Fronthaul network enhancement techniques

Abstract

The embodiment of the invention relates to forward communication equipment, method and device and a computer readable storage medium. The method includes converting, at an aggregator of a forward network, a set of first wireless signals to a set of first signals corresponding to respective wireless channels; applying code division multiplexing on each of the first signals based on a corresponding first orthogonal code set for a respective wireless channel to obtain a set of encoded signals corresponding to the respective wireless channel; aggregating the group of coded signals into a code division multiplexing (CDM) signal; and convert a CDM signal obtained from the CDM to a second signal for delivery in the optical forward link. In a forward transmission mechanism, an A-RoF scheme is utilized to aggregate and send wireless baseband signals through low-complexity CDM, and a forward transmission system with low complexity, low cost and high capacity is realized. Additionally, high performance gains may be achieved by using an NN-enabled equalizer.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to the field of telecommunications, and in particular to devices, methods, apparatuses, and computer-readable storage media for fronthaul communications. Background Art

[0002] In recent years, 5G communication systems have been deployed at a high speed around the world, making many emerging businesses such as self-driving cars, VR / AR, and smart cities possible. In 5G systems, fiber-based fronthaul links that support centralized radio access networks (CRANs) such as bridge baseband units (BBU) pools and remote radio heads (RRHs) are critical network segments. For current Long Term Evolution Advanced (LTE-A) fronthaul networks, the mainstream transmission protocol is the Common Public Radio Interface (CPRI).

[0003] The optical fronthaul link is a key link for current 4G and 5G wireless communication systems, which can be implemented by two methods: Digital Radio over Fiber (D-RoF) and Analog Radio over Fiber (A-RoF). D-RoF directly quantizes the analog signal from the RRH and transmits the digitized data in an on-off keying (OOK) format, with low spectral efficiency and high fidelity. Typically, the data rate for transmitting a 20MHz LTE signal and a 100MHz 5G signal based on the CPRI protocol requires about 1.2Gbps and 5Gbps, respectively, with a bandwidth expansion of 50 to 60 times. This huge bandwidth consumption greatly limits the application of the D-RoF scheme in 5G systems. In order to achieve high spectral efficiency and reduce the bandwidth of optoelectronic devices, A-RoF technology has been proposed and widely studied. In the simplest A-RoF scheme, frequency division multiplexing (FDM) is used to aggregate multiple radio signals and the combined signal is transmitted over a single wavelength. Some other A-RoF schemes use DSP-based channel aggregation and deaggregation methods to achieve simultaneous transmission of a large number of radio signals from antennas. On the other hand, since the A-RoF scheme usually stacks dozens of analog OFDM signals and has a higher peak-to-average ratio (PAPR), it is easily affected by the imperfect optical channel during fiber transmission compared with D-RoF, resulting in relatively poor system performance. Summary of the invention

[0004] Example embodiments of the present disclosure provide a fronthaul scheme based on code division multiplexing (CDM).

[0005] In a first aspect, an aggregator of a fronthaul network is provided. The aggregator includes a set of first analog-to-digital converters (ADCs), a code division multiplexer (CDM), and a first digital-to-analog converter (DAC). The set of first ADCs is coupled to the CDM and configured to convert a set of first wireless signals into a set of first signals corresponding to corresponding wireless channels. The CDM is coupled to the first digital-to-analog converter (DAC) and configured to apply code division multiplexing to each of the first signals based on a corresponding first orthogonal code set for the corresponding wireless channel to obtain a set of coded signals corresponding to the corresponding wireless channel; and aggregate the set of coded signals into a code division multiplexed (CDM) signal. The first DAC is configured to convert the CDM signal obtained from the CDM into a second signal for delivery in an optical fronthaul link.

[0006] In a second aspect, a BBU of a fronthaul network is provided. The BBU includes an ADC, an equalizer, and a code division multiplexer (CD-DM). The ADC is coupled to the equalizer and configured to convert a second signal delivered in an optical fronthaul link into a digital code division multiplexed (CDM) signal, which is processed by an aggregator of the fronthaul network based on code division multiplexing using a first orthogonal code of a corresponding wireless channel. The equalizer is coupled to the CD-DM and configured to equalize the CDM signal with respect to at least one equalization performance. The CD-DM section is configured to apply code division multiplexing to the equalized CDM signal based on a second orthogonal code to obtain a set of CD-DM signals corresponding to the corresponding wireless channel, the second orthogonal code corresponding to the first orthogonal code.

[0007] In a third aspect, a fronthaul system is provided, which includes an aggregator according to the first aspect, a BBU according to the second aspect, and an optical fronthaul link connecting the aggregator and the BBU.

[0008] In a fourth aspect, a method is provided. The method includes: at an aggregator of a fronthaul network, converting a set of first wireless signals into a set of first signals corresponding to corresponding wireless channels; applying code division multiplexing to each of the first signals based on a corresponding first orthogonal code set for the corresponding wireless channel to obtain a set of coded signals corresponding to the corresponding wireless channel; aggregating the set of coded signals into a code division multiplexed (CDM) signal; and converting the CDM signal obtained from the CDM into a second signal for delivery in an optical fronthaul link of the fronthaul network.

[0009] In a fifth aspect, a method is provided. The method includes: at a baseband unit (BBU) of the fronthaul network, converting a second signal delivered in an optical fronthaul link of the fronthaul network into a digital code division multiplexed (CDM) signal, the digital CDM signal being processed by an aggregator of the fronthaul network based on code division multiplexing using a first orthogonal code of a corresponding wireless channel; equalizing the CDM signal with respect to at least one equalization property; and applying code division multiplexing to the equalized CDM signal based on a second orthogonal code to obtain a set of CD-DM signals corresponding to the corresponding wireless channel, the second orthogonal code corresponding to the first orthogonal code.

[0010] In a sixth aspect, a method is provided. The method includes: applying code division multiplexing to each of a set of data streams based on a corresponding third orthogonal code set for a corresponding wireless channel at a baseband unit (BBU) of a fronthaul network to obtain a set of coded signals corresponding to the corresponding wireless channel; aggregating the set of coded signals into a code division multiplexed (CDM) signal; pre-equalizing the CDM signal with respect to at least one equalization property to obtain an equalized CDM signal; and converting the equalized CDM signal into a third signal to be delivered in an optical fronthaul link.

[0011] In a seventh aspect, a method is provided. The method includes: at an aggregator of a fronthaul network, converting a third signal delivered in an optical fronthaul link into a digital CDM signal, the third signal being processed by a baseband unit (BBU) of the fronthaul network based on code division multiplexing using a third orthogonal code of a corresponding wireless channel; performing code division multiplexing on the digital CDM signal based on a fourth orthogonal code to obtain a group of CD-DM signals corresponding to the corresponding wireless channel, the fourth orthogonal code corresponding to the third orthogonal code; and converting the group of CD-DM signals into a group of second wireless signals to be delivered in the corresponding wireless channel.

[0012] In an eighth aspect, there is provided a computer readable medium having stored thereon a computer program which, when executed by at least one processor of a device, causes the device to perform the method according to the fourth aspect.

[0013] In a ninth aspect, there is provided a computer readable medium having stored thereon a computer program which, when executed by at least one processor of a device, causes the device to perform the method according to the fifth aspect.

[0014] In a tenth aspect, there is provided a computer readable medium having stored thereon a computer program which, when executed by at least one processor of a device, causes the device to perform the method according to the sixth aspect.

[0015] In an eleventh aspect, there is provided a computer readable medium having stored thereon a computer program which, when executed by at least one processor of a device, causes the device to perform the method according to the seventh aspect.

[0016] In a twelfth aspect, an apparatus is provided. The apparatus includes a component for converting a group of first wireless signals into a group of first signals corresponding to corresponding wireless channels at an aggregator of a fronthaul network; a component for applying code division multiplexing to each of the first signals based on a corresponding first orthogonal code set for the corresponding wireless channel to obtain a group of coded signals corresponding to the corresponding wireless channel; a component for aggregating the group of coded signals into a code division multiplexed (CDM) signal; and a component for converting the CDM signal obtained from the CDM into a second signal for delivery in an optical fronthaul link.

[0017] In a thirteenth aspect, an apparatus is provided. The apparatus includes a component for converting a second signal delivered in an optical fronthaul link into a digital code division multiplexed (CDM) signal at a baseband unit (BBU) of a fronthaul network, the digital CDM signal being processed by an aggregator of the fronthaul network based on code division multiplexing using a first orthogonal code of a corresponding wireless channel; a component for equalizing the CDM signal with respect to at least one equalization performance; and a component for applying code division multiplexing to the equalized CDM signal based on a second orthogonal code to obtain a set of CD-DM signals corresponding to the corresponding wireless channel, the second orthogonal code corresponding to the first orthogonal code.

[0018] In a fourteenth aspect, an apparatus is provided. The apparatus includes: a component for applying code division multiplexing to each of a group of data streams based on a corresponding third orthogonal code set for a corresponding wireless channel at a baseband unit (BBU) of a fronthaul network to obtain a group of coded signals corresponding to the corresponding wireless channel; a component for aggregating the group of coded signals into a code division multiplexed (CDM) signal; a component for pre-equalizing the CDM signal with respect to at least one equalization property to obtain an equalized CDM signal; and a component for converting the equalized CDM signal into a third signal to be delivered in an optical fronthaul link.

[0019] In a fifteenth aspect, a device is provided. The device includes: a component for converting a third signal delivered in an optical fronthaul link into a digital code division multiplexed CDM signal at an aggregator of a fronthaul network, the third signal being processed by a baseband unit (BBU) of the fronthaul network based on code division multiplexing using a third orthogonal code of a corresponding wireless channel; a component for applying code division multiplexing to the digital CDM signal based on a fourth orthogonal code to obtain a group of CD-DM signals corresponding to the corresponding wireless channel, the fourth orthogonal code corresponding to the third orthogonal code; and a component for converting the group of CD-DM signals into a group of second wireless signals to be delivered in the corresponding wireless channel.

