U.S. patent application number 14/177549 was filed with the patent office on 2014-06-05 for method and apparatus for dynamically allocating harq processes in the uplink.
This patent application is currently assigned to INTERDIGITAL TECHNOLOGY CORPORATION. The applicant listed for this patent is InterDigital Technology Corporation. Invention is credited to Christopher Cave, Sudheer A. Grandhi, Paul Marinier, Alexander Reznik, Stephen E. Terry, Eldad M. Zeira.
Application Number | 20140153529 14/177549 |
Document ID | / |
Family ID | 39107345 |
Filed Date | 2014-06-05 |
United States Patent
Application |
20140153529 |
Kind Code |
A1 |
Marinier; Paul ; et
al. |
June 5, 2014 |
METHOD AND APPARATUS FOR DYNAMICALLY ALLOCATING HARQ PROCESSES IN
THE UPLINK
Abstract
Methods and apparatus for dynamically allocating HARQ processes
are described. A wireless transmit/receive unit (WTRU) includes a
receive unit configured to receive signaling and a transmit unit.
The transmit unit is configured to transmit uplink data
sequentially using a first integer number of hybrid automatic
repeat request (HARQ) processes during normal HARQ operation and
transmit uplink data using a second integer number of HARQ
processes that is less than the first number of HARQ processes in
response to receiving the signaling.
Inventors: |
Marinier; Paul; (Brossard,
CA) ; Zeira; Eldad M.; (Huntington, NY) ;
Reznik; Alexander; (Titusville, NJ) ; Grandhi;
Sudheer A.; (Pleasanton, CA) ; Terry; Stephen E.;
(Northport, NY) ; Cave; Christopher;
(Dollard-des-Ormeaux, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
InterDigital Technology Corporation |
Wilmington |
DE |
US |
|
|
Assignee: |
INTERDIGITAL TECHNOLOGY
CORPORATION
Wilmington
DE
|
Family ID: |
39107345 |
Appl. No.: |
14/177549 |
Filed: |
February 11, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11841156 |
Aug 20, 2007 |
8687508 |
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14177549 |
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60839172 |
Aug 21, 2006 |
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60829457 |
Oct 13, 2006 |
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60863543 |
Oct 30, 2006 |
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60868185 |
Dec 1, 2006 |
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Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04L 1/1812 20130101;
H04L 1/1854 20130101; H04W 72/04 20130101; H04L 1/1822 20130101;
H04L 1/1867 20130101; H04L 1/1825 20130101 |
Class at
Publication: |
370/329 |
International
Class: |
H04L 1/18 20060101
H04L001/18; H04W 72/04 20060101 H04W072/04 |
Claims
1. A wireless transmit/receive unit (WTRU) comprising: a receive
unit configured to receive signaling; and a transmit unit
configured to: transmit uplink data sequentially using a first
integer number of hybrid automatic repeat request (HARQ) processes
during normal HARQ operation, and transmit uplink data using a
second integer number of HARQ processes that is less than the first
number of HARQ processes in response to receiving the
signaling.
2. The WTRU of claim 1, wherein the transmit unit is further
configured to transmit the uplink data using the second integer
number of HARQ processes sequentially.
3. The WTRU of claim 1, wherein the first integer number of HARQ
processes is 8.
4. The WTRU of claim 1, wherein the receive unit is configured to
receive the signaling from a wireless network.
5. The WTRU of claim 1, wherein the transmit unit is further
configured to transmit the uplink data using one HARQ process in
each of a plurality of transmission time intervals (TTIs).
6. A method for use in a wireless transmit/receive unit (WTRU)
comprising: the WTRU receiving signaling; the WTRU transmitting
uplink data sequentially using a first integer number of hybrid
automatic repeat request (HARQ) processes during normal HARQ
operation; and the WTRU transmitting uplink data using a second
integer number of HARQ processes that is less than the first number
of HARQ processes in response to receiving the signaling.
7. The method of claim 6, further comprising the WTRU transmitting
the uplink data using the second integer number of HARQ processes
sequentially.
8. The method of claim 6, wherein the first integer number of HARQ
processes is 8.
9. The method of claim 6, further comprising the WTRU receiving the
signaling from a wireless network.
10. The method of claim 6, further comprising the WTRU transmitting
the uplink data using one HARQ process in each of a plurality of
transmission time intervals (TTIs).
11. A base station comprising: a transmit unit configured to
transmit signaling; and a receive unit configured to: receive
uplink data sequentially using a first integer number of hybrid
automatic repeat request (HARQ) processes during normal HARQ
operation, and receive uplink data using a second integer number of
HARQ processes that is less than the first number of HARQ processes
in response to the signaling.
12. The base station of claim 11, wherein the base station is a
Node-B.
13. The base station of claim 11, wherein the receive unit is
further configured to receive the uplink data sequentially using
the second integer number of HARQ processes.
14. The base station of claim 11, wherein the first integer number
of HARQ processes is 8.
15. The base station of claim 11, wherein the receive unit is
further configured to receive the uplink data using one HARQ
process in each of a plurality of transmission time intervals
(TTIs).
16. A method for use in a base station, the method comprising: the
base station transmitting signaling; the base station receiving
uplink data sequentially using a first integer number of hybrid
automatic repeat request (HARQ) processes during normal HARQ
operation; and the base station receiving uplink data using a
second integer number of HARQ processes that is less than the first
number of HARQ processes in response to the signaling.
17. The method of claim 16, wherein the base station is a
Node-B.
18. The method of claim 16, further comprising the base station
receiving the uplink data sequentially using the second integer
number of HARQ processes.
19. The method of claim 16, wherein the first integer number of
HARQ processes is 8.
20. The method of claim 16, further comprising the base station
receiving the uplink data using one HARQ process in each of a
plurality of transmission time intervals (TTIs).
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/841,156 filed Aug. 20, 2007, which claims
the benefit of U.S. Provisional Application No. 60/839,172, filed
Aug. 21, 2006, U.S. Provisional Application No. 60/829,457, filed
Oct. 13, 2006, U.S. Provisional Application No. 60/863,543, filed
Oct. 30, 2006, and U.S. Provisional Application No. 60/868,185,
filed Dec. 1, 2006, the contents of which are hereby incorporated
by reference herein.
