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WIRELESS NETWORKS 16 Elektronik International 2020 Wireless for robust communication The basis technology was already standardized 1 in early 2018 as telegram splitting ultranarrowband TS-UNB by the European Telecommunications Standards Institute ETSI It works by splitting a data packet including a pilot sequence into several small subpackets Fig 2 then coding it by forward error correction FEC and extending by further pilot sequences The latter serve to both differentiate subpacket types and also estimate the phase needed for coherent demodulation synchronous demodulation These subpackets are then transmitted in the radio bursts as modulated radiofrequency signals in irregular time slots at different frequencies Modulation is either minimum shift keying MSK or Gaussian filtered MSK GMSK with a bandwidth time product BT = 1 and differential precoding Modulation index η in both cases is 0 5 Socalled telegram splitting multiple access TSMA improves resistance to interference coexistence strength and typical narrowband effects Against this background Mioty shows especially high channel capacity and thus particularly good scalability ➔ Stochastic split into different 15-ms time slots each of 36 bits 24 data bits plus 12 pilot bits and narrow frequency slots reduces the mean probability of collision both from other Mioty transmitters and other wireless transmitters in the same frequency band ➔ Frequency hopping compensates on average typical narrowband effects in particular deep fading through interference from multipath signals ➔ Through the overriding forward error correction it is also possible to a certain degree to reconstruct subpackets with partial interference As many as half of the subpackets can be lost before transmission breaks down Different TSMA profiles patterns were defined collected in three groups In the simplest case Mioty works unidirectionally with terminals transmitting their data to a base station e g gateway In this case special requirements are placed on the receiver in the gateway so that as already mentioned above terminals can use costattractive standard transceivers In particular no high synchronism demands are made so that less expensive crystal oscillators with relative accuracy of ±20 ppm can be used On a carrier frequency of about 900 MHz that corresponds to an absolute deviation of approximately ±18 kHz i e more than seven times the symbol rate But since the deviation is constant for an entire short transmission it is primarily noticeable as a time and frequency offset The deviation can be averaged from the pilot sequence estimate of all radio bursts During transmission to the gateway uplink all TSMA profiles of a group must be run through simultaneously which calls for a broadband receiver This will typically mean softwaredefined radio receivers SDR In the case of bidirectional Mioty networks messages are transmitted from the base station downlink e g a gateway in a predefined interval immediately after receiving a message uplink These messages then consist of a core frame for authenticated activation of the receiver wakeup and as confirmation of receiving the previous uplink message This is followed by the extension frame of one to maximally eleven blocks each with 18 radio bursts for transmission of 1 to 250 bytes Overall it is thus possible with the described structure to achieve a data rate of 500 bit s in a channel of 200 kHz bandwidth whereby the base station can aggregate some 65 000 messages per hour Current transceiver ICs produce receiver sensitivity of about 140 dBm for a noise factor of 5 dB Standardizing In addition to marketing activities to get the technology to market the Mioty Alliance has set itself the task to further develop the ETSI TS 103 357 standard technically to make Mioty a possible implementation for new applications and regions for example Atechnical committee TC was thus created the essential purpose of which is to specify the technical level of the entire economic ecosystem based on the standard That includes certification of components guaranteeing interoperability of Mioty devices from different manufacturers The TC is also working on additions and amendments that are to be put into the ETSI standard Two questions are posed Fig 4 The Bridge from Stackforce enables connection of a Mioty network to another network photo Stackforce Fig 3 With the development module for transceiver IC CC1310 2 from Texas Instruments it is possible to implement a Mioty terminal as a transmitter photo Texas Instruments