Agilent Measurement Journal - Issue 3 - 2007 - (Page 37)

expensive. The two major infrastructure costs are the initial site acquisition and equipment costs plus the ongoing rental and backhaul costs. Capital expenditures and some operating expenditures scale linearly with system capacity, which, for satisfactory QoE, must grow substantially — and demands perhaps a 10 times increase in cell density. In addition, the backhaul costs must scale with the system’s peak rate (not the average) which for the next generation represents nearly 100 times what is deployed today. Matching technology to the problem Technology should be appropriate to the problem. We could have our mail delivered by helicopter or commute to work using a drag racer, but we don’t because transportation has had millennia to evolve and we understand what works best. By comparison the broadband wireless industry is in its infancy and remains in search of its raison d’etre. Continuing to evolve the current centrallymanaged cellular model to deliver peak rates presents many challenges. The physics, politics (site availability) and economics all look problematic. This suggests a bifurcation of the market will occur. Traditional cellular can focus on and optimize the all-important ubiquitous average macro-cell experience, and alternative low-cost approaches will have to be developed to deliver localized high-data-rate solutions much closer to the point of demand. Designing cellular networks at just above the expected average performance would considerably simplify the cost and challenge of introducing technology that brings new service capabilities and valuable improvements such as reduced latency. Looking at costs, there are aggressive goals to introduce products in the $300 range based on mobile rather than the more-expensive base station components. Ultimately, sales volumes will deﬁne the costs and this should not prevent the concept from taking off. As for interference mitigation, this cuts both ways. On the negative side, femtocells operating in licensed spectrum have much tougher expectations of not interfering with the cellular network than the ad hoc Wi-Fi systems operating in unlicensed spectrum. On the positive side, however, femtocells are based on cellular technology that is designed to be spectrally aware and has the potential to control its power and frequency in a more sophisticated way than is possible with current Wi-Fi. That said, the 802.11 standard continues to develop and be deployed far faster than cellular with the introduction of 802.11n. The headlines for this evolution are almost always about its MIMO capability, which has perhaps not lived up to early expectations. Of more signiﬁcance, though, especially in demanding enterprise or public environments, is the inclusion of cellular-style access control that prevents the system being brought down by excessive demand. Also, 802.11h has added power control and dynamic frequency selection to allow its use in the 5 GHz band currently occupied by radar. Looking to the future The physical and commercial constraints on implementing highdata-rate cellular services must be considered. As with transportation systems where there is a wide mix of vehicle types to match the range of channels, so it will be with wireless. The cellular industry needs to continue to optimize performance for the average user as deﬁned by the statistics of the radio channel and not risk getting distracted by peak performance. Cellular’s focus should move from technology towards the development of compelling services with high QoE. The battle for the high-datarate home and enterprise wireless markets will continue, and whether the winner is based on Wi-Fi or the more advanced femtocells, Agilent is ready to provide the tools the industry needs to design and optimize the right wireless technology for the future. References 1. 3GPP TS 25.101 v7.8.0 Tables 9.8D3, 9.8D4 and 9.8F3 2. 3GPP TR 25.912 v7.2.0 section 13 3. 3GPP TS 42.056 v4.0.0 GSM Cordless Telephony System “WiMAX” and “Mobile WiMAX” are trademarks of the WiMAX Forum. Comparing Wi-Fi and femtocells for high data rates Today we have signiﬁcant deployment of private and public wireless access based on IEEE 802.11 (Wi-Fi). These have improved in performance and coverage at a remarkable rate. Unfortunately, though, their simpler technologies and unlicensed operating band are very prone to interference and have become a victim of their own success in some areas. The lack of transmit power control considered essential for cellular is a major issue. Fortunately, with over 600 MHz of spectrum at 2.4 and 5 GHz, Wi-Fi has more room to expand and thus fewer efﬁciency worries than cellular. An alternative to Wi-Fi is the emerging cellular “home base station” or femtocell. These have been proposed and even standardized but have never taken off.3 Now, there is evidence that the situation may be changing. The two big challenges for femtocells are cost versus Wi-Fi and interference mitigation to protect the licensed cellular network. Agilent Measurement Journal 37

Table of Contents Feed for the Digital Edition of Agilent Measurement Journal - Issue 3 - 2007

Applying Ingenuity to the Measurement of Emerging Technologies Contents Emerging Innovations Department Delivering Bigger Benefits by Optimizing Customer Workflows Measuring Material Properties at the Nanoscale Utilizing In Situ Atomic Force Microscopy in Life Science, Pharmaceutical and other Bio-Related Applications WiMAX™: Plotting a New Path to Global Mobility Addressing the Triple Complexity of Triple-Play Networks What Next for Mobile Telephony? Exploring the Inner Workings of Tire-Pressure Monitoring Systems Developing, Assessing and Applying a High-Resolution Thin-Film Magnetic Probe Making Accurate Settling-Time Measurements Using a Vector Network Analyzer Applying Metabolomics Methods to the Study of Bacterial Leaf Blight in Rice Plants Measuring Stream Dynamics with Fiber Optics survey

Agilent Measurement Journal - Issue 3 - 2007

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