A comparison of wi-fi and wimax with case studies - Florida State ...
A comparison of wi-fi and wimax with case studies - Florida State ...
A comparison of wi-fi and wimax with case studies - Florida State ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
the uplink b<strong>and</strong><strong>wi</strong>dth periodically for MS <strong>and</strong> <strong>wi</strong>th this feature ertPS can coordinate data services<br />
which the b<strong>and</strong><strong>wi</strong>dth requirements change <strong>wi</strong>th time. [50][121][127][128]<br />
4.3.2.2.2. Power-saving<br />
How to extend the battery life is a very important issue <strong>of</strong> mobility. Therefore power<br />
management is a fundamental requirement <strong>of</strong> a mobile <strong>wi</strong>reless network. The IEEE 802.16e-<br />
2005 de<strong>fi</strong>nes two modes to operate power saving. [50][129] – [132]<br />
4.3.2.2.2.1. Sleep Mode<br />
This mode is an optional mode <strong>of</strong> WiMax power management. The MS is de<strong>fi</strong>ned by two<br />
statuses, sleep <strong>wi</strong>ndow <strong>and</strong> listen <strong>wi</strong>ndow. The sleep <strong>wi</strong>ndow is de<strong>fi</strong>ned as when a MS<br />
temporarily disconnects to the BS for a predetermined period <strong>of</strong> time. The listen <strong>wi</strong>ndow is<br />
follo<strong>wi</strong>ng the sleep <strong>wi</strong>ndow, during which the MS reconnects to the BS. The lengths <strong>of</strong> each<br />
sleep <strong>and</strong> listen <strong>wi</strong>ndow depend on the power-saving classes <strong>and</strong> is negotiated between the MS<br />
<strong>and</strong> BS. When the MS is in sleep <strong>wi</strong>ndow, this period is called unavailability interval. During the<br />
unavailability interval, the MS cannot receive any DL transmission <strong>and</strong> send any UL<br />
transmission. During the availability interval when the MS is in listen <strong>wi</strong>ndow, the MS can<br />
receive DL transmission <strong>and</strong> send UL transmission as normal. BS <strong>wi</strong>ll not send any DL<br />
transmission to MS when it is in sleep <strong>wi</strong>ndow, therefore the MS can turn <strong>of</strong>f one or more<br />
physical components for saving power. The BS buffers the SDUs (Service Data Units) for MS<br />
<strong>and</strong> transmits them later to the MS during availability interval.<br />
For different services, there are three power-saving classes:<br />
1. Power-saving class type 1<br />
Class type 1 is used for BE or nrtPS connections. In this class, the listen <strong>wi</strong>ndow size is<br />
<strong>fi</strong>xed <strong>and</strong> followed by a sleep <strong>wi</strong>ndow. Each sleep <strong>wi</strong>ndow size is t<strong>wi</strong>ce the size <strong>of</strong> the previous<br />
sleep <strong>wi</strong>ndow, but not bigger than the <strong>fi</strong>nal sleep <strong>wi</strong>ndow size. The size <strong>of</strong> the initial sleep<br />
<strong>wi</strong>ndow <strong>and</strong> the <strong>fi</strong>nal sleep <strong>wi</strong>ndow are noti<strong>fi</strong>ed to the MS by the BS before the power-saving<br />
class type 1 begins. During the sleep mode, the BS can reset the <strong>wi</strong>ndow size to the initial sleep<br />
<strong>wi</strong>ndow size at any time. For UL allocations, the reset process happens under the request from<br />
the MS. And for DL allocations, it happens when the BS <strong>fi</strong>nds out that the number <strong>of</strong> listen<br />
<strong>wi</strong>ndow is not enough for the traf<strong>fi</strong>c.<br />
2. Power-saving class type 2<br />
57
Change language