brid ARQ schemes may by classified depending on the content of subsequent re-trans- missions as follows [4,15]: 1. Type I HARQ: in type I HARQ schemes, the same data packet is transmitted in all the re- transmissions. Soft combining may be used to improve the reliability. In this type of HARQ, also referred to as Chase Combining (CC), the blocks of data, along with the CRC code, are encoded using FEC encoder before transmission. If the receiver is unable to correctly decode the data block, a re-transmission is requested. When a re-transmitted coded block is received, it is combined with the previously received block corresponding to the same information bits (using, for example, a maximal ratio combining method) and fed to the decoder. Since each re-transmission is an identical replica of the original transmission, the received Eb/No, i.e., the energy per information bit divided by the noise spectral power density, increases for each re-transmission, improving the likelihood of correct decoding. In chase combining HARQ, the redundancy version of the encoded bits is not changed from one transmission to the next; therefore, the puncturing pattern remains the same. The receiver uses the current and all previous HARQ transmissions of the data block in order to decode the information bits. The process continues until either the information bits are correctly decoded and pass the CRC test, or the maximum number of HARQ re-transmissions is reached. When the maximum number of re-transmissions is reached, the MAC layer resets the process and continues with fresh transmission of the same data block. The chase combining method is used as the mandatory HARQ scheme for data transmissions in Release 1.0 of the mobile WiMAX systems, where an N-process stop-and-wait ARQ along with FEC coding are exploited [8]. A number of parallel channels for HARQ can help improve the throughput as one process is awaiting an acknowledgement; another process can utilize the channel and transmit sub-packets. Figure 7-6 illustrates the operation o