**6. Conclusion**

This chapter is written with an aim to introduce to the readers the fundamental principles of digital signal transmission and detection. When these principles are fully understood, the performance evaluation of any digital system can be handled with ease. The chapter described briefly the history of digital communication . This was followed by definitions of decision hypotheses and formulation of decision process. The error probability calculation is carried out by first finding the probability density function of the received signal energy and noise variance followed by applying the decision hypothesis. The chapter then extended the digital binary communication results to M-ary communications and compared error probabilities for several transmission formats . The chapter introduced channel fading and its impact on performance. The impact of fading was discussed and the concept of diversity was introduced . The wide-band transmission in the form of spread spectrum signals was introduced and its performance evaluated . Several important topics related to modem digital communications like multiuser detection (MUD), OFDM, MIMO and interference mitigation were not discussed due to space limitation.
