| by Kenneth Chase | 52 comments

2.1 – TDD vs FDD in 4G LTE

How do we listen and speak at the same time
over a communication channel? How does a Telecom Operator decide which Duplexing
method to use? Will the device that you use in China work
in other parts of the world? Hi everyone, welcome back to world of Long
term evolution(LTE) 4th Generation of communication system. Today we will be discussing about Duplexing. Duplexing is the process of achieving two
way communication over a communication channel. It can be a half duplex or a full duplex. Half duplex. It is stands for one way communication at
a time, which means other party has to listen when you are talking, and you have to listen
when other party is talking. So friends, Do u have any device in your mind
that uses Half Duplex communication ??? …… How about a Walkie-Talkie device, having a
Push-To-Talk feature?? Now, let us look at second mode of communication, Full Duplex. It is stands for simultaneous communication
between two parties, which means both parties can interact freely. Now let us see how it is implemented in LTE
(Long Term Evolution) FDD:
Frequency-division duplexing (FDD) is a method for establishing a full-duplex communications
link that uses two different radio carrier frequencies for transmitting UPLINK and receiving
DOWNLINK. Both the channels are separated by a defined
offset frequency, which is also known “Guard Band” The main purpose of selecting a guard band
to stop the interference between uplink channel and downlink channel. Now moving forward to TDD:
Time division duplex is a technique by which the Uplink and the Downlink transmissions
are carried over the same frequency by using synchronized time intervals, For example, A TDD communication path has
been setup between Krishna and Base station. Krishna can alternatively transmit and receive
over time. Krishna using timeslot 1 to Transmit, Slot
2 to receive, Slot 3 to Transmit and so on…. exact opposite with Base station. As the transmission periods are relatively
short no time delay is noticed on voice transmissions. In between time slots, there are certain “Guard
Periods”, so that signals travelling from Base station can arrive at Krishna ,before
the Krishna starts transmitting. Let us see what are the factors that helps
an operator to decide whether to use FDD or TDD before rolling out a full fledged. Low Latency :- FDD offers very low latency, since transmit
and receive functions operate simultaneously and continuously, whereas in TDD switch from
transmit to receive incurs a delay that causes traditional TDD systems to have greater inherent
latency. EQUIPMENT COSTS :- No diplexer is needed to isolate the transmitter
and receiver in TDD, whereas in FDD Diplexer is needed. This is a key aspect, As cost of the User
Equipment is of major importance because of the vast numbers that are produced, TDD has
the advantage here. DISTANCE PREFERABILITY :- As the distance increases the Guard Period
also increases in TDD because the point to point signal propagation time increases .The
increased Guard period significantly affects the efficiency. Whereas FDD Does not have a problem with small
or large distances. UNBALANCED TRAFFIC :- In Real life Network Volume consumed in Downlink
is much higher than in Uplink. In TDD it is possible to Dynamically adjust
the capacity by utilising more time slots for Downlink than in uplink. Where as in FDD, the capacity is normally
balanced in both direction. SPECTRAL EFFICIENCY :- TDD uses only one frequency, whereas FDD uses
two different frequencies. So Spectral Efficiency in FDD is not as good
as TDD. MAC Layer Complexity :- MAC layer in TDD system is complex compared
to FDD system, as it has to deal with accurate time synchronization between the systems,
whereas in FDD there is no uplink and Downlink switching mechanism at timescale. Ultimately it depends on the network operator
to choose as per requirement, convenience or feasibility. As far as LTE is concerned, It is defined
to support both the paired spectrum for Frequency Division Duplex and unpaired spectrum for
Time Division Duplex. There is same 3gpp specifications for both
duplexing method (3GPP 36.847) While the majority of the global LTE market
is based on FDD Technology, TDD is expected to see increased adoption in the US, China,
Australia, Middle East, Northern and Eastern Europe, and Southwest Asia to gain a more
pronounced position in the global LTE market. Keeping an eye on the future market,Modern
Devices are being manufactured with support for both Time Division Duplexing and Frequency
Division Duplexing. So, Next time when you buy smartphone, Check,
which technique is used by your service provider and check the frequency bands supported by
your smartphone In the next video we will talk about shared
medium technique which is Multiple Access. So friends, Don’t forget to subscribe to our
channel, like our videos and comments your views, or suggestions. Thanks for watching.


Aditya Varshney

Sep 9, 2016, 12:33 pm Reply

Guys, your channel is one of a kind. You make it look very easy. Thanks

Chinthaka Ekanayake

Oct 10, 2016, 6:42 pm Reply

Nice video. What is the software used to make the video?

PowerFirst Power

Oct 10, 2016, 10:08 am Reply

Everthing from the voice to the images with this video is amazing. WELL DONEEEEEE


Oct 10, 2016, 9:46 am Reply

This is amazing work. Keep it up guys. I would love to watch more videos based on LTE and 5G or anything new going on in Communications. This channel will be very unique in no time and will be noticed.

Amrit Pal Singh

Oct 10, 2016, 2:20 am Reply



Oct 10, 2016, 12:17 pm Reply

absolutly awesome .. πŸ™‚

Dushyant Arya

Nov 11, 2016, 6:28 pm Reply


Praful Dalvi

Nov 11, 2016, 1:28 pm Reply

Please make more videos on VoLTE.

