The IS95 standard defined by the TIA (Telecommuniations Industry Association) of USA, and is compatible with the existing frequency plan in the United States for analog cellular phone. Specified bands are 824 MHz - 849 MHz for reverse-link and 869 MHz - 894 MHz for forward-link.
The channels are separated by 45 Mhz. The user speed is 9.6 Kb / s, and widens at channel MCHIP 1.2288 / s. The enlargement process is different for each link. In the forward-link data are encoded with a convolutional code (1 / 2), mixed (interleaved), and spread out a sequence of 64 bits (Walsh functions).
Each mobile is assigned a different sequence. It also provides a pilot channel (code) for each mobile can determine how to act with respect to the base. This channel has more power than all others and provides a consistent basis using mobile phones to demodulate the traffic. It also provides a time reference for the correlation of the code. In the reverse-link another scheme is used as the data can reach the base by very different paths. Data is encoded with a convolutional code (1 / 3). mixed after each block of 6 bits is used as an index to identify a Walsh code. Finally the signal is widened by using codes that are specific to the user and the base.
The power control is performed in steps of 1 dB, and may be in two ways: One is to refer to the power received from the base station. The other is to receive instructions based on the adjustment to be carried out. Finally, it is worth noting that the signal being transmitted is modulated using QPSK filtering technique based on the mobile and QPSK filtered with a displacement of the mobile to the base
