Controlling TCP ACK Transmission for Throughput Improvement in LTE-Advanced Pro

The 3rd Generation Partnership Project (3GPP) is standardizing LTE-Advanced (LTE-A) Pro. One of the technical challenges is the reduction of the uplink latency, which is larger than the downlink latency, aiming at improving the Transmission Control Protocol (TCP) throughput. A study item called Latency Reduction (LATRED) has been agreed to standardize fast uplink access schemes. The proposed solutions include shortening of the subframe length and fast uplink resource allocation to mobile terminals for the uplink data transmissions. The reason for this is that speeding up the data processing of the layer 1 and the layer 2 protocols reduces the TCP Round Trip Time (RTT) and hence the downlink TCP throughput can be improved. However, the asymmetric bandwidth of the radio link has not been taken into account. The asymmetry tends to cause the uplink congestion and uplink resource shortage for TCP ACK transmission, which has a negative impact on the TCP RTT. In this paper, we propose methods to improve the TCP throughput focusing on the TCP ACK filtering in the LTE-A Pro uplink.