Launch The Study Of Diversity Techniques For Broadband Wireless Communications

The rapid growth of wireless voices subscribers, the growth of the Internet, and the increasing use of portable computing devices suggest that wireless Internet access will rise rapidly over next few years. The push toward higher data rates and higher quality in wireless communications is expected to continue. However physical limitations on wireless channels present a fundamental technical challenge to reliable communications.The two major impairment of wireless communication are the fading caused by destructive addition of multipaths in the propagation scenario and interference from other users. Diversity is the single most important contributor to reliable wireless communication.Transmit diversity, multiple antennas at the receiver, is an effective and promising approach. This dissertation introduces the transmit diversity in frequency-flat fading channels and provides some novel ideals of transmit diversity in frequency-selective fading channels.First, the dissertation provides a review of transmit diversity to improve the performance for frequency-flat fading wireless communications. The layered space-time codes, space-time trellis codes, space-time block codes and some other space-time block codes are introduced. Some results of these codes are verified with simulations.Next, We provide some novel ideas for space-frequency codes in frequency-selective fading wireless communications. We derive the condition of the space-frequency codes to achieve maximum achievable diversity gain. Using the design condition established in the dissertation, we provide a novel design of the space-frequency codes where maximum achievable diversity order is available.