Wi-Fi, an unlicensed wireless technology, has experienced huge success due to high throughput
rates, ease of use for consumers, extensive deployment
by businesses, widespread availability in public places, and large amounts of
available spectrum.
For mobile operators, Wi-Fi can offload data traffic, relieving some stress from capacity demands. To make offload work more effectively, the industry is working to more tightly bind Wi-Fi functionality with cellular operation, as discussed below in more detail under “Wi-Fi Integration and Data Offload.”
Wi-Fi uses spectrum efficiently because its small coverage areas result in high-frequency reuse and high data density (bps per square meter). Less efficient are white-space unlicensed networks, sometimes called “super Wi-Fi,” that have large coverage areas, because the throughput per square meter is much lower. While white-space networks may be a practical broadband solution in rural or undeveloped areas, they face significant challenges in urban areas that already have mobile and fixed broadband available.34 See the section on “White Space Networks” in the appendix for further details.
Advocates argue that unlicensed spectrum
unleashes innovation and that government should allocate greater amounts of
unlicensed spectrum. Although Wi-Fi has been successful,
the core elements
that make unlicensed spectrum extremely successful are also the source of inherent disadvantages: local coverage and its unlicensed
status. Local coverage enables high data density
and high frequency
reuse but makes widespread continuous coverage almost impossible.
Similarly, unlicensed operation facilitates deployment by millions of entities but
results in overlapping coverage and interference.
Wi-Fi cannot replace networks built using licensed spectrum. The two are complementary and helpful to each other, as summarized in Table 1
Table 1: Pros
and Cons of Unlicensed and Licensed Spectrum
|
Unlicensed Pros
|
Unlicensed Cons
|
Licensed Pros
|
Licensed Cons
|
|
Easy and
quick to deploy
|
Potential of other entities
using same frequencies
|
Huge coverage areas
|
Expensive infrastructure
|
|
Low-cost hardware
|
Difficult to impossible to provide wide-scale coverage
|
Able to manage
quality of service
|
Each operator has access
to only a small amount of spectrum
|
Some operators, such as Republic Wireless,
offer a “Wi-Fi first” capability under which devices always attempt to use a Wi-Fi connection and fall back to a cellular connection only if no Wi-Fi is available. Such cellular backup is essential
because Wi-Fi, due to low- power operation in many bands, is inherently
unsuited for providing continuous coverage. The sharp drop-off
in signal strength
makes coverage gaps over large
areas inevitable, especially
outdoors.
Figure 1: Propagation Losses
of Cellular vs. Wi-Fi
A capability being discussed for Release 13 is LTE operating in unlicensed bands. Carrier aggregation would combine a licensed carrier with an unlicensed 20 MHz carrier in the 5 GHz band as a supplemental channel. LTE uses channels differently than Wi-Fi, so engineers are evaluating how LTE could be a fair neighbor in unlicensed bands and how it could meet varying regulatory requirements for unlicensed bands in different parts of the world.
LTE operating in unlicensed bands could eliminate handoffs to Wi-Fi, possibly creating a more seamless user experience. Under heavy load, LTE is spectrally more efficient than Wi-Fi, since it uses more sophisticated over-the-air scheduling algorithms.
A capability being discussed for Release 13 is
LTE operating in unlicensed bands. Carrier aggregation would combine a licensed carrier
with an unlicensed 20 MHz carrier in the 5 GHz band as a supplemental
