Immersive Virtual Reality (VR) and Volumetric Video (VV) technologies enable highly realistic and interactive experiences but impose significant computational and bandwidth demands. This paper presents a comprehensive end-to-end architecture, along associated technological components and workflows specifically designed to support these advanced services and experiences on lightweight devices like smartphones and even standalone VR headsets via Remote Rendering. By offloading demanding processing tasks to a Remote Renderer, the proposed architecture is able to interactively provide low-latency rendered streams from complex VR scenes including live VV feeds (e.g., holoported users), enabling seamless participation via browser-based thin clients. The proposed framework includes the exploration of advanced stereoscopic delivery strategies, supporting viewport-aware projections to concentrate visual quality within the user’s Field of View (FoV) while enabling seamless exploration with reduced bandwidth overhead. Furthermore, it incorporates 6 Degrees of Freedom (6DoF) capabilities and diverse interaction features from the thin clients. Preliminary evaluations demonstrate promising latency outcomes, achieving end-to-end latency levels under 40ms in local scenarios and motion-to-photon latency levels around 180 ms over the Internet, as well as system stability regardless of VR scene complexity. Ultimately, this work proposes a robust foundation for democratizing premium VR experiences, actively supporting versatile one-to-many delivery scenarios.

Smart factories enhance production efficiency and sustainability, but emergencies like human errors, machinery failures and natural disasters pose significant risks. In critical situations, such as fires or earthquakes, collaborative robots can assist first-responders by entering damaged buildings and locating missing persons, mitigating potential losses. Unlike previous solutions that overlook the critical aspect of energy management, in this paper we propose REACT, a smart energy-aware orchestrator that optimizes the exploration phase, ensuring prolonged operational time and effective area coverage. Our solution leverages a fleet of collaborative robots equipped with advanced sensors and communication capabilities to explore and navigate unknown indoor environments, such as smart factories affected by fires or earthquakes, with high density of obstacles. By leveraging real-time data exchange and cooperative algorithms, the robots dynamically adjust their paths, minimize redundant movements and reduce energy consumption. Extensive simulations confirm that our approach significantly improves the efficiency and reliability of search and rescue missions in complex indoor environments, improving the exploration rate by 10% over existing methods and reaching a map coverage of 97% under time critical operations, up to nearly 100% under relaxed time constraint.

Visible light communication (VLC) based on an optical camera system is a promising technology for indoor IoT applications. It offers advantages such as reduced interference and improved performance but also suffers from limited data rate transmission due to the fixed capture rate of an image sensor. This study aims to address this limitation by integrating multiple low-cost CMOS sensors with precise synchronization to receive successive data bits. The paper presents the design of a cost-effective functional prototype implementation of a multi-spatial receiver consisting of multiple image sensors capable to provide a continuous data rate of 500 bps with a theoretical aggregated receive rate of 1.6 Mbps. The system performance is evaluated under varying indoor lighting conditions and distances. The proposed system demonstrates its effectiveness for indoor IoT optical communications. Furthermore, the use of several cameras makes it feasible to provide location capabilities without requiring additional hardware or complex algorithms.

This paper reports on the research being done towards enabling and understanding interactive social VR360 video viewing scenarios, by exclusively relying on web-based technologies, and using different types of consumption devices. After motivating the relevance of the research topic and associated impact, the paper elaborates on key requirements, features, and system components to effectively enable such scenarios, such as: adaptive and low-latency streaming, media synchronization, social presence, interaction channels, and assistive methods. For each of these features and components, different alternatives are assessed and proof of concept implementations are being provided. With an effective combination and integration of all these contributions, an end-to-end platform can be built and used as a research framework to explore the applicability and potential benefits of social VR360viewing in a variety of use cases, like education, culture or surveillance, by tailoring the technological components based on lessons learned from experimental studies. These use case studies can also provide relevant insights into activity patterns, behaviors, and preferences in Social Viewing scenarios.

