| Unmanned aerial vehicle(UAV)is widely used in the professional areas of military,geography and agriculture.UAV prevails especially in the application of remote sensing and mapping in geography domain,for its flexibility in the flight course and lower cost comparing to other schemes.Communication system plays an important role in transmitting high-data-rate and wide-bandwidth geography research data in UAV based remote sensing and mapping system.Since the circumstances vary severely and the flight postures differ in missions,shadowing effect and multi-paths effect and Doppler effect impact the accurate transmission in the communication between UAV and ground controlling center.This article applies OFDM technique in physical layer design of UAV communication system,in order to properly meet the requirements in the high data rate and severely contaminated channel while referring greatly to the scheme of LTE under high velocity application.Above all the article gets into the characteristics of UAV channels in constructing WSSUS model while its discussion covers four scenarios of en-route,departure and arrival,taxi and parking based on Doppler and multi-paths fading.Ultimately it comes out the parameters of specific channels.OFDM physical layer design is discussed later in the article,which includes CP scheme,windowing and virtual carriers insertion scheme,channel estimation and equalization scheme,timing and frequency recovery and OFDM symbol parameters design.After simulation in Matlab,the whole design of PHY is given.Realization in FPGA is in the following section,with discussions of transmission schemes and design of Interleaver when taking trade-off between resources and speed into consideration.Functional and performance test is the final section of the article,whose functions consist of video streaming in UDP protocol as well as performances consist of power,PER and sensitivity of receiver.Ultimately it proves that the design meet the requirements properly. |
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