Efficient LTE PDCP buffer management

Long Term Evolution (LTE) evolved Node Bs (eNB) have dedicated buffers for each Radio Access Bearer (RAB) implemented at the Packet Data Convergence Protocol (PDCP) layer to receive and prepare user data for transmission over the air interface. These buffers multiplex the connections established by the active applications of a single user. Modern applications use the Transmission Control Protocol (TCP) that has a greedy mechanism to transfer data by trying to use all the available resources. If not managed, TCP sources may send large bursts that may eventually overload the PDCP buffer causing tail drops and quality degradation. In order to prevent these incidents, buffer management mechanisms are required. As this paper shows, neither the standard 3GPP Discard Timer nor the conventional Active Queue Management (AQM) techniques are able to properly manage the PDCP buffer. As a solution, two alternative mechanisms are proposed, which are more suited to the PDCP specific environment. Their superior performance is shown with detailed simulations.