Wiring Up The Wireless Way

When the Airports Authority of India (AAI) decided to network its cargo handling facilities at the Indira Gandhi International Airport, it had to find a way out of a problem: How to connect the cargo terminal where all the consignments are sorted and despatched and the cargo disposal unit where the unclaimed cargo is sent to be auctioned away. This had to be done without having to lay cables across the roads that separated the two buildings. Also, in the 1.5 kms space between the two, several buildings were expected to come up over the next few years.

We finally found a solution in radio waves, says B.K. Mehrotra, closely involved with the project. We are now installing a wireless local area network (or wireless LAN in short) linking the two units, he adds. Using radio equipment worth nearly Rs. 18.5 lakhs from Proxim and Digital Transmission Systems (DTS) of the US, AAI will transmit data on the movement of cargo within seconds which is vital to keep an exact tally of the unclaimed packages and those that reach the disposal yard. In all, AAI is spending nearly Rs. 4 crore in software and hardware of different kinds for its wireless network.

 

In the case of the government sponsored software technology parks (STPs) scheme, which is used by software exporters across the country, wireless networks are almost a lifeline for some of the countrys largest software companies including Tata Consultancy Services, Hughes Software Systems, Wipro, Pentafour and HCL-HP. These companies have several development centres scattered around the STPs in Bangalore, Hyderabad, Noida and a dozen other places.

Most of these software companies distribute their work so that two development centres are working on the same project and it is vital for the two to be connected all the time, says Aseem Batla, product manager for Cylink, one of the largest vendors of Wireless LAN and MAN (metropolitan area network) equipment. Cylink has provided nearly 100 such links to various STPs in the country, each link worth between Rs. 5 to 7 lakhs. The videsh sanchar nigam Ltd.. (VSNL) itself has invested nearly Rs. 15 crores over the last two and a half years to install nearly 300 such wireless links to extend 64 kilo bits per second (kbps) international leased links within the country.

Most companies who need to use such communications links have three options : They can use a leased telephone line, a very small aperture terminal (VSAT) or they can use a wireless radio link. Leased telephone lines are the least reliable of the lot. A single connection within a city costs upto a lakh of rupees every year and is prone to frequent breakdowns.

VSATs and wireless cost almost the same. But while VSATs have a recurring charge every year on the volume of data transferred which can easily add upto Rs. 2 to 3 lakhs wireless has only a small royalty to be paid for use of the spectrum to the government. And this is why companies are increasingly turning to wireless to connect their operations within distances of upto 50 kilometres. The Kirloskar group, for example, has connected its factories in Pune to its marketing offices over radio links. IT uses the Airlink product from Cylink to connect to LANs at the two sites. Reliance, the Rs.. 9,000 crore conglomerate, connects its Surat marketing office to its Hazira petrochemical plant located nearly 30 kms

away over 8 wireless links which have a total bandwidth of nearly 512 Kbps, good enough for live video transmissions.

Wireless networks are a booming industry growing at over 50 per cent every year. The total industry size in 1996 for wireless networking products was about Rs. 20 crores. Cylink, the largest player, claims to have notched up nearly Rs. 16 crores of this. It has sold nearly 600 links to some 250 organisations in the country over the last three years. Other players include Proxim and DTS, both distributed by HCL-Comnet, whose products are widely deployed. HCL-Comnet is currently installing wireless networks for organisations like the Industrial Development Bank of India (IDBI), Bank of Punjab and STPI Hyderabad. Breezecom, RAD and AT&Ts (now NCR) WaveLan range of products are a few of the other more popular products available in the market. The wireless LAN industry is expected to notch

up a revenue of nearly Rs. 35-40 crores in 1997.

While wireless LANs, as the name implies, are used for local area networks, they are not LANs in the strictest sense of the term. Traditional LANs are generally those found within a building which link PCs to one another and also connect them to file servers, printers and other network equipment using cables or optical fibers as the transmission medium. Users communicate through the LAN, exchange electronic mail and access multi-user programs and shared databases.

