U.S. patent application number 14/750999 was filed with the patent office on 2016-12-29 for adaptive rohc state transition.
The applicant listed for this patent is QUALCOMM Incorporated. Invention is credited to Chun Chung Patrick CHAN, Tsun Sang CHEONG, Alvin Siu-Chung NG, Tak Wai WU.
Application Number | 20160381598 14/750999 |
Document ID | / |
Family ID | 55967432 |
Filed Date | 2016-12-29 |
United States Patent
Application |
20160381598 |
Kind Code |
A1 |
CHAN; Chun Chung Patrick ;
et al. |
December 29, 2016 |
ADAPTIVE ROHC STATE TRANSITION
Abstract
A method, an apparatus, and a computer-readable medium for
wireless communication are provided. The apparatus may be a first
device. The first device operates a ROHC compressor in a first
state at a ROHC sublayer to compress a first packet to be
transmitted to a second device. The first packet includes
information for a ROHC decompressor to establish a ROHC context.
The information enables the ROHC decompressor to decompress a
second packet compressed by the ROHC compressor when operating in a
second state. The first device determines, at a sublayer or a layer
lower than the ROHC sublayer, whether the first packet has been
successfully received at the second device. The first device
continues operating the ROHC compressor in the first state in
response to a determination that the first packet has not been
successfully received at the second device.
Inventors: |
CHAN; Chun Chung Patrick;
(Hong Kong, HK) ; CHEONG; Tsun Sang; (Hong Kong,
HK) ; NG; Alvin Siu-Chung; (Hong Kong, HK) ;
WU; Tak Wai; (Hong Kong, HK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM Incorporated |
San Diego |
CA |
US |
|
|
Family ID: |
55967432 |
Appl. No.: |
14/750999 |
Filed: |
June 25, 2015 |
Current U.S.
Class: |
370/474 |
Current CPC
Class: |
H04W 28/06 20130101;
H04L 1/1607 20130101; H04L 69/22 20130101; H04L 69/04 20130101 |
International
Class: |
H04W 28/06 20060101
H04W028/06; H04L 1/16 20060101 H04L001/16 |
Claims
1. A method of wireless communication of a first device,
comprising: operating a robust header compression (ROHC) compressor
in a first state at a ROHC sublayer to compress a first packet to
be transmitted to a second device, wherein the first packet
includes information for a ROHC decompressor to establish a ROHC
context, wherein the information enables the ROHC decompressor to
decompress a second packet compressed by the ROHC compressor when
operating in a second state; determining, at a sublayer or a layer
lower than the ROHC sublayer, whether the first packet has been
successfully received at the second device; and operating the ROHC
compressor in the second state to compress the second packet to be
transmitted to the second device in response to a determination
that the first packet has been successfully received at the second
device.
2. The method of claim 1, further comprising continuing operating
the ROHC compressor in the first state in response to a
determination that the first packet has not been successfully
received at the second device.
3. The method of claim 1, wherein the first state is an
initialization and refresh (IR) state, and wherein the second state
is a first order (FO) state or a second order (SO) state.
4. The method of claim 1, wherein the ROHC context is one of a
static context or a full context.
5. The method of claim 1, wherein the first packet is determined to
have not been successfully received at the second device when the
first packet has been discarded at a packet data convergence
protocol (PDCP) layer at the first device.
6. The method of claim 1, wherein the first packet is determined to
have not been successfully received at the second device when the
first packet has not been packaged at a radio link control (RLC)
layer into a RLC protocol data unit (PDU) and then delivered to a
media access control (MAC) layer.
7. The method of claim 6, further comprising operating the RLC
layer in an unacknowledged mode.
8. The method of claim 1, wherein the ROHC compressor operates in a
unidirectional mode, a bidirectional optimistic mode, or a
bidirectional reliable mode.
9. The method of claim 1, wherein the first device is a user
equipment (UE) or a base station.
10. An apparatus for wireless communication, the apparatus being a
first device, comprising: means for operating a robust header
compression (ROHC) compressor in a first state at a ROHC sublayer
to compress a first packet to be transmitted to a second device,
wherein the first packet includes information for a ROHC
decompressor to establish a ROHC context, wherein the information
enables the ROHC decompressor to decompress a second packet
compressed by the ROHC compressor when operating in a second state;
means for determining, at a sublayer or a layer lower than the ROHC
sublayer, whether the first packet has been successfully received
at the second device; and means for operating the ROHC compressor
in the second state to compress the second packet to be transmitted
to the second device in response to a determination that the first
packet has been successfully received at the second device.
11. The apparatus of claim 10, further comprising means for
continuing operating the ROHC compressor in the first state in
response to a determination that the first packet has not been
successfully received at the second device.
12. The apparatus of claim 10, wherein the first state is an
initialization and refresh (IR) state, and wherein the second state
is a first order (FO) state or a second order (SO) state.
13. The apparatus of claim 10, wherein the ROHC context is one of a
static context or a full context.
14. The apparatus of claim 10, wherein the first packet is
determined to have not been successfully received at the second
device when the first packet has been discarded at a packet data
convergence protocol (PDCP) layer at the first device.
15. The apparatus of claim 10, wherein the first packet is
determined to have not been successfully received at the second
device when the first packet has not been packaged at a radio link
control (RLC) layer into a RLC protocol data unit (PDU) and then
delivered to a media access control (MAC) layer.
16. The apparatus of claim 15, further comprising means for
operating the RLC layer in an unacknowledged mode.
17. The apparatus of claim 10, wherein the ROHC compressor is
configured to operate in a unidirectional mode, a bidirectional
optimistic mode, or a bidirectional reliable mode.
18. The apparatus of claim 10, wherein the first device is a user
equipment (UE) or a base station.
19. An apparatus for wireless communication, the apparatus being a
first device, comprising: a memory; and at least one processor
coupled to the memory and configured to: operate a robust header
compression (ROHC) compressor in a first state at a ROHC sublayer
to compress a first packet to be transmitted to a second device,
wherein the first packet includes information for a ROHC
decompressor to establish a ROHC context, wherein the information
enables the ROHC decompressor to decompress a second packet
compressed by the ROHC compressor when operating in a second state;
determine, at a sublayer or a layer lower than the ROHC sublayer,
whether the first packet has been successfully received at the
second device; and operate the ROHC compressor in the second state
to compress the second packet to be transmitted to the second
device in response to a determination that the first packet has
been successfully received at the second device.
20. The apparatus of claim 19, wherein the at least one processor
is further configured to continue operating the ROHC compressor in
the first state in response to a determination that the first
packet has not been successfully received at the second device.
