Interaction Between Gsm And Cdma Information Technology Essay

Published: 2021-07-31 12:55:08
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Furthermore we are going to discuss the Performance Analysis and optimisation of a CDMA system in a noisy channel which means talking about all the coding methods out there which suitable for CDMA networks for example convolution codes and all the modulations techniques that suitable for example PSK, QAM
When analyzing performance of a CDMA technology it is important to take a close look at the bit error rate and how the bit error rate affects the communication. So we are trying to study about the different bit error rate measurement techniques and find out how it works on CDMA
The main intend of this project is to find a best suitable method of modulation and coding technique for a Code division multiple access communication by minimizing the bit rate which is the main factor for measuring the performance of a CDMA communication system
Hence we will calculate the bit error rates of all the modulations techniques and coding techniques that use for CDMA and try to compare the results to get a good idea of which modulation technique is best for the code division multiple access communication
In this project the Matlab software will be used to calculate and simulate the bit error rate related calculations and compare the results to find out how to minimize the bit error rate and hence how to provide a smooth and more reliable service at some reasonable cost
01.02 History
In commercial terms GSM was a bit slow starter; it is an important thing in GSM the skeptics always try point out. In outside the Europe, other digital mobile telephony standards always have a competition with GSM [1].
CDMA had a challenge to overcome from TDMA standard at the beginning, since the whole America was adapted to the TDMA around 1988 ERA victory. TWO Famous electrical engineers named Andrew Viterbi and Irwin Jacobs who contributed to the work of Torleiv Massing’s in 1987 by their algorithm also were the most important backers and contributors of Qualcomm’s company [1].
Andrew Viterbi and Irwin Jacobs were both followed electrical engineering at the same institution and both graduated together (Massachusetts Institute of Technology) later they started their won company called OmniTRACS Company, which deals with satellitesband wirelss networks for the truckers all around the north America [1].
At the beging the proposal of CDMA was given very poor acceptance by the industry body (CTIA), however by the time of 1991 large number of American companies were undertaken soe large scale testes about CDMA technology mainly thanks to the Qualcomm Company. After some extended researches and complicated discussions at the time 1993 CDMA was officially accepted as an American mobile phone standard. [1].
Motorola, for one, "seized upon this new standard to exclude the Europeans, primarily Ericsson and Nokia", write Meurling & Jeans. Splitting of the American market into two camps was expected, one camp based on CDMA and the other one on TDMA [1].
References: The sources are listed in numbered accordingly, as in the following article.
[1] http://www.ericssonhistory.com/changing-the-world/Big-bang/The-launch-of-CDMA/
01.02.01 Japan and China
When travel away from America there was always a new major issue about market representation of standards in Japan and China so it was essential to find out which technology they would opt for [1].
1989 in Japan ERA was given the courtship to involve in the process of specifying digital mobile telephone standard in Japan [1].
Because of this digital mobile telephony was lunched in Japanby the expence of DoCoMo division mobile standard, by the 1994 Japan telecommunication market was fully deregulated to allow CDMA to spread in japan. [1].
Lars Ramqvist describes the entry of Ericsson into Japan as a gamble by "We were dealing with an enormous market and the Americans were applying a lot of pressure, mainly to pave the way for Motorola. But the Japanese wanted to stamp their own identity on the system, and we were successful with the modifications and began to win orders. When I presented the case to Ericsson’s board, I said we would have to wait four years before our investment in Japan yielded a profit. But things went much more quickly than that." [1]
MR Lars Arnfinn Röste, "people describe him as a "lone wolf with an exceptional ability to sniff out and analyze new business possibilities" he was also the one who made the ERA’S mission in to China. Then in 1987 first chines contract was handed to Kurt hellstrom. The contract was for NMT systems as the clients get to know the one in Ireland then it became TACS, without rewriting the of the NMT contract ERA provided TACS to the customers [1].
01.02.02 Banned signal system
Another major problem when deals in China concerning was the banded signals system. American strategic export list had banned the signal system needed for exports to some other countries. Therefore much complicated negotiations held with American authorities, but finally it let to agreement with ERA [1].
The main protagonist was Madame Li Mofang, head of technology at China Mobile. Jan Uddenfeldt describes her as "incredibly competent, wise and amusing". Li could see the advantages of international solutions and soon backed GSM [1] .
In 1994, Ericsson received its first Chinese GSM order. Uddenfeldt recalls: "That was thanks to Li, who maintained that GSM was superior to the American standards. She laid the foundations for an enormous success: China Mobile’s GSM network was eventually to become the largest in the world." [1].
