U.S. patent application number 14/655727 was filed with the patent office on 2016-09-08 for methods and apparatus for cell selection/reselection in millimeter wave system.
This patent application is currently assigned to Mediatek (Beijing) Inc.. The applicant listed for this patent is MEDIATEK (Beijing) Inc.. Invention is credited to Ju-Ya Chen, Jiann-Ching Guey, Yu-Syuan Jheng, Aimin Justin Sang, Yuanyuan Zhang.
Application Number | 20160262077 14/655727 |
Document ID | / |
Family ID | 56848273 |
Filed Date | 2016-09-08 |
United States Patent
Application |
20160262077 |
Kind Code |
A1 |
Zhang; Yuanyuan ; et
al. |
September 8, 2016 |
METHODS AND APPARATUS FOR CELL SELECTION/RESELECTION IN MILLIMETER
WAVE SYSTEM
Abstract
Methods and apparatus for cell selection, cell reselection, and
beam selection in MMW system are provided. The UE measures signal
strength, or signal quality or both of them to get the best
consolidation measurement result. During Cell Selection, the UE
selects the cell with the best consolidation measurement result, or
selects the cell containing the candidate control beam found
firstly. In Cell Reselection, the serving cell and neighboring
cells are ranked based on the consolidation measurement result.
After camping on a cell, the UE selects one or more than one best
control beams as the serving control beam to acquire system
information and monitor paging message. Furthermore, the UE selects
the best control beam or selects one control beam randomly among
the serving control beams to initial access to the network.
Inventors: |
Zhang; Yuanyuan; (Beijing,
CN) ; Sang; Aimin Justin; (San Diego, CA) ;
Guey; Jiann-Ching; (Hsinchu City, TW) ; Jheng;
Yu-Syuan; (Taipei City, TW) ; Chen; Ju-Ya;
(Kaohsiung City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MEDIATEK (Beijing) Inc. |
Beijing |
|
CN |
|
|
Assignee: |
Mediatek (Beijing) Inc.
Beijing
CN
|
Family ID: |
56848273 |
Appl. No.: |
14/655727 |
Filed: |
March 5, 2015 |
PCT Filed: |
March 5, 2015 |
PCT NO: |
PCT/CN2015/073679 |
371 Date: |
June 26, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 43/16 20130101;
H04W 48/20 20130101; H04W 24/10 20130101; H04W 36/0061 20130101;
H04W 36/0083 20130101; H04W 24/08 20130101; H04W 36/30 20130101;
H04W 36/08 20130101 |
International
Class: |
H04W 36/30 20060101
H04W036/30; H04W 48/20 20060101 H04W048/20; H04W 24/08 20060101
H04W024/08 |
Claims
1. A method comprising: detecting multiple control beams in a
millimeter wave (mmW) system by a user equipment (UE), wherein the
mmW system has multiple cells each configured with multiple control
beams; obtaining a signal measurement for each detected control
beam; and calculating a consolidation measurement for each cell
based on a set of qualified control beams associated with each
corresponding cell using a consolidation rule, wherein at least one
cell has more than one associated qualified control beams.
2. The method of claim 1, wherein the signal measurement of a
control beam is obtained based on at least one of the measurements
comprising: a signal strength measurement, a signal quality
measurement, a signal lifetime measurement, signal error rate, and
signal AoA/DoA.
3. The method of claim 1, wherein the set of qualified control
beams of a cell consists of multiple detected control beams
associated with the cell.
4. The method of claim 1, further comprising: determining one or
more candidate control beams, wherein the signal measurement of
each candidate control beam is greater a candidate threshold.
5. The method of claim 4, wherein the set of qualified control
beams of a cell consists of multiple candidate control beams
associated with the cell.
6. The method of claim 1, wherein the UE is camped on a serving
cell and acquires system and control information through one or
more serving control beams associated with the serving cell, and
wherein the set of qualified control beams for the serving cell
consists of multiple serving control beams.
7. The method of claim 1, wherein the consolidation rule determines
the consolidation measurement for the set of qualified control
beams is at least one selected from a group comprising: a number of
qualified control beams in the set, a maximum signal measurement of
the set, a minimum signal measurement of the set, a mean value of
signal measurement of the set, a variance of signal measurement of
the set, and a sum of the signal measurements of the set.
8. The method of claim 1, further comprising: performing a cell
selection based on consolidation measurement results.
9. The method of claim 1, further comprising: performing a cell
reselection based on consolidation measurement results.
10. The method of claim 1, further comprising: performing handover
based on consolidated measurement results.
11. A method comprising: detecting multiple control beams in a
millimeter wave (mmW) system by a user equipment (UE), wherein the
mmW system has multiple cells each configured with multiple control
beams; obtaining a signal measurement for each detected control
beam; performing a cell selection to select a serving cell; and
selecting one or more serving control beams associated with the
serving cell, wherein the UE receives control information and
system information on the serving control beams.
12. The method of claim 11, further comprising: determining one or
more candidate control beams, wherein the signal measurement of
each candidate control beam is greater a candidate threshold.
13. The method of claim 12, wherein the serving cell is selected
upon detecting the first candidate control beam, and wherein the
serving cell is the cell that the first detected candidate control
beams is associated with.
