A radio over fiber (ROF) transmission system and method

Abstract

The application provides a radio frequency signal ROF transmission system and a transmission method. The system comprises a wireless coverage subsystem, a passive optical network PON broadband access subsystem and a first combining and separating filter. The wireless coverage subsystem comprises a base station, at least one remote radio frequency point RFP and a UE. The PON broadband access subsystem comprises an optical line terminal OLT device, a passive optical distribution network ODN and at least one optical network unit ONU device. The base station comprises a first ROF module. The RFP comprises a second combining and separating filter and a second ROF module. Through the ROF transmission system and the transmission method, the radio frequency signal can be transmitted in advance by using the PON network used by the home broadband, the deployment cost of the indoor distribution system is greatly reduced, the ODN network has been effectively utilized, and the technical prejudice that the ROF technology can only be deployed by using a point-to-point architecture on the same wavelength is overcome.

Description

Technical Field

[0001] The present invention relates to the field of 5G new radio transmission technology, and in particular to an optical fiber-carrying radio frequency signal ROF transmission system and a transmission method. Background Art

[0002] In indoor distribution scenarios, to achieve extended reach and distributed coverage of base station RF signals, traditional indoor distribution systems utilize RF cables, couplers, power splitters, and RF antennas to form a P2MP (Point-to-Multipoint) network. Signals transmitted along different distribution system paths are simply split or combined at power splitters and couplers, transmitting the wireless base station's RF signals to multiple remote nodes to achieve signal coverage in complex environments. However, network deployment and construction costs are high, transmission attenuation is significant, and coverage issues caused by non-standard construction are difficult to troubleshoot. Consequently, newer technologies are being adopted in many high-value-added areas.

[0003] In existing technologies, ROF (Radio over Fiber) technology is commonly used to solve the above problems. Its core idea is to combine wireless communication with fiber-optic communication, modulate the wireless signal onto an optical carrier, transmit it to the remote node via fiber, and then demodulate it to obtain the RF signal. Ultimately, the antenna covers the wireless users. However, it mainly relies on point-to-point transmission. Even if a base station corresponds to multiple coverage points, multiple optical interfaces will be deployed at the base station. Each optical interface forms a point-to-point transmission line with the coverage point. The fiber deployment is complex and costly. Summary of the Invention

[0004] The present application provides a ROF transmission system and method for radio frequency signals carried by optical fiber. The system can utilize the PON (Passive Optical Network) network used for home broadband to forward the radio frequency signals. This can greatly reduce the deployment cost of indoor distribution systems, effectively utilize the already deployed ODN (Optical Distribution Network) network, and overcome the technical bias of ROF technology that it can only be deployed in a point-to-point architecture on the same wavelength.

[0005] In a first aspect, an embodiment of the present application proposes an optical fiber-carrying radio frequency signal ROF transmission system, comprising: a wireless coverage subsystem and a passive optical network PON broadband access subsystem, a first combiner / demultiplexer, the wireless coverage subsystem comprising a base station, at least one remote radio frequency coverage point RFP and a UE, the PON broadband access subsystem comprising an optical line terminal OLT device, a passive optical distribution ODN network and at least one optical network unit ONU device, the base station comprising a first ROF module, the RFP comprising a second combiner / demultiplexer and a second ROF module, wherein:

[0006] In the downlink direction, the base station converts the downlink radio frequency signal into a downlink optical signal through the first ROF module, combines it with the optical signal of the OLT device through the first combiner / demultiplexer, multiplexes it through the ODN network and transmits it to at least one RFP. After being demultiplexed by the second combiner / demultiplexer of the RFP, it is transmitted to the connected ONU device and the second ROF module respectively. The second ROF module converts it into a downlink radio frequency signal and sends it to the user terminal UE.

[0007] In the uplink direction, for any RFP, the uplink RF signal of the UE is converted into an uplink optical signal through the second ROF module, and then combined with the optical signal of the ONU device through the second combiner / demultiplexer, and then multiplexed through the ODN network and transmitted to the first combiner / demultiplexer. After being demultiplexed by the first combiner / demultiplexer, it is transmitted to the first ROF module and the OLT device respectively, and then converted into an uplink RF signal by the first ROF module and sent to the base station.

[0008] In some possible embodiments, the RFP further includes a LINE interface, an ONU interface, and a wireless interface, wherein:

[0009] The LINE interface is used to implement communication between the ODN network and the second multiplexer / demultiplexer;

[0010] The ONU interface is used to implement communication between the second multiplexer and splitter and the ONU device;

[0011] The wireless interface is used to implement communication between the second ROF module and the UE.

[0012] In some possible embodiments, the base station is further configured to:

[0013] Receiving scheduling request signaling sent by the UE via a physical uplink channel (PUCCH), the scheduling request signaling including the amount of data to be transmitted and channel state information;

[0014] Based on the amount of data to be transmitted and the channel state information, a media access control scheduling MAC algorithm is used to allocate all subcarriers of a unit time slot to the UE in the time domain with the time slot as the time domain resource allocation unit.

[0015] In some possible embodiments, the channel state information includes at least one of the following: a channel quality indication, a precoding matrix indication, and a rank indication.

