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Abstract:
The major performance objectives of the next-generation wireless communication systems are high page link capacity and increase application/service performance from the user perspective. An attractive technology for providing broadband access is WiMAX network. For the network and application-level capacity and performance analysis, we first provide an overview of WiMAX network architecture and system performance. Afterward we discuss the benefits and challenges of flat architecture for mobile networks. In this kind of architecture the access service network gateway and base stations are consolidated into a single channel. All-IP flat architecture is a promising option. However, performance goals of the WiMAX system are conflicting: maintenance VoIP quality vs. completely utilization of the remaining capacity for TCP. We investigate the approaches in performance optimization based on TCP modification schemes. The solution is to control TCP traffic before entering WiMAX network in conjunction with methods to dynamically estimate available bandwidth in real time.
1 Introduction
The success of WiMAX high data rate communications in metropolitan area networks (MAN) depends on its capability of providing cost-effective solution for a variety of services [1]. In 2001, the first IEEE802.16 standard was published, while in 2005, the standard IEEE802.16e was approved as the official standard for mobile applications [2]. The mobile WiMAX systems have a higher system capacity and a more sophisticated mechanism to provide a better quality of service (QoS) [3]. To evaluate the mobile WiMAX system capacity and performance, all the aspects of the performance evaluation – from air page link to application– are required.
A mobile WiMAX network support both voice and TCP services. However, performance goals of the system are conflicting: maintenance VoIP quality vs. completely utilization of the remaining capacity for TCP. Services VoIP and TCP cannot simply share the WiMAX medium without severe voice quality degradation and/or reduction in TCP capacity [4]. In order to investigate the interaction between these two categories of traffic, we present TCP modification and control schemes. The solution is to control TCP traffic before entering the multihop network.
The article is structured as follows. The next section discusses the state of the art in WiMAX networks and system performance evaluation, together with benefits of flat architecture of mobile network. We then present solution approaches for TCP and VoIP performance optimization based on traffic modification and control.
2 WiMAX networks architecture
WiMAX (Worldwide interoperability for microwave access) has been proposed as an attractive wireless communication technology due to the fact that it can provide high data rate communications for metropolitan areas. Until now, a number of specifications for WiMAX were standardized by the IEEE802.16 Working group [5]. In addition companies in the industry also have formed the WiMAX Forum to promote the development and deployment of WiMAX systems. According to the standards, WiMAX can support up to a 75 Mbps data rate (single channel) and can cover on how it can provide cost-effective solutions for a variety of existing and potential services [6].
The specifications in the current WiMAX standards can be partitioned into two important parts, the physical (PHY) layer and the medium access control (MAC) layer: