Beamforming in 5G mmWave Radios

Beamforming is considered an essential part of mmWave (millimeter wave) 5G

5G mmWave offers huge potential capacity by virtue of providing large numbers of transmitting and receiving antennas as well as enormous channel bandwidth, and beamforming is an essential technology to make the 5G mmWave useful to users.

The limit of large number of antennas (theoretically going to infinite numbers) , small scale fading effects vanish by virtue of channel hardening and channel vectors from the BS to the users tend to become orthogonal. As a result plain channel matched beamforming at base station permits serving several users at the same time–frequency resource slot with no interference.

The Massive MIMO challenge

One problem with massive MIMO systems is the cost and complexity of hardware to efficiently exploit large number of antennas in mm wave region. Based on current vendor mmWave products, the number of antenna elements at the gNB can vary from 128 to more than 1,000

Also with mmWave, support for beam-sweeping is critical to estimate / identify the direction of interest. This procedure increases the overhead from CSI acquisition, which grows with the number of antennas since the beams become narrower and hence arising the need to support more beams.

Beamforming gain at mmWave is high compared to sub-6GHz since more number of antenna elements can be packed in the same form factor, resulting in a sharper beam. Also, this sharper beam can improve spatial separation between users and hence increase MU-MIMO performance.

Beamforming Technology

hybrid beamforming is achieved by a set of antenna arrays. Each antenna array
consists of several antenna elements and each antenna array can be mapped with one RF Chain.

The center lobe gain of each beam is determined by the overall gain achieved by combining the gains from all the antenna elements of the array. The number of phase shifters and number of antenna elements will further determine the number of beam directions that can be generated.

In adaptive beamforming, system can automatically learn based on performance metrics and close loop management, the required beambook to provide optimal coverage in any given cell.

5G mmWave Horizontal and Vertical Beamforming
Horizontal Beamforming Vertical Beamforming

Given the high variation in deployment scenarios, whether the area is highly treed, or composed of street canyons, or wide-open spaces, there will be a large range of path loss to contend with on a case by case basis. For example, in a dense urban deployment where LOS is assumed, the EIRP target may be as low as 50 dBm

5G mmWave Transmit Array Technology for Beamforming
Technology fit per mmWave radio use case

Phased Arrays and Holographic Beamformers

At mmWave frequencies, only Phased Arrays and Holographic Beamformers are viable candidates. Massive MIMO is not mature enough for mmWave deployment. One common design point for gNBs is that of a 60dBm transmit EIRP (@P1dB), single polarization beamformer suitable for mmWave operation.
Phased arrays targeted for this application are frequently 256 element transmit arrays (either 16 row and 16 column or 8 row and 32 column). The antenna array has 28dB of realized gain (29dB for a ‘perfect’ antenna array). Quad-element phased array chipsets becoming common in a variety of technology nodes.
64 of these driver chips would be needed to drive the 256 element array. Phased arrays distribute electronic gain to each element, resulting in a small transmit power requirement of 6.2mW per element for a total transmitted power of 32dBm. The combination of 32dBm electronic gain and 28dB antenna gain meets the 60dBm EIRP target. For Silicon based chips the expected Power Added Efficiency (PAE) is roughly 4% which means such an array will need at least 40W of DC input power. More efficient technology nodes exist (SiGe, GaAs, and GaN) but the cost generally scales with performance

An HBF of equal aperture size to the phased array would have 640 total elements driven by a single high power amplifier (rather than distributed into the array). An HBF of this size would have 26dB of antenna gain and thus need a GaN power amplifier able to source 34dBm (2.5W). GaN is generally higher performance, with off the shelf power amps reaching 25% PAE. This single amplifier approach has the added benefit of being able to exploit digital predistortion techniques to linearize the PA which is normally impossible for phased arrays. HBF also has a small control overhead driven by the number of control ASICs needed for switching the element states. For an array of this size the control overhead is roughly 2.9W.
This quantity is also present in Phased Arrays but is captured within the PAE of the chipset

5G mmWave Beamforming Front end FR2 Millimeter Wave

A typical spectrum of a modulated 5G NR signal is illustrated in Figure 8-27, which consists of many OFDM modulated sub-carriers. Since the transmitter is not ideal, intermodulation between the sub-carriers will occur when the modulated signal is amplified, up-converted and phase-shifted. All odd-number of intermodulation (IM3, IM5, IM7 and so on) will result in intermodulation products falling in-band as well as in the adjacent channels. The power from these intermodulation products that ends up in the adjacent channel is referred to in the 5G NR standard as the Adjacent Channel Leakage power Ratio (ACLR) and is defined as the ratio of the filtered mean power centered on the assigned channel frequency to the filtered mean power centered on an adjacent channel frequency. The ACLR requirement is specified for a scenario in which the adjacent carrier is another NR channel and should be > 17 dB for a mm-wave 5G NR signal.
This requirement can only be fulfilled by a sufficiently linear transmitter, since RF channel filtering is not practical at mm-wave frequencies.

