E911 Must Work From Day 1 on LTE Networks

It’s almost 2 years since Verizon rolled out its first LTE network. I can’t believe how fast time passes by once you start enjoying what you do. I have been using the iPhone 5 for the last six months or more, and I must say that I can’t stop using the phone for more than 15 minutes unless I am sleeping. It’s amazing how smartphones have changed human behaviors and lifestyles. I sometimes wonder if I am interacting with this electronic device more than my family. Reading news, interacting on Skype, texting with iMessage and posting on Facebook (and of course work email never stops), I share my views and thoughts with my friends, family and colleagues through this device. We are able to get so much out of the smartphone because it’s able to send and receive 40 times as much data as a DSL modem was capable of in 2000. Hence, when there is an emergency I naturally expect the smartphone and its built-in advanced technologies to have some smart way of connecting to emergency responders.

Network operators have rolled out data services over LTE with reasonable success. The next challenge is supporting voice over LTE (VoLTE). One major question to answer before voice can be entirely deployed over LTE networks is, “what happens when an E911 call is dialed on a VoLTE-enabled LTE network?” You might say that it can just fall back to a 2G or 3G network and make the call just like it happens today, but that would not be correct. E911 calls on VoLTE networks must be enabled from day one. Why?

Both Verizon and AT&T are deploying LTE in 700 MHz bands, which help extend coverage to the edges of cells and deeper indoor environments when compared to higher frequencies such as 1900 MHz or 2100 MHz. Imagine that you and your family are having a great time in your basement or in an indoor environment such as New York’s Rockefeller Center Shops, when suddenly there is a fire, accident or medical emergency. LTE is the only coverage you have. If you are using LTE in a 700 MHz band and you dial E911, you expect to speak to someone on the other side of the network. Because your E911 call was placed on an LTE network, the call should be routed through the IMS signaling system interconnected with the PSTN. Unless the IMS signaling system is updated to support the Emergency IMS subsystem (and integrated with Location servers such as the SMLC and SUPL 2.0 server supporting LTE Positioning Protocol [LPP] in the core network), the call may not go through. Furthermore, some operators plan to aggressively repurpose 2G and 3G spectrum for 4G use—meaning that falling back to legacy technologies is not an option.

In order for a VoLTE E911 call to be established from day one of a VoLTE service’s deployment, there is a need for extensive interoperability testing between smartphones and location servers as E-SMLC (evolved SMLC). SUPL 2.0 (with support for LPP) must be tested as well. Once I dial a VoLTE E911 call, I expect the call to be established 100% of the time, even if I am moving in a train, bus or subway. Call reliability should at least match performance in 3G/2G networks. I should be able to expect that VoLTE E911 on my device has been tested in moving scenarios as well as static scenarios, and with fading conditions that replicate real-world conditions. Testing these scenarios in the field can be costly and time consuming and does not offer the repeatability required for proper debugging. Fortunately, lab-based test systems simulating real-world conditions with satellite simulations, cellular network emulation and RF channel emulation enables OEMs and Operators to successfully deploy VoLTE with support for VoLTE E911 from Day 1.

Maybe it is appropriate to say that a wireless phone is a true wireless device only if it can help me communicate when I am happy and sad, but also save my life when in danger, no matter what technology is involved.

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