Safety of 5G Frequencies and Networks

Massive MIMO Beamforming 5G

Is 5G Safe? Why do some people think it isn’t?

There’s currently huge controversy in the news today regarding safety of 5G: Is it safe, or not? 5G vendors & scientists say the technology is perfectly safe, and some members of the public allege that 5G isn’t safe. Here we examine the topics factually.

Frequencies used by 5G

There is nothing magic or new about the frequencies used or proposed for 5G. They have ALL been used already, actually for decades! 5G frequencies are split into two sections: FR1 (less than 6GHz) and FR2 (high frequency microwave, or “millimeter wave”).

Almost ALL of the FR1 frequencies have already been used for 4G, and some before that for 3G, and 2G, back to the 1990’s. A good example is 900MHz (the original GSM system) and 1800MHz (second round of GSM). 2100MHz was used extensively for 3G. A few of the FR1 frequencies haven’t been used for 4G before (e.g. 3800 up to 4200MHz) but they have been used for other purposes before.

FR2 frequencies (millimeter wave, or mmWave) have already been used – very widely – for Point-to-Point microwave links. All of the FR2 bands (24Ghz, 26GHz, 28GHz, 38-40GHz, and even the proposed 60GHz) have been used for point-to-point terrestrial microwave links. Those are the parabolic dishes you see everywhere on rooftops or towers. These signals are highly directional “pencil beams” with typically 1 degree or less beam width. The number of these links globally is in the 100,000+ range: they are beaming signals around cities all over the world, usually connecting internet services, beaming signals up to 3G/4G towers or for links between corporate office networks. As a result of the creation of 5G technology, these frequencies are now being re-used (“re-farmed”) for use by 5G base stations to connect end users to the internet, using Point-to-multipoint beamforming technologies. Important note: the use of 5G is no more or less “scary” than the previous use for point to point links. Note that point-to-point microwave has existed since 1930: 90 years ago, and health risks (and lack of risk to public) are very well understood.

Operating Distances

5G in lower frequencies travels longer distances than higher frequencies, due to laws of physics. This is why the lower frequencies are used for Rural locations for wide area coverage, whereas the higher frequencies are reserved for use in cities, where distances are shorter, and user densities higher.

Also, the lower frequencies (lower end of FR1) can be transmitted at higher power levels than the higher frequencies. Conversely, high frequencies (mmWave, FR2) are limited to lower power due to limitation of today’s commercial technology.

5G in the 24GHz, 26GHz, 28GHz range and above (also called millimeter wave, or mmWave bands) uses higher frequencies than 4G. As a result, these high frequency 5G signals are not capable of traveling large distances (over a few hundred meters), unlike 4G or lower frequency 5G signals (sub 6 GHz) so penetration and hence coverage are lower.
This higher frequency therefore requires placing 5G base stations every few hundred meters in order to use higher frequency bands.

5G and RF power levels

Some of the “5G Conspiracists” allege that 5G will cause damage/health risk to humans. There is simply no measured case or evidence of this happening. If there were, there would be scientists & health advisors demanding change. Let’s examine in more detail:

5G sites using FR1 transmit at exactly the SAME power levels as 4G sites. So you’re not irradiated any more than a 4G site was. 40W a typical figure for a macro (big) site, and 1W for a Small Cell (small site).
Note carefully: 5G FR1 sites use EXACTLY the same power levels as 4G sites, which is similar to 3G sites, and before that, 2G sites …
5G uses “sector antennas” (typically 3 on a macro site) just like 4G does.
Therefore any related health risk is therefore the same for 5G as it’s predecessors.

5G sites using FR2 transmit at MUCH lower power levels: less than 1 Watt typically. These high frequency signals have poor penetration of buildings and obstacles, so are generally “line of sight” only. As noted above, ALL of the FR2 frequencies have been used before, for terrestrial microwave links, and at similar power levels (less than 1 Watt).
The use of beamforming steers the signal to the required locations; this reduces the overall amount of transmitted power emitted into the air, and hence total radiation. Put simply, if you aren’t using your device, the base station doesn’t point power at you.

How to 5G power levels compare to other Radio/RF transmitters?

The VERY good question conspiracists & “truthers” never discuss. Let’s go straight there.