The production and consumption of multimedia content is continuously increasing, and this particularly affects to immersive formats, like VR360 video. Even though significant advances have been witnessed with regard to the processing, delivery and consumption of interactive VR360 video, key challenges and research questions still need to be addressed to efficiently provide interactive multi-camera and multi-user VR360 video services over distributed and heterogeneous environments. This research work aims at providing novel and efficient contributions to overcome existing limitations in this topic. First, it will develop an end-to-end modular web-based VR360 video platform, including the measurement of Quality of Service (QoS) and activity metrics, to be used as a research testbed. Second, it will provide lightweight yet efficient viewport-aware video processing and delivery strategies to dynamically concentrate the video resolution on the user’s viewport, with a single stream and decoding process through the web browser. Third, it will propose innovative encoding, signaling and synchronization solutions to enable an effective support for multi-camera and multi-device VR360 services, in a synchronized manner and with the lowest latency possible. Fourth, it will explore how to effectively provide social viewing scenarios between remote users while watching the same or related VR360 videos, assisted with interactive and guiding techniques.

Novel demands from Earth Observation community have emerged due to current climate situation. These needs are mainly oriented on monitoring hydric stress, climate disasters, among others. These applications require satellite systems capable to provide high frequency and sub-metric spatial resolution observations. An hybrid architecture which combines in-space with in-situ measurements emerges as a potential approach. In this scenario, ground sensor devices autonomously perform in-situ measurements with different spatial and temporal resolutions different from satellite ones. These devices must manage their constrained resources and transfer the generated data. The Direct-to-Satellite Internet of Things paradigm proposes the interconnection of Low Earth Orbit satellites with these devices using standardized protocols. This work presents a proof-of-concept that demonstrates the benefits for Earth Observation applications. Specifically, a sensor system is developed to monitor the soil moisture, and installed in a remote location to perform a measurement campaign. The results demonstrate the feasibility of this hybrid architecture.

This paper contains the research proposal of Miguel Fernández Dasí that was presented at the MMSys 2022 doctoral symposium.1 The production and consumption of multimedia content is continuously increasing, and this particularly affects to immersive formats, like VR360 video. Even though significant advances have been witnessed with regard to the processing, delivery and consumption of interactive VR360 video, key challenges and research questions still need to be addressed to efficiently provide multi-camera and multi-user VR360 video services over distributed and heterogeneous environments. This research work aims at providing novel and efficient contributions to overcome existing limitations in this topic. First, it will develop an end-to-end modular VR360 video platform, including the measurement of Quality of Service (QoS) and activity metrics, to be used as a research testbed. Second, it will provide web-compliant viewport-aware video processing and delivery strategies to dynamically concentrate the video resolution on the users' viewport, with a single stream and decoding process through the web browser. Third, it will propose innovative encoding, signaling and synchronization solutions to enable an effective support for multi-camera VR360 services, with personalized, fast and in-sync switching features. Fourth, it will explore how to effectively provide social viewing scenarios between remote users while watching the same or related VR360 videos. The work also plans to contribute with low-latency delivery pipelines as well as with tools and algorithms to assess and model the Quality of Experience (QoE).

The use of Visible Light Communication (VLC) in wake-up communication systems is a potential energy-efficient and low-cost solution for wireless communication of consumer electronics. In this paper, we go one step further and propose the use of visible light both for wake-up communication and energy harvesting purposes, with the final objective of an energy-autonomous wake-up receiver module. We first present the details and the design criteria of this novel system. We then present the results of evaluation of design criteria such as solar panel and capacitor type choices. To evaluate the performance of the developed wake-up system with energy-autonomous receiver system, we perform realistic indoor scenario tests, analyzing the effect of varying distances, angles, and light intensities as well as the effect of presence of interfering lights.

