U.S. patent application number 14/592121 was filed with the patent office on 2015-05-07 for harq handling at relay node reconfiguration.
The applicant listed for this patent is Telefonaktiebolaget L M Ericsson (publ). Invention is credited to Christian HOYMANN, Magnus LINDSTROM, Jessica OSTERGAARD, Riikka SUSITAIVAL.
Application Number | 20150124757 14/592121 |
Document ID | / |
Family ID | 45771854 |
Filed Date | 2015-05-07 |
United States Patent
Application |
20150124757 |
Kind Code |
A1 |
OSTERGAARD; Jessica ; et
al. |
May 7, 2015 |
HARQ HANDLING AT RELAY NODE RECONFIGURATION
Abstract
A radio access network comprises a donor base station node (29)
and a relay base station node (20). The relay base station node
(29) participates in communications across a first radio interface
with a wireless terminal (30) and also participates in
communications over a backhaul link across a second radio
interface, the second radio interface reusing at least some
functionality of the first interface. The donor base station node
(28) configures a subframe configuration pattern. The subframe
configuration pattern is arranged to specify which subframe(s) of a
frame structure may be utilized for the backhaul link. As a result
of subframe configuration, a HARQ process state in a HARQ process
at one of the base station nodes is known by the other base station
node by any of several operational modes.
Inventors: |
OSTERGAARD; Jessica;
(Stockholm, SE) ; HOYMANN; Christian; (Aachen,
DE) ; LINDSTROM; Magnus; (Sollentuna, SE) ;
SUSITAIVAL; Riikka; (Helsinki, FI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Telefonaktiebolaget L M Ericsson (publ) |
Stockholm |
|
SE |
|
|
Family ID: |
45771854 |
Appl. No.: |
14/592121 |
Filed: |
January 8, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13372739 |
Feb 14, 2012 |
8958364 |
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14592121 |
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61442483 |
Feb 14, 2011 |
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Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04W 84/047 20130101;
H04W 72/0426 20130101; H04W 72/0413 20130101; H04L 1/1893 20130101;
H04W 72/1273 20130101; H04W 72/14 20130101 |
Class at
Publication: |
370/329 |
International
Class: |
H04L 1/18 20060101
H04L001/18; H04W 72/14 20060101 H04W072/14 |
Claims
1-42. (canceled)
43. A method of operating a radio access network comprising:
recognizing, by a first base station node, a HARQ process state
comprising a subframe configuration pattern specifying at least one
subframe of a frame structure that is utilized for a backhaul link
between the first base station node and a second base station node;
reconfiguring, by the first base station node the HARQ process
state by modifying the subframe configuration pattern; and in
response to the reconfiguration of the HARQ process state, making,
by the first base station node, the reconfiguration known to the
second base station node.
44. The method of claim 43, wherein the first base station node
comprises a relay base station and the second base station node
comprises a donor base station.
45. The method of claim 43, wherein the first base station node
comprises a donor base station and the second base station node
comprises a relay base station.
46. The method of claim 45, wherein reconfiguring the HARQ process
state is selected from the group consisting of: changing a number
of HARQ processes in at least one of the donor base station or the
relay station; and changing a mapping of HARQ processes to
subframes of the frame structure.
47. The method of claim 43, wherein making the HARQ process state
in known to the second base station node comprises: mapping a HARQ
process executed at the first base station node and a corresponding
HARQ process executed at the second base station node to one or
more subframes; and providing a value for a HARQ process state
variable to the HARQ process executed at the first base station
node and to the corresponding HARQ process executed at the second
base station node.
48. The method of claim 47, wherein the HARQ process state variable
comprises a new data indicator (NDI).
49. The method of claim 43, wherein making the HARQ process state
in a HARQ process at the first base station node known to the
second base station node comprises performing a medium access
control (MAC) reset procedure at the first base station node.
50. The method of claim 43, wherein making the HARQ process state
in a HARQ process at the first base station node known by the
second base station node comprises: flushing uplink HARQ buffers in
the first base station node; and either: considering a next
received transmission of a transport block in the first base
station node as a new transmission; or flushing downlink HARQ
buffers in the first base station node.
51. The method of claim 50, wherein considering the next received
transmission of the transport block as the new transmission is
selected from the group consisting of: setting a new data indicator
(NDI) to a value which is toggled compared to a previously used NDI
value for the transport block for the HARQ process; and considering
the NDI to have been toggled compared to a previous transmission on
the same transport block on the same HARQ process if a change in
the subframe configuration pattern has occurred since the previous
transmission.
52. The method of claim 43, wherein making the HARQ process state
in a HARQ process at the first base station node known by the
second base station node comprises: for a downlink HARQ process
after the subframe configuration, scheduling the first base station
node with a specified value of a new data indicator (NDI) on each
downlink HARQ process corresponding to a toggling of the NDI from a
last transmission on each HARQ process by first scheduling a first
transmission with an NDI, and then scheduling a second transmission
with an NDI which is toggled compared to the first transmission;
for a uplink HARQ process, providing a wireless terminal
communicating with the first base station node with a first uplink
grant and associating with the first uplink grant a new data
indicator (NDI) value for the HARQ process and transport block and
subsequently providing the wireless terminal with a second uplink
grant associated with a new NDI value which is toggled compared to
the first uplink (UL) grant NDI.
53. The method of claim 52, wherein the method further comprises
using dummy data in the first transmission.
54. The method of claim 52, wherein for the downlink HARQ process
scheduling the first base station node with the specified value of
the new data indicator (NDI) on each HARQ process comprises keeping
a record of a previous state of each HARQ process and toggling the
new data indicator (NDI) in a next downlink assignment.
55. The method of claim 43, wherein making the HARQ process state
in a HARQ process at the first base station node known by the
second base station node comprises providing the HARQ process
executed at the first base station node and the corresponding HARQ
process executed at the second base station node with common
knowledge of HARQ process mapping and HARQ process states.
56. The method of claim 55, wherein providing the HARQ process
executed at the first base station node and the corresponding HARQ
process executed at the second base station node with common
information of HARQ process mapping comprises providing common
information regarding at least one of: mapping of HARQ process
number to subframe(s); and pre-configuration HARQ process number to
post-configuration HARQ process number.
57. The method of claim 55, wherein providing common information of
HARQ process mapping and HARQ process states comprises the
providing common information as predetermined information or as
information signaled between the donor base station node and the
relay base station node.
58. The method of claim 55, further comprising reusing
pre-configuration soft information stored in HARQ buffers of the
HARQ processes after the configuration.
59. The method of claim 55, further comprising: determining that a
number of HARQ processes in use after the configuration is less
than a number of HARQ processes in use before the configuration
whereby after the reconfiguration at least one HARQ process is a
superfluous HARQ process; and performing a step selected from the
group consisting of: removing any superfluous downlink HARQ
processes in a predetermined pattern; and for both uplink HARQ
processes and downlink HARQ processes, prioritizing removal of HARQ
processes that have no pending transmission.
60. A first base station node of a radio access network which
participates in communications over a backhaul link across a radio
interface with a second base station node, the first base station
node comprising: a memory configured to store; and a processor in
communication with the memory, the processor operable to:
recognizing a HARQ process state comprising a subframe
configuration pattern specifying at least one subframe of a frame
structure that is utilized for the backhaul link between the first
base station node and the second base station node; reconfiguring
the HARQ process state by modifying the subframe configuration
pattern; and in response to the reconfiguration of the HARQ process
state, making the reconfiguration known to the second base station
node.
61. The first base station node of claim 60, wherein the first base
station node comprises a relay base station and the second base
station node comprises a donor base station.
62. The first base station node of claim 60, wherein the first base
station node comprises a donor base station and the second base
station node comprises a relay base station.
63. The first base station node of claim 62, wherein the processor
is operable to reconfigure the HARQ process state by performing at
least one step selected from the group consisting of: changing a
number of HARQ processes in at least one of the donor base stator
the relay station node; and changing a mapping of HARQ processes to
subframes of the frame structure.
64. The first base station node of claim 60, wherein the processor
is operable to make the HARQ process state known to the second base
station node: mapping a HARQ process executed at the first base
station node and a corresponding HARQ process executed at the
second base station node to one or more subframes; and providing a
value for a HARQ process state variable to the HARQ process
executed at the first base station node and to the corresponding
HARQ process executed at the second base station node.
65. The first base station node of claim 64, wherein the HARQ
process state variable comprises a new data indicator (NDI).
66. The first base station node of claim 60, wherein the processor
is operable to make the HARQ process state in a HARQ process at the
first base station node known to the second base station node by
performing a medium access control (MAC) reset procedure at the
first base station node.
67. The first base station node of claim 60, wherein the processor
is operable to make the HARQ process state in a HARQ process at the
first base station node known by the second base station node by:
flushing uplink HARQ buffers in the first base station node; and
either: considering a next received transmission of a transport
block in the first base station node as a new transmission; or
flushing downlink HARQ buffers in the first base station node.
68. The first base station node of claim 67, wherein when
considering the next received transmission of the transport block
as the new transmission the processor is operable to perform at
least one step selected from the group consisting of: setting a new
data indicator (NDI) to a value which is toggled compared to a
previously used NDI value for the transport block for the HARQ
process; and considering the NDI to have been toggled compared to a
previous transmission on the same transport block on the same HARQ
process if a change in the subframe configuration pattern has
occurred since the previous transmission.
69. The first base station node of claim 60, wherein the processor
is operable to make the HARQ process state in a HARQ process at the
first base station node known by the second base station node by:
for a downlink HARQ process after the subframe configuration,
scheduling the first base station node with a specified value of a
new data indicator (NDI) on each downlink HARQ process
corresponding to a toggling of the NDI from a last transmission on
each HARQ process by first scheduling a first transmission with an
NDI, and then scheduling a second transmission with an NDI which is
toggled compared to the first transmission; for a uplink HARQ
process, providing a wireless terminal communicating with the first
base station with a first uplink grant and associating with the
first uplink grant a new data indicator (NDI) value for the HARQ
process and transport block and subsequently providing the wireless
terminal with a second uplink grant associated with a new NDI value
which is toggled compared to the first uplink (UL) grant NDI.
70. The first base station node of claim 69, wherein the processor
is further operable to use dummy data in the first
transmission.
71. The first base station node of claim 69, wherein for the
downlink HARQ process the processor is operable to schedule the
first base station node with the specified value of the new data
indicator (NDI) on each HARQ process by keeping a record of a
previous state of each HARQ process and toggling the new data
indicator (NDI) in a next downlink assignment.
72. The first base station node of claim 60, wherein the processor
is operable to make the HARQ process state in a HARQ process at the
first base station node known by the second base station node by
providing the HARQ process executed at the first base station node
and the corresponding HARQ process executed at the second base
station node with common knowledge of HARQ process mapping and HARQ
process states.