To connect to the LAN, a user must plug a computer into a wall or floor LAN outlet. These physical connections create an environment of stationary workstations. Moving from one location to another necessitates disconnection from the LAN and reconnection at a new site. It is also difficult to expand the LAN which will mean additional cabling and can add a lot to overheads.

Wireless LANs are an alternative. They allow workstations to communicate and access the network using radio propagation as the transmission medium. The wireless LANs can either be connected to an existing wired LAN as an extension, or can form the basis of a new network. And though they are adaptable to both indoor and outdoor environments, wireless LANs are especially suited to indoor locations such as office buildings, manufacturing floors, hospitals and universities.

In the Indian context though, it is the outdoor environment that has fueled a boom in the wireless LAN industry. For one, it is still cheaper to build an in-house network using cables. A typical 10 node LAN can cost between Rs. 60,000 to 80,000 to build. A wireless PC card costs about $ 700 , after duties. So putting together a wireless LAN for 10 nodes can cost $ 7000 (or roughly Rs. 2.5 to 3 lakhs). However, over larger distances, it is another story. For one, there is a lack of cabled networks in the remote areas with enough bandwidth. The maximum leased line bandwidth that the Department of Telecommunications (DoT) can give is 64kbps, and this is not sufficient in many cases, says Batla. ISDN, which offers bandwidths of upto 128 Kbps is not available in interior regions where most factories and industrial locations are located.

Wireless, on the other hand is not just easy to install but gives large bandwidths. The DTS Skyplex I range of products, for example, have a reach of nearly 100 kms, and support bandwidths ranging from 64 k to 2.048 Mbps (E1 capacity). The basic building block of the wireless LAN is the cell. This is the area in which the wireless communication takes place. The coverage area of a cell depends upon the strength of the propagated radio signal and the type and construction of walls, partitions and other physical characteristics of the indoor environment.

In general, a cell can cover a more-or-less circular area. PC-based workstations, notebook and pen-based computers can move around freely in the cell. All radio communication in the cell is coordinated by a traffic management function. The wireless LANs can be connected to the wired LAN directly.

The access point connects to the backbone of a wired Ethernet LAN via a simple cable. The access point functions as a bridge between the cell and the wired LAN. PCs and other nodes in that cell and other linked cells can

now access all the wired LAN facilities.

Once connected to a wired LAN the network management functions of the wired and

the wireless LANs can also be integrated.

Wireless LANs, however, are not a standalone solution in many cases. At the Delhi stock exchange (DSE) for example, the on-line trading activity for nearly 100 brokers will be conducted over Wireless LANS from August. These brokers, located within a 20 to 25 km range from the stock exchange will be connected to the central DSE server using Cylinks Airlan radio equipment. At the same time, DSE is also using VSATs to connect its far flung members in Chandigarh, Lucknow and other towns in other states.

Gajendra Upadhyay

VSATs mean huge recurring expenses, while wireless LANs require only a small royalty to be paid for use of the spectrum to the government.

What can you do with wireless LANs?

Wireless connection of PC workstations to host computers and/or servers (not widely used in India yet).

Wireless connection of point of sale terminals to host computers (some cases).

Temporary LANs, for field projects and emergencies (used in India).

Hard-to-wire-LANs in. buildings with asbestos materials or in a factory environment (used in India).

Wireless routing between Novell servers (IP/IPX) and between Windows NT servers. (IP) (beginning to be used in India as more Windows NT servers are deployed in the market).

Wireless connection to an Internet Service Provider (beginning to be used in India).

Linking remote LANs to the corporate LAN bypassing commercial telecommunications providers networks (most widely used service in India as an option to leased lines).

Wireless LAN Product list:

Cylink Airlink and AirLink Pro

AT&T Wireless products: WavePOINT & WaveLAN

Proxim RangeLINK group of products

Solectek Wireless products: Solectek AIRLAN

DTS Skyplex I and II