| WiMAX Wars |
| Posted: January 2009 | ||||||
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The downlink C-band, both extended (3.4 – 3.7 GHz) and standard (3.7 – 4.2 GHz), is of great importance to satellite operators especially in countries with high rain rates since, at these frequencies, there is almost no signal attenuation due to rain. WRC-07 added footnotes for some countries designating bands in the extended C-band for International Mobile Telecommunications (IMT).WiMAX is a broadband wireless access (BWA) technology comprised of both fixed and mobile standards. Fixed WiMAX systems can be deployed under the fixed service allocations in the ITU Table of Frequency Allocations and mobile WiMAX can be deployed under the mobile service allocations. Mobile WiMAX is an IMT system and can therefore also be deployed in the IMT designated bands. Whether fixed or mobile, these BWA systems operating in the C-band can cause harmful interference into FSS operation even when there is a separation of frequencies. This type of interference has been widely studied and is well documented and acknowledged even by the WiMAX proponents. This report will examine the following questions: 2.What happened at WRC-07 with respect to allocations for BWA? 3.Where does IMT fit with respect to 3G and 4G networks? 4.Where does WiMAX fit in the BWA picture? 5.What are the differences and similarities between Wi-Fi and WiMAX? 6.What kind of interference can satellite operators expect from WiMAX operation? 7.What can Asian satellite operators expect in terms of future deployment of BWA systems? 1. What is the meaning of the IMT designation?First we need to look at the ITU Table of Frequency Allocations.ITU Table of Frequency Allocations The ITU Table of Frequency Allocations (see Annex 1 for excerpt) lists ranges of frequencies allocated to the various radiocommunication services (eg. fixed-satellite service, mobile service, broadcasting service etc.) In order to make efficient use of the scarce radio spectrum, services that do not co-exist well without special sharing constraints are often allocated to the same frequency bands. Such frequency allocations are made either on a primary or secondary basis. A secondary service cannot cause interference into or claim protection from a primary service. Primary services must coordinate between themselves or share based on some pre-defined constraints. Sometimes primary service allocations are not compatible and administrations favour one or the other service in their national Table of Frequency Allocations. For example, both before and after WRC-07 the FIXED, MOBILE and the FIXED-SATELLITE services (capital letters indicate a primary allocation) in ITU Region 3 (Asia and Oceania) were allocated in the frequency range 3.5 – 4.2 GHz (see Annex 1). Broadband wireless Access (BWA) can be deployed under either the FIXED or MOBILE service depending on whether the service is fixed or mobile. Historically, the FIXED allocation co-existed well with FSS since the FIXED service was point-to-point (usually radio relay) and frequency coordination was feasible. However, fixed BWA is often point-to-multi-point and this service does not coexist well with FSS. Significance of IMT Designation Under WRC-07 agenda item 1.4 many administrations made proposals to have at least some of the C-band designated for International Mobile Telecommunications (IMT). The footnotes adopted designating bands for IMT are for mobile allocations and all contain words to the effect that “This identification does not preclude the use of this band by any application of the services to which it is allocated and does not establish priority in the Radio Regulations.” In spite of this wording, administrations in such a footnote are likely to show a preference for IMT technologies when issuing licenses. Actually, the IMT designation is a restriction since it gives some preference to the IMT technologies. Restrictions are more appropriate in the national table of frequency allocations. In addition, the IMT designation is not technology neutral. Most administrations have a policy of allocating spectrum on a “technology neutral” basis and therefore there is some doubt that the IMT designation should be used even in a national table of frequency allocations, certainly not in the ITU Table of Frequency Allocations. Fourteen (14) Region 2 (Americas) countries wanted to deploy BWA technologies on a primary basis in the band 3.4 – 3.5 GHz and upgraded the existing mobile service from a secondary allocation to a primary allocation but without the IMT designation. These countries did not want to give preference to IMT technologies in the way that was done in Regions 1 and 3 by the IMT designation. The IMT designation is heavily promoted by some European and Asian equipment manufacturers and cellular network operators. 