E-band Benefits Benefits of E-band systems over other solutions
E-Band Communications Corp.
The Benefits of E-band Systems Over Other Wireless Technologies By Jonathan Wells, PhD The 71-76 and 81-86 GHz bands (widely known as “e-band”) are permitted worldwide for ultra high capacity point-to-point communications. E-band wireless systems are available that offer full-duplex Gigabit Ethernet connectivity at data rates of 1 Gbps and beyond in cost effective radio architectures, with carrier class availability at distances of several miles. There are several technologies competing to provide wireless broadband connectivity and bridge the last mile gap. This paper explores how e–band wireless systems compete effectively against these alternatives, and brings significant advantages to wireless system providers and network designers. The High Capacity Wireless Landscape Figure 1 details the major higher capacity wireless technologies presently available, and how they fit together to make up the current broadband wireless landscape. WiFi – 802.11 a/b/g WiFi is a short distance, multi-access technology. Its popularity stems from being able to take a single data connection (usually a residential or equivalent broadband internet connection) and enable several users within a “hot spot” area to share that data connection. Equipment is currently widely available that can offer data rates of up to 54 Mbps and coverage distances of up several tens of yards, enabling users with suitable connection equipment fast and easy wireless access to whatever services are being offered. Extended versions of the WiFi family are constantly evolving, improving performance and speeds. The latest 802.11n version offers improved data rates through the introduction of multiple antennas and wider channel transmissions. Like most technologies, WiFi has a number of limitations. Practically, data rates are dependant on the distance from the access point, the number of users sharing the capacity, and the usually constrained size of the access point’s broadband connection. In commercial hot spot environments, users would typically realize only 1 Mbps or so connectivity. By necessity, WiFi is also an unlicensed, broadcast, point-to-multipoint
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technology, allowing users to easily connect and disconnect from the service. This means interference, data contention and data collisions are difficult to avoid, resulting in network outages, connectivity issues and security concerns.
Figure 1: The high speed wireless and wired technology landscape. For these reasons, WiFi is not a useful technology for wide area high data rate connectivity. It is a very useful wireless technology for easy access, short range coverage within a limited range “hot spot”, properties that have made the technology very popular. 4G – WiMAX, LTE and UMB Fourth-generation (4G) wireless systems – the technologies of WiMAX, LTE and UMB – promise a substantial increase in data rates over existing second and third generation (3G) cellular systems.
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WiMAX is the closest of these technologies to realization. Many proprietary pre-WiMAX networks and true fixed (802.16-2004) and mobile (802.16e-2005) WiMAX installations are already successfully in operation around the world. WiMAX is often described as a “big brother” version of WiFi. The WiMAX standard has addressed many of the qualityof-service (QoS) and security issues inherent with WiFi and when properly implemented, provides a much higher user experience. In addition, WiMAX is usually implemented using licensed technology in frequencies close to the cellular bands, further improving the QoS of the service. Theoretical data rates of many tens of Mbps are possible, and real systems are offering user data rates of 2 to 4 Mbps and up over cell sizes of a few miles. Future extensions to the WiMAX family (for example 802.16m, or mobile WiMAX release 2.0) will further extend user data speeds and experiences. WiMAX does offer the benefit of mobility, making the analogy to advanced cellular systems more accurate than to WiFi networks. LTE and UMB technologies are the next generation of the existing 3G cellular technologies. Theoretically, data rates to 100 Mbps and beyond are possible. Complete standards are likely to be realized in the next few years, and early experimental systems demonstrating improved data throughput are already being seen today. For these reasons, 4G technologies are ideally placed to be useful for wide area, mobile connectivity, with data rates higher than existing cellular standards. WiMAX is already a reality, and announcements from mobile network carriers suggest the other technologies will be reality soon. As 4G technologies are all access technologies, upgrade of the backhaul networks are required to support the 4G increases in data rates. That makes these technologies very complementary to the high data rate point-to-point technologies introduced later in this document. Point-to-Point Microwave Fixed wireless radios at microwave frequencies from 6 to 38 GHz are widely used for point-to-point (PTP) data transmission. Especially in Europe and the developing world, PTP microwave is used to interconnect cell site and fiber points of presence. PTP systems are widely available with data rates from a few Mbps up to several hundred Mbps. To support the higher wireless standards (for example, 100 Mbps fast Ethernet and 155 Mbps STM-1 SDH and OC-3 SONET), PTP microwave radios have to compress the data into the narrow channels that are required in the microwave frequency bands. These can be up to 50 or 56 MHz, but are typically 28 or 30 MHz and below. Thus PTP microwave radios employ sophisticated signal processing circuitry and high order 128 or 256 QAM modulation to squeeze data into the narrow available
