Editing Mobile QoS (section)

[[Quality of service]] (QoS) mechanism controls the performance, reliability and usability of a telecommunications service. Mobile cellular service providers may offer '''mobile QoS''' to customers just as the fixed line [[PSTN]] services providers and [[Internet service providers]] may offer QoS. QoS mechanisms are always provided for [[circuit switched]] services, and are essential for non-elastic services, for example [[streaming multimedia]]. It is also essential in networks dominated by such services, which is the case in today's mobile communication networks.

Mobility adds complication to the QoS mechanisms, for several reasons:<ref name=Miao>{{cite book |author1=Guowang Miao |author-link=Guowang Miao |author2=Jens Zander |author3=Ki Won Sung |author4=Ben Slimane |title=Fundamentals of Mobile Data Networks |publisher=Cambridge University Press |isbn=978-1107143210 |date=2016}}</ref>
* A phone call or other session may be interrupted after a [[handover]], if the new [[base station]] is overloaded. Unpredictable handovers make it impossible to give an absolute QoS guarantee during a session initiation phase. 
* The pricing structure is often based on per-minute or per-megabyte fee rather than [[flat rate]], and may be different for different content services. 
* A crucial part of QoS in mobile communications is [[grade of service]], involving [[outage probability]] (the probability that the mobile station is outside the service coverage area, or affected by co-channel interference, i.e. crosstalk) [[blocking probability]] (the probability that the required level of QoS can not be offered) and [[scheduling starvation]]. These performance measures are affected by mechanisms such as [[mobility management]], [[radio resource management]], [[admission control]], [[fair scheduling]], [[channel-dependent scheduling]] etc.