Scheduling and admission of radio bearers in a communications system applying carrier aggregation

#Embodiments herein relate to a method and networks node in a wireless communications system applying carrier aggregation. In particular embodiments herein relate to scheduling of resources to radio bearers and to admitting a radio bearer to be set-up and be served.

#Communication devices such as wireless devices may be also known as e.g. user equipments (UEs), mobile terminals, wireless terminals and/or mobile stations. A wireless device is enabled to communicate wirelessly in a cellular communications network, wireless communications system, or radio communications system, sometimes also referred to as a cellular radio system or cellular network. The communication may be performed e.g. between two wireless devices, between a wireless device and a regular telephone and/or between a wireless device and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the cellular communications network.

#The wireless device may further be referred to as a mobile telephone, cellular telephone, laptop, Personal Digital Assistant (PDA), tablet computer, surf plate, just to mention some further examples. The wireless device in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and/or data, via the RAN, with another entity, such as another wireless device or a server.

#Examples of embodiments herein are described in more detail with reference to the appended schematic drawings, in which:

#FIG. 1 is a schematic block diagram depicting a simplified example of a wireless communications network applying carrier aggregation, in relation to which embodiments herein will be explained.

#FIG. 2 schematically illustrates, for explaining a principle underlying embodiments herein, two scheduling weight functions for prioritizing scheduling of resources to radio bearers.

#Conventional wireless communications systems not applying carrier aggregation include functionality relating to admission control and/or scheduling of resources. Admission control and scheduling of resources is functionality suggested herein for adapted and/or improved handling in a wireless communications system applying carrier aggregation.

#Admission control refers to a function handling the task of deciding whether to admit or reject a request for a radio bearer setup in a cell served by a base station. The admission control decides whether to accept or reject a request for a radio bearer setup based on a present load in the cell, e.g. in form of usage of certain Monitored System Resources (MSRs) in the cell as well as the type of radio bearer the request relates to. For example, in a wireless communications systems a wireless device may have on-going services, for which the base station serving the wireless device may have set up a number of radio bearers. The services may be of different types. For example, a service may be a Voice over IP (VoIP) call a user of the wireless device initiates. To set up such radio bearer a request for a radio bearer setup is made. In LTE-based systems it is the Mobility Management Entity (MME) that sends requests for radio bearer set up to the base station that receives it and an admission control function in the base station evaluates the current load in the cell in which the base station serves the wireless device. The MME may send the request e.g. in response to that it has been initiated a VoIP call to a wireless device being served by the base station. The VoIP call may e.g. have been initiated through an application running on another wireless device or on a personal computer connected to the Internet. Note that the request for radio bearer set-up may be sent by other another node than the MME in non-LTE based systems and that the admission control functionality may be located in another node than the base station. If the admission control functionality concludes that there are enough resources available for allowing setup of the VoIP call in the cell, the request is accepted, and a radio bearer is set up for the VoIP call. On the other hand, if it is determined that the current load is too high for allowing the VoIP call, the request for resources is rejected. A simple example of an admission control algorithm: For each MSR it is estimated the amount needed by a request for a radio bearer set-up. Then, for each MSR, the value of the MSR plus the estimated amount is compared to an admission threshold for each MSR. If below the threshold for each MSR, the radio bearer is admitted and set-up, else the request is rejected, and/or methods to prioritize among already admitted requests may be triggered in order to make room for the request.

#Radio bearers are sometimes denoted Radio Access Bearers (RABs), or, in evolved packet systems as LTE, Evolved-RABs (E-RABs). A radio bearer may be regarded as a virtual connection between two endpoints, which provides a transport service.