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(searched for: doi:10.1007/s10776-011-0156-y)
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Published: 14 April 2019
by MDPI
Sensors, Volume 19; https://doi.org/10.3390/s19081789

Abstract:
IEEE802.15.4-time slotted channel hopping (TSCH) is a medium access control (MAC) protocol designed to support wireless device networking, offering high reliability and low power consumption, two features that are desirable in the industrial internet of things (IIoT). The formation of an IEEE802.15.4-TSCH network relies on the periodic transmissions of network advertising frames called enhanced beacons (EB). The scheduling of EB transmissions plays a crucial role both in the joining time and in the power consumption of the nodes. The existence of collisions between EB is an important factor that negatively affects the performance. In the worst case, all the neighboring EB transmissions of a node may collide, a phenomenon which we call a full collision. Most of the EB scheduling methods that have been proposed in the literature are fully or partially based on randomness in order to create the EB transmission schedule. In this paper, we initially show that the randomness can lead to a considerable probability of collisions, and, especially, of full collisions. Subsequently, we propose a novel autonomous EB scheduling method that eliminates collisions using a simple technique that does not increase the power consumption. To the best of our knowledge, our proposed method is the first non-centralized EB scheduling method that fully eliminates collisions, and this is guaranteed even if there are mobile nodes. To evaluate our method, we compare our proposal with recent and state-of-the-art non-centralized network-advertisement scheduling methods. Our evaluation does not consider only fixed topology networks, but also networks with mobile nodes, a scenario which has not been examined before. The results of our simulations demonstrate the superiority of our method in terms of joining time and energy consumption.
Carlos M. Garcia Algora, Vitalio Alfonso Reguera, ,
IEEE Access, Volume 5, pp 19536-19561; https://doi.org/10.1109/access.2017.2748178

Abstract:
The so-called Internet of Things (IoT) aims at connecting every single object to the Internet with the purpose to automate every aspect of daily life. The IoT relies heavily on wireless low-power and lossy networks (LLNs) that collect information from the physical world and send the measurements to data aggregation and processing nodes. Most LLNs operate in the non-licensed industrial, scientific, and medical radio band, which is shared by a considerable number of systems. Coexisting wireless systems cause interference to each other, limiting their achievable performance. Multichannel communications enable frequency diversity, which in turn provides robustness against interference as well as increased network capacity. There is a considerable interest in multichannel medium access control (MAC) protocols for LLNs, including an evolving standard for the MAC layer of LLNs. In this paper, we review the latest advances in the topic and introduce a new classification framework for multichannel MAC protocols for LLNs. While our framework builds on previous review and classification studies, it adds aspects of a MAC protocol that reflect its interactions with the surrounding network stack. Seeing the resource constraints of the LLN devices, the study of such interactions—which is missing in prior classification efforts—can be the key for improving future designs. Relevant protocols published since 2006 are discussed and classified using the presented framework, including the recent multichannel MAC protocols for LLNs, such as the latest version of the IEEE 802.15.4 standard for time slotted channel hopping.
Hwa-Chun Lin, Wei-Yu Chen
IEEE Transactions on Wireless Communications, Volume 16, pp 3787-3798; https://doi.org/10.1109/twc.2017.2688442

Abstract:
This paper studies the problem of constructing maximum-lifetime data aggregation trees in wireless sensor networks for collecting sensor readings. This problem is known to be NP-hard. Wireless sensor networks in which transmission power levels of sensors are adjustable and heterogeneous are considered. An approximation algorithm is developed to construct a data aggregation tree whose inverse lifetime is guaranteed to be within a bound from the optimal one. Adjustable transmission power levels of the sensors introduce an additional term in the bound compared with the bound for networks in which transmission power levels of all sensors are fixed. The additional term is proportional to the difference between the maximum and minimum amounts of energy for a sensor to transmit a message using respectively its maximum and minimum transmission power levels. The proposed algorithm is further enhanced to obtain an improved version. Simulation results show that properly adjusting transmission power levels of the sensors yields higher lifetime of the network than keeping their transmission power levels at the maximum level.
Haithem Al-Mefleh,
Published: 1 April 2016
Computer Networks, Volume 99, pp 99-124; https://doi.org/10.1016/j.comnet.2016.02.011

