Impact of channel in wireless communication

BY:Manish Srivastava

What is wireless telecommunication?

In simple language Wireless telecommunications is the transfer of information between two or more points that are not physically connected.

Here distances can be short, such as a few metres for television remote control, or as far as thousands or even millions of kilometres for deep-space radio communications.

Wireless operations permit services, such as long range communications, that are impossible or impractical to implement with the use of wires.It use some form of energy (e.g. radio frequency (RF),acoustic energy, etc.) to transfer information without the use of wires.

J C BOSE IN ROYAL INSTITUTION, LONDON WITH HIS TRANS-

RECEIVER

DIAGRAM OF MICROWAVE RECEIVER AND TRANSMITTER APPARATUS, FROM BOSE'S 1897 PAPER.

CHANNELS

A communication channel, or channel, refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel.

A channel is used to convey an information signal, for example a digital bit stream, from one or several senders (or transmitters) to one or several receivers.

BASIC BLOCK DIAGRAM OF COMMUNICATION SYSTEM

A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second

Bandwidth is limited resources used by different organization due to which wide spread use of wireless network are limited.

The wireless channel (transmission medium) is susceptible to a variety of transmission impediments such as path loss, interference, and blockage.

These factors restrict the range, data rate, and the reliability of the wireless transmission.

The extent to which these factors affect the transmission depends upon the environmental conditions and the mobility of the transmitter and receiver.

VARIATION OF CHANNEL STRENGTH IN WIRELESS COMMUNICATION

One of major characteristic in wireless channel communication is FADING.

In wireless communications, fading is deviation of the attenuation affecting a signal over certain propagation media.

It is of two types: (a) large scale fading, (b) small scale fading.

Fig: Frequency-selective time-varying fading causes a cloudy pattern to appear on a spectrogram. Time is shown on the horizontal axis, frequency on the vertical axis and signal strength as grey-scale intensity.

Large scale fading:

It occurs due to path loss of a signal as a function of distance.

It is shadowing by large objects such as buildings and hills.

Small scale fading:

It happens due to the constructive and destructive interference of the multiple signal paths between the transmitter and receiver.

MIMO technique for increasing spectral efficiency

Increased capacity is achieved by introducing additional spatial channels that are exploited by using space-time coding in this technology.

there are certain environmental factors that affect MIMO capacity. These factors include channel complexity external interference, and channel estimation error.

Adaptive channel width

Adaptation brings unique benefits. For instance, when the throughput required is low, moving to a narrower channel increases range and reduces power consumption.

But in fixed-width systems, these two quantities are always in conflict.

Leads to significant improvement to range and connectivity, low power-consumption, and capacity.

DISADVANTAGES

Limited spectrum available for communications.

In addition to security consideration interfering signals can be generated by other devices in, for example printers and other electromechanical devices.

These devices can temporarily disrupt a communication link through the noise that they generate.

ADVANTAGES

Add in a communication device to the system or remove one from the system without any disruption to the remainder of the system.

It is a simple matter to relocate a communicating device, and no additional cost of rewiring is associated with such a move

CONCLUSION

In conclusion it can be said that although wireless network have several advantages but they also have their unique difficulties .

The need for high bandwidth communication is still relatively new with the rapid growth of the internet and the place of wireless network in it is yet to be determined .

The crucial point could very well be the standards that define the next mobile phone networks if they are universally accepted and given the necessary bandwidth for high speed communication wireless networks

THANK YOU…