Sony PCG-GRX580P - Manual (Page 178)

The data transfer speed is slow.
 The Wireless LAN data transfer speed is affected by distance and obstructions between devices and access points.
Other factors include device configurations, radio conditions, and software compatibility. To maximize the data
transfer speed, move your notebook away from obstructions or closer to any Access Point you may be using.
 If you are using a Wireless LAN Access Point, the device may be temporarily overloaded depending on the number
of other devices communicating via the access point.
 If your access point interferes with other access points, set up the wireless channel with the access point. Refer to
the instructions supplied with the access point.
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