Architectures and protocols for symbol-by-symbol rate adaptation for time-varying channels

For high-speed communication over wireless channels, limited radio spectrum and transmission power of systems pose challenges not found in wire-line channels. Wireless channels also exhibit a highly time-varying nature, which is not present in wire-line channels. Effects such as multi-path fading, shadowing, and path losses contribute to attenuation of the received signal strength, and this attenuation can fluctuate on the order of tens of decibels. Techniques commonly used to cope with the time varying attenuation include dynamically adjusting the transmitted power, symbol rate, code rate/scheme, constellation size, and any combination of these parameters. This thesis focuses on dramatically increasing the data throughput by rapidly adapting the transmission to the time-varying channel.; Much attention has been paid to the idea of adapting transmission parameters to channel conditions. To realize such adaptive systems, stations engaging in communication must continually exchange various types of control messages. For example, to communicate data contents from station A to station B, (i) control messages indicating station A's current data transmission parameters must be delivered from station A to station B, and (ii) station B must deliver to A control messages indicating the current conditions of the channel from station A to B. This thesis presents symbol-by-symbol, implicit-signaling adaptive systems that distinguish themselves in two aspects. First, they enable extremely rapid adaptation (e.g. as frequently as at the symbol rate.) Second, the adaptive systems to be presented in this thesis do not use 'explicit' control messages.; The design presented in this thesis can adapt symbol durations. Thus, theoretically speaking, it can unlimitedly increase signal quality to make the symbol error probability arbitrarily close to 0 even when the system is operated over a bandwidth-limited and power-limited channel. Other adaptation techniques often do not have this privilege. One distinctive advantage our symbol-rate adaptation would be to maintain a reliable communication link even in a power-limited environment. Detailed discussion on system architectures and protocols for the symbol-by-symbol rate adaptation that does not require exchanging control messages explicitly will be provided in this thesis.