73. The first base station node of claim 72, wherein, when
providing the HARQ process executed at the first base station node
and the corresponding HARQ process executed at the second base
station node with common information of HARQ process mapping, the
processor is operable to provide common information regarding at
least one of: mapping of HARQ process number to subframe(s); and
pre-configuration HARQ process number to post-configuration HARQ
process number.
74. The first base station node of claim 72, wherein the processor
is operable to provide common information of HARQ process mapping
and HARQ process states by providing common information as
predetermined information or as information signaled between the
donor base station node and the relay base station node.
75. The first base station node of claim 72, wherein the processor
is operable to reuse pre-configuration soft information stored in
HARQ buffers of the HARQ processes after the configuration.
76. The first base station node of claim 72, wherein the processor
is further operable to: determine that a number of HARQ processes
in use after the configuration is less than a number of HARQ
processes in use before the configuration, whereby after the
reconfiguration at least one HARQ process is a superfluous HARQ
process; and perform a step selected from the group consisting of:
removing any superfluous downlink HARQ processes in a predetermined
pattern; and for both uplink HARQ processes and downlink HARQ
processes, prioritizing removal of HARQ processes that have no
pending transmission.
Description
[0001] This application claims the benefit of and is related to
U.S. Provisional Patent application 61/442,483, filed Feb. 14,
2011, entitled MAC HANDLING AT RN RECONFIGURATION, which is
incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] This invention pertains to telecommunications, and
particularly to method and apparatus for handling relay base
station nodes of a radio access network, including the operation of
HARQ processes of a relay base station node in conjunction with a
relay node (RN) subframe configuration.
BACKGROUND
[0003] In a typical cellular radio system, wireless terminals (also
known as mobile stations and/or user equipment units (UEs))
communicate via a radio access network (RAN) to one or more core
networks. The radio access network (RAN) covers a geographical area
which is divided into cell areas, with each cell area being served
by a base station, e.g., a radio base station (RBS), which in some
networks may also be called, for example, a "NodeB" (UMTS) or
"eNodeB" (LTE). A cell is a geographical area where radio coverage
is provided by the radio base station equipment at a base station
site. Each cell is identified by an identity within the local radio
area, which is broadcast in the cell. The base stations communicate
over the air interface operating on radio frequencies with the user
equipment units (UE) within range of the base stations.
[0004] In some versions of the radio access network, several base
stations are typically connected (e.g., by landlines or microwave)
to a controller node (such as a radio network controller (RNC) or a
base station controller (BSC)) which supervises and coordinates
various activities of the plural base stations connected thereto.
The radio network controllers are typically connected to one or
more core networks.
[0005] The Universal Mobile Telecommunications System (UMTS) is a
third generation mobile communication system, which evolved from
the second generation (2G) Global System for Mobile Communications
(GSM). UTRAN is essentially a radio access network using wideband
code division multiple access for user equipment units (UEs). In a
forum known as the Third Generation Partnership Project (3GPP),
telecommunications suppliers propose and agree upon standards for
third generation networks and UTRAN specifically, and investigate
enhanced data rate and radio capacity.
[0006] The Evolved Universal Terrestrial Radio Access Network
(E-UTRAN) comprises the Long Term Evolution (LTE) and System
Architecture Evolution (SAE). Long Term Evolution (LTE) is a
variant of a 3GPP radio access technology wherein the radio base
station nodes are connected to a core network (via Access Gateways,
or AGWs) rather than to radio network controller (RNC) nodes. In
general, in LTE the functions of a radio network controller (RNC)
node are distributed between the radio base stations nodes
(eNodeB's in LTE) and AGWs. As such, the radio access network (RAN)
of an LTE system has an essentially "flat" architecture comprising
radio base station nodes without reporting to radio network
controller (RNC) nodes.
[0007] In conjunction with Long Term Evolution (LTE) the use of
relay base station nodes is described, e.g., in 3GPP LTE Rel-10. As
shown in FIG. 1, a relay base station node (RN) communicates over
the radio or air interface (e.g., the Uu interface) with one or
more wireless terminals, and over an interface known as the Un
interface with a donor base station node, e.g., a donor dNodeB.
Thus, transmissions between UE and relay are done over the radio
interface denoted Uu, which is the same as for regular eNB to UE
communication. Such being the case, from a UE perspective a relay
appears a regular eNB. Between the relay and the eNB, transmissions
are performed over a radio interface denoted Un, which reuses much
of the functionality of the Uu interface. This means that the DeNB
handles the relay as a UE using the same protocols as when
communicating with a UE, with some additions.
[0008] In general, a relay node (RN)) has the following
characteristics: [0009] The relay node (RN) controls cells, each of
which appears to a UE as a separate cell distinct from the donor
cell [0010] The cells have their own Physical Cell ID (defined in
LTE Rel-8) and the relay node shall transmit its own
synchronization channels, reference symbols, . . . [0011] The UE
receives scheduling information and HARQ feedback directly from the
relay node and send its control channels (SR/CQI/ACK) to the relay
node [0012] The presence and function of the relay node (RN) does
not impact UEs. Moreover, all legacy LTE UEs can be served by the
relay cell.
[0013] If the transmissions on the Un interface and the Uu
interface (e.g., in the relay cell) are performed within the same
frequency band, the relays are referred to as "inband relays". In
case the transmissions are on a separate frequency band, the relays
are referred to as outband relays.
[0014] Transmissions over the Un interface and the Uu interface
typically occur in frames. Each frame usually comprises plural
subframes. A subframe may comprise a signaling portion and a data
portion, with the data portion often being used to include or
transmit, among other things, one or more data transport blocks, or
simply "transport blocks" (TBs). In general, once a HARQ process
has acknowledged successful reception of a transport block, the
next transport block is prepared by the sending node and is then
subject to HARQ processing.
[0015] To enable inband relays to be functional, the relay base
station node should not transmit and receive at the same time on
the same frequency as the donor base station node, since this could
cause severe (self) interference. To preclude such same-time
transmission and attendant interference, transmissions over the
backhaul link (over the Un interface) and the access links (over
the Uu interface) are time multiplexed in a manner intended to
avoid interference. In this regard, the donor base station node
configures, via a Radio Resource Control (RRC) procedure called "RN
reconfiguration" (relay node reconfiguration), a so-called "RN
subframe configuration" (relay node subframe configuration) in the
relay base station node, which governs, among other things, which
subframes are used for the backhaul link.
[0016] The subframes that can be used for backhaul communication
(e.g., across the Un interface) are referred to as the "subframe
configuration pattern". The subframe configuration pattern may be
communicated or signaled by the Radio Resource Control (RRC)
protocol. For example, a change of a subframeConfigPattern
information element or parameter in a message or signal generated
by the RRC protocol may be used to communicate the subframe
configuration pattern. The subframeConfigPattern parameter is
defined, e.g., in 3GPP TS 36.331, section 6.3.2., as
"RN-SubframeConfig", and is a parameter which may differ for FDD
(an 8-bit bitmap) and TDD (an integer).
[0017] For Frequency Division Duplex (FDD), the subframe
configuration pattern is a bitmap, which together with the
Multi-Media Broadcast over a Single Frequency Network (MBSFN)
configurability in the RN cell, specified which downlink (DL)
subframes that are configured for backhaul communication. Uplink
(UL) subframes for backhaul communication are derived from the DL
subframes for backhaul communication such that there is an UL
backhaul subframe n if subframe n-4 were a DL backhaul
subframe.
[0018] For Time Division Duplex (TDD), the subframe configuration
pattern is an index referring to an explicitly specified subframe
pattern in the 3GPP specification 3GPP TS 36.216, "Evolved
Universal Terrestrial Radio Access (E-UTRA); Physical layer for
relaying operation," v.10.1.0 (the "36.216 Specification"), which
is incorporated herein by reference in its entirety, specifying
both DL and UL backhaul subframes.
[0019] For the downlink, to enable the relay to not transmit
anything in its own cell (on the Uu interface) during the subframes
used for the backhaul link (Un), the relay cell configures these
subframes as MBSFN subframes. During an MBSFN subframe, the UEs in
the relay cell do not expect to receive any cell-specific reference
signals from the relay beyond what is transmitted in the first one
or two Orthogonal Frequency Division Multiplexing (OFDM) symbols of
the subframe. The relay node not scheduling any data in these
subframes enables the relay node to listen to the downlink
transmissions on the Un interface during the rest of these
subframes (which are hence used for carrying downlink data from the
donor base station node to the relay base station nodes).
Conversely, subframes not configured for backhaul communication are
used in the relay cell, and not used for the backhaul link. The
donor base station node knows that these subframes are not
available for backhaul communication and hence does not schedule
the relay base station node
[0020] An example of time division between the Un and Uu interfaces
is illustrated in FIG. 2. For example, FIG. 2 shows a series of
blocks representing subframes, with shaded ones of the subframes
being MBSFN subframes. FIG. 2 thus depicts the time multiplexed
downlink (DL) transmissions on the Un interface from the donor base
station node to the relay base station node (such transmissions
being represented by the arrows above the blocks in FIG. 2) and the
transmissions on the Uu interface from the relay base station node
to a wireless terminal (such transmissions being represented by the
arrows below the blocks of FIG. 2).
[0021] In Long Term Evolution (LTE), all regular data transmissions
between a base station node and a wireless terminal, whether
between a donor base station node (e.g., a dNB) and a wireless
terminal or between a relay base station node (RN) and a wireless
terminal, are protected by a process known as Hybrid Automatic
Repeat request (HARQ). In the wireless terminal and the eNB/RN,
respectively, there are a number of HARQ processes available for
the downlink (DL), and a number of HARQ processes available for the
uplink (UL).
[0022] Each HARQ process typically is assigned or associated with a
HARQ process number. The downlink (DL) HARQ process number is part
of the downlink (DL) assignment so it does not have to depend on
the subframe number, e.g., is not necessarily correlated with and
can even be independent of the subframe number. The uplink (UL)
HARQ process number is mapped to subframes according to the 3GPP TS
36.216 standard (section 7.3).
[0023] Moreover, each HARQ process has a HARQ process "state". As
used herein, "HARQ process state" refers to contents of a buffer
and value of at least one state variable or parameter, including a
variable or parameter known as the New Data Indicator (NDI). The
NDI parameter is a 1-bit value that is maintained for each HARQ
process. In terms of a downlink (DL) HARQ process in the relay base
station node, the HARQ process state comprises or is associated
with a soft buffer which includes current soft-decoded information
and the NDI. For an uplink (UL) HARQ process, the HARQ process
state in the relay base station node comprises or is associated
with a buffer for a MAC PDU to be transmitted and state variables,
including the NDI and optionally including other variables such as
the number of times a MAC PDU has been transmitted, current
redundancy version and HARQ feedback. The downlink (DL) HARQ
process in the donor base station node is the sending process, and
hence is similar to the UL HARQ process in the relay node. In like
manner, the uplink (UL) HARQ process in the donor base station node
is similar to the downlink (DL) HARQ process in the relay base
station node.
