U.S. patent application number 16/676033 was filed with the patent office on 2020-03-05 for security key generation and management method of pdcp distributed structure for supporting dual connectivity.
The applicant listed for this patent is Samsung Electronics Co., Ltd.. Invention is credited to Jung-Soo JUNG, Soeng-Hun KIM, Sung-Jin LEE, Jung-Min MOON, Anshuman NIGAM, Sun-Heui RYOO.
Application Number | 20200076774 16/676033 |
Document ID | / |
Family ID | 52461676 |
Filed Date | 2020-03-05 |
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United States Patent
Application |
20200076774 |
Kind Code |
A1 |
RYOO; Sun-Heui ; et
al. |
March 5, 2020 |
SECURITY KEY GENERATION AND MANAGEMENT METHOD OF PDCP DISTRIBUTED
STRUCTURE FOR SUPPORTING DUAL CONNECTIVITY
Abstract
The present disclosure relates to a pre-5th-Generation (5G) or
5G communication system to be provided for supporting higher data
rates Beyond 4th-Generation (4G) communication system such as Long
Term Evolution (LTE). A method for communicating by a user
equipment with a macro cell base station and a small cell base
station in a communication system is provided. The method comprises
applying a first base station security key to a first communication
link with the macro cell base station; generating a second base
station security key to be used for a second communication link
with the small cell base station based on the first base station
security key; applying the second base station security key to the
second communication link with the small cell base station; and
communicating through at least one of the first communication link
and the second communication link.
Inventors: |
RYOO; Sun-Heui; (Yongin-si,
KR) ; KIM; Soeng-Hun; (Suwon-si, KR) ; JUNG;
Jung-Soo; (Seongnam-si, KR) ; MOON; Jung-Min;
(Seoul, KR) ; NIGAM; Anshuman; (Suwon-si, KR)
; LEE; Sung-Jin; (Bucheon-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd. |
Suwon-si |
|
KR |
|
|
Family ID: |
52461676 |
Appl. No.: |
16/676033 |
Filed: |
November 6, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16557130 |
Aug 30, 2019 |
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16676033 |
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16192002 |
Nov 15, 2018 |
10404666 |
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16557130 |
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15895633 |
Feb 13, 2018 |
10142299 |
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16192002 |
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14910580 |
Feb 5, 2016 |
9930016 |
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PCT/KR2014/007312 |
Aug 7, 2014 |
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15895633 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 12/0401 20190101;
H04L 63/062 20130101; H04W 12/04 20130101; H04W 12/04031 20190101;
H04W 12/02 20130101; H04W 36/0038 20130101; H04L 63/0428
20130101 |
International
Class: |
H04L 29/06 20060101
H04L029/06; H04W 12/04 20060101 H04W012/04; H04W 12/02 20060101
H04W012/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 9, 2013 |
KR |
10-2013-0094952 |
Claims
1. A method for communicating by a user equipment (UE) in a
communication system, the method comprising: receiving a radio
resource control (RRC) connection reconfiguration message including
a counter for a second base station from a first base station;
generating a second security key for a second communication with
the second base station based on a first security key and the
counter, wherein the first security key is applied to a first
communication with the first base station; and applying the second
security key to the second communication with the second base
station.
2. The method of claim 1, further comprising: generating an
encryption key; and communicating data through the second
communication with the second base station, wherein the encryption
key is used for encrypting the data.
3. The method of claim 2, wherein, before the communicating of the
data, the method further comprises: transmitting a RRC
reconfiguration complete message to the first base station; and
performing a random access procedure with the second base
station.
4. The method of claim 1, wherein the RRC connection
reconfiguration message including the counter is received when the
second base station is newly added in the communication system, and
wherein the counter is a next hop chaining counter (NCC) for the
second base station.
5. The method of claim 4, wherein the generated second security key
is a new security key for the newly added second base station.
6. A user equipment (UE) communicating in a communication system,
the UE comprising: a transceiver; and a controller configured to:
receive a radio resource control (RRC) connection reconfiguration
message including a counter for a second base station from a first
base station; generate a second security key for a second
communication with the second base station based on a first
security key and the counter, wherein the first security key is
applied to a first communication with the first base station; and
apply the second security key to the second communication with the
second base station.
7. The UE of claim 6, wherein the controller is further configured
to generate an encryption key, wherein the transceiver is further
configured to communicate data through the second communication
with the second base station under control of the controller, and
wherein the encryption key is used for encrypting the data.
8. The UE of claim 6, wherein the controller is further configured
to: transmit a RRC reconfiguration complete message to the first
base station; and perform a random access procedure with the second
base station.
9. The UE of claim 6, wherein the RRC connection reconfiguration
message including the counter is received when the second base
station is newly added in the communication system, and wherein the
counter is a next hop chaining counter (NCC) for the second base
station.
10. The UE of claim 9, wherein the generated second security key is
a new security key for the newly added second base station.
11. A method for communicating by a second base station in a
communication system, the method comprising: receiving, from a
first base station, a second security key to be used for a second
communication with a user equipment (UE); and applying the second
security key to the second communication with the UE, wherein the
second security key is generated based on a counter and a first
security key, wherein the first security key is used for a first
communication with the first base station, and wherein the counter
is included in a radio resource control (RRC) connection
reconfiguration message.
12. The method of claim 11, further comprising: generating an
encryption key; and communicating data through the second
communication with the UE, wherein the encryption key is used for
encrypting the data.
13. The method of claim 12, wherein, before the communicating of
the data, the method further comprises: performing a random access
procedure with the UE.
14. The method of claim 11, wherein the RRC connection
reconfiguration message including the counter is received when the
second base station is newly added in the communication system, and
wherein the counter is a next hop chaining counter (NCC) for the
second base station.
15. The method of claim 14, wherein the generated second security
key is a new security key for the newly added second base
station.
16. A second base station communicating in a communication system,
the second base station comprising: a transceiver; and a controller
configured to: receive, from a first base station, a second
security key to be used for a second communication with a user
equipment (UE); and apply the second security key to the second
communication with the UE, wherein the second security key is
generated based on a counter and a first security key to be used
for a first communication with the first base station, and wherein
the counter is included in a radio resource control (RRC)
connection reconfiguration message.
17. The second base station of claim 16, wherein the controller is
further configured to generate an encryption key, wherein the
transceiver is further configured to communicate data through the
second communication with the UE under control of the controller,
and wherein the encryption key is used for encrypting the data.
18. The second base station of claim 16, wherein the controller is
configured to: perform a random access procedure with the UE.
19. The second base station of claim 16, wherein the RRC connection
reconfiguration message including the counter is received when the
second base station is newly added in the communication system, and
wherein the counter is a next hop chaining counter (NCC) for the
second base station.
20. The second base station of claim 19, wherein the generated
second security key is a new security key for the newly added
second base station.
21. The method of claim 1, wherein the generating of the second
security key further comprises increasing the counter, and wherein
the second security key is generated by applying the first security
key and the counter to a key derivation function (KDF).
22. The UE of claim 6, wherein the controller configured to
increase the counter, and wherein the second security key is
generated by applying the first security key and the counter to a
key derivation function (KDF).
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a continuation application of prior
application Ser. No. 16/557,130 filed on Aug. 30, 2019, which is a
continuation application of prior application Ser. No. 16/192,002,
filed on Nov. 15, 2018, which issued as U.S. Pat. No. 10,404,666 on
Sep. 3, 2019, which is a continuation of U.S. patent application
Ser. No. 15/895,633, filed Feb. 13, 2018, which has issued as U.S.
Pat. No. 10,142,299 on Nov. 27, 2018, which is a continuation
application of U.S. patent application Ser. No. 14/910,580, filed
on Feb. 5, 2016, which has issued as U.S. Pat. No. 9,930,016 on
Mar. 27, 2018, which was the National Stage of an International
application number PCT/KR2014/007312, filed on Aug. 7, 2014, and
was based on and claimed the benefit of a Korean patent application
number 10-2013-0094952, filed on Aug. 9, 2013 in the Korean
Intellectual Property Office, the disclosure of each of which is
hereby incorporated by reference herein in its entirety.
TECHNICAL FIELD
[0002] The present disclosure relates to wireless communications.
More particularly, the present disclosure relates to methods and
apparatuses for generating and maintaining security keys for a
plurality of base stations connected to one terminal in a wireless
communication system supporting a plurality of wireless link
connections to one terminal.
BACKGROUND
[0003] To meet the demand for wireless data traffic having
increased since deployment of 4G (4.sup.th-Generation)
communication systems, efforts have been made to develop an
improved 5G (5.sup.th-Generation) or pre-5G communication system.
Therefore, the 5G or pre-5G communication system is also called a
`beyond 4G network` or a `post LTE system`.
[0004] The 5G communication system is considered to be implemented
in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to
accomplish higher data rates. To decrease propagation loss of the
radio waves and increase the transmission distance, the
beamforming, massive multiple-input multiple-output (MIMO), full
dimensional MIMO (FD-MIMO), array antenna, an analog beam forming,
large scale antenna techniques are discussed in 5G communication
systems.
[0005] In addition, in 5G communication systems, development for
system network improvement is under way based on advanced small
cells, cloud radio access networks (RANs), ultra-dense networks,
device-to-device (D2D) communication, wireless backhaul, moving
network, cooperative communication, coordinated multi-points
(CoMP), reception-end interference cancellation and the like.
