The Fourth Generation Mobile Communication Base Station Digital Conversion And Papr Control Technology

On October 2010, LTE-Advanced was officially established as the fourth generation of mobile communication technology standards to support 100MHz bandwidth at maximum, which the downlink peak rate is up to 1Gbit/s and the uplink peak rate is up to 500Mbit/s. In 2009, Sweden started deploying the first commercially LTE-based 4G base station and at present 4G network has covered 25 cities in Sweden. As the largest telecom operator in China, China Mobile has the plan to deploy 3060 TDD-LTE base stations in six major cities of the country in 2011.LTE-Advanced downlink adopts OFDM modulation, and in that way the signal is provided with high PAPR. To ensure that the signal be undistorted, power amplifiers demand power back, which results in reduced efficiency and increases operating costs of base stations. CFR technology can reduce the signal's PAPR, thereby enhancing the efficiency of power amplifiers, while DUC technology can transform the baseband signal into signal adapting to RF process.Firstly, it analyzes the LTE-Advanced downlink physical layer protocol, and simulates the TDD-based downlink transmission signal model by applying Matlab, giving birth to the 20MHz bandwidth signal, 9.61dB PAPR. Secondly, two programs, including single-stage and multi-level implementation, are proposed in the light of DUC.Single-Stage Implementation: Simulation determines the optimal parameter values of the FIR low-pass filter. It selects 4 asβ, 10.4MHz as the 6dB cutoff frequency, and 160 as the order of the filter. After DUC, the signal bandwidth is 100MHz, and PAPR is 9.73dB, while EVM is 1.29% and ACLR is 64.8dB.Multi-Level Implementation: The first level's interpolation rate is 3 adopting a Kaiser window-based FIR low-pass filter in terms of the order being 78, while the second level's interpolation rate is 2 adopting a half-band filter in terms of the order being 40. After DUC the bandwidth of the signal can come to 100MHz and PAPR is 9.66dB, while EVM equals to 1.36% and ACLR reaches 65.2dB.Thirdly, for PAPR control technology, simulation has compared the simple clipping method, the peak windowing method, the noise shaping method, and pulse cancellation method, the results of which show that the performance of pulse cancellation is the best. Therefore, pulse cancellation is selected as the implementation program. By selecting 127 as the pulse length, employing direct selection method to determine peak, and choosing 2.1 as the clipping rate and 100 MHz as LTE-A signal, PAPR whose signal after two iterations clipping reduces to 6.48dB as well as EVM equals to 4.81% and ACLR is 65.1dB.Finally, the overall design of DUC and the CFR implementation is displayed, the signal's actual performance are as follows after clipping. PAPR is reduced to 6.52dB, and EVM equals to 4.89%, while ACLR is 64.7dB. The data are consistent with the simulation's results, reaching the established design objectives.The results can be directly applied in the fourth generation mobile communication base station.