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WiMAX base station equipment with a sector antenna and wireless modem on tops
A pre-WiMAX CPE of a 26 km connection mounted 13 meters above the ground (2004, Lithuania).

WiMAX, meaning Worldwide Inter-operability for Microwave Access, is a telecommunications technology that provides wireless transmission of data using a variety of transmission modes, from point-to-multipoint links to portable and fully mobile[citation needed] internet access. The technology provides up to 3 Mbit/s [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] broadband speed without the need for cables. The technology is based on the IEEE 802.16 standard (also called Broadband Wireless Access). The name "WiMAX" was created by the WiMAX Forum, which was formed in June 2001 to promote conformity and interoperability of the standard. 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".[14]


[edit] Definitions

The terms "fixed WiMAX", "mobile WiMAX", "802.16d" and "802.16e" are frequently used incorrectly.[15] Correct definitions are the following:

  • 802.16-2004 is often called 802.16d, since that was the working party that developed the standard. It is also frequently referred to as "fixed WiMAX" since it has no support for mobility.
  • 802.16e-2005 is an amendment to 802.16-2004 and is often referred to in shortened form as 802.16e. It introduced support for mobility, amongst other things and is therefore also known as "mobile WiMAX".

[edit] Uses

The bandwidth and range of WiMAX make it suitable for the following potential applications:

  • Connecting Wi-Fi hotspots to the Internet.
  • Providing a wireless alternative to cable and DSL for "last mile" broadband access.
  • Providing data and telecommunications services.
  • Providing a source of Internet connectivity as part of a business continuity plan. That's, if a business has a fixed and a wireless Internet connection, especially from unrelated providers, they are unlikely to be affected by the same service outage.
  • Providing portable connectivity.

[edit] Broadband access

Companies are closely examining Wi-MAX for last mile connectivity.[citation needed] The resulting competition may bring lower pricing for both home and business customers or bring broadband access to places where it has been economically unavailable.[citation needed]

WiMAX access was used to assist with communications in Aceh, Indonesia, after the tsunami in December 2004.[citation needed] All communication infrastructure in the area, other than amateur radio, was destroyed, making the survivors unable to communicate with people outside the disaster area and vice versa. WiMAX provided broadband access that helped regenerate communication to and from Aceh.[citation needed]

In addition, WiMAX was donated by Intel Corporation to assist the FCC and FEMA in their communications efforts in the areas affected by Hurricane Katrina.[16] In practice, volunteers used mainly self-healing mesh, VoIP, and satellite uplinks combined with Wi-Fi on the local link.[17]

[edit] Subscriber units (Client Units)

WiMAX subscriber units are available in both indoor and outdoor versions from several manufacturers. Self-install indoor units are convenient, but radio losses mean that the subscriber must be significantly closer to the WiMAX base station than with professionally-installed external units. As such, indoor-installed units require a much higher infrastructure investment as well as operational cost (site lease, backhaul, maintenance) due to the high number of base stations required to cover a given area. Indoor units are comparable in size to a cable modem or DSL modem. Outdoor units are roughly the size of a laptop PC, and their installation is comparable to the installation of a residential satellite dish.

With the potential of mobile WiMAX, there is an increasing focus on portable units.[citation needed] This includes handsets (similar to cellular smartphones), PC peripherals (PC Cards or USB dongles), and embedded devices in laptops, such as are now available for WiFi. In addition, there is much emphasis from operators on consumer electronics devices (game terminals, MP3 players and the like);[citation needed] it is notable this is more similar to Wi-Fi than to 3G cellular technologies.

Current certified devices can be found at the WiMAX Forum web site. This is not a complete list of devices available as certified modules are embedded into laptops, MIDs (Mobile Internet Devices), and private labeled devices.[citation needed]

[edit] Mobile handset applications

Sprint Nextel announced in mid-2006 that it would invest about US$ 5 billion in a WiMAX technology buildout over the next few years.[18] Since that time Sprint has been dealt setbacks that have resulted in steep quarterly losses. On May 7, 2008, Sprint, Imagine, Google, Intel, Comcast, and Time Warner announced a pooling of 2.5 GHz spectrum and formation of a new company which will take the name Clearwire. 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. Google will contribute Android handset device development and applications and will receive revenue share for advertising and other services they provide. Clearwire Sprint and current Clearwire gain a majority stock ownership in the new venture and ability to access between the new Clearwire and Sprint 3G networks. Some details remain unclear including how soon and in what form announced multi-mode WiMAX and 3G EV-DO devices will be available. This raises questions that arise for availability of competitive chips that require licensing of Qualcomm's IPR.

Some analysts have 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, thrusting competitors into bed together. Also, as wireless broadband networks grow denser and usage habits shift, the need for increased back haul and media service will accelerate, therefore the opportunity to leverage cable assets is expected to increase.

