U.S. patent application number 14/844888 was filed with the patent office on 2016-01-07 for methods and apparatus for measurement configuration support.
The applicant listed for this patent is Telefonaktiebolaget L M Ericsson (publ). Invention is credited to Muhammad Kazmi, Walter Muller, Iana Siomina.
Application Number | 20160007222 14/844888 |
Document ID | / |
Family ID | 44914586 |
Filed Date | 2016-01-07 |
United States Patent
Application |
20160007222 |
Kind Code |
A1 |
Siomina; Iana ; et
al. |
January 7, 2016 |
Methods and Apparatus for Measurement Configuration Support
Abstract
The invention provides a method and a network node for
controlling configuration of measurements to be performed by a user
equipment (150a, 150b) operating in a wireless communication system
(101). A configured measurement corresponds to at least one
reporting criteria and the user equipment (150a, 150b) is able to
support a limited number of parallel reporting criteria.
Measurements to be performed by the user equipment in parallel may
be requested by different network nodes such as a positioning
server (140) and an eNodeB (110a, 110b). By letting a network node,
such as the positioning server (140) or the (eNodeB 110a, 110b),
obtain information on measurements requested by another network
node the network node is able to configure the user equipment with
a set of measurements that does not exceed at least one
predetermined threshold for parallel reporting criteria.
Inventors: |
Siomina; Iana; (Taby,
SE) ; Kazmi; Muhammad; (Bromma, SE) ; Muller;
Walter; (Upplands Vasby, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Telefonaktiebolaget L M Ericsson (publ) |
Stockholm |
|
SE |
|
|
Family ID: |
44914586 |
Appl. No.: |
14/844888 |
Filed: |
September 3, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13696837 |
Nov 8, 2012 |
9131404 |
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PCT/SE2011/050587 |
May 10, 2011 |
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14844888 |
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61442998 |
Feb 15, 2011 |
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61333007 |
May 10, 2010 |
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Current U.S.
Class: |
370/252 |
Current CPC
Class: |
H04W 64/00 20130101;
H04B 7/024 20130101; H04W 4/021 20130101; H04W 24/10 20130101; H04W
24/02 20130101 |
International
Class: |
H04W 24/10 20060101
H04W024/10; H04W 4/02 20060101 H04W004/02; H04B 7/02 20060101
H04B007/02; H04W 24/02 20060101 H04W024/02 |
Claims
1. A method, implemented in a network node, of controlling a
configuration of measurements to be performed by a user equipment
operating in a wireless communication system, wherein a configured
measurement corresponds to at least one reporting criteria, and
wherein the user equipment is configured to support a limited
number of parallel reporting criteria, the method comprising:
obtaining information on a plurality of measurements requested by a
plurality of different network nodes to be performed by the user
equipment in parallel, wherein the plurality of measurements
include at least one positioning measurement; and using the
obtained information to configure the user equipment with a set of
measurements that does not exceed at least one predetermined
threshold for parallel reporting criteria.
2. The method of claim 1, wherein the obtained information
comprises information on: at least one category of positioning
measurement; a number of configured positioning measurement
reporting criteria for each category of positioning
measurement.
3. The method of claim 2, wherein the information on the at least
one category of the positioning measurement comprises information
specifying that a category of positioning measurement comprises: an
Observed Time Difference of Arrival (OTDOA); an Enhanced Cell ID
(E-CID); an intra-frequency Reference Signal Time Difference for
OTDOA measurement; an inter-frequency Reference Signal Time
Difference for OTDOA measurement; an intra-frequency user equipment
receive-transmit time difference for a neighbor cell for E-CID
measurement; an inter-frequency user equipment receive transmit
measurement for E-CID measurement; or an inter-radio access
technology (RAT) positioning measurement for E-CID measurement.
4. The method of claim 1, wherein the plurality of measurements
requested to be performed by the user equipment comprise
measurements to be performed on at least one of a primary carrier
and a secondary carrier.
5. The method of claim 1, wherein the plurality of different
network nodes comprises a positioning server and a radio network
node.
6. The method of claim 5, wherein the method is implemented in the
positioning server.
7. The method of claim 5, wherein the method is implemented in the
radio network node.
8. The method of claim 5: wherein the positioning server comprises
an Evolved Serving Mobile Location Center (E-SLMC) or a Secure User
Plane Location Location Platform (SLP); wherein the radio network
node comprises an evolved NodeB (eNodeB).
9. The method of claim 1: wherein obtaining the information on the
plurality of measurements requested by the plurality of different
network nodes comprises receiving at least one signaling message
with information on at least one requested measurement from at
least one third network node; wherein the third network node
comprises: one of the plurality of different network nodes; the
user equipment; a core network node; a Mobility Management Entity;
a network management node; a Self Organizing Network node; or a
Minimizing Drive Test node.
10. The method of claim 1 wherein obtaining the information on the
plurality of measurements requested by the plurality of different
network nodes comprises sniffing at least one message transmitted
between the user equipment and a positioning server to extract
information on at least one positioning measurement.
11. The method of claim 1, wherein the at least one predetermined
threshold for parallel reporting criteria comprises a threshold
specifying a maximum total number of parallel reporting
criteria.
12. The method of claim 1: wherein the at least one predetermined
threshold for parallel reporting criteria specifies a maximum
number of parallel reporting criteria per measurement category;
wherein a plurality of different measurement categories are
predefined to include different types of measurements.
13. The method of claim 12, wherein the plurality of different
measurement categories comprises at least one category for
positioning measurements.
14. The method of claim 13, wherein the at least one category for
positioning measurements comprises at least one category for at
least one of: an Observed Time Difference of Arrival (OTDOA); an
Enhanced Cell ID (E-CID); an intra-frequency Reference Signal Time
Difference for OTDOA measurement; an inter-frequency Reference
Signal Time Difference for OTDOA measurement; an intra-frequency
user equipment receive-transmit time difference for a neighbor cell
for E-CID measurement; an inter-frequency user equipment receive
transmit measurement for E-CID measurement; and an inter-radio
access technology (RAT) positioning measurement for E-CID
measurement.
15. The method of claim 1, wherein using the obtained information
to configure the user equipment comprises delaying a previously
configured measurement or initiating de-configuration of the
previously configured measurement to give priority to one or
several other measurements.
16. The method of claim 15, further comprising: delaying or
de-configuring a mobility measurement to give priority to a
positioning measurement; or delaying or de-configuring the
positioning measurement to give priority to the mobility
measurement.
17. A network node for controlling configuration of measurements to
be performed by a user equipment operating in a wireless
communication system, wherein a configured measurement corresponds
to at least one reporting criteria, wherein the user equipment is
configured to support a limited number of parallel reporting
criteria, the network node comprising: a receiver; a transmitter; a
processor; wherein the receiver and the processor are configured to
obtain information on a plurality of measurements requested by a
plurality of different network nodes to be performed by the user
equipment in parallel, wherein the plurality of measurements
comprises at least one positioning measurement; wherein the
processor and the transmitter are configured to use the obtained
information to configure the user equipment with a set of
measurements that does not exceed at least one predetermined
threshold for parallel reporting criteria.
18. The network node of claim 17, wherein the obtained information
comprises information on at least one category of positioning
measurement and a number of configured positioning measurement
reporting criteria for each category of positioning
measurement.
19. The network node of claim 18, wherein the information on type
of positioning measurement comprises information specifying that a
category of positioning measurement comprises: an Observed Time
Difference of Arrival (OTDOA); an Enhanced Cell ID (E-CID); an
intra-frequency Reference Signal Time Difference for OTDOA
measurement; an inter-frequency Reference Signal Time Difference
for OTDOA measurement; an intra-frequency user equipment
receive-transmit time difference for a neighbor cell for E-CID
measurement; an inter-frequency user equipment receive transmit
measurement for E-CID measurement; or an inter-radio access
technology (RAT) positioning measurement for E-CID measurement.
20. The network node of claim 17, wherein the plurality of
measurements requested to be performed by the user equipment
comprise measurements to be performed on at least one of a primary
carrier and a secondary carrier.
21. The network node of claim 17, wherein the plurality of
different network nodes comprises a positioning server and a radio
network node.
22. The network node of claim 21, wherein the network node
comprises the positioning server.
23. The network node of claim 21, wherein the network node
comprises the radio network node.
24. The network node of claim 21: wherein the positioning server
comprises an Evolved Serving Mobile Location Center (E-SLMC) or a
Secure User Plane Location Platform (SLP); wherein the radio
network node comprises an evolved NodeB (eNodeB).
25. The network node of claim 17: wherein the receiver is
configured to obtain information on the plurality of measurements
requested by the plurality of different network nodes by receiving
at least one signaling message with information on at least one
requested measurement from at least one third network node; wherein
the third network node comprises: one of the plurality of different
network nodes; the user equipment; a core network node; a Mobility
Management Entity; a network management node; a Self Organizing
Network node, or a Minimizing Drive Test node.
26. The network node of claim 17, wherein the receiver and
processor are configured to obtain at least some of the information
on the plurality of measurements requested by the plurality of
different network nodes by sniffing at least one message
transmitted between the user equipment and a positioning server to
extract information on at least one positioning measurement.
27. The network node of claim 17, wherein the at least one
predetermined threshold for parallel reporting criteria comprises a
threshold specifying a maximum total number of parallel reporting
criteria.
28. The network node of claim 17: wherein the at least one
predetermined threshold for parallel reporting criteria specifies a
maximum number of parallel reporting criteria per measurement
category; wherein a plurality of different measurement categories
are predefined to include different types of measurements.
29. The network node of claim 28, wherein the plurality of
different measurement categories comprises at least one category
for positioning measurements.
