CBRS: Private 4G LTE in Band 48 (3.x GHz)

Introducing Private LTE in Band 48 (CBRS) 3.x GHz

Band 48 CBRS is a great technology for the wireless communications industry specifically within the USA. This technology is available today, just when data growth is inevitably exploding through the new trend of technologies and data-hungry applications.

CableFree Private LTE for CBRS 3.x GHz band

The concept of having a private LTE as easy as a WiFi network and free of charge will likely change the market for LTE & cellular systems generally. We will shift from having a couple of nation-wide networks to a massive collection of small-scale LTE networks.

Explaining Private LTE (Band 48 CBRS)

The Band 48 CBRS (Citizens Broadband Radio Service) is often referred to as the private LTE. It is the frequency band of 3.5GHz, operating in the LTE spectrum in the United States.

LTE was designed to work across a wide range of frequency bands (450 MHz up to 3.8GHz) referred to as E-UTRA. 4G LTE technology is capable of supporting two modes of communication, FDD (Frequency Division Duplex) and TDD (Time Division Duplex).

Key Benefits of Band 48 CBRS:

  1. Improved Security. Network connections use dedicated radio equipment. Band 48 CBRS keeps data local.
  2. Enhanced Mobility & Range. Unlike WiFi, CBRS technology allows high-speed mobility, seamless handovers, and longer signal ranges.
  3. Capacity. Band 48 has enough capacity to allow high capacity applications and a large number of devices at the same time.
  4. Optimized Services. Applications can be customized and improved regarding the specific industry, for services such as QoS, bandwidth, latency, etc.
  5. Interoperability. Devices are capable of communicating with each, from all manufacturers
  6. New Wireless Devices. New wireless technology, such as AGV helmets, security cameras, agricultural sensors, and others.

Behind Band 48: How It All Started

Introduced by the FCC, the CBRS defined new ways to use the 3.5 GHz band in the U.S., and share its spectrum. The CBRS band consists of a total 150MHz within the 3500 MHz spectrum band that stretches between the 3550-3700MHz (or 3.55-3.7GHz).

The 150MHz were taken from the two LTE bands, the 42 (ranging from 3550 to 3660 MHz) and 43 (ranging from 3660 to 3700 MHz). The CBRS with a band total of 150MHz has been allocated and made available, as the name implies, to “citizens” with lower power resources.

CBRS Frequency Band 42, Band 43, Band 48

The entire spectrum for bands 42 and 43 now belongs to CBRS, which is also referred to as Band 48. This frequency band is perfect for services that require ultra-high resources, and it could be a roadmap to 4.9G and 5G technologies deployment.

The CBRS Framework

The CBRS spectrum sharing rules were defined to support wireless access to the general public, but also to protect incumbent users from interference. These rules are crucial, because band 42, and 43 are already being used by the US Military and Navy.

The CBRS framework is organized into three tiers that follow a hierarchical order. This model helps to create new opportunities regarding the use and distribution of wireless access.

  1. Tier 1
  2. Tier 2
  3. Tier 3
LTE band 48 CBRS - Incumbents, PAL, GAA

The first tier is where Incumbent systems are placed. These are systems such as Navy RADARs, US Military, Satellite Stations, etc. This tier has priority on the entire 150MHz (over the lower tiers), but it does not always use the entire band at every location.

The second tier is where priority access devices are placed, this tier is referred to as the Priority Access License or (PAL). This tier offers a non-renewable 3-year license paid to the FCC, to use a 10MHz channel within the 3500-3650MHz portion of the entire band, in a limited geographical area. The license of PAL gives priority over the Tier 3.

And finally, the lowest tier (tier 3) is referred to as the General Authorized Access (GAA). The GAA is a dynamic allocation of 100MHz channels within the entire band (3500-3700 MHz). The idea is that GAA allocates dynamically, so that it does not interfere with the Incumbents or PAL. In other words, the GAA users use the available spectrum that is not occupied by higher tiers. From the 150 MHz, 80-100MHz are available for the GAA or “Private LTE”— WiFi-like authorized devices.

Tier 2 provides a licensed and “reliable service”, but Tier 3 works as an open spectrum without a license, very similar to WiFi.

Uses of LTE Band 48

Band 48 CBRS will likely be used in private and geographically restricted LTE deployments, which is much better than WiFi.

