Your router is only have the issue your wireless nic controls the speed just as much. So if you are using a older nic it will slow your router down to its speed. So it may be that alone if the card is old enough. Otherwise it is likely you are getting errors due to interference. It is the standard solution for interference change the channels and hope to get lucky on one that works better. You can also try to force the router to only use 20mhz (ie narrow) channels. In theory 40mhz should allow you to get more speed but if you are getting lots of interference cutting it back may actually increase your speed because you now have less exposure to interference