Research On Multiple-User Distributed Network MIMO Technology

The technologies of wireless communication are developing continuously, after 3G, ITU has defined very challenging technical requirements for next generation mobile communication system:peak spectrum efficiency higher than 15bps/Hz and thoughput more than 1Gbps over the air interface. To achieve such goal, MIMO technology with multiple antennas to exploit spatial dimention is a promising candidate. However in the actual cellualar network, some factors have limited the deployment of MIMO technology, e.g. size and cost of the user termincal limit the number of antennas which can be implemented within a single terminal, complex interferent situation of cellular network impact the effective perfromance gain of MIMO technology, etc. In order to overcome these limitations, in this paper we study the technologies of multiple-user distributed network MIMO.At first, as a method to overcome the limitation of number of antennas which are available within the sigle user terminal, we focus on the the theory of multiple-user communication. Different from the convertional single-user MIMO channel, multiple-user MIMO channel has its own characteristics, e.g. for the scenario of downlink multiple-user reception i.e. multiple-user broadcast channel, the multiple receivers which belong to different users can not do joint decoding. Similiarly, for the scenario of uplink multiple-user transmission i.e. multiple-user multiple access channel, the multiple transmitter which belong to different users can not do joint transmission. The research according to these characteristics forms the theory of multiple-user communication. In the chapter 2 of this paper, we study the capacity theory of multiple-user channel, including the upbound of total throughput of multiple users, and the possible combinations of channel capacities of multiple users. Based on these theories, we discuss the precoding schemes of multiple-user broadcasting channel, including linear precoding method for orthogonization of inter-user channels e.g. algorithm of "zero forcing" and "Block Diagonization". And the non-linear precoding which pre-cancel the inter-user interference at the transmitter side, e.g. "THP precoding" and "Dirty paper precoding".Another important topic in this paper is the network architecture of distributed multiple-site cooperative communication to overcome the intercell interference of cellular network. Different from the conventional cellular network, in case of distributed multiple-site cooperative communication, multiple sites located at different places may cooperate and provide service for certain user simultaneous. In chapter 3 of this paper, we study the mechanisms of distributed multiple-site cooperative communication. Its atvantages include user-centric distributed serving cell to mitigate the intercell interference, enhanced link situation promoting the usage of MIMO technology, and the distributed sites reduce the effective distance between sites and users, thus improving the power efficiency of system. About the design of distributed multiple-site cooperative, considering the fact that multiple sites may locate at different locations or can be at the same location, relevant factors can impact the system design and performance. In chapter 3, we discuss two main factors. At first, about the degree of communication and cooperation among multiple sites, the communication mechanisms which can be supported among multiple sites determine the possible degree of cooperation. Accordingly, we need to design appropriate technical solutions. On the other hand, multiple sites of different locations may have different large scale propogation loss to the user receiver, analyze the consequent impact to the channel capacity, we need to design appropriate mechanisms to construct the set of sites for certain user.Based on the theoretical study of the first half part of this paper, in the last two chapters, I study the detailed technical solutions, cooperative working mechanisms and the signal processing methods. Use 4G TD-LTE-Advanced as a basic model, I design "the mechanism to construct the set of distributed cooperative sites" and "technical solution suitable for different degrees of cooperation". The study includes several aspects of system modeling, technical solutions designing, system performance simulation and analyzing.