A wireless medium that doesn’t have any physical path in between is also meant to be an unguided transmission media, where the transmission doesn’t need to be guided.

This can also be called wireless transmission media. Generally, the waves get guided while transmission but that is not acceptable in this so there are several techniques or procedures to follow for transmitting them.

The dispersal of waves can be attainable through the vacuum or by the air and seawater.

Working of Unguided Transmission Media

The transmission is done between the destination and source. For making possible transmissions to unguided media, the electromagnetic spectrum is utilized.

Unguided tranmission media

The propagation of signals is done in several ways in wireless media through,

1)ground wave propagation

2)line of sight propagation

3)skywave propagation.

When coming to propagation through the ground, the transmission is possible even over a distance, and the signals which are propagated from the ground travels through an air vacuum.

Refering to the strength of signal, the distance will be covered. It means distance is dependable on the signal strength where the frequency of it is very low.

Propagation through a line of sight, where the antennas are interconnected with one another with extreme frequency. The signal is transmitted from point to point directly between them.

The propagation of waves is even possible through sky waves where the signals get transmitted to the upward direction that is into the ionosphere layer and returns to the ground. These types of propagations are having a higher frequency. And the frequency in this is measurable into two types.

one is the uplink frequency and another one is the downlink frequency.

The transmission of the signal from the ground to the ionosphere and the frequency that is used in it is uplink frequency.

The transmission of the signal that gets back after the uplink frequency that reaches the ground from the ionosphere is the downlink frequency.

Examples of Unguided Media

Radio wave

This type of wave will be making use of omnidirectional antennas that sends out the signals in all directions and provides the frequency of electromagnetic waves that are ranging between 3KHz and 1GHz.

Radio wave

Most of these waves are omnidirectional which means, the sending and receiving antennas do not have to be aligned. The sending antenna sends waves that can be received by any receiving antenna. When the antenna transmits radio waves, they are distributed in every single direction.

The omnidirectional characteristics of radio waves make them useful for multicasting in which there is only one sender but many receivers.

The examples of multicasting in the radio waves are television FM radios, paging and calls with cord less.

Advantages are,

the large wavelength in radio waves.

Bouncing back from the ionosphere.

We can generate the radio waves in a easy manner and can also traverse long distances. And also penetrates the building.

The disadvantages of these radio waves are they are not easily absorbed by the atmosphere.

2)Unguided media in the microwave:

These are unidirectional which means traverse is only in one direction.

The electromagnetic waves are having frequencies between 1 and 300 GHz are defined as microwaves.

The microwave transmits the waves and can only be focused narrowly.

This means the sending and receiving the signals from the antennas are needed to be aligned.

We can interfere the pair of antennes without interfering the other antennes in between. Unidirectional antennes are needed that send out signals in one direction.

There are two types of antennes in the microwave communication.

  • The parabolic dish
  • The horn

The dish antennas are parabolic structure. In this, the line parallel to parabola reflects at the curve at the angle search then all the lines can interconnected at one point focus.

This parabolic wave catches a wide range of waves and directing them to the common point.

In a horn antenna, the outgoing transmissions are deflected outwards in a series of the narrow parallel beam by a curved head.

And the received transmissions are collected by a scoop of the horn.

The characteristics of this are,

microwave propagation is the line of sight.

Repeaters are continuously needed for long-distance communication.

The data with the high frequency cannot penetrate the walls. These are the disadvantage characteristics in the inside buildings. The microwave band is relatively wide, almost 299GHz. Hence, the larger sub bands can be assigned with a high data rate.

The use of certain properties of the band requires permission from authorities.

Microwave unidirectional communities are need in the unicast communication from the sender to the receiver.

The main advantage of the microwave radio systems is,the performance of  broadcast  has a large quantities of data due of the high frequencies.

The Microwave repeators will also has the abilty to transfer the data to the longer distance .

The Microwave constructions are low , and cost effective compared to the  other data transmisions.The wireless technologies comes under the Microwave constructions.

There is no use of the physical and expensive equipment. Similar to the devices that has the signal strength during transmission of data.

All the rooftops, mountain hills, microwave transmission tower are inexpensive and has a accessible bases.

