Sequence Design Of Communication System

With the development of modern society, the requirement for the communication system is becoming more and more urgent. Data transmission in wireless channels with high speed and reliability is goal in future wireless communications systems. In recent years, the multicarrier CDMA communication and the Ultra-wideband (UWB) communication technology obtained people’s widespread attention, and has caused the research upsurge. This article has mainly studied the sequence design and application in the wideband communications system. Sequence design is a crucial technique of multi-carrier CDMA communication systems and can provide multiple access and multiplexing methods for the systems. The correlation properties of sequences have an important effect on multiple access interference and multi-path interference, and hence affect the bit error rate (BER) and data transfer rate of systems to a large extent. The set size of a sequence set usually limits the number of the users accommodated by systems. In order to support more users, a large set size is required. As a result, the design of sequence sets with good correlation properties and large set size is very significant.It is well-known that sequences with good periodic auto-correlation and cross-correlation functions find their applications in the field of spread spectrum communications, CDMA systems, channel estimations, synchronizations system identifications, radar and sonar system, etc. There are many different kinds of sequences and it is clear that different applications may require different sequences with specific properties.In the first part of this dissertation, I introduce some methods to construct2-phase M-sequences and talk about their properties, by using MATLAB I give the simulation of the related properties,and then I give three different ways to find out the primitive polynomials we needed.Secondly, in order to break the limit that the2-phase M sequences have too little address codes and their related performance improvement have been closed to zero, I introduce the poly phase M-sequence, and with the application of the trace function over finite fields, I improve them to be the orthogonal sequences.Finally, I talk about the concept and properties of the cyclic difference sets, quasi-perfect sequence can be constructed using the cyclic difference sets, Then I talk about their properties, and based on them I propose a new sequence——near quasi-perfect sequences. Taking into account the advantages of poly-phase sequences, I give a way to construct the poly-phase sequences with the use of cyclic difference sets.