  • A TV transmitter such as Crystal Palace in London, UK currently transmits digital terrestrial Television at over 1200kW (1.2 MEGAWATT, or 1,200,000 watts), and has been transmitting TV since 1956.  That is 120 MILLION TIMES more power than a V-band 60GHz radio, and transmitting for over 60 years.   Did you hear “5G protesters” complaining about TV transmitters? No, because there’s no widespread history of health effects over 60 years .
  • Airport Radars:   To keep planes flying safely, airport radars transmit pulses up to 25kW (25 kilowatts, or 25,000 Watts) into the air, with average power 2.1kW (2100 Watts).  Interestingly, these signals are at similar frequencies to 3G, 4G and 5G.  In the USA, 2.7 – 2.9 GHz is used.  Yet nobody complains about these high power levels of radar, which has been in constant use since the 1930s:  90 years.
  • Digital Radio (DAB): Crystal Palace transmits digital radio with 18kW (18,000 Watts) of radio power. Compare that with 40W of a large (macro) 5G base station.
  • Emergency Service (TETRA) Radios : used by police, fire & ambulances: transmit at up to 45 Watts. Very similar to the 40W of a large (macro) 5G base station.

You will notice that the HIGHEST powered transmitters are Television transmitters (Megawatt), Radars & Radio stations (10’s of Kilowatts). A macro 5G base station at 40W comes nowhere close. Note that these various transmitters are used on different frequencies, there’s no “one” frequency that is safer (or less safe) than another. It’s only the RF exposure (power) level that matters – specifically, the power incident on your own human body.

Why is there no mass hysteria from “Truthers” about TV, Radar and Radio transmitters? Because if they were THAT bad for our health, they would have been banned and switched off decades ago. Evern the largest (macro) 5G transmit powers are tiny by comparison.

Key “Truther” points examined:

  • 60GHz is absorbed by Oxygen in the bloodstream (Untrue)
    Out in the open air this absorption is true : but not in the body! 60GHz signals are 40% reflected by skin surface, absorbed by water (body is 60% water), and does NOT enter the bloodstream. The “Truthers” invent Pseudo-science , claiming: “This causes Oxygen to not bind well to blood hemoglobin causing the body to become Oxygen starved (hypoxia)”  This statement is hopelessly unscientific.  The ultra low power 60GHz signals do not even penetrate human skin.  The signals are partly reflected and partly absorbed by the skin, preventing them entering the body and cannot cause the claimed effect.  There is NO scientific study which will back up this claimed hypoxia effect on the human body.  The “5G protesters” NEVER provide any, because there is no publication or science that would agree with their unscientific claims – it’s simply not impossible. They make stuff up to make you afraid, and sharing their website gives them more “hits”: Some have adverts on their sites. More clicks means more money for them! (Fear=money for some)
  • 5G is a state-sponsored weapon: Untrue.
    5G is simply a marketing term applied to the work of the 3GPP, a standards body which includes equipment vendors & operators, as a linear development of from work that was labelled 4G and 3G before it. Governments are not included in developing 2G, 3G, 4G, 5G… and future 6G technology – corporations are.
  • Governments want to use 5G to control the population: Untrue,
    in that 5G gives Government agencies no more data than 4G does. Your location, digital activities, content & data usage habits are already well known to Google, Facebook and – on warrant – Law Enforcement Agencies. 5G does not change this at all. You already gave all that data to companies 10 years ago when you bought a 3G smartphone, or signed up with Social Media sites, apps, Apple or Google services. Law enforcement agencies can demand access to that data with a warrant.
  • IoT is scary: Untrue, in any way that relates to 5G.
    “Internet of Things” is a marketing label applied to home gadgets – and industrial devices – that are connected via the Internet by either WiFi or cellular (4G, 5G) networks. The same IoT label applies to a WiFi doorbell. Main concern with IoT is DATA security, particularly physical security (locks, cars) and CCTV camera feeds. That has nothing to do with 5G, because the concern is the data security of the devices & security attitudes of companies that sell them. Note that the WiFi-connected IoT devices are a much greater security risk than 4G, 5G because WiFi is much easier for criminals to hack/spoof.
  • 5G causes cancer: Untrue.
    5G uses the same signals as 4G (FR1), plus some millimeter wave frequencies (FR2) which were previously used by microwave links for decades. There is no link to cancer in 30+ years of medical research and continued exposure to these signals. Microwave & radio signals used by 4G & 5G are NON-ionising radiation which is not hazardous except in massively high power levels (far more than 4G, 5G etc). The “dangerous” radiation type is IONISING radiation, including X-rays and similar. Those are not used for communication for this exact reason: they are dangerous.
    (Side-note: X-Rays used in medicine are VERY carefully controlled. Had an X-Ray? note the operators have shielding everywhere, because they use it every day & could get higher does than patients. They regulate the dose to you carefully for your safety)
  • 5G is linked to Coronavirus: Untrue.
    There’s no link at all. Many of the countries with terrible cases of Coronavirus have no 5G. And vice versa. All the theories connecting the two have been soundly debunked by reputable & international scientists.
    (Side note: there IS a link between Coronavirus deaths and air pollution: because the Coronavirus effect on the body attacks the lungs, putting patients with poor respiration are at great risk. Cleaning up diesel emissions, industrial cities & banning smoking would have saved 1000’s of lives from Coronavirus.)

