Quasi-millimeter-wave-band Fixed Wireless Access (FWA) systems have higher transmission rates than 2.4-GHz or 5-GHz systems, because the available frequency bandwidth for quasi-millimeter-wave-bands is broader than the 2.4-GHz and 5-GHz bands. However, quasi-millimeter-wave-band systems are unsuitable for long-span transmission because the attenuation caused by rain is large. We propose that the symbol rate be lowered for rainfall; i.e., when it rains, a low symbol rate is used. This means narrowing the equivalent noise bandwidth so that a margin for rain attenuation is obtained. We compared a method in which the symbol rate is either high or low with one in which the symbol rate is selectable over a range of values. We verified the beneficial effect of the two-rate method through calculations and simulations. A case study in the Tokyo metropolitan area showed that the service zone radius of this method is double that of conventional systems. Changing to a low symbol rate decreases the transmission rate, but periods of heavy rainfall comprise only about 1% of the amount of time in a year, and so the average decrease in the transmission rate is approximately zero.