[edit] Backhaul/access network applications

WiMAX is a possible replacement candidate for cellular phone technologies such as GSM and CDMA, or can be used as a layover to increase capacity. It has also been considered as a wireless backhaul technology for 2G, 3G, and 4G networks in both developed and poor nations.[19][20]

In North America, "Backhaul" for urban cellular operations is typically provided via one or more copper wireline T1 connections, whereas remote cellular operations are sometimes backhauled via satellite. In most 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, in which case T1 lines may be used). WiMAX is a broadband platform and as such has much more substantial backhaul bandwidth requirements than legacy cellular applications. Therefore traditional copper wireline backhaul solutions are not appropriate. 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. [21] Capacities of between 34 Mbit/s and 1 Gbit/s are routinely being deployed with latencies in the order of 1ms.[citation needed] In many cases, operators are aggregating sites using wireless technology and then presenting traffic on to fibre networks where convenient.

Deploying WiMAX in rural areas with limited or no internet backbone will be challenging as additional methods and hardware will be required to procure sufficient bandwidth from the nearest sources — the difficulty being in proportion to the distance between the end-user and the nearest sufficient internet backbone.

[edit] Technical information

Illustration of a WiMAX MIMO board

WiMAX is a term coined to describe standard, interoperable implementations of IEEE 802.16 wireless networks, similar to the way the term Wi-Fi is used for interoperable implementations of the IEEE 802.11 Wireless LAN standard. However, WiMAX is very different from Wi-Fi in the way it works.

[edit] MAC layer/data link layer

In Wi-Fi the media access controller (MAC) uses contention access — all subscriber stations that wish to pass data through a wireless access point (AP) are competing for the AP's attention on a random interrupt basis.[citation needed] This can cause subscriber stations distant from the AP to be repeatedly interrupted[citation needed] by closer stations, greatly reducing their throughput.[citation needed]

In contrast, the 802.16 MAC uses a scheduling algorithm for which the subscriber station needs to compete only once (for initial entry into the network). After that it 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 it.[citation needed] In addition to being stable under overload and over-subscription[citation needed], the 802.16 scheduling algorithm can also be more bandwidth efficient.[citation needed] The scheduling algorithm also allows the base station to control QoS parameters by balancing the time-slot assignments among the application needs of the subscriber stations[citation needed].

[edit] Physical layer

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. 802.16-2004 was updated by 802.16e-2005 in 2005 and uses scalable orthogonal frequency-division multiple access (SOFDMA) as opposed to the orthogonal frequency-division multiplexing version with 256 sub-carriers (of which 200 are used) 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. 802.16e also adds a capability for full mobility support. The WiMAX certification allows vendors with 802.16d products to sell their equipment as WiMAX certified, thus ensuring a level of interoperability with other certified products, as long as they fit the same profile.

Most commercial interest is in the 802.16d and .16e standards, since the lower frequencies used in these variants suffer less from inherent signal attenuation and therefore give improved range and in-building penetration. Already today, a number of networks throughout the world are in commercial operation using certified WiMAX equipment compliant with the 802.16d standard.

[edit] Complexities of deployment

Being a standard thought to satisfy the needs of next generation data networks, nomadic and mobile (4G), it is distinguished by a dynamic burst algorithm that adapts the current physical digital modulation according to field variables that are dependant on the radio propagation conditions; the current physical mod is chosen to be spectrally more efficient (more bits per OFDM/SOFDMA symbol), that is, when the bursts have a high signal strength (field strength) and a high carrier to noise plus interference ratio (cinr) and they can be easily decoded by the Digital Signal Processing (DSP) Algorithms. In contrast, when some of those conditions are bad, then the system chooses a more robust physical mod (burst profile) which means less bits per OFDM/SOFDMA symbol, but with the advantage that power per bit is higher and therefore accurate decoding is easier. Because of this, higher order burst profiles can only be used (dynamically chosen by an algorithm) when the attenuation is not high which means only for Subscriber Stations located near the BS antenna and therefore the maximum distance can only be achieved by means of selecting the more robust burst profile with the MAC frame allocation inconvenience that it implies as more symbols (more portion of the MAC frame) have to be allocated for transmitting a given amount of data than if the SS was close to the BS. What this means is that data transfer speed goes down as distance from the base station goes up, otherwise it would be too glitchy.

In the MAC Frame the SSs are allocated and their individual burst profiles defined as well as the specific time allocation, but even if that is done automatically practical deployment should avoid high interference and high multipath environments as opposed to what the average radio network planning team (and executive staff from the adopting operator) could think, the reason for it lies in excessive interference and competition during the Initial Ranging (IR) process due to the usage of high transmitting power in BS and SS alike, which can result in unwanted delays and ranging attempts that effectively detracts from a good user experience and can even result in wasted allocated symbols due to continuous connections/re-connections.

The system therefore is very complex to deploy as it is necessary to keep in mind not only the signal strength and cinr (as in systems like GSM) but it is also necessary to think how the spectrum is going to be dynamically assigned (resulting in dynamically changing total available bandwidth)) to the served SSs (other dynamic burst systems have 2 or 3 burst profiles, WiMAX developments have showed up to 7 in use at the same time), the DSP algorithms (Decodification) are tougher that in any other wireless systems yet they cannot reconstruct any burst in any environment; It is usually very effective though, but coupled with OFDM/SOFDMA, it can result in a double edged sword which means by having a tougher set of DSP algorithms, usually deployed on specific purpose chips, the signal could (harmfully) reach farther distances than expected due to tunnel effects (constructive interference with neighbor frequencies) resulting in highly interfered clutters and with highly reflected signals, with very high signal strength though which can fool the non experienced planning staff (usually coming from 3gpp networks).