Typical spectrum of a 5G NR mm-wave signal

mmWave Antennas

Due to the very short wavelength at mmWave frequencies, a single half-wave dipole antenna would be only 4-5mm long. To achieve increased range, a small group of antenna elements (usually 4 or 8) are arranged in an array and phased to concentrate the transmitted power in a relatively narrow beam.
Relative to transmitting the same total power from one antenna, the array achieves added gain of 10logN where N is the number of elements in the array. This gain applies in both transmit and receive. Antenna array factors that degrade the array performance from this ideal include direct coupling between the elements, surface waves with edge reflections, and differences in element patterns due to the finite overall structure size.

Dual/circular polarization antennas

The use of multiple operating arrays provide a mechanism for MIMO operation. In this case, the arrays beamform as needed in different directions into the multipath environment, to create multiple spatial channels, thus widening the total data pipe with proper decoding. If the individual antenna element is of a type that can be driven in orthogonal polarizations (as is the case for a patch antenna), the order of diversity or MIMO for the system can be further extended by driving these polarizations independently.

Reconfigurable antennas/arrays to realize large beam-scan coverage

Reconfigurability can be applied to several aspects of UE mmWave antennas.

  1. Radiation pattern modifications for individual antenna elements
  2. Switching between directional sub-elements
  3. Polarization modifications.
  4. Using 1 and/or 2 in an array to increase scan angle and reduce the arrays required for spherical coverage.

Low-loss beam-steering antenna arrays without phase shifters

The insertion losses of commercially available semiconductor-based phase shifters at mmWave frequencies are too high for passive beam forming in UE arrays thus the arrays require active beam steering circuits. Also, the performance of phased arrays are also limited by the variation in delay with frequency of the phase shifters, leading to shifts in beam pointing over a wide bandwidth. Moreover, the array element distance, which depends on the selected frequency, influences the gain at the lowest frequency and the coverage at the highest frequency of the interval. Smartphone mmWave antennas do not require very high directivity, only what is sufficient to provide the specified peak EiRP and wide spatial coverage, their element power beam-widths typically can stay in the range of 60°-90°. This means the number of beam states can be kept small, e.g. to 4-5 states per panel. While phased arrays can offer much higher resolutions, this is unnecessary for UE applications. In turn this implies beams can be controlled by simple switching schemes instead of phase shifters. Available switches offer <2 dB I.L. throughout 24-40 GHz compare to 4-7 dB phase shifter losses. Additionally, the beam direction of each setting does not depend on the alignment of multiple chains of electronics with and more consistent performance over environmental variation and over the terminal lifetime should be realized. This may also reduce test and calibration time. The antenna configurations utilizing switching schemes can take any of the following forms:  Single directive element (e.g. Yagi) antennas distributed around the UE chassis pointing in different directions  Couplers and delay-lines with switches configured in a Butler Matrix formation for small array Various ESPAR arrays configured by switches or tuners

High performance beam steering / beamforming components

The choice of architecture for beam forming in terminals depends strongly on the performance of the circuit elements available and their effective integration. For example, if small, high-performance switches were available, architectures with switches between the antenna elements and the active circuits would become feasible. Similarly, if integrated low-loss phase shifters were available (1dB or less), passive beam forming would become attractive, leading to reduced interference and easier calibration. Additionally, the
need for beam-steering systems that preserve their performance over multiple FR2 bands may drive a need for mmWave tuning for matching the antenna elements and for side-lobe suppression. The multiband requirement also will likely drive the need for tuning and/or reconfigurability throughout the signal chain.

Technologies for mmWave Base Station radios with Beamforming

The gain of the phased array is proportional to the number of array elements (N). On the Receiver (Rx)side, the array gain improves receive sensitivity (SNR) by a factor of N, whereas on the Transmitter(Tx) side, the combination of array gain and additional power per element results in an N2 increase in output power as compared to a single element. This fundamental property of the phased array enables a tradeoff between semiconductor performance and the size of array needed to meet system requirements. In particular, the N2 reduction in output power per element to achieve the same system EIRP targets makes
silicon technologies an attractive choice for all but the highest power applications.