[0024] In the DL, the HARQ process number and the New Data
Indicator (NDI) are signaled explicitly as two separate variables.
The network signals if a transmission is a new transmission or a
retransmission through or by the NDI. The NDI (being a 1-bit
indicator) is/may be considered to be toggled (new transmission) or
not toggled (retransmission) compared to its previous value.
[0025] In the uplink (UL), the HARQ process number is instead
derived from the subframe in which it is, and the same HARQ process
is tied to subframe n, n+8, n+16, etc. The concept of an NDI is
also used in the uplink (UL) in essentially the same way as in the
downlink (DL).
[0026] In view of the foregoing it will be understood that, for a
relay base station node with an RN subframe configuration, only a
subset of the subframes is available for transmissions on the
backhaul link. This means fewer HARQ processes are needed. A number
of HARQ processes are specified in the 3GPP TS 36.216 Specification
already referenced above. These HARQ processes are laid out on the
subframes available for backhaul transmissions, and used so that
retransmissions are synchronous with respect to the HARQ
process.
[0027] There are times at which the subframe configuration is
changed by the donor base station node. When the subframe
configuration is changed, the change may affect (e.g., also change)
one or both of (1) the number of HARQ processes (e.g., the number
of HARQ processes used on the uplink (UL) over the Un interface and
(2) a mapping of HARQ processes to subframes.
[0028] Earlier releases of Long Term Evolution (LTE) do not
contemplate a change in the number of HARQ process, and thus
heretofore ramifications of such change have been unappreciated and
not addressed. Thus, with the introduction of a specific subframe
configuration and its potential change, it is not clear from prior
practice what may happen to any data which may be pending in HARQ
buffers of the HARQ processes. This ambiguity or uncertainty can
lead to a mismatch in the HARQ process state between the donor base
station node and the relay base station node, and to data loss.
SUMMARY
[0029] In one of its aspects the technology disclosed herein
concerns a method of operating a radio access network comprising a
donor base station node and a relay base station node. The relay
base station node participates in communications across a first
radio interface with a wireless terminal and also participates in
communications over a backhaul link across a second radio
interface, the second radio interface reusing at least some
functionality. In a basic embodiment and mode the method comprises
configuring a subframe configuration pattern; and as a result
thereof (e.g., to counter or address the consequences of the
configuration of the subframe configuration pattern), making a HARQ
process state in a HARQ process at one of the base station nodes
known by the other base station node. The subframe configuration
pattern is arranged to specify which subframe(s) of a frame
structure may be utilized for the backhaul link.
[0030] In an example embodiment and mode, the method further
comprises making a HARQ process state in a HARQ process at the
relay base station node known by the donor base station node and/or
making a HARQ process state a the HARQ process at the donor base
station node known by the relay base station node
[0031] In an example embodiment and mode, the method further
comprises using a processor to make the HARQ process state in the
HARQ process at one of the base station nodes known by the other
base station node
[0032] In an example embodiment and mode, the method further
comprises the act of configuring the subframe configuration pattern
comprises re-configurating the subframe configuration pattern after
a previous configuration of the subframe pattern. The
re-configuring comprises changing a number of HARQ processes in at
least one of the donor base station node or the relay station node
and/or changing a mapping of HARQ processes to subframes of the
frame structure. Making the HARQ process state in the HARQ process
at one of the base station nodes known by the other base station
node is performed in response to the re-configuring.
[0033] In an example embodiment and mode, making the HARQ process
state in the HARQ process at one of the base station nodes known by
the other base station node comprises: mapping a HARQ process
executed at the donor base station node and a corresponding HARQ
process executed at the relay base station node to one or more
subframes; and, providing a value for a HARQ process state variable
to the HARQ process executed at the donor base station node and to
the corresponding HARQ process executed at the relay base station
node.
[0034] In an example embodiment and mode, the HARQ process state
variable comprises a new data indicator (NDI)
[0035] In an example embodiment and mode, making the HARQ process
state in the HARQ process at one of the base station nodes known by
the other base station node comprises performing a medium access
control (MAC) reset procedure at least at the relay base station
node.
[0036] In an example embodiment and mode, making the HARQ process
state in the HARQ process at one of the base station nodes known by
the other base station node comprises: flushing uplink HARQ buffers
in the relay base station node; and either: considering a next
received transmission of a transport block in the relay base
station node as a new transmission; or flushing downlink HARQ
buffers in the relay base station node. Considering the next
received transmission of the transport block as the new
transmission comprises either: setting a new data indicator (NDI)
to a value which is toggled compared to a previously used NDI value
for the transport block for the HARQ process; or considering the
NDI to have been toggled compared to a previous transmission on the
same transport block on the same HARQ process if a change in the
subframe configuration pattern has occurred since the previous
transmission.
[0037] In an example embodiment and mode, making the HARQ process
state in the HARQ process at one of the base station nodes known by
the other base station node comprises: for a downlink HARQ process,
after the subframe configuration scheduling the relay base station
node with a specified value of a new data indicator (NDI) on each
downlink HARQ process corresponding to a toggling of the NDI from a
last transmission on each HARQ process by first scheduling a first
transmission with an NDI, and then scheduling a second transmission
with an NDI which is toggled compared to the first transmission;
for a uplink HARQ process, providing the wireless terminal with a
first uplink grant and associating with the first uplink grant a
new data indicator (NDI) value for the HARQ process and transport
block and subsequently providing the wireless terminal with a
second uplink grant associated with a new NDI value which is
toggled compared to the first uplink (UL) grant NDI.
[0038] In an example embodiment and mode, the method further
comprises using dummy data in the first transmission.
[0039] In an example embodiment and mode, for the downlink HARQ
process scheduling the relay base station node with the specified
value of the new data indicator (NDI) on each HARQ process
comprises keeping a record of a previous state of each HARQ process
and toggling the new data indicator (NDI) in a next downlink
assignment.
[0040] In an example embodiment and mode, making the HARQ process
state in the HARQ process at one of the base station nodes known by
the other base station node comprises providing the HARQ process
executed at the donor base station node and the corresponding HARQ
process executed at the relay base station node with common
knowledge of HARQ process mapping and HARQ process states. In an
example implementation, providing the HARQ process executed at the
donor base station node and the corresponding HARQ process executed
at the relay base station node with common information of HARQ
process mapping comprises providing common information regarding at
least one of: mapping of HARQ process number to subframe(s); and,
pre-configuration HARQ process number to post-configuration HARQ
process number. In an example implementation, providing common
information of HARQ process mapping and HARQ process states
comprises the providing common information as predetermined
information or as information signaled between the donor base
station node and the relay base station node.
[0041] In an example embodiment and mode, the method further
comprises reusing pre-configuration soft information stored in HARQ
buffers of the HARQ processes after the configuration.
[0042] In an example embodiment and mode, if a number of HARQ
processes in use after the configuration is less than a number of
HARQ processes in use before the configuration whereby after the
configuration at least one HARQ process is a superfluous HARQ
process, the method further comprises: removing any superfluous
downlink HARQ processes in a predetermined pattern; or for both
uplink HARQ processes and downlink HARQ processes, prioritizing
removal of HARQ processes that have no pending transmission.
[0043] In another of its aspect the technology disclosed herein
concerns a donor base station node of a radio access network which
participates in communications over a backhaul link across a radio
interface with a relay base station. The donor base station node
comprises a processor arranged: to configure a subframe
configuration pattern and, in response to configuration of the
subframe configuration pattern, to make a HARQ process state in a
HARQ process at one of the base station nodes known by the other
base station node. The subframe configuration pattern is arranged
to specify which subframe(s) of a frame structure may be utilized
for the backhaul link and which subframes(s) of the frame structure
may be utilized for communications between the relay base station
and a wireless terminal.
[0044] In an example embodiment the processor is configured to make
a HARQ process state in a HARQ process at the relay base station
node known by the donor base station node and/or make a HARQ
process state a HARQ process at the donor base station node known
by the relay base station node.
[0045] In an example embodiment the processor is arranged to
configure the subframe configuration pattern as a re-configuration
of the subframe configuration pattern after a previous
configuration of the subframe pattern. The re-configuration
comprises changing a number of HARQ processes in at least one of
the donor base station node or the relay station node and/or
changing a mapping of HARQ processes to subframes of the frame
structure; and wherein the processor is configured to make the HARQ
process state in the HARQ process at one of the base station nodes
known by the other base station node in response to the
re-configuration.
[0046] In an example embodiment the processor is configured to make
the HARQ process state in the HARQ process at one of the base
station nodes known by the other base station node by: mapping the
HARQ process executed at the donor base station node and the
corresponding HARQ process executed at the relay base station node
to one or more subframes; and, providing a HARQ process state
variable to the HARQ process executed at the donor base station
node and the corresponding HARQ process executed at the relay base
station node. In an example embodiment the HARQ process state
variable comprises a new data indicator (NDI).
[0047] In an example embodiment the processor is configured to make
the HARQ process state in the HARQ process at one of the base
station nodes known by the other base station node by performing a
medium access control (MAC) reset procedure.
[0048] In an example embodiment the processor is configured make
the HARQ process state in the HARQ process at one of the base
station nodes known by the other base station node by: for a
downlink HARQ process, after the subframe configuration scheduling
the relay base station node with a specified value of a new data
indicator (NDI) on each downlink HARQ process corresponding to a
toggling of the NDI from a last transmission on each HARQ process
by first scheduling a first transmission with an NDI, and then
scheduling a second transmission with an NDI which is toggled
compared to the first transmission; for a uplink HARQ process,
providing the wireless terminal with a first uplink grant and
associating with the first uplink grant a new data indicator (NDI)
value for the HARQ process and transport block and subsequently
providing the wireless terminal with a second uplink grant
associated with a new NDI value which is toggled compared to the
first uplink (UL) grant NDI.
[0049] In an example embodiment the processor is configured to use
dummy data in the first transmission.
[0050] In an example embodiment the processor is configured to
schedule the relay base station node with the predetermined value
of the new data indicator (NDI) on each HARQ process by keeping a
record of a previous state of each HARQ process and toggling the
new data indicator (NDI) in a next downlink assignment.
[0051] In an example embodiment the processor is configured to make
the HARQ process state in the HARQ process at one of the base
station nodes known by the other base station node by providing the
HARQ process executed at the donor base station node and the
corresponding HARQ process executed at the relay base station node
with common knowledge of HARQ process mapping and HARQ process
states.
