U.S. patent application number 13/912695 was filed with the patent office on 2013-10-17 for power management for multi-carrier transmission.
The applicant listed for this patent is MEDIATEK, INC.. Invention is credited to Yih-Shen Chen, Chung-Hsien Hsu.
Application Number | 20130272183 13/912695 |
Document ID | / |
Family ID | 41796756 |
Filed Date | 2013-10-17 |
United States Patent
Application |
20130272183 |
Kind Code |
A1 |
Chen; Yih-Shen ; et
al. |
October 17, 2013 |
Power Management for Multi-Carrier Transmission
Abstract
A method of power management for a mobile station in a
multi-carrier wireless network is provided. A primary connection
between the mobile station and a serving base station is first
established by performing initial ranging over a primary radio
frequency (RF) carrier. A secondary connection between the mobile
station and the base station is then established by performing
periodic ranging over a secondary RF carrier. To achieve efficient
power management, the mobile station performs Open Loop Power
Control and obtains long-term link measurement (CSI) of the primary
carrier. The mobile station then adjusts carrier-specific
parameters based on the primary carrier CSI. For RF carriers that
convey on-going data traffic, Close Loop Power Control is updated
per RF carrier. When the mobile station enters sleep mode
operation, it receives traffic indication messages on the primary
RF carrier and then dynamically wakes up one or more corresponding
RF carriers for data reception.
Inventors: |
Chen; Yih-Shen; (Hsinchu,
TW) ; Hsu; Chung-Hsien; (Taichung, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MEDIATEK, INC. |
Hsin-Chu |
|
TW |
|
|
Family ID: |
41796756 |
Appl. No.: |
13/912695 |
Filed: |
June 7, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12924196 |
Sep 21, 2010 |
8489152 |
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13912695 |
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12584396 |
Sep 3, 2009 |
8515481 |
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12924196 |
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61094523 |
Sep 5, 2008 |
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61094553 |
Sep 5, 2008 |
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Current U.S.
Class: |
370/311 |
Current CPC
Class: |
H04W 52/10 20130101;
H04W 52/0229 20130101; Y02D 30/70 20200801; H04W 52/06 20130101;
H04W 52/0225 20130101; Y02D 70/24 20180101; H04L 5/0098 20130101;
H04W 52/08 20130101; H04W 52/146 20130101; Y02D 70/23 20180101;
H04W 52/16 20130101; H04L 5/001 20130101; Y02D 70/146 20180101;
H04W 52/34 20130101; Y02D 70/1264 20180101; Y02D 70/25 20180101;
Y02D 70/1262 20180101 |
Class at
Publication: |
370/311 |
International
Class: |
H04W 52/02 20060101
H04W052/02 |
Claims
1. A method of power management for a mobile station in a
multi-carrier wireless network, the method comprising: establishing
a primary connection between the mobile station and a base station
over an activated primary radio frequency (RF) carrier;
establishing a secondary connection between the mobile station and
the base station over an activated secondary RF carrier;
negotiating a set of sleep mode parameters for the primary
connection; receiving a traffic indication message on the activated
primary RF carrier during at least one listening window; and waking
up one or more activated secondary RF carriers for data reception
according to the traffic indication message, wherein the set of
sleep mode parameters for the primary connection is the same as a
set of sleep mode parameters for the secondary connection.
2. The method of claim 1, wherein the set of sleep mode parameters
comprises sleep cycle length, listening window length, and whether
traffic indication is transmitted during each listening window.
3. The method of claim 1, wherein the primary RF carrier is always
activated so that the mobile station uses the primary RF carrier to
execute traffic indication.
4. The method of claim 1, wherein the traffic indication message is
a wakeup indication message that identifies the one or more
activated RF carriers.
5. The method of claim 4, wherein the wakeup indication message has
a bitmap format, and wherein each bit is used to identify the one
or more activated RF carriers.
6. The method of claim 4, wherein the wakeup indication message is
either an independent MAC massage, or part of the traffic
indication message.
7. The method of claim 4, wherein the one or more activated RF
carriers wake up for data reception after receiving the wakeup
indication message plus a wakeup time.
8. The method of claim 7, wherein the waked RF carriers begin
transmission or receptions after the wakeup time.
