Electrical computers and digital processing systems: support – Computer power control
Reexamination Certificate
2000-03-17
2003-09-16
Lee, Thomas (Department: 2185)
Electrical computers and digital processing systems: support
Computer power control
C713S320000, C370S328000
Reexamination Certificate
active
06622251
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of wireless Local Area Network (LAN) communications, and in particular to establishment and coordination of mobile terminal sleep phases within the LAN.
BACKGROUND OF THE INVENTION
A new forthcoming standard for wireless LAN services having high throughput, ETSI HIPERLAN Type 2, promises to open new opportunities for both existing applications and new applications. Current versions and approved portions of the proposed ETSI HIPERLAN Type 2 standard are hereby incorporated by reference. HIPERLAN Type 2 LAN networks use a Time Division Duplex (TDD) airlink, meaning that an Access Point (AP) and a Mobile Terminal (MT) in the LAN network both use the same radio frequency to communicate with each other. The AP is connected to a Network (NW) such as an operator's intranet, and the MT will in most cases be a wireless Network Interface Card (NIC) to a personal computer (PC).
FIG. 1
shows an example configuration for an exemplary HIPERLAN Type 2 system, including an AP
104
within a cell
102
. MTs
106
,
108
and
110
are also located within the cell
102
. As shown in
FIG. 1
, the AP
104
can communicate via a wireless TDD airlink
112
with, for example, the MT
110
. Within each cell, an AP for that cell selects the best frequency with which to communicate with one or more MTs within the cell. The AP's frequency selection can be based on, for example, the AP's measurements of interference at other frequencies, as well on measurements made by MTs within the cell.
In accordance with the proposed HIPERLAN Type 2 wireless LAN standard, a wireless LAN system includes a Medium Access Control (MAC) layer, which is implemented as a reservation-based MAC layer.
FIG. 2
shows an exemplary MAC data frame
200
having an exemplary MAC frame structure, including a Broadcast Control Channel (BCCH)
202
, a Frame Control Channel (FCCH)
204
, a Downlink Channel (DLCHAN)
206
, an Uplink Channel (ULCHAN)
208
, and a Random Access Channel (RACH)
210
. As shown in
FIG. 2
, the boundary between the DLCHAN
206
and the ULCHAN
208
, as well as the boundary between the ULCHAN
208
and the RACH
210
, can be changed in accordance with traffic requirements. Assuming that the MT
110
has been authenticated and a connection has been established between the MT
110
and the AP
104
, then in order to send Uplink (UL) data via the AP
104
, the MT
110
monitors the BCCH
202
and the FCCH
204
for the occurrence of random access opportunities. The MT
110
can then request uplink resources via the RACH
210
, and the AP
104
will acknowledge the request for uplink resources and start scheduling UL resources in the TDD airlink
112
for use by the MT
110
. In other words, when the MT
110
places a request for uplink resources, a reservation-based access starts.
When the AP
104
receives Downlink (DL) data from the network (NW) for the MT
110
, the AP
104
either buffers the data and defers transmission of the data to the MT
110
if the MT
110
is sleeping, or transmits the DL data to the MT
110
at the next possible occasion. The AP
104
announces that it has data for the MT
110
(and/or other MT's within the cell
102
) by broadcasting a frame having the format of the frame
200
, with a MAC-ID and a Data Link Control Channel ID (DLCC-ID) of the MT
110
in the FCCH
204
following the BCCH
202
. In this situation, the FCCH
204
also contains the exact location of the data for the MT
110
, in the DLCHAN
206
of the frame
200
. An MT having a MAC-ID can have several DLCC-IDs.
Since MTs are often powered by finite sources such as batteries, the HIPERLAN Type 2 standard provides for a sleep mode for the MTs to conserve energy usage by the MTs. This sleep mode is outlined in FIG.