[0006] In the 5G system, hybrid FSK and QAM modulation (FQAM) and
sliding window superposition coding (SWSC) as an advanced coding
modulation (ACM), and filter bank multi carrier (FBMC),
non-orthogonal multiple access (NOMA), and sparse code multiple
access (SCMA) as an advanced access technology have been
developed.
[0007] Installing multiple small cells is being researched to
increase the wireless network capability of a macro cell to respond
to soring mobile data traffic.
[0008] Small cells with small cell coverage may recycle limited
frequency resources and enables a high data rate of data
transmission and transmit power savings since small cell base
stations are positioned relatively close to users. The nature of
the small cell base station having small cell coverage may cause
frequent handover and radio link failure. A scheme attracting
attention to address such issue is the dual connectivity that may
allow a terminal to maintain a connection with the base station of
the macro cell while simultaneously receiving data through a small
cell link at a high data rate.
[0009] Presumably, small cell base stations may suffer from weak
security as compared with macro cell base stations. Such assumption
comes from the fact that, while macro cell base stations are
directly managed by the communication network provider, small cell
base stations scattered indoor (or in a home) are confronted with
difficulty in physical management for security maintenance.
[0010] The dual connectivity may allow a macro cell base station to
play a role as an anchor for controlling multiple small cell base
stations. Thus, if the security information regarding the macro
cell base station is exposed through the small cell base stations,
personal information leaks, illegal billing, or other security
issues are more likely to happen.
[0011] Further, assuming a few tens or a few hundreds of small
cells to be installed to increase network cell capacity, control
overhead and latency issues may arise due to procedures such as
security key request and response ensuing when receiving the
respective security keys of the small cells from a higher network
(e.g., a mobility management entity (MME)).
[0012] Therefore, there is a need for a scheme and procedure for
effectively generating and managing an independent security key by
a layered network having a macro cell and multiple small cells.
[0013] The above information is presented as background information
only to assist with an understanding of the present disclosure. No
determination has been made, and no assertion is made, as to
whether any of the above might be applicable as prior art with
regard to the present disclosure.
SUMMARY
[0014] Aspects of the present disclosure are to address at least
the above-mentioned problems and/or disadvantages and to provide at
least the advantages described below. Accordingly, an aspect of the
present disclosure is to provide a method and apparatus for
generating and maintaining a security key for a plurality of base
stations connected to a single terminal in a wireless communication
system. In particular, the instant disclosure provides a method and
apparatus for generating and maintaining a security key in a
wireless communication system under a dual connectivity
environment, i.e., under the circumstance where a terminal is
simultaneously linked to a macro cell base station and a small cell
base station.
[0015] Another aspect of the present disclosure describes a scheme
for applying and operating separate security keys for the
respective packet data convergence protocol (PDCP) layers of a
macro cell and a small cell, if the macro cell and the small cell
have the PDCP layers, in a network where a terminal is
simultaneously linked to the macro cell base station and the small
cell base station that coexists in the coverage of the macro
cell.
[0016] Another aspect of the present disclosure is to provide a
method and apparatus for generating and managing an independent
security key between a macro cell and a small cell layered network
in a wireless communication system simultaneously supporting
multiple transmission links.
[0017] Another aspect of the present disclosure provides an
apparatus and method for generating, removing, or exchanging
security keys when a base station is connected, released, or
exchanged considering the network layer of a source base station
and a target base station due to an issue that arises owing to a
difference in security capacity between per-layer base stations in
the layered network.
[0018] Another aspect of the present disclosure provides a process
for generating a security key and transmitting security key-related
information when a small cell is added to a macro cell base station
and data radio bearer (DRB) starts to be transmitted, when a small
cell is changed (e.g., another small cell is connected), or when a
small cell is released so that the macro cell resumes serving a
corresponding DRB.
[0019] Another aspect of the present disclosure provides an
apparatus and method for independently maintaining the security
keys of the macro cell and the small cells while selectively
maintaining the independence of security keys between the small
cells in order to address the control overhead and latency issues
when independently generating security keys from a higher network
(a mobility management entity (MME)).
[0020] Another aspect of the present disclosure provides an
apparatus and method for addressing the control overhead and
latency issues in such a way as to simultaneously generate multiple
security keys when independently generating security keys from a
higher network (a MME).
[0021] Another aspect of the present disclosure provides an
apparatus and method for continuously maintaining a count value
that is information to identify user data forwarded between base
stations upon handover through a radio resource control (RRC)
reconfiguration process and using the same PDCP configuration to
prevent data loss when changing a connected base station (adding,
releasing, or exchanging).
[0022] In accordance with another aspect of the present disclosure,
a method for communicating by a user equipment with a macro cell
base station and a small cell base station in a communication
system is provided. The method includes applying a first base
station security key to a first communication link with the macro
cell base station; generating a second base station security key to
be used for a second communication link with the small cell base
station based on the first base station security key; applying the
second base station security key to the second communication link
with the small cell base station; and communicating through at
least one of the first communication link and the second
communication link.
[0023] In accordance with another aspect of the present disclosure,
a method for communicating by a macro cell base station with a user
equipment and a small cell base station in a communication system
is provided. The method includes determining a first base station
security key for a first communication link with the user
equipment; generating a second base station security key to be used
for a second communication link between the small cell base station
and the user equipment based on the first base station security
key; and transmitting the generated second base station security
key to the small cell base station.
[0024] In accordance with another aspect of the present disclosure,
a user equipment communicating with a macro cell base station and a
small cell base station in a communication system is provided. The
user equipment includes a controller configured to apply a first
base station security key to a first communication link with the
macro cell base station, generate a second base station security
key to be used for a second communication link with the small cell
base station based on the first base station security key, and
apply the second base station security key to the second
communication link with the small cell base station; and a
transceiver configured to communicate through at least one of the
first communication link and the second communication link.
[0025] In accordance with another aspect of the present disclosure,
a macro cell base station communicating with a user equipment and a
small cell base station in a communication system is provided. The
macro cell base station includes a controller configured to
determine a first base station security key for a first
communication link with the user equipment, and generate a second
base station security key to be used for a second communication
link between the small cell base station and the user equipment
based on the first base station security key; and a transceiver
configured to transmit the generated second base station security
key to the small cell base station.
[0026] In accordance with another aspect of the present disclosure,
a method of performing communication by a user terminal forming a
communication link for data transmission with a macro cell base
station and a small cell base station located in a communication
system is provided. The method includes applying a first base
station security key to a communication link with the macro cell
base station, generating a second base station security key to be
used for a communication link with the small cell base station,
applying the second base station security key to the communication
link with the small cell base station, and communicating user data
through the communication links to which the security keys are
applied.
[0027] In accordance with another aspect of the present disclosure,
a method for performing communication by a macro cell base station
forming a communication link with a user terminal in a
communication system is provided. The method includes a small cell
base station and the user terminal, comprising: determining to add
a small cell base station to form a communication link with the
user terminal, sending a request for a next hop (NH) and a next hop
chaining counter (NCC) to a MME, receiving a response including the
NCC, generating a first base station security key to be used for a
communication link between the added small cell base station and
the user terminal using the NH included in the received response,
and transmitting the generated first base station security key to
the added base station.
[0028] In accordance with yet another aspect of the present
disclosure, a user terminal forming a communication link for data
transmission with a macro cell base station and a small cell base
station located in a communication system is provided. The user
terminal includes a controller configured to apply a first base
station security key to a communication link with the macro cell
base station, to generate a second base station security key to be
used for a communication link with the small cell base station, and
to apply the second base station security key to the communication
link with the small cell base station, and a transceiver configured
to communicate user data through the communication links to which
the security keys are applied.
[0029] In accordance with still another aspect of the present
disclosure, proposes a macro cell base station forming a
communication link with a user terminal in a communication system
including a small cell base station and the user terminal is
provided. The macro cell base station includes a controller
configured to determine to add a small cell base station to form a
communication link with the user terminal, to send a request for a
NH and a NCC to a MME, to receive a response including the NCC, and
to generate a first base station security key to be used for a
communication link between the added small cell base station and
the user terminal using the received NH, and a transceiver
configured to transmit the generated first base station security
key to the added base station.
[0030] Another aspect of the present disclosure, the PDCP layer
exists in each of the macro cell and the small cells and separate
security keys apply and operate for them in a network where the
small cells coexist within the coverage of the macro cell so that
two or more links are simultaneously connected to the terminal.
Thus, the security of the macro cell base station may be maintained
even when using the small cell base stations with relatively weak
security as compared with the macro cell base station.
[0031] Further, according to another aspect of the present
disclosure, there is provided a method for generating security keys
or transmitting information relating to the same under the
circumstance where a small cell is added to the macro cell base
station so that a DRB starts to be transmitted or the small cell is
released so that the macro cell resumes serving the corresponding
DRB. Thus, security keys for multiple small cells may be generated
and control-related overhead issues may be addressed while
maintaining the security of the macro cell base station for the
small cell base stations. That is, an aspect of the present
disclosure is to minimize security key control-related overhead
while maintaining the security for an interface (X2) between the
macro cell base station and a small cell base station with a
relatively weak security as compared with the macro cell base
station.
