T-Mobile accuses cable companies of using LTE-U tests that rely on extremes, not reality

T-Mobile US (NYSE:TMUS) took a stab at its cable rivals in a recent FCC filing, saying that claims by LTE-U opponents that the technology will adversely impact Wi-Fi operations are based on testing "with parameters set at extremes that do not represent realistic deployments or do not reflect actual LTE-U specifications."

"While cable companies defend these tests by noting that carriers have the ability to adjust LTE-U parameters, the ability to adjust parameters allows a carrier to refine operations based on the environment -- a result that will promote equitable sharing," T-Mobile said in the filing. "Further, LTE-U's connection to licensed spectrum through a control channel allows carriers to better address problems if they should occur."

The statements were made as part of an ex-parte filing after T-Mobile's chief technology officer, Neville Ray, and other T-Mobile representatives met with FCC Office of Engineering and Technology (OET) and Wireless Telecommunication Bureau (WTB) staff. T-Mobile reiterated its plans to begin LTE-U trials in 2016.

T-Mobile said it used the meeting with FCC officials to explain that the FCC's technology-neutral approach in the unlicensed bands has been highly successful, and there's no reason to deviate from that approach as LTE-U meets "all Part 15 requirements and includes strong coexistence mechanisms." Testing shows that LTE-U has less of an impact on Wi-Fi operations than would occur by adding an additional Wi-Fi access point, and if multiple operators deploy LTE-U in an area, the access points treat each other as another user and take those operations into account just as they would additional Wi-Fi access points as part of a fair sharing approach, the company said.

T-Mobile isn't alone in its quest to use LTE in unlicensed spectrum. Verizon Wireless (NYSE: VZ) also is pursuing plans to use it. Verizon formed the LTE-U Forum last year with vendors Qualcomm Technologies (NASDAQ:QCOM), Alcatel-Lucent (NYSE: ALU), Ericsson (NASDAQ: ERIC) and Samsung. The forum in March released its first technical report evaluating the use of LTE in unlicensed spectrum, and Verizon said at that time that it believes it can use LTE-U to leverage "every available technology" to help deliver more connectivity for customers.

While the FCC typically doesn't get involved in standards processes, the Commission opened a comment period on LTE-E and Licensed Assisted Access (LAA) back in May after commissioners and staff heard concerns, during the context of its 3.5 GHz and 5 GHz proceedings, that LTE could overcrowd existing unlicensed users -- namely Wi-Fi. In fact, the cable industry argues that LTE-U will disrupt Wi-Fi consumers, and it's particularly concerned about the non-standard LTE-U version, a precursor to the LAA that's being developing through the 3GPP.

In early August, the head of the FCC's OET, Julius Knapp, asked the wireless industry for more information on exactly how LTE operations in unlicensed spectrum will work. Knapp said the FCC would like to know specifically how Carrier Sense Adaptive Transmission (CSAT) works and why a decision was made to have CSAT transmit on a channel even if it appears to be occupied.

In addition, aspects of the anchor channel were unclear, he said. Another question relates to how the LTE system knows what capacity is available in the unlicensed channel and therefore how to manage the traffic between the licensed and unlicensed spectrum.

The Wi-Fi Alliance responded by saying it appreciates the OET and WTB's efforts to learn more about the technologies. It's also asking the FCC to withhold certification of any LTE-U equipment until such time that it is fully satisfied that fair sharing of unlicensed spectrum will be achieved.

The Wi-Fi Alliance says it is developing a comprehensive coexistence test plan aimed at assessing the level of fair sharing between LTE-U and Wi-Fi and the alliance will work with LTE-U vendors to test their products to determine if they pass the Wi-Fi Alliance co-existence tests. The alliance plans to hold workshops about fair spectrum sharing, with an initial workshop expected to be held in northern California in early November.

"Wi-Fi Alliance does not seek to unnecessarily delay the introduction of LTE-U or any other technology," the organization said in an Aug. 14 FCC filing. "However, the continued success of Wi-Fi and the enormous economic engine it drives should not be compromised until there is a thorough assessment -- through true collaborative efforts -- of how LTE-U devices will affect the current wireless ecosystem."

For more:
- see this T-Mobile FCC filing

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