[0020] In a sixteenth aspect, a device is provided, comprising the aggregator of the first aspect.

[0021] In a seventeenth aspect, a device is provided, comprising the BBU of the second aspect.

[0022] Other features and advantages of the embodiments of the present disclosure will also be apparent from the following description of specific embodiments in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the embodiments of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The embodiments of the present disclosure are presented in the form of examples, and their advantages are explained in more detail below with reference to the accompanying drawings, in which

[0024] Figure 1A and Figure 1B A schematic diagram illustrating an example of aggregating 48 20 MHz LTE signals based on FFT / IFFT channel aggregation and deaggregation is shown;

[0025] Figure 1C The diagram shows Figure 1A and Figure 1B The example shown in FIG. 1 aggregates an example spectrum of 48 20 MHz LTE signals;

[0026] Figure 2A and Figure 2B illustrates an example network environment in which example embodiments of the present disclosure may be implemented;

[0027] Figure 3 illustrates a signaling diagram for a training process for a fronthaul network according to some example embodiments of the present disclosure;

[0028] Figure 4 The simulation results of EVM performance and received optical power based on the fronthaul communication scheme according to some example embodiments of the present disclosure are illustrated;

[0029] Figure 5 illustrates a flow chart of an example method of fronthaul communications according to some example embodiments of the present disclosure;

[0030] Figure 6 illustrates a flow chart of an example method of fronthaul communications according to some example embodiments of the present disclosure;

[0031] Figure 7 illustrates a flow chart of an example method of fronthaul communications according to some example embodiments of the present disclosure;

[0032] Figure 8 illustrates a flow chart of an example method of fronthaul communications according to some example embodiments of the present disclosure;

[0033] Fig. 9 shows a simplified block diagram of a device suitable for implementing an example embodiment of the present disclosure; and

[0034] Fig.10 A block diagram of an example computer-readable medium is shown in accordance with certain embodiments of the present disclosure.

[0035] Throughout the drawings, the same or similar reference numerals denote the same or similar elements. DETAILED DESCRIPTION

[0036] The principle of the present disclosure will now be described with reference to some example embodiments. It should be understood that these embodiments are only for illustrative purposes, and contribute to those skilled in the art to understand and implement the present disclosure, without implying any limitation on the scope of the present disclosure. The present disclosure described herein can be implemented in various ways except the way described below.

[0037] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0038] References in this disclosure to "one embodiment," "an embodiment," "an example embodiment," etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Furthermore, these phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an example embodiment, whether or not explicitly described, it should be considered that it is within the knowledge of those skilled in the art to affect such feature, structure, or characteristic in conjunction with other embodiments.

[0039] It should be understood that although the terms "first" and "second" etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish the functionality of the various elements. The term "and / or" used herein includes any and all combinations of one or more of the listed terms.

[0040] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments. As used herein, unless the context clearly indicates otherwise, the singular forms "one", "an" and "the" also include plural forms. It should also be understood that the terms "including", "having" and / or "comprising" when used herein specify the existence of stated features, elements and / or components, etc., but do not exclude the existence or addition of one or more other features, elements, components and / or combinations thereof.

[0041] As used in this application, the term "circuitry" may refer to one or more or all of the following:

[0042] (a) pure hardware circuit implementation (such as implementation in analog and / or digital circuitry only) and

[0043] (b) a combination of hardware circuitry and software such as (where applicable):

[0044] (i) a combination of analog and / or digital hardware circuits and software / firmware, and

[0045] (ii) any portion of hardware processor(s) with software (including digital signal processor(s), software and memory(s) that work together to enable a device (such as a mobile phone or server) to perform various functions) and

[0046] (c) Hardware circuit(s) and / or processor(s) that require software (e.g., firmware) to operate, such as microprocessor(s) or portion(s) of microprocessor(s), but where the software is not required for operation, the software may not be present.

[0047] This definition of circuitry applies to all uses of the term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. By way of example and where applicable to a particular claim element, the term circuitry also covers a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0048] As used herein, the term "communication network" refers to a network that complies with any appropriate communication standard, such as the fifth generation (5G) or new radio (5G NR) or super 5G (e.g., 6G system), long term evolution (LTE), advanced LTE (LTE-A), wideband code division multiple access (WCDMA), high speed packet access (HSPA), narrowband Internet of Things (NB-IoT), Wi-Fi, O-RAN (open RAN), or subsequent developments of communication systems and standards. In addition, the communication between the terminal device and the network device in the communication network can be performed according to any appropriate generation of communication protocols, including but not limited to the first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, fifth generation (5G) new radio (NR) communication protocols, protocols defined by the O-RAN Alliance for O-RAN standards, and / or any other currently known or future protocols to be developed. The embodiments of the present disclosure can be applied to various communication systems. In view of the rapid development of communication, there will certainly be future types of communication technologies and systems that can embody the present disclosure. It should not be construed as limiting the scope of the present disclosure to only the above-described systems.

[0049] As used herein, the term "network device" refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. A network device may refer to a base station (BS), a base transceiver station (BTS), or an access point (AP), such as a NodeB (NodeB or NB), an evolved NodeB (eNodeB or eNB), a NR next generation NodeB (gNB), a remote radio unit (RRU), a radio head (RH), a radio unit (RU), a remote radio head (RRH), a relay, a low power node (such as a femto, micro, small cell, etc.), depending on the terminology and technology applied. A RAN split architecture may include a gNB-CU (centralized unit, hosting, for example, RRC, SDAP, and PDCP) that controls multiple gNB-DUs (distributed units, hosting, for example, RLC, MAC, and PHY). A relay node may correspond to the DU portion of an integrated access and backhaul (IAB) node.

[0050] The term "terminal device" refers to any terminal device capable of wireless communication. As an example and not limitation, a terminal device may also be referred to as a communication device, a user equipment (UE), a subscriber station (SS), a portable subscriber station, a mobile station (MS), or an access terminal (AT). The terminal device may include, but is not limited to, a mobile phone, a cellular phone, a smart phone, a voice over IP (VoIP) phone, a wireless local loop phone, a tablet computer, a wearable terminal device, a personal digital assistant (PDA), a portable computer, a desktop computer, an image capture terminal device such as a digital camera, a game terminal device, a music storage and playback device, a vehicle-mounted wireless terminal device, a wireless endpoint, a mobile station, a laptop embedded device (LEE), a laptop mounted device (LME), a USB dongle, a smart device, a wireless customer premises equipment (CPE), an Internet of Things (IoT) device, a watch or other wearable device, a head mounted display (HMD), a vehicle, a drone, medical equipment and applications (e.g., remote surgery), industrial equipment and applications (e.g., robots and / or other wireless devices operating in industrial and / or automated processing chain environments), consumer electronic devices, devices operating on commercial and / or industrial wireless networks, etc. The terminal device may also correspond to the mobile terminal (MT) part of an integrated access and backhaul (IAB) node (also known as a relay node). In the following description, the terms "terminal device", "communication device", "terminal", "user equipment" and "UE" may be used interchangeably.

[0051] While in various example embodiments, the functionality described herein may be performed in fixed and / or wireless network nodes, in other example embodiments, the functionality may be implemented in a user equipment device (such as a mobile phone or tablet computer or laptop computer or desktop computer or mobile IoT device or fixed IoT device). The user equipment device may, for example, be equipped with corresponding functions described in conjunction with (multiple) fixed and / or wireless network nodes as required. The user equipment device may be a user device and / or a control device, such as a chipset or processor, which is configured to control the user device when installed in the user device. Examples of such functionality include boot server functions and / or home subscriber servers, which may be implemented in the user equipment device by providing the user equipment device with software configured to cause the user equipment device to execute from the perspective of these functions / nodes.

[0052] CPRI is a widely used protocol for optical fronthaul links supporting 4G / 5G wireless communications, which digitizes analog radio signals and transmits the digitized OOK signals over optical fiber. Taking a 100MHz 5G signal as an example, the recommended system parameters based on the CPRI protocol are given in Table 1. After adding the control word (CW) and coding overhead (OH), the final data rate reaches about 5Gbps for only one 100MHz 5G signal, equivalent to a 50-fold bandwidth expansion.

[0053] Table 1 - Example of system parameters based on CPRI protocol

[0054] System Parameters value Baseband signal bandwidth 100MHz Sampling rate 122.88MHz Sampling width 15 bits (x2 for I / Q) Data Rate 30*122.88=3686.4Mbps Data rate with control word 16 / 15*3686.4=3932.16Mbps Data rates with CW and OH 10 / 8*3932.16=4915.2Mbps

[0055] Due to quantization processing, the CPRI protocol requires huge optical bandwidth for data transmission and is not suitable for supporting 5G systems with larger radio signal bandwidth and more antennas. In order to reduce bandwidth consumption, the eCPRI protocol was proposed and developed. Nevertheless, the D-RoF scheme represented by CPRI and eCPRI still has lower spectrum efficiency compared with the A-RoF scheme. Therefore, A-RoF has been intensively discussed and studied in industry and academia.

[0056] The A-RoF transmission solution is implemented based on FFT / IFFT channel aggregation and deaggregation technology. Figure 1A and Figure 1B As shown in FIG, an example 48 20 MHz radio signals from a wireless channel are aggregated by N-point FFT and M-point IFFT operations. The spectrum of the example aggregated signal is shown in FIG. Figure 1C As shown in . Compared with the D-RoF solution, the A-RoF system can deliver 48 20MHz LTE signals and 1.5GHz RF bandwidth on a single wavelength, equivalent to an aggregate CPRI data rate of 59Gbps. However, the EVM (error vector magnitude) performance of the received signal in the A-RoF system is worse than that of the traditional CPRI-based D-RoF system. In addition, as Figure 1A and Figure 1B As shown in , complex FFT / IFFT calculations are required at the transmitter and receiver.