As a result the system has to be initially deployed in conjunction with product development staff (who are usually involved in the technology development in some way) from the given vendor as opposed to service technical staff (radio planning) from the operator or vendor as is usual practise, thus raising the cost of deployment. As with all new technologies, configuration and maintenance will become easier to use as more deployments occur.

[edit] Integration with an IP based Network

The WiMAX Forum WiMAX 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 (ISP); Nevertheless the WiMAX BS provide seamless integration capabilities with other types of architectures as with packet switched Mobile Networks.

The WiMAX forum proposal defines a number of components, plus some of the interconnections (or reference points) between these, labeled R1 to R5 and R8:

  • SS/MS: the Subscriber Station/Mobile Station
  • ASN: the Access Service Network[22]
  • BS: Base station, part of the ASN
  • ASN-GW: the ASN Gateway, part of the ASN
  • CSN: the Connectivity Service Network
  • HA: Home Agent, part of the CSN
  • AAA: AAA Server, part of the CSN
  • NAP: a Network Access Provider
  • NSP: a Network Service Provider

It is important to note that the functional architecture can be designed into various hardware configurations rather than fixed configurations. For example, the architecture is flexible enough to allow remote/mobile stations of varying scale and functionality and Base Stations of varying size - e.g. femto, pico, and mini BS as well as macros.

[edit] Comparison with Wi-Fi

Comparisons and confusion between WiMAX and Wi-Fi are frequent because both are related to wireless connectivity and Internet access.

  • WiMAX uses spectrum to deliver a point-to-point connection to the Internet. Different 802.16 standards provide different types of access, from portable (similar to a cordless phone) to fixed (an alternative to wired access, where the end user's wireless termination point is fixed in location.)
  • Wi-Fi uses unlicensed spectrum to provide access to a network. Wi-Fi is more popular in end user devices.
  • WiMAX and Wi-Fi have quite different Quality of Service (QoS) mechanisms. WiMAX uses a mechanism based on connections between the Base Station and the user device. Each connection is based on specific scheduling algorithms. Wi-Fi has a QoS mechanism similar to fixed Ethernet, where packets can receive different priorities based on their tags. For example VoIP traffic may be given priority over web browsing.
  • Wi-Fi runs on the MAC's CSMA/CA protocol, which is connectionless and contention based, whereas WiMAX runs a connection-oriented MAC.

Both 802.11 and 802.16 define P2P and ad hoc networks, where an end user communicates to users or servers on another LAN using its access point or base station.

[edit] Spectrum allocation issues

The 802.16 specification applies across a wide swath of the RF spectrum, and WiMAX could function on any frequency below 66 GHz,[23] (higher frequencies would decrease the range of a Base Station to a few hundred meters in an urban environment).

There is no uniform global licensed spectrum for WiMAX, although the WiMAX Forum has published three licensed spectrum profiles: 2.3 GHz, 2.5 GHz and 3.5 GHz, in an effort to decrease cost: economies of scale dictate that the more WiMAX embedded devices (such as mobile phones and WiMAX-embedded laptops) are produced, the lower the unit cost. (The two highest cost components of producing a mobile phone are the silicon and the extra radio needed for each band.) Similar economy of scale benefits apply to the production of Base Stations.

In the unlicensed band, 5.x GHz is the approved profile. Telecom companies are unlikely to use this spectrum widely other than for backhaul, since they do not own and control the spectrum.

In the USA, the biggest segment available is around 2.5 GHz,[24] 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 2.3 GHz probably being most important in Asia. Some countries in Asia like India and Indonesia will use a mix of 2.5 GHz, 3.3 GHz and other frequencies. Pakistan's Wateen Telecom uses 3.5 GHz.

Analog TV bands (700 MHz) may become available for WiMAX usage, but await the complete roll out of digital TV, and there will be other uses 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 AT&T.[25] Both of these companies have stated their intention of supporting LTE, a technology which competes directly with WiMAX. EU commissioner Viviane Reding has suggested re-allocation of 500–800 MHz spectrum for wireless communication, including WiMAX.[26]

WiMAX profiles define channel size, TDD/FDD and other necessary attributes in order to have inter-operating products. The current fixed profiles are defined for both TDD and FDD profiles. At this point, all of the mobile profiles are TDD only. The fixed profiles have channel sizes of 3.5 MHz, 5 MHz, 7 MHz and 10 MHz. The mobile profiles are 5 MHz, 8.75 MHz and 10 MHz. (Note: the 802.16 standard allows a far wider variety of channels, but only the above subsets are supported as WiMAX profiles.)