14. The method of claim 11, further comprising: calculating a
consolidation measurement for each cell based on a set of qualified
control beams associated with each corresponding cell using a
consolidation rule, wherein at least one cell has more than one
associated qualified control beams, and wherein the serving cell is
selected based on consolidation measurement results for each
cell.
15. The method of claim 11, wherein the consolidation rule
determines the consolidation measurement for the set of qualified
control beams is one selected from a group comprising: a number of
qualified control beams in the set, a maximum signal measurement of
the set, a minimum signal measurement of the set, a mean value of
signal measurements of the set, a variance of signal measurement of
the set, and a sum of the signal measurements of the set.
16. The method of claim 11, wherein the selected serving control
beams are detected control beams associated with the serving
cell.
17. The method of claim 11, wherein the selected serving control
beams are candidate control beams associated with the serving cell,
and wherein each candidate control beam has its signal measurement
greater than a threshold.
18. The method of claim 11, wherein the control beams of the
serving cell are ranked based on the signal measurement and a
predefined number of best control beams of the serving cell are
selected based on the ranking as the serving control beams.
19. The method of claim 11, further comprising: performing a
serving control beam selection based on multiple control beam
measurements of the serving cell.
20. The method of claim 19, wherein the serving control beam
selection involves: calculating a modified measurement for each
serving control beam by adding an hypothesis value to the signal
measurement of the corresponding serving control beam; ranking all
control beams of the serving cell based on the modified
measurement; and selecting one or more best ranked control beams as
the new serving control beam candidate.
21. The method of claim 20, wherein the hypothesis value is
obtained and configured by a system information.
22. The method of claim 20, wherein the hypothesis value is
obtained and configured by a beam specific information.
23. The method of claim 11, further comprising: selecting an access
control beam from the one or more selected serving control
beams.
24. A method comprising: obtaining a consolidation serving cell
measurement for cell reselection (Res_S) in a millimeter wave (mmW)
system by a user equipment (UE), wherein the Res_S is calculated
based on signal measurements of a set of control beams of the
serving cell; determining a measurement level by comparing the Res
_S with one or more thresholds in descending order comprising: a
first threshold, a second threshold and a third threshold; and
performing consolidation measurement for one or more cells based on
the determined measurement level, wherein the consolidation
measurement for a cell is calculated based on signal measurements
of a set of control beams associated with the cell; and performing
a cell reselection based on consolidation measurement results.
25. The method of claim 24, wherein the signal measurement of a
control beam is obtained based on one or more UE measurements
comprising: a signal strength measurement, a signal quality
measurement, a signal lifetime measurement, signal error rate and
signal AoA/DoA.
26. The method of claim 24, wherein the measurement level is a
first level when the Res_S is greater than the first threshold, and
wherein the consolidation measurement is only performed for the
serving cell based on serving control beams on which the UE
receives system and control information.
27. The method of claim 24, wherein the measurement level is a
second level when the Res_S is smaller than the first threshold and
larger than the second threshold, and wherein the consolidation
measurement is performed on all detected control beams of the
serving cell.
28. The method of claim 24, wherein the measurement level is a
third level when the Res_S is smaller than the second threshold and
larger than the third threshold, and wherein the consolidation
measurement is performed on detected control beams in the serving
cell and detected or configured neighbor cell control beams with a
same frequency of the serving cell.
29. The method of claim 24, wherein the measurement level is a
fourth level when the Res_S is smaller than the third threshold and
wherein the consolidation measurement is performed on all detected
control beams of detected control beams in the serving cell and
detected or configured neighbor cell control beams with a different
frequency of the serving cell.
Description
TECHNICAL FIELD
[0001] The disclosed embodiments relate generally to wireless
communication, and, more particularly, to cell selection and cell
reselection in a millimeter wave system.
BACKGROUND
[0002] The bandwidth shortage increasingly experienced by mobile
carriers has motivated the exploration of the underutilized
millimeter wave (mmW) frequency spectrum between 3 G and 300 G Hz
for the next generation broadband cellular communication networks.
The available spectrum of mmW band is two hundred times greater
than the conventional cellular system. The mmW wireless network
uses directional communications with narrow beams and can support
multi-gigabit data rate. The underutilized bandwidth of the mmW
spectrum has wavelengths ranging from 1 mm to 100 mm. The very
small wavelengths of the mmW spectrum enable large number of
miniaturized antennas to be placed in a small area. Such
miniaturized antenna system can produce high beamforming gains
through electrically steerable arrays generating directional
transmissions.
[0003] With recent advances in mmW semiconductor circuitry, mmW
wireless system has become a promising solution for the real
implementation. However, the heavy reliance on directional
transmissions present particular challenges for the mobile stations
in the mmW network, such as cell selection and cell reselection
procedures during IDLE mode. Unlike the traditional cellular
system, one mmW cell is covered by one or more than one directional
beams. Therefore, the synchronization and broadcast signals for a
cell are also directional and only cover a small area. The mobile
stations need to san over a range of angles before a cell can be
detected. The time latency would be even longer in standalone mmW
system due to the lack of assistance information from the network.
The frequent execution of finding a narrow beam to camp on during
mobile movement is more complicated with more power consumption for
measurement.
[0004] Improvements and enhancements are required for cell
selection and cell reselection in the mmW network.