[0057] To address the above and other potential problems, embodiments of the present disclosure provide an enhanced fronthaul mechanism. In the fronthaul mechanism, the A-RoF scheme is used to aggregate and transmit wireless baseband signals with the help of low-complexity CDM to guide a low-complexity, low-cost and high-capacity fronthaul system. In addition, high-performance gains can be brought to the fronthaul system by using a powerful neural network (NN) equalizer. In this way, the provided fronthaul communication mechanism can be easily implemented at low cost and low overhead.

[0058] The following will refer to Figures 2A to 8 The principles and implementations of the present disclosure are described in detail. Figure 2A An example uplink transmission scenario 201 in a fronthaul system according to an example embodiment of the present disclosure is illustrated. Figure 2B An example downlink transmission scenario 202 in a fronthaul system according to an example embodiment of the present disclosure is illustrated. In the context of the example embodiments, the direction from the UE to the network is referred to as the uplink (UL) and the direction from the network to the UE is referred to as the downlink (DL).

[0059] The example network environment is a fronthaul system, which involves a plurality of RRHs 210-1 to 210-N (hereinafter may be collectively referred to as RRHs 210), an aggregator 220, an optical fronthaul link 230, and a BBU pool 240. The aggregator 220 includes a group of first ADCs 221-1 to 221-n for UL transmission, a CDM 222, and a first DAC 223. In addition, the aggregator 220 includes a second ADC 224 for DL ​​transmission, a CD-DM (code demultiplexer) 225, and a group of second DACs 226-1 to 226-n.

[0060] BBU 240 includes ADC 241, equalizer 242, and CD-DM 243 for UL transmission. In addition, BBU 240 includes equalizer 242, CDM 244, and DAC 245 for DL ​​transmission. Equalizer 242 may be an NN-based equalizer. BBU 240 may include, for example, a combination of CU and DU defined in O-RAN.

[0061] The CDM 222 in the aggregator 220 is configured to apply code division multiplexing to the samples obtained from the set of first ADCs 221-1 based on Walsh codes. The CD-DM 225 is configured to apply code demultiplexing to the equalized signals obtained from the equalizer 242 based on different Walsh codes.

[0062] Hereinafter, for uplink transmission in the fronthaul network, the Walsh code used for code division multiplexing is referred to as the first Walsh code, and the Walsh code used for code division de-multiplexing is referred to as the second Walsh code. The first Walsh code corresponds to the second Walsh code, both of which are a set of mutually orthogonal sequences consisting of '1' and '-1'.

[0063] Similarly, for downlink transmission in the fronthaul network, the Walsh code used for code division multiplexing is called the third Walsh code, and the Walsh code used for code decomposition multiplexing is called the fourth Walsh code, and the third Walsh code corresponds to the fourth Walsh code. The third Walsh code corresponds to the fourth Walsh code, and both of them are a set of mutually orthogonal sequences consisting of '1' and '-1'.

[0064] The signal encoded based on the first Walsh code can be sent by one of the aggregator 220 and the BBU 240 to the other, and the other of the aggregator 220 and the BBU 240 can be decoded based on the second Walsh code to recover the signal. Compared with the FDM scheme adopted by the traditional fronthaul system, the CDM aggregation / deaggregation scheme can achieve greater tolerance to power fading caused by chromatic dispersion (CD) in the optical fiber (i.e., the optical fronthaul link 230).

[0065] For example, for UL transmission, the aggregator 220 assigns a first Walsh code dedicated to each wireless signal corresponding to a corresponding wireless channel in the wireless signal, the corresponding wireless channel having the RRH 210 performing code division multiplexing. Additionally, the aggregator 220 may provide a first code-channel comparison table to the BBU 240 through a control channel. Using the table, in code division multiplexing, the BBU 240 is able to configure a second Walsh code for decoding the signal encoded by the aggregator 220 based on the first Walsh code.

[0066] Another example is that, for DL ​​transmission, the BBU 240 assigns the third Walsh code to the data stream to be transmitted to the UE via the corresponding wireless channel in code division multiplexing. Additionally, the aggregator 220 may provide the BBU 240 with a second code channel comparison table for DL ​​transmission. Accordingly, in code division multiplexing, the BBU 240 is able to configure the third Walsh code for encoding the signal to be delivered in the optical fronthaul link 230. In code division multiplexing, the aggregator 220 configures the fourth Walsh code for decoding by the BBU 240 the signal encoded based on the third Walsh code.

[0067] Different code division multiplexing schemes may be used in UL and DL transmissions. For example, the first code channel comparison table used for UL transmission may be different from the second code channel comparison table used for DL ​​transmission. In this case, the first orthogonal code may be different from the third orthogonal code, and therefore, the second orthogonal code is also different from the fourth orthogonal code.

[0068] In the following description, the fronthaul system is configured using the system parameters shown in Table 2.

[0069] Table 2 - System parameters of the fronthaul system

[0070]

[0071] Now to Figure 2A Reference is made to discuss the UL transmission scenario 201 in the fronthaul system. Figure 2A As shown in , the antennas at RRH210-1 to 210-n receive wireless signals from end users (i.e., UEs). Then, RRH 210-1 to 210-n convert the received wireless signals from the radio frequency (RF) band to the intermediate frequency (IF) band through down-conversion units 212-1 to 212-n. According to the configuration in Table 2, the number of wireless signals is 48, and the bandwidth of each wireless baseband signal is 100 MHz. The wireless signals are modulated by orthogonal frequency division multiplexing (OFDM), and each signal has a cyclic prefix (CP) of 256 subcarriers and 4 symbols. Copper cables are used to connect RRH 210 and aggregator 220.

[0072] Aggregator 220 is adopted to aggregate wireless baseband signals by using code division multiplexing, which is implemented at CDM 222. Specifically, the analog IF signal received via the copper cable is first down-converted to baseband through a mixer and a local oscillator (LO). The first ADC 221-1 to 221-n samples the in-phase (I) and quadrature (Q) baseband signals in each channel at a sampling rate of 122.88 MHz and 15 effective sampling bits. CDM 221 repeats each sample in the sample (which may also be referred to as a set of first signals hereinafter) M times, where M is the code length of the Walsh code, and then multiplies each repeated sample by the corresponding first Walsh code set. Figure 2A and Figure 2B In the example scenario, M is 64, that is, each sample is repeated 64 times, and then multiplied by the corresponding first Walsh code set with a code length of 64 at CDM222. Here, each channel is assigned a corresponding Walsh code set, and all 48 Walsh code sets are mutually orthogonal. After code division multiplexing, the 48 coded signals are added together in the time domain to form a CDM signal.

[0073] In some cases, after forming the CDM signal, CDM 222 may insert a training pilot sequence consisting of '0' and '1' at the beginning of the CDM signal, which will be discussed in detail later. DAC 223 with a sampling rate of 15.73 GHz is employed to convert the CDM signal into an analog CDM signal to be delivered in optical fronthaul link 230.

[0074] The optical fronthaul link 230 may be an optical fiber connected to the BBU 240. In order to reduce system cost, an intensity modulation-direct detection (IM-DD) scheme may be applied in the optical fronthaul link 230. Figure 2A and Figure 2BAs shown in , the electrical signal is E / O converted by using a 1550nm electro-absorption modulated laser (EML). The optical CDM signal is sent into a 20km optical fiber with an output power of 6dBm. After transmission, the photodetector (PD) converts the optical signal into an electrical signal.

[0075] The incoming signal into the BBU 240 is sampled by the ADC 241 at a sampling rate of 31.46 GHz, thereby obtaining a digital CDM signal. The equalizer 242 is configured to equalize the digital CDM signal.

[0076] In some example embodiments, the equalizer 242 may be a NN-based equalizer that utilizes a NN with two layers. Prior to equalization, NN training has been implemented to configure the NN weights and biases of the NN. As previously mentioned, the aggregator 220 may insert a training pilot at the beginning of the CDM signal and use the training pilot as an input to the NN during the training phase. Training of the NN may be stopped until a stopping criterion is met. For example, the stopping criterion may be that at least one equalization performance of the equalizer 242 meets a predetermined requirement, such as exceeding a predetermined threshold, etc. Alternatively, the stopping criterion may be that the training has been performed for a predetermined number of iterations. It should be understood that for example embodiments, any other criteria for stopping iterations may also be used. Therefore, the present disclosure is not limited in this regard.

[0077] The NN weights and biases will converge after several iterations (e.g., about 1e3 iterations), and the loss expressed by the MSE function can reach about 1e-8. In this case, the NN is considered to be trained and can be used to equalize the CDM signal for the purpose of mitigating channel impairments induced in the optical fronthaul link 230. Since the equalized CDM signal has been repeated 64 times, the CD-DM 243 performs code demultiplexing on the equalized CDM signal based on the second orthogonal code to obtain a set of CD-DM signals corresponding to the corresponding wireless channels. In some example embodiments, MIMO demodulation, OFDM demodulation, and one-tap equalization may also be implemented one by one to recover user data.

[0078] In some example embodiments, after the equalized CDM signal is decoded by CD-DM 243, at least one property of the decoded signal (ie, CD-DM signal) may be continuously monitored, and if the performance is degraded, further training may be required. Figure 3 A signaling diagram of a training process for a fronthaul network according to some example embodiments of the present disclosure is shown.

