Tolong jelaskan mengenai Physical layer dari IS-95 dalam bahasa sunda

IS-95 defines the transmission of signals in both the forward (network-to-mobile) and reverse (mobile-to-network) directions.

In the forward direction, radio signals are transmitted by base stations (BTS's). Every BTS is synchronized with a GPS receiver so transmissions are tightly controlled in time. All forward transmissions are QPSK with a chip rate of 1,228,800 per second. éach signal is spréad with a Walsh code of length 64 and a pseudo-random noise code (PN code) of length , yielding a PN roll-over period of  ms.

For the reverse direction, radio signals are transmitted by the mobile. Reverse link transmissions are OQPSK in order to operate in the optimal range of the mobile's power amplifier. Like the forward link, the chip rate is 1,228,800 per second and signals are spréad with Walsh codes and the pseudo-random noise code, which is also known as a Short Code.