Globally, 5G mid-band (3.5G to 6 GHz) spectrum specifically sub 2GHz to 4.2GHz that offers reliable private wireless services to enterprise is becoming a preferred choice of many deployments. In the USA, 3.5G to 3.7GHz (Band 48) is gaining momentum for enterprise private wireless networks. A new generation of vendors and operators are now offering private wireless solutions that take advantage of 5G mid band spectrums. Initial roll out of enterprise wireless solution that utilizes band 48 spectrum is often referred to as private LTE since much of deployments in the USA are using LTE base stations for backhaul connectivity. 

Figure 1. A simplistic diagram depicting deployments of private LTE network that uses band 48.

 

This trend of private LTE may continue until 5G NR (New Radio) is introduced. Industry forums including 3GPP are already working on 5G NR specification for band 48 and some products may potentially be introduced by late 2022 or early 2023.

The concept of having a private wireless network as easy as a WiFi and free of charge will likely change the market for LTE & cellular systems generally. It would be a paradigm shift of cellular networks from a few nation-wide networks to a massive collection of small-scale LTE/5G networks. Globally, private LTE is expected to grow from USD$4Billions in 2020 to USD$7.5Billions at CAGR 13% [1]. The device that serves the 3.5GHz mid-band spectrum market is also expected to grow from USD$300millions in 2020 to $1 Billion by 2023 at a CAGR of 52% [2].

5G Mid-Band Spectrum

The 3.5GHz spectrum is tapped by operators as a key mid-band 5G spectrum around the world for potential deployments in Enterprise private wireless networks. Dubbed as Enterprise 5G, the mid band spectrums deployments are made on roads to enterprise private wireless networks. In the USA, 3.5GHz mid-band (band 48) frequency is known as CBRS (Citizen Broadband Radio Service). It is available as a licensed and unlicensed shared band in the country.

Figure 2. Mid-band shared spectrum.

The CBRS spectrum access is based on a three-tiered licensure system that protects incumbents while opening up the band for operators to augment capacity and for enterprises and industries to facilitate private networks. While the focus has been on deploying LTE in the CBRS band, the CBRS industry forums are working out technical specifications to make shared access to 3.5 GHz compatible with 3GPP’s 5G New Radio (NR) interface. LTE was designed to work across a wide frequency band (450 MHz to 3.8GHz) referred to as E-UTRA [3]. However, the ongoing work to offer CBRS band in the 5G NR will benefit the industry tremendously. Chief among them is the simplified device development and commercialization based on global alignment around 5G in 3.5 GHz [4].

Figure 3. The CBRS shared Spectrum.

Europe also started to allocate 5G mid band spectrum as licensed shared access (LSA) at 2300 MHz – 2400 MHz frequency range. In addition, different countries within Europe also offering their own spectrum range: UK (3800 MHz – 4200 MHz), France (2570 MHz – 2620 MHz), Germany (3700 MHz – 3800 MHz), Netherlands (3400 MHz – 3450 MHz & 3750 MHz – 3800 MHz) and Sweden (3720MHz – 3800MHz). In Asia, Japan has allocated 5G mid band spectrums to some of it’s tier 1 operators as follows: NTT (3.6-3.7 GHz, 4.5GHz – 4.6 GHz), KDDI (3.7GHz – 3.8 GHz, 4.0GHz – 4.1 GHz), Softbank (3.9GHz – 4.0 GHz) and Rakuten (3.8GHz – 3.9 GHz).

The Benefits

The are numerous benefits to enterprise using CBRS technologies apart from those I listed in my previous article on Enterprise 5G:

  • Improved Security: Due to the nature of the network laid out as a private wireless solution, inherently there is less risk of signal or data being compromised. Moreover, CBRS data is kept local. Since data and network is localized, further measures of zero trust security can be applied to devices and users. There is no scope for side channel attacks associated with network slicing in traditional telecom cloud.
  • Enhanced mobility range and better wireless performance: With CBRS, high speed mobility is fully supported unlike WiFi. Additionally, wireless connectivity
  • Capacity: Band 48 or CBRS can achieve up to 1Gbps or more throughput in the near term and much better bandwidth in future.
  • Optimized Service: Better QoS, bandwidth management and control on latency helps optimal services for industry specific applications.
  • Vendor agnostic solutions: CBRS devices can be vendor agnostic allowing enterprises to use multi-vendor solutions for the private wireless network.
  • Connectivity with new wireless devices: CBRS based private wireless network allows different wireless devices to seamlessly connect to the network. Future wireless devices can also be connected to the CBRS network with ease.

North American and Asian Deployments

Many vendors offering 5G mid band solutions globally have partnered with Trimble’s Timing & Frequency division to enable enterprise private wireless network services. Timing solution is critical imperatives of CBRS and other 5G solutions due to the fact that 5G spectrums are transmitted in precise timeslots. Without precise synchronization, 5G service would render in failure. Trimble offers a range of products that best suits operators and vendors offering 5G services.

In North America, Trimble’s timing solution has enabled CBRS operators to successfully deploy a number of private wireless networks in healthcare industries. The CBRS deployments require CBSD (CBRS Service Device). A SAS (Spectrum Access System) is used for environmental scanning for interference and availability of the 3.5GHz band. Once SAS provides authorization of availability of the spectrum, CBSD herein LTE eNB (base station) began transmitting in CBRS band. The Radio Access Points extend the network to each floor of a building allowing cell phone, hand held devices, tablets and other wireless devices to connect in the enterprise private wireless network. 

