### Abstract

In an earlier paper, we investigated the fundamental tradeoff between bandwidth and rate for wideband additive Gaussian channels, when there is a constraint in the error exponent. In this paper, we extend these results to fading channels. Specifically, we consider fading channels with large coherent dimension D, which is the defined to be the product of coherent time and coherent bandwidth. We consider the behavior of R _{z}-(1/D) which is the maximum rate at which one can communicate when the coherent dimension is D and the error exponent is constrained to be at least equal to z. We calculate two quantities: R _{z}(0) and R _{z}(0), which together partially characterize the behavior of R _{Z}(1/D) when D is large. We show that QPSK is near-optimal for fading channels with large coherent dimension, in the sense that both R _{z} (0) and R _{z} (0) can be achieved.

Original language | English (US) |
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Pages (from-to) | 557-561 |

Number of pages | 5 |

Journal | IEEE International Conference on Communications |

Volume | 1 |

State | Published - 2004 |

### ASJC Scopus subject areas

- Computer Networks and Communications
- Electrical and Electronic Engineering