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

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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.

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The Importance of Low-PIM for 5G LTE Networks

5G Technology: NSA & SA modes

In order to understand the importance of low-PIM antennas, cable and connectors in a modern 5G network, it is critical to understand what PIM refers to. PIM stands for Passive Intermodulation. It is a problem that happens largely in passive devices such as antennas, cables and connectors where interfering signals are generated by nonlinearities within a wireless system’s mechanism. Amplitude modulation or the mixing of two signals occurs, producing difference in signals within a specific band leaving behind significant interloping.

5G Networks Low PIM Passive Intermodulation
5G Networks

PIM: Nonlinearity Effects

Passive intermodulation product is also explained as resulting from the mixing of two high power natures at the nonlinearities of devices, such as in corroded connectors, metal oxide intersections and divergent metals. As the signal amplitude goes up, the nonlinearities effect will be very significant. Higher intermodulation result as lots of products on first inspection would show a system that is not just linear but seemingly incapable of producing intermodulation.

PIM Distortion & Telecommunication

A single internet provider such as a broadband carrier can also produce PIM in case it goes through a fault or a surface that generates PIM. Such distortions in telecommunication signals would look like side lobes interfering with end-to-end channels and hinder coverage.  In most communication systems today, PIM is a serious problem. Where there is a sharing of received highly powerful and transmitted signal, PIM interference is a serious vulnerability. After interference of PIM in the path of reception, filtering or unscrambling it is very difficult.

The Real Cause Of Passive Intermodulation

When mechanical components interact, particularly where two distinct metals connect, the result is nonlinear elements. A major cause is mostly unlike material’s junctions leading to Passive Intermodulation manifestation in coax cables, antennas and coax connectors among others. This is brought about by oxidation, loosely done connectors, corrosion, dirt, and rust among others, including any kind of adulteration on the passive devices. PIM is also caused by close metal objects from anchors, pipes, guy wires to roof flashings resulting in a nonlinearity that allows a mix. As the nonlinearity goes up, the PIM reception amplitude also surge.

Other PIM sources to avoid include a number of ferromagnetic materials such as a number of metals like steel, nickel and ferrites. Such elements display hysteresis once they come into contact with backing magnetic fields. Mechanical contacts done shoddily, cracked and cold solder joints, workmanship and manufacturing faults, among others, cause serious levels of PIM.

The Conditions That Bring About PIM

Normally, to bring about Passive Intermodulation, two fairly powerful RF signals rather close in terms of frequency are required. High power transmitters of about 20 watts and above will see the outputs creating PIM. As the power goes up, more severe the PIM effects produced.

Another important aspect to note about Passive Intermodulation is that as the components soar in age, PIM increases. An older system is very susceptible, including surroundings afflicted by high temperatures, lots of air pollution, extreme vibrations or salted air.

Other PIM Negative Effects

Apart from interfering with signals, Passive Intermodulation has other negative effects, especially on a receiver that usually has a high sensitivity. As interference of the signals takes place, the desired signals will be blocked as the noise floor goes up. Interference of the signals has also been deemed to lower the sensitivity of the receiver. In a typical cell signal setting anywhere, the negative end effects would be manifested in serious scenarios such as dropped calls, low system capacity among others.

Which Wireless Networks are Most Affected?

Most PIM problems are mostly susceptible to internet cell networks such as 4G & 5G LTE, HSPA and CDMA. For all of these, Passive Intermodulation is a significant challenge.

FDD-LTE has been cited as being highly sensitive to Passive Intermodulation effects. Where the PIM levels of interference are elevated, the performance and efficiency of LTE networks is greatly hampered. As this occurs, it is possible for the base station to mistake distorted signal as a channel in use thereby refusing to have the channel assigned. The result in the system is the loss of revenue, critical channel capacity and airtime.

Since modern equipment is largely sensitive in its nature, the lowest Passive Intermodulation effect levels are capable of brutally degrading the performance. For instance, a single one decibel loss in uplink sensitivity following PIM interference has been found to lower reception by over 10 percent.