[0016] In some possible embodiments, the base station is specifically configured to:

[0017] The UE device is scheduled through the MAC layer to allocate corresponding uplink resources to the UE device, and the uplink resources include at least one of the following: time domain resource allocation, frequency domain resource allocation, modulation and coding scheme MCS, redundancy version RV, hybrid automatic repeat request HARQ.

[0018] In some possible embodiments, the RFP further includes a signal monitoring module located between the UE and the second ROF module, configured to:

[0019] monitoring the strength of each uplink radio frequency signal received by the RFP;

[0020] When determining that the strength of the uplink radio frequency signal is less than a preset strength, activating a noise suppression function and discarding the uplink radio frequency signal;

[0021] When it is determined that the strength of the uplink radio frequency signal is greater than or equal to the preset strength, the uplink radio frequency signal is transmitted to the second ROF module.

[0022] In a second aspect, an embodiment of the present application further proposes a ROF signal transmission method, in the downlink direction, comprising:

[0023] The downlink radio frequency signal is converted into a downlink optical signal through the first ROF module of the base station;

[0024] Combine the downlink optical signal with the optical signal of the OLT device through a first combiner / demultiplexer, and transmit the combined optical carrier to at least one RFP through a multiplexing ODN network;

[0025] After being split by the second multiplexer / demultiplexer of the RFP, the downlink optical signal and the optical signal are respectively transmitted to the second ROF module of the RFP and the connected ONU device;

[0026] The second ROF module of the RFP converts the downlink optical signal into a downlink radio frequency signal and sends it to the corresponding UE.

[0027] In a third aspect, an embodiment of the present application further proposes a ROF signal transmission method, which includes:

[0028] The second ROF module of any RFP converts the UE's uplink RF signal into an uplink optical signal;

[0029] The uplink optical signal is combined with the optical signal of the ONU device through the second combiner / demultiplexer of the RFP, and the combined optical carrier is transmitted to the first combiner / demultiplexer through the multiplexing ODN network;

[0030] After being split by the first combiner / demultiplexer, the uplink optical signal and the optical signal are transmitted to the connected first ROF module and OLT device respectively;

[0031] The first ROF module converts the uplink optical signal into an uplink radio frequency signal and then sends it to the connected base station.

[0032] In some possible embodiments, the method further includes:

[0033] The base station receives a scheduling request signaling sent by the UE through a physical uplink channel (PUCCH), where the scheduling request signaling includes the amount of data to be transmitted and channel state information;

[0034] Based on the amount of data to be transmitted and the channel state information, a media access control scheduling MAC algorithm is used to allocate all subcarriers of a unit time slot to the UE in the time domain with the time slot as the time domain resource allocation unit.

[0035] In some possible embodiments, the RFP further includes a signal monitoring module located between the UE and the second ROF module, and the method further includes:

[0036] Monitoring the strength of each uplink radio frequency signal received by the RFP through a signal monitoring module of any RFP;

[0037] When determining that the strength of the uplink radio frequency signal is less than a preset strength, activating a noise suppression function and discarding the uplink radio frequency signal;

[0038] When it is determined that the strength of the uplink radio frequency signal is greater than or equal to the preset strength, the uplink radio frequency signal is transmitted to the second ROF module.

[0039] Through the optical fiber-carrying radio frequency signal ROF transmission system and transmission method described in the above embodiments of the present application, based on ROF technology, the ROF signal is multiplexed on the user's existing PON broadband network, reducing the deployment cost of the user's wireless coverage.

[0040] Other features and advantages of the present application will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present application. The purposes and other advantages of the present application can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 This is a structural diagram of a ROF transmission system in an embodiment of the present application;

[0043] Figure 2 This is a schematic diagram of the structure of an RFP in an embodiment of the present application;

[0044] Figure 3 This is a flowchart of a base station performing MAC scheduling on a UE in an embodiment of the present application;

[0045] Figure 4 This is a specific example flow chart of allocating uplink resources to a UE device in an embodiment of the present application;

[0046] Figure 5 A schematic diagram of an uplink resource allocation method in the prior art;

[0047] Figure 6 Schematic diagram of the time domain waveforms of two RFPs in the prior art;

[0048] Figure 7 Schematic diagram of RB allocation and signal strength after scheduling in an embodiment of the present application;

[0049] Figure 8 This is a schematic diagram of the structure of another RFP in an embodiment of the present application;

[0050] Figure 9 This is a flow chart of data transmission in the downlink direction in an embodiment of the present application;

[0051] Figure 10 This is a flow chart of data transmission in the uplink direction in an embodiment of the present application;

[0052] Figure 11 This is a flow chart of a downlink ROF transmission method in an embodiment of the present application;

[0053] Figure 12 This is a flow chart of an uplink ROF transmission method in an embodiment of the present application. DETAILED DESCRIPTION