2. What happened at WRC-07 with respect to allocations for BWA?WRC-07 Changes to C-band Allocations The best result at WRC-07 for satellite operators would have been no IMT designation within the C-band. While not a complete success, the results were good since WRC-07: 1)limited IMT designations through opt-in footnotes in the range 3.4 – 3.6 GHz (see Annex 1); 2)adopted very stringent protection criteria from IMT interference into FSS operation in neighbouring countries. It was important that the footnotes be opt-in footnotes rather than opt-out footnotes. In the case of opt-out footnotes, at each WRC there is an agenda item that encourages administrations to delete their names from footnotes since the service addressed by a footnote is considered an exception to the Table of Frequency Allocation. This would mean that in the long term the satellite community would likely be forced to completely abandon the portion of the C-band covered by the footnote. In Region 3 the great majority of administrations did not want a footnote for IMT designation and an opt-in footnote containing the small number of administrations wanting IMT designation is more appropriate. However, in Region 1, the vast majority of administrations wanted an IMT designation and an opt-out footnote would have been more appropriate for the smaller number of administrations that did not want an IMT designation. Since the footnote is opt-in, it contains a large number of administrations for Region 1. Changes in ITU Region 3: 3.4 – 3.5 GHz, Footnote 5.BBB Some countries wanted the secondary allocation to mobile upgraded to a primary allocation and this band identified for IMT. This is accomplished by the footnote 5.BBB. The following 7 countries (areas) are in this footnote: Bangladesh, China, India, Iran, New Zealand, Singapore and French Overseas Communities in Region 3 Footnote 5.AAA1 Three countries in this footnote wanted to leave the mobile as a secondary allocation but to identify this band for IMT. These countries are Korea, Japan and Pakistan. 3.5 – 3.6 GHz, Footnote 5.CCC Before WRC-07 the MOBILE allocation was one of the primary allocations (along with the FIXED and the FIXED-SATELLITE) in this band. The following 8 countries (and French territories) wanted an IMT designation for this band and are included in this footnote: Bangladesh, China, Korea, India, Iran, Japan, New Zealand, Pakistan and French Overseas Communities in Region 3. (This is the same list as in footnote 5.BBB less Singapore but with the addition of Korea, Japan and Pakistan.) In Region 1 a footnote allocates the band 3.4 – 3.6 GHz to the mobile service on a primary basis and designates the band for IMT in 81 countries. In Region 2 a footnote allocates the band 3.4 – 3.5 GHz to the mobile service on a primary basis (but without a designation for IMT) in 14 countries. 3. Where does IMT fit with respect to 3G and 4G networks?IMT-2000 and IMT-Advanced Standards The ITU has clarified the terms IMT, IMT-2000 and IMT-Advanced as follows: 1)the term “IMT-2000” encompasses also its enhancements and future developments; 2)the term “IMT-Advanced” is applied to those systems, system components, and related aspects that include new radio interface(s) that support the new capabilities of systems beyond IMT-2000; 3)the term “IMT” is the root name that encompasses both IMT-2000 and IMT-Advanced collectively. The next cellular network evolution will be from 3G to 4G although some operators are now deploying what they call 3.5G networks. The main characteristics of 3G and 4G networks are: - backwards compatible with 2G - not backwards compatible with 3G - circuit and packet switched networks - entirely packet switched networks - combination of existing & evolved - all network elements are digital equipment - data rate up to 2Mbps for stationary - peak data rate up to 100Mbps in or walking users, and about 348 Kbps in high mobility applications and up in a moving vehicle to 1 Gbps in low mobility or nomadic applications. IMT-2000 technologies are often described as 3G technologies and IMT-Advanced technologies (still to be developed) as 4G technologies. The mobile WiMAX 802.16e Standard is often described as a 4G network since it has all the characteristics of 4G networks except the speed. However, since the criteria that constitute a 4G network have not yet been defined it is more appropriate to speak of mobile WiMAX 802.16e Standard as a pre-4G standard. IMT-2000 The designation of IMT-2000 was developed within the ITU as an attempt to develop one standard for third generation (3G) systems for mobile communications. However, in spite of what is stated on the ITU site web, it was not possible to agree on one standard. Therefore, all standards with enough support were included in the IMT-2000 designation. Prior to the inclusion of mobile WiMAX (802.16e) in the IMT-2000 standards as defined by ITU Rec. M.1457-6, IMT-2000 supported five radio interfaces and three different access technologies, using CDMA, TDMA, and FDMA. Figure 1 shows the five families of standards of IMT-2000 before the inclusion of WiMAX.  