FIELD OF INVENTION
[0002] The present invention is related to a wireless communication
systems. More particularly, a method and apparatus for dynamically
allocating hybrid automatic repeat request (HARQ) processes for
wireless transmit/receive units (WTRUs) in the uplink is
disclosed.
BACKGROUND
[0003] The uplink capacity in a code division multiple access
(CDMA)-based system, such as high speed packet access (HSPA), or a
single channel frequency division multiple access (SC-FDMA) system,
such as an evolved universal terrestrial radio access network
(E-UTRAN), is limited by interference. For a CDMA-based system,
uplink interference at a specific cell site is typically generated
by WTRUs, (i.e., users) connected to the cell as well as WTRUs
connected to other cells. In the case of an SC-FDMA-based system,
uplink interference stems primarily from WTRUs connected to other
cells. To maintain coverage and system stability, a cell site can
tolerate only up to a certain amount of uplink interference at any
given instant in time. As a result, system capacity is maximized if
interference can be kept constant as a function of time. This
consistency allows a maximum of users to transmit and/or generate
interference without having the uplink interference exceeding a
predetermined threshold at any time.
[0004] High-speed uplink packet access (HSUPA), as defined in the
Third Generation Partnership Project (3GPP) Release 6, employs HARQ
with synchronous retransmissions. When utilizing a 2 millisecond
(ms) transmission timing interval (TTI), the minimum instantaneous
data rate is often larger than the data rate offered by an
application, due to the need to transmit a number of bits that is
at least the size of a single radio link control (RLC) protocol
data unit (PDU) in a given TTI. When this occurs, a WTRU can
utilize only a subset of the available HARQ processes. As a result,
the interference generated by a given active WTRU is not constant
over a time span of eight (8) TTIs. During some TTIs, the WTRU
transmits data and the interference it generates is high. During
other TTIs, the WTRU may only transmit control information and,
therefore, the interference it generates is low. In order to
equalize interference across all TTIs, the system can restrict each
WTRU to use a certain WTRU-specific subset of HARQ processes, and
select different subsets for different WTRUs.
[0005] Transmissions from a WTRU for a certain stream of data may
be managed by non-scheduled transmissions or scheduling grants.
With non-scheduled transmissions, the WTRU can freely transmit up
to a fixed data rate in certain HARQ processes. With scheduling
grants, the WTRU can also transmit up to a certain data rate on
certain HARQ processes, but the maximum data rate is subject to
change dynamically depending on the maximum power ratio signaled by
a Node-B at a given time.
[0006] When the network manages the transmission by allowing
non-scheduled transmissions, the set of HARQ processes is signaled
to the WTRU through radio resource control (RRC) signaling. The
Node-B determines the set of HARQ processes and signals this
information to the radio network controller (RNC), which then
relays it to the user through RRC signaling. An advantage of
managing delay-sensitive traffic with non-scheduled transmissions
is that it eliminates the possibility of any additional delay that
could be caused by insufficiency of the resources granted by the
Node-B when managing the transmissions with scheduling grants.
Another advantage is that it eliminates the signaling overhead due
to the transmission of scheduling information that is required with
scheduling grants.
[0007] With the currently defined mechanisms for non-scheduled
transmissions, however, the performance of the system is
sub-optimal when the application mix is dominated by
delay-sensitive applications that generate traffic patterns
exhibiting periods of high activity alternated with periods of low
activity. An example of this type of application is the voice over
Internet protocol (VoIP) application, in which silence periods
translate into a very low amount of traffic needing to be
transmitted. When the cell or system is dominated by this type of
application, capacity is maximized only if the network is capable
of modifying the subset of HARQ processes used by a WTRU when its
activity state changes, so that the interference is always
equalized across the HARQ processes. Otherwise, the network has to
restrict the number of WTRUs utilizing a certain HARQ process so
that the threshold is not exceeded, even when they are all active
at the same time, resulting in a much lower capacity.
[0008] An issue when utilizing non-scheduled transmissions is that
it allows modification of the subset of allowed HARQ processes only
through RRC signaling, which typically involves latencies of
several hundreds of milliseconds. This latency is significant
compared to a typical interval between changes of activity for
applications such as voice applications. Furthermore, RRC signaling
in the current Release 6 architecture is controlled by the RNC.
Therefore, the Node-B needs to signal the modification of the
subset of allowed HARQ processes to the RNC beforehand. The
interval of time between the change of activity state at the WTRU
and the effective change of HARQ processes may well be larger than
the duration of the activity state. Accordingly, this becomes
unworkable for equalizing interference across HARQ processes.
[0009] It would therefore be beneficial to provide a method and
apparatus for dynamically allocating HARQ processes in the uplink
that would aid in optimizing capacity with non-scheduled
transmissions.
SUMMARY
[0010] Methods and apparatus for dynamically allocating HARQ
processes are described. A wireless transmit/receive unit (WTRU)
includes a receive unit configured to receive signaling and a
transmit unit. The transmit unit is configured to transmit uplink
data sequentially using a first integer number of hybrid automatic
repeat request (HARQ) processes during normal HARQ operation and
transmit uplink data using a second integer number of HARQ
processes that is less than the first number of HARQ processes in
response to receiving the signaling.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] A more detailed understanding of the invention may be had
from the following description of a preferred embodiment, given by
way of example and to be understood in conjunction with the
accompanying drawings wherein:
[0012] FIG. 1 shows an exemplary wireless communication system
including a plurality of WTRUs, and a Node-B;
[0013] FIG. 2 is a functional block diagram of a WTRU and the
Node-B of FIG. 1;
[0014] FIG. 3A is a flow diagram of a method of allocating
processes;
[0015] FIG. 3B is a flow diagram of an exemplary implementation of
the method of FIG. 3A;
[0016] FIG. 4 is a flow diagram of a method of allocating
processes, in accordance with an alternative embodiment;
[0017] FIG. 5 is an exemplary diagram of system resource unit (SRU)
allocation in accordance with the method of FIG. 4;
[0018] FIG. 6 is a flow diagram of a method of allocating
processes, in accordance with an alternative embodiment; and
[0019] FIG. 7 is a flow diagram of a method of allocating
processes, in accordance with an alternative embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] When referred to hereafter, the terminology "wireless
transmit/receive unit (WTRU)" includes but is not limited to a user
equipment (UE), a mobile station, a fixed or mobile subscriber
unit, a pager, a cellular telephone, a personal digital assistant
(PDA), a computer, or any other type of user device capable of
operating in a wireless environment. When referred to hereafter,
the terminology "base station" includes but is not limited to a
Node-B, a site controller, an access point (AP), or any other type
of interfacing device capable of operating in a wireless
environment.