[0054] To make the objectives, technical solutions, and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings. It is apparent that the embodiments described are only some, not all, of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0055] Existing, newer technologies often use ROF technology to address the aforementioned technical challenges of achieving extended and distributed base station RF signal coverage in indoor distribution scenarios. However, in practical applications, if multiple ROF signals are present simultaneously in the uplink direction of data transmission, the base station typically uses multiple optical fibers to transmit the ROF signals separately. These signals are then converted back to RF signals at the base station source and then combined for processing. Alternatively, WDM (wavelength division multiplexing) technology is used to combine the ROF signals and transmit them over a single fiber. However, WDM components are expensive, and the base station also requires multiple optical modules to process multiple signals. The remote radio unit (RRU) also requires specialized optical modules to accommodate different wavelengths. Essentially, WDM is still used to implement multiple P2P links. If multiple ROF signals of the same wavelength are directly merged, the phase and frequency errors between the optical carriers of the multiple ROF signals will cause constructive or destructive phase differences between the directly modulated signals, making it impossible to recover the original signal. Existing technologies for maintaining optical carrier-level phase and frequency synchronization between multiple RRUs are too expensive and not feasible for practical deployment.

[0056] Another updated solution utilizes extended pico base stations, widely used in base stations such as LTE (Long Term Evolution) and 5G NR (5G New Radio). This is a typical P2MP fronthaul network architecture, primarily consisting of a baseband processing unit (BPU), an extension unit (UPU), and a remote coverage unit (RUU). The BPU and RUU utilize transmission media such as optical fiber and Ethernet cables to transmit air interface digital signals via the CPRI (Common Public Radio Interface) or eCPRI (enhanced Common Public Radio Interface) protocol. The RUU further processes the air interface digital signals into RF signals, providing user terminal access and data transmission. The extension unit is an active device, connected to the RUU and BPU via a P2P mechanism to process the digital signals. However, existing extended pico base station RF remote ends are relatively expensive, requiring power and separate fronthaul fiber / network cables. This leads to high cabling costs and construction complexity in older buildings or complex environments.

[0057] In summary, in order to achieve the remote extension and distributed coverage of base station RF signals, although the updated technology has certain advantages over the traditional indoor distribution system, it still faces technical problems such as the difficulty of system deployment and the high cost of system deployment.

[0058] In view of the technical problems in the above-mentioned prior art that the system deployment for realizing the extension and distribution of base station radio frequency signals is difficult and the cost of system deployment is high, the embodiment of the present application proposes a wireless coverage system, such as Figure 1 As shown, the PON network used for home broadband can be used for fronthaul of RF signals, which can greatly reduce the deployment cost of indoor distribution systems and effectively utilize the already deployed ODN network. At the same time, it also overcomes the technical bias of ROF technology that it can only be deployed in a point-to-point architecture on the same wavelength.

[0059] See also Figure 1 The embodiment of the present application provides an optical fiber-carrying radio frequency signal ROF transmission system, comprising:

[0060] A wireless coverage subsystem 101, a passive optical network (PON) broadband access subsystem 102, and a first multiplexer / demultiplexer 103. The wireless coverage subsystem 101 includes a base station, at least one radio frequency point (RFP), and a user equipment (UE). The PON broadband access subsystem 102 includes an optical line terminal (OLT), an optical network (ODN), and at least one optical network unit (ONU). The base station includes a first ROF module, and the RFP includes a second multiplexer / demultiplexer and a second ROF module.

[0061] In the downlink direction, the base station converts the downlink radio frequency signal into a downlink optical signal through the first ROF module, combines it with the optical signal of the OLT device through the first combiner / demultiplexer, multiplexes it through the ODN network and transmits it to at least one RFP. After being demultiplexed by the second combiner / demultiplexer of the RFP, it is transmitted to the connected ONU device and the second ROF module respectively. The second ROF module converts it into a downlink radio frequency signal and sends it to the user terminal UE.

[0062] In the uplink direction, for any RFP, the uplink RF signal of the UE is converted into an uplink optical signal through the second ROF module, and then combined with the optical signal of the ONU device through the second combiner / demultiplexer, and then multiplexed through the ODN network and transmitted to the first combiner / demultiplexer. After being demultiplexed by the first combiner / demultiplexer, it is transmitted to the first ROF module and the OLT device respectively, and then converted into an uplink RF signal by the first ROF module and sent to the base station.

[0063] The base station and at least one RFP of the wireless coverage subsystem are designed as LTE or 5GNR, and use ROF technology to transmit radio frequency signals. In actual applications, any existing radio frequency remote coverage technology can be used according to actual conditions. The OLT equipment, ODN network and ONU equipment constitute a PON network, which is a standard PON access network, including but not limited to GPON (Gigabit-capable Passive Optical Network), EPON (Ethernet Passive Optical Network), XGPON (10-Gigabit-capable Passive Optical Network), XGSPON (10-Gigabit Symmetric Passive Optical Network), and other systems.

[0064] In an embodiment of the present application, in the downstream direction, the downstream optical signal carries the downstream radio frequency signal, and its wavelength is the wavelength pre-assigned to the downstream optical signal. The wavelength of the optical signal of the OLT device is any wavelength within the range of the downstream wavelength specified by the PON access network of the above standard, which depends on the model of the OLT device. For example, the GPON network specifies a downstream wavelength of 1480~1500 nm, and the corresponding downstream wavelength of the OLT device is 1490 nm.