30. The network node of claim 29, wherein the at least one category
for positioning measurements comprises at least one category for at
least one of: an Observed Time Difference of Arrival (OTDOA); an
Enhanced Cell ID (E-CID); an intra-frequency Reference Signal Time
Difference for OTDOA measurement; an inter-frequency Reference
Signal Time Difference for OTDOA measurement; an intra-frequency
user equipment receive-transmit time difference for a neighbor cell
for E-CID measurement; an inter-frequency user equipment receive
transmit measurement for E-CID measurement; and an inter-radio
access technology (RAT) positioning measurement for E-CID
measurement.
31. The network node of claim 17, wherein the processor and the
transmitter are configured to use the obtained information to delay
a previously configured measurement or de-configure the previously
configured measurement to give priority to one or several other
measurements.
32. The network node of claim 31 wherein the processor and the
transmitter are configured to: delay or de-configure a mobility
measurement to give priority to a positioning measurement; or delay
or de-configure a positioning measurement to give priority to a
mobility measurement.
33. A method, implemented in a network node, of controlling a
configuration of measurements to be performed by a user equipment
operating in a wireless communication system, wherein a configured
measurement corresponds to at least one reporting criteria, and
wherein the user equipment is configured to support a limited
number of parallel reporting criteria, the method comprising:
obtaining information on a plurality of measurements requested by a
plurality of different network nodes to be performed by the user
equipment in parallel; and using the obtained information to
configure the user equipment with a set of measurements that does
not exceed at least one predetermined threshold for parallel
reporting criteria.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 13/696,837, filed Nov. 8, 2012, which was the National Stage of
International Application No. PCT/SE2011/050587, filed May 10,
2011, which claims the benefit of U.S. Provisional Application No.
61/442,998, filed Feb. 15, 2011 and U.S. Provisional Application
No. 61/333,007, filed May 10, 2010, the disclosures of each of
which are incorporated herein by reference in their entirety.
TECHNICAL FIELD
[0002] This present disclosure relates in general to measurements
in wireless communication networks and in particular to supporting
configuration of such measurements in wireless network
architectures that utilize signal measurements from multiple cells
for e.g. positioning, location, and location-based services.
BACKGROUND
[0003] The Universal Mobile Telecommunication System (UMTS) is one
of the third generation mobile communication technologies designed
to succeed GSM. 3GPP Long Term Evolution (LTE) is a project within
the 3.sup.rd Generation Partnership Project (3GPP) to improve the
UMTS standard to cope with future requirements in terms of improved
services such as higher data rates, improved efficiency, and
lowered costs. The Universal Terrestrial Radio Access Network
(UTRAN) is the radio access network of a UMTS and Evolved UTRAN
(E-UTRAN) is the radio access network of an LTE system. In an
E-UTRAN, a wireless device such as a user equipment (UE) 150a is
wirelessly connected to a radio base station (RBS) 110a commonly
referred to as an evolved NodeB (eNodeB), as illustrated in FIG.
1a. Each eNodeB 110a, 110b serves one or more areas each referred
to as cells 120a, 120b, and are connected to the core network. In
LTE, the eNodeBs 110a, 110b are connected to a Mobility Management
Entity (MME) (not shown) in the core network. A positioning server
140, also called a location server, in the control plane
architecture in FIG. 1a is connected to the MME. The positioning
server 140 is a physical or logical entity that manages positioning
for a so called target device, i.e. a wireless device that is being
positioned. The positioning server is in the control plane
architecture also referred to as an Evolved Serving Mobile Location
Center (E-SMLC). As illustrated in FIG. 1a, the E-SMLC 140 may be a
separate network node, but it may also be a functionality
integrated in some other network node. In a user plane
architecture, the positioning is a part of a Secure User Plane
Location (SUPL) Location Platform (SLP). The positioning server may
be connected to radio network nodes via logical links while using
one or more physical connections via other network nodes e.g., the
MME. A Network Management (NM) or Operations and Maintenance
(O&M) node 141 may be provided to perform different network
management operations and activities in the network.
[0004] Three key network elements in an LTE positioning
architecture are a Location Services (LCS) Client, an LCS target
and an LCS Server. The LCS Server is a physical or logical entity
managing positioning for a LCS target device by collecting
measurements and other location information, assisting the terminal
in measurements when necessary, and estimating the LCS target
location. The LCS Client is a software and/or hardware entity that
interacts with the LCS Server for the purpose of obtaining location
information for one or more LCS targets, i.e. the entities being
positioned. The LCS Clients may reside in the LCS targets
themselves. An LCS Client sends a request to the LCS Server to
obtain location information, and the LCS Server processes and
serves the received requests and sends the positioning result and
optionally a velocity estimate to the LCS Client. A positioning
request can be originated from a terminal or the network.
[0005] Two positioning protocols operating via the radio network
exist in LTE, LTE Positioning Protocol (LPP) and LPP Annex (LPPa).
The LPP is a point-to-point protocol between a LCS Server and a LCS
target device, used in order to position the target device. LPP can
be used both in the user and control plane, and multiple LPP
procedures are allowed in series and/or in parallel thereby
reducing latency. In the control plane, LPP uses RRC protocol as a
transport.
[0006] LPPa is a protocol between eNodeB and LCS Server specified
mainly for control-plane positioning procedures, although it still
can assist user-plane positioning by querying eNodeBs for
information and eNodeB measurements. Secure User Plane (SUPL)
protocol is used as a transport for LPP in the user plane. LPP has
also a possibility to convey LPP extension messages inside LPP
messages, e.g., currently Open Mobile Alliance (OMA) LPP extensions
(LPPe) are being specified to allow, e.g., for operator- or
manufacturer-specific assistance data or assistance data that
cannot be provided with LPP or to support other position reporting
formats or new positioning methods. LPPe may also be embedded into
messages of other positioning protocol, which is not necessarily
LPP.
[0007] A high-level architecture, as it is currently standardized
in LTE, is illustrated in FIG. 2, where the LCS target is a
terminal 200, and the LCS Server is an E-SMLC 201 or an SLP 202. In
the figure, the control plane positioning protocols with E-SMLC as
the terminating point are shown by arrows 203, 204 and 205, and the
user plane positioning protocol is shown by arrows 206 and 207. The
SLP 202 may comprise two components, SUPL Positioning Centre (SPC)
and SUPL Location Centre (SLC), which may also reside in different
nodes. In an example implementation, the SPC has a proprietary
interface with the E-SMLC 201, and an Llp interface with SLC, and
the SLC part of SLP communicates with a PDN-Gateway (P-GW) (not
shown) and an external LCS Client 208.
[0008] Additional positioning architecture elements may also be
deployed to further enhance performance of specific positioning
methods. For example, deploying radio beacons is a cost-efficient
solution which may significantly improve positioning performance
indoors and also outdoors by allowing more accurate positioning,
for example, with proximity location techniques.
[0009] UE positioning is a process of determining UE coordinates in
space. Once the coordinates are available, they may be mapped to a
certain place or location. The mapping function and delivery of the
location information on request are parts of a location service
which is required for basic emergency services. Services that
further exploit a location knowledge or that are based on the
location knowledge to offer customers some added value are referred
to as location-aware and location-based services. The possibility
of identifying a wireless device's geographical location in the
network has enabled a large variety of commercial and
non-commercial services, e.g., navigation assistance, social
networking, location-aware advertising, and emergency calls.
Different services may have different positioning accuracy
requirements imposed by an application. Furthermore, requirements
on the positioning accuracy for basic emergency services defined by
regulatory bodies exist in some countries. An example of such a
regulatory body is the Federal Communications Commission regulating
the area of telecommunications in the United States.
[0010] Positioning Methods
[0011] To meet Location-Based Services (LBS) demands, the LTE
network will deploy a range of complementary positioning methods
characterized by different performance in different environments.
Depending on where the measurements are conducted and where the
final position is calculated, the methods can be UE-based,
UE-assisted or network-based, each with own advantages. The
following methods are available in the LTE standard for both the
control plane and the user plane:
[0012] Cell ID (CID),
[0013] UE-assisted and network-based E-CID, including network-based
angle of arrival (AoA),
[0014] UE-based and UE-assisted A-GNSS (including A-GPS),
[0015] UE-assisted Observed Time Difference of Arrival (OTDOA).
[0016] Several other techniques such as hybrid positioning,
fingerprinting positioning and adaptive E-CID (AECID) do not
require additional standardization and are therefore also possible
with LTE. Furthermore, there may also be UE-based versions of the
methods above, e.g., UE-based GNSS, e.g., GPS, or UE-based OTDOA,
etc. There may also be some alternative positioning methods such as
proximity based location. UTDOA may also be standardized in a later
LTE release, since it is currently under discussion in 3GPP. More
methods, LTE and non-LTE, are supported with LPPe.
[0017] Similar methods, which may have different names, also exist
for other radio-access technologies (RATs), such as CDMA, WCDMA or
GSM.
[0018] In many environments, a wireless device position can be
accurately estimated by using positioning methods based on Global
Positioning System (GPS). Nowadays, networks also often have a
possibility to assist wireless devices in order to improve the
device receiver sensitivity and GPS start-up performance, as for
example in an Assisted-GPS (A-GPS) positioning method. GPS or A-GPS
receivers, however, may not necessarily be available in all
wireless devices. Furthermore, GPS is known to often fail in indoor
environments and urban canyons. The complementary terrestrial
positioning method OTDOA, has therefore been standardized by
3GPP.
[0019] OTDOA Positioning
[0020] With OTDOA, a wireless device such as a UE measures the
timing differences for downlink reference signals received from
multiple distinct locations, such as eNodeBs. For each measured
neighbor cell, the UE measures Reference Signal Time Difference
(RSTD) which is the relative timing difference between a neighbor
cell and the reference cell. The UE measures the timing of the
received downlink reference signals using assistance data received
from the LCS server, and the resulting measurements are used to
locate the UE in relation to the neighboring cells. As illustrated
in FIG. 3, the UE position estimate is found as the intersection
430 of hyperbolas 440 corresponding to the measured RSTDs. At least
three measurements from geographically dispersed RBSs 410a-c with a
good geometry are needed to solve for two coordinates of the UE. In
order to find the position, precise knowledge of transmitter
locations and transmit timing offsets is needed. Position
calculations may be conducted, for example by a positioning node
such as the E-SMLC or the SLP in LTE, or by the UE. The former
approach corresponds to the UE-assisted positioning mode, and the
latter corresponds to the UE-based positioning mode.
