Introduction
Millimeter-wave systems are an important component of 5G mobile communication systems and a key approach to meeting large bandwidth requirements. This article summarizes the progress of millimeter-wave standardization and the current state of the mmWave industry, analyzes the necessity of mmWave development for 5G systems, and presents typical 5G mmWave application scenarios.
Overview of Millimeter Wave
Millimeter wave generally refers to electromagnetic waves with wavelengths of 1 to 10 mm, corresponding to frequencies of 30 to 300 GHz. In the millimeter-wave bands it is possible to build communication systems with up to 800 MHz of contiguous bandwidth and peak data rates on the order of 10 Gbit/s, which can meet ITU requirements for 5G systems. Millimeter wave has become a necessary part of 3GPP 5G mobile systems [1–4].
1. 5G Millimeter-Wave Standardization and Spectrum Status
1.1 Standardization Progress
Spectrum is the most valuable resource for the mobile communications industry. Formal commercial deployment of any generation of mobile communications technology requires access to appropriate spectrum resources. The ITU agenda item 1.13 for the 2019 World Radiocommunication Conference (WRC-19) aimed to identify globally or regionally harmonized millimeter-wave bands for 5G (IMT). WRC-19 concluded with recommendations for mmWave bands in the 24 to 86 GHz range.
1.1.1 24.25–27.5 GHz
The 24.25–27.5 GHz band was identified for global IMT use. To protect existing satellite services, IMT systems must meet specified technical requirements.
- Out-of-band requirements:
- For the 23.6–24 GHz EESS (passive) band, the out-of-band unwanted emission limit from an IMT base station is -33 dBW per 200 MHz. After September 2027, this limit will be tightened to -39 dBW; base stations deployed before that date are not affected.
- For the 23.6–24 GHz EESS (passive) band concerning IMT mobile terminals, the out-of-band unwanted emission limit is -29 dBW per 200 MHz. After September 2027, this will be tightened to -35 dBW; terminals already in use before that date are not affected.
- In-band requirements:
- Outdoor base station antennas are normally required to point below the horizontal; mechanical tilting should be at the horizontal or below.
- For IMT base stations with per-beam equivalent isotropically radiated power (EIRP) exceeding 30 dB(W/200 MHz), the antenna's maximum radiation direction within the base station line of sight should deviate by no more than ±7.5 degrees from geostationary satellite orbital positions.
- Regulators are encouraged to maintain IMT base station antenna patterns approximately within the envelope recommended by ITU-R M.2101.
1.1.2 37–43.5 GHz
The 37–43.5 GHz range or parts thereof were identified for global IMT use. To protect existing satellite services, IMT systems must meet specific compatibility requirements:
- To protect the 36–37 GHz EESS (passive) band, IMT stations operating in 37–40.5 GHz should meet unwanted emission limits of -43 dB(W/MHz) and -23 dB(W/GHz). For greater protection, regulators are recommended to consider -30 dB(W/GHz).
- For deployments in 42.5–43.5 GHz, outdoor base station antennas should normally point below the horizontal; mechanical tilting should be at the horizontal or below.
- For IMT base stations in 42.5–43.5 GHz with per-beam EIRP above 30 dB(W/200 MHz), the antenna's maximum radiation direction within the base station line of sight should deviate by no more than ±7.5 degrees from geostationary satellite orbital positions.
- Regulators are encouraged to maintain IMT base station antenna patterns approximately within the envelope recommended by ITU-R M.2101.
1.1.3 66–71 GHz
The 66–71 GHz band was identified for IMT in Region 1, Region 3 and parts of Region 2, with compatibility and coexistence technical requirements to protect existing satellite services.
1.1.4 45.5–47 GHz
The 45.5–47 GHz band was identified in some countries for IMT with compatibility requirements to protect existing satellite services.
1.1.5 47.2–48.2 GHz
The 47.2–48.2 GHz band was identified for IMT use in some countries. For deployments in this band:
- Outdoor base station antennas should normally point below the horizontal; mechanical tilting should be at the horizontal or below.
- For IMT base stations with per-beam EIRP exceeding 30 dB(W/200 MHz), the antenna maximum radiation direction within the base station line of sight should deviate by no more than ±7.5 degrees from geostationary satellite orbital positions.