9. The method of claim 7, wherein the wakeup time is a parameter
exchanged between the mobile station and the base station via
either network entry procedure or sleep mode negotiation
process.
10. A mobile station in a multi-carrier wireless network,
comprising: one or more radio frequency (RF) modules operable over
a primary RF carrier and a secondary RF carrier; and a sleep mode
operation module that negotiates a set of sleep mode parameters
with a base station for the primary RF carrier and thereby
establishes sleep mode operation, wherein the mobile station
receives a wakeup indication message on the primary RF carrier,
wherein at least one of the one or more RF modules are waken up for
data reception according to the wakeup indication message, and
wherein the set of sleep mode parameters for the primary RF carrier
is the same as a set of sleep mode parameters for the secondary RF
carrier.
11. The mobile station of claim 10, wherein the set of sleep mode
parameters comprises sleep cycle length, listening window length,
and whether traffic indication is enabled during each listening
window.
12. The mobile station of claim 10, wherein the primary RF carrier
is always activated so that the mobile station uses the primary RF
carrier to execute wakeup indication.
13. The mobile station of claim 10, wherein the one or more RF
modules are operable over one or more corresponding activated RF
carriers identified by the wakeup indication message from the base
station.
14. The mobile station of claim 13, wherein the wakeup indication
message has a bitmap format, and wherein each bit is used to
identify the one or more activated RF carriers.
15. The mobile station of claim 13, wherein the wakeup indication
message is either an independent MAC massage, or part of the
traffic indication message.
16. The mobile station of claim 13, wherein the one or more RF
modules wake up for data reception after receiving the wakeup
indication message plus a wakeup time.
17. The mobile station of claim 16, wherein the waked RF modules
conduct transmission or reception after the wakeup time.
18. The mobile station of claim 16, wherein the wakeup time is a
parameter exchanged between the mobile station and the base station
via either network entry procedure or sleep mode negotiation
process.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation, and claims priority
under 35 U.S.C. .sctn.120 from nonprovisional U.S. patent
application Ser. No. 12/924,196, entitled "Power Management for
Multi-Carrier Transmission," filed on Sep. 21, 2010, the subject
matter of which is incorporated herein by reference.
[0002] Application Ser. No. 12/924,196, in turn, is a continuation,
and claims priority under 35 U.S.C. .sctn.120 from nonprovisional
U.S. patent application Ser. No. 12/584,396, entitled "Power
Management for Multi-Carrier Transmission," filed on Sep. 3, 2009,
the subject matter of which is incorporated herein by
reference.
[0003] Application Ser. No. 12/584,396, in turn, claims priority
under 35 U.S.C. .sctn.119 from U.S. Provisional Application No.
61/094,523, entitled "Power Control Method for Multi-Carrier
Transmission," filed on Sep. 5, 2008; U.S. Provisional Application
No. 61/094,553, entitled "Sleep Mode Operation Design for
Multi-band Broadband Wireless Access Systems," filed on Sep. 5,
2008, the subject matter of which is incorporated herein by
reference.
TECHNICAL FIELD
[0004] The disclosed embodiments relate generally to power
management, and, more particularly, to power management in
multi-carrier wireless communications systems.
BACKGROUND
[0005] In current wireless communications systems, 5 MHz.about.20
MHz radio bandwidths are typically used for up to 100 Mbps peak
transmission rate. Much higher peak transmission rate is required
for next generation wireless systems. For example, 1 Gbps peak
transmission rate is required by ITU-R for IMT-Advanced systems
such as the 4.sup.th generation ("4G") mobile communications
systems. The current transmission technologies, however, are very
difficult to perform 100 bps/Hz transmission spectrum efficiency.
In the foreseeable next few years, only up to 15 bps/Hz
transmission spectrum efficiency can be anticipated. Therefore,
much wider radio bandwidths (i.e., at least 40 MHz) will be
necessary for next generation wireless communications systems to
achieve 1 Gbps peak transmission rate.
