Dejan Drajic

Adaptive Fusion of Multimodal Surveillance Image Sequences in Visual Sensor Networks

In this paper we present a novel method of fusing of the sequences of images obtained from multimodal surveillance cameras and subject to distortions typical for visual sensor networks environment. The proposed fusion method uses the structural similarity measure (SSIM) to measure a level of noise in regions of a received image in order to optimize the selection of regions in the fused image. The region-based image fusion algorithm using the dual-tree complex wavelet transform (DT-CWT) is used to fuse the selected regions. The performance of the proposed method was extensively tested for a number of multimodal surveillance image sequences and proposed method outperformed the state-of-the-art algorithms, increasing significantly the quality of the fused image, both visually and in terms of the Petrovic image fusion metric.

Traffic generation application for simulating online games and M2M applications via wireless networks

In this paper we present results of traffic modeling and simulation of multiplayer real-time games and M2M applications using TCP protocol over Telekom Serbia HSPA mobile network, performed within the FP7 LOLA project. In this experimentation, the RTT (Round Trip Time) and cell statistics are analysed. For this purpose, a traffic generation application is developed for Android phones to generate traffic pattern for emerging Machine Type Communication and online multiplayer games in mobile wireless network for different offset of tests. Application is activated by setting the corresponding parameters related to desired test case, i.e. duration of testing, size and frequency of the data packets that the application sends to the server. The main goal of the cell statistic analysis is to evaluate potential impact of additional simulated traffic in view of increasing data-centric users on the performance of mobile wireless radio network.

M2M device management in LTE networks

The driving concept of device management in M2M systems is establishment of a comprehensive end-to-end resource oriented design. In this paper, OMA-DM protocol for device management of M2M devices in 3GPP LTE networks is proposed and discussed. The OMA-DM represents a stable starting point for device management. Utilization of this protocol in M2M requires efficient message formats and transport replacement such as CoAP, Core Link Format, EXI, etc. The additional wake up mechanisms should also be considered for managing the stand by policies.

Application-layer security mechanism for M2M communication over SMS

With an increasing number of M2M devices communicating over SMS, the need for security was raised because standard SMS messaging service does not provide any light-weight security mechanisms. In this paper we propose hybrid application-layer security with compression for M2M communication over SMS. The signature is calculated using device IMEI, secret key and payload; thus signature is not always the same, which prevents duplicated/stolen signature and replay attack and it provides a content integrity check. The security is implemented on android powered mobile devices and evaluated against non-secure payload for message response time and bandwidth in live GSM network. Evaluation shows that SMS delivery time is not influenced by this security mechanism. In addition compression can save bandwidth for more verbose and longer payloads.

CoAP over SMS: Performance evaluation for machine to machine communication

M2M devices can be deployed at various, often not easy to access locations like rural areas, high on the buildings or on moving vehicles. Mobile networks provide connectivity to such devices over the existing infrastructure. This paper presents an implementation and evaluation of the SMS for M2M communication by utilizing CoAP message semantics. The CoAP is a high-layer protocol that strives to become a standardized solution for M2M communication, and as such is interesting for related activities. The evaluation of regular, concatenated and multicast SMS transport shows that increased SMS traffic can lead to longer delivery time. This may not be a concern for M2M devices that are usually sensors with long sleeping cycles; but for other M2M scenarios that requires higher throughput, higher data rates can be achieved by agreeing over specific SLA with Service Provider.

Impact of Online Games and M2M Applications Traffic on Performance of HSPA Radio Access Networks

In this paper we presented results of the performance evaluation of the WCDMA/HSPA radio access network when loaded with multiplayer real-time games and M2M applications traffic. Evaluation was done in a live network, on one Node B. Traffic, characteristic for the emerging Machine Type Communication and online multiplayer games, was generated by an application running on 10 mobile phones in parallel, all connected to the Node B under test. The focus of the work was on the RTT (Round Trip Time) and radio cell statistics. The main goal of the cell statistics analysis was to evaluate potential impact of the additional traffic on the performance of 3G/HSPA radio access network. It is concluded that system is designed more for continuous traffic patterns with high data rate in general, than for sporadic traffic patterns with very low data rate, like that of M2M or online gaming nodes. Therefore, the cost of signaling and control activity is dominant in comparison to the data rate.

Evaluation of the UTRAN HSPA performance in different configurations in the presence of M2M and online gaming traffic

In this paper, performance analysis of a High Speed Packet Access network in the presence of machine-to-machine M2M and online gaming traffic is described. The evaluation was performed in a live network, using a number of mobile phones to generate additional traffic load. One Node B, with different configurations, was used throughout the experiments. The main areas of impact are identified, and similar underlying mechanisms are later recognised through deployment of a commercial large-scale M2M application. The paper describes the key findings of the analysis of five test cases from the network performance aspect. It further associates perceived network behaviour with the end-user experience in terms of the average delays. At the end, a comparison with the observed impacts of a live M2M application is given, and the main issues highlighted, together with a discussion on possible solutions. Copyright

Turbo Coding with Equalization in WCDMA Downlink

In this paper, the performance of turbo coding in WCDMA downlink is considered in conjunction with receivers using two adaptive channel equalizers. Bit error and frame error rates are compared to the performance of the conventional Rake receiver. Special consideration is given to the cases with two receive antennas, the efficiency of the channel interleaver, the number of iterations in decoding, the performance with various numbers of users, the influence of mobile receiver velocity as well as to the effect of power control. The simulation results show that turbo coding, combined with power control and channel equalizers is a very efficient way to implement reliable data transmissions in WCDMA downlink. The results in the paper also verify that the adaptive channel equalizers is a very promising technique to improve the receiver performance and increase the user capacity.

Evaluation of an XML database based Resource Directory performance

In this paper, an implementation of a Resource Directory, a directory storing descriptions of resources available in an Internet of Things system, based on a native XML database is described. Its performance is compared with performance of a Resource Directory with the same functionality, but implemented using a relational, SQL database. The evaluation results show hat the XML based Resource Directory provides more flexible management of the resources and shorter response time.

On the number of iterations for turbo-coding in 'downlink WCDMA using chip-level

In this paper, some results of an extensive simulation study concerning the efficiency of turbo coding in downlink WCDMA receivers using two type of chip level equalizers - one common pilot channel-trained, the other prefilter-RAKE - are presented. Their performances are compared to the performances of the conventional RAKE receiver under various scenarios. Special consideration is given to the number of iterations needed for an efficient turbo decoding.