Figure 4. Typical deployment of CBRS in North American[1].

It is to be noted that CBRS spectrum is shared in USA and thus SAS controller is used for environmental scanning to find out availability of the spectrum for use in enterprise private wireless network.

In Japan, a top tier 1 operator has deployed Trimble’s timing solutions to offer enterprise private wireless networks in the country. It is one of the largest deployments of 5G mid bands in the world. The following diagram depicts typical deployment of mid band spectrum in Japan for which deployment significantly different than the deployments in North America. 

[1] Building image is taken from freepng.com.


Figure 5. Typical deployment of Enterprise private 5G (mid-band spectrum) in Japan.


Unlike US deployments, Japan enterprise private 5G deployments do not need SAS (Spectrum Access System) environmental scanning for interference. In Japan, mid-band spectrum is only allocated to tier 1 providers and thus no need for environmental scanning for shared opportunity of the spectrum. 

Challenge

Though CBRS provides high capacity and reliability with quick coverage which can result in significant business value to the service providers, there remains some inherent challenges. First, operators in the USA must access the CBRS spectrum based on a tiered category. Tier 1 providers have better access to the CBRS spectrum than tier 2 and tier 3. However, PAL (Priority Access License) also provides guaranteed access of CBRS spectrum to tier 2 providers depending upon geographic location. On the other hand, tier 3 providers get GAA (General Authorized Access) to CBRS spectrum provided that there is no conflict on spectrum sharing with Tier 1 and tier 2 providers in a given location.

In Japan, the 5G mid band spectrum is only distributed to tier 1 providers. As a result, there is no environmental scanning needed to protect against interference. However, the synchronization challenge is the same for both. As stated, CBRS and other 5G spectrums use TDD (Time division duplex) for uplink and downlink transmission requiring precise synchronization end to end. Sync plane is one of the major imperatives of 5G deployment and thus careful consideration is needed.

While many vendors offer sync solutions, very few can match the performance and price that Trimble product offers. Additionally, Trimble timing modules are also an inherent part of Radio Units providing nanosecond level accuracy at radio endpoints.

Solution

The CBRS network in the USA and similar mid band deployments in other parts of the world require careful design of the network. More importantly, enterprise should consider business objectives and how it aligns with enterprise 5G goals. Each industry is different and thus requirements also may vary. For example, healthcare and smart manufacturing must consider environmental consideration while choosing products and solutions. For example, deployments in Japan are more of an extension of the tier 1 network to business parks where each enterprise is connected over fiber to Tier 1 xhaul network. Such networks may be appropriate for some businesses while others may prefer direct interconnect for security reasons.

While there is no direct xhaul connection in CBRS deployments in the USA, Enterprise should further investigate as to how EPC connectivity is done if secure interconnect is of highest priority. A hybrid solution can be developed to keep much of the industrial and business data localized while EPC can be used for phone calls.

Alternatively, private EPC service can be obtained and thus creating private enterprise-wide phone and other mobile transport connectivity.

In general, each enterprise private CBRS network is connected to the SAS (Spectrum Access System) controller which provides environmental scanning to find available spectrum for the deployment. The CBRS deployment that forms the enterprise private 5G/LTE eventually connected to EPC (Evolved Packet Core) for uplink and mobile transport outside of enterprise. However, such connectivity can be managed as a hybrid solution or same way public cloud services are provided. 

Synchronization

One of the critical aspects of CBRS and mid band connectivity is to ensure highly accurate end to end synchronization is provided. Typical sync plane design need to meet few challenges, e.g. price, performance, customization and network asymmetry for a given sync solution.

CBRS operators of both the USA and Japan found Trimble’s Thunderbolt GM200 ideal edge sync product for several reasons: price, performance, flexibility, accuracy and holdover capabilities. Additionally, Thunderbolt® GM200 is a two-in-one product combining boundary clock and grandmaster capabilities in a half rack size box. The Product is hardened to work in the worst indoor environments.

In the Japanese deployments, the product needed to compensate for network asymmetry conditions, an anomaly that is often difficult to deduce for optimal synchronization. The device was flexible to accommodate boundary clock scenarios while giving the capabilities of holdover that comes with expensive grand master clock devices.

Moreover, Thunderbolt® GM200 provided microseconds level accuracy for the network with flexibility to deploy it as boundary clock or grandmaster to extend network reach while failover clock sync is assured through holdover capabilities.

The solution needed customization as well to support various requirements including PoE and GNSS antenna placements. Trimble T&F team worked with operators to adequately consult and provide engineering services for the successful completion of CBRS deployments. Trimble’s T&F division has 35 years of time sync experience with thousands of deployments which enables the team to offer unparalleled engineering and product services to vendors and operators. 

Reference

  1. intrado, 2020. Private LTE Industry to be Worth $7.5 Billion by 2025 – Global Market Growth, Trends and Opportunity Analysis. Source: Research and Markets.
  2. CISION, 2020. Global LTE & 5G NR-Based CBRS Networks Market Report 2020-2030: CBRS Market Remains Largely Unfazed by the Economic Disruption Associated with COVID-19. SOURCE: Research and Markets.
  3. Lowe, J., 2020. Why CBRS frequency bands are perfect for private LTE and private 5G networks. Infovista.
  4. Kinney, Sean, 2019. Where are we today with CBRS and what’s next? RCR Wireless. 

Author: Dhiman Deb Chowdhury