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2. A distributed density optimized scheduling function for IEEE 802.15.4e TSCH networks

Author

Municio, Esteban, Spaey, Kathleen, and Latré, Steven

Subjects
Mass communications
Abstract

The Industrial Internet of Things is a challenge for wireless sensor networks, where ultrareliability, guaranteed performance, and ultralow-power consumption are mandatory requirements to enable critical IoT applications. The time-slotted channel hopping (TSCH) mode of the IEEE 802.15.4e standard is one of the most promising technologies to accomplish these requirements by yielding guaranteed performance and, simultaneously, efficiently combating external interference and multipath fading. One of the challenges in TSCH networks is to build an efficient schedule for managing the access of the nodes to the timeslots and channels. Several scheduling algorithms have been proposed. Currently, the Scheduling Function Zero SFx is one of the proposed scheduling algorithms for 6TiSCH, the ongoing standard for an IPv6-enabled stack working over TSCH. SFx is based on random resource allocation according to the traffic demand, which makes it inadequate for large-scale and dense deployments due to internal collisions. This paper has two main goals. First, we extensively investigate the performance of SFx for large-scale and dense scenarios, analyze its scalability, and identify its scheduling limitations. Second, we present a new TSCH-based scheduling function, ie, the distributed broadcast-based scheduling (DeBraS) algorithm, a scheduling solution designed for dense deployments based on sharing scheduling information between nodes to reduce collisions proactively. We show, through extensive and large-scale simulations, that DeBraS supports much larger densities than state-of-the-art scheduling functions, outperforming the current distributed 6TiSCH algorithm SFx up to 1.61 times in terms of throughput for large network sizes, at the expense of an increase in power consumption.

Published
2018

3. An enhanced weighted performance-based handover parameter optimization algorithm for LTE networks

Author

Sas Bart, Spaey Kathleen, Jansen Thomas, Bălan Irina, Moerman Ingrid, and Demeester Piet

Subjects
LTE, Self-Organization, handover, operator policy, PDP, Telecommunication, TK5101-6720, Electronics, TK7800-8360
Abstract

Abstract This article introduces an enhanced version of previously developed self-optimizing algorithm that controls the handover (HO) parameters of a long-term evolution base station in order to diminish and prevent the negative effects that can be introduced by HO (radio link failures, HO failures and ping-pong HOs) and thus improve the overall network performance. The default algorithm selects the best hysteresis and time-to-trigger combination based on the current network status. The enhancement proposed here aims to maximize the gain provided by the algorithm by improving its convergence time. The effects of this enhancement have been studied in a rural scenario setting and compared to the original algorithm; the results show a clear improvement, faster convergence, and better network performance, because of the enhancement.

Published
2011

4. Modelling the time-varying cell capacity in LTE networks

Author

Universitat Politècnica de València. Departamento de Comunicaciones - Departament de Comunicacions, Ministerio de Educación y Ciencia, Ministerio de Ciencia e Innovación, Sas, Bart, Bernal Mor, Elena, Spaey, Kathleen, Pla, Vicent, Blondia, Chris, Martínez Bauset, Jorge, Universitat Politècnica de València. Departamento de Comunicaciones - Departament de Comunicacions, Ministerio de Educación y Ciencia, Ministerio de Ciencia e Innovación, Sas, Bart, Bernal Mor, Elena, Spaey, Kathleen, Pla, Vicent, Blondia, Chris, and Martínez Bauset, Jorge

Abstract

In wireless orthogonal frequency-division multiple access (OFDMA) based networks like Long Term Evolution (LTE) or Worldwide Interoperability for Microwave Access (WiMAX) a technique called adaptive modulation and coding (AMC) is applied. With AMC, different modulation and coding schemes (MCSs) are used to serve different users in order to maximise the throughput and range. The used MCS depends on the quality of the radio link between the base station and the user. Data is sent towards users with a good radio link with a high MCS in order to utilise the radio resources more efficiently while a low MCS is used for users with a bad radio link. Using AMC however has an impact on the cell capacity as the quality of a radio link varies when users move around; this can even lead to situations where the cell capacity drops to a point where there are too little radio resources to serve all users. AMC and the resulting varying cell capacity notably has an influence on admission control (AC). AC is the algorithm that decides whether new sessions are allowed to a cell or not and bases its decisions on, amongst others, the cell capacity. The analytical model that is developed in this paper models a cell with varying capacity caused by user mobility using a continuous -time Markov chain (CTMC). The cell is divided into multiple zones, each corresponding to the area in which data is sent towards users using a certain MCS and transitions of users between these zones are considered. The accuracy of the analytical model is verified by comparing the results obtained with it to results obtained from simulations that model the user mobility more realistically. This comparison shows that the analytical model models the varying cell capacity very accurately; only under extreme conditions differences between the results are noticed. The developed analytical and simulation models are then used to investigate the effects of a varying cell capacity on AC. Also, an optimisation algorithm that

Published
2014

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