[0065] In order to distinguish the optical signal in the PON network from the ROF signal, the wavelength of the downstream optical signal is set to a wavelength outside the downstream wavelength range specified by the PON network, and the wavelength division multiplexing principle is adopted. The downstream optical signal and the optical signal of the OLT device are combined into one optical carrier through a first combiner / demultiplexer, and the optical carrier is transmitted to the ODN network through optical fiber, and then transmitted to at least one RFP through the multiplexing ODN network. In this way, the ROF signal is multiplexed on the user's existing PON broadband network, reducing the deployment cost of the user's wireless coverage.

[0066] Similarly, in the uplink direction, the uplink optical signal carries the uplink radio frequency signal, and its wavelength is the wavelength pre-assigned to the uplink optical signal. The wavelength of the optical signal of the ONU device is any wavelength within the range of the uplink wavelength specified by the PON access network of the above standard, which depends on the model of the ONU device. For example, the uplink wavelength specified in the GPON network is 1290~1330 nm, and the uplink wavelength of the corresponding ONU device is 1310 nm.

[0067] In order to distinguish the optical signal in the PON network from the ROF signal, the wavelength of the upstream optical signal is set to a wavelength outside the upstream wavelength range specified by the PON network, and the wavelength division multiplexing principle is adopted. The upstream optical signal and the optical signal of the ONU are combined into one optical carrier through the second combiner / demultiplexer inside the RFP, and the optical carrier is transmitted to the passive optical distribution ODN network through the optical fiber, and then transmitted to the first combiner / demultiplexer through the multiplexing ODN network. The upstream optical signal and the optical signal of the ONU are separated by the first combiner / demultiplexer, and respectively transmitted to the corresponding wireless coverage subsystem and PON broadband access subsystem for subsequent processing. In this way, the ROF signal can be reused on the user's existing PON broadband network, reducing the deployment cost of the user's wireless coverage.

[0068] Specifically, in the downlink direction, in the central office, the downlink radio frequency signal generated by the base station is converted into a downlink optical signal through the first ROF module, and is combined with the optical signal generated by the OLT device into an optical carrier through the first combiner / demultiplexer, and is transmitted to each RFP through the existing ODN network through optical fiber multiplexing. Inside the RFP, the optical carrier is separated into a downlink optical signal and an optical signal of the OLT device according to the wavelength, and then the downlink optical signal is converted into a downlink radio frequency signal through the second ROF module inside the RFP, and the downlink radio frequency signal is sent to the corresponding UE device for processing, and the optical signal of the OLT device is forwarded to the corresponding ONU device for processing.

[0069] In the uplink direction, at the terminal UE, the uplink RF signal is transmitted to its corresponding RFP, and the uplink RF signal is converted into an uplink optical signal by the second ROF module in the RFP, and is combined with the optical signal generated by the ONU device into an optical carrier through the second combiner / demultiplexer, and is transmitted to the connected first combiner / demultiplexer through the optical fiber multiplexing ODN network. After the first combiner / demultiplexer separates the optical carrier into an uplink optical signal and an optical signal of the ONU device according to the wavelength, the uplink optical signal is transmitted to the first ROF module, and the first ROF module converts the uplink optical signal into an uplink RF signal and sends it to the base station, and the optical signal of the ONU is transmitted to the OLT device.

[0070] In the embodiment of the present application, each RFP belongs to the same base station cell, covers at least one UE device, and sends the downlink optical signal to each RFP in a broadcast manner. Then, each RFP wirelessly sends the corresponding radio frequency signal to each UE device, so that the wireless coverage system using ROF technology can also realize the P2MP architecture.

[0071] In some possible embodiments, such as Figure 2 As shown, the RFP further includes a LINE interface 201, an ONU interface 202, and a wireless interface 203, wherein:

[0072] The LINE interface is used to implement communication between the ODN network and the second multiplexer / demultiplexer;

[0073] The ONU interface is used to implement communication between the second multiplexer and splitter and the ONU device;

[0074] The wireless interface is used to implement communication between the second ROF module and the UE.

[0075] Among them, the wireless interface module is a wireless interface module corresponding to the above-mentioned LTE or 5GNR. In the embodiment of the present application, when other existing radio frequency remote coverage technologies are adopted, the wireless interface module corresponds to the wireless interface form of other radio frequency remote coverage methods, and no specific restrictions are made in the embodiment of the present application.

[0076] Specifically, in the downstream direction, inside the RFP, an optical carrier from the ODN network is received through the LINE interface, and after separating the optical carrier into a downstream optical signal and an optical signal of the OLT device, the downstream optical signal is converted into a downstream RF signal through the second ROF module inside the RFP, and the downstream RF signal is sent to the corresponding UE device for processing through the wireless interface, and the optical signal of the OLT device is forwarded to the corresponding ONU device for processing through the corresponding ONU interface.

[0077] In the uplink direction, inside the RFP, an uplink RF signal sent from the terminal UE is received through the wireless interface, the uplink RF signal is converted into an uplink optical signal through the second ROF module in the RFP, the optical signal generated by the ONU device is received through the ONU interface, and after being combined into an optical carrier by the second combiner / demultiplexer, it is transmitted to the ODN network through the LINE interface.