References: The sources are listed in numbered accordingly, as in the following article.
[1] http://www.ericssonhistory.com/changing-the-world/Big-bang/The-launch-of-CDMA/
Ramqvist adds: "We were criticized in some quarters for doing business with a dictatorship like China. We responded that we did not feel we should be negative about the idea of people talking to each other." He praises Alf Svensson, Sweden’s minister for foreign aid & human rights from 1991 to 1994, for his support. "Some harsh things were said about Alf Svensson in Sweden but he could see further than his critics and meant a great deal for Sweden’s export industries [1].
References: The sources are listed in numbered accordingly, as in the following article.
[1] http://www.ericssonhistory.com/changing-the-world/Big-bang/The-launch-of-CDMA
01.03 The need and the problem statement
01.03.01 CDMA vs GSM
GSM and CDMA are both well-established wireless technologies in the world even when the GSM has taken over about 82% global market. In the U.S., however in America CDMA is the most well established mobile standard. In Technical concept GSM (Global System for Mobile communications) provides specification for the whole wireless network infrastructure, on the other hand CDMA focus only about the air interface (the propagation part of the technology) [2].
As I mentioned above Code division multiple access mainly defines the access principles of communication channel which also uses special coding (here each and every transmitter is given a unique code) scheme and the spread-spectrum technology. It also refers to as multiple access schemes for digital cellular telephony systems, by QUALCOMM, and W-CDMA by ITU, which is normally operated in GSM’s UMTS [2].
References: The sources are listed in numbered accordingly, as in the following article.
[2] http://www.diffen.com/difference/CDMA_vs_GSM
01.03.02 Subscriber Identity Module (SIM Card)
It is a memory device which defines a specific customer and stores all his data on the mobile device, to enables the easy use of SIM card, you can change it between mobiles or handsets, which also provides the portability of the user stored personal data and other information. CDMA provides much more flexibility with its own unique service that enables users to store his or her data, for example scheduler information, phone book etc on the operator’s database. This service enables not only the customers to change the Subscriber Identity Module between mobile devises quickly and easily but it also enables the ability of easy recovery of data if the mobile device got damage or lost [2].
01.03.03 International Roaming with GSM and CDMA
Since the GSM technology is used around the globe more than 74% of customers, GSM technology is in the driving seat for the title of most Accessible mobile service this is very important when we talk about the traveling and international businesses. Since CDMA provides no multiband service for the users it is may not be possible to use customers mobile devise in multiple countries, on the other hand tri-band or quad-band mobile users can travel almost anywhere in to European counties, and most of the Asian countries like India, to use their mobiles devices in those countries. However, some mobile devise like the "iPhone 5" now provides the GSM built Quad-band in so that those can be used in different countries with some special calling plans from carriers [2].
01.03.04 Data Transfer Methods in GSM vs. CDMA
Speed of data transfer methods on both technologies is another major difference between GSM and CDMA. GSM uses the high-speed wireless data transfer technology called, General Packet Radio Service (GPRS), and it normally provides a slower data rate and smaller bandwidth for wireless data transmission than the carrier radio transmission technology which is the high-speed technology (1xRTT) for CDMA, which also has the ability of providing 144 kilobits per second speed like ISDN (Integrated Services Digital Network). Anyhow, for use 1xRTT technology is required a dedicated connection to the network, on the other hand GPRS sends in packets, that enables the data calls made on a GSM mobile devices do not block out voice calls like it may blocked on CDMA phones [2].
References: The sources are listed in numbered accordingly, as in the following article.
[2] http://www.diffen.com/difference/CDMA_vs_GSM
01.03.05 Interaction between GSM and CDMA
Mainly in cities or highly populated areas, there may be often more concentrations of both GSM technology users and CDMA technology users and those base stations. Theoretically, GSM technology and CDMA technology are differ to each another and should not interfere each other. But in practice, this may not be the case. High powered CDMA transmission signals always have raised the "noise floor" for receivers of GSM, which means there may be a small space within the available band to transmit a clear signal. Therefore the areas with high concentration of CDMA transmissions sometimes make the GSM calls dropped. And also, areas with high powered GSM transmissions have been shown to make CDMA receivers to overloading and jamming because CDMA’s reliance upon transmitting across its whole available band [2].
Because of this minimum cross broadcasting problem has encourage some highly populated areas or cities to reconsider the arrangement of cell towers in the city or the change the height of towers, to provide one technology a some noticed advantage over the other. This is also an important thing to note when considering a wireless provider. Since the narrow band broadcasting GSM phones need constant communication with the tower’s the distance between towers will probably affect connectivity for GSM-based phones [2].
