部分重複チャネル割当を用いた無線メッシュネットワークの展開法に関する研究

Tohoku University加藤寧課

Interference aware cluster-based joint channel assignment scheme in multi-channel multi-radio wireless mesh networks

Wireless Mesh Networks (WMNs) are emerging as a promising solution for robust and ubiquitous broadband Internet access in both urban and rural areas. WMNs extend the coverage and capacity of traditionalWi-Fi islands through multi-hop,multichannel and multi-radio wireless connectivity. The foremost challenge, encountered in deploying a WMN, is the interference present between the co-located links, which limits the throughput of the network. Thus, the objective of this research is to improve the throughput, fairness and channel utilization of WMNs by mitigating the interference using optimized spatial re-usability of joint channels available in the 2.4 GHz Industrial, Scientific, and Medical (ISM) band. Interference is quantified depending on the relative location of the interfering links. Further, the Interference aware Non-Overlapping Channel assignment (I-NOC) model is developed to mitigate the interference by utilizing optimized spectral re-usability of Non-Overlapping Channels (NOCs). NOCs are limited in number. Therefore, I-NOC model is extended by using joint channels available in the free spectrum, and termed as Interference aware Joint Channel Assignment (I-JCA) model. Normally, joint channel assignment is considered harmful due to adjacent channel interference. However, by systematic optimization, the I-JCA model has utilized the spectral re-usability of joint channels. I-JCA model cannot be solved at the time of network initialization because it requires prior knowledge of the geometric locations of the nodes. Thus, Interference aware Cluster-based Joint Channel Assignment Scheme (I-CJCAS) is developed. I-CJCAS partitions the network topology into tangential non-overlapping clusters, with each cluster consisting of intra- and inter-cluster links. I-CJCAS mitigates the interference effect of a cluster’s intra-cluster links by assigning a distinct common channel within its interference domain. On the other hand, the inter-cluster links are assigned to a channel based on the transmitter of the inter-cluster link. I-CJCAS is benchmarked with Hyacinth, Breadth-First Search Channel Assignment (BFS-CA) and Cluster- Based Channel Assignment Scheme (CCAS) in terms of throughput, fairness, channel utilization, and impact of traffic load in single-hop and multi-hop flows. Results show that I-CJCAS has outperformed the benchmark schemes at least by a factor of 15 percent. As a part of future work, I-CJCAS can be extended to incorporate dynamic traffic load, topology control, and external interference from co-located wireless network deployments

Frequency management in a campus-wide Wi-Fi deployment

Over the past years, Internet is spreading more and more. And not only in home devices, but also in other personal devices thus producing a collective mobile lifestyle. At the beginning of its rise, cable solution was the most applied technology. However, in a world becoming a “mobile world”, wired networks can’t fulfil all new challenges. Thus, Wireless networks are increasingly encroaching on the niche of traditional access technologies. In fact, mobile broadband is exponentially being integrated into every aspect of life; and that seems to be only the beginning of what is to come, as the several millions of people using the latest trend gadgets ratify. One of the key technologies that enable mobile Internet access is IEEE 802.11, commonly known by its trademark, Wi-Fi, which assures interoperability and backward compatibility between products. Part of the popularity achieved by Wi-Fi is due to the use of unlicensed (i.e. free) spectrum. Traditionally, only three of the fourteen frequency channels established in the 2.4GHz are used. This is so in order to avoid interference, as these channels (1, 6 and 11) belong to non-overlapping frequencies. However, the recent explosive growth in the number of wireless devices together with the multitude of wireless protocols operating in the unlicensed radio spectrum bands and sharing the same spectrum, lead to a saturation of the limited available spectrum, thus causing the frequency channels assigned to be repeated in close cells. Definitely, it results in interference and performance degradation, and broadly, a non-optimal performance of the network. Within this context, in which the number of users is very large but the radio resources are scarce, efficient channel allocation becomes crucial for the successful deployment and operation of IEEE802.11-based WLANs. And this is indeed the main purpose of this Master Thesis, in which a system able to establish communication with a controller and set a new channel distribution according to a renowned mathematical algorithm is exposed. The presented system has been tested in CBL – UPC Barcelona Tech campus, giving satisfactory outcomes and conclusions as a result. But before going deep into the process details, this work also reviews WLAN 802.11 standards and radio resource management techniques used nowadays, so the reader will easily understand the context which encompasses this work and how the system presented is able to improve an already settled technology.Castellà: Desde hace unos años, Internet se está extendiendo cada vez más. Y no sólo en los hogares, sino también en aparatos de uso personal que están convirtiendo nuestro estilo de vida en un estilo “móvil”. Al principio de su aparición, la tecnología cableada era la más recurrida. Sin embargo, en este mundo cada vez más móvil, nos encontramos con que las redes cableadas no pueden satisfacer los nuevos retos. Es por esto que las redes inalámbricas están invadiendo el espacio de las tecnologías de acceso tradicionales. De hecho, la banda ancha móvil se está acoplando a un ritmo vertiginoso en muchos aspectos de nuestra vida; y esto parece ser sólo el comienzo, como demuestran los varios millones de personas que utilizan los aparatos tecnológicos más modernos. Una de las tecnologías clave que permiten acceso móvil a Internet es IEEE 802.11, más conocida como Wi-Fi, término comercial que asegura interoperabilidad y compatibilidad entre productos. Parte de su popularidad se debe al uso del rango de frecuencias libres de licencia. Tradicionalmente, sólo tres de los catorce canales que establece la banda de 2,4GHz son asignados. Esto ha sido siempre así para evitar interferencias, ya que estos canales (1, 6 y 11) pertenecen a frecuencias que no se solapan. Sin embargo, la reciente explosión en el número de dispositivos inalámbricos así como la cantidad de protocolos que trabajan en el mismo rango frecuencial, provocan una saturación de este espectro limitado, haciendo así que se asignen los mismos canales en celdas cercanas. Sin duda, esto se traduce en interferencias, y en general, hace que el comportamiento de la red no sea el óptimo. En este contexto, en el que el número de usuarios es elevado pero los recursos radio escasos, la asignación eficiente de canales se vuelve crucial para tener buen despliegue y funcionamiento de las redes WLAN basadas en IEEE802.11. Y éste es de hecho el propósito principal de esta Master Thesis, que presenta un sistema capaz de establecer comunicación con una controladora y decidir una nueva distribución de canales según un conocido algoritmo matemático. El sistema que se presenta ha sido probado en el campus CBL–UPC Barcelona Tech, obteniendo resultados y conclusiones satisfactorios. Pero antes de entrar en los detalles del proceso, este trabajo también analiza los estándares IEEE 802.11 así como las técnicas actuales utilizadas en la gestión de recursos, de manera que el lector entenderá fácilmente el contexto en el que este trabajo se realiza y cómo el sistema presentado es capaz de mejorar una tecnología ya asentada