Mobile broadband internet providers (PALs) can use Band 48 to deploy Public LTE Networks and extend and improve their service. To do this, they’ll need to install LTE hardware for Band 48, such as indoor, outdoor antennas, and wireless gateway. Other PALs will likely use private LTE on industrial IoT applications.

Companies can also use an LTE Base Station hardware with Carrier Aggregation with other LTE bands to improve the overall capacity. In this deployment, another band is considered the main one, and band 48 is used to support wider transmission bandwidth.

One of the most popular new use cases of Band 48 will be the use of Private LTE or LTE-U (unlicensed). Any organization, enterprise, or individual, can operate in Band 48 under GAA unlicensed rules. This free LTE license to deploy anywhere operates much like a home Wi-Fi network.

Private LTE Band 48 CBRS Use Cases

  • Wireless Sensor Networks and IoT.
  • Remote control and sensing.
  • Security remote-controlled cameras.
  • Industrial and Agricultural Equipment
  • Customized Smartphone Apps
CBRS: devices, LTE base Station, SAS, EPC

To set up CBRS private LTE you’ll need three basic elements:

  • The Base Station (BS) or Wireless Gateway.
  • The EPC (Evolved Packet Core).
  • CBRS devices or CPE (Customer Premise Equipment).

CBRS 4G Base Station (BS)

An LTE BS for Band 48 usually comes with Carrier Aggregation and multiple advanced features. In order to use the Band 48 CBRS, a device requesting service must be authorized by a Spectrum Allocation System (SAS), which may come embedded in the BS, or can be used as a Cloud service.

The SAS works with a database to store license and access information. It has the important task of analyzing the RF spectrum and channels to avoid any interference with the Incumbents or PAL. With this approach, the traditional channel interference issues are gone. If there is an available RF spectrum, the SAS will make it available for the end-user.

An example Base Station is the CableFree 4G Base station which is available in both Macro and Small Cell versions.

EPC (Evolved Packet Core)

The EPC is the main controller of an LTE network. This is the most complex and resource-consumption equipment in the LTE and it is usually operated in the NOCs of enterprise or ISPs. Today, EPCs are usually deployed on premises, but we will start seeing hybrid and cloud deployments of EPC cores.

Private and small LTE networks deploying Band 48 CBRS will have the option for simplified versions of the EPC, deployed on the cloud in a Data Center as a Service (DCaaS).

The private LTE-EPC is in charge of:

  • Keeping the user database.
  • Enforcing policies.
  • Allocating IP addresses.
  • Managing mobility and tracking.
  • Giving a gateway to the PDN (Public Data Networks).

CBRS devices or CPE (Customer Premise Equipment)

This device provides radio connectivity to the LTE Base Station and must support LTE Band 48. This is the user equipment that gives an interface to the end-user. A CPE can be anything from an indoor, outdoor antennas, to a MiFi (My WiFi or WiFi hotspot). With the rise of IoT, we will start seeing sensors with CBRS base 48 support.


Shared spectrum model of Private LTE CBRS Band 48 has many advantages: comes with improved security, higher reliability, mobility, etc. Exciting aspects of CBRS technology is that it can be the route to 5G and its adoption to IoT applications.

CBRS Band 48 can be used as localised or private LTE which surpasses 1000x, existing WiFi technology. It is better in terms of security, speed, quality, & performance.

We are already seeing WISPs and other enterprises buy PAL licenses and use this technology to improve its existing LTE network or for industrial IoT applications in agriculture, oil rigs, factories, mining, etc. What is most exciting is that we might also start seeing the use of this technology in households.

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Private LTE and eSIM technology

What is eSIM technology?

The term “eSIM” simply means an embedded SIM card. There are no physical SIM cards involved and no physical swapping over required by you.

An embedded-SIM (eSIM) or embedded universal integrated circuit card (eUICC) is a form of programmable SIM card that is embedded directly into a device. The surface mount format provides the same electrical interface as the full size, 2FF, 3FF and 4FF SIM cards, but is soldered to a circuit board as part of the manufacturing process. The eSIM format is commonly designated as MFF2. In machine to machine (M2M) applications where there is no requirement to change the SIM card, this avoids the requirement for a connector, improving reliability and security. An eSIM can be provisioned remotely; end-users can add or remove operators without the need to physically swap a SIM from the device.

eSIM plus SIM card?

