U.S. patent application number 17/672815 was filed with the patent office on 2022-06-02 for method and mobile terminal for performing random access.
The applicant listed for this patent is Optis Cellular Technology, LLC. Invention is credited to Sung-Duck CHUN, Young-Dae LEE, Sung-Jun PARK, Seung-June YI.
Application Number | 20220174595 17/672815 |
Document ID | / |
Family ID | |
Filed Date | 2022-06-02 |
United States Patent
Application |
20220174595 |
Kind Code |
A1 |
YI; Seung-June ; et
al. |
June 2, 2022 |
METHOD AND MOBILE TERMINAL FOR PERFORMING RANDOM ACCESS
Abstract
A mobile terminal performs a random access procedure with a
network that includes transmitting to the network a random access
preamble directly allocated to the mobile terminal by the network
and receiving a random access response from the network in response
to transmission of the random access preamble. The terminal
performs a discontinuous reception (DRX) operation that controls
how the mobile terminal monitors a physical downlink control
channel (PDCCH). The DRX operation employs an active time in which
the mobile terminal monitors the PDCCH, and the active time
includes a time while: (i) an on-duration timer or a DRX Inactivity
timer or a DRX retransmission timer or a contention resolution
timer is operating, (ii) a scheduling request procedure is pending,
(iii) an uplink grant for a retransmission can occur, or (iv) the
PDCCH indicating a new transmission addressed to a Cell-Radio
Network Temporary Identifier (C-RNTI) of the mobile terminal has
not yet been received after successful reception of the random
access response.
Inventors: |
YI; Seung-June; (Anyang-si,
KR) ; PARK; Sung-Jun; (Anyang-si, KR) ; LEE;
Young-Dae; (Anyang-si, KR) ; CHUN; Sung-Duck;
(Anyang-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Optis Cellular Technology, LLC |
Plano |
TX |
US |
|
|
Appl. No.: |
17/672815 |
Filed: |
February 16, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16924294 |
Jul 9, 2020 |
11272449 |
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17672815 |
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16427421 |
May 31, 2019 |
10757650 |
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16924294 |
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15724287 |
Oct 4, 2017 |
10349348 |
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16427421 |
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15231861 |
Aug 9, 2016 |
9807688 |
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15724287 |
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14591399 |
Jan 7, 2015 |
9432937 |
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15231861 |
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13894948 |
May 15, 2013 |
8934391 |
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14591399 |
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13071280 |
Mar 24, 2011 |
8467343 |
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13894948 |
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12457653 |
Jun 17, 2009 |
7933243 |
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13071280 |
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61073743 |
Jun 18, 2008 |
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61074998 |
Jun 23, 2008 |
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International
Class: |
H04W 52/02 20060101
H04W052/02; H04W 24/08 20060101 H04W024/08; H04W 72/04 20060101
H04W072/04; H04W 74/00 20060101 H04W074/00; H04W 74/08 20060101
H04W074/08; H04W 72/10 20060101 H04W072/10; H04L 5/00 20060101
H04L005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 2, 2009 |
KR |
10-2009-0048775 |
Claims
1. A mobile terminal configured to perform a random access
procedure with a network, comprising: a transmitter to transmit to
the network a random access preamble directly allocated to the
mobile terminal by the network; and a receiver to receive a random
access response from the network in response to transmission of the
random access preamble; processing circuitry in communication with
the transmitter and the receiver, the processing circuitry being
configured to perform a discontinuous reception (DRX) operation
that controls how the mobile terminal monitors a physical downlink
control channel (PDCCH), wherein the DRX operation employs an
active time in which the mobile terminal monitors the PDCCH, and
wherein the active time includes a time while: (i) an on-duration
timer or a DRX Inactivity timer or a DRX retransmission timer or a
contention resolution timer is operating, (ii) a scheduling request
procedure is pending, (iii) an uplink grant for a retransmission
can occur, or (iv) the PDCCH indicating a new transmission
addressed to a Cell-Radio Network Temporary Identifier (C-RNTI) of
the mobile terminal has not yet been received after successful
reception of the random access response.
2. The mobile terminal in claim 1, wherein for a configured DRX
cycle, the processing circuitry is configured to start the
on-duration timer when the PDCCH is monitored by the mobile
terminal.
3. The mobile terminal in claim 1, wherein for a configured DRX
cycle for a sub-frame of the PDCCH monitored by the mobile
terminal, the processing circuitry is configured, in response to
determining that an Hybrid Automatic Repeat Request (HARD) round
trip time (RTT) timer expires in the sub-frame and data associated
with the sub-frame was not successfully decoded, start the DRX
retransmission timer.
4. The mobile terminal in claim 3, wherein during the active time
for the sub-frame of the PDCCH monitored by the mobile terminal,
the processing circuitry is configured, in response to the PDCCH
indicating a new downlink transmission or a new uplink
transmission, to start or restart the DRX Inactivity Timer.
5. The mobile terminal in claim 1, wherein the random access
preamble is a dedicated preamble and is explicitly signaled from
the network.
6. The mobile terminal in claim 1, wherein the random access
preamble is part of a handover message.
7. The mobile terminal in claim 1, wherein the random access
response includes at least one of an uplink grant for uplink radio
resources, a C-RNTI, and a value for time synchronization
adjustment.
8. The mobile terminal in claim 1, wherein the mobile terminal is
configured to wake up from an power saving state at a start of the
DRX active time, and wherein the mobile terminal need not monitor
the PDCCH when the DRX active time expires.
9. The mobile terminal in claim 1, wherein the DRX active time
denotes a time from after receiving the random access response to a
time when an indication of radio resource allocation information
for an uplink data transmission is received.
10. The mobile terminal in claim 1, wherein the DRX active time
denotes a time from after receiving the random access response to a
time when scheduling information for an uplink data transmission is
received.
11. A method for a mobile terminal to perform a random access
procedure with a network comprising: transmitting to the network a
random access preamble directly allocated to the mobile terminal by
the network; receiving a random access response from the network in
response to transmission of the random access preamble; performing
a discontinuous reception (DRX) operation that controls how the
mobile terminal monitors a physical downlink control channel
(PDCCH), wherein the DRX operation employs an active time in which
the mobile terminal monitors the PDCCH, and wherein the active time
includes a time while: (i) an on-duration timer or a DRX Inactivity
timer or a DRX retransmission timer or a contention resolution
timer is operating, (ii) a scheduling request procedure is pending,
(iii) an uplink grant for a retransmission can occur, or (iv) the
PDCCH indicating a new transmission addressed to a Cell-Radio
Network Temporary Identifier (C-RNTI) of the mobile terminal has
not yet been received after successful reception of the random
access response.
12. The method in claim 11, wherein for a configured DRX cycle, the
method further comprises starting the on-duration timer when the
PDCCH is monitored by the mobile terminal.
13. The method in claim 11, wherein for a configured DRX cycle for
a sub-frame of the PDCCH monitored by the mobile terminal, the
method further comprises, in response to determining that an Hybrid
Automatic Repeat Request (HARD) round trip time (RTT) timer expires
in the sub-frame and data associated with the sub-frame was not
successfully decoded, start the DRX retransmission timer.
