Commercial WiMAX Based VoIP Priority Scheduling Research And Improvement

With the IP-based technology to a variety of application, especially VOIP/FOIP technology proposed, the data communications network gradually integrated into the traditional voice/fax business. In wireless communications, WiMAX technology which based on IEEE 802.16 became a hot commercial spot because of its unique advantages of less initial investment, high transfer rate and wide coverage. Especially, so called mobile WiMAX, IEEE 802.16e version has been widely used. Because it can upgrade to IEEE 802.16m which has full competition of LTE-Advanced easily through software update.Commercial WiMAX operators (Axtel, Clearwire, etc) who providing VoIP/FoIP functions always use nrtPS service flow carrying SIP signaling of VoIP. The wireless bandwidth waste and admission control kick-in became more seriously since the number of WiMAX user grown up. And this impacted the number of user who can entry WiMAX network and also of the quality. Meanwhile, the packet scheduling algorithm and scheduling order needs to be changed in order to adapt to evolving customer needs. The major work and research of this paper is as follows:Firstly, proposed to use high-priority BE service flow to carry the SIP signaling to increase channel utilization. Sending SIP signaling over nrtPS flow requires base station to reserve a certain bandwidth. The bandwidth would never be released even there is no VoIP Call at all. SIP signaling is bursty, so to let SIP signaling work correctly the operator has to reserve more than what is really required for SIP. Therefore, sending SIP signaling over nrtPS flow would waste wireless bandwidth resources extremely. This paper proposed to use high-priority BE flow carrying SIP signaling, in order to reduce the invalid wireless channel occupation effectively.Secondly, improved and implemented MAC layer scheduling algorithm. The existing MAC layer scheduling order is to schedule non-BE service flow first, thus the SIP signaling over BE may be discarded, leading to phone calls failed as a result. Hence improvement is needed for scheduling order and algorithm. This paper proposed to let part of nrtPS/rtPS whose throughput less than MRR (Minimum Required Rate) have competition with BE service flow based on priority to ensure high priority BE flow can be transferred reliably.At last, proposed and implemented traffic priority multiplier parameter and traffic priority weight. The concept of priority from 802.16e is simple and can not fit diverse business configuration based on priority. This paper proposed to use traffic priority multiplier (TPM) parameter with the traffic priority, so that operators can achieve a more flexible data and voice services segment via setting these two parameters.