Market Analysis of Pak's Cellular Mobile Phone Companies


Currently, six cellular mobile phone companies are operating in pakistan namely, InstaPhone, Paktel(Zong), Mobilink, Ufone, Al-Warid and Telenor. All the cellular mobile phone service providers work under the executive control of Pakistan Telecommunication Authority (PTA) through its Mobile Policy. It initiates new access code for each cellular service provider if it reaches the limit of 5 million subscribers. PTA keeps a visionary watch on the services of the cellular mobile phone service providers to ensure quality services and prevent those providing bad services to the subscribers. If any service provider is not up to the mark in terms of connectivity, voice quality etc…, it is charged for by heavy fine according to the rules and regulations. A brief description of each of these cellular mobile service providers is given below.
§ INSTAPHO is the first cellular service provider company which started its operations in Pakistan. It was established in 1990 and started its operations on September 1990.
Currently, InstaPhone is providing its services with CDMA Technology. From the inception, InstaPhone network had been using Analog Mobile Phone System (AMPS) Technology but, with the advancement in technology it converted its networks to D-MPS Technology which is also referred to as Time Division Multiple Access (TDMA) Technology.
§ PAKTEL:
Paktel is the second cellular service provider company in Pakistan. It was established in 1992 and started its operations in the end 1992. It was set up by cable & wireless and carried out AMPS services until 2004. Later on the company launched GSM services as well. Currently Paktel is providing its services with both Analog Mobile Phone System (AMPS) and Global System for Mobile Communication (GSM) based technologies.It has no GPRS and MMS services.
§ MOBILINK:
Mobilink is the third cellular service provider in Pakistan. It is the subsidiary of ORASCOM telecom. It was established in 1994 and started its operation in early 1994.Mobilink is the first GSM (Global System for Mobile communication) cellular based network of Pakistan. Prior to this, other companies namely InstaPhone and Paktel were using AMPS technology for mobile communication. GSM technology provides higher capacity for data transfer than AMPS technology, and is based on SIM technology. Mobilink, came into the market and became very popular among the users because it was the first SIM based GSM network.
§ Ufone-PTML:
Ufone-PTML (Pakistan Telecom Mobile Limited) is the fourth cellular service provider in Pakistan. Ufone network was established in January 2001.Ufone network also uses state of the art SIM based GSM technologY.
§ AL-WARID:
Warid Telecom is the fifth cellular service provider in Pakistan.Al-Warid network uses state of the art SIM based GSM technology.Warid telecom is providing services like GPRS for internet access, SMS, MMS, and International roaming with very competitive prices to its customers. Besides these, it is also providing free roaming throughout Pakistan, free SMS via internet and the newly introduced 30 second billing system for the first time in Pakistan.
§ TELENOR:
Telenor is the sixth cellular service provider in Pakistan. It was established in 1992 and started its operations in the end of 1992.It was the first cellular network that had introduced a new idea of easy load which is an excellent way of recharging......;)

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MXB7843 interfacing with Microcontroller - Block Diagram

MXB7843 TOUCH SCREEN INTERFACING BLOCK DIAGRAM
Before you read on further, read the working of 4 wire resistive touch screen. This post is for the newbies;  technicalities will be addressed later.

It is always better to use a dedicated controller for touch screens, instead of designing your own. The best option according to me is to use one of the product of MAXIM, MXB7843.

MXB7843 is controller dedicated for 4 wire resistive touch screens. It has a configurable ADC of 8/12 bit resolution. Overall pictorial representation says that to interface a 4 wire resistive touch screen, what you have to have a microcontroller apart from touch screen controller and a touch screen itself. Touch Screen is directly connected to the microcontroller. The microcontroller which is controlling all the affairs gets the coordinates of the touch screen, whenever it is interrupted, via SPI communication. SPI communication is used for high speed synchronous communication. Once the data is received in 8 or 12 bit format, you can play around as you desired.

The schematic of MXB7843 is given below:


More to follow! 

