U.S. patent application number 15/180415 was filed with the patent office on 2017-08-10 for cognitive flow control based on channel quality conditions.
This patent application is currently assigned to Signal Trust for Wireless Innovation. The applicant listed for this patent is Signal Trust for Wireless Innovation. Invention is credited to Yi-Ju Chao, Stephen E. Terry.
Application Number | 20170230861 15/180415 |
Document ID | / |
Family ID | 28792084 |
Filed Date | 2017-08-10 |
United States Patent
Application |
20170230861 |
Kind Code |
A9 |
Terry; Stephen E. ; et
al. |
August 10, 2017 |
COGNITIVE FLOW CONTROL BASED ON CHANNEL QUALITY CONDITIONS
Abstract
A system and method which improve the performance of a wireless
transmission system by intelligent use of the control of the flow
of data between a radio network controller (RNC) and a Node B. The
system monitors certain criteria and, if necessary, adaptively
increases or decreases the data flow between the RNC and the Node
B. This improves the performance of the transmission system by
allowing retransmitted data, signaling procedures and other data to
be successfully received at a faster rate, by minimizing the amount
of data buffered in the Node B. Flow control is exerted to reduce
buffering in the Node B upon degradation of channel qualities, and
prior to a High Speed Downlink Shared Channel (HS-DSCH)
handover.
Inventors: |
Terry; Stephen E.;
(Northport, NY) ; Chao; Yi-Ju; (Minnetonka,
MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Signal Trust for Wireless Innovation |
Wilmington |
DE |
US |
|
|
Assignee: |
Signal Trust for Wireless
Innovation
Wilmington
DE
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20160302103 A1 |
October 13, 2016 |
|
|
Family ID: |
28792084 |
Appl. No.: |
15/180415 |
Filed: |
June 13, 2016 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
14577896 |
Dec 19, 2014 |
9369917 |
|
|
15180415 |
|
|
|
|
13755700 |
Jan 31, 2013 |
8942200 |
|
|
14577896 |
|
|
|
|
13444283 |
Apr 11, 2012 |
8379575 |
|
|
13755700 |
|
|
|
|
10431897 |
May 8, 2003 |
8175030 |
|
|
13444283 |
|
|
|
|
60379858 |
May 10, 2002 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 47/10 20130101;
H04W 28/14 20130101; H04L 5/0057 20130101; H04W 72/1252 20130101;
H04L 47/14 20130101; H04L 47/26 20130101; H04L 47/263 20130101;
H04W 72/1231 20130101; H04L 47/30 20130101; H04W 28/0278 20130101;
H04W 72/1284 20130101; H04W 28/0289 20130101; H04W 92/12 20130101;
H04L 47/17 20130101 |
International
Class: |
H04W 28/02 20060101
H04W028/02; H04W 72/12 20060101 H04W072/12; H04L 12/825 20060101
H04L012/825; H04L 12/801 20060101 H04L012/801; H04L 5/00 20060101
H04L005/00 |
Claims
1. A method performed by a wireless device having a buffer, the
method comprising: monitoring an amount of data within the buffer
and determining whether it is acceptable for additional data to be
sent to the wireless device; calculating a capacity allocation
associated with the wireless device; transmitting the capacity
allocation to a network device; and receiving data at the wireless
device in response to the transmitted capacity allocation, wherein
an amount of the received data is equal to or less than the
capacity allocation.
2. The method of claim 1 wherein the buffer comprises a plurality
of buffers or sub-buffers.
3. The method of claim 1 further comprising: calculating a channel
quality index (CQI) associated with the wireless device, wherein
the capacity allocation is based on the CQI.
4. A wireless device comprising: a buffer; a processor configured
to monitor an amount of data within the buffer and determine
whether it is acceptable for additional data to be sent to the
wireless device; a transmitter configured to transmit a capacity
allocation to a network device; and a receiver configured to
receive data in response to the capacity allocation, wherein an
amount of the received data is equal to or less than the capacity
allocation.
5. The wireless device of claim 4 wherein the buffer comprises a
plurality of buffers or sub-buffers.
