EDGE modulation

EDGE modulation

To get a transfer speed higher than GPRS using GMSK modulation (Gausian Minimum Shift Keying), EDGE uses a different modulation technique with GPRS is 8PSK (8-Phase Shif Keying). Figure below shows the visualization of the GMSK modulation on the GPRS and EDGE 8PSSK pasa depicted a diagram of I / Q, where I is the real axis and Q is the imaginary axis.

By using 8PSK modulation, a symbol is encoded using 3 bits, whereas the symbol coded GMSK with a 1 bit. Because GMSK and 8PSK symbols have the same level, ie for 270 ksimbol / s, the overall level of the 8PSK modulation will be 3 times larger than GMSK, which is for 810 kb / s.

Based on the above explanations, the distance between the 8PSK symbol is shorter than the distance between the GMSK symbols, because the ad 8PSK symbol sedengkan at 8 GMSK there are only 2 symbols. Shorter distances between the symbols of the signal lead between one symbol with another symbol is more difficult to distinguish. So the possibility of greater error.

On the radio signal conditions is quite good, the difference between the symbol distance is less effect on the quality of data sent. At the time of the radio signal conditions are bad, it would require the addition of extra bits that will be used as a correction of errors, so that any data received can be improved. So that the EDGE data quality is not inferior to the quality of data on GPRS using MPSK. After all, EDGE is also used in MPSK modulation is used in CS1 to CS4 - his, and also in the EDGE is the process of "adjustment package" that can change the type of CS used in case of errors in data sent.