Google Data

by Nihar Jindal, Hardware Engineer, Access & Energy

In the 20 years since the Federal Communications Commission (“FCC”) first made spectrum available on an unlicensed basis, technologies such as Wi-Fi and Bluetooth have flourished. Innovation in unlicensed spectrum has given people more opportunity to access the Internet, when and where they need it.

Carriers are also innovating in licensed spectrum, deploying Long Term Evolution (“LTE”) networks that enable the delivery of data traffic faster and more efficiently than previous generations of technology such as 3G. Indeed, a spectrum policy that balances licensed and unlicensed opportunities has allowed expansive growth of the wireless economy, benefiting consumers, innovators, and investors.

With the rapid growth of data services and high bandwidth applications, mobile operators need more capacity than ever. One way to meet the need is to move traffic from their licensed network to the 2.4 GHz and 5 GHz unlicensed bands, known as “Wi-Fi offloading”. Offloading benefits carriers and consumers: carriers find additional capacity to relieve congestion on their network and consumers have a high-quality experience.

In recent months, several carriers and suppliers have announced plans to deploy LTE, a technology historically deployed only in licensed frequencies, in the 5 GHz unlicensed band as a means for providing additional capacity to customers. One part of the LTE stream operates in a licensed frequency, and the mobile operator has the flexibility to determine whether to send other portions over licensed or unlicensed frequencies. This arrangement provides licensed operators access to additional spectrum without the expense of obtaining a license, while allowing them to maintain the quality of service expected for licensed services. This form of LTE cannot be used without access to licensed spectrum.

However, LTE over unlicensed — at least as currently conceived — presents new challenges for coexistence with other unlicensed technologies. A new white paper by Google engineers, which we filed with the FCC this week, summarizes our initial investigation into the issue of coexistence between license-anchored LTE and Wi-Fi in the 5 GHz band. The paper shows that in many circumstances, LTE over unlicensed coexists poorly with Wi-Fi.

Although all players in the wireless ecosystem should have the ability to utilize unlicensed spectrum within the FCC’s rules, LTE over unlicensed has the potential to crowd out unlicensed services. Holders of licensed spectrum shouldn’t be able to convert the unlicensed 5 GHz band into a de-facto licensed spectrum band, and certainly they should not have the ability to drive out other unlicensed users.

The ability for diverse technologies to operate together in the unlicensed bands has typically been resolved through cooperation and without regulatory intervention. Providers of unlicensed services share an incentive to make sure that players are able to deliver services in the band without fundamentally degrading other unlicensed activity. The incentives to coexist may be different when providers can fall back to licensed spectrum in the event of conflicts in unlicensed spectrum. But there is still time for the industry-led cooperation that enables technologies like Wi-Fi and Bluetooth to coexist successfully.

A potential solution that would avoid coexistence problems in the 5 GHz band is for carriers instead to utilize newly available spectrum in the 3.5 GHz band for additional capacity. The FCC recently identified the now-underutilized 3.5 GHz band spectrum as ideal for this kind of use.

The entire wireless ecosystem should be concerned about allowing one innovation to block others — past and future. The best way to stimulate innovation without regulatory intervention is for the industry to maximize use of all available spectrum and develop workable coexistence and coordination mechanisms that encourage widespread access to unlicensed spectrum.