Simplified field analysis of ISM-band OFDM-based industrial wireless sensor networks

Abstract

A novel method is proposed to estimate committed information rate (CIR) variations in typical orthogonal frequency division multiplexing (OFDM) wireless local area networks (WLANs) that are applied in support of industrial wireless sensor networks (IWSNs) and operate within the industrial, scientific and medical (ISM) frequency bands. The method is based on the observation of a phenomenon of which the significance has not previously been recognized nor documented; here termed the service level differential zone (SLDZ). This method, which conforms to the ITU-T Y.1564 test methodology, provides the means to set a CIR reference for IEEE 802.11a/g/n OFDM systems in terms of committed throughput bandwidth between a test node and an access point (AP) at a specific range. An analytical approach is presented to determine the relationship between the maximum operating range (in metres) of a wireless sensor network for a specific committed throughput bandwidth, and its link budget (in dB). The most significant contributions of this study are the analytical tools to determine wireless network capabilities, variations and performance in a simplified method, which does not require specialised measurement equipment. With these it becomes possible for industrial technicians and engineers (who are not necessarily information technology (IT) network experts) to field analyse OFDM WLANs and so qualify their performance in terms of Y.1564 specified service level agreement (SLA) requirements, which is a primary requirement for WSNs that are intended for use in some specialised industrial applications.

Die studie ondersoek ‘n nuwe metode om toevertroude oordraginformasietempo (OIT) van tipiese lokale IWM (industriële, wetenskaplike en mediese) band radiodatanetwerke te bepaal, wat gebaseer op ortogonale-frekwensiedeling multipleksering (OFDM), vir spesifieke toepassing in industriële radiosensor-netwerke (IRSNe) wat breëband deurlaatwerking vereis teen `n gespesifiseerde minimum diensvlak (DV) verwysing. Dié nuwe metode is gebaseer is op die waarneming van `n onbekende verskynsel wat vervolgens na verwys word as die diensvlak differensiële gebied (DVDG). Hierdie metode, wat ‘n aanpassing is vanaf die Internasionale Telekommunikasie Unie (ITU) se toetsmetodologie Y.1564, bemoontlik `n simplistiese wyse om `n gespesifiseerde deurlaatbandwydteverwysing tussen toetsnodus en aansluitingpunt (AP) te bepaal in terme van `n spesifieke reikafstand (in meter). `n Analitiese benadering word voorgestel om op `n eenvoudige wyse die verhouding te bepaal tussen die minimum deurlaat diensvlak bandwydteverwysing en die radioskakelbegroting, in desibel (dB). Die hoofbydrae van die studie is om aan die wetenskaplike gemeenskap die analitiese werktuie te voorsien wat benodig word om radionetwerkvermoëns, variasies en werkverrigting te bepaal, nie alleen volgens die aanvaarbare ruisvrye dinamiese bestek (RVDB) parameters nie, maar ook volgens die Y.1564 toetsmetodologie se voorgeskrewe diensvlakooreenkomste met betrekking tot industriële standaarde.