U.S. patent application number 14/917451 was filed with the patent office on 2016-08-04 for user equipment and evolved node-b and methods for operation in a coverage enhancement mode.
The applicant listed for this patent is INTEL IP CORPORATION. Invention is credited to Seunghee Han, Youn Hyoung Heo, Gang Xiong.
Application Number | 20160227580 14/917451 |
Document ID | / |
Family ID | 52995317 |
Filed Date | 2016-08-04 |
United States Patent
Application |
20160227580 |
Kind Code |
A1 |
Xiong; Gang ; et
al. |
August 4, 2016 |
USER EQUIPMENT AND EVOLVED NODE-B AND METHODS FOR OPERATION IN A
COVERAGE ENHANCEMENT MODE
Abstract
Embodiments of a User Equipment (UE) and an Evolved Node-B (eNB)
and methods for operating in a coverage enhancement (CE) mode are
generally described herein. The UE may include hardware processing
circuitry configured to determine a CE category for the UE based at
least partly on downlink channel statistics related to reception of
one or more downlink signals from an eNB. The CE category may
reflect one of a level of additional link margin and a level of
system resources for performance at or above a performance
threshold. The hardware processing circuitry may be further
configured to transmit, in physical random access channel (PRACH)
frequency resources, a PRACH preamble according to an uplink access
repetition number. The PRACH frequency resources and the uplink
access repetition number may be based at least partly on CE
category for the UE.
Inventors: |
Xiong; Gang; (Beaverton,
OR) ; Han; Seunghee; (San Jose, CA) ; Heo;
Youn Hyoung; (San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTEL IP CORPORATION |
Santa Clara |
CA |
US |
|
|
Family ID: |
52995317 |
Appl. No.: |
14/917451 |
Filed: |
October 28, 2014 |
PCT Filed: |
October 28, 2014 |
PCT NO: |
PCT/US2014/062533 |
371 Date: |
March 8, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61898425 |
Oct 31, 2013 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 72/0486 20130101;
H04W 88/02 20130101; H04W 60/02 20130101; H04W 8/06 20130101; H04L
5/0098 20130101; H04W 56/001 20130101; H04W 72/10 20130101; H04W
60/00 20130101; H04W 72/085 20130101; H04W 76/15 20180201; H04W
88/08 20130101; H04W 4/90 20180201; H04W 36/305 20180801; H04W
52/346 20130101; H04W 8/04 20130101; H04W 84/12 20130101; H04W
88/18 20130101; H04W 92/20 20130101; H04W 48/08 20130101; H04W
76/14 20180201; H04W 76/18 20180201; Y02D 30/70 20200801; H04B
7/0413 20130101; H04W 48/12 20130101; H04L 5/001 20130101; H04W
4/023 20130101; H04W 8/005 20130101; H04W 76/19 20180201; H04W
88/16 20130101; H04B 17/318 20150115; H04L 5/0007 20130101; H04W
4/80 20180201; H04W 36/0069 20180801; H04W 56/002 20130101; H04W
74/0833 20130101; H04W 8/183 20130101; H04W 24/10 20130101; H04J
3/1694 20130101; H04W 36/0055 20130101; H04W 76/10 20180201; H04W
48/18 20130101; H04W 74/004 20130101; H04W 48/06 20130101; H04W
72/0453 20130101; H04W 4/02 20130101; H04W 28/0215 20130101; H04W
28/08 20130101; H04W 72/048 20130101; H04W 4/60 20180201 |
International
Class: |
H04W 74/08 20060101
H04W074/08; H04B 17/318 20060101 H04B017/318 |
Claims
1. A User Equipment (UE) to operate in accordance with a coverage
enhancement (CE) mode, the UE comprising hardware processing
circuitry configured to: determine, from a group of candidate CE
categories, a CE category for the UE based at least partly on
downlink channel statistics related to reception of one or more
downlink signals at the UE from an Evolved Node-B (eNB); and
transmit, in physical random access channel (PRACH) frequency
resources, a PRACH preamble according to an uplink access
repetition number; wherein the PRACH frequency resources and the
uplink access repetition number are based at least partly on the CE
category for the UE.
2. The UE according to claim 1, wherein the CE category for the UE
reflects one of a level of additional link margin and a level of
system resources for performance at or above a performance
threshold associated with a normal operating mode for the UE.
3. The UE according to claim 1, wherein the downlink channel
statistics include reference signal received power (RSRP) or path
loss measurements at the UE.
4. The UE according to claim 1, wherein the group of candidate CE
categories includes a first and a second candidate CE category for
which an uplink access repetition number for the first CE category
is different from an uplink access repetition number for the second
CE category and PRACH frequency resources for the first CE category
are exclusive to PRACH frequency resources for the second CE
category.
5. The UE according to claim 1, the hardware processing circuitry
further configured to receive, from the eNB, a Random Access
Response (RAR) according to a downlink repetition number that is
based at least partly on the CE category for the UE.
6. The UE according to claim 5, wherein: the RAR is received on
physical downlink shared channel (PDSCH) frequency resources that
are based at least partly on the CE category for the UE; and the
PDSCH frequency resources are disjoint from second PDSCH frequency
resources for UEs not operating in the CE mode.
7. The UE according to claim 6, wherein: the hardware processing
circuitry is further configured to receive, from the eNB, a
physical downlink control channel (PDCCH) data block on PDCCH
frequency resources for UEs operating in the CE mode; the PDCCH
data block includes a downlink control information (DCI) block that
includes the downlink repetition number.
8. The UE according to claim 6, wherein the hardware processing
circuitry is further configured to refrain from decoding physical
downlink control channel (PDCCH) data blocks as part of the
reception of the RAR.
9. The UE according to claim 5, the hardware processing circuitry
further configured to transmit, in response to the reception of the
RAR, an uplink control message on physical uplink shared channel
(PUSCH) resources according to an uplink control repetition
number.
10. The UE according to claim 9, wherein the RAR includes the
uplink control repetition number.
11. The UE according to claim 10, wherein the RAR includes an
uplink grant for the UE and the uplink grant includes the uplink
control repetition number.
12. The UE according to claim 9, wherein: the uplink control
message includes a second CE category for the UE; the second CE
category is selected from a second group of candidate CE
categories; and the second CE category is determined at least
partly from the reception of the RAR.
13. The UE according to claim 9, the hardware processing circuitry
further configured to receive, from the eNB, a contention
resolution message according to the downlink repetition number.
14. The UE according to claim 1, wherein the UE is further to
support Machine Type Communication (MTC) and to operate according
to a 3GPP protocol.
15. A non-transitory computer-readable storage medium that stores
instructions for execution by one or more processors to perform
operations for communication by User Equipment (UE) in a coverage
enhancement (CE) mode, the operations to configure the one or more
processors to: determine, from a group of candidate CE categories,
a CE category for the UE based at least partly on downlink channel
statistics related to reception of one or more downlink signals at
the UE from an Evolved Node-B (eNB); and transmit, in physical
random access channel (PRACH) frequency resources, a PRACH preamble
according to an uplink access repetition number; wherein the PRACH
frequency resources and the uplink access repetition number are
based at least partly on the CE category for the UE.
