How we set a new standard for reduced latency of devices
The idea is simple. Yet the landmark development and standardization of the new “inactive state” has set new standards for the resume time, power consumption and security of wireless devices. To get there, it required years of complex and delicate maneuvering from the heart of Ericsson Research to the new 3GPP standard. Below, we share the full story of the inactive state.
In recent years, wireless devices such as smartphones have existed in two primary states – idle and connected. The transition between those states – from idle to connected or vice versa – is currently one of the most frequent high-layer signaling events on 4G LTE networks, occurring about 500-1,000 times each day in each device. In other words, this is a heavy-weight process.
Such an extensive signaling sequence is acceptable when the system is designed for voice calls. Here, the typical behavior of the interaction – where you spend some time on the call and then hang up – meant that it made sense to delete and restart everything every time you made a call.
However today, where data connections and transmissions are quicker, shorter, smaller and more frequent, this is exactly what you don’t want. Here, the signaling is at risk of becoming greater than the actual data being transmitted. Our initial concern was that this would slow down the development and deployment of IoT use cases, owing to the corresponding device latency and power consumption.
It began with a simple idea
The core idea behind the inactive state is to reduce the amount of signaling that occurs during the state transition of a device. The technical features which make this happen are sophisticated, but the core idea is actually simple.
The best analogy I have is the comparison with the sleep mode feature on our computers. Very often, my desktop will be full of many various files, emails and apps. As is often the case I’ll leave my desk and return to find that my computer has timed out into sleep mode and all the various files, emails and applications were exactly as I left them. It’s convenient. The alternative would be to save and close every application before leaving my desk and reopening them every time I return. It would obviously be a very cumbersome process.
So, with the inactive state we wanted to replicate this behavior of computers. And that’s exactly what we did. We found a way to store the wireless terminal’s configuration in the radio network during the transition from connected to the new inactive state, and back again. In doing so, we reduced the amount of signaling that occurs during a state transition which made it possible to significantly lower device latency and battery consumption. These are critical requirements for many IoT and 5G use cases, including enhanced mobile broadband.
The benefits in a nutshell
It’s much faster to retrieve something than create something from the beginning, which helps the latency. If you think about your smartphone and how it is perceived by an end user. Most of the time our smartphones are in some form of dormant state to save battery, similar to the inactive state. If you need to connect, you press a button for an app. This is for the terminal to establish a connection. Making this procedure faster with inactive state basically makes the process of pressing the button for an app and receiving the data much faster.
The amount of signaling which is exchanged in this procedure is reduced because we restore and reuse things. This has an advantage on power savings, because the more messages you exchange, the more power you spend.
The benefits for IoT use cases were clear, and when we got into the process, we also began to realize how it would also be relevant for smartphones, as many apps still rely only on small and frequent data transmission.
To learn more about the technical features, I recommend reading our inactive state article in the Ericsson Technology Review.
Continuing the journey into 3GPP
The milestone began in Ericsson Research long before it arrived in 3GPP. Through early research collaboration with various European academia and industry stakeholders, we were already beginning to map the architecture of the inactive state. In fact, we even published a research paper before it became part of the wider consensus. The previous experiences in 3GPP with 3G and 4G systems in the area of protocol states also helped to build the new concept.
However, this was only a first step in the process. To bring this feature to wider industry and consumer use cases where it can have real impact, it needed to be part of the new 3GPP standard. This next step, perhaps the biggest on the journey, demanded a huge collective effort both internally here at Ericsson, but also externally with our industry peers and colleagues in 3GPP.
Understanding 3GPP standardization
As is often the case, the process through 3GPP was long and delicate. Following months of technical discussion, all operators and vendors form a general consensus based on the best technical proposal.
For the inactive state, most of the proposals we put forward were all agreed. This included some fundamental ones, even following contentious discussions and different views from other parties. One such example is the security framework, such as the ability to encrypt the response message (resume or suspend/release) from the network. At the time, this was a new concept in 3GPP, one which differs from the unencrypted resume messaging of 4G LTE. It also shows another benefit of inactive state, how it allows for future features to be built on top of it. To give an example, upcoming features in 3GPP (such as small data transmission in Rel-17) benefits from that. The adoption of this new security feature can be accredited to the work of our many expert researchers and delegates.
The impact of the inactive state
The development of the inactive state will be a fundamental enabler of many of 5G’s most exciting and critical use cases, such as smart transport and the critical control of remote devices. Our early extensive research activities into novel Radio Resource Control (RRC) state models meant that we were among the first in the industry to break through the technical challenges and shape the new 5G standard.
In doing so, our research and development teams have been decisive in laying a foundation for the next chapter of innovation.
Visit our standardization page to learn more about our 3GPP story.
Read our technical analysis of the inactive state in the Ericsson Technology Review.
Explore future use cases of IoT.