1. A speech or signal coding method for encoding a signal, the coding method comprising: coding an excitation or a fixed codebook excitation wherein the excitation or the fixed codebook excitation includes plurality of pulse pairs called a Dual Pulse Model; wherein said Dual Pulse Model features two pulses of each pair of pulses that are always adjacent to each other with a distance of 1, the two pulses of each pair of pulses have different magnitudes and signs and only one position index for each pair of pulses are transmitted from encoder to decoder.