U.S. patent application number 13/952842 was filed with the patent office on 2013-11-21 for centralized radio network controller.
This patent application is currently assigned to InterDigital Technology Corporation. The applicant listed for this patent is InterDigital Technology Corporation. Invention is credited to James M. Miller, Stephen E. Terry.
Application Number | 20130308605 13/952842 |
Document ID | / |
Family ID | 34381374 |
Filed Date | 2013-11-21 |
United States Patent
Application |
20130308605 |
Kind Code |
A1 |
Terry; Stephen E. ; et
al. |
November 21, 2013 |
CENTRALIZED RADIO NETWORK CONTROLLER
Abstract
In a radio access network, novel systems and methods reduce
processing delay, and improve integration with IP networks, by
separating user data from connection management and control data at
a Node B or at a base station. The user data are routed to an IP
(Internet Protocol) switch, whereas the connection management and
control data are routed to a centralized radio network controller
(RNC). Pursuant to a second embodiment of the invention, a
centralized RNC provides improved radio resource management (RRM)
functionality by handing all connection management and control data
for a plurality of Node B's, thereby simplifying the switching of
user data throughout the radio access network. Pursuant to a third
embodiment of the invention, a smart IP switch is equipped to
switch user data without core network (CN) involvement. Downlink
user data are switched independently of uplink user data.
Inventors: |
Terry; Stephen E.;
(Northport, NY) ; Miller; James M.; (Verona,
NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
InterDigital Technology Corporation |
Wilmington |
DE |
US |
|
|
Assignee: |
InterDigital Technology
Corporation
Wilmington
DE
|
Family ID: |
34381374 |
Appl. No.: |
13/952842 |
Filed: |
July 29, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13156004 |
Jun 8, 2011 |
8498668 |
|
|
13952842 |
|
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|
10853383 |
May 25, 2004 |
7983716 |
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13156004 |
|
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|
60507805 |
Sep 30, 2003 |
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Current U.S.
Class: |
370/331 |
Current CPC
Class: |
H04L 47/14 20130101;
H04W 80/04 20130101; H04W 92/045 20130101; H04W 92/12 20130101;
H04W 40/36 20130101; H04W 88/12 20130101 |
Class at
Publication: |
370/331 |
International
Class: |
H04W 40/36 20060101
H04W040/36 |
Claims
1. A layer 3 smart IP switch configured to communicate with a core
network (CN) comprising: a receiver configured to accept a control
input from a centralized radio network controller (RNC); and a
transmitter configured to route data between the CN and a source
NodeB over a first communication link, wherein one or more
non-terminated data layers are transferred between the CN and the
source NodeB, and wherein the non-terminated data layers include at
least one of an Iu-interface frame protocol data, a user datagram
protocol (UDP) data, or IP data.
2. The layer 3 smart IP switch of claim 1, further configured to
activate a second communication link from a target NodeB on a
condition that a handoff from the source NodeB to the target Node B
occurs.
3. The layer 3 smart IP switch of claim 2, further configured to
transfer data queued in the source NodeB to a target NodeB, on a
condition that the data queued has not yet been delivered to a
wireless transmit/receive unit (WTRU).
4. The layer 3 smart IP switch of claim 3, wherein the transferring
is performed using a tunneling process.
5. The layer 3 smart IP switch of claim 1, further configured to
multiplex a downlink data stream from the one or more
non-terminated layers to the source NodeB and a target NodeB.
6. The layer 3 smart IP switch of claim 1, further configured to
send an uplink data stream from the source NodeB or a target NodeB
to the CN, wherein a general packet radio services tunneling
protocol (GTP) layer or a real-time transfer protocol (RTP) layer
is incorporated into a return data stream.
7. The layer 3 smart IP switch of claim 1, wherein on a condition
that the routed data comprise packet-switched data, the layer 3
smart IP switch functions as a termination point for a general
packet radio services tunneling protocol (GTP) layer between the
layer 3 smart IP switch and the CN, thereby terminating the GTP
layer.
8. The layer 3 smart IP switch of claim 1, wherein on a condition
that the routed data comprise circuit switched data, the layer 3
smart IP switch functions as a termination point for a real-time
transfer protocol (RTP) layer between the layer 3 smart IP switch
and the CN, thereby terminating the RTP layer.