[0021] FIG. 1 shows an exemplary wireless communication system 100
including a plurality of WTRUs 110, a Node-B (NB) 120, and a radio
network controller (RNC) 130. As shown in FIG. 1, the WTRUs 110 are
in wireless communication with the NB 120, which is connected to
the RNC 130. Although three WTRUs 110, one NB 120, and one RNC 130
are shown in FIG. 1, it should be noted that any combination of
wireless and wired devices may be included in the wireless
communication system 100.
[0022] FIG. 2 is a functional block diagram 200 of a WTRU 110 and
the NB 120 of the wireless communication system 100 of FIG. 1. As
shown in FIG. 2, the WTRU 110 is in communication with the NB 120
and both are configured to perform a method of dynamic process
allocation.
[0023] In addition to the components that may be found in a typical
WTRU, the WTRU 110 includes a processor 115, a receiver 116, a
transmitter 117, and an antenna 118. The processor 115 is
configured to perform a dynamic process allocation procedure. The
receiver 116 and the transmitter 117 are in communication with the
processor 115. The antenna 118 is in communication with both the
receiver 116 and the transmitter 117 to facilitate the transmission
and reception of wireless data.
[0024] In addition to the components that may be found in a typical
NB, the NB 120 includes a processor 125, a receiver 126, a
transmitter 127, and an antenna 128. The processor 115 is
configured to perform a dynamic process allocation procedure. The
receiver 126 and the transmitter 127 are in communication with the
processor 125. The antenna 128 is in communication with both the
receiver 126 and the transmitter 127 to facilitate the transmission
and reception of wireless data.
[0025] FIG. 3A is a flow diagram of a method 300 of allocating
processes. In general, the method 300 involves signaling to the
WTRU 110 a subset of allowed HARQ processes. This signaling is
preferably used for those WTRUs 110 utilizing non-scheduled
transmissions with 2 ms TTIs, and those enabled to utilize the
method 300. Also, preferably, the information required for
enablement is communicated to the network through RRC signaling
that is defined over one or more TTIs.
[0026] In step 310, HARQ processes to be activated or deactivated
are identified and signaled to a WTRU 110 or group of WTRUs 110
(step 320). This signaling may be performed in a variety of
ways.
[0027] For example, in one preferred method, each time a signal
command is sent, an individual HARQ process is either activated or
deactivated, depending on its current activation state. In this
way, the number of bits that require encoding depends on the
maximum number of HARQ processes. For eight (8) HARQ processes, as
are used in HSUPA, 3 bits would need to be signaled, plus an
additional bit that indicates whether the HARQ process is to be
activated/deactivated. It could also be implicit that the command
signal toggles between activation and deactivation, where the last
bit would be omitted since it would be unneeded. However, in this
manner, the WTRU 110 would have to know beforehand how to interpret
the signal.
[0028] Another alternative method could be that each time the
command signal is sent, one HARQ process is activated and another
HARQ process is deactivated. In this method, enough bits to encode
two HARQ processes, (e.g., six (6) bits), would be required. In
this manner, a HARQ process that is deactivated may be activated
and a HARQ process that is activated may be deactivated.
Alternatively, all active HARQ processes may be deactivated, and
all deactivated HARQ processes may be activated.
[0029] Steps 310 and 320 of method 300 may also be performed by
implicitly signaling the activation or de-activation of an
individual HARQ process by the transmission time of the signaling,
such as the frame and sub-frame. For example, a rule may be
pre-established between the frame/sub-frame number of the signaling
command and the HARQ process involved. In this way, no bit is
necessarily required to specify an individual HARQ process, but the
NB 120 would be constrained to activate/de-active the individual
HARQ process only at a specific frame or sub-frame. However, a
single bit may be utilized if desirable to signal whether a process
is activated or deactivated. Alternatively, a combination of
methods may be used, such as by indicating de-activation of an
individual process by the transmission time and indicating the
activation of a process by using a bit or bits, or vice versa.
[0030] Yet another alternative for employing steps 310 and 320 of
the method 300 of FIG. 3A is to utilize the signaling command to
specify the activation or deactivation of all HARQ processes at
once. This may be accomplished by defining a bit map where each bit
represents a HARQ process and the value of the bit indicates
whether or not the process should be activated or deactivated, or
the active/deactive state of the process merely switched.
[0031] It should be noted that in the current state of the art,
HARQ process numerators, also referred to as HARQ process indices,
are WTRU specific. However, the RNC 130 may align the numerators so
that broadcast information may be used by all WTRUs 110 in
communication with the RNC 130. Alternatively, a particular WTRU
110 may be signaled before the correspondence between each bit of
the bitmap and each HARQ process numerator.
[0032] For example, there are eight (8) possible HARQ processes for
each WTRU that are identified with an index, (e.g., from 1 to 8).
