  Even real time video telephony services have been pervasively applied,
providing satisfactory quality of experience to users is still a challenge task
especially in wireless networks. Multipath transmission is a promising solution
to improve video quality by aggregating bandwidth. In existing multipath
transmission solutions, sender concurrently splits traffic on default routing
paths and has no flexibility to select paths. When default paths fall into
severe congestion and the available bandwidth decreases, sender has to decrease
video quality by reducing resolution or encoding bitrate. Deploying relay
servers in current infrastructure to form overlay network provides path
diversity. An online learning approach based on multi-armed bandits is applied
for path selection to harvest maximum profit. Further, a congestion control
algorithm adapted from BBR is implemented to probe bandwidth and to avoid link
congestion. To maintain throughput stability and fairness, a smaller probe up
gain value is used and the cycle length in bandwidth probe phase is randomized.
To reduce delay, the inflight packets will be reduced to match with the
estimated bandwidth delay product in the probe down phase. Experiments are
conducted to verify the effectiveness the proposed solution to improve
throughput and quality in video communication service.
