Abstract
Many varied mobile device networks have been developed with the advancement of communication and network technologies. Cellular data networks are currently the most widely used, and the number of cellular network subscriptions has increased steadily. Most recent wireless access technologies employ asymmetric uplinks and downlinks because mobile subscribers usually download contents from the Internet. Therefore, most cellular network service providers allocate more bandwidth to downlinks than uplinks for mobile subscribers. However, this asymmetry can have unexpected influence on network performance, particularly TCP performance. When the uplink interface is congested, TCP ACK packets are delayed by TCP data packets on the uplink, causing considerable TCP retransmissions on the downlink channel. Thus, downlink bandwidth cannot be fully utilized, which results in significantly degraded downlink throughput. To resolve this problem, this paper proposes a feedback scheme, network traffic chunk regulator (NCR). We analyzed the aforementioned problem through the empirical study, and we designed and implemented NCR based on the analysis. NCR adaptively controls TCP according to the degree of link usage asymmetry. We evaluate NCR performance through simulations and experiments with real devices. We verify that the proposed scheme allows the downlink traffic to not interfere with the aggressive uplink traffic. Thus, NCR increases total link utilization and aggregated throughput significantly, without imposing additional overhead on base or mobile stations.
Highlights
Emerging mobile services and systems allow one or more computing elements, such as applications or control programs, to control one or more physical entities, such as sensors or actuators, and generally assume a networked control system between them
(i) We show that asymmetry link capacity can have unexpected influence on network performance, transmission control protocol (TCP) performance, and empirically confirm downlink TCP traffic interference from uplink traffic with unexpected throughput degradation
The proposed network traffic chunk regulator (NCR) solution has several advantages in that (i) it directly addresses asymmetric uplink and downlink capacity assignments and protects downlink traffic from uplink traffic interference, (ii) when multiple heterogeneous network interfaces are enabled in mobile devices or systems, NCR can isolate downlink from uplink traffic and enable any quality of service (QoS) scheme to be implemented on top of multiple networks, and (iii) NCR can differentiate multiple flows according to service quality requirements by changing the weight for each flow
Summary
Emerging mobile services and systems allow one or more computing elements, such as applications or control programs, to control one or more physical entities, such as sensors or actuators, and generally assume a networked control system between them. Worldwide interoperability for microwave access (WiMAX) and long term evolution (LTE) are widely used cellular packet data networks [10,11,12,13] They have network asymmetry with respect to network performance to satisfy demanding mobile subscribers by allocating them more downlink than uplink bandwidth. The proposed solutions generally impose additional overhead of maintaining separate packet queues [15,16,17,18,19,20,21,22,23,24], modifying TCP protocols or parameters [25, 26], or tracking per-flow traffic statistics [18] on access points (i.e., base stations) or mobile stations These solutions are either inappropriate or not sufficiently satisfactory to be applied to emerging wireless technologies.
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