Wimax

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Posted by sonny 03/01/2009 @ 06:02

Tags : wimax, wireless, mobile computing, technology

News headlines
Cisco takes aim at WiMax - Computerworld
By Matt Hamblen Computerworld - Clearwire Corp. and Cisco Systems Inc. last week announced an alliance aimed at expanding high-speed WiMax wireless services nationwide using Cisco products as the core network infrastructure....
ADI's new RF transceivers for WiMAX base stations - EE Herald
Analog Devices' new integrated RF-to-digital baseband transceivers AD9356 and AD9357 for 4G technologies, such as WiMAX and LTE (long term evolution) are cost optimized devices. Targeted more for picocell and microcell type WiMAX and LTE base stations...
Sprint CEO: Sees Pre Shortages For A While - CNNMoney.com
Hesse also commented on wimax and its partnership with Clearwire Corp. (CLWR), noting that Sprint is waiting for more of a deployment before launching the service. He touted the company's wimax mobile hotspot, which uses the wimax network to create a...
Motorola clarifies position on WiMAX, LTE R&D - FierceBroadbandWireless
Motorola's networks division is working to clarify comments from co-CEO Greg Brown during Motorola's first-quarter conference call that indicated the vendor would reduce its investments in WiMAX and Long-Term Evolution (LTE) technology as it looks to...
Clearwire Prepares Mobile WiMax Launch In Atlanta - InformationWeek
By W. David Gardner Clearwire said it will launch its mobile WiMax service in Atlanta next month as the company reported first-quarter revenue of $62.1 million and a loss of $71.1 million. While the company is nibbling at its $2.8 billion hoard of cash...
Indonesia to announce WiMAX winners in July - TeleGeography
Indonesia's Ministry of Communication and Information Technology (MoCI) plans to announce the winners of the tender for WiMAX broadband operating licences in July, The Jakarta Post reports. MoCI minister Muhammad Nuh says the agency is currently in the...
Multilinks snaps up Galaxy's WiMAX licence - TeleGeography
The report states that the other two successful applicants, Mobitel Nigeria and Spectranet, met the payment deadline for the concession to provide WiMAX services. Under the terms of the auction, companies that were among the first four to pay the fee...
Alvarion adds new backhaul platform to BreezeNet B family - Telecompaper
Wimax equipment maker Alvarion has added the BreezeNet B300 to its portfolio of BreezeNET B family of point-to-point systems. The BreezeNet B300 high capacity point-to-point backhaul platform supports high-bandwidth applications with advanced...
Zune-Xbox rumors map to Microsoft organization - CNET News
TeamXbox goes a little dreamy with the speculation, suggesting that this gadget might have built-in WiMax and connectivity to the MyPhone data storage and synchronization services that Microsoft announced for Windows Mobile 6.5....
MetroConnect Subsidiary Names Ben Cavazos Director of Engineering - Market Wire (press release)
His expertise in WiMAX, CDMA, GSM, iDEN and fiber solutions will contribute to the development and deployment of present and future wireless and telecommunication projects. Ben has been the Service Manager for Freedom Communications since 2006....

WiMAX

A WiMAX CPE of a 26 km connection mounted 13 meters above the ground (2004, Lithuania).

WiMAX, meaning Worldwide Interoperability 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 internet access. The technology provides up to 72 Mbit/s symmetric 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".

Companies are closely examining WiMAX for last mile connectivity. 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.

WiMAX access was used to assist with communications in Aceh, Indonesia, after the tsunami in December 2004. 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.

In addition, WiMAX was used by Intel Corporation to assist the FCC and FEMA in their communications efforts in the areas affected by Hurricane Katrina.

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 a the installation of a residential satellite dish.

With the potential of mobile WiMAX, there is an increasing focus on portable units. 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); 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.

Sprint Nextel announced in mid-2006 that it would invest about US$ 5 billion in a WiMAX technology buildout over the next few years. Since that time Sprint has been dealt setbacks that have resulted in steep quarterly losses. On May 7, 2008, Sprint, Clearwire, 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.

