There was a time when visualizing the last mile was pretty straightforward – it was the copper wire that connected a telephone to a local switching office, typically less than a mile away. The telephone service, the local loop and the telephone set were all owned, installed and operated by a telecommunications carrier. Coaxial television cable eventually provided some competition for the last mile, but very few options were really available everywhere. Fast forward fifty years and the landscape has changed dramatically. Wiring options now include fibre optics and fixed wireless, the Internet acts as the multimedia digital backbone, and mobile wireless access is nearly ubiquitous. Telephony is just one of many popular applications – the Cisco Visual Networking Index predicts that video will account for about 82 percent of global data traffic by 2022. Today, the modern last mile represents many types of links that connect edge devices to the core networks.
Source: Alexis Gravel/flickr
So why is the last mile back in the spotlight now? Where does the last mile fit into today’s networking maze and who controls it? And are the new standards for 5G and WiFi 6 competing or complementary?
The modern last mile
The last mile concept has evolved along with the development of mobile technologies, edge computing, consumer networks and the diversification of service providers. Figure 2. illustrates the difference between traditional last mile and the modern wireless last mile concepts. The last mile is still the link between the user’s equipment and the provider’s core network, but the demarcation point could be a user-owned gateway (or edge node), rather than a user device. The network access point could be in the provider’s office, on a cell tower, in a public location or even in the customer’s building. The last mile has become more complex with the development of multiple segments, technologies and providers for link delivery.
Small offices and homes that once used a single telephone may now have multiple Internet-attached devices, including personal computers, cellphones, speakers, entertainment systems, thermostats, smart doors and locks, surveillance cameras, smoke and water detectors, controlled lighting, energy monitors and even smart office appliances (e.g., printers). The modern last mile must support various combinations of technologies, standards and ownership models.
How does 5G cellular impact the last mile?
Standards for 5G, the fifth generation of cellular technology, are being developed by the 3rd Generation Partnership Project (3GPP) along with the International Telecommunications Union (ITU) and the Internet Engineering Task Force (IETF). 5G standards cover the radio access network, core networks and service capabilities. The European Telecommunications Standards Institute (ETSI) states that the primary requirements are speeds of more than one gigabit per second, latency at one millisecond or less, high availability, high capacity and increased radio efficiency.
In a 5G world, support must be available for billions of low cost, low power IoT devices. Not only will people be connected to each other, but so will machines, automobiles, city infrastructure, public safety and more. 5G networks should also be designed to have always-on capabilities and aim to be energy efficient by minimizing the modem’s power usage.
The 5G wireless last mile includes both the radio with its spectrum assignment and modulation technique and the network access protocols. 5G can re-use 4G frequencies but in order to achieve the maximum data transfer rates will require higher frequencies, called the mmWave bands. The downside of the high frequency bands is interference from physical barriers (including walls and floors) and atmospheric conditions, leading to the need for more cell towers that are spaced closer together, i.e., a shorter last mile.
5G networking inside offices and public buildings is at an early stage of development. Services at mmWave frequencies need in-building antenna systems to minimize blocking and ensure high quality. As of mid-2019, mobile 5G services are not yet available in Canada, although 5G-ready fixed wireless links such as the Explornet service in Prince Edward Island are now being deployed. Canadian wireless service providers are working to get their existing networks 5G-ready. In the United States 5G fixed links have been deployed in selected cities since 2018 and mobile 5G is available in some locations, with many more services expected to go live in 2020. Verizon, for example, has announced it is bringing 5G “Ultra Wideband” connectivity to 13 National Football League stadiums ahead of the kickoff to the NFL’s one hundredth season. Ookla publishes a 5G map that tracks worldwide deployment.
