| Infrared communication has become a hot research topic in the indoor wirelessbroadband access because of its rich spectrum resources, low price and high security.Currently, though infrared LED is widely used in most indoor line of sight communicationsystems, the communication system rate and infrared coverage area are limited, so it can’tsatisfy people’s new request of infrared mobile communication. There are some systemsbased on infrared LD which can achieve higher transmission rate than LED, however, hightransmit power is required which easy leads to do harm to human eyes.In order to support user mobility and decrease transmit power of LD, MIMO space-timeblock coding theory is introduced into the indoor infrared communication system and the keytheory and method of infrared diffuse channel’s signal coverage and enhancement areresearched and used in this paper. All of the work contributes to the development of futureinfrared high-speed mobile transmission system. The main contents are as follows:(1)Research the impulse response method of diffuse channel, analyze the spatial powerdistribution under different number of transmitters and find the change regulation of impulseresponse with different receiver’s Field of View, height and position.(2) Calculate thefrequency response of diffuse channel to determine the channel bandwidth of indoor infraredcommunication system.(3) Obtain the system noise power distribution with considering theambient light noise and detector thermal noise.(4) Compare the transmission performance ofindoor infrared MIMO and SISO systems based on MIMO space-time block coding methodand OFDM\QAM modulation. The innovations of this work are that transmission pathsegmentation matrix function transfer method is proposed to calculate the impulse responsefor greatly reducing the computational time and MIMO space-time block coding method isintroduced into indoor infrared communication system to obtain diversity gain.The simulation results show that:(1) compared with classic recursive method under thesame conditions, our matrix function transfer method can greatly decrease the computationaltime of impulse response;(2) compared with SISO diffuse system under the same conditions,the MIMO diffuse system can reduce the bit error rate and obtain higher power utilizationefficiency. This study may provide a technical reference for the realization of indoorhigh-speed infrared diffuse communication system in the eye safety conditions. |
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