We present closed-form analytic expressions for the Signal-To-Noise Ratio (SNR) of the downlink of 3G CDMA systems using Root Raised Cosine (RRC) chip pulse shaping with arbitrary roll-off factors, Quadrature Phase Shift Keying (QPSK) modulation, and Maximum Ratio Combining (MRC) RAKE Receiver. The expressions obtained are also applicable to variable processing gain, chip rate, and data rate for orthogonal codes, random codes, and include adjacent channel interference, outof-cell interference, and Gaussian noise. Moreover, the analysis applies to channel models with arbitrary path separation and delay spread and takes into account the self-interference. The mathematical derivation utilized is both insightful and straightforward.The theoretical expressions produce results at a speed several orders of magnitude faster than Monte-Carlo simulations while closely matching them.Additionally, the so-called orthogonality factor, used for system-level simulations, is also derived in this work.

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