Patent Description:
SIEMENS and its subsidiaries are developing innovative test systems for verification and validation. Such test systems may comprise one or more test devices that can be utilized in a variety of high tech fields, ranging from cellular base stations to the automotive industry. For example, a radio equipment test system or test device, e.g. from the X-STEP product line, allows stimulation and tracing of all the digital interfaces in a modern radio equipment such as a radio equipment control (REC) and/or radio equipment (RE) modules (also known as baseband unit, BBU, and remote radio head, RRH, respectively). The digital interface protocols supported by such a test device may include JESD204B, CPRI, OBSAI RP3, or another Ethernet-based protocol, e.g., <NUM>, <NUM>, <NUM> or <NUM> Ethernet. A test device may further comprise in register-transfer level (RTL) simulation and hardware emulation and may also work with FPGA prototyping, real-time post-silicon board debugging and final product testing. The test device may cover every phase in a radio base station product development cycle, ranging all the way from very first RTL simulations to post-production.

In general, radio frequency (RF) communication systems and devices, like other electronics, require testing and, in some cases, calibration. Testing and calibration can present challenges in the case of an RF communication system or device which supports multiple transmission (Tx) and reception (Rx) channels.

<NPL>, discloses testing of mobile communication device using loopback mode.

<CIT> discloses active antenna testing arrangement using a single control module interfacing with both a calibration radio and the active antenna under test.

<CIT> discloses a system for advanced array performance testing consisting of a test controller interfacing with a probe antenna and an advanced antenna in an anechoic chamber.

<CIT> discloses a network analyzer being connected to a measured antenna and to a measuring antenna.

In particular the fifth generation of cellular mobile communications, <NUM>, requires, due to the smaller cell sizes, a large amount of antenna arrays, in particular to enable beam-forming. Therefore, the testing of antennas and antenna arrays will become a challenge.

According to a first aspect, a test system comprising a radio unit, RU, and a radio equipment test device for testing the RU, according to claim <NUM> is proposed.

Thus, a test device for testing radio equipment is proposed that possesses one or more digital interfaces. Thereby, simplifying the testing of radio equipment. In addition, the amount of cables is reduced by the proposed setup and test device, respectively. Furthermore, the proposed test device and test system, respectively, enable testing of radio equipment such as massive antennas, i.e. a large amount of antennas at the same time. However, according to the proposed aspects testing only a limited number of antennas is possible as well. Another advantage is that the test vectors, i.e. the radio signals used for testing, e.g. the radio signals as generated by the radio equipment test device, are reproducible, i.e. it is assured that identical test signals are used when testing the same radio equipment at different times or different radio equipment. This is because the transmission and/or reception times of the test signals are known to the single radio equipment test device and/or the test vectors are exactly the same since the same single radio equipment test device is used for generating and receiving test signals. When running one or more test vectors through a radio equipment under test the timing for transmission (by the radio equipment under test, in particular an antenna under test) and reception (by reference antenna), or vice versa, of test vectors is known. This can be leveraged e.g. in order to determine transmission delay of the radio equipment under test, in particular said antenna under test. Furthermore, a recording of received RF signals and/or transmitted test vectors can be made. This is particularly advantageous for debugging antennas in different environments as the same recorded test sequence can be used. The recording may be replayed and/or analyzed without the test chamber being present or needed. For example, as will be described by way of the embodiments a measurement probe can be used for recording a test vector and/or the radio signals received, e.g., in the form of IQ data. The recording of the test vector and/or the received RF signal may be replayed at a later point in time. As will be apparent in the following description instead of the measurement probe other measures may be employed for recording received RF signals and/or one or more test vectors.

Embodiments will now be described in more detail in relation to the enclosed drawings:.

A radio base station test system allows stimulation and tracing of the digital interfaces in all fronts of a modern radio base station, in Radio Equipment Control (REC) and Radio Equipment (RE) modules, also known as Baseband Unit (BU) and Remote Radio Head (RRH). Digital interface protocols between the REC and RE include CPRI, OBSAI RP3, and <NUM> Ethernet. Furthermore, 10GbE and similar variants, such as CPRI over Optical Transport Network, are used in the REC - core network boundary. JESD204 is a standard that is widely used between AD/DA converters (in antenna interfaces) and logic devices (RE/RRH).

In <FIG> an exemplary radio communication system is illustrated. The traditional monolithic base transceiver station (BTS) architecture is increasingly being replaced by a distributed BTS architecture in which the functions of the BTS are separated into two physically separate units - a baseband unit (BBU) and a remote radio head (RRH). The BBU performs baseband processing for the particular air interface that is being used to wirelessly communicate over one or more radio frequency channels. The RRH performs radio frequency processing to convert baseband data output from the BBU to radio frequency signals for radiating from one or more antennas coupled to the RRH and/or to produce baseband data for the BBU from radio frequency signals that are received at the RRH via one or more antennas. The RRH is typically installed near the one or more antennas, often at the top of a tower, and the BBU is typically installed in a more accessible location, often at the bottom of the tower. However, as the case may be, RRH and BBU may be collocated, e.g., in a lab. The BBU and the RRH are typically connected through one or more fiber optic links. The interface between the BBU and the RRH is defined by fronthaul communication link standards such as the Common Public Radio Interface (CPRI) family of specifications, the Open Base Station Architecture Initiative (OBSAI) family of specifications, and the Open Radio Interface (ORI) family of specifications.

In the <NUM> architecture, a new frequency domain fronthaul interface will be specified. The frequency domain fronthaul is a functional split where the IFFT/FFT (Inverse Fast Fourier Transform/ Fast Fourier Transform) may be moved from the BBU to the RRH. Frequency domain samples instead of time domain samples are sent over the fronthaul. The RRH will have information through a communication channel about the resource allocation for different UEs. The new eCPRI interface specification "<NPL>)" is already available.

