Suggest the problem is due to incompatiblities in the equipment in the the the AP or the router does not fully support the PSP feature, this can manifest it'self in intermittent disconnections, the may be more frequent when operating under battery power.
Reason: In the mobile computing enviroment some components have a feature that allows the wireless component to periodically power down to extend battery life, this requires a fluid connection between the wireless adapter and the Access point (AP) or Wireless Router (WP) which must communicate correctly to allow the adapter to power back up when required to do so, any incompatibility between the adapter and the AP or WR will therefor cause intermitten signal losses.
Solution: Contact the Adapter Vendor for updated software that may correct the problem.
Workaround: manually set the wireless adapter to CAM (continually aware mode), which disables the PSP capability. To do this, in either Intel® PROSet/Wireless Software or the Network Control Panel Applet (NCPA), in the power management section, uncheck the DEFAULT / AUTO selection and set the slider for HIGHEST / MAXIMUM PERFORMANCE.
Note: this workaround may affect Blue tooth if you use this facility you will need to check with your laptop vendor for more information on how pronounced this will be if at all, it can lead to total blue tooth failure to connect in worse cases.