As the WTRUs 110 are not synchronized with one another, HARQ
process N for a particular WTRU 110 is generally not transmitted at
the same time as HARQ process N for another WTRU 110. However, the
NB 120 may desire to activate or deactivate HARQ processes for
multiple WTRUs 110 that are transmitted at a specific time. To
enable this signaling to take place in a "broadcast" scenario, the
HARQ process indices of the different WTRUs 110 should be
synchronized so that HARQ process N for one particular WTRU 110 is
transmitted at the same time as HARQ process N for any other WTRU
110. Alternatively, each WTRU 110 may be made aware in advance
which process index should be turned on or off if the NB 120
signals that all processes being transmitted at a given time, that
may be specified by some common reference, should be turned on or
off.
[0033] In another way of performing steps 310 and 320 of the method
300 of FIG. 3A, the WTRU 110 may be permitted to utilize an
individual process that has been "toggled off" under conditions
pre-specified or signaled from the network beforehand. One of these
conditions may include the buffer occupancy of data for uplink
transmission by the WTRU 110. The number of bits associated with
each individual process could vary and may indicate a priority of
usage in that different priorities would correspond to respective
different sets of conditions for usage of each individual
process.
[0034] The number of bits may be equal to the maximum number of
HARQ processes. For example, eight (8) bits are used for HSUPA.
Alternatively, the required number of bits could be reduced if the
set of HARQ processes that can potentially be activated for a
particular WTRU 110 is smaller than the maximum number of possible
HARQ processes. The set of potentially activated HARQ processes
could be signaled to the WTRU 110 through higher-layers, (e.g.,
RRC) in the same way that a set of restricted HARQ processes is
signaled.
[0035] The signaling command may also specify the set of allowed
HARQ processes, (i.e., those HARQ processes that the WTRU 110 can
use for uplink transmission), taking effect immediately or at a
fixed delay from when the information is received by the WTRU 110.
Alternatively, the updated set of allowed processes can take effect
at a time specified in the signaling message itself. Preferably,
the set of allowed HARQ processes is signaled as an index into a
table where multiple sets of allowed HARQ processes are already
pre-defined and known at the WTRU 110. The number of bits
representing the index will limit the number of sets that can be
pre-defined. The mapping between the index and set of allowed HARQ
processes can be pre-configured through higher layer signaling or
the set of allowed HARQ processes can be explicitly signaled to the
WTRU 110 by enumerating the specific allowed process numbers.
[0036] Another way to perform steps 310 and 320 of the method 300
of FIG. 3A is for the signaling to specify the probabilities for
which the WTRU 110 should turn on or off individual HARQ processes.
Preferably, a single probability value is signaled per HARQ
process, (e.g., turn off), and a second probability value, (e.g.,
turn on), is calculated by using the signaled value according to a
predefined rule. Alternatively, both the off and on probabilities
may be explicitly signaled to the WTRU 110.
[0037] For any of the above described methods, the signaling
commands may be sent (step 320), or directed, to an individual WTRU
110 or to a plurality of WTRUs 110.
[0038] In one preferred embodiment, the functionality of the
enhanced dedicated channel (E-DCH) absolute grant channel (E-AGCH)
may be extended by defining additional interpretation of the
information bits. The correct interpretation may be known to the
WTRU 110 by time multiplexing in different TTIs and/or by using
different spreading codes. The times and codes may be signaled to
the WTRU 110 by the network. Additionally, the interpretation may
be implied by an identification code embedded in the E-AGCH such as
the WTRU ID. This is equivalent to defining a new physical channel
with a new name, (e.g., enhanced active process indicator channel
(E-APICH), that may be time and/or code-multiplexed with the
E-AGCH.
[0039] Currently, the E-AGCH identifies WTRUs 110 by masking the
cyclic redundancy code (CRC) with enhanced radio network temporary
identifiers (E-RNTIs) of 16 bits. This approach could be extended
by defining additional E-RNTIs for non-scheduled transmissions for
the WTRUs 110 that use both scheduled and non-scheduled
transmissions. The WTRU 110 should respond to more than one E-RNTI.
It is also possible to separate scheduled and non-scheduled
operations in time. For processes that have been allowed use by the
RNC 130 for non-scheduled operation, the AGCH utilizes the bit
interpretation as described in the embodiments above, while in
other processes it utilizes the bit interpretation as utilized in
the current state of the art.
[0040] Additionally, the network may define groups of WTRUs 110 and
E-RNTI values for these groups. This allows faster signaling in
case some HARQ processes need to be deactivated for multiple WTRUs
110. Accordingly, a particular WTRU 110 can be associated with a
set of E-RNTI values, among which some may be common to multiple
WTRUs 110. Further processing may be similar to what is currently
defined for the E-AGCH, such as convolutional encoding followed by
rate matching. There are additional possibilities in terms of
coding rate, amount of rate matching, size of CRC, and the like, to
fit the required number of information bits on the E-AGCH or
E-APICH. Preferably, the coding rate and rate matching should be
kept the same as the prior art E-AGCH to simplify decoding
operation at the WTRU 110. By way of example, the E-AGCH may
contain the WTRU ID information (E-RNTI)/CRC (16 bits) and 6 bits
of payload. Depending on how many bits are needed to encode the
instructions, one or more E-AGCH transmissions may be combined by
concatenating their available bits. In another example, the
E-RNTI/CRC field may be reduced from 16 bits to a smaller number of
bits to increase the available number of bits.
[0041] Another way of signaling the WTRU 110 in step 320 may be to
extend the E-RGCH/E-HICH functionality, or multiplex a newly
defined channel with these channels by utilizing distinct
orthogonal sequences to contain the new signaling. This option
allows the transmission of a binary value every TTI. One or more
WTRUs 110 is identified by an orthogonal sequence (signature). It
is also possible to transmit three (3) binary values by not
combining the sequences in each of the three (3) slots of the TTI.
However, this way may require greater transmission power. If the
number of orthogonal sequences required to support the new
signaling and the existing enhanced relative grant channel
(E-RGCH)/enhanced HARQ indicator channel (E-HICH) is insufficient,
a different spreading code may be utilized to contain the new
signaling, allowing the reuse of the orthogonal sequences of the
E-RGCH/E-HICH.
[0042] Alternatively, the format of the high speed shared control
channel (HS-SCCH) may be modified to include
activation/de-activation commands. The format for the additional
bits may be similar to the methods set forth above for the
E-AGCH.