For the deployment scenario where the remote radio head, RRH, (sometimes also denoted as Radio Remote Unit, RRU, or simply Radio Unit, RU) and the baseband unit, BBU, (sometimes also denoted as radio equipment controller, REC, or nowadays distributed unit, DU) are separated, the signals received from one or more antennas have to be transported over the media that is connecting the RRH with the BBU as normally the signal combination is done at the BBU. In general, the interface that is used for the connection between the BBU and the RRH is called the fronthaul. The signals over the fronthaul could be complex time domain samples such as specified in the legacy Common Public Radio Interface, CPRI. Digitized waveforms may be transported over the fronthaul from the BBU to the RRH, and vice versa, via one or more radio aggregation units (RAU). In order to test one or more radio equipment said digitized waveforms may be in the form of so called test vectors, which in turn may be in the form of IQ data.

RAU is an entity introduced by different <NUM> standard drafts and its function is to connect multiple radios to a BBU and to serve as a time and latency critical data processing unit for the RRHs. The functionality of the RAU is further defined by the functional split chosen between BBU and RRH.

The user equipment's, UE, signals are power limited and as the path loss varies with the distance to the UE a large dynamic range is encountered when those signals are represented digitally, it may be assumed that for the complex frequency sample a large number of bits will be required and in the case of MIMO (Multiple Input Multiple Output) /diversity layers the required fronthaul capacity will multiply with the number of antennas. Furthermore, it is desired to model such propagation of radio signals in order to test the functionality of the radio system and its components. As the capacity on the fronthaul is limited it is desired to find methods that optimize the usage of the fronthaul.

The BBU may be connected to a core network, denoted as "Core" in <FIG>, and possibly to other BBUs (not shown) via one or more backhaul or crosshaul connections, respectively. BBUs increasingly rely on commercial server chips as C-RAN topology is getting deployed. BBUs need to be able to control the evolving fronthaul networks by supporting different types of fronthaul topologies, equipment, protocols and line rates. The complexity of this process makes BBU testing, and radio equipment testing in general, challenging and time consuming. By way of an active antenna the radio and the antenna part can be integrated into one compact, powerful unit. These antennas need to be controlled by the Baseband Unit (BBU), and the exchange of information requires common messages. The content of the messages needs to be understood similarly by the manufacturers of both BBU and active antenna. A radio equipment test device, such as X-STEP, may also support different protocols and interfaces, such as the JESD204B interface, allowing antenna manufacturers to test the antenna interface in a digital way. This way, interoperability can be designed and tested separately in early stages of device development. Active antennas are gaining ground as <NUM> technology keeps of evolving and the launch of <NUM> technology is approaching.

Now turning to the radio equipment test system as shown in <FIG>, in a typical test setup a radio equipment, i.e. a device under test (DUT) (inside the dotted line in <FIG>), is connected via one or more fronthaul protocols (e.g., CPRI, eCPRI, OBSAI, RoE, etc.) to a radio equipment test device that serves for providing digital data, in particular test data or test signals, preferably in the form of IQ data, i.e. serves as a distributed-unit (DU). In <NUM> radio network a base station is denoted as gNodeB or gNB. This gNB may comprise a central unit and one or more distributed units, DUs. This logical node includes a subset of the gNB functions, depending on the functional split option. Its operation is controlled by the central unit, CU, not shown. Evolving from <NUM>/LTE to <NUM> New Radio (NR) transport architecture, the main change is that the original BBU function in <NUM>/LTE is split into three parts: Central Unit (CU), Distributed Unit (DU), and Radio Unit (RU).

The central unit, not shown, is a logical node that may include gNB's functions like transfer of user data, mobility control, radio access network sharing, positioning, session management etc., except those functions are allocated exclusively to the DU. The central unit controls the operation of one or more DUs over one or more fronthaul interfaces, not shown. A central unit is also known as BBU/REC/RCC/C-RAN/V-RAN. Even though in the following mainly the terms RU, DU and <NUM> terminology are used those terms are meant to incorporate the corresponding function, units, modules or device in corresponding radio technologies such as <NUM>, <NUM> and <NUM> or even other radio technologies, such as Wi-Fi.

Now, the DU may be connected to an RU, which for example comprises an (active) antenna unit. Thus, it is possible to connect a DU to either one or more antennas, in particular one or more antenna units (AU) or even one or more active antenna units (AAU), dependent on the functional split selected between DU and RU. In order to test the one or more antennas of the antenna under test AUT, a reference antennas REA comprising one or more antennas is arranged in the test chamber TC together with the antenna unit. It should be understood that as mentioned in the above the DU may be replaced by a radio equipment test device, or test device in short.

In <NUM>/<NUM>/<NUM> the number of antennas (of an antenna unit, e.g. of the antenna under test AUT or a reference antenna REA) is limited, and it is possible to use coaxial cables CC to perform direct RF measurement devices by way of a vector-signal-analyzer, VSA, and/or a vector-signal-generator, VSG. The VSG may generate baseband IQ data vectors for modulated signals. VSA on the other hand analyzes baseband IQ data vectors of modulated signals. Hence, VSA and/or VSG may be used to check a DUT's transmitting and/or receiving performance/functionality as shown in <FIG>. The reference antenna REA may be coupled to a vector-signal-analyzer, VSA. Corresponding devices are commercially available, for example under www. com/find/spectrumanalyzers. On the other hand, the antenna under test AUT may be coupled to a radio equipment test device via which test data, e.g., IQ data, may be transmitted to and/or received from said antenna under test AUT. In the embodiment of <FIG> the DU serves as the radio equipment test device for transmitting and/or receiving, e.g. IQ data, via fronthaul communication link.