14. The method in claim 11, wherein during the active time for a
sub-frame of the PDCCH monitored by the mobile terminal, the method
further comprises, in response to the PDCCH indicating a new
downlink transmission or a new uplink transmission, starting or
restarting the DRX Inactivity Timer.
15. The method in claim 11, wherein the random access preamble is a
dedicated preamble and is explicitly signaled from the network.
16. The method in claim 11, wherein the random access preamble is
part of a handover message.
17. The method in claim 11, wherein the random access response
includes at least one of an uplink grant for uplink radio
resources, a C-RNTI, and a value for time synchronization
adjustment.
18. The method in claim 11, wherein the mobile terminal wakes up
from an power saving state at a start of the DRX active time, and
wherein the mobile terminal need not monitor the PDCCH when the DRX
active time expires.
19. The method in claim 11, wherein the DRX active time denotes a
time from after receiving the random access response to a time when
an indication of radio resource allocation information for an
uplink data transmission is received.
20. The method in claim 11, wherein the DRX active time denotes a
time from after receiving the random access response to a time when
scheduling information for an uplink data transmission is received.
Description
CROSS-REFERENCE(S) RELATED APPLICATION
[0001] This is a continuation of U.S. application Ser. No.
16/924,294, filed Jul. 9, 2020, which is a continuation of U.S.
application Ser. No. 16/427,421, filed May 31, 2019, now U.S. Pat.
No. 10,757,650, which is a continuation of U.S. application Ser.
No. 15/724,287, filed Oct. 4, 2017, now U.S. Pat. No. 10,349,348,
which is a continuation of U.S. application Ser. No. 15/231,861,
filed Aug. 9, 2016, now U.S. Pat. No. 9,807,688, which is a
continuation of U.S. application Ser. No. 14/591,399, filed Jan. 7,
2015, now U.S. Pat. No. 9,432,937, which is a continuation of, U.S.
application Ser. No. 13/894,948, filed May 15, 2013, now U.S. Pat.
No. 8,934,391, which is a continuation of U.S. application Ser. No.
13/071,280, filed Mar. 24, 2011, now U.S. Pat. No. 8,467,343, which
is a continuation of U.S. application Ser. No. 12/457,653, filed
Jun. 17, 2009, now U.S. Pat. No. 7,933,243, which claims priority
benefit to U.S. Provisional Application Nos. 61/073,743, filed Jun.
18, 2008, and 61/074,998, filed Jun. 23, 2008, and Korean Patent
Application No. 10-2009-0048775, filed Jun. 2, 2009, the entire
contents of each of the aforementioned applications are hereby
incorporated by reference for all purposes as fully set forth
herein.
BACKGROUND
[0002] The present invention relates to an apparatus and method for
performing random access procedures. In the related art, random
access procedures were not performed efficiently. As such, the
related art technologies do not sufficiently address such issues,
and thus do not offer appropriate solutions.
SUMMARY
[0003] The present inventors recognized at least the
above-identified drawbacks of the related art. Based upon such
recognition, the various features described hereafter have been
conceived such that a random access procedure between a mobile
terminal and a network is performed based upon the characteristics
of a random access channel (RACH) preamble. As a result, more
efficient monitoring of downlink channels can be performed, which
results in reduced power consumption.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 shows an exemplary network architecture for an E-UMTS
(Evolved Universal Mobile Telecommunications System).
[0005] FIG. 2 shows an exemplary radio interface protocol
architecture for the control plane between the mobile terminal (UE)
and the network (eNB, MME).
[0006] FIG. 3 shows an exemplary radio interface protocol
architecture for the user plane between the mobile terminal (UE)
and the network (eNB, SAE Gateway).
[0007] FIG. 4 shows an exemplary signal flow diagram of a
contention based random access procedure between the mobile
terminal (UE) and the base station (eNB).
[0008] FIG. 5 shows an exemplary relationship among certain
channels (PDCCH and PDSCH) between the base station and mobile
terminal.
[0009] FIG. 6 is a conceptual diagram to explain a contention based
random access procedure performed by the mobile terminal according
to an exemplary embodiment.
[0010] FIG. 7 is a conceptual diagram to explain a non-contention
based random access procedure performed by the mobile terminal
according to an exemplary embodiment.
[0011] FIG. 8 is a conceptual diagram to explain a contention based
random access procedure performed by the mobile terminal according
to an exemplary embodiment for when the RACH procedure was
unsuccessful.
[0012] FIG. 9 shows a flow chart of a random access procedure
performed by the mobile terminal according to an exemplary
embodiment.
[0013] FIG. 10 is a conceptual diagram to explain the random access
procedure of FIG. 9.
DETAILED DESCRIPTION
[0014] The inventive concepts and features herein are explained in
terms of a Long Term evolution (LTE) system or other so-called 4G
communication systems, which is an enhancement to current 3GPP
technologies. However, such details are not meant to limit the
various features described herein, which are applicable to other
types of mobile and/or wireless communication systems and
methods.
[0015] Hereafter, the term "mobile terminal" will be used to refer
to various types of user devices, such as mobile communication
terminals, user equipment (UE), mobile equipment (ME), and other
devices that support various types of wireless communication
technologies.
[0016] Embodiments of the present invention relate to sending and
receiving data between a base station (e.g. Node B, eNB, access
point, etc.) and a mobile station (e.g. mobile terminal, UE, user
device, etc.) in a Long Term Evolution (LTE) system. Power
consumption of the mobile terminal can be reduced to a minimum and
a downlink channel can be more effectively monitored because a
reception time for the downlink channel is determined according to
the characteristics of a preamble for a mobile terminal that
performs random access.
[0017] Second generation (2G) mobile communications relate to
transmitting and receiving voice signals in a digital manner, and
include technologies such as CDMA, GSM, and the like. As an
enhancement from GSM, GPRS was developed to provide packet switched
data services based upon GSM.
[0018] Third generation (3G) mobile communications relate to
transmitting and receiving not only voice signals, but also video
and data. The 3GPP (Third Generation Partnership Project) developed
the IMT-2000 mobile communication system and selected WCDMA as its
radio access technology (RAT). The combination of IMT-2000 and
WCDMA can be referred to as UMTS (Universal Mobile
Telecommunications System), which comprises a UMTS Terrestrial
Radio Access Network (UTRAN).
[0019] As data traffic is expected to increase dramatically, the
standardization for 3.sup.rd generation mobile communications is
underway to establish a Long-Term Evolution (LTE) network that
supports greater bandwidth. LTE technologies are employed for an
Evolved-UMTS (E-UMTS), which has an Evolved-UTRAN (E-UTRAN) that
uses OFDMA (Orthogonal Frequency Division Multiple Access) as its
radio access technology (RAT).
[0020] FIG. 1 shows the exemplary network architecture for an
E-UMTS (Evolved Universal Mobile Telecommunications System) 100,
which is a type of mobile communications system. The E-UMTS system
is a system that has evolved from the UMTS system and its basic
standardization tasks are now being performed by the 3GPP
organization. The E-UMTS system can be said to be a Long Term
Evolution (LTE) system, which is a type of so-called 4G or next
generation system that has evolved from the current 3G mobile
communication systems.
