| Attributed to its special advantages such as low-cost and high mobility, M-WiMAX VoIP services have gain a rapid development and wide application at both home and abroad in recent years. However, M-WiMAX VoIP technology still has problems with its QoS (Quality of Service), and the DTX/CNG technology used in VoIP CODECs can effectively improve the QoS of M-WiMAX VoIP. To ensure full support for M-WiMAX VoIP applications, this paper studied the uplink scheduling algorithms for several major DTX/CNG VoIP CODECs.Firstly, the features and key parameters of six major standards for DTX/CNG VoIP CODECs are studied, and the problems of the traditional algorithms UGS, rtPS and ertPS defined in IEEE 802.16e when applied to the uplink scheduling of DTX/CNG VoIP CODECs are analyzed. Then, considering the changeable data frame duration of DTX/CNG VoIP CODECs, as well as the variable QoS requirements of multi-mode CODECs, the influences of the key parameter "bandwidth request/grant interval" in scheduling process and DSC process for information transaction on the performances of the algorithms are studied. Six more flexible and effective uplink scheduling algorithms are designed for the aforementioned CODECs respectively, based on the improvement of ertPS. After that, system model and performance indicators are established. For numerical validation, simulation experiment has been made on the designed algorithm and three traditional algorithms, using Matlab as our computing tool. Finally, through the comparative analysis of simulation results, we proved the efficiency and superiority of our proposed algorithm. |
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