[0043] In addition to the signaling methods for step 320 described
above, various other techniques may be utilized. For example, the
existing broadcast control channel (BCCH)/broadcast channel (BCH)
may be extended to include the signaling information related the
activation/de-activation of individual HARQ processes. The existing
RRC control signaling may be extended to convey information related
to the activation/de-activation of individual HARQ processes. The
high speed medium access control (MAC-hs) header may be modified to
include activation/de-activation commands, with the format for the
additional bits potentially being similar to one of the options
described above for the E-AGCH. For this particular example, as
retransmissions are asynchronous in the downlink (DL), and since
the WTRU 110 can typically only decode the information once the
downlink PDU decoding is successful, signaling options where an
individual HARQ process is implicitly indicated by the signaling
time should preferably refer to the transmission time of the
HS-SCCH that corresponds to the first transmission for this
downlink PDU.
[0044] To make the signaling compatible with the use of
discontinuous reception (DRX) or discontinuous transmission (DTX)
at the WTRU 110, it may be required to impose rules to force the
WTRU 110 to listen, (i.e., not be in DRX), during TTIs where it
would otherwise be in DRX, when certain conditions are met.
[0045] For example, the WTRU 110 could be required to not utilize
DRX for a certain period of time immediately following resuming or
interruption of voice activity, so that the NB 120 may modify the
activated HARQ processes if needed. Alternatively, it could be
required that the WTRU 110 listens periodically during certain TTIs
when it would otherwise be in DRX, according to a pre-determined
pattern. By way of another example, a WTRU 110 could be required to
stop DRX, (i.e., listen in all TTIs), when the NB 120 deactivates a
HARQ process until another HARQ process is activated. Thus, the NB
120 that desires to modify the HARQ process allocation of a
particular WTRU 110 would start by de-activating one of the HARQ
processes knowing that the WTRU 110 will be listening for the
activation of the new HARQ process. The converse rule, (activate
first and deactivate second), is also possible. More generally, a
rule could be established that allows the WTRU 110 to activate DRX
only when it has a specified number of HARQ processes
activated.
[0046] To ensure that the new set of HARQ processes corresponds to
the DRX/DTX pattern the WTRU 110 is using, the network may signal
DRX activate and/or DTX activate from the NB 120 to the WTRU 110.
Alternatively, signaling could be done by higher layers. Since
individual or group WTRU signaling to enable or disable a process
exists in the current state of the art, it can be extended to
indicate conditions for usage of multiple processes.
[0047] The embodiments may also support macrodiversity. For
example, a particular WTRU 110 may be in a state where it transmits
to one or more NBs 120 (additional NBs not shown) in an active set
in addition to its serving NB 120, which then sends the data to the
RLC to be macro-combined. If the serving NB 120 changes the
allocated HARQ processes, the other cells in the active set may
blindly detect uplink transmissions from the WTRU 110 in the new
HARQ processes, or the serving NB 120 may signal changes to the RNC
130 which then relates them to other NBs 120 in the active set.
[0048] Due to power control, all WTRUs 110 may be considered
interchangeable with respect to their contribution to uplink
interference. The NB 120, therefore, has the ability to choose
which WTRU 110 it transfers between processes. Accordingly, the NB
120 can choose not to change the HARQ process allocation of WTRUs
110 in handover.
[0049] As WTRUs 110 move within the system, changes of E-DCH
serving NB 120 will be required periodically. In order to support
this mobility, several alternatives exist for the behavior of the
WTRU 110 and NB 120 during this period. In one example, the WTRU
110 is allowed to transmit on any HARQ process that is not
restricted by higher layers, (i.e., all processes are active),
until it receives activation/de-activation commands from the new
serving NB 120. Alternatively, the WTRU 110 may be disallowed to
transmit on any HARQ process, (i.e., all processes are inactive),
until it receives activation commands from the new serving NB
120.
[0050] In another preferred embodiment, however, the WTRU 110
maintains the same active/inactive state of each of its HARQ
processes upon change of E-DCH serving NB 120. The new E-DCH
serving NB 120 then sends an activation/de-activation command that
changes the state of each HARQ process. If the new serving NB 120
sends a de-activation command for a HARQ process that was already
inactive, or an activation command for a HARQ process that was
already active, the WTRU 110 may ignore the command. Optionally,
the new serving NB 120 may signal the active/inactive state of HARQ
processes of the WTRU 110 by the RNC 130 upon setup of the radio
link through Iub. Such signaling would require that the old serving
NB 120 signals this information to the RNC 130, again through Iub,
prior to or upon the change of E-DCH (enhanced data channel
handler) serving Node-B.
[0051] The WTRU 110 then reacts to signaling that it receives (step
330). This reaction may include several variations. In one example,
the WTRU 110 may listen at least when the MAC-e state changes from
no uplink data to uplink data. A change from no data to data is
indicated when N1 TTIs have elapsed where new data has arrived in
the buffer. A change from data to no data is indicated when N2 TTIs
have elapsed without new data arriving in buffer. N1 and N2 may be
signaled beforehand by the network to the WTRU 110. If signaled
specifically the WTRU 110 must then enable or disable the processes
as instructed.
[0052] In an alternative example, if the WTRU 110 is signaled as a
part of a group of WTRUs, the WTRU 110 may decide randomly whether
to execute the instruction utilizing a probability that may be
signaled by the network. In order to support synchronous
retransmissions within a HARQ process, preferably the WTRU 110
should only be allowed to switch to a different HARQ process once
the current HARQ process is complete, that is, once a positive ACK
has been received or the maximum number of retransmissions has been
met. Alternatively, if signaled as part of a group, the WTRU 110
may wait a random amount of time before executing the instruction,
where the random amount of time may be signaled to the WTRU 110
beforehand by the network.