Since October 2007, the Radio communication Sector of the International Telecommunication Union (ITU-R) has decided to include WiMAX technology in the IMT-2000 set of standards.[27] This enables spectrum owners (specifically in the 2.5-2.69 GHz band at this stage) to use Mobile WiMAX equipment in any country that recognizes the IMT-2000.

[edit] Spectral efficiency

One of the significant advantages of advanced wireless systems such as WiMAX is spectral efficiency. For example, 802.16-2004 (fixed) has a spectral efficiency of 3.7 (bit/s)/Hertz, and other 3.5–4G wireless systems offer spectral efficiencies that are similar to within a few tenths of a percent. The notable advantage of WiMAX comes from combining SOFDMA with smart antenna technologies. This multiplies the effective spectral efficiency through multiple reuse and smart network deployment topologies. The direct use of frequency domain organization simplifies designs using MIMO-AAS compared to CDMA/WCDMA methods, resulting in more effective systems.[citation needed]

[edit] Limitations

A commonly-held misconception is that WiMAX will deliver 70 Mbit/s over 50 kilometres (~31 miles). In reality, WiMAX can either operate at higher bitrates or over longer distances but not both: operating at the maximum range of 50 km increases bit error rate and thus results in a much lower bitrate. Conversely, reducing the range (to <1m) allows a device to operate at higher bitrates. There are no known examples of WiMAX services being delivered at bit rates over around 3 Mbit/s.

Typically, fixed WiMAX networks have a higher-gain directional antenna installed near the client (customer) which results in greatly increased range and throughput. Mobile WiMAX networks are usually made of indoor "customer premises equipment" (CPE) such as desktop modems, laptops with integrated Mobile WiMAX or other Mobile WiMAX devices. Mobile WiMAX devices typically have omni-directional antennae which are of lower-gain compared to directional antennas but are more portable. In current deployments, throughputs may reach 2 Mbit/s symmetric at 10 km with fixed WiMAX and a high gain antenna. It is also important to consider that a throughput of 2 Mbit/s can mean 2 Mbit/s, symmetric simultaneously, 1 Mbit/s symmetric or some asymmetric mix (e.g. 0.5 Mbit/s downlink and 1.5 Mbit/s uplink or 1.5 Mbit/s downlink and 0.5 Mbit/s uplink), each of which required slightly different network equipment and configurations. Higher-gain directional antennas can be used with a WiMAX network with range and throughput benefits but the obvious loss of practical mobility.

Like most wireless systems, available bandwidth is shared between users in a given radio sector, so performance could deteriorate in the case of many active users in a single sector. In practice, most users will have a range of 2-3 Mbit/s services and additional radio cards will be added to the base station to increase the number of users that may be served as required.

Because of these limitations, the general consensus is that WiMAX requires various granular and distributed network architectures to be incorporated within the IEEE 802.16 task groups. This includes wireless mesh, grids, network remote station repeaters which can extend networks and connect to backhaul.

[edit] Silicon implementations

A critical requirement for the success of a new technology is the availability of low-cost chipsets and silicon implementations.

Intel Corporation is a leader in promoting WiMAX, and has developed its own chipset. However, it is notable that most of the major semiconductor companies have not and most of the products come from specialist smaller or start-up suppliers. For the client-side these include Sequans, whose chips are in more than half of the WiMAX Forum Certified(tm) MIMO-based Mobile WiMAX client devices, GCT Semiconductor, ApaceWave, Altair Semiconductor, Beceem, Comsys, Runcom, Motorola with TI, NextWave Wireless, Redpine Signals, Wavesat, Coresonic and SySDSoft. Both Sequans and Wavesat manufacture products for both clients and network while Texas Instruments, DesignArt, and picoChip are focused on WiMAX chip sets for base stations. Kaben Wireless Silicon is a provider of RF front-end and semiconductor IP for WiMAX applications.

[edit] Standards

The current WiMAX incarnation, Mobile WiMAX, is based upon IEEE Std 802.16e-2005,[28] approved in December 2005. It is a supplement to the IEEE Std 802.16-2004,[29] and so the actual standard is 802.16-2004 as amended by 802.16e-2005 — the specifications need to be read together to understand them.

IEEE Std 802.16-2004 addresses only fixed systems. It replaced IEEE Standards 802.16-2001, 802.16c-2002, and 802.16a-2003.

IEEE 802.16e-2005 improves upon IEEE 802.16-2004 by:

  • Adding support for mobility (soft and hard handover between base stations). This is seen as one of the most important aspects of 802.16e-2005, and is the very basis of 'Mobile WiMAX' (though this has yet to be demonstrated in any installed systems).
  • Scaling of the Fast Fourier transform (FFT) to the channel bandwidth in order to keep the carrier spacing constant across different channel bandwidths (typically 1.25 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 of 1.25 MHz are defined in the standard, but because the allowed FFT subcarrier numbers are only 128, 512, 1024 and 2048, other frequency bands will not have exactly the same carrier spacing, which might not be optimal for implementations.
  • Advanced antenna diversity schemes, and hybrid automatic repeat-request (HARQ)
  • Adaptive Antenna Systems (AAS) and MIMO technology
  • Denser sub-channelization, thereby improving indoor penetration
  • Introducing Turbo Coding and Low-Density Parity Check (LDPC)
  • Introducing downlink sub-channelization, allowing administrators to trade coverage for capacity or vice versa
  • Fast Fourier transform algorithm
  • Adding an extra QoS class for VoIP applications.