[0021] The E-UMTS network 100 can be generally distinguished into
the E-UTRAN (Evolved Universal Terrestrial Radio Access Network)
110 and the CN (core network). The E-UTRAN is comprised of a mobile
terminal 112 (e.g. user equipment (UE), mobile station, handset,
mobile phone, etc.), a base station 114, 116, 118 (e.g., an eNode
B, access point (AP), network node, etc.) a serving gateway (S-GW)
122, 124 located at an end of the network for connection with an
external network, and a mobility management entity (MME) 122, 124
that manages various mobility aspects of the mobile terminal. For a
single eNode B, one or more cells (or regions, areas, etc.) may
exist.
[0022] FIGS. 2 and 3 show the radio interface protocol between the
mobile terminal and base station based on the 3GPP radio access
network standard. This radio interface protocol is divided
horizontally into a physical layer, a data link layer, and a
network layer, and is divided vertically into a user plane for
transmitting data information and a control plane for transferring
control signals (signaling). These protocol layers can be divided
into L1 (Layer 1), L2 (Layer 2), and L3 (Layer 3), which are the
lower three layers of the OSI (Open System Interconnection)
standard model, which is well known in communication systems.
[0023] Hereafter, the control plane of the radio protocol in FIG. 2
and the user plane of the radio protocol in FIG. 3 will be
described respectively.
[0024] In Layer 1, the physical layer 225-245, 325-345 uses one or
more physical channels to provide an information transfer service.
The physical layer is connected to the MAC (Medium Access Control)
layer 224-244, 324-344 located above via one or more transport
channels, and data is transferred between the MAC layer and the
physical layer through these transport channels. Also, between
respectively different physical layers, such as the physical layer
in the transmitter (transmitting side) and the physical layer in
the receiver (receiving side), data is transferred via one or more
physical channels.
[0025] The physical channels that exist for the physical layer in
the transmitting side and in the receiving side include: SCH
(Synchronization Channel), PCCPCH (Primary Common Control Physical
Channel), SCCPCH (Secondary Common Control Physical Channel), DPCH
(Dedicated Physical Channel), PICH (Paging Indicator Channel),
PRACH (Physical Random Access Channel), PDCCH (Physical Downlink
Control Channel) and PDSCH (Physical Downlink Shared Channel) and
the like.
[0026] In L2 (Layer 2), the MAC layer provides service to a RLC
(Radio Link Control) layer 223-243, 323-343, which is an upper
layer, via one or more logical channels. Here, based upon the type
of data being transmitted, the logical channels can be divided into
control channels that are used to transmit control plane data, and
traffic channels that are used to transmit user plane data.
[0027] In L2 (Layer 2), the RLC layer supports the transmission of
data with reliability. Each radio bearer (RB) is responsible to the
guarantee of QoS (Quality of Service) and transmits data
accordingly. In order to guarantee the QoS that is unique to the
RB, one or two independent RLC entities are provided for each RB,
and three types of RLC modes (TM: Transparent Mode, UM:
Unacknowledged Mode, and AM: Acknowledged Mode) are provided to
support various QoS.
[0028] In L2 (Layer 2), the PDCP (Packet Data Convergence Protocol)
layer 322-342 in Layer 2 performs a header compression function to
reduce the header size for Internet Protocol (IP) packets that
contain relatively large and unnecessary control information such
that IP packets (such as for IPv4, IPv6, etc.) may be effectively
transmitted over the radio interface having relatively small
bandwidth. Also, the PDCP layer is used for performing coding of
control plane (C-plane) data, such as RRC messages. The PDCP layer
can also perform coding of user plane (U-plane) data.
[0029] Located at the uppermost portion of Layer 3, the RRC (Radio
Resource Control) layer 222-242 is only defined in the control
plane and is responsible for the control of logical channels,
transport channels and physical channels with relation to the
configuration, re-configuration and release of radio bearers (RBs).
Here, a radio bearer is a service provided by Layer 2 for
transferring data between the mobile terminal and E-UTRAN. Here,
the RB refers to a service provided by Layer 2 to transfer data
between the UE and the E-UTRAN.
[0030] Hereafter, aspects of the RACH (Random Access CHannel)
procedure will be explained. The RACH procedure is used for
transmitting relatively short length data via the uplink. In
particular, the RACH procedure is used when there is a signaling
message or user data to be transmitted via the uplink by a mobile
terminal that did not receive allocation of dedicated radio
resources, or may also be used when the base station should
instruct the mobile terminal to perform a RACH procedure.
[0031] Next, the random access procedure provided in an LTE system
will be explained. The random access procedure provided in the LTE
system can be classified as a contention based random access
procedure and a non-contention based procedure. Such classification
is based upon whether the random access preamble is selected by the
mobile terminal itself (i.e. preamble selected by the MAC in the
mobile terminal) or selected by the base station (i.e. receiving
information about the preamble to be used through explicit
signaling).
[0032] In a non-contention based random access procedure, the
mobile terminal uses the preamble that was directly allocated to it
from the base station. Thus, if the base station had allocated a
particular random access preamble to the mobile terminal, such
random access preamble is only used by that mobile terminal, while
other mobile terminals do not use such random access preamble.
Accordingly, because there is a one-to-one (1:1) relationship
between the random access preamble and the mobile terminal that
uses such random access preamble, there are no contentions (or
conflicts) between multiple mobile terminals. In such case, upon
receipt of such random access preamble, the base station can
immediately know which mobile terminal transmitted such random
access preamble, and thus it can be said that more efficient
operation is possible.
[0033] In contrast, for a contention based random access procedure,
because the mobile terminal sends transmission upon selecting a
particular random access preamble among those that may be used,
there is the possibility that multiple mobile terminals use the
same random access preamble. Thus, even upon reception of a
particular random access preamble, the base station cannot
accurately know which mobile terminal transmitted on such random
access preamble.
[0034] The mobile terminal performs a random access procedure for
at least the following exemplary situations: upon performing an
initial access when there is no radio resource control (RRC)
connection with the base station; upon initial access to a target
cell while the mobile terminal is in handover; upon request by a
command of the base station; upon generation of data for the
uplink, when uplink time synchronization is not correct or when
designated radio resources to be used in appropriate requesting
radio resources have not yet been allocated; during a correction
(e.g. decoding, reconstruction, recovery, etc.) procedure when
there is a radio link failure or handover failure.
[0035] Based upon the above explanations, the operations between
the mobile terminal and the base station for a contention based
random access procedure will be explained with reference to FIG. 4
(that includes steps 1 through 4).
[0036] Step 1
[0037] In a contention based random access procedure, the mobile
terminal selects (e.g. at random) one random access preamble among
a set of random access preambles indicated via system information
or a handover command, then selects PRACH resources that can be
used to transmit such random access preamble, and then performs
transmission. Here, such preamble is called a RACH MSG 1. When the
mobile terminal itself ("randomly") selects the preamble (i.e. the
preamble selected by the MAC itself), such is called a
contention-based RACH procedure, and the preamble is called a
contention-based preamble. If the mobile terminal receives
allocation of the preamble directly from the network through the
RRC or PDCCH (i.e. an explicitly signaled preamble), this is called
a non-contention based RACH procedure, and such preamble is called
a dedicated preamble.