16. The non-transitory computer-readable storage medium according
to claim 15, the operations to further configure the one or more
processors to receive, from the eNB, a Random Access Response (RAR)
according to a downlink repetition number that is based at least
partly on the CE category for the UE.
17. The non-transitory computer-readable storage medium according
to claim 16, the operations to further configure the one or more
processors to transmit, in response to the reception of the RAR, an
uplink control message on physical uplink shared channel (PUSCH)
resources according to an uplink control repetition number that is
based at least partly on the CE category for the UE.
18. A method for communicating in a coverage enhancement (CE) mode
performed by User Equipment (UE), the method comprising:
determining, from a group of candidate CE categories, a CE category
for the UE based at least partly on downlink channel statistics
related to reception of one or more downlink signals at the UE from
an Evolved Node-B (eNB); and transmitting, in physical random
access channel (PRACH) frequency resources, a PRACH preamble
according to an uplink access repetition number; wherein the PRACH
frequency resources and the uplink access repetition number are
based at least partly on the CE category for the UE.
19. The method according to claim 18, further comprising receiving,
from the eNB, a Random Access Response (RAR) according to a
downlink repetition number that is based at least partly on the CE
category for the UE.
20. An Evolved Node-B (eNB) to operate in accordance with a
coverage enhancement (CE) mode, the eNB comprising hardware
processing circuitry configured to: receive, from a User Equipment
(UE) operating in the CE mode, a physical random access channel
(PRACH) preamble on PRACH frequency resources allocated for UEs
operating in the CE mode; determine, based at least partly on the
PRACH frequency resources used for the reception of the PRACH
preamble, a CE category for the UE from a group of candidate CE
categories; and transmit a Random Access Response (RAR) according
to a downlink repetition number that is based at least partly on
the CE category for the UE.
21. The eNB according to claim 20, wherein the group of candidate
CE categories includes a first and a second candidate CE category
for which PRACH frequency resources for the first and second CE
categories are exclusive.
22. The eNB according to claim 20, wherein: the RAR is transmitted
on physical downlink shared channel (PDSCH) frequency resources
that are based at least partly on the CE category for the UE; and
the PDSCH frequency resources are disjoint from second PDSCH
frequency resources for UEs not operating in a CE mode.
23. The eNB according to claim 22, the hardware processing
circuitry further configured to transmit a physical downlink
control channel (PDCCH) data block that includes PDSCH resource
allocations for UEs not operating in the CE mode and to refrain
from transmission of PDCCH data blocks for UEs operating in the CE
mode.
24. The eNB according to claim 22, the hardware processing
circuitry further configured to transmit a control message that
includes an allocation for the PDSCH frequency resources, a
modulation and coding scheme (MCS) indicator for the RAR
transmission, and a timing relationship between PRACH transmission
at the UE and the RAR transmission.
25. The eNB according to claim 20, the hardware processing
circuitry further configured to receive, from the UE, an uplink
control message on physical uplink shared channel (PUSCH) resources
according to an uplink control repetition number.
26. The eNB according to claim 25, wherein the uplink control
repetition number is based at least partly on the CE category for
the UE.
27. The eNB according to claim 25, wherein the RAR includes the
uplink control repetition number.
28. The eNB according to claim 25, the hardware processing
circuitry further configured to transmit, in response to the
reception of the uplink control message, a contention resolution
message according to the downlink repetition number.
29. The eNB according to claim 20, wherein: the hardware processing
circuitry is further configured to receive, from a second UE not
operating in the CE mode, a second PRACH preamble on second PRACH
frequency resources allocated for UEs that are not operating in the
CE mode; and the second PRACH frequency resources are exclusive to
the PRACH frequency resources allocated for UEs operating in the CE
mode.
30. The eNB according to claim 20, wherein the eNB is further to
operate according to a 3GPP protocol.
Description
PRIORITY CLAIM
[0001] This application claims priority to U.S. Provisional Patent
Application Ser. No. 61/898,425, filed Oct. 31, 2013, which is
incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] Embodiments pertain to wireless communications. Some
embodiments relate to wireless networks including LTE networks.
Some embodiments relate to operation in a coverage enhancement
mode. Some embodiments relate to Machine Type Communication
(MTC).
BACKGROUND
[0003] A mobile device operating in a cellular network may
experience performance degradation in some cases, which may affect
the ability of the device to connect or reconnect to the network.
As an example, the mobile device may lose coverage as it moves
toward or beyond the edge of a cell or sector of the network. As
another example, a mobile device may be expected to operate in an
environment with low link quality. Devices that support Machine
Type Communication (MTC), for instance, may exchange small
quantities of data at an infrequent rate in such low link
conditions.
[0004] In any case, connection or reconnection to the network may
be challenging in these and other scenarios. Accordingly, methods
and techniques for connection or reconnection to the network are
needed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a functional diagram of a 3GPP network in
accordance with some embodiments;
[0006] FIG. 2 is a block diagram of a User Equipment (UE) in
accordance with some embodiments;
[0007] FIG. 3 is a block diagram of an Evolved Node-B (eNB) in
accordance with some embodiments;
[0008] FIG. 4 is an example of a scenario in which UEs operating in
a network may experience reduced coverage from an eNB in accordance
with some embodiments;
[0009] FIG. 5 illustrates the operation of a method of
communicating on a random access channel (RACH) in accordance with
some embodiments;
[0010] FIG. 6 illustrates the operation of another method of
communicating on a RACH in accordance with some embodiments;
[0011] FIG. 7 illustrates examples of MAC random access responses
(RARs) in accordance with some embodiments;
[0012] FIG. 8 illustrates a method for connection or reconnection
in accordance with some embodiments; and
[0013] FIG. 9 illustrates an example of a table of repetition
levels in accordance with some embodiments.
DETAILED DESCRIPTION
[0014] The following description and the drawings sufficiently
illustrate specific embodiments to enable those skilled in the art
to practice them. Other embodiments may incorporate structural,
logical, electrical, process, and other changes. Portions and
features of some embodiments may be included in, or substituted
for, those of other embodiments. Embodiments set forth in the
claims encompass all available equivalents of those claims
[0015] FIG. 1 shows a portion of an end-to-end network architecture
of an LTE network with various components of the network in
accordance with some embodiments. The network 100 comprises a radio
access network (RAN) (e.g., as depicted, the E-UTRAN or evolved
universal terrestrial radio access network) 100 and the core
network 120 (e.g., shown as an evolved packet core (EPC)) coupled
together through an S1 interface 115. For convenience and brevity
sake, only a portion of the core network 120, as well as the RAN
100, is shown.
[0016] The core network 120 includes mobility management entity
(MME) 122, serving gateway (serving GW) 124, and packet data
network gateway (PDN GW) 126. The RAN 100 includes Evolved Node-B's
(eNBs) 104 (which may operate as base stations) for communicating
with User Equipment (UE) 102. The eNBs 104 may include macro eNBs
and low power (LP) eNBs.