Figure from ITU web site for IMT-2000, IMT-2000, “International Mobile Telecommunications” Fight between 3G and WiMAX Mobile WiMAX could be a disruptive technology as far as the incumbent cellular network operators are concerned. New entrants not burdened with having to support legacy equipment could establish national networks and potentially offer mobile voice and data services at lower prices. One way in which the 3G operators had tried to keep mobile WiMAX from offering service was by having spectrum designated in the ITU Table of Frequency Allocations for use by IMT-2000 (3G) technologies which support legacy networks. WiMAX is a pre-4G standard and does not support circuit switched networks. However, the fight ended with victory of the WiMAX lobby when the mobile version of WiMAX was included into the IMT-2000 family of standards as specified in Recommendation ITU-R M.1457 (“Detailed specifications of the radio interfaces of International Mobile Telecommunications-2000 (IMT-2000”). IMT-Advanced IMT-Advanced was previously known as “systems beyond IMT-2000”. Again, the ITU has set up working groups to standardize 4G. The full criteria being developed within ITU-R Working Party 8F are not expected until 2008 but they include target peak data rates of up to 100 Mbits/sec in high mobility applications and up to 1 Gbit/sec in low mobility or nomadic applications. The capability proposed by IMT-Advanced is often referred to as “4G.” It is expected that the specification of IMT-Advanced technologies will not be completed until 2010. The IEEE 802.16 (WiMAX) Working Group has initiated a new project designated as “802.16m”. The objective is to develop an IEEE 802.16 Standard compatible with IMT-Advanced. 4. Where does WiMAX fit in the BWA picture?WiMAX Standards The WiMAX standards consist of the IEEE 802.16 family of standards that address the "first-mile/last-mile" connection using a wireless network and therefore is a broadband wireless access (BWA) technology. The standards provide multiple access modes that include fixed, nomadic, portable and mobile connectivity. The mobile WiMAX standard (IEEE 802.16e Standard) can be considered a pre-4G standard and as such is of great interest to network operators. To build a WiMAX network to deliver broadband Internet connectivity targeted at consumers, the customer premise equipment (CPE) must be inexpensive and easy to set up. This goal was facilitated by the development of the non line-of-sight WiMAX standards (see below) which meant that no outdoor antenna was needed i.e. no expensive “truck-roll”. The First IEEE 802.16 Standard The first IEEE 802.16 Standard specifies the WirelessMAN Air Interface for wireless Metropolitan Area Networks (MAN). It focuses on the efficient use of bandwidth between 10 and 66 GHz. This standard supports continuously varying traffic levels at many licensed frequencies (e.g., 10.5, 25, 26, 31, 38 and 39 GHz) for two-way communications. The standard enables interoperability among devices, so carriers can use products from multiple vendors. Engineers from the world's leading operators and vendors created this standard in a two-year, open-consensus process. Further Development of the IEEE 802.16 Standard The two main standards now being deployed are the 802.16d (fixed) and 802.16e (mobile) standards. For these products, WiMAX solutions have been implemented for both licensed and unlicensed bands in the 2 – 11 GHz range. The main mileposts in the development of the WiMAX standards are: 1)December 2001 – 802.16 adopted for wireless Metropolitan Area Network (MAN) in 10-66 GHz frequency range (line-of-sight); 2)January 2003 – 802.16a extension adopted for (2 – 11 GHz, near line-of-sight); 3)June 2004 – 802.16d 2004 Standard adopted for fixed WiMAX (non line-of-sight); 4)December 2005 – 802.16e 2005 Standard adopted for mobile WiMAX; 5)The 802.16m Standard is under development as a 4G technology. Continuing fight between 2G/3G Cellular Network Operators and WiMAX The 2G/3G operators have their own evolutionary path towards 4G. This evolution must be backward compatible since the cellular operators have large investments in existing networks. To further develop their standards including plotting a path towards 4G, the 2G/3G network operators have formed their own associations: 1)3G Partnership Project (3GPP), http://www.3gpp.org/, supported by GSM/UMTS (i.e. TDMA); 2)3G Partnership Project (3GPP2), http://www.3gpp2.org/, supported by CDMA operators. In both cases this path does not (presently) include WiMAX. 5. What are the differences and similarities between Wi-Fi and WiMAX?Wi-Fi and WiMAX were developed for different markets and different applications. The technologies can complement each other with WiMAX to the building and Wi-Fi in the building. WiMAX can also be used to replace or supplement copper or cable. Developing countries stand to benefit from WiMAX's lower infrastructure cost. Main WiMAX Applications 1)Dedicated point-to-point fixed service using outdoor antennas to deliver rates of up to 100 Mbps. Many such networks have been deployed based on the original 802.16 Standard using frequencies between 10 - 66 GHz. These systems require line-of-sight (LOS) and are typically used for corporate data networks networks or backhaul of cellular traffic; 2)Point-to-multi-point service provided by networks based on the 802.16a 2003 or the 802.16d 2004 Standards using frequencies between 2 - 11 GHz in non-line-of-sight applications. This service can used to deliver wireless DSL at speeds comparable to fixed DSL (or cable) i.e. 