Disadvantages : The Micro wave radio systems do not pass through the solid objects.This can be a drawback in cities with a lot of tall buildings or mountain regions if we want to send signals from one end to another.

Microwave radio communication can also be degraded by heavy moisture in the atmosphere like rain and fog.

Infrared wave

The infrared waves have a frequency from 300GHz-400THz, wavelength from 1mm to 770mm that can be used for the short-range of communication.

This advantageous character prevents interference between one to another system, a short-range communication system in one room cannot be affected by another system in the next room.

When we use the infrared remote control, we do not interfere with the use of the remote. Additionally, one cannot use infrared waves outside the building because sun rays containing the infrared can interfere with the communication.

The infrared band of almost 400THz has the potential for data transmission. Usage of such wide bandwidth helps to transmit digital data with a very high data rate. IrDA is an association for the use of infrared waves that have established standards for utilizing these signals for communication among devices such as, keyboards and mouses.

The advantages of infrared waves are indeed in medical leading one to chronic health issues.

It is also used in most cameras for night vision.

The disadvantages are, these waves cannot be used for longer distances.

The performance is gradually dropped when the user range is increased. SO the transmitter and receiver need to be closely aligned to make possible communication within a sight of each other.

Types of wireless transmission media

The types are as follow,

1)Satellite microwave t

Types of wireless transmission media


2)Lightwave transmission

3)Infrared wave transmission

4)Radio wave Transmission

5)Terrestrial microwave transmission.

The data gets transmitted by utilizing the electro radio waves via free space is satellite communication. There are a lot of transponders in satellite communication which are called frequency bands where the transponders are a device that receives radio signals and produces a different type of signals.

In this also there are again two types of transmissions,

a)uplink frequency

b)downlink frequency

When we heard about geosynchronous satellites, the first thing to be noticed is these types of satellites are often used in satellite microwave transmission.

In this type of satellite, the speed of the earth’s rotation and the speed that is used for satellite rotation is the same. So, these are stationary to the earth’s surface.

This is extremely reliable and maintained with high transmission quality. The main objective of this satellite is to, accepting the signals from one of the earth’s stations after reading the signals it needs to transmit back again to another earth station.

Satellites can be divided into two types,

  • Ku-band
  • c-band

C-band is much more reliable than Ku-band, where a C-band satellite frequency is ranged from 3.7 GHz to 4.2 GHz and from 5.9 to 6.4 GHz.

When considering Ku-band satellite the frequency is ranging from 11 to 12 GHz.

The transmission acquired with the help of lasers is called lightwave transmission. Each system must have a photodetector and also must have its laser. This type of transmission is unidirectional.

It is easy to install and it is economically efficient by having higher bandwidth.

As this is a laser beam it cannot proceeds or reach, so this is the drawback.

The transmission which is having a wavelength longer than the visible light but the wavelength is shorter than the radio waves and also the waves which are considered as electromagnetic waves are known to be called infrared waves.

To attain infrared communication the transceivers are used that are only within the range of line of sight.

The frequency is ranging from 300 to 400 THz. As the infrared waves have an interface with the sunrays these waves cannot be used outside of a building.

For the short-range of communication, these types of transmissions are used So the interfaces get prevented between two systems.

Radio wave transmission is the other type of transmission that broadcasts the signals only in a single direction which is dissimilar with microwave transmission.

Where the microwave transmission is in both of the directions.

By using ground and sky waves the propagation of radio waves is possible. There is one advantage with the radio wave transmission that antennas are not required in it.

By utilizing the frequency that is lower than the range of visible light the modulations are done to the electromagnetic waves. And this was made possible by radio waves.

The last transmission is microwave transmission which makes use of microwave link for the transfer of data and signals. This was more suitable with the line of a sight transmission link.

To attain a line of sight, the antennas should be fixed firmly by only focussing on the narrow beam and these antennas are fixed at the highest point so that ignoring or avoiding the barriers the transmission can be made possible without obstructions. The terrestrial microwave uses largely higher antennas to cover the shorter distances.

Features of Unguided Media 

1)Have no guide or direction for transmission of signals or electromagnetic waves.

