U.S. patent application number 13/223598 was filed with the patent office on 2013-03-07 for enhanced mobility for devices using moving relay.
This patent application is currently assigned to NOKIA CORPORATION. The applicant listed for this patent is Lars DALSGAARD, Sassan IRAJI, Antti PIIPPONEN, Elena VIRTEJ. Invention is credited to Lars DALSGAARD, Sassan IRAJI, Antti PIIPPONEN, Elena VIRTEJ.
Application Number | 20130059589 13/223598 |
Document ID | / |
Family ID | 47753534 |
Filed Date | 2013-03-07 |
United States Patent
Application |
20130059589 |
Kind Code |
A1 |
DALSGAARD; Lars ; et
al. |
March 7, 2013 |
ENHANCED MOBILITY FOR DEVICES USING MOVING RELAY
Abstract
Enhanced mobility for devices using a moving relay, or in a
moving relay environment, may be valuable in the Long Term
Evolution (LTE) of the 3rd Generation Partnership Project (3GPP).
In particular, enhanced mobility procedures for user equipment (UE)
can be useful with respect to a moving relay and the radio access
network (RAN) interface (IF) between the user equipment and the
moving relay. Thus, certain embodiments can improve the mobility
procedures between moving relays and macro layer (stationary nodes,
for example, eNodeBs). A method according to certain embodiments
can include determining, by a user equipment, a stable average of a
signal characteristic of a signal from a mobile access point. The
method can also include limiting handover of the user equipment
based on the stable average.
Inventors: |
DALSGAARD; Lars; (Oulu,
FI) ; PIIPPONEN; Antti; (Vantaa, FI) ; VIRTEJ;
Elena; (Espoo, FI) ; IRAJI; Sassan; (Espoo,
FI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DALSGAARD; Lars
PIIPPONEN; Antti
VIRTEJ; Elena
IRAJI; Sassan |
Oulu
Vantaa
Espoo
Espoo |
|
FI
FI
FI
FI |
|
|
Assignee: |
NOKIA CORPORATION
Espoo
FI
|
Family ID: |
47753534 |
Appl. No.: |
13/223598 |
Filed: |
September 1, 2011 |
Current U.S.
Class: |
455/437 |
Current CPC
Class: |
H04W 84/005 20130101;
H04W 88/08 20130101; H04W 36/0088 20130101; H04W 36/32 20130101;
H04W 88/04 20130101; H04W 36/385 20130101; H04W 36/0094 20130101;
H04W 48/04 20130101 |
Class at
Publication: |
455/437 |
International
Class: |
H04W 36/30 20090101
H04W036/30 |
Claims
1. A method, comprising: determining, by a user equipment, a stable
average of a signal characteristic of a signal from a mobile access
point; and limiting handover of the user equipment based on the
stable average.
2. The method of claim 1, further comprising: generating a window
for the signal characteristic based on the stable average, wherein
limiting handover comprises limiting handover only when the signal
remains within the window.
3. The method of claim 1, wherein the determining comprises
measuring the signal by the user equipment.
4. The method of claim 1, wherein limiting handover comprises
prohibiting measurement-based handover.
5. The method of claim 1, further comprising: comparing a signal
characteristic of a macro cell to the signal characteristic of the
mobile access point, and resuming normal handover procedures when
the characteristics of the macro cell exceed those of the mobile
access point by a predetermined amount.
6. A method, comprising: determining that a user equipment is
within or near the coverage area of a mobile access point; and
informing the user equipment that the mobile access point is an
access point with mobile characteristics.
7. The method of claim 6, wherein the informing the user equipment
comprises sending a system information block, or by other
signaling, to the user equipment, wherein the system information
block or other signaling comprises an indicator that the mobile
access point has mobile characteristics.
8. The method of claim 6, further comprising: informing the user
equipment regarding a size of a window for a signal characteristic
for which the user equipment is configured to determine a stable
average.