[0032] Other aspects, advantages, and salient features of the
disclosure will become apparent to those skilled in the art from
the following detailed description, which, taken in conjunction
with the annexed drawings, discloses various embodiments of the
present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The above and other aspects, features, and advantages of
certain embodiments of the present disclosure will be more apparent
from the following description taken in conjunction with the
accompanying drawings, in which:
[0034] FIG. 1 is a view illustrating a case in which a terminal
establishes dual connectivity for a macro cell and small cells that
coexist in a wireless communication system according to an
embodiment of the present disclosure;
[0035] FIG. 2 is a view illustrating a network control plane and
user plane under a dual connectivity situation where a macro cell
and a small cell are simultaneously connected to a terminal in a
wireless communication system according to an embodiment of the
present disclosure;
[0036] FIG. 3 is a view illustrating an example of a protocol stack
structure to support dual connectivity according to an embodiment
of the present disclosure;
[0037] FIG. 4 is a view illustrating another example of a protocol
stack structure to support dual connectivity according to an
embodiment of the present disclosure;
[0038] FIG. 5 is a view illustrating another example of a protocol
stack structure to support dual connectivity according to an
embodiment of the present disclosure;
[0039] FIG. 6 is a view illustrating an example of communication
between a macro cell base station, a small cell base station, and a
user terminal in a protocol stack structure where a macro cell and
a small cell have an independent packet data convergence protocol.
(PDCP) layer according to an embodiment of the present
disclosure;
[0040] FIG. 7 is a view illustrating a structure of a security key
used in a 3rd Generation Partnership Project (3GPP) long term
evolution (LTE) system according to an embodiment of the present
disclosure;
[0041] FIG. 8A is a view illustrating an example of generating a
security key and transmitting related information when handover
occurs between base stations in a communication system according to
an embodiment of the present disclosure;
[0042] FIG. 8B is a flowchart illustrating an example of generating
a security key and transmitting related information when handover
occurs between base stations in a communication system according to
an embodiment of the present disclosure;
[0043] FIG. 9A is a view illustrating an example of generating a
security key and transmitting related information for maintaining a
separate security key when a small cell is added according to an
embodiment of the present disclosure;
[0044] FIG. 9B is a flowchart illustrating an example of generating
a security key and transmitting related information for maintaining
a separate security key when a small cell is added according to an
embodiment of the present disclosure;
[0045] FIG. 10 is a view illustrating a process of generating and
transmitting a security key and an initial setup process of a small
cell link when a macro cell determines to add a small cell on the
control plane according to an embodiment of the present
disclosure;
[0046] FIG. 11 is a view illustrating an process of discarding a
security key and an process in which a terminal resumes
communication with a macro cell base station when the macro cell
determines to release a small cell on the control plane according
to an embodiment of the present disclosure;
[0047] FIG. 12 is a view illustrating an procedure in which a base
station obtains information for generating a security key from an
MME according to an embodiment of the present disclosure;
[0048] FIG. 13 is a view illustrating another procedure in which a
base station obtains information for generating a security key from
an MME according to an embodiment of the present disclosure;
[0049] FIG. 14 is a view illustrating an process of generating
security keys for a macro cell base station, a small cell base
station, and a user terminal and applying the generated security
keys when the macro cell base station determines to add a small
cell according to an embodiment of the present disclosure;
[0050] FIG. 15 is a view illustrating an process of generating
security keys for a macro cell base station, a small cell base
station, and a user terminal and applying the generated security
keys when the macro cell base station determines to release or
replace a small cell according to an embodiment of the present
disclosure;
[0051] FIGS. 16A and 16B are views illustrating an example of
generating and transferring a security key when adding a small cell
base station, when changing a small cell base station, and when
releasing all of the linked small cells in a dual connectivity
environment where the macro cell and the small cells use separated
security keys according to an embodiment of the present
disclosure;
[0052] FIGS. 17A and 17B are views illustrating an example of
establishing a data radio bearer (DRB) path and generating and
transmitting a security key on the control plane and user plane
when adding a small cell base station, when changing a small cell
base station, and when releasing all of the linked small cells in a
dual connectivity environment where the macro cell and the small
cells use separated security keys according to an embodiment of the
present disclosure;
[0053] FIG. 18 is a view illustrating a configuration of a user
terminal according to an embodiment of the present disclosure;
and
[0054] FIG. 19 is a view illustrating a configuration of a base
station according to an embodiment of the present disclosure.
[0055] Throughout the drawings, like reference numerals will be
understood to refer to like parts, components, and structures.
DETAILED DESCRIPTION
[0056] The following description with reference to the accompanying
drawings is provided to assist in a comprehensive understanding of
various embodiments of the present disclosure as defined by the
claims and their equivalents. It includes various specific details
to assist in that understanding but these are to be regarded as
merely exemplary. Accordingly, those of ordinary skill in the art
will recognize that various changes and modifications of the
various embodiments described herein can be made without departing
from the scope and spirit of the present disclosure. In addition
descriptions of well-known functions and constructions may be
omitted for clarity and conciseness.
[0057] The terms and words used in the following description and
claims are not limited to the bibliographical meanings, but, are
merely used by the inventor to enable a clear and consistent
understanding of the present disclosure. Accordingly, it should be
apparent to those skilled in the art that the following description
of various embodiments of the present disclosure is provided for
illustration purpose only and not for the purpose of limiting the
present disclosure as defined by the appended claims and their
equivalents.
[0058] It is to be understood that the singular forms "a," "an,"
and "the" include plural referents unless the context clearly
dictates otherwise. Thus, for example, reference to "a component
surface" includes reference to one or more of such surfaces.
[0059] Such denotations as "first," "second," "A," "B," "(a)," and
"(b)," may be used in describing the components of the present
disclosure. These denotations are provided merely to distinguish a
component from another, and the essence of the components is not
limited by the denotations in light of order or sequence. When a
component is described as "connected," "coupled," or "linked" to
another component, the component may be directly connected or
linked to the other component, but it should also be appreciated
that other components may be "connected," "coupled," or "linked"
between the components.
[0060] Before detailing the present disclosure, examples of
meanings or denotations applicable to some terms used in this
disclosure are proposed. However, it should be noted that the
present disclosure is not limited thereto.
[0061] The present disclosure targets wireless communication
networks. Tasks performed over a wireless communication network may
be done while a system (e.g., a base station) in charge of the
wireless communication network controls the network and transmits
data or may be done by a terminal coupled with the wireless
network.
[0062] The wireless communication system includes at least one base
station (BS). Each base station provides communication services
within a particular geographical area (generally referred to as a
cell). A cell may be divided into multiple areas (referred to as
sectors).
[0063] A base station is an entity communicating with a terminal
and may be denoted as, e.g., a BS, a base transceiver system (BTS),
a NodeB (NB), an eNodeB (eNB), or an access point (AP).
[0064] A cell should be comprehensively interpreted to denote some
area covered by a base station and collectively means a mega cell,
a macro cell, a small cell, a micro cell, a pico cell, a femto
cell, or other various coverage areas. It should be noted that
according to the context of the present disclosure the term "macro
cell" may mean a base station of the macro cell, and the term
"small cell" may mean a base station of the small cell.
[0065] The macro cell base station may also be referred to as a
macro cell eNB, macro eNB, or MeNB.
[0066] The small cell is a cell with a smaller cell area than the
macro cell and may include a pico cell, a femto cell, or a micro
cell. The small cell base station may also be denoted as a small
cell eNB, small eNB, or SeNB.
[0067] A user equipment is a mobile or stationary entity
communicating with a base station and may be denoted as UE, mobile
station (MS), mobile equipment (ME), device, wireless device,
handheld device, terminal, mobile terminal (MT), user terminal
(UT), or subscriber station (SS).
[0068] Downlink means communication from a base station to a
terminal, and uplink means communication between a terminal to a
base station. For downlink, a transmitter may be part of a base
station, and a receiver may be part of a terminal. For uplink, a
transmitter may be part of a terminal, and a receiver may be part
of a base station.
[0069] FIG. 1 is a view illustrating a case in which a terminal
establishes dual connectivity for a macro cell 102 and small cells
that coexist in a wireless communication system.
[0070] Discussion is underway for systems that offload soring
mobile traffic data by adding small cell networks to a wireless
communication system (e.g., a macro cell network). As an example,
the coverage of a macro cell 102 that is served by a macro cell
base station 100 is denoted in solid lines, and coverages 112 and
122 of small cells that are served by small cell base stations 110
and 120 are circled in dotted lines as shown in FIG. 1.
[0071] The small cells 112 and 122 including at least one pico
cell, femto cell, or micro cell have smaller coverage but may have
multiple small cell base stations installed therein, and thus, the
small cells may play a role to offload soring mobile data. The
small cells have a smaller transmission distance and good channel
environment and they may thus provide services to users at a higher
data rate and may easily recycle limited frequency resources
(frequency bands) while saving power consumed by the terminal.
[0072] The small cells may be confronted with frequent handoff when
supporting the mobility of terminals 114 and 124 due to their
smaller coverage. To support such frequent handoff, the terminal
needs to simultaneously connect to the macro cell base station.
Further, one terminal may be served by multiple small cell base
stations.
[0073] Hereinafter, dual connectivity refers to a network structure
in which a terminal is served from two or more base stations
connected thereto. The terminal may be served by a base station
through a control channel or data channel and may be provided
expanded services from multiple base stations without limited to
those from two cells (the macro cell and the small cell).
[0074] FIG. 2 is a view illustrating a network control plane and
user plane under a dual connectivity situation where a macro cell
and a small cell are simultaneously connected to a terminal in a
wireless communication system.
[0075] Referring to FIG. 2, under the dual connectivity situation
where a terminal is simultaneously connected to a macro cell and a
small cell, the user terminal 200 is linked to the macro cell base
station (macro cell eNB (MeNB)) 202 and the small cell base station
(small cell eNB (SeNB)) 204 through the connection of a network
control lane or user plane. The macro cell base station 202 and the
small cell base station 204 may be connected through, e.g., an X2
interface 206.