01.03.04 Popularity and Market Share
As we mentioned above GSM is the technology that has dominated the most of the global market. But networks in countries like United States, Sprint Company and Verizon Company provides CDMA and also AT&T Company and T-Mobile Company provide GSM. Still the bottom line is the almost all Europe uses GSM and also in China. In India, companies like BSNL, Hutch and Bharti provide GSM service and companies like Tata Tele and Reliance provide CDMA service [2].
References: The sources are listed in numbered accordingly, as in the following article.
[2] http://www.diffen.com/difference/CDMA_vs_GSM
01.04 Project Scope Description
This project is initially break down to these following steps however these steps are not the final steps for the work break down structure.
• submission of the project selection form and/or synopsis
• Start the project work that approved by UDC.
- After submitting the project forms From the UDC , the project will be accepted if it up to the qualifications
• Download and configure matlab program.
- Matlab program is a software which need to simulate and calculate the mathematical results.
• Borrow CDMA related books from the library
- Find out the books about CDMA and borrow from local and school library
• Research for the Best methods
- Do some extensive research on the methods that used to monitor the performance of CDMA networks
• Downloaded CDMA related books from internet
- AS well as borrowing books it is necessary to download the CDMA related books and documents
• Start taking short notes
- After go through all the notes and books it is important to make own notes about the necessary information.
• plan the project look and start on the body of the project
- plan the order of the prject
• Start writing the project with by introduction , aims and literature review
- When starting the project , it start according to the guidelines given by the project hand book
• write the literature review
- Write the literature review of all the components and CDMA related services and other related to the project
• Do the calculations on matlab and include the results to the project
- Using the matlab program do the extensive calculations which related to the CDMA performance monitoring and analyzing and then the results will be include in the project
01.05 Aims of this project
Define the different modulations techniques and identifies them and do some extensive research to find out how the bit error rate affect them in the real life communication
By finding out these bit error rates of different techniques, it is intended to do a extensive analysis on performance and optimisation of a CDMA system in a noisy channel. This is done by comparing the results of the bit error rates of different coding techniques, for example convolution codes, together with different modulation schemes, for example PSK, QAM. in order to generate different graphs of the Bit Error Rates with different noise levels over the channels. Simulation will be performed
01.05.01 Project Acceptance Criteria
• The project has been targeted to be completed within 7 months
• Consider different coding techniques, and do a Performance Analysis and optimisation of a CDMA system in a noisy channel.
• Using the convolution codes or any other coding methods, together with different modulation schemes, for example PSK, QAM, to determine the best methods for less bit error rate
• Satellite television has also allows for interactive TV services such as movie-on-demand,
• Generate different graphs of the Bit Error Rates with different noise levels over the channels, Simulation can be performed in MATLAB
01.06 Objectives of this project
Below is a list of objectives in order to successfully achieve the project aim
1) To conduct intensive research in Code Division Multiple access technology and it components to get a better idea of how it work
2) Find out what are the coding methods used in Code Division Multiple access technology
3) Choose the compare among the coding techniques select few coding for the project
4) Find out what are the modulations techniques used by Code Division Multiple access
5) Choose and compare modulations techniques and selects few modulation techniques to do some intensive research and workouts
6) Find out and calculate the bit error rates of different modulations techniques with different coding methods
7) Compare the results each other and find out the best techniques for CDMA communication , here we will use mat lab program to calculate and simulate
01.06.01 Project Assumption
• The project is supposed to provide an clear idea of the CDMA networks , structure , how the technology works
• Since CDMA has advantages of High Capacity, Strong Security, Energy Efficiency over the most other communication systems it is ideal to study and find out more about it
• The project will be completed on the schedule date.
• Convolution codes, together with different modulation schemes, for example PSK, QAM, in order to generate different graphs of the Bit Error Rates with different noise levels over the channels. Simulation can be performed in MATLAB or related software.
01.07 Feasibility study
02.01 Technical Feasibility
02.01.01 Technologies
• Code-Division Multiple Access is a digital cellular technology which uses spread spectrum techniques
• By assigning a specific frequency to each conversation CDMA made sure that the every transmission overlaps on the same carrier frequency hence the full bandwidth is used simultaneously by the each and every conversation
• CDMA uses a unique coding pattern to spreads the digital stream over the full 1 bandwidth which is 25MHz of the channel
• Vocoder is used to compress each voice conversations. Then the convolutional encoder is used to double the output and which increases error checking redundancy. Encoder will replicate 64 times each and every bit from to determine a certain call from the all of other calls the Walsh code and the exclusive OR'd calculations may be used
• Using the analog to digital converter, received frequencies at the receivers end are quantized into chips or bits. Then the Walsh code and PN sequence will run on the output to recover the original signal that transmitted.
