Note: Descriptions are shown in the official language in which they were submitted.
CA 02625076 2008-04-03
SYSTEM AND METHOD FOR FAST DYNAMIC LINK ADAPTATION
This application is a division of Canadian Application Serial
Number 2,463,731 filed internationally on October 18, 2002 and entered
nationally
on April 13, 2004.
BACKGROUND
In Third Generation (3G) communication systems, Dynamic Link
Adaptation (DLA) is used to compensate for degraded radio propagation
conditions
that would require the User Equipment (UE) to transmit at a transmission power
greater then the maximum allowed, or physical maximum, transmission power.
Transmissions that require to be transmitted at a power level greater than the
maximum power level are transmitted at the maximum power level in 3G
communication systems. When these signals are transmitted at the maximum power
level (which is less than their desired transmit power level) they experience
degraded performance and have increased error rates, increasing the likelihood
that
the transmitted data will not be received, and that the system resources being
used
are being wasted.
One prior art method for handling this maximum power condition is to
continue the transmission at the maximum allowed or physical maximum
transmission power and rely on the error correction capabilities of the
receiver to
correct any errors that may occur. This ultimately results in undesirable
system
performance, since the transmission will be made at a power level that is not
adequate to maintain the desired level of error rate performance.
Another method for dealing with the maximum power condition is to reduce
the Uplink (UL) data requirement for the period that the required transmission
power to maintain the desired level of error rate performance is greater than
the
maximum power capability. This method maintains the desired error rate
performance by the reduction of the data rate.
-1-
CA 02625076 2008-04-03
It is also possible to continue UL transmissions when the desired power
would exceed the maximum power capability without effecting the UL data
requirement by allowing the Block Error Rate (BLER) to increase. This effect
is
considered to be unavoidable for the period from when the maximum power
condition is perceived to when the UL transmissions can be reconfigured to a
reduced overall rate. In 3G wireless standards, UE performance requirements
are
specified that limit this period.
There is strong motivation to exceed the specified requirements since
transmissions that require a power level greater than the maximum transmit
power
level are likely to fail. Services that allow for data retransmission of
failed
transmissions result in increased overhead, reduced radio resource efficiency
and
reduced UE battery life. Services that do not allow for retransmission result
in an
increase in the BLER, thereby causing subsequent increased power requests to
attempt to maintain the BLER quality target. Since the UE is already
transmitting at
its maximum power, an increase in signal to interference ratio SIR target used
in the
UL transmit power control algorithm does not improve the BLER performance for
the current channel conditions. If the channel conditions improve, the
increased SIR
target will require the UE to transmit at a power level greater than necessary
to
maintain the desired performance, resulting in reduced radio resource
efficiency and
battery life.
To achieve or exceed the perfonnance requirements for improved Quality of
Service (QoS), an efficient method of adjusting the UL transmission
requirements is
necessary.
In 3G communication systems, individual data streams are assigned to
Transport Channels (TrCHs) with specific QoS capabilities, which are
configured to
achieve specified BLER quality targets. The physical channel(s) assigned to
the UE
support multiple TrCHs simultaneously; this is called a Coded Composite
Transport
Channel (CCTrCH). The CCTrCH allows for varying amounts of data on each
TrCH to exist in any specific Transmission Time Interval (TTI). The TTI period
is
-2-
CA 02625076 2008-04-03
specific to each TrCH. Within each TTI period for a specific TrCH, the amount
of
data transmitted is specified by a Transport Format (TF).
For the CCTrCH in any specific TTI period, the set of TFs for each TrCH is
known as the Transport Format Combination (TFC). The set of all of the
available
TFCs, (i.e. all of the available allowed multiplexing options), is known as
the
Transport Format Combination Set (TFCS).
For each UL CCTrCH, the UE Medium Access Control (MAC) entity
selects a TFC for transmission on a TTI basis. This TFC and associated data is
provided to the physical layer for transmission in the physical data request
primitive.
If the physical layer subsequently determines transmission of this TFC exceeds
the
maximum or allowable UE transmission power, a physical status indication
primitive is generated to the MAC to indicate that maximum power or allowable
transmission power has been reached.