[0079] like Figure 3As shown in , the aggregator 220 sends 305 a CDM signal with a pilot sequence inserted therein for training the NN-based equalizer 242 at the BBU 240. The BBU 240 performs 310 NN training on the equalizer 242 until a stop criterion is met. Then, the aggregator 220 sends 315 another CDM signal to the BBU 240. After decoding the CDM signal, the BBU 240 monitors 320 at least one equalization performance of the decoded signal. For example, the BBU 240 may determine whether at least one performance of interest meets a predetermined requirement (e.g., exceeds a predefined threshold, etc.). If the BBU 240 determines 325 that the performance is below the predefined threshold, the BBU 240 sends 330 a training pilot request for triggering NN training. Upon receiving the training pilot request, the aggregator 220 may generate 325 a CDM signal with a training pilot sequence inserted therein. Then, the aggregator 220 sends 340 the CDM signal to the BBU 240. After receiving such a CDM signal, the BBU 240 may perform 345 NN training on the equalizer 242 in an iterative manner based on the pilot sequence until a stopping criterion is met. Similarly, the stopping criterion may be that at least one equalization performance of the equalizer 242 meets a predetermined requirement, such as exceeding a predetermined threshold. Alternatively, the stopping criterion may be that the training has been performed for a predetermined number of iterations.

[0080] Figure 4 The figure illustrates the simulation results of EVM performance and received optical power based on the fronthaul communication scheme according to some example embodiments of the present disclosure. Figure 4 As clearly shown in FIG. 1 , the NN-based equalizer according to the exemplary embodiment can effectively mitigate the linear and nonlinear distortions induced by the channel and improve the receiving sensitivity by ∼1 dB and ∼3 dB at the EVM thresholds of 8% and 6%. In addition, Figure 4 The simulation results of two different types of signals (ie, CDM signal and OOK signal) as training pilots are also shown. It can be found that no obvious performance difference is observed, which indicates that the training pilot of OOK format is feasible.

[0081] Now to Figure 2B Reference is made to discuss the DL transmission scenario 202 in the fronthaul system. Figure 2BAs shown in , a set of data streams to be delivered to UEs at RRHs 210-1 to 210-n can be sent from the core network. The set of data streams can first be up-converted to an intermediate frequency band. The CDM 244 at the BBU 240 applies code division multiplexing to each of the set of data streams based on the corresponding third orthogonal code set for the corresponding wireless channel. Similar to the code division multiplexing performed at the CDM 222, the CDM 244 repeats each sample M times, where M is the code length of the Walsh code, and then multiplies each repeated sample by the corresponding first Walsh code set. After code division multiplexing, the CDM 244 aggregates the set of coded signals corresponding to the corresponding wireless channel into a CDM signal.

[0082] The equalizer 242 may pre-equalize the CDM signal with respect to at least one equalization property of interest. In some example embodiments, the equalizer 242 may have been well trained based on training data (e.g., training pilot sequences). An equalized CDM signal is thereby obtained. The DAC 242 converts the equalized CDM signal into an analog CDM signal (which may also be referred to as a third signal hereinafter) to be delivered in the optical fronthaul link 230.

[0083] The second ADC 224 in the aggregator 220 samples the third signal to obtain a digital CDM signal. The CD-DM 225 in the aggregator 220 performs code demultiplexing on the digital CDM signal based on a fourth orthogonal code to obtain a set of CD-DM signals corresponding to corresponding wireless channels. The fourth orthogonal code corresponds to the third orthogonal code.

[0084] In some example embodiments, the CD-DM 225 may divide the digital CDM signal into a predetermined number of portions and multiply each portion of the digital CDM signal by a corresponding fourth set of orthogonal codes to obtain the set of CD-DM signals.

[0085] Then, the group of DACs 226-1 to 226-n convert the group of CD-DM signals into a group of analog CD-DM signals for delivery in corresponding wireless channels. Then, the group of analog CD-DM signals can be converted from the IF band to the RF band by down-conversion and sent to the RRH 210 via a copper cable.

[0086] The group of analog baseband signals received by the RRH 210 may be converted from the RF band to the IF band by the up-conversion units 214-1 to 214-n. Thus, a group of second wireless signals are obtained and transmitted to the end user via the antenna at the RRH 210.

[0087] It should also be understood that Figure 2A and Figure 2BThe system parameters / configurations and the number of devices and units in the described exemplary embodiments are given for illustrative purposes only and do not limit the scope of the present disclosure. In practice, the fronthaul communication mechanism provided according to the exemplary embodiments can be implemented by using any other system parameters or settings. In addition, the number of devices or units in the aggregator and BBU pool can be more or less, or even Figure 2A-2B Devices not shown.

[0088] Depending on the communication technology, the network system of the example embodiment can be a code division multiple access (CDMA) network, a time division multiple access (TDMA) network, a frequency division multiple access (FDMA) network, an orthogonal frequency division multiple access (OFDMA) network, a single carrier frequency division multiple access (SC-FDMA) network, an O-RAN compatible network, or any other network. The open radio access network O-RAN (or Open RAN or ORAN) is defined by the Open RAN Alliance and refers to the concept of interoperability of RAN elements between different vendors through a set of defined interfaces. For example, Open RAN defines open interfaces between network elements. Therefore, the O-RAN architecture enables, for example, baseband units and radio unit components from different vendors to operate together.

[0089] The communication discussed in the network, i.e. Figure 2A The UL transmission scenario 201 and Figure 2B The DL transmission scenario 202 shown in the figure may conform to any appropriate standard, including but not limited to New Radio Access (NR), Long Term Evolution (LTE), Evolved LTE, Advanced LTE (LTE-A), Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access (CDMA), cdma2000, and Global System for Mobile Communications (GSM), etc. In addition, communications may be performed according to any generation of communication protocols currently known or developed in the future. Examples of communication protocols include but are not limited to first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, fifth generation (5G), and future sixth generation communication protocols. The techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies.

[0090] According to an exemplary embodiment of the present disclosure, a fronthaul communication mechanism enhanced by a solution based on CDM and NN is provided. In the proposed mechanism, the A-RoF scheme is utilized to achieve high capacity because it can aggregate dozens of wireless baseband signals with high spectral efficiency. The aggregator of the fronthaul system encodes the signal based on CDM, thereby reducing complexity and cost. In addition, CDM can provide relatively large tolerance to power fading caused by chromatic dispersion (CD) in optical fiber and high coding gain.

[0091] Additionally or alternatively, in the proposed mechanism, the equalizer at the BBU can be trained in advance or during operation based on NN technology. Therefore, the NN-enabled equalizer brings high performance gains. This provides a simple implementation and low cost, because the complex calculations are implemented by the BBU pool and only the length of the NRZ data is inserted into the transmission signal at the aggregator. Last but not least, the proposed mechanism benefits from low overhead because the optical channel based on fiber is very stable and the trained NN can be used for a long time.

[0092] Figure 5 A flow chart of an example method 500 of fronthaul communication according to some example embodiments of the present disclosure is illustrated. The method 500 may be performed at an aggregator (e.g., Figure 2A The process 500 is implemented at the aggregator 220 shown in FIG. 1 ) or any other network device of the fronthaul network. The process 500 relates to uplink transmission in the fronthaul network and may involve the RRH 210, the aggregator 220, the optical fronthaul link 230, and the BBU pool 240. For the purpose of discussion, reference will be made to Figure 2A Process 500 is described.

[0093] At 510, the aggregator 220 converts a group of first wireless signals into a group of first signals corresponding to corresponding wireless channels.

[0094] At 520, the aggregator 220 applies code division multiplexing to each of the first signals based on a corresponding first set of orthogonal codes for the corresponding wireless channel to obtain a set of coded signals corresponding to the corresponding wireless channel.

[0095] At 530, the aggregator 220 aggregates the set of coded signals into a CDM signal.

[0096] In some example embodiments, aggregator 220 may repeat each of the first signals a predetermined number of times. The predetermined number of times corresponds to the length of the corresponding first orthogonal code set. Aggregator 220 may then multiply each repeated first signal by the corresponding first orthogonal code set to obtain a set of coded signals. Aggregator 220 may multiplex the set of coded signals into a CDM signal.

[0097] In some example embodiments, aggregator 220 may insert a pilot sequence into the CDM signal for training equalizer 242 in BBU 240, which is configured to receive an uplink signal (e.g., the second signal) or transmit a downlink signal (e.g., the third signal). The pilot sequence may include, but is not limited to, a CDM pilot signal, an NRZ-OOK signal, and the like.

[0098] In some example embodiments, the pilot sequence may be inserted in response to a training pilot request from the BBU 240. For example, if it is monitored that at least one equalization performance of the BBU 240 does not meet a predetermined requirement or does not meet a predetermined criterion, the BBU 240 may send a training pilot request to the aggregator 220. Upon receiving the training pilot request, the aggregator 220 may insert the training pilot sequence at the beginning of the CDM signal generated in the CDM 222. After receiving such a CDM signal, the NN-based equalizer 242 at the BBU 240 will be trained in an iterative manner based on the pilot sequence until a stopping criterion is met. The stopping criterion may be that at least one equalization performance of the equalizer 242 meets a predetermined requirement, such as exceeding a predetermined threshold. Alternatively, the stopping criterion may be that the training has been performed for a predetermined number of iterations. It should be understood that for example embodiments, any other criteria for stopping iterations may also be used. Therefore, the present disclosure is not limited in this regard.

[0099] At 540, the aggregator 220 converts the CDM signal obtained from the CDM into a second signal for delivery in the optical fronthaul link. Specifically, the CDM signal may be converted into the second signal by the DAC 223 in the aggregator 220, and thus the second signal is an analog CDM signal.

[0100] In some example embodiments, the second signal will be processed by the BBU 240 of the fronthaul network based on code demultiplexing using a second orthogonal code corresponding to the first orthogonal code.