DAS Implementations

PIM problems have been cited in lots of macro sites in external environments, an issue that had to be sorted out. In DAS (distributed antenna systems), the reliability and high data amount values are critical; lots of components appear in the path of the radio frequencies leading to PIM effects. These systems require passive components from directional to hybrid couplers, coax, and splitters among others to be placed near the source of the signal. As a result, passive components PIM specification has to be of the utmost level.

Modern Passive Components And PIM

Modern low-PIM passive components such as connector series are designed with installation ease in mind to provide the most desired mechanical and electrical reliability. They come in handy where low-Passive Intermodulation effect connection is required such as in installations in need of coax lengthy cable jumpers for the provision of low Passive Intermodulation levels and superb RF performance.

What Low-PIM Means to the Network Operator

To any consumer, integrator, or installer, high PIM levels mean the cellular reception will be very poor and the bandwidth will be limited. For a carrier, it means customers will not trust their cellular services and will probably move on to competing service provider. Low-PIM passive components mean that the signal will be strong offering extra and reliable bandwidth for customers and a perfect scenario for all involved. As a result, the modern low Passive Intermodulation antennas, cables and connectors among other passive components are designed for everyday use in a design perfectly harnessed to lower Passive Intermodulation. All these components arrive ready for use having been tested for seamless installation.

PIM Testing

Today users expect their cell phones to have a consistent signal no matter the mobile device they are using. All network operators work tirelessly to ensure the signal is highly improved. Cell phone signal boosters offering perfect signal amplifiers for use in residential and commercial setups where the signal is poor and unreliable, including every single passive component maker is alive to the PIM effect. Therefore PIM testing today is a highly critical process that will probably continue being so.

A typical 4G LTE network sees a high capacity 100 Mbps to 1Gbps data rate and increasing each year. Such a high rate of transmission keeps on exposing the susceptibility of networks to PIM interference on a large scale. The fidelity of a 4G LTE is hedged on network superiority than 2G or 3G networks.

The carrier, consumer, low-Passive Intermodulation components manufacturer, cell phone signal boosters and antennas manufacturers as well have to always consider Passive Intermodulation interference in their assembly processes. Passive Intermodulation testing and assuring peak low-PIM performance is thus imperative.

Low-PIM Connectors

Low-PIM connectors for instance are designed with contact connectors on the outside and center using a single construction piece as much as possible. N-type connectors among others are being over-molded in a way that eliminates thermal stresses, vibration and wind effects.

The design incorporates lots of aspects and forces of contact assuring sufficient pressure for the prevention of Passive Intermodulation, including gold or silver-plated mid contacts while the connector bodies are white bronze or silver plated. All passive components from connectors, cables to antennas are being manufactured in controlled environments by highly trained professionals who understand the desirability of low PIM.

Passive Intermodulation DAS Specifications

Low-PIM specification for DAS solutions is very important. To know how low you should aim for, you can stick to the vendors mostly aimed -110 dBc or -153 dBc for top of the range solutions. Note that the specification need to be constantly spread in all the bands from 4G LTE, 3G to 2G right from the 700 MHz frequency to as high as 2.7 GHz. This assures a consistent superb performance for every device and satisfaction for every customer.

Passive Intermodulation Effects During Installation

Even with the proper top quality low-PIM passive components and DAS solutions you can still suffer Passive Intermodulation effects. This can happen as you install or after installing the low-Passive Intermodulation passive device. If you have suspended ceiling grids or you rebar ceiling grids, you have metallic objects on the path of the cell signal, identify this with a view to minimizing Passive Intermodulation. At times, these metal objects are hard to avoid. Directional antennas can help mitigate their effects to a greater extent.

Seek to ensure connectors, cables and other low-Passive Intermodulation passive components installed are periodically inspected to avoid such effects as corrosion. As the component deteriorates without proper inspection Passive Intermodulation will be elevated.

The most important thing is to stick to low-PIM interior antennaslow-PIM RF Splitters, as well as cables, connectors, couplers and other passive components. Low-PIM solutions will eliminate the costly requirement of upgrading these components, ensuring your cell phone signal is never interrupted by high-PIM effects.