[0078] By using the above-mentioned fiber-optic ROF transmission system for radio frequency signals, the ROF signal can be reused on the user's existing PON broadband network. The PON network used for home broadband can be used for fronthaul of the radio frequency signal, greatly reducing the deployment cost of the indoor distribution system. It also realizes the P2MP architecture based on ROF technology and overcomes the original technical prejudice.

[0079] In some possible embodiments, since the ODN network is connected to at least one RFP, and each RFP covers at least one UE device and can receive the uplink RF signals of each covered UE device, in the uplink direction, the uplink optical signals of different RFPs are merged at the optical splitter of the ODN. When multiple ROF signals with the same wavelength are transmitted simultaneously, there are phase differences and frequency errors between the multiple ROF signals, resulting in phase construction or phase cancellation between the ROF signals with the same wavelength, and the original signal cannot be restored. Therefore, in order to avoid the problem of signal distortion caused by different RFPs sending data in the same time slot, it is necessary to schedule the UE device through the MAC layer (Medium Access Control Layer) of the base station and allocate corresponding uplink resources to it so that the ODN network does not process multiple ROF signals at the same time, where Figure 3 As shown, the base station is further configured to:

[0080] Step 301: Receive scheduling request signaling sent by a UE via a physical uplink channel (PUCCH), where the scheduling request signaling includes the amount of data to be transmitted and channel state information.

[0081] The channel state information includes at least one of the following: a channel quality indicator, a precoding matrix indicator, and a rank indicator;

[0082] Step 302: Based on the amount of data to be transmitted and the channel state information, a media access control scheduling MAC algorithm is used to allocate all subcarriers of a time slot to the UE in the time domain using a time slot as a time domain resource allocation unit.

[0083] In traditional technologies, the air interface of LTE or 5GNR systems uses OFDM (Orthogonal Frequency Division Multiplexing) technology, which divides both the time domain and the frequency domain on the physical layer resources. Specifically, in traditional technologies, the time domain is divided into different time slots, and the frequency domain is divided into different subcarriers. Each time slot A subcarrier, as a resource element (RE), is allocated to different UEs based on a pre-defined algorithm at the MAC layer. The allocation of different uplink subcarrier resources to different UEs is driven, on the one hand, by resource utilization considerations. Furthermore, in wide-bandwidth, wide-coverage scenarios, the transmission paths of different subcarriers vary significantly, and the impact of fast fading caused by multipath on different subcarriers varies significantly. The UE, through measurement and CSI reporting, notifies the base station of subcarriers with better conditions. The base station then prioritizes allocating the relevant RBs (resource blocks) to these UEs, ensuring full utilization of air interface resources.

[0084] The resource allocation method proposed in the embodiment of the present application ensures that in the same time slot, only one RFP has an uplink RF signal modulated onto the optical carrier, and the RF signal strength of other RFPs is sufficiently low, and the corresponding uplink optical signal strength is also sufficiently low, that is, less than a preset value, or the optical signal is directly turned off.

[0085] The following is a specific example process of allocating uplink resources to a UE device in an embodiment of the present application. Figure 4 As shown, including:

[0086] Step 1: When it is determined that the UE has data to be transmitted and a corresponding PUSCH (Physical Uplink Shared Channel) is not allocated, the UE sends a scheduling request signaling to the corresponding base station through the PUCCH (Physical Uplink Control Channel), where the scheduling request signaling includes the amount of data to be transmitted and channel state information.

[0087] Step 2: receiving, through the base station, a scheduling request signaling sent by the UE device through the PUCCH;

[0088] Step 3: Through the base station, based on the amount of data to be transmitted and the channel state information, using the MAC algorithm, allocating all subcarriers of the unit time slot to the UE in the time domain with the time slot as the time domain resource allocation unit, and sending a scheduling instruction carrying uplink resources to the UE device through the DCI Format (Downlink Control Information Format), and scrambling it by the C-RNTI (Cell-Radio Network Temporary Identifier) / MCS-C-RNTI (Modulation and Coding Scheme C-RNTI, Modulation and Coding Scheme Cell Radio Network Temporary Identifier);

[0089] Step 4: Receive the scheduling instruction sent by the base station through the UE device, and based on the uplink resources allocated by the base station in the scheduling instruction, modulate the data to be transmitted into an uplink radio frequency signal in the allocated time slot and send the corresponding RFP.

[0090] In some possible embodiments, the uplink resource includes at least one of the following: time domain resource allocation, frequency domain resource allocation, MCS (Modulation and Coding Scheme), RV (Redundancy Version), and HARQ (Hybrid Automatic Repeat Request), where:

[0091] The time domain resource allocation includes a time slot offset (indicated by a 4-bit field), a starting symbol (S), and a time domain length (L), supporting flexible time slot configuration; the frequency domain resource allocation includes an indicated RBG (Resource Block Group) or the starting position of consecutive RBs; the MCS and RV include a modulation and coding scheme and a redundancy version, supporting adaptive modulation; the HARQ information includes an NDI (New Data Indicator), a HARQ process number, and an RV version.