Phones that have eSIM support alongside a standard SIM are basically using it as a substitute for a second SIM. These still have space for a traditional micro SIM that you can use in the normal way, but you can add a second number or data contract via the eSIM – read on for more details on how this works. 


The use of eSIM brings a number of advantages to device manufacturers and networks, but there are also some advantages for you, too, since you can have plans from more than one network stored on your e-SIM. 

So you could use one number for business and another number for personal calls or have a data roaming SIM for use in another country. You could even have completely separate voice and data plans.

e-SIM is a global specification by the GSMA which enables remote SIM provisioning of any mobile device, and GSMA defines eSIM as the SIM for the next generation of connected consumer device, and networking solution using e-SIM technology can be widely applicable to various Internet of things (IoT) scenarios, including connected cars (smart rearview mirrors, on-board diagnostics (OBD), vehicle hotspots), artificial intelligence translators, MiFi devices, smart earphones, smart metering, car trackers, DTU, bike-sharing, advertising players, video surveillance devices, etc

eSIM card and SIM card for mobile cellular networks and devices

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LTE Quality of service, charging and policy control (PCC)

What is PCC in LTE?

The purpose of PCC in LTE is policy and charging control. Policy control is a very generic term and in a network there are many different policies that could be implemented, for example, policies related to security, mobility, use of access technologies etc. When discussing policies, it is thus important to understand the context of those policies. When it comes to PCC, policy control refers to the two functions gating control and QoS control:1.

Gating control is the capability to block or to allow IP packets belonging to IP flow(s) for a certain service. The PCRF makes the gating decisions which are then enforced by the PCEF. The PCRF could, for example, make gating decisions based on session events (start/stop of service) reported by the AF via the Rx reference point.2.

QoS control

QoS control allows the PCRF to provide the PCEF with the authorized QoS for the IP flow(s). The authorized QoS may, for example, include the authorized QoS class and the authorized bit rates. The PCEF or BBERF enforces the QoS control decisions by setting up the appropriate bearers. The PCEF also performs bit rate enforcement to ensure that a certain service session does not exceed its authorized QoS.

Charging Control

Charging Control includes means for both offline and online charging. The PCRF makes the decision on whether online or offline charging shall apply for a certain service session, and the PCEF enforces that decision by collecting charging data and interact with the charging systems. The PCRF also controls what measurement method applies, that is, whether data volume, duration, combined volume/duration or event-based measurement is used. Again it is the PCEF that enforces the decision by performing the appropriate measurements on the IP traffic passing through the PCEF.

With online charging, the charging information can affect, in real-time, the services being used and therefore a direct interaction of the charging mechanism with the control of network resource usage is required. The online credit management allows an operator to control access to services based on credit status. For example, there has to be enough credit left with the subscription in order for the service session to start or an ongoing service session to continue. The OCS may authorize access to individual services or to a group of services by granting credits for authorized IP flows. Usage of resources is granted in different forms. The OCS may, for example, grant credit in the form of certain amount of time, traffic volume or chargeable events. If a user is not authorized to access a certain service, for example, in case the pre-paid account is empty, then the OCS may deny credit requests and additionally instruct the PCEF to redirect the service request to a specified destination that allows the user to re-fill the subscription.

PCC also incorporates service-based offline charging. With offline charging, the charging information is collected by the network for later processing and billing. Therefore, the charging information does not affect, in real-time, the service being used. Since billing is taking place after the service session has completed, for example, via a monthly bill, this functionality does not provide any means for access control in itself. Instead policy control must be used to restrict access and then service-specific usage may be reported using offline charging.

Online and offline charging may be used at the same time. For example, even for billed (offline charged) subscriptions, the online charging system may be used for functionality such as Advice of Charge. Conversely, for prepaid subscribers, the offline charging data generation may be used for accounting and statistics.

LTE Quality of service, charging and policy control (PCC)

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PLMN: What is a Public Land Mobile Network ?

A public land mobile network (PLMN) is any wireless communications system intended for use by terrestrial subscribers in vehicles or on foot. Such a system can stand alone, but often it is interconnected with a fixed system such as the public switched telephone network (PSTN). The most familiar example of a Public Land Mobile Network end user is a person with a cell phone. However, mobile and portable Internet use is also becoming common.