When the MAC is informed of the maximum or allowable transmission
power has been reached, the TFCs that would cause this condition to continue
to
exist are blocked, that is, removed from the set of available TFCs, unless the
TFC is
one of the TFCs which according to the 3GPP standards cannot be blocked.
Blocked TFCs may be later restored to the set of available TFCs by unblocking
them in subsequent periods when the UE transmission power measurements
indicate
the ability to support these TFCs with less than or equal to the maximum or
allowed
UE transmission power.
There are, however serious drawbacks with the current manner in which
TFCs are removed. As aforementioned, the physical layer determines whether the
transmission of a TFC would require exceeding the maximum or allowable UE
transmission power, and then a physical status indication primitive is
generated to
the MAC entity that indicates maximum power or allowable power has been
reached. Using this method, the UE could be in the maximum power state for
approximately 60 milliseconds or more while the MAC reconfigures the set of
available TFCs to remove the blocked TFCs and start selecting TFCs from the
-3-
CA 02625076 2008-04-03
updated set of available TFCs. The UE will reduce the available TFCs only to
the
power requirement for the TFC that exceeded the transmission power capability.
The UE will then likely choose the TFC with the next lower transmission power
requirement. However, there is no guarantee that the reduced set of TFCs will
not
require power in excess of the maximum power. This results in another
iteration of
the process, and an additional delay, to further reduce the set of TFCs. For
each
TFC that is eliminated, data and radio resources are lost for the given TTIs.
Ultimately, the performance of the system is degraded during the maximum power
condition.
Additional performance concerns arise when the UE is attempting to
recover the TFCs that have been blocked due to the maximum power condition. It
is
desirable to unblock, (i.e., recover), TFCs as quickly as possible to have a
more
complete set of TFCs available for the UE to use. Ultimately, the performance
of
the system is improved when the TFCs are recovered efficiently.
Accordingly, the prior art methods of handling the situation where the UE is
in its maximum power state fall far short of acceptable system performance. It
would be desirable to have an improved method of expeditiously reducing the
set of
TFCs for the duration when maximum UE power condition is achieved, and
expeditiously restoring the TFCs when the maximum UE power condition has
passed.
SUMMARY
The present invention is system and method for enabling efficient reduction
of TFCs in the TFCS to support a desired transmission, while remaining within
power and data requirements. In the event that the UE transmission power
requirements exceed the maximum or allowable transmission power, the set of
TFCs
is reduced to only those acceptable TFCs that currently do not exceed the
power
limit. The UE will then chose from among the acceptable reduced set of TFCs.
-4-
CA 02625076 2008-04-03
The invention also supports advanced determination of non-supported
TFCs. The TFCs that require transmission power greater then the maximum or
allowed UE transmission power shall be determined continuously in every TTI,
not
just in TTIs where the maximum power has been exceeded. The TFC selection
process is adjusted to avoid selection of TFCs that exceed transmission power
capabilities in advance of transmission.
The present invention also enables the restoration of the TFCs in the TFCS
when the maximum power condition no longer exists.
According to an embodiment of the present invention there is provided a
method for selecting a transport format combination (TFC). The method
comprises:
selecting a TFC out of a transport format combination set (TFCS) for use in
wirelessly transferring a coded composite transport channel (CCTrCh);
eliminating
the selected TFC for future selection and repeating the selecting a TFC, if a
determined transmission power level for the selected TFC exceeds a maximum
allowed power level; and transmitting the CCTrCh using the selected TFC, if
the
selected TFC was not eliminated.
According to another embodiment of the present invention there is provided
a user equipment for selecting a transport format combination (TFC). The user
equipment comprises: circuitry configured to select a TFC out of a transport
format
combination set (TFCS) for use in wirelessly transferring a coded composite
transport channel (CCTrCh); circuitry configured to eliminate the selected TFC
for
future selection and repeating the selecting of a TFC, if a determined
transmission
power level for the selected TFC exceeds a maximum allowed power level; and
circuitry configured to transmit the CCTrCh using the selected TFC, if the
selected
TFC was not eliminated.
