Contents
How do we generate CDMA signals?
Techniques generally used are direct sequence spread spectrum modulation (DS-CDMA), frequency hopping or mixed CDMA detection (JDCDMA). Here, a signal is generated which extends over a wide bandwidth. A code called spreading code is used to perform this action.
How channel capacity of CDMA system is computed?
CDMA Capacity Capacity in CDMA is soft, CDMA has all users on each frequency and users are separated by code. This means, CDMA operates in the presence of noise and interference. In addition, neighboring cells use the same frequencies, which means no re-use.
What is the role of a pseudorandom sequence generator in the working of the CDMA protocol?
Pseudo-random or pseudo-noise sequences are used in asynchronous CDMA systems. This CDMA system offers a key advantage in the flexible allocation of resources. Asynchronous CDMA is best suited to a mobile network wherein large numbers of transmitters produce relatively small amount of traffic at irregular intervals.
What type of receiver is used in CDMA?
RAKE receiver
Abstract—RAKE receiver is used in CDMA-based (Code Division Multiple Access) systems and can combine multipath components, which are time-delayed versions of the original signal transmission. Combining is done in order to improve the signal to noise ration at the receiver.
What are the types of CDMA?
In general, CDMA belongs to two basic categories: synchronous (orthogonal codes) and asynchronous (pseudorandom codes).
What frequency does CDMA use?
Cell frequencies by provider
| Provider | 3G Frequency | 4G Frequency |
|---|---|---|
| AT | GSM/UMTS/HSPA+ 1900 MHz, 850 MHz | 1900, 1700/2100, 850, 700 2300 |
| Sprint | CDMA 1900 MHz, 800 MHz | 1900, 850, 2500 |
| T-Mobile | GSM/UMTS/HSPA+ 1900 MHz, 1700/2100 MHz | 1900, 1700/2100 700, 600 |
| Verizon | CDMA 850 MHz, 1900 MHz | 1900, 1700/2100, 850, 700 |
What is the nominal frequency of a CDMA radio?
Nominal value of 5 MHz that can be adjusted. 200 kHz (center frequency must be a multiple of 200 kHz). Nominal value of 190 MHz. This value can be either fixed or variable (minimum of 134.8 and maximum of 245.2 MHz).
How to find the maximum sensitivity of a receiver?
To find the maximum allowable receiver noise figure, which meets the minimum specified sensitivity simply solve for NF max, using the receiver sensitivity equation. Step 1: The maximum specified RF input signal at desired sensitivity is -121dBm for WCDMA.
How to find the average modulating signal power?
The average modulating signal power is defined as S = E b / T, where E b is the energy in the bit interval in W-s and T is the bit time interval in seconds. where KTF represents the noise power (N o) in a 1-bit interval. S out / N out = E b /N o × 1 / PG.
What is the sensitivity of a WCDMA signal?
Step 1: The maximum specified RF input signal at desired sensitivity is -121dBm for WCDMA. Step 2: Subtract the E b /N o value of 5dB, which yields the maximum allowable noise level in the user bandwidth (12.2kHz) of -126dBm.