Wireless wideband communication systems provide high data transmission rates suitable for fast mobile Internet access. Factors such as bandwidth efficiencies and cell-to-cell interference are primarily determined by the modulation technique used for data transfer between the network base station and the subscribers' mobile devices. In general, higher order modulation schemes such as 64-QAM offers a higher bandwidth efficiency at the expense of more complex receiver structure requirements and higher cell-to-cell interference that impacts frequency reuse while simple techniques such as QPSK offers better BER but lower data rate. This paper presents a modulation scheme for multicast distribution across an area of up to several kilometers providing services for portable network access devices such as PDAs and notebook computers. The system improves coverage under different weather conditions. Our study shows that 16-QAM offers the best compromise for high speed multimedia services.