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8051 LCD interfacing Command Codes

Before you interface an LCD with any microcontroller , say 8051 or AVR, you should have a knowledge of basic LCD commands. These commands or codes are used to get the LCD perform some particular task, for example, clearing the LCD display screen ornshifting entire data to the right etc. I have gathered here some the commands that might prove for you an important data, because once I was doing 8051 LCD interfacing it really helped me a lot. Here are some of it :-
  1. 01H : Clear Display Screen
  2. 02H : Return Home
  3. 04H: Decrement Cursor
  4. 06H : Increment Cursor
  5. 05H : Shift Dis[;ay Right
  6. 07H : Shift Display Left
  7. 08H : Display off, Cursor off
  8. AH : Display off, Cursor on
  9. CH : Display on, Cursor off
  10. EH : Display on, Cursor Blinking
  11. FH : Display on, Cursor Blinkinf
  12. 10H: Shift Cursor position to left
  13. 14H: Shift Cursor position to right
  14. 18H: Shift the entire display to left
  15. 1CH: Shift the entire display to right
  16. 80H: Force cursor to begin from the Ist line
  17. C0H:Force cursor to begin from the 2nd line
  18. 38H: 2 lines and 5 x 7 matrix
More to folow for 8051 LCD interfacing

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Finding order of Butterworth IIR filter in Matlab GUI


Order of filter is very important as far as the characteristics of filter design is concerned. This particular GUI is for all Butterworth IIR filters. Order of butterworth filter is given by :
where Ap and As are passband and stopband attenuations in dB and wsp is the prototype stopband edge frequency of digital filter and wpp is the prototype passband edge frequency i-e cutoff of frequency of the digital filter to be designed.

You may calculate from the above formula but as far as designing of the problems for student is concerned, it may take a long time to take correct values out of the calculator. There you need an easy interface to get your work done. This assignment was given to us by our Professor, S K Hasnain who is the author of two books on Signals and Systems and Digital Signal Processing. Below you can download the M-File and Fig File. But if you dont have the basic idea about Graphical User Interface, see how to make a simple calculator in MATLAB GUI.


GUI looks like

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Basic Concept of FDM and TDM


Why do we need Multiplexing technique?
In communication, under the simplest conditions, a medium can carry only one signal at any moment in time.For multiple signals to share one medium, the medium must somehow be divided, giving each signal a portion of the total bandwidth. This is where the concept of Multiplexing comes!
Multiplexing means “sharing a medium”. It is a form of data transmission in which one communication channel carries several transmissions at the same time. In simple words, the method of dividing a single channel into many channels so that a number of independent signals may be transmitted on it is known as Multiplexing.



Multiplexing techniques can be divided into two basic categories:
Frequency Division Multiplexing-FDM
Time Division Multiplexing-TDM
Frequency Division Multiplexing-FDM
In FDM the available bandwidth is divided into a number of smaller independent logical channels with each channel having a small bandwidth. It assigns “frequency ranges” to each “user” or “signal” on a medium. Thus, all signals are transmitted at the same time, each using different frequencies.The method of using a number of carrier frequencies, each of which is modulated by an independent signal is in fact frequency division multiplexing.




Time Division Multiplexing-TDM
In TDM, sharing is accomplished by dividing available “transmission time” on a medium/channel among users.
Each user of the channel is allotted a small time interval during which he transmits a message. Total time available in the channel is divided, and each user is allocated a time slice. In TDM, users send message sequentially one after another. Each user can use the full channel bandwidth during the period he has control over the channel.













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Multiplexer



The term Multiplexing means "sharing of a resource/medium" .Resource could be time, frequency, space or any physical medium .Multiplexer is a communication device that multiplexes (combines) several signals for transmission over a single medium.
It helps different sources of data to use a single medium for transmitting their data.Basically the aim is to share an expensive resource

In more simple words, Multiplexer also called as Mux is a device that selects one of several analog or digital input signals and forwards the selected input into a single line.A multiplexer of 2^n inputs has n select lines, which are used to select which input line to send to the output.

A device that performs the reverse process is called a Demultiplexer (DEMUX).

Follow this tutorial for more understanding of Multiplexer

The Operation of a Multiplexer/Demultiplexer Circuit


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E-books

Follow the following simple steps to download a big collection of e-books, of every field!

1-Creat your account :
2-Login and search your required book
3-Click on "ifile.it" in the bottom
4-Click on "Request download ticket"
5-and last, click on "Download "

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Basics of Channel Coding

Environmental interference and physical defects in the communication medium can cause random bit errors during data transmission. Channel coding also known as Error coding is a method of detecting and correcting these errors to ensure that information is transferred from its source to its destination reliably.
The idea behind channel coding is, to make the data more secure and error free. Channel Coding is done to ensure that the signal transmitted is recovered with very low probability of error at the destination. You can think channel coding as a “Security guard” for data .
What happens If Channel coding is not used?
If data is transmitted without channel coding ,and an error occurs in data , the receiver will inform the transmitter that an error has occurred in data, therefore transmit it again.Transmitter will have to retransmit the whole data ! A question may arise in your mind that, incase of error, data will be retransmitted so, what’s the need of using channel coding?
The reason is, if transmitter retransmits the whole data definitely there will be wasteage of power,and delay in communication. Therefore to avoid these factors it is necessary to implement channel coding.
In channel coding extra bits are added along with actual data bits. These extra bits are termed as “Redundant bits” because they actually cause redundancy in data. They ensure minimal or no error.
Error coding uses mathematical formulas to encode data bits at the transmitter or source into longer bits for transmission. The "coded data " is then decoded at the destination to retrieve the information. These bits help the the destination or receiver to determine if the communication medium introduced errors, if yes correct them so that the data need not be retransmitted.
Error coding is used in satellite and deep space communications, network communications, cellular telephone networks, magnetic and optical data storage media, and almost any other form of digital data communication.