21. The apparatus of claim 19, wherein the first state is an
initialization and refresh (IR) state, and wherein the second state
is a first order (FO) state or a second order (SO) state.
22. The apparatus of claim 19, wherein the ROHC context is one of a
static context or a full context.
23. The apparatus of claim 19, wherein the first packet is
determined to have not been successfully received at the second
device when the first packet has been discarded at a packet data
convergence protocol (PDCP) layer at the first device.
24. The apparatus of claim 19, wherein the first packet is
determined to have not been successfully received at the second
device when the first packet has not been packaged at a radio link
control (RLC) layer into a RLC protocol data unit (PDU) and then
delivered to a media access control (MAC) layer.
25. The apparatus of claim 24, wherein the at least one processor
is further configured to operate the RLC layer in an unacknowledged
mode.
26. The apparatus of claim 19, wherein the ROHC compressor is
configured to operate in a unidirectional mode, a bidirectional
optimistic mode, or a bidirectional reliable mode.
27. The apparatus of claim 19, wherein the first device is a user
equipment (UE) or a base station.
28. A computer-readable medium storing computer executable code for
wireless communication at a first device, comprising code for:
operating a robust header compression (ROHC) compressor in a first
state at a ROHC sublayer to compress a first packet to be
transmitted to a second device, wherein the first packet includes
information for a ROHC decompressor to establish a ROHC context,
wherein the information enables the ROHC decompressor to decompress
a second packet compressed by the ROHC compressor when operating in
a second state; determining, at a sublayer or a layer lower than
the ROHC sublayer, whether the first packet has been successfully
received at the second device; and operating the ROHC compressor in
the second state to compress the second packet to be transmitted to
the second device in response to a determination that the first
packet has been successfully received at the second device.
29. The computer-readable medium of claim 28, further comprising
code for continuing operating the ROHC compressor in the first
state in response to a determination that the first packet has not
been successfully received at the second device.
30. The computer-readable medium of claim 28, wherein the first
state is an initialization and refresh (IR) state, wherein the
second state is a first order (FO) state or a second order (SO)
state, and wherein the ROHC context is one of a static context or a
full context.
Description
BACKGROUND
[0001] 1. Field
[0002] The present disclosure relates generally to communication
systems, and more particularly, to techniques of adaptive state
transition at a robust header compression (ROHC) compressor.
[0003] 2. Background
[0004] Wireless communication systems are widely deployed to
provide various telecommunication services such as telephony,
video, data, messaging, and broadcasts. Typical wireless
communication systems may employ multiple-access technologies
capable of supporting communication with multiple users by sharing
available system resources (e.g., bandwidth, transmit power).
Examples of such multiple-access technologies include code division
multiple access (CDMA) systems, time division multiple access
(TDMA) systems, frequency division multiple access (FDMA) systems,
orthogonal frequency division multiple access (OFDMA) systems,
single-carrier frequency division multiple access (SC-FDMA)
systems, and time division synchronous code division multiple
access (TD-SCDMA) systems.
[0005] These multiple access technologies have been adopted in
various telecommunication standards to provide a common protocol
that enables different wireless devices to communicate on a
municipal, national, regional, and even global level. An example
telecommunication standard is Long Term Evolution (LTE). LTE is a
set of enhancements to the Universal Mobile Telecommunications
System (UMTS) mobile standard promulgated by Third Generation
Partnership Project (3GPP). LTE is designed to better support
mobile broadband Internet access by improving spectral efficiency,
lowering costs, improving services, making use of new spectrum, and
better integrating with other open standards using OFDMA on the
downlink (DL), SC-FDMA on the uplink (UL), and multiple-input
multiple-output (MIMO) antenna technology. However, as the demand
for mobile broadband access continues to increase, there exists a
need for further improvements in LTE technology. Preferably, these
improvements should be applicable to other multi-access
technologies and the telecommunication standards that employ these
technologies.
SUMMARY
[0006] The following presents a simplified summary of one or more
aspects of the present disclosure in order to provide a basic
understanding of such aspects. This summary is not an extensive
overview of all contemplated aspects, and is intended to neither
identify key or critical elements of all aspects nor delineate the
scope of any or all aspects. Its sole purpose is to present some
concepts of one or more aspects in a simplified form as a prelude
to the more detailed description that is presented later.
[0007] According to an example, a method for performing adaptive
ROHC state transition is provided. The method may be performed at a
first device. The method includes operating a ROHC compressor in a
first state at a ROHC sublayer to compress a first packet to be
transmitted to a second device. The first packet includes
information for a ROHC decompressor to establish a ROHC context.
The information enables the ROHC decompressor to decompress a
second packet compressed by the ROHC compressor when operating in a
second state. The method includes determining, at a sublayer or a
layer lower than the ROHC sublayer, whether the first packet has
been successfully received at the second device. The method further
includes operating the ROHC compressor in the second state to
compress the second packet to be transmitted to the second device
in response to a determination that the first packet has been
successfully received at the second device.
[0008] According to an example, an apparatus for performing
adaptive ROHC state transition is provided. The apparatus may be a
first device. The apparatus includes means for operating a ROHC
compressor in a first state at a ROHC sublayer to compress a first
packet to be transmitted to a second device. The first packet
includes information for a ROHC decompressor to establish a ROHC
context. The information enables the ROHC decompressor to
decompress a second packet compressed by the ROHC compressor when
operating in a second state. The apparatus includes means for
determining, at a sublayer or a layer lower than the ROHC sublayer,
whether the first packet has been successfully received at the
second device. The apparatus further includes means for operating
the ROHC compressor in the second state to compress the second
packet to be transmitted to the second device in response to a
determination that the first packet has been successfully received
at the second device.
[0009] According to an example, an apparatus for performing
adaptive ROHC state transition is provided. The apparatus may be a
first device. The apparatus includes a memory and at least one
processor coupled to the memory. The at least one processor is
configured to operate a ROHC compressor in a first state at a ROHC
sublayer to compress a first packet to be transmitted to a second
device. The first packet includes information for a ROHC
decompressor to establish a ROHC context. The information enables
the ROHC decompressor to decompress a second packet compressed by
the ROHC compressor when operating in a second state. The at least
one processor is configured to determine, at a sublayer or a layer
lower than the ROHC sublayer, whether the first packet has been
successfully received at the second device. The at least one
processor is configured to operate the ROHC compressor in the
second state to compress the second packet to be transmitted to the
second device in response to a determination that the first packet
has been successfully received at the second device.
