Saturday, August 14, 2010

Wimax an Introduction for Dummies


WiMAX is an IP based,  wireless broadband access technology that provides the delivery of wireless broadband service anytime, anywhereand the performance similar to 802.11/Wi-Fi networks with the coverage and QOS (quality of service) of cellular networks. WiMAX is an acronym meaning "Worldwide Interoperability for Microwave Access (WiMAX).

WiMAX is a wireless digital communications system, also known as IEEE 802.16, that is intended for wireless "metropolitan area networks". WiMAX can provide broadband wireless access (BWA)
up to 30 miles (50 km) for fixed stations, and 3 - 10 miles (5 - 15 km) for mobile stations. In contrast, the WiFi/802.11 wireless local area network standard is limited in most cases to only 100 - 300 feet (30 - 100m).

With WiMAX, WiFi-like data rates are easily supported, but the issue of interference is lessened. WiMAX operates on both licensed and non-licensed frequencies, providing a regulated environment and viable economic model for wireless carriers.

 The primary advantages of the WiMAX standard are to enable the adoption of advanced radio features in a uniform fashion and reduce costs for all of the radios made by companies, who are part of the WiMAX Forum™ - a standards body formed to ensure interoperability via testing. The more recent Long Term Evolution (LTE) standard is a similar term describing a parallel technology to WiMAX that is being developed by vendors and carriers as a counterpoint to WiMAX.

What is IEEE 802.16?

The IEEE(Institute of electrical and electronics engineers) developed the 802.16 in its first version to address line of sight (LOS) access at spectrum ranges from 10 GHz to 66 GHz.  The technology has evolved through several updates to the standard such as 802.16a, 802.16c, the Fixed WiMAX 802.16d (802.16-2004) specification and lastly the mobile 802.16e set that are currently commercially available.  The upcoming 802.16m standard is due to be ratified in 2010.  The first update added support for 2 GHz through 11 GHz spectrum with NLOS capability.  Each update added additional functionality or expanded the reach of the standard.

For example, the 802.16c revision added support for spectrum ranges both licensed and unlicensed from 2 GHz to 10 GHz.  It also improved quality of service (QOS) and certain improvements in the media access control (MAC) layer along with adding support for the HiperMAN European standard.  The number of supported physical (PHY) layers was increased.  Transport mediums such as IP, Ethernet and asynchronous transfer mode (ATM) were added.

For example, older broadband wireless technology such as the Wi-Fi or 802.11b system utilized carrier sense multiple access with collision detection (CSMA/CD) crosstalk methods for base stations and customer premise equipment (CPE) to talk to one another.  Basically, this meant that each radio was constantly talking and creating inefficient overhead.  It also resulted, especially at times of high traffic, in increased packet collisions and retransmissions, further exacerbating the problem. 

Some of the proprietary MAC systems built later utilized the base station to define when the CPE would be polled in order to eliminate this problem.  In the way of a permanent cure the 802.16 protocol supports multiple methods of polling that a vendor can choose to use. 
Fixed WiMAX is the 802.16d standard or as it is sometimes called 802.16-2004.  Its product profile utilizes the OFDM 256-FFT (Fast Fourier Transform) system profile, which is just different enough from its sister standard of Mobile WiMAX (802.16e) that the two are incompatible.  Interestingly, both standards support both protocols within the technology protocol as well as the one chosen for Mobile WiMAX and the Korean WiBro/Mobile WiMAX standard. 
The 802.16e version of WiMAX also incorporates support for multiple-input-multiple-output (MIMO) antenna technology as well as Beamforming and Advanced Antenna Systems (AAS), which are all "smart" antenna technologies that significantly improve gain of WiMAX systems as well as throughput.  The 802.16e standard is being utilized primarily in licensed spectrum for pure mobile applications.  Many firms have elected to develop the 802.16e standard exclusively for both fixed and mobile versions.  The 802.16e version of WiMAX is the closest comparable technology to the emerging LTE mobile wireless standard.  Or rather, it is more proper to say that LTE is the most comparable to Mobile WiMAX in terms of capabilities as well as technology.  The two competing technologies are really very much alike technically.
The 802.16m mobile WiMAX standard is a follow-on to 802.16e standard and is a candidate to the International Telecom Union's (ITU) consideration as an IMT advanced (4G) technology - specifically, providing downlink speeds of at least 100 Mbps in a wide area with high-mobility.

new 802.16m standard will provide increased performance advantages over 802.16e.   From a technological perspective, 802.16m is capable of providing up to 120 Mbps down and 60 Mbps up in an urban setting, using 4x2 MIMO antennas on a single 20MHz-wide channel.   Even higher data rates can be achieved with additional spectrum resources or more complex antenna schemes.  

While 802.16m will provide increased performance for users, the main, driving factor for operators adopting the technology will be increased network capacity to accommodate the massive bandwidth increases driven by smartphones, tablets and other wireless devices.

In addition to capacity and performance advantages, 802.16m will be backward compatible with existing WiMAX networks, providing ease-of-mind for operators deploying networks today.   Most mobile WiMAX operators can easily convert from 802.16e to 802.16m by updating some circuit plate units and software in their bases stations.