SUMMARY
[0005] Methods and apparatus are provided for cell selection, cell
reselection and beam selection in mmW system. In one novel aspect,
consolidation measurements are used for cell selection and cell
reselection for a UE in the mmW system. The UE measures signal
strength, signal energy/power, signal quality, signal lifetime,
signal error rate, signal angle of arrival (AoA)/direction of
arrival (DoA) or a combination of the above to get the best
consolidation measurement result. In one embodiment, the UE selects
a set of control beams for each cell as qualified control beam to
obtain the consolidation measurement. In one embodiment, the set of
qualified control beams are multiple detected control beams
associated with the cell. In another case, the set of qualified
control beams are all the detected control beams associated with
the cell. In another embodiment, the set of qualified control beams
are multiple candidate control beams associated with the cell,
where the candidate control beams is a subset of the detected
control beams meeting a predefined criterion. In yet other
embodiments, different consolidation rules are used to obtain the
consolidation measurement.
[0006] In another novel aspect, during cell selection, the UE
selects the cell with the best consolidation measurement result, or
selects the cell containing the candidate control beam found
firstly. In another embodiment, the UE selects one or more control
serving beams from the control beams of the serving cell. The UE
receives control information and system information on the serving
control beams. In another embodiment, the UE selects an access
control beam from the selected serving control beam(s) to initiate
RRC connection.
[0007] In yet another novel aspect, during cell reselection, the
serving cell and neighboring cells are ranked based on the
consolidation measurement result. In one embodiment, the UE
compares the serving-cell consolidation measurement with a set of
measurement thresholds. The UE determines the measurement level
based on the comparison. The measurement level includes measuring
the serving control beams of the serving cell, measuring the
serving and non- serving control beams of the serving cell,
measuring the neighboring cells with the same frequency, and
measuring the neighboring cells with different frequencies.
[0008] In one novel aspect, after the UE camps on a cell, the UE
selects one or more than one best control beams as the serving
control beam(s) to acquire system information and monitor paging
message. Furthermore, the UE selects the best control beam or
selects one control beam randomly among the serving control beams
to initial access to the network.
BRIEF DESCRIPTION OF DRAWINGS
[0009] The accompanying drawings, where like numerals indicate like
components, illustrate embodiments of the invention.
[0010] FIG. 1 is a schematic system diagram illustrating an
exemplary wireless network with mmW connections in accordance with
embodiments of the current invention.
[0011] FIG. 2 shows an exemplary flow chart of a UE performing cell
selection and cell reselection in the IDLE mode in the mmW
system.
[0012] FIG. 3 illustrates an exemplary control beam configuration
for UL and DL of the UE in accordance with the current
invention.
[0013] FIG. 4 shows an exemplary flow chart for a cell selection in
mmW system in accordance with embodiments of the current
invention.
[0014] FIG. 5 illustrates an exemplary table that shows the
consolidation measurement results based on different consolidation
rules/methods in accordance with embodiments of the current
invention.
[0015] FIG. 6 illustrates exemplary flow charts of consolidation
measurements performed for serving cells and neighbor cells for the
cell reselection in the mmW system.
[0016] FIG. 7 shows an exemplary flow chart of the UE performing
cell reselection measurement based on measurement rules according
to a set of threshold in accordance with embodiments of the current
invention.
[0017] FIG. 8 illustrates different sets of control beam selections
for the UE measurement for cell reselection in accordance with
embodiments of the current invention.
[0018] FIG. 9 shows an exemplary flow chart for the cell
reselection process in the mmW system in accordance with
embodiments of the current invention.
[0019] FIG. 10 illustrates an exemplary flow chart for beam
selection for the UE in the mmW system in accordance with
embodiments of the current invention.
[0020] FIG. 11 is an exemplary flow chart for obtaining the
consolidation measurement of each cell by the UE in the mmW
system.
[0021] FIG. 12 is an exemplary flow chart for cell selection
process of the UE in the mmW system in accordance with embodiments
of the current invention.
[0022] FIG. 13 is an exemplary flow chart for cell reselection
process of the UE in the mmW system in accordance with embodiments
of the current invention.
DETAILED DESCRIPTION
[0023] Reference will now be made in detail to some embodiments of
the invention, examples of which are illustrated in the
accompanying drawings.
