Downlink Link Aggregation Performance with Delay Adjustment Capability in Multi-Radio Access System

Heterogeneous radio network which efficiently utilizes the resources of multi-radio access systems is one of promising approaches for flexible, reliable and high-capacity communication. Regarding the cooperative controlling functionality in the heterogeneous system, two schemes are considered to be applicable to the efficient usage of multi-radio systems. One is a link selection and the other is a link aggregation which bundles multi-radio access systems. In this paper, the link aggregation is focused and its improvement of the Transmission Control Protocol (TCP) transmission performance over the aggregated link is discussed. The key function of the aggregation is a delay adjustment capability, which compensates the time delay difference among multiple links by addition of the time delay. The performance characteristics are measured by the experimental testbed including LTE, WiMAX and Wi-Fi. The throughput improvement provided by the link aggregation and the effect of the packet re-transmission caused by the link aggregation are addressed.