With the integration of heterogeneous wireless technologies and the popularization of all-IP networks, network-layer soft handoff approaches have gradually evolved to improve the performance of vertical handoffs (VHOs). Unfortunately, the existing soft handoff approaches lead to plenty of out-of-order packets during downward VHOs. In this paper, the authors present a new network-layer soft vertical handoff scheme, called SHORDER. In the scheme, the mobile node (MN) starts or stops buffering packets from its new network based on a few interactive messages with its home agent (HA). With the buffering technique, the scheme can prevent mobile terminals from receiving reordered packets caused by downward VHOs, and is compatible with various transport-layer protocols and their variants due to its independence. Then, the authors theoretically analyze the influence of the proposed scheme on the handoff latency, the goodput and the congestion window of the TCP in comparison with a typical existing network-layer soft VHO method. Additionally, the authors also derive the applicable condition of the SHORDER scheme. Experiments show that the deployment of the proposed scheme is easy and the scheme has better performance under its applicable condition, further, experimental and analytical results are consistent with each other. Finally, based on the applicable condition of the SHORDER scheme, the scheme further is improved.
- Fast retransmission
- Heterogeneous wireless networks
- Packet reordering
- Soft downward vertical handoffs
- TCP goodput