[0076] Under the dual connectivity situation where the small cell
is added to the existing macro cell (e.g., the cellular network),
the terminal is not controlled by the macro cell alone. That is,
under the dual connectivity situation, the terminal may also be
controlled (e.g., resource allocation) by one or more small cell
base stations.
[0077] A protocol stack structure in which the small cell base
stations, as well as the macro cell base station, also has an
independent PDCP to support dual connectivity according to an
embodiment of the present disclosure is described with reference to
FIGS. 3 to 5.
[0078] FIG. 3 is a view illustrating an example of a protocol stack
structure for supporting dual connectivity according to an
embodiment of the present disclosure.
[0079] The macro cell base station 300 and the small cell base
station 310, respectively and independently, include packet data
convergence protocol (PDCP) layers 302 and 312, radio link control
(RLC) layers 304 and 314, medium access control (MAC) layers 306
and 316, and physical (PHY) layers 308 and 318.
[0080] Referring to, FIG. 3 exemplifies the structure in which the
user plane of the small cell base station 310 is directly connected
to a core network (CN) via a separate S1 interface 320
distinguished from the user plane S1 interface 330 of the macro
cell base station 300.
[0081] The small cell base station 310 is directly connected to the
core network (CN) via the Si interface 320, and the small cell base
station 310 may transmit user plane data via a separate path, not
through the macro cell base station or inter-base station
connection (e.g., the X2 interface).
[0082] FIG. 4 is a view illustrating another example of a protocol
stack structure for supporting dual connectivity according to an
embodiment of the present disclosure.
[0083] Referring to FIG. 4, the macro cell base station 300 and the
small cell base station 310, respectively and independently,
include PDCP layers 302 and 312, RLC layers 304 and 314, MAC layers
306 and 316, and PHY layers 308 and 318.
[0084] In particular, FIG. 4 exemplifies the structure in which the
user plane of the small cell base station 310 is connected to the
core network (CN) via the macro cell base station 300 through the
Xn interface (e.g., the X2 interface) 420.
[0085] In such case, since the data of all the user planes is
transmitted via the macro cell base station through the inter-base
station connection (X2), the transmission capacity may be limited
by the latency and restricted capacity of the backhaul. That is,
the connection structure shown in FIG. 4 is a structure in which
one DRB for small cells is served through one base station (any one
of the macro cell base station or small cell base stations) without
occurrence of DRB split for small cells.
[0086] FIG. 5 is a view illustrating another example of a protocol
stack structure for supporting dual connectivity according to an
embodiment of the present disclosure.
[0087] Referring to FIG. 5, the macro cell base station 300 and the
small cell base station 310 respectively and independently include
PDCP layers 502 and 302 and a PDCP layer 312, RLC layers 504 and
304 and an RLC layer 314, MAC layers 506 and 306 and an MAC layer
316, and PHY layers 508 and 308 and a PHY layer 318, and the user
plane of the small cell base station 310 is connected to the small
cell base station via the macro cell base station from the CN.
[0088] In such case, since the data of all the user planes is
transmitted via the macro cell base station through the inter-base
station connection (the Xn interface 520), the transmission
capacity may be limited by the latency and restricted capacity of
the backhaul. The connection structure shown in FIG. 5 is a
structure in which a DRB split for small cells occurs (a split from
the S1 interface 500 to the Xn interface 520), and one DRB is
served through multiple base stations (the macro cell base station
and small cell base stations).
[0089] Now described is a scheme for generating, managing, and
operating a security key when a macro cell and a small cell
respectively include independent PDCP layers as described above in
connection with FIGS. 3 to 5.
[0090] FIG. 6 is a view illustrating an example of communication
between a macro cell base station, a small cell base station, and a
user terminal in a protocol layer structure where a macro cell and
a small cell have an independent PDCP layer according to an
embodiment of the present disclosure.
[0091] Data of the control plane is transferred through the macro
cell base station 300 (a link 600) in the embodiment of FIG. 6.
Further, data of the user plane is served to the user terminal 630
through two DRBs, i.e., one through the macro cell base station 300
(particularly between EPS bearer 1 and the PDCP 612 of the link
602) and the other through the small cell base station 310
(particularly between EPS bearer 2 and the PDCP 614 of the link
604).
[0092] The user terminal 630 forms links 600 and 602 with the macro
cell base station 300 and a link 604 with the small cell base
station 310 and communicate data via separate protocol layers (PHY,
MAC, RLC, and PDCP layers).
[0093] The PDCP layers 610, 612, and 614 independently present in
the macro cell and the small cell are in charge of security. In
this case, required is a design as to whether the same or separate
and independent security keys are used for the link 602 through the
macro cell in the PDCP layer 612 of the macro cell and the link 604
through the small cell in the PDCP layer 614 of the small cell.
[0094] FIG. 7 is a view illustrating a structure of a security key
used in a 3GPP LTE system according to an embodiment of the present
disclosure.
[0095] A lower level key may be generated from a higher level
key.
[0096] The top level key K (700) used to authenticate the user
terminal is present in the universal subscriber identity module
(USIM) or authentication center (AuC).
[0097] The lower level keys CK, IK (702) that may be generated from
the higher level key K (700) may be known only to the UE or the
home subscriber server (HSS). That is, the lower level keys CK, IK
(702) is present in the UE or the HSS.
[0098] The MME may generate K.sub.ASME (704), which is a key of the
access security management entity (ASME), based on the lower level
key CK, IK (702). The ASME is an entity receiving the top level key
of the access network from the HSS, and for the evolved universal
mobile telecommunications system terrestrial radio access network
(E-UTRAN), the MME may correspond to the ASME.
[0099] The UE or the base station may generate an integrity key
K.sub.NASint (708) and an encryption key K.sub.NASenc (706) for the
non access stratum (NAS) based on K.sub.ASME (704). Further, the UE
or base station may generate K.sub.eNB 710 which is a base key for
the security key of each base station.
[0100] The UE or the base station may generate K.sub.RRCint (716),
K.sub.RRCenc (714), and K.sub.UPenc which are security keys for the
access stratum (AS) based on K.sub.eNB (710).
[0101] Subsequently, generation and transfer of a security key are
described, focusing on the authentication process.
[0102] UE-MME LTE mutual authentication is carried out via an
evolved packet system authentication and key agreement (EPS AKA)
procedure performed between the UE, the MME, and the HSS as mutual
authentication between the UE and the network. In the EPS AKA
procedure, the HSS transmits an authentication vector (AV) to the
MME, and the MME and the UE may perform mutual authentication using
the authentication vector. As a result of the authentication, the
UE and the MME share K.sub.ASME (704) and obtain, from K.sub.ASME
(704), K.sub.NASint (708) and K.sub.NASenc (706), which are
security keys of the NAS, and K.sub.eNB (710), which is the base
key of the base station.
[0103] It is K.sub.ASME (704) that the MME receives from the HSS.
Since K.sub.ASME (704) cannot be transferred to the UE via the
E-UTRAN, K.sub.ASME (704) may be identified by KSI.sub.ASME that
corresponds to K.sub.ASME (704) in a one-to-one manner and replaces
K.sub.ASME (704).
[0104] An integrity check and encryption may be performed on the
NAS signaling message that is the control plane protocol between
the UE and the MME. The integrity check is a mandatory function,
and encryption is an optional function. The base key for NAS
security is K.sub.ASME (704) that is positioned in the UE and the
MME and is obtained through authentication between the subscriber
and the network. NAS security keys are obtained from K.sub.ASME
(704) in the UE and the MME and come in such types as integrity
keys K.sub.NASint (708) and encryption keys K.sub.NASenc (706).
[0105] The control plane between the UE and the eNB performs an
integrity check (mandatory) and encryption (optional) on RRC
signaling, and the user plane performs encryption (optional) on IP
packets. For access stratum (AS) security, the base key is
K.sub.eNB (710), and K.sub.eNB (710) is positioned in the UE and
the eNB and is obtained from K.sub.ASME (704). The eNB does not
include K.sub.ASME (704). Thus, the MME generates K.sub.eNB (710)
from K.sub.ASME (704) and transfers to the eNB.
[0106] AS security keys are obtained from K.sub.eNB (710) in the UE
and the eNB and come in such types as K.sub.RRCint (716),
K.sub.RRCenc (714), and K.sub.UPenc (712). K.sub.RRCint (716) and
K.sub.RRCenc (714), respectively, are used for integrity check and
encryption on RRC signaling, and K.sub.UPenc (712) is used for
encryption on user plane data (IP packets).
[0107] The base station (macro cell base station or small cell base
station) may receive a next hop (NH) 718 and a next hope chaining
counter (NCC) 720 from the MME. When the NCC 720 is transferred to
the terminal, the terminal may determine the NH 718 using the NCC
720. The terminal or the base station may generate KeNB* (722) that
is a security key of the base station using the NH 718 and may
apply the generated security key as the security key of the base
station. KeNB* (722) may be generated based on the NH 718 or may be
generated based on a previous security key 710 of the base
station.
[0108] FIG. 8A is a view illustrating an example of generating a
security key and transmitting related information when handover
occurs between base stations in a communication system according to
an embodiment of the present disclosure.
[0109] FIG. 8B is a flowchart illustrating an example of generating
a security key and transmitting related information when handover
occurs between base stations in a communication system according to
an embodiment of the present disclosure.
[0110] If the user terminal 800 reports a result of channel
measurement (measurement report) to the serving base station 810,
the serving base station 810 or the MME 830 determines to hand the
user terminal 800 over to the target base station 820 based on the
channel measurement result at operation 801.
