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Unformatted text preview: IEEE Wireless Communications • August 2006 31 1536-1284/06/$20.00 © 2006 IEEE IFFT CP OMOD OMOD OMOD MIMO-OFDM is an attractive air-interface solution for next-generation wireless local area networks (WLANs), wireless metropolitan area networks (WMANs), and fourth-generation mobile cellular wireless systems. A DVANCES IN S MART A NTENNAS I NTRODUCTION The key challenge faced by future wireless com- munication systems is to provide high-data-rate wireless access at high quality of service (QoS). Combined with the facts that spectrum is a scarce resource and propagation conditions are hostile due to fading (caused by destructive addition of multipath components) and interfer- ence from other users, this requirement calls for means to radically increase spectral efficiency and to improve link reliability. Multiple-input multiple-output (MIMO) wireless technology  seems to meet these demands by offering increased spectral efficiency through spatial- multiplexing gain, and improved link reliability due to antenna diversity gain. Even though there is still a large number of open research problems in the area of MIMO wireless, both from a theoretical perspective and a hardware implementation perspective, the technology has reached a stage where it can be considered ready for use in practical systems. In fact, the first products based on MIMO technology have become available, for example, the pre-IEEE 802.11n wireless local area network (WLAN) systems by Airgo Networks, Inc., Atheros Com- munications, Inc., Broadcom Corporation, Mar- vell Semiconductor, Inc., and Metalink Technologies, Inc. Current industry trends sug- gest that large-scale deployment of MIMO wire- less systems will initially be seen in WLANs and in wireless metropolitan area networks (WMANs). Corresponding standards currently under definition include the IEEE 802.11n WLAN and IEEE 802.16 WMAN standards. Both standards define air interfaces that are based on the combination of MIMO with orthogonal frequency division multiplexing (OFDM) modulation (MIMO-OFDM). Ongo- ing fourth-generation mobile cellular system prestandardization efforts in Europe, which are carried out in the context of various “Integrated Projects,” funded by the European Commission within its Sixth Framework Program (FP6), also show strong support for a MIMO-OFDM air interface. The goal of this article is to provide a high- level review of the basics of MIMO-OFDM wireless systems with a focus on transceiver design, multiuser systems, and hardware imple- mentation aspects. The remainder of this arti- cle is organized as follows. The next section contains a brief introduction into MIMO wire- less and OFDM. We then discuss space-fre- quency signaling and corresponding receiver design for MIMO-OFDM systems. An overview of multi-user MIMO-OFDM systems is fol- lowed by a summary of recent results on the VLSI implementation of a four-stream spatial- multiplexing MIMO-OFDM transceiver. Final- ly, we provide a list of relevant open areas for...
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This note was uploaded on 09/21/2010 for the course ECE 567 taught by Professor Attkin during the Spring '10 term at Academy of Design Tampa.
- Spring '10