[0092] In the traditional solution, the ultimate goal of the above-mentioned MAC layer is to schedule wireless resources to each device for transmission / reception resources based on the amount of data to be transmitted and channel status information reported by the UE device, and according to the existing favorable channel conditions in the time domain and frequency domain. That is, it relies on the existing favorable channel conditions and derives the scheduling result based on the amount of data to be transmitted and channel status information reported by the device.

[0093] See also Figure 5 This is the allocation method of the MAC layer in the prior art based on the preset algorithm to allocate uplink resources to UEs in both the time domain and the frequency domain. For example, there are 8 subcarriers in a time slot. One color block represents a subcarrier in the current time slot. The dark and light colors represent the uplink resources allocated to two UEs respectively. Assuming that the two UEs transmit through different RFPs, the time domain waveforms of the two RFPs are as follows: Figure 5 As shown, the intensity of the modulated optical signal is Figure 6 As shown in Figure 2, both RFPs have upstream optical signals at the same time. After being transmitted to the ODN network and combined, the frequency error and phase deviation between the optical signals will cause constructive or destructive phase shifts, seriously affecting the signal quality.

[0094] like Figure 7 As shown, it is a schematic diagram of the RB allocation method and signal strength after scheduling according to the scheduling method in the above embodiment of the present application. It can be seen that the uplink wireless subcarrier resources in the same time slot are only allocated to the same UE device for use, and in this time slot, there is and only the uplink wireless subcarrier signal in this time slot, or the signal power of the uplink wireless subcarrier signal in this time slot is dominant, which overcomes the problem of signal distortion caused by data transmission of different RFPs in the same time slot.

[0095] In indoor coverage scenarios, especially those in conference rooms, homes, and street shops, UE devices are close to the RFP and, in most cases, transmission is line-of-sight. Even if multipath exists, the delay difference between the multiple paths is small compared to the carrier wavelength, and the impact of fast fading caused by multipath is minimal. Therefore, the channel conditions of multiple subcarriers are relatively small, creating conditions for allocating all subcarriers in a timeslot to a UE device.

[0096] In an embodiment of the present application, when scheduling uplink resources, the time slot is used as the time domain resource allocation unit in the time domain, and all subcarriers of the unit time slot are allocated to the UE, so that the uplink wireless subcarrier resources of the same time slot are only allocated to the same UE device for use. Since most deployment scenarios of distributed base stations have a high degree of isolation, the radio frequency signals of the same UE device are mostly transmitted through the same RFP. Therefore, under this scheduling method, in the same time slot, only one RFP has an uplink signal modulated onto the optical carrier. Therefore, the different UE devices perform data transmission in the uplink direction according to the uplink resources allocated by the MAC layer of the base station. In the same time slot, the ODN network only transmits one ROF signal, and only one RFP has an uplink signal, or only one RFP has a dominant uplink signal power. This overcomes the problem of signal distortion caused by data transmission in the same time slot by different RFPs.

[0097] In addition, to further reduce the impact of interference from multiple RFP light sources, see Figure 8 The RFP further includes a signal monitoring module located between the UE and the second ROF module, configured to:

[0098] Step 1: monitoring the strength of each uplink radio frequency signal received by the RFP;

[0099] Step 2: When it is determined that the strength of the uplink radio frequency signal is less than a preset strength, a noise suppression function is activated to discard the uplink radio frequency signal;

[0100] Step 3: When it is determined that the strength of the uplink radio frequency signal is greater than or equal to the preset strength, the uplink radio frequency signal is transmitted to the second ROF module.

[0101] Specifically, the signal monitoring module is located between the wireless interface module and the second ROF module, and detects the strength of each uplink radio frequency signal received by the RFP through the wireless interface module.

[0102] The signal monitoring module monitors in real time the uplink RF signals received by the RFP through the wireless interface module. When it is determined that the strength of the uplink RF signal is greater than a preset value, ROF modulation and transmission of the uplink RF signal are performed normally. When the strength of the uplink RF signal is lower than the preset value, it is considered that the received signal is background noise, or an uplink RF signal sent by a UE device located in an area not covered by the RFP. In this case, the noise suppression function is activated and the uplink RF signal is discarded. The above-mentioned signal monitoring module can further reduce the impact of interference from multiple RFP light sources and also reduce the background noise on the base station side.

[0103] A specific data transmission process in the downlink direction is given below, such as Figure 9 As shown, is the wavelength of the downlink ROF signal, is the specified downlink signal wavelength, where .

[0104] See also Figure 9 , the downlink RF signal is sent to the first ROF module through the base station, and the first ROF module converts it into a wavelength The downlink ROF signal is generated by the OLT device with a wavelength of The first optical signal is combined into a downlink optical signal by the first combiner / demultiplexer and transmitted to each RFP through the optical fiber and ODN network. Inside the RFP, the downlink optical signal is received by the LINE interface module and sent to the second combiner / demultiplexer. The second combiner / demultiplexer receives the downlink optical signal according to the wavelength. and , separate the downlink optical signal into a downlink ROF signal and a first optical signal, and send the downlink ROF signal to the second ROF module. After the downlink ROF signal is demodulated into a downlink RF signal by the second ROF module, it is sent to the corresponding UE device for processing through the wireless interface module. At the same time, the second combiner / demultiplexer sends the first optical signal to the ONU interface module, and the ONU interface module forwards the first optical signal to the corresponding ONU device for processing.