802.16d vendors point out that fixed WiMAX offers the benefit of available commercial products and implementations optimized for fixed access. It is a popular standard among alternative service providers and operators in developing areas due to its low cost of deployment and advanced performance in a fixed environment. Fixed WiMAX is also seen as a potential standard for backhaul of wireless base stations such as cellular, or Wi-Fi.

SOFDMA (used in 802.16e-2005) and OFDM256 (802.16d) are not compatible thus most equipment will have to be replaced if an operator wants or needs to move to the later standard. However, some manufacturers are planning to provide a migration path for older equipment to SOFDMA compatibility which would ease the transition for those networks which have already made the OFDM256 investment. Intel provides a dual-mode 802.16-2004 802.16-2005 chipset for subscriber units.

[edit] Conformance testing

TTCN-3 test specification language is used for the purposes of specifying conformance tests for WiMAX implementations. The WiMAX test suite is being developed by a Specialist Task Force at ETSI (STF 252).[30]

[edit] Associations

[edit] WiMAX Forum

The WiMAX Forum is a non profit organization formed to promote the adoption of WiMAX compatible products and services.[31]

A major role for the organization is to certify the interoperability of WiMAX products.[32] Those that pass conformance and interoperability testing achieve the "WiMAX Forum Certified" designation, and can display this mark on their products and marketing materials. Some vendors claim that their equipment is "WiMAX-ready", "WiMAX-compliant", or "pre-WiMAX", if they are not officially WiMAX Forum Certified.

Another role of the WiMAX Forum is to promote the spread of knowledge about WiMAX. In order to do so, it has a certified training program that is currently offered in English and French. It also offers a series of member events and endorses some industry events.

[edit] WiMAX Spectrum Owners Alliance

WiSOA logo

WiSOA was the first global organization composed exclusively of owners of WiMAX spectrum with plans to deploy WiMAX technology in those bands. WiSOA focussed on the regulation, commercialisation, and deployment of WiMAX spectrum in the 2.3–2.5 GHz and the 3.4–3.5 GHz ranges. WiSOA merged with the Wireless Broadband Alliance in April 2008.[33]

[edit] Competing technologies

Speed vs. Mobility of wireless systems: Wi-Fi, HSPA, UMTS, GSM

Within the marketplace, WiMAX's main competition comes from existing, widely deployed wireless systems such as UMTS and CDMA2000, as well as a number of Internet-oriented systems such as HiperMAN, and of course long range mobile Wi-Fi and mesh networking.

3G cellular phone systems usually benefit from already having entrenched infrastructure, having been upgraded from earlier systems. Users can usually fall back to older systems when they move out of range of upgraded equipment, often relatively seamlessly.

The major cellular standards are being evolved to so-called 4G, high-bandwidth, low-latency, all-IP networks with voice services built on top. The worldwide move to 4G for GSM/UMTS and AMPS/TIA (including CDMA2000) is the 3GPP Long Term Evolution effort. A planned CDMA2000 replacement called Ultra Mobile Broadband has been discontinued. For 4G systems, existing air interfaces are being discarded in favour of OFDMA for the downlink and a variety of OFDM based techniques for the uplink, similar to WiMAX.

In some areas of the world, the wide availability of UMTS and a general desire for standardization has meant spectrum has not been allocated for WiMAX: in July 2005, the EU-wide frequency allocation for WiMAX was blocked.

[edit] Mobile Broadband Wireless Access

Mobile Broadband Wireless Access (MBWA) is a technology being developed by IEEE 802.20 and is aimed at wireless mobile broadband for operations from 75 to 220 mph (120 to 350 km/h). The 802.20 standard committee was first to define many of the methods which were later funneled into Mobile WiMAX, including high speed dynamic modulation and similar scalable OFDMA capabilities. It apparently retains fast hand-off, Forward Error Correction (FEC) and cell edge enhancements.

The Working Group was temporarily suspended in mid-2006 by the IEEE-SA Standards Board because it had been the subject of a number of appeals. A preliminary investigation of one of these "revealed a lack of transparency, possible 'dominance,' and other irregularities in the Working Group".[34]

In September 2006, the IEEE-SA Standards Board approved a plan to enable the working group to continue under new conditions, and on 12 June 2008, the IEEE approved the new standard.

Qualcomm, a leading company behind 802.20, has dropped support for continued development in order to focus on LTE.[35]

[edit] Internet-oriented systems

Early WirelessMAN standards, the European standard HiperMAN and Korean standard WiBro have been harmonized as part of WiMAX and are no longer seen as competition but as complementary. All networks now being deployed in South Korea, the home of the WiBro standard, are now WiMAX.

As a short-range mobile Internet technology, such as in cafes and at transportation hubs like airports, the popular Wi-Fi 802.11b/g system is widely deployed, and provides enough coverage for some users to feel subscription to a WiMAX service is unnecessary.

