WiMAX Quick Guide
Summary As the demand for broadband services continues to grow worldwide, traditional solutions, such as digital cable and fiber optics, are often difficult and expensive to implement, especially in rural and remote areas. The emerging WiMAX system satisfies the growing need for high data-rate applications such as voiceover IP, video conferencing, interactive gaming, and multimedia streaming. WiMAX deployments not only serve residential and enterprise users but can also be deployed as a backhaul for Wi-Fi hotspots or 3G cellular towers.
By providing affordable wireless broadband access, the technology of WiMAX will revolutionize broadband communications in the developed world and bridge the digital divide in developing countries. The book describes the logical architecture of IEEE In addition, the book examines the backhaul requirements of a large fixed wireless network and the problem of centralized routing and scheduling for IEEE With the revolutionary technology of WiMAX, the lives of many will undoubtedly improve, thereby leading to greater economic empowerment.
Burbank and William T. Practical Network Design Techniques: The Handbook of Optical Communication Networks. Enabling Technologies and Services. The Bookshelf application offers access: Offline Computer — Download Bookshelf software to your desktop so you can view your eBooks with or without Internet access. The country you have selected will result in the following: Product pricing will be adjusted to match the corresponding currency.
We can compare it with Wi-Fi based on the following factors.
However, both are IEEE standards. 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. 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.
Here a small antenna on your computer connects to the WiMAX tower. 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. WiMAX is capable of supporting very high peak data rates. 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.
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. WiMAX supports automatic retransmission requests ARQ at the link layer for connections that require enhanced reliability. ARQ-enabled connections require each transmitted packet to be acknowledged by the receiver; unacknowledged packets are assumed to be lost and are retransmitted.
Both uplink and downlink resource allocation are controlled by a scheduler in the base station. Capacity is shared among multiple users on a demand basis, using a burst TDM scheme. The WiMAX solution has a number of hooks built into the physical-layer design, which allows for the use of multiple-antenna techniques, such as beamforming, space-time coding, and spatial multiplexing. 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 non-real-time traffic flows, in addition to best-effort data traffic. The mobile WiMAX variant of the system has mechanisms to support secure seamless handovers for delay-tolerant full-mobility applications, such as VoIP.
WiMAX: Applications
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.
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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. A WiMAX tower station can connect directly to the Internet using a high-bandwidth, wired connection for example, a T3 line. 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.
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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 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. Additional functions that may be part of the BS are micro mobility management functions, such as handoff triggering and tunnel establishment, radio resource management, QoS policy enforcement, traffic classification, DHCP Dynamic Host Control Protocol proxy, key management, session management, and multicast group management.
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.
WiMAX - Quick Guide
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-of-sight or multipath radio environment. 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.
Because the physical layer of WiMAX is quite flexible, data rate performance varies based on the operating parameters. Parameters that have a significant impact on the physical-layer 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 increases 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 inter-carrier 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. 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. 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. User data is encrypted using cryptographic schemes of proven robustness to provide privacy.