- Regulators are encouraged to maintain IMT base station antenna patterns approximately within the envelope recommended by ITU-R M.2101.
Within 3GPP, RF standardization work for mmWave bands is led by RAN4. The study was divided into two phases: Phase 1 covered frequencies below 40 GHz to meet urgent commercial needs and completed in December 2018. Phase 2, beginning in 2018 with completion planned by December 2019, focused up to 100 GHz to realize the IMT-2020 vision. 5G frequency allocations cover both sub-6 GHz and mmWave ranges (24.25–52.6 GHz); Phase 1 defined bands below 52.6 GHz.
These mmWave bands and the 3.5 GHz NR system were standardized in parallel in 3GPP, with Rel-16 finalized in early 2020.
1.2 Spectrum Allocation and Use
In the initial mmWave deployment phase, most countries focused on the 26 GHz and 28 GHz bands, where the most resources were allocated. The United States, South Korea, and Japan have completed mmWave spectrum assignments and auctions, clarifying commercial deployment prospects. The UK, Germany and other countries have confirmed mid/high band 5G bands pending allocation or auction [10].
China has not yet formally published specific mmWave spectrum planning. In July 2017, China's Ministry of Industry and Information Technology approved 24.75–27.5 GHz and 37–42.5 GHz for 5G mmWave research and experimental use. Test sites include the China Academy of Information and Communications Technology labs and outdoor test fields in Huairou and Shunyi, Beijing. The IMT-2020 (5G) promotion group in China established a high-frequency discussion group to define mmWave technical requirements and outdoor performance test methods. RF test specifications have been clarified and internal and external field tests have begun. In 2019 the focus was on verifying key mmWave technologies and system characteristics; in 2020 the focus was on verifying mmWave base station and terminal functions, performance and interoperability; and in 2020–2021 typical scenario verifications were planned.
2. Millimeter-Wave Industry Chain
Millimeter-wave baseband functions have maturity similar to sub-6 GHz 5G equipment, but RF-related functions and performance lag behind sub-6 GHz equipment. Because China has not yet finalized mmWave spectrum planning, vendor equipment tends to support North American and Northeast Asian bands; devices provide basic functions but features such as beam management and mobility require further refinement. Qualcomm offers commercial mmWave terminal modem X55, which supports single-carrier bandwidth of 100 MHz and does not yet support single-carrier 400 MHz or 800 MHz. Commercial terminals based on X55 from vendors such as OPPO, VIVO and ZTE were expected in early 2020.
High-frequency components and chips are foundational for mmWave systems. To support higher-order modulation and multiuser communications, high-frequency power amplifiers and low-noise amplifiers need improved output power, efficiency, and linearity; phase-locked loop systems require better phase noise and tuning range; filters need wider bandwidth and lower insertion loss; mixed-signal and data converters must sample at least 1 GHz channel bandwidth with high precision and reduced power; novel high-frequency array antennas must provide high-gain beams and wide angle scanning. China has accumulated research and technical prototypes in high-speed high-precision data converters, high-frequency power amplifiers, low-noise amplifiers, filters, and integrated packaged antennas, but many results are oriented toward defense use. There is a gap between prototype systems and industrialization for commercial communications, and device, material and process maturity for consumer communications remains behind global leaders.
Low-cost, reliable packaging and test technologies are key for practical deployment. Currently China has relatively few mmWave chips and terminal models; product range and form factors are limited. The industrial chain maturity for mmWave lags sub-6 GHz 5G and is behind the United States and Europe, which constrains mmWave deployment and application in China.
3. Necessity of 5G Millimeter Wave
3.1 Extending Mobile Systems to mmWave Responds to Service Demand
To meet growing service data rate demands, mobile systems must both improve spectral efficiency via techniques such as higher-order modulation and massive MIMO and increase system bandwidth through carrier aggregation and dual connectivity. However, sub-6 GHz spectrum allocations are largely exhausted, making it difficult to find contiguous wideband spectrum to support ultra-high data rates.
Compared with lower bands, mmWave offers abundant bandwidth, enabling up to 800 MHz channels and enabling ultra-high-speed services. The short wavelengths allow smaller component sizes, facilitating device integration and miniaturization.