[0052] In an example embodiment the processor is configured to
provide common information regarding at least one of: mapping of
HARQ process number to subframe(s); and pre-configuration HARQ
process number to post-configuration HARQ process number.
[0053] In an example embodiment the processor is configured to
re-use pre-configuration soft information stored in HARQ buffers of
the HARQ processes after the configuration.
[0054] In an example embodiment, if a number of HARQ processes in
use after the configuration is less than a number of HARQ processes
in use before the configuration, the processor is configured to:
remove downlink HARQ processes in a predetermined pattern; or for
both uplink HARQ processes and downlink HARQ processes, prioritize
removal of HARQ processes that have no pending transmission.
[0055] In another of its aspects the technology disclosed herein
concerns a relay base station node of a radio access network which
participates in communications over a backhaul link across a radio
interface with a donor base station node. The relay base station
node comprises a transceiver and a processor. The transceiver is
configured to receive an indication of a change in a subframe
configuration pattern, the subframe configuration pattern being
arranged to specify which subframe(s) of a frame structure may be
utilized for the backhaul link and which subframes(s) of the frame
structure may be utilized for communications between the relay base
station and a wireless terminal. The processor is configured, in
response to the received indication, to make a HARQ process state
in a HARQ process at one of the base station nodes known by the
other base station node.
[0056] In an example embodiment the processor is configured to make
a HARQ process state in a HARQ process at the relay base station
node known by the donor base station node and/or make a HARQ
process state a HARQ process at the donor base station node known
by the relay base station node.
[0057] In an example embodiment the change in the subframe
configuration pattern comprises changing a number of HARQ processes
in at least one of the donor base station node or the relay station
node and/or changing a mapping of HARQ processes to subframes of
the frame structure.
[0058] In an example embodiment the processor is configured to
perform at least the following for making the HARQ process state in
the HARQ process at one of the base station nodes known by the
other base station node: mapping the HARQ process executed at the
donor base station node and a corresponding HARQ process executed
at the relay base station node to one or more subframes; and,
providing a value for a HARQ process state variable to the HARQ
process executed at the donor base station node and to the
corresponding HARQ process executed at the relay base station
node.
[0059] In an example embodiment the HARQ process state variable
comprises a new data indicator (NDI).
[0060] In an example embodiment the processor is configured to
perform a medium access control (MAC) reset procedure at the relay
base station node for making the HARQ process state in the HARQ
process at one of the base station nodes known by the other base
station node.
[0061] In an example embodiment the processor is configured to
perform at least the following to make the HARQ process state in
the HARQ process at one of the base station nodes known by the
other base station node: flushing uplink HARQ buffers in the relay
base station node; and either: considering a next received
transmission of a transport block as a new transmission; or
flushing downlink HARQ buffers in the relay base station node.
[0062] In an example embodiment, when considering the next received
transmission of the transport block as the new transmission
comprises the processor either: sets a new data indicator (NDI) to
a value which is toggled compared to a previously used NDI value
for the transport block for the HARQ process; or considers the NDI
to have been toggled compared to a previous transmission on the
same transport block on the same HARQ process if a change in the
subframe configuration pattern has occurred since the previous
transmission.
[0063] In an example embodiment the processor is provided with
common knowledge of HARQ process mapping and HARQ process states.
In an example embodiment the common information comprises at least
one of: mapping of HARQ process number to subframe(s); and
pre-configuration HARQ process number to post-configuration HARQ
process number.
[0064] In an example embodiment the processor is configured to use
pre-configuration soft information stored in HARQ buffers of the
HARQ processes after the configuration.
[0065] In an example embodiment, if a number of HARQ processes in
use after the configuration is less than a number of HARQ processes
in use before the configuration, the processor is further
configured to: remove downlink HARQ processes in a predetermined
pattern; or for both uplink HARQ processes and downlink HARQ
processes, prioritize removal of HARQ processes that have no
pending transmission.
BRIEF DESCRIPTION OF THE DRAWINGS
[0066] The foregoing and other objects, features, and advantages of
the invention will be apparent from the following more particular
description of preferred embodiments as illustrated in the
accompanying drawings in which reference characters refer to the
same parts throughout the various views. The drawings are not
necessarily to scale, emphasis instead being placed upon
illustrating the principles of the invention.
[0067] FIG. 1 is a diagrammatic view of portions of a radio access
network including a donor base station node and a relay base
station node.
[0068] FIG. 2 is a diagrammatic illustration depicting an example
time division of subframes between the Un and Uu interfaces of a
radio access network such as that of FIG. 1.
[0069] FIG. 3 and FIG. 4 are diagrammatic view of different example
scenarios of changing a subframe configuration pattern.
[0070] FIG. 5 is a schematic view of portions of a radio access
network comprising a donor base station node and a relay base
station node for illustrating context and environment for
implementation and operation of embodiments and modes of the
technology disclosed herein as well as basic example constituent
functionalities and/or units of the nodes.
[0071] FIG. 6 is a schematic view of certain example structural
aspects of a donor base station node and a relay base station node
according to an example embodiment.
[0072] FIG. 7 is a schematic view of selected example details of
HARQ processes for both the uplink (UL) and the downlink (DL) for
both a donor base station node and relay base station node
according to an example embodiment.
[0073] FIG. 8 is a flowchart showing example acts or steps involved
in a generic method of operating a communications system in a
manner to make a HARQ process state in a HARQ process at one of the
base station nodes known by the other base station node.
[0074] FIG. 9 is a diagrammatic view depicting example acts or
steps comprising a first mode of implementation an act of the
generic method of FIG. 8.
[0075] FIG. 10 is a diagrammatic view depicting example acts or
steps comprising a second mode of implementation an act of the
generic method of FIG. 8.
[0076] FIG. 11 is a diagrammatic view depicting example acts or
steps comprising a third mode of implementation an act of the
generic method of FIG. 8.
[0077] FIG. 12A is a diagrammatic view depicting a first example
implementation of transmission of a mapping rule in accordance with
a fourth mode of implementation an act of the generic method of
FIG. 8.
[0078] FIG. 12B is a diagrammatic view depicting a second example
implementation of transmission of a mapping rule in accordance with
a fourth mode of implementation an act of the generic method of
FIG. 8.
DETAILED DESCRIPTION
[0079] In the following description, for purposes of explanation
and not limitation, specific details are set forth such as
particular architectures, interfaces, techniques, etc. in order to
provide a thorough understanding of the present disclosure.
However, it will be apparent to those skilled in the art that the
present disclosure may be practiced in other embodiments that
depart from these specific details. That is, those skilled in the
art will be able to devise various arrangements which, although not
explicitly described or shown herein, embody the principles of the
present disclosure and are included within its spirit and scope. In
some instances, detailed descriptions of well-known devices,
circuits, and methods are omitted so as not to obscure the
description of the present embodiments with unnecessary detail. All
statements herein reciting principles, aspects, and embodiments of
the disclosure, as well as specific examples thereof, are intended
to encompass both structural and functional equivalents thereof.
Additionally, it is intended that such equivalents include both
currently known equivalents as well as equivalents developed in the
future, i.e., any elements developed that perform the same
function, regardless of structure.
[0080] Thus, for example, it will be appreciated by those skilled
in the art that block diagrams herein may represent conceptual
views of illustrative circuitry or other functional units embodying
the principles of the technology. Similarly, it will be appreciated
that any flow charts, state transition diagrams, pseudocode, and
the like represent various processes which may be substantially
represented in computer readable medium and so executed by a
computer or processor, whether or not such computer or processor is
explicitly shown.
[0081] The functions of the various elements including functional
blocks, including but not limited to those labeled or described as
"computer", "processor" or "controller", may be provided through
the use of hardware such as circuit hardware and/or hardware
capable of executing software in the form of coded instructions
stored on computer readable medium. Thus, such functions and
illustrated functional blocks are to be understood as being
hardware-implemented and/or computer-implemented, and thus
machine-implemented.
[0082] In terms of hardware implementation, the functional blocks
may include or encompass, without limitation, digital signal
processor (DSP) hardware, reduced instruction set processor,
hardware, e.g., digital or analog, circuitry including but not
limited to application specific integrated circuit(s) (ASIC), and,
where appropriate, state machines capable of performing such
functions.
[0083] In terms of computer implementation, a computer is generally
understood to comprise one or more processors or one or more
controllers, and the terms computer and processor and controller
may be employed interchangeably herein. When provided by a computer
or processor or controller, the functions may be provided by a
single dedicated computer or processor or controller, by a single
shared computer or processor or controller, or by a plurality of
individual computers or processors or controllers, some of which
may be shared or distributed. Moreover, use of the term "processor"
or "controller" shall also be construed to refer to other hardware
capable of performing such functions and/or executing software,
such as the example hardware recited above.
[0084] As mentioned above, a donor base station node may change a
subframe configuration pattern, and thus change which subframes of
a frame are used for the backhaul (e.g., over the Un interface). As
different example scenarios, FIG. 3 and FIG. 4 illustrate with
cross hatching certain subframes included in the subframe
configuration pattern for use over the backhaul (e.g., the Un
interface) both before and after two different subframe
reconfiguration operations. In the first example scenario of FIG.
3, the donor base station node may change the subframe
configuration pattern so that, although a same number of subframes
are used over the backhaul (e.g., over the Un interface), there is
a change in which particular subframes are utilized on the
backhaul. In the second example scenario of FIG. 4, the donor base
station node may change the subframe configuration pattern so as to
change (e.g., increase or diminish) a number of subframes used over
the backhaul. In the example of FIG. 4 the number of subframes used
over the backhaul decreases from two to one. Other examples of
changes in the subframe configuration pattern, such as adding more
subframes to the subframe configuration pattern, are also possible.
Thus, as a result of a change in the subframe configuration
pattern, there may be a changed number (e.g., more or fewer) of
HARQ processes, or the same number of HARQ processes but mapped to
different subframes.
[0085] It is unclear in conventional practice what happens to the
state of the HARQ processes when the HARQ processes in use are
changed due to a (re)configuration of the subframe configuration
pattern. Such unclarity regarding the state of the HARQ processes
occurs both in the uplink (UL) and the downlink (DL).
[0086] In the downlink (DL), the HARQ process number is signaled
explicitly. This means that if the HARQ processes change, the donor
base station node is still in full control of which HARQ process is
used in the relay base station node for a specific downlink (DL)
assignment, as the donor base station node signals which HARQ
process to use. However, the signaling for the new
transmission/retransmission is done in terms of a
toggled/non-toggled new data indicator (NDI), which hence depends
on the previous state of the new data indicator. Without knowledge
of the NDI state, the relay base station node may assume a
retransmission when the transmission is an initial transmission, or
vice versa.