[0010] According to an example, a computer-readable medium storing
computer executable code for performing adaptive ROHC state
transition at a first device is provided. The code includes code
for operating a ROHC compressor in a first state at a ROHC sublayer
to compress a first packet to be transmitted to a second device.
The first packet includes information for a ROHC decompressor to
establish a ROHC context. The information enables the ROHC
decompressor to decompress a second packet compressed by the ROHC
compressor when operating in a second state. The code includes code
for determining, at a sublayer or a layer lower than the ROHC
sublayer, whether the first packet has been successfully received
at the second device. The code further includes code for operating
the ROHC compressor in the second state to compress the second
packet to be transmitted to the second device in response to a
determination that the first packet has been successfully received
at the second device.
[0011] To the accomplishment of the foregoing and related ends, the
one or more aspects comprise the features hereinafter fully
described and particularly pointed out in the claims. The following
description and the annexed drawings set forth in detail certain
illustrative features of the one or more aspects. These features
are indicative, however, of but a few of the various ways in which
the principles of various aspects may be employed, and this
description is intended to include all such aspects and their
equivalents.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a diagram illustrating an example of a network
architecture.
[0013] FIG. 2 is a diagram illustrating an example of an access
network.
[0014] FIG. 3 is a diagram illustrating an example of a radio
protocol architecture for the user and control planes.
[0015] FIG. 4 is a diagram illustrating an example of an evolved
Node B (eNodeB) and user equipment (UE) in an access network.
[0016] FIG. 5 is a diagram illustrating communications between a UE
and an eNodeB employing ROHC.
[0017] FIG. 6 is a diagram illustrating a voice over LTE (VoLTE)
call between a UE and an eNodeB employing ROHC.
[0018] FIG. 7 is a diagram illustrating adaptive ROHC state
transition operations at a device.
[0019] FIG. 8 is a flow chart of a method/process of adaptive ROHC
state transition performed by a device.
[0020] FIG. 9 is a conceptual data flow diagram illustrating a data
flow between different modules/means/components in an exemplary
apparatus.
[0021] FIG. 10 is a diagram illustrating an example of a hardware
implementation for an apparatus employing a processing system.
DETAILED DESCRIPTION
[0022] The detailed description set forth below in connection with
the appended drawings is intended as a description of various
configurations and is not intended to represent the only
configurations in which the concepts described herein may be
practiced. The detailed description includes specific details for
the purpose of providing a thorough understanding of various
concepts. However, it will be apparent to those skilled in the art
that these concepts may be practiced without these specific
details. In some instances, well known structures and components
are shown in block diagram form in order to avoid obscuring such
concepts.
[0023] Several aspects of telecommunication systems will now be
presented with reference to various apparatus and methods. These
apparatus and methods will be described in the following detailed
description and illustrated in the accompanying drawings by various
blocks, modules, components, circuits, steps, processes,
algorithms, etc. (collectively referred to as "elements"). These
elements may be implemented using electronic hardware, computer
software, or any combination thereof. Whether such elements are
implemented as hardware or software depends upon the particular
application and design constraints imposed on the overall
system.
[0024] By way of example, an element, or any portion of an element,
or any combination of elements may be implemented with a
"processing system" that includes one or more processors. Examples
of processors include microprocessors, microcontrollers, digital
signal processors (DSPs), field programmable gate arrays (FPGAs),
programmable logic devices (PLDs), state machines, gated logic,
discrete hardware circuits, and other suitable hardware configured
to perform the various functionality described throughout this
disclosure. One or more processors in the processing system may
execute software. Software shall be construed broadly to mean
instructions, instruction sets, code, code segments, program code,
programs, subprograms, software modules, applications, software
applications, software packages, routines, subroutines, objects,
executables, threads of execution, procedures, functions, etc.,
whether referred to as software, firmware, middleware, microcode,
hardware description language, or otherwise.
[0025] Accordingly, in one or more exemplary embodiments, the
functions described may be implemented in hardware, software,
firmware, or any combination thereof. If implemented in software,
the functions may be stored on or encoded as one or more
instructions or code on a computer-readable medium.
Computer-readable media includes computer storage media. Storage
media may be any available media that can be accessed by a
computer. By way of example, and not limitation, such
computer-readable media can comprise a random-access memory (RAM),
a read-only memory (ROM), an electrically erasable programmable ROM
(EEPROM), compact disk ROM (CD-ROM) or other optical disk storage,
magnetic disk storage or other magnetic storage devices,
combinations of the aforementioned types of computer-readable
media, or any other medium that can be used to store computer
executable code in the form of instructions or data structures that
can be accessed by a computer.
[0026] FIG. 1 is a diagram illustrating an LTE network architecture
100. The LTE network architecture 100 may be referred to as an
Evolved Packet System (EPS) 100. The EPS 100 may include one or
more user equipment (UE) 102, an Evolved UMTS Terrestrial Radio
Access Network (E-UTRAN) 104, an Evolved Packet Core (EPC) 110, and
an Operator's Internet Protocol (IP) Services 122. The EPS can
interconnect with other access networks, but for simplicity those
entities/interfaces are not shown. As shown, the EPS provides
packet-switched services, however, as those skilled in the art will
readily appreciate, the various concepts presented throughout this
disclosure may be extended to networks providing circuit-switched
services.
[0027] The E-UTRAN includes the evolved Node B (eNB) 106 and other
eNBs 108, and may include a Multicast Coordination Entity (MCE)
128. The eNB 106 provides user and control planes protocol
terminations toward the UE 102. The eNB 106 may be connected to the
other eNBs 108 via a backhaul (e.g., an X2 interface). The MCE 128
allocates time/frequency radio resources for evolved Multimedia
Broadcast Multicast Service (MBMS) (eMBMS), and determines the
radio configuration (e.g., a modulation and coding scheme (MCS))
for the eMBMS. The MCE 128 may be a separate entity or part of the
eNB 106. The eNB 106 may also be referred to as a base station, a
Node B, an access point, a base transceiver station, a radio base
station, a radio transceiver, a transceiver function, a basic
service set (BSS), an extended service set (ESS), or some other
suitable terminology. The eNB 106 provides an access point to the
EPC 110 for a UE 102. Examples of UEs 102 include a cellular phone,
a smart phone, a session initiation protocol (SIP) phone, a laptop,
a personal digital assistant (PDA), a satellite radio, a global
positioning system, a multimedia device, a video device, a digital
audio player (e.g., MP3 player), a camera, a game console, a
tablet, or any other similar functioning device. The UE 102 may
also be referred to by those skilled in the art as a mobile
station, a subscriber station, a mobile unit, a subscriber unit, a
wireless unit, a remote unit, a mobile device, a wireless device, a
wireless communications device, a remote device, a mobile
subscriber station, an access terminal, a mobile terminal, a
wireless terminal, a remote terminal, a handset, a user agent, a
mobile client, a client, or some other suitable terminology.
