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In mobile communication environments, traditional routing protocols designed for static wireless sensor networks may fail to deliver data timely. The aim of this work is to identify improvements that can be obtained considering mobility and to recognize its research challenges. We briefly describe different levels of mobility in wireless sensor networks (WSNs) and highlight the efficiency of routing...
Interference and delay are considered as the main reasons limiting the capacity and increasing the new call blocking probability in the cellular systems. The Probability of handover failure is considered a common criterion for performance evaluation of handovers in cellular systems. In this paper we discuss and analyze cognitive radio handover managements based on social agent technology in cellular...
In delay- and disruption-tolerant wireless communication networks, capacity is commonly traded off for delay. That is the case of spatial intermittent connectivity (SIC) networks. SIC networks are designed to provide high data rates to mobile nodes in small disjoint geographical areas. However, because of userspsila mobility, these high data rates come at the expense of significant connectivity delay...
Seamless IP mobility protocols like Fast Mobile IPv6 (FMIPv6) requires the knowledge of candidate access routers, to which the mobile node will hand over its connection to, well in advance while the mobile node is still connected to its current AR. The candidate access router discovery (CARD) protocol is one such protocol that provides the identity and capabilities information of the candidate access...
This paper presents an accuracy enhancement solution to mobilepsilas location and tracking systems in indoor wireless local area network (WLAN) environments. The enhancement method consists of the Kalman filtering application to an artificial neural network (ANN) based fingerprinting location technique. The application of Kalman filtering has the advantage of using information about the mobilepsilas...
Future generations of mobile operator networks, based on an all-IP-based flat architecture and a multitude of different access technologies, require a proper IP-based mobility management in place. In this article, a scalable and completely distributed mobility management is presented which is based on a Distributed Hash Table data structure. The Distributed IP Mobility Approach (DIMA) remains completely...
The distance measurements are biased for various reasons in location systems, e.g. non-line-of-sight path, propagation speed, and sensor calibration error. The impact of measurement biases is investigated in the time of arrival (TOA) systems and time difference of arrival (TDOA) systems. The TDOA estimator is robust to biases when measurements bias their true values toward the same direction, either...
The current computing and communication services are driven by various technologies. The creation of such services is however not an easy task. The different platforms lack openness that simplifies interoperability. Service development is still mainly technical oriented, where service creation tools are meant for serving and assisting the professional developers. Service creation is not seen as a...
PESQ is the international standard for objective speech quality measurement and has been widely used in industry for voice quality assessment for VoIP products and systems. However, current research efforts involving PESQ are mainly focused on simulated IP networks. The need remains to establish how accurate PESQ is when used in real wireless systems, especially in new wireless VoIP environment. The...
From a network perspective, the major challenge in providing seamless connectivity whilst maintaining the required level of QoS to users results from the negative interactions that occur between mobility and QoS. These interactions, particularly those of mobility and QoS, have been the subject of much research. In this paper, we discuss the various approaches that have already been taken to combine...
The introduction of the upcoming GERAN evolution feature package in current GSM/EDGE deployments offers operators significant boost in network capacity and mobile data users UMTS/HSPA like high speed packet data services along with competitive latency. Intelligent radio resource management supports novel dual-carrier capable mobile stations by dynamic configuration of GPRS/EDGE packet data channels...
This paper targets mobile streaming in which Series 60 smart phones are the stream creators and PC-s are the stream consumers. The aim is to provide experimental data reflecting under which conditions video streaming from smart phones is feasible and whether duplex interactive video between a phone and a PC can be achieved or not. Phones used corporate WiFi and UMTS, PC-s were on the corporate Intranet...
As a radio access technology for next generation cellular networks, 3GPP and 3GPP2 are standardizing long term evolution (LTE) and ultra mobile broadband (UMB), respectively. In this paper, we compare the handover schemes of both technologies in three aspects, i.e., interruption time of a user plane, required wireless resources and the overhead for avoiding packet reordering. The comparison results...
The wideband channel measurements at 580 MHz, 2.35 GHz and 4.90 GHz have been performed in the urban micro- and macrocell scenarios in the cities of China with multiple-input multiple-output (MIMO) channel sounder. The measured cases include line-of-sight (LOS) and non-line-of-sight (NLOS) propagation. Statistical results and comparative analysis for both scenarios are presented in this paper, including...
This paper introduces interference cartography, a simple and effective concept that helps detect, identify and use spectrum opportunities in a secondary spectrum usage context. Interference cartography combines measurements performed by different network entities (mobile terminals, base stations, access points) with the geo-location information and applies simple and effective spatial interpolation...
The problem of tandem vocoders and their effect on voice quality is well-known. In the case of international mobile-to-mobile calls, there can be up to three vocoding stages - between each mobile and its base station controller, as well as a digital circuit multiplication equipment (DCME) or voice over IP (VoIP) stages on the international link. The ITU standards for 2G and 3G networks define the...
The use of licensed spectrum for wireless communication is driven by the need to control interference between different operators. However, with this mode of regulation, spectrum utilization is far from efficient and the growth of wireless networks is hindered by the shortage of free frequency bands and the vast investments for the acquisition of a license. In view of this situation, we present an...
Anonymity in telecommunication services means much more than protecting the identity of participants. It requires mechanisms and protocols that unlink the communication parties, unlink users from their location, and avoid statistical analysis. These functional requirements apply also when providing anonymity services to SIP, whereas the identities of caller and the callee(s) should be secured. On...
This paper proposes a user-centric access point selection scheme to minimize the number of unnecessary reconfigurations of cognitive terminal. In this scheme, number of terminal reconfigurations is defined based on the dwell-time of terminal which is estimated from userpsilas mobility and coverage area of the access point (AP). Each terminal selects one AP from a candidate list that is generated based...
A simple technique to estimate the position of a mobile node inside a building is based on the Received Signal Strength (RSS). In previous publications, we investigated the effectiveness of using circular array antennas and beamforming in order to enable an access point to estimate the position of a mobile inside a building. We also discussed the feasibility of using model-based radio maps to reduce...
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