12-04-2011, 11:23 AM
ABSTRACT
wimax.doc (Size: 398.5 KB / Downloads: 38)
ABSTRACT
In recent years, Broadband technology has rapidly become an established, global commodity required by a high percentage of the population. The demand has risen rapidly, with a worldwide installed base of 57 million lines in 2002 rising to an estimated 80 million lines by the end of 2003. This healthy growth curve is expected to continue steadily over the next few years and reach the 200 million mark by 2006. DSL operators, who initially focused their deployments in densely-populated urban and metropolitan areas, are now challenged to provide broadband services in suburban and rural areas where new markets are quickly taking root. Governments are prioritizing broadband as a key political objective for all citizens to overcome the “broadband gap” also known as “digital divide”.
Wireless DSL (WDSL) offers an effective, complementary solution to wireline DSL, allowing DSL operators to provide broadband service to additional areas and populations that would otherwise find themselves outside the broadband loop. Government regulatory bodies are realizing the inherent worth in wireless technologies as a means for solving digital-divide challenges in the last mile and have accordingly initiated a deregulation process in recent years for both licensed and unlicensed bands to support this application. Recent technological advancements and the formation of a global standard and interoperability forum - WiMAX, set the stage for WDSL to take a significant role in the broadband market. Revenues from services delivered via Broadband Wireless Access have already reached $323 million and are expected to jump to $1.75 billion.
INTRODUCTION
E-Mail Newsletters
There are several ways to get a fast Internet connection to the middle of nowhere. Until not too long ago, the only answer would have been "cable" — that is, laying lines. Cable TV companies, who would be the ones to do this, had been weighing the costs and benefits. However this would have taken years for the investment to pay off. So while cable companies might be leading the market for broadband access to most people (of the 41% of Americans who have high-speed Internet access, almost two-thirds get it from their cable company), they don't do as well to rural areas. And governments that try to require cable companies to lay the wires find themselves battling to force the companies to take new customers.
Would DSL be a means of achieving this requisite of broadband and bridging the digital divide?
The lines are already there, but the equipment wasn't always the latest and greatest, even then. Sending voice was not a matter of big concern, but upgrading the system to handle DSL would mean upgrading the central offices that would have to handle the data coming from all those farms.
The most rattling affair is that there are plenty of places in cities that can't handle DSL, let alone the country side. Despite this, we’ll still read about new projects to lay cable out to smaller communities, either by phone companies, cable companies, or someone else. Is this a waste of money? Probably because cables are on their way out. Another way to get broadband to rural communities is the way many folks get their TV: satellite, which offers download speeds of about 500 Kbps —faster than a modem, but at best half as fast as DSL — through a satellite dish. But you really, really have to want it. The system costs $600 to start, then $60 a month by the services provided by DIRECWAY in the US.
There are other wireless ways to get broadband access.
MCI ("Microwave Communications Inc.") was originally formed to compete with AT & T by using microwave towers to transmit voice signals across the US. Unlike a radio (or a Wi-Fi connection), those towers send the signal in a straight line —unidirectional instead of omni directional. That's sometimes called fixed wireless or point-to-point wireless. One popular standard for this is called LMDS: local multipoint distribution system. Two buildings up to several miles apart would have microwave antennas pointing at each other. One (in, say, the urban area) would be connected to the Internet in the usual way, via some kind of wire; the other (in the rural area you want to connect) would send and receive data over the microwave link, and then be connected to homes and farms via cables. Those cables would be much shorter and less expensive, with the bulk of the transmission being done through the ether.
WiMAX:
WiMax delivers broadband to a large area via towers, just like cell phones. This enables your laptop to have high-speed access in any of the hot spots. Instead of yet another cable coming to your home, there would be yet another antenna on the cell-phone tower. This is definitely a point towards broadband service in rural areas. First get the signal to the area, either with a single cable (instead of one to each user) or via a point-to-point wireless system. Then put up a tower or two, and the whole area is online. This saves the trouble of digging lots of trenches, or of putting up wires that are prone to storm damage.