Duty-cycled Medium Access Control (MAC) protocols certainly improve the energy efficiency of wireless networks. However, most of these protocols still suffer from severe degrees of overhearing and idle listening. These two issues prevent optimum energy usage, a crucial aspect in energy-constrained wireless networks such as wireless sensor networks (WSNs). Wake-up radio (WuR) systems drastically reduce these problems by completely switching off the nodes' microcontroller unit (MCU) and main radio transceiver until a secondary, extremely low-power receiver is triggered by a particular wireless transmission, the so called wake-up call. Unfortunately, most WuR studies focus on theoretical platforms and/or custom-built simulators. Both these factors reduce the associated usefulness of the obtained results. In this paper, we model and simulate a real, recent, and promising WuR hardware platform developed by the authors. The simulation model uses time and energy consumption values obtained in the laboratory and does not rely on custom-built simulation engines, but rather on the OMNET++ simulator. The performance of the WuR platform is compared to four of the most well-known and widely employed MAC protocols for WSN under three real-world network deployments. The paper demonstrates how the use of our WuR platform presents numerous benefits in several areas, from energy efficiency and latency to packet delivery ratio and applicability, and provides the essential information for serious consideration of switching duty-cycled MAC-based networks to WuR.

In this paper we introduce a novel reliable asynchronous protocol that allows to establish a VLC link between a LED luminary and an off-the- shelf smartphone. Our protocol and decoding algorithms benefit from the access to advanced camera settings available in the latest generations of mobile devices to outperform previous VLC designs in the state of the art. In particular, in the paper we provide an experimental evaluation using a commercial Nexus 5 device where it is shown how our designed prototype can achieve transmission speeds of up to 700 bps and operating distances of up to 3 meters. The previous performance figures have the potential to spark a wide set of novel applications.

One of the most promising energy-efficient communication methods is the use of wake-up receivers. In this paper, we propose and develop a novel wake-up communication system that uses Visible Light Communication (VLC) and an indoor solar panel as the receiver of the wake-up signal. After the reception of the wake-up signal, an interrupt generated by the wake-up receiver wakes up the wireless device attached. Through experiments we show the feasibility of the system and characterize its performances in terms of wake-up probabilities for different distances. We present two configuration options: an addressable and a broadcast-based wake-up configuration. We evaluate the effect of light interferences and show that the achieved wake-up distances under these conditions are reasonable for indoor scenarios.

The development of IPv6 stacks for wireless constrained devices that have limited hardware resources has paved the way for many new areas of applications and protocols. The Constrained Application Protocol (CoAP) has been designed by the IETF to enable the manipulation of resources for constrained devices that are capable of connecting to the Internet. Due to the limited radio channel capacities and hardware resources, congestion is a common phenomenon in networks of constrained devices. CoAP implements a basic congestion control mechanism for the transmission of reliable messages. Alternative CoAP congestion control approaches are a recent topic of interest in the IETF CoRE Working Group. New Internet-Drafts discuss the limitations of the default congestion control mechanisms and propose alternative ones, yet, there have been no studies in the literature that compare the original approach to the alternative ones. In this paper, we target this crucial study and perform evaluations that show how the default and alternative congestion control mechanisms compare to each other. We use the Cooja simulation environment, which is part of the Contiki development toolset, to simulate CoAP within a complete protocol stack that uses IETF protocols for constrained networks. Through simulations of different network topologies and varying traffic loads, we demonstrate how the advanced mechanisms proposed in the drafts perform relative to the basic congestion control mechanism.

The use of duty-cycling in Medium Access Control (MAC) protocols effectively helps improving the energy efficiency of wireless networks. However, while the benefits of these protocols are unquestionable, most of them still suffer from overhearing and idle listening, two issues that prevent duty-cycled systems from achieving optimum energy usage, which is a crucial aspect in specific types of wireless networks such as Wireless Sensor Networks (WSN).Wake-up Radio (WuR) systems have been employed recently to overcome these issues. Under this approach, the nodes' MicroController Unit (MCU) and main radio transceiver are completely switched off and only activated when a secondary, extremely low-power receiver in the node is triggered by a particular wireless transmission. Wake-up Radio systems allow for drastic energy savings since receiver nodes are only activated on-demand, maximizing their battery lifetimes. In this paper, we have modeled and simulated a real, recent and promising WuR hardware platform based on its time and energy consumption characterization. By comparing such WuR approach to B-MAC and IEEE 802.15.4, two well-known and widely employed MAC protocols, we show it effectively out-performs the conventional WSN MAC approaches in terms of energy efficiency. To the best of authors' knowledge, this is the first study to include a comparative analysis for multi-hop networks based on a real WuR platform, which shows WuR systems represent an energy-efficient solution that also provides a good tradeoff between latency, packet delivery ratio and applicability..

Energy-efficient operation is a challenge for wireless sensor networks (WSNs). A common method employed for this purpose is duty-cycled operation, which extends battery lifetime yet incurs several types of energy wastes and challenges. A promising alternative to duty-cycled operation is the use of wake-up radio (WuR), where the main microcontroller unit (MCU) and transceiver, that is, the two most energy-consuming elements, are kept in energy-saving mode until a special signal from another node is received by an attached, secondary, ultra-low power receiver. Next, this so-called wake-up receiver generates an interrupt to activate the receiver node's MCU and, consequently, the main radio. This article presents a complete wake-up radio design that targets simplicity in design for the monetary cost and flexibility concerns, along with a good operation range and very low power consumption. Both the transmitter (WuTx) and the receiver (WuRx) designs are presented with the accompanying physical experiments for several design alternatives. Detailed analysis of the end system is provided in terms of both operational distance (more than 10 m) and current consumption (less than 1 μA). As a reference, a commercial WuR system is analyzed and compared to the presented system by expressing the trade-offs and advantages of both systems.

Wake-up radios present a promising alternative to traditional duty-cycle approaches, by reducing overhearing and by eliminating idle listening completely. However, energy-efficient operation of the wake-up mechanism is required for the success of such systems. In particular, addressing is an important component of the wake-up procedure that can consume a significant portion of the energy required. Hence, in this paper we propose a novel energy-efficient scheme for addressing. The proposed method is called Time-Knocking (TicK), since it utilizes the time duration of the MicroController Unit (MCU) sleeping to encode an address. In this paper, it is shown through mathematical analysis that TicK is much more energy efficient compared to the two common addressing mechanisms: MCU-decoding and correlator-based addressing. For realistic performance evaluations, physical measurements are performed to extract the parameter values of each method or the parameter values from well-documented off-the-shelf devices are used. TicK enables significant energy savings, especially in environments where false addressing initiations are frequent due to interference or where multiple nodes are addressed frequently.

Presence information contains all the context about users, services and devices that applications need to take more proactive and intelligent decisions. SIP/SIMPLE is the de facto framework for initiating, managing and personalizing presence-based communications in the Next-Generation Networks. However, SIMPLE subscription model generates a traffic overload that is restraining mobile operators from implementing advanced presence-based applications. RLS is a widely-adopted optimization of SIMPLE subscription traffic in mobile applications. We analytically measure the presence traffic on the access link between an end-user and the network with and without an RLS. We present the parameters that affect the RLS' performance and give some guidelines when considering whether or not to use an RLS.

Presence information was the key enabler to the great success of instant messaging applications. First, this information was limited to simple binary states such as online, offline or busy. However, this is, currently, evolving towards a much more generic, flexible concept to include all context that allows users or applications to adapt and control communications in a more efficient and personalized manner. Presence paves the way for the deployment of advanced communication services and is therefore a key component in the Next-Generation Networks (NGNs). These networks aim to unify fixed and mobile networks in order to provide users with global connectivity to always-on multimedia services. The main barrier to the implantation of next-generation presence-based services is the great amount of traffic involved in the distribution of presence information across domains. We study two strategies described in IETF drafts and one novel solution for reducing inter-domain presence traffic. We present the analytical formulas that calculate the traffic for the three strategies. Building on the analytical results, we analyze the factors that have impact on these strategies and study the suitability of each one under different conditions.