01.07.02 Operational Feasibility
3.1 Technological components available in the current environment
- We normally don’t need more components from environment since this project is based on simulations , but we need to install matlab program for the simulation
3.2 Problem concerning project
- Getting the information for the project about the CDMA technology is limited since very few companies offers CDMA technology for their customers
3.3 Manpower
- This project can be done by single person since its only need to have simulate the results to show the community about the best modulation technique available for CDMA
01.08 WORK BREAKDOWN STRUCTURE (WBS)
In the work break down structure the work to be done in specific time period for this project will be mentioned properly
• In the requesting the permission phase every student needs to submit project selection form and/or synopsis which normally consists with most liking projects would like to do from the list of projects that given
After submitting the project selection form the UDC will approve a project and we have to conduct the work according to the selection by the UDC
• After requesting the permission phase Gathering Resources is important, research about the best CDMA technology and how it works, what are the advantages, how CDMA better than the other communication technologies out there and since the project is about Performance Analysis and optimization of a CDMA system in a noisy channel it is important to research about the all the coding methods for example convolution codes, together with different modulation schemes, for example PSK, QAM. Then finally research about the differences of each of those methods when using with CDMA this is done by finding out which method has the lowest bit error rate for CDMA.
First of all it is important to download and install the matlab programs which will needs to calculate the bit error rates and copier with the other methods.
These researches will be conduct from books which borrowed from libraries and notes and other related books downloaded from the internet. And also, most impotently more information will be acquired from the MTML Company which is a CDMA specialist company base on Mauritius
• After Gathering Resources next step would be documenting the project, first of all it is important to make own short notes about the whole literature on the project. After the above step the Initial study will start with Aims and objectives, insight, background, identification of relevant information/data sources, applicability. AS soon as the initial study is done then Project Management will be documented about how time management has been done so far. Then the literature review which take in to account all the related work, state-of-the-art knowledge
Figure 0.1 Work breakdown structure
This show how the work in this project has carried on for different stages and time allocation
Figure 0.2 Timeline
This show this time allocation for the project at different stages
Figure 0.3 Work breakdown structure with time line
Figure 0.4 WBS chart
WBS chart show who the work in this project has broken down to parts
02) Literature Review
02.01) CDMA (Code-Division Multiple Access)
Code-Division Multiple Access is a digital cellular technology which uses spread spectrum techniques. There are some other kinds of systems available for digital cellular like GSM and TDMA, which are assigned a specific frequency to each user. However the different of the CDMA with other technologies is the every channel uses the full available spectrum; this is doing by encoding the conversations with a pseudo-random digital sequence. Compare to the other commercial mobile technologies CDMA always manage to give better capacity for voice and data communications hence at any given time more subscribers can connect, and also it is the general concept that the technologies of 3G based on [3].
CDMA was first used by English friendly sides against the German to jam their transmissions during World War two. The allies needed to make it Germans difficult to pick up the complete signal by transmitting over several frequencies, instead of one, which making it difficult for the anomies [3].
02.01.01 Spread Spectrum
By assigning a specific frequency to each conversation CDMA made sure that the every transmission overlaps on the same carrier frequency hence the full bandwidth is used simultaneously by the each and every conversation On the other hand GSM and earlier digital systems, are still uses Time division multiple access to divide the channel into time slots, This scenario of CDMA can be explained by an analogy is the in a room full of students who speaking different languages and also able to identifies one's own language [3].
As I said before when the speech codec has done converting the user's voice to digital, CDMA uses a unique coding pattern to spreads the digital stream over the full 1 bandwidth which is 25MHz of the channel. The rate of the signal spread is called as the "chip rate," and a "chip," is and individual bit in the spreading signal. This gives the receiving circuit a huge amount of information data by multiplying each bit of a conversation into 128 coded bits, [3].
References: The sources are listed in numbered accordingly, as in the following article.
[3] http://www.pcmag.com/encyclopedia/term/39462/cdma
02.01.02 More Secure
It is difficult to detect and jam the CDMA transmission since it uses wide spreading signal so this was used by the army for secure signal transmission over FDMA and TDMA, [3]
02.01.03 How the Technology Works
At the base station Bits are encoded and in the cell phone they are decoded. The following example shows how the Boolean math involves using a single bit example [3].
