Microwave Engineering Europe - September 2008 - (Page 12)

12 COVER FEATURE — TESTING LTE/WiMAX Uncovering test and measurement’s role in advancing LTE and Mobile WiMAX™ By Frank Palmer and Jan Whitacre, Agilent Technologies s cellular and wireless connectivity merge, there will be extraordinary potential for growth in wireless data. Much of this growth will be driven by the increasingly busy and mobile consumer lifestyle. The need for increased bandwidth and capacity, coupled with improved spectrum efﬁciency and cell-edge performance, to meet the demand for higher data rates and innovative new functionality will also be a contributing factor. Two wireless technologies promising to address these critical challenges, while vying for leadership position as the 3.9G technology of choice, are the Third Generation Partnership Project Long-Term Evolution (3GPP LTE) and Mobile WiMAX™. Despite the fact that LTE and Mobile WiMAX are seen as competitors in the marketplace, they are at different stages in their development. This can be seen in the current certiﬁcation process for instance. There are currently certiﬁed devices for Mobile WiMAX while the basic LTE standards documents are still under development. There are potentially markets where LTE and WiMAX overlap, but there are also others, such as point to point, where WiMAX is already being used. They do actually share some common ground, including a focus on capacity enhancement and multiplexing schemes such as MIMO and Orthogonal Frequency Division Multiple Access (OFDMA) digital modulation. Some in the industry have even surmised that the Mobile WiMAX and LTE agendas will eventually merge. Regardless of any future outcome on that front, one thing is certain; the availability of test and measurement solutions that parallel standards development is key to driving either standard forward. Examining the technologies To better understand the emerging role of LTE and Mobile WiMAX in the industry today, it’s ﬁrst important to gain a clear understanding of each technology. LTE is the 3GPP’s new air interface for wireless A Figure 1: Peak data rate targets for LTE. access and has the ability to support video services. As the evolution of Universal Mobile Telecommunication System (UMTS) it follows Mobile WiMAX towards an all-IP network, which provides a framework for increasing capacity, improving spectrum efﬁciency and cell-edge performance, and reducing latency. Many of the targets for LTE are similar to those for High Speed Packet Access (HSPA). Both WiMAX and LTE have some speciﬁc additional capabilities such as ﬂexible channel bandwidths and the advantages of OFDMA (Figure 1). LTE and WiMAX have similar spectral performance, largely driven by the radio channel and infrastructure design. LTE offers a 100-Mbps download rate and 50Mbps upload rate for every 20 MHz of spectrum, with scalable channel bandwidth from 1.25 to 20 MHz. It can also provide a headline cell data rate of 326.4 Mbps in the downlink, using multiple antenna conﬁgurations. It is optimized for low speeds (0 - 15 km/h), but can provide performance up to 120 km/h with support for mobility maintained up to 350 km/h. Higher speeds of up to 500 km/h are currently under consideration. Mobile WiMAX is an extension of Fixed WiMAX™ for mobile use in the 2 to 6 GHz band (Figure 2) Based on the IEEE 802.16e standard, soon to become “Rev 2”, it is designed to deliver superior data rates and scalability, lower costs, and reduced network complexity, while providing the foundation for enabling delivery of feature- rich, mobile multimedia experiences. The Mobile WiMAX proﬁle supports mobile broadband services at speeds greater than 120 km/hour. Several important features in Mobile WiMAX include OFDMA and sub-channelization which provide a large amount of ﬂexibility when assigning the time and frequency resources within the wireless channel. Mobile WiMAX provides the ﬁrst truly mobile incarnation of the increasingly popular wireless networking technologies (e.g., Bluetooth and WLAN/WiFi). Where other technologies support “nomadic” users — those who are connected at one location, then move and reconnect at a different location — Mobile WiMAX will support hand-offs from one base station to another to allow continuous (or the appearance of continuous) connectivity for the user. WiMAX is also more immune to interference, allows more efﬁcient use of bandwidth and is intended to allow higher data rates over longer distances. Because it operates on licensed spectrum, in addition to unlicensed frequencies, WiMAX provides a regulated environment and viable economic model for wireless carriers. Challenges ahead The technology challenges and increased complexity of LTE and Mobile WiMAX create new engineering challenges for designers. Some of those challenges relate to the increased complexity and demand for processing power, which stems from the use Microwave Engineering Europe ● September 2008 ● www.mwee.com 012-013-014_MWEE.indd 12 3/09/08 13:52:18 http://www.mwee.com

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Microwave Engineering Europe - September 2008 News Contents Comment Cover Feature: Uncovering Test and Measurement’s Role in Advancing LTE and Mobile WiMAX WiMax: WiMax and LTE Need to Address Issues of Backhaul, Cost and Efficiency for Successful Deployment WiMax: Manufacturing Communications Technology Products in India Test and Measurement Mobile Platforms Evolve to Meet Future Demands Products Calendar

Microwave Engineering Europe - September 2008

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