To drop or not to drop: On the impact of handovers on TCP performance

Abstract

Abstract-This paper presents a comparison between two handover schemes: drop and forward. In the drop scheme, packets received by the base station after the host has disconnected are dropped, whereas in the forward scheme these packets are forwarded to the new base station. We analyze various TCP flavors and compare our findings to simulation results. Our results can be used to determine which handover scheme and which TCP flavor should be employed to minimize the negative effect of handovers on TCP performance.

Handovers with Forward Admission Control for Adaptive TCP Streaming in LTE-Advanced with Small Cells

“…While soft handovers may improve the throughput of VoIP applications [18], it is known to have a negative impact on data applications [19], [20]. In [4] and [6], the authors present performance studies of the standard LTE handover schemes: drop and forward. They show that by forwarding packets from the old eNB to the new one, TCP throughput increases notably because unnecessary timeouts are avoided.…”

“…They show that by forwarding packets from the old eNB to the new one, TCP throughput increases notably because unnecessary timeouts are avoided. In addition, [6] compares the behavior of various TCP flavors during handover. One of the main conclusions is that SACK is the best TCP algorithm for drop, since it can handle multiple packet losses without entering slow-start.…”

“…A similar reference model was proposed by [1], [4], [5], [6]. There is a routing path from the GW to eNB 1 and a routing path to eNB 2 .…”

“…Throughout the paper we consider TCP SACK, because it was shown to be the best TCP flavor for managing multiple packet losses [6]. Suppose that all cwnd packets pass the GW before it is aware of the handover and arrive at eNB 1 after the UE has moved to eNB 2 .…”

“…Since new packets are routed directly from the sender to the UE through eNB 2 , some of the forwarded packets might be received out of order. Forwarding the packets of a connection from the old eNB to the new one rather than dropping them and leaving the recovery to TCP can significantly improve TCP performance and reduce variance [4], [5], [6]. Therefore, if enough network resources are available for packet forwarding, it is the preferred Fig.…”