[edit] Comparison

The following table should be treated with caution because it only shows peak rates which are potentially very misleading. In addition, the comparisons listed are not normalized by physical channel size (i.e., spectrum used to achieve the listed peak rates); this obfuscates spectral efficiency and net through-put capabilities of the different wireless technologies listed below.

 v  d  e 
Comparison of Mobile Internet Access methods
Standard Family Primary Use Radio Tech Downlink (Mbit/s) Uplink (Mbit/s) Notes
LTE UMTS/4GSM General 4G OFDMA/MIMO/SC-FDMA 326.4 86.4 LTE-Advanced update to offer over 1 Gbit/s speeds.
802.16 WiMAX Mobile Internet MIMO-SOFDMA 3 3
Flash-OFDM Flash-OFDM Mobile Internet
mobility up to 200mph (350km/h)
Flash-OFDM 5.3
Mobile range 18miles (30km)
extended range 34 miles (55km)
HIPERMAN HIPERMAN Mobile Internet OFDM 56.9 56.9
Wi-Fi Wi-Fi Mobile Internet OFDM/MIMO/CDMA 108 108 Mobile range (3km)
iBurst iBurst 802.20 Mobile Internet HC-SDMA/TDD/MIMO 64 64 3–12 km
EDGE Evolution GSM Mobile Internet TDMA/FDD 1.9 0.9 3GPP Release 7

HSDPA widely deployed. Typical downlink rates today 2 Mbit/s, ~200 kbit/s uplink; HSPA+ downlink up to 42 Mbit/s.
UMTS-TDD UMTS/3GSM Mobile Internet CDMA/TDD 16 16 Reported speeds according to IPWireless using 16QAM modulation similar to HSDPA+HSUPA
1xRTT CDMA2000 Mobile phone CDMA 0.144 0.144 Succeeded by EV-DO
EV-DO 1x Rev. 0
EV-DO 1x Rev.A
CDMA2000 Mobile Internet CDMA/FDD 2.45
Rev B note: N is the number of 1.25 MHz chunks of spectrum used. Not yet deployed.

Notes: All speeds are theoretical maximums and will vary by a number of factors, including the use of external antennae, distance from the tower and the ground speed (e.g. communications on a train may be poorer than when standing still). Usually the bandwidth is shared between several terminals. The performance of each technology is determined by a number of constraints, including the spectral efficiency of the technology, the cell sizes used, and the amount of spectrum available. For more information, see Comparison of wireless data standards.

LTE is expected to be ratified at the end of 2008, with commercial implementations becoming viable within the next two years.

[edit] Future development

Mobile WiMAX based upon 802.16e-2005 has been accepted as IP-OFDMA for inclusion as the sixth wireless link system under IMT-2000. This can hasten acceptance by regulatory authorities and operators for use in cellular spectrum. WiMAX II, 802.16m will be proposed for IMT-Advanced 4G.

The goal for the long term evolution of both WiMAX and LTE is to achieve 100 Mbit/s mobile and 1 Gbit/s fixed-nomadic bandwidth as set by ITU for 4G NGMN (Next Generation Mobile Network) systems through the adaptive use of MIMO-AAS and smart, granular network topologies. 3GPP LTE and WiMAX-m are concentrating much effort on MIMO-AAS, mobile multi-hop relay networking and related developments needed to deliver 10X and higher Co-Channel reuse multiples.

Since the evolution of core air-link technologies has approached the practical limits imposed by Shannon's Theorem, the evolution of wireless has embarked on pursuit of the 3X to 10X+ greater bandwidth and network efficiency by advances in the spatial and smart wireless broadband networking technologies.

[edit] Interference

A field test conducted by SUIRG (Satellite Users Interference Reduction Group) with support from the U.S. Navy, the Global VSAT Forum, and several member organizations yielded results showing interference at 12 km when using the same channels for both the WiMAX systems and satellites in C-band.[36] The WiMAX Forum has not answered yet.

[edit] Current deployments

[edit] Networks

The WiMAX Forum now claims there are over 400 WiMAX networks deployed in over 130 countries.

[edit] By territory

This section gives details of regulatory decisions in various parts of the world. For information on deployments around the world see the List of deployed WiMAX networks

[edit] Europe

Commission Decision of 2008-05-21 on the harmonisation of the 3400-3800 MHz frequency band for terrestrial systems capable of providing electronic communications services in the Community.[37]

It includes:

