Hybrid Power Saving Mechanism for VoIP Services with Silence Suppression in IEEE 802.16e Systems

Hyun-Ho Choi, Jung-Ryun Lee, and Dong-Ho Cho

IEEE Communications LettersVolume 11, Issue 5, May 2007 Page(s):455 - 457

Outline

Introduction Proposed Hybrid Power Saving Mechanism Numerical Analysis Simulation Results Conclusion

Introduction

IEEE 802.16e (mobile WiMAX) is targeting for Mobile Subscriber Stations (MSSs)

To efficiently manage energy in IEEE 802.16e 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 802.16e power management (PSC I)

2n until reach its TmaxFixed size

The overview of the IEEE 802.16e power management (PSC II)

BS

MSsL

Tk-1

Sleep mode

L L L

Fixed length

When some data to transmit in IEEE 802.16e sleep mode

BS

MSsL

Tk

a SDU want to transmit

MO

B-T

RF

-

IND

L

MO

B-T

RF

-

IND

Tk-1

awake mode

Dat

a Dat

a Dat

a

BS

MSs

Tk

a SDU want to transmit

LM

OB

-TR

F-

IND

Tk-1

awake mode

Dat

a Dat

a Dat

a Reque

st

Response

delay

SDU transmission

interarrival time TI

Hybrid Power Saving Mechanism

Silence Insertion Descriptor (SID) frame

Sleep Interval

PSC I

PSC II The MS sleeps during a sleep interval with fixed si

ze TS

Ti: the length of the i-th sleep interval

TL: listening interval with fixed size

Tmax: a maximum sleep cycle TP: 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 TI

M: the value of k when Tk = Tmax

Numerical Analysis (cont.)

The probability that there is a arriving SDU during t

At least one arriving MAC SDU in wi 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 TP =4 frames, TS=3 frames, TL=1 frame, ES=0.

045 W, EL=1.5 W VoIP end-to-end delay requirement: 270 ms delay constraint: 88 ms We change the value of Tmax from 4 to 1024

Energy consumption and drop probability vs. Tmax

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 appropri

ate value of Tmax according to the various delay constraints to current IEEE 802.16e systems.

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