 structure should be designed for the 4G system to meet the requirements of future mobile communication services. With respect to the evolution of E3G standards, this trend has emerged in the standardization process of 3GPP LTE, and OFDM technology has been accepted by E3G standards to accommodate the burst transmission of packet data. The function of CDMA is being weakened, and it is applied more in the allocation of radio resources. It can be predicted that the OFDM will be a competitive air interface technology in the 4G system because of its high spectrum efficiency and flexible spectrum usage. The peak data rate of the 4G system should be tens or hundreds of times higher than that of the 3G system, and it will be 100 Mb/s-1 Gb/s or even more. The frequency band of 2 GHz for traditional cellular mobile communication is now not enough, SO the spectrum resource with higher frequency will be used. But the problem is that the attenuation of electromagnetic waves will increase, and the transmitted power should be increased accordingly tens or hundreds of times, while the cell coverage would be decreased if the traditional cellular mobile communica- tion technologies are still adopted. The novel cellular network infrastructure needs to be researched to solve this problem. The frequency resource used by mobile communication is limited, and in order to provide higher data rates for users within the limited frequency bandwidth, the overall spectrum efficiency of the system should become 10 times higher by adopt- ing some new technologies. It has been proved by information theory that mul- tiantenna technology such as MIMO can greatly improve the capacity of mobile communication systems, and the research result guides the development direction of the future mobile communication technologies. But in the practical system- especially in the mobile terminal with limited volume- there are still many challeng- ing problems in theory and technology to be solved for implementing the MIMO. The peak data rate of the 4G system wi