[0038] Step 2
[0039] After transmitting the random access preamble as selected
above, the mobile terminal attempts to receive its random access
response within a random access response reception window indicated
from the base station via system information or handover command.
In more detail, the random access response information (typically
called a RACH MSG 2) is transmitted in the form of a MAC PDU, which
is delivered via the PDSCH, and the information related to the
radio resources for the PDSCH is delivered through the PDCCH via
the RA-RNTI.
[0040] The random access response includes values comprising a
random access preamble identifier (ID), a UL Grant (for uplink
radio resources), a Temporary C-RNTI (a temporary cell identifier),
and a Time Alignment Command (a value for time synchronization
adjustment).
[0041] If the random access preamble identifier (ID) is the same as
(i.e. matches) the random access preamble transmitted in step 1)
above, especially while a contention based random access preamble
procedure is in progress, the mobile terminal uses the information
related to the uplink radio resources and performs the following
step 3). If a dedicated preamble is used in step 1), and if the
random access preamble identifier (ID) included in RACH MSG 2 and
the random access preamble transmitted by the mobile terminal in
step 1) are the same (i.e. matches), the RACH procedure is
considered to be ended or terminated.
[0042] Step 3
[0043] If the mobile terminal receives a random access response
(RAR) that is meant for itself (i.e. the RAR is a valid response
for that mobile terminal), the information within such random
access response is processed, respectively. Namely, the mobile
terminal applies the Time Alignment Command and stores the
Temporary C-RNTI. Also, the UL Grant is used to transmit the data
stored in its buffer or to transmit newly generated data to the
base station. Here, the data transmitted by using the UL Grant
(i.e., the MAC PDU) is commonly called RACH MSG 3. Among the data
(i.e. RACH MSG 3) included in the UL Grant, the mobile terminal
identifier (ID) must be included. This is because in a contention
based random access procedure, the base station cannot determine
which mobile terminal performed such random access procedure, and
in order to prevent or resolve any future contentions or conflicts,
information that can be used to identify the mobile terminal would
be required.
[0044] In the above procedure, there are two ways to include the
identifier for the mobile terminal. For the first way, if the
mobile terminal already has a valid cell identifier (C-RNTI)
allocated from the base station (eNB) of the corresponding cell
before the random access procedure is performed, the mobile
terminal transmits such cell identifier via the UL Grant. For the
second way, if the mobile terminal did not receive allocation of a
unique cell identifier from the eNB, the mobile terminal includes
its core network identifier (e.g., S-TMSI, Random ID, etc.) and
performs transmission. After transmitting data using the UL Grant,
the mobile terminal starts a contention resolution timer in order
to solve any contention (conflict) problems.
[0045] Step 4
[0046] After transmitting data (that includes its identifier) using
the UL Grant included in the random access response, the mobile
terminal waits for commands from the base station for resolving
contentions. Namely, reception of the PDCCH is attempted in order
to receive a particular message. There are two ways to receive the
PDCCH. As stated previously, if the identifier transmitted by using
the UL Grant is a cell identifier (C-RNTI) allocated to the mobile
terminal from the eNB, the mobile terminal attempts reception of
the PDCCH by using its cell identifier, and if the identifier is an
identifier that was allocated through the core network, attempt to
receive the PDCCH is performed by using the Temporary C-RNTI
included in the random access response.
[0047] Afterwards, for the former case (i.e. C-RNTI), if the PDCCH
(referred to a RACH MSG 4 hereafter) is received (by using its cell
identifier) before expiration of the contention resolution timer,
then it is considered that the mobile terminal performed the ransom
access procedure in a normal manner and the random access procedure
is ended (terminated). For the latter case (i.e. Temporary C-RNTI),
if the PDCCH was received through the temporary cell identifier
before expiration of the contention resolution timer, the data
(referred to as RACH MSG 4 hereafter), which is delivered by the
PDSCH that is indicated by the PDCCH, is checked. If such data
contains a unique identifier for the mobile terminal itself, it is
considered that the mobile terminal performed the random access
procedure in a normal manner, and the random access procedure is
ended (terminated). The message or MAC PDU received in this step 4)
is commonly called RACH MSG 4.
[0048] Step 5
[0049] In case the contention resolution timer has expired (i.e., a
Temporary C-RNTI or a cell identifier for the mobile terminal is
not received before expiration of the contention resolution timer),
the mobile terminal considers the RACH procedure to be a failure.
As a result, an appropriate back-off timer is operated (started)
and the RACH procedure beginning from step 1) above is started
again after expiration of such back-off timer.
[0050] Hereafter, a method for the mobile terminal in an LTE system
to receive downlink data will be explained.
[0051] On the downlink, there are basically two types of physical
channels: PDCCH and PDSCH. The PDCCH is not directly related to
transmitting user data, but used in transmitting control
information needed for implementing (or using) physical channels.
In more basic terms, it can be said that the PDCCH is used in
controlling other physical channels. In particular, the PDCCH is
used in transmitting information necessary for the mobile terminal
to receive the PDSCH. With respect to data that is transmitted at a
particular point in time using a particular frequency bandwidth,
information about what mobile terminal such data is intended for,
the size of such data being transmitted, and the like is
transmitted via the PDCCH. Accordingly, each mobile terminal
receives the PDCCH at a particular time (e.g., TTI: transmission
time interval) and checks whether any data (that should be
received) was transmitted. If there is an indication that data
(which should be received) was indeed transmitted, the PDSCH is
additionally received by using the information (such as the
appropriate frequency, etc.) indicated by the PDCCH. It can be said
that information indicating as to what mobile terminal (i.e. a
single UE or multiple UEs) the data of the PDSCH is being
transmitted to, information indicating how the mobile terminal(s)
should receive and decode the PDSCH data, and the like are
transmitted via a physical channel, i.e. the PDCCH (Physical
Downlink Control Channel).
[0052] For example, in a particular sub-frame, let us assume that
radio resource information A (e.g. frequency location),
transmission format information B (e.g. transmission block size,
modulation and coding information, etc.), and RNTI (Radio Network
Temporary Identity) information C undergo CRC (Cyclic Redundancy
Check) masking and transmitted via the PDCCH. One or more mobile
terminals in a corresponding cell use the RNTI information that it
has in order to monitor the PDCCH, and referring to the above
assumption, for a mobile terminal having RNTI information C, when
the PDCCH is decoded, CRC errors do not occur. Accordingly, such
mobile terminal uses the transmission format information B and
radio resource information A to decode the PDSCH in order to
receive data. In contrast, with respect to the above assumption, in
a mobile terminal that does not have RNTI information C, CRC errors
occur when the PDCCH is decoded, and thus such mobile terminal does
not receive the PDSCH.