9. The layer 3 smart IP switch of claim 2, further configured to
maintain the second communication link between the CN and a target
NodeB, and releasing the first communication link between the CN
and the source NodeB.
10. The layer 3 smart IP switch of claim 1, further comprising an
apparatus for switching downlink (DL) user data and uplink (UL)
user data independently.
11. A method on a layer 3 smart IP switch of communicating with a
core network (CN) , the method comprising: a receiver accepting a
control input from a centralized radio network controller (RNC);
and a transmitter routing data between the CN and a source NodeB
over a first communication link, wherein one or more non-terminated
data layers are transferred between the CN and the source NodeB,
and wherein the non-terminated data layers include at least one of
an Iu-interface frame protocol data, a user datagram protocol (UDP)
data, or IP data.
12. The method of claim 11, further comprising: activating a second
communication link from a target NodeB on a condition that a
handoff from the source NodeB to the target Node B occurs.
13. The method of claim 12, further comprising: transferring data
queued in the source NodeB to a target NodeB, on a condition that
the data queued has not yet been delivered to a wireless
transmit/receive unit (WTRU).
14. The method of claim 13, wherein the transferring is performed
using a tunneling process.
15. The method of claim 11, further comprising: multiplexing a
downlink data stream from the one or more non-terminated layers to
the source NodeB and a target NodeB.
16. The method of claim 11, further comprising: sending an uplink
data stream from the source NodeB or a target NodeB to the CN,
wherein a general packet radio services tunneling protocol (GTP)
layer or a real-time transfer protocol (RTP) layer is incorporated
into a return data stream.
17. The method of claim 11, further comprising: on a condition that
the routed data comprises packet-switched data, the layer 3 smart
IP switch functioning as a termination point for a general packet
radio services tunneling protocol (GTP) layer between the layer 3
smart IP switch and the CN, thereby terminating the GTP layer.
18. The method of claim 11, further comprising: on a condition that
the routed data comprise circuit switched data, the layer 3 smart
IP switch functioning as a termination point for a real-time
transfer protocol (RTP) layer between the layer 3 smart IP switch
and the CN, thereby terminating the RTP layer.
19. The method of claim 12, further comprising: maintaining the
second communication link between the CN and a target NodeB; and
releasing the first communication link between the CN and the
source NodeB.
20. The method of claim 11, further comprising: switching downlink
(DL) user data and uplink (UL) user data independently.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/156,004, filed Jun. 8, 2011, which is a
continuation of U.S. patent application Ser. No. 10/853,383, filed
on May 25, 2004, which issued as U.S. Pat. No. 7,983,716 on Jul.
19, 2011, which claims priority from U.S. Provisional Patent
Application Ser. No. 60/507,805, filed Sep. 30, 2003, the contents
of which are incorporated by reference herein.
FIELD OF THE INVENTION
[0002] The present invention relates generally to wireless
communication systems. More specifically, the present invention is
directed to an improved radio network controller (RNC) and
Universal Terrestrial Radio Access Network (UTRAN) architecture for
more efficiently processing of user data and control signaling.
BACKGROUND
[0003] Current wireless communication networks typically utilize a
distributed radio access architecture. For example, the Third
Generation Partnership Project (3GPP) universal terrestrial radio
access network (UTRAN), utilizes a distributed RNC architectural
configuration as shown in FIG. 1. A serving RNC (S-RNC) 104 manages
one or more user equipment (UEs) 114, 116. User and control data
from an S-RNC 104 is passed directly through a Node B 108 via Uu
interfaces to the UEs 114, 116 that it manages. The S-RNC is also
coupled with the Core Network (CN) 100 via an Iu interface, which
provides a control and user data interface to the regular
terrestrial circuit or packet networks. A controlling RNC (C-RNC)
106 manages one or more Node Bs 108, 110, 112 via Iub interfaces.
The Node Bs 108, 110, 112, in turn, each control one or more base
stations (not shown).
