CTIA 2x2 MIMO Over-the-Air Performance测试计划

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“CTIA-Certification-Test-Plan-for-MIMO-Over-the-Air-Performance-V1.2.1.pdf”是关于CTIA（无线通信行业协会）认证的2x2下行链路MIMO（多输入多输出）和传输分集的空中性能测试计划的文档，版本1.2.1，发布于2020年11月。该测试计划详细规定了无线设备在实际无线环境中的性能评估标准。 MIMO技术是现代无线通信系统中一种关键的信号处理技术，通过利用多个天线同时发送和接收数据，显著提高了无线通信系统的数据速率和频谱效率。在2x2 MIMO配置中，两个发射天线和两个接收天线协同工作，可以实现更高的数据传输速度和更好的信号稳定性。此测试计划旨在确保无线设备在真实环境条件下的性能，包括但不限于信号强度、误码率、覆盖范围以及多路径传播环境下的性能。测试内容可能涉及信道建模、多径衰落模拟、空间分集和空间多工等MIMO特性。这些测试对于保证设备在各种复杂无线环境中的可靠性和兼容性至关重要。 CTIA（ Cellular Telecommunications and Internet Association）是美国的无线通信行业协会，负责制定和维护无线设备的认证标准。根据文档内容，任何对测试计划的复制、修改或未经授权的使用都是违反联邦版权法的。测试计划只能在CTIA认证计划内使用，若需其他用途，必须获得CTIA的书面授权。测试计划的执行必须在CTIA认证授权的测试实验室进行，可以通过PTCRB（PCS Type Certification Review Board）认证请求或提交OTA（Over-the-Air）测试计划用户请求来完成。PTCRB是一个国际组织，负责GSM、UMTS和LTE设备的互操作性测试和认证。 "CTIA-Certification-Test-Plan-for-MIMO-Over-the-Air-Performance-V1.2.1.pdf"提供了一套详尽的测试框架，用于评估和确保2x2 MIMO设备的空中性能，符合CTIA的高标准，并且只允许在特定的授权环境中执行。这个文档对于无线通信设备制造商、测试机构以及对MIMO技术感兴趣的工程师具有重要的参考价值。

Test Plan Version 1.2.1

however, that if the automatic measurement function of the channel emulator is used on a CW

signal, the crest factor setting must be adjusted to address the effect of the applied modulation for

EUT testing and avoid overdriving the inputs. The effect of this adjustment must also be accounted

for in the total path loss correction.

IGURE 2.2.2.1-1: TYPICAL INPUT CALIBRATION SETUP TO BALANCE INPUT REFERENCE LEVELS USING A

SINGLE CW SOURCE

IGURE 2.2.2.1-2: TYPICAL INPUT CALIBRATION SETUP TO BALANCE INPUT REFERENCE LEVELS

SING A DUAL CW SOURCE

Output

Ports

Base Station

Emulator

(LTE eNodeB)

To Input 1

Spatial

Channel

Emulator

To Input 2

Splitters

Spatial

Channel

Emulator

Stable CW

Signal

Generator

TX Port

Flexible

Loopback

Cable

Min. 6 dB

Pad

(a) (b)

Output

Ports

Base Station

Emulator

(LTE eNodeB)

To Input 1

Spatial

Channel

Emulator

To Input 2

Splitters

Spatial

Channel

Emulator

Stable CW

Signal

Generator

TX Port

Min. 6 dB

Pad

Flexible

Loopback

Cable

Output

Ports

Base Station

Emulator

(LTE eNodeB)

in CW Mode

To Input 1

Spatial

Channel

Emulator

To Input 2

Splitters

Spatial

Channel

Emulator

Test Plan Version 1.2.1

FIGURE 2.2.2.1-3: EXAMPLE OF USING THE CHANNEL EMULATOR POWER METER TO OBTAIN A

REFERENCE FOR DETERMINING NET PATH LOSS OF EACH INPUT PATH

The following list describes a typical process for determining the relative and absolute input path

losses using a single CW source.

1 Connect an isolation attenuator (minimum 6 dB recommended) to the end of an RF cable

attached to a stable CW signal generator.

2 Attach the attenuated end of the cable to the end of the system cable that normally

connects to the first output of the communication tester.

3 Set the signal generator and channel emulators to the frequency to be measured.

Alternately, multiple frequencies may be calibrated for a single center frequency setting of

the channel emulator (CE), provided the same center frequency setting of the CE is used

for subsequent tests of the same frequency range(s).

4 For the corresponding input of each channel emulator, measure the received power,

ensuring that the power is at or below the reference level setting of the channel emulator in

order to avoid overdriving, but close enough to remain in the linearity region of the input.

5 Repeat steps 3 and 4 for each frequency to be calibrated.

6 For each subsequent input cable (communication tester output connection), move the end

of the signal source cable to the corresponding input cable and repeat steps 3 through 5.

7 If it is necessary to determine net path loss of each cable in each frequency band of

interest, measure the power at the attenuated end of the signal source cable, ideally using

a direct connection to one of the inputs of the channel emulator, applying the same

considerations used in steps 3 and 4 above.

8 Compute the relative difference between the highest power measured across all inputs and

the rest of the inputs. This offset is then applied to the reference level for each input for all

subsequent tests to bring all digitized inputs to the same level.