[0021] In UTRAN Frequency Division Duplex (FDD), an SFN-SFN type 2
measurement (SFN stands for System Frame Number) performed by the
UE is used for the OTDOA positioning method. This measurement is
the relative timing difference between cell j and cell i based on
the primary Common Pilot Channel (CPICH) from cell j and cell i.
The UE reported SFN-SFN type 2 is used by the network to estimate
the UE position.
[0022] Positioning Reference Signals
[0023] To enable positioning in LTE and facilitate positioning
measurements of a proper quality and for a sufficient number of
distinct locations, physical signals dedicated for positioning,
such as positioning reference signals (PRS), have been introduced,
and low-interference positioning subframes have been specified in
3GPP. PRS are transmitted from one antenna port R6 according to a
pre-defined pattern, as described in more detail below.
[0024] A frequency shift, which is a function of a Physical Cell
Identity (PCI), can be applied to the specified PRS patterns to
generate orthogonal patterns and model an effective frequency reuse
of six, which makes it possible to significantly reduce neighbor
cell interference on the measured PRS and thus improve positioning
measurements. Even though PRS have been specifically designed for
positioning measurements and in general are characterized by better
signal quality than other reference signals, the standard does not
mandate using PRS. Other reference signals, e.g., cell-specific
reference signals (CRS) may also be used for positioning
measurements.
[0025] PRS are transmitted according to a pre-defined pattern and
following one of the pre-defined PRS configurations. PRS are
transmitted in pre-defined positioning subframes grouped by a
number Nprs of consecutive subframes, i.e. one positioning
occasion, as illustrated in FIG. 4. Positioning occasions occur
periodically with a certain periodicity of N subframes,
corresponding to a time interval T_prs between two positioning
occasions. The standardized time intervals T_prs are 160, 320, 640,
and 1280 ms, and the number of consecutive subframes Nprs are 1, 2,
4, and 6. Each pre-defined PRS configuration comprises at least PRS
transmission bandwidth, N_prs and T_prs.
[0026] OTDOA Assistance Information
[0027] Since for OTDOA positioning PRS signals from multiple
distinct locations need to be measured, the UE receiver often will
have to deal with PRS that are much weaker than those received from
the UE's serving cell. Furthermore, without approximate knowledge
of when the measured signals are expected to arrive in time and
what is the exact PRS pattern used, the UE would need to do signal
search within a large window, which would impact the time and
accuracy of the measurements as well as the UE complexity. To
facilitate UE measurements, assistance information, also referred
to as assistance data, is transmitted to the UE, which includes
e.g. reference cell information, a neighbor cell list containing
PCIs of neighbor cells, the number of consecutive downlink
subframes N-prs, PRS transmission bandwidth, and frequency. The
assistance information is signaled over LPP from the positioning
server, e.g., an E-SMLC in the control plane for an LTE system, to
the UE.
[0028] OTDOA Inter-Frequency Measurements and Measurement Gaps
[0029] In LTE OTDOA, the UE measures Reference Signal Time
Difference (RSTD) which has been defined in the standard as the
relative timing difference between cell j and cell i, defined as
T.sub.SubframeRxj-T.sub.subframeRxi, where: T.sub.SubframeRxj is
the time when the UE receives the start of one subframe from cell
j, T.sub.SubframeRxi is the time when the UE receives the
corresponding start of one subframe from cell i that is closest in
time to the subframe received from cell j. The reference point for
the observed subframe time difference shall be the antenna
connector of the UE. The measurements are specified for both
intra-frequency and inter-frequency and conducted in the
RRC_CONNECTED state.
[0030] The inter-frequency measurements, including RSTD, are
conducted during periodic inter-frequency measurement gaps which
are configured in such a way that each gap starts at an SFN and
subframe meeting the following condition:
SFN mod T=FLOOR(gapOffset/10);
[0031] subframe=gapOffset mod 10; with T=MGRP/10, where MGRP stands
for "measurement gap repetition period" and mod is the modulo
function. The E-UTRAN is required according to the standard to
provide a single measurement gap pattern with constant gap duration
for concurrent monitoring of all frequency layers and Radio Access
Technologies (RATs). Two configurations are according to the
standard required to be supported by the UE, with MGRP of 40 and 80
milliseconds (ms), both with a measurement gap length of 6 ms. In
practice, due to switching time, this leaves less than 6 but at
least 5 full subframes for measurements within each such
measurement gap.
[0032] In LTE, measurement gaps are configured by the network, i.e.
the eNodeB, to enable measurements on different LTE frequencies
and/or different RATs such as e.g., UTRA, GSM and CDMA2000. A
measurement is configured using the Radio Resource Control (RRC)
protocol to signal a measurement configuration to the UE. The gap
configuration is signaled to the UE as part of the measurement
configuration. Only one gap pattern can be configured at a time.
The same pattern is used for all types of configured measurements,
e.g. inter-frequency neighbor cell measurements, inter-frequency
positioning measurements, inter-RAT neighbor cell measurements,
inter-RAT positioning measurements, etc.
[0033] In multi-carrier LTE, the inter-frequency measurement gaps
are so far intended mainly for performing cell identification and
mobility measurements, such as Reference Signal Receiver Power
(RSRP) and Reference Signal Received Quality (RSRQ). These
measurements require a UE to perform measurements over the
synchronization signals, i.e., the primary synchronization signals
(PSS) and secondary synchronization signals (SSS), and
cell-specific reference signals (CRS) to enable inter-frequency
handover and enhance system performance. Synchronization signals
are transmitted over 62 resource elements in the center of the
allocated bandwidth in subframes 0 and 5. The PSS is transmitted in
the last OFDM symbol and the SSS is transmitted in the second to
last OFDM symbol of the first slot of a subframe. CRS symbols are
transmitted every subframe and over the entire bandwidth according
to one of the standardized time-frequency patterns. Different cells
can use 6 different shifts in frequency, and 504 different signals
exist. With two transmit (TX) antennas, the effective reuse for CRS
is three.
[0034] As can be seen from the above, both synchronization signals
and CRS are transmitted relatively often, although PSS and SSS are
transmitted less frequently than CRS. This leaves enough freedom
when deciding the exact timing of measurement gaps so that a gap
can cover enough symbols with the signals of interest, i.e.,
PSS/SSS and/or CRS. With a 6 ms measurement gap, at most two SSS
and two PSS symbols are possible with very precise timing, while
capturing one SSS symbol and one PSS symbol is possible almost
without any timing restriction on the measurement gaps since the
minimum required effective measurement time is 5 ms on average.
[0035] In LTE OTDOA, the network, i.e. the eNodeB, can signal a
list of cells operating on up to three frequency layers, including
the serving cell frequency. The 3GPP RAN4 requirements for RSTD
inter-frequency measurements are defined for two frequency layers,
including the serving cell frequency. Furthermore, the measurement
gaps are to be defined such that they do not overlap with PRS
occasions of the serving cell layer, which would otherwise increase
the effective measurement time for both the serving and the
inter-frequency cell. Since the measurement gaps configured for the
UE are used for RSTD measurements and also for mobility
measurements, it has been agreed that the pre-defined "Gap Pattern
#0", which specifies relatively dense and frequent measurement
gaps, can be used only when inter-frequency RSTD measurements are
configured. According to the pre-defined Gap Pattern #0 a
measurement gap of 6 ms occurs every 40 ms.
[0036] E-CID Positioning
[0037] The enhanced cell ID (E-CID) positioning method determines
the UE location based on UE and/or BS reporting measurements.
Examples of UE measurements are UE Rx-Tx time difference
measurement, signal strength e.g., RSRP and signal quality e.g.,
RSRQ. Examples of BS measurements are BS Rx-Tx time difference
measurement, angle of arrival etc.
[0038] In LTE release 9 the UE Rx-Tx time difference measurement is
performed by the UE from the serving cell. It is reported to both
the eNodeB and the E-SMLC.
[0039] However, in general at least some of the E-CID measurements
may be inter-frequency, inter-band or inter-RAT measurements, e.g.,
RSRP or RSRQ. Examples of inter-RAT E-CID measurements are UTRA
CPICH measurements, GSM carrier RSSI, etc.
[0040] Event Triggering and Reporting Criteria
[0041] The standard specification 3GPP TS 36.133 V9.3.0 (2010-03)
Evolved Universal Terrestrial Radio Access (E-UTRA), Requirements
for support of radio resource management (Release 9) (March 2010)
specifies requirements on UE capabilities for support of event
triggering and reporting criteria. The current requirements are
primarily defined for the mobility measurements. The requirements
comprise:
[0042] a set of reporting criteria categories,
[0043] the number of reporting criteria per category that the UE
shall be able to support in parallel, and
[0044] the maximum total number of reporting criteria.
[0045] The current set of reporting criteria comprises three
measurement categories used for mobility: intra-frequency,
inter-frequency and inter-RAT measurements.
[0046] For the intra-frequency category, measurements for up to 9
E-UTRAN intra-frequency cells may be configured in parallel. For
the inter-frequency category, measurements of up to 7 E-UTRAN
inter-frequency cells may be configured in parallel. And for
inter-RAT, up to 5 parallel measurements per supported RAT are
supported in 3GPP TS 36.133 V9.3.0. The maximum total number of
reporting criteria is thus 21 in 3GPP TS 36.133 V9.3.0. This means
depending upon the UE capability, e.g., inter-RAT capabilities, the
eNodeB can configure the UE to perform up to 21 measurements in
parallel. As long as the measurement configuration does not exceed
the reporting criteria requirements above, the UE is required to
meet the relevant performance requirements, e.g., measurement
reporting delay, measurement accuracy of the configured
measurements, etc.