[0004] In practice, any RNC takes on the role of both an S-RNC 104
and a C-RNC 106. For example, the RNC may provide S-RNC services to
UEs that initiate calls with base stations coupled to Node Bs
controlled by the RNC but might have roamed to other base stations
controlled by other RNCs; and may also provide C-RNC services to
the base stations it controls. As a general consideration, S-RNCs
control UEs, whereas C-RNCs control Node Bs. S-RNCs control and
receive UE measurements. C-RNCs control and receive Node B
measurements.
[0005] A distributed RNC architecture is utilized so that user
plane (U-Plane) data and control plane (C-Plane) data is combined
within the RNC 102, for forwarding through the Node Bs, such as
Node B 108, to the UEs, such as UEs 114, 116. The U-Plane is
responsible for conveying user data to and from UEs. The C-Plane is
responsible for setting up and removing UE connections and for
implementing network signaling functions. This permits most of the
complex processing to be performed within the RNC 102, thus
simplifying the construction and lowering the costs of the Node Bs
108-112.
[0006] With reference to FIG. 2, a UE (such as UE X 115) may move
between Node Bs 108-112 in a series of inter-Node B cell changes.
Although some of the inter-Node B cell changes do not involve a
C-RNC change, eventually, such an inter-Node B cell change may
involve a change to a new Node B under control of another C-RNC;
such as the change between Node B 112 (which is controlled by C-RNC
106) and Node B 113 (which is controlled by C-RNC 107).
[0007] It is not practical in many circumstances to move the
connection between a first RNC such as RNC 1 (102) and the CN 100,
to between a second RNC such as RNC 2 (103) and the CN 100 to
follow a UE as it moves between Node Bs 108-113. Provisions are
made to keep the connection between RNC 1 (102) and the CN 100
while permitting control of the UE by RNC 2 (103). In this case,
RNC 2 (103) is referred to as a "drift RNC" (D-RNC). Communications
between RNCs are conducted over a connection referred to as an Iur
interface.
[0008] There is a partial control change between RNCs in that UE X
115 communicates with RNC 2 (103), which transparently passes user
and control data from RNC 1 (102) to UE X 115. User and control
data for UE X 115 is still controlled by RNC 1 (102) and all user
and control data that goes to UE X 115, comes from RNC 1 (102).
Although RNC 2 (103) does not control UE X 115 and does not know
what user or control data has been sent to or from UE X 115, RNC 2
(107) controls cell measurements (via an Iub interface) pertaining
to the Node B 113 in communication with UE X 115. As a result, more
than one RNC controls UE X 115.
[0009] Since the CN 100 is limited in terms of how fast it can
reroute the U-Plane and the C-Plane from one RNC to another, it is
not always possible to synchronize the relocation of the U-Plane
and the C-Plane functions from the CN 100 to the new C-RNC 107. As
a result, measurements necessary to implement radio resource
management (RRM) functions for UE X 115 are distributed between
RNCs (i.e., RNC 1 102 and RNC 2 103). For example, the user
admission control function that allows UE X 115 to establish a
connection exists in RNC 1 (102), but the call admission control
function that allocates dedicated resources exists in RNC 2
(103).
[0010] Distributed RNC systems are designed to handle expected or
anticipated U-Plane traffic over a wireless system in a given
geographic area. In large metropolitan areas, the amount of U-Plane
traffic over a wireless system is often orders of magnitude greater
than the amount of C-Plane traffic. Thus, U-Plane connectivity
requirements generally dictate the location and number of RNCs 102,
103 that are needed to support the wireless system. RNCs are
expensive hardware elements since they must support both U-Plane
and C-Plane functions. The cost of providing a distributed RNC
architecture escalates in regions where RNCs are called upon to
handle relatively large amounts of U-Plane traffic. Additionally,
in rural areas where U-Plane data communication requirements are
distributed over large areas, it may not be economically feasible
to provision terrestrial resources in the form of a centralized
point of presence.
[0011] Another drawback with an architecture having RNCs which are
distributed is that the efficiency of RRM functions is reduced. RRM
functions are performed most efficiently within a single RNC that
has all of the data for an RRM function available to it. For
example, as aforementioned, S-RNCs control and receive UE
measurements, whereas C-RNCs control and receive Node B
measurements. RRM functions often require both UE and Node B
measurements. In order to operate most efficiently, the RNC
performing the particular RRM function should have all of the
information, both uplink (UL) and downlink (DL) for all cells in
UE. With the distributed architecture, one RNC will have the
information for the cell-based measurements (the UL measurements)
whereas another RNC will have the UE-based measurements (the DL
measurements). Accordingly, a single RNC does not have all of the
information required to efficiently make decisions.
