Josep Paradells Aspas

TCP/IP over wireless links: performance evaluation

The Transmission Control Protocol (TCP) is a large extended transport protocol, mainly used in fixed networks. It works well in those networks in which the main cause of packet loss is congestion. Some mechanisms included in TCP optimise their use in this kind of networks. Today, Internet users need access it over wireless links in order to get this service anywhere they are. However, TCP does not work well in wireless environments where losses are due to high bit error rates (BER). We evaluate the end-to-end throughput of a TCP connection with a wireless link. First, we demonstrate the impact of high BER in TCP performance. Then, we evaluate the impacts of header compression.

Improving fast handovers for mobile IPv6: optimal crossover discovery using geopaging routing tables

Fast handovers for mobile IPv6 (FMIPv6) reduces packet loss by providing fast IP connectivity as soon as a new link is established. It does so by fixing up the routing during link configuration and binding update, so that packets delivered to the old care of address are forwarded to the new. This forwarding produces a non-optimal routing, that is, it increases end-to-end delay and wastes bandwidth. In this paper, a mechanism called optimal crossover router discovery (OCRD) is introduced in combination with an extension of FMIPv6 in order to solve this problem. An OCRD approach is presented It relies on the routing tables of geopaging, an IPv6 multicast protocol designed to efficiently transport paging.

A bluetooth low energy indoor positioning system with channel diversity, weighted trilateration and Kalman filtering

Indoor Positioning Systems (IPS) using Bluetooth Low Energy (BLE) technology are currently becoming real and available, which has made them grow in popularity and use. However, there are still plenty of challenges related to this technology, especially in terms of Received Signal Strength Indicator (RSSI) fluctuations due to the behaviour of the channels and the multipath effect, that lead to poor precision. In order to mitigate these effects, in this paper we propose and implement a real Indoor Positioning System based on Bluetooth Low Energy, that improves accuracy while reducing power consumption and costs. The three main proposals are: frequency diversity, Kalman filtering and a trilateration method what we have denominated “weighted trilateration”. The analysis of the results proves that all the proposals improve the precision of the system, which goes up to 1.82 m 90% of the time for a device moving in a middle-size room and 0.7 m for static devices. Furthermore, we have proved that the system is scalable and efficient in terms of cost and power consumption. The implemented approach allows using a very simple device (like a SensorTag) on the items to locate. The system enables a very low density of anchor points or references and with a precision better than existing solutions.Indoor Positioning Systems (IPS) using Bluetooth Low Energy (BLE) technology are currently becoming real and available, which has made them grow in popularity and use. However, there are still plenty of challenges related to this technology, especially in terms of Received Signal Strength Indicator (RSSI) fluctuations due to the behaviour of the channels and the multipath effect, that lead to poor precision. In order to mitigate these effects, in this paper we propose and implement a real Indoor Positioning System based on Bluetooth Low Energy, that improves accuracy while reducing power consumption and costs. The three main proposals are: frequency diversity, Kalman filtering and a trilateration method what we have denominated “weighted trilateration”. The analysis of the results proves that all the proposals improve the precision of the system, which goes up to 1.82 m 90% of the time for a device moving in a middle-size room and 0.7 m for static devices. Furthermore, we have proved that the system is scalable and efficient in terms of cost and power consumption. The implemented approach allows using a very simple device (like a SensorTag) on the items to locate. The system enables a very low density of anchor points or references and with a precision better than existing solutions.

Analysis of Consecutive Idle Time Slots in Mobile Networks

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

Radio Resource Allocation Strategies to Guarantee Data Traffic in Cellular Networks

In this paper, we focus on different strategies of radio resource allocation in cellular mobile networks. The paper proposes two models of ordered allocation of the time slots in a frame (with or without time slots reserved for data traffic) and in such a way that the available resources for an user can be maximized if we take into account the number of consecutive idle time slots. The analytical model is presented and the probabilities of finding any given number of consecutive idle time slots for the different models are shown. The results are presented for three different scenarios, which have two, one or none reserved resources available just for data traffic. For the different scenarios the quality of service requirements of data traffic is compared, without degrading in any case the voice service.

Geopaging: a novel multicast approach to IP paging delivery

This paper introduces a new global solution in order to achieve a very efficient IP paging delivery. This efficiency is accomplished in terms of number of messages sent in both, wireless access and core networks. Reduction of signalling is achieved using a distance-based dynamic strategy combined with multicast.

