This document discusses Code Division Multiple Access (CDMA) wireless communication technology. It provides an overview of CDMA, including that it uses unique digital codes to allow multiple users to access the same radio channel simultaneously. The document also covers CDMA specifications and standards like IS-95, as well as comparing CDMA to other multiple access technologies like TDMA and FDMA. It addresses topics such as the near-far problem and how CDMA provides advantages like increased network capacity but also challenges like potential self-interference.
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you can be friend with me on orkut
"mangalforyou@gmail.com" : i belive in sharing the knowledge so please send project reports ,seminar and ppt. to me .
Near-Far Resistance of MC-DS-CDMA Communication SystemsIDES Editor
In this paper, the near-far resistance of the minimum
mean square error (MMSE) detector is derived for the
multicarrier direct sequence code division multiple access
(MC-DS-CDMA) communication systems. It is shown that
MC-DS-CDMA has better performance on near-far resistance
than that of DS-CDMA.
Welcome to International Journal of Engineering Research and Development (IJERD)IJERD Editor
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Courier management system project report.pdfKamal Acharya
It is now-a-days very important for the people to send or receive articles like imported furniture, electronic items, gifts, business goods and the like. People depend vastly on different transport systems which mostly use the manual way of receiving and delivering the articles. There is no way to track the articles till they are received and there is no way to let the customer know what happened in transit, once he booked some articles. In such a situation, we need a system which completely computerizes the cargo activities including time to time tracking of the articles sent. This need is fulfilled by Courier Management System software which is online software for the cargo management people that enables them to receive the goods from a source and send them to a required destination and track their status from time to time.
Automobile Management System Project Report.pdfKamal Acharya
The proposed project is developed to manage the automobile in the automobile dealer company. The main module in this project is login, automobile management, customer management, sales, complaints and reports. The first module is the login. The automobile showroom owner should login to the project for usage. The username and password are verified and if it is correct, next form opens. If the username and password are not correct, it shows the error message.
When a customer search for a automobile, if the automobile is available, they will be taken to a page that shows the details of the automobile including automobile name, automobile ID, quantity, price etc. “Automobile Management System” is useful for maintaining automobiles, customers effectively and hence helps for establishing good relation between customer and automobile organization. It contains various customized modules for effectively maintaining automobiles and stock information accurately and safely.
When the automobile is sold to the customer, stock will be reduced automatically. When a new purchase is made, stock will be increased automatically. While selecting automobiles for sale, the proposed software will automatically check for total number of available stock of that particular item, if the total stock of that particular item is less than 5, software will notify the user to purchase the particular item.
Also when the user tries to sale items which are not in stock, the system will prompt the user that the stock is not enough. Customers of this system can search for a automobile; can purchase a automobile easily by selecting fast. On the other hand the stock of automobiles can be maintained perfectly by the automobile shop manager overcoming the drawbacks of existing system.
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
Vaccine management system project report documentation..pdfKamal Acharya
The Division of Vaccine and Immunization is facing increasing difficulty monitoring vaccines and other commodities distribution once they have been distributed from the national stores. With the introduction of new vaccines, more challenges have been anticipated with this additions posing serious threat to the already over strained vaccine supply chain system in Kenya.
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Event Management System Vb Net Project Report.pdfKamal Acharya
In present era, the scopes of information technology growing with a very fast .We do not see any are untouched from this industry. The scope of information technology has become wider includes: Business and industry. Household Business, Communication, Education, Entertainment, Science, Medicine, Engineering, Distance Learning, Weather Forecasting. Carrier Searching and so on.
My project named “Event Management System” is software that store and maintained all events coordinated in college. It also helpful to print related reports. My project will help to record the events coordinated by faculties with their Name, Event subject, date & details in an efficient & effective ways.
In my system we have to make a system by which a user can record all events coordinated by a particular faculty. In our proposed system some more featured are added which differs it from the existing system such as security.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
2. Introduction
What is Multiple Access?
