Digital Communication Systems Standards Overview; The W-Cdma Communication System - Agilent Technologies ESA-E Series User And Programming Manual

Understanding Modulation Analysis

Digital Communication Systems Standards Overview

Digital Communication Systems Standards Overview

The W-CDMA Communication System

Wideband code division multiple access (W-CDMA) is the first of the most
popular air interface technologies for the third generation RF cellular
communication systems. In this system, the cells operate asynchronously. Hence, it
makes the mobile synchronization more complex, but offers the advantage of
flexibility in placement of the base stations. Both reverse and forward transmitter
power controls are implemented with 0.625 ms intervals. W-CDMA is a direct
sequence spread spectrum digital communications technique that supports a wider
RF bandwidth at 5 MHz.
The CDMA2000 Communication System
Code division multiple access 2000 (cdma2000) is the second of the two most
popular wideband air interface technologies for the third generation RF cellular
communication systems. This system relies on the Global Positioning System
(GPS) for intercell synchronization. Both reverse and forward transmitter power
controls are implemented with 1.25 ms intervals. cdma2000 is a direct sequence
spread-spectrum digital communications technique that supports a wider
RF bandwidth at 1.25 MHz.
W-CDMA and cdma2000 Advantages
The main advantages of cdma2000 and W-CDMA over other types of
communication schemes are:
• Greater capacity
• Immunity to signal loss and degradation due to high-level broadband
interference, multipath scattering and fading
• Power consumption of mobile stations is strictly minimized by base station and
mobile controls
• Supports variable data rates up to 144 kbits/second for mobile (vehicular) data
rate, up to 384 kbits/second for portable (pedestrian) data rate, and up to
2 Mbits/second for fixed installations
• Provides increased security
W-CDMA and cdma2000 uses correlative codes to distinguish one user from
another. Frequency division is still used, as is done with Frequency Division
Multiple Access (FDMA) and Time Division Multiple Access (TDMA).
Frequency division is used in a much larger bandwidth such as 1.25 MHz or
greater (for cdma 2000) and 5 MHz or greater (for W-CDMA). For W-CDMA, an
initial baseband data rate is spread to a transmitted data rate of 3.840 Mcps, which
is also called chip rate or spread data rate. W-CDMA and cdma2000 both realize
increased capacity from 1:1 frequency reuse and sectored cells. The capacity limit
is soft. That is, capacity can be increased with some degradation of the error rate or
voice quality.
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