By Marc Serra Jaumot – Chief Marketing Officer and Corporate Development Officer, Infovista

In today’s hyper-networked world, we live in an environment where consumers put monetary value on how they experience a business or service. The better the experience, the more they are willing to pay for it, and the longer they are willing to stay loyal to the brand or service operator, hence the effort of Tier One Operators to differentiate on network quality. The minute that changes, and the experience is negatively impacted, so is the integrity of that service – causing customers to look for a better service elsewhere and increasing churn.

In a recent report, PwC surveyed 15,000 consumers and found that as many as 1 in 3 would leave a brand they love after just one bad experience, while 92% would completely abandon a company after two or three negative interactions. In our content-focused society, the same rules apply to mobile operators and Software-as-a-Service (SaaS) providers.

5G is ushering in a new class of data-heavy services over mobile networks such as AR/VR, cloud gaming, real-time multimedia, and the remote control and supervision of machinery. While providing new opportunities for operators, all these high bandwidth, low-latency services come with the challenge of evaluating and optimizing a new dimension of user experience: namely “INTERACTIVITY”. All of this comes alongside data-heavy apps like Netflix, WhatsApp, YouTube, Disney+, Spotify, and any number of OTT applications including mobile gaming with titles such as Fortnite through apps like Twitch.

While today this is a 4G and 5G problem, we can extrapolate from here to 6G. As customers get used to a certain performance – even if it is initially at the leading edge of what is possible – it tends to spread into the mainstream. Video calling is one example of this: the performance characteristics of video calls a decade ago, while revolutionary then, would be unacceptable now for most people. Likewise, basic consumer experiences in XR, cloud gaming and so on are liable to spur demand for further, more realistic and more engaging, experiences. A similar evolution is likely in the enterprise, where digital twins, XR, AI and other technology elements are still nascent.

Service providers understand that it isn’t just about how the content reaches users but about the integrity of the data and content when it arrives, what it looks like when it does, and of course the experience it engenders.

As a result, the job of testing and evaluating users’ Quality of Experience has evolved to require operators to plan and optimize network resource allocation for the best user experience (UX) interactivity. Put simply, if the network can deliver the promised UX for the most demanding bandwidth and latency services, then they can be confident that similar apps and services will perform to a similar level. This is leading to the development of network testing solutions able to evaluate and score a user’s experienced interactivity – or UxIntActQS (User Experience Interactivity Quality Score) – from the network perspective.

Let’s take the rapidly growing application area of cloud gaming over mobile as an example. The popular First Person Shooter (FPS) game genre, specifically Counter Strike Global Offensive (CS:GO), is an obvious choice not simply due to its popularity, but also because its rich visual motion graphics, high quality surround sound audio and gameplay interactions make it one of the most sensitive to mobile network impairments.

So, what can mobile operators do to confidently support high bandwidth, latency sensitive, interactive apps? By researching how CS:GO impacts the network, and how the network impacts gamers’ UX, Infovista found  some important lessons about UX interactivity for cloud gaming over mobile from the network perspective.  Understanding gaming quality dimensions and their dependency on network conditions is vital to ensuring a high-quality and low-latency gaming experience for mobile users – free from the impediments (and frustrations) caused by latency and rendering issues.

Cloud gaming experience

Cloud gaming experience is characterized by four primary dimensions: input quality, output quality, gaming experience, and gamer performance.

Although tightly interconnected, these dimensions can be divided in two main categories of quality: one determined by the system/network impact and the other by the game and the gamer. From a network improvement perspective, we are only concerned with input quality and output quality since we cannot affect the design of the game or the skill of the gamer.

Input quality is perhaps the most obvious contributor to a UX interactivity score with performance of the network directly affecting controllability, responsiveness, and immediacy of feedback. Output quality (video and audio) of the game, however, also impacts the interactivity. Without good image and sound quality, a gamer will not know where to aim and what they have achieved while playing. The UxIntActQS therefore needs to consider both the input and the output quality for cloud gaming.

