Space-Time Coding Technique in Wireless Communication
Multi-antenna systems will be the most important technology in 3rd generation, even in the future 4th generation, of mobile communications. In this paper, the Up-to-date development of Space-Time Coding technology which combines transmit diversity with coding technology is surveyed. Space-time codes consist of Space-Time Trellis Code and Space-Time Block Code, which are discussed respectively. Emphasis of discussion is paid on one kind of Space-Time Block Code, namely Unitary Space-Time Code. Using this coding technique, channel estimation is not necessary both at the transmitter and the receiver. At last, the research trend of space-time codes and some conclusions are given.
Abstract Characterizing the spatial variation of allele frequencies in a population has a wide range of applications in population genetics. This article introduces a new nonparametric method, which provides a two-dimensional representation of a structural parameter called the genetical bandwidth, which describes genetic structure around arbitrary spatial locations in a study area. This parameter corresponds to the shortest distance to areas of significant allele variation, and its computation is based on the Womble's systemic function. A simulation study and application to data sets taken from the literature give evidence that the method is particularly demonstrative when the fine-scale structure is stronger than the large-scale structure, and that it is generally able to locate genetic boundaries or clines precisely.