[0017] The MME is similar in function to the control plane of
legacy Serving GPRS Support Nodes (SGSN). The MME manages mobility
aspects in access such as gateway selection and tracking area list
management. The serving GW 124 terminates the interface toward the
RAN 100, and routes data packets between the RAN 100 and the core
network 120. In addition, it may be a local mobility anchor point
for inter-eNB handovers and also may provide an anchor for
inter-3GPP mobility. Other responsibilities may include lawful
intercept, charging, and some policy enforcement. The serving GW
124 and the MME 122 may be implemented in one physical node or
separate physical nodes. The PDN GW 126 terminates an SGi interface
toward the packet data network (PDN). The PDN GW 126 routes data
packets between the EPC 120 and the external PDN, and may be a key
node for policy enforcement and charging data collection. It may
also provide an anchor point for mobility with non-LTE accesses.
The external PDN can be any kind of IP network, as well as an IP
Multimedia Subsystem (IMS) domain. The PDN GW 126 and the serving
GW 124 may be implemented in one physical node or separated
physical nodes.
[0018] The eNBs 104 (macro and micro) terminate the air interface
protocol and may be the first point of contact for a UE 102. In
some embodiments, an eNB 104 may fulfill various logical functions
for the RAN 100 including but not limited to RNC (radio network
controller functions) such as radio bearer management, uplink and
downlink dynamic radio resource management and data packet
scheduling, and mobility management. In accordance with
embodiments, UEs 102 may be configured to communicate OFDM
communication signals with an eNB 104 over a multicarrier
communication channel in accordance with an OFDMA communication
technique. The OFDM signals may comprise a plurality of orthogonal
subcarriers.
[0019] In accordance with some embodiments, a UE 102 may transmit,
for reception at an eNB 104, a physical random access channel
(PRACH) preamble according to an uplink access repetition number.
The UE 102 may also receive, from the eNB 104, a random access
response (RAR) message according to a downlink repetition number.
These embodiments are described in more detail below.
[0020] The S1 interface 115 is the interface that separates the RAN
100 and the EPC 120. It is split into two parts: the S1-U, which
carries traffic data between the eNBs 104 and the serving GW 124,
and the S1-MME, which is a signaling interface between the eNBs 104
and the MME 122. The X2 interface is the interface between eNBs
104. The X2 interface comprises two parts, the X2-C and X2-U. The
X2-C is the control plane interface between the eNBs 104, while the
X2-U is the user plane interface between the eNBs 104.
[0021] With cellular networks, LP cells are typically used to
extend coverage to indoor areas where outdoor signals do not reach
well, or to add network capacity in areas with very dense phone
usage, such as train stations. As used herein, the term low power
(LP) eNB refers to any suitable relatively low power eNB for
implementing a narrower cell (narrower than a macro cell) such as a
femtocell, a picocell, or a micro cell. Femtocell eNBs are
typically provided by a mobile network operator to its residential
or enterprise customers. A femtocell is typically the size of a
residential gateway or smaller, and generally connects to the
user's broadband line. Once plugged in, the femtocell connects to
the mobile operator's mobile network and provides extra coverage in
a range of typically 30 to 50 meters for residential femtocells.
Thus, a LP eNB might be a femtocell eNB since it is coupled through
the PDN GW 126 Similarly, a picocell is a wireless communication
system typically covering a small area, such as in-building
(offices, shopping malls, train stations, etc.), or more recently
in-aircraft. A picocell eNB can generally connect through the X2
link to another eNB such as a macro eNB through its base station
controller (BSC) functionality. Thus, LP eNB may be implemented
with a picocell eNB since it is coupled to a macro eNB via an X2
interface. Picocell eNBs or other LP eNBs may incorporate some or
all functionality of a macro eNB. In some cases, this may be
referred to as an access point base station or enterprise
femtocell.
[0022] In some embodiments, a downlink resource grid may be used
for downlink transmissions from an eNB 104 to a UE 102, while
uplink transmission from the UE 102 to the eNB 104 may utilize
similar techniques. The grid may be a time-frequency grid, called a
resource grid or time-frequency resource grid, which is the
physical resource in the downlink in each slot. Such a
time-frequency plane representation is a common practice for OFDM
systems, which makes it intuitive for radio resource allocation.
Each column and each row of the resource grid correspond to one
OFDM symbol and one OFDM subcarrier, respectively. The duration of
the resource grid in the time domain corresponds to one slot in a
radio frame. The smallest time-frequency unit in a resource grid is
denoted as a resource element. Each resource grid comprises a
number of resource blocks, which describe the mapping of certain
physical channels to resource elements. Each resource block
comprises a collection of resource elements and in the frequency
domain, this represents the smallest quanta of resources that
currently can be allocated. There are several different physical
downlink channels that are conveyed using such resource blocks.
With particular relevance to this disclosure, two of these physical
downlink channels are the physical downlink shared channel and the
physical down link control channel.
[0023] The physical downlink shared channel (PDSCH) carries user
data and higher-layer signaling to a UE 102 (FIG. 1). The physical
downlink control channel (PDCCH) carries information about the
transport format and resource allocations related to the PDSCH
channel, among other things. It also informs the UE 102 about the
transport format, resource allocation, and H-ARQ information
related to the uplink shared channel. Typically, downlink
scheduling (assigning control and shared channel resource blocks to
UEs 102 within a cell) is performed at the eNB 104 based on channel
quality information fed back from the UEs 102 to the eNB 104, and
then the downlink resource assignment information is sent to a UE
102 on the control channel (PDCCH) used for (assigned to) the UE
102.
[0024] The PDCCH uses CCEs (control channel elements) to convey the
control information. Before being mapped to resource elements, the
PDCCH complex-valued symbols are first organized into quadruplets,
which are then permuted using a sub-block inter-leaver for rate
matching. Each PDCCH is transmitted using one or more of these
control channel elements (CCEs), where each CCE corresponds to nine
sets of four physical resource elements known as resource element
groups (REGs). Four QPSK symbols are mapped to each REG. The PDCCH
can be transmitted using one or more CCEs, depending on the size of
DCI and the channel condition. There may be four or more different
PDCCH formats defined in LTE with different numbers of CCEs (e.g.,
aggregation level, L=1, 2, 4, or 8).
[0025] FIG. 2 shows a block diagram of a UE 200 in accordance with
some embodiments, while FIG. 3 shows a block diagram of an eNB 300
in accordance with some embodiments. It should be noted that in
some embodiments, the eNB 300 may be a stationary non-mobile
device. The UE 200 may be a UE 102 as depicted in FIG. 1, while the
eNB 300 may be an eNB 104 as depicted in FIG. 1. The UE 200 may
include physical layer circuitry 202 for transmitting and receiving
signals to and from the eNB 300, other eNBs, other UEs or other
devices using one or more antennas 201, while the eNB 300 may
include physical layer circuitry 302 for transmitting and receiving
signals to and from the UE 200, other eNBs, other UEs or other
devices using one or more antennas 301. The UE 200 may also include
medium access control layer (MAC) circuitry 204 for controlling
access to the wireless medium, while the eNB 300 may also include
medium access control layer (MAC) circuitry 304 for controlling
access to the wireless medium. The UE 200 may also include
processing circuitry 206 and memory 208 arranged to perform the
operations described herein, and the eNB 300 may also include
processing circuitry 306 and memory 308 arranged to perform the
operations described herein.