[0012] Although is possible to forward or request measurements
between S-RNCs and D/C-RNCs, the amount of measurement information
that can be forwarded or requested is limited, and the transfer of
information incurs delays. Moreover, although it is useful for RRM
functions to consider measurements and channel allocations from
neighboring cells, this is not always possible, in particular when
a neighboring cell is controlled by another RNC.
[0013] When RNCs are distributed and each RNC manages fewer cells,
less neighbor cell information is available for the performance of
RRM functions. Furthermore, as the distribution of RNCs is
increased across a given service area, the efficiency of RRM
functions is reduced.
[0014] What is needed is an improved architectural scheme that
overcomes the disadvantages of a distributed RNC configuration.
SUMMARY OF THE INVENTION
[0015] In a wireless communication network, the system and method
of the present invention separate U-Plane data from C-Plane data at
a Node B or at a base station to more efficiently process
transmission data, improve Radio Resource Management (RRM), and
provide improved integration with Internet Protocol (IP) networks.
The user data is routed via the U-Plane to a smart IP switch,
whereas the connection management and control data are separately
routed via the C-Plane to a centralized RNC. The smart IP switch
accepts control input from the centralized RNC specifying the
manner in which to route data, and is also equipped to switch DL
and UL data independently.
[0016] The centralized RNC only handles C-Plane data whereas the
smart IP switch only handles U-Plane data. Therefore, the more
resource-intensive task of switching potentially large amounts of
U-Plane data has been shifted to a less complex and costly
component; namely, the smart IP switch.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] A more detailed understanding of the invention may be had
from the following description of a preferred embodiment, to be
understood in conjunction with the accompanying drawings
wherein:
[0018] FIG. 1 is a block diagram of a prior art UTRAN system.
[0019] FIG. 2 is a block diagram of distributed RNC functionality
in a prior art UTRAN system.
[0020] FIG. 3 is a generalized block diagram of centralized RNC
functionality in accordance with the present invention.
[0021] FIG. 4 is a block diagram of a centralized RNC and a smart
IP switch in accordance with the present invention.
[0022] FIGS. 5A-5D are data flow diagrams of a handover process
between a source Node B and a target Node B using the smart IP
switch in accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] Hereinafter, the terminology "wireless transmit/receive
unit" (WTRU) includes but is not limited to a user equipment,
mobile station, fixed or mobile subscriber unit, pager or any other
type of device capable of operating in a wireless environment. In
CDMA systems specified by the Third Generation Partnership Project
(3GPP), base stations are called Node Bs and subscriber units are
called User Equipment (UEs). When referred to hereinafter, the
terminology "base station" includes but is not limited to a Node-B,
site controller, access point or other interfacing device in a
wireless environment.
[0024] In accordance with the present invention, transmission data
is more efficiently processed, RRM performance is improved, and
integration with IP networks is improved by separating user data
from connection management and control data, (hereinafter, "control
data"). The user data is routed to a smart IP switch, whereas the
connection management and control data is routed to a centralized
RNC.
[0025] Referring to FIG. 3, a first preferred embodiment of a
system 300 in accordance with the present invention is shown. The
system 300 includes a CN 100, a centralized RNC 303, a smart IP
switch 309, and first and second Node Bs 310, 312. A WTRU 316 is
shown as being wirelessly coupled to the second Node B 312.
Although only one WTRU 316 is shown for simplicity, it should be
understood that a plurality of WTRUs are able to be supported by
the present invention. Additionally, although only two Node Bs 310,
312 are shown, it would be appreciated by those of skill of the art
that the present invention applies to a single Node B as well as
many Node Bs.
[0026] A C-Plane runs from the centralized RNC 303 to each Node B
310, 312. For example, a first C-Plane 329 runs between the
centralized RNC 303 and the first Node B 310, and a second C-Plane
331 runs from the centralized RNC 303 to the second Node B 312. A
U-Plane couples each Node B 310, 312 to the smart IP switch 309.
