Aggregation of Wi-Fi Links: When Does it Work?

We conducted a systematic experimental and simulation study on the behaviour of aggregated Wi-Fi links for WLAN access. The Wi-Fi links were aggregated by bonding multiple Wi-Fi interfaces. We demonstrated a close to linear improvement in maximum throughput with the number of aggregated links. We analyse unstable behaviour which appears in both UDP and TCP based applications when flows are split over multiple Wi-Fi links, even when the links are statistically symmetric. We show that this unstable behaviour is due to the short term variations in packet latencies, and occurs in distinct regimes, starting before the saturation of throughput. Our analysis suggests that since the origin of the instability is local, it could be suppressed by intelligent control applied locally at the wireless interfaces.