LTE Downlink Test Model (E-TM) Waveform Generation

打开脚本

This example shows how to generate a test model using LTE Toolbox™.

Overview

The LTE specifications define conformance test models for transmitter tests. These include transmit signal quality, output power dynamics, Error Vector Magnitude (EVM) for various modulation schemes, Base Station (BS) output power, Reference Symbol (RS) absolute accuracy, etc. This example demonstrates how these different test model waveforms can be generated using LTE Toolbox functions.

The following general parameters are used by all E-UTRA test models as defined in TS 36.141, Section 6.1.2 [1] :

单个天线端口，1个代码字，1层没有任何预编码
Duration is 10 subframes (10 ms)
Normal cyclic prefix
Virtual resource blocks of localized type
User Equipment (UE)-specific reference signals are not used

将生成以下物理渠道和信号：

Reference Signals (CellRS)
Primary Synchronization Signal (PSS)
Secondary Synchronization Signal (SSS)
Physical Broadcast Channel (PBCH)
物理控制格式指示灯通道（PCFICH）
Physical Hybrid-ARQ Indicator Channel (PHICH)
Physical Downlink Control Channel (PDCCH)
Physical Downlink Shared Channel (PDSCH)

Test models are selected according to required test cases. In our example, the considered test model, E-TM1.1, should be used for tests on:

BS output power
不需要的排放 - 占据带宽，邻近的频道泄漏功率比（ACLR），操作带不需要的排放，发射器杂散排放
Transmitter intermodulation
参考信号绝对准确性

Test Model Selection

A number of test models are defined in TS 36.141 Section 6.1 [1]. This example will generate test model 1.1 as shown below.

tm ='1.1';％测试型号

全部owed test model values in the toolbox are ('1.1', '1.2', '2', '2a', '3.1', '3.1a', '3.2', '3.3').

带宽选择

The test model generation function in the toolbox requires the bandwidth to be specified as shown below:

bw ='1.4MHz';% Bandwidth

测试模型生成

The channel model number and the bandwidth determine the physical channel and signal parameters as specified in TS 36.141. The generated waveformtimeDomainSig是一个执行OFDM modu后时域信号吗lation, cyclic prefix insertion and windowing.txGridis a 2-dimensional array representing the resource grid spanning 10 subframes.

[timeDomainSig, txGrid, txInfo] = lteTestModelTool(tm,bw);

绘图传输资源网格

Plot the resource gridtxGrid，传说描述了哪些资源元素分配给了哪些物理渠道和信号。

hPlotDLResourceGrid(txInfo,txGrid);

情节谱图

Plot a spectrogram of the time domain signal.

% Compute spectrogram[y,f,t,p] = spectrogram(timeDomainSig, 512, 0, 512, txInfo.SamplingRate);% Re-arrange frequency axis and spectrogram to put zero frequency in the% middle of the axis i.e. represent as a complex baseband waveformf = (f-txInfo.SamplingRate/2)/1e6; p = fftshift(10*log10(abs(p)));% Plot spectrogramfigure; surf(t*1000,f,p,'EdgeColor','none'); xlabel('Time (ms)'); ylabel('Frequency (MHz)'); zlabel('Power (dB)'); title(sprintf(“测试模型E-TM％S，％s”的频谱图,tm, bw));