  • Pursuant to Article 4(2) of Decision 676/2002/EC (of the European Parliament and of the Council of 7 March 2002 on a regulatory framework for radio spectrum policy in the European Community - Radio Spectrum Decision -),[38] the Commission gave a mandate dated 4 January 2006 to the European Conference of Postal and Telecommunications Administrations (hereinafter the “CEPT”) to identify the conditions relating to the provision of harmonised radio frequency bands in the EU for Broadband Wireless Access (BWA) applications.
  • In response to that Mandate, the CEPT issued a report (CEPT Report 15) on BWA, which concludes that the deployment of fixed, nomadic and mobile networks is technically feasible within the 3400-3800 MHz frequency band under the technical conditions described in the European Conference of Postal and Telecommunications Administrations Decision ECC/DEC/(07)02 and Recommendation ECC/REC/(04)05.
  • No later than six months after entry into force of this Decision, Member States shall designate and make available, on a non-exclusive basis, the 3400-3600 MHz band for terrestrial electronic communications networks.
  • By 1 January 2012 Member States shall designate and subsequently make available, on a non-exclusive basis, the 3600-3800 MHz band for terrestrial electronic communications networks.
  • The designation of the 3400-3800 MHz band for fixed, nomadic and mobile applications is an important element addressing the convergence of the mobile, fixed and broadcasting sectors and reflecting technical innovation. Member States shall allow the use of the 3400-3800 MHz band in for fixed, nomadic and mobile electronic communications networks.
  • This Decision is addressed to the Member States.

[edit] Germany

German Federal Network Agency has begun assigning frequencies for wireless Internet access in the band 3400 to 3600 MHz (in some places up to 4000 MHz).[39]

[edit] United Kingdom

The UK telecoms industry is waiting for OFCOM the UK’s telecoms regulator, to launch the tender process for the 2.6 GHz spectrum range for a number of services which can include WiMAX, including mobile services based on the 802.16e standard. This is currently expected in mid-2009.

[edit] America

[edit] Africa

In South Africa Telecoms Regulator ICASA has only issued four licences for commercial WiMAX services: to wireless broadband solutions provider iBurst, state-owned signal distributor Sentech, second network operator Neotel, [Amatole Telecommunication Services] (under serviced area license holder in S.A.) and Telkom, all on the 3.5 GHz band.

[edit] Asia

[edit] Indonesia

  • The Indonesian government announced on January 22, 2009 two ministry decrees and three regulations releasing spectrum at 2.3GHz and 3.3GHz for wireless broadband access across all regions of Indonesia. This means Indonesia will be using 2.3-GHz band for the Wimax 16.e standard while 3.3-GHz will be used for the 16.d standard.[40]

[edit] Literature

  • K. Fazel and S. Kaiser, Multi-Carrier and Spread Spectrum Systems: From OFDM and MC-CDMA to LTE and WiMAX, 2nd Edition, John Wiley & Sons, 2008, ISBN 978-0-470-99821-2

