rmation about the network the UE can use to attempt random access: Preamble format of the PRACH used Number of PRACH opportunities CHAPTER 2 SELF-ORGANIZING NETWORKS IN LTE DEPLOYMENT System frames during which the PRACH opportunities are configured Subframes where the PRACH opportunities are configured by the network The preamble format and parameters are shown in Figure 2-13. Sequence Random access preamble format Random access preamble parameters Preamble format 3168T 24576T 21024Ts 24576T 6240-T 2.24576.T 21024T 2.24576.T 4096T Figure 2-13. Preamble format and paramters used for PRACH For an FDD deployment, the number of PRACH opportunities within a subframe cannot exceed 1. However, due to the shortage of uplink opportunities in the TDD network, there can be up to six PRACH opportunities. In order to reduce the call setup delays or handover delays, one of the parameters that can be optimized is the Prach-ConfigIndex, which can enable multiple PRACH opportunities for a UE wanting to establish connection. Mobility Robustness Optimization Mobility robustness optimization aims to improve system performance by optimizing the handover parameters. There are three popular reasons for handover failures for any LTE network: too early handover, too late handover, and handovers to a wrong cell. The mobility robustness optimization feature tries to optimize the cell offsets for two neighboring cells in order to reduce the failures that occur for these reasons. Optimization of these failures not only helps reduce the call drop ratio, but also significantly brings down the signaling load on a cell or eNodeB. Mobility robustness is part of the 3GPP's SON use cases (TR 36.902 V9.0.0). During deployment, the operator defines a default set of configuration for the mobility parameters based on the type of deployment (e.g., urban, dense urban, small office, rural). This set of parameters (default parameterization) not always optimal and might not yield the desired KPIs upon deployment. Mobility robustness features aim to target 