Packet Centric vs. Radio Centric Link Layer Approaches: A Quantitative Analysis

A well-known concept to adapt the transmitted pay- load to the current channel capacity is to perforin segmentation of the uncoded user payload. A new cross layer approach to hybrid ARQ was introduced that performs first channel coding and then segmentation of coded bits. In this paper, we denote the traditional approach as radio centric, while the latter is denoted as packet centric. By changing the order of coding and segmentation, it is possible to overcome the conflicting first requirements of link adaptation and hybrid ARQ in terms of packet size. Although the packet centric concept is not introduced here for the first time, a detailed performance analysis has been lacking so far. This paper presents a study that explores the characteristics of the packet centric approach in more detail and provides performance results and a comparison with the traditional approach. The new method is compared to the radio centric approach by means of a theoretical model and a cellular network simulator. It is shown that users with a weak channel can benefit from the former, leading to some gain in capacity.