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5G NR: New Radio

5G NR (New Radio) is a new radio access technology (RAT) developed by 3GPP for the 5G (fifth generation) mobile network. It was designed to be the global standard for the air interface of 5G networks.

The 3GPP specification 38 series provides the technical details behind NR, the RAT beyond LTE.

The study on NR within 3GPP started in 2015, and the first specification release was made available by the end of 2017. While the 3GPP standardization process was ongoing, industry had already begun efforts to implement infrastructure compliant with the draft standard, with the expectation that the first large scale commercial launch of 5G New Radio would occur in 2019.

5G NR: 3GPP Release 16 includes 5G definitions
5G New Radio: 3GPP Release 16 includes 5G definitions

Frequency bands

The Frequency bands for 5G New Radio are being separated into two frequency ranges:[4]

Frequency Range 1 (FR1), including sub-6 GHz frequency bands
Frequency Range 2 (FR2), including frequency bands in the mmWave range (20-60GHz)

5G NR:  New Radio Interface

5G NR Development

In 2018, 3GPP published Release 15, which include what is described as “Phase 1” standardization for the 5G NR standard. 3GPP is expected to publish Release 16, which include the “Phase 2” of 5G NR, by the end of year 2019

5G NR Deployment modes

Initial launches will depend on existing LTE 4G infrastructure in non-standalone (NSA) mode, before maturation of the standalone (SA) mode with the 5G core network.

Non-Standalone mode

Non-Standalone (NSA) mode of 5G New Radio refers to an option of 5G NR deployment that depends on the control plane of existing LTE network for control functions, while 5G NR exclusively focused on user plane. The advantage of doing so is reported to speed up 5G adoption, however some operators and vendors have criticized prioritizing the introduction of 5G NR NSA on the grounds that it could hinder the implementation of the standalone mode of the network.

Standalone mode

Standalone (SA) mode of 5G New Radio refers to using 5G cells for both signalling and information transfer. It includes the new 5G Packet Core architecture instead of relying on the 4G Evolved Packet Core. It would allow the deployment of 5G without the LTE network. It is expected to have lower cost, better efficiency, and assist development of new use cases.

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5G Frequency Bands

5G Networks

Frequency bands for 5G are divided into “sub 6GHz” and “mmWave” bands. “Sub 6” is generally for longer range coverage, with in-building penetration. “mmWave” bands use higher frequencies which offer short range, and no or little penetration of building structures.

This list of 5G frequency bands is taken 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 1