[0006] Orthogonal Frequency Division Multiplexing (OFDM) is an
efficient multiplexing protocol to perform high transmission rate
over frequency selective channel without the disturbance from
inter-carrier interference. There are two typical architectures to
utilize much wider radio bandwidth for OFDM system. In a
traditional OFDM system, a single radio frequency (RF) carrier is
used to carry one wideband radio signal, and in an OFDM
multi-carrier system, multiple RF carriers are used to carry
multiple narrower band radio signals. The multi-carrier operation
is also known as carrier aggregation or bandwidth extension. An
OFDM multi-carrier system has various advantages as compared to a
traditional OFDM system such as lower Peak to Average Power Ratio,
easier backward compatibility, and more flexibility. Thus, OFDM
multi-carrier wireless systems have become the baseline system
architecture in IEEE 802.16m and LTE-Advanced draft standards to
fulfill system requirements.
[0007] In a multi-carrier environment, there exists some channel
relationship among different RF carriers. For example, path-loss
and shadowing fading are typically the same for all RF carriers.
When RF carriers span over a continuous RF band, its channels are
highly correlated. It is thus possible to exploit channel
correlation for carrier activation process. In addition, Open Loop
Power Control (OLPC) is preferred to provide efficient power
management. On the other hand, short-term fading is
frequency-selective, and Interference over Thermal (IoT) may also
be carrier-dependent due to scheduling and carrier properties. For
example, IoT is carrier-specific if each RF carrier is applied in
different fractional frequency reuse (FFR) region. As a result,
Close Loop Power Control (CLPC) per RF carrier is required for RF
carriers conveying on-going data traffic.
[0008] In order to minimize power consumption, a mobile station
(MS) sometimes enters sleep mode operation, during which the MS
conducts pre-negotiated periods of absent time from its serving bas
station (BS). When sleep mode operation is active, a series of
alternating listening windows followed by sleep windows are
provided for the MS. In each listening window, the MS wakes up to
receive and transmit data packets. In each sleep window, the
serving BS does not transmit any data packets to the MS. Traffic
indication is executed by the BS during the MS's listening window,
a procedure for the BS to indicate whether any downlink traffic
allocation is addressed to the MS. In multi-carrier sleep mode
operation, more than one RF carrier may be used to execute the
traffic indication procedure. In addition, more than one RF carrier
may be awakened for data transmission.
[0009] FIG. 1 (prior art) illustrates an example of multi-carrier
sleep mode operation using "wakeup all" method. As illustrated in
FIG. 1, a primary RF carrier is used to execute the traffic
indication procedure. When the MS receives traffic indication
message (TRF-IND) via primary carrier, all secondary carriers are
awakened at the same time regardless of whether TRF-IND indicates
data arrival or not. However, such "wakeup all" method introduces
power wasting when there is no data to be received for some of the
listening windows. Other solutions have been sought to provide more
efficient power management for multi-carrier sleep mode operation.
For example, Ericsson has proposed to the LTE-Advanced draft
standards that Discontinuous Downlink Reception (DRX) parameters
may be configured for one component carrier independently of other
component carriers (see R2-092959, Apr. 28, 2009). While this
proposal increases scheduling flexibility, it also unnecessarily
wakes up the MS for non-periodic services.
SUMMARY
[0010] A method of power management for a mobile station in a
multi-carrier wireless network is provided. A primary connection
between the mobile station and a serving base station is first
established by performing initial ranging over a primary radio
frequency (RF) carrier. Initial ranging procedure is used by the
mobile station to evaluate and modify physical layer parameters
such as power, frequency, and timing of its transmission with the
serving base station. A secondary connection between the mobile
station and the base station is then established by performing
periodic ranging over a secondary RF carrier. In one novel aspect,
to achieve efficient power management in carrier activation, the
mobile station uses the same timing, frequency and power adjustment
parameters for the secondary RF carrier as in the primary RF
carrier for initial transmission. By performing optional periodic
ranging without performing initial ranging, the mobile station is
able to have more power saving in activating the secondary RF
carrier.
[0011] To achieve efficient power management in link maintenance,
the mobile station performs Open Loop Power Control (OLPC) and
obtains long-term link measurement, also referred to as Channel
State Information (CSI), of the primary carrier. The mobile station
then derives Carrier-Offset parameter and adjusts carrier-specific
parameters based on the primary carrier CSI and the Carrier-Offset
parameter. For RF carriers that convey on-going data traffic, Close
Loop Power Control (CLPC) is updated carrier-by-carrier.