[0028] In certain configurations, the UE 102 includes a ROHC
management module 152 that manages a ROHC compressor. The UE 102 is
a first device. In certain configurations, the ROHC management
module 152 may be configured to operate the ROHC compressor in a
first state at a ROHC sublayer to compress a first packet to be
transmitted to a second device. The first packet includes
information for a ROHC decompressor to establish a ROHC context.
The information enables the ROHC decompressor to decompress a
second packet compressed by the ROHC compressor when operating in a
second state. The ROHC management module 152 may be configured to
determine, at a sublayer or a layer lower than the ROHC sublayer,
whether the first packet has been successfully received at the
second device. The ROHC management module 152 may be configured to
operate the ROHC compressor in the second state to compress the
second packet to be transmitted to the second device in response to
a determination that the first packet has been successfully
received at the second device. In certain configurations, the ROHC
management module 152 may be configured to continue operating the
ROHC compressor in the first state in response to a determination
that the first packet has not been successfully received at the
second device.
[0029] In certain configurations, the eNB 106 includes a ROHC
management module 156 that manages a ROHC compressor. The eNB 106
is a first device. In certain configurations, the ROHC management
module 156 may be configured to operate the ROHC compressor in a
first state at a ROHC sublayer to compress a first packet to be
transmitted to a second device. The first packet includes
information for a ROHC decompressor to establish a ROHC context.
The information enables the ROHC decompressor to decompress a
second packet compressed by the ROHC compressor when operating in a
second state. The ROHC management module 156 may be configured to
determine, at a sublayer or a layer lower than the ROHC sublayer,
whether the first packet has been successfully received at the
second device. The ROHC management module 156 may be configured to
operate the ROHC compressor in the second state to compress the
second packet to be transmitted to the second device in response to
a determination that the first packet has been successfully
received at the second device. In certain configurations, the ROHC
management module 156 may be configured to continue operating the
ROHC compressor in the first state in response to a determination
that the first packet has not been successfully received at the
second device.
[0030] The eNB 106 is connected to the EPC 110. The EPC 110 may
include a Mobility Management Entity (MME) 112, a Home Subscriber
Server (HSS) 120, other MMEs 114, a Serving Gateway 116, a
Multimedia Broadcast Multicast Service (MBMS) Gateway 124, a
Broadcast Multicast Service Center (BM-SC) 126, and a Packet Data
Network (PDN) Gateway 118. The MME 112 is the control node that
processes the signaling between the UE 102 and the EPC 110.
Generally, the MME 112 provides bearer and connection management.
All user IP packets are transferred through the Serving Gateway
116, which itself is connected to the PDN Gateway 118. The PDN
Gateway 118 provides UE IP address allocation as well as other
functions. The PDN Gateway 118 and the BM-SC 126 are connected to
the IP Services 122. The IP Services 122 may include the Internet,
an intranet, an IP Multimedia Subsystem (IMS), a PS Streaming
Service (PSS), and/or other IP services. The BM-SC 126 may provide
functions for MBMS user service provisioning and delivery. The
BM-SC 126 may serve as an entry point for content provider MBMS
transmission, may be used to authorize and initiate MBMS Bearer
Services within a PLMN, and may be used to schedule and deliver
MBMS transmissions. The MBMS Gateway 124 may be used to distribute
MBMS traffic to the eNBs (e.g., 106, 108) belonging to a Multicast
Broadcast Single Frequency Network (MBSFN) area broadcasting a
particular service, and may be responsible for session management
(start/stop) and for collecting eMBMS related charging
information.
[0031] FIG. 2 is a diagram illustrating an example of an access
network 200 in an LTE network architecture. In this example, the
access network 200 is divided into a number of cellular regions
(cells) 202. One or more lower power class eNBs 208 may have
cellular regions 210 that overlap with one or more of the cells
202. The lower power class eNB 208 may be a femto cell (e.g., home
eNB (HeNB)), pico cell, micro cell, or remote radio head (RRH). The
macro eNBs 204 are each assigned to a respective cell 202 and are
configured to provide an access point to the EPC 110 for all the
UEs 206 in the cells 202. There is no centralized controller in
this example of an access network 200, but a centralized controller
may be used in alternative configurations. The eNBs 204 are
responsible for all radio related functions including radio bearer
control, admission control, mobility control, scheduling, security,
and connectivity to the serving gateway 116. An eNB may support one
or multiple (e.g., three) cells (also referred to as a sectors).
The term "cell" can refer to the smallest coverage area of an eNB
and/or an eNB subsystem serving a particular coverage area.
Further, the terms "eNB," "base station," and "cell" may be used
interchangeably herein.
[0032] The modulation and multiple access scheme employed by the
access network 200 may vary depending on the particular
telecommunications standard being deployed. In LTE applications,
OFDM is used on the DL and SC-FDMA is used on the UL to support
both frequency division duplex (FDD) and time division duplex
(TDD). As those skilled in the art will readily appreciate from the
detailed description to follow, the various concepts presented
herein are well suited for LTE applications. However, these
concepts may be readily extended to other telecommunication
standards employing other modulation and multiple access
techniques. By way of example, these concepts may be extended to
Evolution-Data Optimized (EV-DO) or Ultra Mobile Broadband (UMB).
EV-DO and UMB are air interface standards promulgated by the 3rd
Generation Partnership Project 2 (3GPP2) as part of the CDMA2000
family of standards and employs CDMA to provide broadband Internet
access to mobile stations. These concepts may also be extended to
Universal Terrestrial Radio Access (UTRA) employing Wideband-CDMA
(W-CDMA) and other variants of CDMA, such as TD-SCDMA; Global
System for Mobile Communications (GSM) employing TDMA; and Evolved
UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE
802.20, and Flash-OFDM employing OFDMA. UTRA, E-UTRA, UMTS, LTE and
GSM are described in documents from the 3GPP organization. CDMA2000
and UMB are described in documents from the 3GPP2 organization. The
actual wireless communication standard and the multiple access
technology employed will depend on the specific application and the
overall design constraints imposed on the system.