The last mile for WiFi
WiFi 6 (also known as IEEE802.11ax) is the sixth generation of wireless local area network. The Institute of Electrical and Electronic Engineers (IEEE) produced the standards that it is based on, and the WiFi Alliance oversees product certification. WiFi 6 is an incremental improvement over the current W-Fi 5 (IEEE802.11ac), which increases speed and capacity but it also supports higher densities, new applications and more device types, including IoT devices. Like its predecessors, WiFi 6 is not a cellular service and does not compete with 5G for wide area communications. However, WiFi 6 introduces several new technology elements, one of which is called orthogonal frequency division multiple access (OFDMA), to address connectivity needs in challenging environments such as a stadium or apartment complex. OFDMA manages airtime utilization, improves radio efficiency and supports dynamic division of a radio channel, resulting in quality support for more devices simultaneously. WiFi 6 allows traffic (e.g., high bandwidth video, interactive voice and low bandwidth IoT) to be bundled together for more efficient data transport.
Pre-standard WiFi 6 products, which are available now, are based on what manufacturers believe will reflect the final standard in early 2020. The WiFi Alliance announced in September 2019 its certification program called WiFi CERTIFIED™ to provide assurance that products meet the standards. Another important step is the recent Apple announcement of WiFi 6 support in the new iPhone 11 smartphones (5G is not included in the iPhone 11 but is anticipated to become available in 2020).
Comparing 5G and WiFi 6 scenarios
Comparing 5G and WiFi 6 is like comparing apples and oranges – both are round, each tastes good and yet they aren’t equivalent or used in the same recipes. Several deployment scenarios, including the following, can be envisioned.
Scenario 1. is the complete elimination of WiFi. The last mile is the link between the user’s device and a nearby cell tower. In 5G, only public 5G cellular networks are used and all data is transferred over the 5G network (which could be expensive with metered billing). This scenario leads to high 5G usage and a strong possibility of coverage limitations. It also ignores current investments in WiFi and does not accommodate devices that are ethernet or WiFi only.
Scenario 2. (not shown on Figure 3.) is a variation that displaces WiFi with an in-building 5G system linked to wired or wireless access networks, either provider-managed or customer-owned. How easily indoor cells to provide complete in-building 5G coverage could be set up remains uncertain. Replacing WiFi with in-building 5G would require a good technical justification and would also have attachability limitations and migration challenges. Since WiFi 6 is backward compatible and WiFi 5 has a very large customer base today, the displacement of WiFi seems to be an unlikely outcome.
Scenario 3. is in-building WiFi 6 connected to a fixed wireless link, a public 5G cellular link or a dedicated network. The last mile would be a combination of the in-building WiFi link and the network access link. Here, WiFi 6 may be useful as an on-ramp to a 5G network using a router that provides WiFi, ethernet and a 5G network interface (i.e., a SIM card), similar to how a mobile phone can be used as a hotspot for tablets. Examples are the FRITZ!Box 6890 or the D-link 5G NR Enhanced Gateway DWR-2010 (which also includes Zigbee for use as an IoT gateway).
These scenarios can become complicated if mixed environments combining old and new standards are involved or not all services are available in all locations. No technology offers as much mobility and reach as cellular technology but WiFi addresses a huge number of enterprise, home, vehicle and IoT use cases that mobile services don’t address. Another benefit of privately-owned networks comes from the ownership itself, not the technology. For example, a retailer that provides in-store WiFi can garner real-time, analytic insights from their own network which would not be the case if the retailer was using a mobile carrier who would control the data.
The bottom line
The last mile is back in the spotlight because new and increasingly pervasive digital customer experience services, video and IoT demand enhanced connectivity capabilities, which are now delivered by a complex mix of technologies and providers. The last mile, once a simple pair of copper wires from a physical telephone to a telecommunications office, is now the path that connects multiple devices to a range of digital applications. The last mile could be a short WiFi link to a provider-owned building gateway or it could be a combination of local and wide area wired and wireless links. Both 5G and WiFi 6 provide valuable new last mile options. But what seems clear is that no one approach will emerge as owner of the last mile in the near term, rather both the old (e.g., 4G and WiFi 5) and the new (5G and WiFi 6) technologies will need to coexist for a lengthy transition period.