9. An apparatus, comprising: at least one memory including computer
instructions; and at least one processor, wherein the at least one
memory and computer instructions are configured to, with the at
least one processor, cause the apparatus at least to determine a
stable average of a signal characteristic of a signal from a mobile
access point to a user equipment, and limit handover of the user
equipment based on the stable average.
10. The apparatus of claim 9, wherein the at least one memory and
computer instructions are also configured to, with the at least one
processor, cause the apparatus at least to generate a window for
the signal characteristic based on the stable average, wherein the
at least one memory and computer instructions are configured to,
with the at least one processor, cause the apparatus at least to
limit handover only when the signal remains within the window.
11. The apparatus of claim 9, wherein the at least one memory and
computer instructions are configured to, with the at least one
processor, cause the apparatus at least to determine the stable
average by measuring the signal by the user equipment.
12. The apparatus of claim 9, wherein the at least one memory and
computer instructions are configured to, with the at least one
processor, cause the apparatus at least to limit handover by
prohibiting measurement-based handover.
13. The apparatus of claim 9, wherein the at least one memory and
computer instructions are also configured to, with the at least one
processor, cause the apparatus at least to compare a signal
characteristic of a macro cell to the signal characteristic of the
mobile access point, and resume normal handover procedures when the
characteristics of the macro cell exceed those of the mobile access
point by a predetermined amount.
14. The apparatus of claim 9, wherein the mobile access point
comprises a relay node.
15. An apparatus, comprising: at least one memory including
computer instructions; and at least one processor, wherein the at
least one memory and computer instructions are configured to, with
the at least one processor, cause the apparatus at least to
determine that a user equipment is within or near the coverage area
of a mobile access point, and inform the user equipment that the
mobile access point is an access point with mobile
characteristics.
16. The apparatus of claim 15, wherein the informing the user
equipment comprises sending a system information block, or other
signaling, to the user equipment, wherein the system information or
other signaling comprises an indicator that the mobile access point
has mobile characteristics.
17. The apparatus of claim 15, wherein the at least one memory and
computer instructions are further configured to, with the at least
one processor, cause the apparatus at least to inform the user
equipment regarding a size of a window for a signal characteristic
for which the user equipment is configured to determine a stable
average.
18. A non-transitory computer readable medium encoded with
instructions that, when executed in hardware, perform a process,
the process comprising: determining, by a user equipment, a stable
average of a signal characteristic of a signal from a mobile access
point; and limiting handover of the user equipment based on the
stable average.
19. The non-transitory computer readable medium of claim 18, the
process further comprising: generating a window for the signal
characteristic based on the stable average, wherein limiting
handover comprises limiting handover only when the signal remains
within the window.
20. The non-transitory computer readable medium of claim 18,
wherein the determining comprises measuring the signal by the user
equipment.
21. The non-transitory computer readable medium of claim 18, the
process further comprising: comparing a signal characteristic of a
macro cell to the signal characteristic of the mobile access point,
and resuming normal handover procedures when the characteristics of
the macro cell exceed those of the mobile access point by a
predetermined amount.
Description
BACKGROUND
[0001] 1. Field
[0002] Enhanced mobility for devices using a moving relay, or
otherwise in a moving relay environment, may be valuable in the
Long Term Evolution (LTE) of the 3.sup.rd Generation Partnership
Project (3GPP). In particular, enhanced mobility procedures for
user equipment (UE) can be useful with respect to a moving relay
and the radio access network (RAN) interface (IF) between the user
equipment and the moving relay. Thus, certain embodiments can
improve the mobility procedures between moving relays and macro
layer (stationary nodes, for example, eNodeBs).
[0003] 2. Description of the Related Art
[0004] Mobile relay nodes (MRNs) are conventionally treated the
same as other relay nodes. In other words, there are not any
special requirement in the conventional approach when it comes to
mobility on the radio level. For example, there are no requirements
in the current radio access network level implementations related
to optimized mobility and mobile relay node with respect to various
issues, such as cell detection, measurements, measurement
reporting, cell reselection, and the like.