Public Land Mobile Network (PLMN)

PLMN code

A Public Land Mobile Network is identified by a globally unique PLMN code, which consists of a MCC (Mobile Country Code) and MNC (Mobile Network Code). Hence, it is a five- to six-digit number identifying a country, and a mobile network operator in that country, usually represented in the form 001-01 or 001-001.

A PLMN is part of a:

  • Location Area Identity (LAI) ( Public Land Mobile Network and Location Area Code)
  • Cell Global Identity (CGI) (LAI and Cell Identifier)
  • IMSI (see PLMN code and IMSI)

PLMN code and IMSI

The IMSI, which identifies a SIM or USIM for one subscriber, typically starts with the Public Land Mobile Network code. For example, an IMSI belonging to the PLMN 262-33 would look like 262330000000001. Mobile phones use this to detect Roaming, so that a mobile phone subscribed on a network with a Public Land Mobile Network code that mismatches the start of the USIM’s IMSI will typically display an “R” on the icon that indicates connection strength.

PLMN services

A Public Land Mobile Network typically offers the following services to a mobile subscriber:

The availability, quality and bandwidth of these services strongly depends on the particular technology used to implement a Public Land Mobile Network.

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Diameter Protocol in 4G LTE

What is Diameter in LTE?

Diameter is an AAA (Authorization, Authentication and Accounting ) protocol which works at the application layer in OSI model over TCP/SCTP or TLS/DTLS (for security) protocol. Diameter is the successor of RADIUS (Remote Remote Authentication Dial In User Service) protocol that runs over UDP.

This AAA technology is a message based protocol, where AAA nodes exchange messages and receive Positive or Negative acknowledgment for each message exchanged between nodes. For message exchange it internally uses the TCP and SCTP which makes diameter reliable. Its technical specifications are given in RFC-6733 Diameter Base Protocol. (Please refer to this link to RFC-6733 for the original definition)

Advantages of Diameter compared to Radius

This AAA technology has following improvements over RADIUS:   

a) More Reliable
b) Transport Layer Security                   
c) Fail-over Mechanism
d) Server Initiated Messages
e) Agent Support
f) Audit-ability
g) Transition Support
h) Capability Negotiation
i) Roaming Support
j) Peer Discovery & Configuration

Defaults Ports                      

The default port is 3868 for TCP/SCTP and 5868 for TLS/DTLS.

More details on AAA in LTE

LTE Evolved Packet Core (EPC) generally have 5 nodes:

1) Mobility Management Entity (MME)
2) Home Subscriber Server (HSS)
3) Serving Gateway (S-GW)
4) PDN Gateway (P-GW)
5) Policy and Charging control entity/Function (PCRF)

These nodes interact then uses diameter based interfaces. Please see the diagram below for more detailed information on this topic:

Diameter Protocol in LTE

The Dark Lines in the diagram show the major Interfaces in the LTE EPC (Evolved Packet Core). Sometimes the CSS data is not stored at HSS then S7a interface is used to communicate with the MME. S7a is also a diameter based interface.

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Private LTE Market could grow to $31B by 2022

Private LTE Market

The Private LTE Market is expected to grow to around $31 billion by 2022, say some market analysts. Market growth will occur in several vertical markets with a wide area of industries likely to take advantage of new 4G and 5G LTE technologies.

Private LTE Market for 4G & 5G devices expected to grow

Specific sectors for the growing Private LTE Market include:

  • Manufacturing
  • Hospitals
  • Laboratories
  • Power Generation
  • Oil & Gas Rigs, Distribution, Transport
  • Water Treatment
  • Surface and Underground Mining
  • Distribution Warehouses
  • Shipping Ports
  • Transportation
  • Security, CCTV, Safe City
  • Smart Cities

Additional Markets for Private LTE

In addition, there are expected to be future markets created to exploit growing demand for always-on, connected devices, IoT, Machine Vision and Robotics and more.

Equipment needed for Private LTE

Organisations intending to build a Private LTE network will need LTE Base Station (eNodeB, gNodeB), Core Infrastructure (EPC, HSS), Custom private SIM cards and CPE devices. Some vendors offer a complete range of products for end-to-end solution with proven interoperability between devices.

