Since system capacity is one of the most important parameters to consider in design of wireless systems, in this project a thorough investigation has been carried out about the integrated voice and data transmission system in order to increase its capacity. The work has been extended by examining the effectiveness of changing rate adaptation for various data rates and the effectiveness of changing modulation techniques. Since forward error correction code (FECC) can improve system capacity for fading channel in similar way as rate adaptation, rate adaptation and FECC have been compared for the effect on the system capacity. BCH code of different code rates are investigated in detail to improve the system performance during fading. The obtained results have been compared with those of the power adaptation system alone for both voice and data under the same conditions. After that the capacity of the combined rate and power adaptation system under different conditions and with system using FECC will be discussed. Finally the main points are summarized in the conclusion. The results show that, the system using combined adaptations provides higher capacity than that using power adaptation alone for both voice and data. This is because rate adaptation provides power gain to data users that produce less interference to other users leading to capacity increase. The results also indicate that the capacity in both schemes (combined and power adaptation) increases as modulation techniques change from BPSK to MPSK for small modulation level (M). However, these capacities increase as the modulation level (M) decreases. The system using 4PSK provides highest capacity. Moreover, using BCH Code for both schemes will extend the system capacity. Therefore, the capacity can be enhanced greatly by choosing the right combination of modulation level (M) and code rate (I). I is clear from the results that systems using 4PSK with code rate of r=0.286 and r=0.5 provide the highest capacity.