[0111] The serving base station 810 generates a base station
security key, KeNB*, to be used in the new base station (target
base station) 820 at operation 802. That is, the procedure of
generating (or regenerating) the base station security key KeNB* to
be used in the target base station 820 may be initiated by the
serving base station 810 or the MME 830.
[0112] The serving base station 810 forwards KeNB* and the NCC to
the target base station 820 at operation 803.
[0113] The target base station 820 informs the user terminal 800 of
the NCC (804), and the user terminal 800 generates KeNB* based on
the NCC at operation 805.
[0114] The user terminal 800 and the target base station 820
perform data transmission by applying the new base station security
key KeNB* at operation 806.
[0115] Selectively, the target base station 820 may also receive a
new NH-NCC pair (i.e., {NH, NCC}) from the MME 830 in preparation
for next handover at operation 807.
[0116] Meanwhile, the communication network including a small cell
may be installed so that the coverage of the small cell overlaps
the coverage of the macro cell within the macro cell coverage, and
the user terminal may establish a link with each of the macro cell
base station and the small cell base station at the same time
(i.e., two or more links). Although handover occurs between
equivalent base stations in the 3GPP LTE system, the small cell
network according to an embodiment of the present disclosure
overlaps the macro cell, and thus, the small cell link may be added
to the link that is served only by the macro cell, the small cell
link may be released, or the small cell link may be replaced with a
link with a new small cell base station (by handover between the
small cells).
[0117] If the same security key as the one used in the macro cell
is used for small cells subjected to RRC control by the macro cell,
the complexity of generation of security keys may be reduced
(because there is no computation for generating security keys for
small cells), but if the security keys of the small cells that are
relatively security vulnerable leak, the security key of the macro
cell would be highly likely to leak as well. By contrast, if the
macro cell and the small cell use separate independent security
keys, they may have robust security but may cause complicated
control and overhead in generating and managing security keys.
Receiving security keys from a higher network (e.g., the MME) every
handover or when installing a few tens or a few hundreds of small
cells to increase network cell capacity would cause control
overhead and latency issues.
[0118] Accordingly, the present disclosure proposes a scheme for
independently generating and managing each security key or sharing
and managing a single security key according to a predetermined
standard or condition in a network where a macro cell and small
cells coexist.
[0119] Further, the present disclosure proposes a scheme for
generating, transmitting, and managing a security key for a
transmission link based on a security key corresponding to another
transmission link and a scheme in which each base station directly
generates and manages a security key.
[0120] In other words, there are proposed a scheme for generating
and managing a security key considering layers between a macro cell
and a small cell in generating and managing a security key per
network layer, a scheme for generating, sharing, and using the same
security key between the network layers of the macro cell link and
the small cell link, a scheme for generating and managing separate
security keys between the network layers of the macro cell link and
the small cell link, a scheme for generating a security key for the
small cell link based on a security key of the macro cell link,
transmitting the security key for the small cell link to the small
cell base station, and managing the same, and a scheme for
generating a security key for the small cell link independently
from a security key of the macro cell link, transmitting the
security key to the small cell base station, and managing the
same.
[0121] FIG. 9A is a view illustrating an example of generating a
security key and transmitting related information for maintaining a
separate security key when a small cell is added according to an
embodiment of the present disclosure.
[0122] FIG. 9B is a flowchart illustrating an example of generating
a security key and transmitting related information for maintaining
a separate security key when a small cell is added according to an
embodiment of the present disclosure.
[0123] If the user terminal 900 reports a result of channel
measurement (measurement report) to the macro cell base station
910, the macro cell base station 910 determines whether to add the
small cell base station 920 to the user terminal 900 based on the
channel measurement result at operation 901.
[0124] The macro cell base station 910 or the small cell base
station 920 may generate a security key, KeNB*, of the small cell
base station 920 (902). That is, the procedure of generating (or
regenerating) the base station security key KeNB* to be used in the
small cell base station 920 may be initiated by the macro cell base
station 910 or the small cell base station 920. Selectively, the
procedure of generating (or regenerating) the base station security
key KeNB* to be used in the small cell base station 920 may also be
initiated by the procedure of varying (or regenerating) the base
station security key used in the macro cell base station 910 (the
variation or regeneration of the macro cell base station security
key may be initiated in the MME or the macro cell).
[0125] The security key of the small cell base station 920 may be
used by the user terminal 900 for a new link for connection with
the small cell base station 920. Selectively, the macro cell base
station 910 may inquire and obtain information to generate a base
station security key to be used for the new link from the MME
930.
[0126] The macro cell base station 910 forwards the generated KeNB*
and NCC to the added small cell base station 920 at operation
903.
[0127] The macro cell base station 910 informs the user terminal
900 of security key-related information (e.g., the NCC) at
operation 904, and the user terminal 900 generates a base station
security key KeNB* to be used for the link with the small cell base
station based on the security key-related information.
[0128] Thereafter, the user terminal 900 and the added small cell
base station 920 may perform any DRB transmission by applying the
security key KeNB* that they generated on their own or received at
operation 905.
[0129] Embodiments of sharing security key information considering
the relationship between base stations forming links with a user
terminal are now described.
[0130] According to an embodiment of the present disclosure, the
security key of the macro cell base station may be shared by the
small cell base station.
[0131] In such case, the small cell base station may generate and
use the security key of the small cell base station using (based
on) the shared (transferred) security key of the macro cell base
station.
[0132] Further, the small cell base station may transmit the
security key of the macro cell base station or the generated
security key of the small cell base station to another small cell
base station so that the other small cell base station by itself
may generate and use its security key.
[0133] Meanwhile, the security key of the other small cell base
station may also be generated by the macro cell base station. That
is, the security key of the small cell base station may be
transferred (shared) to the macro cell base station, and the macro
cell base station receiving the security key of the small cell base
station may generate the security key of the other small cell base
station using (based on) the security key of the small cell base
station and transfer to the other base station so that the other
small cell base station may use the same.
[0134] According to another embodiment of the present disclosure,
the security key of the macro cell base station might not be shared
by the small cell base station.
[0135] In this case, the small cell base station receives and uses
the security key (not the security key of the macro cell base
station) of the small cell base station that is generated and
transferred by the macro cell base station.
[0136] The security key of the small cell base station may be
shared or not by the macro cell base station.
[0137] In case the security key of the small cell base station is
shared by the macro cell base station, the macro cell base station
generates the security key of the other small cell base station
using (based on) the shared security key of the small cell base
station and transmits the generated security key of the other small
cell base station so that the other small cell may use it.
[0138] Unless the security key of the small cell base station is
shared by the macro cell base station, the small cell base station
generates the security key of the other small cell base station and
transmits the security key to the other small cell base station, or
the macro cell base station generates a security key independent
from the security key of the small cell base station and transmits
the independent security key to the other small cell base station
so that the other small cell base station may use it.
[0139] FIG. 10 is a view illustrating the process of generating and
transmitting a security key and an initial setup process of a small
cell link when a macro cell determines to add a small cell on the
control plane according to an embodiment of the present
disclosure.
[0140] If the user terminal 900 reports a result of channel
measurement (measurement report) to the macro cell base station 910
(1002), the macro cell base station 910 determines whether to
additionally link the small cell base station to the user terminal
900 based on the channel measurement result and generates a base
station security key KeNB* to be used for the new link to be
connected to the small cell base station 920 (1004).
[0141] The macro cell base station 910 includes KeNB* and/or NCC in
a small cell add request message (SCELL ADDITION REQUEST) and
forwards the same to the small cell base station 920 (1006).
[0142] The added small cell base station 920 responds by
transferring a small cell add acknowledgement message (SCELL
ADDITION ACK) to the macro cell base station 910 (1008).
Selectively, the small cell add acknowledgement message may contain
an NCC value.
[0143] The macro cell base station 910 transfers a message for RRC
reconfiguration (rrcConnectionReconfiguration) to the user terminal
900 (1010). Selectively, the message for RRC reconfiguration may
contain the NCC value transferred from the small cell base station
920.
[0144] Having received security key-related information (e.g., the
NCC) through the RRC reconfiguration message 1010, the user
terminal 900 may generate a base station security key KeNB* for a
new link to be connected with the small cell base station 920
(1012).
[0145] The macro cell base station 910 receives a message
(rrcConnectionReconfigurationComplete) responding to the RRC
reconfiguration message from the user terminal 900 (1014).
[0146] The macro cell base station 910 transmits the RRC
reconfiguration message rather than sending out an RRC release
message or RRC reset message to the user terminal 900 in order to
prevent data transferred to the user terminal 900 from being lost
while forwarded from the macro cell base station 910 to the small
cell base station 920. That is, use of the RRC release message or
RRC reset message may cause the COUNT value forwarded to identify
the user data to be initialized, thus leading to data loss.
Accordingly, upon RRC configuration, an RRC reconfiguration process
is performed to maintain the COUNT value. The COUNT value is a
value recorded in the PDCP layer and is an index to identify data
transferred to the user terminal. For example, the COUNT value may
be a value ranging from 0 to 500 and may be used for retransmission
of data that may be lost upon data forwarding.
[0147] Selectively, the macro cell base station 910 may perform a
process 1016 of transferring the COUNT value through, e.g., a
sequence number status transfer (SN STATUS TRANSFER) message from
the previous transmission link (i.e., the macro cell base station)
to the target transmission link (i.e., the small cell base station)
before forwarding the data to the small cell base station 920.