Power levels and Distance (very important topic)

The RF power emitted from the transmitter antenna spreads with distance. This means that a person some distance away from the tower only receives a weak signal. As you DOUBLE the distance, you receive one QUARTER the power level. This is called the “inverse square law”. What it means in practice is that a person 100’s of metres away from a base station is radiated with only microwatts of power, which is insignificant, especially compared to this next point:

The highest radiation of Radio signals you will get is from …. wait for it …
Your cellphone is on your person – and when used in the worst case, held directly against your head. The cellphone transmits at up to 1 Watt power – in all directions – which means the signals go into your head as well as the air around you. This topic remains the same since the first cordless phones in the 1980’s, analogue cellphones and GSM phones in the 1990’s. Using the phone means the signal is close to your head – and the most sensitive item, your brain. The HIGHEST amount of radiation you will receive from any wireless system is from your OWN HANDSET when you hold it to your head to make a voice call. Therefore, if you are really worried about cellphone safety – STOP using your OWN phone. The radiation your body receives from it is 1000’s of times stronger than that you receive from the mast.

If you’re worried about 2G, 3G, 4G, 5G masts: stop now. The FIRST thing you must do is switch off your OWN phone, and never hold it against your head to talk. And if it’s in your pocket/jacket/handbag do remember, it’s still transmitting to the mast, updating it’s location to the network, and often up/downloading data to your apps continually. It’s still transmitting, even in “standby”.
If you’re not prepared to turn off your OWN PHONE, then stop worrying about masts at all. The signal from masts signal is over 1000 times weaker than your OWN PHONE when it reaches your body.

Massive MIMO Beamforming 5G
Diagram courtesy Qualcomm

5G FR2 mmWave Penetration

Also, these higher frequency 5G signals cannot penetrate solid objects easily, such as cars, trees, and walls, because of the nature of these higher frequency electromagnetic waves. 5G cells can be deliberately designed to be as inconspicuous as possible, which finds applications in places like restaurants and shopping malls.

Cell types
5G NR FR2
Deployment environmentMax. number ​of usersOutput power ​(mW)Max. distance from ​base station
FemtocellHomes, businessesHome: 4–8
Businesses: 16–32
indoors: 10–100
outdoors: 200–1000
10s of meters
Pico cellPublic areas like shopping malls,
airports, train stations, skyscrapers
64 to 128indoors: 100–250
outdoors: 1000–5000
10s of meters
Micro cellUrban areas to fill coverage gaps128 to 256outdoors: 5000−10000few hundreds of meters
Metro cellUrban areas to provide additional capacitymore than 250outdoors: 10000−20000hundreds of meters
Wi-Fi
(for comparison)
Homes, businessesless than 50indoors: 20–100
outdoors: 200–1000
few 10s of meters
5G NR mmWave FR2 coverage

Challenges for 5G Safety – for EVERYONE !

5G Networks
5G Networks

It is the responsibility of the 4G/5G cellular industry, national regulators, safety agencies and all academics to be truthful about the safety of all radio transmitters. There must be no cover-ups, lying, or partial truths. Medical research into possible risks of RF exposure must continue and be well funded. The industry needs to deliver reliable cellullar service without putting populations at risk. “Profit” cannot come at cost of public safety.

Conversely – “truthers” making up pseudo-science & invented “facts”, with blogs written by uneducated persons have so far resulted in:

  • Violence and threats against telecom employees doing their jobs on sites
  • 4G/5G sites being burned down (resulting in loss of service to Hospitals, including those treating Coronavirus and critical health conditions)
  • Death threats and threats of violence against business owners.

Now think clearly and rationally: EVERYONE has a legal & moral responsibility to behave within the law and not to threaten the health of others.
Clearly those posting non-factual “truther” content on Internet websites & social medahave a responsibility to bear. If you are one of those authors, think carefully. Your action could well cause harm or death of others.

I simply don’t believe you!

That’s the frequent response of someone when confronted with information that conflicts with their previously held opinion or prejudices. In the case of 5G, we have we have plenty of information sources. On the “5G is safe” side we have:

  • All reputable Scientists Worldwide
  • All national Governments
  • Biologists Worldwide
  • All safety Agencies Worldwide
  • The Cellphone industry
  • 30+ years of no measurable health effects of cellphones on worldwide population

And on the “5G is unsafe” side we have:

  • Conspiracists without facts
  • Non-scientific blog writers, some whom earn $ from adverts on their blogs (!)
  • Narcissists who want “likes” on posts, or TV appearances
  • Easily-swayed but highly opinionated people
  • NO evidence of health effects over 30+ years
  • NO reputable scientists !

