TD-SCDMA smart antenna automated testing (1)

Introduction

Smart antenna (or beamforming) can be ' beam ' at a specific user, significant increase user receives the signal to noise ratio and reduce interference to other users, thereby increasing system capacity.

TD-SCDMA largely power-constrained systems, at the same time is a self-jamming system, because the natural TDD system up and down the channel symmetry, so from the beginning of TD-SCDMA design starts on the actual deployment of smart antenna.

Smart antennas in the application and in the beginning TD-SCDMA maturing. In the subsequent evolution, evolution to TD-LTE TD-SCDMA, LTE greater introduces bandwidth-constrained, so smart antenna/MIMO adaptive technology is TDD number of antenna technology direction.

Any product features require a large number of laboratory tests.

Laboratory testing is not only significant cost savings, faster product launch cycle, but also easier than in-situ testing structures of various test environment reproducibility of tests, thus improving the quality of products.

Automated testing to simplify testing, automated device configuration, repeat the analysis of the resulting records/,/report output and other steps to greatly improve efficiency, accelerate testing products are rolled out, expand test coverage.

Generally, test devices provides a common interface, such as GPIB, Ethernet, etc., call for software programming.

We in practice, through automatic control complete SR5500M smart antennas for various tests. Further, we will be on the base station and mobile phone (or other terminal equipment) and complete automation control, and smart antenna test will have a much higher performance and more features.

1 smart antenna application in TD-SCDMA

TD-SCDMA as TDD system, downlink channels completely symmetrical, so pass on uplink signal channel estimation to get the right value for the downlink signal (the right vector), thereby achieving Beamforming (Beamforming), without the need for redundant signal design or resource consumption.

TD-SCDMA base station antenna element for 8-Planar antennas, antenna cell spacing ¦ë/2, low space means that the antenna signal high correlation between, you can usually assume that correlation is 1, i.e. the same experienced all antenna channel instantaneous fading, the difference between channel antenna is dependent on the direction of phase difference.

By different antenna element Adaptive adjustment phase offset as the antenna unit weights to control (steer) antenna beam, so as to align the corresponding user and increase gain while reducing interference to other users.

But TD-SCDMA is not confined to the high correlation between antenna configuration, for example, in order to reduce the antenna size and weight, in recent years developed a dual-polarized antenna, equivalent to two completely unrelated 4 antennas cell array.

At this time, apart from the antenna phase offset between units, two antenna between the instantaneous fading is not necessarily the same, therefore, need to be based on the antenna unit of channel estimation (H) to obtain the amplitude and phase are not the same as the complex vector antenna unit of weight. In order to complete the Adaptive beamforming.

The two cases of algorithm design is not a contradiction, low related configuration contains high related configuration algorithm, TD-SCDMA base station implementations under every day wire channel estimation by total weight vector, so whether it is a high correlation between the antenna or low, can be used directly.

In the up direction, the base station as a receiver, mainly leverages multiple antenna diversity function, through the maximum SNR merge (MRC) algorithm for diversity gain.

It should be noted that different antenna relevance affect smart antenna performance.

This discussion is beyond the scope of this article, please refer to the related thesis.

2 Spirent SR5500M-a smart antenna test

Spirent SR5500M launched in late 2007 when you take into account the commercial TD-SCDMA smart antenna test, that is, the modular design.

As shown in Figure 1, 4 SR5500M either for different teams in different locations, such as test-test antenna performance, etc., can also be combined into the system, for the same location of several team test single antenna performance, or for the same team test 8 antenna performance, greatly improve the equipment utilization:

Figure 1 Spirent SR5500M

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