[0053] Through the above procedures, in order to inform about which
mobile terminals have been allocated radio resources, a RNTI (Radio
Network Temporary Identifier) is transmitted via each PDCCH, and
such RNTI can be classified as a dedicated RNTI or a common RNTI. A
dedicated RNTI is allocated to a single mobile terminal and is used
for transmitting and receiving data corresponding to that mobile
terminal. Such dedicated RNTI is only allocated to those mobile
terminals having their information registered in the base station
(eNB). In contrast, a common RNTI is used by those mobile terminals
that do not have their information registered in the base station
(eNB) and cannot be allocated a dedicated RNTI, in order to send
and receive data with the base station or used for transmitting
information (such as system information) that is commonly applied
to a plurality of mobile terminals.
[0054] Meanwhile, the two main elements that comprise the E-UTRAN
are the base station and the mobile terminal. The radio resources
for a single cell are comprised of uplink radio resources and
downlink radio resources. The base station is responsible for the
allocation and control of uplink radio resources and downlink radio
resources of a cell. Namely, the base station determines what radio
resources are to be used by what mobile terminals at certain
moments in time. For example, the base station can determine that
3.2 seconds from now, the frequency from 100 MHz to 101 MHz will be
allocated to user 1 for a duration of 0.2 seconds to allow downlink
data transmissions. Also, after the base station makes such
determination, these matters can be informed to the corresponding
mobile terminal such that this mobile terminal receives downlink
data. Likewise, the base station can determine when a certain
mobile terminal should use what amount of which radio resources for
data transmission via the uplink, and the base station informs the
mobile terminal about its determination, to thus allow the mobile
terminal to transmit data during the determined time period using
the determined radio resources.
[0055] Unlike the related art, if the base station manages radio
resources in a dynamic manner, efficient use of radio resources
would be possible. Typically, a single mobile terminal continuously
uses a single radio resource during a call connection. This is not
preferable considering that most recent services are IP
packet-based. The reason is that most packet services do not
continuously generate packets during the duration of a call
connection, and there are many time periods in which nothing is
transmitted during the call. Despite this, continued allocation of
a radio resource to a single mobile terminal is inefficient. To
solve this, the mobile terminal of a E-UTRAN system uses a method
in which radio resources are allocated to the mobile terminal only
while service data exists.
[0056] Hereafter, some concepts of DRX will be explained. DRX
refers to discontinuous reception and signifies the operations
about when (i.e. at when point in time) the base station should
send information related to radio resource allocation to the mobile
station during the process of communication between the base
station and the mobile terminal. Namely, a mobile terminal having
to always monitor the downlink channel, in particular the PDCCH,
would result in undesirable power consumption for the mobile
terminal. Thus, to resolve this issue, the mobile terminal and the
base station operate according to pre-established consistent rules,
such that the base station sends radio resource allocation
information via the PDCCH to the mobile terminal only at specific
times. As a result, the mobile terminal only needs to monitor the
PDCCH at certain specified times, which reduces power consumption
thereof.
[0057] Some types of DRX operations are performed in the following
manner.
[0058] Initially, an active time is defined. This active time
denotes the time at which that the mobile terminal should wake up
(from its idle state) to monitor a downlink channel, namely the
PDCCH. After such active time, the mobile terminal need not monitor
the PDCCH.
[0059] The active time may include the following types of time
periods:
[0060] 1) a time during which an On-Duration timer, or a DRX
Inactivity timer, or a DRX Retransmission timer, or a Contention
Resolution timer operates (=condition 1);
[0061] 2) a time during which a Scheduling Request procedure is
being performed;
[0062] 3) a time during which a radio resource allocation message
(for retransmissions) is sent, with respect to uplink
transmissions;
[0063] 4) a time during from after the RACH MSG 2 is transmitted up
to the time when a C-RNTI or a Temporary C-RNTI (that indicates the
allocation of radio resources for an initial or new transmission)
is received (=condition 4).
[0064] With reference to the technical description thus far, the
technical solution provided by the embodiments of the present
invention can be described as follows.
[0065] In order to reduce power consumption, the DRX is performed
also for the RACH procedure. The active time explained above can be
considered in view of the RACH procedure.
[0066] FIGS. 6 and 7 shows RACH procedures performed by a mobile
terminal for (a) Contention based and (b) Non-contention based
situations. In (a) Contention based RACH, the active time denotes
the time during which the mobile terminal should monitor the
downlink channel. In (b) Non-contention based RACH, unlike in
contention based RACH, there is no RACH MSG 3 transmission being
performed. Also, a Temporary C-RNTI is not used.
[0067] Referring to FIG. 6, when the mobile terminal monitors a
downlink channel (namely, the PDCCH), in order to reduce power
consumption, discontinuous receptions (DRX) are performed with
respect to the RACH procedure.
[0068] As this is a contention based random access procedure, the
mobile terminal selects a preamble and this selected preamble is
transmitted to the base station (network) (see S1 and S2). If the
mobile terminal receives a random access response (RAR: RACH
response, i.e. RACH MSG 2) from the base station, the information
included in such random access response are individually processed
(S3). Also, as a procedure for receiving a C-RNTI or a Temporary
C-RNTI from the base station that informs about radio resource
allocation, the mobile terminal sends data (i.e. a MAC PDU referred
to as RACH MSG 3) via an uplink (UL) grant (S4). Additionally, the
downlink channel (via which the C-RNTI or the Temporary C-RNTI will
be transmitted) is monitored from the time when the preamble was
selected until the C-RNTI or the Temporary C-RNTI is actually
received (S5). Here, a DRX timer is operated (or started) and
active from after receiving the RACH MSG 2 until the C-RNTI or the
Temporary C-RNTI is received. A contention based resolution timer
is operated (or started) after the RACH MSG 3 is transmitted until
the C-RNTI or the Temporary C-RNTI is received.
[0069] FIG. 7 shows a conceptual diagram to explain a
non-contention based random access procedure performed by the
mobile terminal according to an exemplary embodiment. When compared
to FIG. 6, the mobile terminal does not perform the step of
transmitting the RACH MSG 3 to the base station (i.e. S4 of FIG. 6
is not performed) in the non-contention based situation. Also, the
Temporary C-RNTI is not employed in the non-contention based
situation. Here, the downlink channel monitoring period or duration
of the RACH procedure is equivalent to that in FIG. 6.
[0070] It should be noted that in FIG. 6, the Contention based RACH
shows the situation when the mobile terminal successfully performs
the RACH procedure. However, if the mobile terminal actually fails
in performing the RACH procedure, namely, if the C-RNTI or the
Temporary C-RNTI is not received, then such failure situation in
shown in FIG. 8.
[0071] In FIG. 8, active time 1 refers to the time duration as
defined according to the active time condition 4 described above,
while active time 2 refers to the time duration as defined
according to the active time condition 1 described above.
[0072] As can been seen in FIG. 8, based upon the active time
definitions above, the downlink channel must be monitored even
during the back-off time. However, the actual back-off time is not
a time period during which a contention resolution timer is being
operated, and thus the network does not allocate radio resources to
the mobile terminal by using the C-RNTI or the Temporary C-RNTI.
Accordingly, because the mobile terminal need not actually perform
monitoring, power consumption in unnecessarily wasted during this
time period.
[0073] In order to solve this drawback, when performing a RACH
procedure and monitoring a downlink channel in order to receive
scheduling information, the mobile terminal should receive the
downlink channel is a more efficient manner.