[0148] Subsequently, the macro cell base station 910 may forward
user data to be transferred to the user terminal 900 to the small
cell base station 920 (1018). Selectively, the small cell base
station 920 may perform management to detect or prevent data loss
during the process 1018 of forwarding data from the macro cell base
station 910 to the small cell base station 920 by using the COUNT
value included in the sequence number status transfer (SN STATUS
TRANSFER) message 1016.
[0149] Then, the user terminal 900 may perform transmission of a
DRB with the small cell base station 920 based on the newly
generated security key KeNB*. Selectively, the process of
transmitting the DRB may include one or more of random access of
the user terminal 900 to the small cell base station 920 (1020),
PDCP status reporting (1022), applying the newly generated security
key KeNB* to the newly generated data radio bearer (denoted "DRB
2") (1024), and transmitting a physical downlink shared channel
(PDSCH) and/or physical uplink shared channel (PUSCH) for the DRB 2
(1026).
[0150] FIG. 11 is a view illustrating a process of discarding a
security key and a process in which a terminal resumes
communication with a macro cell base station when the macro cell
determines to release a small cell on the control plane according
to an embodiment of the present disclosure.
[0151] If the user terminal 900 reports the channel measurement
result (measurement report) to the macro cell base station (macro
ENB) 910 (1102), the macro cell base station 910 determines whether
to release the link to the small cell base station 920 connected
with the user terminal 900 (i.e., the small cell link) based on the
channel measurement result and determines whether to apply the data
radio bearer DRB2 used to be connected to the small cell base
station 920 back to itself (i.e., the macro cell base station 910)
(1104).
[0152] The macro cell base station 910 transmits a small cell
release request (SCELL RELEASE REQUEST) message to the small cell
base station 920 (1106), and the small cell base station 920
responds by transmitting a small cell release acknowledgment (SCELL
RELEASE ACK) message to the macro cell base station 910 (1108).
[0153] Selectively, the small cell base station 920 may perform a
process 1110 of transferring a COUNT value to identify user data to
the macro cell base station 910 through a sequence number status
transfer (SN STATUS TRANSFER) message before forwarding data to the
macro cell base station 910 as the small cell link is released.
[0154] Subsequently, the small cell base station 920 may forward
user data to be transferred to the user terminal 900 to the macro
cell base station 910 (1112). Selectively, the macro cell base
station 920 may perform management to detect or prevent data loss
during the process 1112 of forwarding data from the small cell base
station 920 to the macro cell base station 910 by using the COUNT
value included in the sequence number status transfer (SN STATUS
TRANSFER) message 1110.
[0155] The macro cell base station 910 transmits, to the user
terminal 900, a message (rrcConnectionReconfiguration) for RRC
reconfiguration (1114) and receives an RRC reconfiguration complete
message (rrcConnectionReconfigurationComplete) from the user
terminal 900 (1116). Selectively, the RRC reconfiguration message
1114 may contain an NCC value.
[0156] The macro cell base station 910 transmits the RRC
reconfiguration message rather than an RRC release message or RRC
reset message to the user terminal 900 for RRC configuration in
order to continuously maintain the COUNT value.
[0157] The user terminal 900 may discard the security key KeNB*
generated for the small cell link and applies the security key KeNB
of the macro cell base station to DRB 2 (1118) and may perform DRB
2 PDSCH and/or PUSCH transmission (1120).
[0158] The macro cell base station or the small cell base station
may previously receive multiple security key-related information
items from a higher network entity (e.g., the MME) upon generating
independent security keys and may use the information items to
generate security keys.
[0159] At this time, the macro cell base station may access the MME
and receive multiple security key-related information items (seed)
to generate a security key and may transmit the security key to the
small cell link. Further, a representative small cell base station
may directly access the ME to receive multiple security key-related
information items (seed) and forward them to a neighboring small
cell base station, or each small cell base station may directly
access the MME to receive security key-related information (e.g.,
seed) to generate an independent security key.
[0160] A base station should receive an NH from the MME in order to
generate a new next hope (NH)-based security key that is not based
on the security key KeNB of the macro cell base station. A process
for the same is described with reference to FIGS. 12 and 13.
[0161] FIG. 12 is a view illustrating a procedure in which a base
station obtains information for generating a security key from an
MME according to an embodiment of the present disclosure.
[0162] Referring to FIG. 12, an NH/NCC request (NH/NCC REQUEST)
message is used as a new message to receive the NH/NCC from the
MME.
[0163] If the macro cell base station 910 determines to generate a
security key which requires a new NH-NCC pair (i.e., generating a
vertical key) (1202), the macro cell base station 910 transmits an
NH/NCC request (NH/NCC REQUEST) message to the MME 930 (1204). The
MME 930 responds by sending out an NH/NCC response (NH/NCC
RESPONSE) message to the macro cell base station 910 (1206).
[0164] Here, the NH/NCC response message 1206 may contain the
NH-NCC pair. Selectively, the NH/NCC response message 1206 may
include a plurality of NH-NCC pairs {NH, NCC}. Since the small cell
base station has small cell coverage, handover or adding, release,
or change of small cells may be frequent, and thus, more NH-NCC
pairs {NH, NCC} are required for generating security keys for base
stations.
[0165] Although the macro cell base station is an entity to send
out the NH/NCC request message 1204 to request {NH, NCC}, for
example, the small cell base station may, in some cases, send out
the message to obtain {NH, NCC} from the MME.
[0166] FIG. 13 is a view illustrating another procedure in which a
base station obtains information for generating a security key from
an MME according to an embodiment of the present disclosure.
[0167] A path switch request (PATH SWITCH REQUEST) message is a
message transmitted from a base station to the MME to change or
switch data transmission paths (PATH) when handover occurs between
base stations. In the embodiment shown in FIG. 13, the path switch
request (PATH SWITCH REQUEST) message is used to receive the NH/NCC
from the MME.
[0168] If the macro cell base station 910 determines to generate a
security key which requires a new NH-NCC pair (i.e., generating a
vertical key) (1302), the macro cell base station 910 transmits the
path switch request (PATH SWITCH REQUEST) message to the MME 930
(1304).
[0169] In case a small cell base station is added, released, or
changed, the data transmission path to the small cell base station
may be varied or not depending on the structure of the user
plane.
[0170] As an example, since the data transmission path interface
320 of the small cell becomes different from the data transmission
path interface 330 of the macro cell in the case shown in FIG. 3, a
path switch occurs.
[0171] As another example, in the case shown in FIGS. 4 and 5,
although a small cell is added, the data transmission path is not
changed (the same path passing through the macro cell as the one
before the small cell is added). In such case, the path switch
request message may contain, e.g., the same transmission layer
address as the present one and E-radio access bearer (E-RAB)
information.
[0172] Unless the path switch request (PATH SWITCH REQUEST) message
received from the macro cell base station 910 indicates a path
switch or change (e.g., the case shown in FIGS. 4 and 5), the MME
930 performs only operations regarding the NH and NCC without a
path switch, while in case the path switch request (PATH SWITCH
REQUEST) message indicates a path switch, the MME 930 performs
operations regarding the NH and NCC and a data path switching
operation (1306). That is, the MME 930 transmits a path switch
request acknowledgment (PATH SWITCH REQUEST ACK) message containing
the NH-NCC pair to the macro cell base station 910 in response to
the path switch request message (1308).
[0173] Selectively, the path switch request acknowledgment (PATH
SWITCH REQUEST ACK) message 1308 may include a plurality of NH-NCC
pairs {NH, NCC}. Since the small cell base station has small cell
coverage, handover or adding, release, or change of small cells may
be frequent, and thus, more NH-NCC pairs {NH, NCC} are required for
generating security keys for base stations.
[0174] Although the macro cell base station is an entity to send
out the path switch request (PATH SWITCH REQUEST) message 1304 to
request {NH, NCC}, for example, the small cell base station may, in
some cases, send out the message to obtain {NH, NCC} from the
MME.
[0175] Described is an embodiment of independently generating and
managing a security key when a user terminal adds a link with a
small cell base station.
[0176] According to an embodiment of the present disclosure, there
is proposed a scheme for selectively maintaining the independence
of security keys between small cell base stations while managing a
security key of a macro cell and security keys of small cells to be
independently generated. That is, the security keys between the
small cells may be determined to be generated independently from
each other in some cases or to be dependent, the same or similar to
each other in other cases.
[0177] Specifically, a small cell first added to the macro cell
coverage may be rendered to generate a security key independent
from the security key of the macro cell base station. A small cell
added next to the first small cell may generate a dependent
security key based on the security key of the first small cell.
[0178] Further, under a certain condition, it may be determined to
generate a security key independent from a small cell base station
added. For example, the condition to generate a security key
independent from a small cell base station added may include when a
cluster of small cells positioned within a predetermined physical
distance is varied or when a timer to generate an independent
security key expires (i.e., a predetermined time or more elapses
after a previous independent security key is generated).
[0179] FIG. 14 is a view illustrating a process of generating
security keys for a macro cell base station, a small cell base
station, and a user terminal and applying the generated security
keys when the macro cell base station determines to add a small
cell according to an embodiment of the present disclosure.
[0180] Selectively, the small cell base station may be notified
that small cell ServCell_s is added by receiving information such
as SCellToAddRemove information element (IE) from the macro cell
base station (1400). Here, ServCell_s means a serving cell
controlled by the small cell base station. For example, the
SCellToAddRemove IE may be contained in a small cell add request
(SCELL ADD REQUEST) message.