6. The wireless device of claim 4 wherein the processor is further
configured to calculate a channel quality index (CQI) associated
with the wireless device, and wherein the capacity allocation is
based on the CQI.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 14/577,896, filed Dec. 19, 2014, which is a
continuation of U.S. patent application Ser. No. 13/755,700, filed
Jan. 31, 2013, which issued as U.S. Pat. No. 8,942,200 on Jan. 27,
2015, which is a continuation of U.S. patent application Ser. No.
13/444,283, filed Apr. 11, 2012, which issued as U.S. Pat. No.
8,379,575 on Feb. 19, 2013, which is a continuation of U.S. patent
application Ser. No. 10/431,897, filed May 8, 2003, which issued as
U.S. Pat. No. 8,175,030 on May 8, 2012, which claims priority from
U.S. patent application Ser. No. 60/379,858, filed May 10, 2002,
which are incorporated by reference as if fully set forth.
FIELD OF INVENTION
[0002] The present invention relates to the field of wireless
communications. More specifically, the present invention relates to
the exertion of flow control for data transmissions between a radio
network controller (RNC) and a Node B in a third generation (3G)
telecommunication system.
BACKGROUND
[0003] A 3G Universal Terrestrial Radio Access Network (UTRAN)
comprises several RNCs, each of which is associated with one or
more Node Bs, and each Node B being further associated with one or
more cells.
[0004] The 3G Frequency Division Duplex (FDD) and Time Division
Duplex (TDD) modes typically use the RNC to distribute (i.e.,
buffer and schedule), data transmissions to at least one User
Equipment (UE). However, for the high speed channels of a 3G
cellular system, data is scheduled for transmission by the Node B.
One of these high speed channels, for example, is the High Speed
Downlink Shared Channel (HS-DSCH). Since data is scheduled by the
Node B, it is necessary to buffer data in the Node B for
transmission to the UE(s).
[0005] There are many scenarios where large amounts of data
buffered in the Node B have a negative impact on the overall
operation of the system. Several of these scenarios will be
described hereinafter.
[0006] The first scenario is related to the retransmission
mechanisms in 3G systems to achieve high reliability of end-to-end
data transmissions. It would be understood by those of skill in the
art that the transmission failure between the Node B and the UE
could be due to many different reasons. For example, the Node B may
have retried the transmission several times without success.
Alternatively, the transmission time allotted for a particular
transmission may have expired. The present invention which will be
described in further detail hereinafter is intended to cover both
these situations and any other situations where the failure of a
data transmission necessitates a radio link control (RLC)
retransmission.
[0007] There are many levels of retransmission mechanisms. One
mechanism, for example, is the retransmissions of the Hybrid
Automatic Repeat Request (H-ARQ) process for High Speed Downlink
Packet Access (HSDPA). The H-ARQ process provides a mechanism where
transmissions that are received in error are indicated to the
transmitter, and the transmitter retransmits the data until the
data is received correctly.
[0008] In addition to the H-ARQ process, there are entities in the
RNC and the UE. The sending RLC entity signals a sequence number
(SN) in the header of a particular protocol data unit (PDU) which
is used by the receiving RLC entity to ensure that no PDUs are
missed in the transmission. If there are PDUs missed during the
transmission, as realized by an out-of-sequence delivery of PDUs,
the receiving RLC entity sends a status report PDU to inform the
sending RLC entity that certain PDUs are missing. The status report
PDU describes the status of successful and/or unsuccessful data
transmissions. It identifies the SNs of the PDUs that are missed or
received. If a PDU is missed, the sending RLC entity will
retransmit a duplicate of the missed PDU to the receiving RLC
entity.
[0009] The impact of retransmissions in system performance will be
described with reference to FIG. 1. As shown, when the PDU with
SN=3 is not received successfully by the UE, the RLC within the UE
requests its peer entity in the RNC for a retransmission. In the
interim, the PDUs with SNs=6 and 7 are queued in the buffer of the
Node B.