[0074] To achieve this, it is proposed that the mobile terminal
should determine whether or not downlink channel monitoring should
be performed at a particular point in time (or during a specific
time period) based upon information regarding the type of on-going
procedure that is being performed.
[0075] The mobile terminal may determine that it should monitor the
downlink channel based upon whether or not the on-going procedure
is a random access (RACH) procedure.
[0076] In performing downlink channel monitoring, for the mobile
terminal to determine whether a particular time point (or period)
is that for which downlink channel monitoring actually needs to be
performed, and if the on-going procedure is a RACH procedure, then
the information about the specific type of RACH procedure being
performed should be referred to.
[0077] Namely, the mobile terminal will determine whether downlink
channel monitoring should be performed or not by considering
whether a contention based RACH procedure is being used or a
non-contention based RACH procedure is being used.
[0078] A contention based RACH procedure means that the mobile
terminal selects (at random or by some other criteria) a RACH
preamble to be used in the RACH procedure. Namely, in this case, it
is assumed that the MAC entity (in the mobile terminal) begins the
RACH procedure. Thus, such MAC entity would select the preamble to
be used.
[0079] A non-contention based RACH procedures means that the RACH
procedure is performed by the mobile terminal using a directly
(explicitly) indicated specific RACH preamble.
[0080] The specifics for the above procedures will be further
explained hereafter.
[0081] Determining whether to receive the downlink channel
according to the type of RACH procedure is used refers to the
following. After the mobile terminal begins the RACH procedure, it
is checked whether the RACH procedure is a contention based RACH
procedure or a non-contention based RACH procedure.
[0082] If a non-contention based RACH procedure, the downlink
channel is monitored during the period from when the RACH MSG 2
(i.e. random access response) was received up until a C-RNTI (that
indicates allocation of radio resources for a new transmission) is
received via the PDCCH. Namely, the time period, from after
reception of the RACH MSG 2 (random access response) until
reception of the C-RNTI (that indicates radio resource allocation
for a new transmission) via the PDCCH, is included in the active
time.
[0083] If a contention based RACH procedure, the downlink channel
does not need to be monitored during the period from when the RACH
MSG 2 (i.e. random access response) was received up until a C-RNTI
(that indicates allocation of radio resources for a new
transmission) is received via the PDCCH. Namely, the time period,
from after reception of the RACH MSG 2 (random access response)
until reception of the C-RNTI (that indicates radio resource
allocation for a new transmission) via the PDCCH, is not included
in the active time.
[0084] In other words, with respect to the time period (or
duration) that begins from when the RACH MSG 2 (i.e. random access
response) was received and ends when a C-RNTI (that indicates
allocation of radio resources for a new transmission) is received
via the PDCCH, such time period is not included in the active time
for contention based RACH procedures, while such time period is
included in the active time for non-contention based RACH
procedures.
[0085] Put differently, the active time definition according to
condition 4 (mentioned previously) is applied for instances where
the RACH procedure is non-contention based (i.e., the RACH preamble
is directly allocated from an external source to the MAC entity),
while such condition 4 is not applied for other situations.
[0086] Thus, in embodiments of the present invention, the RACH
procedure being used is checked to see if it is contention based or
non-contention based, and depending on such checking, the time
period from reception of the RACH MSG 2 up to the reception of
information via the PDCCH in the form of a C-RNTI that indicates
radio resource allocation for a new transmission, is included in
the active time such that downlink channel reception can be
determined.
[0087] FIG. 9 shows a flow chart of a random access procedure
performed by the mobile terminal according to an exemplary
embodiment, while FIG. 10 is a conceptual diagram to explain the
random access procedure of FIG. 9.
[0088] The MAC entity of the mobile terminal (UE) selects the RACH
preamble, which is transmitted to the network (S10, S11). If the UE
receives a random access response (RAR: RACH MSG 2) from the
network, the information included in such RAR is processed (S12).
Namely, by using the information in the RAR, it is determined
whether the RACH preamble was selected by the MAC of the UE or
explicitly signaled (or selected) by the network 9S13). If the RACH
preamble was not selected by the MAC of the UE, namely, if
explicitly signaled by the network, the UE monitors the downlink
channel (PDCCH) until a new transmission is indicated by the radio
resource allocation information (or scheduling information, such as
C-RNTI) received from the network (S14).
[0089] However, if the RACH preamble was selected by the UE MAC,
the contention resolution timer is started (S15). As such, the
operation in FIG. 9 can also be understood from FIG. 10. Namely, as
in the DRX procedure, when the UE receives a random access response
(RAR: RACH MSG 2) from the network, the contention resolution timer
is operated and the downlink channel (PDCCH) is monitored. However,
if a C-RNTI is not received upon expiration of the contention
resolution timer via the downlink channel being monitored, the UE
performs the random access procedure again after a back-off time is
applied. Here, the downlink channel is not monitored upon
expiration of the contention resolution timer. The downlink channel
is monitored when the random access procedure is performed again
after the back-off time. As shown in FIGS. 9 and 10, as the UE does
not monitor the downlink channel during the back-off time, power
consumption due to unnecessary DRX operations can be avoided.
[0090] The mobile terminal may include a communication module
(which may consist of hardware, software, or a combination thereof)
that is configured to implement the operations described with
respect to FIGS. 6 through 10. Also, the mobile terminal according
to the present invention includes various types of hardware, such
as an input/output means (e.g. display screen, keypad, speakers,
etc.) and a microprocessor (or other control means) that provide
control operations, as well as software used to implement various
operations.
[0091] FIG. 10 illustrates how the concepts in the embodiments of
the inventive features described herein can be implemented. Here,
the situation where the mobile terminal failed in performing the
RACH procedure, namely, when the C-RNTI or Temporary C-RNTI is not
received, is shown.
[0092] As understood from FIG. 10, the active time defined
according to condition 4 (mentioned previously) is not applicable
because a contention based RACH procedure is being used. Thus,
during the time in which the back-off time is applied, the mobile
terminal need not monitor the downlink channel. As a result,
undesired power consumption can be reduced.
[0093] Regarding the effects from implementing the embodiments
described herein, with respect to downlink channel monitoring
performed by the mobile terminal, the specific monitoring period
(of the downlink channel, e.g. PDCCH) can be set in a more improved
manner such that battery power efficiency (i.e. power source
control) is enhanced.
[0094] Some more details about the concepts and features of the
inventive embodiments described herein can also be summarized as
follows.
[0095] The DRX Command MAC CE may be used to put a UE directly into
either short or long DRX Cycle. But when a DRX Command MAC CE is
received while the DRX Short Cycle Timer is running, the timer
should not be affected. If the timer is started again (i.e.
re-started), the UE is further put in wake-up state, causing more
battery consumption. This situation can occur when HARQ
Re-transmission Grant for a MAC PDU which includes the DRX Command
MAC CE is received while the Short DRX Cycle Timer is running.
Here, the terms "start" and "re-start" may be distinguished such
that "start" is used when the timer is not running, while
"re-start" is used when the timer is running. Thus, when the Short
DRX Cycle Timer is running, it cannot be started, but it can be
restarted.
