Alistu i think he needs more of literature survey as of now. He is not sure about what techniques to use. First he must survey about current schemes used in current scenario and compare them and decide which one to use for his design.
Currently TWDM is very hot topic.
Gulkaran please refer to the following link. It may help.
http://www1.huawei.com/en/about-huawei/publications/communicate/hw-201329.htm