[0010] Referring to FIG. 2, since the retransmission process takes
a finite amount of time and data is continuing to be transmitted,
two more PDUs with SNs=8 and 9 have queued up behind the PDUs with
SNs=6 and 7, and in front of the retransmitted PDU with SN=3. The
PDU with SN=3 will have to wait until the PDUs with SNs=6-9 have
been transmitted to the UE. Additionally, due to the requirement of
in-sequence delivery of data to higher layers, the PDUs with
SNs=4-9 will not be passed through higher layers until the PDU with
SN=3 is received and in-sequence delivery of data can be
performed.
[0011] The UE will be required to buffer the out-of-sequence data
until the missing PDU can be transmitted. This not only results in
a delay of the transmission, but requires the UE to have a memory
capable of data buffering for continuous data reception until the
missed data can be successfully retransmitted. Otherwise, the
effective data transmission rate is reduced, thereby affecting
quality of service. Since memory is very expensive, this is an
undesirable design constraint. Accordingly, this first scenario is
when there is a need for RLC retransmission and a large amount of
data buffered in the Node B results in a larger data retransmission
delay and higher UE memory requirements.
[0012] A second scenario when the buffering of data in the Node B
negatively affects system performance is in the case that layer 2
(L2) or layer 3 (L3) messages and data transmissions are processed
by the same scheduling processes or share a single buffer in the
Node B. While data is being buffered and processed and an L2/L3
message comes behind it, the message cannot circumvent the
transmission queue. The greater the amount of data within a
transmission buffer, (which operates as first-in-first-out (FIFO)
buffer), the longer it takes for an L2/L3 message or data to get
through the buffer. Any higher priority L2/L3 messages are thus
delayed by the data in the buffers.
[0013] A third scenario where the buffering of data in the Node B
could negatively impact the performance of the system is in the
event of a serving HS-DSCH cell change. Since the Node B performs
scheduling and buffering of data for an HS-DSCH, when the UE
performs a serving HS-DSCH cell change from a source Node B to a
target Node B, there is a possibility that considerable amounts of
data may still be buffered in the source Node B after the handover.
This data is not recoverable because there is no mechanism that
exists within the UTRAN architecture for data buffered as the
source Node B to be transmitted to the target Node B. Upon a
serving HS-DSCH cell change, the RNC has no information regarding
how much, if any, data is lost since the RNC it does not know what
data is buffered in the source Node B. The greater the amount of
data that is buffered in the Node B in the event of an HS-DSCH cell
change, the greater the amount of data which will ultimately be
stranded in the source Node B and will have to be
retransmitted.
[0014] Accordingly, it would be desirable for the aforementioned
reasons to limit the amount of data that is buffered in the Node
B.
SUMMARY
[0015] The present invention is a system and method which improve
the performance of a wireless transmission system by intelligent
use of the control of the flow of data between the RNC and the Node
B. The system monitors certain criteria and, if necessary,
adaptively increases or decreases the data flow between the RNC and
the Node B. This improves the performance of the transmission
system by allowing retransmitted data, signaling procedures and
other data to be successfully received at a faster rate than in
prior art systems, by minimizing the amount of data buffered in the
Node B. Flow control is exerted to reduce buffering in the Node B
upon degradation of the channel quality, and prior to an HS-DSCH
handover.
[0016] In a preferred embodiment, the present invention is
implemented in a wireless communication system including a radio
network controller (RNC) in communication with a Node B having at
least one buffer therein for storing data. The RNC signals the Node
B with a request that the RNC send a certain amount of data to the
Node B. The Node B monitors a selected quality indicator and
calculates a capacity allocation for the buffer based on the
selected quality indicator. The Node B signals the capacity
allocation to the RNC. In response to receipt of the capacity
allocation, the RNC transmits data to the Node B at a data flow
rate determined in accordance with the capacity allocation and at
least one predetermined criterion. The Node B adjusts the buffer
accordingly.
BRIEF DESCRIPTION OF THE DRAWING(S)
[0017] A more detailed understanding of the invention may be had
from the following description, given by way of example and to be
understood in conjunction with the accompanying drawings
wherein:
[0018] FIG. 1 shows prior art buffering of data in the RNC, the
Node B and the UE.
[0019] FIG. 2 shows prior art buffering of data in the RNC, the
Node B and the UE in the event of a retransmission.