[0026] In some embodiments, mobile devices or other devices
described herein may be part of a portable wireless communication
device, such as a personal digital assistant (PDA), a laptop or
portable computer with wireless communication capability, a web
tablet, a wireless telephone, a smartphone, a wireless headset, a
pager, an instant messaging device, a digital camera, an access
point, a television, a medical device (e.g., a heart rate monitor,
a blood pressure monitor, etc.), or other device that may receive
and/or transmit information wirelessly. In some embodiments, the
mobile device or other device can be the UE 200 or the eNB 300
configured to operate in accordance with 3GPP standards. In some
embodiments, the mobile device or other device may be configured to
operate according to other protocols or standards, including IEEE
802.11 or other IEEE standards. In some embodiments, the mobile
device or other device may include one or more of a keyboard, a
display, a non-volatile memory port, multiple antennas, a graphics
processor, an application processor, speakers, and other mobile
device elements. The display may be an LCD screen including a touch
screen.
[0027] The antennas 201, 301 may comprise one or more directional
or omnidirectional antennas, including, for example, dipole
antennas, monopole antennas, patch antennas, loop antennas,
microstrip antennas or other types of antennas suitable for
transmission of RF signals. In some multiple-input multiple-output
(MIMO) embodiments, the antennas 201, 301 may be effectively
separated to take advantage of spatial diversity and the different
channel characteristics that may result.
[0028] Although the UE 200 and eNB 300 are each illustrated as
having several separate functional elements, one or more of the
functional elements may be combined and may be implemented by
combinations of software-configured elements, such as processing
elements including digital signal processors (DSPs), and/or other
hardware elements. For example, some elements may comprise one or
more microprocessors, DSPs, field-programmable gate arrays (FPGAs),
application specific integrated circuits (ASICs), radio-frequency
integrated circuits (RFICs) and combinations of various hardware
and logic circuitry for performing at least the functions described
herein. In some embodiments, the functional elements may refer to
one or more processes operating on one or more processing
elements.
[0029] Embodiments may be implemented in one or a combination of
hardware, firmware and software. Embodiments may also be
implemented as instructions stored on a computer-readable storage
device, which may be read and executed by at least one processor to
perform the operations described herein. A computer-readable
storage device may include any non-transitory mechanism for storing
information in a form readable by a machine (e.g., a computer). For
example, a computer-readable storage device may include read-only
memory (ROM), random-access memory (RAM), magnetic disk storage
media, optical storage media, flash-memory devices, and other
storage devices and media. Some embodiments may include one or more
processors and may be configured with instructions stored on a
computer-readable storage device.
[0030] In accordance with embodiments, the UE 102 may determine a
coverage enhancement (CE) category for the UE 102 based at least
partly on downlink channel statistics related to reception of one
or more downlink signals from the eNB 104. The CE category may
reflect one of a level of additional link margin and a level of
system resources for performance at or above a performance
threshold. The UE 102 may also transmit, in physical random access
channel (PRACH) frequency resources, a PRACH preamble according to
an uplink access repetition number. The PRACH frequency resources
and the uplink access repetition number may be based at least
partly on the CE category for the UE 102. These embodiments are
described in more detail below.
[0031] In some scenarios, the UE 102 operating in a cellular
communication network (such as 100) may lose connectivity to the
network or may have difficulty in remaining connected to the
network for various reasons. As an example, the UE 102 may move
toward an area with reduced coverage, such as the edge of a sector
or cell. As another example, the UE 102 may operate in an area that
is essentially out of the normal coverage of the network, such as
in a basement of a building. As another example, the UE 102 or
other device may support Machine Type Communication (MTC). MTC
devices or devices operating in an MTC mode may be expected to
operate in highly challenging link budget scenarios while
exchanging small quantities of data at an infrequent rate.
[0032] Referring to FIG. 4, an example of a connection scenario 400
is shown, in which a tower eNB 405 (which can be the eNB 104) and
three UEs 410, 415, 420 (which can be the UE 102) located at
various distances from the eNB 405 are operating, or attempting to
operate, as part of a 3GPP or other network. It should be noted
that the eNB 405 is not limited to the tower configuration and that
scenarios described herein are not limited to the number or
distribution of eNBs 405 or UEs 410, 415, 420 as shown in FIG. 4.
The first UE 410 is in communication with the eNB 405 over the link
430, and is comfortably located within the coverage area 450 of the
eNB 405. As such, it is expected that the first UE 410 may not be
involved in a reconnection procedure. The second UE 415 is located
outside of the coverage area 450 in a demarcated zone 460, and may
be attempting a reconnection procedure over the link 435 (note the
link may not actually be established or stable yet). Similarly, the
third UE 420 is also located outside of the coverage area 450 in
another demarcated zone 470 that is further away from the eNB 405
than the first demarcated zone 460. The third UE 420 may also be
attempting a reconnection procedure over the link 440 (which may
not actually be established or stable yet).
[0033] The second UE 415 and third UE 420 may be described as
needing "coverage enhancement," or operating in "coverage
enhancement mode," as they are out of the coverage area 450.
Additionally, while both UEs 415, 420 are outside of the coverage
area 450, the third UE 420 may have more trouble or challenges in
reconnecting than would the second UE 415, as the third UE 420 is
further away from the eNB 405. Accordingly, it may be possible to
formulate different categories of coverage enhancement for UEs
depending on how far out of coverage they are located or other
factors. In some embodiments, descriptions may be used in the
categories. For instance, the third UE 420 may be considered in a
"high" category of coverage enhancement mode while the second UE
415 may be considered in a "low" category of coverage enhancement
mode. In some embodiments, the categories may be numerical, such as
5 dB, 10 dB, and 15 dB, which may represent an additional amount of
link budget that may be added to the UEs 415, 420 in order to
realize a "normal operation." The normal operation may be
characterized by any suitable criteria such as a target packet
error rate, acquisition time, data throughput or the like.
[0034] It should be pointed out that the above discussion focuses
on path loss due to distance only, for purposes of illustration,
but this is not limiting. It is known in the art that path loss,
signal loss, coverage holes or the like may result from effects
other than distance, such as obstacles or indoor location. For
instance, a device located in a basement of a building close to the
eNB 405 may actually be in need of a coverage enhancement while
another device located much further away, but outdoors, may have a
stronger connection to the eNB 405 and may be in need of less or no
coverage enhancement.
[0035] Referring to FIG. 5, a method 500 of operating in accordance
with a coverage enhancement mode is shown. It is important to note
that embodiments of the method 500 may include additional or even
fewer operations or processes in comparison to what is illustrated
in FIG. 5. In addition, embodiments of the method 500 are not
necessarily limited to the chronological order that is shown in
FIG. 5. In describing the method 500, reference may be made to
FIGS. 1-4 and 6-9, although it is understood that the method 500
may be practiced with any other suitable systems, interfaces and
components. For example, reference may be made to the scenario 400
in FIG. 4 described earlier for illustrative purposes, but the
techniques and operations of the method 500 are not so limited.
