New Solution for the Year of the Tiger: R16 Air Interface Test and Analysis
With the completion and release of more and more Release 16 new function standard specifications, such as TDD/FDD CA carrier aggregation, DC dual link mode, or RIM remote interference management, or new DCI message mode, etc.
A new problem for 5G developers
Focus
▼
How to quickly and effectively
Verification/Optimization
Performance of wireless communication equipment ?
Today we also invited two senior technical veterans
Share their
Frontline practical case sharing and 5G R&D tips
/ Liu Liwei /
More than ten years of experience in wired network and wireless communication testing. Including packet switching performance testing, Wi-Fi function and performance testing, and signal acquisition and analysis testing for multi-mode MIMO transmission. Participated in the construction of terminal application test systems for operators, 4G base station test channel simulation support, etc. Currently in the wireless product line of Keysight Technologies, he is mainly responsible for the technical solution-level application of 5G wireless channel test products and 5G wireless protocol analysis products.
/ Dr. Yang Huaizhi /
He graduated from Beijing Institute of Technology with a Ph.D. in Electromagnetic Field and Microwave Technology. He is a member of the 9th Beijing Communications Association Communication Terminal Professional Committee. He has served as the leader of the 5G Base Station Test Working Group of GTI. He has written 13 scientific articles and 4 invention patents. With more than ten years of experience in the communications testing industry, he joined Keysight Technologies in 2016 following the PROPSIM production line. Dr. Yang has been deeply involved in channel emulator products and related performance test solutions. He has contributed standard documents to standard associations such as 3GPP/CCSA and participated in standard formulation work.
Article Outline:
•
Case 1: The throughput of the latest chip phone is not as good as that of the old chip phone
•
Case 2: Unexplained bit errors in wireless device downlink
•
5G Tips and Solutions Sharing
First, let’s share with you the 5G engineers.
In the daily life of R-16 product development
Encounter problems
Some functions of the device have abnormal results
Throughput does not meet expectations
Not sure what the problem is
Solve the problem
Diagnostic analysis for additional information
Requires an external instrument, such as a signal analyzer or Wavejudge5000 wireless protocol analyzer
It requires a lot of external cables and devices, which is very troublesome
Pain points
It is necessary to connect additional instruments and equipment, and even change the physical topology of the original test.
Increased R&D test cycle and uncertainty factors
Today, the author gives you an in-depth analysis
Two real cases
Let you know how we use
New 5G R&D tips to solve these testing problems
Case 1: The throughput of the latest chip phone is not as good as that of the old chip phone
Case background: A manufacturer's test environment is equipped with a set of real base station signals. The 3GPP channel scenario and AWGN noise test items are carried out through the channel emulator environment. When testing the new and old firmware versions of the mobile phone under test, it is found that the throughput performance of the new version of the mobile phone under test is not as good as the old version of the mobile phone with the same chip solution. The old version of the mobile phone under test can be tested to a peak uplink throughput of 260Mbps, while the new version can only be tested to a peak uplink throughput of 195Mbps. The channel configuration parameters are exactly the same.
Specific problem: No specific reason can be found through the mobile phone log tool, only the scheduling of error retransmission with a certain probability on another terminal can be seen. In the Propsim channel simulator environment, but the channel model is switched to Butler or bypass mode without multipath, the difference in peak throughput data remains. However, if the environment of different channel simulators is used, the base station and the mobile phone are directly connected, and a 20dB custom attenuator is added, there is no such difference. The customer repeatedly switched terminals, checked the base station log and terminal log, and failed to find the cause of the problem after testing for many days.
Traditional solution: Connect vector signal analyzers to the base station antenna and mobile phone antenna for data collection. However, the data transmission mode is MIMO, and ordinary single-port VSA equipment cannot collect and decode MIMO signals. In addition, due to the adaptive bit transmission, the service PUSCH scheduling parameters of each slot of the base station are not consistent. If the traditional vector analysis software is manually configured to decode the PUSCH channel, it is necessary to enter more parameters and verify them frame by frame.
