Javier Poncela

Wireless Underwater Communications

The depths of the oceans have a high potential for future industrial development and applications. Robotic autonomous systems will greatly depend on a reliable communications channel with operators and equipment either performing joint operations or on the surface. However, communications must face harsh conditions that hinder the performance. Neither electromagnetic nor optical technologies are suitable for communication because of their short range in this medium. Due to this, acoustic equipment is envisaged as the most appropriate technology, even though it suffers several negative effects such as strong attenuation at high (ultrasonic) frequencies, Doppler shifts and a time-varying multipath. In this paper, we describe the characteristics of the acoustic underwater channel and how it impacts the mechanisms at the link and network layers.

Quality Assessment in 3G/4G Wireless Networks

The convergence of wireless networks and multimedia communications, linked to the swift development of services and the increasing competition, has caused user expectations of network quality to raise. Network quality has become one of the main targets for the network optimization and maintenance departments. Quality of experience (QoE) has been traditionally assessed via subjective tests, but this is a costly method. In recent years, different methods for assessing QoE from objective parameters have been proposed. In this paper we describe a non-intrusive system for the analysis and measurement of QoE in wireless networks from these objective parameters. The system consists of mobile agents running on the mobile terminals and one or more network entities that collect and analyze the information.

Implementation of UMTS protocol layers for the radio access interface

SDL has been promoted by ITU as the design language for communication systems. The technology and tools have improved and SDL has been adopted by most manufacturers and integrated in their prototype and product lines. In this paper we describe an implementation of UMTS elements using this formal language. First, basic UMTS concepts are introduced. Next, we present some SDL limitations that have affected design decisions and the available solutions provided by SDL-2000. Afterwards, the high level design is shown, together with a description of the main aspects of the implementation and tests performed on the system. Finally, conclusions are presented.

M2M Challenges and Opportunities in 4G

Abstract4G technology includes a profile for M2M communications in order to improve the efficiency of the foreseeable connection of hundreds of devices to the broadband wireless networks. These devices impose different requirements to those of human communications, most significantly their bursty nature and the small payload usually associated with each transmission. Due to this, typical signalling procedures overload the network causing a very low efficiency for these communications. This paper is a review of current literature, commenting on challenges that LTE technology must overcome to be a true opportunity for M2M devices.

Subjective Quality Assessment of Underwater Video for Scientific Applications

Underwater video services could be a key application in the better scientific knowledge of the vast oceanic resources in our planet. However, limitations in the capacity of current available technology for underwater networks (UWSNs) raise the question of the feasibility of these services. When transmitting video, the main constraints are the limited bandwidth and the high propagation delays. At the same time the service performance depends on the needs of the target group. This paper considers the problems of estimations for the Mean Opinion Score (a standard quality measure) in UWSNs based on objective methods and addresses the topic of quality assessment in potential underwater video services from a subjective point of view. The experimental design and the results of a test planned according standardized psychometric methods are presented. The subjects used in the quality assessment test were ocean scientists. Video sequences were recorded in actual exploration expeditions and were processed to simulate conditions similar to those that might be found in UWSNs. Our experimental results show how videos are considered to be useful for scientific purposes even in very low bitrate conditions.

Impact Analysis of Renewable Energy in National Grids for Energy Deficit Countries

For countries like Pakistan where demand of energy is being increased every year, the design of a framework that analyzes the impact of adding renewable energy to the power grid is of high interest. Such analysis may help ensure a reliable energy supply, and identify energy savings opportunities. Appropriate simulation tools are needed in order to discover the best approach. Such impact analysis also results in cost-effective generation and, further, in environmental improvements. In this paper, one analysis frame work is proposed. The main objective of this study is to propose a framework that helps optimize development and implementation of renewable energy resources focusing on their probable advantages to improve both the electricity system and the environment. The results of this analysis will be helpful in determining the performance issues related to generation, transmission and green technology. Prime locations inside system may be identified where adequate renewable generation may efficiently address transmission crisis.

