Hybrid Wireless Mesh Protocol Research Articles

IEEE 802.11s Wireless Mesh Networks for Last-Mile Internet Access: An Open-Source Real-World Indoor Testbed Implementation

Due to their easy-to-deploy and self-healing features, WMNs (Wireless Mesh Networks) are emerging as a new promising technology with a rich set of applications. While the IEEE standardization of this new technology is still in progress, its main traits are already set, e.g., architecture and MAC routing. WMNs are attracting considerable research in academia and industry as well, but the lack of open-source testbeds is restricting such a research to simulation tools. The main problem with simulation tools is that they do not reflect the complexity of RF propagation, especially in indoor environments, of which IEEE 802.11s WMNs are an example. This paper presents an open-source implementation of an indoor IEEE 802.11s WMN testbed. The implementation is transparent, easy-to-deploy, and both the source code and deployment instructions are available online. The implementation can serve as a blueprint for the WMN research community to deploy their own testbeds, negating the shortcomings of using simulation tools. By delving into the testbed implementation subtleties, this paper is shedding further light on the details of the ongoing IEEE 802.11s standard. Major encountered implementation problems (e.g., clients association, Internetworking, and supporting multiple gateways) are identified and addressed. To ascertain the functionality of the testbed, both UDP and TCP traffic are supported and operational. The testbed uses the default IEEE 802.11s HWMP (Hybrid Wireless Mesh Protocol) routing protocol along with the default IEEE 802.11s Airtime routing metric.

Implementation frameworks for IEEE 802.11s systems

The standardisation process of IEEE 802.11s requires some effort to be devoted to assess the effectiveness of the proposed solutions. Specifically, the path selection and forwarding facilities, embodied by the Hybrid Wireless Mesh Protocol (HWMP), are the major and most delicate components. A working prototype can be profitably used to experimentally evaluate such features, thus returning immediate and significant feedback. In this scenario, the paper offers a threefold contribution. First, we review the current 802.11s implementation efforts, such as the Open 80211s and One Laptop Per Child projects, highlighting the pros and cons of each solution. Then, we describe a prototype IEEE 802.11s Mesh Access Point (MAP) we developed starting from common off-the-shelf hardware and software. The main innovation of this prototype is the support of both modes of operation of HWMP. Conversely to the other projects, which implement only the reactive mode, our device also supports the proactive mode, and runs it in the same way as suggested by the draft standard, thus becoming a more complete evaluation platform. As a final contribution, we provide some simulation results to assess the behaviour of the mixed proactive–reactive mode. From this evaluation, we can confirm that employing the proactive algorithm can bring some benefits to the operation of the 802.11s network, even though a careful approach must be taken to avoid some drawbacks.

EFT: a high throughput routing metric for IEEE 802.11s wireless mesh networks

In this paper, we present a throughput-maximizing routing metric, referred to as expected forwarding time (EFT), for IEEE 802.11s-based wireless mesh networks. Our study reveals that most of the existing routing metrics select the paths with minimum aggregate transmission time of a packet. However, we show by analyses that, due to the shared nature of the wireless medium, other factors, such as transmission time of the contending nodes and their densities and loads, also affect the performance of routing metrics. We therefore first identify the factors that hinder the forwarding time of a packet. Furthermore, we add a new dimension to our metric by introducing traffic priority into our routing metric design, which, to the best of our knowledge, is completely unaddressed by existing studies. We also show how EFT can be incorporated into the hybrid wireless mesh protocol (HWMP), the path selection protocol used in the IEEE 802.11s draft standard. Finally, we study the performance of EFT through simulations under different network scenarios. Simulation results show that EFT outperforms other routing metrics in terms of average network throughput, end-to-end delay, and packet loss rate.