Google trends is a fascinating tool that provides unparalleled insight into what people across the world are thinking and doing. A quick glance at the search trend for the term “5G” reveals a growing interest in this wireless connectivity technology (in case you are curious, here is the comparison against the search trend for “WiFi” and here it is against the trend for “4G”). At CES 2020, Lenovo announced Yoga 5G, the world’s first 5G laptop. Although it has yet to ship, its technical specs list 5G and Bluetooth 5.0 as the only two supported connectivity technologies. Wi-Fi is conspicuously absent on this laptop, which has a starting price of $1499. Is this a precursor of what’s to come or does the Yoga 5G merely address a small market segment? Several other questions arise: Is Wi-Fi going to be replaced by 5G? Is 5G superior to Wi-Fi? What is Wi-Fi’s role in a 5G world? Before we answer these questions, let us start with a quick primer on 5G.
What is 5G?
Over the last 40 years, the world has witnessed a new generation of mobile communication technologies every decade. The first-generation technologies (1G), which emerged around 1980, were based on analog transmission and limited to voice services. The first major upgrade to mobile communication arrived in the early 1990s with the introduction of second generation (2G) technologies based on digital transmission. The target service was still voice, although the use of digital transmission allowed 2G systems to support limited data services – and almost accidentally created text messaging. The third generation (3G) was introduced in 2001 to facilitate greater voice and data capacity, thereby laying the foundations for mobile broadband. While the first two generations were designed to operate in paired spectrum based on Frequency Division Duplex (FDD), 3G introduced operation in unpaired spectrum based on Time Division Duplex (TDD), although this was rarely implemented. We are currently in the 4G era, which began in 2010. 4G technologies leverageOFDM and MIMO techniques to achieve higher efficiency and higher end-user data rates – enabling mobile broadband and harmonizing the fractured ecosystem.
5G is the fifth and the latest generation mobile communication technology that supports three primary use cases: enhanced mobile broadband (higher speeds to current users), low latency with high reliability (to enable services such as safety systems and automatic control), and massive machine to machine communication (the ability to concurrently connect a lot more devices – IoT). 5G operates in many different frequency bands — from 600 MHz to 39 GHz — to service a wide variety of use cases. Signal propagation and bandwidth availability at mmWave (24 – 39 GHz) is very different from signals below 6 GHz. While mmWave can achieve 10+ Gbps data rates by leveraging as much as 800 MHz bandwidth, its range is limited because of the higher path loss at higher frequencies. On the other hand, sub 6 GHz has good range, but the data rate is less since the bandwidth is limited to 100 MHz.
Is Wi-Fi going to be replaced by 5G?
We often debate whether 5G will replace Wi-Fi. Ultimately, we concluded that both Wi-Fi and cellular technologies will continue to be strong complements to each other for the foreseeable future.
- Total Ownership Cost: IP licensing costs associated with cellular technologies make cellular infrastructure and clients more expensive than their Wi-Fi counterparts. Unlike Wi-Fi, each new cellular generation is typically accompanied by new, and often expensive, spectrum. In addition, cellular services typically come with subscription fees paid to the network operator who owns the infrastructure and spectrum.
- Installed Base: Wi-Fi is ubiquitous. There are more than 13 billion Wi-Fi devices in active use worldwide and many of them have a long replacement cycle. Every new generation of Wi-Fi ensures that these devices can continue to connect to the new Wi-Fi infrastructure just as they did with the older ones, thereby protecting the existing investment in legacy devices. On the other hand, cellular chips don’t provide complete backwards compatibility and typically support only one or two generations.
- Ease of deployment: Wi-Fi uses free unlicensed spectrum and does not require any complex backend infrastructure such as a packet core. It can be deployed in minutes without requiring a skilled technician. Cloud management has further simplified Wi-Fi deployment, making it as simple as plug and play. Now that the Wi-Fi calling feature is natively supported on most smart phones, Wi-Fi is a good alternative to deploying dual systems for calling.
- In-building coverage: We spend most of our time indoors, yet outdoor cellular signals have trouble penetrating buildings. While there are several ways to bring cellular services into a building, this has not proven economical for wireless service providers. Thus, Wi-Fi remains the preferred choice and offers an additional benefit for the tenant, as the spectrum is unlicensed and can be controlled entirely.
