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Carrier aggregation is one of the most distinct features of 4G systems including LTE-A (Long Term Evolution Advanced), which is being standardized in 3GPP as part of LTE Release 10. The closed-loop concept with codebook based precoding MIMO (multiple-input multiple-output) and transmission mode selection, termed as RI (rank indicator) selection, have been deployed in LTE-A systems to provide high system performance required by 4G systems. This article focuses on the study of adaptive transmission mode selection in LTE-A carrier aggregation scenarios. We propose an adaptive transmission mode selection scheme using average channel capacity and BER to maximize the average spectral efficiency (ASE) with a given target bit error ratio (BER). Numerical results demonstrate improvement over each fixed modern terms of average spectral efficiency.

Based on the actual operation of the system and QoS status, the 3G mobile network optimization consists of system dynamic testing, analysis and adjustment to the existing system configuration to provide the highest QoS, the optimum coverage and the lowest network cost-effective. Capacity planning and pilot pollution are two of the key issues in CDMA network optimization. By coverage optimization, power control, access control, network capacity can be improved. And eliminating RF pollution by parameters adjustment can furtherly improve performance of CDMA network.