Optimized mathematical model for cell receivers running in spatially problematic multi path channels for wireless systems in smart antennas

摘要

The explosive escalation of mobile internet with strong progression in every socio-geographic region with a perspective to support wireless multimedia applications is exceedingly demanding big transmission data rates and high quality. Distribution in Non-omnidirectionalfor power in space of multipath requires fading statistics for understanding wireless systems that operate in realistic propagation channels or employ smart antennas, adaptive arrays, and other Multiple Input Multiple Output (MIMO) technologies. Mathematical models for the design of mobile receivers are characterized by Level-Crossing Rates (LCR) (how frequently a received signal fades below a threshold/doorstep voltage) and Average Fade Durations (AFD) (the average interval of time a received signal spends below a threshold voltage). LCR and AFD are spatially correlated to transceivers. Like Doppler frequency, LCR and AFD are apparently related to antenna spacing and speed of the mobile station, reflecting correlation properties. To minimize packet loss and packet error rate, LCR and AFD help in selecting optimal packet lengths and characterizing fading impact on the transmitted signals. LCR becomes oscillatory and convergent, and finally unnoticeable when antenna spacing becomes larger. However, when the mobile is moving perpendicular to the antenna axis, AFD is loosely dependent on the antenna spacing. For devising efficient Protocols such as automatic repeat request (ARQ) and quantifying of the channel fading on the system performance in dynamic effect, AFD is an important criterion for any communication system. The transition probabilities between different states of a Markov model such as connected, transitional, and disconnected for fading channels can be calculated based on LCR at different levels. These are essential to qualify a certain quality of service which are necessary for proper selection of the signal correlation properties, such as adaptive symbol rates, interleaver depth, power and bandwidth (BW) allocation for multiple hops, handoff, fading rate, velocities of the transmitter and the receiver, and packet length and time slot duration; depending on the type of modulation used and the type of application supported.