[0012] In one embodiment, the mobile station (MS) enters sleep mode
operation to minimize power consumption. Before entering sleep mode
operation, the mobile station first negotiates sleep cycle
parameters with the serving base station. The mobile station then
enters sleep mode operation and receives traffic indication
messages on the primary RF carrier during each listening window.
The mobile station then dynamically wakes up one or more
corresponding RF carriers for data reception if traffic indication
message indicates positive data traffic for the one or more
corresponding RF carriers. The one or more corresponding RF
carriers may be identified by a wakeup indication message.
[0013] In one example of multi-carrier sleep mode operation, the
serving base station sends a MAC management message requesting the
mobile station to change its primary carrier to another activated
carrier upon entering the sleep mode operation or during the
listening window. Such primary carrier switching is performed to
enhance reliability and power saving in case of channel quality
deterioration, and to achieve better Quality of Service or load
balancing. A status bit may be included in the MAC management
message indicating whether the main purpose of the next listening
window is used to receive data traffic or to detect the downlink
resource allocation MAC management messages that indicate arrival
of data traffic.
[0014] In another example of multi-carrier sleep mode operation, if
data traffic is highly predictable, then the mobile station may be
ready to receive data traffic on one or more pre-designated
carriers without detecting any traffic indicator. The
pre-designated RF carriers simply wake up at pre-allocated
listening window to transmit and receive data traffic.
[0015] Other embodiments and advantages are described in the
detailed description below. This summary does not purport to define
the invention. The invention is defined by the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The accompanying drawings, where like numerals indicate like
components, illustrate embodiments of the invention.
[0017] FIG. 1 (Prior Art) illustrates an example of multi-carrier
sleep mode operation using "wakeup all" method.
[0018] FIG. 2 is a simplified diagram of a multi-carrier wireless
network in accordance with one novel aspect.
[0019] FIG. 3 is a simplified diagram of a multi-carrier mobile
station in connected state in accordance with one novel aspect.
[0020] FIG. 4 is a power management flow chart for carrier
activation of a multi-carrier mobile station.
[0021] FIG. 5A is a power management flow chart for link
maintenance of a multi-carrier mobile station.
[0022] FIG. 5B illustrates open loop power control and close loop
power control in a multi-carrier environment.
[0023] FIG. 6 is a power management flow chart for multi-carrier
sleep mode operation.
[0024] FIG. 7 illustrates an example of multi-carrier sleep mode
operation using wakeup indication.
[0025] FIG. 8 illustrates one embodiment of MAC management message
for carrier switching and wakeup indication and an example of sleep
mode operation without traffic indication.
DETAILED DESCRIPTION
[0026] Reference will now be made in detail to some embodiments of
the invention, examples of which are illustrated in the
accompanying drawings.
[0027] FIG. 2 is a simplified diagram of a multi-carrier wireless
network 21 in accordance with one novel aspect. Multi-carrier
wireless network 21 comprises a multi-carrier serving base station
(BS) 22 and a multi-carrier mobile station (MS) 23. MS23 comprises
a plurality of radio frequency (RF) modules, depicted in FIG. 1 as
RF module (RF module #1) coupled to antenna 27, RF module 25 (RF
module #2) coupled to antenna 28, and RF module 26 (RF module #N)
coupled to antenna 29. Different RF modules are operable to receive
and transmit data over different RF carriers. For example, RF
module #1 is operable over a first RF carrier #1 and RF module #2
is operable over a second RF carrier #2. MS23 also comprises a
novel carrier activation and link maintenance module 31 and a novel
sleep-mode operation module 32, which provide efficient power
management.
[0028] FIG. 3 is a simplified diagram of MS23 operating in
connected state in accordance with one novel aspect. As illustrated
in FIG. 3, MS23 has different operational states such as access
state, connected state, and idle state. MS23 operates in connected
state when it enters wireless network 21 by activating one or more
RF carriers and completes related capability negotiation and
registration operations over the one or more RF carriers with its
serving BS22. In LTE, the corresponding state of the connected
state is referred to as "RRC connected state." Within the connected
state, MS23 has different operation modes, such as sleep mode,
active mode, and scanning mode. During active mode operation, MS23
actively receives and transmits data packets with its serving BS22.