[0024] FIG. 1 is a schematic system diagram illustrating an
exemplary wireless network 100 with mmW connections in accordance
with embodiments of the current invention. Wireless system 100
includes one or more fixed base infrastructure units forming a
network distributed over a geographical region. The base unit may
also be referred to as an access point, an access terminal, a base
station, a Node-B, an eNode-B, or by other terminology used in the
art. As an example, base stations 101, 102 and 103 serve a number
of mobile stations 104, 105, 106 and 107 within a serving area, for
example, a cell, or within a cell sector. In some systems, one or
more base stations are communicably coupled to a controller forming
an access network that is communicably coupled to one or more core
networks. eNB 101 is a conventional base station served as a macro
eNB. eNB 102 and eNB 102 are mmW base stations, whose serving area
partially or wholly overlap with the serving area of eNB 101, or
does not overlap, as well as at least partially overlap with each
other at the edge. mmW eNB 102 and mmW eNB 103 has multiple sectors
each with multiple control beams to cover a directional area,
wherein each control beam further comprises multiple dedicated
beams in hierarchy. Control beams 121, 122, 123 and 124 are
exemplary control beams of eNB 102. Control beams 125, 126, 127 and
128 are exemplary control beams of eNB 103. As an example, UE or
mobile station 104 is only in the service area of eNB 101 and
connected with eNB 101 via a link 111. UE 106 is connected with mmW
network only, which is covered by control beam 124 of eNB 102 and
is connected with eNB 102 via a link 114. UE 105 is the overlapping
service area of eNB 101 and eNB 102. In one embodiment, UE 105 is
configured with dual connectivity and can be connected with eNB 101
via a link 113 and eNB 102 via a link 115. UE 107 is in the service
areas of eNB 101, eNB 102 and eNB 103. During cell selection in the
mmW system, UE 107 measures multiple cells covered by eNB 102 and
eNB 103. Each of mmW cells has one or more control beams. UE 107
measures the detected beams and calculates a consolidation
measurement for each cell. In one embodiment, UE 107 performs cell
selection and cell reselection based on consolidation measurements
for each cell.
[0025] FIG. 1 further illustrates simplified block diagrams 130 and
150 for UE 107 and eNB 103, respectively. Mobile station 107 has an
antenna 135, which transmits and receives radio signals. A RF
transceiver module 133, coupled with the antenna, receives RF
signals from antenna 135, converts them to baseband signals, and
sends them to processor 132. RF transceiver module 133 is an
example, and in one embodiment, the RF transceiver module comprises
two RF modules (not shown), first RF module is used for mmW
transmitting and receiving, and another RF module is used for
different frequency bands transmitting and receiving, which is
different from the mmW transceiving. RF transceiver 133 also
converts received baseband signals from processor 132, converts
them to RF signals, and sends out to antenna 135. Processor 132
processes the received baseband signals and invokes different
functional modules to perform features in mobile station 107.
Memory 131 stores program instructions and data 134 to control the
operations of mobile station 107. Mobile station 107 also includes
multiple function modules that carry out different tasks in
accordance with embodiments of the current invention. A
control-beam selection module 141 selects a set of control beams
for a cell to obtain the consolidation measurement. A consolidate
measurement module 142 calculates the consolidation measurement
based on the selected set of control beams and a consolidation
rule. A cell selection module 143 performs cell selection for UE
107 in the mmW system. A cell reselection module 144 performs cell
reselection for UE 107 in the mmW system. Beam selection module 145
selects a set of serving control beams for UE 107.
[0026] Similarly, eNB 103 has an antenna 155, which transmits and
receives radio signals. A RF transceiver module 153, coupled with
the antenna, receives RF signals from antenna 155, converts them to
baseband signals, and sends them to processor 152. RF transceiver
module 153 is an example, and in one embodiment, the RF transceiver
module comprises two RF modules (not shown), the first RF module is
used for mmW transmitting and receiving, and another RF module is
used for different frequency bands transmitting and receiving which
is different from the module used for mmW. RF transceiver 153 also
converts received baseband signals from processor 152, converts
them to RF signals, and sends out to antenna 155. Processor 152
processes the received baseband signals and invokes different
functional modules to perform features in eNB 103. Memory 151
stores program instructions and data 154 to control the operations
of eNB 103. eNB 103 also includes multiple function modules that
carry out different tasks in accordance with embodiments of the
current invention. An mmW handler 161 handles mmW functions for eNB
103.
[0027] FIG. 1 further shows functional procedures that handle cell
selection and cell reselection procedures in the mmW system. UE 105
has a consolidation measurement procedure 191 that processes
consolidation measurement for UE 105. UE 105 also has cell
selection procedure 192 that performs cell selection functions for
UE 105 in the mmW system. A cell reselection procedure 193 of UE
105 performs cell reselection functions in the mmW system.
[0028] FIG. 2 shows an exemplary flow chart of a UE performing cell
selection and cell reselection in the IDLE mode in the mmW system.
After the UE powers on or returns to RRC_IDLE from RRC_CONNECTED at
step 200, the UE in the IDLE mode transits from three processes, a
cell selection process 201, a beam selection/camp-on process 202
and a cell reselection 203. At the top level, upon the UE powers on
or returns to RRC_IDLE from RRC_CONNECTED, the UE starts cell
selection at step 210. If upon completion of cell selection 210,
the UE moves step 220 to camp on the selected cell, which is also
called as serving cell. The UE continues monitors the signal
strength in the serving cell as well as neighboring cells if
needed. The UE moves step 230 to perform cell reselection. Upon
completion of the cell reselection, the UE moves back to step 220
to camp on the serving cell.
[0029] In connected mode, consolidation measurements could be used
for handover. In one embodiment, in idle mode, consolidation
measurements are used for cell selection in the mmW system. When
the UE starts cell selection, at step 211 the UE obtains signal
measurements for multiple cells consisting of multiple control
beams. The UE in the mmW system detects multiple control beams
associated with one or more mmW cells. The signal measurement can
signal strength, signal energy, signal power, signal quality,
signal lifetime, signal error rate, signal AoA, or signal DoA. The
signal measurement for each control beam can also be any
combination of the above or other related measurements that can be
obtain to indicate the control beam status. Based on the
measurement, the UE can determine a set of candidate control beams
of each cell of multiple cells. The candidate control beams are the
subset of the detected control beams that meets a predefined
criterion. For example, a candidate control beam is a candidate
control beam whose signal measurement is greater than a predefine
threshold. At step 212, the UE obtains the consolidation
measurement results for each cell. The consolidation measurement
result for each cell is to computes the measurement results based
on a set of signal measurements of one or more control beams
associated with the cell. At step 213, the UE applies cell
selection criterion based on the obtained consolidation measurement
results. At step 214, the UE performs cell selection and selects a
cell to camp on.
