The aim of this chapter is to overview some problems of WiFi access networks, to explain some solutions, and to present a combined tool (that implements these solutions) to allow the user access to multimedia information efficiently. The combined tool allows: Traffic classification to make heterogeneous bandwidth reservation, the management of the dynamic association of static mobile devices to WiFi Access Points to better balance their load sharing (number of associated mobile devices), and the management of Access Points’ load sharing, guiding mobile devices to another position so that they may be associated to a low load sharing Access Point. The tool is an application’s level software based on manager/agent architecture. The agents manage link level’s information picked up in the mobile device and the manager regulates the access to the Internet in the Access Points. There are some works that implement solutions for the problems reviewed in this chapter, but there are not tools like the one presented here. The chapter’s main contribution is the combination of these solutions to practical case studies. The experimental results presented in this chapter demonstrate that the tool improves the QoS of WiFi access networks.
TopIntroduction
Nowadays, research in wireless networks is a priority in communication networks, technologies and services research areas. The traffic generated at present by home and enterprise wireless networks represents the bigger amount of traffic injected in the Fixed Internet Backbone. Moreover, the number of mobile devices grows geometrically every year. There are also an increasing growth of users and kinds of devices that use successfully wireless networks technologies. Services like mobile Voice over Internet Protocol (VoIP), Hypertext Transfer Protocol (HTTP) and Simple Mail Transfer Protocol (SMTP) are massively used. New multimedia services are a reality due to the use of mobile devices (Portable Personal Computer [PC], Personal Digital Assistant [PDA], tablets, Smartphone, e-readers...) provided with Wireless Fidelity (WiFi) and Third Generation (3G) technologies.
A mobile device in a WiFi access network can access Internet using a typical Access Point (AP), Tethering or a PC with two network interfaces (WiFi and Ethernet) in which a free operating system (hence referred to as Linux Wireless Router (LWR)) is installed. The Service Set IDentifier (SSID) of the WiFi network is defined by the AP or the LWR which identifies a particular work frequency (channel) and a method of authentication. Each mobile device that wants to use the WiFi network must be associated to that SSID. After the association process, the AP or LWR will have a record of all their associated mobile devices. Mobile devices in modern Wireless Spontaneous Networks (WSN) (Silva & Salgado, 2006) use Tethering to access Internet. In this chapter we will present some experimental results using LWRs.
The Quality of Service (QoS) of the WiFi access networks is low (Sobrinho, 1999). Different parameters affect QoS: reduced bandwidth, radio interference, limited number of available channels, overhead of security traffic and saturated spectrum... (Jangeun, 2003). The QoS is also affected by the Medium Access Control (MAC) (IEEE, 1999) which does not limit the amount of time of transmission of mobile devices. Therefore, the only traffic class WiFi access networks support is best effort which imposes severe restrictions to multimedia communication. WiFi has been improved along the last years, for example: a) International Engineering Electric and Electronic (IEEE) 802.11n takes advantage of radio reflections, fading and multipath radio signals using Multiple Input Multiple Output (MIMO) technology. b) Compliant IEEE 802.11e (Xiao, 2004; Boggia, 2004) APs add changes in the waiting time among mobile devices and introduce queues to classify and prioritize data packets (Qiang, 2005). Vinnakote (2006) proposes a new MAC which defines traffic classes: voice, video, best effort and prioritization of packets. The adoption of these solutions by the Market is still reduced. This is in part due to the full adoption of solutions introduces changes in the firmware or driver of the mobile device WiFi interface card. But these changes do not guarantee the compatibility with previous WiFi standards or mobile device’s firmware or driver versions. The QoS of multimedia communication is typically measured combining parameters like speed, throughput, latency and jitter. The user experience is affected by aspects like automatic re-association of mobile devices to APs (Rodrigues, 2009), efficient control of APs’ load sharing (Toh, 2002) and adverse effects of service disruptions.