[0047] As mentioned earlier, the above requirements cover mobility
related measurements which are configured by the serving eNodeB. UE
requirements in terms of the maximum number of reporting criteria
for the mobility measurements are defined. This ensures that the UE
is able to perform and report certain number of measurements in
parallel, e.g., event triggered RSRP reporting, periodic RSRP
reporting, event triggered RSRQ reporting etc. The total number of
parallel measurement reporting criteria is 21 including inter-RAT
measurements. The requirements were introduced in Release 8 of the
3GPP standards and do not take into account the positioning
measurements, such as OTDOA and E-CID, which were introduced in
Release 9. The positioning measurements are configured by a
positioning server, such as the E-SMLC. Accordingly measurements to
be performed by the UE may be configured by different network
nodes. Therefore there is a need for coordination with respect to
parallel reporting criteria requirements.
SUMMARY
[0048] An object of at least some embodiments in this disclosure is
to provide methods and devices for controlling UE measurement
configuration when a positioning service is used.
[0049] The above stated object is achieved by means of methods and
devices according to the independent claims.
[0050] A first embodiment provides a method in a network node of
controlling configuration of measurements to be performed by a user
equipment operating in a wireless communication system. A
configured measurement corresponds to at least one reporting
criteria and the user equipment is able to support a limited number
of parallel reporting criteria. The method comprises obtaining
information on a plurality of measurements requested by a plurality
of different network nodes. The measurements are to be performed by
the user equipment in parallel and include at least one positioning
measurement. The method comprises a further step of using the
obtained information to configure the user equipment with a set of
measurements that does not exceed a predetermined threshold for
parallel reporting criteria.
[0051] A second embodiment provides a network node for controlling
configuration of measurements to be performed by a user equipment
operating in a wireless communication system. A configured
measurement corresponds to at least one reporting criteria and the
user equipment is able to support a limited number of parallel
reporting criteria. The network node comprises a receiver, a
transmitter and a processor (74). The receiver and the processor
are adapted to obtain information on a plurality of measurements
requested by a plurality of different network nodes. The
measurements are to be performed by the user equipment in parallel
and include at least one positioning measurement. The processor and
the transmitter of the network node are adapted to use the obtained
information to configure the user equipment with a set of
measurements that does not exceed a predetermined threshold for
parallel reporting criteria.
[0052] An advantage of some of the embodiments described herein is
that it is made possible for a node of the wireless communication
system to monitor and control that UE requirements and/or
capabilities with respect to parallel reporting criteria are not
exceeded in when positioning is used. By providing a network node
with information regarding UE measurements requested by different
network nodes, which may request positioning measurements as well
as non-positioning measurements, the network node is able to
control that the UE is configured with measurements that do not
exceed one or several predetermined thresholds for parallel
reporting criteria. A predetermined threshold may e.g. be a
standardized UE requirement regarding a total number of parallel
reporting criteria or a UE capability with respect to a specific
measurement category, such as the UEs capability of parallel
positioning measurements.
[0053] Further advantages and features of embodiments of the
present invention will become apparent when reading the following
detailed description in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0054] FIG. 1 is a schematic block diagram of a cellular
communication system in which embodiments described herein may be
implemented.
[0055] FIG. 1a is a schematic block diagram of wireless
communication system, including a positioning server, in which
embodiments described herein may be implemented.
[0056] FIG. 2 is a schematic block diagram illustrating an LTE
system with positioning functionality.
[0057] FIG. 3 is a schematic block diagram illustrating positioning
of a user equipment (UE) by determining an intersection of
hyperbolas corresponding to measured Reference Signal Time
Differences (RSTDs).
[0058] FIG. 4 is a schematic block diagram illustrating a
measurement gap pattern.
[0059] FIG. 5 is a schematic block diagram illustrating a
Positioning Reference Signal pattern when one or two antennas are
used for a Physical Broadcast Channel (PBCH).
[0060] FIG. 6 is a flow diagram illustrating an exemplary method of
controlling configuration of measurements to be performed by the
UE.
[0061] FIG. 7 is a schematic block diagram illustrating an
embodiment of a network node.
DETAILED DESCRIPTION
[0062] The term "UE" is used throughout this description as a
non-limiting term which means any wireless device or node, e.g.
PDA, laptop, mobile, sensor, fixed relay, mobile relay or even a
small base station that is being positioned when timing
measurements for positioning are considered, i.e. a LCS target in
general. The UE may also be an advanced UE capable of such advanced
features as carrier aggregation.
[0063] A cell is associated with a radio network node, where a
radio network node comprise in a general sense any node capable of
transmitting and/or receiving radio signals that may be used for
positioning and/or measurements, such as e.g., an eNodeB,
macro/micro/pico base station, home eNodeB, relay, beacon device,
or repeater. The radio network node may be a single-RAT or
multi-RAT or multi-standard radio base station. Note that downlink
and uplink transmissions do not need to be between the UE and the
same radio network node.
[0064] A positioning server described in different embodiments is a
node with positioning functionality. The terms "positioning server"
and "positioning node" are used synonymously herein. For example,
for LTE it may be understood as a positioning platform in the user
plane, e.g., SLP in LTE, or a positioning server in the control
plane, e.g., E-SMLC in LTE. SLP may also consist of SLC and SPC, as
explained above, where SPC may also have a proprietary interface
with E-SMLC. In a testing environment, at least the positioning
server may be simulated or emulated by test equipment.
[0065] The signalling described in the different embodiments is
either via direct links or logical links, e.g. via higher layer
protocols such as RRC and/or via one or more network nodes. For
example, in LTE in the case of signalling between E-SMLC and the
LCS Client the positioning result may be transferred via multiple
nodes, at least via MME and Gateway Mobile Location Centre
GMLC.
[0066] Herein the term "measurement indication" will be used to
refer to a message which provides information related to a
measurement to allow for monitoring of a predetermined threshold
with respect to parallel reporting criteria of a UE. The
measurement indication may comprise different types of information.
If the predetermined threshold to be monitored relates to a limit
on the total number of parallel reporting criteria of the UE, the
measurement indication may be a simple message indicating that the
UE is requested to perform a measurement. However, if the
predetermined threshold relates to a specific category of
measurement the measurement indication will need to include enough
information to determine the measurement category to which the
measurement indication relates. The measurement indication may also
contain additional information such as information specifying a
frequency to which the measurement relates, information relating to
timing of reference signals to be used for the measurement and
other parameters which may be required for configuration of the
measurement. Specific measurement indications may be used for
specific types of measurements, such as mobility measurements and
different types of position measurements e.g. OTDOA measurement and
E-CID measurements.
[0067] At least in some embodiments, inter-frequency measurements
in the current invention shall be understood in a general sense
comprising, e.g., inter-frequency, inter-band, or inter-RAT
measurements. Some non-limiting examples of inter-frequency
positioning measurements are inter-frequency E-CID measurements
such as UE Rx-Tx time difference, RSRP and RSRQ, and
inter-frequency RSTD measurements for OTDOA positioning.
[0068] At least some embodiments described herein are not limited
to LTE, but may apply with any RAN, single- or multi-RAT. Some
other RAT examples are LTE-Advanced, UMTS, GSM, cdma2000, WiMAX,
and WiFi.
[0069] As mentioned above FIG. 1a shows a positioning architecture.
As illustrated in FIG. 1a there is an interface 163, e.g. X2,
between the two eNodeBs 110a and 110b and an interface 164 between
an eNodeB and a network management and/or operation and maintenance
(O&M) block 141. The positioning node or positioning server 140
is here assumed to be an E-SMLC server in E-UTRAN. The protocol for
messaging between the E-SMLC 140 and the eNodeBs 110a is called
LPPa. The radio interface protocol between the E-SMLC 140 and the
UE 150a, 150b is called LPP. Note that a link between different
network entities may be a physical or a logical link. A path for
higher layer protocols is a logical link which may comprise one or
several physical links.
[0070] Assuming an architecture such as shown in FIG. 1a, exemplary
embodiments will be described below.
[0071] When positioning is used a mechanism is needed for
monitoring the total number of configured parallel reporting
criteria. The fact that positioning measurements and
non-positioning measurements generally are configured or requested
by different network nodes complicates the monitoring since no
network node has full knowledge of all configured measurements.
Embodiments which address this will be described in detail below.
The embodiments focus on the following major aspects:
[0072] First, methods of obtaining information regarding
measurements requested by different network nodes, such as methods
in a network node of determining the total number of configured
parallel measurement reporting criteria for the UE which is capable
of supporting the positioning measurements.
[0073] Second, methods in the network node of configuring, i.e.,
increasing or decreasing, the number of parallel measurement
reporting criteria when at least one positioning measurement
reporting category is used. This configuration may include
increasing or decreasing the total number of parallel reporting
criteria.
[0074] Third, pre-defined rules enabling the UE to configure
measurements that fulfill requirements on parallel reporting
criteria. The UE may e.g. apply pre-defined rules according to
which certain specific measurements, e.g., OTDOA measurements, are
always performed when the total number of parallel measurement
reporting criteria exceeds a certain threshold.