Base stations and handsets have different output power specifications and specifications are also quite different depending on chosen architecture (phase array complexity and system integration approach).
Nowadays, all silicon and compound semiconductor technologies are competing for 5G mmWave base stations as well as handset.

Tx Power vs Operating frequencies for Power amplifiers using different technologies

Typical gNodeB mmWave 5G implementations

Several RAN vendors have well defined products and roadmap features to support mmWave bands. Products typically support BW up to 800MHz and EIRP ranging between 55-60dBm.

Typical 5G mmWave product specifications – published by Nokia (C) 2018

Maximum Output Power for 5G mmWave

In term of maximum transmission power of UE in mmWave, FCC has set the max radiated total EIRP limit for mobile station as 43 dBm, including mobile handset, for mmWave bands from 28 GHz to 39 GHz.
Also, FCC sets the max EIRP limit for transportable station (transmitting equipment that is not intended to be used while in motion, but rather at stationary locations) as 55 dBm.

Conclusions for 5G mmWave and Beamforming

While mmWave frequencies have been used in the past for satellite or point-to-point and point-to-multipoint backhaul connections, this is the first time that those frequencies have become part of 3GPP global standards for the intended use of terrestrial mobile along fixed access networks. Such progression has been made possible through various technological advancements, including massive MIMO coupled with beamforming technologies, advancement in chipset processing power, and the overall RF front-end/antenna subsystem integration/innovation for base station equipment as well as user equipment.

The limited propagation characteristics of mmWave spectrum due to their high frequency range, poor outdoor-to-indoor penetration due to building materials attenuation, as well as other environmental and weather factors have been well understood in the past. However, advancements in Massive-MIMO systems coupled with beamforming technologies related to fast beam-tracking, assignment, and switching intend to compensate for some of these shortcomings when mmWave spectrum is deployed in mobile networks

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5G mmWave Deployments Globally (July 2020)

5G mmWave Deployments Globally (July 2020):

Key statistics for mmWave:

Key statistics:

  • ninety-seven operators in 17 countries/territories hold public licences (many of them regional) enabling operation of 5G networks using mmWave spectrum.
  • twenty-two operators are known to be already deploying 5G networks using mmWave spectrum.
  • thirteen countries/territories have announced formal (datespecified) plans for assigning frequencies above 24 GHz between now and end-2021.
  • eighty-four announced 5G devices explicitly support one or more of the 5G spectrum bands above 24 GHz (though note that details of spectrum support are patchy for pre-commercial devices), up from 59 at the end of November 2019. Twenty-seven of those devices are understood to be commercially available.

Deployments today

The mmWave spectrum bands are being explicitly opened up to enable provision of 5G services. The 24.25–29.5 GHz range covering the overlapping bands n257 (26.5–29.5 GHz), n258 (24.25–27.5 GHz) and n261 (27.5–28.35 GHz) has been the most-licensed/deployed 5G mmWave spectrum range to date.

  • One hundred and twenty-three operators in 42 countries/ territories are investing in 5G (in the form of trials, licences, deployments or operational networks) across the 24.25-29.5 GHz spectrum range.
  • Seventy-nine operators are known to have been licensed to deploy 5G in this range.
  • Twenty-one operators are understood to be actively deploying 5G networks using this spectrum.

Band n260, covering 37–40 GHz, is also used, with 33 companies in six countries/territories investing in networks using this spectrum. Of those, 32 hold licences (with the majority of those 32 based in the USA and its territories). Three operators in the USA have launched 5G using band n260.

5g mmWave deployments and networks deployed

Recent 5G suitable spectrum awards and assignments concerning mmWave spectrum (2017 onwards)

5g mmWave deployments and networks deployed

*Note that due to the typically technology-neutral status of licences in the USA, multiple historic auctions are relevant for 5G including 28 GHz (March 1998 and May 1999) and 39 GHz (May 2000) and others. See www.fcc.gov/auctions for full details.

5G mmWave Global Availability

5G mmWave is starting to be deployed globally. A large increase in numbers of network deployments and user count is expected.

5g mmWave Planned deployments:

Thirteen countries/territories have announced formal (date-specified) plans for assigning 5G-suitable mmWave frequencies between now and end-2021 (including technology-neutral licences or licences for mobile broadband services). Many countries/territories are still deciding whether and when to hold auctions/assignments for mmWave spectrum. Announced events are shown here:

5g mmWave deployments and networks deployed

Summary:

mmWave spectrum is becoming increasingly important for mobile
telecoms and a number of trends will underpin the continued
emergence of a 5G market that uses mmWave spectrum:

  • increasing numbers of operators with spectrum assignments in mmWave bands suitable for 5G deployments.
  • further auctions of mmWave spectrum in the coming years.
  • increasing investment in networks using these spectrum bands
  • by operators.
  • commitments to launch compatible devices by device vendors.

