TDMA provides many users to access the same frequency channel but different time slots.
In FDMA provides many users can be used different frequency channel but at same time. circuit board
When we see WDMA, we usually think of frequency division multiple access, which is a protocol for use on optical transmission systems. FDMA is frequency division multipleaccess, and we see that as a protocol for RF electromagnetic transmission systems, particularly in cellular phone networks operating in microwave frequencies.
By concept both are same, but the terminology depends on the range of frequency of the electromagnetic wave to be used for multiplexing. In the RF range it is termed as FDM whereas in the optical domain of frequency the other one.
Both these techniques allow multiple transmitters to transmit simultaneously over a single communication channel. In FDMA, available bandwidth is divided into different frequency ranges and each transmitter is assigned a specific frequency range.
In CDMA, a special signal called carrier is used to encode the data signal. In this case, each transmitter uses a distinguished carrier signal to form the resultant signal.
tdma and fdma
In CDMA all the stations can sends data simultaneously. But in FDMA only one channel occupies the entire bandwidth of the link so each channel can be assigned to only one user at a time. So CDMA is better than FDMA.
The basic difference between OFDMA and SC-FDMA is that, there there is an additional block of N point DFT before the sub-channel mapping in SC-FDMA. This will effectively reduce the PAPR, thus the power amplifier will have a lesser linear range in SC-FDMA when compared with OFDMA
The basic difference between fdm and fdma is that fdm is used in wired system where as fdma is used in wireless communication.
1G is based on frequency modulation,analog technology,TDMA 2G is based on digital technology,FDMA 3G is based on CDMA which is a faster internet access source
Hand off
da-fdma
- CDMA800 (low band) is at freq 800MHz whereas CDMA1900 (high band) is at 1900MHz. - TX power of CDMA800 is lower than the CDMA1900.
Unlocking usually refers to a GSM network and flashing usually refers to CDMA networks. When you unlock a phone you can use it on any carrier that uses the same radio (GSM/CDMA), or if you have a world phone, either a GSM or CDMA. Flashing the phone just allows you to use one specific CDMA carrier.
The Nexus S 4G is a CDMA phone and the Nexus S is a GSM Phone. This is the basic difference between these two phones. Most of the remaining configurations are same.
A frequency-division multiple access system (FDMA) is much less sensitive to near-far problems than code-division multiple access systems (CDMA). A FDMA receiver must select signals from a desired transmitter tuned to one frequency, and block signals from transmitters tuned to other frequencies -- this is fairly easy and low-cost to do with standard bandpass filters, even when the near-far problem causes undesired transmitters to sound much louder than the desired transmitter, as long as adequate "guard bands" separate one transmitter from the next. A DSS CDMA receiver must select signals from a desired transmitter and block signals from other transmitters, even when they are all transmitting on the same frequencies at the same time -- this cannot be done with standard bandpass filters. The techniques DSS CDMA receivers use to select the desired signals are much more sensitive to near-far problems.
In FDMA all users share the satellite simultaneously but each user transmits at single frequency.FDMA can be used with both analog and digital signal.FDMA requires high-performing filters in the radio hardware, in contrast to TDMA and CDMA