[0075] As described earlier, the UE requirements in terms of
performing parallel intra-frequency, inter-frequency and inter-RAT
measurements in E-UTRAN are specified in 3GPP TS 36.133, which
lists the minimum number of reporting criteria that the UE shall be
able to support in parallel per measurement category. In total
there are 21 parallel reporting criteria, which are primarily
related to the mobility measurements and which are configured by
the eNodeB. The UE is not required to support more than 21
reporting criteria in parallel. Accordingly the UE has a limited
capability for parallel reporting criteria, i.e. it is capable to
support a limited number of reporting criteria in parallel. It is
to be noted however that the UEs capability of parallel reporting
criteria may be higher than the requirements according to 3GPP TS
36.133. The above UE requirements enable the eNodeB to configure an
appropriate number of parallel measurements. Otherwise, if the
configured criteria are larger than 21 then the UE cannot meet the
desired performance for the configured measurements.
[0076] However, the positioning measurements, e.g., E-CID and
intra-frequency RSTD and inter-frequency RSTD, may be configured by
the positioning node. The E-CID measurement, e.g., UE Rx-Tx time
difference measurement may also be configured by the eNodeB. This
means the UE can be configured to report the UE Rx-Tx time
difference measurement to the eNodeB and the E-SMLC in parallel.
When any of the positioning measurements are performed by the UE,
the eNodeB should be aware of these additional positioning
measurements, which are configured by a different node, i.e.,
positioning node and not eNodeB, if the eNodeB is to be able to
ensure that requirements on parallel reporting criteria are not
exceeded for the UE. Further, positioning measurements may also be
intra-frequency, inter-frequency, and inter-RAT measurements.
[0077] There may also be UL positioning measurements which are not
UE measurements, but for which other UE measurements may also be
needed. For instance, UE UL Tx power and power headroom may also be
useful for estimating UL path loss or for properly configuring the
UL measurements while taking UE power into account. The UE power
can provide information about, for example, the cell coverage or
changes in coverage when power changes for the given transport
format.
[0078] Some embodiments of this disclosure enable:
[0079] a first network node to acquire information about the
configured parallel measurement reporting criteria for the UE which
is capable of performing positioning measurements; and
[0080] the first network node to adjust or reconfigure the parallel
measurement reporting criteria when the total number exceeds a
certain number for the UE which supports positioning
measurements.
[0081] The embodiments described in detail below, refer to first,
second, and/or third network nodes/nodes, which for this disclosure
are defined as follows:
[0082] First network node: This is a network node that is capable
of configuring the UE to perform at least one measurement. The
measurement can be of any type, e.g., mobility, positioning, etc.
It is also the network node that acquires the information about any
measurement configured by another node. Examples of the first
network node are: base station (e.g., eNodeB), network controller
(e.g., BSC, RNC etc), relay node, donor node serving relay, SON
node, measurement unit (e.g., LMU), etc.
[0083] Second network node: This is a node that can only configure
one or more positioning measurements, e.g., RSTD, E-CID etc.
Examples of a second node are: positioning nodes e.g., E-SMLC or
SLP.
[0084] Third (network) node: This is a network node that can
provide information to the first network node or to the second
network node about at least one measurement, which can be
configured by any other node. The third node may also be the user
equipment and will therefore be referred to as `the third node`
rather than `the third network node` in the following. In some
cases, the third node and the first network node can be the same.
Also, in some cases the third node and the second network node can
be the same. Examples of the third node are: user equipment, base
station (e.g., eNodeB), core network (e.g., MME/access gateway)
positioning node (e.g., E-SMLC), network controller (e.g., BSC, RNC
etc), relay node, donor node serving relay node, SON node,
minimization of drive test (MDT) node etc.
[0085] According to some exemplary embodiments a network node
determines configured parallel reporting criteria. The network
node, which may be the first network node or the second network
node, determines the configured parallel measurement reporting
criteria based on information obtained from the third node. Several
examples are described below.
[0086] According to one example the first network node determines
configured parallel reporting criteria by explicit signaling from
one or several third nodes. The first node may be a radio network
node, e.g., eNodeB, relay node, donor eNodeB etc. as described
above. The first node acquires information or an indication about
configured positioning measurements from the third node. The third
note sends an explicit measurement indication to the first network
node. In one variant the third node is a positioning node such as
an E-SMLC in LTE. When the positioning node configures the UE to
perform the positioning measurements (e.g., RSTD) it also signals a
measurement indication with relevant information about the
positioning measurement to the radio network node (e.g., eNodeB)
i.e. to the first network node. The measurement indication may be
sent to the eNodeB using the LPPa protocol. The measurement
indication may comprise information on types of configured
positioning measurements, e.g., intra-frequency RSTD,
inter-frequency RSTD, E-CID UE Rx-Tx time difference etc. As
mentioned above, the E-SMLC sends the assistance data to the UE for
performing the positioning measurements. The E-SMLC may also
forward this information element (IE) containing the assistance
data or any information about the positioning measurement to the
eNodeB as the measurement indication. Hence the idea of this
embodiment is that the positioning node (E-SMLC) indicates to the
eNodeB the type of positioning measurements, which have been
requested by the positioning node to be performed by the UE. The
eNodeB can then use the received information to configure the UE
with appropriate number of measurements.
[0087] Another example of the third node is a the core network node
e.g. a MME. When the MME requests the E-SMLC to initiate the
positioning session, the indication about the possible positioning
measurements is also signaled to the radio network node e.g., over
the S1 interface to the eNodeB from the MME.
[0088] Yet another example of the third node is the network
management node, e.g., a Self Organizing Network (SON) node or a
Minimizing Drive Test (MDT) node, which might be aware of the
ongoing positioning measurements. Hence the network management node
may signal this information or any indication to the radio network
node as the measurement indication.
[0089] Still another example of the third node is the user
equipment (e.g., user terminal, target device etc), which is
configured by the positioning node to perform one or more
positioning measurements. The UE can therefore signal the
information about the configured positioning measurements (e.g.,
intra-frequency RSTD, inter-frequency RSTD, E-CID etc) to its
serving radio network node (e.g., eNodeB). The measurement
indication can be a simple indication, e.g., identifiers of the
configured measurement. The UE may also forward the received
positioning measurement configuration IE or part of it to the
serving radio network node. According to another aspect of the
measurement indication, the UE may also send an indication when the
total number of parallel measurement reporting criteria exceeds a
threshold. The threshold may correspond to the minimum requirements
pre-defined in the standard or any suitable pre-determined or
configured value. Furthermore, the parallel measurements may
correspond to all types of configured measurements (e.g., mobility,
positioning etc) or they may correspond to a specific type of
measurements, e.g., only positioning measurements configured by the
positioning node.
[0090] Based on the measurement indication from one or more third
nodes described above, the first network node (e.g., eNodeB) can
determine the parallel positioning measurements configured by the
positioning node. The first network node is thus aware of the
measurements that the UE is requested to perform, both positioning
measurements requested by the positioning node as well as
measurements requested by the first network node. The radio network
node can then take appropriate action as will be described
below.
[0091] According to another exemplary embodiment the second network
node determines parallel reporting criteria by explicit signaling
from the third node. This embodiment is similar to the previously
described embodiment in which the first network node determined the
parallel reporting criteria. In this embodiment, however, the
second node (e.g., positioning node) acquires the information or an
indication about the configured measurements from the third node.
Furthermore, the configured measurements correspond to any
measurements which are configured by the first network node, e.g.,
eNodeB. The configured measurements may be e.g. mobility or
positioning measurements.
[0092] Similar to the previously described embodiment, the second
network node may determine the number of configured parallel
measurements by receiving the measurement indication or relevant
information from one or more of the following third nodes:
[0093] radio network node, e.g., eNodeB, which may send the
measurement indication using LPPa,
[0094] core network node, e.g., MME,
[0095] network management node, e.g., SON node
[0096] the UE, e.g., terminal, target device etc, using e.g. the
LPP or LPPe protocol.
[0097] It is also possible that the UE signals the maximum number
of supported reporting criteria, in total or per carrier, e.g.,
over LPP, LPPe or RRC to the second network node (e.g. E-SMLC) so
that the second network node is made aware of one or several
relevant thresholds related to supported parallel reporting
criteria. Alternatively or additionally the UE may also signal the
number of frequencies available for OTDOA. The second network node
(E-SMLC) takes the received information into account when creating
neighbor cell lists for the UE.
[0098] Based on the measurement indication from one or more third
nodes described above, the second network node (e.g., E-SMLC) can
determine the parallel measurements configured by the first network
node. The second network node can then take appropriate action as
will be described below.
[0099] Instead of using explicit signaling for conveying the
measurement indication, alternative exemplary embodiments use
packet sniffing. These alternative embodiments are useful in the
event that e.g. the eNodeB does not have explicit information about
the positioning measurements to be carried out by the UE. The
eNodeB sniffs packets with LPP or similar messages, or information
elements that are sent to the UE by the positioning sever (e.g.,
E-SMLC). The eNodeB may also read the messages or measurement
reports sent by the UE to the positioning sever. The messages from
the E-SMLC to the UE contain the assistance information to be used
by the UE for performing the positioning measurements (e.g.,
intra-, inter-frequency RSTD, carrier aggregation RSTD etc). The
messages from the UE contain the measurement results about the
positioning measurements. These messages pass over the eNodeB
transparently. Hence the eNodeB can sniff these messages by reading
and inspecting the headers of these messages. The acquired
assistance information by the virtue of sniffing enables the eNodeB
to know about the configured positioning measurements.
[0100] In another embodiment, the eNodeB counts separately the
number of higher-layer protocol sessions associated with the UE,
where the higher-layer protocol sessions may be parallel LPP
sessions that use RRC as transport. The eNodeB also tracks the
total number of parallel sessions for the UE, including those
associated with positioning and compares to the maximum pre-defined
limit.
[0101] Accordingly there are several different alternatives for the
first or second network node to obtain information about UE
measurements which are requested or configured by different network
nodes. Once the information about the measurements is obtained,
this information can be used to control that the UE is configured
with appropriate number of measurements with respect to limits on
parallel reporting criteria.
[0102] According to exemplary embodiments, if it is determined that
the configured total parallel measurement reporting criteria for
the UE exceed a certain threshold, the first network node or the
second network node or both nodes reconfigure the parallel
measurements.
