Cuopom: Mobile transport is the right ingredient for 5G FWA success

Globally, demand for broadband connections to both residential and businesses has been strong over several years. Furthermore, many countries are focusing on infrastructure improvements associated with digital transformation and expansion of broadband connectivity for social economic benefits. The recent Covid pandemic proved the need for ubiquitous broadband.

High adoption of connected devices, video streaming and online gaming services are among the drivers of higher-quality broadband access. At the same time broadband infrastructure is lacking in rural areas. For example, over a quarter of rural Americans do not have access to broadband download speed of 25 Megabits per second (Mbps).

As a result, communication service providers (CSP) are working through strategic decisions on broadband market expansions and what technologies to deploy. Existing mobile operators may leverage their wireless footprint with FWA for new revenue opportunities while new operators want to leverage free spectrum to provide broadband access using FWA. With government subsidized rural broadband taking hold globally, these programs help supplement business cases for broadband service expansion that would never have been feasible. Furthermore, more broadband solution architectures are available to service providers to address a variety of deployment challenges for both residential and business customers.

These challenges include the breadth of subscriber densities, varying terrains, access to radio spectrum and fiber for backhaul. With the introduction of new spectrum such as mid-band (e.g. CBRS 3.55-3.7 GHz) or even mmWave (28-39GHz), wireless broadband solutions are now more feasible than ever before. Additionally, a variety of radio solutions can be optimized based on subscriber density to provide cost effective and robust broadband service plans. Figure 1 below provides an overview of subscriber density where Fixed Wireless Access (FWA) is a feasible broadband solution to address both residential and small business needs.

Figure 1: FWA market segmentation in North America
Source: Ericsson and US Census

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Grandpa Magnus’ recipe for FWA connectivity

The FWA network will consist of a variety of sites types that will require connectivity back to the packet core (i.e. brain of the network) – see Figure 2. Dependent on the target market and subscriber density, the number of these FWA type sites will vary, but in general you will see:

End site – These are the cell site locations that provide local FWA service to residential and small businesses.
Repeater site or intermediate site – As the name implies, these sites provide intermediate connectivity to end site(s) and may include cell site equipment for local FWA services.
Aggregation site – This site is usually a fiber anchored site in the network and aggregates multiple intermediate site(s) and potentially local market FWA end site(s).

Figure 2: Typical FWA site types

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Base ingredient - end sites

Based on the service provider broadband strategy, FWA may be a complement to existing wireline broadband services or may completely replace it. The FWA end site includes the necessary cell site or radio access network (RAN) equipment to provide wireless broadband service to residential and business customers along with backhaul connectivity towards the packet core. Backhaul capacity for end sites can vary from 500Mb/s to 3Gb/s based on subscriber density, RAN technology deployed, and offered broadband service packages. End sites are typically standalone locations with an antenna tower and outdoor cabinet for equipment.

The specific architecture and spectrum deployed at the end site will depend on the CSP spectrum holdings, strategy and packages offered. There are several important considerations for backhaul connectivity based on the architecture and spectrum.

Figure 3: Example of an FWA end site

Precision Timing Protocol (PTP) Support: Mid-band spectrum is based on Time Division Duplex (TDD) technology. Radios operating in this spectrum require more stringent time and phase synchronization since the same RF frequencies are used for downlink and uplink between radio and user equipment (UE). To protect TDD radios against a local GPS failure and associated broadband service outage, we recommend synchronization backup using the PTP with G.8275 Telecom Profiles over the transport network.
Multiple 10GE interfaces: End sites using mmWave spectrum or advanced RAN features like carrier aggregation or massive MIMO will require higher speed interfaces and backhaul capacity. Thus, multiple 10GE interfaces are key to support current traffic demands and any future growth.
Comprehensive microwave solutions: The lack of fiber connectivity for end sites drive the need for comprehensive and scalable microwave backhaul.
Robust quality of Service: Don’t forget the importance of robust QOS capabilities such as hierarchical QoS (H-QOS) to support a mixture of voice, video, and data traffic to provide a rich customer experience that complements or replaces the wireline broadband experience.
Temperature hardened equipment: Transport equipment for end sites will typically be deployed in outside plant cabinets so extended operating temperature range is vital.

Summarizing, the key transport ingredients for End Sites include cell site router for direct fiber connectivity along with microwave transport options that support time and phase synchronization like PTP with the G.8275 Telecom Profiles, a number of high capacity 10GE interfaces, and robust QoS features. Finally, the transport equipment must be outdoor temperature rated or “hardened” to support deployments in outside plant cabinets.

