TCP Performance Improvement in Mobile Networks with Coverage Problems

Due to the evolution of mobile technology and the emergence of terminals like smart phones, Internet based applications mostly accessed over the Transmission Control Protocol (TCP) have become dominant on mobile platforms. However, since the TCP flow control mechanisms were designed for wired environments, short-term degradations on the air interface of radio access systems may lead to unnecessary performance drops. TCP freeze is a possible solution to improve such situations by triggering the persist mode of the TCP sender, preventing TCP timeouts and rate reductions during poor radio conditions. This paper investigates a network element based implementation of the TCP freeze mechanism, which has the advantage that it can accurately follow the radio conditions of the User Equipments (UE) while being completely transparent to the TCP sender and receiver. The possible performance gain of the solution was investigated by simulating a network with coverage holes. Results indicate that the network side freeze can considerably reduce the time the TCP connections spend in outage and thus it can increase the responsivity and data throughput provided by the system.