Have a careful think about what sources of information you take in forming your world view. Just two hundred years ago, our ancestors burned and drowned innocent people for “witchcraft”. Why are we any better informed than our ancestors? Answer: SCIENCE and EDUCATION. We use logic, rather than irrational and uninformed fear.

Conclusion for 5G & Safety

There is a huge media frenzy and “truther sites” full of pseudo-science about 5G & safety. We suggest we make our decisions based on science and facts. Here’s our summary:

  • 5G is no less safe than 4G. If you didn’t protest 4G, stop protesting 5G.
  • (If you DID protest 4G, then carry on protesting, but remember, 5G is no less safe!)
  • Millimeter wave” frequencies have already been used for 3 decades or more for terrestrial microwave links. We’ve already been irradiated by them for 30+ years, with no harm to us. 5G just re-uses these same frequencies.
  • There is no measured health risk from “Millimeter Wave” signals in any credible study or publication. 60GHz doesn’t stop O2 in the blood, that’s a non-scientific myth invented by “truther” blogs. No medical reports or science to back up claims.
  • “Millimeter wave” (FR2) transmitters are on average 50x less powerful than the lower frequency FR1 macro (main site) transmitters.
  • The HIGHEST radiation you will get is from your OWN cellphone: it’s right next to your body, and transmits even in your pocket/jacket/handbag. If you’re worried, turn it off.
  • Turning off 5G transmitters on masts makes AlMOST NO DIFFERENCE because the 2G, 3G, 4G transmitters on the mast are still transmitting, all at very similar power levels and frequencies, and distance to you is the same. Power levels radiated to your body remains almost unchanged whether you turn 5G on or off.
  • Turning OFF all the cellphone masts will cause deaths. A LOT of them, as your loved ones can’t dial an ambulance, lost persons, persons caught in fires & crash victims can’t call help. Emergency responders also rely on the masts. Conversely, there’s no measured death rate from cellphone masts, in over 40 years of widespread use.
  • LOGIC as well as ETHICS says leave the masts turned on.

For Further Information

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5G Coverage using FR2 mmWave frequencies

Massive MIMO Beamforming 5G

5G FR2 Coverage and Penetration

5G in the 24GHz, 26GHz, 28GHz range and above (also called millimeter wave, or mmWave bands) uses higher frequencies than 4G. As a result, these high frequency 5G signals are not capable of traveling large distances (over a few hundred meters), unlike 4G or lower frequency 5G signals (sub 6 GHz) so penetration and hence coverage are lower.
This higher frequency therefore requires placing 5G base stations every few hundred meters in order to use higher frequency bands.

5G FR2 mmWave Penetration

Also, these higher frequency 5G signals cannot penetrate solid objects easily, such as cars, trees, and walls, because of the nature of these higher frequency electromagnetic waves. 5G cells can be deliberately designed to be as inconspicuous as possible, which finds applications in places like restaurants and shopping malls.

5G mmWave FR2 Penetration and Coverage
Diagram courtesy Qualcomm
Cell types
5G NR FR2
Deployment environmentMax. number ​of usersOutput power ​(mW)Max. distance from ​base station
FemtocellHomes, businessesHome: 4–8
Businesses: 16–32
indoors: 10–100
outdoors: 200–1000
10s of meters
Pico cellPublic areas like shopping malls,
airports, train stations, skyscrapers
64 to 128indoors: 100–250
outdoors: 1000–5000
10s of meters
Micro cellUrban areas to fill coverage gaps128 to 256outdoors: 5000−10000few hundreds of meters
Metro cellUrban areas to provide additional capacitymore than 250outdoors: 10000−20000hundreds of meters
Wi-Fi
(for comparison)
Homes, businessesless than 50indoors: 20–100
outdoors: 200–1000
few 10s of meters
5G NR mmWave FR2 coverage

Challenges for 5G Coverage:

Transmissions in mmWave bands suffer from significantly higher path loss and susceptibility to blockage. In addition, mmWave RF complexity makes meeting the cost and power constraints of mobile devices extremely challenging, which is why mmWave for mobile communications has historically been not feasible—until now. 5G NR mmWave is changing this.

Uses for 5G mmWave

While the initial focus for mobile operators is to quickly expand network capacities by starting deployments of 5G NR mmWave in existing dense urban markets, there are even more opportunities for mmWave beyond traditional macro networks. One area of interest is to bring mmWave indoors to address the exploding demand of fiber-like wireless broadband access in crowded venues, such as convention centers, concert halls, and stadiums. These venues have traditionally been challenged with limited network capacity, thereby constrained with the quality of service (e.g., slow speeds and unreliable connectivity) they can deliver. With mmWave’s significantly wider bandwidth and high spatial multiplexing gains, mobile operators and service providers could rapidly make multi-Gigabit, low-latency connectivity available to a large number of users.