Sprinkle in repeater sites

Given different FWA deployment markets, Repeater Sites or Intermediate Sites will likely exist to connect small cities and municipalities in a linear chain. Like end sites, some of these locations may be quite rural and have limited access to fiber backhaul. As a result, microwave backhaul will be needed for connectivity to the packet core. Microwave solutions offer high capacity, low-latency, and cost-efficient transport and are an excellent FWA transport solution together with fiber connectivity.

The Repeater Sites will need to provide backhaul capacity for its local market FWA service plus backhaul capacity for any connected End Sites. Thus, total backhaul capacity from a repeater site will include local market backhaul plus a multiple for the subtended end sites. While traffic oversubscription and QoS can be leveraged to reduce the overall backhaul capacity, it will likely be in the order of 1-5Gb/s.

Key mobile transport requirements for repeater sites include:

Latest microwave technology: For markets lacking fiber connectivity, microwave transport options with the latest technology enhancements such as high modulation and multi-carrier aggregation like multi-band booster will provide sufficient backhaul aggregation capacity. See Figure 4 for details on key microwave technology enhancements.

Figure 4: Microwave technology enhancements that drive higher capacity links

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Multiple hop directions: Microwave equipment must support multiple hop directions to connect with subtended end sites and connected repeater sites.
Router capacity: The cell site router (CSR) should provide higher switching capacity and a larger number of 10GE interfaces.
PTP synchronization and QoS: Cell site router (CSR) along with any microwave transport must support distribution of PTP synchronization to end sites along with robust QoS features to prioritize aggregated traffic flows and provide optimal Quality of Experience (QoE).
Temperature hardened equipment: Similar to End sites, all equipment for Repeater sites should be temperature hardened for outside plant deployments.

Summarizing, the essential transport ingredients for Repeater sites include cell site router for direct fiber backhaul connectivity along with higher capacity microwave transport options. Key features include support for PTP distribution, an increased number of 10GE interfaces and switching capacity, higher backhaul capacity with robust QoS features, and support of multiple hop directions for microwave backhaul. Ideally, the transport portfolio of routers and microwave radios used with have scalable models to address a breadth of deployment scenarios.

Mix in a few aggregation sites

Aggregation sites are typically fiber anchored to the service provider network. These locations will aggregate multiple repeater or intermediate sites along with local market end site(s). Aggregated capacity will likely be Nx10GEs to 100GE based on the quantity of sites connected and the associated subscriber market densities.

Fundamental attributes for transport equipment at aggregation sites include:

Access ports and backhaul capacity: The router interfaces will include N x 10GE access ports and even higher backhaul capacity (e.g. Nx10GE LAG or 100GE) to interface to the backbone transport network or to the regional packet core.
Enhanced QoS: the ability to provide enhanced QoS such as H-QoS will ensure optimal user experience while optimizing network capacity to ensure profitable total cost of ownership (TCO).
Grand master clock source location: The aggregation sites may be an optimal location for a grand master clock source (e.g. Primary Reference Source like GPS). The aggregation site router can distribute PTP as either primary or back-up timing source to all the repeater and subtended end-sites. Support of PTP across the transport network of routers and microwave hops provides a robust network synchronization design to protect against GPS outages and associated broadband service outages.
Microwave flexibility: For aggregation of repeater or end sites that do not have fiber connectivity, the microwave solution at the aggregation site must be scalable to support a number of microwave hop directions with high capacity.
Security: The aggregation site may also serve as a Security Gateway, supporting encrypted IPsec tunnels for any off-network locations that are transported over “un-trusted” network facilities. Support of IPsec on the aggregation router is a must to support this capability.

Figure 5: Example equipment configurations based on site type. Note: Microwave equipment is highlighted in green, routers in blue, and radio basebands in red.

Ericsson’s transport recipe for FWA Success

Ericsson is committed to helping our customer prepare for all wireless scenarios. With our portfolio of 5G-ready transport solutions, CSP can build for the future in today’s networks. So when planning your FWA network, don’t let the legacy transport network ruin your FWA recipe for broadband success. Ericsson has a robust 5G transport portfolio that is purpose built as part of the Ericsson Radio Solution (ERS) to enable quick time to market (TTM) and provide the lowest total cost of ownership (TCO).