Impacto de mecanismos de seguridad en sensores IEEE 802.15.4

En la actualidad son muchos los mecanismos de seguridad que el estándar IEEE 802.15.4 permite a las redes inalámbricas de sensores [1] Dicho estándar define las especificaciones de la Capa de Acceso al Medio y la Capa Física de los dispositivos inalámbricos de área personal. La última revisión corresponde al 2006. Dichas revisiones y actualizaciones son hechas por el grupo de trabajo 802.15. Sin embargo estos mecanismos consumen recursos como memoria y batería, que son un poco limitados en estos dispositivos. Además de contribuir a los retardos en la comunicación. Por lo cual, en el presente trabajo se presenta de manera práctica el impacto que el uso de mecanismos de seguridad tienen en el desempeño de este tipo de redes. Para ello se hizo una comparación de dicho desempeño de manera teórica basándose en lo presentado en [2], con los valores óptimos apegados a lo especificado en el estándar IEEE 802.15.4, en contraste con pruebas reales. Para estas pruebas se hizo uso del sistema operativo TinyOS [3] y de las operaciones de seguridad MAC (Capa de Acceso al Medio) ofrecidas por el chip CC2420 usado en las motas TelosB. Además se presenta el desgaste de la batería, el cual es otro punto importante que se desea conservar en los sensores.Postprint (published version

A transmit power control proposal for IEEE 802.11 cellular networks

Actually, the idea of designing an outdoor cellular network based on WLAN IEEE 802.11 results very attractive, due to the several advantages that this technology presents. It offers the equipment at a lower cost, operates in unlicensed spectrum and allows higher data rates.If we realize a comparison of the system performance between a cellular environment and an isolated single cell scenario we observe that the first situation exhibits a considerable decrease, due to co-channel interference, that rises with the growth of the transmission data rate employed. In this paper, we propose a power control mechanism, as a method to reduce the interference influence on network performance, and to homogenize the behavior of the different stations in the system. We present its performance under different load conditions and compare this behavior with the original case, without the employment of any power control mechanism.Peer Reviewe

Wake-up radio systems for cooperative-intelligent transport systems architecture

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Cooperative-Intelligent Transport systems are new applications developed on top of communications between vehicles and between vehicles and fixed infrastructure. Their architecture envisages devices deployed along the routes and streets, transmitting and receiving different kind of messages belonging to different services. Quite often, these devices will be located in isolated places with very low number of vehicles passing nearby. Being in isolated places, these devices will require to be feed with rechargeable batteries and alternative power sources, the usage of which need to be very efficient. The fact of continuously transmitting messages whenever there is no vehicle to receive them demands a solution. In this paper, we propose to use a well-known saving power strategy already used in Internet of Things, the Wake-up Radio systems. As vehicular communications are based on IEEE 802.11 standard, we propose to use a Wake-up Radio system based on this standard as well, being thus no additional hardware needed for the wake-up transmitter. The paper analyses the feasibility of using this solution on several vehicular applications.Peer ReviewedPostprint (author's final draft

Study of asymmetric traffic influence on IEEE 802.11 WLAN family, enhancement proposals

This paper is focused on the study of WLAN performance in IEEE 802.11 networks that are in a situation of asymmetric traffic, where the access point (AP) transmits much more than the user stations (US). This situation is very different from the symmetric one, wherein all the stations have the same traffic load. The paper also presents a discussion of the different mechanisms in order to increase AP priority under the asymmetric traffic situation.Peer Reviewe

Evaluation of IEEE 802.11 coexistence in WLAN deployments

This is a pre-print of an article published in Wireless Networks. The final authenticated version is available online at: https://doi.org/10.1007/s11276-017-1540-z.Wi-Fi has become a successful technology since the publication of its first WLAN standard due to continuous advances and updates while remaining always backwards compatible. Backwards compatibility among subsequent standards is an important feature in order to take advantage of previous equipment when publishing a new amendment. At present, IEEE 802.11b support is still mandatory to obtain the Wi-Fi certification. However, there are several harmful effects of allowing old legacy IEEE 802.11b transmissions in modern WLAN deployments. Lower throughput per device is obtained at slow rates, but also the effect known as performance anomaly, which nearly leads to starvation of fast stations, has to be taken into account. Finally, backwards compatibility mechanisms pose an important penalty in throughput performance for newer specifications. This paper presents a thorough analysis of the current state of IEEE 802.11, comparing coverage range and throughput performance among subsequent amendments, and focusing on the drawbacks and benefits of including protection mechanisms.Peer ReviewedPostprint (author's final draft

