5G Over-the-Air Performance Measurement and Evaluation

アプリケーションノート

Introduction

5G is not simply an iteration of 4G. It is truly revolutionary and will change everything we know today. For the past 30 years, we have traversed through:

• 1G (the 1980s, AMPS/ETACS) mobile network, which brought analog voice to the masses.

• 2G (the 1990s, GSM/CDMA), which made digital voice available and increased network capacity dramatically with the advancement of the integrated circuit and digital signal processing.

• 3G (the 2000s, WCDMA/EVDO), which combined mobile data with voice enabling customers to make a voice call while replying to email for the first time.

• 4G (the 2010s, LTE), which was all about wireless internet (mobile IP) at higher speed, and desktop applications finally arrived on smartphones.

Nevertheless, there is still segmentation between the communications industry and customers. There are wireline/internet providers, cable TV, and internet service providers, wireless operators, over-the-top (OTT) application providers, and more. Consumers and businesses get connections from various operators on different platforms that often do not communicate with each other. There are significant overhead expenses in the networks, and providers allocate substantial resources to manage these expenses (signaling, billing, and device management).

5G is a connected application ecosystem for end users. Each application will adaptively manage data speed, latency, and reliability, depending on the tasks. For example, a vehicle on autopilot requires a reliable instant response and a secure link at highway speeds. A 5G network will provide wide coverage, low latency, and an encrypted communication link. Blindly assigning a 100-MHz channel for the car will not work because higher throughput does not equal to short latency and reliable coverage.

From the perspective of network operators, 5G will consolidate all their communication systems under one package to meet end-user application needs, such as data, voice, video, internet of things, and critical communications. 5G will provide much higher throughput, ultra-low latency, increased network capacity, reliability, and secure services.

The 5G network architecture should provide:

• massive capacity; 1000 times more than 4G

• super-fast data rate; 100 times more than 4G

• ultra-low latency; < 1ms

To achieve these goals, network and user equipment manufacturers must invent innovative technologies to make the network drastically more efficient. They must also deploy a new spectrum to support much wider bandwidth requirements.

There are three key technologies that 5G requires: millimeter-wave (mmWave) network deployment, massive multiple-input multiple-output (MIMO), and beamforming.

5G presents uncharted territory for RF engineers. How to characterize a mmWave air interface? How to measure antenna efficiency? What are the potential interference issues in 5G networks? What solutions can address 5G over-the-air (OTA) measurements to help evaluate 5G trial networks?

mmWave Band for 5G Deployment

LTE with 20 MHz bandwidth and 64 QAM can achieve 100 Mbps data rates on the downlink. However, for 5G to provide 100x higher data rates, it will require much wider bandwidth standards. The current sub-3 GHz cellular band cannot support wider bandwidths. The only way to implement 5G is to move the system to a higher frequency band.

5G requires a much higher bandwidth; as much as 800 MHz to 2 GHz. The frequency bands that have such potential are mmWave bands. The deployment of satellite communication in the Ka band (26.5 GHz to 40 GHz) increased channel bandwidth — from a typical bandwidth of 54 MHz to 500 MHz through 2 GHz, and was accompanied with spot beam frequency reuse to achieve gigabit IP connection.

In October 2015, the FCC allocated three mmWave bands for 5G services; these bands are the frontier spectrum for 5G services. Spectrum above 24 GHz is currently under investigation. The 28 GHz band supports 850 MHz of bandwidth, and the 37 – 40 GHz band supports 3 GHz of bandwidth. An unlicensed band from 64 – 71 GHz supports 7GHz of bandwidth. These spectrum and bandwidth allocations make the 5G service possible.

mmWave Link Propagation and Link Budget

Commercial wireless service frequencies are below 6 GHz including Wi-Fi. The channel characteristics of these bands are well understood with many design tools available to use. However, deploying mmWave frequency bands to provide a link between user equipment (UE) and base station presents many technical challenges. It is essential to understand mmWave path loss properties and build a predictable mathematical model.