiation due to noise superimposed in FH can be reduced by FFT processing and demapping processing.

[0165] Also, in Embodiments 1 and 2, error correction coding processing for FH transmission is not executed, but errors that may occur in FH transmission may be corrected by error correction coding processing for a radio section (for example, the section between the radio base station 1 and the UE2). The error correction coding processing for the radio section is executed, for example, by the coding unit 205 in FIGS. 3A and 7A in the DL. Also, the decoding processing of the error correction coding for the radio section is executed, for example, by the decoding unit 905 in FIGS. 6B and 9B in the UL.

[0166] Note that, in this case, the error correction coding processing for the radio section may be set according to the transmission characteristics in FH.

[0167] For example, the higher the coding rate (in other words, the lower the redundancy), the higher the transmission efficiency but the lower the error correction ability tends to be. Conversely, the lower the coding rate (in other words, the higher the redundancy), the lower the transmission efficiency but the higher the error correction ability tends to be.

[0168] Therefore, for example, the coding rate may be set according to the transmission characteristics of the wireless section and the transmission characteristics in FH. For example, in DL, the coding rate used in the coding unit 205 may be set according to the transmission characteristics of the wireless section and the transmission characteristics in FH. Also, in UL, the coding rate used by the UE2 may be set according to the transmission characteristics of the wireless section and the transmission characteristics in FH. For example, in UL, the radio base station 1 may set the coding rate used by the UE2 and notify the UE2 of the control information indicating the set coding rate.

[0169] In addition, the optical signal transmitted or received in the FH section may include information related to the transmission control between the master station device and the slave station device. For example, error correction coding processing for FH transmission may be performed on this information related to the transmission control.

[0170] For example, in the case of eCPRI, the payload part of the signal includes, for example, a radio transmission signal (e.g., signals of PDSCH and PDCCH) that has been signal-processed in the master station device or the slave station device. "PDSCH" is an abbreviation of "physical downlink shared channel", and "PDCCH" is an abbreviation of "physical downlink control channel". The radio transmission signal is subjected to error correction processing on the transmission side.

[0171] When error correction is performed on the payload part of the signal in the master station device for wireless section transmission, even if an error occurs in the payload part in the FH transmission section, error correction is possible on the wireless reception side (e.g., the UE in the downlink).

[0172] On the other hand, the header part of the signal may include, for example, information related to the transmission control between the master station device and the slave station device. For example, a plurality of destination information corresponding to a plurality of slave station devices may be included in the header part.

[0173] When an error occurs in the header part, the payload part to which the header part is attached may fail to be restored and be discarded on the receiving side. Therefore, the header part has a higher importance level than the payload part, and high error tolerance is desired. Therefore, in the header part, error correction coding processing for FH transmission is executed, and for the subcarrier signal corresponding to the payload part, the transmission method of the above-described Embodiment 1 and / or Embodiment 2 may be applied without executing error correction coding processing for FH transmission.

[0174] The present disclosure can be realized by software, hardware, or software in cooperation with hardware.

[0175] Each functional block used in the description of the above embodiment may be realized as an LSI which is an integrated circuit, partially or entirely, and each process described in the above embodiment may be controlled partially or entirely by one LSI or a combination of LSIs. The LSI may be composed of individual chips, or may be composed of one chip so as to include a part or all of the functional blocks. The LSI may be provided with input and output of data. Depending on the degree of integration, the LSI may also be referred to as an IC, a system LSI, a super LSI, or an ultra LSI.

[0176] The method of integrating into an integrated circuit is not limited to an LSI, and may be realized by an application specific circuit, a general-purpose processor, or a dedicated processor. Further, after manufacturing the LSI, an FPGA (Field Programmable Gate Array) that can be programmed, or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used. The present disclosure may be realized as digital processing or analog processing.

[0177] Furthermore, if an integrated circuit technology that replaces the LSI appears due to the progress of semiconductor technology or another derived technology, naturally, the technology may be used to integrate the functional blocks. The application of biotechnology or the like is possible as an example.

[0178] [Summary of the Present Disclosure] The master station apparatus according to a non-limiting embodiment of the present disclosure includes a processing unit that outputs a subcarrier modulation signal, and a transmission unit that maps the I component and the Q component of the subcarrier modulation signal to an optical signal transmitted to the fronthaul.

[0179] In the master station apparatus according to a non-limiting embodiment of the present disclosure, the transmission unit maps the I component and the Q component of the subcarrier modulation signal as the I component and the Q component of the optical signal, respectively.

[0180] In the master station apparatus according to a non-limiting embodiment of the present disclosure, the transmission unit sets, as the optical signal, a candidate signal point among a plurality of candidate signal points in the IQ plane of the optical signal, the relationship of which with the signal point represented by the I component and the Q component of the subcarrier modulation signal is a predetermined relationship.

