The way how WiFi networks work poses certain problems. Replacing a problematic link with Ronja can solve these problems because Ronja operates on different principles:
Low speed. The data rates normally associated with WiFi are raw data rates (1,2,5.5,11,22,54 Mbps etc.). However due to the CSMA/CA method that is used, the actual net data rates reached in a TCP connection are substantially lower. According to Wikipedia, "in practice the maximum 802.11b throughput that an application can achieve is about 5.9 Mbit/s over TCP and 7.1 Mbit/s over UDP." Similarly reduction affects the speed of the 802.11a devices, too: "The 802.11a [... has] a maximum raw data rate of 54 Mbit/s, which yields realistic net achievable throughput in the mid-20 Mbit/s."
That means that a 802.11b device is always slower than Ronja where the net throughput for TCP is 9.5Mbps. In case where both directions of the link are equally loaded, the throughput of WiFi falls further to a half, because the directions have to share the channel capacity. In case of 802.11b that drops to 3Mbps for TCP and 3.5Mbps for UDP. In case of 802.11a it makes around 12.5Mbps, which is still faster than Ronja with 9.5Mbps.