Károly Lendvai

Optimized packet size for energy efficient delay-tolerant sensor networks

In wireless smart metering optimization for energy efficiency is indispensable, because in case of systems without external power supply, battery life is a key factor regarding the usability of the whole system. Sensor networks are less sensitive for delay, this is why aggregation of packets is possible. The aim of this paper is to determine analytically the amount of meter records to aggregate in one packet, regarding the SNR which characterizes the quality of the channel, so that the energy usage is optimal. The introduced formulas, help determining scheduling parameters in wireless smart metering systems. The calculations are presented on a real world scenario and system using GFSK modulation.

Service Mediation in multihop Bluetooth Low Energy networks based on NDN approach

The 4.1 version of Bluetooth Low Energy (BLE) specification introduced the support of scatternet topology. As a result, the range limit of the technology is no more present, which enables the creation of extensive, and complex network applications. However the modifications were done only in the lower layers, leaving the Attribute Protocol (ATT), and the Generic Attribute Profile (GATT) layers untouched, which is a significant drawback in the development of multihop network applications. In this paper the concept of Service Mediation is introduced, that is based on Named Data Networking (NDN) approach, and not only holds the solution of this problem within, but also shows great potential to create intelligent, automatic and teachable networks and applications. The experimental development and the preliminary validation tests showed satisfactory results also, which enables the approach to be used in real-world environments.

Radio Propagation Modeling on 433 MHz

In wireless network design and positioning it is essential to use radio propagation models for the applied frequency and environment. There are many propagation models available for both indoor and outdoor environments; however, they are not applicable for 433 MHz ISM frequency, which is perfectly suitable for smart metering and sensor networking applications.

Precise Location Prediction Algorithms Using Improved Random Walk-based and Generalized Markovian Mobility Models

As in recent 3G UMTS networks the number of users is increasing dynamically and the packet-switched data transfer become dominant, the network providers and operators face the increasing complexity of the network management and operation tasks.

Accurate mobility modeling and location prediction based on pattern analysis of handover series in mobile networks

The efficient dimensioning of cellular wireless access networks depends highly on the accuracy of the underlying mathematical models of user distribution and traffic estimations. The optimal placement/deployment of e.g. UMTS, IEEE 802.16 WiMAX base stations or IEEE 802.11 WLAN access points is based on user distribution and traffic characteristics in the service area. In this paper we focus on the tradeoff between the accuracy and the complexity of the mathematical models used to describe user movements in the network. We propose a novel Markov chain based model capable of utilizing users movement history thus providing more accurate results than other models in the literature. The new model is applicable in real-life scenarios, because it relies on information effectively available in cellular networks (e.g. handover history). The complexity of the proposed model is analyzed, and the accuracy is justified by means of simulation.

Research on Payload Aggregation of Packets in WSNs

Creating wireless sensor networks requires a different approach than traditional communication networks because energy efficiency plays a key role in sensor networks, which consist of devices without external power. The amount of energy used determines the lifetime of these devices. In most cases data packets are less sensitive to delay, thus can be aggregated, making it possible to gather more useful information reducing the energy required to transmit information. This article discusses the energy efficiency of different Forward Error Correction algorithms and presents a method to calculate the optimal amount of aggregation of the data packets in terms of power consumption, while taking into account the Bit Error Rate characteristics of the wireless channel. The contribution of this paper is a general method to improve the energy efficiency of wireless sensor networks by using the optimal amount of aggregation in case of different FEC codes and channel characteristics. The presented results can be applied to any packet-based wireless protocol.

Ring Based Call Admission Control Scheme for Future Mobile Networks

The bandwidth of cellular mobile systems is remarkably growing with emerging new network technologies. LTE is a key step towards future high speed cellular networks, but large bandwidth on its own does not fulfill the QoS requirements of real- time multimedia connections. It is more important to guarantee the amount of network resources required by real-time VoIP and video connections. In this paper, we introduce a Ring based Call Admission Control (CAC) Scheme which enables the prediction of the future position of the users thus enhancing CAC decisions. We examined the required number of rings for optimal prediction using analytical methods. Furthermore we present a vector based extension of the newly proposed algorithm.