[0087] In the uplink (UL), it will not be known between the donor
base station node and relay base station node which HARQ process is
in use in a particular subframe. As the HARQ processes may or may
not have been in use before the subframe configuration pattern
change, the donor base station node may receive an adaptive or
non-adaptive retransmission from a non-empty HARQ buffer, filled
before the subframe configuration pattern was changed. An adaptive
retransmission would occur if the donor base station node grants
the HARQ process with a non-toggled NDI. A non-adaptive
retransmission would occur if the donor base station node does not
grant the HARQ process at all. But there may be data in the buffer
that has not been acknowledged as received. If such a
retransmission happens (adaptive or non-adaptive), the donor base
station node does not know which HARQ process this data is from;
the donor base station node cannot map the received data to the
correct receive buffer where the result of the decoding of the
initial transmission and older retransmissions are stored; and the
donor base station node may not be able to decode the data at all.
This is especially the case when the retransmission is the
transmission of a redundancy version which is not decodable on its
own.
[0088] Thus, in both the downlink (DL) and the uplink (UL), the
consequence of not knowing the HARQ process state is ambiguity at
the receiving side. The receiver will not know if the transmission
received is a new transmission or a retransmission. Thus, the
receiver will also not know if the transmission should be soft
combined with previously stored soft information, and if so, which
particular soft information.
[0089] As explained below, the technology disclosed herein provides
method and apparatus to ensure that the state of HARQ processes in
use after the initial configuration or later reconfiguration of the
subframe configtiration pattern (subframe configuration pattern
change, or change of the subframeConfigPattern parameter in RRC) is
known in both the relay base station node and donor base station
node. This can be achieved, at subframe configuration pattern
change or after the change, before each individual HARQ processes
is used again. This coordination of knowledge of the HARQ process
states may be achieve using several different embodiments and
modes, four general embodiments and modes being described
subsequently here. Before describing the general embodiments and
modes, discussion is first provided below (first with reference to
FIG. 5 and then with reference to FIG. 6 and FIG. 7) regarding
structural and other aspects of generic embodiments and modes.
Structure: Overview of Nodes
[0090] FIG. 5 shows portions of an example, representative
embodiment of a radio access network 20 comprising donor base
station node 28, relay base station node 29, and wireless terminal
30. The example network may include one or more instances of such a
donor base station node 28 (e.g., a donor eNode B as shown in FIG.
1), the relay base station node 29, and the wireless terminal 30
along with any additional elements suitable to support
communication between wireless terminals or between a wireless
terminal and another communication device (such as a landline
telephone).
[0091] As shown in FIG. 5, the example base station (e.g., donor
base station node 28) includes processor 32, memory 34, transceiver
36, antenna 37, and network interface 38. The transceiver 36 and
antenna 37 cooperate for performing, e.g., communications over the
Un interface with relay base station node 29. The network interface
38 may connect to a core network. In particular embodiments, some
or all of the functionality of donor base station node 28 as
described herein may be provided by the processor 32 executing
instructions stored on a computer-readable medium, such as
non-transient instructions memory 34. Alternative embodiments of
donor base station node 28 may include additional components
responsible for providing additional functionality, including any
of the functionality identified herein and/or any functionality
necessary to support one or more of the solution(s) described
herein.
[0092] The example relay base station node 29 of FIG. 5 comprises
relay node processor 42; memory 44; one or more transceivers 46 and
antennas 47 for communication across the Uu interface with one or
more wireless terminals 30; and one or more transceivers 48 and
antennas 49 for communication across the Un interface with donor
base station node 28. Some or all of the functionality described
above as being provided by donor base station node 28 may be
provided by the relay processor 30 executing non-transient
instructions stored on a computer-readable medium, such as memory
44. Alternative embodiments of relay base station node 29 may
include additional components responsible for providing additional
functionality, including any of the functionality identified herein
and/or any functionality necessary to support one or more of the
solution(s) described herein.
[0093] In different implementations of the technology disclosed
herein, either one or both of the processor 32 of donor base
station node 28 and the relay node processor 42 of relay base
station node 29 serve to make a HARQ process state in a HARQ
process at relay base station node 29 known by donor base station
node 28 and/or make a HARQ process state in a HARQ process at the
donor base station node 28 known by the relay base station node 29.
Thus, the technology disclosed herein makes a HARQ process state in
a HARQ process at one of the base station nodes known by the other
base station node, e.g., by a HARQ process of the other base
station node. For example, in one example implementation a HARQ
process state in a HARQ process at the relay base station node 29
is made known to a HARQ process in the donor base station node 28.
In a second example implementation a HARQ process state in a HARQ
process at the donor base station node 28 is made known to a HARQ
process in the relay base station node 29. In a third example
implementation, the HARQ process states of the HARQ processes of
donor base station node 28 and relay base station node 29 are
mutually made known to each other.
[0094] The technology disclosed herein makes a HARQ process state
in a HARQ process at one of the base station nodes known by the
other base station node, e.g., by a HARQ process of the other base
station node, and does so without hardwire or other physical (e.g.,
non-radio) interconnections between the donor base station node 28
and the relay base station node 29.
[0095] When a processor implements one or more actions to ensure
that a HARQ process state of one base station node is "made known"
to the other base station node, the processor seeks to ensure that
post-configuration operation of the HARQ process(es) at one of the
base station nodes is coordinated and compatible with
post-configuration operation of the other base station node. For
example, a processor of relay base station node 29 may seek to
ensure one or more of its HARQ process states is/are coordinated
and compatible with post-configuration operation of the donor base
station node, e.g., of the HARQ process(es) in the donor base
station node. For example, one or both of donor processor 32 and
relay node processor 42 may implement one or more actions to render
the HARQ process state of the HARQ process at the relay base
station node 29 operationally compatible after the configuration
with the HARQ process in the donor base station node 28. Rendering
the HARQ process state of the HARQ process at one of the base
station nodes "operationally compatible" after the configuration
comprises, in various embodiments and modes described herein, means
or involves adjusting contents of buffers of the HARQ process and
values of the HARQ process state variables (e.g., NDI) such that
such contents and values will be known or assumed known by the
other base station node so that the HARQ processes of donor base
station node 28 and relay base station node 29 may continue to
operate in coordination and with successful decoding after the
subframe configuration.
[0096] In its basic form the example wireless terminal (UE) 30 of
FIG. 5 comprises processor 52; memory 54; transceiver 56; and one
or more antenna 57. Some or all of the functionality described
herein as being provided by wireless terminal 30, by mobile
communication devices or other forms of UE may be provided by the
UE processor 52 executing non-transient instructions stored on a
computer-readable medium, such as memory 54. Alternative
embodiments of the UE may include additional components beyond
those shown in FIG. 5 that may be responsible for providing certain
aspects of the functionality of the wireless terminal 30, including
any of the functionality described herein and/or any functionality
necessary to support one or more of the solution(s) described
herein.
[0097] The wireless terminal 30 may be called by other names and
comprise different types of equipment. For example, the wireless
terminal may also be called a mobile station, wireless station, or
user equipment unit (UE), and may be equipment such as a mobile
telephone ("cellular" telephone) and a laptop with mobile
termination, and thus may be, for example, portable, pocket,
hand-held, computer-included, or car-mounted mobile devices which
communicate voice and/or data with radio access network.
Structure: HARQ Aspects
[0098] FIG. 6 and FIG. 7 illustrate certain example structural
aspects of donor base station node 28 and relay base station node
29 in more detail according to an example embodiment. FIG. 6
particularly shows donor base station node 28 as comprising Medium
Access Control (MAC) entity 60 and Radio Resource Control (RRC)
manager 62. The Radio Resource Control (RRC) manager 62 in turn
comprises subframe controller 64. The Medium Access Control (MAC)
entity 60 comprises scheduler 68 and HARQ controller 70. The HARQ
controller 70 hosts (e.g., performs, executes, or constitutes)
plural HARQ downlink (DL) processes, depicted in FIG. 6 as
processes DL#1 through DL#n, as well as plural HARQ uplink (UL)
processes, depicted as processes UL#1 through UL#n. In addition,
HARQ controller 70 comprises HARQ coordinator for subframe
configuration 72. It should be appreciated that Medium Access
Control (MAC) entity 60 and Radio Resource Control (RRC) manager 62
may comprise or otherwise be realized by, at least in part,
processor 32 (see FIG. 5). In at least some example embodiments the
HARQ coordinator for subframe configuration 72 may serve as a
portion of processor 32 which makes a HARQ process state in a HARQ
process at one of the base station nodes known by the other base
station node. That is, the subframe configuration 72 may serve as
the portion of processor 32 which implements one or more actions to
ensure that a HARQ process state in a HARQ process at the relay
base station node 29 is known by the donor base station node 28
and/or that a HARQ process state in a HARQ process at the donor
base station node is known by the relay base station node, e.g.,
which makes the HARQ process state in the HARQ process at relay
base station node 29 known by donor base station node 28 after the
subframe configuration and vise-versa.
[0099] In an example embodiment, subframe controller 64 may be the
entity which initializes or makes any changes in the subframe
configuration pattern, e.g., the entity which implements a subframe
reconfiguration. The scheduler 68 is generally the entity which
decides which wireless terminal or relay base station node gets a
downlink (DL) transmission or gets to transmit on the uplink (UL)
on certain resources.
[0100] As also shown in FIG. 6, relay base station node 29
comprises Medium Access Control (MAC) entity 74 and Radio Resource
Control (RRC) unit 76. The Medium Access Control (MAC) entity 74
comprises scheduler 78 and HARQ controller 80. The HARQ controller
80 hosts (e.g., performs, executes, or constitutes) plural HARQ
downlink (DL) processes, depicted in FIG. 6 as processes DL#1'
through DL#n', as well as plural HARQ uplink (UL) processes,
depicted as processes UL#1' through UL#n'. In addition, HARQ
controller 80 comprises HARQ coordinator for subframe configuration
82. It should be appreciated that Medium Access Control (MAC)
entity 74 and Radio Resource Control (RRC) unit 76 may comprise or
otherwise be realized by, at least in part, the relay processor 42
(see FIG. 5). In at least some example embodiments the HARQ
coordinator for subframe configuration 82 may serve as a portion of
relay node processor 42 which makes a HARQ process state in a HARQ
process at one of the base station nodes known by the other base
station node. That is, the subframe configuration 82 may serve as
the portion of relay node processor 42 which implements one or more
actions to ensure that a HARQ process state in a HARQ process at
the relay base station node 29 is known by the donor base station
node 28 and/or to ensure that a HARQ process state in a HARQ
process at the donor base station node is known by the relay base
station node, e.g., which makes the HARQ process state in the HARQ
process at relay base station node 29 known by donor base station
node 28 after the subframe configuration.