With the demand for high user throughput in limited radio spectrum, a Massive MIMO active antenna unit is the solution to use a large number of built-in antennas to set up dedicated connections to different users by sharing the same radio spectrum.

In general, the antenna count is increasing, in particular in <NUM> and especially when beamforming is in use. Therefore, it is not reasonable to use a direct connection via coaxial cables CC to the individual antennas. Furthermore, often the antennas, e.g. combined to an antenna array, are in the same mechanical case or enclosing together with a radio unit (RU), such a setup is also referred to as an active antenna. Nowadays the radio equipment test device for providing test signals, such as IQ data, to the DUT and the measurement device for monitoring/examining/analyzing the test signals transmitted by the DUT, such as a VSA, are separate devices, and there is no central control between those. The RF test chamber, TC, is needed for radiation protection, internal and external. The size of the RF test chamber TC can vary between the size of a suit-case and a big hall. The interior surfaces of the test chamber TC may be covered with radiation absorbent material (RAM) to define a RF anechoic test chamber TC.

Now turning to <FIG>, as can be seen the DU and the VSA and/or the VSG are combined into a single radio equipment test device, TA. This allows usage of a single device TA with one or more digital interfaces, I1 and/or <NUM>, as the case may be, for testing of radio equipment. Of course, in particular interface <NUM> for providing the VSA and/or VGA functionality may be an analog interface for receiving analog input from the radio signals received and/or for transmitting radio signals via reference antenna REA, thereby simplifying the testing of radio equipment. For example, as shown in <FIG> the device under test, DUT, may comprise an RU, i.e. an active antenna unit, or the antenna array, AUT, only. In addition, the amount of cables is reduced by the proposed setup. Furthermore, testing of radio equipment may comprise testing massive antennas, i.e. a large amount of antennas at the same time. The proposed test device, TA, allows for testing of such a massive-MIMO setup but also allows for testing only a limited number of antennas. Another advantage is that the test vectors, i.e. the radio signals used for testing, e.g. the radio signals as generated by the radio equipment test device, TS, are reproducible, i.e. it is assured that identical test signals are used when testing the same or different radio equipment. This is because the transmission and/or reception times of the test signals are known to the single radio equipment test device, TA, and/or the test vectors are (exactly) the same since the same single radio equipment test device, TA, is used. Furthermore, the recording of received RF signals and/or transmitted test vectors can be made. This is particularly advantageous to debug antennas in different environments. The recording may be replayed and/or analyzed without the test chamber and/or the DUT being present or needed. For example, as will be described by way of the embodiments in the following a measurement probe can be used for recording a test vector and/or the radio signals received, e.g., in the form of IQ data. The recording of the test vector and/or the received RF signal may be replayed at a later point in time. Of course, as will be apparent in the following description instead of the measurement probe other measures may be employed for recording received RF signals and/or one or more test vectors.

In general, testing may be performed in accordance with certain requirements, such as conformance testing, in particular as described in <NPL>) or any earlier or even a forthcoming future version of the 3GPP standard. Therein certain test procedures for performance measurements of User Equipment (UE) / Mobile Station (MS) are described. For example, uplink and downlink frequencies to be tested as well as the positioning of the device under test are specified therein.

The embodiment as shown in <FIG> and the individual parts may otherwise correspond to the embodiment as described in <FIG>. One or more functions and/or functionalities of the DU and the VSA/VSG may be implemented by a control unit of the test device, TA. Such a control unit may comprise one or more processors for executing the said functions and/or functionalities. The single radio equipment test device TA may comprise a single housing, enclosure or casing in which the one or more processors and preferably a storage unit such as a memory are arranged. The single radio equipment test device, TA, may thus be operatively connected to the device under test DUT and the reference antenna REA at the same time. The device under test, DUT, could either be the radio unit, RU, as a whole, or only part of the radio unit, RU, such as the antenna or antenna array of the radio unit, RU.

Now turning to <FIG>, an antenna under test AUT may be placed in a test chamber TC together with a reference antenna REA (comprising one or more antennas) in order to test desired functioning of the antenna under test AUT and/or the RU. Antenna under test AUT and the RU may form an active antenna (unit), AAU, and which is subject to testing, thus may be denoted as device under test, DUT.

As already mentioned, in order to receive the radio signals emitted by the antenna under test AUT, a reference antenna REA, also denoted as measurement antenna, may be placed in the test chamber TC. The reference antenna REA may serve for receiving the radio signals emitted by the antenna under test AUT and/or for amplifying the radio signals received. The reference antenna REA may also serve for transmitting radio signals to the AUT and/or DUT, e.g. when it is connected to a VSG.

According to an aspect of the present disclosure, the one or more functions of a VSA and/or the VGA are now included in the radio equipment test device TA, cf. <FIG>, and/or a cloud platform CP to which the radio equipment test device TA may be operatively connected to. In particular, digital signal processing performed by the VSA is now part of the radio equipment test device TA and/or the cloud platform CP. Digital signal processing may include FFT/IFFT of the radio signal received, or more precisely the signal representative of the radio signals transmitted and/or received by the antenna under test. In particular, digital signal processing may include FFT of the radio signal received by the one or more reference antennas. Further functions now part of the radio equipment test device TA may include one or more demodulation algorithms, including for example inter alia (sub-)sampling, (quadrature-)mixing and baseband modulation of the radio signals. Preferably, the functions just mentioned are performed by a first processor P1, e.g., an FPGA, of the test device. Instead, another digital signal processor, DSP, may be used in order to carry out one or more of the above mentioned functions. In addition to those functions the first processor P1 may provide the test signals or test data for testing the AUT and/or DUT as explained in connection with <FIG>.

