A multi-relay assisted orthogonal frequency division multiplexing (OFDM) system with index modulation (OFDM-IM) is proposed in this letter, assuming that amplify-and-forward (AF) relaying protocol is adopted at relays. Two commonly used AF protocols are considered: fixed-gain (FG) AF and variable-gain (VG) AF relaying protocols. To utilize relays in an efficient manner, we also employ two multi-carrier relay selection schemes termed bulk and per-subcarrier (PS) relay selection in the proposed system. We analyze the outage performance of the proposed system and derive closed-form expressions of the average outage probabilities (AOPs) for all cases with different AF relaying protocols and multi-carrier relay selection schemes. In addition, we obtain the asymptotic expressions of AOPs in the high signal-to-noise ratio (SNR) region, by which it is proven that the full diversity gain equaling the number of relays is attainable.
Tens of thousands of wireless industrial monitoring deployments exist today, logging more than 18 billion operating hours. These solutions have been around for over a decade and are based on standards such as WirelessHART and ISA100.11a to provide performance guarantees to the applications. The new trend in industry deployments is the convergence of operational and information technologies happening through the Industrial Internet of Things (IIoT) paradigm. The challenge is to bridge the performance of these well-proven industrial standards with the interoperability of IP-based systems. The Internet Engineering Task Force (IETF), the organization behind most of the technical solutions of the Internet, has produced a set of specifications with this requirement in mind. The output of this effort is the 6TiSCH protocol stack based on open standards, such as those that have played a key role in the Internet's ubiquitous adoption. The standardization of 6TiSCH is done. The state-of-the-art research work focus is on important, but niche, optimizations and performance evaluations of the 6TiSCH stack. This paper takes a different approachit evaluates the performance of the standards-compliant 6TiSCH solution from the end user point of view. It does so on two experimental testbeds, in typical IoT test scenarios based on a well-defined experimentation methodology. We provide a set of Key Performance Indicators (KPIs) useful for the end user to decide whether the 6TiSCH technology is a good fit performance-wise for a particular use case. We demonstrate reliability of a vanilla open-source implementation of 6TiSCH above 99.99%, upstream latency on the order of a second and radio duty cycle well below 1%.
A great number of Internet of Things (IoT) and machine-to-machine (M2M) based applications, which are telecommunication areas with the highest foreseen growth in the future years, require energy efficient, long range and low data rate wireless communication links. In order to offer a competitive solution in these areas, IEEE 802.11 standardization group has defined the "ah" amendment, the first sub-1GHz WLAN standard, with flexible channel bandwidths, starting from 1MHz, up to 16MHz, and many other physical and link layer improvements, enabling long-range and energy efficient communications. However, for some regions, like Europe, the maximum transmitted power in dedicated frequency band is limited to only 10mW, thus disabling the achievement of ranges which would be close to targeted of up to 1km. In this paper we examine possibilities for range extension through implementation of half-duplex decode-and forward (DF) relay station (RS) in communication between an access point (AP) and an end-station (ST). Assuming a Rician fading channel between AP and RS, and a Rayleigh fading channel on the RS -ST link, we analytically derive results on achievable ranges for the most robust modulation and coding schemes (MCSs), both on downlink (DL) and uplink (UL). Analyses are performed for two different standard adopted deployment scenarios on the RS -ST link, and variable end-to-end link outage probabilities. Moreover, we have analyzed whether the considered most robust MCSs, known for supporting the longest range, but the lowest data rates, can meet the defined requirement of at least 100kb/s for the greatest attainable AP -RS -ST distances. We examine data rate enhancements, brought by coding and using of short packets, for both DL and UL. Finally, we present bit error rate (BER) results, obtained through simulations of a dual-hop DF IEEE 802.11ah relay system for the considered MCs. All presented results confirm that IEEE 802.11ah systems, through deployment of relay stations, become an interesting solution for M2M and IoT based applications, due to flexibility they offer in many aspects, meeting requirements for wide transmission ranges in such applications.Keywords -IEEE 802.11ah· decode-and-forward relay· range · data rate· BER Enis Kocan,
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.