1) Transmitting from the Base Station (fig 1)
Vocoder is used to compress each voice conversations. Then the convolutional encoder is used to double the output and which increases error checking redundancy. Encoder will replicate 64 times each and every bit from to determine a certain call from the all of other calls the Walsh code and the exclusive OR'd calculations may be used [3].
Here the PN sequence is the string of bits from a random pseudo number generator which after the output of the Walsh code which is exclusive OR'd. In a particular cell's sector this PN sequence is used to identify all the calls. At this point, the vocoder's output is multiplied by 128 times which means120 times many bits than were from the vocoder output. All the calls are modulated and combined onto a 800 MHz range carrier frequency [3].
References: The sources are listed in numbered accordingly, as in the following article.
[3] http://www.pcmag.com/encyclopedia/term/39462/cdma
Figure 1 Transmitting from the Base Station
Source: http://www.pcmag.com/encyclopedia/term/39462/cdma
2) Receiving at the Cell phone (fig 0.02)
Using the analog to digital converter, received frequencies at the receivers end are quantized into chips or bits. Then the Walsh code and PN sequence will run on the output to recover the original signal that transmitted. As soon as 20 ms of voice data received, errors will be corrected using convolutional code by the Viterbi decoder. The output from Viterbi decoder then directly send to vocoder and to digital to analog converter, then the bits are decompressed and transforms them back to the sound waveforms [3].
Figure 02 Receiving at the Cell phone
Source: http://www.pcmag.com/encyclopedia/term/39462/cdma
References: The sources are listed in numbered accordingly, as in the following article.
[3] http://www.pcmag.com/encyclopedia/term/39462/cdma
02.02) Modulation techniques
02.02.01 Phase-shift keying
Phase-shift keying (PSK) it is a digital modulation scheme that use to transfer data by changing the phase of a carrier signal (the reference signal) [4].
Any known digital modulation techniques use a selected number of different signals for representing the digital data. In Phase-shift keying finite number of phases is used to represent the signal, by each signal assigning a unique pattern zeros and ones (binary digits). Usually, same number of bits will be used to encode each phase. Each and every sequence of bits forms the symbols which are represented by the specific phases. When recovering the original data demodulator, is normally specifically designed for the same symbol set used at the modulator, demodulator calculates the phase of the received signal and to provide a correct representation of the original data it maps back to the symbols, thus. Therefore requires the receiver to have the ability to perform a comparison of received signal’s phase with the reference signal, such a system is define as a coherent (and also referred to as CPSK) [4].
And also, instead of operating and comparing with respect to a reference wave, the broadcast can also perform according to itself. If we consider a single broadcast waveform any changes in phase must be noted as important items. Here, the demodulator rather explores the changes in the phase of received signal than the phase itself to the reference wave. Since this system is depended on the difference between ancillary phases, it is termed as differential phase shift keying. DPSK is definitely easier to implement than normal PSK it is because the ability of determining the correct phase of the received signal without the demodulator to having a copy of the reference. [4].
References: The sources are listed in numbered accordingly, as in the following article.
[4] https://www.princeton.edu/~achaney/tmve/wiki100k/docs/Phase-shift_keying.html
02.02.01) Quadrature Phase Shift Keying
Quadrature Phase Shift Keying (QPSK) is also a digital modulation technique. Where it is a form of Phase Shift Keying but the difference of the QPSK is the two bits are made to modulat at the same time, this is done by using carrier phase shifts out of fore possibilities (0, Π/2, Π, and 3Π/2) [5].
Phase of the In phase carrier will be changed from 0° to 180° and also the Quadrature phase carrier will be changed from 90° and 270° to perform the QPSK. Hence it ll indicate the four different distinct states of a two bit binary code. These carriers are normally referred to as Symbols in each state [5].
As I mentioned above QPSK transfer the digital information by modifying or modulating the carrier signal phase and it is widely used around the world. In QPSK digital data is used represent by 4 points 360 degrease circle those four points are corresponded to four phases of the carrier signal. And those points are defined as symbols. [5].
Figure 03 QPSK constellation diagram
Source: Fig: QPSK diagram showing how four different binary codes can be transmitted [5}
References: The sources are listed in numbered accordingly, as in the following article.