BandDuplex mode[A 1]ƒ (MHz)Common nameSubset of bandUplink[A 2] (MHz)Downlink[A 3] (MHz)Duplex spacing (MHz)Channel bandwidths[5] (MHz)
n1FDD2100IMTn651920 – 19802110 – 21701905, 10, 15, 20
n2FDD1900PCS[A 4]n251850 – 19101930 – 1990805, 10, 15, 20
n3FDD1800DCS1710 – 17851805 – 1880955, 10, 15, 20, 25, 30
n5FDD850CLR824 – 849869 – 894455, 10, 15, 20
n7FDD2600IMT‑E2500 – 25702620 – 26901205, 10, 15, 20
n8FDD900Extended GSM880 – 915925 – 960455, 10, 15, 20
n12FDD700Lower SMH699 – 716729 – 746305, 10, 15
n14FDD700Upper SMH788 – 798758 – 768−305, 10
n18FDD850Lower 800 (Japan)815 – 830860 – 875455, 10, 15
n20FDD800Digital Dividend (EU)832 – 862791 – 821−415, 10, 15, 20
n25FDD1900Extended PCS[A 5]1850 – 19151930 – 1995805, 10, 15, 20
n28FDD700APT703 – 748758 – 803555, 10, 15, 20
n30FDD2300WCS[A 6]2305 – 23152350 – 2360455, 10
n34TDD2100IMT2010 – 2025N/A5
n38TDD2600IMT‑E[A 7]2570 – 2620N/A5, 10, 15, 20
n39TDD1900DCS–IMT Gap1880 – 1920N/A5, 10, 15, 20, 25, 30, 40
n40TDD2300S-Band2300 – 2400N/A5, 10, 15, 20, 25, 30, 40, 50, 60, 80
n41TDD2500BRSn902496 – 2690N/A10, 15, 20, 40, 50, 60, 80, 90, 100
n48TDD3500CBRS (US)3550 – 3700N/A5, 10, 15, 20, 40, 50, 60, 80, 90, 100
n50TDD1500L‑Band (EU)1432 – 1517N/A5, 10, 15, 20, 30, 40, 50, 60, 80[A 8]
n51TDD1500Extended L‑Band (EU)1427 – 1432N/A5
n65FDD2100Extended IMT1920 – 20102110 – 22001905, 10, 15, 20
n66FDD1700Extended AWS[A 9]1710 – 17802110 – 2200[6]4005, 10, 15, 20, 40
n70FDD2000AWS‑41695 – 17101995 – 20203005, 10, 15, 20[A 8], 25[A 8]
n71FDD600Digital Dividend (US)663 – 698617 – 652−465, 10, 15, 20
n74FDD1500Lower L‑Band (US)1427 – 14701475 – 1518485, 10, 15, 20
n75SDL1500L‑Band (EU)N/A1432 – 1517N/A5, 10, 15, 20
n76SDL1500Extended L‑Band (EU)N/A1427 – 1432N/A5
n77TDD3700C-Band3300 – 4200N/A10, 20, 40, 50, 60, 80, 90, 100
n78TDD3500C-Bandn773300 – 3800N/A10, 20, 40, 50, 60, 80, 90, 100
n79TDD4700C-Band4400 – 5000N/A40, 50, 60, 80, 100
n80SUL1800DCS1710 – 1785N/AN/A5, 10, 15, 20, 25, 30
n81SUL900Extended GSM880 – 915N/AN/A5, 10, 15, 20
n82SUL800Digital Dividend (EU)832 – 862N/AN/A5, 10, 15, 20
n83SUL700APT703 – 748N/AN/A5, 10, 15, 20
n84SUL2100IMT1920 – 1980N/AN/A5, 10, 15, 20
n86SUL1700Extended AWS1710 – 1780N/AN/A5, 10, 15, 20, 40
n90TDD2500BRS2496 – 2690N/A10, 15, 20, 40, 50, 60, 80, 90, 100
BandDuplex
mode[A 1]
ƒ (MHz)Common nameSubset of bandUplink[A 2] (MHz)Downlink[A 3] (MHz)Duplex spacing (MHz)Channel bandwidths[5] (MHz)
  1. ^ Frequency division duplexing (FDD); time division duplexing (TDD); FDD supplemental downlink (SDL); FDD supplemental uplink (SUL)
  2. ^ UE transmit; BS receive
  3. ^ UE receive; BS transmit
  4. ^ Blocks A–F
  5. ^ Blocks A–G
  6. ^ Blocks A–B
  7. ^ Duplex Spacing
  8. ^ Downlink only
  9. ^ Blocks A–J

Chart showing 5G Frequency Bands

5G Frequency Bands
5G Frequency Bands

Frequency Range 2 (mmWave bands)

Bandƒ (GHz)Common nameSubset of bandUplink / Downlink[B 1] (GHz)Channel bandwidths[5] (MHz)
n25726LMDS26.50 – 29.5050, 100, 200, 400
n25824K-band24.25 – 27.5050, 100, 200, 400
n26039Ka-band37.00 – 40.0050, 100, 200, 400
n26128Ka-bandn25727.50 – 28.3550, 100, 200, 400
Bandƒ (GHz)Common nameSubset of bandUplink / Downlink[B 1] (GHz)Channel bandwidths[5] (MHz)
  1.  Time division duplexing (TDD) mode

Chart showing 5G mmWave bands

5G mmWave Spectrum
5G mmWave Spectrum

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5G NR frequency bands

RF Frequency bands for 5G NR are being separated into two different frequency ranges.