Tips:
The problem was solved by using WaveJudge wireless protocol and Propsim F64. We imported the multi-channel IQ channels collected by Propsim F64 into Keysight's new WaveJudge wireless protocol analysis system software, and saw the frequency, cell bandwidth, and sampling rate parameters of the configured 5G NR cell. The parameters of the broadcast channel of the test cell can be automatically blindly decoded, and the cell ID, frame number, and internal messages such as SSB, MIB, and SIB1 can be displayed. It also supports the Dedicated channel content of the majority transmission channels of multiple UEs. It only needs to read the corresponding RRCSetup or RRCReconfiguration message from the UE or base station, so that WaveJudge can match the search/decoding related parameters of each UE's dedicated transmission through the configuration message of the base station, just like the UE, and decode the content of the corresponding PDSCH or PUSCH data transmission message block, CRC status, etc. according to each DCI message, including various encapsulation formats from the MAC layer to the PDCP layer, the IP data transmission packet of the user plane, or the RRC and NAS messages of the control plane can be decoded.
WaveJudge wireless analysis software interface
In addition to the traditional dynamic scheduling decoding of layer 2 and layer 3 messages, after the signal is imported into the WaveJudge analysis software, the physical layer related indicators of each PDSCH or PUSCH can be viewed in a targeted manner. Through the timestamp linkage function of the left and right windows, we can view the time domain power diagram, spectrum diagram and constellation diagram of the EVM indicator of each PUSCH. If you are concerned about the resource utilization of the cell, you can also view the 2D power icon to view the RB scheduling resource status of each slot.
WaveJudge wireless analysis software interface
With the help of WaveJudge's graphical interface, we quickly found that when the downlink power was the same, the power values of the uplink time slots of the two DUTs differed by several dB. The power of the DUT with low peak throughput was slightly lower, and the EVM quality also showed a rotation of the constellation diagram.
WaveJudge Wireless Analysis Software Interface - EVM Constellation Diagram
conclusion of issue:
The difference in peak throughput between the two devices is mainly due to the low uplink transmission power of the mobile phone and the large signal quality distortion. In the case of a good test environment, the peak uplink transmission can be achieved. If the path loss in the test environment is large, the EVM of the uplink signal to the base station is too low. Under the same environmental noise, there will be a low SNR of the object under test, and the high-order output TB signal may not reach the demodulation threshold of 64QAM. After retransmission, the base station will reduce the MCS rate to improve the bit error situation, but the total throughput cannot reach the peak like the terminal with normal power and signal quality. After the customer replaced the hardware RF board and recalibrated the terminal, the problem was solved.
Case 2: Unexplained bit errors in wireless device downlink
Case background & problem: When a customer's 5G base station and terminal were tested under the 3GPP channel scenario, the throughput test results showed a certain proportion of downlink TB transmission block errors under low attenuation and low Doppler conditions.
Traditional method: For downlink bit errors, manually check the configuration parameters of the base station and find that the downlink message scheduling and sending status have not changed, so periodic downlink bit errors should not occur. In addition, the log collected on the mobile phone shows that the verification of the received PDSCH is normal, so there should be no bit errors.
Tips:
The problem was solved by using the WaveJudge wireless protocol and Propsim F64. While performing channel simulation and throughput streaming, Propsim collected a period of uplink and downlink test code streams, and imported them into WaveJudge for analysis. It can be seen that the PDSCH decoding in the message list was successfully verified, and the EVM was also around -36dB. The WaveJudge software decodes the PDSCH based on the DCI scheduling information of the base station, and can determine that the downlink signal transmission status is normal, but the ACK status in the PUCCH replied by the UE is sometimes decoded to have a 0 position. Therefore, the base station sees that the UE's reply Ack is abnormal, and the statistics of the base station background have generated some statistics on downlink transmission errors.