[0103] The reconfiguration of the parallel measurement reporting
criteria depends upon the pre-defined requirements of parallel
reporting criteria. The requirements of parallel reporting criteria
may be unchanged, i.e. as defined in 3GPP TS 36.133 V9.3.0 as
explained above, or may be extended with specific requirements for
e.g. positioning measurements.
[0104] One embodiment extends the list of reporting criteria by
introducing additional reporting criteria, specifically for LTE
positioning for the UE which supports this positioning capability.
This means, for example, extending the pre-defined criteria from 21
to 21+N, where the additional N criteria are for positioning
measurements. N may for example be 4 to accommodate a UE Rx-Tx time
difference measurement configured by E-SMLC, a UE Rx-Tx (or E-CID
in general) time difference measurement configured by eNodeB, an
intra-frequency RSTD measurement and an inter-frequency RSTD
measurement.
[0105] Accordingly the standard 3GPP TS 36.133 could be updated
with new reporting criteria categories as shown in the table
below:
TABLE-US-00001 Measurement category E.sub.cat Note Intra-frequency
9 E-UTRA intra-frequency cells Intra-frequency UE Rx-Tx 1
Intra-frequency UE Rx-Tx time time difference(*) difference
measurement reported to E-UTRAN for UE supporting E-CID
Intra-frequency E-CID(*) 1 Intra-frequency E-CID measurements
reported to E-SMLC for UE supporting E-CID Intra-frequency RSTD(*)
1 Intra-frequency RSTD measure- ment reporting for UE supporting
OTDOA Inter-frequency 7 E-UTRA inter-frequency cells
Inter-frequency RSTD(*) 1 Inter-frequency RSTD measure- ment
reporting for UE supporting OTDOA Inter-RAT (E-UTRAN FDD 5 Only
applicable for UE with this or TDD, UTRAN FDD, (inter-RAT)
capability. This UTRAN TDD, GSM, cdma2000 requirement (E.sub.cat =
5) is per 1 x RTT and HRPD) supported RAT. (*)example new reporting
criteria categories
[0106] The table above indicates that the UE shall be able to
support in parallel per category up to E.sub.cat reporting
criteria.
[0107] In another example, N is 3 and additional measurement
reporting categories are UE Rx-Tx time difference, intra-frequency
RSTD and inter-frequency RSTD.
[0108] In a further example, N is 3 and additional measurement
reporting categories are intra-frequency E-CID measurements
configured by eNodeB, intra-frequency positioning measurements
(E-CID or OTDOA) configured by positioning node and inter-frequency
RSTD (or OTDOA) measurements.
[0109] In yet another example, inter-frequency E-CID measurements
may also be added to the list of reporting criteria categories.
According to an embodiment Rx-Tx difference measurements are
defined for a non-serving/non-primary carrier in LTE, e.g.,
intra-frequency UE Rx-Tx for neighbor cells and inter-frequency
Rx-Tx measurements for neighbor cells, where inter-frequency Rx-Tx
may further be UE Rx-Tx and E-UTRAN Rx-Tx. This may also apply for
carrier aggregation (CA) networks and CA-capable UEs.
[0110] In still another example, at least one new reporting
criterion is added for inter-RAT positioning measurements, which
may also be specified for different positioning methods separately
or by the initiating node, e.g., the positioning node or the
eNodeB.
[0111] According to a further example, for multi-carrier and/or CA
systems, the set of reporting criteria for positioning may be
further defined for primary and non-primary (i.e. secondary)
carriers, e.g., as in the table below:
TABLE-US-00002 Measurement category E.sub.cat Note Intra-frequency
9 E-UTRA intra-frequency cells Intra-frequency UE Rx-Tx time 1
Intra-frequency UE Rx-Tx time difference, primary carrier (*)
difference measurement reported to E-UTRAN for UE supporting E-CID
Intra-frequency E-CID, primary 1 Intra-frequency E-CID carrier (*)
measurements reported to E-SMLC for UE supporting E-CID
Intra-frequency RSTD, primary 1 Intra-frequency RSTD measure-
carrier (*) ment reporting for UE supporting OTDOA Intra-frequency
UE Rx-Tx time 1 Intra-frequency UE Rx-Tx time difference, secondary
carrier (*) difference measurement reported to E-UTRAN for UE
supporting E-CID Intra-frequency E-CID, 1 Intra-frequency E-CID
secondary carrier (*) measurements reported to E-SMLC for UE
supporting E-CID Intra-frequency RSTD, 1 Intra-frequency RSTD
measure- secondary carrier (*) ment reporting for UE supporting
OTDOA Inter-frequency 7 E-UTRA inter-frequency cells
Inter-frequency RSTD, primary 1 Inter-frequency RSTD measure-
carrier (*) ment reporting for UE supporting OTDOA Inter-frequency
RSTD, 1 Inter-frequency RSTD measure- secondary carrier (*) ment
reporting for UE supporting OTDOA Inter-RAT (E-UTRAN FDD 5 Only
applicable for UE with this or TDD, UTRAN FDD, (inter-RAT)
capability. This UTRAN TDD, GSM, cdma2000 requirement (E.sub.cat =
5) is per 1 x RTT and HRPD) supported RAT. (*) example new
reporting criteria categories
[0112] As mentioned above it is also possible that the total
measurement reporting criteria requirement is unchanged, i.e. as
specified in 3GPP TS 36.133 V9.3.0, even for the UE which supports
the positioning feature.
[0113] It is particularly important that the node, which is to
control that requirements on parallel reporting criteria are not
exceeded, is able to reconfigure the parallel measurements in the
case that the total measurement reporting criteria including
positioning measurements are the same as without positioning
measurements. Assuming that the eNodeB is to control that limits on
parallel reporting criteria are not exceeded it is important that
the eNodeB is made aware of the UE positioning capabilities and
also when the UE performs a particular positioning measurement. The
positioning node (e.g. E-SMLC) or any other network node may
indicate to the eNodeB the UE positioning measurement capabilities
of the UE. The positioning node also indicates which type of
positioning related measurements are currently requested to be
performed by the UE. Alternatively the UE itself reports its
measurement capability (e.g., enhanced cell ID etc) to the eNodeB.
The eNodeB can use this information to configure the UE with the
appropriate number of measurements without exceeding a desired
limit, such as the capability requirement, supported parallel
reporting criteria or other lower limit. In addition the E-SMLC may
acquire the UE measurement capability and use it to set appropriate
parameters in the assistance data to be used by the UE for
performing the positioning measurements.
[0114] The eNodeB can for example reduce the number of parallel
measurements for mobility in the event that the positioning node
configures the UE to perform positioning measurements, thereby
giving the positioning measurements priority over the mobility
measurements. For example, assume that the positioning node
configures the UE to perform intra-frequency RSTD measurements,
while the eNodeB has also configured UE to perform and report 21
parallel measurements. Upon acquiring this information, the eNodeB
may de-configure one of the mobility measurements e.g., periodic
RSRP reporting. According to another example the positioning node
configures the UE to perform intra- and inter-frequency RSTD
measurements while the eNodeB has configured 21 parallel
measurements for mobility purposes. In this case, the positioning
node may de-configure the inter-frequency RSTD measurement.
Alternatively, the positioning node may also explicitly request the
eNodeB to de-configure one of the mobility measurements to make
sure that total configured measurements do not exceed the UE
measurement capability requirement with respect to parallel
reporting criteria.
[0115] Even if the total requirement on parallel measurement
reporting criteria is extended with specific criteria for
positioning, the network may still benefit from the acquired
information about the requested parallel UE measurements. Assume
that the total UE parallel measurement capability is 25 including
positioning measurements. The positioning measurements are not used
all the time for all UEs. Further assume that the eNodeB does not
receive any measurement indication that the UE is currently doing
any positioning measurements. Hence the eNodeB can configure the UE
to perform additional parallel measurements for mobility or for any
other purpose such as for network planning, SON, MDT etc i.e., more
than 21 measurements. In this way the performance of the mobility
or other network operation can be enhanced by dynamically
adjusting/configuring the parallel measurement reporting
criteria.
[0116] In summary, the network node (i.e., first and/or second
network node) uses the following set of information to configure or
reconfigure appropriate number of measurements, without exceeding
the desired limit:
[0117] Obtained information regarding parallel UE measurements that
are requested or configured by different network nodes.
[0118] Information related to the desired limit, such as
requirements for the parallel measurement reporting criteria or
other predetermined threshold relating to the total number of
parallel measurements or to one or several specific categories of
measurements.
[0119] The above described measurement indication is used to convey
information to a network node about UE measurements requested or
configured by another network node. However, such a measurement
indication may not be needed if the UE itself is able to control
that the configured measurements do not exceed the predetermined
threshold(s) of parallel reporting criteria. According to an
exemplary embodiment the UE itself controls the configuration of
parallel measurements to ensure that one or several predetermined
thresholds for parallel reporting criteria are not exceeded. This
control is based on a pre-defined rule in the UE. According to this
embodiment, when the total number of configured parallel
measurement criteria exceeds the predetermined threshold(s), e.g.,
predefined requirements such as 21, the UE autonomously decides
which of the measurements should be prioritized or performed and
which one should not be performed or delayed. The autonomous
decision in the UE is based on the pre-defined rule. For instance
it can be predefined that a particular type of measurement shall
always be performed. This means that the UE may have to stop
reporting another low priority measurement, e.g., periodical
RSRP.
[0120] For example, it can be predefined that an OTDOA measurement
shall always be performed by the UE in case the total number of
parallel reporting criteria exceeds the threshold. It may even be
predefined that a particular type of OTDOA measurement (e.g.,
intra-frequency RSTD) shall always be performed by the UE in case
the total number of parallel reporting criteria exceeds the
threshold. Another exemplary rule could be that at least two
positioning measurements are always performed by the UE. This is to
make sure that the emergency call requirements are met or at least
the emergency calls are furnished. Another exemplary rule could be
that measurements tagged with a higher priority are always
performed by the UE. The priority tag can be signaled for the
configured measurement, or it can be predefined in a standard.
