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WiMAX

WiMAX (Worldwide Interoperability for Microwave Access) is a wireless communications standard designed to provide 30 to 40 megabit-per-second data rates, with the 2011 update providing up to 1 Gbit/s for fixed stations. WiMAX refers to interoperable implementations of the IEEE 802.16 family of wireless-networks standards ratified by the WiMAX Forum. WiMAX can provide at-home or mobile Internet access across whole cities or countries. In many cases this has resulted in competition in markets which typically only had access through an existing incumbent DSL (or similar) operator.

The bandwidth and range of WiMAX make it suitable for the following potential applications:

  • Providing portable mobile broadband connectivity across cities and countries through a variety of devices.
  • Providing a wireless alternative to cable and digital subscriber line (DSL) for “last mile” broadband access.
  • Providing data, telecommunications (VoIP) and IPTV services (triple play).
  • Providing a source of Internet connectivity as part of a business continuity plan.
  • Smart grids and metering

Mobile WiMAX was a replacement candidate for cellular phone technologies such as GSM and CDMA, or can be used as an overlay to increase capacity. Fixed WiMAX is also considered as a wireless backhaul technology for 2G, 3G, and 4G networks in both developed and developing nations. Devices that provide connectivity to a WiMAX network are known as subscriber stations (SS). Portable units include handsets (similar to cellular smartphones); PC peripherals (PC Cards or USB dongles); and embedded devices in laptops, which are now available for Wi-Fi services. In addition, there is much emphasis by operators on consumer electronics devices such as Gaming consoles, MP3 players and similar devices. WiMAX is more similar to Wi-Fi than to other 3G cellular technologies. USB can provide connectivity to a WiMAX network through what is called a dongle. Generally these devices are connected to a notebook or net book computer. Dongles typically have omnidirectional antennas which are of lower gain compared to other devices. As such these devices are best used in areas of good coverage. Mobile_wimax_usb

Comparisons and confusion between WiMAX and Wi-Fi are frequent, because both are related to wireless connectivity and Internet access.

  • WiMAX is a long range system, covering many kilometres, that uses licensed or unlicensed spectrum to deliver connection to a network, in most cases the Internet.
  • Wi-Fi uses the 2.4 GHz, 3 GHz, 5 GHz, and 60 GHz radio frequency bands to provide access to a local network.
  • Wi-Fi is more popular in end-user devices.
  • Wi-Fi runs on the Media Access Control’s CSMA/CA protocol, which is connectionless and contention based, whereas WiMAX runs a connection-oriented MAC.
  • WiMAX and Wi-Fi have quite different quality of service (QoS) mechanisms:
    • WiMAX uses a QoS mechanism based on connections between the base station and the user device. Each connection is based on specific scheduling algorithms.
    • Wi-Fi 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.
  • Both IEEE 802.11, which includes Wi-Fi, and IEEE 802.16, which includes WiMAX, define Peer-to-Peer (P2P) and wireless ad hoc networks, where an end user communicates to users or servers on another Local Area Network (LAN) using its access point or base station. However, 802.11 supports also direct ad hoc or peer to peer networking between end user devices without an access point while 802.16 end user devices must be in range of the base station.

Although Wi-Fi and WiMAX are designed for different situations, they are complementary. WiMAX network operators typically provide a WiMAX Subscriber Unit that connects to the metropolitan WiMAX network and provides Wi-Fi connectivity within the home or business for local devices, e.g., computers, Wi-Fi handsets and smartphones. This enables the user to place the WiMAX Subscriber Unit in the best reception area, such as a window, and still be able to use the WiMAX network from any place within their residence.

The local area network inside one’s house or business would operate as with any other wired or wireless network. If one were to connect the WiMAX Subscriber Unit directly to a WiMAX-enabled computer, that would limit access to a single device. As an alternative for a LAN, one could purchase a WiMAX modem with a built-in wireless Wi-Fi router, allowing one to connect multiple devices to create a LAN.

Using WiMAX could be an advantage, since it is typically faster than most cable modems with download speeds between 3 and 6 Mbit/s, and generally costs less than cable.

Gundruk

Gundruk (गुन्द्रुक) (Nepali) is fermented leafy green vegetable and is a popular food in Nepal and claimed to be one of the national dishes. It is popular not only in Nepal but also in the Himalayan region. The annual production of gundruk in Nepal is estimated at 2,000 tons and most of the production is carried out at the household level. Gundruk is obtained from the fermentation of leafy vegetables (Nepali: saag). It is served as a side dish with the main meal and is also used as an appetizer. Gundruk is an important source of minerals particularly during the off-season when the diet consists of mostly starchy tubers and maize which tend to be low in minerals.

In the months of October and November, during the harvest of the first broad mustard, radish and cauliflower leaves, large quantities of leaves accumulate — much more than can be consumed fresh. These leaves are allowed to wilt for one or two days and then shredded with a knife or sickle. Not only the leaves of the radish, the roots are also used to make a better quality gundruk. The roots of radish can be mixed with the leaves and smashed together. When it is smashed, care should be taken not to make pieces too small. In mountainous regions of central part of Nepal, the smashed Radish and leaves are put into a earthenwares, compressed, and the mouth of container is closed tightly. It is then buried in safe and sunny place. It may be placed in an open place. After a few days, the acidity can be tasted or when it is ready, it can readily be known from it’s smell as well.It is then dried in sunlight. Thus made gundruk is more tasty, more flavorous and more acidic.

The shredded leaves are tightly packed in an earthenware pot, and warm water (at about 30°C) is added to cover all the leaves. The pot is then kept in a warm place. After five to seven days, a mild acidic taste indicates the end of fermentation and the gundruk is removed and sun-dried. This process is similar to sauerkraut production except that no salt is added to the shredded leaves before the start of gundruk fermentation. The ambient temperature at the time of fermentation is about 18°C. Pediococcus and Lactobacillus species are the predominant microorganisms active during gundruk fermentation. During fermentation, the pH drops slowly to a final value of 4.0 and the amount of acid (as lactic) increases to about 1% on the sixth day. It has been found that a disadvantage with the traditional process of gundruk fermentation is the loss of 90% of the carotenoids, probably during sun-drying. Improved methods of drying might reduce the vitamin loss.

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