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Improving Receivers for Increasingly Crowded Spectrum

Chris Pearson, President, 5G Americas – February 2023

If you use a smart mobile device, you already know how wireless cellular networks are offering unparalleled video performance with greater clarity and speed. But today’s modern cellular networks are running up against some spectrum constraints that have to be addressed if we’re going to make the experience even better.

To give some context, let’s think back a ways – to 1979, when a 1G device was launched by Nippon Telegraph and Telephone to the residents of Tokyo. It was an analog device that offered no data capabilities and could barely eke out voice calls amounting to a mere 2.4 kilobits per second. But fast forward a few decades and we’re seeing amazing 4K and 8K ultra high-definition streaming video over a 5G wireless connections and data transfers up to 1 gigabit per second (Gbps), which could theoretically reach 10 Gbps before the next generation of wireless cellular.

Along with this speed comes demand for mobile data, which continues to reach new highs. Mobile data per smartphone reached 15 GB per month in North America and 10.5 GB per month in Latin America, according to the November 2022 Ericsson Mobility Report. That growth in mobile data is expected to reach 55 GB per month for North America and 41 GB in Latin America by 2028, which represents a staggering CAGR of 21 percent and 25 percent respectively.

But all that data comes at a real cost: the need for additional licensed spectrum for mobile communications commercial uses.

Back in the early days of mobile devices, it may have been okay to use a mere 30 kilohertz (KHz) wide spectrum channel to communicate, but modern 5G networks perform best with wide blocks of spectrum—think 100 MHz blocks. 

Clearly, our commercial spectrum airwaves are becoming increasingly crowded. As the crowding has gotten worse, spectrum regulators around the world, including the Federal Communications Commission (FCC) and National Telecommunications and Information Administration (NTIA) in the US, have been working hard to pave the way to open up new lanes for all the data traffic to smoothly flow. This has primarily been done by adding more spectrum bands, and more carefully delineating who gets to use them by setting up guard rails so that radio transmissions do not accidentally spill over into someone else’s band.

Without this work, wireless “cross-talk” and signal attenuation can disrupt the quality of a communication link. This could cause a particular device to stop working, lose signal, or see a performance hit on data transfer.

It is important for all key stakeholders to work together and this includes current users (“incumbents”) and new owners of spectrum licenses to ensure spectrum is utilized and managed efficiently without interference. But in order to do so, we have to ensure that devices do not transmit or receive on the bands where they are not licensed. Regulators have long realized that both transmitters and receivers are important to consider, as spectrum becomes increasingly crowded. However, most past regulation has focused on transmitters only. But as more spectrum bands become used for data, there is an increasing challenge coming from legacy receivers that were never designed for the harsher, crowded conditions of today’s airwaves.

Recently, FCC has started to take a fresh look at the role of radio frequency receiver performance to improve spectral efficiency and increase security. On April 21, 2022, the FCC adopted a Notice of Inquiry (NOI) to examine receiver performance, picking back up on its work started in 2003, when it issued another NOI and its Technology Advisory Council (TAC) issued white papers involving harm claim thresholds, interference resolution and enforcement, and basic principles for spectrum compatibility. Through the years many agencies have examined this significant issue.

5G Americas lends its expertise on this topic with the publication of “Radio Frequency Receiver Performance” which includes perspectives from the wireless cellular industry on how to best proceed on improving performance of wireless radio frequency receivers. From a technical standpoint, receiver performance involves several issues, such as the receiver noise floor, sensitivity, linearity, dynamic range, protection ratio, selectivity, blocking and overloading, and spurious response rejection.

Additionally, increasing use of shared spectrum, such as with technologies like Dynamic Spectrum Sharing (DSS), shared spectrum bands like Citizens Broadband Radio Service (CBRS), and access technologies like Wi-Fi or 5G NR-Unlicensed may introduce additional challenges, such as unrealistic requirements on interfering transmitters, the need for improved model transparency and reproducibility in co-existence studies, and the need to select key receiver characteristics depending on the service.

Finally, industry-specific concerns may arise. For instance, different possible scenarios may arise in adjacent dissimilar systems, such as in public safety, consumer products, aviation, or healthcare which are unique to the challenges of the industry. One example might be sensitive radar systems used by governments, which may rely on decades-old equipment and systems which were never designed to filter out signals now in use by modern 5G networks. But at the same time, poor receiver performance may not be a problem across all spectrum bands – as the history of a particular industry’s evolution may have shaped the upgrade path of their receivers to deal with modern data networks.

Overall, 5G Americas makes several recommendations, such as:

      • Keeping a measured touch on regulation to compensate for inadequate legacy receiver performance, to ensure technology innovation is not impeded.

      • A one-size fits all policy approach may not be suitable, as industry-specific concerns may arise.

      • A national plan for more spectrum is needed to enable a predictable timeline of equipment upgrades.

      • Execution policy involves relying on voluntary standards, using standardized coexistence models (like 3GPP, ITU).

      • Upgrade paths for legacy receivers should be created, clear and transparent policy statements made, and long-range spectrum planning established.

    In the end, it’s important to recognize the great efforts and initiative being undertaken by government regulators to ensure that our increasingly crowded airwaves can continue to operate in an orderly and transparent manner. Engaging stakeholders from various different industries to warn, educate, and urge them to replace and upgrade their legacy equipment will not be an easy task. But as it does not look like the demand for mobile data will be slowing down any time soon, this work will be critical to the future success of not only the wireless industry – but all industries.

    -Chris

    Reduce Impacts of Spectrum Interference

    Radio frequency receiver performance is just as important as transmitters when it comes to reducing interference. Can industries come together with regulators on a path forward?

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