RLC buffer occupancy when using a TCP connection over UMTS

This paper analyzes a TCP connection over UMTS radio access bearer in RLC acknowledged mode. The stacking of RLC and TCP protocols is highly beneficial for the global system behavior. Protocol mechanisms used by RLC are well adapted to wireless constraints and the ARQ function implemented by RLC hides the wireless channel unreliability to TCP. However, RLC protocol parameters have to be carefully tuned otherwise the TCP performance can degrade due to RLC. One of the factors that can influence the TCP performance is the RLC buffer size. We analyzed some of factors that affect the RLC buffer occupancy and we show that an insufficient buffer size degrades the TCP performance.