e., the PCID values of neighbors of direct neighbor cells must again not use the same PCID values) Avoidance of PCID group associations with PCID groups in use nearby Avoidance of PCID group affinity, preferring assigning three values that form a PCID group Avoidance of PCID sector uniqueness, preferring assigning three unique PCID sector values Avoidance of PCID sector alignment with antenna bearing, preferring PCID alignment with antenna direction PCID allocation in a SON feature should also support collision and confusion detection and resolution. CHAPTER 2 SELF-ORGANIZING NETWORKS IN LTE DEPLOYMENT Automatic PCID Assignment Background The PCID is a fundamental input for the physical layer, which implies potential radio interference if PCID assignment is not done carefully. As mentioned earlier, every cell in the system must be assigned one of 504 PCID values; therefore, PCID values will need to be reused in large systems. The automatic PCID assignment feature of SON removes the planning (reuse pattern) and provisioning issues from the process. Common Ground Initial PCID assignment provides the following capabilities: Operator can manually assign PCID values or use a planning tool Operator can choose to overwrite PCID values at any time It is inevitable that some PCID conflicts will occur regardless of the initial PCID assignment solution (e.g., vendor boundaries, RF oddities). When PCID conflicts occur, they can be resolved with a distributed algorithm. To do conflict resolution, eNodeBs use their neighborhood data obtained via X2 for new PCID selection(s) and automatically resolve the conflict. PCID Collision PCID collision occurs when the eNodeB cell is using the same PCID value and frequency as another cell with a direct neighbor relationship. Figure 2-4 provides an example of PCID collision. ENodeB 2 X2-link ENodeB 1 PCI 3 PCI 3 PCI 5 PCI 4 Figure 2-4. Example of PCID collision This figure shows that the two neighboring eNodeBs, eNodeB1 and eNodeB2, both having cells with the same PCID (i.e., PCI3). This 