Albert Banchs

An overview of IEEE 802.21: media-independent handover services

In recent years multitechnology-enabled terminals have become available. Such multimode terminals pose new challenges to mobility management. In order to address some of these challenges, the IEEE is currently working on a new specification on media-independent handover services (IEEE 802.21 MIH). The main aim of this specification is to improve user experience of mobile terminals by enabling handovers between heterogeneous technologies while optimizing session continuity. In this article we provide an overview of the current status of the IEEE 802.21 specification.

Providing throughput guarantees in IEEE 802.11 wireless LAN

In this paper, we propose ARME (Assured Rate MAC Extension), an extension of the IEEE 802.11 MAC protocol to provide throughput guarantees. The proposed extension relies on the distributed coordination function (DCF) with a modified algorithm for the computation of the contention window (CW). Best effort service (with no throughput guarantee) is supported by the functionality of the current 802.11 standard in such a way that legacy IEEE 802.11 terminals behave as best effort terminals in ARME. The performance of the proposed extension has been extensively evaluated through simulation; simulation results show that IEEE 802.11 devices using ARME behave well for different types of traffic and different source rates.

An architecture for software defined wireless networking

Software defined networking, characterized by a clear separation of the control and data planes, is being adopted as a novel paradigm for wired networking. With SDN, network operators can run their infrastructure more efficiently, supporting faster deployment of new services while enabling key features such as virtualization. In this article, we adopt an SDN-like approach applied to wireless mobile networks that will not only benefit from the same features as in the wired case, but will also leverage on the distinct features of mobile deployments to push improvements even further. We illustrate with a number of representative use cases the benefits of the adoption of the proposed architecture, which is detailed in terms of modules, interfaces, and high-level signaling. We also review the ongoing standardization efforts, and discuss the potential advantages and weaknesses, and the need for a coordinated approach.

Proportional fair throughput allocation in multirate IEEE 802.11e wireless LANs

Under heterogeneous radio conditions, Wireless LAN stations may use different modulation schemes, leading to a heterogeneity of bit rates. In such a situation, 802.11 DCF allocates the same throughput to all stations independently of their transmitting bit rate; as a result, the channel is used by low bit rate stations most of the time, and efficiency is low. In this paper, we propose a more efficient throughput allocation criterion based on proportional fairness. We find out that, in a proportional fair allocation, the same share of channel time is given to high and low bit rate stations, and, as a result, high bit rate stations obtain more throughput. We propose two schemes of the upcoming 802.11e standard to achieve this allocation, and compare their delay and throughput performance.

Throughput analysis and optimal configuration of 802.11e EDCA

One of the main challenges with 802.11e EDCA is the configuration of the open parameters of this mechanism, namely AIFS, CWmin, CWmax and TXOP_limit. In this paper, we address the issue of finding the optimal configuration of these parameters in order to maximize the throughput performance of the WLAN. We first present a model to analyze the throughput performance of an EDCA WLAN as a function of these parameters. Then, based on this model, we search for the optimal EDCA configuration. We find out that, surprisingly, one of the EDCA parameters, the AIFS, is not used in the optimal configuration. We provide closed formulae, based on some approximations, for the configuration of the parameters CWmin and CWmax. The configuration of the TXOP__limit parameter is discussed based on a delay analysis provided elsewhere.

Applications and challenges of the 802.11e EDCA mechanism: an experimental study

In this article we conduct an experimental study of the enhanced distributed channel access mechanism of the upcoming 802.11e standard. The main focus of the study is on two applications of EDCA: traffic engineering and service guarantees. With traffic engineering we aim at distributing the bandwidth in the WLAN according to a given throughput allocation criterion. With service guarantees the objective is to ensure that the performance metrics (throughput and delay) experienced by a station meet a given quality criterion. We build a testbed with wireless cards that support a substantial subset of the EDCA functionality and analyze performance against different sets of requirements. Experimental results show that EDCA can effectively be used for traffic engineering purposes. The goal of providing service guarantees with EDCA is shown to be more challenging; we identify future research directions that need to be addressed in order to achieve this goal.

Optimal Configuration of 802.11e EDCA for Real-Time and Data Traffic

The enhanced distributed channel access (EDCA) mechanism of the IEEE 802.11e standard provides quality-of-service (QoS) support through service differentiation by using different medium-access-control (MAC) parameters for different stations. The configuration of these parameters, however, is still an open research challenge, as the standard provides only a set of fixed recommended values that do not take into account the current wireless local area network (WLAN) conditions and, therefore, lead to suboptimal performance. In this paper, we propose a novel algorithm for EDCA that, given the throughput and delay requirements of the stations that are present in the WLAN, computes the optimal configuration of the EDCA parameters. We first present a throughput and delay analysis that provides the mathematical foundation upon which our algorithm is based. This analysis is validated through simulations of different traffic sources (both data and real time) and EDCA configurations. We then propose a mechanism to derive the optimal configuration of the EDCA parameters, given a set of performance criteria for throughput and delay. We assess the effectiveness of the configuration provided by our algorithm by comparing it against 1) the recommended values by the standard, 2) the results from an exhaustive search over the parameter space, and 3) previous configuration proposals, which are both standard and nonstandard compliant. Results show that our configuration outperforms all other approaches.

Nemo-enabled localized mobility support for internet access in automotive scenarios

This article surveys the major existing approaches and proposes a novel architecture to support mobile networks in network-based, localized mobility domains. Our architecture enables conventional terminals without mobility support to obtain connectivity either from fixed locations or mobile platforms (e.g., vehicles) and move between them, while keeping their ongoing sessions. This functionality offers broadband Internet access in automotive scenarios such as public transportation systems, where users spend time both in vehicles and at stations. The key advantage of our proposal, as compared with current alternatives, is that the described mobile functionality is provided to conventional IP devices that lack mobility functionality. We also performed an experimental evaluation of our proposal that shows that our architecture improves the quality perceived by the end users.

Energy consumption anatomy of 802.11 devices and its implication on modeling and design

A thorough understanding of the power consumption behavior of real world wireless devices is of paramount importance to ground energy-efficient protocols and optimizations on realistic and accurate energy models. This paper provides an in-depth experimental investigation of the per-frame energy consumption components in 802.11 Wireless LAN devices. To the best of our knowledge, our measurements are the first to unveil that a substantial fraction of energy consumption, hereafter descriptively named cross-factor, may be ascribed to each individual frame while it crosses the protocol/implementation stack (OS, driver, NIC). Our findings, summarized in a convenient new energy consumption model, contrast traditional models which either neglect or amortize such energy cost component in a fixed baseline cost, and raise the alert that, in some cases, conclusions drawn using traditional energy models may be fallacious.

Multicasting multimedia streams with active networks

Active networks allow protocol processing code to be loaded dynamically into network nodes at run-time. This code can perform tasks specific to a stream of packets or even a single packet. In this paper we compare two active network architectures: the active node transfer system (ANTS) and the messenger system (M0). We have implemented a robust audio multicast protocol and a layered video multicast protocol with both active network systems. We discuss the differences of the two systems, evaluate architectural strengths and weaknesses, compare the runtime performance, and report practical experience and lessons learned.