[0101] FIG. 6 depicts by broken lines that each of the HARQ
processes of donor base station node 28 is preferably paired with a
corresponding HARQ process of relay base station node 29. For
example, in terms of the downlink (DL) (e.g., transmissions across
the Uu interface from donor base station node 28 to relay base
station node 29) the HARQ process DL#1 of donor base station node
28 is paired with HARQ process DL#1' of relay base station node 29.
Similarly, in terms of the uplink (UL) (e.g., transmissions across
the Uu interface from relay base station node 29 to donor base
station node 28) the HARQ process UL#1 of donor base station node
28 is paired with HARQ process UL#1' of relay base station node
29.
[0102] Thus, in this nomenclature and notation, a HARQ downlink
(DL) process is a process which provides an acknowledgement
(whether positive or negative) for a transmission on the downlink
(DL) from the donor base station node 28 to the relay base station
node 29. Both HARQ process DL#1 and HARQ process DL#1' cooperate to
provide such an acknowledgement for one such downlink (DL)
transmission, with the acknowledgement being sent on the uplink
from relay base station node 29 to donor base station node 28.
Conversely, a HARQ uplink (UL) process is a process which provides
an acknowledgement (whether positive or negative) for a
transmission on the downlink (DL) from the donor base station node
28 to the relay base station node 29. Both HARQ process UL#1 and
HARQ process UL#1' cooperate to provide such an acknowledgement for
one such uplink (UL) transmission, with the acknowledgement being
sent on the downlink (DL) from donor base station node 28 to relay
base station node 29.
[0103] It was stated above that each of the HARQ processes of donor
base station node 28 is preferably paired with a corresponding HARQ
process of relay base station node 29. While the states of these
paired HARQ process should always be in synchronization, there may
be error cases where the two states are actually different. But in
general there is a tight correlation/interaction between the HARQ
process #j in the donor base station node 28 and the HARQ process
#j' in the relay base station node 29.
[0104] FIG. 7 illustrates selected example details of
representative HARQ processes for both the uplink (UL) and the
downlink (DL) for both donor base station node 28 and relay base
station node 29. FIG. 7 illustrates in particular functional
elements of HARQ downlink (DL) process DL#j of donor base station
node 28 and its corresponding HARQ downlink (DL) process DL#j' of
relay base station node 29, as well as elements of HARQ uplink (UL)
process UL#j of donor base station node 28 and its corresponding
HARQ uplink (UL) process UL#j' of relay base station node 29.
[0105] As understood, e.g., from the foregoing, HARQ process DL#j
of donor base station node 28 and HARQ process DL#j' of relay base
station node 29 cooperate to provide an acknowledgement for a
downlink (DL) transmission, with the acknowledgement being sent on
the uplink from relay base station node 29 to donor base station
node 28. Thus, for the downlink (DL) the HARQ process DL#j' of
relay base station node 29 comprises acknowledgement generator 83
and the HARQ process DL#j of donor base station node 28 comprises
acknowledgement receiver/processor 84. Both downlink (DL) HARQ
processes DL#j and DLV comprise one or more state variables, e.g.,
a memory for state variables, depicted by state variable(s) 85 in
donor base station node 28 and state variable(s) 86 in relay base
station node 29. Each of state variable(s) 85 and state variable(s)
86 include the NDI, which can be conceptualized either as a single
NDI value or dual storage of an old NDI value and a current NDI
value. In addition, the state variable(s) 86 may comprise other
state variables such as the number of times a MAC PDU has been
transmitted, current redundancy version, and HARQ feedback.
Further, each HARQ process comprises a buffer whose contents may
also at least partially represent state information, and thus a
buffer handler for handing the respective buffer. For example, for
the HARQ downlink (DL) process DL#j' the relay base station node 29
comprises buffer handler 87 which operates upon one or more soft
buffers and a soft combiner. The for the HARQ downlink (DL) process
DL#j the donor base station node 28 comprises MAC PDU buffer 88,
for storing a MAC PDU that is to be sent to the relay base station
node 29.
[0106] Conversely, HARQ process UL#1 of donor base station node 28
and HARQ process UL#1' of relay base station node 29 cooperate to
provide an acknowledgement for an uplink (UL) transmission, with
the acknowledgement (ACK or NACK, collectively referred to as
"ACK") being sent on the downlink (DL) from donor base station node
28 to relay base station node 29. Thus, for the uplink (UL) the
HARQ process DL#j of donor base station node 28 comprises
acknowledgement generator 93 and the HARQ process DL#j' of relay
base station node 29 comprises acknowledgement receiver/processor
94. As understood with respect to the previous discussion of the
downlink (DL) HARQ process, uplink (UL) HARQ processes UL#j and
UL#j' comprise one or more state variables, e.g., a memory for
state variables, depicted by state variable(s) 95 in relay base
station node 29 and state variable(s) 96 in donor base station node
28, each of which include the NDI (which again can be
conceptualized either as a single NDI value or dual storage of an
old NDI value and a current NDI value). In addition, the state
variable(s) 96 may comprise other state variables such as the
number of times a MAC PDU has been transmitted, current redundancy
version, and HARQ feedback. As also understood with respect to the
previous discussion of the downlink (DL) HARQ process, for the HARQ
uplink (UL) process UL#j' the donor base station node 28 comprises
buffer handler 97 (which operates upon one or more soft buffers)
and a soft combiner; for the HARQ uplink (UL) process UL#j' the
relay base station node 29 comprises MAC PDU buffer 98, for storing
a MAC PDU that is to be sent to the donor base station node 28.
[0107] In FIG. 7 both buffer handler 87 and buffer handler 97 are
illustrated as comprising plural buffers, e.g., a first buffer and
a second buffer, as well as a soft combiner for soft combining the
contents of the first buffer and the second buffer. It should be
appreciated, however, that in some example embodiments there may be
just one "soft" buffer per HARQ process, as explained, for example,
in Dahlman, Erik; Parkvall, Stefan; and Skoeld, Johan, in 4G
LTE-Advanced for Mobile Broadband, section 12.1, page 249. In this
regard, multiple "softbits" may represent one bit of "hard"
information.
[0108] Moreover, it should be noted that while the buffers managed
by buffer handler 87 and buffer handler 97 logically comprise the
respective HARQ processes, there is not always a physical memory
location constantly allocated to a certain HARQ process, since
buffer memory may be shared dynamically between HARQ processes.
Accordingly, the FIG. 7 representation should be understood as
being a functional view and further that other implementations may
arrange or structure functionality in different ways or have
different physical incarnations of the functionalities.
[0109] Similarly, the state variable(s) 86 of relay base station
node 29 and the state variable(s) 96 of donor base station node 28
are illustrated as including both an old NDI value register and a
(current) NDI value register. In some example embodiments only one
instance of NDI need be stored, e.g., the old NDI. The new NDI is
compared to the old NDI once, and after that the old NDI is no
longer relevant and can be replaced by the "new" NDI.
Modes of Operation: Overview
[0110] Having described example structure of a generic donor base
station node 28 and relay base station node 29, discussion now
turns to a generic method of operation of radio access network 20
such as that of FIG. 5. As understood from the previous
discussions, radio access network 20 comprises a donor base station
node such as donor base station node 28 and a relay base station
node such as relay base station node 29, with relay base station
node 29 participating in communications across a first radio
interface (e.g., the Uu interface) with a wireless terminal and
also participating in communications over a backhaul link across a
second radio interface (e.g., the Un interface). The second radio
interface (e.g., the Un interface) reuses at least some
functionality of the first radio interface (e.g., the Uu
interface), such reused functionality including in some (but not
necessarily all) cases at least some of the frequencies within the
system bandwidth of the Uu interface.
[0111] Basic example, representative acts or steps of the generic
method are depicted in FIG. 8. Act 8-1 comprises configuring a
subframe configuration pattern. The subframe configuration pattern
is arranged to specify which subframe(s) of a frame structure may
be utilized for the backhaul link. In an example embodiment and
mode the re-configuring comprises changing, for example, a number
of HARQ processes in the donor base station node and the relay
station node and/or changing a mapping of HARQ processes to
subframes of the frame structure. Act 8-1 may be performed by a
processor such as processor 32 of donor base station node 28, and
in an example embodiment by subframe controller 64.
[0112] Act 8-2 follows as a result of the configuring of act 8-1,
and in various modes may be triggered by generating and/or
transmission of the indication of the subframe reconfiguration
(e.g., the subframe reconfiguration notification of FIG. 6). As
used herein "as a result" encompasses, e.g., address or countering
the consequences of the configuration of the subframe configuration
pattern. Act 8-2 comprises making a HARQ process state in a HARQ
process at one of the base station nodes (either donor base station
node 28 or relay base station node 29) known by the other base
station node (e.g., relay base station node 29 or donor base
station node 28).
[0113] Act 8-2 may involve implementing one or more actions to
ensure that post-configuration operation of the HARQ process(es) at
one of the base station nodes including the HARQ process state(s)
is/are coordinated and compatible with post-configuration operation
of the other base station node, e.g., of the HARQ process in the
other base station node. For example, act 8-2 may comprise
rendering the HARQ process state of the HARQ process at one of the
base station nodes operationally compatible after the configuration
by adjusting or setting contents of state buffers of the HARQ
process and values of the HARQ process state variables (e.g., NDI)
of HARQ processes in either of the base station nodes so that such
that such contents and values will be known or assumed known by the
other node and thus enable the two nodes to continue to operate in
coordination and with proper decoding after the subframe
configuration. As explained herein, in different implementations
either one or both of the processor 32 of donor base station node
28 and the relay node processor 42 of relay base station node 29
may be involved in performing act 8-2.
[0114] Thus, the technology disclosed herein makes a HARQ process
state in a HARQ process at one of the base station nodes known by
the other base station node, e.g., by a HARQ process of the other
base station node. For example, in one example implementation a
HARQ process state in a HARQ process at the relay base station node
29 is made known to a HARQ process in the donor base station node
28. In a second example implementation a HARQ process state in a
HARQ process at the donor base station node 28 is made known to a
HARQ process in the relay base station node 29. In a third example
implementation, the HARQ process states of the HARQ processes of
donor base station node 28 and relay base station node 29 are
mutually made known to each other.
[0115] Performance of act 8-2, e.g., making the HARQ process state
in the HARQ process at one of the base station nodes known by the
other base station node, may be realized in various embodiments and
modes. Four different embodiments and modes are discussed in more
detail below, and some comprise various options and optional
implementations. Before discussing each embodiment and mode
separately, a brief overview of the four embodiments and modes is
provided below:
[0116] 1. First Mode: the relay base station node resetting Medium
Access Control (MAC).