According to another embodiment of the present invention there is provided
a user equipment for selecting a transport format combination (TFC). The user
equipment comprises: a medium access control entity for selecting a TFC out of
a
transport format combination set (TFCS) for use in wirelessly transferring a
coded
-5-
CA 02625076 2008-04-03
composite transport channel (CCTrCh); for eliminating the selected TFC for
future
selection and repeating the selecting a TFC, if a determined transmission
power
level for the selected TFC exceeds a maximum allowed power level; and a
physical
layer processing entity for transmitting the CCTrCh using the selected TFC, if
the
selected TFC was not eliminated; and performing the transmission power level
determination for the selected TFC.
According to another embodiment of the present invention there is provided
a method for selecting a transport format combination (TFC). The method
comprises: providing a list of blocked TFCs out of TFCs of a transport format
combination set (TFCS) for use in wirelessly transferring a coded composite
transport channel (CCTrCh), the TFCS previously having a determined
transmission
power level exceeding a maximum allowed power level; determining, for each
blocked TFC, whether the blocked TFC has a determined transmission power level
exceeding the maximum allowed power level; restoring, for each blocked TFC not
exceeding the maximum allowed power level based on the determination, that
blocked TFC to a list of available TFCs of the TFCS; and selecting a TFC out
of the
list of available TFCs.
According to another embodiment of the present invention there is provided
a user equipment for selecting a transport format combination (TFC). The user
equipment comprises: circuitry configured to provide a list of blocked TFCs
out of
TFCs of a transport fonnat combination set (TFCS) for use in wirelessly
transferring
a coded composite transport channel (CCTrCh), the TFCS previously having a
determined transmission power level exceeding a maximum allowed power level;
circuitry configured to determine a blocked TFC for each blocked TFC, for
determining whether the blocked TFC has a determined transmission power level
exceeding the maximum allowed power level; circuitry configured to restore an
unblocked TFC for each blocked TFC not exceeding the maximum allowed power
level based on the determination, for restoring that blocked TFC to a list of
available
-6-
CA 02625076 2008-04-03
TFCs of the TFCS; and circuitry configured to select a TFC out of the list of
available TFCs.
According to another embodiment of the present invention there is provided
a user equipment for selecting a transport format combination (TFC). The user
equipment comprises: a medium access control entity for providing a list of
blocked
TFCs out of TFCs of a transport format combination set (TFCS) for use in
wirelessly transferring a coded composite transport channel (CCTrCh), the TFCS
previously having a detennined transmission power level exceeding a maximum
allowed power level; a physical layer processing entity for each blocked TFC,
for
determining whether the blocked TFC has a determined transmission power level
exceeding the maximum allowed power level; and the medium access control
entity
for each blocked TFC not exceeding the maximum allowed power level based on
the detennination, for restoring that blocked TFC to a list of available TFCs
of the
TFCS; and for selecting a TFC out of the list of available TFCs.
According to another embodiment of the present invention there is provided
a method for selecting a transport format combination (TFC) out of a transport
format combination set (TFCS) for use in wirelessly transferring a coded
composite
transport channel (CCTrCh). The method comprises: determining which TFCs of
the TFCS have a determined transmission power level exceeding a maximum
allowed power; producing a list of available TFCs based on the detennination;
selecting a TFC out of the list of available TFCs; and determining which TFCs
of
the TFCS have a determined transmission power level exceeding a maximum
allowed power, producing a list of available TFCs based on the determination,
and
selecting a TFC out of the list of available TFCs on a periodic basis.
According to another embodiment of the present invention there is provided
a user equipment for selecting a transport format combination (TFC). The user
equipment comprises: circuitry configured to periodically determine which TFCs
of
a transport format combination set (TFCS) used in wirelessly transferring a
coded
composite transport channel (CCTrCh) have a determined transmission power
level
-7-
CA 02625076 2008-04-03
exceeding a maximum allowed power; circuitry configured to produce a list of
available TFCs; and circuitry configured to select a TFC out of the list of
available
TFCs.
