Dynamic regulation of mobile 3G/HSPA uplink buffer with Receiver-side Flow Control

We show that the performance of downloads in a 3G/HSPA mobile network can be significantly degraded by a concurrent upload that saturates the uplink buffer on the mobile device. In particular, we found in some instances that download speeds can be reduced by over an order of magnitude from 2,000 kbps to 100 kbps. To mitigate this problem, we propose a new algorithm called Receiver-side Flow Control (RSFC) that regulates the uplink buffer on 3G/HSPA data senders. It uses a feedback loop to monitor the available upload capacity and dynamically adjusts the TCP receiver window (rwnd) accordingly. We evaluated RSFC on the 3G/HSPA networks of three different mobile ISPs and show that for one of them, RSFC can improve the download throughput from less than 400 kbps to up to 1,400 kbps. In the presence of a concurrent upload, RSFC can also reduce website load times from more than 2 minutes to less than 1 minute 90% of the time. Our technique is compatible with existing TCP implementations and can easily be deployed at 3G web proxies without requiring any modification to existing mobile devices.