Showing papers presented at "IFIP Wireless Days in 2016"

LTE-A random access channel capacity evaluation for M2M communications

Abstract: The densification of the urban population and the rise of smart cities applications foster the need for capillary networks collecting data from sensors monitoring the cities. Among the multiple networking technologies considered for this task, cellular networks, such as LTE-A, bring an ubiquitous coverage of most cities. It is therefore necessary to understand how to adapt LTE-A, and what should be the future 5G architecture, in order to provide efficient connectivity to Machine-to-Machine (M2M) devices alongside the main target of mobile networks, Human-to-Human devices. Indeed, cellular random access procedures are known to suffer from congestion in presence of a large number of devices, while smart cities scenarios expect huge density of M2M devices. Several solutions have been investigated for the enhancement of the current LTE-A access management strategy. In this paper, we contribute to the modeling and computation of the capacity of the LTE-A Random Access Channel (RACH) in terms of simultaneous successful access. In particular, we investigate the hypothesis of piggybacking the payload of Machine Type Communications from M2M devices within the RACH, and show that M2M densities considered realistic for smart cities applications are difficult to sustain by the current LTE-A architecture.

DecaDuino: An open framework for Wireless Time-of-Flight ranging systems

Abstract: One of the objectives of applications based on Wireless Sensor Networks, and more generally the Device Layer of the Internet of Things, is to make human life better. In order to seamlessly become part of our daily lives, future networks may require nodes with the ability to self-localise: for instance, to map collected measurements to a precise location without human intervention. Localisation techniques have been studied for years, but a particular Physical Layer proposed in the IEEE 802.15.4-2011 standard, based on Ultra Wide Band (UWB), enables very precise ranging between neighbour nodes. By using the Time-of-Flight principle over UWB, a cm-level precision can be achieved. As UWB transceivers are hitting the market, evaluating this Physical Layer on a real testbed becomes possible. The aim of the paper is to present an Open Source Framework called DecaDuino, which enables fast prototyping of protocols based on this UWB Physical Layer. After a presentation of the related work and a classification of the localisation techniques used in the Wireless Network context, the DecaDuino Framework is presented, with several results from the implementation of classic protocols such as TWR and SDS-TWR, but also the original 2M-TWR, to illustrate the possibilities of the framework.

Modeling, implementation and evaluation of IEEE 802.11ac in NS-3 for enterprise networks

Abstract: In this work we implement features for IEEE 802.11ac in the NS-3 simulator, in particular wider channels and bit-error calculations for higher modulation coding schemes. We also implement four wireless LAN deployment scenarios from the 802.11ax working group scenario document, and evaluate their performance under different operating conditions. Our simulation results demonstrate that many nodes in an enterprise network will yield lower average throughput to each AP and several APs on the same channel will create unreliable networks with some stations getting high throughput and some not able to send at all. Significant improvement in throughput was also observed with the use of frame aggregation.

Monitoring KPIs in synchronized FTDMA multi-hop wireless networks

Abstract: Smart Cities rely on smart devices connected to the Internet of Things (IoT). The wireless multi-hop networks are a key building block to enable the IoT. We focus on a mutualized deployment, where a network operator offers IoT connectivity to multiple urban clients, with their specific Quality of Service (QoS) requirements. Hence, such a network must guarantee some minimum level of end-to-end delivery ratio and delay, and isolate each traffic from the others. In this paper, we aim at providing the tools to individually monitor and verify the requirements of each client. We propose to use the IETF 6TiSCH stack (IPv6 over the Time Slotted Channel Hopping mode of IEEE 802.15.4e), because it is a promising basis for meeting the latency and packet delivery ratio constraints, and because it intrinsically provides flow isolation. We propose a mechanism that collects the monitoring blocks for each client / application, by piggybacking Information Elements (IEs) onto the data packets. We show that, by using piggybacking, we save up to 45% on the monitoring overhead compared to a traditional approach.

Why is frequency channel diversity so beneficial in wireless sensor networks

Abstract: In dense wireless sensor networks, a multichannel MAC is a good means to reduce channel contention and increase frame reception probability. In this paper, we report on experiments with transmissions on various channels in the 2.4GHz ISM band and find more channel diversity than expected: this effect is particularly exacerbated at a short range, but it also has a significant impact at any distance. Moreover, we find that wireless sensor nodes have a radiation pattern that changes significantly with the frequency channel. This feature is inherent to the size of the sensor node, in which the antenna necessarily interferes with other components. The first consequence of this finding is that frequency diversity in sensor networks is even more effective than generally thought, and conversely, single channel communication schemes should be avoided as long as the power budget is not very comfortable.