An Analysis of Mobile IPv6 Signaling Load in Next Generation Mobile Networks

To date, mobile communication has been dominated by voice services. This is likely to be valid also for the foreseeable future, but at the same time a multitude of data services are also emerging. This trend in mobile communication has fueled the introduction of packet-switched mobile networks, thus introducing the IP suite into the field of mobile communications. This technological shift can be already observed in today’s 2.5 and 3G networks. In the first phases, however, mobile devices have an IP point of attachment which seldom changes throughout the lifetime of a communication session. Mobility management is handled below this point of attachment by means of access-specific mechanisms. A unified mobility management mechanism at the IP layer may enable streamlined network architectures, for example as complementary access technologies emerge in next generation mobile networks. Mobile IPv6 represents a key candidate mechanism to fulfill this vision of unified IP-based mobile communication networks. This paper analyses and quantifies the signaling overheads in a mobile communication network that uses Mobile IPv6 for mobility management.

Network Performance Testing System Integrating Models for Automatic QoE Evaluation of Popular Services: YouTube and Facebook

Smartphones have significantly changed the traffic pattern usage of mobile subscribers. In addition to the classical file sharing and web browsing usage, social networking applications and access to video content are now a significant percentage of the typical user data traffic consumption. As the change in usage pattern affects the performance of mobile networks, operators need methods to estimate how well the network behaves. The metrics to use for the evaluation of the quality of experience (QoE) are only well documented for traditional applications. In this paper a novel QoE system that automatically captures and processes the metrics needed to evaluate two commonly used applications, the social networking application Facebook and the video download application YouTube, is presented. The system uses a test application developed for Android phones, which report the results to a centralized platform capable of processing and presenting the results in different formats. The system has been used to test those two services over 3G/LTE network technologies. In the case of the YouTube services, performance results show a subjective score very similar for the 3G and LTE because of the automatic adaptation of the video coding rate to the network conditions. Testing of the Facebook application has led to the proposal of a new MOS expression that takes into account the content type being posted, which provides more reasonable MOS estimations than the generic web browsing models available in the literature and commonly used to estimate Facebook QoE.

A Testbed for Evaluating Video Streaming Services in LTE

With the deployment of the first commercial long term evolution (LTE) networks, mobile operators need to understand how quality of service (QoS) network indicators and codec parameters affect subjective quality in video streaming services as perceived by customers. In this paper, the development of a testbed for evaluating the quality of experience (QoE) of 3D video streaming service over LTE is described. The proposed system consists of three elements: a streaming server, an internet protocol-level mobile network emulator, based on NetEm tool, and a streaming client. The main contribution of this testbed is the modification of NetEm code to model the impact of time correlation between packet arrivals on the packet delay in a video stream. In the testbed, different network conditions are configured by setting network emulator parameters based on the results obtained by a system-level LTE simulator. Results show how average network load and user position inside a cell have a strong impact on the QoS and QoE perceived by the end video user.

Optimal Fair Scheduling in S-TDMA Sensor Networks for Monitoring River Plumes

Underwater wireless sensor networks (UWSNs) are a promising technology to provide oceanographers with environmental data in real time. Suitable network topologies to monitor estuaries are formed by strings coming together to a sink node. This network may be understood as an oriented graph. A number of MAC techniques can be used in UWSNs, but Spatial-TDMA is preferred for fixed networks. In this paper, a scheduling procedure to obtain the optimal fair frame is presented, under ideal conditions of synchronization and transmission errors. The main objective is to find the theoretical maximum throughput by overlapping the transmissions of the nodes while keeping a balanced received data rate from each sensor, regardless of its location in the network. The procedure searches for all cliques of the compatibility matrix of the network graph and solves a Multiple-Vector Bin Packing (MVBP) problem. This work addresses the optimization problem and provides analytical and numerical results for both the minimum frame length and the maximum achievable throughput.