[5] http://turboblogsite.com/quadrature-phase-shift-keying-qpsk-modulation.html
Figure 04 QPSK transmitter
Source: Fig: Block diagram of a QPSK transmitter [5]
In Figure 04 shows the example of normal QPSK transmitter block diagram. First with a help of unipolar to bipolar converter, unipolar binary message is converted into a sequence called bipolar non return to zero. Then the bipolar non return to zero is then break into 2 types of streams called in phase (I) and Quadrature (Q) .those streams are also called the even and Odd streams. [5].
References: The sources are listed in numbered accordingly, as in the following article.
[5] http://turboblogsite.com/quadrature-phase-shift-keying-qpsk-modulation.html
02.03 Bit error rate BER definition and basics
Bit error rate is defined as the errors rate that occurs in a transmission system. This can be more simplified that the in an array or string of a random number of bits how many number of errors that occur over the transmission. Bellow it shows the formula that defines the bit error rate [6]:
BER = number of errors / total number of bits sent
To have small or insignificant/unnoticeable effect from bit error rate to the overall transmitting system is the goal of any modulations techniques this is done by having smooth transmitter and receiver medium and also having a high signal to noise ratio. However if there is noise on the medium detected then there is a definite chance of having bit error rate hence it is important to take it in to consideration [6].
The main reasons for the transmission bit error rate and the degeneration of a data channel are noise in the medium and the changes to the propagation path (normally signal paths are radio). In transmission systems it is normally model of propagation may follows a Rayleigh model and the noise follows the Gaussian probability functions. This means that using statistical analysis techniques analysis of the channel characteristics are normally performed [6].
In the fibre optic systems transmission, bit errors can be seen due to imperfections of the components used to make the fiber link, for examples optical receiver, driver, connectors and may be the fibre itself. Another cause of bit error for fiber optics is the attenuation that may be present in the fiber itself and optical dispersion. And also noise may be introduced in the receiver of the optical fiber itself. Since the photodiodes and amplifiers are needed to respond to very small changes there may be high noise levels present with them [6].
And also any phase jitter present in the system is another main factor for bit errors to be occurred since this can modify the sampling data [6].
References: The sources are listed in numbered accordingly, as in the following article.
[6] http://www.radio-electronics.com/info/rf-technology-design/ber/bit-error-rate-tutorial-definition.ph
02.03.01 BER and Eb/No (the energy per bit to noise power spectral density ratio)
When we talk about the radio links and radio communications systems, SNR and Eb/No are some important parameters that are more associated with. In terms of these parameters, the bit error rate also may explain in terms of the probability of error (POE). To find this, three important variables may use. They are the energy in one bit, error function and the noise power spectral density [6].
It is important to note that each and every different modulations types have their own unique value of error function, mainly because in the presence of noise different types of modulations perform differently. For example, higher order modulation techniques like 64QAM has the ability to transmit higher data rates, but not that much strong in the noisy environments. However lower order modulation formats like BPSK, QPSK offer lower data rates but are more error proof [6].
The energy per bit, Eb, can be defined by bit rate over carrier power and this is a measure of energy and the units are in Joules. And the No is the power per Hz and hence it has the units of power/Second (Js). When we consider the units of the ratio Eb/No all the units cancel out and give a unit less ratio. It is important to remember that Eb/No is proportional to probability of error and it is actually a form of SNR (signal to noise ratio) [6].
02.03.02 Factors that affecting bit error rate, BER
Bit error rate can be caused by number of factors and it can be explained by using Eb/No. To provide a optimize performance levels that are required can be achieved by changing the variables that can be controlled. At the design stages of an information transmission system this should be normally implemented, so that at the initial design concept stages performance parameters can be changed [6].
However external factors like interference levels affect to the system cannot be reduce by the system design. However by reducing the bandwidth of the system it is possible to reduce the level of interference. However reducing bandwidth means the limiting the data throughput this could reduce the overall system performance [6].
It is also able to increase the power per bit by increasing the whole power level of the system. This need to be done very carefully considering the factors like the increasing of power output may be not suitable for the power amplifier, interference levels for other customers, battery lifetime and power consumption [6]
. References: The sources are listed in numbered accordingly, as in the following article.
[6] http://www.radio-electronics.com/info/rf-technology-design/ber/bit-error-rate-tutorial-definition.php
Using lower order modulation techniques may be able to s solve this problem, but this will always reduce the data throughput.
To achieve a manageable bit error rate it is always important to balance all the available factors. It is normally not possible to achieve 100% of requirements hence some trade-offs may be required. Even with a bit error rate below which is initially required, more extended trade-offs can be made for example the error corrections can be introduced into the transmitting data, sometime this may leads to transmitting redundant data with the more complex of error correction, but this can help to reduce the effects of any bit errors, therefore it will reduce the overall bit error rate [6].