[0053] When DRX or DTX is activated, and if the WTRU 110 was
previously instructed to behave so by higher layer signaling, the
WTRU 110 adjusts the reference for its DRX and DTX pattern to
correspond to the time of the last DRX or DTX activation signal,
respectively. Alternatively the WTRU 110 adjusts the DRX/DTX
pattern to correspond to the set of HARQ processes signaled. The
mapping of HARQ processes to DRX/DTX patterns could be
pre-determined, or could be signaled ahead of time by higher layer
signaling.
[0054] In the current 3GPP Release 6 architecture, the RRC layer is
terminated at the RNC 130. When leaving control of the HARQ process
activation to the NB 120, the NB 120 may require information about
the quality of service (QoS) requirements of the WTRU 110 to avoid
an excessive reduction in the number of activated processes. Such a
reduction of the number of activated processes in a non-scheduled
operation would undesirably force the WTRU 110 to increase its
instantaneous data rate during its active processes and reduce the
area over which it can meet its QoS. Accordingly, it may be useful
to have the RNC 130 communicate information to the NB 120 regarding
the WTRUs 110, or have the NB 120 acquire the information in some
other way.
[0055] For example, the RNC 130 may estimate the minimum number of
HARQ processes that need to be activated at a given time to support
the WTRU 110 transmissions. The RNC 130 has the capability of
performing this estimation since it knows what the guaranteed bit
rate is and has control over the throughput of the HARQ process
through outer-loop power control and HARQ profile management. The
RNC 130 communicates this number of HARQ processes to the NB 120
through NBAP signaling. The NB 120 ensures that the WTRU 110 has at
least this number of HARQ processes activated at any time. Because
of the simplicity, this process may be desirable for the NB
120.
[0056] Additionally, the RNC 130 may provide the guaranteed bit
rate to the NB 120 through NBAP signaling. Based on the guaranteed
bit rate, the NB 120 estimates how many active HARQ processes are
required at a given time and activates individual processes
accordingly. The NB 120 may also determine to deactivate certain
processes during periods of inactivity.
[0057] Alternatively, the RNC 130 may not provide any information
to the NB 120. Instead, the NB 120 may endeavor to maintain the
number of active HARQ processes for a given WTRU 110 to the
smallest possible value with the constraint that it never has to
transmit more than one RLC PDU at a time unless all HARQ processes
are already activated. The NB 120 could detect the transmission of
more than one RLC PDU by inspecting the content of successfully
decoded MAC-e PDUs. This approach provides significant flexibility
to the NB 120, but may be more complex to implement.
[0058] Any HARQ process allocation changes and resulting DRX/DTX
pattern or reference changes determined by NB 120 may be signaled
to the RNC 130, which may signal those changes to a target NB 120
in case of handover.
[0059] In the current state of the art, the set of HARQ processes
that the WTRU 110 is allowed to use is indicated by the RNC 130
through L3 signaling. This signaling could be maintained,
indicating the allowed HARQ processes for the WTRU 110, which may
be activated or deactivated by the NB 120 as per the various
schemes described above. In addition, the RNC 130 could indicate to
the WTRU 110 the initial set of HARQ processes to be activated.
[0060] FIG. 3B is a flow diagram of an exemplary implementation 305
of the method 300 of FIG. 3A. In particular, the implementation 305
allows the RNC 130, NB 120 and WTRU 110 to optimize capacity, such
as for VoIP or any other delay sensitive application. Upon call
setup initiation (step 370), a particular WTRU 110 is preferably
provided with a list of potentially activated HARQ processes (step
375). Alternatively, if a list is not provided, the WTRU 110 may
assume that it can potentially use all HARQ processes. The RNC 130
also provides information to the NB 120, preferably through NBAP to
aid the NB 120 in determining the required number of HARQ
processes.
[0061] After the WTRU 110 commences transmission, the NB 120 begins
de-activating HARQ processes for which the interference in the
system is the greatest (step 380). Additionally, the NB 120
maintains as active the HARQ processes for which interference was
minimal.
[0062] The NB 120 then continuously monitors the activity of all
admitted WTRUs 110 in the system with non-scheduled transmissions
(step 385) and tries to maintain the interference across all HARQ
processes below a particular threshold by changing the active HARQ
processes as a function of activity (step 390). There are numerous
ways in which to perform step 390.
[0063] One way is that when the NB 120 detects that a previously
inactive WTRU 110 becomes active, the NB 120 changes the set of
active HARQ processes for this WTRU 110 to HARQ processes where the
interference is the least. Alternatively, if a previously active
WTRU 110 becomes inactive, it can swap its set of active HARQ
processes with the set of another active WTRU 110. Additionally,
the NB 120 could also deactivate most HARQ processes of a
particular WTRU 110 that has become inactive, and activate other
HARQ processes, such as where interference is minimal, when
activity resumes.
[0064] Another alternative is that the NB 120 may monitor the
interference on each HARQ process and periodically re-allocate one
of the HARQ processes of one WTRU 110 from the most interfered HARQ
process to the least interfered HARQ process, provided that the
maximum level of interference over all processes does not increase.
That is, a most interfered with HARQ process in the WTRU 110 is
deactivated and a least interfered with HARQ process in the WTRU
110 is activated.
[0065] FIG. 4 is a flow diagram of a method 400 of allocating
processes, in accordance with an alternative embodiment. Since the
purpose of the E-APICH is to maintain an uplink interference
profile that is as uniform as possible between HARQ processes, a
group-wise allocation of system resources is possible to the WTRUs
110.
[0066] In step 410 of the method 400 of FIG. 4, a system resource
unit (SRU) is defined. Preferably, the SRU is defined to be a
combination of a HARQ process and a granular amount of an
interfering system resource, such as rate or power. The interfering
system resource is preferably defined by considering that in an
interference limited system, such as a CDMA uplink, there is only a
finite amount of power or rate that can be utilized by transmitters
simultaneously. Usage of more resources than is available will
cause interference and likely loss of packets. Although in a
preferred embodiment, the interfering system resource is typically
measured using rate or power, other measures can be used.
Additionally, required signal-to-interference ratio (SIR), received
power, uplink load, (i.e., a fraction of UL pole capacity) are
measures that may also be utilized.