According to another embodiment of the present invention there is provided
a user equipment for selecting a transport format combination (TFC). The user
equipment comprises: a physical layer processing entity for periodically
determining
which TFCs of a transport format combination set (TFCS) used in wirelessly
transferring a coded composite transport channel (CCTrCh) have a determined
transmission power level exceeding a maximum allowed power; and a medium
access control entity based on the determination for producing a list of
available
TFCs; and for selecting a TFC out of the list of available TFCs.
According to another embodiment of the present invention there is
provided a method of selecting a transport format combination (TFC) without
exceeding an established maximum allowed power requirement. The method
comprises: selecting a TFC out of a transport format combination set (TFCS);
performing a first determination to determine a required transmission power of
the
selected TFC; performing a second determination to determine whether use of
the
selected TFC by a user equipment (UE) would cause the established maximum
power
requirement of the UE to be exceeded; selecting a TFC out of the TFCS and
performing
the first and second determinations for each TFC in the TFCS; and assigning an
availability status to each selected TFC out of the TFCS.
According to another embodiment of the present invention there is
provided a user equipment (UE) for selecting a transport format combination
(TFC) out
of a transport format combination set (TFCS) for use by the UE without
exceeding an
established maximum allowed power requirement. The UE comprises: a medium
access control (MAC) entity configured to select each TFC out of the TFCS; and
a
physical layer processing entity in communication with the MAC entity, the
physical
layer processing entity configured to determine a required transmission power
of each
selected TFC, determine whether use of each selected TFC by the UE would cause
the
-8-
CA 02625076 2008-04-03
established maximum power requirement of the UE to be exceeded, assign an
available
availability status to each selected TFC out of the TFCS which, when used by
the UE,
would not cause the established maximum power requirement of the UE to be
exceeded
and assign a non-available availability status to each selected TFC out of the
TFCS
which, when used by the UE, would cause the established maximum power
requirement
of the UE to be exceeded.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a flow diagram for efficient removal of TFCs in accordance with
the present invention.
Figure 2 is a flow diagram for restoration of TFCs in the TFCS.
Figure 3 is a flow diagram for advance removal of TFCs in accordance with
the present invention.
Figures 4 and 5 are flow diagrams for two alternatives to determining TFC
transmit power requirements on a periodic basis.
Figure 6 is a block diagram of the MAC entity and the physical entity.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
The present invention will be described with reference to the drawing
figures wherein like numerals represent like elements throughout.
There are three basic aspects to dynamic link adaption in accordance with
the present invention. First, when a condition exists where the UE
transmission
power requirement exceeds the maximum, or maximum allowed, power of the UE,
the TFCs that require power in excess of the maximum power limit are
efficiently
blocked. The MAC is informed, for subsequent TFC selection, of all TFCs that
currently exceed this limit. Thereafter, only TFCs that do not require power
in
excess of the UE transmission power limit capability are available for
selection.
Secondly, the present invention supports efficient recovery of TFCs in the
TFCS when the maximum power condition no longer exists.
-9-
CA 02625076 2008-04-03
Finally, the invention supports advance determination of non-supported
TFCs; i.e. those TFCs that require transmission power greater then the maximum
or
allowed UE transmission. These TFCs are determined continuously and
periodically, such as in every TTI, not just in TTIs where the maximum power
condition exists. Every TTI may or may not include TTIs where no data is
transmitted. Since TFC requirements change over time, this allows for advance
determination of TFCs that will not be supported.
It should be noted that although the present invention relates to removal and
restoration of TFCs, a minimum set of TFCs within the configured TFCS should
always be available for transmission. Preferably, this minimum set is exempt
from
the TFC removal and restoration processes that will be described hereinafter.
The processes for TFC removal and restoration are performed periodically.
Although the period for these processes is described hereinafter as being
based on a
TTI, it is also possible to perform actions approximately every TTI, (i.e.,
more then
once per TTI), or every several TTIs. It should also be noted that every TTI
may or
may not include TTIs where no data is transmitted.
