Dear Dr. Saad

Please check my paper which includes scalability of Probabilistic Key Management approaches for WSN, I wish it will help you

"Toward Secure Non-Deterministic Distributed Wireless Sensor Network Using Probabilistic Key Management Approaches"

Here is the link:

https://www.researchgate.net/publication/259292886_Toward_Secure_Non-Deterministic_Distributed_Wireless_Sensor_Network_Using_Probabilistic_Key_Management_Approaches_Qasem_Abu_Al-Haija?ev=prf_pub

Article Toward Secure Non-Deterministic Distributed Wireless Sensor ...

Here is the paper

Article Toward Secure Non-Deterministic Distributed Wireless Sensor ...

I would recommend the phenomenal work by Gupta Kumar on their capacity paper,

"http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=825799&tag=1".

Although the work is for ad-hoc network but the mathematical treatment is so rigorous and deliver an insight about how to do it for other networks.