Σάββατο, 6 Ιουλίου 2013

Introduction

Technical University of Eindhoven – Regulations and Standards for Wireless Communication-0EL70 (Introduction)
This is the first of a series of posts about WiMax (IEEE 802.16) for the course “Regulations and Standards for Wireless Communication” of Technical University of Eindhoven, a regular elective for the Broadband Telecommunications Track of the Master Program of the Department of Electrical Engineering. We will start with a technical description of the protocol, then present the standardization process of it and finally analyze the security issues and the (suggested) uses of it. Both the so far and the potential future applications and markets will be described.
Figure 1: Coverage and bitrate of several wireless technologies
WiMax refers to Worldwide Interoperability for Microwave Access, with a designed offered bitrate of 30 to 40 Megabits per second (Mbps) initially, which extended to 1 Gigabit per second (Gbps) for fixed stations in 2011. The maximum range is about 50 kilometers in radius [11]. There have been several updates of the IEEE 802.16 standard. It started in 2001, which was superseded. The first final version was 802.16-2004 in 2004 and the most recent final version is 802.16m in 2011, while 802.16n and 802.16p are still being processed, as of July 2013 [12].
WiMax has been suggested as a solution and alternative to several different technologies, such as LTE (Long Term Evolution) mobile networks (often called 4G), DVB-T (Digital Video Broadcasting – Terrestrial), commercial triple-play (data, voice and video) at the last mile of copper today and even as a substitute for backhaul and backbone links of telecommunications providers [11].
Despite the initial expectations that had arisen, WiMax has not met those expectations yet, achieving very small penetration percentages in most countries worldwide (especially in the “Western World”, ie the European Union, the USA, Japan, South Korea, Canada and Australia) compared to the GSM/CDMA services and in general failing to prove as a real alternative to any of the technologies mentioned above [2]. A comparison of WiMax to similar technologies is shown in Figure 1.

The efficiency of WiMax is dramatically affected by the distance between the user and the Base Station (where the antenna and the transceiver are placed). The theoretical maximum bitrate is achieved only inside the area of 1 kilometer radius , while for subscribers at the edge of the range of 50 kilometer, the practical achieved bitrate indoors has been observed to be 4 Mbps and less [11]. This dictates that coverage at the top limit of the range faces many problems and does not correspond to the theoretical technical specifications. 

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