Wireless sensor networks (WSNs) have gained momentum as a technology for monitoring and control applications in a plethora of scenarios. Some examples include home automation, industrial control and environmental monitoring. In fact, these networks may enable the futuristic paradigm called ambient intelligence. Despite the challenges that present these networks, a variety of solutions (many of which are proprietary) have emerged. In parallel, the Internet Engineering Task Force (IETF) is devoting a lot of effort to the development of standard networking solutions for WSNs based on the Internet Protocol (IP). This work will allow straightforward interoperability between WSNs and the Internet and will also constitute a significant step towards the ‘Internet of Things’.

Abstract As the number of WLAN users grows, the need to perform efficient radio resource management strategies becomes essential due to the fact that most popular technologies, those based on IEEE 802.11 standards, use unlicensed frequency bands. A good channel assignment improves the network performance, producing benefits that are perceived by the users and also by the network administrators. In this paper, we present a new frequency management scheme for IEEE 802.11 WLANs in the 2.4 GHz ISM band that minimizes interference to increase the throughput available to client stations by adapting a weighted DSATUR algorithm for graph coloring. The algorithm takes both co‐channel and adjacent channel interference into account, and makes use of all available channels instead of the traditional non‐overlapping three. In this way, collisions as well as transmission errors are minimized, thus improving the network capacity and the user experience. Different architectures are discussed for the implementation of our approach, including the possibility to incorporate client stations into the management system. Copyright © 2008 John Wiley & Sons, Ltd.

IEEE 802.11 WLANs (Wi-Fi) are widely deployed for providing Internet access in public spaces, known as hot spots. In these scenarios, users tend to be ldquogregariousrdquo and essentially static. Since association and roaming decisions are made by client devices following signal strength criterions (i.e. a client station selects the AP that provides the strongest signal), the users and their load are unevenly distributed between neighboring APs. In this paper we propose a distributed algorithm with which the APs in an IEEE 802.11 WLAN are able to tune their cell size according to their load and also to their neighborpsilas load. This technique improves the fairness and the performance levels and is known as cell breathing.

Next generation mobile networks (NGN) will be based on IPv6. Then, NGNs will require mobility protocols such as MIPv6 and HMIPv6. Also, they should support quality of service by means of technologies such as the integrated services architecture. In this context, a problem to distinguish reservations arises when resource reservations within tunnels are required. The current solution to this problem in the standard IntServ has some disadvantages such as reservations differentiation at the transport layer level. However, a new approach to support QoS over integrated services mobile networks has appeared. It is named IntServ6. This approach resolves the Reservations within Tunnels problem in a natural and simple way by means of the Flow Label field of the IPv6 packet header. Subsequently, it resolves this problem at the network layer level. This paper describes and evaluates such approach to support Reservations within Tunnels. Both QoS technologies, IntServ and IntServ6 are compared. Results show that IntServ6 serves more traffic than IntServ over Simple reservations and reservations within tunnels.

Web download performance is dramatically degraded in UMTS, resulting in perceived throughputs of around 25% of the expected bandwidth even in favorable conditions. We analyze the main factors that lead to this low performance. We then propose end-to-end mechanisms and proxy-based approaches to improve overall performance and maximize link utilization in UMTS. We evaluate these solutions in a real UMTS scenario. The results show an improvement of up to 50% in terms of download time and a saving of around 10% of the exchanged information in UMTS networks with channel switching mechanisms.