Data and graphs from and (C) the GSA (Global mobile Suppliers Association)

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5G NR mmWave FR2 Frequency Bands

5G mmWave FR2 Bands

Frequency bands for 5G NR FR2 are being separated into two different frequency ranges:

Frequency Range 1 (FR1)

Frequency Range 1 (FR1) includes sub-6GHz frequency bands, some of which are bands traditionally used by previous standards, but has been extended to cover potential new spectrum offerings from 410 MHz to 7125 MHz.

Frequency Range 2 (FR2)

Frequency Range 2 (FR2) includes frequency bands from 24.25 GHz to 52.6 GHz. Bands in this millimeter wave range have shorter range but higher available bandwidth than bands in the FR1.

Frequency bands and channel bandwidths

From the latest published version of the 3GPP TS 38.101, the following tables list the specified frequency bands and the channel bandwidths of the 5G NR standard.

Note that the NR bands are defined with prefix of “n”. When the NR band is overlapping with the 4G LTE band, they share the same band number.

Frequency Range 2 (mmWave)

Bandƒ (GHz)Common nameSubset of bandUplink / Downlink (GHz)Channel bandwidths (MHz)
n25728LMDS26.50 – 29.5050, 100, 200, 400
n25826K-band24.25 – 27.5050, 100, 200, 400
n26039Ka-band37.00 – 40.0050, 100, 200, 400
n26128Ka-bandn25727.50 – 28.3550, 100, 200, 400
5G mmWave FR2 Frequency Bands

5G mmWave FR2 bands:

5G mmWave FR2 Frequency Bands

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Introducing 5G mmWave

What is mmWave 5G Wireless?

The emergence of new 5G New Radio (5G NR or just 5G) standards for mobile cellular networks offer huge increases in capacity and performance. 5G has the potential to deliver a complete transformation of wireless communications. The spectrum for 5G services not only covers bands below 6 GHz, including bands currently used for 4G LTE networks, but also extends into much higher frequency bands not previously considered for mobile communications. It is the use of frequency bands in the 24 GHz to 100 GHz range, known as millimeter wave (mmWave), that provide new challenges and benefits for 5G networks.

The emergence of mmWave wireless is a key part of the 5G revolution, with available spectrum for mmWave, the supported bandwidths, and how antenna technologies work together to deliver multiple Gigabit data rates to end users. Deployment scenarios are considered where 5G mmWave networks will start to make an impact on everyday wireless communications.

The 5G mmWave Spectrum

The incredible demand for wireless data bandwidth shows no sign of slowing down now or in the near future. As a result, the mobile data experience for users continues to expand and develop, putting an increasing strain on network use of available wireless spectrum. To meet this projected growth, the cellular industry looked to other frequency bands that could possibly be utilized in the development of new 5G wireless technologies. The high-frequency bands in the spectrum above 24 GHz were considered as having the potential to support large bandwidths and high data rates, ideal for increasing the capacity of wireless networks. These high-frequency bands are often referred to as “mmWave” due to the short wavelengths that can be measured in millimeters. Although the mmWave bands extend all the way up 300 GHz, it is the bands from 24 GHz up to 100 GHz that are expected to be used for 5G. The mmWave bands up to 100 GHz are capable of supporting bandwidths up to 2 GHz, without the need to aggregate bands together for higher data throughput.

The available mmWave bands in the United States provides a good example of the spectrum that can be utilized for 5G networks. The FCC have made more spectrum available for 5G and have signaled that more licensed bands will be opened up for use.

The Challenges of 5G mmWave Deployment

Previouslythe use of frequency bands much above 6 GHz was considered unsuitable for mobile communications due to the high propagation losses and the ease with which signals are blocked by not only building materials and foliage, but also by the human body. Although these challenges place limitations on mmWave deployments, new antenna technologies together with a better understanding of channel characteristics and signal propagation enable a number of deployment scenarios to be considered.

The high penetration losses and blocking mean that mmWave deployments will cover outdoor or indoor environments, but not provide outdoor to indoor connectivity. The mmWave cell sizes will, therefore, be smaller and higher in density. Also, it can be expected that mmWave will coexist in a tight integration with 5G deployments below 6 GHz as well as 4G LTE. Fast adaptation to changing channel conditions will enable switching within and across cells to maintain performance and coverage. In addition, there will almost certainly be a key role for Software-defined networking (SDN) and network functions virtualization (NFV) in how networks operate and provide seamless connectivity for users.