[0101] The first orthogonal code and the second orthogonal code may be pre-configured at aggregator 220. In some example embodiments, aggregator 220 may send a first code channel comparison table to BBU 240 for determining the first orthogonal code and the second orthogonal code. In this way, BBU 240 may perform code division multiplexing and code demultiplexing based on the first and second orthogonal codes, respectively.

[0102] Figure 6 A flow chart of an example method 600 for fronthaul communication according to some example embodiments of the present disclosure is illustrated. The method 600 may be performed at a BBU (e.g., Figure 2A The process 600 is implemented at the BBU pool 240 shown in the figure) or any other network device of the fronthaul network. The process 600 involves uplink transmission in the fronthaul network and may involve RRH 210, aggregator 220, optical fronthaul link 230 and BBU pool 240. For the purpose of discussion, reference will be made to Figure 2A Process 600 is described.

[0103] At 610, the BBU 240 converts the second signal delivered in the optical fronthaul link 230 into a CDM signal. Specifically, the second signal received from the aggregator 220 may be an analog CDM signal, and the CDM signal has been processed by the aggregator 220 of the fronthaul network based on code division multiplexing using the first orthogonal code of the corresponding wireless channel. Specifically, the ADC 241 in the BBU 240 may convert the incoming second signal into a digital CDM signal. Figure 5 The code division multiplexing applied by aggregator 220 is described.

[0104] At 620, the BBU 240 equalizes the CDM signal with respect to at least one equalization property. For example, the CDM signal may be equalized by the NN-based equalizer 242 in the BBU 240. In some example embodiments, the NN-based equalizer 242 may be trained based on a training pilot sequence.

[0105] In some example embodiments, a pilot sequence may be inserted into the CDM signal to train at least one equalization property of the equalizer 242 in the BBU 240. The equalizer may be an NN-based equalizer configured to be trained in an iterative manner based on the pilot sequence until a stopping criterion is met. The stopping criterion may be that at least one equalization property meets a predetermined requirement, such as a predetermined threshold. Alternatively, the stopping criterion may be that the training has been performed for a predetermined number of iterations. It should be understood that for example embodiments, any other criteria for stopping iterations may also be used. Therefore, the present disclosure is not limited in this regard.

[0106] NN training is performed using the training data, and NN weights and biases are generated. Finally, the NN is configured with the trained NN parameters and in turn is used to balance the payload signal.

[0107] The BBU 240 may monitor at least one equalization property of the equalized CDM signal, and the monitoring may be implemented by a controller of the BBU 240 .

[0108] In some example embodiments, if BBU 240 determines that at least one equalization performance of the equalized CDM signal does not meet the predetermined requirement, BBU 240 may send a training pilot request to aggregator 220. Aggregator 220, upon receiving the training pilot request, may send a CDM signal into which a pilot sequence is inserted. The pilot sequence may include, but is not limited to, a CDM pilot signal, an NRZ-OOK signal, etc. In this case, BBU 240 will obtain the CDM signal into which the pilot sequence is inserted for training equalizer 242 with respect to at least one equalization performance.

[0109] At 630, the BBU 240 applies code demultiplexing to the equalized CDM signal based on a second orthogonal code for obtaining a set of CD-DM signals corresponding to corresponding wireless channels. The second orthogonal code corresponds to the first orthogonal code.

[0110] Code demultiplexing may be implemented by CD-DM 243 in BBU 240. CD-DM 243 may divide the equalized CDM signal into a predetermined number of parts, and the predetermined number corresponds to the length of the corresponding second orthogonal code set. CD-DM 243 may then multiply each part of the equalized CDM signal by the corresponding second orthogonal code set to obtain the group of CD-DM signals.

[0111] The first orthogonal code and the second orthogonal code may be preconfigured at aggregator 220. In some example embodiments, BBU 240 may receive a first code channel comparison table from aggregator 220, and the code channel comparison table is configured to determine the first orthogonal code and the second orthogonal code.

[0112] Methods 500 and 600 may be implemented in an uplink transmission from RRH 210 to BBU 240. In some example embodiments, the fronthaul system may include aggregator 220, BBU 240, and an optical fronthaul link connecting aggregator 220 and BBU 240.

[0113] According to an example embodiment of the present disclosure, an enhanced communication mechanism for a fronthaul link in a 5G and above wireless communication system is provided. In the enhanced mechanism, the aggregator and BBU of the fronthaul network can adopt CDM aggregation / deaggregation. In addition, the equalization in the BBU can be achieved by a neural network. In this way, the proposed solution can provide the advantages of high capacity, low cost, easy implementation, and greater tolerance to channel impairments.

[0114] Figure 7 1 is a flow chart illustrating an example method 700 for fronthaul communication according to some example embodiments of the present disclosure. The method 700 may be performed at a BBU (e.g., Figure 2B The process 700 is implemented at the BBU pool 240 shown in the figure) or any other network device of the fronthaul network. The process 700 involves downlink transmission in the fronthaul network and may involve RRH 210, aggregator 220, optical fronthaul link 230 and BBU pool 240. For the purpose of discussion, reference will be made to Figure 2B Process 700 is described.

[0115] At 710, the BBU 240 applies code division multiplexing to each of a set of data streams based on a corresponding third set of orthogonal codes for a corresponding wireless channel to obtain a set of coded signals corresponding to the corresponding wireless channel.

[0116] Code division multiplexing may be implemented by CDM 244 in BBU 240. In some example embodiments, CDM 244 may repeat each of a set of data streams a predetermined number of times, and the predetermined number of times corresponds to the length of the corresponding third orthogonal code set. CDM 244 may multiply each repeated data stream by the corresponding third orthogonal code set to obtain the set of coded signals. CDM 244 may multiplex the set of coded signals into a CDM signal.

[0117] At 720, the BBU 240 aggregates the set of coded signals into a CDM signal.

[0118] At 730 , the BBU 240 pre-equalizes the CDM signal with respect to at least one equalization property to obtain an equalized CDM signal.

[0119] At 740, the BBU 240 converts the equalized CDM signal into a third signal to be delivered in the optical fronthaul link 230. The third signal will be processed by the aggregator 220 of the fronthaul network by code demultiplexing based on a fourth orthogonal code corresponding to the third orthogonal code.

[0120] The third and fourth orthogonal codes may be preconfigured at aggregator 220. In some example embodiments, BBU 240 may receive a second code channel comparison table from aggregator 220, and the second code channel comparison table is configured to determine the third and fourth orthogonal codes.

[0121] In some example embodiments, different code division multiplexing schemes are used in UL and DL transmissions. For example, the first code channel comparison table used for UL transmission can be different from the second code channel comparison table used for DL ​​transmission. In this case, the first orthogonal code can be different from the third orthogonal code, and therefore, the second orthogonal code is also different from the fourth orthogonal code.

[0122] Figure 8 A flow chart of an example method 800 of fronthaul communication according to some example embodiments of the present disclosure is illustrated. The method 800 may be performed at an aggregator (e.g., Figure 2B The process 800 is implemented at the aggregator 220 shown in FIG. 1 ) or any other network device of the fronthaul network. The process 800 involves downlink transmission in the fronthaul network and may involve RRH 210, aggregator 220, optical fronthaul link 230, and BBU pool 240. For ease of discussion, reference will be made to Figure 2B Process 800 is described.

[0123] At 810, the aggregator 220 converts the third signal delivered in the optical fronthaul link 230 into a digital CDM signal. The third signal may have been processed by the BBU 240 of the fronthaul network based on code division multiplexing using a third orthogonal code of the corresponding wireless channel. Figure 7Code division multiplexing applied by the BBU 240 is described.

[0124] At 820, the aggregator 220 performs code demultiplexing on the digital CDM signal based on a fourth orthogonal code to obtain a set of CD-DM signals corresponding to corresponding wireless channels. The fourth orthogonal code corresponds to the third orthogonal code.

[0125] Code decomposition multiplexing may be implemented by CD-DM 243 in aggregator 220. In some example embodiments, CD-DM 243 may divide the digital CDM signal into a predetermined number of parts, and the predetermined number may correspond to the length of the corresponding fourth orthogonal code set. CD-DM 243 may multiply each part of the digital CDM signal by the corresponding fourth orthogonal code set to obtain the group of CD-DM signals.

[0126] At 830, the aggregator 220 converts the set of CD-DM signals into a set of second wireless signals to be delivered in corresponding wireless channels.

[0127] The third orthogonal code and the fourth orthogonal code may be pre-configured at aggregator 220. In some example embodiments, aggregator 220 may send the second code channel comparison table to BBU 240 for determining the third orthogonal code and the fourth orthogonal code. In this way, BBU 240 may perform code division multiplexing and code demultiplexing based on the third and fourth orthogonal codes accordingly.

[0128] In some example embodiments, different code division multiplexing schemes are used in UL and DL transmissions. For example, the first code channel comparison table used for UL transmission may be different from the second code channel comparison table used for DL ​​transmission. In this case, the first orthogonal code may be different from the third orthogonal code, and accordingly, the second orthogonal code is also different from the fourth orthogonal code.

[0129] According to an exemplary embodiment of the present disclosure, an enhanced communication mechanism for an optical fronthaul link in a 5G and above wireless communication system is provided. In the enhanced mechanism, the aggregator of the fronthaul network assigns dedicated Walsh codes to different wireless signals and sends the corresponding code channel comparison table to the BBU via a control channel. By using this table, the BBU can configure the corresponding different Walsh codes for code decomposition multiplexing.