The antenna under test AUT may be an active antenna, i.e. an antenna that contains electronic components, such as transistors. The same applies to the reference antenna REA, which can be an active antenna too. Now, the antenna under test AUT is preferably connected to the test device TA via a first interface I1 of the test device TA. The antenna under test AUT may comprise a corresponding interface, not shown in <FIG>, to operatively, preferably communicatively, couple to the test device TA. Hence, the test device TA may transmit and/or receive data, e.g. I/Q data, relating to the radio signals to be transmitted or received by the antenna under test AUT via the first interface I1. For example, the data relating to the transmitted and/or received radio signals may be transmitted via a digital communication protocol, such as (e)CPRI. The data relating to the radio signals to be transmitted may be converted by the antenna under test AUT into radio signals. Accordingly, the radio signals received by the antenna under test AUT may be converted from the analog to the digital domain.

Now, the first processor P1 may exchange data relating to radio signals, e.g., in the form of IQ data, with the second processor P2. To this end, the first processor P1 of a control unit CT may be communicatively coupled to a second processor P2 of the control unit CT. For example, IQ data may be transmitted from the first processor P1 to the second processor P2 in order to be analyzed by the second processor P2. On the other hand, the second processor P2 may transmit IQ data, generated by the second processor P2, to the first processor. The first processor P1 may further process the IQ data either received from the DUT and/or received from the second processor according to one or more RF channel models. A channel model may characterize of radio signal propagation as a function of frequency, distance and other conditions. Hence, a radio equipment test device TA is proposed, wherein the control unit operative to provide the functions as described throughout the present disclosure is integrated in said test device TA:
The radio equipment test device TA comprises a control unit CT that in turn comprises said first processor P1 and said second processor P2. Furthermore, the control unit CT may be operative to receive a result of a determination of an antenna fault from a cloud platform CP. The step of determining an antenna fault may be based on one or more antenna fault characteristics stored in the cloud platform CP. The one or more antenna fault characteristics may arise from fault characteristics of one or more different test devices TA. That is to say, one or more radio equipment test devices TA of the same or of a different type may record one or more antenna fault characteristics and said characteristics may be stored in said cloud platform CP. Thus, said antenna fault characteristics stored in the cloud platform CP may be used in order to determine one or more antenna faults, or the likelihood of the same, for the current antenna under test. To this end, data representative of said one or more antenna fault characteristics may be retrieved, e.g., download, from the cloud platform CP to the radio equipment test device TA, preferably via said third interface I3 of the test device or the control unit CT, respectively. Alternatively, at least part of the signals representative of the radio signals transmitted and/or received by the antenna under test AUT may be transmitted, e.g. uploaded, to the cloud platform CP. In both cases however, said signals representative of the radio signals transmitted and/or received by the antenna under test AUT may be compared to the data representative of said one or more antenna fault characteristics. In yet another embodiment, certain antenna fault characteristics may be determined by way of the control unit CT of the radio equipment test device TA, whereas other antenna fault characteristics may be determined in the remote cloud platform CP. For example, a preliminary check for an antenna fault may be done by the test device TA, whereas another more elaborated or resource intensive check for antenna faults is done via the cloud platform CP, e.g. one or more services of the cloud platform.

Thus, a radio equipment test device TA with a first and second processor P1, P2 operative and/or configured to execute one or more of the above functions is proposed. The test device further comprising an interface I1 for receiving and/or transmitting test data, e.g., in form of I/Q data to and/or from a radio equipment under test.

Furthermore, the first processor P1 may process data related to radio signals received and/or to be transmitted by the antenna unit, i.e. the AUT, the RU and the DUT in parallel to data related to radio signals received and/or to be transmitted by the reference antenna REA. For example, different pipelines or data paths may be configured for processing data relating to the radio signals received and/or to be transmitted by the AUT, RU, DUT and reference antenna REA, as the case may be. A pipeline or data path may comprise different tasks such as performing a Fourier-transformation, or Fast-Fourier-Transformation as the case may be, on data received, performing a filtering of said transformed data and performing an Inverse-Fourier-transformation, or Inverse-FFT respectively. In addition, the first processor P1 may in case the signals received or to be transmitted via the reference antenna are in analog form perform conversion to or from analog to digital domain or digital to analog domain. Corresponding implementation guidelines for the above mentioned tasks may be found in "<NPL>". It should be understood that the first processor P1 may apply one or more (different) channel models to the radio signals received or to be transmitted by the antenna under test AUT and/or the reference antenna REA.

For the purpose of integrating the VSA and/or VSG into the test device TA the functions of a VSA and/or VSG are implemented by way of the second processor P2. That is to say, the radio signals data pre-processed by the first processor P1 may be analyzed by way of the second processor P2. For example, the radio equipment test device may thus be suitable to determine error vector magnitude, code domain power, and/or spectral flatness of the radio signals transmitted/received by the antenna under test AUT and/or the reference antenna REA. Test signals received and/or to be transmitted by the reference antenna are transmitted via the interface I2 of the control unit CT or more precisely of the first processor P1.

Although the interface I1, I2, I3 in <FIG> are shown to be separate from the first and second processor P1, P2, respectively, it should be understood that said interface may be interfaces of the first processor P1 and P2, respectively, may be directly connected, e.g. interfaces I1, I2 are digital interfaces of processor P1 and interface I3 is a digital interface of processor P2. Alternatively, interface I2 may be an analog interface of processor P1.

Hence, it is proposed to have a central control unit CT, i.e. the control unit CT, that provides the functionality of a combined test device and a VSA and/or VSG. This is achieved by the architectures as depicted throughout the figures and the corresponding description. According to an aspect of the present disclosure, the one or more functions of a VSA and/or the VGA are now included in the radio equipment test device TA and/or a cloud platform CP to which the radio equipment test device TA may be operatively connected to.