At the core of basic 5G mmWave technology is a new air interface based on time-division duplexing and robust orthogonal frequency division multiplexing (OFDM) methods similar to those as used in LTE and Wi-Fi networks. With peak throughput speeds of 10 Gbps or more and the ability to support a huge number of devices, 5G mmWave has performance targets that will deliver a transformation in how wireless communications are utilized.

 challenges of 5G mmWave deployment

5G mmWave uses Massive MIMO Antennas

Smaller cell sizes of 5G mmWave not only provides high throughput, but also allows for efficient use of spectrum as frequencies can be reused over relatively small distances. It is projected that outdoor cell sizes will be typically 100m to 200m and indoor high-density deployments might be as small as 10m. An important part of 5G mmWave performance is therefore dependent on line-of-sight (LOS) and non-line-of-sight (NLOS) propagation of signals and antenna design.

Great advancements made in RF silicon allow a large number RF chains to be supported in large antenna arrays. The computational and switching capacity available enables “massive multiple-input-multiple-output (massive MIMO)” antennas to create highly directional beams that focus transmitted energy in ways that can overcome path losses and NLOS conditions. A fundamental characteristic of mmWave, the short wavelengths, means that even massive MIMO antennas can be relatively compact and small effective antennas can be easily integrated into user devices. Whereas MIMO antennas for under 6 GHz wireless may support eight elements, at mmWave frequencies the number of massive MIMO elements might be 128, 256, or higher. These “phased arrays” perform the beam-forming, beam-steering, and beam-tracking techniques that enable a 5G mmWave network to deliver such high capacity and efficiency.

massive mimo antennas for 5g

Likely 5G Millimeter Wave Deployment Scenarios

When outlining the requirements for 5G services, the International Telecommunication Union (ITU) identified three main categories for the 5G NR architecture; Enhanced Mobile Broadband (eMBB) for greater mobile capacity, Ultra-reliable and Low-latency Communications (uRLLC) for mission-critical services, and Massive Machine Type Communications (mMTC) for vast numbers of low-cost, low-energy devices (Internet of Things). These broad areas provide plenty of early deployment possibilities for 5G mmWave, such as the following:

  • Fixed wireless Internet access. The Gigabit data rates of 5G mmWave could completely replace a number of Internet access technologies with hybrid fiber and wireless networks connecting subscriber homes. Although not truly a mobile system, it could provide competition to existing Wi-Fi systems that provide this type of fixed wireless access.
  • Outdoor urban/suburban small cells. An expected deployment scenario for 5G mmWave would be to provide increased capacity in high-demand public spaces and venues. With cell sizes around 100m, small 5G mmWave access points can be placed on poles or buildings to provide the required coverage.
  • Mission-critical control applications. Autonomous vehicles, vehicle-to-vehicle communications, drone communications, and other latency-sensitive, high-reliability applications provide other possible deployment scenarios for 5G mmWave with a projected network latency of less than a millisecond.
  • Indoor hotspot cells. Shopping malls, offices, and other indoor areas require a high-density of 5G mmWave micro cells. These small cells will potentially support download speeds of up to 20 Gbps, providing seamless access to cloud data and the ability to support multiple applications, as well as various forms of entertainment and multimedia.
  • Internet of Things. The general connectivity of objects, sensors, appliances and other devices for data collection, control, and analysis. Potentially could cover smart home applications, security, energy management, logistics and tracking, healthcare, and a multitude of other industrial operations.

The 5G mmWave Revolution

Implementation of new 5G mobile standards and the use of mmWave spectrum is expected to make major changes to the cellular industry. These mmWave bands being made available for mobile networks will provide increased performance, better coverage, and a closer integration across multiple wireless technologies from 4G LTE to Wi-Fi, to sub-6GHz 5G, as well as extending to the higher frequency 5G mmWave bands. Bringing all networks together will be an SDN architecture overlay that will provide seamless connectivity for an increasing number of users and networked devices.

5G mmWave is now being deployed in low-cost, small cell networks using massive MIMO antennas to deliver as much as 20 Gbps download rates to users, bringing the huge promise of 5G to fruit. When widely deployed, most expect a great increase in the number of applications and deployment scenarios that exploit the new mmWave 5G technology.

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Welcome to 5GmmWave !

5G mmWave FR2 Bands

Find out more about 5G Networking with mmWave (Millimeter Wave) Technology

We will be sharing information on latest-generation mmWave technology and products ideal for building next-generation 5G Networks

Please feel welcome to follow our site as we add more information on this exciting technology.

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