[0181] The macro cell base station (or small cell base station or
user terminal) determines whether the small cell to be added is a
small cell first added (1402). Further, the user terminal may
generate a security key for the small cell base station (a security
key for a DRB to be added) through operations 1410 and 1412 for
determining an NCC value transmitted from the macro cell base
station (or small cell base station). That is, different security
key generating methods may apply depending on the NCC value
transmitted from the base station.
[0182] A process of generating and applying a security key is
described in detail.
[0183] In case as a result of the determination 1402 the small cell
is first added, the user terminal sets the sum of the received
NCC_s value and one, i.e., NCC_s+1, to a local NCC_s value (1404).
Here, NCC_s is an NCC maintained for the security key KeNB_s of the
small cell base station. The next hop chaining counter (NCC) may be
represented in three bits, and at this time, may be used to
distinguish the security keys for eight base stations for one
K.sub.ASME.
[0184] The user terminal selects the ID of the macro cell base
station, physical cell ID (PCI), and operation frequency,
downlink-EUTRAN absolute radio frequency channel number
(DL-EARFCN), according to a predetermined rule (1406).
[0185] Subsequently, the user terminal may generate a security key
KeNB_s* for the small cell base station as in Equation 1 by
applying the received NCC_s, the PCI, and the DL_EARFCN to a key
derivation function (KDF) (1408).
KeNB_s*=KDF[NH(NCC_s), PCI, DL-EARFCN] Equation 1
[0186] Here, NH(NCC_s) is a function to calculate next hop (NH)
using NCC_s.
[0187] As such, the method of generating a new security key using
the NH value to independently maintain the security keys of the
macro cell base station and the small cell base station is called
vertical security key derivation. That is, when the received NCC
value differs from the previous NCC (local NCC), it may be
determined to generate a new security key according to the vertical
security key derivation method.
[0188] If it is determined in 1402 that the small cell is not first
added (i.e., when there are one or more small cells already added),
the user terminal determines whether the NCC_s has been signaled
from the macro cell base station (1410).
[0189] In case it is determined in 1410 that the NCC_s has not been
signaled, the user terminal may determine to use (recycle) the
existing security key of the small cell base station without
generating a security key (1424).
[0190] Thus, the user terminal applies the security key KeNB_s for
a logical channel LCH_s served by the small cell and applies the
security key KeNB_m for a logical channel LCH_m served by the macro
cell (1422).
[0191] Meanwhile, in case it is determined in 1410 that the NCC_s
has been signaled, the user terminal determines whether the
signaled (received) NCC_S is the same as the local NCC_S
(1412).
[0192] In case a result of the 1412 determination indicates "the
same," the user terminal may select a PCI and DL-EARFCN according
to a predetermined rule (1416) and may apply the present security
key KeNB_s of the small cell base station, the PCI, and the
DL-EARFCN to the key derivation function to generate a security key
KeNB_s* for the small cell base station as in Equation 2
(1418).
KeNB_s*=KDF[KeNB_s, PCI, DL-EARFCN] Equation 2
[0193] The method of generating a new security key based on an
existing base station security key as shown in Equation 2 is called
a horizontal security key derivation method. That is, when the
received NCC value is the same as the previous NCC (local NCC), it
may be determined to generate a new security key according to the
horizontal security key derivation method.
[0194] In other words, even though the small cell base station (or
the macro cell base station) does not receive control information
(e.g., NH or NCC) to generate a new security key from the MME, the
user terminal generates a new security key based on the existing
small cell base station security key. This way may reduce overhead
that may be caused by control signaling in the MME due to frequent
security key generation tasks.
[0195] Unless the result of the 1412 determination indicates "the
same," the user terminal sets the received NCC_s value to the local
NCC_s value (1414) and performs the selection of PCI and DL-EARFCN
(1406) and generation of a key using the NCC_s (1408).
[0196] If the security key of the small cell base station is
generated through the operation 1418 or 1408, the user terminal
sets the generated base station security key KeNB_s* to the new
base station security key KeNB_s (1420) and may apply the security
key to the logical channel for data transmission (1422).
[0197] Selectively, independent security keys respectively for the
macro cell base station and the small cell base station may be
generated according to a determination by the macro cell or a rule
under a particular condition or need. For example, the macro cell
base station or the small cell base station (or the user terminal)
may operate a security key generation timer to perform management
so that if a predetermined time elapses, security keys may be
independently and periodically generated or may perform management
so that independent security keys may be generated when the number
of small cell base stations recycling security keys exceeds a
predetermined number.
[0198] FIG. 15 is a view illustrating a process of generating
security keys for a macro cell base station, a small cell base
station, and a user terminal and applying the generated security
keys when the macro cell base station determines to release or
replace a small cell according to an embodiment of the present
disclosure.
[0199] Selectively, the small cell base station may be notified
that small cell ServCell_s is released by receiving information
such as SCellToAddRemove IE from the macro cell base station
(1500). For example, the SCellToAddRemove IE may be contained in a
small cell release request (SCELL RELEASE REQUEST) message.
[0200] The macro cell base station (or small cell base station or
user terminal) determines whether the small cell to be released is
a small cell released last (1502). Further, the user terminal may
determine a base station security key to be used through the
operation of determining an NCC value transmitted from the macro
cell base station (or the small cell base station). That is,
different base station security key applying methods may apply
depending on the NCC value transmitted from the base station.
[0201] A process of generating and/or applying a security key is
described in detail.
[0202] In case it is determined in 1502 that the small cell is
released last, the user terminal releases the existing security key
KeNB_s of the small cell base station and resets (i.e.,
initializes) the local NCC_s value (1504). Accordingly, the
security key of the macro cell base station, KeNB_m, may apply to
both the logical channel LCH_m served by the macro cell and the
logical channel LCH_s served by the small cell (i.e., the logical
channel to replace the released small cell) (1506). Here, although
the logical channel when the small cell is released is denoted as
LCH_s for convenience, the logical channel LCH_s with the small
cell base station released (accordingly not present any longer)
should be interpreted to mean a logical channel with the macro cell
base station (however it is denoted).
[0203] If it is determined in 1502 that the small cell is not
released last (i.e., when there are one or more small cells left
after the release), the user terminal determines whether the NCC_s
has been signaled from the macro cell base station (1508).
[0204] In case it is determined in 1508 that the NCC_s has not been
signaled, the user terminal does not generate a security key. The
user terminal determines to use (i.e., recycle) the existing
security key of the small cell base station as a base station
security key to replace the released small cell (1514).
[0205] In case it is determined in 1508 that the NCC_s has been
signaled, the user terminal generates a security key of the small
cell base station to replace the released small cell using the
vertical security key derivation method or horizontal security key
derivation method according to the signaled (or received) NCC_s
value similar to when a small cell is added (1510).
[0206] If the security key of the small cell base station is
determined (generated) according to operation 1514 or 1510, the
security key KeNB_m of the macro cell base station applies to the
logical channel LCH_m served by the macro cell, and the determined
(generated) security key KeNB_s of the small cell base station
applies to the logical channel LCH_s served by the small cell
(i.e., the logical channel with the base station to replace the
released small cell) (1512).
[0207] FIGS. 16A and 16B are views illustrating an example of
generating and transferring a security key when adding a small cell
base station, when changing a small cell base station, and when
releasing all of the linked small cells in a dual connectivity
environment where the macro cell and the small cells use separated
security keys according to an embodiment of the present
disclosure.
[0208] The embodiment shown in FIGS. 16A and 16B is regarding a
scenario in which the user terminal initially receiving two DRBs
through the macro cell base station using the security key KeNB of
the macro cell base station receives one of the DRBs (referred to
as DRB 2 and indicating the LCH_s as shown in FIGS. 16A and 16B)
through a small cell base station 1 added and then hands over to a
small cell base station 2 for the DRB 2 and finally releases the
link with the small cell base station 2 to receive both the DRBs
from the macro cell base station.
[0209] The security key KeNB_m of the macro cell base station may
be obtained, as in Equation 3, using a key derivation function
whose input values include the macro cell base station ID, which is
the physical cell ID (PCI), the operation frequency, which is the
downlink-EUTRAN absolute radio frequency channel number
(DL_EARFCN), and the next hop (NH) (1610).
KeNB_m=KDF[NH(n), PCI, DL-EARFCN]=K1 Equation 3
[0210] Initially, the user terminal 1600 is served two DRBs (DRB 1
indicating LCH_m and DRB 2 indicating LCH_s) by the macro cell base
station 1602, and the security key of the macro cell base station
is commonly used for the two DRBs (1612 and 1614).
[0211] In case a variation in channel status is detected based on a
channel measurement report of the user terminal, the macro cell
base station 1602 adds a new small cell and determines to connect
one (here, DRB 2) of the user DRBs to the small cell base station
1604 (1616). The macro cell base station 1602 generates an NH value
for use in vertical security key generation (1618).
[0212] At this time, the security key for the new small cell base
station 1604 is obtained as in Equation 4 using the KDF whose input
values include the PCI, which is the ID of the small cell base
station, the DL-EARFCN, which is the operation frequency, and the
new NH value (1620). That is, the security key for the new small
cell base station 1604 may be generated by the vertical security
key derivation method.
KeNB_s*=KDF[NH(n+1), PCI, DL-EARFCN]=K2 Equation 4
[0213] Here, n is the value of NCC_m which is an NCC maintained by
the security key of the macro cell base station.
[0214] If the macro cell base station 1602 transmits the security
key KeNB_s* generated for the small cell base station to the small
cell base station (1656), the small cell base station applies the
received KeNB_s* as a security key of the new base station.
