WiMAX 802.16d/e

[WiMax - 802.16d/e] WiMAX is a term coined to describe standard, interoperable implementations of IEEE 802.16 wireless networks, in a rather similar way to Wi-Fi being 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 distant nodes from the AP to be repeatedly interrupted by closer nodes, greatly reducing their throughput. This makes services such as Voice over IP (VoIP) or IPTV, which depend on a predetermined type of "quality of service" (QoS), difficult to maintain for large numbers of users. In contrast, the 802.16 MAC uses a scheduling algorithm, where the subscriber station only has to compete once (for initial entry into the network). After that it is allocated a time slot by the base station. The time slot can enlarge and contract, but it remains assigned to the subscriber station, meaning that other subscribers cannot use it. This scheduling algorithm is stable under overload and over-subscription (unlike 802.11). It can also be more bandwidth efficient. The scheduling algorithm also allows the base station to control Quality of Service parameters by balancing the time-slot assignments among the application needs of the subscriber stations. The original WiMAX standard (IEEE 802.16) specified WiMAX in the 10 to 66 GHz range. 802.16a, updated in 2004 to 802.16-2004 (also known as 802.16d), added support for the 2 to 11 GHz range. 802.16d was updated to 802.16e in 2005. 802.16e uses scalable orthogonal frequency-division multiplexing (OFDM) as opposed to the non-scalable version in .16d. This brings potential benefits in terms of coverage, self installation, power consumption, frequency re-use and bandwidth efficiency. .16e also adds a capability for full mobility support. Most interest will probably be in the 802.16d and .16e standards, since the lower frequencies suffer less from signal attenuation and therefore give improved range and in-building penetration. The WiMAX specification improves upon many of the limitations of the Wi-Fi standard by providing increased bandwidth and range and stronger encryption. It provides connectivity between network endpoints without need for direct line of sight in favourable circumstances. The non-line-of-sight propagation (NLOS) performance requires the .16d or .16e variants, since the lower frequencies are needed. It relies upon clever use of multi-path signals.

Comments

Post a Comment

Popular posts from this blog

MSAN and DSLAM Technologies

In the realm of telecommunications, the demand for high-speed internet connectivity continues to grow. To meet this demand, telecommunication providers have employed various technologies, including Multi-Service Access Nodes (MSANs) and Digital Subscriber Line Access Multiplexers (DSLAMs). This essay aims to shed light on these technologies, their functions, and their impact on improving connectivity for end-users.   MSAN (Multi-Service Access Node): MSAN, also known as Multi-Service Access Gateway (MSAG), is a device that plays a crucial role in delivering multiple services, such as voice, data, and video, over a single network infrastructure. It serves as a convergence point, allowing service providers to offer a range of services to end-users efficiently. The primary function of an MSAN is to aggregate traffic from multiple sources and provide connectivity to various customer premises equipment (CPE) such as modems, routers, and set-top boxes. By consolidating multiple s...
Read more

What is IoT?

  In today's interconnected world, technology continues to advance at an astonishing pace, transforming the way we live, work, and interact. One remarkable innovation that has captured the imagination of both consumers and businesses alike is the Internet of Things (IoT). The IoT has emerged as a game-changer, promising to revolutionize industries, enhance efficiency, and improve our daily lives through its vast network of interconnected devices. In this blog post, we will explore the concept of the IoT, its potential applications, and the impact it has on various aspects of our society.   Understanding the Internet of Things: At its core, the Internet of Things refers to a vast network of physical objects, vehicles, appliances, and even people, all embedded with sensors, software, and connectivity, enabling them to exchange data and communicate with each other over the internet. These interconnected devices collect and transmit data, allowing for real-time monitorin...
Read more

Ground Wave Propagation

Image
the ground wave used for radio communications signal propagation on the long, and medium wave bands for local radio communications Ground wave propagation is particularly important on the LF and MF portion of the radio spectrum. Ground wave radio propagation is used to provide relatively local radio communications coverage, especially by radio broadcast stations that require to cover a particular locality. Ground wave radio signal propagation is ideal for relatively short distance propagation on these frequencies during the daytime. Sky-wave ionospheric propagation is not possible during the day because of the attenuation of the signals on these frequencies caused by the D region in the ionosphere. In view of this, radio communications stations need to rely on the ground-wave propagation to achieve their coverage. A ground wave radio signal is made up from a number of constituents. If the antennas are in the line of sight then there will be a direct wave as well a...
Read more