For example, a first U-Plane 325 couples the IP switch 309 to the
first Node B 310, and a second U-Plane 327 couples the smart IP
switch 309 to the second Node B 312.
[0027] In contrast to the prior art system shown in FIGS. 1 and 2
wherein the user and control data were sent together from the UEs
to the RNC for processing, as shown in FIG. 3, control data is
separated from user data at the one or more Node Bs 310, 312. User
data is carried on the U-Planes 325, 327, and control data is
carried on the C-Planes 329, 331. It should be noted that this
separation function could also be provided at the base stations
(not shown) without departing from the spirit and scope of the
present invention.
[0028] FIG. 4 is a block diagram showing the centralized RNC 303,
the smart IP switch 309 and the first Node B 310 in greater detail.
Since control data is separated from user data at the first Node B
310, several RNC functions and protocol termination points which
traditionally have been handled by the RNC in prior art
architectural designs are now performed in a more efficient manner
by the smart IP switch 309 or the first Node B 310.
[0029] The first Node B 310 is the logical node responsible for
radio transmission and reception in one or more cells with the
WTRUs, such as WTRU 426. The first Node B 310 provides a Uu
interface to the WTRU 426, a control data interface 402 to the
centralized RNC 303, and a user data interface 417 to the smart IP
switch 309. The first Node B 310 also includes a resource control
unit 421.
[0030] The Uu interface with the WTRU 426 is a radio interface.
This radio interface is divided into three layers, layer 1 (L1)
which is referred to as the "physical layer"; layer 2 (L2) which is
referred to the "link layer"; and layer 3 (L3) which is referred to
as the "control layer".
[0031] Layer 1 includes both physical channels and transport
channels. It provides for the encoding and decoding of the
transport channels, and the mapping of transport channels onto
physical channels. Layer 1 also includes RF processing, such as
modulation, demodulation, spreading and despreading.
[0032] Layer 2 is divided into two sublayers: the media access
control (MAC) sublayer, and the radio link control (RLC) sublayer.
The MAC sublayer is responsible for multiplexing data from multiple
sources onto a physical channel. The RLC sublayer segments the data
streams into frames that are small enough to be transmitted over
the Uu radio interface.
[0033] The Layer 3 interface radio resource control (RRC), which
controls the use of radio resources, and attributes of physical and
transport channels over the Uu interface, (i.e. the air
interface).
[0034] Employing both a control data interface 402 to support the
C-Plane, (329 shown in FIG. 3), and a user data interface 417 to
support the U-Plane, (325 shown in FIG. 3), permits user data to be
separated from control data at the first Node B 310. The control
data interface 402 permits the first Node B 310 to communicate with
the centralized RNC 303 over an IP network 401. The control data
interface 402 may comprise one or more types of interfaces, shown
as a Dedicated Control Channel Frame Protocol (DCCH FP) interface
407, a Node B Application Part (NBAP) interface 405 and any other
type of control interface (graphically illustrated as an XXXAP
interface 415). Although these particular types of interfaces have
been shown by way of example, it should be understood by those of
skill in the art that any type of control data interface, either
now known or future envisioned, may be employed in a similar manner
without departing from the spirit and scope of the present
invention.
[0035] The DCCH FP interface 407 provides the frame protocol
interface for the DCCH signaling. In the prior art, this function
was included within the Dedicated Channel frame protocol within the
RNC.
[0036] The NBAP interface 405 provides control signaling between
the RNC 303 and Node B 310.
[0037] The XXXAP interface 415 provides the primitives between the
RRC and the Layer 2 MAC/RLC functions. In the prior art, this was
previously internally transmitted within the prior art RNC.
[0038] The user data 417 interface, such as Iu interface, is
similar to the Iu U-Plane connection in the prior art. The user
data interface 417 is first termination point for the U-Plane (such
as U-Planes 327, 331 shown in FIG. 3). The second termination point
is within the smart IP switch 309, which will be described in
detail hereinafter. Therefore, the CN 100 can interoperate between
a prior art RNC and the centralized RNC 303 made in accordance with
the present invention.
