WCDMA base station testing solves key deployment problems

With the convening of the Olympic Games, the third generation mobile communication system is getting closer and closer to our lives, the trial commercial use of China Mobile TD-SCDMA, this gives our Chinese people the opportunity to enjoy the various high-speed data transmission services 3G brings to us in China. I believe that in the near future, there will be two other technologies (WCDMA and CDMA) we will also enter our lives to enrich Chinese people's technical selectivity. However, a key factor that determines whether the network is good is the RF performance of the base station equipment. Therefore, how to test it has become a hot spot. Rode & Schwarz can provide comprehensive testing solutions for the three 3G technologies. This article mainly introduces the test solution for WCDMA base stations.

Basic Principle of base station Testing

The WCDMA base station test is different from the terminal test. According to the requirements of 3GPP Test Specification 25.141, all the test items can be completed in non-signaling mode. Compared with GSM base stations, WCDMA base stations adopt Code Division Multiple Access Technology. Therefore, their different code channel configurations (or channel models), especially the number of code channels, will affect the test results, in particular, modulation-related indicators. Therefore, specification 25.141 defines a variety of different test models for testing the transmitters, receivers, and performance of WCDMA base stations.

The transmitter test (TransmitterTests) is an indicator for testing the downlink signals emitted by the base station's transmitters, including the transmit power, modulation quality (such as EVM), occupied channel bandwidth, and spectrum emission templates, the leakage ratio of adjacent channels, stray lines, and code errors. All of these tests must be performed at 3GPPTS25. the corresponding test model (TestMode) defined in 141 is tested to ensure that the base station meets the standard requirements and make the test results of different base stations of different manufacturers comparable.

The receiver test (ReceiverTests) is to test the Receiving Performance of the base station receiver under certain conditions. For example, the received mobile phone signal is very strong (dynamic range test), very weak (refer to sensitivity testing), and receive error rate in interference conditions (such as adjacent channel selectivity, blocking, intermodulation, and stray. This part of the test assumes that the base station does not support diversity. If the base station supports diversity, the Diversity function should be disabled and each antenna should be tested separately.

The performance test (PerformanceTests) is also used to test the demodulation performance of the base station receiver. Unlike the receiver test, it is used to test the performance of the base station in the receiving Diversity state, the block rate is added with different fading and Gaussian white noise conditions. Therefore, to test the performance, you must test the signal-to-noise ratio (SNR) of the base station at different frequencies and rates as well as the BLER rate of the base station ).

Test Solution

It is critical to perform tests on the base station in full compliance with the specifications, because the test results are the basis for measuring whether the base station is qualified. At the same time, we also need other richer test functions, to meet R & D and troubleshooting needs. As a result, rode and Schwarz have released two RF testing solutions, namely FSMU and a single solution base station integrated tester CMU300, to meet the needs of different departments of different companies.

1. FSMU test combination

Rode & Schwarz's FSMU is composed of a vector signal source SMU200A and a vector signal analyzer FSQ. Figure 1 shows the test connection diagram of the WCDMA base station. The red NodeB in the upper left is the WCDMA base station, it is connected to FSMU, a test combination consisting of rod and Schwarz's SMU and FSQ through RF lines or air ports, to test its RF indicators. FSMU not only provides full support for R99 of WCDMA, but also tests various RF indicators of HSPA. If automatic testing is required, you can use the free software pai_fsmu_nodeb provided by rode and Schwarz to perform automatic testing. The program integrates various test setting parameters in the 25.141 test specification, therefore, you only need to click a few simple buttons to conveniently perform the test according to the specifications.

2. Single test solution CMU300

The Base Station Integrated tester CMU300 is a single test solution, which combines a signal source and a signal analyzer, with a signaling mode and a non-signaling mode. We know that in non-signaling mode (FSMU or CMU300 non-signaling mode), all the test items defined in standard 25.141 of the transmitter and receiver of the base station can be tested under static conditions; however, in practical applications, the base station will change its parameters in normal working conditions, such as transmitting power and re-distributing code channel resources, therefore, we need to ensure that the base station makes corresponding actions at the right time. The CMU300 signaling mode provides us with the possibility of verifying this function, so that we can establish a Signaling connection with the base station, in the signaling mode, the base station is tested on the transmitter, receiver, and performance (Data loop is performed under the Signaling connection) to fully simulate real use cases. In addition, CMU300 is a single instrument with a very cost-effective performance. It covers the main test items in 25.141 and also supports 3GPPTS25. 141R5 includes HSDPA technology testing, so it is particularly suitable for R & D and production.

The above FSMU not only supports all kinds of RF tests for WCDMA base stations and terminals, but also supports various standard base stations and terminals such as GSM, CDMA 2000, TD-SCDMA and WiMAX. CMU300 also supports the signaling and non-signaling RF tests of GSM base stations.

Support for LTE

As demand increases, the WCDMA technology is constantly changing and updated to meet people's needs for higher transmission rates. Rode and Schwarz keep up with the development of technology and maintain support for the latest test specifications in their products. For example, after HSPA, people proposed LTE (LongTermEvol-ution) to achieve higher transmission rates, rode & Schwarz quickly launched support for LTE in its FSMU combination.

1. Analysis on evolution and deployment of WCDMA networks
2. WCDMA coverage system design features and skills