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channels. These highly complex systems result in increased product costs and system performance tradeoffs, yet still limit practical data rates in the most advanced products to 311 Mbps. Systems are available that can achieve higher data rates, employing such techniques as Cross Polarization Interference Cancellers (XPIC) to reuse frequencies for dual data streams. However such configurations require doubled-up hardware (multiple units and antennas) resulting in multiplications of system costs and increased system install and maintenance. Microwave radios have an important role to play for high quality PTP connectivity. Systems can be engineered to reliably transmit for several miles and the use of licensed technology means the systems will be robust and reliable. However limited regulated channel sizes in the microwave bands means that even the most complex and sophisticated widely available systems are limited to 311 Mbps or so data rates. 60 GHz Wireless 60 GHz has been used as a wireless transmission frequency for many years, due to the property that oxygen in the atmosphere strongly absorbs radio waves at this frequency. Users, particularly in the military, have exploited this characteristic by developing short range systems that will transmit a few hundred yards before the signal rapidly deteriorates and so cannot be eavesdropped. The availability of large amounts of bandwidth at these frequencies has resulted in recent commercial interest for high data rate short range commercial applications. Differing worldwide spectrum allocations of the 60 GHz bands means regional differences in available equipment. In the USA, large amounts of bandwidth are available, enabling cost effective systems that can transmit data rates to 1 Gbps to be realized. However the natural oxygen attenuating properties and low regulated power limits means such system can only reliability transmit a few hundred yards. With “best effort” connectivity, system can be engineered to transmit up to half a mile. Since the band is designated as license exempt in the US, systems are potentially at risk from interference, either from other links or from future services which might use the open bands. In Europe, the bands are managed very differently, with narrow channels limiting the data throughput of systems. For these reasons, 60 GHz radios are very useful for providing high data rate interconnections in the USA. However systems are limited in distance to just a few hundred yards, and the unlicensed nature of the bands poses problems for sophisticated users who do not want to risk downtime due to interference outages.
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Free Space Optics Free space optic (FSO) systems use modulated lasers to transmit very high data rates in the invisible optical spectrum close to the visible bands. Systems are available that can transmit data rates of 1 Gbps and beyond. FSO suffers from the disadvantage that as a highly focused optical technology, any deterioration or blockage of the laser-like signal path will affect the link quality. Atmospheric effects such a fog, dust, sand, air turbulence and sunlight shimmer limit practical link distances to just a few hundred yards in many parts of the world. In addition, practical effects such as flying objects breaking the beams, or tiny building or tower movements unlocking the precisely pointed equipment, means that sophisticated tracking mounts and multiple transmitters and receivers are required. This results in high complexity equipment, adding to system cost, and introducing reliability and maintenance concerns. Finally the use of lasers raises eye safety concerns, and also reliability questions due to the naturally high failure rate of optical devices. Like 60 GHz radios, FSO systems are useful for high data rate transmission over distances of a few hundred yards. High performance systems can be very complex and expensive to maintain, with equipment reliability and failure rates much higher than standard radio systems. The Fiber Optic / Wireless “Gap” Fiber optic cable is the panacea of high data rate technologies. The wide bandwidths available and the substantial investment made in fiber technology and optical transmission networks means that very high data rates can be transmitted over very long distances over most of the developed world. Despite these advantages, fiber is not everywhere. The vast majority of commercial buildings do not have fiber connections, and those that do are charged very high lease rates for high data rate services. Current lease rates for 155 Mbps and up data rates can run as high as $10,000 per month, making investment in alternative high capacity systems attractive. Trenching fiber can also be very expensive, with costs per mile approaching $250,000 in large urban cities. Until recently, there was a large “gap” between fiber and other wireless technologies (see figure 1). Of the technologies discussed so far, only two can reach fiber-like gigabit per second speeds. These are both limited in distance of just a few hundred yards, significantly limiting their effectiveness as part of wide area networks. There are
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numerous longer distance wireless alternatives, but these are limited in data rate to around 100 Mbps or so. For many years, fiber optics remained the only way to realize medium and long distance communications at the prevalent GigE networking interface speed, but the economics of installing and maintaining meant its accessibility was limited to just a limited number of incumbents. For these reasons, the FCC and many other regulators around the world have opened up the e-band 71-76 GHz and 81-86 GHz frequency bands. The availability of this spectrum enables fiber-like gigabit per second and up interconnection speeds, multiple mile transmission distance systems, and products with significantly lower cost and improved economics over buried fiber. E-band Wireless The 71-76 and 81-86 GHz e-band frequencies were implemented in part to address the shortfalls of these other wireless technologies. The bands are globally available for fixed wireless point-to-point communications. The 10 GHz of bandwidth available – the largest ITU bandwidth allocation for such services – provides such a large bandwidth that ultra-high data rate wireless capacities of 1 Gbps and beyond can be realized with relatively simple, low cost radio architectures. The 71-86 GHz frequencies occur in an “atmospheric window”, whereby atmospheric attenuation is similar to the well used lower frequency microwave bands of 23 and 38 GHz. With similar propagation characteristics to these popular bands, and well characterized weather attributes allowing rain fade to be understood and predicted, link distances of several miles can confidently be realized. To encourage uptake of services in these bands, the FCC, along with various other wireless regulatory agencies around the world, have implemented “light licensing” regimes for the bands, whereby the full benefits of interference protection are awarded to system providers, but with licenses that can be quick and cheaply obtained. High Data Rate Wireless and Fiber Comparisons E-band wireless systems offer a compelling alternative to these different broadband technologies, often with many advantages over other systems. A summary of how the most important system parameters and network characteristics compare are detailed in the following table.
