Another important aspect is the channel coding to protect the speech and the data from noise and channel errors. You have the block evolutional codes and interleaving is used, soft recession techniques are implemented with very useful application for decoding the error control codes. You have today and in future concatenated codes and turbo codes giving better efficiency.
Similarly, the third important technique is the modulation, which takes whether it is data or voice into the RF domain, but then you require bandwidth efficient modulation techniques like QPSK, GMSK, TCM.
The multiple access plays a very important role because the large number of users have to access the common radio medium and the earlier technique of the FDMA was used in the first generation systems. The second generation systems used the time divisible multiple access, the third generation systems would primarily use CDMA as well as TDMA.
Then, very important considerations on techniques on channel assignment and control have to be developed, fading has to be taken care, which is a big problem, equalisation adaptive or non adaptive has to be brought in and interference reduction with the help of filtering and the antennas itself may be quite useful.
When the mobile moves from one cell to another hand off becomes a very important consideration and useful and efficient hand off algorithms have been worked out. And they now could be quite small and you require other devices like the amplifiers, both the power amplifiers as well the low noise amplifiers. To have a small volume, small weight and compactness of the mobile terminals we should have low power consumption and small batteries. Then networking the wireless communication becomes very important and the capabilities like ISDN has to be included.
