中文摘要：

为了提高无线系统数据速率，目前广泛地采用物理层自适应调制编码（AMC）和链路层自动重发请求（ARQ）协议相结合的跨层设计，这种设计方法能大大提高系统频谱利用率。本文在瑞利衰落信道模型下，在给定包时延和丢包率的情况下，推导出了联合AMC和ARQ的跨层设计频谱利用率的公式。同时也与纯AMC和纯ARQ的情况作了比较。

英文摘要：

The cross-layer design in combining of adaptive modulation and coding with truncated ARQ is now extensively adopted to enhance data rate in wireless communication systems, which increases spectral efficiency greatly. In this paper, a closed-form spectral efficiency expression is derived for combining of adaptive modulation and coding with truncated ARQ, under prescribed packet delay and probability of packet loss over Rayleigh fading channels. And it is also compared with that in the situation of AMC-only and ARQ- only.