Merits(Advantages) of CDMA Cellular System
CDMA cellular system has many merits and demerits as outlined below.
Following are merits (advantages) of CDMA system:
• As the transmitted signal spread across larger bandwidth, CDMA system is robust against
frequency dependent impairments such as fading and noisy bursts. This is referred as frequency diversity.
• CDMA uses different chipping codes for each users. This codes exhibit low cross correlation and
low auto correlation. Hence signal delayed by more than one chip period, does not interfere with the main dominant signal
compare
to other multipath environments.
Hence CDMA is resistant to multipath effect.
• Privacy is inherent in CDMA system due to use of unique codes used by mobile users.
• In FDMA and TDMA only fixed number of users can access the system simultaneously.
In CDMA more users can access the system at the same time.
Demerits(Disadvantages) of CDMA Cellular System
Following are demerits (disadvantages) of CDMA system:
• To have multiple users aligned on chip boundaries, mobile users need to be synchronized.
Hence if users are not synchronized than spreading sequences are not orthogonal and they will have some sort of
cross correlation.
• Signals closer to the base station will have less attenuation compare to
farthest mobile subscriber. Due to this transmissions from farthest subscriber is difficult to recover due to
lack of complete
orthogonality.
• Soft handoff in CDMA requires mobile to establish connection with new cell before it
releases connection from old cell. This is more complex compare to hard handoff.
WCDMA UMTS RELATED LINKS
UMTS Network Architecture
UMTS Protocol Stack
UMTS Logical, Transport and physical channels
UMTS Spreading,scrambling and modulation
WCDMA MO CS call
WCDMA PS Call
CDMA vs GSM
WCDMA Compressed mode