[0030] Unlike traditional cellular system, once camped on a cell,
the UE needs to perform beam selection in the serving cell. At step
221, the UE selects one or more serving control beams. The serving
control beams are control beams in the serving cell on which the UE
acquires system information, receives paging messages, and/or
initial access to the network. The serving control beams are a
subset of the candidate control beams of the serving cell. There
can be one or more serving control beams for the UE. At step 222,
the UE acquires system information through the serving control
beams. At step 223, the UE monitors the paging message via the
serving control beams. At step 224, the UE further selects the
access control beam in the serving control beams. The access
control beam is a serving control beam that meets a predefined
criterion. For example, the access control beam is the serving
control beam that has the best signal measurement. In another
embodiment, the UE can randomly select one serving control beam as
the access control beam.
[0031] The UE performs cell reselection in the IDLE state. At step
231, the UE performs priority selection. The UE prioritize
different mmW frequencies or inter-RAT (radio access technology)
frequencies. In one embodiment, the UE receives the priority
configuration information in the dedicated message when the UE
release RRC connection, or inherits from another RAT at inter-RAT
cell selection or cell reselection. In another embodiment, the UE
capable of supporting both EUTRAN and mmW will always consider the
EUTRAN frequency as highest priority frequencies. At step 232, the
UE obtains consolidation measurement results for the serving cell.
At step 233, the UE applies the measurement rules based on the
obtained serving cell consolidation-measurement result. If at step
233, the UE determines that neighbor cell measurement is need, the
UE moves to step 234. At step 234, the UE measures neighbor cell
control beams. At step 235, the UE obtains consolidation
measurement results for multiple cells. At step 236, the UE applies
cell reselection criterion based on the consolidation measurement
results. At step 237, the UE performs cell reselection.
[0032] FIG. 3 shows exemplary diagrams and a table illustrating
multiple control beam measurement of UE in a mmW network. A UE 303
locates in an area served by with an mmW eNB 301 and mmW eNB 302.
eNB 301 and eNB 302 are directionally configured with multiple
sectors/cells. Each sector/cell is covered by a set of coarse TX
control beams. In one example, three sectors/cells are configured,
each covering a 120.degree. sector. In one embodiment, each cell is
covered by eight control beams. Different control beams are time
division multiplexed and distinguishable. Phased array antenna is
used to provide moderate beamforming gain. The set of control beams
is transmitted repeatedly and periodically. Each control beam
broadcasts the cell-specific information such as synchronization
signal, system information, and beam-specific information.
[0033] As an example, eNB 301 covers three cells #0 and cell #1 and
cell #2. Similarly, eNB 302 covers three cells #3 and cell #4 and
cell #5. UE 303 detects control beams for cell selection. As an
example shown in FIG. 3, each cell is configured with eight control
beams. UE 303 detects multiple control beams and performs signal
measurements on the detected multiple control beams. Up detecting
control beams, UE 303 may determine whether the detected control
beam is a candidate control beam based on a candidate rule. In one
embodiment, the detected control beam is a candidate control beam
if the signal measurement is larger than a threshold. As an
example, FIG. 3 illustrates a table 300 of detected control beams
and candidate control beams for UE 303. A list of control beams is
listed for each cell in a descending order of the signal
measurement. UE 303 detects control beams (CBs) CB8, CB7, CB6 and
CB3 in descending order from cell #0. UE 303 determines that CB8,
CB7, and CB6 are candidate control beams from cell #0. Similarly,
UE 303 detects control beams CB2, CB1 and CB4 in descending order
from cell #1. UE 303 determines that CB2, and CB1 are candidate
control beams from cell #1. For Cell #2, UE 303 detects control
beams CB8 and CB7 and determines that CB8 is the candidate control
beam. UE 303 detects control beams CB2, CB1, CB3 and CB6 in
descending order from cell #3. UE 303 determines that CB2, CB1, and
CB3 are candidate control beams from cell #3. Once the UE detects
control beams and determines candidate control beams, the UE
calculates the consolidation measurement for each cell based on the
one or more signal measurement obtained associated with the
corresponding cell.
[0034] FIG. 4 shows an exemplary flow chart for a cell selection in
mmW system in accordance with embodiments of the current invention.
At step 401, the UE detects control beams and performs signal
measurement for each detected control beam. At step 402, the UE
determines whether the control beam is a candidate control beam. In
one embodiment, the UE compares the signal measurement of the
control beam with a predefined threshold to determine if the signal
measurement is larger than the threshold. If step 402 determines
no, the control beam is only a detected control beam at step 403.
