Rohde & Schwarz SMBV100A与WinIQSIM2TM：打造高效MIMO测试指南

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本文档是Rohde & Schwarz公司提供的关于多输入多输出(MIMO)测试设置的指南，适用于4x4和8x8 MIMO系统的测试。MIMO技术是现代无线通信标准中的关键组成部分，它通过利用多个天线同时传输数据，显著提高了数据传输速率，而无需额外占用频谱资源。该指南详细阐述了如何使用Rohde & Schwarz的SMBV100A信号发生器在静态条件下进行测量，并涵盖了复杂衰落情况的模拟。在第1部分，作者首先介绍了应用笔记的目的和涉及的产品，包括SMBV100A信号发生器和WinIQSIM2TM工具。指南的结构包括以下几个部分： 1. **导言**：提供背景信息，强调MIMO在无线通信中的重要性以及Rohde & Schwarz的解决方案。 2. **概述**：对MIMO系统的基本概念进行概述，解释什么是衰落（fading），它是无线通信中常见的信号干扰现象，影响数据传输质量。 3. **简要介绍MIMO**： - **衰落**：讲解衰落的不同类型，如快衰落（Rayleigh或多径衰落）和慢衰落（阴影衰落）。 - **MIMO系统**：描述MIMO工作原理，包括空间复用和空间分集，以及它们如何提高数据吞吐量和可靠性。 - **测试MIMO系统**：说明测试MIMO系统的目标和方法，强调了在不同环境条件下确保性能的关键性。 4. **4x4 MIMO设置**： - **设置**：具体步骤指导用户如何配置4x4 MIMO系统，包括硬件连接和布局。 - **同步信号发生器**： - **电缆布线**：描述了所需的电缆连接，确保信号在多个天线间正确传输。 - **仪器设置**：详细说明了如何调整SMBV100A信号发生器的参数，以适应4x4 MIMO的测试需求。 - **信号生成**：讨论了如何生成适合4x4 MIMO测试的特定信号模式。 5. **8x8 MIMO设置**：这部分扩展了4x4的设置，可能涉及到更多的天线配置和更复杂的测试场景。整个指南旨在帮助用户充分利用Rohde & Schwarz的工具来有效评估和优化MIMO系统的性能，确保在实际通信环境中达到最佳的通信效果。通过遵循这些步骤，用户能够提升对MIMO技术的理解，增强其在无线通信项目中的应用能力。

Brief Introduction to MIMO

Fading

1GP50_0E Rohde & Schwarz Guidelines for MIMO Test Setups – Part 1 7

3 Brief Introduction to MIMO

This section gives a brief introduction to MIMO systems. A more detailed description of

the MIMO technology is given in the application note “Introduction to MIMO” (1MA142).

3.1 Fading

Under real-world conditions, the signal of one transmit antenna arrives at a receive

antenna not just by direct line of sight, but also via multiple propagation paths. This

multi-path propagation is called fading. This is especially prevalent in urban

environments where the transmitted signal is reflected from objects such as buildings.

As a result, the transmitter signal travels along different reflection paths to the receiver

(Fig. 1). The receiver detects all these signals, which typically have different time

delays, levels, phases and even frequency shifts due to Doppler effects (caused by

moving transmitters or receivers). In a MIMO system a complex fading channel exists

between each transmit and receive antenna pair. While the performance of a single

input, single output (SISO) system with only one transmit and one receive antenna is

degraded by the fading process, MIMO systems work best under multi-path conditions,

i.e. in environments with strong fading. Fading is an essential component in MIMO

systems, since sufficiently different – i.e. in the best case, uncorrelated – fading

channels are required to distinguish the data streams coming from the different

transmit antennas.

Fig. 1: Fading principle.

direct

Tx antenna

speed

reflected

Brief Introduction to MIMO

MIMO Systems

1GP50_0E Rohde & Schwarz Guidelines for MIMO Test Setups – Part 1 8

Uncorrelated fading channels are, however, only a best-case scenario. Under real

operating conditions, the different fading channels are not fully independent of each

other, due to the geometric arrangement of the antennas. For MIMO tests, it is

therefore essential to simulate variable correlations between the different fading

channels. Only by correlating the individual channels with each other can a realistic

simulation of the entire MIMO system be achieved. This is important, since the benefit

f MIMO systems depends on the degree of channel correlation, i.e. the higher the

statistical independence of the different fading channels, the better the achievable data

transfer rate.

3.2 MIMO Systems

When discussing MIMO systems, one must distinguish between spatial diversity

systems and spatial multiplexing systems.

Spatial diversity is a MIMO technique that uses multiple transmit and receive antennas

to increase the robustness of data transmission and thus indirectly the effective data

rates. Spatial diversity means transferring essentially the same data stream

simultaneously on the same frequency, such that the receive antennas obtain replicas

of the signal. Typically, an additional antenna-specific coding is applied to the signals

before transmission to increase the diversity effect. This means that each antenna

transmits the same information stream, but with different coding. Often, Alamouti

space-time coding is used. On the receiver side, the signal of the transmit antennas is

received by the antennas over different, ideally uncorrelated propagation paths. This

mitigates fading effects, because it is unlikely that the signals are affected in the same

way by fading processes along the different propagation paths. Therefore, the signal-

to-noise ratio at the receiver side and thus the robustness of data transmission is

improved. Transmit diversity (multiple input, single output – MISO) and receive

diversity systems (single input, multiple output – SIMO) are both special types of

spatial diversity systems (Fig. 2).

Spatial multiplexing or “true” MIMO is a different MIMO technique that is used to

significantly increase data rates or channel capacity. Spatial multiplexing means

transferring different data streams simultaneously on the same frequency by using

multiple transmit and receive antennas, i.e. fully exploiting the spatial dimension of the

radio channel. In contrast to spatial diversity, no redundant data is transmitted. The

data stream to be transmitted is split up into independent data streams, which are sent

via the different transmit antennas. Spatial multiplexing thus increases the data rate of

a single user, or the overall capacity in the case of multiple users. For single-user (SU)

MIMO, the transmitted data streams belong to one user only, thus increasing the data

rate of this single user. For multi-user (MU) or collaborative MIMO, the transmitted data

streams belong to different users sharing the same radio channel. In this case, the

overall capacity of the radio channel is increased, while the data rate of an individual

user remains unchanged. Also, the user equipment (UE) must be equipped with just

one transmit antenna (Fig. 2).

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Rohde & Schwarz SMBV100A与WinIQSIM2TM：打造高效MIMO测试指南

tes.rar_TES_mimo_mimo ofdm_mimo test bed _mimo-ofdm m-file pdf

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