[edit] See also

[edit] Notes and references

  1. ^ "Mobilink FAQ". http://www.mobilinkinfinity.com/faqs/. Retrieved on 2009-03-30. 
  2. ^ "goBroadband". http://convergence.in/blog/2008/03/24/is-wimax-a-failure-tata-communications-acknowledges-shortcomings/. Retrieved on 2009-03-30. 
  3. ^ "Primer on WiMAX". http://cellstrat.wordpress.com/2008/04/24/a-primer-on-wimax/. Retrieved on 2009-03-30. 
  4. ^ "Deutsche Breitland, offering up to 3Mbps download". http://www.wimaxforum.org/files/case_studies/dbd_deutsche_breitband_dienste.pdf/. Retrieved on 2009-03-30. 
  5. ^ "Danske Telecom, offers up to 2mbps downstream, up to 192kbps upstream". http://www.wimaxforum.org/files/case_studies/danske_telecom.pdf/. Retrieved on 2009-03-30. 
  6. ^ "Digital Bridge, 3mbps/2Mbps". http://www.wimaxforum.org/files/case_studies/digital_bridge.pdf/. Retrieved on 2009-03-30. 
  7. ^ "KT WiBro, offering up to 3Mbps down/1Mbps up". http://www.wimaxforum.org/files/case_studies/kt_wibro_v1.6.pdf/. Retrieved on 2009-03-30. 
  8. ^ "Max Telecom, provides data chart showing up to 1mbps down and almost 273kbps up". http://www.wimaxforum.org/files/case_studies/max_telecom_1.2.pdf/. Retrieved on 2009-03-30. 
  9. ^ "Packet One, offers up to 2.4 Mbps downstream". http://www.wimaxforum.org/files/case_studies/packet_one.pdf/. Retrieved on 2009-03-30. 
  10. ^ "Wateen, has offerings up to 1mbps downstream". http://www.wimaxforum.org/files/case_studies/wateen.pdf/. Retrieved on 2009-03-30. 
  11. ^ "WiMAX Telecom, up to 2mbps down, up to 500kbps up". http://www.wimaxforum.org/files/case_studies/wimax_telecom.pdf/. Retrieved on 2009-03-30. 
  12. ^ "Yota, has the highest speed claim on the WiMAX forum of up to 10Mbps downstream". http://www.wimaxforum.org/files/case_studies/yota.pdf/. Retrieved on 2009-03-30. 
  13. ^ "Yota services are however not yet available". http://www.yota.ru/en/prices/. Retrieved on 2009-03-30. 
  14. ^ "WiMax Forum - Technology". http://www.wimaxforum.org/technology/. Retrieved on 2008-07-22. 
  15. ^ "IEEE 802.16 WirelessMAN Standard: Myths and Facts". ieee802.org. http://www.ieee802.org/16/docs/06/C80216-06_007r1.pdf. Retrieved on 2008-03-12. 
  16. ^ "FCC Pushes WIMax OK for Katrina Victims, Intel supplies the hardware". mobilemag.com. http://www.mobilemag.com/content/100/102/C4618/. Retrieved on 2008-01-08. 
  17. ^ "Volunteers use mesh, wimax, wi-fi, in katrina-hit regions". wifinetnews.com. http://wifinetnews.com/archives/2005/10/volunteers_use_mesh_wimax_wi-fi_in_katrina-hit_regions.html/. Retrieved on 2009-03-31. 
  18. ^ "4G Mobile Broadband". sprint.com. http://www2.sprint.com/mr/cda_pkDetail.do?id=1260. Retrieved on 2008-03-12. 
  19. ^ "Sprint Eyes WiMax Backhaul". lightreading.com. http://www.lightreading.com/document.asp?doc_id=104349. Retrieved on 2008-03-22. 
  20. ^ "WiMax signals get stronger in India". eetimes.com. http://www.eetimes.com/news/latest/showArticle.jhtml?articleID=206901605. Retrieved on 2008-03-22. 
  21. ^ "Overcoming the wireline bottleneck for 3G wireless services". supercommnews.com. http://supercommnews.com/wireless/features/wireline_wireless_networks_060305/. Retrieved on 2009-01-03. 
  22. ^ "The Access Service Network in WiMAX: The Role of ASN-GW". mustafaergen.com. http://www.mustafaergen.com/asn-gw.pdf. Retrieved on 2008-03-12. 
  23. ^ "Practical tips on making WiMAX field measurements, Part 1". rfdesignline.com. http://www.rfdesignline.com/197000698;jsessionid=QTVQPMTGVCCPCQSNDLQSKH0CJUNN2JVN?printableArticle=true. Retrieved on 2008-03-25. 
  24. ^ "U.S. Frequency Allocation Chart". Department of Commerce. http://www.ntia.doc.gov/osmhome/allochrt.pdf. Retrieved on 2008-03-12. 
  25. ^ "Auctions Schedule". FCC. http://wireless.fcc.gov/auctions/default.htm?job=auctions_sched. Retrieved on 2008-01-08. 
  26. ^ "European Commission proposes TV spectrum for WiMax". zdnetasia.com. http://www.zdnetasia.com/news/communications/0,39044192,62021021,00.htm. Retrieved on 2008-01-08. 
  27. ^ "ITU Radiocommunication Assembly approves new developments for its 3G standards". itu.int. http://www.itu.int/newsroom/press_releases/2007/30.html. Retrieved on 2008-03-12. 
  28. ^ "IEEE 802.16e Task Group (Mobile WirelessMAN)". ieee802.org. http://www.ieee802.org/16/tge/. Retrieved on 2008-03-12. 
  29. ^ "IEEE 802.16 Task Group d". ieee802.org. http://www.ieee802.org/16/tgd/. Retrieved on 2008-03-12. 
  30. ^ "HiperMAN / WiMAX Testing". ETSI. http://www.etsi.org/WebSite/technologies/HiperMAN-WiMAXTesting.aspx. Retrieved on 2008-03-28. 
  31. ^ "WiMAX Forum Overview". http://www.wimaxforum.org/about. Retrieved on 2008-08-01. 
  32. ^ "WiMAX Forum — Frequently Asked Questions". wimaxforum.org. http://www.wimaxforum.org/technology/faq. Retrieved on 2008-03-12. 
  33. ^ "WBA and WiSOA join efforts on WiMAX global roaming)". http://www.wimaxday.net/site/2008/04/24/wba-and-wisoa-join-efforts-on-wimax-global-roaming. Retrieved on 2008-12-10. 
  34. ^ "Status of 802.20". ieee.org. http://grouper.ieee.org/groups/802/mbwa/email/pdf00015.pdf. Retrieved on 2008-03-12. 
  35. ^ "Qualcomm halts UMB project, sees no major job cuts". Reuters. 2008. http://www.reuters.com/article/marketsNews/idUSN1335969420081113?rpc=401&. Retrieved on 2008-12-02. 
  36. ^ "SUIRG full interference test report". suirg.org. http://www.suirg.org/pdf/SUIRG_WiMaxFieldTestReport.pdf. Retrieved on 2008-03-16. 
  37. ^ http://ec.europa.eu/information_society/policy/radio_spectrum/docs/in_transit/bwa/bwa_en.pdf
  38. ^ http://ec.europa.eu/information_society/policy/radio_spectrum/docs/policy_outline/decision_6762002/en.pdf
  39. ^ "Federal Network Agency begins assigning frequencies for wireless Internet access". bundesnetzagentur.de. http://www.bundesnetzagentur.de/media/archive/4564.pdf. Retrieved on 2008-06-01. 
  40. ^ "Wimax frequencies allocation in Indonesia". http://www.earthtimes.org/articles/show/tranzeo-and-trg-advance-indonesian-wimax-joint-development,694186.shtml. 

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