This paper has been prepared on behalf of the WiMAX Forum and the broader range of WiMAX Forum members have had the opportunity to review and. Basic concept is same as Walkie talkies. • A Wi-Fi hotspot is created by installing an access point to an internet connection. • An access point. Tutorial Aims. By the end of this tutorial, you will know. • what a GENI WiMAX testbed offers to experimenters,. • how to design a non-trivial.
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WiMAX is one of the hottest broadband wireless technologies around today. It is based This is a brief tutorial that covers the fundamentals of WiMAX. Audience. coverage. For more detail on Wi-Fi, please look into our Wi-Fi Tutorial. WiMAX is one of the hottest broadband wireless technologies around today. WiMAX. Fundamentals of WiMAX is written in an easy-to-understand tutorial fashion. PDF (probability density function) of Nakagami fading is parameterized by m.
Clearly, broadband wireless has until now had a checkered record, in part because of For a deeper tutorial exposure the interested reader is referred to . We consider a MIMO wireless communication system employing mt transmit and nr receive antennas, hence, This can be clearly seen by comparing Figures 3. Tutorial Aims. By the end of this tutorial, you will know.
By utilising the multiple signal paths that exist, the use of MIMO either enables operation with lower signal strength levels, or it allows for higher data rates.
Note on MIMO: MIMO is a form of antenna technology that uses multiple antennas to enable signals travelling via different paths as a result of reflections, etc. It has been set up to support and develop WiMAX technology worldwide, bring common standards across the globe to enable the technology to become an established worldwide technology. One of the aims of the forum is to enable a standard to be adopted that will enable full interoperability between products.
Learning from the problems of poor interoperability experienced with previous wireless standards, and the impact that this had on take up, the WiMAX Forum aims to prevent this from happening. Ultimately vendors will be able to have products certified under the auspices of the Forum, and then be able to advertise their products as "Forum Certified".
The focus is on IP operations because this is the now the main protocol that is used.
WiMAX history The history of WiMAX starts back in the s with the realisation that there would be a significant increase in data traffic over telecommunications networks. With wired telecommunications networks being very expensive, especially in outlying areas and not installed in many countries, methods of providing wireless broadband were investigated.
WiMAX history started with these investigations into what was termed the last mile connectivity - methods of delivering high speed data to a large number of users who may have no existing wired connection. The possibility of low cost last mile connectivity along with the possibility of a system that could handle backhaul over a wireless link proved to be a compelling argument to develop a new wireless data link system. The The first These amendments addressed issues of radio spectrum and interoperability and came under the designations In September a major revision project was commenced.
It was also intended to incorporate conformance test specifications within the overall standard. The project was completed in and the standard was released as WiMAX is to A scalable wireless platform for constructing alternative and complementary broadband networks. A certification that denotes interoperability of equipment built to the IEEE The IEEE What is WiMAX is such an easy term that people tend to use it for the The It can be used to connect WiMax Speed and Range WiMAX is expected to offer initially up to about 40 Mbps capacity per wireless channel for both fixed and portable applications, depending on the particular technical configuration chosen, enough to support hundreds of businesses with T-1 speed connectivity and thousands of residences with DSL speed connectivity.
WiMAX can support voice and video as well as Internet data. WiMax developed to provide wireless broadband access to buildings, either in competition to existing wired networks or alone in currently unserved rural or thinly populated areas. WiMAX is also intended to provide broadband connectivity to mobile devices. It would not be as fast as in these fixed applications, but expectations are for about 15 Mbps capacity in a 3 km cell coverage area.
With WiMAX, users could really cut free from today's Internet access arrangements and be able to go online at broadband speeds, almost wherever they like from within a MetroZone.
WiMAX could potentially be deployed in a variety of spectrum bands: WiMAX can satisfy a variety of access needs. Potential applications include extending broadband capabilities to bring them closer to subscribers, filling gaps in cable, DSL and T1 services, WiFi, and cellular backhaul, providing last meter access from fiber to the curb and giving service providers another cost-effective option for supporting broadband services.
WiMAX can support very high bandwidth solutions where large spectrum deployments i. WiMAX can help service providers meet many of the challenges they face due to increasing customer demands without discarding their existing infrastructure investments because it has the ability to seamlessly interoperate across various network types. WiMAX can provide wide area coverage and quality of service capabilities for applications ranging from real-time delay-sensitive voice-over-IP VoIP to realtime streaming video and non-real-time downloads, ensuring that subscribers obtain the performance they expect for all types of communications.
WiMAX, which is an IP-based wireless broadband technology, can be integrated into both wide-area third-generation 3G mobile and wireless and wireline networks allowing it to become part of a seamless anytime, anywhere broadband access solution. WiMAX has stepped forward to help solve barriers to adoption, such as interoperability and cost of deployment.
