Microwave Engineering Europe - January/February 2008 - (Page 31)

WiMAX 31 WiMAX remote-tilt antenna solution, such as the APXVx56516-RET model pictured, will be an essential feature of large-scale WiMAX network deployments. Similarly, the complex spectrum allocations of WiMAX, coupled with its predicted ‘hot-spot’ style deployments, will inevitably present new and challenging colocation interference scenarios. WiMAX ﬁlters will need to be tailored to suit the unique frequencies, channel bandwidths and co-location scenarios of each region. The unpredictable and critical nature of such co-location interference has focused the attention of key RF technology players. In this area, RFS is working with OEMs and carriers in North America and Europe to develop a range of WiMAX integrated base station ﬁlters — classic cavity ﬁlters, ceramics and hybrids — to meet these needs. Most particularly, RFS is exploring the development of a generic narrow-band ﬁlter that would be ‘site conﬁgurable’ to suit the wide range of prospective requirements with both the bandwidth and centre frequency being adjustable — a generic WiMAX ﬁlter to meet most needs. This will provide the dual beneﬁts of reduced price-point (due to economy-ofscale), plus a globally common ﬁlter platform. Tower-top diversity The diverse range of prospective WiMAX carriers — and their equally diverse business models — demands a uniquely wide selection of tower-top solutions. WiMAX carriers have already demonstrated a need for conventional single-polarized sector antennas, cross-polarized single-array sector antennas, electrical-tilt antennas, beamforming ‘adaptive antenna systems’ with multiple arrays, and full MIMO solutions. In addressing all these needs, RFS has opted for wideband WiMAX antenna solutions, which support the broadest range of WiMAX bands and channels in a limited number of models. Tower-mount ampliﬁers (TMAs) speciﬁcally designed for TDD application will also be required. Here, RFS has developed unique WiMAX TDD TMAs that automatically switch between transmit and receive bursts in precise synchronization with the base station. WiMAX duplexers, diplexers and triplexers will, no doubt, be added to this mix. The transmission line solution applied in WiMAX’s link-budget-demanding spectrum must be low-loss and broadband. While premium attenuation coaxial transmission line solutions address these needs, other solutions — such as ‘ﬁbre-to-the-tower-top’ (remote radio head (RRH)) technologies — are also being explored. RRH architectures centrally house the base-band radio equipment in socalled ‘hotels’, which are connected via ﬁbre links of up to 15 km to the non base-band RRH radio components located at the base of the tower or the tower-top. The RRH approach makes great sense in the WiMAX domain. The reduced line losses and at-tower ampliﬁcation support WiMAX’s inherent PA power limitations, while the ‘hotel-and-ﬁbre’ approach streamlines network deployment, particularly given the granular nature of WiMAX site mapping. MIMO and the future The attraction of MIMO solutions in the WiMAX domain are tempered somewhat by its non-standard band and channel allocations. Currently, WiMAX MIMO antenna solutions are tailored to suit — in essence, the OEM’s MIMO signal processing design and the MIMO antenna solution are ‘tuned’ together as a matched pair. RFS is currently working to obviate this problem, by developing a cross-polarized ‘generic’ MIMO antenna solution — an open-interface MIMO antenna solution that will suit multiple OEMs and a wide range of spectrum allocations. The ‘off-the-shelf’ nature of this solution will provide enormous price-point advantages, plus faster site deployment cycle times. The ultimate evolutionary goal for WiMAX is to realize the International Telecommunications Union’s 4G ‘Next Generation Mobile Network’ objectives — 100Mbps mobile and 1Gbps ﬁxed/portable throughput. Here, much effort is being focused on beam-forming, MIMO and ‘smart antenna’ solutions, coupled with advanced signal processing algorithms. This is a clear indicator of the importance of the RF interface in the WiMAX realm. Perhaps more than any platform before it, RF technology will play a pivotal role in the commercial success and evolution of WiMAX. Jörg Springer, Vice President Global Marketing & Communications with the wireless technology group Radio Frequency Systems (RFS). About the author Jörg Springer is Vice President Global Marketing & Communications with the wireless technology group Radio Frequency Systems (RFS). RFS is a global designer and manufacturer of cable and antenna systems plus active and passive RF conditioning modules, providing total-package solutions for wireless infrastructure. The company serves OEMs, distributors, system integrators, carriers and installers in the wireless communications, microwave, landmobile and broadcast sectors. Mr Springer has over 15 years of experience in global marketing and business development. He has held executive positions in Mercosul, North America and Europe, such as Director of Product Line Communications with a multinational European OEM and Head of Business Development with a Brazilian group based in Rio de Janeiro. Mr Springer is publisher of the quarterly wireless industry journal STAY CONNECTED, and is a member of the German Association of Journalists. He holds a Masters degree in Business Administration (MBA). Microwave Engineering ● January/February 2008 ● www.mwee.com 030_031_MWEE.indd 31 24/01/08 15:24:22 http://www.mwee.com

Table of Contents Feed for the Digital Edition of Microwave Engineering Europe - January/February 2008

Microwave Engineering Europe - January/February 2008 Contents News Comment Radio: Raising the Bar for the Radio: Making 802.11n Work Cover Feature: The RF-System-In-Package Trend - Efficient Design with Advanced Design System 2008 Wireless Sensor Networks: The Zigbee PRO Feature Set: More of a Good Thing Very Fast Measurements of Wireless Devices with Small Antennas in Reverberation Chambers WiMAX Update 2008 Bridging the Gap from the CMOS DSP to the Antenna in OFDM Systems Products Calendar

Microwave Engineering Europe - January/February 2008

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