3
. As shown in
FIG. 3
, at a first step
302
, an MT sends a sleep request signal, which can include a suggestion by the MT as to how long the sleep interval should be, or in other words, the sleep duration, to an AP. The AP accepts the sleep request signal, decides the starting time and the sleep duration, and then in step
304
sends a sleep reservation signal to the MT indicating the starting time at which the MT should enter the sleep mode, and the sleep duration or time the MT should remain asleep before “waking” to monitor the BCCH of a MAC frame from AP for the occurrence of DL data pending for the MT. The sleep duration can be, for example, an arbitrary number of MAC frames. At step
306
the MT enters the sleep mode, and then when the sleep duration expires at step
308
, the MT awakens and monitors the BCCH for indications of DL data pending for the MT. If DL data is pending, the AP will notify the MT via the BCCH and schedule downloading of the DL data to the MT. An alternative is to poll the MT prior to scheduling data to avoid using unnecessary airlink resources, or, for robustness of the sleep concept, the AP can poll the MT prior to sending data to make sure that the MT has changed its sleep state and is prepared to receive data.
In particular, if the MT discerns that the BCCH contains a signal such as a pending data indicator, indicating that downlink data is pending at the AP for an as-yet undetermined MT, then the MT will analyze the content of a Slow Broadcast Channel (SBCH) in the MAC frame for a dedicated wakeup Protocol Data Unit (PDU) directed to the MT. The SBCH location in the MAC frame is given by an Information Element (IE) in the FCCH. In other words, the MT will check further to determine whether it is the MT (or one of the MTs) for which data is pending. If no downlink data is pending for any MT, then the MT returns to the sleep mode for another sleep duration time period, at the end of which it will awaken and repeat the cycle by monitoring the BCCH for a pending data indicator, etc. If no pending data indicator is present, or if the indicator indicates that no downlink data is pending, then the MT will go back to sleep.
FIG. 4
shows the case where an MT analyzes the SBCH in the MAC frame for a dedicated wakeup PDU. As shown in
FIG. 4
, when an MT sleep time expires at time
420
, the MT first examines the BCCH
410
to determine whether the BCCH
410
contains a pending data indicator indicating that the MAC frame
406
contains data for an MT. The pending data indicator does not indicate which MT that the data, if present, is intended for. If a pending data indicator in the BCCH
410
does indicate that the MAC frame
406
contains data for an as yet unspecified MT, then the MT seeks to determine whether the MAC frame
406
contains data for it. It does so by analyzing the FCCH
412
for an indication as to where the SBCH
418
begins in the MAC frame. For example, the FCCH
412
can contain a predefined Information Element (IE)
414
that indicates where the SBCH
418
begins. For example, the predefined IE
414
can be defined to include a MAC-Identification (MAC-ID)=0 and a Downlink Control Channel Identification (DLCC-ID)=0.
The SBCH is located in the DLCHAN of the MAC frame
406
. A DLCHAN can contain, or host, several logical channels, including the SBCH. These channels can include, for example, a User Data Channel (UDC), a DLC Control Channel (DLCH), where DLC stands for “Data Link Control”, a Dedicated Control Channel (DCCH), an In-Band Channel (IBCH), and the Slow Broadcast Channel (SBCH) mentioned above.
The MT then analyzes the SBCH
418
to determine if the SBCH
418
contains any wake-up PDUs that include the MT's MAC-ID. If yes, then the MT knows that downlink data is pending for it, and the MT will stay active to receive the downlink data. If no, then the MT knows that no downlink data is pending for it, and it returns to the sleep mode automatically without announcement to the AP.
In a case where the MT has pending uplink data for transfer to the AP, then the MT can cut short its sleep duration timer or time period and request uplink resources from the AP by, for example, sending an uplink resource request signal on the RACH
210
of a MAC
Almehag Lorens
Ebenhard Johan
Hansson Ulf
Lindskog Jan
Malmgren Göran
Lee Thomas
Suryawanshi Suresh K
Telefonaktiebolaget LM Ericsson (publ)
LandOfFree
Method to put a mobile terminal into sleep when a frame... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method to put a mobile terminal into sleep when a frame..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method to put a mobile terminal into sleep when a frame... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3084667