[0181] In the master station apparatus according to a non-limiting embodiment of the present disclosure, the predetermined relationship is the relationship with the closest distance in the IQ plane.

[0182] In the master station apparatus according to a non-limiting embodiment of the present disclosure, the subcarrier modulation signal is a signal mapped to radio resources in a radio transmission interval, and error correction coding corresponding to the radio transmission interval is performed among the radio transmission interval and an optical transmission interval including the fronthaul.

[0183] The master station apparatus according to a non-limiting embodiment of the present disclosure includes a reception unit that receives an upstream optical signal via the fronthaul, and the processing unit identifies the upstream subcarrier modulation signal based on the I component and the Q component of the upstream subcarrier modulation signal mapped in the upstream optical signal.

[0184] The slave station device according to a non-limiting embodiment of the present disclosure includes a receiving unit that receives an optical signal via a fronthaul, and a processing unit that identifies the subcarrier modulation signal based on the I component and the Q component of the subcarrier modulation signal mapped in the optical signal.

[0185] In the slave station device according to a non-limiting embodiment of the present disclosure, the processing unit includes a transmitting unit that outputs an uplink subcarrier modulation signal and maps the I component and the Q component of the uplink subcarrier modulation signal to an uplink optical signal transmitted to the fronthaul.

[0186] A wireless communication system according to a non-limiting embodiment of the present disclosure includes a master station device and a slave station device. The master station device includes a processing unit that outputs a subcarrier modulation signal, and a transmitting unit that maps the I component and the Q component of the subcarrier modulation signal to an optical signal transmitted to the fronthaul. The slave station device includes a receiving unit that receives the optical signal via the fronthaul, and a processing unit that identifies the subcarrier modulation signal based on the I component and the Q component of the subcarrier modulation signal mapped in the optical signal.

Industrial Applicability

[0187] The present disclosure is suitable for, for example, a wireless communication system.

Description of Symbols

[0188] 1 Radio base station 2 UE 11 Master station device 12 Slave station device 13 Fronthaul (FH) 20, 90 Master station signal processing unit 30, 30A, 70, 70A FH transmitting unit 40, 40A, 80, 80A FH receiving unit 50, 60 Slave station signal processing unit

Claims

1. A processing unit that outputs a subcarrier modulation signal; A transmission unit that maps the I component and the Q component of the subcarrier modulation signal to an optical signal transmitted to the fronthaul; comprising: The transmission unit sets, in the optical signal, a candidate signal point among a plurality of candidate signal points in the IQ plane of the optical signal, the relationship between which and the signal point represented by the I component and the Q component of the subcarrier modulation signal is a predetermined relationship; The predetermined relationship is the relationship with the closest distance in the IQ plane. Master station device.

2. The transmission unit maps the I component and the Q component of the subcarrier modulation signal as the I component and the Q component of the optical signal, respectively. The master station device according to claim 1.

3. The subcarrier modulation signal is a signal mapped to radio resources in a radio transmission section, and error correction coding corresponding to the radio transmission section is performed among the radio transmission section and an optical transmission section including the fronthaul. The master station device according to claim 1.

4. comprising a reception unit that receives an upstream optical signal via the fronthaul; The processing unit identifies the upstream subcarrier modulation signal based on the I component and the Q component of the upstream subcarrier modulation signal mapped in the upstream optical signal. The master station device according to claim 1.

5. A reception unit that receives an optical signal via the fronthaul; A processing unit that identifies the subcarrier modulation signal based on the I component and the Q component of the subcarrier modulation signal mapped in the optical signal; comprising: The receiving unit receives the optical signal in which a candidate signal point, among a plurality of candidate signal points in the IQ plane of the optical signal, has a predetermined relationship with the signal point represented by the I component and the Q component of the subcarrier modulation signal. The predetermined relationship is the relationship with the closest distance in the IQ plane. Sub-station device.

6. The processing unit outputs an uplink subcarrier modulation signal. The apparatus further includes a transmitting unit that maps the I component and the Q component of the uplink subcarrier modulation signal to an uplink optical signal transmitted to the front hall. The sub-station device according to claim 5.

7. An apparatus includes a master station device and a slave station device. The master station device includes: a processing unit that outputs a subcarrier modulation signal; a transmitting unit that maps the I component and the Q component of the subcarrier modulation signal to an optical signal transmitted to the front hall; and The transmitting unit sets, in the optical signal, a candidate signal point having a predetermined relationship with the signal point represented by the I component and the Q component of the subcarrier modulation signal among a plurality of candidate signal points in the IQ plane of the optical signal. The predetermined relationship is the relationship with the closest distance in the IQ plane. The slave station device includes: a receiving unit that receives the optical signal via the front hall; a processing unit that identifies the subcarrier modulation signal based on the I component and the Q component of the subcarrier modulation signal mapped in the optical signal; and Wireless communication system.

Images