This paper focuses on the the emerging transmission technologies dedicated to IoT networks. We first analyze the classical cellular network technologies when taking into account the IoT requirements, and point out the need of dedicated technologies for IoT. Then, we present the PHY and MAC layers of the technologies that are already deployed, or likely to be deployed: UNB by SigFox, CSS by LoRa T M , Weighless, and RPMA by Ingenu. We then compare their performances to highlight their pros and cons. Finally, we discuss on the open research challenges that still need to be addressed.
Ultra narrow band transmission (UNB) systems have already been deployed and have proved to be ultra-efficient for point-to-point communications. This paper presents this technology and gives some insights on the scalability of UNB for a multi-point to point network. This configuration corresponds to an uplink scenario where multiple nodes compete to send their packets, with neither coordination nor feedback from the sink. In particular, we present and analyze two multiple access schemes based on random frequency selection: discrete random FDMA (DR-FDMA) and the new continuous random FDMA (CR-FDMA). An ideal system where the carrier frequencies are exactly obtained is first considered and extended to a more realistic case, with rough carrier frequencies. We analyze the system performance in terms of bit error rate and outage probability. The presented results clearly show that, even if in the ideal case, the DR-FDMA scheme outperforms the CR-FDMA scheme; in the realistic case, both schemes lead to similar performance. Thus, this paper highlights the fact that the use of CR-FDMA is very relevant in a realistic network as it bypasses the need of an accurate carrier frequency control, and thus permits the use of even the cheapest transmitters without loss of performance.
The ALOHA protocol is regaining interest in the context of the Internet of Things (IoT), especially for Ultra Narrow Band (UNB) signals. In this case, the classical assumption of channelization is not verified anymore, modifying the ALOHA performances. Indeed, UNB signals suffer from a lack of precision on the actual transmission carrier frequency, leading to a behavior similar to a frequency unslotted random access. In this paper, the success probability and throughput of ALOHA is generalized to further describe frequency-unslotted systems such as UNB. The main contribution of this paper is the derivation of a generalized expression of the throughput for the random time-frequency ALOHA systems. Besides, this study permits to highlight the duality of ALOHA in time and frequency domain.
Abstract-This paper concentrates on characterizing energy, latency and capacity trade-offs in multi-hop wireless ad-hoc networks. Therefore, a multiobjective framework is proposed to derive the Pareto-optimal set of solutions with respect to these three criteria. The work presented in this paper assumes a linear network where transmission powers and relay positions are optimization variables. We study the asymptotic state where the distance between source and destination is very high such that the number of hops tends to infinite. Two types of traffic are considered in the following. First, low rate traffic is analyzed by characterizing the multiobjective performance of a single packet transmission using an interference free multi-hop relaying strategy. Second, a continuous flow of packets from a unique source is considered. In the first case, we show an important theorem which states that all Pareto optimal solutions with respect to delay and energy metrics provide the same target SNR at the receiver side. In the second case, our analytical results highlight how the energy/delay Pareto front moves when considering a capacity constraint and the optimal re-use factor is derived.
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