Another exciting opportunity for mmWave is for private indoor enterprises, including offices, shop floors, meeting rooms and more. Imagine having virtually unlimited capacity and fiber-like wireless connectivity for your devices at work, no matter if it’s a smartphone, tablet, laptop, or mobile extended reality (XR). For these indoor deployment scenarios, we have also performed extensive study to show that significant coverage (i.e., >90%) and multi-Gbps median speeds can be achieved simply by co-siting mmWave small cells with existing LTE or Wi-Fi access points.

For Further Information

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Massive MIMO and Beamforming in 5G

5G Networks

Massive MIMO (mMIMO) and beamforming are key acronyms widely used in the telecom industry when referring to 5G and latest advancements of 4G LTE. We note that MIMO comes in many different variants, some of them having been in use already for years in today’s 4G LTE networks.

SU-MIMO vs. MU-MIMO

In 4G LTE, the term MIMO usually refers to Single User MIMO (SU-MIMO). In Single User MIMO, both the base station and UE have multiple antenna ports and antennas, and multiple data streams are transmitted simultaneously to the UE using same time/frequency resources, doubling (2×2 MIMO), or quadrupling (4×4 MIMO) the peak throughput of a single user.

In MU-MIMO, base station sends multiple data streams, one per UE, using the same time-frequency resources. Hence, MU-MIMO increases the total cell throughput, i.e. cell capacity. The base station has multiple antenna ports, as many as there are UEs receiving data simultaneously, and one antenna port is needed in each UE.

Beamforming: principles of operation

The terms beamforming and mMIMO are sometimes used interchangeably. One may consider that beamforming is used in mMIMO, or beamforming is a subset of mMIMO. In general, beamforming uses multiple antennas to control the direction of a wave-front by appropriately weighting the magnitude and phase of individual antenna signals in an array of multiple antennas. That is, the same signal is sent from multiple antennas that have sufficient space between them (at least ½ wavelength). In any given location, the receiver will thus receive multiple copies of the same signal. Depending on the location of the receiver, the signals may be in opposite phases, destructively averaging each other out, or constructively sum up if the different copies are in the same phase, or anything in between. Beamforming is further divided to subcategories as explained in the following chapters.

Massive MIMO Beamforming 5G
Diagram courtesy Qualcomm

Digital beamforming (Baseband beamforming, precoding)

In this scenario, the signal is pre-coded (amplitude and phase modifications) in baseband processing before RF transmission. Multiple beams (one per each user) can be formed simultaneously from the same set of antenna elements. In the context of LTE/5G, MU-MIMO equals to digital beamforming. Multiple TRX chains, one per each simultaneous MU-MIMO user, are needed in the base station. Digital beamforming (MU-MIMO) is used in LTE Advanced Pro (transmission modes 7,8, and 9) and in 5G NR. Digital beamforming improves the cell capacity as the same PRBs (frequency/time resources) can be used to transmit data simultaneously for multiple users.

Analog beamforming

Here, the signal phases of individual antenna signals are adjusted in RF domain. Analog beamforming impacts the radiation pattern and gain of the antenna array, thus improves coverage. Unlike in digital beamforming, only one beam per set of antenna elements can be formed. The antenna gain boost provided by the analog beamforming overcomes partly the impact of high pathloss in mmWave. Therefore analog beamforming is considered mandatory for the mmWave frequency range 5G NR.

Hybrid beamforming

Hybrid beamforming combines the analog beamforming and digital beamforming. It is expected that mm-wave gNB (5G base station) implementations will use some form of hybrid beamforming. One approach is to use analog beamforming for coarse beamforming, and inside the analog beam use a digital beamforming scheme as appropriate, either MU-MIMO or SU-MIMO.

Massive MIMO

Most common definitions are that mMIMO is a system where the number of antennas exceeds the number of users. In practice, massive means there are 32 or more logical antenna ports in the base station It is expected that NEMs will start with a maximum of 64 logical antenna ports in 5G.

This diagram illustrates how mMIMO works in practice. An antenna array of 50 omni elements, with ½ wavelength spacing in between the antenna elements is used. The 50 elements transmit 4 distinct streams of data via 4 logical antenna ports, one stream for each UE. All four streams are transmitted using the same physical resource blocks, i.e. the same time/frequency resources. The data streams do not interfere between each other because each of them has a distinct radiation pattern, where the signal strength in the direction of the target UE is optimized, and in the directions of the other UEs (victim UEs) the signal strength is minimized.

