Digital Cellular Systems (CDMA)

1. Voice Activities Cycles. CDMA is the only technique that successfully takes advantage of the nature of human conversation. The human voice activity cycle is 35%, the rest of the time we are listening. In CDMA all the users are sharing one radio channel. Because each channel user has active just 35% of the entire cycle, all others benefit with less interference in a single CDMA radio channel. So, the mutual interference is in a nice-free way, reduced by 65%; and thus, the channel capacity is increased about three times.

2. No Equalizer Needed . When the transmission rate is much higher than 10kb/s in both FDMA and TDMA, an equalizer is required. On the other hand, CDMA only needs a correlator, which is cheaper than the equalizer.

3. No Hard Handoff. In CDMA, every cell uses the same radio, the only difference is the code sequences. This feature avoids handoff from one freceuncy to another while moving from one cell to another.

4. No Guard Time in CDMA . TDMA requires the use of guard time between time slots. Of course, the guard time does occupy the time period for certain bits. This "waste" of bits does not exists in CDMA, because guard time is not needed in CDMA technique

5. Less Fading . Less fading is observed in the wide-band signal while propagating in a mobile ratio environment.

6. Capacity Advantage . Given concrete parameters, CDMA can have four times the TDMA radio capacity; and twenty times FDMA radio capacity per channel/cell.

7. No frequency management or assignment needed. In both, TDMA and FDMA, the frequency management is always a critical task to carry out. Since there is only one channel in CDMA, no frequency management is needed.

8. Soft Capacity. Because in CDMA all the traffic channels share a single CDMA radio channel, we can add one additional user so the voice quality is just slightly degraded.

9. Coexistence. Both systems, analog and CDMA can operate in two different spectras, with no interference at all.

10. For Microcell and in-building Systems: CDMA is a natural wafeform suitable for microcell and in-building.