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.

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 E1 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. Capacities of between 34Mbit/s and 1 Gbit/s are routinely being deployed with latencies in the order of 1ms. 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.

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.

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. This can cause subscriber stations distant from the AP to be repeatedly interrupted by closer stations, greatly reducing their throughput. This makes services such as Voice over Internet Protocol (VoIP) or IPTV, which depend on an essentially-constant Quality of service (QoS) depending on data rate and interruptibility, difficult to maintain for more than a few simultaneous users.

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. In addition to being stable under overload and over-subscription (unlike 802.11), the 802.16 scheduling algorithm can also be more bandwidth efficient. 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.

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.

The WiMAX Forum has defined an architecture that defines how a WiMAX network connects with other networks, and a variety of other aspects of operating such a network, including address allocation, authentication, etc. An overview of the architecture is given in the illustration.

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.

Comparisons and confusion between WiMAX and Wi-Fi are frequent, possibly because both begin with the same two letters, are based upon IEEE standards beginning with "802.", and are related to wireless connectivity and Internet access. However, the two standards are aimed at different applications.

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.

The 802.16 specification applies across a wide swath of the RF spectrum, and WiMAX could function on any frequency below 66 GHz, (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, 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. 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.

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. 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.

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.

A commonly-held misconception is that WiMAX will deliver 70 Mbit/s over 31 miles/50 kilometers. In reality, WiMAX can only do one or the other — operating over maximum range (31 miles/50 km) increases bit error rate and thus must use a lower bitrate. Lowering the range allows a device to operate at higher bitrates.

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 an omni-directional antenna which is of lower-gain compared to directional antennas but are more portable. In practice, this means that in a line-of-sight environment with a portable Mobile WiMAX CPE, speeds of 10 Mbit/s at 6 miles/10 km could be delivered. However, in urban environments they may not have line-of-sight and therefore users may only receive 10 Mbit/s over 2 km. In current deployments, throughputs are often closer to 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 Mobile 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, many users will have a range of 2-, 4-, 6-, 8-, 10- or 12 Mbit/s services and additional radio cards will be added to the base station to increase the capacity as required.

Because of this, various granular and distributed network architectures are being incorporated into WiMAX through independent development and within the IEEE 802.16j mobile multi-hop relay (MMR) task group. This includes wireless mesh, grids, network remote station repeaters which can extend networks and connect to backhaul.

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 to date been more cautious of involvement 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. The large number of suppliers during introduction phase of WiMAX demonstrates the low entry barriers for IPR.

The current WiMAX incarnation, Mobile WiMAX, is based upon IEEE Std 802.16e-2005, approved in December 2005. It is a supplement to the IEEE Std 802.16-2004, 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.

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, Wi-Fi or even Mobile WiMAX.

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. This affects a relatively small number users and operators.

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).

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

A major role for the organization is to certify the interoperability of WiMAX products. 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.

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.

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.

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. With GSM/UMTS, the move to 4G is the 3GPP Long Term Evolution effort. For AMPS/TIA derived standards such as CDMA2000, a replacement called Ultra Mobile Broadband is under development. In both cases, existing air interfaces are being discarded, in favour of OFDMA for the downlink and a variety of OFDM based techniques for the uplink, much akin 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.

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".

In September 2006, the IEEE-SA Standards Board approved a plan to enable the working group to continue under new conditions, and the standard is now expected to be completed by Q2 2008.

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

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.

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.

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.

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.

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. The WiMAX Forum has not answered yet.

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

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.

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).

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List of deployed WiMAX networks

This is a list of WiMAX networks as proposed and deployed.

The first WiMAX Network deployed in Iran, with 80% coverage of Tehran. Provides VPN Service to Banks and Insurance companies.

G-MAXTM is a registered trademark of Galaxy Wireless Communications Limited for its product lines that best combine mobility with high data rates and ease of use by providing and offering a scalable, nationwide wireless broadband access network.