5G-Massive-MIMO-Test

In MU-MIMO/mMIMO, the base station applies distinct precoding for the data stream of each UE where the location of the UE, as well as the location of all the other UEs, are taken into account to optimize the signal for target UE and at the same time minimize interference to the other UEs. To do this, the base station needs to know how the downlink radio channel looks like for each of the UEs.

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CPRI and eCPRI in 5G and open vRAN

5G Band n77 Remote Radio Head (RRH)

CPRI, eCPRI and open vRAN: What’s happening?

Common Public Radio Interface (CPRI) has been around for quite some time. But now, enhanced CPRI (eCPRI) is becoming an important technology to understand for 5G.
 
Before looking in detail at eCPRI, it’s helpful to understand some of the basic topology of the cellular network, which currently uses CPRI.

CPRI, Remote Radio Heads (RRH) in 4G and 5G

5G Band n77 Remote Radio Head (RRH)
5G Remote Radio Head (RRH) with CPRI or eCPRI fibre optic interface

At the outer circle of a cellular network topology, remote radio units (RRUs) are distributed every few miles in cities and suburban areas. These RRUs comprise antennas and also some compute functionality.
 
Fiber runs from a cluster of these RRUs to connect to a more centralized baseband unit. The baseband unit is also sometimes called the “central processing unit.” Baseband units are typically distributed within approximately 10-mile circles for good coverage in populated areas. The connection between the RRUs and the base station is often referred to as “fronthaul.”

eCPRI

CPRI is an interface that sends data from the RRUs to the baseband unit: CPRI is a serial interface, which is a very high-speed connection, a way to translate all those radio signals back to the computing function.

As we go to 5G, the fiber between the RRUs and the baseband unit is going to carry much more traffic, and that makes it more difficult to do a serial interface. Extreme 5G requirements are stretching the limits of fiber bandwidth.

Enter eCPRI, which is a way of splitting up the baseband functions and putting some of that functionality in the RRU to reduce the burden on the fiber.

AT&T is among many carriers that are working on eCPRI. AT&T has made “the world’s first” eCPRI connection for mmWave at its 5G Labs in Redmond, Washington. AT&T made calls testing eCPRI, using systems from both Nokia and Samsung Electronics America.

This opens the door for higher network throughput with less fiber, which will create more efficient mmWave deployments, among other benefits, This is also a significant step in creating an open architecture within the radio access network (RAN).

Vendor lock-in

Another problem with the CPRI interface today is that it has become a proprietary technology.
 
In addition to supporting more bandwidth across fewer fibers, the enhanced CPRI also addresses the proprietary concerns. eCPRI will be an open interface, making it easier for carriers to mix and match vendor equipment for their RRUs and their baseband units.
 
Historically, because each vendor would have its own implementation of CPRI, it became proprietary. This forces carriers to buy both their RRUs and their baseband unit from the same vendor in order for the interface to work. With O-RAN this interface will be open. Carriers such as AT&T who implement eCPRI will be able to run equipment from different vendors, or even generic off-the-shelf equipment.
 
However, existing networks with CPRI installed will most likely remain in place for years to come.

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5G NR gNodeB Functional Split : CU DU split

This article explains details of the 5G gNodeB (gNB) architecture and choices for Central Unit (CU) and Distributed Unit (DU) Split (CU DU Split)

How is the gNodeB Comprised?

The logical architecture of gNB is shown in figure below with Central Unit (CU) and Distributed Unit (DU). Fs-C and Fs-U provide control plane and user plane connectivity over Fs interface.

5G gNodeB CU DU Split

In this architecture, Central Unit (CU) and Distribution Unit (DU) can be defined as follows:

Central Unit (CU): It is a logical node that includes the gNB functions like Transfer of user data, Mobility control, Radio access network sharing, Positioning, Session Management etc., except those functions allocated exclusively to the DU. CU controls the operation of DUs over front-haul (Fs) interface. A central unit (CU) may also be known as BBU/REC/RCC/C-RAN/V-RAN

Distributed Unit (DU): This logical node includes a subset of the gNB functions, depending on the functional split option. Its operation is controlled by the CU. Distributed Unit (DU) also known with other names like RRH/RRU/RE/RU.

The CU DU Split options:

Central Unit (CU) and Distributed Unit (DU) Functional Split Options

As a part of study item for New Radio (NR), 3GPP started studying different functional splits between central and distributed units. For the initial phase, 3GPP has taken LTE protocol stack as a basis for the discussion, until RAN2 defines and freezes the protocol stack for New Radio (NR). They have proposed about 8 possible options shown in below figure.