In <FIG> another exemplary embodiment of a test device TA is illustrated. The components as shown in <FIG> may be arranged in a common housing or enclosure. Connections between the interfaces I1, I2 and the first processor P1, preferably an FPGA, are parallel and/or independent. Each interface I1, I2 may have an individual connection and individual protocol, for example the first interface I1 may implement the CPRI protocol and the second interface I2 may implement the JESD204B protocol. Inside the first processor P1 both connections may comprise individual data paths DP1, DP2. Additionally, as shown in <FIG> the individual data paths DP1, DP2 are connected to a common data path part CP. The common data path part CP may serve for data transmission between the first processor P1 and the second processor P2. Said data paths DP1, DP2 can be configured to suit the protocols used, e.g. CPRI, eCPRI, JESD, etc. The common data path part CP may be a memory mapped register or memory space, such as AXI4. The connection to the second processor P2 may thus be implemented by way of memory mapped protocol (PCIe). Via the data paths DP1 and/or DP2 the common data path part, i.e. the respective memory, may be accessed and optionally data may be streamed from/to said memory.

In general, an FPGAs typically consist of an array of logic cells that implement small logical operations and are surrounded by peripheral I/O which can be programmed for different signaling standards.

According to an embodiment of the architecture proposed for the test device TA, data processing is partially executed by the FPGA. Mainly, lower physical layer processing like serialization and/or deserialization, line coding, and/or other operation of incoming data, e.g. via interface I1 and/or interface I2 is performed by the FPGA. Thus, processing of the transmission line data received is performed by the FPGA, whereas the actual data processing, e.g. analysis of the content of the data representing radio signals received/transmitted, is performed by the second processor and/or via one or more services of the cloud platform CP. Mainly, all payload data processing is made by processor P2 and/or via one or more services of the cloud platform CP.

For example, VITA <NUM> carrier card may be used to implement the interface I1 and for connecting to the first processor P1, preferably an FPGA. Furthermore, VITA <NUM> carrier card may be used to implement the interface I2 and for connecting to first processor P1.

Now turning to <FIG>, the one or more antennas of a reference antenna REA may be coupled to a multiplexer, MUX. The multiplexer may be external on internal of the test device TA. The multiplexer MUX may be coupled, as depicted in <FIG>, to an interface I2 of the test device TA. Said interface I2 may be a software-defined-radio, i.e. one or more amplifiers and/or analog-to-digital-signal converters. The interface I2 may be part of a digital signal processor, e.g., said first processor p1, preferably implemented by way of an FPGA. Hence, the test device TA may comprise a control unit CT, comprising a first processor P1 coupled to said first and second interface I2. The first processor P1 may be capable of digital signal processing, such as measuring, filtering and/or compressing signals received from the reference antenna REA via the second interface I2. In addition, said first processor P1 may be capable of processing data according to one or more digital protocols for communication via the first interface with the antenna under test AUT and/or the radio unit RU, as the case may be.

As shown in <FIG> the reference antenna REA may comprise multiple antennas arranged in an antenna array. In order to operatively connect to the individual antennas of the antenna array the multiplex MUX as described in the above may be used. If multiple antennas are in use, then it is possible to use multiplexer MUX for antenna selection. In such a case the interface I2 of the first processor P1 may be a software-defined radio implemented by way of the first processor P1. Preferably an FPGA. Such an interface I2 can handle multiple RF connections. That is to say, a single interface I2 for multiple antennas may be provided to sample the radio signal received directly (instead of applying additional hardware, such as one or more variable-frequency oscillators, mixers and filters).

The advantage with this setup is to get accurate test repeatability. All signals generated and measured and all digital data captured is controlled by a single test device. The data relevant for further analysis may be linked to one another and stored in cloud platform CP for further analysis. The cloud platform may comprise one or more services, i.e. cloud services, running on the cloud platform. The cloud platform CP may also possess a data store for storing received data and for retrieving data from said data store. For example, SIEMENS provides a cloud platform comprising multiple services for data processing called MindSphere. MindSphere is a cloud-based, open IoT operating system for the Industrial Internet of Things.

It should be understood that by way of the term "antenna" one or more antennas may be understood and that an antenna may comprise one or more antenna arrays, i.e. multiple connected antennas which work together as a single antenna. Furthermore, the antenna, may it be the antenna under test AUT or the reference antenna REA, is preferably suitable for beam-forming of radio signals, in particular according to the <NUM> specification of beamforming. Further details regarding the active antennas, passive antennas, antenna arrays, beamforming and the <NUM> use-case may be found in the whitepaper "Rohde & Schwarz Antenna Array Testing - Conducted and Over the Air: The Way to <NUM>", retrievable via http://www. rohde-schwarz. com/appnote/1MA286.

In another embodiment the test device TA may monitor the antenna under test AUT by way of the reference antenna REA. That is to say, the reference antenna REA may receive the radio signals emitted by the antenna under test AUT. Control and/or monitoring of the antenna under test AUT and the reference antenna REA is integrated in the control unit CT. The control unit comprising a first and a second processor P1, P2, wherein preferably the first processor P1 is an FPGA and the second processor is a CPU, e.g., a general purpose CPU. The test device TA serves for generating test data, e.g., I/Q data, in particular by the FPGA and the CPU. Herein the second antenna located in the test chamber is denoted as reference antenna REA but is also known as measurement antenna, throughout the art.

In the embodiments of <FIG> and <FIG> the first interface preferably receives digital data as input and the second interface receives an analog signal as input. Alternatively, the second interface P2 is digital interface and receive digital data as input. For example, the second interface P2 is operative and/or configured to receive and transmit data via digital (fronthaul) protocol, such as (e)CPRI.

It is proposed to have a new, single test device architecture, in particular for <NUM> (massive-MIMO), that manages the reference antennas in a test chamber and the antennas of a device under test (DUT) within that chamber. Thus, a single base band processor (FPGA) and a single processor for controlling the test routine may be used. Previously, two separate devices have been used.

