The minimum unit of capacity in WCDMA is code while on the other hand it is RB (resource block) in LTE. So there is no more code in LTE now is RB which is a combination of subcarieers in frequency domain and symbol periods in time domain hence the concept of OFDMA. i can say that it is the enhancement in FDMA from basic. PCI (Physical cell id) is a combination of Cell group id and cell id and its range is 0-503.
When you plsn PSC in WCDMA you have enough codes and it is much easier than PCI planning even though you have big range in PCI too. The limitation is that during PCI planning you have to avoid same MOD (like MOD3) values PCI in same facing sectors otherwise the situation will worst. This MOD is actually the reminder which inreal is the difference between two reference signals and its mapping is different in different MIMO stratagies.
In short you have to plan PCI in such a way to avoid collisions in RS. Anyways you have to read in details to understand all concepts.