512 Kbps to 2-3 Mbps. The key to this application is the availability of inexpensive non-line-of-sight (NLOS) customer premises equipment (CPE) that can be self-installed; 3)Mobile/nomadic applications using the 802.16e mobile WiMAX Standard at frequencies below 6 GHz. This application is in direct competition with the data services provided by the 2G/3G cellular network operators. Consumers want broadband Internet connectivity. The WiMAX network is optimized for IP connectivity and should be able to provide a better service at a lower cost. WiMAX networks can deliver good VOIP quality and if this service becomes popular it will threaten the core voice business of cellular network operators. Main Characteristics of Wi-Fi 1)Wi-Fi is designed as a wireless extension to local area networks (LAN) for indoor use with a range up to 100m; 2)Wi-Fi was developed as consumer product. There may be interference due to widespread deployment of Wi-Fi but the limited range of the Wi-Fi equipment alleviates this problem; 3)Wi-Fi operates exclusively in the Industrial Scientific Medical (ISM) bands (2.4 GHZ and 5.8 GHZ) and in almost all countries a license is not required. One reason for the success of Wi-Fi was the use initially of 2.4 GHz band worldwide with later standards adding the 5.8 GHz band. Main Characteristics of WiMAX 1)WiMAX was originally designed to provide fixed BWA in metropolitan area networks (MAN) with a range of up to 50 km. Extensions of the WiMAX standard now provide for mobile applications with a range of up to 6 km; 2)WiMAX was developed as a commercial product for use by network operators. In the licensed bands there will be few operators and the interference environment can be controlled; 3)WiMAX can operate over a wide range of frequencies including both licensed and unlicensed bands. Due to its longer range, it makes more sense for most applications to operate in licensed bands; 6. What kind of interference can satellite operators expect from WiMAX operation?At the FSS earth station antenna the BWA terrestrial signal is much more powerful than the signal from the satellite. Typically, the power-flux density (pfd) of a C-band satellite signal at the FSS earth station antenna is about -122 dBW/m2 while the pfd of a 25 watt BWA transmitter at a distance of 500 meters is around -50 dBW/m2. There is difference in power between the two signals of 72 dB. It is difficult to overcome this power difference either by shielding or filtering. At best, the FSS earth station antenna has a sidelobe/backlobe discrimination of about 30 dB. The interference caused into the FSS earth station can be divided into three types1: a) Co-frequency Interference If no shielding is available at the satellite antenna site, then interference can be caused as distances up to about 150 km. (b) Out-of-band Interference With the existing out-of-band emission limits for BWA transmitters, interference can be caused at distances up to 2 km. If additional filtering is implemented at the BWA base station and the use of outdoor BWA terminal stations is not allowed, the distance may be shortened to about 0.5 km. (c) FSS Receiver Saturation Problem Signals from nearby BWA equipment transmitting in the 3.4 – 3.6 GHz band will cause saturation of FSS receivers with their LNB operating in the 3.7 – 4.2 GHz range. In this case saturation can be caused in satellite receivers located at a distance up to about 1.2 km. Off-the-shelf filters can reduce the interference level by about 10 dB in which case the interference can be caused at distances up to about 0.5 – 0.6 km. 7. What can Asian satellite operators expect in terms of future deployment of BWA technologies?1) Most of the administrations that decided to be included in the new footnotes in the 3.4 – 3.6 GHz band have tested BWA technologies (usually WiMAX) and have licensed or are considering licensing BWA networks. In Asia there are 10 countries in these footnotes. These countries are: Bangladesh, China, India, Iran, Japan, Korea, New Zealand, Pakistan, Singapore and French Overseas Communities in Region 3. 2) Both Australia and Fiji have licensed BWA (WiMAX) networks in the band 3.4 – 3.6 GHz using existing allocations. (Neither Australia nor Fiji are in the footnotes.)3) In the future, administrations not in the IMT footnotes may still deploy BWA in the C-band (both fixed and mobile) under the existing allocations in the band 3.5 – 4.2 GHz. In addition, administrations may request at upcoming WRC’s to be included in footnote 5.BBB for the band 3.4 – 3.5 GHz. a) Countries with highly developed telecommunications infrastructure need new spectrum for high capacity mobile BWA networks (eg. Japan, Korea, Australia); b) Countries with large under served rural areas need new spectrum for fixed BWA networks (eg. China, India, Australia). (Note: the above countries, except Australia, are all in the new footnotes in 3.4 – 3.6 GHz bands) As a result, more countries in Region 3 may decide to deploy BWA networks in the 3.5 GHz band and may join the opt-in footnotes at future WRCs. Add this page to your favorite Social Bookmarking websites       
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