Mobile network conditions

Mobile network conditions can be defined by the main agnostic network access metrics: round trip time (RTT), jitter and packet loss (PL) with various values ranges and distributions. However, there are couple of nuances to be considered for the mobile access.

First, RTT, which represents the minimum time it takes the system to deliver a packet under close to ideal conditions, is fairly constant and often referred to as “static” delay.

Second, jitter represents the RTT variability and reflects live radio conditions and the network’s adaptability to them using mechanisms such as re-scheduling and retransmission. There are two categories of jitter which can be seen in mobile access as cumulative effects on top of a “static delay” value: random jitter and jitter spikes.

Random jitter is frequent, with small delay changes from packet to packet. The largest contributor to this is the radio link transmission time interval (TTI) and hybrid automatic repeat request (HARQ) in the mobile access network, in conjunction with load from other users and resource scheduling on the radio resource control (RRC) layer. This includes scheduling of devices in “inner” and “outer” parts of the cell coverage.

Jitter spikes are characterized by amplitude values larger than 50ms and possibility of frequency of occurrence between 0.01-1Hz. Frequency of occurrence is typically lower with larger jitter spike amplitudes. In mobile access networks these jitter spikes are often observed in poorer radio conditions near borders between cells and amplified by load and reduced radio resources in “outer” cell coverage.

Testing the UX

Infovista has carried out extensive subjective testing to thoroughly understand the impact of mobile network conditions on the UX cloud gaming quality dimensions outlined above. The test involved real gamers playing on mobile devices within a controlled emulated mobile network environment. For the purposes of the study, we used the following cloud gaming quality dimensions: QoE (quality of experience), VQ (video quality), AQ (audio quality), and CN (controllability of the interaction with the game).

The analysis of the test results determined that all network metrics (round trip time, packet loss and jitter), and more importantly the combination of them, should be of concern to mobile operators aiming to deliver mobile access that supports high quality cloud gaming applications. However, the metrics have different levels of impact on the various dimensions of the gaming experience quality, depending on the specific metric and value, or combination of metrics and their values.

From this we can deduce some key learnings about UX interactivity for cloud gaming over mobile from the network perspective.

All network metrics (round trip time, packet loss, jitter) as well as their combination and interdependencies impact the cloud gaming experience, predominantly QoE and control over interaction within the game (CN); less so video and audio gaming experience (VQ, AQ).

Each of the two types of jitters, random jitter and jitter spikes, impact the cloud gaming experience differently.

All four quality dimensions of cloud gaming over mobile networks show consistently good quality up to high packet loss values, which are defined by the performance of the gaming client error concealments scheme.

The mobile access exhibits a non-linear interdependency between round trip time and packet loss, especially at low packet loss values (0.2-2%) and RTT >50ms, which for cloud gaming impact all four quality dimensions by about 10-20% (0.5-1MOS on the 1-5MOS scale).

What does it all mean?

Quality of Experience is a key differentiator in delivering content and increasingly a way to navigate a dynamic environment.

Communication service providers (CSPs) are under pressure to transform and adapt to ensure they can deliver the quality they promised customers all while new data-heavy OTT applications place unprecedented pressure on networks. Decreased loyalty to CSPs means customer satisfaction is critical to their long- term strategy.

Today’s networks need to be well positioned to support varied services simultaneously from text messages to high bandwidth video streaming and low-latency gaming. The increased use of 5G, and the promises already being made for a 6G future, mean that consumers will anticipate unprecedented, high-quality experiences over mobile that operators need to deliver. Testing and planning for native voice services such as VoNR and VoLTE, OTT voice services, OTT video streaming and interactive services like e-gaming, remote drone control and videoconferencing, are therefore going to be critical.

By combining machine learning algorithms with sophisticated traffic modeling, the right partners can enable operators to understand the user experience for all of these intensive, bandwidth hungry applications and services, anticipate behaviors and plan networks that are capable and robust enough to support OTT media applications with consistency and confidence – delivering on the promise of a ubiquitous and seamless, quality 5G experience.