5G gNodeB Split
5G gNodeB CU DU Split
  • Option 1 (RRC/PCDP 1A-like split)
  • Option 2 (PDCP/RLC Split 3C-like split)
  • Option 3 (High RLC/Low RLC splitIntra RLC split)
  • Option 4 (RLC-MAC split)
  • Option 5 (Intra MAC split)
  • Option 6 (MAC-PHY split)
  • Option 7 (Intra PHY split)
  • Option 8 (PHY-RF split)

Option 1 (RRC/PDCP, 1A-like split)In this split option, RRC is in the central unit while PDCP, RLC, MAC, physical layer and RF are kept in the distributed unit. Thus the entire user plane is in the distributed unit.

Option 2 (PDCP/RLC split): Option 2 may be a base for an X2-like design due to similarity on U-plane but some functionality may be different e.g. C-plane since some new procedures may be needed. There are two possible variants available in this option.

  • Option 2-1 Split U-plane only (3C like split): In this split option, RRC, PDCP are in the central unit. RLC, MAC, physical layer and RF are in the distributed unit.
  • Option 2-2: In this split option, RRC, PDCP are in the central unit. RLC, MAC, physical layer and RF are in the distributed unit.  In addition, this option can be achieved by separating the RRC and PDCP for the CP stack and the PDCP for the UP stack into different central entities.

Option 3 (High RLC/Low RLC Split): In this option, two approaches are taken based on Real time/Non-Real time functions split which are as follows:

  • Option 3-1 Split based on ARQ
  • Option 3-2 Split based on TX RLC and RX RLC

Option 3-1 Split based on ARQ

  • Low RLC may be composed of segmentation functions;
  • High RLC may be composed of ARQ and other RLC functions;

This option splits the RLC sublayer into High RLC and Low RLC sublayers such that for RLC Acknowledge Mode operation, all RLC functions may be performed at the High RLC sublayer residing in the central unit, while the segmentation may be performed at the Low RLC sublayer residing in the distributed unit. Here, High RLC segments RLC PDU based on the status reports while Low RLC segments RLC PDU into the available MAC PDU resources.

Option 3-2 Split based on TX RLC and RX RLC

  • Low RLC may be composed of transmitting TM RLC entity, transmitting UM RLC entity, a transmitting side of AM and the routing function of a receiving side of AM, which are related to downlink transmission.
  • High RLC may be composed of receiving TM RLC entity, receiving UM RLC entity and a receiving side of AM except for the routing function and reception of RLC status reports, which are related to uplink transmission.

Option 4 (RLC-MAC split)In this split option, RRC, PDCP, and RLC are in the central unit. MAC, physical layer, and RF are in the distributed unit.

Option 5 (Intra MAC split)

Option 5 assumes the following distribution:

  • RF, physical layer and lower part of the MAC layer (Low-MAC) are in the Distributed Unit
  • Higher part of the MAC layer (High-MAC), RLC and PDCP are in the Central Unit

Therefore, by splitting the MAC layer into 2 entities (e.g. High-MAC and Low-MAC), the services and functions provided by the MAC layer will be located in the Central Unit (CU), in the Distributed Unit (DU), or in both. An example of this kind distribution given below.

  • In High-MAC sublayer the centralized scheduling in the High-MAC sublayer will be in charge of the control of multiple Low-MAC sublayers. It takes high-level centralized scheduling decision. The inter-cell interference coordination in the High-MAC sublayer will be in charge of interference coordination methods such as JP/CS CoMP.
  • In Low-MAC sublayer the time-critical functions in the Low-MAC sublayer include the functions with stringent delay requirements (e.g. HARQ) or the functions where performance is proportional to latency (e.g. radio channel and signal measurements from PHY, random access control). It reduces the delay requirements on the fronthaul interface. Radio specific functions in the Low-MAC sublayer can for perform scheduling-related information processing and be reporting. It can also measure/estimate the activities on the configured operations or the served UE’s statistics and report periodically or as requested to the High-MAC sublayer.

Option 6 (MAC-PHY split): The MAC and upper layers are in the central unit (CU). PHY layer and RF are in the DU. The interface between the CU and DUs carries data, configuration, and scheduling-related information (e.g. MCS, Layer Mapping, Beamforming, Antenna Configuration, resource block allocation, etc.) and measurements.

Option 7 (Intra PHY split): Multiple realizations of this option are possible, including asymmetrical options which allow obtaining benefits of different sub-options for UL and DL independently.

This option requires some kind of compression technique to reduce transport bandwidth requirements between the DU and CU.

  • In the UL, FFT, and CP removal reside in the DU and for the two sub-variants, 7-1 and 7-2 are described below. Remaining functions reside in the CU.
  • In the downlink, iFFT and CP addition reside in the DU and the rest of the PHY resides in the CU.

Considering above there are three sub-variant available for this option described as below

Option 7-1 In this option the UL, FFT, CP removal and possibly PRACH filtering functions reside in the DU, the rest of PHY functions reside in the CU. In the DL, iFFT and CP addition functions reside in the DU, the rest of PHY functions reside in the CU.