[0033] The eNBs 204 may have multiple antennas supporting MIMO
technology. The use of MIMO technology enables the eNBs 204 to
exploit the spatial domain to support spatial multiplexing,
beamforming, and transmit diversity. Spatial multiplexing may be
used to transmit different streams of data simultaneously on the
same frequency. The data streams may be transmitted to a single UE
206 to increase the data rate or to multiple UEs 206 to increase
the overall system capacity. This is achieved by spatially
precoding each data stream (i.e., applying a scaling of an
amplitude and a phase) and then transmitting each spatially
precoded stream through multiple transmit antennas on the DL. The
spatially precoded data streams arrive at the UE(s) 206 with
different spatial signatures, which enables each of the UE(s) 206
to recover the one or more data streams destined for that UE 206.
On the UL, each UE 206 transmits a spatially precoded data stream,
which enables the eNB 204 to identify the source of each spatially
precoded data stream.
[0034] In certain configurations, the UE 206 includes a ROHC
management module 252 that manages a ROHC compressor. The UE 206 is
a first device. In certain configurations, the ROHC management
module 252 may be configured to operate the ROHC compressor in a
first state at a ROHC sublayer to compress a first packet to be
transmitted to a second device. The first packet includes
information for a ROHC decompressor to establish a ROHC context.
The information enables the ROHC decompressor to decompress a
second packet compressed by the ROHC compressor when operating in a
second state. The ROHC management module 252 may be configured to
determine, at a sublayer or a layer lower than the ROHC sublayer,
whether the first packet has been successfully received at the
second device. The ROHC management module 252 may be configured to
operate the ROHC compressor in the second state to compress the
second packet to be transmitted to the second device in response to
a determination that the first packet has been successfully
received at the second device. In certain configurations, the ROHC
management module 252 may be configured to continue operating the
ROHC compressor in the first state in response to a determination
that the first packet has not been successfully received at the
second device.
[0035] In certain configurations, the eNB 204 includes a ROHC
management module 256 that manages a ROHC compressor. The eNB 204
is a first device. In certain configurations, the ROHC management
module 256 may be configured to operate the ROHC compressor in a
first state at a ROHC sublayer to compress a first packet to be
transmitted to a second device. The first packet includes
information for a ROHC decompressor to establish a ROHC context.
The information enables the ROHC decompressor to decompress a
second packet compressed by the ROHC compressor when operating in a
second state. The ROHC management module 256 may be configured to
determine, at a sublayer or a layer lower than the ROHC sublayer,
whether the first packet has been successfully received at the
second device. The ROHC management module 256 may be configured to
operate the ROHC compressor in the second state to compress the
second packet to be transmitted to the second device in response to
a determination that the first packet has been successfully
received at the second device. In certain configurations, the ROHC
management module 256 may be configured to continue operating the
ROHC compressor in the first state in response to a determination
that the first packet has not been successfully received at the
second device.
[0036] Spatial multiplexing is generally used when channel
conditions are good. When channel conditions are less favorable,
beamforming may be used to focus the transmission energy in one or
more directions. This may be achieved by spatially precoding the
data for transmission through multiple antennas. To achieve good
coverage at the edges of the cell, a single stream beamforming
transmission may be used in combination with transmit
diversity.
[0037] In the detailed description that follows, various aspects of
an access network will be described with reference to a MIMO system
supporting OFDM on the DL. OFDM is a spread-spectrum technique that
modulates data over a number of subcarriers within an OFDM symbol.
The subcarriers are spaced apart at precise frequencies. The
spacing provides "orthogonality" that enables a receiver to recover
the data from the subcarriers. In the time domain, a guard interval
(e.g., cyclic prefix) may be added to each OFDM symbol to combat
inter-OFDM-symbol interference. The UL may use SC-FDMA in the form
of a DFT-spread OFDM signal to compensate for high peak-to-average
power ratio (PAPR).
[0038] FIG. 3 is a diagram 300 illustrating an example of a radio
protocol architecture for the user and control planes in LTE. The
radio protocol architecture for the UE and the eNB is shown with
three layers: Layer 1, Layer 2, and Layer 3. Layer 1 (L1 layer) is
the lowest layer and implements various physical layer signal
processing functions. The L1 layer will be referred to herein as
the physical layer 306. Layer 2 (L2 layer) 308 is above the
physical layer 306 and is responsible for the link between the UE
and eNB over the physical layer 306.
[0039] In the user plane, the L2 layer 308 includes a media access
control (MAC) layer 310, a radio link control (RLC) layer 312, and
a packet data convergence protocol (PDCP) layer 314, which are
terminated at the eNB on the network side. Although not shown, the
UE may have several upper layers above the L2 layer 308 including a
network layer (e.g., IP layer) that is terminated at the PDN
gateway 118 on the network side, and an application layer that is
terminated at the other end of the connection (e.g., far end UE,
server, etc.).
[0040] The PDCP layer 314 provides multiplexing between different
radio bearers and logical channels. The PDCP layer 314 also
provides header compression for upper layer data packets to reduce
radio transmission overhead, security by ciphering the data
packets, and handover support for UEs between eNBs. In certain
configurations, the PDCP layer 314, when operating at a first
device, includes a ROHC sublayer 313 that manages a ROHC compressor
within the ROHC sublayer 313. In certain configurations, the ROHC
sublayer 313 may be configured to operate the ROHC compressor in a
first state to compress a first packet to be transmitted to a
second device. The first packet includes information for a ROHC
decompressor to establish a ROHC context. The information enables
the ROHC decompressor to decompress a second packet compressed by
the ROHC compressor when operating in a second state. The ROHC
sublayer 313 may be configured to determine, at a sublayer or a
layer lower than the ROHC sublayer 313 (e.g., the PDCP layer 314,
RLC layer 312, the MAC layer 310, the physical (PHY) layer 306),
whether the first packet has been successfully received at the
second device. The ROHC sublayer 313 may be configured to operate
the ROHC compressor in the second state to compress the second
packet to be transmitted to the second device in response to a
determination that the first packet has been successfully received
at the second device. In certain configurations, the ROHC sublayer
313 may be configured to continue operating the ROHC compressor in
the first state in response to a determination that the first
packet has not been successfully received at the second device.
[0041] The RLC layer 312 provides segmentation and reassembly of
upper layer data packets, retransmission of lost data packets, and
reordering of data packets to compensate for out-of-order reception
due to hybrid automatic repeat request (HARQ). The MAC layer 310
provides multiplexing between logical and transport channels. The
MAC layer 310 is also responsible for allocating the various radio
resources (e.g., resource blocks) in one cell among the UEs. The
MAC layer 310 is also responsible for HARQ operations.