Frequency Range 1 (FR1)

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)

FR2 includes frequency bands from 24.25 GHz to 52.6 GHz. Bands in this millimeter wave (mmWave, MMW) range have much 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 legacy 4G LTE band, they share the same band number.

Frequency Range 1

BandDuplex modeƒ (MHz)Common nameSubset of bandUplink (MHz)Downlink (MHz)Duplex spacing (MHz)Channel bandwidths (MHz)
n1FDD2100IMT1920 – 19802110 – 21701905, 10, 15, 20
n2FDD1900PCS[A 4]n251850 – 19101930 – 1990805, 10, 15, 20
n3FDD1800DCS1710 – 17851805 – 1880955, 10, 15, 20, 25, 30
n5FDD850CLR824 – 849869 – 894455, 10, 15, 20
n7FDD2600IMT‑E2500 – 25702620 – 26901205, 10, 15, 20
n8FDD900Extended GSM880 – 915925 – 960455, 10, 15, 20
n12FDD700Lower SMH699 – 716729 – 746305, 10, 15
n20FDD800Digital Dividend (EU)832 – 862791 – 821−415, 10, 15, 20
n25FDD1900Extended PCS1850 – 19151930 – 1995805, 10, 15, 20
n28FDD700APT703 – 748758 – 803555, 10, 15, 20
n34TDD2100IMT2010 – 2025N/A5
n38TDD2600IMT‑E[A 5]n412570 – 2620N/A5, 10, 15, 20
n39TDD1900DCS–IMT Gap1880 – 1920N/A5, 10, 15, 20, 25, 30, 40
n40TDD2300S-Band2300 – 2400N/A5, 10, 15, 20, 25, 30, 40, 50, 60, 80
n41TDD2500BRS2496 – 2690N/A5, 10, 15, 20, 40, 50, 60, 80, 100
n50TDD1500L‑Band (EU)1432 – 1517N/A5, 10, 15, 20, 40, 50, 60, 80[A 6]
n51TDD1500Extended L‑Band (EU)1427 – 1432N/A5
n66FDD1700Extended AWS[A 7]1710 – 17802110 – 2200[6]4005, 10, 15, 20, 40
n70FDD2000AWS‑41695 – 17101995 – 20203005, 10, 15, 20[A 6], 25[A 6]
n71FDD600Digital Dividend (US)663 – 698617 – 652−465, 10, 15, 20
n74FDD1500Lower L‑Band (US)1427 – 14701475 – 1518485, 10, 15, 20
n75SDL[A 8]1500L‑Band (EU)N/A1432 – 1517N/A5, 10, 15, 20
n76SDL[A 8]1500Extended L‑Band (EU)N/A1427 – 1432N/A5
n77TDD3700C-Band3300 – 4200N/A10, 20, 40, 50, 60, 80, 100
n78TDD3500C-Bandn773300 – 3800N/A10, 20, 40, 50, 60, 80, 100
n79TDD4700C-Band4400 – 5000N/A40, 50, 60, 80, 100
n80SUL[A 9]1800DCS1710 – 1785N/AN/A5, 10, 15, 20, 25, 30
n81SUL[A 9]900Extended GSM880 – 915N/AN/A5, 10, 15, 20
n82SUL[A 9]800Digital Dividend (EU)832 – 862N/AN/A5, 10, 15, 20
n83SUL[A 9]700APT703 – 748N/AN/A5, 10, 15, 20
n84SUL[A 9]1900IMT1920 – 1980N/AN/A5, 10, 15, 20
n86SUL[A 9]1700Extended AWSn801710 – 1780N/AN/A5, 10, 15, 20, 40

Frequency Range 2

Bandƒ (GHz)Common nameSubset of bandUplink / Downlink(GHz)Channel bandwidths (MHz)
n25726LMDS26.50 – 29.5050, 100, 200, 400
n25824K-band24.25 – 27.5050, 100, 200, 400
n26039Ka-band37.00 – 40.0050, 100, 200, 400
n26128Ka-bandn25727.50 – 28.3550, 100, 200, 400

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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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