In the next section, we will see that the latest generation of Wi-Fi performs on par with 5G for most use cases.
Is 5G superior to Wi-Fi?
As with cellular, Wi-Fi has gone through several generations of evolution over the last three decades. Client and infrastructure products supporting the sixth generation of Wi-Fi, commonly referred to as Wi-Fi 6, have been shipping since 2018. Notably, all models of Samsung Galaxy S10 and all models of iPhone 11 ship with Wi-Fi 6 connectivity.
Both Wi-Fi 6 and 5G use OFDM and OFDMA for PHY layer signaling and support up to 8 MIMO streams. While Wi-Fi 6 supports peak data rate of 9.6 Gbps, smartphone clients with two transmit and two receive chains can achieve over 1.7 Gbps TCP throughput in both uplink and downlink. This is comparable to the performance achievable with 5G. Wi-Fi 6 achieves a spectral efficiency of 62.5 bps/Hz, which exceeds the 5G requirement of 30 bps/Hz. It also includes several new features that enable AR, VR, and IoT applications through higher data rates, reduced latency, increased range, and extended battery life (similar to many of the features of 5G).
Wi-Fi 6 is optimized for extremely dense environments, with a single Wi-Fi 6 access point capable of serving a whopping 1024 clients concurrently. The trigger frame feature of Wi-Fi 6 enables scheduled access, similar to cellular, resulting in improved reliability of transmissions due to the elimination of collisions.
With the introduction of Passpoint, network discovery and selection have been fully automated rendering Wi-Fi roaming as seamless as cellular roaming. The latest security protocols, such as WPA3 and Enhanced Open supported on all Wi-Fi 6 devices have made Wi-Fi as secure as cellular. These protocols provide more secure and individualized encryption, making it difficult for hackers to snoop traffic even in an “open” network. Furthermore, features such as Rogue Detection supported on Wi-Fi access points protect users from “man-in-the-middle” attacks.
One of the areas where Wi-Fi falls short is mobility, as it is not specifically designed for high speed mobility. While cellular systems avoid interference by using different set of licensed frequencies from neighboring cells and provide guaranteed service quality, this is not the case, especially for unmanaged Wi-Fi networks.
The bottom line: Wi-Fi 6 is widely deployed today and measures up well against 5G.
What is Wi-Fi’s role in the world of 5G?
Given the favorable economics and high performance of Wi-Fi 6, Wi-Fi will remain a very attractive choice for indoor and enterprise applications. While cellular has its origins outdoors, we expect Wi-Fi and 5G to co-exist both indoors and outdoors.
Moreover, Wi-Fi continues to evolve faster than cellular with new Wi-Fi technology introduced once every 5 years – compared to the 10-year cadence of cellular technologies. Work has already started on the seventh generation of Wi-Fi, based on IEEE 802.11be. Wi-Fi 7 is targeting a peak throughput of at least 30 Gbps and strives to reduce the worst-case latency and jitter.
Recent efforts by Federal Communications Commission and OFCOM to open up in excess of 500 MHz of spectrum in the 6 GHz band for unlicensed use is expected to be another major game changer for Wi-Fi. This clean spectrum will double the number of lanes on the Wi-Fi superhighway and turbocharge the user base with added capacity for existing and new applications. This spectrum is expected to bring significant reductions in latency, since it will be occupied only by highly efficient Wi-Fi 6 devices (also known as Wi-Fi 6E devices), further enabling latency sensitive applications.
There has been cross fertilization of ideas between Wi-Fi and cellular, and this trend will continue as the two technologies move closer and closer together. For example, Wi-Fi introduced OFDM as part of its third-generation technology ratified in 1999, while cellular leveraged OFDM as part of its fourth-generation technology introduced in 2010. The latest sixth generation of Wi-Fi (2018) supports OFDMA, which cellular has supported since 4G (2010). Wi-Fi 6 introduced scheduled access, in addition to the traditional Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA), bringing the Wi-Fi and cellular channel access methods closer. While Wi-Fi has always restricted itself to unlicensed bands, cellular dabbled with deployments in the unlicensed 5 GHz spectrum using LTE-U (although it wasn’t as successful).
In summary, Wi-Fi and 5G will move closer together and coexist as complementary technologies for the foreseeable future.