Abstract 2.5 Generation (2.5G) and Third Generation (3G) cellular wireless networks allow mobile Internet access with bearers specifically designed for data communications. However, Internet protocols under‐utilize wireless wide area network (WWAN) link resources, mainly due to large round trip times (RTTs) and request‐‐reply protocol patterns. Web browsing is a popular service that suffers significant performance degradation over 2.5G and 3G. In this paper, we review and compare the two main approaches for improving web browsing performance over wireless links: (i) using adequate end‐to‐end parameters and mechanisms and (ii) interposing a performance enhancing proxy (PEP) between the wireless and wired parts. We conclude that PEPs are currently the only feasible way for significantly optimizing web browsing behavior over 2.5G and 3G. In addition, we evaluate the two main current commercial PEPs over live general packet radio service (GPRS) and universal mobile telecommunications system (UMTS) networks. The results show that PEPs can lead to near‐ideal web browsing performance in certain scenarios. Copyright © 2006 John Wiley & Sons, Ltd.

Abstract Session setup delay in Packet Switched Streaming (PSS) services over Third Generation (3G) wireless networks is impacted by Real‐Time Streaming Protocol (RTSP) and Session Description Protocol (SDP) signalling exchange and negotiation, as well as media buffering at the terminal before playback. The paper discusses PSS session setup delay over 3G, and proposes two RTSP and SDP protocol extensions to reduce this delay, namely: RTSP Early Setup and usage of SDP Templates. The rationale behind this proposal is presented, particularly when a Secondary Packed Data Protocol Context (PDP‐Context) is used to support media delivery with Quality of Service (QoS) support. The RTSP Early Setup mechanism facilitates pipelining of RTSP messages and early trigger of Secondary PDP‐Context setup. The SDP Template mechanism proposes using a generic procedure to avoid transmission of frequently used SDP fields. Copyright © 2006 John Wiley & Sons, Ltd.

Since the advent of the first IEEE 802.11 standard, many research efforts have been spent on evaluating different aspects of the specification. In this paper, we present a new method to predict the capacity of a multicell IEEE 802.11 network. The mechanism takes the effect of co-channel and adjacent channel interference into account. In addition, the study of a common rate adaptation algorithm is included. When the effect of rate adaptation is considered within the throughput computation, the results provided by our algorithm are closer to the measurements obtained in a real scenario. To the best of our knowledge, this paper presents the first analytical study of throughput performance including both types of interferences and the effect of bit rate adaptation.

This paper analyzes the effect of multi-rate transmissions in a CSMA wireless LAN environment. Observations in a real testbed\nshowed that bandwidth resources (in Bytes/s) are shared fairly among all stations even though transmissions carried out at lower\nrates capture the medium for longer periods, which drastically reduces the overall throughput. The intrinsic concept of fairness in a CSMA scheme with multiple rates is quantified by means of a new formulation which is validated through simulations and practical measurements. The algorithm presented provides the maximum achievable bandwidth that can be offered to a given IEEE 802.11 station. Having this information has evident applications in realtime multimedia transmissions over WLANs. The algorithm was\nalso run in commercial APs as a proof of concept, after analyzing its implementation issues.

Current growth in the number of IEEE 802.11 wireless LAN networks, whether they be to provide cordless access to private home or enterprise networks, or to provide public access in Hot-Spots, brings the need to apply smart load balancing techniques with the aim to improve network performance. These techniques require the provision of radio measurements from physical and medium access layers. IEEE 802.11k Task Group is currently working on the standardization of new mechanisms to supply the required measurements which will assist in the radio resource management. In this paper we provide a comprehensive survey of different load balancing mechanisms and then, we discuss how the future 802.11k functionalities could be applied to facilitate the implementation of these load balancing techniques in 802.11 WLAN

In this paper, we address the issue of the radio resource allocation in a cellular mobile network. We propose a new method to reach high peak rates which improves the requirements of mobile users. The method consists of managing the available time slots, in order to obtain groups of idle consecutive time slots to allocate them in a sequential order. We develop an analytical closed expression for the probabilities of finding these groups of idle consecutive time slots. The results are useful to a network operator to reconfigure radio resources, fulfilling the quality of service (QoS) requirements to serve both voice and data traffic.

