General exact and accurate approximate formulations for the crossing rates of multibranch diversity receivers over non-identical correlated Weibull channels

General exact expressions for the average level crossing rate (LCR) of multibranch selection (SC), equal-gain (EGC), and maximal-ratio (MRC) combiners operating over non-identical correlated Weibull fading channels are provided. They are given in terms of finite-range multifold integrals. Our exact formulations generalize those obtained recently in the literature for the dual-branch case. The exact solution requirements are then loosened to allow for simpler accurate approximate expressions. They appear in a fairly simple closed-form fashion, for the SC, and still as multiple integrals, for the EGC and MRC, but with much simpler integrands, which drastically reduces the calculation time. Sample numerical results are discussed by specializing the general expressions to a space-diversity system using three collinear horizontally spaced omnidirectional antennas at the mobile station.