[0130] After decoding, the performance of the received signal can be continuously monitored. When the performance is below a predefined threshold, the BBU can send a training pilot request to the aggregator. In response to the request, the aggregator can send a training sequence in CDM format or NRZ format. In this way, NN training is implemented at the equalizer of the BBU using training data, and weights and biases are generated for the NN, and finally, the NN will be configured with the trained NN parameters and used in turn to equalize the payload signal. In this way, the NN-enabled equalizer can bring higher performance gains. Additionally, at the aggregator, only the length of the NRZ data is inserted in the transmitted signal, and the relatively complex calculations are performed by the BBU pool, so the mechanism can be easily implemented at low cost.

[0131] Fig. 9 900 is a simplified block diagram of a device suitable for implementing an embodiment of the present disclosure. The device 900 may be provided to implement a communication device, such as Figure 2A and Figure 2B The aggregator 220 and the BBU 240 shown in FIG. As shown, the device 900 includes one or more processors 910, one or more memories 920 coupled to the processors 910, and one or more transmitters and / or receivers (TX / RX) 940 coupled to the processors 910.

[0132] TX / RX 940 may be configured for bidirectional communication. TX / RX 940 has at least one antenna to facilitate communication. The communication interface may represent any interface required to communicate with other network elements.

[0133] Processor 910 may be of any type suitable for the local technology network, and may include, as non-limiting examples, one or more of a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. Device 900 may have multiple processors, such as application specific integrated circuit chips that are time slaved to a clock that synchronizes a main processor.

[0134] The memory 920 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memories include, but are not limited to, read-only memory (ROM) 924, electrically programmable read-only memory (EPROM), flash memory, hard disk, compact disk (CD), digital video disk (DVD), and other magnetic storage and / or optical storage media. Examples of volatile memories include, but are not limited to, random access memory (RAM) 922 and other volatile memories that do not persist during the duration of a power outage.

[0135] The computer program 930 includes computer executable instructions that can be executed by the associated processor 910. The program 930 can be stored in the ROM 924. The processor 910 can perform any appropriate actions and processes by loading the program 930 into the RAM 922.

[0136] The embodiments of the present disclosure can be implemented by means of program 930, so that the device 900 can execute the Figure 3 Any process of the present disclosure discussed. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0137] In some embodiments, the program 930 may be tangibly contained in a computer-readable medium, which may be included in the device 900 (e.g., in the memory 920) or in other storage devices accessible by the device 900. The device 900 may load the program 930 from the computer-readable medium to the RAM 922 for execution. The computer-readable medium may include any type of tangible non-volatile memory, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc. Fig.10 An example of a computer readable medium 1000 in the form of a CD or DVD is shown. The computer readable medium has a program 1030 stored thereon.

[0138] Various embodiments of the present disclosure may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software that may be executed by a controller, microprocessor, or other computing device. Although various aspects of the embodiments of the present disclosure are illustrated and described as block diagrams, flow charts, or using some other graphical representations. It should be understood that, as non-limiting examples, the blocks, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuits or logic, general hardware or controllers or other computing devices, or some combination thereof.

[0139] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer executable instructions, such as those included in a program module, which are executed in a device on a target real or virtual processor to perform the above-referenced Figure 5-Figure 8Described method 500,600,700 or 800.Generally, program modules can include routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types.In various embodiments, the functionality of program modules can be combined or split between program modules as desired.Machine executable instructions for program modules can be executed in local or distributed devices.In distributed devices, program modules can be located in local and remote storage media.

[0140] The program code for executing the method of the present disclosure can be written in any combination of one or more programming languages. These program codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer or other programmable data processing device so that when the program code is executed by the processor or controller, the functions / operations specified in the flow chart and / or block diagram are implemented. The program code can be executed completely on the machine, partially on the machine, as an independent software package, partially on the machine and partially on a remote machine, or completely on a remote machine or server.

[0141] In the context of the present disclosure, computer program codes or related data may be carried by any suitable carrier to enable an apparatus, device or processor to perform various processes and operations as described above. Examples of carriers include signals, computer readable media, etc.

[0142] The computer readable medium may be a computer readable signal medium or a computer readable storage medium. The computer readable medium may include, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared or semiconductor system, device or apparatus, or any suitable combination of the foregoing. More specific examples of computer readable storage media include an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0143] In addition, although each operation is described in a specific order, it should not be understood as requiring to perform these operations in the specific order shown or in order, or requiring to perform all illustrated operations to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details are included in the above discussion, these should not be interpreted as limitations on the scope of the present disclosure, but should be interpreted as descriptions of features that may be specific to a particular embodiment. Certain features described in the context of separate embodiments may also be combined in a single embodiment. On the contrary, the various features described in the context of a single embodiment may also be implemented separately in multiple embodiments or in any suitable sub-combination.

[0144] Although the disclosure has been described in language specific to structural features and / or methodological acts, it should be understood that the disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

[0145] Various example embodiments of these techniques have been described. In addition to or as an alternative to the above, the following examples are described. Features described in any of the following examples can be used with any other examples described herein.

[0146] In some aspects, an aggregator of a fronthaul network is provided. The aggregator includes a set of first analog-to-digital converters (ADCs), a code division multiplexer (CDM), and a first digital-to-analog converter (DAC). The set of first ADCs is coupled to the CDM and configured to convert a set of first wireless signals into a set of first signals corresponding to corresponding wireless channels. The CDM is coupled to the first digital-to-analog converter (DAC) and configured to apply code division multiplexing to each of the first signals based on a corresponding first orthogonal code set for the corresponding wireless channel to obtain a set of coded signals corresponding to the corresponding wireless channel; and aggregate the set of coded signals into a code division multiplexed (CDM) signal. The first DAC is configured to convert the CDM signal obtained from the CDM into a second signal for delivery in an optical fronthaul link.

[0147] In some embodiments, CDM is configured to apply code division multiplexing by: repeating each of the first signals a predetermined number of times corresponding to the length of the corresponding first orthogonal code set; and multiplying each repeated first signal by the corresponding first orthogonal code set to obtain the group of coded signals; and multiplexing the group of coded signals into a CDM signal.

[0148] In some embodiments, the second signal will be processed by a baseband unit (BBU) of the fronthaul network based on code demultiplexing with a second orthogonal code corresponding to the first orthogonal code.

[0149] In some embodiments, the aggregator also includes a second ADC, which is coupled to the code division multiplexer CD-DM and configured to convert a third signal delivered in the optical fronthaul link into a digital CDM signal, the third signal being processed by a baseband unit (BBU) of the fronthaul network based on code division multiplexing utilizing a third orthogonal code of the corresponding wireless channel; the CD-DM, which is coupled to a group of second DACs and configured to: apply code division multiplexing to the digital CDM signal based on a fourth orthogonal code to obtain a group of CD-DM signals corresponding to the corresponding wireless channels, the fourth orthogonal code corresponding to the third orthogonal code; and a group of second DACs configured to convert the group of CD-DM signals into a group of second wireless signals to be delivered in the corresponding wireless channels.

[0150] In some embodiments, the CD-DM is configured to apply code decomposition multiplexing by: dividing the digital CDM signal into a predetermined number of parts, the predetermined number corresponding to the length of the corresponding fourth orthogonal code set; and multiplying each part of the digital CDM signal by the corresponding fourth orthogonal code set to obtain the group of CD-DM signals.

[0151] In some embodiments, the first and second orthogonal codes and the third and fourth orthogonal codes are pre-configured at the aggregator, and the aggregator is further configured to: transmit a first code channel comparison table to the BBU for determining the first orthogonal code and the second orthogonal code; and send a second code channel comparison table to the BBU for determining the third orthogonal code and the fourth orthogonal code.

[0152] In some embodiments, the CDM is further configured to insert a pilot sequence into the CDM signal for training an equalizer in a baseband unit (BBU) of the fronthaul network, the BBU being configured to receive the second signal or to transmit the third signal.

[0153] In some embodiments, the aggregator also includes a second ADC, which is coupled to a code division multiplexer (CD-DM) and configured to convert a third signal delivered in the optical fronthaul link into a digital CDM signal, the third signal being processed by a baseband unit (BBU) of the fronthaul network based on code division multiplexing utilizing a third orthogonal code of the corresponding wireless channel; the CD-DM, which is coupled to a group of second DACs and configured to: apply code division multiplexing to the digital CDM signal based on a fourth orthogonal code to obtain a group of CD-DM signals corresponding to the corresponding wireless channels, the fourth orthogonal code corresponding to the third orthogonal code; and a group of second DACs configured to convert the group of CD-DM signals into a group of second wireless signals to be delivered in the corresponding wireless channels.

[0154] In some embodiments, the first and second orthogonal codes and the third and fourth orthogonal codes are pre-configured at the aggregator, and the aggregator is further configured to: send a first code channel comparison table to the BBU for determining the first orthogonal code and the second orthogonal code; and send a second code channel comparison table to the BBU for determining the third orthogonal code and the fourth orthogonal code.

[0155] In some embodiments, the CDM is further configured to insert a pilot sequence into the CDM signal for training an equalizer in a baseband unit (BBU) of the fronthaul network, the BBU being configured to receive the second signal or transmit the third signal.

[0156] In some embodiments, the pilot sequence comprises a CDM pilot signal or a non-return-to-zero on-off keying (NRZ-OOK) signal.

[0157] In some embodiments, the pilot sequence is inserted in response to a training pilot request from the BBU.

[0158] In some aspects, a BBU of a fronthaul network is provided. The BBU includes an ADC, an equalizer, and a code division multiplexer (CD-DM). The ADC is coupled to the equalizer and is configured to convert a second signal delivered in an optical fronthaul link into a digital CDM signal, which is processed by an aggregator of the fronthaul network based on code division multiplexing using a first orthogonal code of a corresponding wireless channel. The equalizer is coupled to the CD-DM and is configured to equalize the CDM signal in at least one equalization performance aspect. The CD-DM is configured to apply code division multiplexing to the equalized CDM signal based on a second orthogonal code to obtain a set of CD-DM signals corresponding to the corresponding wireless channel, and the second orthogonal code corresponds to the first orthogonal code.

