One of the accepted ways to evaluate link is to use the BLE devices in Direct Test Mode (or DTM). In this mode, the BLE controller communicates with External Tester using HCI command/response. Using the commands, you can send a certain data from tester to device under test and then compare the data received to find the performance or link quality parameters. There are already various testers outside which have a pre-defined set of test commands which are run automatically and give you the complete link analysis at the end. Rohde & Schwarz CBT testers are few of them.
For PSoC 4 BLE/PRoC BLE, you can enable this mode by selecting HCI in the BLE component. There is already an example project as part of the CY8CKIT-042-BLE Kit content (download the installer from www.cypress.com/CY8CKIT-042-BLE ) and allows HCI commands/responses to be transferred over UART. Refer to the Kit user guide, section 4.6 (http://www.cypress.com/file/138606/download ) for more details.