However there is one promising technology that still uses cables to deliver a broadband signal to, well, wherever. It doesn't require laying any new wires (like cable Internet), and it doesn't require overhauling a lot of existing systems (like DSL).It's BPL: (broadband over power lines). As the name suggests, it piggybacks a high speed data signal on those ubiquitous power lines. Those aren't the low-voltage ones that come to your house, but the medium-voltages ones that travel from neighborhood to neighborhood. The signal, like those power lines, can travel a long way thanks to "regenerators" that not only pass the data along, but clean the signal so it doesn't degrade over distance. That means the signal can travel as long as the lines do. Those regenerators can also include Wi-Fi antennas, so if you space them properly they can be placed near homes and farms and whatnot. You can also connect a cable to one to take the signal to the door if you don't feel like going the W-Fi way.
However there have been certain hiccups in the case of BPL. Unlike some early (and ongoing) attempts to do Internet through power lines, BPL doesn't go into individual homes. That's because in order to do so, the signal would have to make its way through a transformer and through a circuit-breaker box, both of which play havoc with it. The result is that the data get through, but much more slowly than leaving the power line before the transformer.
Combine BPL with Wi-Fi, WiMAX, or even (short) cables, and we have an inexpensive way to get the power of the Internet down on the farm using the power of power.
WiMAX is revolutionizing the broadband wireless world, enabling the formation of a global mass-market wireless industry. Putting the WiMAX revolution in the bigger context of the broadband industry, this paper portrays the recent acceleration stage of the Broadband Wireless Access market, determined by the need for broadband connectivity and by the following drivers:
A) The worldwide deregulation process
B) The standardization progression; and
C) Revolutionary wireless technology.
Deregulation:
Creating new opportunities on the horizon
A major driver impacting the broadband wireless explosion is the advent of global telecom deregulation, opening up the telecommunications/Internet access industries to a host of new players. As more and more countries enable carriers and service providers to operate in a variety of frequencies, new and lucrative broadband access markets are springing up everywhere. Wireless technology requires the use of frequencies contained within a given spectrum to transfer voice and data. Governments allocate a specific range of that spectrum to incumbent and competitive carriers, as well as cellular operators, ISPs, and other service providers, enabling them to launch a variety of broadband initiatives based exclusively on wireless networking solutions.
There are two main types of spectrum allocation: licensed and unlicensed.
Licensed frequencies are typically awarded through an auction or “beauty contest” to those who present the soundest business plans to the regulatory authorities overseeing the process.
Unlicensed frequencies allow multiple service providers to utilize the same section of the spectrum and compete with each other for customers.
Standardization
WiMAX - Worldwide Interoperability for Microwave Access
The WiMAX Forum is a non-profit trade organization, founded in April 2002 by leading vendors of wireless access equipment and telecommunications components. The Forum's mission is to lay the groundwork for an industry-wide acceptance and implementation of the IEEE 802.16 and ETSI HiperMAN standard, covering the 2-11 GHz bands for Wireless Metropolitan Area Networks (Wireless
MAN). The Forum hopes to jump-start this crucial industry by establishing rigorous definitions for testing and certifying products for interoperability compliance. The issuing of a “WiMAX-Certified” label will serve as a seal of approval that a particular vendor’s system or component fully corresponds to the technological specifications set forth by the new Wireless MAN protocol.
In order to ensure the success of wireless technology as a stable, viable and cost effective alternative for delivering broadband access services in the last mile, the introduction of industry standards is essential. The companies that have already joined the WiMAX Forum represent over 75% of revenues in the global
BWA market. Moreover, membership of the WiMAX Forum is not limited to industry leading BWA providers; numerous multinational enterprises like Intel and Fujitsu have also joined the WiMAX Forum. The Forum represents a cross-industry group of valued partners, including chip set manufacturers, component makers and service providers. All of these organizations recognize the long-term benefits of working with standardized, interoperable equipment and are committed to the design, development and implementation of WiMAX-compliant solutions.
OVERVIEW OF THE 802.16 IEEE STANDARDS
The 802.16 standard, amended by the IEEE to cover frequency bands in the range between 2 GHz and 11 GHz, specifies a metropolitan area networking protocol that will enable a wireless alternative for cable, DSL and T1 level services for last mile broadband access, as well as providing backhaul for 801.11 hotspots.
