What is the difference between QCI and ARP priority?

Question

I have a question concerning QoS management in LTE: there are two parameters for an EPC bearer: QCI (QoS class identifier that resumes a set of parameters(priority, packet delay, packet error rate…) and ARP (Allocation and retention priority) that defines the priority of a bearer. My question is : what is the difference between the QCI priority and the ARP priority ?

Answer 1

The difference between priority mapped from QCI and ARP based priority is as follows:

1. QCI Priority refers to priority in terms of resource allocation for a specific service i.e. in case where the UE is running concurrently VoIP (higher QCI priority) session and browsing WWW (lower QCI priority), the resources are assigned firstly to packets of VoIP and then to WWW (and e.g. if we don’t have in the particular TTI resources to assign both packets, WWW need to wait and VoIP goes through).

2. ARP priority refers to priority in terms of allocation of a service / bearer, i.e. if the eNB is highly loaded and a UE would like to setup VoIP (higher ARP priority) and WWW (lower ARP priority), the eNB would typically set only VoIP session, in order not to get overloaded. Or in other case if it is already overloaded it would kick off (retent) the bearers / services with lower ARP priorities.