Range of WiMAX

In the early days of WiMAX it was common to see statements in the media describing WiMAX multipoint coverage extending 30 miles(50 km). In a strict technical sense (in some spectrum ranges) this is correct, with even greater ranges being possible in point to point links. In practice (and especially in the license-free bands) this is wildly overstated especially where non line of sight (NLOS) reception is concerned.
The average cell ranges for most WiMAX networks will likely boast 4-5 mile range (in NLOS capable frequencies) even through tree cover and building walls. Service ranges up to 10 miles (16 Kilometers) are very likely in line of sight (LOS) applications (once again depending upon frequency).

RF Frequencies of WiMAX

The most recent versions of both WiMAX standards in 802.16 cover spectrum ranges from at least the 2 GHz - 66 GHz range.  This is an enormous spectrum range. The International standard of 3.5 GHz spectrum was the first to enjoy WiMAX products.  The technology appears easily extensible to lower frequencies including the valuable 700 MHz spectrum range. To generalize, the higher the spectrum frequency the greater the amount of bandwidth that can be transported lower frequencies transport less bandwidth.  Secondly, the lower the frequency the greater the carry range and penetration of a signal.  For example: A 900 MHz license free radio will travel farther and penetrate some tree cover fairly easily at ranges up to one to two miles.  But it can carry much less bandwidth than a 2.4 GHz signal which cannot penetrate any tree cover whatsoever, but can deliver a lot more data.

Key elements of WiMAX technology

A key differentiator for WiMAX is the interoperability of WiMAX Forum Certified equipment, resulting in mass volume economy of scale and assurance for service providers that when buying equipment from more than one company, the technologies are interoperable.
·       Standard for all usage models (fixed to mobile): By leveraging the same technology networks, WiMAX technology will become the most cost-effective solution for carriers to deploy for any usage model including fixed, portable, nomadic and mobile.
·       Wider coverage: The technology behind WiMAX is optimized to provide excellent non-line-of-sight (NLoS) coverage. NLoS advantages are coverage of wider areas, better predictability of coverage and lower cost as it means fewer base stations and backhaul, simple RF planning, shorter towers and faster CPE install times.
·       Higher capacity: WiMAX technology utilizes Orthogonal Frequency-Division Multiplexing (OFDM) over EDGE, GPRS, HSPA to deliver higher bandwidth efficiency and therefore higher data throughput, with more than one Mbps downstream and higher data rates.
·       Lower cost: A standards based platform for WiMAX technology drives down costs delivering volume economics to WiMAX equipment.

WiMAX services offer to the average consumer

In India, Basic internet services are not available in most homes . Currently broadband penetration in India is four million out of the more than one billion consumers, which is one broadband connection per 300 consumers. There are  already several operators offering WiMAX services in India today. For instance,BSNL, Reliance & Tata Communications plans to bring a mix of fixed and mobile broadband services to homes and small businesses around the country to meet the growing need for such services. Tata’s goal is to develop a profitable business model with single digit ARPU and affordable devices that can be replicated in other developing countries.

The factors that greatly affect range for WiMAX products

Many factors affect range for any broadband wireless product.  Some factors include
·       The terrain and density/height of tree cover.  
·       Hills and valleys can block or partially reflect signals.
·        Bodies of water such as rivers and lakes are highly reflective of RF transmissions.
·       The RF shadow of large buildings can create dead spots directly behind them, particularly if license-free spectrums are being used (with their attendant lower power allotments).
·       The greater the range between the base station and customer radio, the lower the amount of bandwidth that can be delivered, even in extremely well-designed network.
·       The climate can affect radio performance
 Fortunately OFDM(Orthogonal Frequency-Division Multiplexing ) can often turn this to an advantage but not always. Increasingly WiMAX radio antenna technology coupled with the inherent advantages of OFDM/OFDMA based radios can be a major factor in range and bandwidth capability.  The new multiple input multiple output (MIMO) and adaptive antenna systems (AAS) based antenna systems promise to maintain and even link connection and link budgets with much higher bandwidth than older technology.

What types of upgrades will operators have to do to deploy WiMAX services?

A single upgrade move to WiMAX technology’s all IP architecture is a direct step to 4G. It can provide a less costly long term approach compared to LTE and HSPA+ and also provides a significant Time to Market advantage. LTE is not a simple 3G upgrade as LTE represents a major upgrade from CDMA-Based HSPA (or EV-DO); it is not and never was a "simple" software upgrade.

WiMAX Security scheme/protocol

WiMAX security supports two quality encryptions standards, that of the DES3 and AES, which is considered leading edge.  The standard defines a dedicated security processor on board the base station for starters.  There are also minimum encryption requirements for the traffic and for end to end authentication---the latter of which is adapted from the data-over-cable service interface specification (DOCSIS) BPI+ security protocol.
Basically, all traffic on a WiMAX network must be encrypted using Counter Mode with Cipher Block Chaining Message Authentication Code Protocol (CCMP) which uses AES for transmission security and data integrity authentication.
The end-to-end authentication the PKM-EAP (Extensible Authentication Protocol) methodology is used which relies on the TLS standard of public key encryption.
At least one chip company designed processors to support this standard of onboard security processor.

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