[0036] In addition, while the method 500 and other methods
described herein may refer to eNBs 104 or UEs 102 operating in
accordance with 3GPP or other standards, embodiments of those
methods are not limited to just those eNBs 104 or UEs 102 and may
also be practiced on other mobile devices, such as a Wi-Fi access
point (AP) or user station (STA). Moreover, the method 500 and
other methods described herein may be practiced by wireless devices
configured to operate in other suitable types of wireless
communication systems, including systems configured to operate
according to various IEEE standards such as IEEE 802.11. In
addition the method 500 and other methods described herein may be
practiced by UEs or other devices that support or are configured to
support Machine Type Communication (MTC) operation.
[0037] At operation 505 of the method 500, a coverage enhancement
(CE) category may be determined for the UE 102. The CE category for
the UE 102 may reflect one of a level of additional link margin and
a level of system resources for performance at or above a
performance threshold associated with a normal operating mode for
the UE 102. In some embodiments, the CE category may be determined
from a group of candidate CE categories. As an example, the
candidate CE categories may include 5, 10 or 15 dB, which may refer
to a link budget addition that may enable a level of performance
for the UE 102 in terms of error rate, throughput or other
performance measure. An additional CE category may include "no CE"
or similar, which may reflect that the UE 102 is not operating in a
CE mode. In addition, previously described examples related to CE
categories may also be used, such as "high" and "low."
[0038] The determination of the CE category may be based at least
partly on downlink channel statistics related to reception of one
or more downlink signals at the UE from an Evolved Node-B (eNB). In
some embodiments, the downlink channel statistics may include
reference signal received power (RSRP) or other path loss
measurements at the UE. As an example, a determined path loss at
the UE 102 may be compared with a predetermined link budget path
loss to determine the CE category for the UE 102. The predetermined
link budget path loss may indicate a maximum path loss for "normal"
operation in terms of packet error rate or other measure. The
statistics may be based on or collected over any suitable time
period, which may be on the order of symbol periods, sub-frames,
seconds, minutes or longer. The measurements may include averages,
moving averages, weighted averages or other suitable statistics,
and may refer to scalar or logarithmic (dB) quantities.
[0039] At operation 510, a PRACH preamble may be transmitted in
PRACH frequency resources according to an uplink access repetition
number. The PRACH frequency resources may be based at least partly
on the CE category for the UE 102. In some embodiments, the group
of candidate CE categories may include a first and a second
candidate CE category for which PRACH frequency resources for the
first CE category are exclusive to PRACH frequency resources for
the second CE category. In addition, the group of candidate CE
categories may include more than the first and second candidate CE
categories, and some or all of the candidate CE categories may be
associated with different PRACH frequency resources that may be
exclusive to each other. Accordingly, the frequency resources used
for the transmission of the PRACH preamble may indicate or reflect
the determined CE category for the UE 102. Mappings or assignments
of PRACH frequency resources to candidate CE categories may be
predetermined, may be part of 3GPP or other standards or may be
determined by the network. In addition, the PRACH frequency
resources used by the UE 102 when operating in the CE mode may be
disjoint from PRACH frequency resources used by UEs not operating
in the CE mode.
[0040] In some embodiments, a random access radio network temporary
identifier (RA-RNTI) computed for the PRACH preamble transmission
may depend on whether or not the UE 102 is in the CE mode. As an
example, the RA-RNTI may be computed as (1+t_id+10*f id+c*MTC_id),
in which t_id is the index of the first sub-frame of the specified
PRACH preamble, f_id is the index of the specified PRACH preamble
within that sub-frame, the value of "c" may be 60, and the MTC_id
is 0 or 1 when the UE 102 is not, or is, in the CE mode.
[0041] The uplink access repetition number may be based at least
partly on the CE category for the UE 102. In some embodiments, the
group of candidate CE categories may include a first and a second
candidate CE category for which an uplink access repetition number
for the first CE category is different from an uplink access
repetition number for the second CE category. The uplink access
repetition number may refer to a number of repetitions of the PRACH
preamble to be transmitted by the UE 102. In addition, the group of
candidate CE categories may include more than the first and second
candidate CE categories, and some or all of the candidate CE
categories may be associated with uplink access repetition numbers
that may be different. In some embodiments, an uplink access
repetition number (or other repetition numbers or levels described
herein) for a CE category considered "high" may be larger than an
uplink access repetition number for a CE category considered "low."
For instance, the UE 102 may repeat the PRACH preamble 100 times
when operating in the CE category of 15 dB and may repeat the PRACH
preamble only 20 times when operating in the CE category of 5 dB.
Accordingly, the larger number of repetitions may provide
additional diversity or energy gain for the UE 102 when it operates
in a higher CE category. The number of repetitions for the
candidate CE categories may be pre-determined through simulation or
analysis or other techniques. In some embodiments, the repetitions
of the PRACH preamble may be transmitted during different time
periods.
[0042] At operation 515 of the method 500, a Random Access Response
(RAR) may be received from the eNB 104 according to a downlink
repetition number. As previously described, the PRACH frequency
resources used by the UE 102 may indicate the determined CE
category for the UE 102, which may be ascertained by the eNB 104
using knowledge of the previously described mappings and
assignments between PRACH frequency resources and CE categories.
The downlink repetition number may refer to a number of repetitions
of the RAR to be transmitted by the eNB 104, and the number of
repetitions for some or all of the candidate CE categories may be
different. Accordingly, the downlink repetition number may be based
at least partly on the CE category for the UE 102, and may be
pre-determined through simulation or analysis or other
techniques.
[0043] In some embodiments, the downlink repetition number may be
included in a PDCCH. A new downlink control information (DCI)
format, or an existing DCI format such as "1A" or other in 3GPP
standards, may include the downlink repetition number or an
indicator of it. As an example, the downlink repetition number may
include a bit field of two bits corresponding to "no repetition"
and repetition levels of 0, 1, and 2, in which the number of
repetitions associated with each repetition level may be
pre-defined or signaled in other messages. As another example, the
downlink repetition number may be a single bit corresponding to "no
repetition" or repetition according to a pre-defined or previously
signaled repetition number. As another example, the downlink
repetition number may be a bit field that explicitly states a
number of repetitions to be used. Embodiments are not limited to
the number of bits or levels described in the above examples,
however, as the downlink repetition number may describe or specify
the amount of repetition in any suitable manner. In some
embodiments, the downlink repetition number may refer to a "PDSCH
repetition level" as will be described later.
[0044] In some embodiments, the RAR may be received on PDSCH
frequency resources that are based at least partly on the CE
category for the UE 102. In addition, the PDSCH frequency resources
for the RAR may be disjoint from PDSCH frequency resources used for
RARs or other messages for UEs not operating in the CE mode. In
some embodiments, a pre-defined frequency allocation for the PDSCH
may be determined Accordingly, the PDCCH may not need to be decoded
at the UE 102, which may be beneficial due to the fact that a large
number of repetitions of the PDCCH may have to be used when the UE
102 operates in the CE mode. That is, the UE 102 may refrain from
decoding the PDCCH as part of the reception of the RAR. Such an
arrangement may be considered "PDCCH-less" operation.