[0096] However, such potential problem may be avoided by
implementing the following concept: when DRX Command MAC CE is
received while Short DRX Cycle Timer is running, the MAC CE is
ignored.
[0097] The Active Time may include "a PDCCH indicating a new
transmission addressed to the C-RNTI or Temporary C-RNTI of the UE
has not been received after successful reception of a Random Access
Response (RAR)." This would cover the period between the time of
RAR reception and the time of starting the contention resolution
timer. Otherwise, the UE would monitor the DL channels longer than
needed. For example, even after the contention resolution timer
expires due to reception of no temporary C-RNTI, the UE would still
monitor the DL channels.
[0098] However, such potential problem may be avoided by
implementing the following: setting the Active Time to include the
period between the time of successful reception of RAR and the time
of starting the Contention Resolution timer (for the case of
contention-based preamble).
[0099] In other words, the situations for a contention-based
preamble can be clarified as above.
[0100] If UE has to wake up until the reception of C-RNTI
regardless of other problems, the features described herein can be
applied to situations for a dedicated preamble.
[0101] The maintenance of Uplink Time Alignment will be
explained.
[0102] The UE may have a configurable Time Alignment Timer. The
Time Alignment Timer is valid only in the cell for which it was
configured and started.
[0103] If the Time Alignment Timer has been configured, the UE
shall: when a Timing Advance MAC control element is received: apply
the Timing Advance Command; start the Time Alignment Timer (if not
running) or restart the Time Alignment Timer (if already running).
when a Time Alignment Command is received in a Random Access
Response message:
if the Random Access Preamble and PRACH resource were explicitly
signaled: apply the Time Alignment Command; start the Time
Alignment Timer (if not running) or restart the Time Alignment
Timer (if already running). else, if the Time Alignment Timer is
not running or has expired: apply the Time Alignment Command; start
the Time Alignment Timer; when the contention resolution is
considered not successful, stop the Time Alignment Timer. else:
ignore the received Time Alignment Command. when the Time Alignment
Timer has expired or is not running: prior to any uplink
transmission, use the Random Access procedure in order to obtain
uplink Time Alignment. when the Time Alignment Timer expires:
release all PDCCH resources; release any assigned SRS
resources.
[0104] Discontinuous Reception (DRX) will be explained. The UE may
be configured by the RRC with a DRX functionality that allows it to
not continuously monitor the PDCCH. The DRX functionality consists
of a Long DRX cycle, a DRX Inactivity Timer, a DRX Retransmission
Timer, and optionally a Short DRX Cycle and a DRX Short Cycle
Timer.
[0105] When a DRX cycle is configured, the Active Time includes the
time: while the On-Duration Timer or the DRX Inactivity Timer or a
DRX Retransmission Timer or the Contention Resolution Timer is
running; or while a Scheduling Request is pending; or while an
uplink grant for a retransmission can occur; or from the successful
reception of a Random Access Response (RAR) to the starting of the
Contention Resolution Timer.
[0106] Here, the Active Time can also be defined as: while a PDCCH
indicating a new transmission addressed to the C-RNTI of the UE has
not been received after successful reception of a Random Access
Response, if the Random Access Preamble was explicitly signaled; or
while the DL resuming timer is running. The DL resuming timer is
started when successful RAR is received in case that the Random
Access Preamble was explicitly signaled; (here, the DL resuming
timer is stopped when the C-RNTI of the UE is received) (instead,
it is also possible that the DL-resolution timer is started when a
dedicated preamble is received over the PDCCH) or, from the
successful reception of a Random Access Response (RAR) to the
starting of the Contention Resolution Timer, if the Random Access
Preamble was selected by the UE MAC.
[0107] When a DRX cycle is configured, the UE shall perform the
following procedures for each sub-frame: start the On Duration
Timer when [(SFN*10)+sub-frame number]modulo(current DRX Cycle)=DRX
Start Offset; if a HARQ RTT Timer expires in this sub-frame and the
data in the soft buffer of the corresponding HARQ process was not
successfully decoded: start the DRX Retransmission Timer for the
corresponding HARQ process. if a DRX Command MAC control element is
received: stop the On Duration Timer; stop the DRX Inactivity
Timer. if the DRX Inactivity Timer expires or a DRX Command MAC
control element is received in this sub-frame: if the short DRX
cycle is configured: if the DRX Short Cycle Timer is not running,
start the DRX Short Cycle Timer; use the Short DRX Cycle. else: use
the Long DRX cycle. if the DRX Short Cycle Timer expires in this
sub-frame: use the long DRX cycle. during the Active Time, for a
PDCCH-sub-frame except if the sub-frame is required for uplink
transmission for half-duplex FDD UE operation: monitor the PDCCH;
if the PDCCH indicates a DL transmission: start the HARQ RTT Timer
for the corresponding HARQ process; stop the DRX Retransmission
Timer for the corresponding HARQ process. if the PDCCH indicates a
new transmission (DL or UL): start or restart the DRX Inactivity
Timer. if a DL assignment has been configured for this sub-frame
and no PDCCH indicating a DL transmission was successfully decoded:
start the HARQ RTT Timer for the corresponding HARQ process. when
not in active time, CQI and SRS shall not be reported.
[0108] Regardless of whether the UE is monitoring PDCCH or not the
UE receives and transmits HARQ feedback when such is expected.
[0109] The inventive embodiments described herein can further be
described as follows.
[0110] In the related art, the RACH preamble being contention based
and non-contention based was not distinguished when performing a
RACH procedure. This drawback can be overcome by defining the
active time and certain conditions thereof accordingly. The PDCCH
needs to be continuously monitored during the time between MSG2 and
MSG 4. After receiving the MSG 2, it is determined whether the RACH
preamble is contention based or non-contention based, and
conditions are applied for situations that are contention based or
non-contention based.
[0111] Here, it should be noted that the features about contention
based and non-contention based RACH preambles could be described in
other terms and expressions. For example, it can be said that a
PDCCH indicating a new transmission addressed to the C-RNTI of the
UE has not been received after successful reception of a Random
Access Response for the explicitly signaled preamble. Here, the
phrase `explicitly signaled` typically refers to dedicated
signaling, but there may be some situations where `explicitly
signaled` refers to non-dedicated signaling. Also, a preamble that
is not explicitly signaled is equivalent to a preamble that is not
selected by MAC. Additionally, if the PDCCH order is a specific
value (=00000), then the procedure can go back to contention
based.
[0112] This disclosure provides a method of performing
discontinuous receptions (DRX), comprising: transmitting a RACH
preamble to the network; receiving RAR (MSG 2) from the network;
determining whether the transmitted preamble was explicitly
signaled by the network; if explicitly signaled, monitoring a
downlink channel (PDCCH) until a new transmission is indicated by a
C-RNTI received from the network; and if not explicitly signaled,
starting a contention resolution timer.
[0113] Also, this disclosure provides a method of performing
discontinuous receptions (DRX), comprising: transmitting a RACH
preamble to the network; receiving RAR (MSG 2) from the network; if
the transmitted RACH preamble was determined to be explicitly
signaled by the network, monitoring a downlink channel (PDCCH)
until a new transmission is indicated by a C-RNTI received from the
network; or if the transmitted RACH preamble was determined to be
not explicitly signaled by the network, starting a contention
resolution timer.
