Study On Universal Diversity Technology In Broadband Wireless Communication

With the developing of mobile wireless communications, it should be addressed that high-speed, reliable communication is needed in the mobile wireless environment. Wireless channel is easy to be vulnerable to channel noise, channel interference and other factors. Because of moving of subscriber, dynamic changing of channel, and multi-path transmission, it will be caused the receiver signal fluctuations, and may lead to the channel deep fading, resulting in the failure to receive. Due to randomness of radio channel, we must take full account of this randomness in the new communication technologies to the aim of the high reliable communication.At first, the author introduces the faced problems in wireless communication, and study the reason of the poor performance feature in mobile channel: the existence of the deep fade.Second, the author discusses the characteristics of the channel, and classifies the channel by these characteristics. Due to the randomness of the wireless channel, the author shows the model of the channel including discrete base-band equivalent model, statistic model, and tapped-delay model. In the mean while, the author shows the system performance measures of communicating in wireless channel.And then, the article enters the important parts which are detection, channel capacity, and trade-off theory. On the basis of the Gaussian channel, the author shows the detection performance and the capacity of the fading channel. At the same time, the author shows that the designer should consider the trade-off among data rate, power, latency, bandwidth, complexity and diversity technology and other aspects.Then, the author discusses the mitigating technologies --- diversity. We can see that all of the mitigating technology can be viewed as diversity from universal aspect. The core thought is: communication over several independent transmission paths to receiver.According to the difference of transmission paths, the author researches the inner mechanism among time, space, and frequency diversity technologies, gives the determination of the diversity order, as well as specific diversity technology in one specific envirement. And at the same time, the author shows that it is needed to consider different dimension of degree of freedom when we use one of the diversity technologies.The last but not the least, the author discusses one new technology --- signal space diversity. On the basis of study of the communication mechanism, the author researches the detection algorithm in receiver: vector Gaussian approximation algorithm and scalar Gaussian approximation algorithm. From the simulation result, we can see that the more of the rotation matrix of the lattice dimension, the better performance of the vector Gaussian approximation algorithm. The bit error rate degrading rapidly when do first iteration, but it near slowly when iteration number is larger than 4. Regarding to scalar Gaussian approximation algorithm, the larger iteration number is, the better performance. With regarding to the lower order modulation, the bit error rate degrading rapidly when do first iteration, but near slowly when iteration number is larger than 4. However, when we use higher order modulation, the larger iteration number is, the better performance.