[0042] In the control plane, the radio protocol architecture for
the UE and eNB is substantially the same for the physical layer 306
and the L2 layer 308 with the exception that there is no header
compression function for the control plane. The control plane also
includes a radio resource control (RRC) layer 316 in Layer 3 (L3
layer). The RRC layer 316 is responsible for obtaining radio
resources (e.g., radio bearers) and for configuring the lower
layers using RRC signaling between the eNB and the UE.
[0043] FIG. 4 is a block diagram of an eNB 410 in communication
with a UE 450 in an access network. In the DL, upper layer packets
from the core network are provided to a controller/processor 475.
The controller/processor 475 implements the functionality of the L2
layer. In the DL, the controller/processor 475 provides header
compression, ciphering, packet segmentation and reordering,
multiplexing between logical and transport channels, and radio
resource allocations to the UE 450 based on various priority
metrics. The controller/processor 475 is also responsible for HARQ
operations, retransmission of lost packets, and signaling to the UE
450.
[0044] The transmit (TX) processor 416 implements various signal
processing functions for the L1 layer (i.e., physical layer). The
signal processing functions include coding and interleaving to
facilitate forward error correction (FEC) at the UE 450 and mapping
to signal constellations based on various modulation schemes (e.g.,
binary phase-shift keying (BPSK), quadrature phase-shift keying
(QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude
modulation (M-QAM)). The coded and modulated symbols are then split
into parallel streams. Each stream is then mapped to an OFDM
subcarrier, multiplexed with a reference signal (e.g., pilot) in
the time and/or frequency domain, and then combined together using
an Inverse Fast Fourier Transform (IFFT) to produce a physical
channel carrying a time domain OFDM symbol stream. The OFDM stream
is spatially precoded to produce multiple spatial streams. Channel
estimates from a channel estimator 474 may be used to determine the
coding and modulation scheme, as well as for spatial processing.
The channel estimate may be derived from a reference signal and/or
channel condition feedback transmitted by the UE 450. Each spatial
stream may then be provided to a different antenna 420 via a
separate transmitter 418TX. Each transmitter 418TX may modulate a
radio frequency (RF) carrier with a respective spatial stream for
transmission.
[0045] At the UE 450, each receiver 454RX receives a signal through
its respective antenna 452. Each receiver 454RX recovers
information modulated onto an RF carrier and provides the
information to the receive (RX) processor 456. The RX processor 456
implements various signal processing functions of the L1 layer. The
RX processor 456 may perform spatial processing on the information
to recover any spatial streams destined for the UE 450. If multiple
spatial streams are destined for the UE 450, they may be combined
by the RX processor 456 into a single OFDM symbol stream. The RX
processor 456 then converts the OFDM symbol stream from the
time-domain to the frequency domain using a Fast Fourier Transform
(FFT). The frequency domain signal comprises a separate OFDM symbol
stream for each subcarrier of the OFDM signal. The symbols on each
subcarrier, and the reference signal, are recovered and demodulated
by determining the most likely signal constellation points
transmitted by the eNB 410. These soft decisions may be based on
channel estimates computed by the channel estimator 458. The soft
decisions are then decoded and deinterleaved to recover the data
and control signals that were originally transmitted by the eNB 410
on the physical channel. The data and control signals are then
provided to the controller/processor 459.
[0046] The controller/processor 459 implements the L2 layer. The
controller/processor can be associated with a memory 460 that
stores program codes and data. The memory 460 may be referred to as
a computer-readable medium. In the UL, the controller/processor 459
provides demultiplexing between transport and logical channels,
packet reassembly, deciphering, header decompression, control
signal processing to recover upper layer packets from the core
network. The upper layer packets are then provided to a data sink
462, which represents all the protocol layers above the L2 layer.
Various control signals may also be provided to the data sink 462
for L3 processing. The controller/processor 459 is also responsible
for error detection using an acknowledgement (ACK) and/or negative
acknowledgement (NACK) protocol to support HARQ operations.
[0047] In the UL, a data source 467 is used to provide upper layer
packets to the controller/processor 459. The data source 467
represents all protocol layers above the L2 layer. Similar to the
functionality described in connection with the DL transmission by
the eNB 410, the controller/processor 459 implements the L2 layer
for the user plane and the control plane by providing header
compression, ciphering, packet segmentation and reordering, and
multiplexing between logical and transport channels based on radio
resource allocations by the eNB 410. The controller/processor 459
is also responsible for HARQ operations, retransmission of lost
packets, and signaling to the eNB 410.
[0048] Channel estimates derived by a channel estimator 458 from a
reference signal or feedback transmitted by the eNB 410 may be used
by the TX processor 468 to select the appropriate coding and
modulation schemes, and to facilitate spatial processing. The
spatial streams generated by the TX processor 468 may be provided
to different antenna 452 via separate transmitters 454TX. Each
transmitter 454TX may modulate an RF carrier with a respective
spatial stream for transmission.
[0049] The UL transmission is processed at the eNB 410 in a manner
similar to that described in connection with the receiver function
at the UE 450. Each receiver 418RX receives a signal through its
respective antenna 420. Each receiver 418RX recovers information
modulated onto an RF carrier and provides the information to a RX
processor 470. The RX processor 470 may implement the L1 layer.
[0050] The controller/processor 475 implements the L2 layer. The
controller/processor 475 can be associated with a memory 476 that
stores program codes and data. The memory 476 may be referred to as
a computer-readable medium. In the UL, the controller/processor 475
provides demultiplexing between transport and logical channels,
packet reassembly, deciphering, header decompression, control
signal processing to recover upper layer packets from the UE 450.
Upper layer packets from the controller/processor 475 may be
provided to the core network. The controller/processor 475 is also
responsible for error detection using an ACK and/or NACK protocol
to support HARQ operations.
[0051] FIG. 5 is a diagram 500 illustrating communications between
a UE and an eNodeB employing ROHC. A UE 502 is in communication
with an eNodeB 552 or an eNodeB 554. The UE 502 may communicate
data packets with a UE 504 via the eNodeB 552 or the eNodeB 554,
the EPC 110, and the E-UTRAN 104. In this example, the UE 502 wants
to transmit data packets to the eNodeB 552. The UE 502 may include
a ROHC compressor 510. The eNodeB 552 and the eNodeB 554 each may
include a ROHC decompressor 560. As described infra in more detail,
in this example, the UE 502 may employ the ROHC compressor 510 to
compress packets to be transmitted to the eNodeB 552. The ROHC
compressor 510 and the ROHC decompressor 560 may operate in a
unidirectional mode (U-mode), a bi-directional optimistic mode
(O-mode), or a bi-directional reliable mode (R-mode). In each mode,
the ROHC compressor 510 may be in an initialization and refresh
(IR) state 524, a first order (FO) state 526, or a second order
(SO) state 528. The ROHC decompressor may operate in a no-context
state 574, a static-context state 576, or a full-context state 578.
