Design And Implementation Of The Diversity For The PLC Fading Channel

The Power Line Carrier Communication is a communicating manner which uses power line network to transfer data. For the merit of few line investment and easy connecting, It has the broad application prospects. With the rapidly development of PLC communication technology, it has become a hot spot in the current scientific and technological research. However, the bad environment on power line channel seriously affects the reliability of data communication. It has been unable to meet the demand for the traditional power line communication system which uses single-frequency modulation. The diversity technique is an anti-fading technology, it is able to improve the reliability of signal transmission on the frequency selective fading channel. This topic research the diversity technique which is used to improve the anti-fading performance of the power line carrier communicationAccording to the domestic power line letter channel environment, it analysis the power line channel characteristics, which has the characteristics of strong signal interference, the complex types of noise, strong signal attenuation. And it has a frequency-selective fading characteristics and strong time-varying characteristics. On this basis, the corresponding power line fading channel model.is established.According to influence of the fading channel for low-voltage power line communication system, the modulation and demodulation techniques, diversity combining technology and error correction coding techniques are analyzed and system scheme are designed, the diversity scheme is researched to be suitable on power line communication. And Error correction coding such as Hamming code and convolutional code is added on the base of diversity techniques. It uses MATLAB to model and simulate the power line communication system, including multi-frequency FSK modulation, FSK demodulation based on DSTFT, combined processing module, error correction encoding and decoding module etc. The different combination of the demodulation module, the combined judgment and the decoding module is studied to improve system performance further.The Power line carrier commumcation system uses the TI’s high-performance 32-bit DSP chip TMS320F2812 as the core,and programming main modules of the core algorithm in the multi-frequency frequency diversity PLC communications system, including modulation module, demodulation module, error correction coding and decoding module, and serial port transceiver modules. The corresponding peripheral circuits are designed, including the transmitter amplifier, the coupling and receiving signal amplifying circuit etc. The whole system is simple and flexible. These key technologies are easy to be implemented, which has better anti-fading performance on the low voltage power line. In the practical applications, the diversity scheme on the PLC can be designed based on the above technologies in order to achieve the low cost, easy to realize and reliable communication, according to the demand of applications and software and hardware resource allocation.A low-voltage PLC experimental system is build, and it is tested and analysis. The experimental data shows that the designed diversity schemes and error correction coding technology can effectively improve the anti-fading performance of the power line carrier communication system and the communication reliability in the harsh power line channel environment.