Very tight coupling between LTE and WiFi: From theory to practice

Abstract: The use of the large number of deployed WiFi access points is an interesting solution to offload LTE networks. In the perspective of convergence between fixed and mobile access, it is possible to connect WiFi access points to eNodeBs. With very tight coupling, WiFi and LTE flows are merged just below the IP layer. The objective is to accelerate the process of attachment to a WiFi Access Point and to allow dual WiFi/LTE transmission while providing a seamless experience to the end user. In this paper, we describe a possible architecture for very tight coupling and define the main building blocks of the protocols. We show an implementation of very tight coupling on a testbed based on the OpenAir Interface framework and perform some experiments.

Evaluation of medium access and a positioning system in wireless underground sensor networks

Abstract: Wireless Underground Networks (WUN) have many applications, such as border surveillance, agriculture monitoring, and infrastructure monitoring. Recent studies have shown that they are feasible and have deployment advantages over wired networks, but only a few WUN evaluations in multiple access scenarios have been done. This paper presents a simulation study on medium access for a WUN with 4 nodes buried, and one node aboveground. The simulations were carried out using the ns-3 simulator and they evaluate both Wi-Fi, and Lr-Wpan networks for dry and wet soils. We verified that for the same number of concurrent nodes, the use of the RTS/CTS mechanism has a much higher influence than the soil water content. Furthermore, a study about the feasibility of using Wi-Fi fingerprinting for positioning above the ground based on the buried infrastructure revealed promising results.

Confident-based Adaptable Connected objects discovery to HArmonize smart City Applications

Abstract: With the advent of the Internet of Things (IoT) and its need to boost cooperation between different objects in order to improve the quality and the completeness of the produced information, it is important to understand and to evaluate data which comes out and goes into each thing. In this paper we propose CACHACA, a ranking mechanism for Sensor Networks that facilitate the discovery of services provided by each network element. By running the proposed algorithm, it is possible to evaluate and classify the neighborhood and the available services for each node. Performances of CACHACA has been first evaluated through extensive simulations and them stressed when facing a realistic environment through experimentations run on the FIT IoT-LAB testbed. Achieved results demonstrate its effectiveness in the discovery of services process with regards to traditional approaches.

Simba: Similar-evolution based aggregation in Wireless Sensor Networks

Abstract: Data aggregation is an important mechanism to reduce energy consumption in Wireless Sensor Networks (WSNs). By investigating spatial and/or temporal correlation of raw data, sensor nodes can aggregate raw data to a meaningful digest instead of directly sending raw data to sink, this process is considered as data aggregation. Several aggregation works focus on the raw data, they use raw data to cluster the nodes or to do aggregation. While analysis of datasets of real projects shows that some nodes perform similar evolution. Thus we propose a raw data-independent aggregation, i.e., Similar-evolution Based Aggregation (Simba), to consider the evolution of data rather than the raw data. Simba creates a group out of isolated nodes, nodes in the group can cooperatively execute data aggregation, this process reduces the energy consumption on each node. Besides, similar evolution of nodes guarantees the recover accuracy. Our experiments demonstrate that Simba can save more than 91% energy comparing no aggregation, and save more 30% energy than original aggregation functions, and Simba can recover data with higher fidelity comparing with the works relying on raw data.

MCLSPM: Multi-constraints link stable multicast routing protocol in adhoc networks

Abstract: In MANETs, real-time multimedia applications make Quality of Service (QoS) support, a crucial issue regarding terms of increased throughput, reduced jitter and available bandwidth. The highly dynamic topology of the network, large variation of received signal strength at nodes and frequently varying link characteristics make QoS provisioning, a challenging task. Most of the existing routing protocols focus on straight forward hop-count metric and are less adaptable to densely distributed and highly mobile networks. Therefore, Multicast communication with QoS in densely populated highly dynamic network an interesting research challenges. The objective of the present paper is to introduce a QoS aware routing metric that determines a reliable forwarding node based on Link Stability cost Function (LSF). The principle theme underlying our protocol is optimum contention count that can be estimated with the help of received signal strength. Our proposed protocol has been demonstrated on an existing mesh-based Multicast routing protocols, ODMRP. Simulations are carried out on Exata/Cyber simulator, and obtained results are compared with that of ODMRP. The comparative analysis reveals that our protocol is more efficient in contrast to ODMRP, LSMRP and MMRNS, regarding performance parameters like PDR, latency and route lifetime.