Furthermore, an automated error type recognition is proposed. For example, when testing a massive-MIMO antenna unit a database is created. The database contains identified (i.e. known) error types and their signature/profile. Now, when testing a device (DUT) a check whether one or more channel profiles match the profiles stored is performed. Thereby an error type can be automatically identified. The test device may include a connection to a cloud platform. That is now, test routines and the error signatures may be stored and/or accessed by way of a cloud platform. It should be understood that in this embodiment but also in any other embodiments as the case may be the radio equipment under test may be the (active) antenna (unit) or the electronics part of the (active) antenna, e.g. a System-On-a-Chip as shown for example in <FIG> and <FIG>.

Now turning to the cloud platform CP, the cloud platform CP may comprise a data storage associated with the cloud platform. For example, a user may want to store a certain behavior of an antenna under test as an antenna fault characteristic in the cloud platform. The user may record the behavior of the antenna subject to certain test conditions by way of the test device and transmit this data as a certain antenna fault characteristic in the cloud platform CP.

In addition, a user may want to store one or more additional antenna fault characteristics in the radio equipment test device itself. For this purpose, the user may update the one or more antenna fault characteristics stored locally in the radio equipment test device. This can be done by sending a request, e.g., for synchronization of one or more antenna fault characteristics, to a user account in the cloud platform. Transmission and/or reception of the antenna fault characteristics to and/or from said cloud platform CP may occur via the third interface I3. Connection to the cloud platform CP may be established through the internet.

Now turning to <FIG>, testing of the RU of the DUT is shown in more detail. In this embodiment, only the digital (data processing) part of RU is under test. The RU comprises a System-On-a-Chip, SoC. An exemplary implementation of a RU, also denoted as RRH, using a SoC is shown in "Remote Radio Heads and the evolution towards <NUM> networks, by Christian F. Lanzani, Georgios Kardaras, Deepak Boppana", retrievable from: http://www. mti-mobile. com/wp-content/uploads/<NUM>/<NUM>/radiocomp altera MWC white paper2.

The digital uplink and/or downlink radio signals are transmitted along a digital data path, the data path comprising for example the SoC of the RU. That is to say, digital signals representing radio signals are received and/or transmitted via the SoC of the RU and the first interface I1 of the test device TA. Those digital signals, which may also be denoted as one or more test vector, are generated by the first and/or second processor of the test device. For regular operation the digital signals are forwarded from the SoC of the RU to the one or more antennas of the antenna unit. Now for the purposes of testing proper functioning of the RU, the signals are returned to test device TA, in particular via the second interface of the test device TA. To this end, several options are available. As the SoC of the RU is assembled on a printed circuit board (PCB) the contacts pads of the PCB may be used to return the digital signals processed by the SoC to the test device TA. First, it is proposed to provide a probe with a specific interface (adapted to the geometric arrangement of the contact pads on the circuit board) for coupling to the contact pads of a printed circuit board (PCB) of the RU under test, i.e. the DUT. That is, instead of capacitively coupling, i.e. AC coupling, to the one or more capacitors of the PCB it is proposed to directly couple of the testing device via a connection cable to the contact pads, i.e. by physical contact. Thereby capacitive coupling occurs directly from the contact pads into the connection cable. In other words, a DC coupling (contrary to AC coupling) between the contact pads and the connection cable connecting the DUT with the test device is proposed. This results in less capacitive noise due to avoiding the AC coupling filter effects. Second, it is proposed to use an optical connection link between the DUT and the test device TA in addition to the DC coupling to the contact pads of the PCB. This results in less signal distortion when compared to a regular wire-based measurement probe. Third, an optical transceiver may be brought close to the electrical connection to the PCB's contact pads, e.g. by way of a small-form-factor, SPF, transceiver module. Again, this results in less signal distortion. All of the above can be combined into a single measurement probe for connecting to the DUT. The digital signals picked up at the contact pads of the PCB of the DUT can be transmitted to the test device TA. The incoming digital signals can be received by the test device via the second interface I2.

As can be seen in <FIG>, the RU under test may comprise an antenna unit or may be coupled to an antenna unit. The antenna unit may, as described in the above, comprise one or more antennas. The radio signals received via the antenna unit may be transmitted to an analog front end, AFE, from where the radio signals are further transmitted to the SoC of the RU. The SoC may comprise a first protocol interface IF1 for coupling to the AFE. Either the AFE or the protocol interface may comprise one or more analog-to-digital-converters for processing the incoming signals. Subsequently the digital signals may be processed by a digital front end, DFE. Details of the functioning of an exemplary digital front end are described in "<NPL>. The DFE may output data via a second protocol interface IF2. Here, a protocol according to a functional split, such as (e)CPRI, may be used. Instead another digital protocol, such as JESD204B may be used, to communicatively couple the RU to the test device TA via the first interface I1.

A probe, preferably as described in the above, may be attached between Analog and Digital Front End (AFE/DFE), e.g. via the contact pads of a PCB, in order receive or transmit test signals. Typically, already at the interface between the AFE and the DFE a digital protocol, such as JESD204B/C protocol, are employed. The coupling between the contact pads and the probe may be AC-coupling or DC-coupling, although as proposed in the above DC-coupling has certain advantages.

According to the invention and as shown in <FIG>, an SoC internal loopback is used for testing purposes. In that case, the SoC is operationally connected to the first interface I1 and the second interface I2 of the test device TA. To this end, a data path within the SoC is established that allows for processing data in the forward run, e.g. from the test device TA via the SoC, and allows for the processed data to be transmitted back to the test device TA via another or the same interface IF2 of the SoC. Thereby no probe is necessary for picking up processed signals between the antenna unit and the SoC. The processed data is received by the test device TA via the second interface I2. For data transmission in the forward run, interface I1 of the test device TA is used and for data transmission in the return path, interface I2 of the test device is used.