WiMAX will help ignite the wireless MAN industry by defining and conducting interoperability testing and labeling vendor systems with a "WiMAX Certified" label once testing has been completed successfully.
WiMAX is similar to the wireless standard known as Wi-Fi, but on a much larger scale and at faster speed. A nomadic version would keep WiMAX-enabled devices connected over large areas, much like todays cell phones.
We can compare it with Wi-Fi based on the following factors. However, both are IEEE standards. Range Wi-Fi typically provides local network access for a few hundred feet with the speed of up to 54 Mbps, a single WiMAX antenna is expected to have a range of up to 40 miles with the speed of 70 Mbps or more.
Fixed channel sizes 20MHz. Flexible channel sizes from 1. Bit Rate Wi-Fi works at 2. WiMAX is a wireless broadband solution that offers a rich set of features with a lot of flexibility in terms of deployment options and potential service offerings.
Some of the more salient features that deserve highlighting are as follows:. Non-line-of-sight service is a WiFi sort of service.
Here a small antenna on your computer connects to the WiMAX tower. Line-of-sight service, where a fixed dish antenna points straight at the WiMAX tower from a rooftop or pole.
The line-of-sight connection is stronger and more stable, so it's able to send a lot of data with fewer errors. Line-of-sight transmissions use higher frequencies, with ranges reaching a possible 66 GHz. Scalable Bandwidth and Data Rate Support WiMAX has a scalable physical-layer architecture that allows for the data rate to scale easily with available channel bandwidth. This scaling may be done dynamically to support user roaming across different networks that may have different bandwidth allocations.
Adaptive Modulation and Coding AMC WiMAX supports a number of modulation and forward error correction FEC coding schemes and allows the scheme to be changed as per user and per frame basis, based on channel conditions.
AMC is an effective mechanism to maximize throughput in a time-varying channel. ARQ-enabled connections require each transmitted packet to be acknowledged by the receiver; unacknowledged packets are assumed to be lost and are retransmitted.
Flexible and Dynamic per User Resource Allocation Both uplink and downlink resource allocations are controlled by a scheduler in the base station. Capacity is shared among multiple users on a demand basis, using a burst TDM scheme.
Support for Advanced Antenna Techniques The WiMAX solution has a number of hooks built into the physical-layer design, which allow for the use of multiple-antenna techniques, such as beamforming, space-time coding, and spatial multiplexing. Quality-of-service Support The WiMAX MAC layer has a connection-oriented architecture that is designed to support a variety of applications, including voice and multimedia services.
WiMAX system offers support for constant bit rate, variable bit rate, real-time, and nonreal-time traffic flows, in addition to best-effort data traffic. Support for Mobility The mobile WiMAX variant of the system has mechanisms to support secure seamless handovers for delay-tolerant full-mobility applications, such as VoIP.
All end-to-end services are delivered over an IP architecture relying on IP-based protocols for end-to-end transport, QoS, session management, security, and mobility. A WiMAX base station can provide coverage to a very large area up to a radius of 6 miles. Any wireless device within the coverage area would be able to access the Internet. The WiMAX base stations would use the MAC layer defined in the standard, a common interface that makes the networks interoperable and would allocate uplink and downlink bandwidth to subscribers according to their needs, on an essentially real-time basis.
Each base station provides wireless coverage over an area called a cell. Theoretically, the maximum radius of a cell is 50 km or 30 miles however, practical considerations limit it to about 10 km or 6 miles.
This is also referred as customer premise equipment CPE. WiMAX base station is similar to accessing a wireless access point in a WiFi network, but the coverage is greater.
It can also connect to another WiMAX tower using a line-of-sight microwave link. Backhaul refers both to the connection from the access point back to the base station and to the connection from the base station to the core network.
It is possible to connect several base stations to one another using high-speed backhaul microwave links. This would also allow for roaming by a WiMAX subscriber from one base station coverage area to another, similar to the roaming enabled by cell phones. The network reference model envisions a unified network architecture for supporting fixed, nomadic, and mobile deployments and is based on an IP service model.
The overall network may be logically divided into three parts:. The access service network ASN , which comprises one or more base stations and one or more ASN gateways that form the radio access network at the edge. The following figure shows some of the more important functional entities. Base station BS: The BS is responsible for providing the air interface to the MS. Additional functions that may be part of the BS are micro mobility management functions, such as handoff triggering and tunnel establishment, radio resource Additional functions that may be part of the ASN gateway include intra-ASN location management and paging, radio resource management, and admission control, caching of subscriber profiles, and encryption keys, AAA client functionality, establishment, and management of mobility tunnel with base stations, QoS and policy enforcement, foreign agent functionality for mobile IP, and routing to the selected CSN.
