29-09-2010, 01:36 PM
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This article is presented by:
Malathy Elumalai
Advance topics in Communication
Spring 2010
This article is presented by:
Malathy Elumalai
Advance topics in Communication
Spring 2010
COMPARISON OF CDMA AND TDMA SYSTEMS
ABSTRACT
In this report two candidates for high capacity cellular systems are simulated and analyzed, one CDMA and one TDMA system. Simulations of the CDMA example indicate a high sensitivity to variations in certain system parameters. The TDMA example is a GSM system using random frequency hopping and operating without frequency planning. The outage probabilities of both the systems that have been compared in the reference IEEE paper are also simulated in this project.
An important question when designing and standardizing cellular systems is the
Selection of the multiple access schemes. Multiple Access methods address the problem of how many users can share the same spectrum resources in an efficient manner. We distinguish between them as follows
• Multiple access within one cell, i.e., a fixed assignment of resources in time or bandwidth to specific users
• Random access, i.e., a dynamic assignment of spectrum resources in time or bandwidth to users, according to their needs
• Frequency reuse, i.e., assignment of spectrum resources considering the location of users and the attenuation of radio signals that travel over sufficiently large distances
Examples of multiple access schemes are FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access), and CDMA (Code Division Multiple Access). All three principles allow
Multiple users to share the same physical channel. But the two competing technologies differ in the way user sharing the common resource. TDMA allows the users to share the same frequency channel by dividing the signal into different time slots. Each user takes turn in a round robin fashion for transmitting and receiving over the channel. CDMA uses a spread spectrum technology that is it spreads the information contained in a particular signal of interest over a much greater bandwidth than the original signal. In TDMA users can only transmit in their respective time slot. Unlike TDMA, in CDMA several users can transmit over the channel at the same time.
INTRODUCTION
In today’s world cell phone have become the single greatest tool in day today life. It has become a necessity that business associates should be able to communicate on the go. That’s why it has become so important to make choices in choosing which handheld device one should go for. A handheld device is selected according to its features and benefits, like does it provide access to internet and email or does it look slick and more.An important question when designing and standardizing cellular systems is the
Selection of the multiple access schemes. Multiple Access methods address the problem of how many users can share the same spectrum resources in an efficient manner. We distinguish between them as follows
• Multiple access within one cell, i.e., a fixed assignment of resources in time or bandwidth to specific users
• Random access, i.e., a dynamic assignment of spectrum resources in time or bandwidth to users, according to their needs
• Frequency reuse, i.e., assignment of spectrum resources considering the location of users and the attenuation of radio signals that travel over sufficiently large distances
Examples of multiple access schemes are FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access), and CDMA (Code Division Multiple Access). All three principles allow
Multiple users to share the same physical channel. But the two competing technologies differ in the way user sharing the common resource. TDMA allows the users to share the same frequency channel by dividing the signal into different time slots. Each user takes turn in a round robin fashion for transmitting and receiving over the channel. CDMA uses a spread spectrum technology that is it spreads the information contained in a particular signal of interest over a much greater bandwidth than the original signal. In TDMA users can only transmit in their respective time slot. Unlike TDMA, in CDMA several users can transmit over the channel at the same time.
