| The link of communication can be divided as up-link and down-link. Thedown-link is fixed on. The most important thing is to figure out the up-link now. Devicethat used by user is not so big and the up-link can not use OFDM as transform method.As the business at the user part current to optimize to IP. So, the state of synchronizeand non-synchronize convert to each is very often. So, it is important to study theRACH problem. How to save the source of frequency and time are the points of thedesign of RACH and the communication system. So, the study of the up-link transformmethod and RACH is very important for the development of the communication.This paper just focuses on the problems of the up-link multi-access and RACH.Thepurpose is to constract two popular up-link multi-accesses and to propose some newmethods of the RACH. The method of study the multi-access is to contract theircharacters. Frequency offset is studied for the two kind of access are sencentive to thefrequency offset. To solve the frequency offset problem, a method is proposed. Newmethod is pointed out when we studied the problem of the RACH. Then, we simulatethe performance. Form the outcomes of the simulation, we know DFT-SOFDM has agood performance. The package access, IDMA used in RACH and a kind CCSKmethod are proposed and simulated.At the begining, the meaning and the states in quo is been introduced. Problemsneed to be solved is summed up and the direction is point out.Two method of the transform have been included in chapter two to four. In thechapter two, one of the transform methods named IFDMA is introduced. Threeequalizers have been used in IFDMA respectively and simulations show the character ofthem. At last, the number of user's impact is investigated. Another transform methodnamed DFT-SOFDM is introduced in chapter three. As the chapter two goes, threeequalizers have been studied here and different modulation forms have been looked.Chapter four is an outcome of contrast of the chapter of two and chapter three. Here theimplement complex of IFDMA and DFT-SOFDM is studied. Then it is PAPR. And then it comes to the utilization of the efficiency of the bandwidth. Because of IFDMA andDFT-SOFDM use the frequency to distinguish user. So they are sensitive to thefrequency offset. The method used to solve this problem is pointed out.The point of the chapter five is to analysis the problem of RACH. The problems ofRACH can be apart into two kinds: synchronize and non-synchronize random access. Tosolve the problems in synchronize, package access is put forward. Simulations havebeen done in different channels and bandwidths. The characters of preamble ofsynchronize RACH is introduced. The idea of include the IDMA technology in thetransform of the message in the synchronized in points out.Another point part of chapter five introduce the non-synchronize RACH. First,character of the non-synchronize RACH is introduced. The next is the calculation of thelength of the preamble. At last, two kind of the methods of transform the message innon-synchronize RACH is points out. The first method uses the shift of the CCSK torepresent the message and different user use different CCSK sequence. The othermethod is use CCSK also. But it is different to the first one at the receiver. It uses allusers as the elements of the demodulation of the message. This is the current of thecommunication.The sixth chapter is to conclude the work and the main contribution in this paperand point out the study direction in next. |
PDF Full Text Request