ICACT20230156 Slide.19
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That's all, thanks for your listening!
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ICACT20230156 Slide.18
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By deconstructing the VSG and VSA architecture into the core VSG/VSA software, cross-platform control interface, and radio platforms parts, we built up a cost-effective, flexible test platform. Since we master the core technology of Wi-Fi 6 VSG and VSA, we can ensure the correctness of the signal generation and try our best to improve the analysis performance. In addition, we can also develop more analysis functions and applications to achieve faster and more accurate measurement. On the other hand, because different radio platforms have different interfaces, specifications and performances, we develop the cross-platform control interface to be able to integrate the core VSG/VSA software and the radio platforms, and built the power calibration process for the USRP SDRs, enabling it can perform power measurement. To sum up, the proposed cost-effective test platform has been tested and verified by the commercial instruments, and can be used in R&D test or the mass production phase. In the future, we will integrate more radio platforms and expected to upgrade the core VSG/VSA software for supporting Wi-Fi 7.
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ICACT20230156 Slide.17
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To verify the VSA, we setup the platform and execute the loopback test. The generated baseband IQ waveform will be sent to the radio platform, and RF output will feed into RF input. Then, the received IQ baseband waveform will be analyzed by the CSPLab VSA and Keysight 89600 VSA.
By testing several waveform, we compare the EVM results from them. We can see that the EVM is about -39dB and they have almost the same performance.
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ICACT20230156 Slide.16
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By the analysis results form Keysight 89600 VSA, we can verify the transmitted waveform is standard compliant.
With the spectrum plot, we can observe that the bandwidth is 160MHz, and the preamble, signal field, and data field are all demodulated correctly and listed in the INFO table. The EVM is below -40dB (1%).
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ICACT20230156 Slide.15
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After completing the above work, we conduct cross-validation through commercial instruments as shown in the figure. First, we use the self-developed VSG software with the USRP X310 (with UBX-160 RF daughter board) platform to transmit Wi-Fi 6 160MHz bandwidth signals. At the receiving end, we use a Keysight oscilloscope to intercept the RF signal to the Keysight 89600 analyzer software.
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ICACT20230156 Slide.14
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Currently supported platforms and their spec. are listed in the table. Since the NI VST aims for high-end test instruments, itˇŻs with calibrated power and excellent EVM performance (about -50dB in loopback test). However, USRP is an uncalibrated software defined radio, its power can only be controlled by TX/RX gain settings, but this only changes the relative value of the power magnitude, and its power also varies with frequency band. Therefore, the TX/RX power calibration process must be completed before one can set the TX power or measure the RX power in dBm.
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ICACT20230156 Slide.13
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Once the core VSG/VSA software design phase is complete, the cross-platform control interface is designed to transfer the RF setting parameters like transmit/receive center frequency, gain, bandwidth, sample rate etc. Besides, the interface has to deliver complex IQ samples generated from VSG software to the radio platform, and also send back the received complex IQ samples to the VSA software for analysis.
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ICACT20230156 Slide.12
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In the Demod. Domain Tab, there are EVM vs. Symbol, EVM vs. Subcarrier, and Constellation.
By these plots, we can observe the EVM performance in time (symbols) and frequency (subcarrier) domain, and help users to debug in advance.
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ICACT20230156 Slide.11
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In the Frequency Domain Tab, there are Power spectrum density (PSD), Spectrum Emission Mask (SEM), and Spectral Flatness for users to check the frequency characteristic of the waveform.
We also provide the Spectrum Emission Mask (SEM) and Spectral Flatness limits according to the test specification(red line in the plot), and make it easier to find out if the DUT passes or fails the spec.
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ICACT20230156 Slide.10
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Except the plots in General Tab, one can refer to the analysis and measurement plots in Time, Frequency, and Demodulation Domain Tabs.
In the Time Domain Tab, there are PvT and IQ plots for users to observe the time domain characteristic of the waveform.
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ICACT20230156 Slide.09
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In the VSA tab, there are two panels for Signal Demod. Setting and RF Setting.
And the analyzed waveform can be observed by power vs. time, PSD, and constellation plots in the General Tab.
The test and measured items will be listed in the table.
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ICACT20230156 Slide.08
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Second, we design the IEEE 802.11ax waveform demodulation and analysis algorithm as illustrated in this block diagram. The received IQ baseband waveform from the radio platform will be fed into demodulation and analysis process. In this process, we will detect the data packet from the input IQ raw data, and then the coarse CFO (carrier frequency offset) estimation will be performed and used to correct the data packet. The L-LTF are employed for fine timing, CFO, IQ gain imbalance and quadrature error estimation before the fast fourier transformation. In the frequency domain, the SISO/MIMO channel are extracted with the HE-LTF and the common phase error and the sampling clock offset are estimated and used to correct the data. Finally, the spectral flatness are measured and the EVM (error vector magnitude) can be calculated from the equalized data.
