This paper presents a structured approach for 4G (LTE) wireless networks performance monitoring, using field measurements. This is achieved using specific equipment with multiple sensoring capabilities, which enables full layer LTE data capture. A measurement campaign in partnership with a Portuguese mobile operator was produced, which focused on areas where a LTE pilot network has been implemented. The proposed approach allowed to validate LTE's performance targets, set by 3GPP. The obtained performance results are rather promising, foreseeing a strong kick-off for 4G LTE based wireless networks.