Referring to Figure 1, the procedure 10 for efficient removal of TFCs in
accordance with the present invention is shown. The procedure 10 commences
with
selection of TFCs using the available set of TFCs (step 16). The available set
of
TFCs is the initial full transport format combination set (TFCS) configured
for the
establishment of the CCTrCH. The selected TFC is sent to the physical entity
14
(step 18). The physical entity 14 determines the TFC transmission power
requirement (step 22) and makes a determination of whether the required UE
transmit power for this TFC is over the maximum, or maximum allowable, UE
power (step 24). If not, steps 16, 18, 22 and 24 are repeated until the
transmission
power requirement for a TFC exceeds the maximum allowed power. If for
transmission of a TFC the UE power requirement is over the maximum allowed
power, the physical entity 14 determines all TFCs within the TFCS that are in
"excess power state" (step 25). The physical entity 14 indicates the available
or
-10-
CA 02625076 2008-04-03
not-available (i.e. blocked) status of the TFCs to the MAC entity 12 (step
26). It
should be noted that the physical entity 14 can indicate the status of the
available
TFCs, the not-available TFCs or both. The MAC entity 12 removes TFCs in the
excess power state as indicated by the physical layer entity 14 from the
available set
of TFCs (step 28). The procedure 10 is then repeated for each TTI.
Although functionality is specifically identified as being performed in the
physical layer, it is also possible to perform some of these actions in the
MAC layer.
Referring to Figure 2, the procedure 50 for restoration of TFCs in the excess
power state is shown. The MAC entity 12 selects a TFC using the available set
of
TFCs (step 52). The available set of TFCs is either the initial full Transport
Format
Combination Set (TFCS) configured upon the establishment of the CCTrCH, or a
reduced available set of TFCs from the TFCS, which were previously indicated
from the physical entity 14. The selected TFC is sent to the physical entity
14 (step
53).
The physical entity 14 determines whether any TFCs are in the excess
power state (step 54). The determination is performed on a periodic basis only
for
those TFCs within the configured TFCS that are in the excess power state. This
periodic basis may be, for example, every TTI. The physical entity 14 then
determines whether any of the TFCs that were in the excess power state no
longer
exceed the maximum or maximum allowed power, and can be restored to the set of
available TFCs (step 55). The physical entity 14 then indicates restored TFCs
to the
MAC entity 12 (step 56). If there is a change in available TFCs, (i.e. if the
TFCs are
unblocked), the MAC entity 12 updates its list of available TFCs (step 58).
Steps
52-58 are continuously repeated by the MAC and physical layer entities 12, 14.
This procedure 50 ensures that when TFCs are blocked, recovery of available
TFCs
are continuously determined every TTI, not just in TTIs where the maximum
power
has been exceeded.
The restoration of TFCs is much more efficient when unblocked TFCs are
indicated on a periodic basis, rather than being determined by the UE
calculated
-11-
CA 02625076 2008-04-03
transmitted power measurements on the transmitted signal, since the normal
measurement reporting and processing mechanism is slow. This enables the UE to
avoid reducing the transmitting rate to less than the data rate that is
supported by the
current channel conditions. The UE can restore the desired TFCs based on the
predicted transmitted power requirement prior to transmission, reducing the
time
required to restore the TFCs by one or more TTIs.
Referring to Figure 3, the procedure 150 advance removal of TFCs in
accordance with the present invention is shown. The procedure 150 commences
CCTrCh establishment and the configuration of the complete TFCS (step 151). A
TFC is then selected from the available set of TFCs (step 152). The MAC entity
12
sends the selected TFC to the physical entity 14 (step 154). The physical
entity 14
continuously determines the available TFCs on a periodic basis (step 156),
such as
in every TTI as shown in Figure 3. The ability to transmit all available TFCs
is
verified. A determination is made (step 157) as to whether any previously
unblocked TFCs are now in the excess power state. If not, the procedure 150
returns to step 152, to repeat the procedure 150. If so, the new TFCs now in
the
excess power state are indicated to the MAC entity 12 (step 158). The MAC
entity
12 updates the list of all available TFCs (step 160). It should be noted that
steps
152, 154 and 160 performed by the MAC entity 12 and steps 156, 157, 158
performed by the physical entity 14 are continuously repeated, not necessarily
in
each TTI as represented in Figure 3.
