Capacity and Weight Coefficients in MIMO Wireless Communication Channels Based on Adaptive Multi-beam Antennas in Urban Environment with Fading
Keywords:
Multiple Input Multiple Output, Multi-Beam Antenna, Ricean K-Factor, Capacity, Spectral Efficiency, Weight Coefficients of Antenna ElementsAbstract
Purpose: Long-Term Evolution (LTE) system has had as many as 12 implementations, the later ones using multi-beam adaptive antennas. LTE development and usage have demonstrated that such systems cannot be adapted to environmental changes, to different locations of every subscriber in the service areas, either open or close for connection, or to the acknowledgement from every wireless channel of a Multiple Input Multiple Output (MIMO) system which goes through an environment with different fading of signals along every individual channel — especially with the permanent need to increase the connection channel capacity and minimize the errors when sending information via time-varying fading channels. As we still lack a general model fully reflecting the fading in every individual wireless channel of a MIMO system, the problem is to
connect the signal fading determined by Ricean K-factor with the parameters of an individual channel: its capacity, spectral efficiency and errors in transmitting the information flow. Methods: In order to minimize the effects of fading which is the source of multiplicative noise in every individual MIMO chanel, a mathematical model was developed based on the wellknown and experimentally tested model of radiowave propagation in various urban and suburban areas. The Ricean K-factor was found via the known parameters of the environment: building density and profile, distances between the antennas, etc. Then, using the Ricean K-factor, a modification of Shannon’s postulate was obtained, which takes into account not only the Gaussian noise but the multiplicative noise, too. Results: For the first time analytical expressions were obtained which
connect the weight coefficients used in multi-beam adaptive antenna theory with the parameters of urban environment. The behaviour of Ricean K-factor was described in various suburban and urban environments. This helped to analize the capacity and spectral efficiency of urban channels depending on their fading level and structure of the surrounding buildings. Then, in order to maximize the capacity and spectral efficiency of the MIMO wireless channels, taking into account the direct connection between the fading parameter K and the weight coefficient of a multi-beam antenna, it was analyzed whether it is possible to efficiently connect non-correlated and correlated elements of MIMO antennas. Practical relevance: It was shown for the first time how the weight coefficients of MIMO antenna elements change in an azimuthal plane. This helps to predict the quality of wireless connection for every subscriber located at various angles and various distances from a MIMO antenna system, under various conditions of transceiving the signals along channels with fading.