<FIG> shows a more detailed illustration of the data path comprising a feedback loop within the SoC as described in connection with <FIG>. In this scenario as well as in <FIG> and <FIG> the radio equipment under test, i.e. the DUT, may be the RU or more particularly the SoC or some other digital data processing components of the RU. The RU may, as described in the above, be coupled to an antenna unit or the antenna unit may be an integral part of the RU. The antenna unit may thus be arranged in the same enclosing. The feedback loop comprises in the forward run the interface IF2, the DFE and the interface IF1. The signals arriving at the interface IF1 of the SoC are returned via a return path via the DFE and the interface IF2 again. It should be understood, that the signals may be processed in the forward run only and are looped through the DFE for the sake of transmitting the signals back to the test device. Now, instead of receiving data signals at the test device TA via the interface I2, data signals may be transmitted from the test device TA via the interface I2. These digital signals may then be processed by the SoC of the RU and transmitted via the first interface I1 to the test device TA again.

In <FIG> yet another setup of a radio equipment test system is shown. Therein the reference antenna REA comprises a RU and antenna unit. The reference antenna REA may thus be an active antenna. Hence, in the example shown the device under test DUT and the reference antenna REA may be identical in construction and arranged in the same test chamber. As described in the examples in the above the DUT is connected to a first interface P1 of the first processor P1 of the test device TA, whereas the reference antenna is an active antenna and is connected to a second interface P2 of the control unit of the test device. More particular, the DUT is connected to a first interface of the first processor P1 of the control unit CT and the reference antenna is connected to a second interface of the control unit CT.

Thus, it is also possible to use a (tested) reference antenna REA as a golden unit against which all later devices are tested. A golden unit or golden device is an ideal example of a device (such as a unit of measure) against which all later devices are tested and judged. The term "golden" is used to describe the precision of the device to standard specifications. This test method is especially useful when an analog RF path is needed to test, and there is no available suitable test equipment for the testing purpose.

Now turning to <FIG> where exemplary method steps of testing a radio equipment by way of a single radio equipment test device are shown. The method may be performed by a test setup, i.e. test system, as depicted in one of the <FIG>. However, other setups are possible by way of which the method steps as described in the following are executed.

In a first step S1 controlling and/or monitoring an antenna under test in a test chamber via a first interface of a control unit of a radio equipment test device may be performed. In a second step S2 controlling and/or monitoring a reference antenna via a second interface of the control unit of the radio equipment test device may be performed.

Herein controlling may comprise but is not limited to receiving and/or transmitting radio signals, e.g. in the form of IQ data, by the test device. Monitoring may comprise but is not limited to storing and/or displaying radio signals (or digital representations thereof) received and/or transmitted, e.g. in the form of IQ data, by the test device. Monitoring may further comprise comparing radio signals received and/or transmitted by the test device with one or more threshold values, e.g. of constellation points of the radio signals.

By way of a single test device a central control for generating and measuring/analyzing behavior of an antenna under test is provided. Therefore, uniform test runs can be performed avoiding irregularities due to usage of different devices, e.g. by different vendors. In addition, different devices may have different characteristics when it comes to signal processing and/or due to different setting options which may not correspond.

Now turning to <FIG> further exemplary method steps of testing a radio equipment by way of a single radio equipment test device are shown. A step S3 of operating the antenna under test as a transmitting antenna may be performed, wherein the first interface of the control unit preferably comprises one or more digital ports allowing transmission of I/Q data. Furthermore, a step S4 of operating the reference antenna as a receiving antenna may be performed, wherein the second interface of the control unit comprises RF I/O ports allowing receiving RF signals.

The first and/or the second interface may comprise one or more I/O cells, also known as I/O blocks, of the first processor, preferably an FPGA. One or more of the I/O cells may provide an interface between internal circuits of the first processor and (sampled) radio signals of the antenna under test and/or the reference antenna. The one or more I/O cell may be programmable and may comprise a bi-directional buffer, logic circuitry like flipflops or multiplexers, and routing resources.

For example, there may be a first mode of operation (for testing) during which the control unit is operative to operate the antenna under test as a transmitting antenna, wherein the first interface of the control unit comprises digital ports allowing transmission of I/Q data, e.g. to a RU integrated with the antenna under test and/or the test chamber, and during which the control unit is operative to operate the reference antenna as a receiving antenna, wherein the second interface of the control unit comprises RF I/O ports allowing receiving RF signals, in particular RF I/O ports allowing conductive measurements, by operatively coupling to the reference antenna, e.g., by way of a cable.

The interface between the first and the second processor may be implemented by way of a bus or a switch, e.g. by Peripheral Component Interconnect Express, RapidIO, serial peripheral interface (SPI) interface or a custom bridge. This allows for optimizing performance and cost by offloading pre- and/or post-processing of data to the first or second processor, respectively.

Furthermore, by using a single FPGA, dedicated FPGA resources may be created for co-processing data received via the first and the second interface. The single control unit or single test device also allows for reduced design for a test system for performing radio equipment testing.

The control unit, in particular the first processor, may be configured to generate digital test signals which are subsequently transmitted by the antenna under test and may be configured to receive via the reference antenna during the transmitter test mode, i.e. first mode of operation.

Now turning to <FIG> further exemplary method steps of testing a radio equipment by way of a single radio equipment test device are shown. A step S5 of operating the antenna under test as a receiving antenna may be performed, wherein the first interface of the control unit comprises digital ports that allow reception of I/Q data. In a step S6 operating the reference antenna as a transmitting antenna may be performed, wherein the second interface of the control unit comprises RF I/O ports allowing transmitting RF signals. For example, there may be an Analog-to-Digital-converter, ADC, or Digital-to-Analog-converter, DAC, necessary for converting IQ data from the FPGA into RF signals for driving the reference antenna or the other way around.

