Co-Simulation Based Platform for Wireless Protocols Design Explorations Alain Fourmigue, Bruno Girodias, Gabriela Nicolescu, El Mostapha Aboulhamid Ecole Polytechnique de Montr´ eal Abstract—Longer range, faster speed and stronger link are to- day’s wireless mandatory characteristics. Tremendous efforts are being deployed to create new and improved wireless protocols. How- ever, these new protocols are being tested in harsh and uncontrolled environments. Simulation tools help to capture the expected behav- ior, but the proposed designs might not work in real life situations due to lack of accurate simulation models. Testbed platforms are able to test designs in real life settings, but the flexibility of the design is reduced and design exploration becomes a complex task. This paper presents a hybrid platform composed of a simulation tool and a testbed environment, which makes it possible easily design and accurately test new wireless protocols. I. I NTRODUCTION Wireless is ubiquitous and new applications are multiplying every day. Remote medical assistance, just-in-time logistics systems, mobile live video streaming conferencing will all take advantage of wireless [1]. Slowly but surely, the 3G is becom- ing integrated into our daily lives. Meanwhile, the 4G prepares and promises to integrate various wireless technologies such as WiFi (LAN), WiMAX (MAN), GSM/WCDMA (WAN)[2]. Users demand more and wireless applications are getting more complex. The Physical (PHY) layer needs to be reconfig- urable. The Media Access Control (MAC) layer needs to sup- port QoS and security. The network layer needs more complex algorithms to support more sophisticated network topologies like mesh networks. In the wireless domain, there is still a gap between the mod- eled and the real-life designs. Tools like Matlab/Simulink[4] are frequently used for modeling PHY layers and IF/RF interface. However, these tools are forced to have a very high abstraction of the upper layers like the MAC layer and may compromise on important details. Also, the emergence of cross-layer designs necessitates a tightly coupled simulation/test of all the protocol layers. For a complete conception flow, model-based design simulation necessitates its seamless integration to a testbed plat- form. We make it possible by using co-simulation with model- based tools like Matlab/Simulink and a real-life environment. This article presents a platform for designing wireless proto- cols. This platform uses Matlab/Simulink as a simulation tool and Linux as a testbed environment. Matlab/Simulink provides us with model-based design and Linux offers us a flexible environment with real-life applications and drivers which can host real final MAC implementation. The main contribution of this article is to provide a set of generic interfaces to embed a MAC layer in a Linux driver and communicate both with the PHY layer simulated in Mat- lab/Simulink and the Linux network stack. Therefore, it is possible to evaluate the MAC and PHY layers working together with the Linux TCP/IP stack, processing real data produced by any of the various network applications that run under Linux. The remainder of this paper is organized as follows : section 2 discusses related work, section 3 overviews the platform, section 4 describes the needed interface, section 5 gives an example of protocol in the proposed platform, and section 6 presents the concluding remarks. II. RELATED WORK Wireless networking is a very active research domain, conse- quently there exist a very large number of network simulators and testbeds [5-13]. The two most popular network simulators are NS-2[14] and OPNET[7], which both support simulation of TCP/IP protocols and classic MAC protocols. Another simulator, the TrueTime simulator, is more recent in the networking domain and has the pecularity to use model based designs [10]. This platform consists of a Simulink block library which is used to simulate networked control systems. TrueTime introduces a kernel block to simulate a real-time environment. However, compared to NS-2 and OPNET, the TrueTime’s layers models are not as accurate [7]. Although network simulators provide a good degree of flex- ibility and reusability, they are often criticized for their lack of accuracy and precision [6, 8]. Therefore, network’s simulators may not be able to truthfully capture a real wireless environ- ment, since they lack in accurate protocol implementations. To evaluate protocols with representative traffic and applications, many designers choose to evaluate their designs and concepts by using real environment platforms called testbeds [6, 8]. Most of the proposed testbeds [5, 6, 8, 5, 11] in the litera- ture preferred the Linux platform. The possibility to integrate specific hardware like antennas or FPGAs (through device drivers) to a real networking implementation (i.e. the Linux TCP/IP stack), makes it a really attractive environment for researchers and designers. Any application built on TCP/IP can be used as an application for testing purposes. However, producing a testbed is time consuming and requires a lot of effort, whereas pure simulation has the advantage of being flexible and reusable. Therefore, a growing number of platforms for wireless protocol design try to merge simulation and testbed environments [6] to get the best of the two worlds. Hydra [15] seems to be currently the best effort towards these types of environments. It is a flexible Linux-based testbed that can be used to validate wireless protocols. Hydra uses software based MAC and PHY. To facilitate experimentations, 978-3-9810801-5-5/DATE09 © 2009 EDAA