Spectrum allocation edit There is no uniform global licensed spectrum for wimax, however the wimax forum published three licensed spectrum profiles:.3 ghz,.5 ghz and.5 ghz, in an effort to drive standardisation and decrease cost. In the usa, the biggest segment available was around.5 ghz, 21 and is already assigned, primarily to Sprint Nextel and Clearwire. Elsewhere in the world, the most-likely bands used will be the forum approved ones, with.3 ghz probably being most important in Asia. Some countries in Asia like india and Indonesia will use a mix.5 ghz,.3 ghz and other frequencies. Pakistan 's Wateen Telecom uses.5 GHz. Analog tv bands (700 MHz) may become available, but await the complete digital television transition, and other uses have been suggested for that spectrum. In the usa the fcc auction for this spectrum began in January 2008 and, as a result, the biggest share of the spectrum went to verizon Wireless and the next biggest to.
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However, even if this is done automatically then the practical deployment should avoid high interference and multipath environments. The reason for which is obviously that too much interference causes the network to function poorly and can also misrepresent the capability of the network. The system is complex to deploy as it is necessary to track not only the signal strength and cinr (as in systems like gsm ) but also how the available frequencies will be dynamically assigned (resulting in dynamic changes to the available bandwidth.) This could. As a result, the system has to be initially designed in consensus with the base station product team to accurately project frequency use, interference, and general product functionality. The Asia-pacific region has surpassed the north American region in terms of 4G broadband wireless subscribers. There were around.7 million pre-wimax and wimax customers in Asia 29 of the overall for market compared.4 million in the usa and Canada. 19 Integration with an ip-based network edit The wimax forum architecture The wimax forum has proposed an architecture that defines how a wimax network can be connected with an ip based core network, which is typically chosen by operators that serve as Internet Service Providers. The wimax forum proposal defines a number of components, plus some of the interconnections (or essays reference points) between these, labeled R1 to R5 and R8: SS/MS: the subscriber Station/Mobile Station asn: the Access Service network 20 BS: Base station, part of the asn asn-gw: the. For example, the architecture is flexible enough to allow remote/mobile stations of varying scale and functionality and Base Stations of varying size. Femto, pico, and mini bs as well as macros.
Specifications edit As a standard intended to satisfy needs of next-generation data networks ( 4g wimax is distinguished by its dynamic burst algorithm modulation adaptive to the physical environment the rf signal travels through. Modulation is chosen to be more spectrally efficient (more bits per ofdm / sofdma symbol). That is, when the bursts have a high book signal strength and a high carrier to noise plus interference ratio (cinr they can be more easily decoded using digital signal processing (DSP). In contrast, operating in less favorable environments for rf communication, the system automatically steps down to a more robust mode (burst profile) which means fewer bits per ofdm/sofdma symbol; with the advantage that power per bit is higher and therefore simpler accurate signal processing can. Burst profiles are used inverse (algorithmically dynamic) to low signal attenuation; meaning throughput between clients and the base station is determined largely by distance. Maximum distance is achieved by the use of the most robust burst setting; that is, the profile with the largest mac frame allocation trade-off requiring more symbols (a larger portion of the mac frame) to be allocated in transmitting a given amount of data than. The client's mac frame and their individual burst profiles are defined as well as the specific time allocation.
802.16-2004 was updated by 802.16e-2005 in 2005 and uses scalable orthogonal frequency-division multiple access 17 (sofdma as opposed to the fixed orthogonal frequency-division multiplexing (ofdm) version with 256 sub-carriers (of which 200 are used) rehabilitation in 802.16d. More advanced versions, including 802.16e, also bring multiple antenna support through mimo. (see wimax mimo ) This brings potential benefits in terms of coverage, self installation, power consumption, frequency re-use and bandwidth efficiency. Wimax is the most energy-efficient pre-4G technique among lte and hspa. 18 Media access control layer edit The wimax mac uses a scheduling algorithm for which the subscriber station needs to compete only once for initial entry into the network. After network entry is allowed, the subscriber station is allocated an access slot by the base station. The time slot can enlarge and contract, but remains assigned to the subscriber station, which means that other subscribers cannot use. In addition to being stable under overload and over-subscription, the scheduling algorithm can also be more bandwidth efficient. The scheduling algorithm also allows the base station to control quality of Service (QoS) parameters by balancing the time-slot assignments among the application needs of the subscriber station.
