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Wi-Fi: A new dimension in wireless networks
Enforcing flyash utilisation Prof Yash
Pal UNDERSTANDING THE UNIVERSE |
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Wi-Fi: A new dimension in wireless networks Wi-Fi enables the user to access the Internet without wires from his home, a hotel room or a conference room at office. This wireless technology is similar to cell phones. Wi-Fi enabled computers can transmit and receive data at a fast speed anywhere in the vicinity of base station. The only requirement is a Wi-Fi certified PC card and the places having Wi-Fi access. IEEE 802.11b operates in the 2.4 GHz band with a maximum throughput of 11 Mbps. IEEE 802.11 has a bandwidth around 300 MHz and throughput of 54 Mbps. The wi-fi base station is the core element of the wireless network and provides wireless connectivity to all the wi-fi devices in its range (300 feet). The latest Laptop computers are equipped with an inbuilt wi-fi radio. This is a set of computer chips and an antenna that can send and receive wi-fi transmissions from a laptop, PDA, cell phone, access point or any other wireless device. Windows XP has built-in support for wi-fi. It will automatically detect the presence of a wi-fi network and connect to it. A wireless access point (AP) is a wireless network node which acts as a link between the base station and the wired network. A wi-fi router also serves this purpose and transmits through the network wirelessly. It also serves the purpose of a firewall and NAT (network address translator). Wi-Fi NIC (network interface card) enables the computer to access and communicate with a computer network. Wi-Fi networks achieve security by means of Wireless Equivalent Privacy or WEP. WEP encrypts the data transferred between two wireless devices using an encryption key system. With WEP encryption the neighbouring user will be unable to interpret the data of first user. Another security feature is the unique MAC-48 bit address of the Wi-Fi card. Wi-Fi and the Bluetooth technology are competing with each other in the wireless world. Bluetooth is the king in the shortrange, whereas Wi-Fi excels in the large range. Bluetooth operates at about 720 kbps and Wi-Fi at 11 Mbps, which is a big speed difference. Bluetooth is very slow for video transfers. Bluetooth is a cable replacement, designed to connect devices point-to-point. Wi-Fi is designed to hook up the entire network. Bluetooth is more secure than Wi-Fi and has a lesser power requirement. Bluetooth and Wi-Fi share the same band of frequencies and can interfere, though nothing significant has been reported in this regard. In India, the cities of Bangalore and Mumbai have taken the lead in Wi-Fi hot spots. Tata Teleservices and the ISPs like Sify and Dishnet are building Wi-Fi hot spots. Barista, a national cafe chain will be soon Wi-Fi enabled. Similar developments are taking place at major airports, hotels and restaurants. The Wi-Fi browser will pay around Rs 100, for an hour’s access, in advance, in the form of a card with an ID number for access. The WLAN environment in India is not friendly. The number of Laptop and PDA users is very less. These are the potential customers for Wi-Fi hot spots. WLAN is not a truly mobile technology; it is just a wireless technology with limited range. Wi-Fi is an opportunity for cellular operators. Wi-Fi, Bluetooth and 3G are all competing for presence in wireless networking. There is significant overlapping amongst these technologies. The ultimate goal is the convergence of these to provide anything, anywhere, anytime results where the technology is transparent to the user. Wireless and mobile technologies shall encompass every aspect of our lives and ultimately lead to an always-on society. |
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Enforcing flyash utilisation A
notification issued by the Central Government some years ago is being enforced on the brick kilns in Punjab. This requires the use of flyash to the tune of 25% while making bricks. The kilns located within 100-km radius from a thermal plant fall under the category. The enforcement of the notification has led to a strike by all the brick kilns in Punjab and this has created a shortage of bricks. A recent order by the Haryana Government preventing the export of bricks from that State has further compounded the situation. The availability of bricks has not only become more scarce, but has also resulted in pushing up the price per thousand bricks to Rs 2500. Thus one brick now costs more than Rs 2.50 to a house builder. The situation has led to resentment in the public and many questions are being asked. In the write-up an attempt has been made to answer some of the most common questions. Q: What is the objective of this notification? A:
This is aimed at improving the flyash utilisation so that adverse impact on the environment is mitigated. Q: Are the thermal plants in Punjab ready to dispense the required dose of flyash to the brick kiln operators? A:
No. Unlike the Badarpur thermal plant in Delhi, where flyash is available free of cost in day form from a Central Bin located outside the security limits, Punjab’s thermal plants don’t have this facility as yet. Only pond-ash is available for supply to the brick-kilns. Q: Will the PSEB permit the trucks to collect the ash from the ash pond? A: No. The PSEB authorities do not favour the above mode as it will endanger the “safety” of the ash ponds. Some other arrangement will have to be made and this has not yet been made public as yet. Q: Is the ash-pond flyash suitable for use for mixing with soil available in Punjab for making the bricks? A:
No. Punjab Soils are ‘loamy’ i.e. sandy in nature, and contain clay content of around 14-15%, whereas the soils suitable for making bricks should contain at least 20% clay. The pond-ash carries excess sandy material and does not meet the requirements of lime-reactivity (not less than 30 kg/cm2). So bricks made with pond ash will lack adequate strength. In view of the situation as discussed above, the enforcement of the ordinance should be suspended till the thermal plants are in a position to dispense flyash as being done at Badarpur thermal plant. This will free the house builders in Punjab from the nexus in which they are caught at present. The question which will have to be answered is: will the conditions required be met? As the fly use through the mode contemplated is hardly 1% of the flyash being generated by the thermal plants, the postponement of use of the exhaust smoke belching trucks to fetch the flyash will help counter any adverse impact on environment likely on account of suspending the enforcement of the notification. |
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UNDERSTANDING THE UNIVERSE What are the benefits of using GSLV to launch satellites into geo-stationary orbit? Communication satellites are usually placed in a geo-stationary orbit. This is an orbit over the equator at a height such that the period of revolution of the satellite around the earth is exactly the same as the period of rotation of the earth - namely 24 hours. The advantage is that the satellite in such an orbit appears to be stationary with respect to any point on earth. The communication antennas on the ground can then be pointed in a fixed direction without worrying about the rotation of the earth. We already have several such satellites providing communication, including television broadcast and networking services. The demand for such services is continuously increasing. Therefore, we do need more satellite transponders in the orbit. We also need to replace the satellites that are close to the end of their lives. So far, we have depended on European or American launchers to raise our satellites into the geo-stationary transfer orbit. However, we are now beginning to use our own launch vehicle. Some of the rocket stages and associated technologies already developed for putting satellites in polar orbits around the earth (for remote sensing) were upgraded and modified for GSLV. A new rocket stage using liquid hydrogen and liquid oxygen was added, in addition to other additions and modifications in the launch systems developed for polar launches. The payload for this attempt was an experimental satellite. Given our track record in this area, it seems certain that we will soon have a full-fledged capability for launching our own geo-stationary satellites. The flexibility of space communication and observation systems is a remarkable boon for countries like India and we must keep enhancing our capabilities in this direction. What happens if a body moves at the speed of light? A “body” can do it only if it has zero mass. If you wanted to run at the speed of light, you will have two choices. You could disappear into nothing - or something like a “thought”, with zero mass. Or you could be arrested trying to steal all the energy supply of the world or more. Can anything travel faster than the speed of light? I do not know of any “thing” that has mass or energy that can travel faster than the speed of light in vacuum. You can make equations in which particles of imaginary mass might travel faster than the speed of light. I do not know of any such particles. Yes, there is something that can move at any speed, and that is human imagination, but remember: that is not a “thing”. It has no mass, energy or momentum. |
WI-Fi, a short form of Wireless Fidelity, is an emerging development in wireless networking. It is a commercial name given to IEEE 802.11b communications standard for WLAN. A wireless network connecting two or more computers over a short distance of 50 to 600 feet constitutes a wireless LAN (WLAN).