IEEE 802.11ac Production Test Overview (1)

IEEE 802.11ac is a brand new WLAN (WLAN) standard being integrated into wireless devices. Currently, products supporting this standard are available in the market, and various manufacturers have begun to enter the mass production stage. Production and testing engineers must be able to support new 802.11ac test specifications and be compatible with existing WLAN standards and other wireless connection technologies. Based on the draft technical specifications, this article introduces the main production and testing projects of the 802.11ac standard, their usage and related testing methods.

802.11ac Introduction

802.11ac is a brand new WLAN standard proposed by the IEEE 802.11ac Working Group (TGac). Its goal is to provide local wireless connection technology with ultra-high speed (VHT). The peak transmission rate is 10 times higher than the current WLAN 802.11n HT standard, the communication bandwidth can reach up to 160 MHz (four times higher than the 802.11n standard) and up to 8 MIMO signal channels.

Based on technical specifications [1], this article introduces the testing requirements for mass production of 802.11ac devices.

Production Test requirements

From the perspective of production testing, you must understand the changes and evolution of WLAN standards and make plans in advance. For example, because the communication bandwidth reaches 80 MHz, the 802.11ac test device obviously needs a wider processing bandwidth for Signal Analysis and generation to test the tested objects. This is exactly the case when the 802.11n standard was introduced in that year. At that time, we needed to deploy a testing device with sufficient bandwidth to reach 40 MHz.

Test the physical connection plan

When the 802.11n standard is introduced, an important question is how to build a test system to test a MIMO system composed of multiple antennas. This poses a new challenge to the production and testing engineers-how to test multiple RF paths while keeping the cost of the testing equipment unchanged and minimizing the impact on the testing time/throughput.

802.11ac further expands this challenge, but the demand for MIMO testing has not changed, so the existing test configuration is still available. For the test items listed in the 802.11ac test specification, the following physical connection test methods can be used:

Figure 1: Test Device settings

The signal analyzer is used for transmitter-related testing, and the signal generator is used to provide the downstream signals required for receiver testing. For simplicity, configure the test device as a single port and connect it to the tested device as an RF port (TX/RX. This configuration can be used to test any of the following scenarios:

802.11ac SISO (1x1) devices supporting a single RF signal Link

802.11ac MIMO (nxm) devices support a single RF signal link. Each RF channel on the device is measured independently (n transmitters can be tested in sequence ).

Additional hardware is required if you want to connect multiple devices at the same time for parallel testing. For the modular Testing Equipment platform, hardware addition and upgrade are very simple.

Test Plan

Like the 802.11n test plan, the 802.11ac test plan is expected to include a series of test items to cover various situations in the actual use of the device. Similar to the old and HT working modes of the tested device, the 802.11ac testing plan is also compatible with the 802.11n testing plan (a very important feature in technical specifications ). In the face of possible 802.11ac testing requirements, test engineers prefer this approach.

Obviously, this is the main way to meet the new design and new standard mandatory testing needs. For example, the test engineer may evaluate the spectrum template features of signals with at least 80 MHz transmission bandwidth, and test the modulation accuracy in the MCS 9256 QAM modulation mode, the performance of the receiver is also evaluated based on the 802.11ac MCS 9 signal.

The specific test items in the test plan are very similar to those in 802.11n. The following is a list of test items based on the standard [1:

Adjacent and non-adjacent channel suppression tests require independent modulation signal sources to provide additional interference signals. These tests should be completed before production, rather than the items to be tested during the production test phase. Therefore, this article will not discuss them further.