Hassan Ali

Nov 11, 2016, 6:54 am Reply

Nice vedio , helped me alot to understand the concept.


Dec 12, 2016, 7:23 am Reply

Thank You for the video,
It helps me a lot !
again Thank you and God Bless you.

Christos Vrettos

Dec 12, 2016, 5:48 pm Reply

Great work! Really high quality material. Thank you for assisting me to understand the base concepts of these techniques!


Jan 1, 2017, 8:51 am Reply

Awesome videos.. learned more from it than any other video πŸ™‚ .. please keep uploading.


Jan 1, 2017, 11:44 pm Reply

What a great material, keep the awesome work. Congrats.

David Moscoso

Jan 1, 2017, 12:09 am Reply

Great material, very complete.

Ranjeet Badhe

Jan 1, 2017, 5:59 am Reply

Excellent Video. Thanks for posting.

Rubia Sabri

Jan 1, 2017, 5:18 pm Reply

Thank you for this.(and all other videos) πŸ™‚

Abhilasha Bhatt

Feb 2, 2017, 8:17 pm Reply

Thanks alot!

Sanjaya Gangatkar

Feb 2, 2017, 10:01 am Reply

Thank You, good way to learn LTE concepts.

francisco gerardo hernandez rivera

Mar 3, 2017, 7:10 pm Reply

Impressive material. Makes reading the books much easier.

Pravin kumar Rai

Mar 3, 2017, 6:26 pm Reply

great effort.

Shah Rukh

Mar 3, 2017, 7:31 am Reply

made my day !!!<.,.
thanx alot

Shine G Sukumaran

Mar 3, 2017, 10:37 am Reply

This is fantastic!!!! please keep uploading…!

Behzad Zahid

Mar 3, 2017, 7:25 am Reply

Superb !!!


Mar 3, 2017, 9:18 am Reply

like that u also answer all the comments <3 keep it up if u got time
also u can give some ns3 examples with simulation and use the code to help us πŸ˜€ ty

Nkemayim t

Apr 4, 2017, 1:52 pm Reply

Thank you for this great and explicit demonstration.

Sajid Bashir

Apr 4, 2017, 8:05 pm Reply

plz keep it a bit simple and slow,its too fast to understand

karem badreddine

May 5, 2017, 2:08 pm Reply

excellent cours,, the translater work very well with this video ,#sound

yuvraj patil

May 5, 2017, 4:52 am Reply

guys are from mumbai ? if yes please share your address details …
i would lilke to meet

Juju-Lips Talia

Jun 6, 2017, 3:26 am Reply

This is fantastic. I remember looking for a video like this a few years to explain fundamental characters between FDD and TDD and there were none available. This is perfect. I like how you have also painted a commercial lens as this helps to understand business decisions. Very well rounded presentation for such a short clip.

Michel Santiago

Aug 8, 2017, 2:06 pm Reply

very good!

Mohammed Al-Haddad

Aug 8, 2017, 7:12 pm Reply

Thanks for the good presentation.

miron abdullah

Oct 10, 2017, 6:43 pm Reply

fuck robotic too fast


Oct 10, 2017, 5:25 pm Reply

Strangely educational.

sujoy saha

Nov 11, 2017, 7:23 am Reply

HI!! Can anybody explain why we can not communicate both ways for Half Duplexing method?


Nov 11, 2017, 11:23 am Reply

the voice and music on this thing is grossly annoying especially listening with a headset

Ann Ayson

Nov 11, 2017, 1:08 pm Reply

Very useful material!

Mohammed Kadhum

Nov 11, 2017, 6:49 pm Reply

Great work! Really high-quality material

Jyoti Vohra

Dec 12, 2017, 5:12 am Reply

Good material presented in a extraordinary way. Was able to learn in a much better way. Thanks for your efforts and keep up the great work.

Bindupriya Karedla

Dec 12, 2017, 1:38 am Reply

tq very much


Dec 12, 2017, 1:49 pm Reply

Very helpful, and well presented in layman terms.

aL Quarter

Feb 2, 2018, 8:07 am Reply

i fucking hate this robot voice

Alternate Personality

Feb 2, 2018, 9:43 pm Reply

Please change into human voice


Mar 3, 2018, 9:25 am Reply

As many of our subscribers were complaining about the Text-To-Speech converter that we used, we uploaded a new version of the same video with human voice.
Here is the link to it.
Happy Learning.

Horizon Brave

Jun 6, 2018, 11:55 pm Reply

So I'm not getting the difference between tdma..and tdd or fdma vs fdd

Aiman Jaouni

Jun 6, 2018, 6:33 pm Reply

fdd is better

Ba Toan

Jul 7, 2018, 8:24 am Reply

Thanks you alot !


Aug 8, 2018, 6:51 am Reply



Oct 10, 2018, 11:53 am Reply

krishna ? what in the new world order is this video about. annoying music

joseph fabro

Dec 12, 2018, 4:09 am Reply

Verry well said, ❀️❀️

Maor Ozana

Nov 11, 2019, 2:43 pm Reply

perfect video.

Somala Jaya Deepika

Jan 1, 2020, 12:54 pm Reply

Voice and the music is annoying…can u please change the voice.

Trong Hung Le

Feb 2, 2020, 8:24 am Reply

good informative video, but the abusive use of special effects kinda makes my eyes hurt

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