IEEE 802.11g performance in presence of beacon control frames

Most studies of the performance of IEEE 802.11 consider scenarios of ad-hoc topology networks and do not contemplate the network broadcast information contained in beacon frames. The paper presents a study of the performance of a WLAN whose infrastructure's topology is such that the access point is in charge of broadcasting the beacon frames. Thus, it is more realistic than previous studies, because beacon frames are usually transmitted in order to announce control information and network identity. Furthermore, in the coverage area, user stations are likely to be working at different data rates, depending on their signal quality. Because beacon frames must be received by all stations, they are transmitted at the lowest data rate operating in the coverage area. The article introduces a mathematical method to calculate the influence of beacon frames on the total throughput, collision probability and delays of the IEEE 802.11g protocol. The model is validated by simulation analysis.Peer Reviewe

Integration of wireless communications in a GIS platform

This paper presents a new developed platform for the Commercialisation of Advanced Services of Geographical Information, focussed in portables devices, and that makes use of the telecommunication networks available today: Internet as the backbone and cellular networks (GSM + GPRS) as access networks. The platform implements a system for commercialising cartographic information in form of vectorial maps for different amount of time, guarantying property rights of the provided information. The problem with vectorial maps is that they have additional information, as points of interest or street names, that is very important to have them updated. So it is more interesting, for both the provider and the customer, to rent the maps for a small period of time, and also for a low fee, than selling them for ever and for a big amount of money. The client accesses to the service using a vectorial map player, that runs over PC or PDA (Personal Digital Assistant) platforms, and using a GPS receiver, it has navigation facilities. Before accessing to the information the player will request authorization to the server. Mobile devices will access Internet, where the server is connected, using WLAN, circuit switched cellular network (GSM) or packet switched cellular network (GPRS). The server side will control user access and download required maps. The platform includes also a system to improve GPS localization (Differential GPS). The communication between the client and the server uses SMS messages of GSM system, one for the request and another for the answer. This operation is very sensitive to response delay and it has been optimised in order to work properly.Peer Reviewe

Sobre la justicia en las redes IEEE 802.11e: desincronización de su mecanismo de acceso al medio

Since the advent of the first IEEE 802.11 standard, several papers have proposed means of providing QoS to IEEE 802.11 networks and evaluate various traffic-prioritization mechanisms. Nevertheless, studies on the assignment of AIFS times defined in IEEE 802.11e reveal that the various priority levels work in a synchronized manner. The studies show that, under large loads of high-priority traffic, EDCA starves low-priority frames, which is undesirable. We argue that QoS traffic needs to be prioritized, but users sending best-effort frames should also obtain the expected service. High-priority traffic can also suffer performance degradation when using EDCA because of heavy loads of low-priority frames. Thus, we have proposed a mechanism based on desynchronizing the IEEE 802.11e working procedure. It prevents stations that belong to different priority classes from attempting simultaneous transmission, prioritizes independent collision groups and achieves better short-term and long-term channel access fairness. We have evaluated the proposal based on extensive analytical and simulation results. It prevents the strangulation of low-priority traffic, and, moreover, reduces the degradation of high-priority traffic with the increased presence of low-priority frames.Peer Reviewe

Performance enhancement of WLAN IEEE 802.11 for asymmetric traffic

Most studies about the performance of IEEE 802.11 consider scenarios of ad-hoc topology and networks where all stations have the same traffic load (symmetric traffic conditions). This paper presents a study of performance parameters of more realistic networks. We focus the attention on WLAN with infrastructure networks, where the traffic distribution is asymmetric. In this case, the traffic load at the access point is much heavier than that at user stations. These studies are more realistic because most nowadays installed WLAN are infrastructure topology type, due to the fact that they are used as access networks. In this case, the access point has to retransmit all incoming traffic to the basic service set and therefore its traffic load is higher. Finally, the paper presents the tuning of the contention window, taken from IEEE 802.11e, used to increase the system performance under asymmetric traffic conditions, and the proposal of an adaptive algorithm to adapt the MAC layer settings to the system traffic load.Peer Reviewe

Performance of wireless LAN access methods in multicell environments

In this paper, we address the issue of evaluating performance of wireless LANs in multicell scenarios. We try to understand the complex behavior of the DCF (Distributed Coordination Function) access method defined in the IEEE 802.11 standard [1] and its modifications proposed for improving performance: Slow Decrease [2], Asymptotically Optimal Backoff [3], and Idle Sense [4]. We analyze the influence of overlapping cells and large multicell environments on their performance. Our results show that the IEEE 802.11 DCF and its two modifications (Slow Decrease and AOB) exhibit important unfairness between stations close to the access point and those near the border of a neighbor cell. Idle Sense performs much better: it provides much better fairness than the IEEE 802.11 DCF and its modifications. It also obtains the highest throughput when stations adapt their bit rate to channel conditions.Peer Reviewe