[0039] The resource control unit 421, performs Layer 2 MAC and RLC
processing by implementing RLC protocols and various MAC functions,
such as MAC-common channel (MAC-c), MAC-dedicated channel (MAC-d),
MAC-shared channel (MAC-sh), and MAC-paging channel (MAC-p). It
should be noted that, prior art approaches performed Layer 2
processing in the RNC.
[0040] The centralized RNC 303 includes a control unit 404, a
control data interface 402, a radio access network application part
(RANAP) 406 interface and an interface to the smart IP switch 309.
The control unit 404 supports control signaling for configuring
each resource that is needed for the call including the centralized
RNC 303, the Node B 310 and the WTRU 426. The resource control unit
404 interface with the first Node B 310 through the control data
interfaces 402. The control data interface 402 supports the C-Plane
and includes an NBAP interface 405, an XXXAP interface 415, and
DCCH FP interface 407, which are the counterpart interfaces to
those explained with reference to the first Node B 310, and which
operate in the same manner. A common control channel (CCCH)
interface (not shown) may also be used in the same manner as the
DCCH interface 407.
[0041] The resource control unit 404 performs control signaling for
the Radio Access Network (RAN), and therefore is responsible for
controlling and coordinating use of the radio resources. The
resource control unit 404 manages the WTRUs 426 via RRC signaling,
and manages Node Bs 310, 312 using NBAP signaling, both of which
are sent over the C-Plane interfaces 329, 331. This functionality
allows the centralized RNC 303 to function as a common entity for
managing both WTRUs 316 and Node Bs 310. These management features,
not provided by any known prior art architecture, improve network
performance because both UL and DL measurements are available to
RRM algorithms with minimal latency. Moreover, measurements from
all WTRUs within one or more cells are available to the RRM
algorithm at the centralized RNC 303. These factors allow improved
RRM decisions that result in a more efficient use of physical
resources.
[0042] The IP switch 309 includes a router resource control 411,
and first and second termination points 409, 410. The first
termination point 409 terminates the U-Planes (such as U-Planes
325, 327 shown FIG. 3) in the IP switch 309. The termination point
409 serves as a location where the Iub protocol headers are added
and the other protocol functions like retransmission/error recovery
take place. As aforementioned, the first Node B 310 is the first
termination point for the Iub protocol, (at the user data interface
417) as in the prior art. However, unlike the prior art, the other
termination point was the RNC, not the IP switch 309 as with the
present invention. Since Layer 2 processing requirements are
removed from the IP switch 309, the IP switch 309 provides layer 3
switching of user data more efficiently than can be accomplished
pursuant to prior art distributed RNC architectures. Termination
point 410 allows for combining or splitting of data when multiple
Node B termination points are created during user plane
relocation.
[0043] The termination points 409, 410 are controlled by the router
resource control 411. The router resource control 411 binds
together the termination points 409 and 410 for each user and
forwards the data in each direction between the points. This can
include multiple 409 termination points for the relocation of the
user plane.
[0044] The smart IP switch 309 is "smart" in the sense that it is:
1) equipped to accept a control input 408 from the centralized RNC
303 specifying the manner in which to route data; and 2) is also
equipped to switch DL and UL data independently. In contrast to a
traditional IP router/switch which uses a preset operator
configuration to statically route IP packets through the network,
the IP switch 309 routes the data streams based on configuration
from the centralized RNC 303 and is modified on a call-by-call
basis. Although prior art IP switches normally have the ability to
route UL and DL data, the smart IP switch 309 in accordance with
the present invention will perform the actions necessary for UTRAN
operation, such as duplicating data paths in one direction while
combining data paths in the other. Thus, the call-by-call
configuration from the centralized RNC 303 permits the IP switch
309 to manipulate the data streams for each user. This
configuration may also be modified for a particular user multiple
times within a single call. This will be explained further with
reference to FIGS. 5A-5D
[0045] In order to minimize the requirement for synchronized WTRU
316 inter-Node B handovers, (such as from the second Node B 312 to
the first Node B 310), and U-Plane relocations within the CN 100,
U-Plane establishment, release, and routing is performed within the
IP switch 309. The U-Plane is terminated in the Node B 310 at data
interface 417. However, for an inter-Node B handover, the data
interface point 417 moves from one Node B to another, since the
call is handed off from one Node B to another. Using the mechanisms
in accordance with the present invention, the termination point is
moved from the data interface 417 of one Node B to another, without
the other end of the Iu U-Plane connection (within the CN 100)
being aware of the change.
