Power allocation in carrier aggregation MIMO systems with different power constraints

The target set by the International Telecommunication Union (ITU) for the next generation of mobile communications, IMT-Advanced, is to achieve up to 1 Gb/s peak data rates. The 3rd Generation Partnership Project (3GPP) introduced Carrier Aggregation (CA) technology in its latest Long Term Evolution Advanced (LTE-Advanced) standards in order to meet the performance goals of the next generation, the fourth generation, 4G. The introduction of CA in LTE-Advanced system poses a challenge to the power control function of a CA-MIMO radio link. The problem appears when multiple Carrier Components (CCs), within a single or multiple frequency bands, are allocated to a user. The two challenges studied in this thesis are the different channel characteristics in the different CCs and the multiple power constraints imposed on the mobile equipment: per-CC, per-antenna and per-total transmit power available. This thesis studies the bit error rate (BER) performance of a CA-MIMO radio link with the Modified Hybrid Gradient Optimal Power Allocation (MHGOPA) algorithm. In order to examine the validity of the MHGOPA algorithm, the results are compared to a baseline uniform power allocation approach. The results of the simulations are obtained for different environments: Indoor Hotspot, Urban Microcell, Suburban Microcell and Urban Macrocell. The results show that the MHGOPA algorithm generally outperforms the baseline uniform power allocation when the channel conditions are good with typical SNR values above 8-10 dB, depending on the environment. The results also show a marginal improvement on the BER in some scenarios when relaxing the constraints on the antennas. The simulations also show that giving primary carrier components (PCC) a privilege in power results in a large degradation in overall performance