[0045] In some embodiments, dedicated PDSCH frequency resources may
be pre-defined and configured appropriately for coverage-limited
MTC UEs. In addition, knowledge of a fixed timing relationship
between PRACH transmission and RAR reception may be used at the UE
102. Knowledge of a transport format for PDSCH transmission may
also be used at the UE 102. In some embodiments, a control message,
such as an SIB-2 or other System Information Block (SIB) message,
may include information such as the timing relationship or
transport format just described. The control message may be
transmitted to the UE 102 by the eNB 104, either as a dedicated or
broadcast message. In addition, information such as the timing
relationship or transport format just described may also be
pre-defined in some embodiments.
[0046] At operation 520, an uplink control message may be
transmitted on PUSCH resources according to an uplink control
repetition number. The transmission may be in response to the
reception of the RAR at the UE 102. In some embodiments, the uplink
control message may be an "L2/L3" message or may include or be
included in one or more L2/L3 messages.
[0047] The uplink control repetition number may refer to a number
of repetitions of the uplink control message to be transmitted by
the UE 102, and the number of repetitions for some or all of the
candidate CE categories may be different. In some embodiments, the
uplink control repetition number may be based at least partly on
the CE category for the UE 102, and may be pre-determined through
simulation or analysis or other techniques. In some embodiments,
the uplink control repetition number may be included in the RAR
message received at the UE 102 at operation 515. In some
embodiments, the uplink control repetition number may be included
in RAR content of the RAR message or may be included in an uplink
grant included in the RAR message, as will be described in more
detail regarding the method 600 and FIG. 7. In addition, the uplink
control repetition number may be a "PUSCH repetition level" that
refers to a repetition number to be used for PUSCH
transmission.
[0048] The uplink control message may be transmitted on PUSCH
frequency resources that are based at least partly on the CE
category for the UE 102. In addition, the PUSCH frequency resources
for the uplink control message may be disjoint from PUSCH frequency
resources used for uplink control or other messages for UEs not
operating in the CE mode.
[0049] In some embodiments, the uplink control message may include
a second CE category for the UE 102, which may be determined at the
UE 102 based at least partly on the reception of the RAR at
operation 515. For instance, based on a signal quality, signal
level or other measurement for the reception of the RAR, the UE 102
may select a second CE category for the UE 102. The second category
may be selected from a second group of candidate CE categories that
may or may not be different from the group of candidate CE
categories used in other operations such as 505-520. For instance,
the second group of candidate CE categories may cover a larger
range or provide finer granularity. Accordingly, the second CE
category may be a new or refined value that may provide more
information to the eNB 104 about coverage enhancement for the UE
102.
[0050] At operation 525, a contention resolution message may be
received from the eNB according to the downlink repetition number.
In some embodiments, the downlink repetition numbers for operations
515 and 525 may be the same. However, this arrangement is not
limiting, and the two numbers may be different in some embodiments.
As previously described, the downlink repetition number used at
operation 525 may refer to a number of repetitions of the
contention resolution message transmitted by the eNB 104, and the
number of repetitions for some or all of the candidate CE
categories may be different. In some embodiments, the downlink
repetition number used at operation 525 may be based at least
partly on the CE category for the UE 102, and may be pre-determined
through simulation or analysis or other techniques.
[0051] Referring to FIG. 6, a method 600 of operating in a coverage
enhancement mode is shown. As mentioned previously regarding the
method 500, embodiments of the method 600 may include additional or
even fewer operations or processes in comparison to what is
illustrated in FIG. 6 and embodiments of the method 600 are not
necessarily limited to the chronological order that is shown in
FIG. 6. In describing the method 600, reference may be made to
FIGS. 1-5 and 7-9, although it is understood that the method 600
may be practiced with any other suitable systems, interfaces and
components. For example, reference may be made to the scenario 400
in FIG. 4 described earlier for illustrative purposes, but the
techniques and operations of the method 600 are not so limited. In
addition, embodiments of the method 600 may refer to eNBs 104, UEs
102, APs, STAs or other wireless or mobile devices.
[0052] It should be noted that the method 600 may be practiced at
the eNB 104, and may include exchanging of signals or messages with
the UE 102. Similarly, the method 500 may be practiced at the UE
102, and may include exchanging of signals or messages with the eNB
104. In some cases, operations and techniques described as part of
the method 500 may be relevant to the method 600. For instance, an
operation of the method 500 may include transmission of a message
by the UE 102 while an operation of the method 600 may include
reception of the same message at the eNB 104.
[0053] At operation 605 of the method 600, a PRACH preamble may be
received at the eNB 104 from the UE 102 operating in a coverage
enhancement (CE) mode on PRACH frequency resources. The PRACH
preamble may be received according to an uplink access repetition
number, which may refer to a number of repetitions of the PRACH
preamble transmitted by the UE 102. In some embodiments, uplink
access repetition numbers may be based at least partly on a CE
category for the UE, which may be selected from a group of
candidate CE categories, as previously described. The uplink access
repetition numbers for the CE categories may be different and may
also be known at the eNB 104 for use in the reception of the PRACH
at operation 605.
[0054] At operation 610, a CE category may be determined for the UE
102 from a group of candidate CE categories, and the determination
may be based at least partly on the PRACH frequency resources used
for the PRACH preamble. As previously described, some or all of the
candidate CE categories may be associated with different PRACH
frequency resources that may be exclusive to each other. Mappings
or assignments of PRACH frequency resources to candidate CE
categories may be known at the eNB 104. Accordingly, the eNB 104
may determine the CE category for the UE 102 based on which PRACH
frequency resources are used. In some embodiments, the PRACH
frequency resources used by the UE 102 when operating in the CE
mode may be disjoint from PRACH frequency resources used by UEs not
operating in the CE mode.
[0055] At operation 615, a Random Access Response (RAR) may be
transmitted according to a downlink repetition number, which may be
based at least partly on the CE category for the UE 102. In some
embodiments, PDSCH frequency resources that are based at least
partly on the CE category for the UE 102 may be used for
transmission of the RAR, and the PDSCH frequency resources may be
disjoint from second PDSCH frequency resources for UEs not
operating in a CE mode. In some embodiments, the RAR message may be
transmitted in response to the reception of the PRACH preamble at
operation 605.
[0056] A physical downlink control channel (PDCCH) data block that
includes PDSCH resource allocations for UEs not operating in the CE
mode may be transmitted. In addition, the eNB 104 may refrain from
transmission of PDCCH data blocks for UEs operating in the CE mode.
Accordingly, UEs operating in the CE mode may receive the RAR on
pre-determined PDSCH frequency resources. Such an arrangement may
be considered "PDCCH-less" operation, as the UEs operating in the
CE mode may receive the RAR (or other messages) on PDSCH resources
without decoding a PDCCH data block.