[0105] A specific data transmission process in the uplink direction is given below, such as Figure 10 As shown, is the specified upstream signal wavelength, is the wavelength of the uplink ROF signal, where .

[0106] See also Figure 10 , through the UE device, based on the uplink resources allocated by the base station, the data to be transmitted is modulated into an uplink radio frequency signal and the corresponding RFP is sent. At the same time, the ONU device sends a wavelength of The optical signal is sent to the corresponding RFP, and the uplink RF signal is received by the wireless interface module inside the RFP and sent to the second ROF module, and the uplink RF signal is loaded into the wavelength of The uplink ROF signal is obtained on the optical carrier and sent to the second combiner / demultiplexer, which receives the wavelength of The optical signal is sent to the second combiner / demultiplexer, and the uplink ROF signal and the optical signal are combined into an uplink optical signal by the second combiner / demultiplexer inside the RFP, and transmitted to the ODN network through the optical fiber, and sent from the ODN network to the first combiner / demultiplexer, and the uplink optical signal is transmitted to the first combiner / demultiplexer according to the wavelength. and , separate the uplink ROF signal and the optical signal, and send the separated uplink ROF signal to the first ROF module, which is restored to an uplink RF signal by the first ROF module and sent to the base station for subsequent processing, and the separated optical signal is sent to the corresponding OLT device for related processing of the PON network.

[0107] The ROF transmission system described in the above embodiment of the present application, based on ROF technology, reuses ROF signals on the user's existing PON broadband network, reducing the deployment cost of user wireless coverage and implementing a P2MP network architecture using ROF technology. Furthermore, in the uplink direction, the UE device is scheduled via the base station's MAC layer, and uplink resources are allocated to the UE device in units of a time slot. This ensures that only data from the same UE device is allocated to the wireless resources in the same time slot, avoiding signal distortion caused by interference between ROF signals from multiple RFPs on the same wavelength. Furthermore, by introducing a signal monitoring module on the RFP, optical carrier interference during transmission can be further reduced.

[0108] Based on the same inventive concept, the embodiment of the present application also proposes a ROF signal transmission method, in the downlink direction, such as Figure 11 As shown, including:

[0109] Step 1101: Convert a downlink radio frequency signal into a downlink optical signal through a first ROF module of a base station;

[0110] Step 1102: Combine the downlink optical signal with the optical signal of the OLT device through a first combiner / demultiplexer, and transmit the combined optical carrier to at least one RFP through a multiplexing ODN network.

[0111] Step 1103: After being demultiplexed by the second multiplexer / demultiplexer of the RFP, the downlink optical signal and the optical signal are respectively transmitted to the second ROF module of the RFP and the connected ONU device;

[0112] Step 1104: The second ROF module of the RFP converts the downlink optical signal into a downlink radio frequency signal and sends it to the corresponding UE.

[0113] Based on the same inventive concept, the embodiment of the present application also proposes a ROF signal transmission method, in the uplink direction, such as Figure 12 As shown, including:

[0114] Step 1201: Convert the uplink radio frequency signal of the UE into an uplink optical signal through the second ROF module of any RFP;

[0115] Step 1202: Combine the uplink optical signal with the optical signal of the ONU device through the second combiner / demultiplexer of the RFP, and transmit the combined optical carrier to the first combiner / demultiplexer through the multiplexing ODN network;

[0116] Step 1203: After being demultiplexed by the first multiplexer / demultiplexer, the uplink optical signal and the optical signal are transmitted to the connected first ROF module and OLT device respectively;

[0117] Step 1204: The first ROF module converts the uplink optical signal into an uplink radio frequency signal and sends the signal to the connected base station.

[0118] In some possible embodiments, the method further includes:

[0119] The base station receives a scheduling request signaling sent by the UE through a physical uplink channel (PUCCH), where the scheduling request signaling includes the amount of data to be transmitted and channel state information;

[0120] Based on the amount of data to be transmitted and the channel state information, a media access control scheduling MAC algorithm is used to allocate all subcarriers of a unit time slot to the UE in the time domain with the time slot as the time domain resource allocation unit.

[0121] In some possible embodiments, the RFP further includes a signal monitoring module located between the UE and the second ROF module, and the method further includes:

[0122] Monitoring the strength of each uplink radio frequency signal received by the RFP through a signal monitoring module of any RFP;

[0123] When determining that the strength of the uplink radio frequency signal is less than a preset strength, activating a noise suppression function and discarding the uplink radio frequency signal;

[0124] When it is determined that the strength of the uplink radio frequency signal is greater than or equal to the preset strength, the uplink radio frequency signal is transmitted to the second ROF module.

[0125] Through the ROF transmission method described in the above embodiment of the present application, the passive optical network (PON) network used for home broadband can be used for the front transmission of radio frequency signals, greatly reducing the deployment cost of the indoor distribution system, effectively utilizing the already deployed ODN network, and overcoming the technical bias of ROF technology that it can only be deployed using a point-to-point architecture on the same wavelength.

