In today's scenario mobile phones are not used only for messaging and talking, now the people use mobiles also to access Internet. For that the authors need higher data rates. Mobiles use wireless communication channel, which is very fast varying channel. To increase the data rate they have to utilize the full channel based on the channel condition. For that they have to estimate the channel condition and based on that they have to vary the data rate so that their communication system performance parameters (bit error rate, throughput) do not change beyond the accepted level. To increase the data rate they are also using the multi-carrier CDMA system in conjunction with the above described adaptive modulation.