SUMMARY
[0005] A method according to certain embodiments includes
determining, by a user equipment, a stable average of a signal
characteristic of a signal from a mobile access point. The method
also includes limiting handover of the user equipment based on the
stable average.
[0006] According to certain embodiments, a method includes
determining means for determining that a user equipment is within
or near the coverage area of a mobile access point. The method also
includes informing the user equipment that the mobile access point
is an access point with mobile characteristics.
[0007] An apparatus includes, in certain embodiments, at least one
memory including computer instructions and at least one processor.
The at least one memory and computer instructions are configured
to, with the at least one processor, cause the apparatus at least
to determine a stable average of a signal characteristic of a
signal from a mobile access point to a user equipment. The at least
one memory and computer instructions are also configured to, with
the at least one processor, cause the apparatus at least to limit
handover of the user equipment based on the stable average.
[0008] In certain embodiments, an apparatus includes at least one
memory including computer instructions and at least one processor.
The at least one memory and computer instructions are configured
to, with the at least one processor, cause the apparatus at least
to determine that a user equipment is within or near the coverage
area of a mobile access point. The at least one memory and computer
instructions are also configured to, with the at least one
processor, cause the apparatus at least to inform the user
equipment that the mobile access point is an access point with
mobile characteristics.
[0009] An apparatus includes, in certain embodiments, determining
means for determining a stable average of a signal characteristic
of a signal from a mobile access point to a user equipment. The
apparatus also includes limiting means for limiting handover of the
user equipment based on the stable average.
[0010] According to certain embodiments, an apparatus includes
determining means for determining that a user equipment is within
or near the coverage area of a mobile access point. The apparatus
also includes informing means for informing the user equipment that
the mobile access point is an access point with mobile
characteristics.
[0011] A non-transitory computer-readable medium, according to
certain embodiments, is encoded with instructions that, when
executed in hardware perform a process. The process includes
determining, by a user equipment, a stable average of a signal
characteristic of a signal from a mobile access point. The method
also includes limiting handover of the user equipment based on the
stable average.
[0012] According to certain embodiments, a non-transitory
computer-readable medium is encoded with instructions that, when
executed in hardware perform a process. The process includes
determining that a user equipment is within or near the coverage
area of a mobile access point. The process also includes informing
the user equipment that the mobile access point is an access point
with mobile characteristics.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] For proper understanding of the invention, reference should
be made to the accompanying drawings, wherein:
[0014] FIG. 1 illustrates a system according to certain
embodiments.
[0015] FIG. 2 illustrates a method according to certain
embodiments.
[0016] FIG. 3 illustrates an example implementation according to
certain embodiments.
[0017] FIG. 4 illustrates a reference signal received power window
for mobile relay node reference signal received power.
[0018] FIG. 5 illustrates a method according to certain
embodiments.
[0019] FIG. 6 illustrates another method according to certain
embodiments.
[0020] FIG. 7 illustrates a system according to certain
embodiments.
DETAILED DESCRIPTION
[0021] Moving relay nodes (sometimes simply referred to as "moving
relays" or "mobile relays") may benefit from various enhancements
when it comes to handling of radio access network (RAN) level
mobility procedures. Examples of those enhancements may involve
specialized measurements, measurement reporting, and techniques for
inbound and outbound handover (HO) as well as similar techniques.
The moving relays need not always be moving. For example, a moving
relay can be installed in aircraft, train, hovercraft, boat, or
other vehicle, which may be stationary at times.
[0022] A situation can arise in which a user equipment (UE) camped,
idle or connected, to a moving or mobile relay node (MRN) while
still being able to detect and possibly reselect to or report cells
from a macro layer network. For example, the user equipment may be
able to detect and possibly reselect to or report cells not in a
mobile relay node group. Optimizations, in the sense of improved
mobility procedure(s) and/or the area of mobility robustness and
reduced signaling load over the air, can be helpful to reduce the
system and user experience impact from having mobile relay nodes
deployed.