Focusing the Study on Wireless Multihop Networks

Presents a 100-slide tutorial on wireless multihop networks. Wireless mesh networks, mobile ad-hoc networks and wireless sensor networks are some of the names related to a more general concept that can be described as wireless multihop networks. Recently, the research community has devoted a lot of attention to this topic since now it may become applied in a general manner leaving the niche market it has had since its origins. Sometimes, the research community is overoptimistic about the application of this technology, and in fact, in the technology itself. This enthusiasm brings to unrealistic research scenarios and, so, to unrealistic models and conclusions. The topic of the tutorial is motivated for this feeling of lack of connection between reality and theory in the study of this kind of networks. The main ideas presented are based on practical experiences in using this technology and in some well known papers that cover the same issues. The tutorial starts with an introduction to some applications and the technologies available. From this point, different key aspects such as mobility, range, interference, metrics, routing or power consumption are presented considering different degrees of complexity and realism. The tutorial presents measurements from real systems (e.g. WLAN mesh networks and wireless sensor networks) related to range, packet losses, reconfiguration times and the effects of mobility. The tutorial is intended to focus the research in the area, avoiding too general scenarios that provide no clear solutions and to provide some reference behaviors and values to validate simulation or theoretical results.

Design and implementation of a multimedia content delivery system for portable devices

This paper describes the design of a multimedia contents delivery system able of offering TV, radio, podcast and file services to portable devices. These services are distributed using reliable multicast, specifically FLUTE protocol (File Delivery over Unidirectional Transport). An alternative mechanism for transmitting TV contents is also proposed in this paper. This mechanism is based in podcast and seeks to take advantage of the mobile broadcasting networks currently in development. In addition, an Electronic Service Guide (ESG) has been designed to inform the users about the available contents. Such ESG allows client applications to personalize contents according to users tastes and interests. The paper is structured as follows: first, it provides an introduction about mobile television; second, it explains briefly key aspects for the reliable multicast transport and mobile broadcasting technologies; then, our system design is exposed and finally, the system implementation is described.

IEEE 802.11 networks with dormant mode support: an IP paging approach and its performance analysis

IEEE802.11 networks are changing its primary role of extension of private LANs to become an access technology in competition or collaboration with current cellular networks. In addition, large-scale IEEE802.11 deployments are a reality that mesh networks can contribute to expand. But not only, networks are changing; their users are doing the same. More portable devices as WiFi enabled PDAs or phones will allow an increase of their number and mobility, but suffering from severe battery constraints. In addition, the interest in VoIP over WLAN will introduce the need of establishing sessions to WLAN users and not only from them. In order to support similar conditions, current cellular systems make use of a dormant mode with paging support which is inexistent in the IEEE802.11 networks. In this paper we propose the introduction of IP paging in IEEE802.11 networks in order to solve this problem. The aim of this paper is to demonstrate the usability of IP paging in order to reduce the mobility signaling cost. This is achieved through a new analytical approach that evaluates the following parameters: the call-to-mobility ratio (CMR), the size of the radio access network (RAN) and the size of the paging area. The solutions analyzed are the Hierarchical Mobile IPv6 (HMIPv6) protocol and a new extended version of this with IP paging support. The novelty of this latter version lies in its use of distance-based dynamic paging areas and its specific design for IEEE802.11 networks.

Deploying Large-Scale IEEE802.11 Networks Using IP Paging with Link-Specific Capabilities: A Standard Compliant Approach and its Performance Analysis

IEEE802.11 is a layer two technology that offers limited mobility support. It suffers from scalability problems caused by the performance of the mechanisms related to the address resolution and the discovery and maintenance of the path information. In this paper, we propose using IP paging with link-specific capabilities to solve this problem. The need of these capabilities is justified showing the limitations of pure-IP solutions when they interact with IEEE802.11 specific functions, mainly the power save mode (PSM). Then, a comprehensive proposal for an IP paging solution that is an extension of the Mobile IPv4 Regional Registration (MIPv4-RR) protocol is presented. Its strengths lie in the fact that there are no interaction problems with PSM, and it is fully compliant with existing IEEE802.11 devices. Finally, in order to show the excellent scalability of our link-specific solution, we carry out an analytical study of its mobility signaling and compare it with the standard MIPv4-RR protocol and IIPP (Integrated IP Paging Protocol), another IP paging solution that does not implement link-specific functions.IEEE802.11 is a layer two technology that offers limited mobility support. It suffers from scalability problems caused by the performance of the mechanisms related to the address resolution and the discovery and maintenance of the path information. In this paper, we propose using IP paging with link-specific capabilities to solve this problem. The need of these capabilities is justified showing the limitations of pure-IP solutions when they interact with IEEE802.11 specific functions, mainly the power save mode (PSM). Then, a comprehensive proposal for an IP paging solution that is an extension of the Mobile IPv4 Regional Registration (MIPv4-RR) protocol is presented. Its strengths lie in the fact that there are no interaction problems with PSM, and it is fully compliant with existing IEEE802.11 devices. Finally, in order to show the excellent scalability of our link-specific solution, we carry out an analytical study of its mobility signaling and compare it with the standard MIPv4-RR protocol and IIPP (Integrated IP Paging Protocol), another IP paging solution that does not implement link-specific functions.