Hybrid Power Saving Mechanism for VoIP Services with Silence Suppression in IEEE e Systems Hyun-Ho Choi, Jung-Ryun Lee, and Dong-Ho Cho IEEE Communications Letters Volume 11, Issue 5, May 2007 Page(s):

Outline Introduction Proposed Hybrid Power Saving Mechanism Numerical Analysis Simulation Results Conclusion

Introduction IEEE e (mobile WiMAX) is targeting for Mobile Subscriber Stations (MSSs) To efficiently manage energy in IEEE e systems  Sleep-mode operation

Power saving classes (PSCs) PSC I is used for nonreal-time traffic with bursty behavior PSC II is designed for real-time traffic, such as VoIP services Enhanced voice codecs, can use a silence suppression scheme It is known that silent periods occupy about 60 percent of the total duration of a VoIP call

The overview of the IEEE e power management (PSC I) 2 n until reach its T max Fixed size

The overview of the IEEE e power management (PSC II) BS MSs L T k-1 Sleep mode LLL Fixed length

When some data to transmit in IEEE e sleep mode BS MSs L TkTk a SDU want to transmit MOB-TRF-IND L T k-1 awake mode Data BS MSs TkTk a SDU want to transmit L MOB-TRF-IND T k-1 awake mode Data Request Response delay SDU transmission interarrival time T I

Hybrid Power Saving Mechanism Silence Insertion Descriptor (SID) frame

Sleep Interval PSC I PSC II  The MS sleeps during a sleep interval with fixed size T S T i : the length of the i-th sleep interval T L : listening interval with fixed size T max : a maximum sleep cycle T P : a minimum sleep cycle

Numerical Analysis Brady proposed a general six-state model that provides good statistical analysis of two- way conversation 19%

Numerical Analysis Each MAC SDU is assumed to arrive at an MSS with Poisson process with rate λ (MAC SDUs per unit of time)  1/λ, equal to T I M: the value of k when T k = T max

Numerical Analysis (cont.) The probability that there is a arriving SDU during t At least one arriving MAC SDU in w i sleep cycle

Numerical Analysis (cont.) The average duration of PSC I The average buffering delay

Energy Consumption The energy consumption per unit time in PSC I The energy consumption per unit time in PSC II

Simulation Results the frame length is 5 ms T P =4 frames, T S =3 frames, T L =1 frame, E S =0.045 W, E L =1.5 W VoIP end-to-end delay requirement: 270 ms delay constraint: 88 ms We change the value of T max from 4 to 1024

Energy consumption and drop probability vs. T max

Conclusion the proposed HPSM can result  energy being saved by up to 20%,  maintaining a low drop probability of less than 1.9% The results can be used to select an appropriate value of T max according to the various delay constraints to current IEEE e systems.

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