[0117] 2. Second Mode: ensuring new transmissions by flushing the
relay base station node buffers and/or NDI toggling.
[0118] 3. Third Mode: the donor base station node ensuring NDI
toggling by scheduling on each HARQ process and transport block to
ensure that the NDI is considered toggled when the next
transmission is due.
[0119] 4. Fourth Mode: the relay base station node and the donor
base station node applying a predetermined, known mapping rule
between HARQ processes in use before the subframe configuration
pattern change, and HARQ processes in use after the subframe
configuration pattern change.
Modes of Operation: First Mode
[0120] In a first example mode, act 8-2 (making the HARQ process
state in the HARQ process at one of the base station nodes known by
the other base station node) comprises performing a medium access
control (MAC) reset procedure at the donor base station node and at
the relay base station node.
[0121] As all HARQ status is maintained in the MAC layer, a MAC
reset will ensure that all status is cleared and give all HARQ
processes a fresh start. The MAC reset procedure is described in
3GPP TS specification 3GPP TS 36.321, "Evolved Universal
Terrestrial Radio Access (E-UTRA); Medium Access Control (MAC)
protocol specification," v10.0.0 (the "36.321 Specification"),
which is incorporated herein by reference in its entirety. In
general, a MAC reset (described in 3GPP TS 36.321, paragraph 5.9)
serves to reset, e.g., a number of MAC-related timers, buckets for
prioritization between logical channels, and also certain
procedures (if ongoing) are stopped. A MAC reset typically occurs
in the prior art at handover, at handover failure, when the
wireless terminal or relay base station node leaves RRC Connected,
at reception of a RRCConnectionReestablishment message, at
reception of a RRCConnectionReject message, when an
RRCConnectionRequest times out or the wireless terminal performs
cell reselection before the RRCConnectionRequest has been
answered.
[0122] According to this first mode, the MAC reset procedure
involves both Medium Access Control (MAC) entity 60 in donor base
station node 28 and Medium Access Control (MAC) entity 74 in relay
base station node 29. In prior art, the wireless terminal performs
a MAC reset at defined instances (standardized), meaning that the
donor base station node knows when the wireless terminal performs a
MAC reset. But in this first mode of the technology disclosed
herein, the indication of the subframe reconfiguration (e.g., the
subframe reconfiguration notification of FIG. 6) as sent from donor
base station node 28 to relay base station node 29 serves as a
signal to relay base station node 29 to perform the MAC reset
procedure.
[0123] The following excerpts from the aforementioned 3GPP TS
36.321 are particularly of interest, keeping in mind however that
actions in the 3GPP TS 36.321 described as "UE actions" for the
purpose of the technology disclosed herein concern instead actions
of the relay base station node 29:
TABLE-US-00001 excerpt from the 36.321 Specification If a reset of
the MAC entity is requested by upper layers, the UE shall: [...] -
consider timeAlignmentTimer as expired and perform the
corresponding actions in subclause 5.2; - set the NDIs for all
uplink HARQ processes to the value 0; [...] - flush the soft
buffers for all DL HARQ processes; - for each DL HARQ process,
consider the next received transmission for a TB as the very first
transmission;
[0124] The actions on timeAlignmentTimer expiry further involve the
flushing of all HARQ buffers, ensuring that there are no leftover
MAC PDUs in UL buffers, which in its turn ensures that the next
transmission on that HARQ process will be a new transmission.
[0125] As used herein "flushing" of a buffer means that the
contents of the buffer are unavailable or irretrievable. In some
implementations such flushing may involve a disposal or removal of
the contents of a buffer, e.g., the contents of a HARQ process
buffer. In other example implementations the flushing may be
handled by removing a pointer to the flushed contents of the
buffer, or setting a flag to indicate that the buffer has no data,
even though the physical data may still be present. In any
implementation, a flushed buffer is one whose contents immediately
after the flushing is not meant to be retrieved.
TABLE-US-00002 excerpt from the 36.321 Specification - if the
uplink grant was received on PDCCH for the C-RNTI and the HARQ
buffer of the identified process is empty; or [...] - instruct the
identified HARQ process to trigger a new transmission.
[0126] Thus, as understood from the foregoing and illustrated by
the basic acts of FIG. 9, the first mode comprises, e.g., setting
the NDIs for all uplink HARQ processes to the value 0 (act 9-1);
flushing the soft buffers for all DL HARQ processes (act 9-2); and
flushing all HARQ buffers, thereby ensuring that there are no
leftover MAC PDUs in UL buffers (act 9-3).
[0127] The MAC reset procedure resets the entire MAC layer, which
of course implies more than just the reset of HARQ buffers. Among
other things, the MAC reset procedure makes the time alignment
expire, which causes the wireless terminal 30/relay base station
node 29 to perform a random access procedure to get back its timing
alignment. For the purpose of achieving a known HARQ process state,
a random access procedure is not needed. Furthermore, the contents
(if any) of the HARQ buffers that are flushed is lost making soft
combining for that data impossible. To recover the data,
retransmissions on higher layers, e.g., RLC, may be implemented,
which will take time. In case the RLC Unacknowledge D mode (UM) is
used, it may even lead to data loss. In the RLC UM mode the RLC
does not provide acknowledgement of data, and hence does not
provide retransmissinons. In the RLC UM mode an RLC PDU, once sent,
is not resent even if not acknowledged.
[0128] The donor base station node need not perform a MAC reset.
The donor base station nodes needs to know that/when the relay base
station node performs its MAC reset, but there is no standardized
"MAC reset procedure" for the donor base station node (or for the
eNodeB in the case of eNB-wireless terminal communication).
Instead, the donor base station nodes actions are left to
implementation. The donor base station node should empty its uplink
(UL) receive buffers to avoid soft combining with new data (or that
the donor base station node will empty its uplink (UL) receive
buffers when new data is received) and it is useful (not necessary)
that the donor base station node puts new data into its DL transmit
buffers.
[0129] The MAC reset procedure is an already specified procedure
already in use for other purposes, which is now recognized for
achieving the purpose of a known HARQ process state after a change
in the subframe configuration pattern.
Modes of Operation: Second Mode
[0130] In a second example mode, act 8-2 (making the HARQ process
state in the HARQ process at one of the base station nodes known by
the other base station node) essentially comprises performing an
abbreviated or modified (e.g., a light-weight) version of the first
mode, e.g., performing only a subset of the MAC reset procedure
that is required to achieve a known HARQ process state.
[0131] The subset of operations involved in this second mode for
the uplink (UL) is depicted by either by act 10-1 or act 10-2 of
FIG. 10. Acts 10-1 and 10-2 are thus two alternative acts, either
of which may be implemented as an option.
[0132] Act 10-1 comprises flushing the UL HARQ buffers in relay
base station node 29. This flushing ensures that the next
transmission on each HARQ process will be a new transmission and
that the donor base station node 28 should not attempt to soft
combine a new transmission with any previously stored decoding
result of any HARQ buffer. In other words, the flushing of act 10-1
ensures that the relay base station node 29 always sends new data,
irrespective of NDI as it has no old data in its HARQ process
buffers to send. However, this does not ensure that the donor base
station node 28 does not try to combine the new data with
previously stored data (it may be left up to the donor base station
node 28 to keep track of subframe reconfiguration and determine for
itself that it should not soft combine.
[0133] Act 10-2 comprises toggle processing of the NDI. A toggled
NDI on the uplink (UL) guarantees that the relay base station node
29 sends a new transmission rather than a retransmission.
[0134] The subset of operations involved in this second mode for
the downlink (DL) is depicted by either by act 10-3 or act 10-4 of
FIG. 10. Acts 10-3 and 10-4 are thus two alternative acts, either
of which may be implemented as an option.
[0135] Act 10-3 comprises considering a next received transmission
of a transport block as a new transmission. Act 10-3 in turn may be
performed in either of two alternative ways, as depicted by acts
10-3A and 10-3B in FIG. 10.
[0136] Act 10-3A comprises explicitly making the next received
transmission a new transmission by setting the NDI to a value which
is toggled compared to the previously used NDI value for this
transport block on this HARQ process.
[0137] The alternative act 10-3B comprises (artificially, by
specification) considering the NDI to have been toggled compared to
the previous transmission on the same transport block on the same
HARQ process, if a change in the subframe configuration pattern has
occurred since the previous transmission. In act 10-3B, the donor
base station node 28 considers the NDI signaled by the donor base
station to be toggled for the uplink (UL) HARQ process with which
the NDI is associated.
[0138] Further explaining act 10-3A and act 10-3B, the NDI is a
value, 0 or 1, signaled by the DeNB. The relay base station node 29
keeps an NDI value per HARQ process. When a new NDI is received,
say 0, for example, the relay base station node 29 compares the 0
with the previously stored NDI value and concludes "toggled" or
"not toggled". In that conclusion, the relay base station node 29
has a choice. Assume that signaled value is 0. The stored NDI value
is also 0 so the NDI is not toggled, but as act 10-3B the relay
base station node 29 "may consider the NDI toggled". In particular,
the relay base station node 29 would consider the NDI signaled as
being toggled compared to the previous NDI value for the same HARQ
process, irrespective of the NDI value signaled. This is what is
meant herein by "artificially". "By specification" means that the
relay base station node 29 is instructed, e.g., by code, to
consider the NDI toggled, and that the donor base station node 28
knows that the relay base station node 29 will consider the NDI
toggled. The RN does not physically toggle the NDI as the NDI, but
instead, per definition, the NDI signaled by the donor base station
node 28.
[0139] In conjunction with act 10-3, as depicted by act 10-3-1 the
relay base station node 29 may optionally flush its downlink (DL)
buffers. However, the NDI toggling involved in act 10-3 is
sufficient to ensure that the next downlink (DL) transmission is
considered a new transmission.
[0140] Act 10-4, which may be performed for the downlink (DL) as an
alternative to act 10-3, comprises flushing the downlink (DL) HARQ
buffers of relay base station node 29. The next transmission for a
specific HARQ process will then be considered either a new
transmission or a retransmission, depending on the NDI state. If it
is considered a new transmission, the problem is solved. If it is
considered a retransmission, the newly transmitted data will be
combined with the data in the HARQ buffer, but since there is no
data in the HARQ buffer, the net effect is that the new data is
stored in the HARQ buffer as if it had been a new transmission. See
the 3GPP TS 36.321 Specification including the excerpt below, where
since there is no data in the HARQ buffer, the condition that the
data has not yet been successfully decoded will always be true.
TABLE-US-00003 excerpt from the 36.321 Specification - else if this
is a retransmission: - if the data has not yet been successfully
decoded: - combine the received data with the data currently in the
soft buffer for this TB.