Since TFC transmission power requirements, which change over time, are
checked for restoration on a periodic basis, such as in each TTI, this method
150
allows for advance determination of TFCs that will not be supported. TFC power
requirements are checked each TTI in step 156 to detennine if the maximum or
maximum allowed power is exceeded. If the power requirement cannot be
satisfied
for a TFC currently not blocked, the physical entity 14 indicates to the MAC
entity
12 that this TFC should be blocked (step 158). The TFC selection process is
adjusted to avoid selection of TFCs that exceed transmission power
capabilities in
-12-
CA 02625076 2008-04-03
advance of transmission of that TFC. Additionally, if the power requirement
can be
satisfied for a currently blocked TFC, the list of allowable TFCs is
continuously
updated so that previously blocked TFCs may be restored.
Advance determination may additionally employ logic that determines
change in radio propagation conditions over time. For example, the change in
pathloss from a received reference channel, or the change in reported uplink
interference. These and other changes in radio propagation conditions allow
the UE
to predict future transmission power requirements and block TFCs in advance of
interference, pathloss or other conditions that would cause TFCs to enter an
excess
power state.
The result of the advance determination method 150 is the reduced loss of
UL data and more efficient use of radio resources by the proper TFC selection
for
successful transmission. By blocking TFCs before TFC selection and
transmission,
user QoS is improved by reduced BLER, and physical resources are better
utilized
by reducing the need for retransmissions. Since TrCH BLER is reduced,
corresponding unnecessary increases in the UL SIR target is avoided, further
increasing overall radio resource efficiency by reducing UL transmit power.
Although the methods 10, 50 and 150 to continuously update the available
TFCs provide for improved performance, the computational resources required to
calculate the power requirements for every TFC every TTI is great.
Accordingly,
referring to Figures 4 and 5, two alternatives to determining TFC transmit
power
requirements on a periodic, or TTI basis, are shown.
The method 70 of Figure 4 commences with the MAC entity 12 using the
set of TFCs which were determined upon CCTrCH establishment or reconfiguration
(step 72). Upon CCTrCH establishment or reconfiguration the configured TFCS is
sorted by TFC according to transmission power requirements (step 74). Note
that
although indicated in the physical layer 14, the sorted TFC list may be
determined in
either layer 2 or layer 3 entities as well. In TDD systems, this list of TFCs
may be
timeslot specific, such as a sorted TFC list per timeslot. The physical entity
14
-13-
CA 02625076 2008-04-03
periodically verifies the ability to transmit the TFC with the highest
transmission
power requirement (step 76). A detennination is made as to whether the TFC can
be
transmitted (step 77). If this TFC can be transmitted, a determination is made
(step
79) as to whether there were any blocked TFCs. If so, all the previously
blocked
TFCs are made available (step 81) and the physical layer entity 14 goes to
step 82
and indicates to the MAC entity 12 that all TFCs within the TFCS should be
unblocked and are now available. If not, the procedure 70 returns to step 76.
However, if it is determined (step 77) that the TFC with the highest
transmission power requirement cannot be transmitted or if the TFC with
highest
transmit power requires a transmission power greater than the maximum allowed
power, a procedure is implemented to approximate the status of each TFC in the
sorted list (step 78). The specific process to efficiently determine which
TFCs
should be blocked is not central to the present invention, since there are
numerous
alternative options that could be utilized. In a first alternative of the
present
invention, for example, since there is a sorted TFC list, the middle TFC
within the
list is checked to see whether it can be transmitted. If it is cannot be
transmitted, the
TFC in the middle of the lower half of the list is checked to see if it can be
transmitted. Likewise, if the TFC in the middle of the list can be
transmitted, the
TFC in the middle of the upper half of the list is checked to see whether it
can be
transmitted. This process is repeated until the TFC with the highest power
requirements that can be transmitted. Another alternative is to apply a
hashing
function to approximate the list index that exceeds the power capability.
The physical entity 14 determines the TFCs that are not supported and
previously blocked TFCs that are now supported (step 80), and indicates the
updated
available and blocked TFCs to the MAC entity (step 82).
An alternative to sending an updated complete list of unblocked TFCs, or a
list of newly unblocked TFCs, from the physical entity 14 to the MAC entity 12
is to
transmit only an "index" to the sorted TFC list. For example, when the TFC
list is
sorted, entries above the index are blocked and entries below are unblocked.