The G-MAXTM brand provides fixed and mobile wireless broadband Internet and data services at highly affordable costs designed to massively increase Internet penetration in Nigeria. It is the first plug-and-play nomadic broadband solution in Nigeria based on a hybrid of the Smart AntennaTM, Multi Carrier Wireless Information Local LoopTM and emerging WiMAX technologies.

Currently, Pakistan has the largest fully functional WiMAX network in the world. Wateen Telecom installed the network (with an initial rollout in seventeen cities) throughout Pakistan using Motorola hardware.

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WiMAX MIMO

Illustration of a WiMAX MIMO board with a WiMAX MIMO RFIC

WiMAX MIMO refers to the use of Multiple-input multiple-output communications (MIMO) technology on WiMAX, which is the technology brand name for the implementation of the standard IEEE 802.16.

WiMAX is the technology brand name for the implementation of the standard IEEE 802.16. 802.16 specifies the air interface at the PHY (Physical layer) and at the MAC (Medium Access Control layer) . Aside from specifying the support of various channel bandwidths and adaptive modulation and coding, it also specifies the support for MIMO antennas to provide good Non-line-of-sight (NLOS) characteristics.

MIMO stands for Multiple Input and Multiple Output, and refers to the technology where there are multiple antennas at the base station and multiple antennas at the mobile device. Typical usage of multiple antenna technology includes cellular phones with two antennas, laptops with two antennas (e.g. built in the left and right side of the screen), as well as CPE devices with multiple sprouting antennas.

The predominant cellular network implementation is to have multiple antennas at the base station and a single antenna on the mobile device. This minimizes the cost of the mobile radio. As the costs for radio frequency (RF) components in mobile devices go down, second antennas in mobile device may become more common. Multiple mobile device antennas are currently used in Wi-Fi technology (e.g. IEEE 802.11n), where WiFi-enabled cellular phones, laptops and other devices often have two or more antennas.

WiMAX implementations that use MIMO technology have become important. The use of MIMO technology improves the reception and allows for a better reach and rate of transmission. The implementation of MIMO also gives WiMAX a significant increase in spectral efficiency.

The 802.16 defined MIMO configuration is negotiated dynamically between each individual base station and mobile station. The 802.16 specification supports the ability to support a mix of mobile stations with different MIMO capabilities. This helps to maximize the sector throughput by leveraging the different capabilities of a diverse set of vendor mobile stations.

The 802.16 specification supports the Multiple-input and single-output (MISO) technique of Transmit Diversity, which is commonly referred to Space Time Code (STC). With this method, two or more antennas are employed at the transmitter and one antenna at the receiver. The use of multiple receive antennas (thus MIMO) can further improve the reception of STC transmitted signals.

With a Transmit Diversity rate = 1 (aka "Matrix A" in the 802.16 standard), different data bit constellations are transferred on two different antennas during the same symbol. The conjugate and/or inverse of the same two constellations are transferred again on the same antennas during the next symbol. The data transfer rate with STC remains the same as the baseline case. The received signal is more robust with this method due to the transmission redundancy. This configuration delivers similar performance to the case of two receive antennas and one transmitter antenna.

The 802.16 specification also supports the MIMO technique of Spatial Multiplexing (SMX), also known as Transmit Diversity rate = 2 (aka "Matrix B" in the 802.16 standard). Instead of transmitting the same bit over two antennas, this method transmits one data bit from the first antenna, and another bit from the second antenna simultaneously, per symbol. As long as the receiver has more than one antenna and the signal is of sufficient quality, the receiver can separate the signals. This method involves added complexity and expense at both the transmitter and receiver. However, with two transmit antennas and two receive antennas, data can be transmitted twice as fast as compared systems using Space Time Codes with only one receive antenna.

One specific use of Spatial Multiplexing is to apply it to users who have the best signal quality, so that less time is spent transmitting to them. Users whose signal quality is too low to allow the spatially multiplexed signals to be resolved stay with conventional transmission. This allows an operator to offer higher data rates to some users and/or to serve more users. The WiMAX specification's dynamic negotiation mechanism helps enable this use.