The new 802.16a standard specifies a protocol that among other things supports low latency applications such as voice and video, provides broadband connectivity without requiring a direct line of sight between subscriber terminals and the base station (BTS) and will support hundreds if not thousands of subscribers from a single BTS. The standard will help accelerate the introduction of wireless broadband equipment into the marketplace, speeding up last-mile broadband deployment worldwide by enabling service providers to increase system performance and reliability while reducing their equipment costs and investment risks.
However it has been shown repeatedly that adoption of a standard does not always lead to adoption by the intended market. For a market to be truly enabled, products must be certified that they do adhere to the standard first, and once certified it must also be shown that they interoperate. Interoperability means the end user can buy the brand they like, with the features they want, and know it will work with all other like certified products.
For the Broadband Wireless Access (BWA) market and its 802.16 standard,
this role is played by the Worldwide Microwave Interoperability Forum or WiMAX. WiMAX is instrumental in removing the barrier in adopting the standard by assuring demonstrable interoperability between system components developed by OEMs. WiMAX will develop conformance and interoperability test plans, select certification labs and will host interoperability events for IEEE 802.16 equipment
vendors..
Satisfying the growing demand for BWA in underserved markets has been a continuing challenge for service providers, due to the absence of a truly global standard. A standard that would enable companies to build systems that will effectively reach underserved business and residential markets in a manner that supports infrastructure build outs comparable to cable, DSL, and fiber. For years, the wildly successful 802.11x or WiFi wireless LAN technology has been used in BWA applications along with a host of proprietary based solutions. When the
WLAN technology was examined closely, it was evident that the overall design and feature set available was not well suited for outdoor BWA applications. It could be done, it is being done,but with limited capacity in terms of bandwidth and subscribers, range and a host of other issues made it clear this approach while a great fit for indoor WLAN was a poor fit for outdoor BWA.
WiMAX and the IEEE 802.16a PHY Layer
The first version of the 802.16 standard released addressed Line-of-Sight (LOS) environments at high frequency bands operating in the 10-66 GHz range, whereas the recently adopted amendment, the 802.16a standard, is designed for systems operating in bands between 2 GHz and 11 GHz. The significant difference between these two frequency bands lies in the ability to support Non-Line-of-Sight (NLOS) operation in the lower frequencies, something that is not possible in
higher bands. Consequently, the 802.16a amendment to the standard opened up the opportunity for major changes to the PHY layer specifications specifically to address the needs of the 2-11 GHz bands. This is achieved through the introduction of three new PHY-layer specifications (a new Single Carrier PHY, a 256 point FFT OFDM PHY, and a 2048 point FFT OFDMA PHY);major changes to the PHY layer specification as compared to the upper frequency, as well as significant MAC-layer enhancements. Although multiple PHYs are specified as in the 802.11 suite of standards (few recall that infrared and frequency hopping were and are part of the base 802.11 standard), the WiMAX Forum has determined that
the first interoperable test plans and eventual certification will support the 256 point FFT OFDM PHY (which is common between 802.16a and ETSI HiperMAN), with the others to be developed as the market requires.
The OFDM signaling format was selected in preference to competing formats such as CDMA due to its ability to support NLOS performance while maintaining a high level of spectral efficiency maximizing the use of available spectrum. In the case of CDMA (prevalent in 2G and 3G standards), the RF bandwidth must be much larger than the data throughput, in order to maintain processing gain adequate to overcome interference. This is clearly impractical for broadband wireless below 11 GHz, since for example, data rates up to 70 Mbps would require RF bandwidths exceeding 200 MHz to deliver comparable processing gains and NLOS performance.
Some of the other PHY layer features of 802.16a that are instrumental in giving this technology the power to deliver robust performance in a broad range of channel environments are; flexible channel widths, adaptive burst profiles, forward error correction with concatenated Reed-Solomon and convolutional encoding, optional AAS (advanced antenna systems) to improve range/capacity, DFS (dynamic frequency selection)-which helps in minimizing interference, and STC (space-time coding) to enhance performance in fading environments through spatial diversity.
