This paper deals with the problem of severe wireless performance degradation when multiple wireless technologies are concurrently utilized in a same user device. This type of usage is already frequent in most smartphones and laptops, such as streaming Bluetooth audio while using a Wi-Fi download, and is more intensifying with IoT device deployment which triggers the coexistence of heterogeneous wireless technologies. To lower the form factor and the cost, chip vendors package multiple wireless interfaces into a single combo-chip where a common antenna is shared by multiple network technologies in a time division multiplexing manner. We issue that the careless operations of combo-chip design incur indeed performance degradation for in-device wireless coexistence and show the experimental results via TCP performance measurements in several smartphones and laptops. Our analysis reveals that the behavior negatively affects not only on the transmit power management of wireless access point, but also on the congestion control of TCP sender. We propose a cooperative switching scheme which incorporates TCP control behaviors for better coexistence and implement it on Android and Linux devices. Under the simultaneous use of in-device network interfaces, our approach led a WLAN throughput increment up to eight times without the mentioned issues. Further, this does not require any modification of TCP sender and wireless access point. Thus, the approach is directly applicable to existing mobile devices and also easily extendable to the combination of other in-device wireless technologies.
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