This is seen as one of the most important aspects of 802.16e-2005, and is the very basis of Mobile wimax. Scaling of the fast fourier transform (FFT) to the channel bandwidth in order to keep the carrier spacing constant across different channel bandwidths (typically.25 mhz, 5 mhz, 10 mhz or 20 MHz). Constant carrier spacing results in a higher spectrum efficiency in wide channels, and a cost reduction in narrow channels. Also known as scalable ofdma (sofdma). Other bands not multiples.25 mhz are defined in the standard, but because the allowed fft subcarrier numbers are only 128, 512, 10, other frequency bands will not have exactly the same carrier spacing, which might not be optimal for implementations. Carrier spacing.94 kHz. Advanced antenna diversity schemes, and hybrid automatic repeat-request (harq) Adaptive antenna systems (AAS) and mimo technology denser sub-channelization, thereby improving indoor penetration Intro and low-density parity check (ldpc) Introducing downlink sub-channelization, allowing administrators to trade coverage for capacity or vice versa Adding an extra quality. Physical layer edit The original version of the standard on which wimax is based ( ieee 802.16 ) specified a physical layer operating in the 10 to 66 ghz range. 802.16a, updated in 2004 to 802.16-2004, added specifications for the 2 to 11 ghz range.
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Dongles typically have omnidirectional antennas which are of lower gain compared to other devices. As such these devices are best used in areas of good coverage. Mobile phones edit wrong htc announced the first wimax enabled mobile phone, the max 4g, on november 12, 2008. 12 The device was only available to certain markets in Russia on the yota network until 2010. 13 htc and Sprint Nextel released the second wimax enabled mobile phone, the evo 4g, march 23, 2010 at the ctia conference in Las Vegas. The device, made available on June 4, 2010, 14 is capable of both ev-do(3G) and wimax(pre-4G) as well as simultaneous data voice sessions.
Sprint Nextel announced at ces 2012 that it will no longer be offering devices using the wimax technology due to financial circumstances, instead, along with its network partner Clearwire, sprint Nextel will roll out a 4G network deciding to shift and utilize lte 4G technology. Technical information edit The ieee 802.16 Standard edit wimax is based upon ieee std 802.16e-2005, 15 approved in December 2005. It is a supplement to the ieee std 802.16-2004, 16 and so the actual standard is 802.16-2004 as amended by 802.16e-2005. Thus, these specifications need to be considered together. Ieee 802.16e-2005 improves upon ieee 802.16-2004 by: Adding support for mobility (soft and hard handover between base stations).
Gateways edit wimax gateway devices are available as both indoor and outdoor versions from several manufacturers including Vecima networks, alvarion, airspan, zyxel, huawei, and Motorola. The list of deployed wimax networks and wimax forum membership list 11 provide more links to specific vendors, products and installations. The list of vendors and networks is not comprehensive and is not intended as an endorsement of these companies above others. Many of the wimax gateways that are offered by manufactures such as these are stand-alone self-install indoor units. Such devices typically sit near the customer's window with the best signal, and provide: An integrated wi-fi access point to provide the wimax internet connectivity to multiple devices throughout the home or business. Ethernet ports to connect directly to a computer, router, printer or dvr on a local wired network.
One or two analog telephone jacks to connect a land-line phone and take advantage of voip. Indoor gateways are convenient, but radio losses mean that the subscriber may need to be significantly closer to the wimax base station than with professionally installed external units. Outdoor units are roughly the size of a laptop pc, and their installation is comparable to the installation of a residential satellite dish. A higher- gain directional outdoor unit will generally result in greatly increased range and throughput but with the obvious loss of practical mobility of the unit. External modems edit airstream 1200 usb modem usb can provide connectivity to a wimax network through a dongle. Generally these devices are connected to a notebook or net book computer.
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Also, as wireless broadband networks grow denser and usage habits shift, the need for increased backhaul and media service will accelerate, therefore the opportunity to leverage cable assets is expected to increase. Connecting edit a wimax usb modem for mobile access to the Internet devices that provide connectivity to a wimax network are known as subscriber stations (SS). Portable units include handsets (similar to cellular smartphones pc peripherals (pc cards or usb dongles and embedded devices in laptops, which are now available for wi-fi services. In addition, there is much emphasis by operators on consumer electronics devices such as Gaming consoles, mp3 players and similar devices. Wimax is more similar to wi-fi than to other 3G cellular technologies. The wimax forum website provides a list of certified devices. However, this is not a complete list of devices available as certified modules are embedded into laptops, mids ( Mobile Internet devices and other private labeled devices.