Connectivity service network CSN: The design of WiMAX network is based on the following major principles:. IP connectivity: Mobility management: IEEE Standard The WiMAX framework is based on several core principles:.
Well-defined interfaces to enable Functional extensibility to support future migration to full mobility and delivery of rich broadband multimedia. The WiMAX physical layer is based on orthogonal frequency division multiplexing.
OFDM is an elegant and efficient scheme for high data rate transmission in a non-line-ofsight or multipath radio environment. Adaptive Modulation and Coding in WiMAX WiMAX supports a variety of modulation and coding schemes and allows for the scheme to change on a burst-by-burst basis per link, depending on channel conditions.
Using the channel quality feedback indicator, the mobile can provide the base station with feedback on the downlink channel quality. For the uplink, the base station can estimate the channel quality, based on the received signal quality. The following table provides a list of the various modulation and coding schemes supported by WiMAX: Downlink Modulation. Parameters that have a significant impact on the physicallayer data rate are channel bandwidth and the modulation and coding scheme used.
Other parameters, such as number of sub-channels, OFDM guard time, and oversampling rate, also have an impact. Following is the PHY-layer data rate at various channel bandwidths, as well as modulation and coding schemes. OFDM belongs to a family of transmission schemes called multicarrier modulation, which is based on the idea of dividing a given high-bit-rate data stream into several parallel lower bit-rate streams and modulating each stream on separate carriers, often called subcarriers or tones.
Therefore, in high-data-rate systems in which the symbol duration is small, being inversely proportional to the data rate splitting the data stream into many parallel streams increase the symbol duration of each stream such that the delay spread is only a small fraction of the symbol duration. OFDM is a spectrally efficient version of multicarrier modulation, where the subcarriers are selected such that they are all orthogonal to one another over the symbol duration, thereby avoiding the need to have non-overlapping subcarrier channels to eliminate intercarrier interference.
By making the guard interval larger than the expected multipath delay spread, ISI can be completely eliminated.
Adding a guard interval, however, implies power wastage and a decrease in bandwidth efficiency.
For received transmissions, the MAC layer does the reverse. The MAC incorporates several features suitable for a broad range of applications at different mobility rates, such as the following:. Strong QoS control is achieved by using a connection-oriented MAC architecture, where all downlink and uplink connections are controlled by the serving BS.
WiMAX also defines a concept of a service flow. A service flow is a unidirectional flow of packets with a particular set of QoS parameters and is identified by a service flow identifier SFID. The user is allowed to take a fixed subscriber station and reconnect from a different point of attachment.
Nomadic access is provided to a portable device, such as a PC card, with expectation of a best-effort handover. Simple mobility: The subscriber may move at speeds up to 60 kmph with brief interruptions less than 1 sec during handoff.
Full mobility: It is likely that WiMAX networks will initially be deployed for fixed and nomadic applications and then evolve to support portability to full mobility over time.
In particular, the standard defines signaling mechanisms for tracking subscriber stations as they move from the coverage range of one base station to another when active or as they move from one paging group to another when idle. The standard also has protocols to enable a seamless handover of ongoing connections from one base station to another. The architecture also supports IP-layer mobility using mobile IP.
WiMAX systems were designed at the outset with robust security in mind. The standard includes state-of-the-art methods for ensuring user data privacy and preventing unauthorized access with additional protocol optimization for mobility. The key aspects of WiMAX security are as follow:. Support for Privacy User data is encrypted using cryptographic schemes of proven robustness to provide privacy. The bit or bit key used for deriving the cipher is generated during the authentication phase and is periodically refreshed for additional protection.
WiMAX terminal devices come with built-in X. Flexible Key-management Protocol The Privacy and Key Management Protocol Version 2 PKMv2 is used for securely transferring keying material from the base station to the mobile station, periodically reauthorizing and refreshing the keys. A three-way handshake scheme is supported to optimize the re-authentication mechanisms for supporting fast handovers, while simultaneously preventing any man-inthe-middle attacks.
These standards are issued by IEEE The WiMAX umbrella currently includes Following is the chart of various IEEE A nonprofit organization called WiMAX Forum was formed in , with the aim of harmonizing standards, testing, and certifying interoperability between equipment from different manufacturers.
The WiMAXForum is working on setting up a baseline protocol that allows equipment and devices from multiple vendors to interoperate and also provides a choice of equipment and devices from different suppliers. We have covered just the very basics of WiMAX in this tutorial. There is plenty of good reference material available out there that you should refer to become a master of WiMAX.
Here is a quick recapitulation of the points that we discussed in this tutorial:. WiMAX is similar to the wireless standard known as Wi-Fi, but on a much larger scale and at faster speeds.
The physical layer supports several advanced techniques for increasing the reliability of the link layer.