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-wenkub
2023-01-21 17:27:10 本頁面
【正文】 ormation 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 SNR by other layers or entities would be misleading, since it is impossible to, ., infer the goodness of a wireless link from SNR without technologyspecific knowledge such as the type of modulation and FEC/ARQ schemes used. 2022/2/3 13/15 Challenges of Cognitive Crosslayering(4) ? Imprecision and uncertainty: Most information to be exported by the different layers is obtained from measurements, which are affected by errors in precision and accuracy. These issues can often be properly dealt with by jointly designing all layers of a specifically targeted crosslayer optimization system. Unfortunately this is not feasible in a modular crosslayer system where all pon
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