Table 1 gives a high level overview of some of the PHY layer features of the IEEE 802.16a standard.
wimax.doc (Size: 398.5 KB / Downloads: 38)
ABSTRACT
In recent years, Broadband technology has rapidly become an established, global commodity required by a high percentage of the population. The demand has risen rapidly, with a worldwide installed base of 57 million lines in 2002 rising to an estimated 80 million lines by the end of 2003. This healthy growth curve is expected to continue steadily over the next few years and reach the 200 million mark by 2006. DSL operators, who initially focused their deployments in densely-populated urban and metropolitan areas, are now challenged to provide broadband services in suburban and rural areas where new markets are quickly taking root. Governments are prioritizing broadband as a key political objective for all citizens to overcome the “broadband gap” also known as “digital divide”.
Wireless DSL (WDSL) offers an effective, complementary solution to wireline DSL, allowing DSL operators to provide broadband service to additional areas and populations that would otherwise find themselves outside the broadband loop. Government regulatory bodies are realizing the inherent worth in wireless technologies as a means for solving digital-divide challenges in the last mile and have accordingly initiated a deregulation process in recent years for both licensed and unlicensed bands to support this application. Recent technological advancements and the formation of a global standard and interoperability forum - WiMAX, set the stage for WDSL to take a significant role in the broadband market. Revenues from services delivered via Broadband Wireless Access have already reached $323 million and are expected to jump to $1.75 billion.
INTRODUCTION
E-Mail Newsletters
There are several ways to get a fast Internet connection to the middle of nowhere. Until not too long ago, the only answer would have been "cable" — that is, laying lines. Cable TV companies, who would be the ones to do this, had been weighing the costs and benefits. However this would have taken years for the investment to pay off. So while cable companies might be leading the market for broadband access to most people (of the 41% of Americans who have high-speed Internet access, almost two-thirds get it from their cable company), they don't do as well to rural areas. And governments that try to require cable companies to lay the wires find themselves battling to force the companies to take new customers.
Would DSL be a means of achieving this requisite of broadband and bridging the digital divide?
The lines are already there, but the equipment wasn't always the latest and greatest, even then. Sending voice was not a matter of big concern, but upgrading the system to handle DSL would mean upgrading the central offices that would have to handle the data coming from all those farms.
The most rattling affair is that there are plenty of places in cities that can't handle DSL, let alone the country side. Despite this, we’ll still read about new projects to lay cable out to smaller communities, either by phone companies, cable companies, or someone else. Is this a waste of money? Probably because cables are on their way out. Another way to get broadband to rural communities is the way many folks get their TV: satellite, which offers download speeds of about 500 Kbps —faster than a modem, but at best half as fast as DSL — through a satellite dish. But you really, really have to want it. The system costs $600 to start, then $60 a month by the services provided by DIRECWAY in the US.
There are other wireless ways to get broadband access.
MCI ("Microwave Communications Inc.") was originally formed to compete with AT & T by using microwave towers to transmit voice signals across the US. Unlike a radio (or a Wi-Fi connection), those towers send the signal in a straight line —unidirectional instead of omni directional. That's sometimes called fixed wireless or point-to-point wireless. One popular standard for this is called LMDS: local multipoint distribution system. Two buildings up to several miles apart would have microwave antennas pointing at each other. One (in, say, the urban area) would be connected to the Internet in the usual way, via some kind of wire; the other (in the rural area you want to connect) would send and receive data over the microwave link, and then be connected to homes and farms via cables. Those cables would be much shorter and less expensive, with the bulk of the transmission being done through the ether.
WiMAX:
WiMax delivers broadband to a large area via towers, just like cell phones. This enables your laptop to have high-speed access in any of the hot spots. Instead of yet another cable coming to your home, there would be yet another antenna on the cell-phone tower. This is definitely a point towards broadband service in rural areas. First get the signal to the area, either with a single cable (instead of one to each user) or via a point-to-point wireless system. Then put up a tower or two, and the whole area is online. This saves the trouble of digging lots of trenches, or of putting up wires that are prone to storm damage.