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What is Bit Error Rate ?

When data is transmitted to its destination over a communication channel there is a possibility of errors being introduced into the the data. In digital communication performance of the system is assessed by a term called as bit error rate, BER. BER is also known by the term Probability of Error.

In simple words, it is actually the ratio of number of bits in error to the total number of bits transmitted.
BER = Bits in Error/Total Number of Bit transmitted
For instance, If 10 bits were transmitted, and 5 bits get in error,then :
BER=5/10
=0.2
In BER curve if a value is mentioned, say 0.01, it means ,out of 100 transmitted bits, 1 bit got error [1/100=0.01]
Example:
Let's consider an example, assume a transmitted bit sequence:
0 1 1 0 0 0 1 0 1 1
and the following received bit sequence:
0 0 1 0 1 0 1 0 0 1,
The number of bit errors (the underlined bits) is in this case 3. The BER is 3 incorrect bits divided by 10 transmittedbits, resulting in a BER of 0.3 or 30%.


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M-PSK Modulation

Uptill now, we have discussed the basic concepts of digital modulation techniques.Let’s move one step ahead!
In digital modulation two commonly used terms are Symbols n Modulation order(M) Symbol:
It is actually a combination of bits.For instance, So and S1 are two symbols.Where ,So=00,S1=11 etc
Modulation order-M:
It refers to the number of states used in modulation,or the number of symbols.If M=2 it means two distinct states are being used in modulation. States could be different frequencies, amplitudes, or phase angles.If M is represented in power of ‘2’, that shows the number of bits per symbol.
For M=4
There will be 4 symbols(S0, S1, S2, S3).4=2^2.Therefore ,each symbol will be represented by Two bits.S0=00,S1=01,S2=10,S3=11
Keeping in view the ‘M’ factor, let’s restate the modulations techniques as:
M-PSK,M-FSK,M-ASK, and M-QAM
M-PSK:
For M=2: It is called as BPSK,(where B stands for Binary).Number of symbols are two. S0 and S1.As 2=2^1, so each symbol is represented by a single bit, therefore we wil have, S0=0 and S1=1
For M=4: It is called as 4-PSK.Number of symbols are Four.S0,S1,S2,and S3.As 4= 2^2,so each symbol is a combination of two bits,so we will have,S0=00,s1=01,s2=10,s4=11
So on and so forth for M=8,16,32,64
As PSK is phase modulation ,therefore the number of states actually refer to distinct Phase angles.These phase angles are used to modulate the carrier.

For M=2 , we have 2 phases/states
 Total angle is 360 degree
360/M =180 deg
So.’S0’ will b represented by 0 degree and ‘S1’ will be represented by 180(phase difference of 180 between symbols).That is, if 0 bit appears in signal, it will modulate the carrier wave with 0 degree, and 1 bit will modulate the carrier with 180 deg phase.
For M=4, we have 4 distinct phases
360/4 =90
So, Symbols will be represented as:
S0=0 deg,S1=90 deg,S2=135 deg,S3=180 deg
As we have the following symbols ,S0=00,s1=01,s2=10,s4=11.So, if 00 bits appear in signal, they will modulate the carrier wave with 0 degree,01 will modulate the carrier with 90 deg phase.10 will modulate the carrier with 135 deg n 11 will modulate it with 180 deg.
For M=8,we have 8 phases
360/8=45 deg
So,So=0deg,S1=45 deg,S2=90 deg,S3=135 deg,S4=180 deg,S5=225 deg,S6=270deg deg,S7=360 deg
Each symbol is represented by three bits here,
S0=000,S1=001,S2=010,S3=011,S4=100,S5=101,S6=110,S7=111
So, 000 bits will indicate 0 degree phase shift ,001 will represent 90 deg phase.010 will modulate the carrier with 135 deg ,0 11 will refer to 180 deg, n so on .
Similarly, for M-FSK, M frequencies are used to modulate a carrier and for M-ASK , M amplitude levels will be used.