[0023] FIG. 1 illustrates a system according to certain
embodiments. As shown in FIG. 1, a system can include a macro base
station (BS) in communication range of a user equipment (UE) that
is aboard a train. The user equipment can be connected to a mobile
relay node (MRN), which is also aboard the train. The train is
moving at a speed of 200 km/h (about 125 mph). Thus, the user
equipment's velocity relative to the macro base station (macro-BS)
is quite high (depending on the position of the macro base station
relative to the train). The velocity of the user equipment relative
to the mobile relay node in the train, is much slower (typically,
at most, walking speed--for example, 3 km/h or about 2 mph). This
difference can be seen by comparison of the two points of time (T)
and (T+.DELTA.T). Therefore the mobile relay node reference signal
received power (RSRP) changes slowly even if the train is moving
fast.
[0024] FIG. 2 illustrates a method according to certain
embodiments. As shown in FIG. 2, a relay node can identify itself
as a moving relay at 210. The relay node can provide this
identification to a user equipment (UE) or to a base station of a
macro network, such as an eNodeB. The moving relay node (RN)
information can be actively used in the user equipment, at 220, for
optimizing the mobility procedure in order to improve the mobility
robustness and reducing the network mobility signaling.
[0025] The information regarding the mobile relay node being a
mobile node can be used in the system in various ways. When within
mobile relay node coverage and camped/connected to it, the user
equipment can have a relatively stable reference signal received
power with respect to the relay node. That may be because the user
equipment to/from mobile relay node link is a non-moving scenario
or at least a slow-moving scenario, for example, walking speed.
Thus, at 230, the user equipment may determine that it is connected
to a mobile relay node.
[0026] The fact that the user equipment is connected to the mobile
relay node can be used, at 240, by the user equipment to find
reference signal received power average of the relay node. The user
equipment can create, at 250, a reference signal received power
window, of average reference signal received power (RSRP_a)+/-an
acceptable amount of reference signal received power. As long as
the relay node reference signal received power is within the
reference signal received power window, no mobility events are
triggered, at 255. Thus, no measurements reports may be sent to the
relay node, at 257, and no handover (HO) mobility happens. The user
equipment can remain connected to the relay node despite the
surrounding changes.
[0027] Mobility procedures between moving relays and macro layer
(stationary nodes) can be complex and can be implemented variously.
The approach outlined above can be realized in many ways. Below is
one illustration how the approach could be realized, but this
example should not be considered limiting.
[0028] In this example, a user equipment in evolved universal
terrestrial radio access network (E-UTRAN) radio resource
controller (RRC) connected mode serves to illustrate an
implementation. Similar approach can be applied also in idle mode,
and can also be applied in other systems than E-UTRAN.
[0029] FIG. 3 illustrates an example implementation according to
certain embodiments. As shown in FIG. 3, a user equipment in radio
resource control connected mode can, at 310, entering an area
covered by a moving relay node (MRN), which may also be referred to
as a mobile relay station. The user equipment can, at 320, perform
measurements on the carrier on which the mobile relay node is
located--if mobile relay node is not deployed on the same
carrier--in order to enable inbound mobility towards the mobile
relay node if needed.
[0030] Subsequently, at 330, the user equipment can be handed over
to the mobile relay node. Then, when the user equipment is
connected to the mobile relay node (for example, following an
inbound handover from a macro cell), the user equipment can be
informed that it is now connected to a mobile relay node, at 340.
This informing of the user equipment can be made through, for
example, a system information (SIB) or dedicated signaling (for
example, measurement configuration or handover command). This
information can be provided to the user equipment by the base
station of the macro cell or by the mobile relay node.
[0031] The moving relay node information, received by the user
equipment, can be actively used in the user equipment for
optimizing the mobility procedure. The fact that the link between
the user equipment and mobile relay node will (maybe after some
settling time) become stable and equal a non-moving scenario (since
the user equipment and mobile relay node are moving at similar
rates of speed), can be used to enhance the otherwise normally
continuously ongoing mobility procedures. Specifically, this fact
can be taken into account to reduce the load from the normal
mobility procedures on the user equipment and on the network.