2)The data signals can flow freely

3)It does not bound to a specific or particular channel.

3)This can be distributed in the flow of the air.

4)Maintains Omnidirectional

5)Easy to install

6)Easy to maintain

7) No need to struggle with a bundle of wires and make them connected.

Guided media VS Unguided media

Guided Transmission Media

  • Guided media is a wired one that guides the signals.
  • There needs to be a physical path or a physical medium for signal transmission.
  • Another name for this transmission is wired communication or bounded transmission media.
  • The signal energy which is connected with wired is within the solid media.
  • An additional transmission level of capacity is produced by adding wires.
  • The wired media is used for point to point communication.
  • A certain direction is provided to signals for traveling.
  • The classification in guided media is, a)Fiber optics

b)Twisted pair

c)Coaxial cable.

Unguided Transmission Media

  • Sometimes the signals get propagated through seawater or by air.
  • This is alternatively named wireless communication or unbounded transmission media.
  • Here, the signal energy propagates in the form of unguided electromagnetic waves.
  • unguided media is used for radio broadcasting directions.
  • This doesn’t guide or provide the directions for the transmission of the signals.
  • In wireless media, it is not possible to enhance capacity.

Types in this kind of transmission are,

a)Radio wave

b)Infrared wave



e)terrestrial microwave.

Unguided Transmission Media Security

The wired networks are lacking in the flexibility and mobility of freedom so the wireless network will be covering the drawbacks of a wired network. This provides mobility and flexibility to travel all the way.

But the concerning issue is as it is an open network the users can enter into the network easily.

The users may be unauthorized users can be called intruders who hack the network. And the hackers are even able to decrypt the ciphertext. Certain securities are needed to be provided.

This wireless network is made possible with the help of unguided media only.

So some of the principles or methods that are defined for providing security to the wireless medium.

The security principle is like computer security where resources like, confidentiality, integrity, authentication, non-repudiation, availability, and access control are included.

These will be safeguarding the information.

The process of disclosing the information or preventing the disclosure of information to unauthorized individual or to the unauthorized systems is a confidentiality.

Where, these will be holding the confidential information that need to be secured too.

The confidentiality will be imposing a rule and specifies that there should be only one sender and the intended receiver for whom we sending information or data to.

Only these will be accessing and are able to access the control of the message.

Example for confidentiality is credit card where it holds confidential information and the otp that the user need not to be shared and kept securely.

If there is a loss of confidentiality then the type of attack is defined as interception.

Authentication is the basic word that defines the proof of one person identity. It ensures while transitting if the user is authenticated or not.

The authentication process ensures that the origin of an electronic message ior document is correctly identified or not.

If there is a loss of authentication then the user identity will be lost and the hacker will be acted as the orignal user and tries to grasp the data.

This type of attack isfabrication, which is absence of process of authentication.

Integrity, it means the data can’t be modified or change without any authentications.

This type of attack is active type of attack as the modifiactions can be observed.

For example, if there is any manual deletions or change in important files or fake data is entered.

So the attack in the integrity is called as modification in simple terms.

For example, consider if user A sends the message to user B to”transfer $100 to user XYZ” but when the modification is done the hacker(user C) will be modifying the data or message and sent it as “transfer $100 to user C”.

And the other side receiver will assumes the message is from user A and make a transfer so the user C facilitates.

If the user have a power to deny the transaction then this known as Non-repudiation. Where the receiver holds the proof of fake message and other user like user A can deny it was not send by him or her.

For example, proof of an ATM transaction.

Access control,This principle defines who should be able to do what and where the access control list is a subset of access control. The access control list is consists of whch user can get access with what type of resource.

There is a rule management, it is a user side about what can he/her do. And also a role management which defines which resources are accessible and under what cirumstances. It is a client side or resource side.

The user should be available will all the resources no one resource should be jammed to the authorized user. The principle states that resources need to be available all the time. For example,logins and logouts.

If there is a jamming of signals then the attack is known as interruption that the intruder is interrupting with the resources.

Summary of Unguided Media Transmission

Without usage of any media, physical path, a wire, or a cable the electromagnetic signals gets propagated or distributed by providing flexibility and mobility to users by providing longer distance communication with the low frequency signals.

