The term “Quality of Experience” (also known as QoE) pops up a great deal in the telecommunications space. Most generally, it can be defined as a subjective measure of a service or product. Note that this definition distinguishes from QoE from its close relative Quality of Service (QoS). QoS is an objective measure of a set of quality requirements, and typically has a network view, whereas when service providers speak of QoE they are usually talking in terms of the quality perceived by the end user.
We’ve already talked about subscriber expectations regarding web page load times on broadband connections. However, consider a subscriber’s expectation of a web page load time on a dial-up connection, or on free Wifi, or on a mobile handset. Most subscribers would expect the load time to vary across these technologies. Now, what if instead of talking about a web page, we examine streaming video, or voice-over-IP, or downloading a movie file…would the expectations be consistent? And here we find the biggest challenge in measuring Quality of Experience – expectations change based on technology, application, and subscriber.
We can loosely identify some characteristics that differentiate a good experience from a bad one:
- Web Browsing: pages load quickly, without errors
- Voice and Video Conferencing: voice/video is smooth, conversational, and audible/visible
- Gaming: movements are smooth, network is responsive, you don’t get ‘fragged’ or ’pwned’
- On-demand Entertainment: video or audio starts quickly, there is no re-buffering, no compression artifacts, video and audio are synchronized
- Bulk Downloads: completes in a reasonable time
Of course, words like “quickly”, “smooth”, “responsive”, and “reasonable” betray a certain amount of subjectivity and have the potential to greatly from subscriber to subscriber.
To muddy the picture even further, subscribers vary greatly in the applications they use. A subscriber who relies on the Internet for web browsing and e-mail could have a terrific experience on a network that is hated by a hardcore gamer with a roommate who loves BitTorrent. Finally, the consumer hardware will impact perceived quality, too. Imagine having a 50 Mbps connection that is squeezed through an 802.11b router before heading to a computer that was state-of-the-art in 2001.
Minimally, different applications require different measures of QoE. Web Browsing QoE can be measured in terms of the average time to load a page, VoIP QoE can be assessed by combining quantitative measures such as R-factor and Mean Opinion Scores (MOS), and gaming QoE can be determined through some measure of network latency, packet loss, and jitter.
Once a service provider is confident that application QoE can be accurately determined, then they can apply network and subscriber models to determine the average QoE across the entire subscriber base, or even for individual subscribers.