Output

Ports

Base Station

Emulator

(LTE eNodeB)

To Input 1

Spatial

Channel

Emulator

To Input 2

Splitters

Spatial

Channel

Emulator

Stable CW

Signal

Generator

TX Port

Flexible

Loopback

Cable

Min. 6 dB

Pad

Test Plan Version 1.2.1

9 Alternately, determine the average power level of each output of the communication tester

and subtract the path loss to each input port to set the corresponding reference level.

10 To obtain the target reference levels using the communication tester in CW mode instead

of a single CW source, attach the communication tester as it will be used for device testing

and repeat steps 3 to 4 for each input of the channel emulator. The measured levels are

then used to set the required reference level for the corresponding communication tester

output power settings. In the event that specific implementation details differ from these

steps, proper documentation shall be generated describing the method to be employed.

2.2.2.2 Output Calibration

The primary goal of the output calibration is to balance the outputs of the channel emulator to

compensate for the differences in path loss to the center of the test volume. Thus, for SIR testing,

only the relative path losses between each output, as well as any relative losses between signal

source and interference source, are required to sufficiently calibrate the system. The net path loss

of the calibrated system is only required for throughput vs. power testing, and is useful for ensuring

that the signal is sufficiently above the platform noise to obtain the desired SIR. However, if a

suitable calibrated reference antenna is used during the output calibration, then the necessary end-

to-end path loss correction can also be extracted from the same set of measured data. Otherwise,

once the relative corrections have been applied to the outputs, a separate path loss measurement

can be performed on any one of the individual paths to determine the net path loss, since all of the

relative errors are compensated separately.

Figure 2.2.2.2-1 illustrates a single path from the communication tester to the center of the test

volume. While the channel emulation and other components are part of the signal path, the

definition of the total path loss from the communication tester to the center of the test volume

remains the same as that for the OTA test plan. Thus, the mechanisms for measuring the end-to-

end loss are the same. Since the channel model and other input and output level setting controls of

the channel emulator will alter the net path loss, the components can be separated into the internal

gain or loss of the channel emulator and the external gain or loss of all of the other system

components, as shown in Figure 2.2.2.2-2. By measuring the end-to-end loss and subtracting the

internal loss term, the resulting external loss corrections can be combined with any other channel

emulator settings to determine the signal levels in the test volume. For isolated signal paths that are

not altered between the calibration step and the EUT measurement step (e.g., between the channel

emulator and amplifier or amplifier and antenna) any standing wave contributions from these

components can be assumed to be corrected by the range calibration. The calibration also embeds

any residual offsets from the inputs and outputs of the channel emulator into the net path loss that

is measured.

Alternatively, subsets of these paths may be measured independently, and the total path gain/loss

of each component combined, minus the loss terms of any additional cables, switches, or other

accessories used during the calibration process that are not part of the test signal path.

Test Plan Version 1.2.1

will attach to the transmit port (typically this is the same cable and attenuator used for the

input calibration step in the previous section).

2 Following the guidance of steps 1 through 4 of Section 4.4.2 of the CTIA Certification OTA

Test Plan [7], attach the attenuated end of the transmit cable to the end of the system cable

that normally connects to the first output of the communication tester. (Note the choice of

input cable is arbitrary so long as only one input is enabled on each channel emulator.)

3 Set the signal generator and channel emulators to the frequency to be measured.

Alternately, multiple frequencies may be calibrated for a single center frequency setting of

the channel emulator (CE), provided the same center frequency setting of the CE is used

for subsequent tests of the same frequency range(s). At each frequency, apply the relative

offsets determined from the input calibration to the reference level setting of the channel

emulator to correct for any relative input path loss. Ensure that the power into the channel

emulator is at or below the reference level setting of the channel emulator in order to avoid

overdriving, but close enough to remain in the linearity region of the input.

4 Set the output level of each used port of the channel emulator to the maximum level

supported for each frequency to be tested, being sure to remain in the linear region of any

external amplification to the test volume.

5 Use a static constant tap (straight through) channel model to produce a direct connection

from the input to the output of the channel emulator.

6 Iterate through each output port of the channel emulator, enabling only one path from the

input cable to the center of the test volume at a time, and ensuring that the reference

antenna is oriented at bore sight to the direction and polarization of the active array

element.

7 Measure the total path loss following the guidance of Section 4.4.2 of the CTIA Certification

OTA Test Plan [7] for each frequency of interest.

8 Repeat steps 3 through 7 for each frequency and output path to be calibrated. The order of

iteration through frequencies and outputs can be interchanged as necessary for speed or

ease of operation.

9 Compute the relative difference between the worst path loss and all other paths at each

frequency. These offsets are then applied to the output power setting for each

corresponding output to create the same net path loss between the channel emulator and

the center of the test volume for each output path. Since the signal generators of the CE

can never go above maximum output, the outputs of the paths with lower losses must be

reduced to correspond to the path with the highest path loss.

10 The loss for the worst-case path, corrected for the channel model and number of active

inputs and outputs (the internal gain of the CE) then becomes the reference path loss of the

entire system. This loss is used to compute the power in the test volume relative to the

output power of the communication tester.

11 After applying the relative offsets to each output, it is recommended to perform a spot

check of the residual relative error, determined by repeating the calibration process with

offsets applied. This provides a validation of the calibration process and an estimate of the

residual error due to the total path loss and non-linearities in the system components. In the

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