Hey dear friends, How are you and you is your practice?? Hope, You are doing well by the grace of Almighty Allah. Alhamdulilah, I have been Well too.
Well, you have already known about my writing topics. Yesterday, I got an email that my final exam will start from next month. But I didn’t read anything. I can assume that from the following month, I will be under immense pressure if Allah keeps me alive. But I am not afraid but feeling little bit pressure because I am a lazy girl. Don’t think, I will leave my writing practice. As usual, I will bother you with my daily writing activities .
One hour ago, I felt so boring to use just facebook. I told my brother ” Keep my phone and don’t allow me to touch my phone within one hour ”
Then I tried to read my subject by following eye reading method which I am going to share with you. Let’s begin……
Bandwidth :
Ooh, this is the most common word to all. Bandwidth means data throughput capacity of any communication channels where channel are two types as analog and digital. If you have high bandwidth, you will get more information through the channel at a time. For better understanding, you can imagine a pipe as communication channel. The bigger the pipe, the more water will flow through it at a faster rate.
In a common sense, Bandwidth describes the information carrying capacity of a given transmission medium . It can be measured how much informed are transmitted in a given time period .
If you think it technically, then bandwidth is a width or the range of frequencies. In the field of telecommunication, bandwidth is the width of the band of frequencies ” one simply subtracts the lower limit (3 Db point) of the frequencies used from the upper limit of the frequencies. It is commonly measured in cycles per second or hertz(Hz).
Analog Signal and Analog Bandwidth :
Generally analog signals means which are associated with voice, music or vision but they are represented by a Sine wave. Analog signals are not only vary in amplitude but also in frequency .
Now if you want to know Analog bandwidth which can be calculated easily by finding difference between the minimum and maximum amplitude or frequencies on the particular communication channel. Ok, let’s have an example. For telephone voice grade channel, Bandwidth is normally about 4000Hz but the voice channel frequency range is from 300 to 34Hz. Then try to calculate bandwidth by subtracting maximum from minimum which is 3100 Hz. What you are confusing, because you know total band is 4000hz but we got only 3100 hz. Ok, these additional space are acted as guard to prevent signal overlap with adjacent channel.
Digital Signal and Digital Bandwidth :
Hey friends, I am sure , you know about digital signal. Absolutely that signal are in computing environment are digital. This signal can be discontinuous or discrete which are transmitted in small separate units called bits. Digital channel capacity are measured in either bit per second or signal changes per second which is also known Baud rate. This is a little difference between baud rate and but rate like Baud rate measures the actual number if signal changes that occur per second where bit rate means the number of bits actually transmitted per second .
Digital bandwidth means a time acquired of how much information can be carried in a given time period over a wired or wireless communication link.
Channel Capacity :
In the field of engineering and information theory, Channel capacity is the tight upper bound on the rate at which the information can be reliably transmitted over a communication channel.
Spectral Efficiency :
Spectral efficiency, Spectrum efficiency or bandwidth efficiency refers to the information rate that can be transmitted over a given bandwidth in a specific communication system . It is a measure of how efficiently a limited frequency spectrum is utilized by the physical layer Protocol and sometimes channel access Protocol.
Broadband Communication :
For the demanding of high speed data for financial and other business activities, software download, video conferencing and distance education, Broadband is a well known term to all. Basically this term is used to refer to hardware and media that xan support a wide bandwidth. Broadband can be classified as Coaxial cable and microwave transmission where they are using 500 Megahertz for cable television and 10,000 Hz respectively.
Upload Versus Download Bandwidth:
Please just have a look on the top side of your phone about data connection signal. You will see two up and down sign besides your sim network sign. Or if you uae moden then go to yhe software front oage where you will see the amount of uplaod and download data.
For upstream transmission, it will occur when you will send request to the Internet Service Provider (ISP) and when you will receive information frim ISP, the downstream transmission occurs. Downlaod takes more data than upload like if upload needs one Mbos then Download needs Ten Mbps.
Spread Spectrum Modulation :
Thia technique is used before sending a signal to provide a secure communication by preventing interference whether it is intentional or unintentional. An intruder or third party cannot access this signal. Especially the techniques are used for military purpose . Some of example of this techniques are
Pseudo-Noise Sequence : A coded sequence is nade with 1s and 0 s with auto – correlation properties. It is a maximum -length sequence which is a type if cyclic code.
Narrow band and Spread spectrum signals :
For narrow band signal the following features should be have
– Band of signals occupy a narrow range of frequencies
– Power density is high
— Spectral of Energy is low and concentrated
To describe, spread spectrum signal, they have the opposite features will have like
— Band if Signals occupy a wide range of Frequencies
— Power density is very low
— Energy level is wide spread
With these features, The spread spectrum signals are highly resistant to interference or jamming.
FHSS and DSSS :
Spread spectrum multiple access techniques uses signals which have a transmissions bandwidth of a magnitude greater than the minimum required RF bandwidth.
They can be classified as
– Frequency Hopped Spread Spectrum (FHSS)
— Direct Sequence Spread Spectrum (DSSS)
FHSS : In this technical, the users can change their frequency from one to another in a specific time interval. For example, if user 1 one hold a frequency on a particular period. Then user 1 hops to another frequency and user 2 will use the frequency which one user1 already used. The same frequency are using technique with users is called frequency reuse and the amount of time how much one user spending one hop is called Dwell time.
DSSS:
in this technique, the user data are multiplied by a secret code to transmitter while the receiver will use the same secret code to recover the original message .
That’s All, I have read today..
I don’t know, you will be benefited or not but I wrote it as my daily task as well as to understand myself.
Thank you..
Allah Hafez.