The camera is upgradable via a wireless connection, but this procedure is not recommended since a loss of connectivity can result in an upload failure and render the DCS-2332L unusable. Of course a failure can also occur via a wired connection, but this situation is less likely.
If you are intent on upgrading via wireless, you can significantly reduce the risk by first downloading the firmware to a PC wired to your LAN. Next, log into the wireless DCS-2332L web UI using a browser on the host PC where the firmware was downloaded. Finally, through the web UI, select the downloaded firmware and apply the upgrade. This procedure is far safer then allowing the DCS-2332L to upload the firmware directly from the remote D-Link site over the Internet. The devices on your LAN are likely to be more stable and the upload should be quicker since the file is local. To further minimize risk, if/when you perform the upgrade, make sure the host PC isn't running any CPU/network intensive applications or being used by another user until the upgrade is complete.
P.S. If the downloaded firmware is inside a .zip or .rar archive, make sure to extract the file before uploading.