In order to minimize power consumption, MS23 sometimes enters sleep
mode operation, during which MS23 conducts pre-negotiated periods
of absent time from its serving BS22. In addition, MS23 sometimes
enters scanning mode operation to perform necessary measurements of
neighboring base stations. Scanning mode operation is similar to
sleep mode operation in the concept of data transmission, that is,
MS23 scans neighboring cells during each sleep window and receives
downlink data during each listening window. Therefore, power
management of a mobile station in connected stat is related to both
active mode and sleep mode. During both active mode operation and
sleep mode operation in a multi-carrier environment, efficient
power management and power saving are achieved by carrier
activation and link maintenance module 31 and sleep mode operation
module 32.
[0029] FIG. 4 is a power management flow chart for carrier
activation of a multi-carrier mobile station during active mode
operation. For carrier activation, a primary RF carrier connection
is first established (step 101). Carrier activation of a primary RF
carrier includes steps 102 to 107. First, a first inactive RF
module of the mobile station is initialized (step 102). The
initialized RF module is operable over an RF carrier that is
referred to as the primary RF carrier. Downlink (DL) channel
synchronization between the mobile station and its serving base
station is then performed (step 103). Downlink (DL) preamble is
also measured (step 104). Next, the mobile station performs initial
ranging over the primary RF carrier (step 105). Initial ranging
procedure is used by the mobile station to evaluate and modify
physical layer parameters such as power, frequency, and timing of
its transmission with the serving base station. After initial
ranging, the mobile station performs network entry procedure and
completes capability negotiation and registration operation with
the serving base station over the primary RF carrier (step 106).
Finally, a primary carrier connection between the mobile station
and the serving base station is established over the primary RF
carrier (step 107).
[0030] In a multi-carrier environment, in addition to the primary
carrier connection, a secondary carrier connection may be
established over a secondary RF carrier between the mobile station
and its serving base station (step 111). The carrier activation of
a secondary RF carrier includes steps 112 to 114. First, the mobile
station performs periodic ranging upon activation of the secondary
RF carrier if necessary (step 112). To perform periodic ranging,
the mobile station starts with the timing, frequency, and power of
the primary RF carrier for initial transmission and then derives
"Carrier-Offset" parameters for the secondary RF carrier. Next, the
mobile station adjusts carrier-specific parameter based on the
Carrier-Offset (step 113). That is,
CSI_secondary=CSI_primary+Carrier-Offset. In the meantime, the
mobile station only keeps measuring long-term link measurement
(also referred to as Connection State Information (CSI))
CSI_primary for the primary carrier. Finally, a secondary carrier
connection is established over the secondary RF carrier (step 114).
In one novel aspect, the mobile station does not need to perform
initial ranging in activating the secondary RF carrier. Instead,
the mobile station performs periodic ranging only if necessary. If
periodic ranging is also skipped, then the same timing, frequency,
and power setting of the primary RF carrier are applied for the
secondary RF carrier. By performing optional periodic ranging
without performing the initial ranging procedure, the mobile
station is able to have more power saving in activating the
secondary RF carrier.
[0031] FIG. 5A is a power management flow chart for link
maintenance of a multi-carrier mobile station after the primary
carrier connection and the secondary carrier connection are
established. For the primary RF carrier, the mobile station
performs Open Loop Power Control (OLPC) for link maintenance (step
121). More specifically, such OLPC involves periodically
calculating and updating long-term link measurement, also referred
to as Connection State Information (CSI), without using any
feedback mechanism (step 122). In one novel aspect, the long-term
link measurement (CSI) for OLPC parameters is performed in the
primary RF carrier only, while power update is done per RF carrier
with the same CSI. Thus, the mobile station is able to have more
power saving because OLPC parameters are applied in all RF carriers
without measuring the secondary carriers. On the other hand, Close
Loop Power Control (CLPC) is required per RF carrier for primary or
secondary RF carriers that convey on-going data traffic (step 131).
More specifically, the power update in CLPC is done
carrier-by-carrier using specific Transmission Power Control (TPC)
command.