However there is one promising technology that still uses cables to deliver a broadband signal to, well, wherever. It doesn't require laying any new wires (like cable Internet), and it doesn't require overhauling a lot of existing systems (like DSL).It's BPL: (broadband over power lines). As the name suggests, it piggybacks a high speed data signal on those ubiquitous power lines. Those aren't the low-voltage ones that come to your house, but the medium-voltages ones that travel from neighborhood to neighborhood. The signal, like those power lines, can travel a long way thanks to "regenerators" that not only pass the data along, but clean the signal so it doesn't degrade over distance. That means the signal can travel as long as the lines do. Those regenerators can also include Wi-Fi antennas, so if you space them properly they can be placed near homes and farms and whatnot. You can also connect a cable to one to take the signal to the door if you don't feel like going the W-Fi way.
However there have been certain hiccups in the case of BPL. Unlike some early (and ongoing) attempts to do Internet through power lines, BPL doesn't go into individual homes. That's because in order to do so, the signal would have to make its way through a transformer and through a circuit-breaker box, both of which play havoc with it. The result is that the data get through, but much more slowly than leaving the power line before the transformer.
Combine BPL with Wi-Fi, WiMAX, or even (short) cables, and we have an inexpensive way to get the power of the Internet down on the farm using the power of power.
WiMAX is revolutionizing the broadband wireless world, enabling the formation of a global mass-market wireless industry. Putting the WiMAX revolution in the bigger context of the broadband industry, this paper portrays the recent acceleration stage of the Broadband Wireless Access market, determined by the need for broadband connectivity and by the following drivers:
A) The worldwide deregulation process
B) The standardization progression; and
C) Revolutionary wireless technology.
Deregulation:
Creating new opportunities on the horizon
A major driver impacting the broadband wireless explosion is the advent of global telecom deregulation, opening up the telecommunications/Internet access industries to a host of new players. As more and more countries enable carriers and service providers to operate in a variety of frequencies, new and lucrative broadband access markets are springing up everywhere. Wireless technology requires the use of frequencies contained within a given spectrum to transfer voice and data. Governments allocate a specific range of that spectrum to incumbent and competitive carriers, as well as cellular operators, ISPs, and other service providers, enabling them to launch a variety of broadband initiatives based exclusively on wireless networking solutions.
There are two main types of spectrum allocation: licensed and unlicensed.
Licensed frequencies are typically awarded through an auction or “beauty contest” to those who present the soundest business plans to the regulatory authorities overseeing the process.
Unlicensed frequencies allow multiple service providers to utilize the same section of the spectrum and compete with each other for customers.
Standardization
WiMAX - Worldwide Interoperability for Microwave Access
The WiMAX Forum is a non-profit trade organization, founded in April 2002 by leading vendors of wireless access equipment and telecommunications components. The Forum's mission is to lay the groundwork for an industry-wide acceptance and implementation of the IEEE 802.16 and ETSI HiperMAN standard, covering the 2-11 GHz bands for Wireless Metropolitan Area Networks (Wireless
MAN). The Forum hopes to jump-start this crucial industry by establishing rigorous definitions for testing and certifying products for interoperability compliance. The issuing of a “WiMAX-Certified” label will serve as a seal of approval that a particular vendor’s system or component fully corresponds to the technological specifications set forth by the new Wireless MAN protocol.
In order to ensure the success of wireless technology as a stable, viable and cost effective alternative for delivering broadband access services in the last mile, the introduction of industry standards is essential. The companies that have already joined the WiMAX Forum represent over 75% of revenues in the global
BWA market. Moreover, membership of the WiMAX Forum is not limited to industry leading BWA providers; numerous multinational enterprises like Intel and Fujitsu have also joined the WiMAX Forum. The Forum represents a cross-industry group of valued partners, including chip set manufacturers, component makers and service providers. All of these organizations recognize the long-term benefits of working with standardized, interoperable equipment and are committed to the design, development and implementation of WiMAX-compliant solutions.
OVERVIEW OF THE 802.16 IEEE STANDARDS
The 802.16 standard, amended by the IEEE to cover frequency bands in the range between 2 GHz and 11 GHz, specifies a metropolitan area networking protocol that will enable a wireless alternative for cable, DSL and T1 level services for last mile broadband access, as well as providing backhaul for 801.11 hotspots.