In this paper we introduce a new approach to support QoS on wireless networks. It uses a new solution for QoS support on IPv6 networks named IntServ6 and introduce some extensions to bring resource reservations mobility. Our solution works over hierarchical mobile IPv6 networks. IntServ6 takes advantage of the IPv6 header flow label field to improve the router performance. It also improves the current standard solution for the resource reservation within tunnels for integrated services networks. Evaluation results show that this approach has a better router performance respect to the traditional integrated services solutions for mobile networks

Availability of GPRS and UMTS networks constitutes a significant piece in the path towards a ubiquitous Internet. To ensure continuity of service, handover from UMTS to GPRS (U2G) and vice versa (G2U) is a key feature for mobile operators and user experience. This paper presents an empirical study on the impact of intersystem handover (ISHO) over the TCP/IP protocol suite. Trials include a variety of different conditions, such as two mobile operators' GPRS and UMTS public networks, uplink and downlink data transmissions, as well as indoor and outdoor scenarios. Measurements have been performed at both IP and TCP layers. Results show that significant connectivity gaps, dramatically increased delays and varying amounts of losses take place as a result of ISHO. We describe the harmful effects of such phenomena on TCP.

The IEEE 802.15.4 standard is expected to enable a wide variety of envisaged low-cost control and monitoring applications with relaxed throughput requirements and a strong emphasis on power conservation. A routing protocol is needed for the mesh topology approach, which must take into account the very limited features of the network. In this paper we provide a three-fold contribution. We first review and discuss the main AODV based routing protocol proposals and/or implementations suitable for the quoted environments. Next, we present NST-AODV, a new AODV implementation designed to provide benefits in terms of data delivery latency, network reliability and power consumption, specially in dynamic topology networks. Finally, we evaluate the tradeoffs and most critical features of our solution in a real IEEE 802.15.4 mesh sensor network testbed

Technologies involved in Web information distribution services are evolving to adapt themselves to new user requirements. Usually, these new technologies are used separately. ELIN (electronic newspaper initiative) project is a European Commission funded project that tries to integrate the newest standards and technologies involved in multimedia delivery applied to web newspapers. It has as objective the delivery of any type of media format to any kind of user terminal in an efficient way. In order to do that, it takes the approach of using MPEG standards: MPEG-4 for video delivery, MPEG-7 for data classification and MPEG-21 for data management and adaptation. So it integrates the totality of solutions provided for the MPEG group.

A key element for MANET performance is the routing protocol. Surprisingly, little effort has been devoted up to now to analyzing the impact of routing protocol parameter settings on MANET performance. We define and study in detail the route change latency (RCL) after link failures, a critical performance metric in a non-static ad-hoc scenario, and its dependence on routing protocol parameter settings and implementation issues using OLSR. We experiment with a set of OLSR settings in a real network environment and derive its potential effect in a generic situation, showing that end-to-end connectivity can be enhanced using different parameter settings from the default ones.

This paper proposes an approach to support end-to-end quality of service over IPv6 networks. In our solution, IPv6 flow labels are used to give better performance into the process of packet classification on network routers. In order to evaluate our proposal, a router model is obtained and it is compared with other technologies as IntServ and MPLS. As result, we obtain a solution with benefits of QoS support and label switching in IPv6 routers.

Mobile ad-hoc network (MANET) technology is an essential piece in the path towards ubiquitous networking. In the past, most MANET research has been performed assuming the random waypoint mobility model for determining nodes movements. In the last years, some researchers have focused on alternative mobility models. In this paper, we perform a simulation based joint analysis of ad-hoc network performance at three layers (physical layer, network layer and transport layer) using four different mobility models, AODV as the routing protocol and TCP as the transport protocol. In some cases, we obtain counterintuitive results, which can be explained by correlating the behavior measured at the three considered layers

Mobile ad-hoc network (MANET) technology is an essential piece in the path towards a ubiquitous Internet. MANET routing protocol parameter configuration should be further analyzed since it may significantly impact network performance. In this paper, we perform tests in real MANET environments using the ad-hoc on-demand distance vector (AODV) routing protocol. We study the influence of the protocol, the implementation and a set of AODV link maintenance mechanisms parameter values on network performance, suggesting that usage of different settings from those proposed by default increase reactivity after topology changes with small impact on bandwidth and power consumption in a set of scenarios