[0032] FIG. 5B is a diagram that illustrates Open Loop Power
Control and Close Loop Power Control in a multi-carrier
environment. As illustrated in FIG. 5B, for the primary RF carrier,
the mobile station performs OLPC (i.e., slow control as depicted in
FIG. 5B) when it does not convey on-going data traffic, and
performs CLPC (i.e., fast control as depicted in FIG. 5B) when it
conveys on-going data traffic. On the other hand, for the secondary
RF carrier, the mobile station performs CLPC (i.e., fast control as
depicted in FIG. 5B) when it conveys on-going data traffic.
[0033] In addition to carrier activation and link management in
active mode operation, power saving in sleep mode operation is also
desirable. FIG. 6 is a power management flow chart for
multi-carrier sleep mode operation of a mobile station. When sleep
mode operation is active, a series of sleep cycles having
alternating listening window followed by sleep window are provided
for the mobile station. In each sleep window, the serving base
station does not transmit any data packets to the mobile station.
In each listening window, the mobile station is expected to wake up
and transmit/receive data packets as in active mode operation.
During each listening window, the serving base station may transmit
a traffic indication message to the mobile station to indicate
whether any downlink traffic allocation is addressed.
[0034] As illustrated in FIG. 6, the mobile station starts with
active mode operation (step 201). Before entering sleep mode
operation, the mobile station negotiates sleep cycle parameters
with the serving base station (step 202). The sleep cycle
parameters include sleep cycle length, listening window length, and
whether traffic indication is enabled during each listening window.
If traffic indication is enabled (depicted as TIMF=1 in FIG. 6),
then the mobile station enters sleep mode operation (step 203) and
waits for the next listening window (step 204). If it is time for
the next listening window, then the mobile station receives a
traffic indication (TRF-IND) message and decodes the content of the
TRF-IND message (step 205). IF the TRF-IND message indicates
negative data traffic, then the mobile station goes back to sleep
mode. If the TRF-IND message indicates positive data traffic, then
the mobile station wakes up corresponding RF carriers (step 207)
for data transmission and reception (step 208).
[0035] In one novel aspect, traffic indication is always executed
on the mobile station's primary RF carrier. The serving base
station transmits TRF-IND messages on the mobile station's primary
RF carrier. The mobile station receives and decodes the TRF-IND
messages on its primary RF carrier and wakes up corresponding RF
carriers to process data traffic. The corresponding RF carriers to
be awakened are the activated secondary RF carriers identified by a
wakeup indication message. By executing wakeup indication on
demand, more power savings can be achieved because RF carriers will
not be awakened if there is no data to be processed in the upcoming
listening window.
[0036] FIG. 7 illustrates an example of multi-carrier sleep mode
operation of a mobile station using wakeup indication method. The
mobile station supports four RF carriers, one primary carrier and
three secondary carriers with logic indexes #1, #2, and #3
respectively. As illustrated in FIG. 7, the mobiles station
receives wakeup indication messages from the serving base station
on its primary carrier during each of the listening windows. The
wakeup indication message may be in the form of a bitmap, with each
bit representing whether an associated RF carrier needs to be
awakened in the upcoming listing window. The wakeup indication
message may also be a number that represents the logic index of an
RF carrier to be awakened in the upcoming listening window. In one
embodiment, the wakeup indication message is an independent MAC
message. In another embodiment, the wakeup indication message is
part of a TRF-IND message.
[0037] In the example of FIG. 7, each wakeup indication message is
in the form of a multi-carrier bitmap. The first multi-carrier
bitmap is equal to 000, which indicates that none of the secondary
carriers needs to be awakened. The second multi-carrier bitmap is
equal to 001, which indicates that the secondary carrier with logic
index #1 needs to be awakened in the upcoming listening window for
data reception. Similarly, the third multi-carrier bitmap is equal
to 010, which indicates that the secondary carrier with logic index
#2 needs to be awakened in the upcoming listening window for data
reception. From the time the mobile station receives the wakeup
indication message, it takes an additional Wakeup Time for the
mobile station to wake up the corresponding RF carriers. This
Wakeup Time is a critical system parameter and may be exchanged in
initial network entry procedure (or "cell camping" in 3GPP
terminology) or sleep mode negotiation process. The value is
related to the mobile station's terminal capability and can be
negotiated between the mobile station and the serving base
station.