Second Explanation of Unguided Transmission

Unguided Transmission Media: In any communication network, transmission media is important as it serves as a physical path between the sender and receiver. In a computer network, the transmission media could be divided broadly into two categories, they are Guided Transmission Media (GTM) and Unguided Transmission Media (UTM). To know more about the Unguided Transmission Media keep reading this article till the end you will get to know more about this.

In the case of GTM, the communication signals, which contain information, travel through the physical media to reach its destination.  On the other hand, in the case of UTM or wireless transmission media (WTM), the signals get broadcasted in all directions without any guiding physical medium, i.e. there is no physical link between the communicating devices.

Such wireless transmission can be done in air or even in a vacuum. They are not limited by the physical media hence they could be broadcasted over longer distances. The examples of UTM are cellular radio, a communications satellite, microwaves, etc.

There are four types of Unguided Transmission Media (UTM), they are

  • Microwave
  • Radio waves
  • Infrared waves
  • Light

These wireless signals once broadcasted are received by antennas. Then they are further processed to extract the information encoded in them.

Radio waves

The radio waves are the most commonly used wireless transmission media. They could even penetrate walls and other structures; hence they could be received easily at a lot of places. They can have frequencies as low as 3 Hertz to as high as 300 Giga-Hertz.

Their wavelength, similarly, could be as low as 1 mm to as high as 100000 km. depending upon the frequency radio waves could bounce back or travel through walls. High-frequency radio waves could be absorbed by rain or clouds or other obstacles.

The HF and VHF (Very high frequency) bands of radio waves could be refracted back to the earth’s surface by the ionosphere. This property makes such radio waves a useful medium to transmit over long distances on the surface of the earth, the surfaces which are not in direct sight or not directly available over the curvature of the earth.

Radio waves are Omni-directional, which means that such signals could propagate in all directions. It also means that in the case of radio waves the sending and receiving antennas may not be aligned towards each other but still, they can exchange signals. This also means that radio waves could be broadcast and any receiving antenna (tuned to the frequency of transmission) may pick up such signals.

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Basically, in the case of microwave communication, the sending and receiving antenna should be aligned towards each other in order to successfully transmit and receive. This means that microwaves are unidirectional, as the microwave beams have to be focused in a given direction.  The antennas also have to be in the line of sight to work effectively.

The microwave communication is of two types, Terrestrial and Satellite microwave. The frequency of the terrestrial microwave is from 4-6 Giga-Hertz to 21-23 Giga-Hertz. These are inexpensive for short distances and have a bandwidth in the range of 1 to 10 Mbps. For longer distances, taller and more powerful antennas are required; hence microwave transmission becomes an expensive proposition and has their physical limitations.

There are certain advantages of using microwaves. They are cheaper than cables, as there doesn’t arise a need to install cables the costs are low. Also, they could be set up for the ease of communications in terrains where it is difficult to lay cables.

There are certain disadvantages to using microwaves. Eavesdropping, in which any outsider can intercept the signal by using their antenna. Since the waves depend upon the line of sight for communication; they are susceptible to weather conditions prevalent between the antennas. For instance, a rainy or cloudy day can distort the signal.


This wireless technology is used to establish communication over very short ranges of distance (typically a few meters or tens of centimeters). The frequency is extremely high, in the range of 300 Giga-Hertz to 400 Terra-Hertz. Hence, it is only used for communication between devices that are in a very close range. For instance, it is used for data exchange between two mobile phones, operates the remote of a TV, etc.

The bandwidth of infrared is high, so the data transfer rate would be high. They cannot penetrate obstacles such as walls. These mediums, therefore, are less prone to external signal interference.


Light is the upper limit in the electromagnetic spectrum which can be used for data transmission. The communication is established using Laser beams. The beams must be in a straight line of sight. Laser beams are unidirectional, hence both ends need a laser and a photo-detector to detect the incoming laser from the other side.

The laser beams used for transmission are very thin, almost a millimeter wide. This makes laser beams difficult to tap. But the inherent disadvantages of using Laser beams is that they cannot penetrate walls, rain, dense fog, and could get distorted by variations in wind velocity and atmospheric temperature.

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