The UE 502 may transmit a packet compressed by the ROHC compressor
510 to the eNodeB 552. The eNodeB 552 may employ the ROHC
decompressor 560 to decompress the compressed packet received from
the UE 502. Further, when a feedback channel 590 is available, the
ROHC decompressor 560 may send feedback regarding the decompression
performed to the ROHC compressor 510 on the feedback channel
590.
[0052] In certain configurations, the ROHC compressor 510 can
compress the protocol headers of a packet, as redundancy exists in
the header fields of the same packet as well as consecutive packets
of the same packet stream. The ROHC compressor 510 may employ a
packet classifier to identify different packet streams by the
combination of parameters such as protocol headers being carried in
the packet, the source and destination addresses, and the source
and destination ports, etc. Initially, the ROHC compressor 510
sends to the ROHC decompressor 560 a few (e.g., 4) uncompressed
packets, which are used to establish the context at both the ROHC
compressor 510 and the ROHC decompressor 560. The context includes
information about static fields, dynamic fields, and the change
patterns of the fields in protocol headers. This information is
used by the ROHC compressor 510 to efficiently compress the packet
and then by the ROHC decompressor 560 to decompress the packet to
the original state of the packet.
[0053] In the U-mode, packets are sent in one direction, from the
ROHC compressor 510 to the ROHC decompressor 560. In cases where
the feedback channel 590 is not available, the ROHC compressor 510
compresses the packets without feedback from the ROHC decompressor
560. If the feedback channel 590 is available, the feedback channel
590 may be used by the ROHC decompressor 560 to acknowledge
successful decompression.
[0054] In the O-mode, the feedback channel 590 is established
between the ROHC compressor 510 and the ROHC decompressor 560. The
ROHC decompressor 560 can send feedback in the form of requests for
error recovery (e.g., NACKs) and indication of successful context
update (e.g., ACKs). The ROHC compressor 510 relies on the
optimistic approach or ACKs from the ROHC decompressor 560 to move
to higher states. The ROHC decompressor 560 sends ACKs for the
received IR packets (i.e., packets processed by the ROHC compressor
510 in the IR state 524). For other context updating packets, the
ROHC decompressor 560 may optionally send ACKs. To recover from
error conditions, the ROHC decompressor 560 sends NACKs or static
NACKs depending on the state of the ROHC decompressor 560.
[0055] In the R-mode, the feedback channel 590 is established
between the ROHC compressor 510 and the ROHC decompressor 560 and
may be used to avoid packet loss due to context invalidation. The
R-mode uses the secure reference principle rather than the
optimistic approach as in the other modes. In secure reference
principle, confidence of the ROHC compressor 510 depends on ACKs
from the ROHC decompressor 560 for every context updating
packet.
[0056] As described supra, the ROHC compressor 510 may operate in 3
states: the IR state 524, the FO state 526, and the SO state 528.
The states describe the increasing level of confidence about the
correctness of the context at the ROHC decompressor 560. This
confidence is reflected in the increasing compression of packet
headers. In case of error conditions, as indicated by the ROHC
decompressor 560 using feedback packets, the ROHC compressor 510
can move to a lower state to send packets that carry enough
information to fix the error in the context of the ROHC
decompressor 560. In some cases, the ROHC compressor 510
periodically moves to a lower state of operation to ensure the
context validity at the ROHC decompressor 560.
[0057] The ROHC compressor 510 starts in the IR state 524. In this
state, the ROHC compressor 510 sends uncompressed packets 542 to
the ROHC decompressor 560 to establish the context at the ROHC
decompressor 560. Once the ROHC compressor 510 gains the confidence
that the ROHC decompressor 560 has the context information, the
ROHC compressor 510 moves to higher states of operation, either via
the FO state 526 to the SO state 528 or directly to the SO state
528. The ROHC compressor 510, operating in the SO state 528, sends
compressed packets 546 to the ROHC decompressor 560. The ROHC
compressor 510 may dynamically change its states to react to link
conditions and error conditions as observed and reported by the
ROHC decompressor 560.
[0058] As described supra, the ROHC decompressor 560 may operate in
3 states: the no-context state 574, the static-context state 576,
and the full-context state 578. The ROHC decompressor 560 starts in
the no-context state 574, as it has no context information
available in the beginning of the packet flow. The successful
processing of an IR packet, which contains both static and dynamic
information, from the ROHC compressor 510 will create the context
information at the ROHC decompressor 560. At this point, the ROHC
decompressor 560 can move to the full-context state 578 to
decompress SO packets (i.e., packets compressed by the ROHC
compressor 510 in the SO state 528) as the ROHC decompressor 560
has received both static and dynamic information. Once in the
full-context state 578, the ROHC decompressor 560 moves to lower
states in error conditions. When moving to a lower state, the ROHC
decompressor 560 moves to the static-context state 576. The ROHC
decompressor 560 waits for compressed packets 544 sent by the ROHC
compressor 510 operating in the FO state 526. The ROHC decompressor
560 can move back to the full-context state 578 by restoring the
context after successfully decompressing FO packets (i.e., the
compressed packets 544 compressed by the ROHC compressor 510 in the
FO state 526). If the ROHC decompressor 560 still fails to
decompress, it moves to the no-context state 574. In this case, the
ROHC compressor 510 needs to send IR packets to restore the context
at the ROHC decompressor 560.
[0059] As such, the ROHC decompressor 560 operating in the
no-context state 574 may process IR packets. The ROHC decompressor
560 operating in the static-context state 576 may decompress FO
packets. The ROHC decompressor 560 operating in the full-context
state 578 may decompress SO packets.
[0060] In one example, the UE 502 may transmit VoLTE data to the UE
504 via the eNodeB 552, the EPC 110, and the E-UTRAN 104. The UE
502 employs the ROHC compressor 510 to compress packets carrying
the VoLTE data to be transmitted to the eNodeB 552. Upon receiving
the compressed packets, the eNodeB 552 may employ the ROHC
decompressor 560 to decompress the compressed packets in order to
obtain the VoLTE data. Further, the UE 502 may move from the cell
of the eNodeB 552 to the cell of the eNodeB 554. Thus, the
reception of the VoLTE data transmitted from the UE 502 may be
handed over to the eNodeB 554. The eNodeB 554 similarly has a ROHC
decompressor 560 that can decompress the packets compressed by the
ROHC compressor 510.