[0057] In addition, a control message may also be transmitted by
the eNB 104 for reception at the UE 102 that may include an
allocation for the PDSCH frequency resources. The control message
may also include other information, such as a modulation and coding
scheme (MCS) indicator for the RAR transmission. The MCS indicator
may be an index that refers to an MCS of a group of pre-determined
candidate MCSs, and each candidate MCS may refer to a modulation
type (such as BPSK, QPSK, QAM or other) and a forward error
correction (FEC) coding rate. A timing relationship between PRACH
transmission at the UE 102 and the RAR transmission may also be
included in the control message. In some embodiments, the timing
relationship may be fixed. In some embodiments, the control message
may be an SIB-2 or other System Information Block (SIB) message of
3GPP or other standards.
[0058] At operation 620, an uplink control message may be received
from the UE 102 on PUSCH resources according to an uplink control
repetition number. In some embodiments, the uplink control
repetition number may be based at least partly on the CE category
for the UE 102, and may also be predetermined In some embodiments,
the RAR transmitted at operation 615 (or another message from the
eNB 104) may include the uplink control repetition number for the
UE 102 to use. The value transmitted in the RAR may override or
replace, in some cases, a predetermined value for the uplink
control repetition number that the UE may otherwise use, such as a
value based on the CE category as described above.
[0059] PUSCH frequency resources that are at least partly based on
the CE category for the UE 102 may be used for reception of the
uplink control message at the eNB 104, and the PUSCH frequency
resources may be disjoint from second PUSCH frequency resources for
UEs not operating in a CE mode.
[0060] At operation 625, a contention resolution message may be
transmitted according to the downlink repetition number. As
previously described, the downlink repetition number may be based
at least partly on the CE category for the UE 102. In addition, the
downlink repetition number used at operation 625 may be the same as
the downlink repetition number used at operation 615, but is not
limited as such. In some embodiments, PDSCH frequency resources
that are at least partly based on the CE category for the UE 102
may be used for transmission of the contention resolution message.
The PDSCH frequency resources may or may not overlap the PDSCH
frequency resources used at operation 615 for transmission of the
RAR.
[0061] At operation 630 of the method 600, a second PRACH preamble
may be received from a second UE not operating in the CE mode. The
second PRACH preamble may be received on second PRACH frequency
resources allocated for UEs that are not operating in the CE mode.
In some embodiments, the second PRACH frequency resources may be
exclusive to the PRACH frequency resources allocated for UEs
operating in the CE mode. It should also be pointed out that UEs
not operating in the CE mode may include legacy UEs that do not
support coverage enhancement.
[0062] Referring to FIG. 7, examples of RAR messages, or MAC RAR
messages, are shown in accordance with some embodiments. The RAR
message 705 may include other parameters or information 710 that
may or may not be related to coverage enhancement or connection or
reconnection operations. The RAR message 705 may also include an
uplink grant 715, which may include a PUSCH repetition level 725
and other parameters or information 720 that may or may not be
related to coverage enhancement or connection or reconnection
operations. As will be explained below, the PUSCH repetition level
725 may be the same as or may play the same role as the uplink
control repetition level previously described in relation to
methods 500 and 600.
[0063] Another example RAR 755 may include other parameters or
information 760 that may or may not be related to coverage
enhancement or connection or reconnection operations. The RAR 755
may also include an uplink grant 765 and a PUSCH repetition level
770. Accordingly, the PUSCH repetition level 770 may be external to
the uplink grant 765, in contrast to the PUSCH repetition level 725
which may be included in the uplink grant 715.
[0064] In some embodiments, the PUSCH repetition level 725 may be
included as part of the RAR 705 transmitted by the eNB 104 at
operation 615, or may be included as part of the RAR 705 received
at the UE 102 at operation 515. In some embodiments, the PUSCH
repetition level 770 may be included as part of the RAR 755
transmitted by the eNB 104 at operation 615, or may be included as
part of the RAR 755 received at the UE 102 at operation 515. It
should be pointed out that the RARs 705, 755 serve to illustrate
the concept of an RAR, but are not limiting, and other suitable
arrangements for the RAR may be used.
[0065] Referring to FIG. 8, a signal flow diagram illustrates an
example of a method 800 for connection or reconnection between the
UE 102 and the eNB 104. It should be noted that some of the
operations of the method 800 may be similar to operations included
in the methods 500 or 600. In such cases, descriptions of such
operations in the methods 500 or 600 may be applicable to
corresponding operations included in the method 800. In addition,
the method 800 shown in FIG. 8 may serve to illustrate the concept
of a connection or reconnection procedure, but it is not limiting.
Fewer or additional operations may be included in other embodiments
of connection or reconnection methods, and the chronological order
of operations is not limited to that shown in FIG. 8.
[0066] At operation 805, a PRACH preamble may be transmitted from
the UE 102 to the eNB 104 according to an uplink access repetition
number. At operation 810, the eNB 104 may transmit a random access
response (RAR) to the UE 102 according to a downlink repetition
number. At operation 815, the UE 102 may adjust its uplink timing.
It should be noted that the UE 102 may perform operations 805
without timing synchronization with the eNB 104, and may acquire or
refine its timing during the reception of the RAR at operation 810.
At operation 820, the UE 102 may transmit an uplink control message
(such as an L2/L3 message) to the eNB 104 according to an uplink
control repetition number. At operation 825, the eNB 104 may
transmit a contention resolution message to the UE 102 according to
the same downlink repetition number used at operation 810.
[0067] As previously described, repetition numbers may quantify how
many repetitions of a message, such as the PRACH preamble or RAR,
may be transmitted, and may depend on the CE category of the UE
102. For instance, the uplink access repetition number may refer to
a number of repetitions of the PRACH preamble. For a connection or
reconnection procedure, messages exchanged between the UE 102 and
eNB 104 may be repeated according to predetermined values, which
may be determined through simulation or analysis. In some
embodiments, a table may include repetition values for different CE
categories, and may be used in operations described previously.
[0068] An example of such a table 900 is shown in FIG. 9. The
column 910 includes three CE categories 912, 914, 916, which
correspond to 5, 10, and 15 dB in this example. The row associated
with each of the three CE categories 912, 914, 916 may include
repetition values for use when the UE 102 operates in that
particular CE category. The values for the columns 920, 930, 940,
950 may correspond to PRACH repetition level 920, (E)PDCCH
repetition level 930, PDSCH repetition level 940, and PUSCH
repetition level 950. These labels on columns 920, 930, 940, 950
may be the same as or related to repetition values previously
described. As an example, the PRACH repetition level 920 may be the
same as or related to the uplink access repetition number. As
another example, the PDCCH repetition level 930 or the PDSCH
repetition level 940 may be the same as or related to the downlink
repetition number. As another example, the PUSCH repetition level
950 may be the same as or related to the uplink control repetition
number.
[0069] A User Equipment (UE) to operate in accordance with a
coverage enhancement (CE) mode is disclosed herein. The UE may
include hardware processing circuitry configured to determine, from
a group of candidate CE categories, a CE category for the UE based
at least partly on downlink channel statistics related to reception
of one or more downlink signals at the UE from an Evolved Node-B
(eNB). The hardware processing circuitry may be further configured
to transmit, in physical random access channel (PRACH) frequency
resources, a PRACH preamble according to an uplink access
repetition number. In some embodiments, the PRACH frequency
resources and the uplink access repetition number may be based at
least partly on the CE category for the UE. In some embodiments,
the CE category for the UE may reflect one of a level of additional
link margin and a level of system resources for performance at or
above a performance threshold associated with a normal operating
mode for the UE. In some embodiments, the downlink channel
statistics may include reference signal received power (RSRP) or
path loss measurements at the UE.
