Unfortunately, only one patch, provided by "Anders Lindgren" , was available for the same. But, currently the link provided by him is not working. You can directly ask the authors to provide you the path for PCF mode.

Even if I get hold of that patch it won't be working on newer ns-2 versions. I heard that 802.11e HCCA can be used as 802.11 PCF if certain parameters are changed, e.g., setting txop=0. Now I am trying to install HCCA patch but that also works only on ns-2.29 and giving me a lot of troubles while installing it on older ubuntu distributions.

Thanks for your reply, anyway.