This paper proposes a heterogeneous wireless network with handover in the application layer. The proposed network requires no upgrade of wireless infrastructure and mobile terminals to convert the present homogeneous networks to the proposed heterogeneous network. Only installing application programs on the content server side and the mobile terminal side is required. The performance of the proposed network has been evaluated in a field trial using a mobile broadband wireless access (MBWA) air interface with wide coverage and a wireless local area network (WLAN) air interface with high throughput. The field trial results show that the maximum value of the handover outage time is only 170ms. The proposed heterogeneous wireless network is promising since both high throughput and wide coverage area are attained by a combination of the proposed handover scheme with the present homogeneous wireless networks.
We have proposed hotspot network based on layer 2 forwarding for seamless handover. Key functions of the proposed hotspot network are movement notification packet sending for changing forwarding path and adaptive flow control at handover for keeping throughput. A mobile terminal sends the movement notification packet in order to change address table in nodes of the hotspot network after changing connection from previous access point to new access point. To realize adaptive flow control, MT controls transmission control protocol (TCP) offered window size. The mobile terminal closes the offered window before handover and opens the window after handover. We have evaluated performance of the proposed network using network test bench. IEEE802.11b modems were used as wireless interfaces. The degradation of throughput at handover was reduced compared with that of conventional method without adaptive flow control.
We have proposed hotspot network based on layer 2 forwarding for seamless handover. A mobile terminal sends movement notification packet to new access point when the terminal changed connection from previous access point to the new access point. All nodes which received the movement notification packet change address table. The previous access point sends buffered packets to the new access point. We have evaluated performance of the proposed network using network test bench. IEEE802.11a modems were used as wireless interfaces. Measured delay time depending on the buffered packet forwarding was confirmed negligibly small. No packet loss was measured. The degradation of throughput at handover was suppressed to compare with that of conventional method without packet forwarding