To measure the performance of a data link, bit error rate BER would be a very good parameter and it will gives an excellent indication of how good the radio or fibre optic system. Number of errors that occur in any data link would always be one of the main parameters; the bit error rate also a key parameter. [6]
In digital and analog communications, signal-to-noise ratio, is the measure of signal strength that corresponding to the background noise, it is normally written S/N or SNR, is a. And the ratio is normally measured in decibels [6].
If the receiving signal strength measure in microvolts ( Vs) and the noise level, also measure microvolts( Vn,) then the below formula provides the signal to noise ratio( SNR) in db[6]
Then if Vs = Vn, and then SNR = 0. When this happen end result would be the unreadable signal borders, since the noise level soundly conflicts with it. Normally for digital communications, this will lead reduction in data transmission speed due to regular errors that require the source transmitter to resend some packets of data [6].
Second case consider Vs > Vn, so SNR become positive. For an example, suppose that Vs = 10.0 mV and Vn = 1.00 mV. Then [6]
S/N = 20 log10(10.0) = 20.0 dB
This is the best possible scenario and it will result in the received signal to be clearly readable. Let’s say if the the signal is weaker but still may above the noise for example 1.30 mV [6]
S/N = 20 log10(1.30) = 2.28 dB
References: The sources are listed in numbered accordingly, as in the following article.
[6] http://www.radio-electronics.com/info/rf-technology-design/ber/bit-error-rate-tutorial-definition.php
There may be reduction in data speed can be experienced under when this happen [6].
For the case Vs. is smaller than Vn then SNR become negative. And when this happened, reliability of the communication may reduce unless measures are taken to increase the signal strength and decrease the noise level at the receiving end terminal [6].
Communications engineers always try to find the ways to maximize the signal to noise ratio. Normally, this is done by using the smallest possible receiving system bandwidth consistent with the data speed desired. However, there are some other methods like spread spectrum techniques can be used to improve system performance. Providing the source with a higher level of signal output power the S/N ratio can be increased if necessary. By lowering the temperature of the receiving circuitry, in some complex systems such as radio telescopes, internal noise can be minimized to acceptable level. In wireless systems, it is always important to optimize the performance of the transmitting and receiving antennas [6].
02.03.03 BER VS SNR Process
In all the phase modulation techniques the information is represented in terms of phase of the carrier. According to the input binary data, Phase of the carrier signal is shifted. BPSK is calld two state phase shift keying (PSK) phase the value of the receiving bit of the radio carrier is set to 0 or π. Each bit of the digital signal produces a transmit symbol with duration Ts, which is equal to the bit duration Tb. Four-state or quadriphase PSK is called QPSK, in which two bits are combined and the radio carrier is phase-modulated according to the four possible patterns of two bits. Transmitting a symbol takes twice as long as a bit (Ts = 2•Tb) which means that the bandwidth efficiency of QPSK is twice that of BPSK [7].
Bit error rate (BER) of a communication system is defined as the ratio of number of error bits and total number of bits transmitted during a specific period. It is the likelihood that a single error bit will occur within received bits, independent of rate of transmission. There are many ways of reducing BER. Here, we focus on spreading code & modulation techniques [7].
References: The sources are listed in numbered accordingly, as in the following article.
[6] http://www.radio-electronics.com/info/rf-technology-design/ber/bit-error-rate-tutorial-definition.php
[7] Electronic engineering/BER Vs SNR Performance Comparison of DSSSCDMA FPGA Based Hardware by N. B. Kanirkar and J. N. Sarvaiya
02.03.04 BER VS SNR Design & Results
in order to have accurate performance measurement of BER vs SNR the different pseudo codes are used for example GOLD, MLS and Barker with two famous code modulation techniques for example BPSK & QPSK for CDMA mobile communication. [7]
The FPGA BER module different register values are expressively calculated and feed into the microcontroller for the specific performance. Register 16 Signal value and Register 17 additive white Gaussian noise. Decimal values are converted from the feed Hex values and it is for the further calculation and BER. [7]
And Similarly method is used to change of transmitted bits from 1,000 bits, 1, 00,000 bits, 1,00,00,000 bits and 1,00,00,00,000 bits. The complex calculations are done for the tabulation of results to get better performance comparison of BER vs SNR. [7]
Figure 05 BER VS SNR Design & Results
Source: electronic engineering/BER Vs SNR Performance Comparison of DSSSCDMA FPGA Based Hardware by N. B. Kanirkar and J. N. Sarvaiya
References: The sources are listed in numbered accordingly, as in the following article
[7] Electronic engineering/BER Vs SNR Performance Comparison of DSSSCDMA FPGA Based Hardware by N. B. Kanirkar and J. N. Sarvaiy
02.03.05 Symbol Error Rate vs SNR per bit (Eb/No) for digital modulation schemes
The relation amoung bit energy Eb/No and symbol energy Es/No is well known.