Modeling aeronautical data traffic demand

Abstract: Determining the amount of air traffic in an area can help to identify the traffic demands of current and future airborne communication systems. Many mobility models for pedestrians and road vehicles exist, but hardly any for aircraft. Aircraft traces for three exemplary scenarios are analyzed to derive such a model with regard to traffic demand in a certain area, e.g. a cell. The number of aircraft inside the area is considered as state space of a Markov Process. For each state the arrival and departure process is fitted according to the hypothesis to follow a Poisson distribution. The goodness of fit is evaluated by Chi-Squared testing. Results considering all aircraft show predominant Poissonian behavior for areas with low aircraft density and little take-off and landing activities due to airports. In an urban area with high aircraft density and several airports the Chi-Squared Test often rejects the hypotheses. In a second step the problem was limited to only analyze transit traffic since take-off and landing seem to follow a different statistical behavior. The number of states where the Chi-Squared Test passes increases significantly for the scenarios with high aircraft densities. This work shows that aircraft arrivals and departures can be modeled as a Markov Process with state-dependent arrival and departure rates λ(i) and μ(i).

Machine-to-machine communications over the Internet of Things: Private Wi-Fi access prospects

Abstract: Machine-to-machine (M2M) applications are expected to be the main traffic contributors through the Internet of Things (IoT) paradigm. One of the most prevalent communication access technologies is Wi-Fi. While open Wi-Fi hotspots can be easily used by M2M communications of static or mobile devices, this is not the case for private Wi-Fi installations that are normally secured against unauthorized access. In this study, we explore the possibility of enabling machine type communication devices (MTCDs) for Internet access through private Wi-Fi networks. We discuss the system architecture, main functional elements and the possibility for compensating network owners for such access.

QoE optimization of ON/OFF video streaming strategy in wireless networks

Abstract: Video traffic constitutes the majority of traffic in bytes that mobile and fixed line operators deliver to their customer. This type of traffic is both resource consuming and QoE sensitive. A third characteristics is that user abandon, in a lot of cases, viewing prematurely. Several strategies have been devised to account for all those dimensions. Dominant approaches are fast-caching where the server pushes traffic as fast as possible to the client and on-off strategies where the client forces the server to pause the transfer regularly. In this paper, we take a mobile operator perspective and focus on the QoE when using fast-caching or on-off strategies. We develop an analytical model which takes into account user's dynamics and allows us to derive the probability of starvation (frozen video) that the client may experience. We show that the probability of starvation of the end user is equivalent under the fast-caching and on-off strategies and we explore the trade-off between two dimensions of QoE in the on-off case: the initial startup delay and the starvation probability.

Reliability assessment of wireless sensor network deployments

Abstract: Evaluating the reliability of Wireless Sensor Networks (WSNs) is of great importance especially for WSNs designed for mission-critical applications. In this paper, we propose a novel reliability metric for WSNs. Unlike existing metrics in the literature, the proposed metric takes into account both aspects of WSN functionality, namely, coverage and connectivity. In addition, it does not assume a specific configuration of the WSN deployment and it is valid for heterogeneous deployments. The proposed metric is based on the practical assumption that Sensor Nodes (SNs) are subject to two distinct types of random failures: sensor failure and transceiver failure. Based on this assumption, SNs are modeled as three-mode (on, relay and off) systems instead of the conventional two-mode (on and off) model adopted in the existing metrics. Results show the significance of using the proposed metric on the accuracy of reliability assessment as compared to an existing metric which uses the two-mode SN model. Results also show that for real-world WSN deployments, which are usually cost-optimized, the lower bound of the proposed metric can be used as a reasonable approximation for the exact value of reliability at only a fraction of its computation cost.

How to wake up an access point

Abstract: The significant growth in the number of access points deployed in WLAN stimulates research efforts to focus on finding solutions to reduce the power consumed by their components. One promising approach is to put the access points (or at least its radio interface) into sleep mode when no activity is detected on the channel. In this paper we designed and implemented a measurement platform which can automatically send repeated sleep/wake up request to an access point, and measure the energy it consumes in each state. We define and conduct several experiments to evaluate four different techniques to control and manage the sleep/wake up procedure of an access point. We compare their performance in terms of the time needed to complete the wake up, the energy consumed, and the changes, if any, needed in the mobile terminals.

Massive M2M deployments: LTE attachment prospects

Abstract: Machine-to-Machine (M2M) communications are expected to be the main contributor of traffic over the Internet by the time frame of the launch of 5G. Wireless access via a cellular infrastructure is expected to be the main M2M traffic passage into the Internet. Long Term Evolution (LTE) is the main cellular technology for 5G. The method by which user devices are normally allowed to attach to an LTE network is not practical for the mostly simple M2M devices that maybe deployed in large numbers. We therefore explore the prospects of attaching M2M devices to LTE especially in the cases of massive deployments.