Smooth handoff with enhanced packet buffering-and-forwarding in wireless/mobile networks

Abstract

Packet buffering-and-forwarding is a simple mechanism and has been widely used to provide seamless handoffs in many wireless/mobile networks. However, some undesirable side effects of this mechanism, if not managed appropriately, can easily diminish its effectiveness in providing seamless inter-cell transitions during a handoff. We first examine these side effects and show how inappropriate buffer management by a mobility agent could affect the TCP performance. The throughput of TCP is then studied with special emphasis on the effects of a handoff. We then propose a Last-Come-First-Drop (LCFD) buffer management policy (to be employed by mobility agents) and post-handoff acknowledgement suppression (to be used by mobile nodes) to improvement the TCP performance. Our enhancements are backward compatible and suitable for the gradual/incremental deployment. By deriving an analytical model and conducting numerical analysis, we show that our scheme can improve the TCP throughput up to 30%. Finally, we conduct the ns-2-based simulation to confirm these numerical results, and demonstrate the applicability of the analytic model for predicting TCP throughput in other handoff schemes.

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

“…They show that this model indeed improves TCP performance in cellular networks. In [3], the authors analyze the throughput gained by New-Reno when packets are forwarded from eNB 1 to eNB 2 . They propose an improvement to the buffer management algorithm in order to prevent overflow, and show that it is better to drop new packets than old ones.…”

“…The handover procedure in LTE, described in [1] and expanded in [2], [3], works as follows. When the UE moves between two cells, the source eNB (eNB 1 ) uses measurement reports from that UE to determine the target cell (eNB 2 ) and asks whether eNB 2 has enough resources to accommodate the UE.…”

“…Then, eNB 1 decides whether to forward or to drop the packets received for the UE after the handover decision has been made, depending on the type of traffic and on the availability of resources: 1) Drop: the packets are silently dropped by eNB 1 [1], [2]. 2) Forward: the packets are forwarded to eNB 2 and then to the UE [1], [3]. 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.…”

Predictive routing of contexts in an overlay network

“…Song et al [33] presented a case study that quantifies the possible gains with mobility prediction in a VoIP application. Chou and Shin [10] improve a packet buffering-and-forwarding mechanism, thereby resulting in smooth handovers.…”

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

“…In [17], the authors analyze the forward scheme for NewReno. They suggest improvement to the buffer management algorithm in order to prevent overflow, and show that it is better to drop new packets rather than old ones.…”