[0067] In step 420 of the method 400 of FIG. 4, the SRUs are
allocated to the WTRUs 110. In fact, all allocation in the present
alternative embodiment of the invention is done using SRUs.
Preferably, a group of WTRUs 110 is selected and allocated the same
non-scheduled SRUs. Depending on how the SRU is defined this can be
performed in a variety ways. For example, if SRU=(HARQ process,
power), then HARQ processes can be allocated via RRC signaling,
where power is allocated via a mechanism such as the E-AGCH. All
SRU processes within a group are assumed active, and therefore, all
HARQ processes are active. Fast allocation is used only to allocate
SRUs within the group. Optional "banning" of SRUs in a group is
possible to make sure that no WTRU 110 in a group uses a particular
HARQ process at a given time.
[0068] The allocation of SRUs to WTRU groups may be performed by
allocating SRUs to single groups such that if this is the only
group transmitting, system resources are now exceeded and
successful communication is assured. However, when multiple groups
are present, the total number of SRUs allocated in a cell may
exceed the total number of available SRUs.
[0069] FIG. 5 is an exemplary diagram of system resource unit (SRU)
allocation in accordance with the method 400 of FIG. 4. In the
example shown in FIG. 5, it may be assumed that a system supports 8
HARQ processes and only 3 SRUs can be supported simultaneously. No
WTRU group is allocated SRUs such that it can induce
self-interference. However, a total of twice as many SRUs as are
available have been allocated, making it possible that interference
will occur if the WTRUs 110 all transmit at the same time. As shown
in FIG. 5, the SRUs are allocated to groups of WTRUs 110 designated
as Group 1, Group 2, Group 3, and Group 4. However, it should be
noted that the depiction of four groups is exemplary, and any
number of groups could be envisioned. By allocating one or several
SRUs to groups of WTRUs 110, fast allocation of SRUs is then
signaled by the NB 120, preferably using the E-APICH, where the NB
120 ensures that no two WTRUs 110 in a particular group are
allocated the same SRU.
[0070] There are several advantages and challenges to a group-wise
approach as described in method 400. By grouping the WTRUs 110,
scheduling in the NB 120 may be simplified. For example, HARQ
allocations are semi-static between groups and dynamic only within
a group. On the other hand, a group provides both sufficient
freedom and sufficient response time to keep the interference
profile relatively stable.
[0071] Additionally, signaling overhead may be reduced since only a
single E-APICH per group is required. All WTRUs 110 in a group
monitor the same E-APICH. Moreover, there is no need for individual
"power grant" to a WTRU 110. A particular WTRU 110 can always be
granted more or less power in a given HARQ process by providing it
more SRUs or by removing some.
[0072] However, as WTRUs 110 enter and leave the cell, a group may
need to be updated, which may lead to an increase in signaling
overhead. This problem may be mitigated by not updating a full
group every time a WTRU 110 enters or leaves a group. Because a
particular WTRU 110 only needs to know its own group and its ID
within a group the group update overhead can be reduced.
[0073] For example, if a WTRU 110 leaves a cell, it group is
maintained intact, but the NB 120 does not allocate any SRUs to
that WTRU 110. Similarly, if a WTRU 110 enters a cell, it may be
added to a group which has an opening, for example due to a WTRU in
a group previously leaving a cell, or a new group may be created,
with this WTRU 110 as the only member. Other WTRUs 110 may
subsequently be added to the newly created group. In any case, the
NB 120 may occasionally have to reconfigure the groups. However,
this will likely be a very infrequent event.
[0074] Depending on the scheduler of the NB 120, the rate required
or services supported by the group size of the WTRUs 110 may vary.
Therefore, there are a variety of ways in which to form the
groups.
[0075] For example, the total SRUs per group may be fixed. The
number of WTRUs 110 per group may be fixed. The total of a
particular individual resource, (e.g., rate, power, HARQ processes)
per group may be fixed. A group may be comprised of WTRUs 110 with
similar receiver characteristics, (e.g. Multi-in-Multi-out (MIMO)
enabled, Type-x receiver). A group may also be comprised of WTRUs
110 with similar channel qualities.
[0076] Although multiplexing and signaling options for group-wise
E-APICH are similar to those described above for the per-WTRU fast
allocation, the signaling options may need to be modified. Since
all HARQ processes are assumed active for a group, the E-AGCH in a
given TTI includes the group index of the WTRU 110 to which this
process is allocated. A special index or non-existing WTRU index
may be used to ban the HARQ process for all WTRUs 110 in a
group.
[0077] Additionally, implicit signaling via timing of transmission
may not be practical for a group, although it may be used as an
overlay for banning the HARQ process. Also, instead of a bit field,
a symbol, (i.e., multi-bit), field is used, where each symbol
indicates which WTRU 110 is permitted a particular HARQ process and
a special symbol or non-existing WTRU index may be used to ban the
process. For example, each WTRU 110 may be assigned a position of a
bit field. A "0" may indicate that the WTRU assigned to this
position cannot use the process while a "1" may indicate that the
WTRU can use the particular process. Additionally, one of the
positions of the bit field might be assigned to no specific WTRU
110, and rather be used to indicate that the process either can or
cannot be used by any, or all, of the WTRUs 110.
[0078] FIG. 6 is a flow diagram of a method 600 of allocating
processes, in accordance with an alternative embodiment. In the
present alternative embodiment, non-scheduled operation may be
enhanced by sending minimal downlink signaling that includes enough
information to a WTRU 110 for dynamically changing HARQ processes
within the constraints specified in the downlink signaling. The
current RRC signaling of HARQ allocation for non-scheduled
operation may be made such that the HARQ processes are restricted
and staggered for the WTRUs 110 so that there is a smooth WTRU load
distribution across the HARQ processes. However, this does not
smooth out the voice activity variations which can cause high
interference during some HARQ processes.