The 802.16 specification also supports the use of four antennas. Three configurations are supported.

With rate = 1 using four antennas, data is transmitted four times per symbol, where each time the data is conjugated and/or inverted. This does not change the data rate, but does give the signal more robustness and avoids sudden increases in error rates.

With rate = 2 using four antennas, the data rate is only doubled, but increases in robustness since the same data is transmitted twice as compared to only once with using two antennas.

The third configuration that is only available using four antennas is Matrix C, where a different data bit is transmitted from the four antennas per symbol, which gives it four times the baseline data rate.

Note: MRC (Maximum Ratio Combining) is vendor discretionary and improves rate and range. In WiMAX, MRC at the Base Station is sometimes also referred to as Receive Beamforming.

A related technique is called Uplink Collaborative MIMO, where users transmit at the same time in the same frequency. This type of spatial multiplexing improves the sector throughput without requiring multiple transmit antennas at the mobile device. The common non-MIMO method for this in OFDMA is by scheduling different mobile stations at different points in an OFDMA time-frequency map. Collaborative Spatial Multiplexing (Collaborative MIMO) is comparable to regular spatial multiplexing, where multiple data streams are transmitted from multiple antennas on the same device.

In the case of WiMAX, Uplink Collaborative MIMO is spatial multiplexing with two different devices, each with one antenna. These transmitting devices are collaborating in the sense that both devices must be synchronized in time and frequency so that the intentional overlapping occurs under controlled circumstances. The two streams of data will then interfere with each other. As long as the signal quality is sufficiently good and the receiver at the base station has at least two antennas, the two data streams can be separated again. This technique is sometimes also termed Virtual Spatial Multiplexing.

A MIMO-related technique that can be used with WiMAX is called AAS or Beamforming. Multiple antennas and multiple signals are employed, which then shape the beam with the intent of improving transmission to the desired station. The result is reduced interference because the signal going to the desired user is increased and the signal going to other users is reduced.

Another MIMO-related technique that can be used in WiMAX systems, but which is outside of the scope of the 802.16 specification, is known as Cyclic Delay Diversity. In this technique, one or more of the signals are delayed before transmission. Because the signals are coming out of two antennas, their receive spectrums differ as each spectrum is characterized by humps and notches due to multi-path fading. At the receiver the signals combine, which improves reception because the joint reception results in shallower spectral humps and fewer spectral notches. The closer the signal can get towards a flat channel at a certain power level, the higher the throughput that can be obtained.

The WiMax Forum has a set of standardized conformance test procedures for PHY and MAC specification compliance called the Radio Conformance Test (RCT). Any technology aspect of a particular implementation of a radio interface must first undergo the RCT. Generally, any aspect of the IEEE 802.16 standard that does not have a test procedure in the RCT may be assumed to not yet be widely implemented.

Companies that make RFICs that support WiMAX MIMO include Intel, Beceem, NXP Semiconductors and PMC-Sierra.

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4G

4G (also known as Beyond 3G), an abbreviation for Fourth-Generation, is a term used to describe the next complete evolution in wireless communications. A 4G system will be able to provide a comprehensive IP solution where voice, data and streamed multimedia can be given to users on an "Anytime, Anywhere" basis, and at higher data rates than previous generations.

As the second generation was a total replacement of the first generation networks and handsets, and the third generation was a total replacement of second generation networks and handsets, so too the fourth generation cannot be an incremental evolution of current 3G technologies, but rather the total replacement of the current 3G networks and handsets. The international telecommunications regulatory and standardization bodies are working for commercial deployment of 4G networks roughly in the 2012-2015 time scale. At that point it is predicted that even with current evolutions of third generation 3G networks, these will tend to be congested.

There is no formal definition for what 4G is; however, there are certain objectives that are projected for 4G. These objectives include: that 4G will be a fully IP-based integrated system. 4G will be capable of providing between 100 Mbit/s and 1 Gbit/s speeds both indoors and outdoors, with premium quality and high security.

