Adaptive coding and modulation for hybrid FSO/RF systems

Abstract

Hybrid free space optical (FSO)/RF communication systems can provide high throughput short range "lastmile" connectivity. Since channel conditions are highly variable, adaptive symbol rate and modulation schemes are attractive for this application to make better use of available resources. This paper focuses on the information-theoretic analysis of such FSO/RF systems and introduces an adaptive communication scheme resulting in a capacity-approaching and seamless joint system. Numerical and simulation results give insight into the relation between adaptive parameters and system performance, and provide guidance for the design of a practical hybrid system.

Fair resource allocation for hybrid FSO/RF network

“…Implementing the adaptive coding and modulation methods of [11] into hybrid networks could significantly improve the performance.…”

Link adaptation for parallel channels with encoder rate and modem symbol rate constraints

“…This situation is discussed in detail in [7]. Because of the tradeoff shown above, symbol rates cannot be arbitrarily large due to the encoder rate constraint.…”

“…The expression for the available conditional capacity of the parallel channel in bits/second, i.e the maximum possible throughput, defined as T , associated with the CS and the choice of system parameters, is given by [7] …”

“…In this paper, we consider a more realistic model incorporating symbol rate constraints together with an encoder rate constraint. This results in a coupled optimization procedure instead of the separate channel optimizations obtained in [7], since the This research was funded by the National Science Foundation under grant number ECCS-0636598. The remainder of the paper is organized as follows.…”

“…In [7] we developed an information-theoretic parallel channel model and expressed the throughput as a function of channel state and system parameters. Based on this formulation, we proposed a communication scheme resulting in a capacityapproaching and seamless jointly encoded system.…”