Wireless WANs

PCQ Bureau
New Update

Wire line technologies for WAN connectivity have evolved significantly and are continuing to do so for quick and efficient data transmission. However, there are conditions where wired data communication solutions cannot meet the requirements; don't make economic sense; offer less convenience; are difficult to set up (as in rural or hilly terrain) or are not present at all. For such conditions going wireless is the best solution. 


To create a private WAN covering several buildings or offices, located, say across the road or within a city, putting up wires is not feasible. Wireless data transmission technologies can do that job very easily. Other specific applications of wireless connectivity can be of a bank connecting its ATM centers wirelessly or an ISP providing wireless connectivity to its cyber cafes across the city or country. 

But just as there are various wire line technologies, there are various wireless technologies as well, each suited to a particular type of application and having its own set of advantages and disadvantages. Below we will look at the technical details, applications, benefits and limitations of various wireless technologies.

Outdoor Wireless LAN

Wi-Fi or 802.11 has become the de-facto technology for wireless LANs, but the same technology can be used for building wireless WANs as well. Technology-wise, wireless WAN equipment is just like wireless LAN equipment, but with bigger antennae, and higher transmitting power and receiving sensitivity. 


These devices can provide a wireless coverage in the range of 5-8 Km. This is suitable for building a campus area network or connecting buildings located across the road or any other obstruction. 

A laser-based WAN wireless access point (If you may) that works on line of sight

Wi-Fi devices are based on different versions of the IEEE 802.11 standard, namely 802.11b, 'g' and 'a'. 802.11b operates on the 2.4GHz frequency band and offers a theoretical maximum throughput of 11 Mbits/s. 802.11g and 802.11a provide a maximum throughput of 54 Mbits/s and operate on 2.4 GHz and 5 GHz band, respectively. A few device manufacturers also provide their proprietary extensions to the above standards to effectively double the data throughput rates. However, the actual data throughput experienced by the end user may decrease as the distance between him and the base equipment increases. Data throughput is also hampered by obstructions and the number of users connected to a single base device. Out of 'a', 'b' and 'g', the 802.11b has been most widely used, but 802.11g with its backward compatibility with 802.11b is fast becoming a

better option.


Microwave Radio

Microwave Radio can be used to provide fixed wireless connectivity and for wireless broadband internet services.

Microwave technologies are also called terrestrial wireless. Microwave is particularly suitable for providing Internet access to rural or tough terrain areas that are far out of reach of fixed lines. They are also appropriate for connecting offices, ATM networks or point of sale terminals within a city.

Microwave wireless systems work in the 900 MHz to 40 GHz frequency band. Higher frequencies carry far more data but cannot travel as far as lower frequencies, often requiring line of sight. Higher frequencies also require more complex equipment that can be more expensive. Lower frequencies on the other hand, travel further and are cheaper, but cannot transmit large amounts of data. The range varies from 2-3 kilometers to more than 50 kilometers depending on the frequency used, power of the signals and line of sight conditions. Microwave systems can be used in point-to-point (P-T-P) or point-to-multipoint (P-T-M) configurations. P-T-P can be used to connect two far off office locations and P-T-M is useful for connecting several offices or for providing wireless Internet services to subscribers.


Microwave wireless solutions are available as two types of distribution systems.


Multipoint microwave distribution system (MMDS) works in the frequency band of 2.1 GHz to 2.7 GHz and does not require straight line of sight. With MMDS, a transmitting tower must be placed at a high elevation and users must have a unidirectional dish that can be connected wirelessly to the tower or to repeaters that extend the range of the signal. MMDS is capable of providing data speeds of up to 10Mbits/s over a 48-56 Km radius.


Local multipoint distribution system (LMDS) uses the spectrum above 20 GHz and require line of sight between communicating devices. Due to higher frequency and the limitation of line of sight requirement, LMDS offers lesser range - up to 8 Km - than




Very Small Aperture Terminal (VSAT) uses satellite to provide network connectivity and is the only technology which can cover almost 100 percent of the world. VSAT equipment includes a satellite ground station device and an antenna dish smaller than 3 meters in size. Like Microwave, VSAT is also suitable for rural areas (even the remotest of them), ATMs, point of sale and credit card applications. 

A microwave radio network consisting of a base tower and end users

However, while it offers ubiquitous coverage, VSAT suffers from latency problems, which make it not very suitable for real time voice and video applications. Other limitations are less bandwidth, poor signal quality and security considerations. Nonetheless, VSAT, with fewer points of failure, provides a good solution for disaster recovery centers.


Microwave radio-based dish and delivering equipment


Free Space Optics (FSO) uses laser technology to provide wireless data communication between two points. The equipment includes laser device that can quickly turn on and off, signaling to a receiver at the other end. FSO requires line-of-sight between the communicating devices. FSO throughputs start from 100 Mbps and go up to Gigabit capacities and can cover distances of few kilometers. The benefits of FSO include quick setup, inexpensive operation and it doesn't require the radio spectrum like other wireless technologies. But, since lasers send data through the atmosphere, they are easily affected by atmospheric disturbances like humidity, fog and electrical activity (storms). Another problem is scintillation caused by heated air, which can cause disruption to the signal. Other disturbances could be temporary interruptions due to moving objects, such as flying birds, etc.



Asynchronous Transfer Mode or ATM is designed for the specific needs of users or network providers who want guaranteed real time transfer of voice, data and images. 

ATM is a switching and multiplexing technology that ensures minimum transmission delay and guarantees ban\dwidth. The ATM network consists of a set of switches interconnected point to point links/interfaces. The idea behind ATM is to fragment the data into smaller fixed-sized data units (53 bytes each) called cells and then send them out using cell switching.

ATM switches incorporate a self routing technique for all cell relay functions. Each cell carries the routing information in the cell header and thus can find its own way through the network. Each cell is independent of the user information, which instead is transmitted through another pre-established path between two ATM network end points (a network end point is where a connection is either initiated or terminated). 

ATM technology has been chosen as the transport mechanism for Broadband ISDN (B-ISDN). B-ISDN is used for those services that require channel speeds higher than 2 Mbps.

The advantage of ATM technology is that is can offer a wide range of traffic rates ranging from 1.5 Mbps to 2.4 Gbps. It also supports multiplexing of multiple data types which include voice, data and video; thereby integrating various network services. For the users the benefits of ATM technology are higher transmission speed and protection against network congestion. 

Dial Up

Dial up is not exactly WAN class but can be used for remote offices with low data

transfers. Dial up refers to connecting a 

device via a modem and the public telephone network. 

Dial-up access is just like phone connection, except that the parties at the two ends are computer devices rather than people.

Because this kind of access uses normal telephone lines, the quality of the connection is not always good and data rates 

are limited. 

Earlier the maximum data rate with dial-up access was 56 Kbps, but new technologies such as ISDN are providing faster rates. Now even Reliance has come up with a dial up connection whose speed can go up to 153 Kbps. 

In dial-up access the client uses a regular computer modem to dial the ISP (Internet

Service Provider) node, to establish a modem-to-modem link, which is then routed to the


There are many other technologies such as ISDN, ATM etc which provide much faster connectivity as compared to Dial-up. 

Thus it is not a very popular connectivity option any longer for organizations or business houses which have a need to stay online for a large part of the day and have to send or receive huge amounts of data . 

Still dial-up connections are being used mainly by SOHO users and individuals, who need to connect a couple of times a day for a few hours for minimalist applications like sending and receiving emails or using a reference website.