Combining LANs (wired,wireless or DSL)
1-Turn everything on, i.e. your computer, modems (in case
of DSL).
2-Connect them on the relative ports.
3-Dial, or do whatever you need to do to establish internet
connection and test each one by one, separately.If all good
proceed to the next step.
4-While each one is active and connected navigate to the
"Network Devices" folder of your computer.It usually stays
under control panel.
*.Windows 8 or Windows 8.1: Press Windows D to navigate
to the desktop, and rest is same as windows 7 below.
*.For Windows 7 and Vista: Click the network icon on the
task bar-> then click "Open Network and Sharing Center".
Then click "Change Adapter settings".
*.For XP: Click Start > Control Panel.Then on the Control
Panel window, double-click Network Connections.
5-Review the window showing all of your network
connections.The active connections will be two blue
desktops without a red cross sign.
6-Drag and select Active LAN (Wired, Wireless or DSL
Modem) connections.
7-Right click on one of the selected-> click "Bridge
Connections" .Then wait and a network bridge with different
icon will appear. You might have to provide administrative
right.
Enjoy double speed.
Combine All Other Types of Connection (i.e. bluetooth
modem, mobile broadband, OTA modem, dial-up)
1-Power up everything and connect to the required ports.
2-Check each connections separately.
3-Follow the process above to navigate to your network
device (adapter) folder.
4-Right click one network adaptor at a time (out of your
active and working adapters (connections)).Change the
Interface Id to the same number (say choose 10 for all).
Repeat this for each connection.

Possibly Related Threads…
How to Increase Speed of BSNL Broadband Connection ?