[0046] One benefit of the present invention is that since the IP
switch 309 provides IP routing of U-Plane traffic, it is more
efficient in data transport processing, and has a greatly reduced
cost, relative to a network entity that performs layer 2 processing
and CN 100 U-Plane protocols. In addition to IP routing capability,
the IP switch 309 performs IP address translation and splitting
(duplication)/combining multiple IP data streams, which allows
U-Plane relocations from one Node B to another (i.e., from Second
Node B 312 to first Node B 310 to be hidden from CN 100.
[0047] As shown, since MAC and RLC processing requirements are
removed from the centralized RNC 303, constraints on designing
large RNCs are removed. Layer 2 processing, including MAC and RLC
functions, is now provided by one or more Node Bs. This results in
further enhancements to RRM functionality, which is attributable to
increasing the availability of neighboring cell information.
Operator cost is also greatly reduced by the reduction in the
number of RNCs required to support a given network.
[0048] Since RLC and MAC functions need not be present in
centralized RNC 303, some internal messaging that used to exist
within prior art RNCs is now incorporated into the NBAP 405
protocol. For example, it is preferred that traffic volume
measurements (TVM) and timing deviation measurements (TDM), which
in the architecture of the present invention are recorded in first
Node B 310, are reported to centralized RNC 303. This can be
accomplished with modification of the NBAP protocol by expanding
the reporting mechanism already existing within NBAP for Node B
measurement reporting.
[0049] As aforementioned, the Iub protocol refers to an interface
between a Node B (such as first Node B 310) and an RNC (such as
centralized RNC 303). Iur refers to an interface between two RNCs,
such as RNC 1 (102, FIG. 2) and RNC 2 (103, FIG. 2). The Iub frame
protocol interface between centralized RNC 303 and first Node B 309
requires changes to support the dedicated control channel (DCCH)
407 and common control channel (CCCH) logical channels generated by
the control unit 404. These channels are used to control the WTRUs
in an identical manner as prior art. The Iub frame protocol
supports a logical channel, and does not support the transport
channels of the Iub frame protocol of the current architecture. By
adapting the frame protocols used on the Iur interface for
MAC-d/MAC-c service data units (SDUs); (also non-transport channel
of MAC 424), the logical control channel(s) can be supported
between centralized RNC 303 and first Node B 310.
[0050] The C-Plane of the Iub is also modified for mobility
procedures. Paging and cell update, for example, are transferred
from MAC 424 in the Node B to the centralized RNC 303. Mobility
control messages previously used on the Iur can be applied to the
Iub to support the aforementioned functionality between centralized
RNC 303 and first Node B 310.
[0051] As in the prior art, the C-Plane exists separately for each
RNC/Node B connection. Accordingly, moving from one C-Plane to the
other is simple; the centralized RNC 303 starts transmitting on the
new C-Plane when necessary and stops using and releases the old
C-Plane when the U-Plane has moved.
[0052] However, one of the problems in terminating the U-Plane in a
Node B is that inter-Node B handovers are still required to move
the U-Plane between Node Bs, such as for example the first Node B
310 to the second Node B 312. Movement of the U-Plane anchor is
called relocation, and requiring the CN 100 to be involved in every
inter-Node B cell change is not acceptable.
[0053] A sequence within the IP switch 309 for allowing inter-Node
B handovers of the U-Plane without CN 100 interaction is shown in
FIGS. 5A-5D. The IP switch 309 provides an anchor point to the CN
100. A switching mechanism within the IP switch 309 allows
rerouting of the U-Plane from a Source Node B 503 to a Target Node
B 505 without CN 100 intervention. The CN 100 anchor point remains
connected to the IP switch 309 throughout the entire U-Plane
rerouting sequence.