Balanced Multi-Channel Data Collection in Wireless Sensor Networks

Data collection is an essential task in Wireless Sensor Networks (WSNs). In data collection process, the sensor nodes transmit their readings to a common base station called Sink. To avoid a collision, it is necessary to use the appropriate scheduling algorithms for data transmission. On the other hand, multi-channel design is considered as a promising technique to reduce network interference and latency of data collection. This technique allows parallel transmissions on different frequency channels, thus time latency will be reduced. In this paper, we present a new scheduling method for multi-channel WSNs called Balanced Multi Channel Data Collection (Balanced MC-DC) Algorithm. The proposed protocol is based on using both Non-Overlapping Channels (NOC) and Partially Overlapping Channels (POC). It uses a new approach that optimizes the processes of tree construction, channel allocation, transmission scheduling and balancing simultaneously. Extensive simulations confirm the superiority of the proposed algorithm over the existing algorithms in wireless sensor networks

AP Deployment Research Based on Physical Distance and Channel Isolation

Aiming at the problem of inefficiency of wireless local area networks (WLAN) access point (AP) deployment in urban environment, a new algorithm for AP deployment based on physical distance and channel isolation (DPDCI) is proposed. First, it detects the position information of deployed APs and then calculates the interference penalty factor combined with physical distance and channel isolation, and finally gets the optimal location and channel of the new AP through the genetic algorithm. Comparing with NOOCA algorithm and NOFA-2 algorithm, the results of numerical simulation show that the new algorithm can minimize the mutual interference between basic service sets (BSS), can ensure the maximum of throughput based on quality of service (QoS) in BSS, and can effectively improve the system performance

Robust Fuzzy learning for partially overlapping channels allocation in UAV communication networks

With significantly dynamic characteristics of the new aerial users, the emerging cellular-enabled unmanned aerial vehicle (UAV) communication paradigm raises great challenges to current research of UAV applications. As far as the robust channel allocation is concerned, the high mobility of UAV nodes and the unexpected disturbance of external environment would render most existing methods which rely on definite information and are vulnerable to dynamic environment, become less attractive or even invalid. In this paper, we particularly investigate a cellular-enabled mesh UAV network exploiting partially overlapping channels (POCs), and propose a distributed fuzzy space based learning scheme for POCs allocation to combat the dynamic environment. Rather than the perfect channel state information (CSI) assumption, the dynamic and uncertain CSI of UAVs is characterized by fuzzy number. On this basis, the allocation process can be implemented in a mapped fuzzy space. Integrating fuzzy-logic and game based learning, we formulate the problem of POCs assignment as a fuzzy payoffs game (FPG), and demonstrate the existence of fuzzy Nash equilibrium for our designed FPG. Then, with the derived priority vector in the fuzzy space, the equilibrium solution can be achieved by the proposed algorithm. Numerical simulations demonstrate the advantages of our new scheme