If step 402 determines yes, the control beam is considered as a
candidate control beam at step 404. Steps 402, 403 and 404 are
optional. In some embodiments, the UE takes consolidation
measurement based on detected control beams for each cell and steps
402, 403 and 404 are skipped. In another embodiment, upon detecting
the first candidate control beam at step 402, the UE selects the
first found associated cell as the serving cell. In other
embodiments, the UE moves to step 405 to determine which set of
control beams should be used for consolidation measurement for each
cell. In one embodiment, all detected control beams are used. In
the second embodiment, multiple control beams of all detected
control beams are used. In the third embodiment, only candidate
control beams are used, or part of the candidate control beams of
all the candidate control beams are used. In the fourth embodiment,
the UE can select other sets of control beams for each cell based
on qualified-control-beam rules.
[0035] Once the UE selected the set of qualified control beams for
consolidation measurement, the UE moves to step 411 wherein the UE
obtains consolidation measurement for each cell. The UE obtains the
consolidation measurement based on a consolidation rule 421. The
consolidation rule can be configured or predefined. Different
consolidation rules can be used. Each applied to the selected set
of qualified control beams associated with the cell as determined
in step 405. In one embodiment (method #1), the resulting
consolidation measurement of the set of qualified control beams of
the cell is the number of qualified control beams in the set. In
other embodiments the resulting consolidation measurement of the
set of qualified control beams of the cell is the maximum signal
measurement of the set (method #2), or the minimum signal
measurement of the set (method #3), or the mean value of signal
measurements of the set (method #4), or the variance of signal
measurements of the set (method #5), or the sum of the signal
measurements of the set (method #6). Other consolidation methods
can be used. In other embodiments, a combination of different
methods may be used, for example, a combination of method #1 and
method #2.
[0036] Once the consolidation measurements is determined for each
cell, the UE moves to step 412 and finds the cell with the best
consolidation result following a cell selection rule 422. Examples
of the cell selection rule 422 includes determining the best cell
being the cell whose consolidation measurement has the largest
number of qualified control beams in the set, or has the largest
maximum signal measurement of the set, or has the largest minimum
signal measurement of the set, or has the largest mean value of
signal measurements of the set, or has the smallest variance of
signal measurement of the set, or has the largest sum of signal
measurements of the set. Other cell selection rules can be used or
combinations of the cell selection rules can be used.
[0037] Upon successfully selecting a serving cell, the UE moves to
step 413 and finds one or more serving control beams of the serving
cell using a beam selection rule 423. The UE receives control and
signal information on the selected serving control beams.
[0038] FIG. 5 illustrates an exemplary table that shows the
consolidation measurement results based on different consolidation
rules/methods in accordance with embodiments of the current
invention. A table 500 lists the resulting consolidation
measurement rules/methods assuming the detecting control beams
shown in table 300 of FIG. 3. Table 500 assumes that candidate
control beams are selected as qualified control beams for the
consolidation measurement. Using method #1, Cell #0 has 3CBs, Cell
#1 has 2CBs, Cell #2 has 1CB, and Cell #3 has 3CB. Similarly, the
UE can use different consolidation method as listed in table 500 to
get a consolidation measurement for the corresponding cells. The
resulting consolidation measurement for each cell can be the
maximum signal measurement of the CB of the set (method #2), or the
minimum signal measurement of the CB of the set (method #3), or the
mean value of measurements of all candidate CBs of the set (method
#4), or the variance of measurement of all candidate CBs of the set
(method #5), or the sum of the measurements of all candidate CBs of
the set (method #6).
[0039] In other embodiments, combinations of the above methods are
used for the signal measurement of each cell. For example, the
signal measurement results for each cell contains two measurements:
a first weighted resulting consolidation measurement for each cell
is the maximum signal measurement of the CB of the set (method #2)
and a second weighted resulting consolidation measurement for each
cell is the number of qualified control beams (method #1). The
ranking of cells may be the same or may be different based on
different measurements contained in the signal measurement.
Providing a combination signal measurement for each cell presents a
more complete picture of the cell condition such that the UE can
select a better cell for cell selection, cell reselection, and/or
handover. For example, using method #2, cell #2 may rank higher
than cell #0 with a slightly higher maximum signal strength.
However, using method #1, cell #0 may rank higher than cell #2 with
a higher number of candidate control beams. In one embodiment, the
UE uses an algorithm to select the target cell for cell selection,
cell reselection, and/or handover. For example, a signal threshold
is set such that the best-ranked cell using method #2 is selected
if the maximum signal measurement is greater than the signal
threshold; otherwise, the best-ranked cell using method #1 is
selected. Similarly, a number threshold is set such that the
best-ranked cell using method #1 is selected if the number of
qualified control beams is greater than the number threshold;
otherwise, the best-ranked cell using method #2 is selected. In
other embodiments, a set of thresholds and/or a combination of
thresholds are used for cell ranking Multiple signal measurements
can be combined with corresponding cell ranking algorithms.