[0079] The RRC signaling of restricted and staggered HARQ
allocation may be utilized to enhance non-scheduled operation. In
step 610 of method 600, the RNC 130 makes a HARQ allocation. Once
that HARQ allocation is made, a known-controlled pattern/hopping
allocation may be utilized (step 620). This known-controlled
pattern/hopping may be used to move the WTRUs 110 that are on top
of the RNC 130 allocation in such a way that the load of WTRUs per
HARQ process remains as before, but the voice activity is smoothed
out across HARQ processes. Preferably, the known-controlled
pattern/hopping distributes and smooths the variations of voice
activity while not disturbing the WTRU load distribution benefits
achieved by restriction and staggering of HARQ processes.
Additionally, it may be bounded below by a non-scheduled HARQ
process allocation that is restricted and staggered.
[0080] The known-controlled pattern/hopping is sent to a particular
WTRU 110 (step 630) in a variety of ways. For example, it may be
sent by RRC signaling or other downlink signaling, such as by the
new physical channel E-APICH signaling described above. The pattern
may be signaled at call setup time or during a call/session on a
semi-static basis which may be needed to fine tune previous
allocations due to changes in the system such as in
load-variations.
[0081] Additionally, the known-controlled pattern/hopping may take
the form of any pattern that generally preserves the load balance
of the WTRUs 110 across the HARQ processes, as provided by the RRC
allocation of non-scheduled operation. For example, it may take the
form of sequential hopping of HARQ processes, from the initial RNC
allocation, based on a multiple of TTI period that may be specified
in RRC or other downlink signaling. The sequential hopping is
circular over the maximum number of HARQ processes and the hopping
direction is picked randomly, for example, with a 0.5
probability.
[0082] Alternatively, the RRC may initially allocate a set of HARQ
processes to the WTRU 110 and the WTRU 110 may "hop" among them
periodically with some multiple of TTIs specified in the RRC or
other downlink signaling. In another alternative, the WTRU 110
hopping may be randomized based on a pseudo-random pattern and the
hopping period specified by RRC or other downlink signaling.
[0083] In yet another alternative, the WTRU 110 may randomly select
a signaled number of processes to be used in each cycle of 8
processes, for example, or the WTRU 110 may randomly decide, each
TTI, whether to transmit or not according to a probability that may
be signaled to the WTRU 110 beforehand. In another alternative, the
probability could depend on the WTRU uplink buffer occupancy that
is defined by the network and signaled beforehand.
[0084] FIG. 7 is a flow diagram of a method 700 of allocating
processes, in accordance with an alternative embodiment. In the
method 700 described in FIG. 7, HARQ processes uses for uplink (UL)
transmissions are randomly selected by particular WTRUs 110 during
selection opportunities. Thes selection opportunities occur every M
TTIs, where M is preferably a multiple of the total number of HARQ
processes, (e.g., 8, 16). The WTRU should be pre-configured through
higher layers to select P HARQ processes on which it is allowed to
transmit until the next selection opportunity.
[0085] In step 710, the RAN assigns a selection opportunity to each
HARQ process. Preferably, the RAN provides a selection probability
between 0 and 1 for each of the allowed HARQ processes, where the
sum of the probabilities for all HARQ processes equals 1. This
allows the RAN to favor some processes over others, based on such
factors as interference generated from scheduled WTRUs 110 and
intercell interference. The random distribution that is used to
select the HARQ processes is signaled by the RAN to the WTRU 110 or
WTRUs 110. The signaling of these parameters may be achieved using
any of the signaling mechanisms described above. The parameters can
be signaled individually to each WTRU 110, to a group of WTRUs 110
or for all WTRUs 110 at once. Preferably, updates to the parameters
may be made at the frequency at which WTRUs 110 select HARQ
processes or at a slower frequency.
[0086] At every selection opportunity, the WTRU 110 should retrieve
the latest set of parameters signaled from the RAN (step 720). The
WTRU 110 then selects a first HARQ process by randomly selecting a
HARQ process among potential processes (step 730), taking into
consideration the selection probability of each process.
[0087] If another process is required (step 740), then the WTRU 110
randomly selects among the remaining processes (step 730), taking
into consideration the selection probability of the remaining
processes. The process continues until the number of processes on
which the WTRU is allowed to transmit until the next selection
opportunity (P) have been selected.
[0088] In order to support synchronous retransmissions within a
HARQ process, preferably the WTRU 110 should only be allowed to
select a different HARQ process once the current HARQ process is
complete, for example once a positive ACK has been received or the
maximum number of retransmissions has been met.
[0089] Although the features and elements are described in the
preferred embodiments in particular combinations, each feature or
element can be used alone without the other features and elements
of the preferred embodiments or in various combinations with or
without other features and elements. The methods or flow charts
provided may be implemented in a computer program, software, or
firmware tangibly embodied in a computer-readable storage medium
for execution by a general purpose computer or a processor.
Examples of computer-readable storage mediums include a read only
memory (ROM), a random access memory (RAM), a register, cache
memory, semiconductor memory devices, magnetic media such as
internal hard disks and removable disks, magneto-optical media, and
optical media such as CD-ROM disks, and digital versatile disks
(DVDs).
[0090] Suitable processors include, by way of example, a general
purpose processor, a special purpose processor, a conventional
processor, a digital signal processor (DSP), a plurality of
microprocessors, one or more microprocessors in association with a
DSP core, a controller, a microcontroller, Application Specific
Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs)
circuits, any other type of integrated circuit (IC), and/or a state
machine.
[0091] A processor in association with software may be used to
implement a radio frequency transceiver for use in a wireless
transmit receive unit (WTRU), user equipment (UE), terminal, base
station, radio network controller (RNC), or any host computer. The
WTRU may be used in conjunction with modules, implemented in
hardware and/or software, such as a camera, a video camera module,
a videophone, a speakerphone, a vibration device, a speaker, a
microphone, a television transceiver, a hands free headset, a
keyboard, a Bluetooth.RTM. module, a frequency modulated (FM) radio
unit, a liquid crystal display (LCD) display unit, an organic
light-emitting diode (OLED) display unit, a digital music player, a
media player, a video game player module, an Internet browser,
and/or any wireless local area network (WLAN) module.
* * * * *