[0114] The features described herein can be summarized as
follows.
[0115] A method of performing a random access procedure in a mobile
communications system having a network and a mobile terminal, the
method performed by the mobile terminal and comprising:
transmitting a random access channel (RACH) preamble to the
network; receiving a RACH response from the network that received
the RACH preamble; monitoring a downlink channel using information
included in the RACH response according to whether the RACH
preamble is contention based or non-contention based; checking
whether the random access preamble is contention based or
non-contention based; and performing a discontinuous reception
procedure according to whether the random access preamble is
contention based or non-contention based.
[0116] Here, the information included in the RACH response can be
used to determine whether the random access preamble is contention
based or non-contention based. The monitoring can be performed
until a new transmission is indicated by a C-RNTI received from the
network.
[0117] A method of performing discontinuous receptions (DRX) in
mobile communications employing a network and a mobile terminal,
the method comprising: transmitting a RACH preamble to the network;
receiving random access response (MSG 2) from the network;
monitoring a downlink channel (PDCCH) until a new transmission is
indicated by a C-RNTI received from the network, wherein the
monitoring is performed if the transmitted RACH preamble was
determined to be explicitly signaled by the network; or starting a
contention resolution timer, wherein the starting is performed if
the transmitted RACH preamble was determined to be not explicitly
signaled by the network.
[0118] The RACH preamble explicitly signaled by the network is a
preamble that is not selected by UE MAC. The RACH preamble
explicitly signaled by the network is information included in a
PDCCH order.
[0119] A method of performing a discontinuous reception (DRX)
procedure in mobile communications employing a network and a mobile
terminal, the method performed by the mobile terminal and
comprising: starting a random access procedure by sending a random
access preamble to the network; receiving a random access response
from the network that received the random access preamble; checking
whether the random access preamble is contention based or
non-contention based; and performing a discontinuous reception
procedure according to whether the random access preamble is
contention based or non-contention based.
[0120] The discontinuous reception procedure is performed by either
monitoring a downlink channel (PDCCH) if the random access preamble
is non-contention based or starting a contention resolution timer
if the random access preamble is contention based. The mobile
terminal performs the random access procedure if at least one of
the following conditions are met: upon performing an initial access
when there is no radio resource control (RRC) connection with the
base station; upon initial access to a target cell while the mobile
terminal is in handover; upon request by a command of the base
station; upon generation of data for the uplink, when uplink time
synchronization is not correct or when designated radio resources
to be used in appropriate requesting radio resources have not yet
been allocated; and during a correction, decoding or reconstruction
procedure when there is a radio link failure or handover
failure.
[0121] Furthermore, the features described herein can be summarized
as follows.
[0122] A method of performing a random access procedure between a
mobile terminal and a network, the method comprising: transmitting
a RACH (Random Access CHannel) preamble to the network; and
monitoring a downlink channel by using information included in a
RACH response received from the network.
[0123] The monitoring step comprises determining whether the RACH
preamble was selected by a MAC entity of the mobile terminal by
using the information included in the RACH response. The downlink
channel is further monitored until a new transmission is indicated
by a C-RNTI received from the network, if it is determined that the
RACH preamble was explicitly signaled by the network. The method
further comprising: starting a contention resolution timer, if it
is determined that the RACH preamble was selected by the MAC entity
of the mobile terminal. The downlink channel is a PDCCH (Physical
Downlink Control CHannel).
[0124] A method of performing a random access procedure between a
mobile terminal and a network, the method comprising: transmitting
a RACH (Random Access CHannel) preamble to the network; receiving a
RACH response from the network; monitoring a downlink channel until
a new transmission is indicated according to radio resource
allocation information received from the network, if the RACH
preamble was explicitly signaled by the network; and starting a
contention resolution timer, if the RACH preamble was selected by a
MAC entity of the mobile terminal.
[0125] If the contention resolution timer expires, the downlink
channel is no longer monitored. The downlink channel is a PDCCH
(Physical Downlink Control CHannel). The method further comprising:
using the information included in the RACH response to determine
whether the RACH preamble was either explicitly signaled by the
network or selected by the MAC entity of the mobile terminal. The
radio resource allocation information is a C-RNTI (Radio Network
Temporary Identifier).
[0126] A method of performing a random access procedure between a
mobile terminal and a network, the method comprising: transmitting
a RACH (Random Access CHannel) preamble to the network; receiving a
RACH response from the network; determining whether the RACH
preamble was explicitly signaled by the network; if the RACH
preamble was explicitly signaled by the network, monitoring a
downlink channel until a new transmission is indicated according to
radio resource allocation information received from the network;
and if the RACH preamble was not explicitly signaled by the
network, starting a contention resolution timer.
[0127] The radio resource allocation information is a C-RNTI (Radio
Network Temporary Identifier. The downlink channel is a PDCCH
(Physical Downlink Control CHannel). If the contention resolution
timer expires, the downlink channel is no longer monitored.
[0128] A mobile terminal comprising: a communications module
configured to transmit a RACH (Random Access CHannel) preamble to
the network, receive a RACH response from the network, determine
whether the RACH preamble was explicitly signaled by the network,
monitor a downlink channel until a new transmission is indicated
according to radio resource allocation information received from
the network if the RACH preamble was explicitly signaled by the
network, and start a contention resolution timer if the RACH
preamble was selected by a MAC entity of the mobile terminal.
[0129] The various features and concepts described herein may be
implemented in software, hardware, or a combination thereof. For
example, a computer program (that is executed in a computer, a
terminal or a network device) for a method and system for
performing a random access procedure between a mobile terminal and
a network is performed based upon the characteristics of a RACH
preamble may comprise one or more program code sections for
performing various tasks. Similarly, a software tool (that is
executed in a computer, a terminal or a network device) for a
method and system for performing a random access procedure between
a mobile terminal and a network is performed based upon the
characteristics of a RACH preamble may comprise program code
portions for performing various tasks.
[0130] The method and system for processing random access
procedures according to the present invention are compatible with
various types of technologies and standards. Certain concepts
described herein are related to various types of standards, such as
GSM, WCDMA, 3GPP, LTE, IEEE, 4G and the like. However, it can be
understood that the above exemplary standards are not intended to
be limited, as other related standards and technologies would also
be applicable to the various features and concepts described
herein.
INDUSTRIAL APPLICABILITY
[0131] The features and concepts herein are applicable to and can
be implemented in various types of user devices (e.g., mobile
terminals, handsets, wireless communication devices, etc.) and/or
network entities that can be configured for performing a random
access procedure in a mobile communications system having a network
and a mobile terminal.
[0132] As the various concepts and features described herein may be
embodied in several forms without departing from the
characteristics thereof, it should also be understood that the
above described embodiments are not limited by any of the details
of the foregoing description, unless otherwise specified, but
rather should be construed broadly within its scope as defined in
the appended claims. Therefore, all changes and modifications that
fall within such scope or equivalents thereof are therefore
intended to be embraced by the appended claims.
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