This chapter examines the evolution of processing strategies used for wireless communications, aiming to seek their underlying thoughts that may ignite inspiration for the future. Various physical channels encountered in wireless communications are imperfect in the sense that they introduce additive noise, distortion, and interference, therefore requiring various signal processing strategies for remedy. One could introduce an equalizer to combat inter‐symbol interference (ISI), introduce spreading codes to prevent multiuser interference (MUI), and transmit along eigen beams of multi‐input multi‐output (MIMO) to eliminate inter‐antenna interference (IAI), and finally perform decoding separately. The traditional strategy is characterized by isolated design and isolated processing. The pillar of the traditional strategy of isolation is the paradigm of orthogonality, which is the simplest and most effective technique to prevent the occurrence of interference. Turbo codes and the turbo processing principle (or simply the turbo principle) are two facets that constitute Berrou's unified framework.