[0020] FIGS. 3A and 3B, taken together, are a method in accordance
with the present invention for monitoring the channel quality and
adjusting the flow of data between the RNC and the Node B.
[0021] FIG. 4 is the buffering of data in the RNC, the Node B and
the UE in the event of a retransmission using the method of FIGS.
3A and 3B.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0022] The present invention will be described with reference to
the drawing figures wherein like numeral represent like elements
throughout. Although the present invention will be described by
referring to a specific number of PDUs being queued in a buffer
(such as ten PDUs), this number of PDUs is referred to only for
simplicity. The actual number of PDUs which is being transmitted
and buffered in accordance with the aforementioned scenarios is
more likely on the order of several hundred PDUs or more. The
present invention and the teachings herein are intended to be
applicable to any number of PDUs and any size transmission
buffer.
[0023] In general, the present invention reduces the flow of data
to the Node B for a UE when there is a degradation of channel
quality of the UE, and increases the flow of data to the Node B
when there is an improvement in channel quality of the UE. In order
to control the flow of the transmission of data between the RNC and
the Node B, the present invention monitors one or more parameters
for channel quality. This flow control can be based on one
criterion, or a combination of many different criteria.
Additionally, as will be explained in detail hereinafter, the
criterion may be internally-generated by the Node B, or may be
generated by an external entity, (such as the UE), and sent to the
Node B.
[0024] Referring to FIG. 3A, a method 50 in accordance with the
present invention for monitoring the quality of a communication
channel and adjusting the flow of data between the RNC 52 and the
Node B 54 is shown. This method 50 handles the transmission of data
between the RNC 52 and the Node B 54. The RNC 52 transmits a
capacity request to the Node B 54 (step 58). The capacity request
is basically a request from the RNC 52 to the Node B 54 that the
RNC 52 would like to send a certain amount of data to the Node B
54. The Node B 54 receives the capacity request and monitors the
selected quality indicator (step 60). This selected quality
indicator may be based upon data transmitted from the UE (as will
be described in detail hereinafter), or may be based upon an
internally-generated quality indicator, such as the depth of the
buffer in the Node B 54.
[0025] The Node B 54 also monitors the status of the buffer within
the Node B (step 62). As would be understood by those with skill in
the art, although the present invention is described with reference
to a single buffer within the Node B 54 for simplicity, most likely
the buffer comprises a plurality of buffers or a single buffer
segmented into a plurality of sub-buffers, each buffer or
sub-buffer being associated with one or more data flows. Regardless
of whether there is one or more multiple buffers, an indicator
which indicates the amount of data within the buffer is generated
internally within the Node B. This permits the Node B 54 to monitor
the amount of data within the buffer, and also to monitor the
amount of additional data the buffer may accept.
[0026] The Node B 54 calculates and transmits a capacity allocation
(step 64) to the RNC 52. The capacity allocation is an
authorization by the Node B 54 to permit the RNC 52 to transmit a
certain amount of data. The RNC 52, upon receiving the capacity
allocation, transmits the data in accordance with the allocation
(step 66). That is, the RNC 52 sends data to the Node B 54, the
amount of which may not exceed the capacity allocation. The Node B
then adjusts its buffer accordingly to receive and store the data
(step 69). The amount of data stored in the buffer will change in
accordance with the incoming data that is transmitted from the RNC
52 and the outgoing data that is transmitted to the UE 82 (shown in
FIG. 3b).
[0027] It would be appreciated by those of skill in the art that
the method 50 shown in FIG. 3A is constantly repeated as data flows
from the RNC 52 to the Node B 54, and as the flow rate is
continually adjusted by the Node B 54. It should also be noted that
method steps 58, 60, 62, 64, 66 and 69 are not necessarily
performed in sequence, and any one step may be applied multiple
times before a different step in method 50 is applied.
Additionally, some of the steps, such as the capacity allocation
step 64, may indicate a repetitive data allocation that allows for
the transmission of data (step 66) to be periodically
implemented.
[0028] Referring to FIG. 3B, a method 80 in accordance with the
present invention for monitoring the quality of a communication
channel between the Node B 54 and a UE 82 is shown. The Node B 54
transmits data to the UE 82 (step 84). The UE 82 receives the data
and transmits a signal quality indicator (step 86) such as the
channel quality index (CQI) to the Node B 54. This signal quality
indicator may then be used as the selected quality indicator in
step 60 of FIG. 3A.