[0040] FIG. 6 illustrates exemplary flow charts of consolidation
measurements performed for serving cells and neighbor cells for the
cell reselection in the mmW system. At step 601, the UE determines
a set of qualified control beams for consolidation measurement for
the serving cell. For example, the set of qualified control beams
may be the detected control beams in the serving cell, or the
candidate control beams of the serving cell or the serving control
beams of the serving cell. At step 602, the UE calculates the
consolidation measurement for the serving cell based on the control
beam selection at step 601. At step 603, the UE obtains the serving
cell consolidation-measurement result RES_S. Similarly, the UE At
step 611, the UE determines a set of qualified control beams for
consolidation measurement for the neighboring cells. For example,
the set of qualified control beams may be the detected control
beams in the neighbor cells, or the candidate control beams of the
neighboring cells. At step 612, the UE calculates the consolidation
measurement for the neighboring cells based on the set of qualified
control beams at step 611. At step 613, the UE obtains the
neighboring cells consolidation-measurement result RES_N.
[0041] In the mmW system, the UE needs to monitor multiple beams in
a cell to obtain the measurement result. The power consumption is a
concern for frequent measurement. In one embodiment for cell
reselection, the UE determines the set of control beams to measure
based on a comparison between the consolidation measurement result
of the serving cell and a set of thresholds. FIG. 7 shows an
exemplary flow chart of the UE performing cell reselection
measurement based on measurement rules according to a set of
threshold in accordance with embodiments of the current invention.
In one embodiment, the UE is configured with a set of measurement
thresholds, Threshold_1, Threshold_2, and Threshold_3 in a
descending order. Threshold_1 is defined for intra-cell
measurement. Threshold_2 is defined for intra-frequency
measurements. Threshold_3 is defined for inter-frequency and
inter-RAT measurements. Threshold_1 can be broadcasted in the
system information or beam-specific information.
[0042] Threshold_2 and Threshold_3 can be broadcasted in the system
information.
[0043] At step 701, the UE compares the serving cell consolidation
measurement RES_S, as shown in FIG. 6, with a set of thresholds. At
step 702, the UE determines if RES_S is smaller than Threshold_3.
If step 702 determines yes, the UE moves step 711 of a first
measurement level. The UE performs inter-frequency control beams
measurement at step 711. If step 702 determines no, the UE moves
step 703. At step 703, the UE determines if RES_S is smaller than
Threshold_2. If step 702 determines yes, the UE moves step 712 of a
second measurement level. The UE performs intra-frequency control
beams measurement at step 712, where only the UE measures control
beams of neighbor cells with the same frequency as the serving
cell. If step 702 determines no, the UE moves step 704. At step
704, the UE determines if RES_S is smaller than Threshold_1. If
step 704 determines yes, the UE moves step 713 of a third
measurement level. The UE does not measure control beams from
neighbor cells. The UE measures non-serving control beams of the
serving cell. If step 704 determines no, the UE moves step 714 of a
fourth measurement level. At step 714, the UE only measures the
serving control beams of the serving cell.
[0044] FIG. 8 illustrates different sets of control beam selections
for the UE measurement for cell reselection in accordance with
embodiments of the current invention. Diagram 801 shows different
control beam configurations for the serving cell. The serving cell
has a set of control beams. The UE detects multiple control beams
in the serving cell, namely detected control beams 811. Candidate
control beams 812 is a subset of detected control beam 811. Serving
control beams 813 is a subset of candidate control beams 812. For
neighbor cells, there is no serving control beam set. Diagram 802
shows different control beam configurations for a neighboring cell.
The neighboring cell has a set of control beams. The UE detects
multiple control beams in the neighboring cell, namely detected
control beams 821. Candidate control beams 822 is a subset of
detected control beam 821.
[0045] For cell reselection measurement, the UE can use different
sets of control beams for serving cell and neighbor cells. FIG. 8
shows an exemplary table 800 of different combinations of
measurement the UE can take for cell reselection. Table 800 assumes
the measurement of Table 300 as shown in FIG. 3. The UE can use
different control beam sets for cell reselection measurement. For
example, shown in the first row of Table 800, the UE uses serving
control beams for the serving consolidation measurement while using
candidate control beams for neighboring cells' consolidation
measurements. Shown in the second row of Table 800, the UE uses
serving control beams for the serving consolidation measurement
while using detected control beams for neighboring cells'
consolidation measurements. Similarly, shown in the third row of
Table 800, the UE uses candidate control beams for the serving
consolidation measurement while using detected control beams for
neighboring cells' consolidation measurements. In another
embodiment, the UE can use the same set of control beams for the
serving cell and the neighboring cells. Both the serving cell and
neighboring cells use candidate control beams for the consolidation
measurement, as shown in the fourth row of Table 800. Similarly,
both the serving cell and neighboring cells use detected control
beams for the consolidation measurement, as shown in the fifth row
of Table 800.
[0046] FIG. 9 shows an exemplary flow chart for the cell
reselection process in the mmW system in accordance with
embodiments of the current invention. The cell reselection process
includes three stages, a stage 910 wherein cells with higher
priority frequency are considered, a stage 920 wherein cells with
lower priority frequency are considered and a stage 930 wherein the
cells with equal priority frequency are considered. At step 911,
the UE determines if a cell of higher priority frequency fulfills a
predefined condition for cell reselection. If step 911 determines
yes, the UE moves to step 912 to check if a timer T1 has elapsed
since the UE camped on the current serving cell. If step 912
determines yes, the UE moves to step 913 and performs a cell
reselection to a cell of higher priority frequency. If at step 912,
the UE determines no, or the UE determines no at step 911, the UE
moves out of stage 910 and moves to step 921 of stage 920.