[0121] FIG. 6 is a flow diagram illustrating an exemplary method of
controlling configuration of measurements to be performed by the UE
in line with the description above. The method may be performed in
the first network node or the second network node or even in the UE
itself. A first step 61 of the method involves obtaining
information on a plurality of measurements requested by a plurality
of different network nodes to be performed by the user equipment in
parallel. The plurality of measurements includes at least one
positioning measurement. The step 61 may involve receiving a
measurement indication from one or several of the network nodes
that request measurements as explained above.
[0122] The obtained information may include information on type of
positioning measurement and the number of positioning measurements
of each type of requested positioning measurement. Information on
type of positioning measurement may e.g. specify is the positioning
measurement is an OTDOA or E-CID measurement. Alternatively or
additionally the type of OTDOA or E-CID measurement is specified,
such as intra-frequency UE Rx-Tx time difference for a serving
cell, intra-frequency RSTD and inter-frequency RSTD for OTDOA
measurement, or intra-frequency UE Rx-Tx time difference for a
neighbor cell, inter-frequency UE Rx-Tx measurement, and
inter-frequency E-UTRAN Rx-Tx measurement, and inter-RAT
positioning measurement for E-CID measurement.
[0123] In a step 62, the obtained information is used to configure
the user equipment with a set of measurements that does not exceed
at least one predetermined threshold for parallel reporting
criteria. The set of measurements comprises all or a subset of the
plurality of measurements requested by the plurality of different
network nodes. The step 62 may involve reconfiguration to reduce or
delay previously configured measurements of a specific type as
explained above. The one or several predetermined thresholds for
parallel reporting criteria may specify a maximum total number of
parallel reporting criteria and/or a maximum number of parallel
reporting criteria per measurement category. There may be different
levels of measurement categories. On a higher level there may e.g.
be a category for positioning measurements and a category for
non-positioning measurements. On a more specific level there may
e.g. be a measurement category for OTDOA positioning measurements
and a category for E-CID positioning measurements. OTDOA and E-CID
positioning measurements may then be categorized in different types
of measurements as exemplified above.
[0124] The measurements requested to be performed by the user
equipment maybe measurements to be performed on a primary carrier
and/or a secondary carrier.
[0125] As mentioned above obtaining the information on the
requested measurements may e.g. involve sniffing messages
transmitted between the UE and a positioning server or receiving
measurement indications signaled from the third node. The third
node will thus need to be configured to transmit the measurement
indications. Different embodiments of the third node are possible
as is apparent from the following itemized list of exemplary
embodiments of the third node:
Embodiment 1
[0126] A third node of a wireless communication system of
supporting configuration of measurements to be performed by a user
equipment operating in the wireless communication system, wherein a
configured measurement corresponds to at least one reporting
criteria, wherein the user equipment is able to support a limited
number of parallel reporting criteria, wherein a plurality of
different network nodes are adapted to request a plurality of
measurements to be performed by the user equipment in parallel, and
wherein said plurality of measurements includes at least one
positioning measurement, the third node comprising a transmitter
configured to transmit to another network node information on at
least one measurement requested by at least one of said plurality
of different network nodes to be performed by the user equipment to
enable said another network node to monitor that the user equipment
is not configured with a set of measurements that exceeds at least
one predetermined threshold for parallel reporting criteria.
Embodiment 2
[0127] The third node according to embodiment 1, wherein the third
node is a positioning server, which is one of said plurality of
different network nodes and wherein said another network node is an
eNodeB.
Embodiment 3
[0128] The third node according to embodiment 2, wherein said
transmitter is configured to include, in the information sent to
the eNodeB, information on any positioning measurements that the
positioning server is requesting the user equipment to perform in
parallel.
Embodiment 4
[0129] The third node according to embodiment 3, wherein said
information on the positioning measurements includes information on
any positioning measurements of type intra-frequency UE Rx-Tx time
difference for a serving cell, intra-frequency RSTD,
inter-frequency RSTD, intra-frequency UE Rx-Tx time difference for
a neighbor cell, inter-frequency UE Rx-Tx measurement,
inter-frequency E-UTRAN Rx-Tx measurement, and inter-RAT
positioning measurement that the user equipment is requested to
perform.
Embodiment 5
[0130] The third node according to embodiment 1, wherein said third
node is the user equipment.
Embodiment 6
[0131] The third node according to embodiment 1, wherein said third
node is an eNodeB, which is one of said plurality of different
network nodes and wherein said another network node is a
positioning server.
[0132] FIG. 7 is a schematic block diagram of a network node 71 for
controlling configuration of measurements to be performed by the
user equipment. The network node 71 may be the first network node
or the second network node. The network node 71 comprises a
receiver 73, a transmitter 72 and a processor 74, which are
particularly configured for carrying out the method illustrated in
FIG. 6. The receiver is particularly configured to obtain
information regarding requested UE measurements e.g. in the form of
the above described measurement indication, which is illustrated
here as an arrow indicated by reference numeral 76. The processor
may obtain information regarding measurements that the network node
71 itself configures or requests. The processor is also configured
to use the obtained information to configure a set of measurements
that does not exceed the predetermined threshold(s) for parallel
reporting criteria and the transmitter is configured to transmit
configuration information 75 to the UE to initiate the UE to
perform the configured set of measurements.
[0133] The functional blocks depicted in FIG. 7 can be combined and
re-arranged in a variety of equivalent ways, and many of the
functions can be performed by one or more suitably programmed
digital signal processors and other known electronic circuits e.g.,
discrete logic gates interconnected to perform a specialized
function, or application-specific integrated circuits. Moreover,
connections among and information provided or exchanged by the
functional blocks depicted in FIG. 7 can be altered in various ways
to enable the network node 71 to implement the methods described
above and other methods involved in the operation of the network
node in a wireless communication system.
[0134] As mentioned above the UE may be configured to use
predefined rules to control that one or several predetermined
thresholds for parallel reporting criteria are not exceeded. Thus
different embodiments of the UE and methods performed in the UE are
possible as is apparent from the following itemized list of
embodiments:
Embodiment 7
[0135] A method in a user equipment of controlling configuration of
measurements to be performed by the user equipment operating in a
wireless communication system, wherein a configured measurement
corresponds to at least one reporting criteria and wherein the user
equipment is able to support a limited number of parallel reporting
criteria, the method comprising
[0136] obtaining information on a plurality of measurements
requested by a plurality of different network nodes to be performed
by the user equipment in parallel, wherein said plurality of
measurements includes at least one positioning measurement, and
[0137] using the obtained information to configure the user
equipment with a set of measurements that does not exceed at least
one predetermined threshold for parallel reporting criteria.
Embodiment 8
[0138] The method according to embodiment 7, wherein the obtained
information includes information on any type of positioning
measurement that the user equipment is requested to perform.
Embodiment 9
[0139] The method according to embodiment 8, wherein the obtained
information includes information on any positioning measurements of
type intra-frequency UE Rx-Tx time difference for a serving cell,
intra-frequency RSTD, inter-frequency RSTD, intra-frequency UE
Rx-Tx time difference for a neighbor cell, inter-frequency UE Rx-Tx
measurement, inter-frequency E-UTRAN Rx-Tx measurement, and
inter-RAT positioning measurement that the user equipment is
requested to perform.
Embodiment 10
[0140] The method according to any of embodiments 7-9, wherein the
user equipment uses the obtained information to configure the user
equipment with the set of measurements based on a predefined
rule.
Embodiment 11
[0141] The method according to embodiment 10, wherein according to
the predefined rule a type and/or number of positioning
measurements is prioritized to be configured.
Embodiment 12
[0142] A user equipment for operating in a wireless communication
system which includes a transmitter, receiver and processor which
are configured to carry out the method according to any of
embodiments 7-11.
[0143] The embodiments above generally provide a number of
technical advantages, each of which are achieved by at least some
embodiments. First, some embodiments of methods described above
enable the network node to be aware of the configured total
parallel measurements including positioning measurements. Second,
some embodiments enable the positioning node to be aware of the
configured total parallel measurements, including non-positioning
measurements. Third, some embodiments described herein enable the
network node ensure that requirements on parallel reporting
criteria of the UE are not exceeded. Furthermore, some embodiments
enable the positioning node to ensure that requirements on parallel
reporting criteria of the UE are not exceeded.
[0144] Many aspects of the embodiments presented herein are
described in terms of sequences of actions that can be performed
by, for example, elements of a programmable computer system.
Embodiments of UEs include, for example, mobile telephones, pagers,
headsets, laptop computers and other mobile terminals, and the
like. Moreover, some embodiments described herein can additionally
be considered to be embodied entirely within any form of
computer-readable storage medium having stored therein an
appropriate set of instructions for use by or in connection with an
instruction-execution system, apparatus, or device, such as a
computer-based system, processor-containing system, or other system
that can fetch instructions from a medium and execute the
instructions. As used here, a "computer-readable medium" can be any
means that can contain, store, or transport the program for use by
or in connection with the instruction-execution system, apparatus,
or device. The computer-readable medium can be, for example but not
limited to, an electronic, magnetic, optical, electromagnetic,
infrared, or semiconductor system, apparatus, or device. More
specific examples (a non-exhaustive list) of the computer-readable
medium include an electrical connection having one or more wires, a
portable computer diskette, a random-access memory (RAM), a
read-only memory (ROM), an erasable programmable read-only memory
(EPROM or Flash memory), and an optical fiber. Thus, there are
numerous different embodiments in many different forms, not all of
which are described above, that fall within the scope of the
appended claims. For each of the various aspects, any such form may
be referred to as "logic configured to" perform a described action,
or alternatively as "logic that" performs a described action.