[0029] It would be noted by those of skill in the art that steps 84
and 86 are not necessarily sequential in practice. For example, in
the FDD mode, signal quality indicators are periodically sent from
the UE 82 regardless of whether or not a data is transmitted. In
such a case, the UE 82 transmits a signal quality indicator either
periodically or in response to a specific event to the Node B 54.
This signal quality indicator may then be used as selected quality
indicator in step 60 of FIG. 3A.
[0030] As aforementioned, the selected quality indicator may be
internally generated by the Node B, or externally generated by
another entity such as the UE and sent to the Node B. In accordance
with a first embodiment, the criterion is the channel quality
feedback from the UE. In this embodiment, the CQI which is an
indicator of the downlink channel quality is used.
[0031] In a second embodiment, the criterion is the ACK or NACK
that the UE produces in accordance with the H-ARQ process. For
example, the number of ACKs and/or the number of NACKs over a
certain time period can be used to derive an indication of the
quality of the channel.
[0032] In a third embodiment, the criterion is the choice by the
Node B of the modulation and coding set (MCS) that is needed to
successfully transmit data. As would be understood by those of
skill in the art, a very robust MCS is used when channel conditions
are poor. Alternatively, a less robust MCS may be utilized when the
channel conditions are good and a large amount of data may be
transmitted. The choice of the most robust MCS set may be utilized
as an indicator of poor channel quality conditions, whereas the use
of the least robust MCS may signify that channel quality conditions
are favorable.
[0033] In a fourth embodiment, the criterion is the depth of the
queue inside the Node B transmission buffer(s). For example, if the
Node B 54 buffer is currently storing a large amount of data, it is
an indicator that channel quality conditions may be poor since the
data is "backing up" in the Node B buffer. A buffer which is
lightly loaded may be an indicator that channel quality conditions
are good and the data is not backing up.
[0034] In a fifth embodiment, the criterion is the amount of data
that is "dropped" in the Node B. As understood by those of skill in
the art, the dropped data is data which the Node B has attempted to
retransmit several times and has given up after a predetermined
number of retries. If a large number of transmissions are dropped
by the Node B, it is an indicator that channel quality conditions
are poor.
[0035] In a sixth embodiment, the criterion is the amount of data
that can be transmitted by the Node B within a predetermined
duration, such as one hundred milliseconds. Depending upon the
quality of a communication channel, the number of PDUs that are
buffered in the Node B may change. Although the predetermined
duration may be fixed, due to changing channel quality conditions
the amount of PDUs that may be transmitted within the predetermined
duration may change dramatically. For example, if channel quality
conditions are good, a hundred PDUs may be able to be transmitted
within a hundred millisecond duration; whereas if channel quality
conditions are very poor, only ten PDUs may be able to be
transmitted within the hundred second duration.
[0036] It should be understood by those of skill in the art that
other criteria which may directly or indirectly indicate the
condition of the channel may be utilized in accordance with the
present invention. Additionally, a combination of two or more of
the above-described criteria may be utilized or weighted
accordingly, depending upon the specific needs of the system
users.
[0037] Referring to FIG. 4, the benefits of adaptively controlling
the flow of data between the RNC and the Node B can be seen. This
example is the scenario where a retransmission is required due to a
failed transmission and the flow of data between the RNC and the
Node B is decreased. As a result of the data flow decrease, only
one additional PDU with SN=8 is queued in front of the
retransmitted PDU with SN=3. The exertion of flow control as shown
in FIG. 4 reduces the latency of the retransmission of the PDU with
SN=3 as compared to the prior art handling of retransmissions as
shown in FIG. 2 where the PDUs with SNs=8 and are queued in front
of the PDU with SN=3. Therefore, the PDU with SN=3 can be
retransmitted to the UE earlier. The in-sequence delivery
requirement results in faster processing and delivery of PDUs 4
through 8 to higher layers.
[0038] While the present invention has been described in terms of
the preferred embodiment, 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.
* * * * *