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ICACT20230156 Slide.07
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The figure shows the graphical user interface (GUI) for users to set the parameters and observe the generated waveform.
In the software, there are VSG and VSA tab.
In the VSG tab, there are two panels for Signal Generation Setting and RF Setting.
And the generated waveform can be observed in power vs. time, PSD, and constellation plots.
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ICACT20230156 Slide.06
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We start from VSA software development. There are 4 packet types defined in the IEEE 802.11ax specification and listed in the table 1. Different packet formats will be used according to different usage scenarios. Let's take HE SU PPDU Packet format as an example. In the s/w development, we refer to the specification and generate each field (table 2) of the packet with different bandwidth, modulation and coding schemes (MCS) and number of spatial streams. The available settings are listed in Table 3. The generated complex IQ waveform will be verified by the commercial VSA software (Keysight 89600) to ensure that the waveform is correctly generated and the SIGNAL information can be decoded.
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ICACT20230156 Slide.05
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We propose a cost-effective cross-platform Wi-Fi 6 VSG/VSA, which is able to gain the flexibility and make a trade-off between the cost and performance. With the concept of software defined radio (SDR), we deconstruct the conventional VSG/VSA architectures into the core VSG/VSA software, cross-platform control interface, and radio platforms parts.
The core VSG/VSA software includes the Wi-Fi 6 signal generation and analysis functions.
The VSG software can generate baseband complex IQ waveform according to the IEEE 802.11ax specification.
And we design the receiver algorithm to demodulate the Wi-Fi 6 baseband complex IQ waveform.
To be able to test and measure the DUT, we also develop some desired test items in the VSA software, e.g., error vector magnitude (EVM), center frequency offset, sampling clock offset, spectrum flatness, spectrum emission mask etc.
In the cross-platform control interface part, we design a software interface which can transfer the RF setting parameters like transmit/receive center frequency, gain, bandwidth, sample rate etc.
Besides, the interface has to deliver complex IQ samples generated from VSG software to the radio platform, and also send back the received complex IQ samples to the VSA software for analysis.
The radio part is for arbitrarily matching different radio platforms according to different usage requirements. We currently integrate various series of NI high-end VST instruments and NI USRP SDRs.
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ICACT20230156 Slide.04
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With the increase in testing requirements such as 5G, Wi-Fi 6/6E devices, etc., these instruments significantly increase R&D and testing costs.
By the forecast reports below, both the Wi-Fi market and the wireless testing market are expected to substantial growth from 2022 to 2027.
However, the requirements for test instruments vary with different test cases.
For example, R&D debugging, testing, and verification require high instrument accuracy, and detailed analysis items and charts are required to verify or clarify problems; for production line testing, it is important to detect whether the device under test passes the specification and generate the test report in a very short period of time.
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ICACT20230156 Slide.03
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Vector signal generator (VSG) and vector signal analyzer (VSA) are instruments that can generate and analyze standard compliant baseband IQ vector signal.
With the radio frequency up/down converter, VSG and VSA can test and analyze the wireless devices work at the standard specific frequency, e.g., 2.4/5GHz for Wi-Fi and 3.5GHz for 5G FR1.
VSG and VSA are widely used to verify and test the designed wireless communication system algorithm or devices at the research and development (R&D) , design, and mass production phase.
A DUT must meet the TX and RX requirement defined in the specification. For example, a wi-fi device has to perform transmitter test likeˇ¦ and receiver test likeˇ¦
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ICACT20230156 Slide.01
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In this presentation, IˇŻll first introduce the background of this work, including the motivation of the study and the explanation and introduction of related terms.
And then, IˇŻll talk about the main architecture of the Cost-effective VSG/VSA which is mainly divided into three parts: core VSG/VSA software, cross-platform control interface and radio platform, and the above three parts will be discussed.The platform and experimental results will be presented as well.Finally, IˇŻll mention our future work and make a conclusion.
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ICACT20230156 Slide.00
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Hello everyone! I am Chien-Min Chen from Yuan-Ze University, Taiwan. Thanks for coming.
In this presentation, IˇŻll share our research work with you, and the topic is on Development of Cost-Effective Wi-Fi 6 SISO/MIMO Vector Signal Generator and Analyzer.
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