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Introduction to FDM, OFDM, OFDMA

Frequency Division Multiplexing (FDM)

In FDM system, signals from multiple users/transmitters are transmitted simultaneously (at the same time slot) over multiple frequencies. That is each user is assigned a different frequency for communication. Each frequency range is called as sub-carrier, n it is modulated separately by different data stream, that is there are different sources of data (users/transmitters) for each subcarrier frequency. A spacing (guard band) is placed between sub-carriers to avoid signal overlap.


Orthogonal Frequency Division Multiplexing (OFDM)



Like FDM, OFDM also uses multiple sub-carriers but the sub-carriers are closely spaced to each other without causing interference, removing guard bands between adjacent sub-carriers. This is possible because the frequencies (sub-carriers) are orthogonal. In OFDM multiple subcarriers are modulated by single source of data. If I am a transmitter, n using OFDM technique, my data will be modulated by multiple subcarrier frequencies , instead of single carrier frequency ,as it happens in normal modulation .if I assume that 3 subcarriers are being used for modulation so, they will modulate the data of just one Transmitter ,unlike FDM where 3 frequencies will b used to modulate three different sources of data (three transmitters).
In an OFDM system, a very high rate data stream is divided into multiple parallel low rate data streams. Each smaller data stream is then mapped to individual data sub-carrier and modulated using some sorts of PSK or QAM modulation . let’s assume that I have a high rate data stream, X=[abcdefghi] ,
I divide it into three low rate data streams [p=abc, q=def, r=ghi ].Assume that there are three sub-carrier frequencies: f1,f2 n f3
Each low data rate stream will be modulated individually by each sub-carrier,that is data stream ‘p’ will be modulated by carrier f1, data stream ‘q’ by f2 n similarly data stream ‘r’ by f3 and finally all are combined.If it were FDM technique ,the data stream X would have been modulated by a single carrier frequency instead of multiple carriers.Therefor OFDM is called as multi-carrier modulation

Orthogonal Frequency Division Multiple Access (OFDMA)


Like OFDM, OFDMA employs multiple closely spaced sub-carriers, but the sub-carriers are further divided into groups of sub-carriers. Each group is named a sub-channel, different colors in figure show a different sub channel. The sub-carriers that form a sub-channel need not be adjacent. Sub-channels actually used for multiple access (multi users communication). Each sub-channel consists of multiple carrier frequencies. For instance I have two sub-channels, S1 n S2. S1 has carrier frequencies f1 ,f2,f3, and S2 has carrier frequencies, f4,f5, n f6 . sub-channel 1 will b used to entertain one user/transmitter and sub-channel 2 will b used by another user/transmitter.

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Introduction to QAM modulation

In previous post we started about basic digital modulation techniques,ASK,PSK and FSK.Let’s look at another digital modulation technique called as QAM [Quadrature Amplitude Modulation],which is actually a combination of ASK and PSK .
QAM is the combination of Amplitude modulation and Phase modulation. More technically, QAM is a system of modulation in which data or signal is transferred by modulating the amplitude of two separate carrier waves, mostly sinusoidal, which are out of phase by 90 degrees (sine and cosine). The modulated carriers are then summed, and the resulting signal is a combination of both phase shift keying (PSK) and amplitude shift keying (ASK).
Keep in mind that,the term Quadrature refers to their phase difference of 90 degrees. As Sine and Cosine are 90 degree out of phase.
[Any two periodic waveforms whose phase difference is 1/4 th of their output period are said to have a Quadrature phase relationship].As Sine n Cosine have time period of 360 degrees so, 1/4 th of 360 degree is 90 degree! :)
In next post we will talk about different orders of ASK,PSK n QAM modulation

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Digital Modulation with introduction to ASK, FSK and PSK

Firstly, what do we mean by digital modulation? Typically the objective of a digital communication system is to transport digital data between two or more nodes. In radio communications this is usually achieved by adjusting a physical characteristic of a sinusoidal carrier, either the frequency, phase, amplitude. This is performed in real systems with a modulator at the transmitting end to impose the physical change to the carrier and a demodulator at the receiving end to detect the resultant modulation on reception. We begin our discussion by three basic types of digital modulations:
  • ASK [Amplitude Shift Keying]
  • FSK [Frequency Shift Keying]
  • PSK [Phase Shift Keying]
All of these techniques vary the parameter of a sinosoid to represent the information we wish to transmit.
A sinusoid has three parameters that can be varied, these are amplitude ,phase and frequency.

  • In FSK we change the frequency in response to information. One particular frequency for ‘1’ and another frequency for ‘0’.



  • In PSK, we change the phase of carrier signal to indicate information.