[0159] In some embodiments, the CD-DM is configured to apply code decomposition multiplexing by: dividing the equalized CDM signal into a predetermined number of parts, the predetermined number corresponding to the length of the corresponding second orthogonal code set; and multiplying each part of the equalized CDM signal by the corresponding second orthogonal code set to obtain a set of CD-DM signals.

[0160] In some embodiments, the BBU further comprises: a code division multiplexer (CDM) coupled to the equalizer and configured to: apply code division multiplexing to each of a group of data streams based on a corresponding third orthogonal code set for the corresponding wireless channel to obtain a group of coded signals corresponding to the corresponding wireless channel; and aggregate the group of coded signals into a code division multiplexed (CDM) signal; and the equalizer is further configured to pre-equalize the CDM signal with respect to at least one equalization performance to obtain an equalized CDM signal; and a digital-to-analog converter DAC coupled to the equalizer and configured to convert the equalized CDM signal into a third signal to be delivered in the optical fronthaul link.

[0161] In some embodiments, CDM is configured to apply code division multiplexing by: repeating each of a set of data streams a predetermined number of times corresponding to the length of a corresponding third orthogonal code set; multiplying each repeated data stream by a corresponding third orthogonal code set to obtain the set of coded signals; and multiplexing the set of coded signals into a CDM signal.

[0162] In some embodiments, the third signal will be processed by an aggregator of the fronthaul network based on code demultiplexing using a fourth orthogonal code corresponding to the third orthogonal code.

[0163] In some embodiments, the first and second orthogonal codes and the third and fourth orthogonal codes are pre-configured at the aggregator, and the BBU is further configured to: receive a first code channel comparison table from the aggregator for determining the first orthogonal code and the second orthogonal code; and receive a second code channel comparison table from the aggregator for determining the third orthogonal code and the fourth orthogonal code.

[0164] In some embodiments, a pilot sequence is inserted into the CDM signal for training at least one equalization property of the equalizer.

[0165] In some embodiments, the equalizer comprises a neural network based equalizer configured to be trained in an iterative manner based on a pilot sequence until a stopping criterion is met.

[0166] In some embodiments, the stopping criterion includes: at least one equalization performance meets a predetermined requirement.

[0167] In some embodiments, a controller is also included, which is configured to: send a training pilot request to an aggregator based on determining that at least one equalization performance of the equalized CDM signal does not meet a predetermined requirement; and obtain a CDM signal with a pilot sequence inserted for training the equalizer in at least one equalization performance.

[0168] In some embodiments, the pilot sequence comprises a CDM pilot signal or a non-return-to-zero on-off keying (NRZ-OOK) signal.

[0169] In some aspects, a fronthaul system is provided, comprising an aggregator according to the first aspect, a BBU according to the second aspect, and an optical fronthaul link connecting the aggregator and the BBU.

[0170] In some aspects, a method is provided. The method includes: at an aggregator of a fronthaul network, converting a set of first wireless signals into a set of first signals corresponding to corresponding wireless channels; applying code division multiplexing to each of the first signals based on a corresponding first orthogonal code set for the corresponding wireless channel to obtain a set of coded signals corresponding to the corresponding wireless channel; aggregating the set of coded signals into a code division multiplexed (CDM) signal; and converting the CDM signal obtained from the CDM into a second signal for delivery in an optical fronthaul link of the fronthaul network.

[0171] In some aspects, a method is provided. The method includes: at a baseband unit (BBU) of the fronthaul network, converting a second signal delivered in an optical fronthaul link of the fronthaul network into a digital code division multiplexed (CDM) signal, the digital CDM signal being processed by an aggregator of the fronthaul network based on code division multiplexing using a first orthogonal code of a corresponding wireless channel; equalizing the CDM signal in at least one equalization performance aspect; and applying code division multiplexing to the equalized CDM signal based on a second orthogonal code to obtain a set of CD-DM signals corresponding to the corresponding wireless channel, the second orthogonal code corresponding to the first orthogonal code.

[0172] In some aspects, a method is provided. The method includes: applying code division multiplexing to each of a set of data streams based on a corresponding third orthogonal code set for a corresponding wireless channel at a baseband unit (BBU) of a fronthaul network to obtain a set of coded signals corresponding to the corresponding wireless channel; aggregating the set of coded signals into a code division multiplexed (CDM) signal; pre-equalizing the CDM signal in at least one equalization performance aspect to obtain an equalized CDM signal; and converting the equalized CDM signal into a third signal to be delivered in an optical fronthaul link.

[0173] In some aspects, a method is provided. The method includes: at an aggregator of a fronthaul network, converting a third signal delivered in an optical fronthaul link into a digital CDM signal, the third signal being processed by a baseband unit (BBU) of the fronthaul network based on code division multiplexing with a third orthogonal code for a corresponding wireless channel; applying code division multiplexing to the digital CDM signal based on a fourth orthogonal code to obtain a set of CD-DM signals corresponding to the corresponding wireless channel, the fourth orthogonal code corresponding to the third orthogonal code; and converting the set of CD-DM signals into a set of second wireless signals to be delivered in the corresponding wireless channel.

[0174] In some aspects, a computer readable medium is provided, on which a computer program is stored, and when the computer program is executed by at least one processor of a device, the device is caused to perform the method according to the above aspects.

[0175] In some aspects, an apparatus is provided. The apparatus includes means for converting a set of first wireless signals into a set of first signals corresponding to respective wireless channels at an aggregator of a fronthaul network; means for applying code division multiplexing to each of the first signals based on a corresponding first orthogonal code set for the respective wireless channels to obtain a set of coded signals corresponding to the respective wireless channels; means for aggregating the set of coded signals into a code division multiplexed (CDM) signal; and means for converting the CDM signal obtained from the CDM into a second signal for delivery in an optical fronthaul link.

[0176] In some aspects, an apparatus is provided. The apparatus includes a component for converting a second signal delivered in an optical fronthaul link at a baseband unit (BBU) of a fronthaul network into a digital code division multiplexed (CDM) signal, the digital CDM signal being processed by an aggregator of the fronthaul network based on code division multiplexing using a first orthogonal code of a corresponding wireless channel; a component for equalizing the CDM signal with respect to at least one equalization property; and a component for applying code division multiplexing to the equalized CDM signal based on a second orthogonal code to obtain a set of CD-DM signals corresponding to the corresponding wireless channel, the second orthogonal code corresponding to the first orthogonal code.

[0177] In some aspects, an apparatus is provided. The apparatus includes: means for applying code division multiplexing to each of a set of data streams based on a corresponding third orthogonal code set for a corresponding wireless channel at a baseband unit (BBU) of a fronthaul network to obtain a set of coded signals corresponding to the corresponding wireless channel; means for aggregating the set of coded signals into a code division multiplexed (CDM) signal; means for pre-equalizing the CDM signal with respect to at least one equalization property to obtain an equalized CDM signal; and means for converting the equalized CDM signal into a third signal to be delivered in an optical fronthaul link.

[0178] In some aspects, an apparatus is provided. The apparatus includes: a component for converting a third signal delivered in an optical fronthaul link at an aggregator of a fronthaul network into a digital CDM signal, the third signal being processed by a baseband unit (BBU) of the fronthaul network based on code division multiplexing with a third orthogonal code for a corresponding wireless channel; a component for applying code division multiplexing to the digital CDM signal based on a fourth orthogonal code to obtain a set of CD-DM signals corresponding to the corresponding wireless channel, the fourth orthogonal code corresponding to the third orthogonal code; and a component for converting the set of CD-DM signals into a set of second wireless signals to be delivered in the corresponding wireless channel.

[0179] In some aspects, an apparatus is provided, including an aggregator according to an embodiment of the present disclosure.

[0180] In some aspects, an apparatus is provided, which includes a BBU according to an embodiment of the present disclosure.

Claims

1. An aggregator of a fronthaul network, comprising: a group of first analog-to-digital converters ADC, the group of first analog-to-digital converters ADC being coupled to the code division multiplexer CDM and configured to convert a group of first wireless signals into a group of first signals corresponding to corresponding wireless channels; The CDM is coupled to a first digital-to-analog converter DAC and is configured to: applying code division multiplexing to each of the first signals based on a corresponding first set of orthogonal codes for a corresponding wireless channel to obtain a set of coded signals corresponding to the corresponding wireless channel; as well as Aggregating the set of coded signals into a code division multiplexed (CDM) signal; and the first DAC, the first DAC being configured to convert the CDM signal obtained from the CDM into a second signal for delivery in an optical fronthaul link.

2. The aggregator of claim 1, wherein the CDM is configured to apply the code division multiplexing by: repeating each of the first signals a predetermined number of times, the predetermined number corresponding to the length of the corresponding first orthogonal code set; as well as multiplying each repeated first signal by the corresponding first orthogonal code set to obtain the set of coded signals; as well as The set of coded signals is multiplexed into the CDM signal.

3. The aggregator according to claim 1, wherein the second signal is to be processed by a baseband unit (BBU) of the fronthaul network based on code demultiplexing using a second orthogonal code corresponding to the first orthogonal code.

4. The aggregator of claim 1, further comprising: a second ADC coupled to the code division multiplexer CD-DM and configured to convert a third signal delivered in the optical fronthaul link into a digital CDM signal, the third signal being processed by a baseband unit BBU of the fronthaul network based on code division multiplexing using a third orthogonal code of a corresponding wireless channel; the CD-DM coupled to a set of second DACs and configured to: apply code demultiplexing to the digital CDM signals based on a fourth orthogonal code to obtain a set of CD-DM signals corresponding to the respective wireless channels, the fourth orthogonal code corresponding to the third orthogonal code; as well as The set of second DACs is configured to convert the set of CD-DM signals into a set of second wireless signals to be delivered in the corresponding wireless channels.