Software and Services required for Private LTE

Some vendors provide all required software for LTE, which can include:

  • RF planning software
  • Dimensioning Tools
  • Device Management Software
  • Network Management Software
  • LTE Billing Systems
  • EPC core software
  • HSS core software

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Private LTE introduced: 4G & 5G

Private LTE 4G & 5G Networks

Private LTE is growing in many sectors: Modern corporations, government, enterprises, and cities are run is being transformed by rapidly advancing mobile communications technology.

One advance is in the area of Private LTE: deploying their own high capacity, high speed 4G mobile communications capability in the shape of a Private Long Term Evolution (LTE) network, organisations can enhance their operational efficiency, innovate more quickly, get closer to their customers and reduce their energy footprint.

Private LTE 4G & 5G Networks
Privately-owned LTE 4G & 5G Networks

Private LTE networks free enterprises from the restrictions of conventional connectivity technologies such as Ethernet, which is secure and reliable but high cost and inflexible, and Wi-Fi, which offers low cost but also lower reliability.

A Private 4G or 5G LTE network can support both human and machine communications on a single, reliable network that offers mobility without cumbersome portable radios and that opens up the world of the Internet of Things (IoT).

By complementing existing Ethernet and Wi-Fi, building your own LTE will help to enable digital transformation in many industries and pave the way towards the adoption of even more capable 5G mobile technologies.

Most LTE networks are considered public, serving the general public or enterprise subscribers. An LTE network is considered to be private when its main purpose is to connect people/things belonging to an enterprise (normally in an enterprise campus), and where data needs to be kept totally secure by avoiding sending it through the core network of a mobile operator.

Advantages of Privately-owned LTE:

Enterprises can deploy by building their own LTE network using technology like MulteFire or Citizen’s Broadband Radio Service (CBRS) which run on unlicensed spectrum not tied to mobile operators. Various vendors support this option with their own end-to-end solutions.

LTE for any industry

Many industries are eager to use their own LTE to connect people and IoT devices:

Industry Areas for Private LTE

  • Utilities can benefit by converging legacy networks into a single, smart grid network
  • For Mining and Minerals, LTE can be used to automate remote facilities using a SmartMine concept
  • Oil and Gas
  • Ports are getting smarter, with LTE-based networks meeting their needs. Licensed bands, unlicensed MulteFire, or shared spectrum CBRS are all possibilities to build private LTE networks and take advantage modern technology solutions
  • For Aviation, LTE boosts efficiency by enabling secure control of operations over a single intelligent airport communications network

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Build Private LTE 4G & 5G Networks

Private LTE brings major benefits compared to Public LTE networks. A Private LTE network connects people/things belonging to an enterprise (normally across a campus or site), and where data needs to be kept totally secure by avoiding transmitting it through the core network of a mobile operator.  Full private ownership of the whole LTE network – including Base Stations and Core – has several advantages.

Major Benefits of Private LTE

The many benefits of a Private LTE network can include:

  • Guaranteeing coverage and capacity in the target coverage area. Organisations can design, engineer and update the RAN to meet their specific performance demands, including for coverage, configuring uplink and downlink, set usage policy, determine which users connect, how traffic is prioritised, and other key parameters.
  • Optimising parameters in the LTE radio to operate in challenging physical environments (e.g., warehouse or oil/gas facility with lots of metal). This can include fast recovery from failure, or optimizations for reliability, and for latency. This is not possible when connecting to a public network, where such parameters are under control of the operator, not the user.
  • Retaining control of critical data: In private networks, the organization controls its own security and can ensure that sensitive information does not leave the network; this is an essential requirement for many types of businesses and security-focused organisations. Another benefit of keeping data and the core network on the private LTE network is the risk of service disruption due to a WAN link outage is eliminated.
  • Dedicated coverage and capacity of high speed 4G network with the ability to customise performance to enterprise needs
  • High speed, high capacity, reliable and secure mobile broadband communication layer for mission-critical and business-critical people, machines and applications
  • A fast route to digital transformation and IoT, bringing intelligent insights for more efficient operation, agility, quality and innovation
  • LTE mobility – the use of advanced applications on mobile platforms (vehicles, robots, etc) and transparent hand-over to public LTE networks outside of private LTE network coverage
  • In mining and minerals, private LTE can be used to automate remote facilities and enhance security
  • Enabling IoT applications which can run over a Private LTE network

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