With the growth of high-capacity, high-rate, and low-latency services, communications will inevitably extend into mmWave bands. The basic 5G architecture already adopts a hybrid approach combining mid/low bands and mmWave bands.
3.2 Accelerating mmWave Industry Development Is Required for International Competition
Mobile communications significantly drive economic growth. 5G and future 6G technologies and industries are key areas of international competition. Millimeter wave is a key part of 5G and a technology preparation for higher-frequency 6G systems. The focus on mmWave band allocations at WRC-19 shows industry and economic attention. GSMA analysis on socioeconomic benefits from deploying 5G in mmWave bands indicates early mmWave leadership in Asia-Pacific and the Americas could generate substantial GDP contributions, and Europe could see significant relative GDP growth from mmWave deployment.
The Chinese mmWave industry chain overall currently lags the United States, particularly in commercialization of high-frequency components. Major issues identified through research include the gap between prototype systems/chips and mass production; prototype development and testing require long cycles and substantial investment, necessitating industrial policy support. China's Ministry of Industry and Information Technology and Ministry of Science and Technology have major projects and policy support in this area, and economically developed provinces have targeted support for high-frequency industry chains. Industry, academia and research institutes in China are actively working to raise domestic mmWave device and chip capabilities and industrialization levels.
3.3 mmWave Application Scenarios Are Becoming Clearer
Considering mmWave propagation and coverage characteristics, 5G mmWave is suitable for relatively open or lightly obstructed campus and venue environments. After industry discussions, typical deployment scenarios have emerged:
- Private network scenarios. 5G mmWave combined with MEC&AI can provide high-capacity, localized intelligent solutions meeting low-latency, high-bandwidth and isolated-security needs for industry customers.
- Brand-value zones. In early deployments mmWave will be combined with sub-6 GHz 5G to form mixed high/low frequency networks for coverage of high-value brand zones, crowded venues, and hotspots, improving user experience and offloading traffic while providing greater uplink capacity.
- High-bandwidth backhaul. mmWave can serve as a wireless backhaul link, using up to 800 MHz bandwidth and peak system rates of 10 Gbit/s to address fixed wireless broadband scenarios where fiber deployment is impractical or costly, including self-backhauled mmWave network topologies.
3.4 mmWave as a Competitive Differentiator for Operators
Compared with sub-6 GHz 5G, mmWave offers advantages in bandwidth, latency and flexible air interface configuration, which can meet future wireless capacity, throughput and differentiated service needs. Early mmWave research and pilot deployments help operators influence standards and device development directions and prepare networks and equipment to capture ten-gigabit-class capabilities.
4. Typical mmWave Application: Smart Winter Olympic Venues
Smart Winter Olympic venues exemplify mmWave use. Within large indoor venues, mixed low/high frequency networks can create purely wireless venues capable of supporting 4K/8K broadcast operations, real-time VR feeds, athlete-perspective streams, public livestreaming, and security services. Outdoors along race tracks, mmWave self-backhaul systems enable high-bandwidth camera video return without complex cabling, and avoid safety risks associated with cables in harsh environments.
- Broadcast and camera links. Given multiple venues and frequent location changes, high-bandwidth mmWave links allow flexible camera deployment and avoid repeated cabling.
- 360-degree panoramic video. Deploying 360-degree cameras plus 5G mmWave networks enables viewers to select camera angles freely for immersive viewing.
- Wearable AR/VR for athletes. Lightweight wearable AR/VR devices for athletes can provide multi-angle, athlete-perspective replays augmented with graphics, commentary and 3D models for richer viewing and analysis.
- Influencer livestreams and selfie uploads. High uplink bandwidth demands from livestreaming and user-generated content can be addressed by mmWave, beyond what sub-6 GHz systems can support.
- AI video surveillance and face recognition. Mobile robots, inspection drones and mobile face recognition combined with fixed systems improve venue security. A 5G mmWave private network with MEC&AI can upload video to edge nodes for fast intelligent recognition and real-time situational analysis.
Conclusion
This article reviewed mmWave standardization progress and the current industry status, analyzed the necessity of mmWave systems from the perspectives of industrial development, competitive demand and application scenarios, and presented smart Winter Olympic venues as a representative mmWave deployment with typical service examples.
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