Now turning to <FIG> further exemplary method steps of testing a radio equipment by way of a single radio equipment test device are described. Optionally, a step S7 of storing in a storage unit one or more antenna fault characteristics and/or one or more radio channel models may be performed. The storage unit may be within the enclosure or housing of the test device or may be connected a cloud platform which comprises said storage unit. A step S8 of determining an antenna fault of the antenna under test based on radio signals received via the first and/or second interface and/or one or more antenna fault characteristics received from the storage unit may be performed. For example, a recorded frequency spectrum may serve as a fault characteristic for an antenna under test. An exemplary, antenna fault characteristic is shown in <FIG>.

In addition, there may be a second mode of operation (for testing) during which the control unit is operative to operate the antenna under test as a receiving antenna, wherein the first interface of the control unit comprises digital ports that allow reception of I/Q data, e.g. from a remote radio head integrated with the antenna under test and/or the test chamber,
and wherein the control unit is operative to operate the reference antenna as a transmitting antenna, wherein the second interface of the control unit comprises RF I/O ports allowing transmitting RF signals, in particular RF I/O ports allowing transmission of RF test signals, by operatively coupling to the reference antenna, e.g., by way of a cable.

In certain embodiments, the control unit, in particular the first processor is configured to send RF test signals via the one or more reference antennas to the antenna under test of the DUT during the receiver test mode, i.e. second mode of operation, to generate digital signals to be analyzed by the control unit.

The main advantage of digital signal processing within an FPGA is the ability to tailor the implementation to match system requirements. This means in a multiple-channel or high-speed system, advantage can be taken of the parallelism within the FPGA to maximize performance. Multiple channels, i.e. to and/or from the antenna under test and the reference antenna are likely and similar processing takes place in each channel.

Memory is required for data and coefficient storage. This may be a mixture of RAM and ROM internal to the FPGA. RAM is used for the data samples and is implemented using a cyclic RAM buffer. The number of words is equal to the number of filter taps and the bit width is set by sample size. ROM is required for the coefficients.

The second processor may serve as a radio frequency (RF) signal generator and analyzer configured to send and receive RF test signals.

The first processor and the second processor may be communicatively coupled via a chip-to-chip interface. The first processor may be an FPGA and may be regarded as a coprocessor to the second processor. The control unit may comprise a second processor, preferably a CPU, communicatively coupled to the first processor.

Now turning to <FIG> further exemplary method steps of testing a radio equipment by way of a single radio equipment test device are shown. A step S9 of receiving, by the test device, signals representative of the radio signals transmitted and/or received by the antenna under test, e.g. via the first interface of the control unit of the test device, is performed. This may take place during operation of the test device. Subsequently a step S10 of determining a frequency spectrum or a digital representation, e.g., I/Q data, of the signals received is performed. Preferably, the radio signals are first sampled and converted to IQ data and processed according to one or more radio channel models. The one or more radio channel models representing radio wave propagation as a function of frequency, distance and/or other conditions. Preferably said processing of the sampled radio signals is performed by the first processor of the control unit of the test device. The processed radio signals may subsequently be forwarded to the second processor of the control unit of the test device. Subsequently, a step S11 of analyzing at least part of the frequency spectrum and/or a digital representation of the signals received, e.g., in the form of I/Q data, preferably based on one or more antenna fault characteristics received from the storage unit, may be performed. For example, a recorded frequency spectrum may serve as a fault characteristic for an antenna under test and may be compared to the frequency spectrum determined based on the radio signals received. An analysis may then comprise comparing the two frequency spectra or at least one or more parts with each other in other to receive a result of the analysis. As a consequence, a step S12 of receiving a result of the determination of an antenna fault may be performed. For example, the result may be presented to a user conducting or supervising the testing of the antenna under test. Presentation may be for example by way of an indication on a display, in particular of test device or another control device, such as a handheld. Additionally, or alternatively, the result may be stored in a memory, e.g., above mentioned storage unit.

<FIG> shows an exemplary power spectrum of an antenna. The power spectrum of a radio signal is shown as function of the amplitude of the signal received (y-axis), e.g. by the reference antenna, and the respective bandwidth (x-axis), i.e. frequency. As can be seen in the "Pass"-case the power spectrum lies within an upper and lower threshold. The thresholds are represented by the dashed lines as shown in <FIG>, whereas the power spectrum is depicted as a continuous line. Said one or more upper and lower thresholds may serve for identifying proper functioning of the antenna and/or for identifying an antenna fault. In the "Fail"-case, the power spectrum of the antenna under test lies outside the desired frequency response of the antenna. Hence, an antenna fault may be determined and a corresponding indication may be outputted by the test device. The one or more thresholds may thus serve for identifying an antenna fault characteristic and thereby identify a specific antenna fault based on the radio signals received. For example, one or more thresholds may be used to determine a phase error between antenna elements of an antenna array. Other antenna faults such as amplitude errors and/or timing and/or frequency errors may be determined the same way. An antenna fault may be due to the production process, e.g., due to certain tolerances and/or due to thermal or other effects.

Claim 1:
A test system comprising a radio unit, RU, and a radio equipment test device (TA) for testing the RU RU, the RU comprising a System-on-a-Chip, SoC,
wherein an SoC internal loopback is used for testing purposes,
wherein the SoC is operationally connected to a first interface (I1) and a second interface (I2) of the test device (TA),
wherein for data transmission in the forward run, interface (I1) of the test device (TA) is used and for data transmission in the return path, interface (I2) of the test device (TA) is used, wherein the feedback loop comprises in the forward run an first interface (IF1), a digital front end, DFE, and a second interface (IF2) of the SoC, wherein signals arriving at the first interface (IF1) of the SoC are returned via a return path via the DFE and the second interface (IF2) of the SoC.