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WiFi Variable, typically 1 Mbps
3/4 G Variable, typically 10 Mbps
Microwave 2 to 311 Mbps
60 GHz 100 Mbps to 1 Gbps
FSO 100 Mbps to 1 Gbps
Fiber To 40 Gbps
Typical distances for carrier class performance Spectrum availability and licensing
20 yards
2 miles
5 miles
500 meters
200 meters
Unlimited
Freely available for unlicensed use
No
Usually available for area licensing from country regulators Yes
Varies country by country. Available for unlicensed use in USA No
Spectrum freely available as technology not regulated No
n/a
Guaranteed interference and regulatory protection Relative cost of ownership Install and commissioning time
Spectrum very scarce. Owned and fiercely protected by select incumbents Usually
Yes
Available worldwide, usually as a low cost rapidly obtained “light license” Yes
Low
High
Medium
Medium
Medium
High
Medium
Hours
Months/Years
Weeks / Months
Hours/Days
Hours/Days
Months/Years
Hours/Days
Data Rates
E-band 100 Mbps to 3 Gbps today; to 10 Gbps in the future 1-3 miles & higher
Table 1: Comparison of key system parameters for leading high data rate technologies. E-band Wireless Benefits E-band wireless systems offer the most compelling alternative to buried fiber. Of all the high capacity wireless technologies, e-band systems offer numerous benefits. These include: • Highest data rates – E-band offers the highest data rates of any wireless technology, with systems available that offer 1 Gbps and above full-duplex throughput. • Guaranteed data rates – Unlike WiFi, WiMAX and other broad-coverage technologies whose system performance depends heavily on the radio environment, number of users, distance from base station and even installation quality, e-band systems offer guaranteed data throughput performance, even under deteriorated transmission conditions.
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•
•
•
•
•
Long distance transmissions – With the exception of lower data rate and more complex microwave systems, e-band wireless offers the longest transmission distances of the higher capacity wireless systems. Under any environmental condition, a 1 Gbps e-band system can transmit many times further than similar data rate 60 GHz or FSO systems. Robust weather resilience – All the higher frequency wireless systems – microwave, 60 GHz, FSO and e-band – are susceptible to rain fades. Proper path planning techniques, using established and proven precipitation models, enable system designers to implement robust wireless networks that meet their system availability requirements. Unlike FSO, e-band is not subject to fog, dust, air turbulence or any other atmospheric impairment that can take down optical links for hours over regular cycles. Guaranteed interference protection – Since e-band is a licensed technology, all links have to be registered with national wireless regulators and coordinated with other links in the area. This gives links full interference protection from other nearby wireless sources. In the unlikely event of interference, the full weight of the wireless regulator is available to identify and remove the interference source. Low cost, rapid license availability – In many countries, links are licensed under a “light license” process, whereby licenses can be obtained quickly and cheaply. Such licenses provide the full benefits of traditional link licenses, but at a fraction of the cost and time. (In the USA, for example, a 10-year e-band link registration can be obtained over the internet in minutes at a cost of just $75.) Cost effective, fiber-like wireless solution – High capacity wireless systems are available at a fraction of the cost of buried fiber alternatives. Installed wireless systems have payback periods of months when compared to the costs of trenching new fiber. Installing dedicated wireless technology can often be more economic than leasing fiber-provided high capacity services.
Conclusions The 71-76 and 81-86 GHz e-band frequencies are globally available for ultra high capacity point-to-point communications, providing Gigabit Ethernet data rates of 1 Gbps and beyond. Cost effective radio architectures have been realized that enable carrier class availability at distances of a mile and further. There are numerous technologies available to provide wireless broadband connectivity and provide fiber-like services to bridge the last mile gap. This paper explores these alternatives and shows how e-band wireless offers significant benefits over other technologies. These attributes clearly position e-band wireless as the most robust high
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capacity wireless system technology; with a price point that makes it a competitive alterative to buried fiber. About E-Band Communications E-Band Communications Corporation is the leading supplier of ultra-high capacity 70/80 GHz wireless solutions, serving 4G carriers (WiMAX, LTE) and enterprises. In 2009, EBand achieved the highest market share in the U.S., based on publicly available annual FCC license data. A key advantage is its Monolithic Microwave Integrated Circuit (MMIC) technology originally designed for high-end military applications and now under exclusive field-of-use license from a major defense contractor. E-Band's investors include Avalon Ventures, Hercules Technology Growth Capital, Reliance ADA Group, ADC Telecommunications, Investec, Express Ventures, OpenAir Ventures and a topthree U.S. telecommunications carrier. www.e-band.com E-Band Communications Corp. 10095 Scripps Ranch Ct, Suite A San Diego, CA 92131 USA
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