5. The aggregator of claim 4, wherein the CD-DM is configured to apply code demultiplexing by: dividing the digital CDM signal into a predetermined number of parts, the predetermined number corresponding to the length of a corresponding fourth orthogonal code set; and Each portion of the digital CDM signal is multiplied by the corresponding fourth set of orthogonal codes to obtain the set of CD-DM signals.

6. The aggregator according to claim 3 or claim 4, wherein the first and second orthogonal codes and the third and fourth orthogonal codes are pre-configured at the aggregator, and the aggregator is further configured to: sending a first code channel comparison table to the BBU for determining the first orthogonal code and the second orthogonal code; and A second code channel comparison table is sent to the BBU for determining the third orthogonal code and the fourth orthogonal code.

7. The aggregator of claim 1, wherein the CDM is further configured to: A pilot sequence is inserted into the CDM signal for training an equalizer in a baseband unit BBU of the fronthaul network, wherein the BBU is configured to receive the second signal or to send the third signal.

8. The aggregator of claim 7, wherein the pilot sequence comprises: CDM pilot signal, or non-return-to-zero on-off keying NRZ-OOK signal.

9. The aggregator of claim 7, wherein the pilot sequence is inserted in response to a training pilot request from the BBU.

10. A baseband unit BBU of a fronthaul network, comprising: an analog-to-digital converter ADC, the ADC being coupled to the equalizer and configured to convert a second signal delivered in the optical fronthaul link into a digital code division multiplexed CDM signal, the second signal being processed by an aggregator of the fronthaul network based on code division multiplexing using a first orthogonal code of a corresponding wireless channel; the equalizer coupled to the code demultiplexer CD-DM and configured to equalize the digital CDM signal with respect to at least one equalization property; as well as The CD-DM is configured to apply code demultiplexing to the equalized CDM signal based on a second orthogonal code to obtain a set of CD-DM signals corresponding to the corresponding wireless channels, wherein the second orthogonal code corresponds to the first orthogonal code.

11. The BBU of claim 10, wherein the CD-DM is configured to apply code division multiplexing by: dividing the equalized CDM signal into a predetermined number of parts, the predetermined number corresponding to the length of a corresponding second orthogonal code set; and Each portion of the equalized CDM signal is multiplied by the corresponding second set of orthogonal codes to obtain the set of CD-DM signals.

12. The BBU according to claim 10, further comprising: a code division multiplexer CDM, the CDM being coupled to the equalizer and configured to: applying code division multiplexing to each of a set of data streams based on a corresponding third set of orthogonal codes for a corresponding wireless channel to obtain a set of coded signals corresponding to the corresponding wireless channel; as well as Aggregating the set of coded signals into a code division multiplexed (CDM) signal; and the equalizer, the equalizer being further configured to pre-equalize the CDM signal with respect to the at least one equalization property to obtain an equalized CDM signal; as well as A digital-to-analog converter DAC is coupled to the equalizer and configured to convert the equalized CDM signal into a third signal to be delivered in the optical fronthaul link.

13. The BBU of claim 12, wherein the CDM is configured to apply code division multiplexing by: repeating each of a set of data streams a predetermined number of times, the predetermined number of times corresponding to the length of the corresponding third orthogonal code set; multiplying each repeated data stream by the corresponding third orthogonal code set to obtain the set of coded signals; and The set of coded signals is multiplexed into a CDM signal.

14. The BBU of claim 12, wherein the third signal is to be processed by an aggregator of the fronthaul network based on code demultiplexing using a fourth orthogonal code corresponding to the third orthogonal code.

15. The BBU according to claim 12 or claim 14, wherein the first and second orthogonal codes and the third and fourth orthogonal codes are pre-configured at an aggregator, and the BBU is further configured to: receiving a first code channel comparison table from the aggregator for determining the first orthogonal code and the second orthogonal code; and A second code channel comparison table is received from the aggregator for use in determining the third orthogonal code and the fourth orthogonal code.

16. The BBU of claim 10, wherein a pilot sequence is inserted into the CDM signal for training at least one equalization performance of the equalizer.

17. The BBU of claim 16, wherein the equalizer comprises a neural network based equalizer configured to be trained in an iterative manner based on the pilot sequence until a stopping criterion is met.

18. The BBU of claim 17, wherein the stopping criteria comprises: At least one equalization property meets a predetermined requirement.

19. The BBU according to claim 10, further comprising: A controller, the controller being configured to: transmitting a training pilot request to the aggregator based on a determination that the at least one equalization performance of the equalized CDM signal does not meet a predetermined requirement; as well as A CDM signal with a pilot sequence inserted therein is obtained for use in training the equalizer with respect to the at least one equalization property.

20. The BBU according to claim 16 or claim 19, wherein the pilot sequence comprises: CDM pilot signal, or non-return-to-zero on-off keying NRZ-OOK signal.

21. A fronthaul system, comprising: An aggregator according to any one of claims 1 to 9; The BBU according to any one of claims 10 to 20; as well as An optical fronthaul link connecting the aggregator to the BBU.

22. A method comprising: At an aggregator of the fronthaul network, converting a set of first wireless signals into a set of first signals corresponding to corresponding wireless channels; applying code division multiplexing to each of the first signals based on a corresponding first set of orthogonal codes for a corresponding wireless channel to obtain a set of coded signals corresponding to the corresponding wireless channel; Aggregating the set of coded signals into a code division multiplexed (CDM) signal; as well as The CDM signal obtained from the CDM is converted into a second signal for delivery in an optical fronthaul link.

23. A method comprising: At a baseband unit (BBU) of the fronthaul network, converting a second signal delivered in the optical fronthaul link into a digital code division multiplexed (CDM) signal, the digital CDM signal being processed by an aggregator of the fronthaul network based on code division multiplexing using a first orthogonal code of a corresponding wireless channel; equalizing the CDM signal with respect to at least one equalization property; as well as Code demultiplexing is applied to the equalized CDM signals based on a second orthogonal code corresponding to the first orthogonal code to obtain a set of CD-DM signals corresponding to the respective wireless channels.

24. A method comprising: At a baseband unit (BBU) of the fronthaul network, code division multiplexing is applied to each of a set of data streams based on a corresponding third orthogonal code set for a corresponding wireless channel to obtain a set of coded signals corresponding to the corresponding wireless channel; Aggregating the set of coded signals into a code division multiplexed (CDM) signal; pre-equalizing the CDM signal with respect to at least one equalization property to obtain an equalized CDM signal; as well as The equalized CDM signal is converted into a third signal to be delivered in the optical fronthaul link.

25. A method comprising: At an aggregator of the fronthaul network, converting a third signal delivered in the optical fronthaul link into a digital code division multiplexed CDM signal, the third signal being processed by a baseband unit BBU of the fronthaul network based on code division multiplexing using a third orthogonal code of a corresponding wireless channel; applying code demultiplexing to the digital CDM signal based on a fourth orthogonal code to obtain a set of CD-DM signals corresponding to the corresponding wireless channels, the fourth orthogonal code corresponding to the third orthogonal code; as well as The set of CD-DM signals is converted into a set of second wireless signals to be delivered in the corresponding wireless channels.

26. A non-transitory computer readable medium comprising program instructions for causing an apparatus to at least perform the method according to any one of claims 22 to 25.

27. An apparatus comprising: means for converting, at an aggregator of the fronthaul network, a set of first wireless signals into a set of first signals corresponding to respective wireless channels; means for applying code division multiplexing to each of the first signals based on a corresponding first set of orthogonal codes for a corresponding wireless channel to obtain a set of coded signals corresponding to the corresponding wireless channel; A means for aggregating the set of coded signals into a code division multiplexed (CDM) signal; as well as Means for converting said CDM signal obtained from said CDM into a second signal for delivery in an optical fronthaul link.

28. An apparatus comprising: means for converting, at a baseband unit BBU of the fronthaul network, a second signal delivered in the optical fronthaul link into a digital code division multiplexed CDM signal, the digital CDM signal being processed by an aggregator of the fronthaul network based on code division multiplexing using a first orthogonal code of a corresponding wireless channel; means for equalizing the CDM signal with respect to at least one equalization property; as well as Means for applying code demultiplexing to the equalized CDM signals based on a second orthogonal code corresponding to the first orthogonal code to obtain a set of CD-DM signals corresponding to the respective wireless channels.

29. An apparatus comprising: means for applying code division multiplexing to each of a set of data streams based on a corresponding third orthogonal code set for a corresponding wireless channel at a baseband unit BBU of a fronthaul network to obtain a set of coded signals corresponding to the corresponding wireless channel; A means for aggregating the set of coded signals into a code division multiplexed (CDM) signal; means for pre-equalizing the CDM signal with respect to at least one equalization property to obtain an equalized CDM signal; as well as means for converting said equalized CDM signal into a third signal to be delivered in said optical fronthaul link.

30. An apparatus comprising: means for converting, at an aggregator of the fronthaul network, a third signal delivered in the optical fronthaul link into a digital code division multiplexed CDM signal, said third signal being processed by a baseband unit BBU of said fronthaul network based on code division multiplexing using a third orthogonal code of a corresponding wireless channel; means for applying code demultiplexing to the digital CDM signals based on a fourth orthogonal code to obtain a set of CD-DM signals corresponding to the respective wireless channels, the fourth orthogonal code corresponding to the third orthogonal code; Means for converting said set of CD-DM signals into a set of second wireless signals to be delivered in said corresponding wireless channels.

31. An apparatus comprising the polymerizer according to any one of claims 1 to 9.

32. A device comprising a baseband unit (BBU) according to any one of claims 10 to 20.

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