Option 7-2 In this option the UL, FFT, CP removal, resource de-mapping and possibly pre-filtering functions reside in the DU, the rest of PHY functions reside in the CU. In the DL, iFFT, CP addition, resource mapping and precoding functions reside in the DU, the rest of PHY functions reside in the CU.

Option 7-3 (Only for DL): Only the encoder resides in the CU, and the rest of PHY functions reside in the DU.

Option 8 (PHY-RF split)This option allows to separate the RF and the PHY layer. This split permit centralization of processes at all protocol layer levels, resulting in very tight coordination of the RAN. This allows efficient support of functions such as CoMP, MIMO, load balancing, mobility.

Benefits of RAN Spilt Architecture

Some of the benefits of an architecture with the deployment flexibility to split and move New Radio (NR) functions between central and distributed units are below:

  • Flexible HW implementations allows scalable cost-effective solutions
  • A split architecture (between central and distributed units) allows for coordination for performance features, load management, real-time performance optimization, and enables NFV/SDN
  • Configurable functional splits enables adaptation to various use cases, such as variable latency on transport
Which CU DU split function to use where?

The choice of how to split New Radio (NR) functions in the architecture depends on some factors related to radio network deployment scenarios, constraints and intended supported services. Some examples of such factors are:

  • Support of specific QoS per offered services (e.g. low latency, high throughput)
  • Support of specific user density and load demand per given geographical area (which may influence the level of RAN coordination)
  • Availability transport networks with different performance levels, from ideal to non-ideal
  • Application type e.g. Real-time or Non- Real Time
  • Features requirement at Radio Network level e.g. CA, eICIC, CoMP etc.

Reference: 3GPP TR 38.801 Radio Access Architecture and Interfaces Release 14

For Further Information

For more information on 5G Networks, gNodeB Architecture and CU DU Split, Please Contact Us

RadioMobile for 5G Network Planning

CableFree RadioMobile 5G LTE Coverage Planning example

RadioMobile: Popular software for 5G Network Coverage planning

RadioMobile is a widely-available software package which can be used for 5G Network Coverage planning, including path profiling and clearance criteria, power budgets, choosing antenna sizes and tower heights.

CableFree RadioMobile 5G LTE Coverage Planning example

For website for RadioMobile, please see this link here:

RadioMobile functions

For 5G Coverage Planning, the software package can be configured with the characteristics of your required radio network.

  • Transmit Power
  • Frequency Band
  • Antenna Gain
  • Receiver Sensitivity
  • Antenna heights
  • System losses
  • CPE types and locations

CableFree RadioMobile 5G LTE Coverage Planning example
CableFree RadioMobile 5G LTE Coverage Planning example

Link Budget & Fade Margins

The software enables quick and rapid calculation of link budget and fade margins for any frequency band.

Terrain Database

The software uses the freely available SRTM terrain data which can download “on demand” for calculation of terrain heights.  Combined with LandCover, this enables estimation of trees/forests also.

Line of Sight

The software uses the terrain database to allows quick establishment of available Line of Sight and “what if” adjustment of antenna/tower heights in a 5G radio network design

Radio Fresnel Zone

RadioMobile automatically calculates the Fresnel Zone for any required link, with graphical display enabling quick feasibility and identification of any obstacles to be noted.

Radio Parameters & Network Properties

Any new user to Radio Mobile will have to enter link parameters for the chosen equipment.  This includes transmit power, receive sensitivity and antenna gains.  Some vendors such as CableFree include this data as a planning service with their products

CableFree RadioMobile 5G LTE Coverage Planning example

Radio Mobile: Free to Use

The Radio Mobile software is free to use including for commercial use.  Radio Mobile software is a copyright of Roger Coudé.  The author notes:

Although commercial use is not prohibited, the author cannot be held responsible for its usage. The outputs resulting from the program are under the entire responsibility of the user, and the user should conform to restrictions from external data sources.

For Further information

For More Information about Microwave Link Planning, we will be delighted to answer your questions. Please Contact Us

5G Terminology: The gNB

5G specifications are ongoing, so there are new acronyms to remember.
So after the BTS (Base Transceiver Station) in 2G, the NodeB in 3G, the eNB in 4G, here comes the gNB in 5G.

Tnew radio access technology is called “NR” and replaces “LTE”, and the new base station is called gNB (or gNodeB), and replaces the eNB (or eNodeB or Evolved Node B).

GenerationRadio TechnologyBase Station Name
2GGSMBTS (Base Transceiver Station)
3GUMTSNodeB
4GLTEeNB, Evolved NodeB
5GNRgNB, G???? NodeB

The “g” in gNB stands for “Next Generation NodeB”

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