[0145] In addition, embodiments described above can be incorporated
in user- and/or control-plane positioning solutions, although the
latter is currently believed to be more common, and in other
positioning methods and their hybrids, in addition to OTDOA and
E-CID. It will be understood that this description is given in
terms of an eNodeB as the radio network node, but the invention can
be embodied in other types of radio network nodes, e.g., pico BSs,
home NodeBs, etc.
[0146] Several of the embodiments described above use an LTE
scenario as an exemplary application scenario. LTE standard
specifications can be seen as an evolution of the current wideband
code division multiple access (WCDMA) specifications. An LTE system
uses orthogonal frequency division multiplex (OFDM) as a multiple
access technique (called OFDMA) in a downlink (DL) from system
nodes to user equipments (UEs). An LTE system has channel
bandwidths ranging from about 1.4 MHz to 20 MHz, and supports
throughputs of more than 100 megabits per second (Mb/s) on the
largest-bandwidth channels. One type of physical channel defined
for the LTE downlink is the physical downlink shared channel
(PDSCH), which conveys information from higher layers in the LTE
protocol stack and to which one or more specific transport channels
are mapped. Control information is conveyed by a physical uplink
control channel (PUCCH) and by a physical downlink control channel
(PDCCH). LTE channels are described in 3GPP Technical Specification
(TS) 36.211 V9.1.0, Physical Channels and Modulation (Release 9)
(December 2009), among other specifications.
[0147] An IMT-Advanced communication system uses an internet
protocol (IP) multimedia subsystem (IMS) of an LTE, HSPA, or other
communication system for IMS multimedia telephony (IMT). In the IMT
advanced system (which may be called a "fourth generation" (4G)
mobile communication system), bandwidths of 100 MHz and larger are
being considered. The 3GPP promulgates the LTE, HSPA, WCDMA, and
IMT specifications, and specifications that standardize other kinds
of cellular wireless communication systems.
[0148] In an OFDMA communication system, the data stream to be
transmitted is portioned among a number of narrowband subcarriers
that are transmitted in parallel. In general, a resource block
devoted to a particular UE is a particular number of particular
subcarriers used for a particular period of time. Different groups
of subcarriers can be used at different times for different users.
Because each subcarrier is narrowband, each carrier experiences
mainly flat fading, which makes it easier for a UE to demodulate
each subcarrier. OFDMA communication systems are described in the
literature, for example, U.S. Patent Application Publication No. US
2008/0031368 A1 by B. Lindoff et al.
[0149] FIG. 1 depicts a typical cellular communication system 10.
Radio network controllers (RNCs) 12, 14 control various radio
network functions, including for example radio access bearer setup,
diversity handover, etc. In general, each RNC directs calls to and
from a UE, such as a mobile station (MS), mobile phone, or other
remote terminal, via appropriate base station(s) (BSs), which
communicate with each other through DL (or forward) and uplink (UL,
or reverse) channels. In FIG. 1, RNC 12 is shown coupled to BSs 16,
18, 20, and RNC 14 is shown coupled to BSs 22, 24, 26. Each BS, or
eNodeB which is a BS in an LTE system, serves a geographical area
that is divided into one or more cell(s). In FIG. 1, BS 26 is shown
as having five antenna sectors S1-S5, which can be said to make up
the cell of the BS 26, although a sector or other area served by
signals from a BS can also be called a cell. In addition, a BS may
use more than one antenna to transmit signals to a UE. The BSs are
typically coupled to their corresponding RNCs by dedicated
telephone lines, optical fiber links, microwave links, etc. The
RNCs 12, 14 are connected with external networks such as the public
switched telephone network (PSTN), the internet, etc. through one
or more core network nodes, such as a mobile switching center (not
shown) and/or a packet radio service node (not shown).
[0150] It will be understood that the arrangement of
functionalities depicted in FIG. 1 can be modified in LTE and other
communication systems. For example, the functionality of the RNCs
12, 14 can be moved to the eNodeBs 22, 24, 26, and other
functionalities can be moved to other nodes in the network. It will
also be understood that a base station can use multiple transmit
antennas to transmit information into a cell/sector/area, and those
different transmit antennas can send respective, different pilot
signals.
[0151] The use of multiple antennas plays an important role in
modern wireless communication systems, such as LTE systems, to
achieve improved system performance, including capacity and
coverage, and service provisioning. Acquisition of channel state
information (CSI) at the transmitter or the receiver is important
to proper implementation of multi-antenna techniques. In general,
channel characteristics, such as the impulse response, are
estimated by sending and receiving one or more predefined training
sequences, which can also be called reference signals. To estimate
the channel characteristics of a DL for example, a BS transmits
reference signals to UEs, which use the received versions of the
known reference signals to estimate the DL channel. The UEs can
then use the estimated channel matrix for coherent demodulation of
the received DL signal, and obtain the potential beam-forming gain,
spatial diversity gain, and spatial multiplexing gain available
with multiple antennas. In addition, the reference signals can be
used to do channel quality measurement to support link
adaptation.
[0152] In the case of OFDM transmission, a straightforward design
of a reference signal is to transmit known reference symbols in the
OFDM frequency-vs.-time grid. Cell-specific reference signals and
symbols are described in Clauses 6.10 and 6.11 of 3GPP TS 36.211
V9.0.0, Evolved Universal Terrestrial Radio Access (E-UTRA),
Physical Channels and Modulation (Release 9) (December 2009). Up to
four cell-specific reference signals corresponding to up to four
transmit antennas of an eNodeB are specified. Such reference
signals are used by the eNodeB for codebook-based, multiple-stream,
spatial multiplex transmission. A codebook is a predefined finite
set of a number of precoding matrices having different ranks. In
codebook based precoding, the UE estimates the channel matrix based
on the cell-specific reference signals, carries out an exhaustive
search over all precoding matrices, and reports a preferred
precoding matrix indicator (PMI) to the eNodeB according to certain
criteria, thereby maximizing system throughput, etc. The PMI
determined by a UE can be overridden by the eNodeB.
[0153] 3GPP TS 36.211 also defines a UE-specific reference signal
on an antenna port 5 that is transmitted only on resource blocks
upon which a corresponding physical downlink shared channel (PDSCH)
is mapped. The UE-specific reference signal supports non-codebook
based, single-stream beamforming transmission. In non-codebook
based precoding, the precoding weight matrix applied both on
UE-specific reference symbols and the data symbols is not from the
codebook set but is directly calculated by the eNodeB in terms of
various criteria, e.g., the weight matrix can be calculated based
on eigen decomposition or on direction of arrival. In a
time-division duplex (TDD) system, due to channel reciprocity,
non-codebook based beamforming/precoding can reduce further uplink
feedbacks and improve beamforming gain.
[0154] The DL of a LTE system can use both codebook-based precoding
and non-codebook based beamforming/precoding for up to four
transmit antennas. The transmission mode switch between
codebook-based, multiple-stream spatial multiplexing transmission
and non-codebook-based, single-stream beamforming transmission is
semi-statically configured via higher layer signaling.
[0155] Some communication systems, such as LTE-Advanced that is
currently being specified by 3GPP, can employ more than four
transmit antennas in order to reach more aggressive performance
targets. For example, a system having eNodeBs with eight transmit
antennas need extension of current LTE codebook-based precoding
from precoder and reference signal perspectives.
[0156] PRS are transmitted from one antenna port (R6) according to
a pre-defined pattern, as described for example in Clause 6.10.4 of
3GPP TS 36.211 V9.0.0, Evolved Universal Terrestrial Radio Access
(E-UTRA), Physical Channels and Modulation (Release 9) (December
2009). One of the currently agreed PRS patterns is shown in FIG. 5,
which corresponds to the left-hand side of FIG. 6.10.4.2-1 of 3GPP
TS 36.211, where the squares containing R.sub.6 indicate PRS
resource elements within a block of twelve subcarriers over
fourteen OFDM symbols (i.e., a 1-ms subframe with normal cyclic
prefix).
[0157] A set of frequency shifts can be applied to the pre-defined
PRS patterns to obtain a set of orthogonal patterns which can be
used in neighbor cells to reduce interference on the PRS and thus
improve positioning measurements. The effective frequency reuse of
six can be modelled in this way. The frequency shift is defined as
a function of Physical Cell ID (PCI) as follows:
v.sub.shift=mod(PCI,6)
[0158] in which v.sub.shift is the frequency shift, mod( ) is the
modulo function, and PCI is the Physical Cell ID. The PRS can also
be transmitted with zero power, or muted.
[0159] To improve hearability of the PRS, i.e., to enable detecting
the PRS from multiple sites and with a reasonable quality,
positioning subframes have been designed as low-interference
subframes, i.e., it has also been agreed that no data transmissions
are allowed in general in positioning subframes. As a result,
synchronous networks' PRS are ideally interfered with only by PRS
from other cells having the same PRS pattern index, i.e., the same
vertical shift (v_shift), and not by data transmissions.
[0160] In partially aligned asynchronous networks, PRS can still be
interfered with by transmissions over data channels, control
channels, and any physical signals when positioning subframes
collide with normal subframes, although the interference is reduced
by the partial alignment, i.e., by aligning the beginnings of
positioning subframes in multiple cells within one-half of a
subframe with respect to some time base. PRS are transmitted in
pre-defined positioning subframes grouped by several consecutive
subframes (N.sub.PRS), i.e., one positioning occasion, which occur
periodically with a certain periodicity of N subframes, i.e., the
time interval between two positioning occasions. The currently
agreed periods N are 160, 320, 640, and 1280 ms, and the number of
consecutive subframes N.sub.PRS can be 1, 2, 4, or 6, as described
in 3GPP TS 36.211 cited above.
* * * * *