[0126] The above is a detailed introduction to the technical solution provided by the present application. Specific examples are used in the present application to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for those skilled in the art, according to the ideas of the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

[0127] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. An optical fiber-carrying radio frequency signal ROF transmission system, characterized in that: include: A wireless coverage subsystem and a passive optical network (PON) broadband access subsystem, and a first combiner / demultiplexer. The wireless coverage subsystem includes a base station, at least one remote radio frequency coverage point (RFP), and a user terminal (UE). The PON broadband access subsystem includes an optical line terminal (OLT), a passive optical distribution (ODN) network, and at least one optical network unit (ONU). The base station includes a first ROF module, and the remote radio frequency coverage point (RFP) includes a second combiner / demultiplexer and a second ROF module. In the downlink direction, the base station converts the downlink RF signal into a downlink optical signal through the first ROF module, combines it with the optical signal of the OLT device through the first combiner / demultiplexer, multiplexes it through the ODN network and transmits it to at least one RFP. After being demultiplexed by the second combiner / demultiplexer of the RFP, it is transmitted to the connected ONU device and the second ROF module respectively. The second ROF module converts it into a downlink RF signal and sends it to the UE. In the uplink direction, for any RFP, the uplink RF signal of the UE is converted into an uplink optical signal through the second ROF module, and then combined with the optical signal of the ONU device through the second combiner / demultiplexer, and then multiplexed through the ODN network and transmitted to the first combiner / demultiplexer. After being demultiplexed by the first combiner / demultiplexer, it is transmitted to the first ROF module and the OLT device respectively, and then converted into an uplink RF signal by the first ROF module and sent to the base station.

2. The system according to claim 1, wherein: The remote radio frequency coverage point RFP further includes a LINE interface, an ONU interface, and a wireless interface, wherein: The LINE interface is used to implement communication between the ODN network and the second multiplexer / demultiplexer; The ONU interface is used to implement communication between the second multiplexer and splitter and the ONU device; The wireless interface is used to implement communication between the second ROF module and the UE.

3. The system according to claim 1, wherein: The base station is further configured to: Receiving scheduling request signaling sent by the UE via a physical uplink channel (PUCCH), the scheduling request signaling including the amount of data to be transmitted and channel state information; Based on the amount of data to be transmitted and the channel state information, a medium access control scheduling MAC algorithm is utilized to allocate all subcarriers of a unit time slot to the UE in the time domain with the time slot as the resource allocation unit.

4. The system according to claim 3, characterized in that The channel state information includes at least one of the following: a channel quality indication, a precoding matrix indication, and a rank indication.

5. The system according to claim 1 or 2, characterized in that The remote radio frequency coverage point RFP further includes a signal monitoring module located between the UE and the second ROF module, configured to: monitoring the strength of each uplink radio frequency signal received by the RFP; When determining that the strength of the uplink radio frequency signal is less than a preset strength, activating a noise suppression function and discarding the uplink radio frequency signal; When it is determined that the strength of the uplink radio frequency signal is greater than or equal to the preset strength, the uplink radio frequency signal is transmitted to the second ROF module.

6. A ROF signal transmission method, characterized in that: In the downstream direction, these include: The downlink radio frequency signal is converted into a downlink optical signal through the first ROF module of the base station; Combine the downlink optical signal with the optical signal of the OLT device through a first combiner / demultiplexer, and transmit the combined optical carrier to at least one RFP through a multiplexing ODN network; After being split by the second multiplexer / demultiplexer of the RFP, the downlink optical signal and the optical signal are respectively transmitted to the second ROF module of the RFP and the connected ONU device; The second ROF module of the RFP converts the downlink optical signal into a downlink radio frequency signal and sends it to the corresponding UE.

7. A ROF signal transmission method, characterized in that: In the upstream direction, this includes: The second ROF module of any RFP converts the UE's uplink RF signal into an uplink optical signal; The uplink optical signal is combined with the optical signal of the ONU device through the second combiner / demultiplexer of the RFP, and the combined optical carrier is transmitted to the first combiner / demultiplexer through the multiplexing ODN network; After being split by the first combiner / demultiplexer, the uplink optical signal and the optical signal are transmitted to the connected first ROF module and OLT device respectively; The first ROF module converts the uplink optical signal into an uplink radio frequency signal and then sends it to the connected base station.

8. The method according to claim 7, characterized in that The method further comprises: The base station receives a scheduling request signaling sent by the UE through a physical uplink channel (PUCCH), where the scheduling request signaling includes the amount of data to be transmitted and channel state information; Based on the amount of data to be transmitted and the channel state information, a media access control scheduling MAC algorithm is used to allocate all subcarriers of a unit time slot to the UE in the time domain with the time slot as the time domain resource allocation unit.

9. The method according to claim 7, characterized in that The RFP further includes a signal monitoring module located between the UE and the second ROF module. The method further includes: Monitoring the strength of each uplink radio frequency signal received by the RFP through a signal monitoring module of any RFP; When determining that the strength of the uplink radio frequency signal is less than a preset strength, activating a noise suppression function and discarding the uplink radio frequency signal; When it is determined that the strength of the uplink radio frequency signal is greater than or equal to the preset strength, the uplink radio frequency signal is transmitted to the second ROF module.

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