| posts: 5,889 | Location: Australia
If you have a 300 MBPS router, it is very difficult to connect at that rate! You will find that even if you are getting that speed to begin with, it may drop off the more data you try and transfer. The way around this is to get better signal strength.
Better signal strength can be achieved it a multitude of ways. The antennas on a router (even external or internal) can be at least slightly directional, so turning the router around on the spot can give you a fractionally better signal (if you have a wifi settings program on your computer that can measure receive/transmit signals, both in speed, strength, and quality (the Windows speed identifier is useless for this purpose).
If the router has external antennas, try moving them around slightly if possible, sometimes an off-axis orientation (not perfectly vertical or horizontal) can be beneficial. Try moving the router, sometimes 30 cm difference is all that is required for the signal to change noticeably.
If there are a lot of signals around you, and you have external antennas for your router and computer, put the antennas in a horizontal axis as most people have them in the vertical axis. This will reduce interference from your neighbours.
Choose channels that are least used. Sometimes setups without any other signals around can work on some channels better than others, so try switching that around a bit. Apart from that, there really isn't much you can do. A 'more extreme' option is to play around with signal reflection using aluminium foil; this can work really well but it can be hit or miss if you don't know what you are doing.