Core entities Dimensioning

Hi All,

i have been working in core network for 3 year on differt product-commissioning and O&m (Huawei).Now i am planning to move forward and learn how to design/dimension core network entities. Could anybody will help me regarding high level design which is transformed into low level design (vendor specific).which trafic models are applicalble while dimensioning these entities,how to calclute BHCA,Erlang and all design paramters etc.A,C,D E, interfaces designing. more over how can i builup my knowledge in disign and planning field any guide line. i will truely appriciate such guidence