[0215] The macro cell base station transmits the NCC_s information
to the user terminal 1600 as well (1658). The user terminal 1600
may restore (generate) and use the security key KeNB_s* for the DRB
2 connected to the small cell base station 1 1604 based on the
received NCC_s.
[0216] Specifically, the user terminal 1600 makes comparison as to
the received NCC_s (1622). The NCC_s is initialized to the local
NCC when handover occurs (or the initial small cell is added), and
in case the new NCC_s value is signaled, it is updated with the
received NCC_s value. When the received NCC_s value differs from
the local NCC_s value, the user terminal 1600 may generate an NH
with the received NCC_s value (1624) and may generate a value K2 of
the security key KeNB_s of the small cell base station using the
PCI and the DL-EARFCN values (1626). Then, the security key KeNB m
may apply to DRB 1 (1628), and the security key KeNB_s may apply to
DRB 2 (1630).
[0217] Next, the channel condition changes, and the macro cell base
station 1602 determines to switch (i.e. handover) the DRB 2
connection of the user terminal 1600 from the small cell base
station 1 1604 to the new small cell base station 2 1606 (1632). At
this time, the security key for the small cell base station 2 1606
is obtained as in Equation 5 using the key derivation frequency
(KDF) based on the PCI, which is the ID of the small cell base
station 2 1606, the operation frequency DL-EARFCN, and the security
key KeNB_s of the previous small cell base station. That is, the
security key for the replacing small cell base station 1606 may be
generated by the horizontal security key derivation method
(1634).
KeNB_s*=KDF[KeNB_s, PCI, DL-EARFCN]=K3 Equation 5
[0218] The macro cell base station 1602 may transmit the security
key KeNB_s* (K3) generated for the small cell base station 2 1606
to the small cell base station 2 1606 (1660). Further, the macro
cell base station 1602 transmits the NCC_s information to the user
terminal 1600 as well (1662). The user terminal 1600 may make
comparison as to the received NCC_s (, SeNB_NCC), and restore
(generate) and use the security key KeNB_s* for the DRB 2 connected
to the small cell base station 2 1606 based on the NCC_s (1636 and
1638). As a result, the user terminal may apply the base station
security keys for DRB 1 and DRB 2 (1640 and 1642).
[0219] Next, the channel condition changes, and if the macro cell
base station 1602 determines to release the DRB 2 which is the
connection of the user terminal 1600 to the small cell base station
2 1606 and to connect the same to the macro cell base station 1602
(hand over) (1644), the macro cell base station 1602 transmits a
small cell release (SCELL RELEASE) message to the user terminal
1600 (1646).
[0220] When releasing the last small cell base station (1648)
(i.e., when there is no more serving cell to be linked to the
LCH_s), the macro cell base station 1602 discards the security key
KeNB_s of the small cell base station 2 that has been used and
resets the NCC_s (1650). It performs transmission with the security
key KeNB_m (k1) of the macro cell base station 1602 applied to DRB
2 as well as DRB 1 (1652 and 1654).
[0221] FIGS. 17A and 17B are views illustrating an example of
establishing a DRB path and generating and transmitting a security
key on the control plane and user plane when adding a small cell
base station, when changing a small cell base station, and when
releasing all of the linked small cells in a dual connectivity
environment where the macro cell and the small cells use separated
security keys according to an embodiment of the present
disclosure.
[0222] The embodiment shown in FIGS. 17A and 17B is also regarding
a scenario in which the user terminal initially receiving two DRBs
through the macro cell base station using the security key KeNB of
the macro cell base station receives one of the DRBs (referred to
as DRB 2 and indicating the LCH_s as shown in FIGS. 17A and 17B)
through a small cell base station 1 added and then hands over to a
small cell base station 2 for the DRB 2.
[0223] In case the user terminal 1700 which has initially been
connected with the macro cell base station 1702 alone determines to
add a small cell base station to receive a service (1710), the
macro cell base station 1702 transmits a small cell add request to
the small cell base station 1704 while generating and forwarding a
security key KeNB_s* (1712). The small cell base station 1 1704
responds to the request 1712 (1714). The macro cell base station
1702 transmits a sequence number status transfer (SN STATUS
TRANSFER) message including a COUNT value to the small cell base
station 1704 (1720), and forwards user data to be transmitted to
the user terminal to the small cell base station 1704 (1722).
[0224] The macro cell base station 1702 stops the logical channel
LCH_s through which the user terminal 1700 connects to the macro
cell base station 1702 (1716) and transmits an RRC reconfiguration
message for connection with the small cell base station 1 1704 and
the user terminal 1700 to the user terminal 1700 while informing
the user terminal 1700 of the NCC_s information (1718).
[0225] The user terminal 1700 stops the logical channel LCH_s
connecting with the macro cell base station (1724) and generates
the KeNB s based on the NCC_s information and applies the same to
the DRB 2 (1726). Here, although the logical channel through which
the user terminal communicates with the macro cell base station is
denoted LCH_s for convenience, the LCH_s when the communication
with the macro cell base station is stopped for communicating with
a new small cell base station should be interpreted to mean a
logical channel with the macro cell base station (regardless of
however it is denoted).
[0226] Subsequently, the user terminal 1700 sends an RRC
reconfiguration complete message to the macro cell base station
1702 (1728). The user terminal 1700 starts to transmit DRB 2 with
the small cell base station 1704 (1732). In this case, the security
key KeNB_s applies for a logical channel LCH_s served by the small
cell, and the security key KeNB_m applies for a logical channel
LCH_m served by the macro cell (1734 and 1736).
[0227] Selectively, PDCP status reporting 1738 may occur between
the user terminal 1700 and the small cell base station 1704, and
radio environment measurement reporting 1740 may occur from the
user terminal 1700 to the macro cell base station 1702.
[0228] Next, in case the macro cell base station 1702 determines to
change the small cell base station to be used for DRB 2 from the
small cell base station 1 1704 to the small cell base station 2
1706 (1742), the macro cell base station 1702 sends a request
message to release the small cell base station 1 1704 to the small
cell base station 1 1704 (1744). At this time, the small cell base
station 1 1704 stops transmitting the DRB 2 (1746) and sends a
response to the request message 1744 to the macro cell base station
1702 (1748). At this time, the macro cell base station 1702 may
generate and transfer the security key KeNB_s* while sending a
request to add a small cell to the small cell base station 2 1706
(1750). The small cell base station 2 1706 responds to the add
request 1750 (1752).
[0229] The macro cell base station 1702 performs RRC
reconfiguration for connection with the new small cell base station
2 1706 and the user terminal 1700 (1754 and 1760). The macro cell
base station 1702 may pass the NCC_s over while sending the RRC
connection reconfiguration message 1754 to the user terminal 1700.
The user terminal 1700 stops the logical channel LCH_s for DRB 2
(1756), generates a new small cell base station security key
KeNB_s* (i.e., a horizontal base station security key) based on the
received NCC_s, and applies the same to the DRB 2 (1758).
[0230] FIG. 18 is a view illustrating a configuration of a user
terminal according to an embodiment of the present disclosure.
[0231] The UE 1800 includes a transceiver 1810 to communicate
signals and a controller 1805 to control the overall operation of
the UE 1800. The transceiver 1810 may play a role to communicate
various control signals and data with a macro cell base station or
a small cell base station. The operations of the user terminal as
exemplified herein may be appreciated as performed under the
control the controller 1805.
[0232] Although the transceiver 1810 and the controller 1805 are
shown as if they are separate components, they may also be
implemented in a single component.
[0233] FIG. 19 is a view illustrating a configuration of a base
station according to an embodiment of the present disclosure.
[0234] The base station 1900 is an example of a macro cell base
station or small cell base station as described herein.
[0235] The base station 1900 includes a transceiver 1910 to
communicate signals and a controller 1905 to control the overall
operation of the base station 1900. The transceiver 1910 may play a
role to communicate various control signals and data with a user
terminal or a small cell base station. The operations of the macro
cell base station or small cell base station as exemplified herein
may be appreciated as performed under the control the controller
1905.
[0236] Although the transceiver 1910 and the controller 1905 are
shown as if they are separate components, they may also be
implemented in a single component.
[0237] It should be noted that examples of inter-system signal
transfer, generation of security keys, and configuration of the
apparatus as illustrated in FIGS. 3 to 19 are not intended to limit
the scope of the present disclosure. In other words, all the
entities, operations or components illustrated in FIGS. 3 to 19
should not be construed as essential components to practice the
present disclosure, and the present disclosure may be rather
implemented with only some of the components without departing from
the gist of the present disclosure.
[0238] The above-described operations may be realized by equipping
a memory device retaining their corresponding codes in the entity,
base station, or user terminal of the communication system. That
is, the controller in the entity, the base station, or user
terminal may execute the above-described operations by reading and
executing the program codes stored in the memory device by a
processor or central processing unit (CPU).
[0239] As described herein, various components or modules in the
entity, the base station, or the user terminal may be operated
using a hardware circuit, e.g., a complementary metal oxide
semiconductor-based logic circuit, firmware, software, and/or using
a hardware circuit such as a combination of hardware, firmware,
and/or software embedded in a machine-readable medium. As an
example, various electric structures and methods may be executed
using electric circuits such as transistors, logic gates, or
ASICs.
[0240] While the present disclosure has been shown and described
with reference to various embodiments thereof, it will be
understood by those skilled in the art that various changes in form
and details may be made therein without departing from the spirit
and scope of the present disclosure as defined by the appended
claims and their equivalents.
* * * * *