WLAN IEEE 802.11 standards are living at present a popularity momentum, but this fact is translated into a new headache to network administrators. The more WLAN networks there are in a region, the more interference they will suffer, and that means an evident decrease in their performance. In this paper we present the application of a new distributed algorithm for the frequency assignment problem in 802.11 networks which is intended to reduce interferences among cells. In addition the proposed algorithm has been implemented and tested in commercial Access Points obtaining the expected results.

3G wireless networks such as UMTS are currently providing wide area Internet access. However, the Internet protocols exhibit a suboptimal performance in such scenarios. In this paper we first characterize a live UMTS link from the IP level. We identify critical features such as high latency, delay spikes, high packet loss probability and connectivity gaps, specially when the user moves between cells. Next, we test a set of TCP configurations, demonstrating that TCP performance can be optimized over UMTS by the usage of adequate end-to-end mechanisms and parameter values.

The paper shows the need to transmit extra assistance data in hybrid location systems. The proposal presented here uses the current network protocols in order to deliver these non-standardized assistance data in 2G/2.5G location systems. To this end, a complete analysis of the available protocols and methods of identifying a non-standard assistance data source is performed.

This paper presents a procedure for estimating the mean access delay of calls in public access mobile radio (PAMR) trunking systems. For this purpose, an approximation of the mean waiting time in the M/G/C queue with non-preemptive priority is developed and numerically tested. The proposed approximation is based on other existing approximations and has been tested for the conditions commonly found in PAMR systems with very accurate results.

This paper examines the hysteresis margin (/spl Delta/) as a way of avoiding the 'ping-pong' effect when making hard handovers, and limiting the number of transceivers per base station (BS) when making soft handovers. Perfect power control is assumed and some parameters with direct consequences on the capacity of the system are calculated anew, such as the power margin needed to guarantee as many as 10% of mobiles out of coverage, the overlapping achieved or the mean number of transceivers per BS needed. It is shown that both hard and soft solutions need the same power margin.

This paper examines the hysteresis margin (/spl Delta/) as a way of avoiding the 'ping-pong' effect when making hard handovers, and limiting the number of transceivers per base station (BS) when making soft handovers, Perfect power control is assumed and the external interference with the cell under study, with direct consequences on the capacity of the system, is calculated anew. It is shown that both hard and soft solutions have similar external interference. As most external interference is caused by adjacent cells, an FDMA/CDMA system is also considered. Under the above assumptions, the SIR of a FH/FDMA system was evaluated for some /spl sigma/. These results re-evaluated the capacities of FH/FDMA, a CDMA, a FDMA/CDMA and a TDMA/CDMA system.

The Digital European Cordless Telecommunication System (DECT) is gaining acceptance in environments different to the ones the system has been designed for. In particular outdoors environments as the radio local loop (RLL) or public cordless terminal mobility (CTM). The main difference between indoors, where DECT was supposed to work, and outdoors is that for this latter environment the signal propagation is not limited between walls and further studies have to be performed to determine its capacity. In this paper a study of a CTM system in an urban environment is presented. Static or mobile users appear on a surface with a regular distribution of buildings and streets. An evaluation of the traffic capacity and related parameters of the system is performed by simulation. The main focus is on the influence of different base station locations on the static or mobile terminals.

The DECT (Digital European Cordless Telecommunication) system has been designed to be used in three different environments: domestic, telepoint and business. For the business one voice and data services have to be offered allowing one to build a wireless network with integrated traffic. The DECT basic channel is symmetric and has a transmission rate of 32 kbps. This channel seems not very suitable for data applications so the DECT standard defines some procedures to handle data traffic in a better way. These procedures allows one to create connection oriented (symmetric or asymmetric) communications with a higher data transmission rate. These channels are created using multibearer connections.>