Many companies have taken self-serving definitions and distortionsabout 4G to suggest they have 4G already in existence today, such as several early trials and launches of WiMAX. Other companies have made prototype systems calling those 4G. While it is possible that some currently demonstrated technologies may become part of 4G, until the 4G standard or standards have been defined, it is impossible for any company currently to provide with any certainty wireless solutions that could be called 4G cellular networks that would conform to the eventual international standards for 4G. These confusing statements around "existing" 4G have served to confuse investors and analysts about the wireless industry.

In summary, the 4G system should dynamically share and utilise network resources to meet the minimal requirements of all the 4G enabled users.

As described in 4G consortia including WINNER, WINNER - Towards Ubiquitous Wireless Access, and WWRF, a key technology based approach is summarized as follows, where Wireless-World-Initiative-New-Radio (WINNER) is a consortium to enhance mobile communication systems.

According to the 4G working groups, the infrastructure and the terminals of 4G will have almost all the standards from 2G to 4G implemented. Although legacy systems are in place to adopt existing users, the infrastructure for 4G will be only packet-based (all-IP). Some proposals suggest having an open internet platform. Technologies considered to be early 4G include Flash-OFDM, the 802.16e mobile version of WiMax (also known as WiBro in South Korea), and HC-SDMA (see iBurst). 3GPP Long Term Evolution may reach the market 1-2 years after Mobile WiMax.

An even higher speed version of WiMax is the IEEE 802.16m specification. LTE Advanced will be the later evolution of the 3GPP LTE standard. .

As the wireless standards evolved, the access techniques used also exhibited increase in efficiency, capacity and scalability. The first generation wireless standards used plain TDMA and FDMA. In the wireless channels, TDMA proved to be less efficient in handling the high data rate channels as it requires large guard periods to alleviate the multipath impact. Similarly, FDMA consumed more bandwidth for guard to avoid inter carrier interference. So in second generation systems, one set of standard used the combination of FDMA and TDMA and the other set introduced a new access scheme called CDMA. Usage of CDMA increased the system capacity and also placed a soft limit on it rather than the hard limit. Data rate is also increased as this access scheme is efficient enough to handle the multipath channel. This enabled the third generation systems to used CDMA as the access scheme IS-2000, UMTS, HSXPA, 1xEV-DO, TD-CDMA and TD-SCDMA. The only issue with CDMA is that it suffers from poor spectrum flexibility and scalability.

Recently, new access schemes like Orthogonal FDMA (OFDMA), Single Carrier FDMA (SC-FDMA), Interleaved FDMA and Multi-carrier code division multiple access (MC-CDMA) are gaining more importance for the next generation systems. WiMax is using OFDMA in the downlink and in the uplink. For the next generation UMTS, OFDMA is being considered for the downlink. By contrast, IFDMA is being considered for the uplink since OFDMA contributes more to the PAPR related issues and results in nonlinear operation of amplifiers. IFDMA provides less power fluctuation and thus avoids amplifier issues. Similarly, MC-CDMA is in the proposal for the IEEE 802.20 standard. These access schemes offer the same efficiencies as older technologies like CDMA. Apart from this, scalability and higher data rates can be achieved.

The other important advantage of the above mentioned access techniques is that they require less complexity for equalization at the receiver. This is an added advantage especially in the MIMO environments since the spatial multiplexing transmission of MIMO systems inherently requires high complexity equalization at the receiver.

In addition to improvements in these multiplexing systems, improved modulation techniques are being used. Whereas earlier standards largely used Phase-shift keying, more efficient systems such as 64QAM are being proposed for use with the 3GPP Long Term Evolution standards.

Unlike 3G, which is based on two parallel infrastructures consisting of circuit switched and packet switched network nodes respectively, 4G will be based on packet switching only. This will require low-latency data transmission.

By the time that 4G is deployed, the process of IPv4 address exhaustion is expected to be in its final stages. Therefore, in the context of 4G, IPv6 support is essential in order to support a large number of wireless-enabled devices. By increasing the number of IP addresses, IPv6 removes the need for Network Address Translation (NAT), a method of sharing a limited number of addresses among a larger group of devices.