WaveJudge Wireless Analysis Software Interface – Message List
conclusion of issue:
Combining the decoding results of WaveJudge and UE, we can conclude that the downlink bit error counted by the system is not a problem with the terminal performance indicator, that is, the downlink signal after channel model processing is successfully decoded, but there are some problems when the UE replies or generates PUCCH messages, resulting in the presence of nack status information to the base station. The terminal-related protocol stack department needs to further analyze and handle the pucch coding problem.
The following will introduce you
The secret to solving the above two problems
Using the WaveJudge wireless protocol
Joint solution with Propsim F64
Wireless communication equipment air interface performance analysis solution supporting Rel16 virtual field environment
Keysight Propsim Channel Emulator + Wavejudge Wireless Protocol Analysis Tool
Keysight's Propsim channel emulator can help customers build a virtual field test environment in the laboratory that is close to the requirements of the new functions of Release 16, which can greatly shorten the R&D cycle of wireless communication equipment; and Keysight's WaveJudge wireless protocol analysis tool can help customers quickly locate problems in wireless layers one to three.
Channel emulator lab test connection diagram
The above picture shows a typical FR1 macro station multi-terminal laboratory test environment built based on the Keysight Propsim F64 channel emulator.
Connection diagram of traditional air interface performance analysis solution
Keysight's latest air interface performance analysis solution directly utilizes the powerful hardware platform of the Propsim F64 channel emulator. Through the newly added IQ Capture digital signal acquisition function, the converted IQ digital signal can be directly exported without affecting the channel simulation. In this way, Keysight's advanced WaveJudge unlimited analysis software can be used to conveniently perform in-depth analysis of the RF layer and protocol layer, thus providing customers with a more effective means to quickly locate the root cause of the problem.
Propsim F64+Wavejudge
Schematic diagram of the new analytical test scheme
With Keysight's new air interface performance analysis solution, when customers find abnormal results of wireless communication equipment in the test environment of the Rel16 laboratory, there is no need to change the test environment. The Propsim channel emulator can directly collect the downlink and uplink channel source codes to perform air interface layer 1 and layer 3 analysis. Especially for MIMO signals, Propsim can simultaneously collect multi-stream downlink and uplink signals, saving the cumbersome connection and high cost of multiple external VSA or RF boards.
Summarize:
In the new hybrid solution of the new IQ Capture acquisition function of the Propsim channel emulator and the import function of the WaveJudge protocol analysis software, the function of collecting MIMO's bidirectional IQ code stream signal without changing the test wiring is realized, which not only avoids the introduction of other unnecessary attenuation interference factors, but also saves the time of adjusting the environment for debugging the signal. Through the cross-layer linkage analysis function of the WaveJudge wireless protocol analysis software, the physical layer indicators of the wireless signal and its uplink and downlink scheduling message parameters are displayed graphically, so that users can quickly view the physical layer indicators and corresponding scheduling resource parameter contents of the message that needs to be analyzed.
The new channel simulation and protocol analysis integration solution extends from the wireless signal testing function to support signal acquisition, vector indicator analysis and wireless protocol analysis, and fully provides the function of rapid analysis and location of wireless layer 1 to layer 3 problems of 4G and 5G signals. It can accelerate the decoding and viewing of multiple layers of messages required for problem location, especially viewing the specific message content and the complexity of the time slot synchronization operation of the corresponding physical layer indicators.
Click to view:
• Propsim Channel Emulator
• Wavejudge wireless protocol analysis tool
About Keysight Technologies
We are committed to helping enterprises, service providers and government customers accelerate innovation and create a secure and connected world. Since the founding of HP in 1939, Keysight Technologies has been operating independently as a new electronic test and measurement company on November 1, 2014. We continue to uphold the same entrepreneurial spirit and passion to start a new journey, inspire global innovators and help them achieve goals beyond imagination. Our solutions are designed to help customers innovate in 5G, automotive, IoT, network security and other fields.
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