The new 802.16a standard specifies a protocol that among other things supports low latency applications such as voice and video, provides broadband connectivity without requiring a direct line of sight between subscriber terminals and the base station (BTS) and will support hundreds if not thousands of subscribers from a single BTS. The standard will help accelerate the introduction of wireless broadband equipment into the marketplace, speeding up last-mile broadband deployment worldwide by enabling service providers to increase system performance and reliability while reducing their equipment costs and investment risks.
However it has been shown repeatedly that adoption of a standard does not always lead to adoption by the intended market. For a market to be truly enabled, products must be certified that they do adhere to the standard first, and once certified it must also be shown that they interoperate. Interoperability means the end user can buy the brand they like, with the features they want, and know it will work with all other like certified products.
For the Broadband Wireless Access (BWA) market and its 802.16 standard,
this role is played by the Worldwide Microwave Interoperability Forum or WiMAX. WiMAX is instrumental in removing the barrier in adopting the standard by assuring demonstrable interoperability between system components developed by OEMs. WiMAX will develop conformance and interoperability test plans, select certification labs and will host interoperability events for IEEE 802.16 equipment
vendors..
Satisfying the growing demand for BWA in underserved markets has been a continuing challenge for service providers, due to the absence of a truly global standard. A standard that would enable companies to build systems that will effectively reach underserved business and residential markets in a manner that supports infrastructure build outs comparable to cable, DSL, and fiber. For years, the wildly successful 802.11x or WiFi wireless LAN technology has been used in BWA applications along with a host of proprietary based solutions. When the
WLAN technology was examined closely, it was evident that the overall design and feature set available was not well suited for outdoor BWA applications. It could be done, it is being done,but with limited capacity in terms of bandwidth and subscribers, range and a host of other issues made it clear this approach while a great fit for indoor WLAN was a poor fit for outdoor BWA.
WiMAX and the IEEE 802.16a PHY Layer
The first version of the 802.16 standard released addressed Line-of-Sight (LOS) environments at high frequency bands operating in the 10-66 GHz range, whereas the recently adopted amendment, the 802.16a standard, is designed for systems operating in bands between 2 GHz and 11 GHz. The significant difference between these two frequency bands lies in the ability to support Non-Line-of-Sight (NLOS) operation in the lower frequencies, something that is not possible in
higher bands. Consequently, the 802.16a amendment to the standard opened up the opportunity for major changes to the PHY layer specifications specifically to address the needs of the 2-11 GHz bands. This is achieved through the introduction of three new PHY-layer specifications (a new Single Carrier PHY, a 256 point FFT OFDM PHY, and a 2048 point FFT OFDMA PHY);major changes to the PHY layer specification as compared to the upper frequency, as well as significant MAC-layer enhancements. Although multiple PHYs are specified as in the 802.11 suite of standards (few recall that infrared and frequency hopping were and are part of the base 802.11 standard), the WiMAX Forum has determined that
the first interoperable test plans and eventual certification will support the 256 point FFT OFDM PHY (which is common between 802.16a and ETSI HiperMAN), with the others to be developed as the market requires.
The OFDM signaling format was selected in preference to competing formats such as CDMA due to its ability to support NLOS performance while maintaining a high level of spectral efficiency maximizing the use of available spectrum. In the case of CDMA (prevalent in 2G and 3G standards), the RF bandwidth must be much larger than the data throughput, in order to maintain processing gain adequate to overcome interference. This is clearly impractical for broadband wireless below 11 GHz, since for example, data rates up to 70 Mbps would require RF bandwidths exceeding 200 MHz to deliver comparable processing gains and NLOS performance.
Some of the other PHY layer features of 802.16a that are instrumental in giving this technology the power to deliver robust performance in a broad range of channel environments are; flexible channel widths, adaptive burst profiles, forward error correction with concatenated Reed-Solomon and convolutional encoding, optional AAS (advanced antenna systems) to improve range/capacity, DFS (dynamic frequency selection)-which helps in minimizing interference, and STC (space-time coding) to enhance performance in fading environments through spatial diversity.
Table 1 gives a high level overview of some of the PHY layer features of the IEEE 802.16a standard.