Chapter 12: Efficient Use of Radio Resources

Jérôme Brouet,

Alcatel, France

12.1 Introduction

WiMAX systems are designed to provide high spectral efficiency in order to offer very high data rates to users. The robust physical layer based on the OFDM/OFDMA technique and the use of high-performance coding are partly responsible for the resulting high spectral efficiency (see Chapters 5 and 6).

On the one hand, spectral efficiency is enhanced by WiMAX Radio Resource Management (RRM) mechanisms (see Section 12.3). Those mechanisms, specified in the IEEE 802.16 standards include admission control, power control, link adaptation and dynamic frequency selection ^[1],[22]. In addition to these radio mechanisms, the WiMAX Forum defines a framework and a functional split of the radio resource management procedures in the WiMAX radio access network (WiMAX architecture is described in Chapter 13). This framework actually further optimise RRM procedures (mainly for admission control and handover) and is especially needed for consistent RRM operations in a multivendor WiMAX radio network.

On the other hand, high spectral efficiency and performance superiority over the other radio systems is also achieved by the use of advanced antenna technology systems. The IEEE 802.16 standards and associated WiMAX profiles are presently defining and taking provisions for several alternatives for implementing advanced antenna technologies (see Section 12.4). In the present version of a mobile WiMAX, both adaptive antenna technology with beamforming and MIMO technology are possible. While multiple antenna technologies had only been adopted in enhanced releases for 3GPP and 3GPP2 standards, which makes their massive deployment challenging in an existing mature network, these technologies are actually supported from the very first release of mobile WiMAX systems, making them a real feature for first WiMAX radio network deployments and consequently the key cornerstone for excellent radio performance.

Whereas previous techniques are clearly improving the performance of the systems for unicast connections between a BS and an MS (Mobile Station), the WiMAX Forum has also taken provision for an efficient support of Multicast/Broadcast Services (MBS) over the WiMAX air interface. In order to achieve high performance, WiMAX system deployment should follow some guidelines exposed hereafter.

^[1]IEEE 802.16-2004, IEEE Standard for Local and Metropolitan Area Networks, Air Interface for Fixed Broadband Wireless Access Systems, October 2004.

^[22]Rappaport, T.S., Wireless Communications; Principles and Practice, Prentice-Hall, 1996.