[0038] In addition to wakeup indication messages, the serving base
station may also send other types of MAC management messages to the
mobile station. The serving base station may send a MAC message
indicating that the main purpose of the next listening window is
used for detecting traffic (i.e., detection of TRF-IND) instead of
receiving traffic. For example, the serving base station may send a
MAC management message requesting the mobile station to change its
primary carrier to another activated carrier upon entering the
sleep mode operation or during the listening window. Such primary
carrier switching is performed to enhance reliability and power
saving in case of channel quality deterioration, and to achieve
better Quality of Service or load balancing.
[0039] FIG. 8 illustrates one embodiment of a MAC management
message for primary carrier switching and wakeup indication. As
illustrated in FIG. 8, the MAC management message comprises a
status bit followed by a multi-carrier bitmap. If the status bit is
equal to zero, then the main purpose of the next listening window
is used to receive data traffic, and the multi-carrier bitmap
indicates on which carrier traffic will be transmitted in the next
frame within the same listening window. On the other hand, if the
status bit is equal to one, then the main purpose of the next
listening window is used to detect traffic (i.e., for primary
carrier switching), and the carrier bitmap indicates on which
carrier traffic will be transmitted in the next listening
window.
[0040] In the example of FIG. 8, the serving base station first
transmits a MAC message with content "110" to the mobile station
during its first listening window. This MAC message indicates that
the second listening window will be operated on the mobile
station's primary RF carrier #1 (the first bit after the status bit
is set to "1"), and the main purpose of the second listening window
is used to detect data traffic, such as for the purpose of primary
carrier switching. The serving base station then transmits a MAC
message with content "001" to the mobile station during its second
listening window. This MAC message indicates that the next frame in
the same listening window will be operated on the mobile station's
secondary RF carrier #2 (the second bit after the status bit is set
to "1"), and the main purpose of that frame is used to receive data
traffic.
[0041] If data traffic is highly predictable, such as Voice of IP
type of data traffic, then the mobile station may be ready to
receive data traffic on one or more pre-designated carriers without
detecting any traffic indicator. This is represented as TIMF=0 in
multi-carrier sleep operation. Referring back to FIG. 6, when
TIMF=0, one or more RF carriers are pre-designated with
pre-allocated listening windows to receive data traffic (step 210).
After the mobile station enters sleep mode (step 211), it then
determines whether it is time for pre-allocated listening windows
(step 212). If so, then the mobile station wakes up the one or more
pre-designated RF carriers (step 213) to receive data traffic (step
214).
[0042] FIG. 8 also illustrates an example of multi-carrier sleep
mode operation without traffic indication. In the example of FIG.
8, the secondary RF carrier #2 is a pre-designated RF carrier. When
the serving base station receives data traffic in a third listening
window, the mobile station subsequently wakes up the secondary RF
carrier #2 for data reception without receiving any traffic
indicator.
[0043] Although the present invention has been described in
connection with certain specific embodiments for instructional
purposes, the present invention is not limited thereto. In one
embodiment, the bitmap indicator in TRF-IND can be cross-carrier
assignment parameter. For a multi-carrier communication system, a
downlink assignment message can indicate resource allocation for
the current carrier and/or other carriers. For multi-carrier sleep
mode operation, the base station can send a downlink assignment
message to the mobile station with an additional parameter to
assign downlink assignment for other carriers that are still not
waked up yet.
[0044] In another embodiment, the concept of wakeup indicator can
be implemented as early-termination indicator. Since there is one
set of sleep mode parameters, the start time of listening window in
secondary carriers is scheduled to be delayed by T_wakeup, compared
to the start time of the listening window in primary carrier. If
the early-termination indicator along with TRF-IND and the
indicator represent the absence of downlink traffic of a specific
secondary carrier, then the secondary carrier is not required to be
waked up at the scheduled time.
[0045] In addition, although power management is the focus
throughout the above description, the present invention is not
limited to power management. Using FIG. 4 as an example, when the
mobile station omits the initial ranging for the secondary carrier,
it may use the same timing, frequency as well as power adjustment
parameters for the secondary carrier as in the primary carrier for
initial transmission. Later on, the mobile station may perform fine
timing, frequency and power adjustment on the secondary carrier
through measuring the synch and/or pilot on the secondary
carrier.
[0046] Accordingly, various modifications, adaptations, and
combinations of various features of the described embodiments can
be practiced without departing from the scope of the invention as
set forth in the claims.
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