This work proposes model design in securing the IEEE 802.16 WiMAX Physical and MAC layer, using Orthogonal Frequency Division Multiplexing (OFDM) and STBC model. Typically, it addresses the physical and MAC layer security concerns, using a Space Time Block Coding (STBC), link encryption, and Message Authentication Code (MAC) technique. The model conforms to Multiple Input Single Output (MISO) fading channels which model two or more transmitters and a receiver in multiuser environment. The two fading link parameters are assumed to be same. Channel estimate for each link, in combination to the received signal is based on Reed Solomon Convolution Coding (RS-CC) algorithm, which occurs as a result of the Space-Time Diversity Combiner block. In addition the model explore using communication blocks to measure and display bit error rate after encryption algorithm and Message Authentication Code (MAC) have been adapted in Forward Error Correction (FEC) mode. Channel SNR and estimation in rate ID is applied. The final results shows authentication, and the Reed-Solomon decoding of the final information or data received.