Modes of Operation: Third Mode
[0141] In a third example mode, act 8-2 (making the HARQ process
state in the HARQ process at one of the base station nodes known by
the other base station node) essentially comprises the donor base
station node 28 scheduling the relay base station node 29 with a
certain or specified value of the NDI on each HARQ process to be
used after the subframe configuration pattern change. The
scheduling of the certain value of the NDI may occur before or
after changing the subframe configuration pattern, and
advantageously does not require any change of specification of MAC
handling at subframe configuration pattern change.
[0142] As shown by FIG. 11, in conjunction with the third example
mode for the downlink (DL) the donor base station node 28 may first
performed either act 11-1A or act 11-1B. Act 11-1A comprises the
donor base station node 28, e.g., Medium Access Control (MAC)
entity 60, keeping a record of the previous state of each HARQ
process and hence ensure a toggled NDI in the next downlink (DL)
assignment. In keeping a record of the previous state of each HARQ
process the donor base station node 28 will know the NDI associated
with that previous state when a subframe reconfiguration occurs,
and thus will easily be able then to generate a record or table
showing what value the NDI will have for each HARQ process when
toggled after the subframe reconfiguration.
[0143] Alternatively, rather than keep track of the NDI states, as
a simplification represented by act 11-1B the donor base station
node 28 may schedule a transmission with an arbitrary NDI value.
This scheduling would be done not primarily for the purpose of data
transmission, but to achieve a known NDI state on each HARQ
process. After such scheduling, the NDI value of the previous
transmission will be known again in both the relay base station
node 29 and the donor base station node 28 and any subsequent
downlink (DL) assignment can indicate an NDI which will be
considered toggled from the previous, hence indicating a new
downlink (DL) transmission.
[0144] As shown by optional act 11-2 for the downlink (DL), the
data transmission may consist of dummy data, inserted only for the
purpose of this special transmission, to ensure that no data is
lost.
[0145] For the third example mode for the downlink (DL) a similar
method can be used. On the uplink (UL) the donor base station node
28 cannot know the NDI state of a HARQ process, as it does not know
which HARQ process is in use. But in accordance with this third
mode, as act 11-3 the donor base station node 28 give the relay
base station node 29 an uplink (UL) grant with a fixed NDI value
per HARQ process and transport block. The donor base station node
28 will not know whether the transmission corresponding to this
grant will be a transmission or a retransmission, but for any the
subsequent grants, the NDI state of the HARQ processes will again
known to the donor base station node 28.
[0146] For the uplink (UL), the donor base station node 28 cannot
control what data is sent on the UL grant. But to ensure that there
is no data loss, the donor base station node 28 may give a very
small grant, e.g., a grant not large enough for any payload data
(only large enough to hold headers and padding).
[0147] If indeed real payload data is scheduled, in DL and/or UL,
and such data is successfully decoded on the MAC layer, higher
layers may ensure removal of duplicates in case a retransmission
occurred when giving the NDI a known state.
[0148] This kind of scheduling solution naturally uses air
interface resources which could otherwise have been used for real
data, and causes delay, but avoids specification impact, e.g.,
change of standardization specifications.
Modes of Operation: Fourth Mode
[0149] In a fourth example mode, act 8-2 (making the HARQ process
state in the HARQ process at one of the base station nodes known by
the other base station node) essentially comprises providing the
donor base station node 28 and the relay base station node 29 with
common knowledge of the HARQ process mapping and HARQ process
states. This may be done by applying a predetermined, known mapping
rule between the HARQ processes in use before and after the
subframe configuration pattern change.
[0150] The HARQ processes mapping, e.g., the HARQ processes mapping
rule, may take various forms. In a first form, represented by
mapping rule 12-1, the mapping rule may be a mapping of old HARQ
process number to new HARQ process number. In a second form,
represented by mapping rule 12-2, the mapping rule may be a mapping
of HARQ process number to subframe number. The mapping rules may
take the form of a table such as shown in FIG. 12A and FIG. 12B, or
any other appropriate association.
[0151] As shown in FIG. 12A, the mapping rule (either mapping rule
12-1 or mapping rule 12-2) may be predetermined or specified, e.g.,
pre-stored (e.g., stored at least before the subframe configuration
pattern change) in both donor base station node 28 and relay base
station node 29. By "predetermined" or "specified" may mean that
the information is common information that is mutually agreed by
the donor base station node 28 and relay base station node 29. The
mapping rule may be stored in or maintained by the HARQ controller
70 of the donor base station node 28 and the HARQ controller 80 of
relay base station node 29, for example.
[0152] Alternatively, the mapping rule (either mapping rule 12-1 or
mapping rule 12-2) may be stored in one of the nodes and then
signaled to the other node. For example, as shown in FIG. 12B, the
mapping rule may be stored in donor base station node 28 (e.g., at
the HARQ controller 70) and then signaled, e.g., before or after
the subframe configuration pattern change, to relay base station
node 29 (e.g., to HARQ controller 80 of relay base station node
29).
[0153] Once the relay base station node 29 and the donor base
station node 28 have a common understanding of which "old" HARQ
process each "new" HARQ process corresponds to, the HARQ process
state is also known in both nodes, and thus act 8-2 is
fulfilled.
[0154] Known mapping (e.g., use of a mapping rule) means that
stored soft information in. HARQ buffers may be reused and the full
advantage of HARQ may be utilized. Mapping also ensures that there
is not any data loss at HARQ level, as would be caused when HARQ
buffers are flushed.
[0155] As the mapping is known, and the state of the HARQ processes
before the subframe configuration pattern change was known, the
state of the HARQ processes after the change will be known. This is
true in all cases, except for HARQ processes that were not in use
before the change. As there are never more HARQ processes in use
for an relay base station node with an RN subframe configuration
than for that same relay node before it had its RN subframe
configuration, all HARQ processes have at some point in time been
used, but the assumption so far has been that only the history of
the HARQ processes before the latest change was taken into account.
This issue can be solved by either (1) looking back in time until
the last time each HARQ process was used, in which case each HARQ
process will have a known state, or (2) specifying a known HARQ
process state for HARQ processes not in use before the change in
subframe configuration pattern, including setting NDI to a fixed
value (e.g., NDI=0) and ensuring empty buffers.
[0156] Conversely, when the number of HARQ processes decreases
after a subframe configuration pattern change, some HARQ processes
will not be used after the change and thus are superfluous HARQ
processes. The mapping rule can in this case be (without precluding
other mapping rules): (1) in the downlink (DL), remove the
superfluous HARQ processes with the highest or lowest number (HARQ
process ID), or (2) for both uplink (UL) and downlink (DL),
prioritize for removal those HARQ processes that have no pending
retransmissions (e.g., the superfluous HARQ processes).
[0157] The HARQ process ID is signaled for the downlink (DL). This
means that for the downlink (DL), and the downlink (DL) only, the
donor base station node 28 and relay base station node 29 have a
common understanding of which HARQ process is HARQ process #1, HARQ
process #2, etc. But for the uplink (UL), a HARQ process just has a
peer in the other node, without there necessarily being a number,
or the number being the same in the donor base station node 28 and
the relay base station node 29.
[0158] An advantage of this mapping solution allows transmission to
continue smoothly despite the occurrence of a subframe
configuration pattern change (i.e., initial transmission before and
retransmission after the change).
Operation: Data Loss
[0159] In all embodiments where the contents of a buffer is flushed
or the NDI is explicitly or artificially toggled, data can be lost.
"Data loss" means that a MAC PDU is not properly decoded, and thus
"lost", e.g., that the content of the PDU (payload data and
possibly the MAC control information) is not delivered to or usable
by the respective receivers, whether in the donor base station node
28 or in the relay base station node 29. If an upper layer Radio
Link Control (RLC) procedure is run in acknowledged mode, the RLC
may provide retransmissions of the RLC PDU, which contains the MAC
PDU. Thus, the "data loss" may be captured on higher layers (e.g.,
the RLC) by retransmissions. These retransmissions may cause some
transmission delay, or in some cases, depending on the
configuration of higher layers, will lead to permanent data loss.
This has to be taken into account before the change of the subframe
configuration pattern.
[0160] In particular embodiments, various example embodiments
described herein ensure that the state of HARQ processes is known
after an RN reconfiguration including the subframe configuration
pattern. This removes ambiguity at the donor node side upon
receiving an uplink (UL) transmission from the relay base station
node 29 after a subframe configuration pattern, and ensures that
the donor base station node 28 can schedule downlink (DL)
transmissions (with associated HARQ process numbers and redundancy
version) in an optimized way.
[0161] The acts which have above been described as being
implemented or executed by a processor may be performed by any
suitable machine. The machine may take the form of electronic
circuitry in the form of a computer implementation platform or a
hardware circuit platform. A computer implementation of the machine
platform may be realized by or implemented as one or more computer
processors or controllers as those terms are herein expansively
defined, and which may execute instructions stored on non-transient
computer-readable storage media. In such a computer implementation
the machine platform may comprise, in addition to a processor(s), a
memory section (which in turn can comprise random access memory;
read only memory; an application memory (a non-transitory computer
readable medium which stores, e.g., coded non instructions which
can be executed by the processor to perform acts described herein);
and any other memory such as cache memory, for example). Another
example platform suitable is that of a hardware circuit, e.g., an
application specific integrated circuit (ASIC) wherein circuit
elements are structured and operated to perform the various acts
described herein.
[0162] Although the description above contains many specificities,
these should not be construed as limiting the scope of the
technology disclosed herein but as merely providing illustrations
of some of the presently preferred embodiments of the disclosed
technology. Thus the scope of this technology disclosed herein
should be determined by the appended claims and their legal
equivalents. Therefore, it will be appreciated that the scope of
the technology disclosed herein fully encompasses other embodiments
which may become obvious to those skilled in the art, and that the
scope of the technology disclosed herein is accordingly to be
limited by nothing other than the appended claims, in which
reference to an element in the singular is not intended to mean
"one and only one" unless explicitly so stated, but rather "one or
more." All structural, chemical, and functional equivalents to the
elements of the above-described preferred embodiment that are known
to those of ordinary skill in the art are expressly incorporated
herein by reference and are intended to be encompassed by the
present claims. Moreover, it is not necessary for a device or
method to address each and every problem sought to be solved by the
technology disclosed herein for it to be encompassed by the present
claims. Furthermore, no element, component, or method step in the
present disclosure is intended to be dedicated to the public
regardless of whether the element, component, or method step is
explicitly recited in the claims. No claim element herein is to be
construed under the provisions of 35 U.S.C. 112, sixth paragraph,
unless the element is expressly recited using the phrase "means
for."
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