The wireless industry has always had to deal with regular (and alarming) pronouncements that we’re somehow running out of radio spectrum. We’re not. But the misconception regardless gives many IT and network managers pause. After all, if the availability, reliability and especially the capacity of wireless were to degrade to the point of a de-facto shortage, the situation would be dire for communications at the edges of both the LAN and WAN.
So let’s start putting to rest any conjecture regarding a spectrum shortage and focus on reality: Thanks to a combination of continual advances in wireless technologies, recent enhancements to spectrum regulatory policy, and novel thinking around spectrum allocation, we can be assured that a “spectrum shortage” is, and will remain, an abstract theoretical concept.
Understanding the concern: RF characteristics and limitations
We can always take advantage of more spectrum, but frequencies broadly applicable to radio communications (RF) represent only a tiny fraction of the overall electromagnetic spectrum, the regulated portion of which in the United States extends from 9 KHz. to 300 GHz. Despite the complexity inherent in building today’s wideband radios, advances in wireless communications technologies over the past three decades have been quite successful in boosting the availability, reliability, price/performance, and especially the throughput of deployed solutions – all the way to the gigabit+ speeds today featured in IEEE 802.11ax and (eventually) 5G.
The key to these achievements has centered on a variety of techniques that advance just one technical aspect of wireless communications: spectral efficiency. The improvement to spectral efficiency is determined by the number of bits successfully transferred per unit of time, bandwidth, and, in the case of increasingly applied multiple-input/multiple-output (MIMO) techniques, space as well.
Among the most important advances in this area are: denser modulation schemes, such as 802.11ax’s 1024-QAM, which can encode 10 bits per Hertz; more efficient channel codes, which otherwise add (albeit necessary) overhead; higher-order MIMO, with, for example, up to eight transmitters and receivers specified in both 802.11ac and .11ax; and techniques like multi-user MIMO (MU-MIMO), beamforming, beamsteering, bandsteering (as a form of load balancing), and even a wide variety of newer upper-layer traffic-management capabilities based on real-time analytics, artificial intelligence (AI), and machine learning (ML).
Greater spectral efficiency, however, doesn’t eliminate a particularly challenging artifact of the unlicensed bands. With ever-increasing demand for Wi-Fi and other technologies operating in this spectrum, interference remains a legitimate concern. Contemporary RF spectrum management (RFSM), radio resource management (RRM) solutions, and applications of AI/ML can do a very good job of dealing with interference in many cases, by adjusting transmit power, channel assignment, and modulation and coding on the fly. A larger concern, however, is mutual interference from otherwise disjoint technologies operating simultaneously at a given frequency, such as that which can occur between Wi-Fi and unlicensed LTE or LTE-A. Local deployment policies coupled with RFSM and RRM techniques, however, can also aid in the mitigation of this otherwise very real concern.
A third challenge comes with a hidden silver lining. This is signal fading, which represents what is perhaps the most important technical opportunity under the control of network managers in furthering the goal of optimal spectrum utilization. Signal fading, which occurs in many forms in wireless communications, essentially limits the range of a given terrestrial transmission. While many view fading as a technical problem to be overcome, taking advantage of this artifact, as we’ll discuss below, is instead an important key to maximizing the capacity of a given wireless installation.
Technology defines what’s possible in a given band of spectrum. But as we mentioned above, the availability of additional spectrum for any given application is an important element in avoiding congestion and maximizing productive spectrum utilization. The industry has benefitted when regulatory authorities have reassigned spectrum to more-contemporary and higher-demand applications (the technical term here is refarmed).
Spectrum refarming is gaining in importance as wireless communications become essential to the overall economy. Unfortunately,