-14-
CA 02625076 2008-04-03
Transmission of the index will reduce the amount of control signaling required
between the physical entity 14 and the MAC entity 12.
A second alternative to sending an updated complete list of unblocked
TFCs, or a list of newly unblocked TFCs, from the physical entity 14 to the
MAC
entity 12 is to send a measured or calculated value from the physical entity
14 to the
MAC entity 12 (or any other layer 2 entity) which would allow the layer 2
entity to
determine the new set of available TFCs. It should be noted that many of the
steps
shown in Figure 4 as being performed by the physical entity 14 could also be
performed by the MAC entity 12 such as steps 78 and 80.
Steps 76-82 are then repeated. Once the physical entity 14 transmits the
updated list, (or TFCS index or measured/calculated value) of allowable TFCs
to the
MAC entity 12, the MAC entity 12 updates the list of available TFCs (step 84).
Referring to Figure 5, a second alternative method 100 to periodically
determining TFC transmit power requirements is shown. The MAC entity 12
initially uses the set of TFCs configured upon CCTrCH establishment or
reconfiguration (step 102). Upon CCTrCH establishment or reconfiguration, each
TFC is associated with a relative sensitivity. This can be done by the MAC
entity
12, the physical entity 14 or any layer 2 or layer 3 entities. This
sensitivity can be an
En/No requirement under a certain propagation channel assumption, a maximum
tolerable path loss under a propagation channel/transmit power assumption or
other
method mapped onto integers 0-N. Additionally in TDD systems, this relative
sensitivity may be timeslot specific.
The MAC entity 12 forwards the selected TFC to the physical entity 14
(step 104). The physical entity 14 transmits a TFC (step 106) and determines
the
margin relative to the maximum power (step 108). The physical entity 14 uses
the
margin to identify blocked and unblocked TFCs (step 110). It should be noted
that
this margin may be negative, which indicates a potential blocking, or
positive,
which indicates a potential recovery. These blocked and unblocked TFCs are
then
identified to the MAC entity (step 112). The physical entity 14 then repeats
steps
-15-
CA 02625076 2008-04-03
106-112 upon each TFC transmission. Having received the blocked and unblocked
TFC indications from the physical entity 14, the MAC entity 12 updates the
list of
blocked and unblocked TFCs (step 114). Steps 104 and 114 are then repeated by
the
MAC entity 12.
Referring to Figure 6, a block diagram of the MAC entity 12 and the
physical entity 14 is shown. The MAC entity 12 includes a TFC selection
processor
13, which selects the TFCs for transmission associated with a particular
CCTrCH
supporting the desired TrCHs. Likewise, the physical entity 14 has an allowed
TFC
processor 15 which determines blocked and unblocked TFCs and indicates the
blocked and unblocked TFCs to the TFC selection processor 13. Although
physical
layer processing is preferable, it is also possible to perform some of the
aforementioned processing within the MAC layer or other layer 2 entities. In
accordance with the embodiments shown in Figures 4 and 5, the TFC processor 15
also performs the sorting of the TFCs by UE transmission power requirements.
The
sorted list or the determination of the relative sensitivity can also be
determined in
the TFC selection processor 13. Accordingly, this processing may be performed
in
the physical layer, the MAC or other layer 2 entities, or even a layer 3
entity. The
MAC entity 12 forwards the selected TFCs 17 (chosen from the available TFCs in
the configured TFCS) to the physical entity 14. In response, the physical
entity 14
indicates blocking and unblocking (removal and restoration) of TFCs 19.
It should be noted that although the methods 10, 50, 150 have been
described hereinbefore as separate procedures, it should clearly be understood
by
those of skill in the art that the methods may be combined as desired for
particular
applications and processing may be performed at the same time. When combining
logic in methods 10, 50 and 150, some changes in the logic specified for each
method are necessary for integration of the methods to achieve proper
operation. As
such, while the present invention has been described in terms of the preferred
embodiments, other variations, which are within the scope of the invention, as
outlined in the claims below will be apparent to those skilled in the art
-16-
