Calix: For residential gateways Wi-Fi transmit power – and enclosure size – matters!

By Claus Hetting, CEO & Chairman

What are the common technical differences between carrier-grade Wi-Fi residential gateways and consumer Wi-Fi routers – and how do such differences impact performance? Operating at the maximum permitted Wi-Fi power is paramount when you want to deliver both high data rates and excellent whole-home coverage. Conversely, consumer-grade equipment often comes up short on both fronts, Calix says.

In the US, the Federal Communications Commission (FCC) permits a maximum power level (called EIRP or Effective Isotropic Radiated Power) of 36 dBm for Wi-Fi equipment operating in the 2.4 GHz and 5 GHz bands. In practice the maximum transmit power for a Wi-Fi residential gateway is 30 dBm (equivalent to 1 Watt) because 6 dBm is typically allocated for antenna gain.

But wireless equipment vendors often approach the issue of transmit power in very different ways when designing residential gateways or consumer-grade routers and mesh systems. “Some vendors – and Calix is in this category – engineer their systems to transmit at the maximum allowable power of 30 dBm, also known as high power. We do this to achieve maximum coverage, reach, and performance in and around the home,” says Shane Eleniak, Executive Vice President of Products at Calix.

But consumers and ISPs should be aware that not all vendors operate at the full 30 dBm of transmit power. In general, small form factors and lower power leads to poor performance. “Some mesh Wi-Fi vendors engineer their systems to transmit at mid power levels of 23-25 dBm. They do this in order to target the consumer market with lower-priced, smaller physical units such as plug-in pods or similar. Ultimately, this approach sacrifices Wi-Fi performance for aesthetics and price,” says Shane Eleniak.

The performance of small form factor Wi-Fi routers or gateways often deteriorates even further as a result of inadequate space for antennas. “The best solution is to position antennas at least one full wavelength apart in order to minimise their mutual interference. In the case of 2.4 GHz and 5 GHz radios, the wavelengths are 4.9” and 2”, respectively,” Shane Eleniak says.

Unfortunately, most consumer-grade Wi-Fi systems are smaller than 4.9″ along one axis. This means that such units do not allocate enough space for adequate separation of antennas. This results in overlapping signals, which in turn limits coverage. “It is often the case that the performance degradation of consumer-grade routers is compounded, meaning significantly reduced because of lower transmit power combined with inadequate space for antennas. This is why some mesh Wi-Fi solutions require multiple systems to deliver adequate in-home coverage,” Shane Eleniak says.

Calix has the experience and data to back up their design approach: It turns out that only a few percent of deployed Calix home systems need mesh units to complete whole-home coverage. Also read more here.

Here’s this months Pro Tip:

“Operating Wi-Fi gateways at maximum permitted power and designing gateway enclosures for optimum antenna spacing translates into high Wi-Fi performance and excellent coverage. Many consumer-grade home Wi-Fi solutions come up short.”