The publisher has not yet granted permission to display this abstract.
Published: 15 June 2015
by MDPI
Electronics, Volume 4, pp 359-379; https://doi.org/10.3390/electronics4020359

Abstract:
Using multiple channels in wireless sensor networks helps increase the overall throughput and avoid interferences. In addition, introducing multi-interface nodes further helps in increasing the packet delivery rate for those specific nodes. In this paper, we evaluate a channel allocation method based on neighborhood discovery up to 3 hops and a hybrid MAC protocol designed for high data rate wireless sensor networks. We propose a network segmentation that takes into consideration the existence of multi-interface sink in order to further increase to packet delivery ratio. Our protocol, called HMC-MAC, uses Time Devision Multiple Access (TDMA) for sequencing nodes activity, and Carrier Sense Multiple Access (CSMA)/CA with Frequency Devision Multiple Access (FDMA) for simultaneous data exchange. We evaluated our method using NS2 simulator and results show that HMC-MAC protocol improves the overall network performance compared to other protocols especially with high data rate and burst traffic.
David Rodenas-Herraiz, , Felipe Garcia-Sanchez,
Future Generation Computer Systems, Volume 45, pp 95-113; https://doi.org/10.1016/j.future.2014.11.012

Abstract:
Wireless Mesh Sensor Networks (WMSNs) have recently received a great deal of attention in the scientific and developers communities due to the significant advances of this technology in the wireless communication field. The main reason was that competing WMSN approaches that emerged in the last few years provide mesh capabilities ( e . g ., robustness, scalability, multi-hop mesh routing, or energy efficiency, among others) to conventional WSN-based applications, encouraging researchers and end users to adopt new perspectives and solutions. Unfortunately, each one of these approaches lacks some (or many) of the aforementioned mesh capabilities, not assuring, a priori, the feasibility and, especially, the long-term stability of WMSN applications. The IEEE 802.15.5 standard and, in particular, its Asynchronous Energy Saving (ASES) mode was conceived to fill this gap since it integrates, in a single solution, most of these capabilities, guaranteeing, among other benefits, a long network lifetime. However, the ASES mode has no built-in mechanisms to mitigate the negative effects of hidden terminals, which sharply degrades the network performance. This fact leads us to conclude that any current WMSN approach is non-exempt of some problem, which prevents the definitive boost of this technology in the consumer market. Under these circumstances, our contribution to the WMSN field in this paper is a twofold proposal addressed to alleviating the hidden terminal problems in a scenario running under the most relevant design premises of ASES mode. Therefore, we first formulate a multi-objective optimization and then solve it by using Goal Programming. Both mathematical techniques are applied to obtain the best solution that simultaneously minimizes the aggregate message collision time due to hidden terminals and maximizes the network lifetime. Secondly, we propose the design of a MULti-channel TIme-scheduled algorithm for the HIdden Terminal problem avoidance (MULTI-HIT) which appropriately exploits the available bandwidth and accomplishes a straightforward coordination between any sender-receiver pair. Finally, the analysis and simulation experiments are presented and their results carefully discussed, demonstrating the effectiveness of both proposals in the WMSN arena. WMSN approaches offer new perspectives to conventional WSN-based applications.Among WMSN proposals, the ASES mode guarantees the most relevant mesh capabilities.ASES has no mechanisms to mitigate the negative effects of hidden terminals (HT).Under ASES rules, we propose an optimization model and a multi-channel time-slotted algorithm to alleviate the HT problem.An intensive performance evaluation study is discussed to validate our proposals.
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