[0032] The user equipment can actively use this information in
order to improve mobility related procedures in the following ways,
referring again to FIG. 2. The user equipment connected to the
mobile relay node can measure serving cell (MRN) to find, for
example, average reference signal received power or other
characteristics of the relay node. Based on the averaged value of,
for example, reference signal received power of the mobile relay
node, the user equipment can determine a stable reference signal
received power average value, at 240. This stable average can be
based on the user equipment's own measurements and not signaled by
network. As an alternative, the stable average can be based on the
measurements of another user equipment. For example, if a cluster
of user equipments are associated with a single user, the
measurements made by one or several of the user equipments can be
shared with the other user equipments in the cluster.
[0033] One reason that a user equipment specific average is useful,
is that the stabilized reference signal received power average
point may depend heavily on user equipment placement relative to
the mobile relay node, particularly because the mobile relay node
may have lower power than a typical macro cell base station, such
as an eNodeB and because the mobile relay node may be moving at a
high speed relative to fixed nodes in the system, but may be
relatively motionless with respect to the user equipment.
[0034] When the user equipment has obtained a stable reference
signal received power average point, which may be referred to as
RSRP_a, it can define an reference signal received power window, at
250. The window can be defined in terms of RSRP_lower <=RSRP_a
<=RSRP_higher, where RSRP_a is a stable reference signal
received power average point, RSRP_lower is a lower boundary of the
window, and RSRP_higher is the upper boundary of the window.
[0035] The relative boundaries RSRP_lower and RSRP_higher do not
have to be calculated by the user equipment. Instead the relative
boundaries RSRP_lower and RSRP_higher can be controlled and
signaled by the network (for example, either the mobile relay node
or a macro eNode B) to the user equipment. Thus, the network can
provide the user equipment with either a single magnitude for the
window (for example, the overall size of the window or the
difference between RSRP_a and RSRP_higher) or the particular values
for RSRP_lower and RSRP_higher. Alternatively, the network can
provide a factor to the user equipment so that the user equipment
will calculate a window of a size that is based on the factor
provided by the network.
[0036] When the reference signal received power window has been
defined, the user equipment can use this information as follows. As
long as instantaneous reference signal received power of the mobile
relay node is within the reference signal received power window, at
255, no event triggering happens (no mobility events, in
particular). Additionally, at 257, no measurement reports are sent
to the serving cell (MRN). Thus, no handover mobility occurs based
on measurement reporting and the user equipment will remain with
the relay node despite the surrounding changes. Of course, there
does not need to be any restriction on handover occurring for other
reasons (such as to obtain different services).
[0037] If the measured reference signal received power goes outside
the reference signal received power window, the user equipment can,
at 265, re-start normal measurement procedures, for example, as
configured by network. Thus, for example, when macro cell goes
above max window level/threshold above, this would lead to
handover/radio link failure (RLF). FIG. 4 illustrates a departure
from the window, and will be discussed below.
[0038] When the reference signal received power window has been
defined, but the reference signal received power difference between
the mobile relay node link and, for example, macro cell reference
signal received power exceed a given threshold, then normal
mobility procedures can be triggered at 265. This approach of
triggering normal mobility procedures when a macro cell appears to
have better performance can be done in order to be able to manage
interference. However, it may be valuable to require both a time
and performance threshold. In other words, it may be valuable to
require that the macro cell outperform the mobile relay node for at
least some minimum amount of time before triggering normal
measurement and mobility procedures at 265.
[0039] FIG. 4 illustrates an reference signal received power window
for mobile relay node reference signal received power. As shown in
FIG. 4, the reference signal received power can fluctuate around an
average reference signal received power. However, when the
reference signal received power goes outside a pre-defined window
(RSRP_low to RSRP_high centered around RSRP_average), the user
equipment can re-start normal measurements. It should be noted that
although the window is shown as symmetrical, the window can be
generated asymmetrically, since a very high received power from the
mobile relay node may be more tolerable than a very low received
power from the mobile relay node.
