認(rèn)知無線電與認(rèn)知網(wǎng)絡(luò)ch08認(rèn)知網(wǎng)絡(luò)的跨層設(shè)計(jì)-在線瀏覽
2025-02-23 17:27本頁面
【正文】 2) ? Modularity: traditionally, protocol encapsulation has always been effective in providing modularity, ., in allowing independent implementation of all layers (., wireless interfaces, drivers, protocol stacks, applications). In the definition of a crosslayer framework, care should be taken in preserving the modularity of the architecture, in order to allow ponents with crosslayer capabilities to be designed independently of each other, and to be used interchangeably. Abstracting from the underlying technology is a key prerequisite to this concept of modularity. As an example, suppose we are designing a cognitive transport protocol implementation which can exploit link state information from the link layer to provide enhanced performance. If we can get the necessary information from the link layer in an abstract way, say channel error and congestion status, we can succeed in designing a modular transport layer which will work with different technologies. If, on the other hand, we are forced to rely on technologyspecific information, ., the value of Network Allocation Vector as a measure of link congestion, our design will be unusable when we switch to a different link layer technology such as UMTS or WiMax. 2022/2/3 12/15 Challenges of Cognitive Crosslayering(3) ? Information interpretability: As stated above, in order to achieve modularity it is necessary to choose a knowledge representation base which can acodate different implementations of layer modules. While necessary, this practice brings further design challenges related to information interpretability. Suppose for instance that we identify SNR as being a generic and useful information shared by all wireless technologies, and as such we include it as a relevant linklayer information in the crosslayer knowldege base. The interpretation of
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