Research On New Technologies Of Transmitter And Receiver In MIMO Systems

The physical layer of digital communication system is of concern of the information flow transmission problem between the sending nodes and receiving nodes, such as channel coding, signal modulation and demodulation. To further improve the transmission performance of wireless MIMO system, some physical layer technical improvements are proposed for the sending end and receiving end, as follows:1) The new transmission signal design:In order to carry digital information, the traditional modulation methods utilize the waveform difference of amplitude, phase or frequency, or two or more different combinations of signal parameters. But we introduce power difference as a new waveform different way, its core idea is to insert certain continuous zero signal intervals into the energy signal waveform according to some mapping relationship. Theoretical calculation indicates that the receiver with multiple antennas can get many copies of signal, and then distinguish the noise pollution signals and the pure noise signals by the signal power difference with a very low error probability. Based on these results, some novel space-time signal designs are proposed for various systems, such as coherent SIMO and non-coherent MIMO. Analysis and simulation results all show that the new encoding schemes are superior to traditional programs.2) Receive signal preprocessing:using the minimum-energy wavelet frame in the discrete space to pre-process the receive signal before demodulation. We first give the definition of minimum energy frame in discrete signal space, and prove some good characteristics of it. Then the denoising pre-processing algorithms are proposed for the polluted rectangular and raised cosine pulse signal by additive Gaussian noise using these characteristics. Simulation results show that, if adding a signal pre-processing part in the receiver, due to take full advantage of a priori information of signal, the signal pre-processing algorithms can reduce some adverse effects from transmission for the receive signal and improve the output signal-to-noise-rate of signal demodulation, and then obtain greater performance gain.3) Network coding theory based on two-way transmission:a network communication system can be regarded as the collection of the nodes which try to communicate with each other and their channels between them. Currently, most of the researches on wireless network communications are considering one-way information flow, namely, in a communication process, the intersection set between the source nodes and destination nodes is empty. In fact, with the broadcast characteristics of wireless channel, this division will cause great waste of network resources. Because of the new flat network architecture of next generation mobile communication systems, based on two-way flow of information transmitted, this paper introduces the network code and collaborative communication ideas, and carry out some basic coding theory research for some basic network topology. These include:multi-dimensional network error-correcting codes, multi-dimensional network linear block codes and convolutional codes, multi-dimensional space-time code and dual-constellation space-time code design for the exchange node; two-dimensional and three-dimensional network error-correcting code design, as well as two-dimensional and three-dimensional network of space-time code design for cooperative relay node. Theoretical analysis and simulation results show that, compared to the traditional coding theory based on one-way information flow, the novel coding schemes can make better use of the broadcast nature of wireless channel and wireless networking space resources, and effectively improve the utilization of energy emission and obtain more coding gain.In the physical layer, the source nodes and relay nodes need encoding and signal processing algorithms, while the destination nodes will need signal processing and decoding algorithm. the design of transmission signals, the pre-processing algorithm for the received signal, the error correction coding and space-time coding based on the network coding and collaborative communication are put together to carry out the optimization of communication. They are throughout all communication process and bring great gain for the wireless network. Compared to traditional methods, these novel technologies will obtain many gains on the performance of spectral efficiency energy consumption, encoding and decoding complexity, bit error rate and system throughput.