[0040] Certain embodiments can provide various features. For
example, certain embodiments can reduce mobility signaling,
measurements, and cell changes in a network employing mobile relay
nodes. Moreover, certain embodiments can permit a user equipment to
stay linked to a mobile relay node when within stable
conditions.
[0041] FIG. 5 illustrates a method according to certain
embodiments. As shown in FIG. 5, a method can include, at 510,
determining, by a user equipment, a stable average of a signal
characteristic of a signal from a mobile access point. The signal
characteristics can include, for example, reference signal received
power. The determining can be entirely done by the user equipment
or the user equipment can receive assistance from another node. For
example, at 512, the determining can include measuring the signal
by the user equipment.
[0042] The method can also include, at 520, limiting handover of
the user equipment based on the stable average. Limiting handover
can include, at 522, prohibiting measurement-based handover.
[0043] The method can further include, at 530, generating a window
for the signal characteristic based on the stable average, wherein
limiting handover comprises limiting handover only when the signal
remains within the window.
[0044] The method additionally include, at 540, comparing a signal
characteristic of a macro cell to the signal characteristic of the
mobile access point, and, at 550, resuming normal handover
procedures when the characteristics of the macro cell exceed those
of the mobile access point by a predetermined amount.
[0045] FIG. 6 illustrates a method according to alternative
embodiments of the present invention. As shown in FIG. 6, a method
can include determining, at 610, that a user equipment is within or
near the coverage area of a mobile access point. The method can
also include, at 620, informing the user equipment that the mobile
access point is an access point with mobile characteristics. The
informing the user equipment can include, at 630, sending a system
information block, or by other signaling means, to the user
equipment, wherein the system information (or other signaling)
comprises an indicator that the mobile access point has mobile
characteristics. The method can further include, at 640, informing
the user equipment regarding a threshold (such as the size of a
window) for a signal characteristic for which the user equipment is
configured to do determine a stable average. This method may be
performed by a mobile relay node or an evolved node B or by a
combination of the two. Additionally, this informing the user
equipment may be performed in connection with providing the user
equipment with information about neighbor nodes.
[0046] FIG. 7 illustrates a system according to certain
embodiments. As shown in FIG. 7, a system can include user
equipment 710, mobile relay node 720, and eNodeB 730. The various
devices or nodes in the system may be able to communicate with one
another over wireless links 740, and may be provided with
appropriate antennas, receivers, transmitters, and network
interfaces in order to be able to accomplish such
communications.
[0047] Each of the devices or nodes in the system can be equipped
with, among other things, at least one processor 750 and at least
one memory 760, which can include computer instructions.
[0048] The at least one processor 750 can be variously embodied by
any computational or data processing device, such as a central
processing unit (CPU) or application specific integrated circuit
(ASIC). The at least one processor 750 can, for example, be
implemented as one or a plurality of controllers.
[0049] The at least one memory 760 can be any suitable storage
device, such as a non-transitory computer-readable medium. For
example, a hard disk drive (HDD) or random access memory (RAM) can
be used in the at least one memory 760. The at least one memory 760
can be on a same chip as the at least one processor 750, or may be
separate from the at least one processor 750.
[0050] The computer instructions may be any suitable form of
computer program code. For example, the computer instructions may
be a compiled or interpreted computer program.
[0051] The at least one memory 760 and computer instructions can be
configured to, with the at least one processor 750, cause a
hardware apparatus (for example, user equipment 710, mobile relay
node 720, or eNodeB 730) to perform a process, such as the
processes shown in FIGS. 2, 3, 5, and 6 or any other process
described herein.
[0052] One having ordinary skill in the art will readily understand
that the invention as discussed above may be practiced with steps
in a different order, and/or with hardware elements in
configurations which are different than those which are disclosed.
Therefore, although the invention has been described based upon
these preferred embodiments, it would be apparent to those of skill
in the art that certain modifications, variations, and alternative
constructions would be apparent, while remaining within the spirit
and scope of the invention. In order to determine the metes and
bounds of the invention, therefore, reference should be made to the
appended claims.
* * * * *