[0070] In some embodiments, the group of candidate CE categories
may include a first and a second candidate CE category for which an
uplink access repetition number for the first CE category is
different from an uplink access repetition number for the second CE
category. In some embodiments, the group of candidate CE categories
may include a first and a second candidate CE category for which
PRACH frequency resources for the first CE category are exclusive
to PRACH frequency resources for the second CE category.
[0071] The hardware processing circuitry may be further configured
to receive, from the eNB, a Random Access Response (RAR) according
to a downlink repetition number that is based at least partly on
the CE category for the UE. In some embodiments, the RAR may be
received on physical downlink shared channel (PDSCH) frequency
resources that may be based at least partly on the CE category for
the UE and the PDSCH frequency resources may be disjoint from
second PDSCH frequency resources for UEs not operating in the CE
mode. The hardware processing circuitry may be further configured
to receive, from the eNB, a physical downlink control channel
(PDCCH) data block on PDCCH frequency resources for UEs operating
in the CE mode. In some embodiments, the PDCCH data block may
include a downlink control information (DCI) block that includes
the downlink repetition number. The hardware processing circuitry
may be further configured to refrain from decoding physical
downlink control channel (PDCCH) data blocks as part of the
reception of the RAR.
[0072] The hardware processing circuitry may be further configured
to transmit, in response to the reception of the RAR, an uplink
control message on physical uplink shared channel (PUSCH) resources
according to an uplink control repetition number. In some
embodiments, the RAR may include the uplink control repetition
number. In some embodiments, the RAR may include an uplink grant
for the UE and the uplink grant may include the uplink control
repetition number. In some embodiments, the uplink control message
may include a second CE category for the UE, the second CE category
may be selected from a second group of candidate CE categories, and
the second CE category may be determined at least partly from the
reception of the RAR. The hardware processing circuitry may be
further configured to receive, from the eNB, a contention
resolution message according to the downlink repetition number. In
some embodiments, the UE may further support Machine Type
Communication (MTC). In some embodiments, the UE may operate
according to a 3GPP protocol.
[0073] A non-transitory computer-readable storage medium that
stores instructions for execution by one or more processors to
perform operations for communication by a User Equipment (UE) in a
coverage enhancement mode is disclosed herein. The operations may
configure the one or more processors to determine, from a group of
candidate CE categories, a CE category for the UE based at least
partly on downlink channel statistics related to reception of one
or more downlink signals at the UE from an Evolved Node-B (eNB) and
transmit, in physical random access channel (PRACH) frequency
resources, a PRACH preamble according to an uplink access
repetition number. In some embodiments, the PRACH frequency
resources and the uplink access repetition number may be based at
least partly on the CE category for the UE. The operations may
further configure the one or more processors to receive, from the
eNB, a Random Access Response (RAR) according to a downlink
repetition number that is based at least partly on the CE category
for the UE. The operations may further configure the one or more
processors to transmit, in response to the reception of the RAR, an
uplink control message on physical uplink shared channel (PUSCH)
resources according to an uplink control repetition number that is
based at least partly on the CE category for the UE.
[0074] A method for communicating in a coverage enhancement mode
performed by User Equipment (UE) is disclosed herein. The method
may include determining, from a group of candidate CE categories, a
CE category for the UE based at least partly on downlink channel
statistics related to reception of one or more downlink signals at
the UE from an Evolved Node-B (eNB). The method may further include
transmitting, in physical random access channel (PRACH) frequency
resources, a PRACH preamble according to an uplink access
repetition number. In some embodiments, the PRACH frequency
resources and the uplink access repetition number are based at
least partly on the CE category for the UE. The method may further
include receiving, from the eNB, a Random Access Response (RAR)
according to a downlink repetition number that is based at least
partly on the CE category for the UE. The method may further
include transmitting, in response to the reception of the RAR, an
uplink control message on physical uplink shared channel (PUSCH)
resources according to an uplink control repetition number that is
based at least partly on the CE category for the UE.
[0075] An Evolved Node-B (eNB) to operate in accordance with a
coverage enhancement (CE) mode is disclosed herein. The eNB may
include hardware processing circuitry configured to receive, from a
User Equipment (UE) operating in the CE mode, a physical random
access channel (PRACH) preamble on PRACH frequency resources
allocated for UEs operating in the CE mode. The hardware processing
circuitry may be further configured to determine, based at least
partly on the PRACH frequency resources used for the reception of
the PRACH preamble, a CE category for the UE from a group of
candidate CE categories and transmit a Random Access Response (RAR)
according to a downlink repetition number that is based at least
partly on the CE category for the UE. In some embodiments, the
group of candidate CE categories may include a first and a second
candidate CE category for which PRACH frequency resources for the
first and second CE categories are exclusive. In some embodiments,
the RAR may be transmitted on physical downlink shared channel
(PDSCH) frequency resources that are based at least partly on the
CE category for the UE and the PDSCH frequency resources may be
disjoint from second PDSCH frequency resources for UEs not
operating in a CE mode.
[0076] The hardware processing circuitry may be further configured
to transmit a physical downlink control channel (PDCCH) data block
that includes PDSCH resource allocations for UEs not operating in
the CE mode and to refrain from transmission of PDCCH data blocks
for UEs operating in the CE mode. The hardware processing circuitry
may be further configured to transmit a control message that
includes an allocation for the PDSCH frequency resources, a
modulation and coding scheme (MCS) indicator for the RAR
transmission, and a timing relationship between PRACH transmission
at the UE and the RAR transmission.
[0077] The hardware processing circuitry may be further configured
to receive, from the UE, an uplink control message on physical
uplink shared channel (PUSCH) resources according to an uplink
control repetition number. In some embodiments, the uplink control
repetition number may be based at least partly on the CE category
for the UE. In some embodiments, the RAR may include the uplink
control repetition number. The hardware processing circuitry may be
further configured to transmit, in response to the reception of the
uplink control message, a contention resolution message according
to the downlink repetition number. The hardware processing
circuitry may be further configured to receive, from a second UE
not operating in the CE mode, a second PRACH preamble on second
PRACH frequency resources allocated for UEs that are not operating
in the CE mode. In some embodiments, the second PRACH frequency
resources may be exclusive to the PRACH frequency resources
allocated for UEs operating in the CE mode. In some embodiments,
the eNB may operate according to a 3GPP protocol.
[0078] The Abstract is provided to comply with 37 C.F.R. Section
1.72(b) requiring an abstract that will allow the reader to
ascertain the nature and gist of the technical disclosure. It is
submitted with the understanding that it will not be used to limit
or interpret the scope or meaning of the claims The following
claims are hereby incorporated into the detailed description, with
each claim standing on its own as a separate embodiment.
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