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White Paper

Radio Resource Management – Radio Admission Control and Bearer Control

 

In this white paper, we provide an insight into the admission and management of bearers for the efficient use of radio resources. The admission deals with the establishment of a new bearer depending on the feasibility and availability of resources. The management of bearers is taken care of by the bearer control, which deals with the modification or deletion of bearers.

The primary goal of Radio Resource Management (RRM) is to control the use of radio resources in the system while also ensuring that the Quality of Service (QoS) requirements of the individual radio bearers are met and the overall usage of radio resources on the system level is minimized. The objective of RRM is to satisfy the service requirements at the smallest possible cost to the system, ensuring optimized use of spectrum.

Some of main functions of RRM include the following:

  • Radio Admission Control (RAC)
  • Radio Bearer Control (RBC)
  • Connection Mobility Control
  • Dynamic allocations of resources to UEs in both uplink and downlink (DRA)
  • Inter-Cell Interference Co-ordination (ICIC)
  • Load Balancing (LB) 

Radio Admission Control Algorithm
RAC admits or rejects establishment requests for new radio bearers. One of the approaches has been described below, based on the Priority Guaranteed Bit Rate (GBR). In priority GBR-based algorithm, it is important to realize that Admission Control (AC) is not as standardized as it should be. Different realizations of LTE Radio Access Network (RANs) will run different AC algorithms. The algorithm in contention situation triggers RBC in which case the allocation happens on the basis of the Allocation and Retention Priority (ARP) parameters.

Pros:

  • High priority GBR requests are granted first.
  • In a contention situation, higher priority E-utran Radio Access Bearer (ERABs) can pre-empt lower priority ones. 

Cons:

  • Pre-emption would lead to the release of lower priority ERABs. 

Radio Bearer Control Algorithm
RBC involves the establishment, maintenance and release of radio bearers. One of the approaches has been described below, based on fair-share.

The prioritized / weighted max-min fair-share bandwidth allocation technique tries to maximize the minimum share for non-satisfied flows. Priority / weight is considered during allocation so the higher priority gets a higher share than lower ones.

Pros:

  • Normalize demands with corresponding weights.
  • Allocate resources in order of increasing demands, normalized by weight.
  • Satisfy users with relatively small demands.
  • Ensure that users do not get a resource share larger than their demand.
  • Ensure that users with unsatisfied demands get an equal share of unused resources proportional to their weights. 

Cons:

  • Max-min fairness in communication networks assumes that resources (capacities of communication links) are allocated to flows in advance, as opposed to best-effort networks.