[0054] FIG. 5A shows data flow between CN 100 and Source Node B 503
prior to a handover. In the case of packet data, the IP switch 309
terminates a general packet radio services tunneling protocol (GTP)
layer (S1). In the case of circuit switched data, IP switch 309
terminates a real-time transfer protocol (RTP) layer (S1). For both
cases (packet switched and circuit switched data), the remaining
data are transferred to/from CN 100 and Source Node B 503 (S2 and
S3). The remaining data may include at least one of: (a)
Iu-interface frame protocol data (IUFP); (b) user datagram protocol
(UDP) data; or (c) Internet Protocol (IP) data.
[0055] Referring to FIG. 5B, when a handoff from Source Node B 503
to Target Node B 505 is to take place, a new link is activated from
Target Node B 505 to the IP switch 309 (S4 and S5). Data that are
queued in Source Node B 503 but not yet delivered are transferred
to Target Node B 505 using standard tunneling techniques that are
used for prior art lossless and seamless handovers. The GTP tunnel
is set up so that the user data is forwarded from the source Node B
to the target Node B. This is a similar procedure as used in the
prior art, with the exception that the tunneling is from Node B to
Node B instead of RNC to RNC as it is done in the prior art.
[0056] Turning now to FIG. 5C, as the handover from Source Node B
503 to Target Node B 505 progresses, the DL stream is multiplexed
to both Source Node B 503 (S6 and S7) and Target Node B 505 (S8 and
S9). The UL stream coming from either Source Node B 503 or Target
Node B 505 is sent to the same GTP/RTP termination so that the
GTP/RTP can be added for the stream going back to CN 100. However,
data will be present in only one Node B at a time in a given frame
in time division duplex (TDD) systems, since the type of handover
employed in such systems is a hard handover. On a frame boundary,
data transfer moves from Source Node B 503 to Target Node B
505.
[0057] The IP switch 309, in accordance with the present invention
duplicates the data paths so that the exact moment of handover does
not need to be known to the IP switch 309. Throughout these
procedures an interface between the centralized RNC 303 and the IP
switch 309 is necessary. This allows for the centralized RNC 303 to
control the setup and release of IP routing, and includes the
ability to duplicate or combine data flows as shown in FIGS. 5A-5D.
To allow for non time-critical signaling between the centralized
RNC 303 and the IP switch 309, both links are present during this
time even though only one link will be receiving data at one time.
The alternative is to have the RNC attempt to coordinate in exact
time the handover at the UE and the switchover at the IP switch
309, a difficult process given the variable delays and
synchronization throughout the network.
[0058] Finally, at FIG. 5D, the handover from Source Node B 503 to
Target Node 505 is completed. The IP switch 309 maintains the
existing link between CN 100 and Target Node B 505 (S10), but
releases the link between CN 100 and Source Node B 503.
[0059] Pursuant to a further embodiment of the invention, an AP
protocol is added between the centralized RNC 303 (FIG. 4) and
first Node B 310 (FIG. 4) to perform relocation involving only the
IP switch 309, Source Node B 503, and Target Node B 505. This AP
protocol allows for the centralized RNC 303 to signal the Node B so
that it is properly setup such that the termination point of the
U-Plane and C-Plane of the user can be moved, including any
contexts that are necessary to make the move transparent to the
core network. In this manner, retaining the same anchor point in
the IP switch 309 renders relocation of the U-Plane transparent to
CN 100. The switching, duplication and combining of data streams in
the IP switch 309 are coordinated by the centralized RNC 303. A new
interface as shown in FIG. 4, (the router resource control channel
between the control unit 404 and the router resource control 411),
is defined for this control signaling. In this signaling the
centralized RNC 303 can signal the IP switch to setup additional
switching points to allow for the combining and/or splitting of
data streams in each direction separately to allow a handover to
occur seamlessly without involvement of the CN 100. This signaling
is used to set up the channels and provide the splitting and/or
combining that is necessary during handover as shown in FIGS.
5A-5D.
[0060] Although the preferred embodiments are described in
conjunction with a 3GPP wideband code division multiple access
(W-CDMA) system utilizing the time division duplex (TDD) mode, the
embodiments are applicable to any code division multiple access
(CDMA) system or hybrid CDMA/time division multiple access (TDMA)
communication system.
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