You don't say what OS your laptop is running, but here's a couple of suggestions...
- If your laptop is not waking up, check in the advanced power settings to make sure that wake timers are enabled.
- Leave your laptop plugged into the power supply (but you can leave it sleeping). The reason is that (at least as far as Windows 7 is concerned), if the power supply is plugged in, the WiFi adapter will run at maximum performance.
You can leave the "Allow the computer to turn off this device to save power" checked for the WiFi card. Because this is a WiFi card, actually, you should find that the "Allow this device to bring the computer out of standby" is always grayed out.
The reason is that the "Wake-on LAN" function only applies to wired connections, not to WiFi adaptors. It's a Wake Timer (set by the Windows Home Server Connector Software on your laptop) that's triggering the start of the WHS backup, not activity on the LAN, which is why you have to have the Wake Timers enabled.
The comment in Molly's answer about "choosing incremental backup only" is irrelevant for WHS.