The Need Of Cdma Technology

Published Date: 02 Nov 2017

In this project it is intended to take a close look at the Code division multiple access technology and how it operates in details for examples all the components in a CDMA network, how it operates, what are the advantages over other communication technologies out there like GSM, TDMA, etc.

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 of CDMA technology

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

Where international business travel is an issue, GSM leaps forward in the race for the title of "Most Accessible." Because GSM is used in more than 74% of the markets across the globe, users of tri-band or quad-band handsets can travel to Europe, India, and most of Asia and still use their cell phones. CDMA offers no multiband capability, however, and therefore you can’t readily use it in multiple countries. However, certain phones like the iPhone 5 now have Quad-band GSM built in so they can be used overseas with special calling plans from carriers [2].

01.03.04 Data Transfer Methods in GSM vs. CDMA

Another difference between GSM and CDMA is in the data transfer methods. GSM’s high-speed wireless data technology, GPRS (General Packet Radio Service), usually offers a slower data bandwidth for wireless data connection than CDMA’s high-speed technology (1xRTT, short for single carrier radio transmission technology), which has the capability of providing ISDN (Integrated Services Digital Network)-like speeds of as much as 144Kbps (kilobits per second). However, 1xRTT requires a dedicated connection to the network for use, whereas GPRS sends in packets, which means that data calls made on a GSM handset don’t block out voice calls like they do 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

In cities and densely populated areas, there are often high concentrations of GSM and CDMA connection bases. In theory, GSM and CDMA are invisible to one another and should "play nice" with one another. In practice, however, this is not the case. High-powered CDMA signals have raised the "noise floor" for GSM receivers, meaning there is less space within the available band to send a clean signal. This sometimes results in dropped calls in areas where there is a high concentration of CDMA technology. Conversely, high-powered GSM signals have been shown to cause overloading and jamming of CDMA receivers due to CDMA’s reliance upon broadcasting across its entire available band [2].

The result of this little cross-broadcasting joust has led some cities to pass ordinances limiting the space between cell towers or the height they can reach, giving one technology a distinct advantage over the other. This is something to note when choosing a wireless provider. The distance between towers will severely affect connectivity for GSM-based phones because the phones need constant access to the tower’s narrow band broadcasting [2].

01.03.04 Popularity and Market Share

GSM is a lot more widespread in Europe and Asia. In the United States, Sprint and Verizon networks are CDMA whereas AT&T and T-Mobile are on GSM. Most of Europe uses GSM and so does China. In India, Hutch, Bharti and BSNL are on GSM whereas Reliance and Tata Tele are on CDMA networks [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

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 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

• Satellites used for television signals are generally in either naturally highly elliptical (with inclination of +/-63.4 degrees and orbital period of about 12 hours, also known as Molniya orbit) or geostationary orbit 37,000 km (23,000 mi) above the earth’s equator

• Transmitting antenna located at an uplink facility in this case it is the antenna of Multichoice's DStv

• Since transmitting antenna transmit the signal at C-band (4–8 GHz) or KU-band (12–18 GHz) or both, we need the small disks that support for those frequencies to receive the single in Mauritius

• Since the downlinked satellite signal, quite weak after traveling the great distance we need a LNB with the disk to amplifies the relatively weak signals,

• UHF TV tuners which selected the satellite television channel for down conversion to another lower intermediate frequency centered on 70 MHz where it was demodulate

• Integrated receiver/decoder or IRD is need with the disk

- T base 10 Ethernet wires need at least 10m for each house connect the TV to disk

- A top box that decrypt the signal is required for each user

- A KU or C band supported disk is needed for each user

01.07.02 Operational Feasibility

3.1 Technological components available in the current environment

- We normally don’t need more components from environment but the current environment can be useful when with satellite disks away from power sources in order to achieve clear signal

3.2 Problem concerning land, buildings, utilities

- Some lands close to power sources may not receive clear signal

- Always satellite disks should be in a high ground .hose top is recommended

3.3 Manpower

- when installing the disks at house special knowledge is not required but a for customer service it’s important to have a technician for installation process

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 program 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

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 consistently provides better capacity for voice and data communications hence at any given time more subscribers can connect, and also it is the common platform on which 3G technologies are built [3].

CDMA was first used by English allies to foil German attempts at jamming transmissions during World War II. The allies needed a 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 the ability to detect 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, when decoding the signal it can average just to determine the value of a single bit [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 has been used by the military for secure phone calls 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 redundancy for error checking. Each bit from the encoder is replicated 64 times to identify a specific call from the rest of the 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 (ADC) the received frequencies are quantized into bits ("chips"). The output is run through the Walsh code and PN sequence correlation receiver to recover the transmitted bits of the original signal. When 20 milliseconds of voice data are received, a Viterbi decoder corrects the errors using the convolutional code. The Viterbi output goes to the vocoder and digital-to-analog converter (DAC), which decompresses the bits and turns them back into waveforms (sound) [3].

Figure 02 Receiving at the Cell phone

Source: http://www.pcmag.com/encyclopedia/term/39462/cdma

This exclusive OR truth table shows you the Boolean algebraic rules to prove the single bit example in the illustrations above. The example bit is a 1, and the Walsh and PN codes are 0 [3].