engleski

Modelling and Characterization of Wireless Channels in Harsh Environments

The increased interest of industry in wireless networking technology has led to many recent advances in wireless LANs and PANs, and has also increased research in new domains. Since it is vital to enable highly reliable delivery in industrial area, error control is used. It can be realized in different ways: automatic repeat request (ARQ), forward error correction (FEC) and hybrid automatic repeat-request (HARQ). In order to predict radio channel quality and improve it by the use of suitable error correction technique we need to know channel characteristics. Since we experimentally investigated performances of received signal strength indicator (RSSI) and packet error rate (PER) of real components for 2.4 GHz radio environment, with particular attention to IEEE 802.15.4 andWirelessHART, the resulting findings can serve as the basis of required characterization. Average RSSI and PER for each link measurement were calculated over more than 10000 transmitted packets. In wireless communications, the relative strength of the direct and scattered components of the received signal, as expressed by the Rician factor K, provides an indication of link quality. For this reason K-factor is estimated for the best-fitted Rician model. We illustrate detected phenomena and correlations and provide a coarse view on channels behaviour. There is a clear evidence of unisotropic nature of our metrics. Specifically, nodes with the same line-of-sight distance did not necessarily have similar average RSSI or PER, or, more precisely, a relationship between the attenuation of a signal and the distance was not linear. The available evidence clearly leads to the conclusion that the attenuation is not only a function of path distance alone but also indicates complex dependency on multipath effects caused by the surrounding obstacles.

RSSI; PER; Wireless communication; industry; RF power measurement; channel characteristics; IEEE 802.15.4; WirelessHART

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