General Specifications
Classification of Existing
Systems
Classification of CDMA
Systems
Multiple Access
IS-95
CDMA spread spectrum
◦ CDMA Specs
Comparison between
CDMA and TDMA/FDMA
Advantages of CDMA
Disadvantages of CDMA
CDMA Codes
CDMA Operation
TDMA/FDMA/CDMA
The Near-Far Problem
CDMA Carriers
Summary
References
April 19, 2015 2
3. CDMA stands for Code Division Multiple Access
A channel access method used by various radio
communication technologies
Where several transmitters can send information
simultaneously over one channel
Allows users to share a band of frequencies
April 19, 2015 3
4. Used as the access method in many mobile phone
standards (cdmaOne, CDMA2000)
Spread spectrum technology
Special coding scheme where each transmitter is
assigned a code
Digital air interface standard, claiming eight to fifteen
times the capacity of analog
Users have control of a very wide channel bandwidth
1.5 to 5Mhz
April 19, 2015 4
5. April 19, 2015 5
1. When multiple users want to
communicate in a common
geographic area
2. Many people can talk on the
phone at the same time
3.Each phone must communicate
with a base station
6. Rx: 869-894MHz Tx: 824-849MHz
20 Channels spaced 1250kHz apart
(798 users/channel)
QPSK/(Offset) OQPSK modulation scheme
1.2288Mbps bit rate
IS-95 standard
Operates at both 800 and 1900 MHz frequency bands
April 19, 2015 6
9. Each user is assigned a unique PN code
Each user transmits its information by spreading with
unique code
Direct Sequence spread spectrum is used
Users are separated by code not by time or frequency
slot
April 19, 2015 9
10. IS-95 was first operating system to use CDMA
◦ Invented by Qualcomm
◦ Began production in 1995
Being supplanted by CDMA2000 (WCDMA) and
UMTS, fully 3G systems
Both had been using CDMA
Wideband System
April 19, 2015 10
11. A signal takes up to 6-10 times the bandwidth that it
needs at a minimum
This is used for military communications as well
Much more difficult to tune into a certain frequency
Difficult to block, listen in on, and identify from noise
April 19, 2015 11
12. All users share the same 1.25MHz bandwidth
They all transmit the same size signal
Unique digital codes are used to separate each of the
mobile phones
.02Mhz of a guard band
Each bit of the conversation is encoded with this
special code
April 19, 2015 12
13. In TDMA/FDMA, cell design needs more frequency
planning while in CDMA frequency planning is
minimal
TDMA is Band Limited system, CDMA is power
limited system
CDMA systems entire spectrum is used which
enhances voice quality. In TDMA band width available
is small which leads to compromise of transmission
quality
April 19, 2015 13
14. No limit to the number of concurrent users
Low power requirements
Little cell-to-cell coordination needed by operators
Carrier can serve more subscribers
Precision clocks that do not limit the distance a tower
can cover
April 19, 2015 14
15. Capacity-can accommodate more users per Mhz of
bandwidth than any other technology
Small phones
Extended reach
Cell size is larger but consumes less power and covers
large areas
Impossible for hackers to decipher the code sent
April 19, 2015 15
16. Well-defined path to higher data rates
Uses Soft Handoff to reduce drop calls
Variable rate voice orders reduce the rate being
transmitted when speaker is not talking, allows channel
to be packed more efficiently
April 19, 2015 16
17. Near far problem
Not as mature as the GSM network
Cannot offer international roaming
Demands high pea power on uplink in transient mode
The only limit to the system is the computing prowess
of the base station and its ability to separate noise from
actual data
Self-jamming
April 19, 2015 17
18. CDMA covers a small portion of the world compared
to GSM
Multiple Path Distortion
GSM has more subscribers
GSM is in more countries overall
Most technologies are patented and must be licensed
from Qualcomm
April 19, 2015 18
19. The base station and mobile phone use an algorithm for
generating pseudo random numbers
Mathematical function called Walsh Vectors
◦ Generates 128 bit random numbers that are
orthogonal to every other random number generated
◦ Large period
Both the mobile station and base station should
generate the same random numbers (32 bits)
April 19, 2015 19
20. Time stand and error codes are added to the random
number convoluted with the data
Results in 128 bits that represent only 1 bit of data
The original 9600 bps of conversation has been
multiplied to 1.23 Mbps
Code are designed to never interfere with any other
codes to a very high probability
April 19, 2015 20
21. April 19, 2015 21
Spread Spectrum Multiple Access
Technology
24. Users near the base station are received with high
power
Users far from the base station are received with low
power
For a path loss exponent of 4 and a cell size of 1km
P2/P1=(1000/50)^4= 52db
Nearby users will completely swamp far away users
Solution: Power Control
April 19, 2015 24
26. Sprint
Verizon
U.S Cellular
These companies use CDMA to authenticate there
phones on home networks. There is no Sim Card used
like GSM where switching phones is easy.
April 19, 2015 26
28. Graceful degradation as traffic increases
Strong against interference
CDMA allows efficient use of spectrum by putting all
users on top of each other in time and frequency
CDMA is used as the access method in many mobile
phone standards such as cdmaOne, CDMA2000 (the
3G evolution of cdmaOne), and WCDMA (the 3G
standard used by GSM carriers), which are often
referred to as simply CDMA
April 19, 2015 28
29. CDMA becomes more important in radio
communication systems because it is superior to the
FDMA and TDMA cellular systems
The military can use this because it is based on the
spread spectrum technique
Channel access method used by various radio
communication technologies
April 19, 2015 29
30. 1.http://en.wikipedia.org/wiki/Code_division_multiple_access
2. K.S. Gilhousen et al, “On the capacity of a cellular CDMA
system,'' IEEE Trans. on Vehicular Tech., May 1991.
3.http://www.math.niu.edu/~beachy/courses/523/cdma_lec.pdf
4. http://www.pcmag.com/article2/0,2817,2407896,00.asp
5. http://www.cdg.org/technology/cdma.asp
April 19, 2015 30