Wimax in this application competes with microwave radio, e-line and simple extension of the fiber network itself. Triple-play edit wimax directly supports the technologies that make triple-play service offerings possible (such as praise quality of service and multicasting ). These are inherent to the wimax standard rather than being added on as carrier Ethernet is to Ethernet. On may 7, 2008 in the United States, Sprint Nextel, google, intel, comcast, bright house, and Time warner announced a pooling of an average of 120 mhz of spectrum and merged with Clearwire to market the service. The new company hopes to benefit from combined services offerings and network resources as a springboard past its competitors. The cable companies will provide media services to other partners while gaining access to the wireless network as a mobile virtual network operator to provide triple-play services. questioned how the deal will work out: Although fixed-mobile convergence has been a recognized factor in the industry, prior attempts to form partnerships among wireless and cable companies have generally failed to lead to significant benefits to the participants. Other analysts point out that as wireless progresses to higher bandwidth, it inevitably competes more directly with cable and dsl, inspiring competitors into collaboration.
fiber networks edit mobile wimax was a replacement candidate for cellular phone technologies such as gsm and cdma, or can be used as an overlay to increase capacity. Fixed wimax is also considered as a wireless backhaul technology for 2g, 3g, and 4G networks in both developed and developing nations. 7 8 In North America, backhaul for urban operations is typically provided via one or more copper wire line connections, whereas remote cellular operations are sometimes backhauled via satellite. In other regions, urban and rural backhaul is usually provided by microwave links. (The exception to this is where the network is operated by an incumbent with ready access to the copper network.) wimax has more substantial backhaul bandwidth requirements than legacy cellular applications. Consequently, the use of wireless microwave backhaul is on the rise in North America and existing microwave backhaul links in all regions are being upgraded. 9 Capacities of between 34 Mbit/s and 1 Gbit/s 10 are routinely being deployed with latencies in the order of 1 ms. In many cases, operators are aggregating sites using wireless technology and then presenting traffic on to fiber networks where convenient.
Wi-fi alliance.) wimax forum certification allows vendors to sell fixed or mobile products as wimax certified, thus ensuring a level of interoperability with other certified products, as long as they fit the same profile. The original ieee 802.16 standard (now called "Fixed wimax was published in 2001. Wimax adopted some of its technology from. Wibro, a service marketed in Korea. 4, mobile wimax (originally based on 802.16e-2005) is the revision that was deployed in many countries, and is the basis for future revisions such as 802.16m-2011. Wimax is sometimes referred to as "wi-fi on steroids" 5 and can be used for a number of applications including broadband connections, cellular backhaul, hotspots, etc. It is similar to long-range wi-fi, but it can enable usage at much greater distances. 6 Uses of wimax edit The bandwidth and range of wimax make it suitable for the following potential applications: Providing portable mobile broadband connectivity across cities and countries through various devices Providing a wireless alternative to cable and digital subscriber line (DSL) for " last. In purpose many cases this has resulted in competition in markets which typically only had access through an existing incumbent dsl (or similar) operator.
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Wimax worldwide Interoperability for Microwave access ) is a family of wireless communication standards based on the, ieee 802.16 set of standards, which provide multiple physical layer (PHY) and Media access Control (MAC) options. The name "wimax" was created by the wimax forum, which was formed in June 2001 to promote conformity and interoperability of the standard, including the definition of predefined system profiles for commercial vendors. The forum describes wimax as "a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and, dSL ". 2, ieee 802.16m or Wirelessman-advanced was a candidate for the 4g, in competition with the, lte advanced standard. Wimax was initially designed to provide 30 to 40 megabit-per-second data rates, 3 signalman with the 2011 update providing up to 1 Gbit/s 3 for fixed stations. Terminology edit, wimax refers to interoperable implementations of the. Ieee 802.16 family of wireless-networks standards ratified by the wimax forum. (Similarly, wi-fi refers to interoperable implementations of the. Ieee 802.11, wireless lan standards certified by the.