  • In ASK amplitude of carrier is changed in response to information n all else is kept fixed. Bit ‘1’ is transmitted by a carrier of one particular amplitude.To transmit ‘0’ we change the amplitude

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PIC Microcontroller USART (Asynchronous ) transmission Steps

It is necessary to follow some steps inorder to implement asynchronous transmission on PIC microcontrollers. And these steps are summarized below:
  • Initialize the SPBRG register for the appropriate baud rate. In the case high speed baud rate is rquired, set bit BRGH.
  • Dont forget to enable the asynchronous serial port by clearing bit SYNC and setting bit SPEN.
  • For interrupt based transmission enable bit TXIE.
  • For 9-bit transmission is desired, then set transmit bit TX9.
  • Enable the transmission by setting bit TXEN, which will also set bit TXIF.
  • If 9-bit transmission is selected, the ninth bit should be loaded in bit TX9D.
  • Load data to the TXREG register (starts transmission). It is to be noted, transmission starts immediately after  TXREG is loaded.
  • If using interrupts, ensure that GIE bit and PEIE bit (bits 7 and 6 of the INTCON register) are set.
Details to follow!

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Making decisions based on EPC

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PCB Design Rules for Sensitive Circuits to avoid EMI problems

PCB designing is usually done on the very popular E-CAD software called OrCAD. Imagine a circuit like that of Ethernet kit using ENC28J60 that has different voltage level such as Low-voltage (3.3V), TTL/CMOS voltage level (5V) and the LAN standard signals levels. It also has the high frequency signals of SPI interface with clock of 10MHz and the LAN standard signals with modulation rate of 20MHz. All these signals may interfere with each other if the tracks of the PCB are not properly routed and the components are not placed to appropriate location due to EMI, this interference may cause the malfunctioning of the circuit. Some rules should be followed to avoid the EMI problems
  • Keep the tracks length as short as possible
  •  Do not route the analog signal and the digital signal together
  •  Keep the clock track separate from the other signal
  • Keep the high frequency signals tracks separate from the other signals.
  • Keep the Ground track as short as possible.
  • Keep the lengths of the connector short of high frequency signals such as SPI clock (!important)
  •  Do not turn the route at 90o.
  •  Never run the clock signal tracks to outer edge of the PCB
  • No unrelated component should be closer than 1 inch to the crystal
  • Put the crystal not farther than 1 cm form oscillator pin
  • Put RBIAS resistor as close as possible to pin.

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AVR based Multiple Input Digital Data Acquisition System using SDHC Card

Contributed by:
S/LT KAMRAN   (NUST)                      
Mr. KASHIF ALI (NUST) - Trainee Engineer at P&G
Report available only for educational purpose. 

Download the Project Report :

 Download Project Report as a PDF Document (140 pages)

ABSTRACT

‘DATA   ACQUISITION SYSTEM’ is a system in which we have considered a scenario of a ship’s bridge in which different consoles are getting different data which is then manipulated and used accordingly. Our plan was to develop such a prototype system which would be getting data from different sensors simultaneously. The data is then stored in SDHC card which is being used first time in PNEC.

            GUI has also been made which would be showing different graphs of different data of different time. We have made GUI in C sharp which is also not very common here. We got so many hindrances in its making but with continuous efforts and some guideline from Mr Sajid from IIEE university helped us a lot to accomplish this task.

This system will be helpful for the OOW to monitor and control the data and then after analyzing situation, he may take the necessary steps properly

 AIM OF THE PROJECT

Our aim of the project is to design such a digital system which would be having multiple inputs and the data coming from these inputs is stored in the SDHC card (of huge memory). Once the data is stored in this memory card then it can be retrieved as well in form of graph. For this specific purpose we have made a GUI (graphical user interface) which made the data display in a required manner.
                                                                                                              
SCOPE OF THE PROJECT

Once the ship is in the sea, it needs to keep the record of different data coming from different sensors. For this purpose ship’s log is to be maintained, which is keeping the data of different time. These all are in physical form and also done manually, which is quite time taking. In any case of emergency it can be burnt or misplaced as well and can cause a lot of trouble at the time of requirement.

Normally, data acquisition and then keeping it for further use is also very much necessary almost in every part of field. Industries which are of critical nature or performing continuous processes at fields may require data storing as well.

So, keeping this scenario in mind we tried to advance this system with the help of some reliable sources. Here our idea is to design such a prototype system in which different sensors are installed and the digital data is being stored in SDHC card, then using serial communication it is connected with computer. GUI has also been made through which data of any installed sensor can be extracted and seen. This system is keeping the record of different sensors at the same time and can be used at any time in future for further use.

Download the Project Report  :
 Download Project Report as a PDF Document (140 pages)

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