For M-PSK/M-QAM modulation, the number bits in each constellation symbol are k hence [8]
Since each symbol carries bits, the symbol to noise ratio is times the bit to noise ratio , ie.
.
Plugging in the above formula, the symbol error rate vs bit energy (SNR per bit, Eb/No) is given as [8]
References: The sources are listed in numbered accordingly, as in the following article.
[8] http://www.dsplog.com/2008/03/29/comparing-16psk-vs-16qam-for-symbol-error-rate/
Figure 06 Symbol error rate vs EB/NO
Source: http://www.dsplog.com/2008/03/29/comparing-16psk-vs-16qam-for-symbol-error-rate/
As we can see here QPSK and BPSK‘s symbol error rate of 10^-5 only required around 10db of EB/NO. so compare to other modulation techniques EB/NO level QPSK and BPSK are the best choices
References: The sources are listed in numbered accordingly, as in the following article.
[8] http://www.dsplog.com/2008/03/29/comparing-16psk-vs-16qam-for-symbol-error-rate/
02.03.06 Bandwidth requirements and Capacity
Minimum required bandwidth for transmitting symbols with symbol period T without causing inter symbol interference (ISI) is Hz. [8]
If the transmission is pass band, PAM transmission requires bandwidth of Hz. But, the spectral efficiency can be improved by [8]
(a) To get the single sideband modulation filter the unwanted half of the bandwidth from the pass band PAM, this will give the result of bandwidth requirement of Hz (SSB) [8]
(b) I and Q arm for modulations can be used to get the result in a bandwidth requirement of Hz and it is called QAM (quadrature amplitude modulation) [8]
Capacity in bits per second per Hz for various modulation schemes can be derived using the knowledge of symbol duration and bandwidth requirement. For example, as each symbol carries 4 bits for 16QAM the bit rate will be 4bits per second [8]
Figure 7: Bandwidth, Capacity and Eb/No requirements for symbol error rate of 10^-5
References: The sources are listed in numbered accordingly, as in the following article.
[8] http://www.dsplog.com/2008/03/29/comparing-16psk-vs-16qam-for-symbol-error-rate/
The data from the above shown table can be translated into Shannon's capacity vs Eb/No curve. [8]
Figure 08: Shannon's capacity curve for various digital modulation schemes.
Source: http://www.dsplog.com/2008/03/29/comparing-16psk-vs-16qam-for-symbol-error-rate/
When we analyze the above figure we can see the overlapping points of 2PAM (SSB) and QPSK are; the points 4PAM (SBB) and 16QAM also overlapping. This means the SNR per bit (Eb/No) required for achieve the symbol error rate for 2PAM / QPSK and 4PAM /16QAM are the same. [8]. But, from the symbol error rate vs Eb/No plot, the value of SNR per bit (Eb/No), the symbol error rate for QPSK is twice that of BPSK and the symbol error rate of 16QAM is twice of 4PAM. So that the points should not overlap (actually it should be offset by around 0.3dB) [8]
References: The sources are listed in numbered accordingly, as in the following article.
[8] http://www.dsplog.com/2008/03/29/comparing-16psk-vs-16qam-for-symbol-error-rate/
02.03.07 Symbol Error rate (SER) to Bit Error Rate (BER)
Normally most communication systems use Gray coded techniques for modulation, which means only one symbols differ by bit at once. But this may sometime fails when wrongly decoded and the bit may fall into the adjacent the symbol bin. So, each symbol error gives one bit out of bits to be in error [8]
Therefore relation between symbol error and bit error is,
.
With above expression, the bit error rate equations would be:
References: The sources are listed in numbered accordingly, as in the following article.
[8] http://www.dsplog.com/2008/03/29/comparing-16psk-vs-16qam-for-symbol-error-rate/
Figure 9: BER vs SNR per bit (Eb/No) for digital modulation schemes
AS we can see here QPSK and BPSK‘s bit error rate of 10^-5 only required around 10db of EB/NO. So compare to other modulation techniques EB/NO level QPSK and BPSK are the best choices

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