[0047] At step 921, the UE determines if a cell of lower priority
frequency fulfills a predefined condition for cell reselection. If
step 921 determines yes, the UE moves to step 922 to check if a
timer Ti has elapsed since the UE camped on the current serving
cell. If step 922 determines yes, the UE moves to step 923 and
performs a cell reselection to a cell of lower priority frequency.
If at step 922, the UE determines no, or the UE determines no at
step 921, the UE moves out of stage 920 and moves to step 931 of
stage 930.
[0048] At step 931, the UE calculates serving cell consolidation
measurement results Rs and neighboring cell consolidation
measurement results Rn are based on RES_S and RES_N as shown in
FIG. 6, respectively. The UE then moves to step 932. At step 932,
the ranks of the serving cell and neighboring cells are determined
based on Rs and Rn values. At step 933, the UE determines if there
exists a new cell better than the current serving cell for a T2
period. If step 933 determines yes, the UE moves to step 934 and
determines if the UE has camped on the current serving cell for T1
period. If step 934 determines yes, the UE moves to step 935 and
performs cell reselection to the new cell. If step 933 determines
no, or step 934 determines no, the UE moves back to step 911.
[0049] Upon successful cell selection or cell reselection, the UE
in the mmW system needs to select serving control beams. Further,
while the UE camps on a serving cell, the UE performs beam
selection to select better control beams to be serving control
beams. FIG. 10 illustrates an exemplary flow chart for beam
selection for the UE in the mmW system in accordance with
embodiments of the current invention. At step 1001, the UE performs
control beam measurement. At step 1002, the UE obtains the
measurement results for each control beam of the serving cell,
where the serving control beams have the result denoted as Bmeas_s
and none-serving control beam has the measurement of Bmeas_ns. At
step 1003, the UE calculates the measurements of serving control
beams Bs and none-serving control beams Bns. In one embodiment, the
Bs for serving control beams equals to the measured result for the
serving beam Bmeas_s plus a hypothesis vale, Q_h while Bn for the
none-serving control beams equals to the measurement result of
Bmeas_n. Therefore, for the i-th serving control beam,
Bs_i=Bmeas_n,i+Q_h. For the j-th none-serving control beam,
Bns_j=Bmeas_ns,j. In one embodiment, the Q_h is broadcasted in the
system information or beam specific information. At step 1004, the
UE ranks the serving control beams and non-serving control beams
based on the Bs and Bns. At step 1005, the UE determines if one or
more non-serving control beams are better ranked than one or more
current serving-control-beams. If step 1005 finds no, the UE moves
back to 1001. If step 1005 finds yes, the UE moves to step 1011 and
checks if the new control beams have been better ranked for a Tb1
period. If step 1011 finds yes, the UE moves to step 1012 and
checks if the current control beams had been used for Tb2 period.
If step 1012 finds yes, the UE moves to step 1013 and determines
the number N of better-ranked non-serving control beams. At step
1014, the UE replaces the worst N serving control beams with the N
better-ranked control beams as the new serving control beams. If
step 1011 finds no, or step 1012 finds no, the UE moves to step
1001.
[0050] FIG. 11 is an exemplary flow chart for obtaining the
consolidation measurement of each cell by the UE in the mmW system.
At step 1101, the UE detects multiple control beams in a millimeter
wave (mmW) system, wherein the mmW system has multiple cells each
configured with multiple control beams. At step 1102, the UE
obtains a signal measurement for each detected control beam. At
step 1103, the UE calculates a consolidation measurement for each
cell based on a set of qualified control beams associated with each
corresponding cell using a consolidation rule, wherein at least one
cell has more than one associated qualified control beams.
[0051] FIG. 12 is an exemplary flow chart for cell selection
process of the UE in the mmW system in accordance with embodiments
of the current invention. At step 1201, the UE detects multiple
control beams of multiple cells in a millimeter wave (mmW) system,
wherein the mmW system has multiple cells each configured with
multiple control beams. At step 1202, the UE obtains a signal
measurement for each detected control beam. At step 1203, the UE
performs a cell selection to select a serving cell. At step 1204,
the UE selects one or more serving control beams associated with
the serving cell, wherein the UE receives control information and
system information on the serving control beams.
[0052] FIG. 13 is an exemplary flow chart for cell reselection
process of the UE in the mmW system in accordance with embodiments
of the current invention. At step 1301, the UE obtains a
consolidation serving cell measurement for cell reselection (Res_S)
in a millimeter wave (mmW) system, wherein the Res_S is calculated
based on signal measurements of a set of qualified control beams of
the serving cell. At step 1302, the UE determines a measurement
level by comparing the Res_S with one or more thresholds in
descending order comprising: a first threshold, a second threshold
and a third threshold. At step 1303, the UE performs consolidation
measurement for one or more cells based on the determined
measurement level, wherein the consolidation measurement for a cell
is calculated based on signal measurements of a set of control
beams associated with the cell. At step 1304, the UE performs a
cell reselection based on consolidation measurement results.
[0053] Although the present invention has been described in
connection with certain specific embodiments for instructional
purposes, the present invention is not limited thereto.
Accordingly, various modifications, adaptations, and combinations
of various features of the described embodiments can be practiced
without departing from the scope of the invention as set forth in
the claims.
* * * * *