In the context of 4G, IPv6 also enables a number of applications with better multicast, security, and route optimization capabilities. With the available address space and number of addressing bits in IPv6, many innovative coding schemes can be developed for 4G devices and applications that could aid deployment of 4G networks and services.

The performance of radio communications obviously depends on the advances of an antenna system, refer to smart or intelligent antenna. Recently, multiple antenna technologies are emerging to achieve the goal of 4G systems such as high rate, high reliability, and long range communications. In the early 90s, to cater the growing data rate needs of data communication, many transmission schemes were proposed. One technology, spatial multiplexing, gained importance for its bandwidth conservation and power efficiency. Spatial multiplexing involves deploying multiple antennas at the transmitter and at the receiver. Independent streams can then be transmitted simultaneously from all the antennas. This increases the data rate into multiple folds with the number equal to minimum of the number of transmit and receive antennas. This is called MIMO (as a branch of intelligent antenna). Apart from this, the reliability in transmitting high speed data in the fading channel can be improved by using more antennas at the transmitter or at the receiver. This is called transmit or receive diversity. Both transmit/receive diversity and transmit spatial multiplexing are categorized into the space-time coding techniques, which does not necessarily require the channel knowledge at the transmit. The other category is closed-loop multiple antenna technologies which use the channel knowledge at the transmitter.

SDR is one form of open wireless architecture (OWA). Since 4G is a collection of wireless standards, the final form of a 4G device will constitute various standards. This can be efficiently realized using SDR technology, which is categorized to the area of the radio convergence.

The Japanese company NTT DoCoMo has been testing a 4G communication system prototype with 4x4 MIMO called VSF-OFCDM at 100 Mbit/s while moving, and 1 Gbit/s while stationary. In February 2007, NTT DoCoMo completed a trial in which they reached a maximum packet transmission rate of approximately 5 Gbit/s in the downlink with 12x12 MIMO using a 100MHz frequency bandwidth while moving at 10 km/h, and is planning on releasing the first commercial network in 2010.

Digiweb, an Irish fixed and wireless broadband company, has announced that they have received a mobile communications license from the Irish Telecoms regulator, ComReg. This service will be issued the mobile code 088 in Ireland and will be used for the provision of 4G Mobile communications.. Digiweb launched a mobile broadband network using FLASH-OFDM technology at 872 MHz.

Pervasive networks are an amorphous and at present entirely hypothetical concept where the user can be simultaneously connected to several wireless access technologies and can seamlessly move between them (See vertical handoff, IEEE 802.21). These access technologies can be Wi-Fi, UMTS, EDGE, or any other future access technology. Included in this concept is also smart-radio (also known as cognitive radio technology) to efficiently manage spectrum use and transmission power as well as the use of mesh routing protocols to create a pervasive network.

Sprint plans to launch 4G services in trial markets by the end of 2007 with plans to deploy a network that reaches as many as 100 million people in 2008 and has also announced WiMax service called Xohm. Tested in Chicago, this speed was clocked at 100 Mbit/s.

Verizon Wireless announced on September 20, 2007 that it plans a joint effort with the Vodafone Group to transition its networks to the 4G standard LTE. The time of this transition has yet to be announced.

Telus and Bell Canada have announced that they will be cooperating towards building a fourth generation (4G) wireless broadband network in Canada. It is expected to be complete by early 2010.

At the present rates of 15-30 Mbit/s, 4G is capable of providing users with streaming high-definition television. At rates of 100 Mbit/s, the content of a DVD-5 (for example a movie), can be downloaded within about 5 minutes for offline access.

3GPP is currently standardizing LTE Advanced as future 4G standard. A first set of 3GPP requiremens on LTE Advanced has been approved in June 2008. The working groups are currently evaluating various proposals for standardization. LTE Advanced will be standardized as part of the Release 10 of the 3GPP specification.

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Source : Wikipedia