[0061] The UE 502 initiates the ROHC compressor 510 in the IR state
524 of the U-mode. Due to the low efficiency nature of the IR state
524, the UE 502 may quickly switch to the SO state 528 or the FO
state 526 to reach higher efficiency and larger VoLTE capacity. The
duration of the ROHC compressor 510 staying in the IR state 524
depends on implementation and is adjustable depending on how
confident the ROHC compressor 510 is that the ROHC decompressor 560
of the eNodeB 552 has acquired the ROHC context. If the ROHC
compressor 510 stays in the IR state 524 for too long, the VoLTE
capacity may be lowered. If the ROHC compressor 510 stays in the IR
state 524 for too short, the VoLTE calls, which relies on the
correct ROHC compression, may be dropped. For example, if the ROHC
compressor 510 has already moved to the SO state 528 but the ROHC
decompressor 560 of the eNodeB 552 has not established any ROHC
context (i.e., the ROHC decompressor 560 is still in the no-context
state 574), the SO packets subsequently sent by the UE 502 will not
be correctly decompressed by the ROHC decompressor 560 at the
eNodeB 552.
[0062] In certain configurations, ROHC signaling may be carried
in-band in real-time transport protocol (RTP) packets carrying the
VoLTE data. The RTP packets may be transported utilizing an
unacknowledged mode (UM) at the RLC layer. Further, the RTP
packets, packaged in PDCP packets and buffered at the PDCP layer of
the UE 502, may be discarded upon PDCP discard timer expiration. In
addition, the PDCP packets may be lost due to poor RF conditions.
As such, the IR packets carrying the full ROHC context may be
discarded at the UE 502 or lost during transmission, without ever
reaching the eNodeB 552. Nonetheless, the ROHC compressor 510 at
the UE 502 may optimistically assume that the ROHC decompressor 560
at the eNodeB 552 has received the IR packets and has established
the full-context state 578 or the static-context state 576.
Accordingly, the ROHC compressor 510 moves to the SO state 528 or
the FO state 526, and the UE 502 subsequently transmits SO packets
or FO packets to the eNodeB 552. As stated, the ROHC decompressor
560 may not have received the IR packets and may still in the
no-context state 574. Consequently, the ROHC decompressor 560 may
not be able to decompress the received compressed packets 548
(e.g., SO or FO packets). This ROHC state mismatch can lead to
VoLTE call drops.
[0063] FIG. 6 is a diagram 600 illustrating a VoLTE call between a
UE and an eNodeB employing ROHC. At operation 623, the UE 502 and
the UE 504, via the eNodeB 552 and an IMS service 606, setup a
VoLTE call communication. At operation 626, the UE 502 and the UE
504 may transmit RTP packets carrying the VoLTE data to each other.
As described supra, after allowing the initial establishment of the
ROHC context at the eNodeB 552, the ROHC compressor 510 of the UE
502 may switch to operate in the SO state 528 of the O-mode. In
other words, the ROHC compressor 510, operating in the SO state
528, may compress the RTP packets carrying the VoLTE data to
generate SO packets and may send the SO packets to the eNodeB 552.
The ROHC decompressor 560 at the eNodeB 552, operating in the
full-context state 578, can decompress the SO packets.
[0064] Subsequently, the UE 502 may move to the edge of the cell of
the eNodeB 552.
[0065] The UE 502 measures the cell of the eNodeB 554 and reports
the measurement results to the eNodeB 552. The UE 502 may not
receive any handover messages and may subsequently declare, due to
high block error rate (BLER) at the downlink, a radio link failure
(RLF). The RLF may result in an RLF interruption period 629 at the
UE 502.
[0066] The UE 502 may choose to perform an RLF recovery procedure
633 with the eNodeB 554 (e.g., based on the previous cell
measurements). At this time point, the ROHC decompressor 560 of the
eNodeB 554 may not have any context for decompressing the RTP
packets from the UE 502. Further, due to the RLF, the ROHC
compressor 510 of the UE 502 switches to the U-mode in the IR state
524.
[0067] In one scenario, the RLF interruption period 629 and the RLF
recovery procedure 633 may interrupt the transmission of the RTP
packets on the user plane for a period of time (e.g., about 500
ms). On the other hand, the UE 502 may have a PDCP discard timer
set at a period of time (e.g., 150 ms) shorter than the
interruption and recovery time period (i.e., the RLF interruption
period 629 and the time period of the RLF recovery procedure 633).
An RTP packet is buffered at the PDCP layer during the interruption
and recovery time period until the PDCP discard timer associated
with that packet expires. When the PDCP discard timer expires, the
PDCP layer may discard the buffered RTP packet.
[0068] After a successful RLF recovery procedure 633, in an IR time
period 636, the
[0069] ROHC compressor 510, operating in the IR state 524 of the
U-mode, processes the RTP packets and buffers the processed RTP
packets (i.e., IR packets) as PDCP packets at the PDCP layer. The
buffered PDCP packets may be further processed sequentially at the
PDCP layer and then sent to the lower layers (e.g., the MAC and
physical (PHY) layers). Thus, the IR packets may be buffered for a
prolonged time period at the PDCP layer as the PDCP layer may have
a substantial number of packets queued to be processed after the
RLF recovery procedure 633. As described supra, when the IR packets
are not sent to the lower layers prior to the expiration of the
associated PDCP discard timer, the IR packets may be dropped at the
PDCP layer.
[0070] On the other hand, after the ROHC compressor 510 has sent a
configurable number of IR packets (e.g., 4 IR packets), the ROHC
compressor 510 may be configured to gain confidence to transition
to the SO state 528 and to enter a SO time period 639. In this
example, at time point 643, the PDCP discard timer associated with
the last IR packet (e.g., the 4.sup.th packet) sent by the ROHC
compressor 510 expires, and the last IR packet (e.g., the 4.sup.th
packet) is still buffered at the PDCP layer while all prior IR
packets (e.g., the 1.sup.st, 2.sup.nd, and 3.sup.rd IR packets)
have been dropped. The PDCP layer further drops the last IR packet.
In other words, none of the IR packets has been transmitted by the
UE 502 and received by the eNodeB 554. As the ROHC compressor 510
is optimistically confident that the eNodeB 554 should have
received the IR packets and transitioned to the full-context state
578 after the IR time period 636, the ROHC compressor 510, in
operation 646, transmits SO packets carrying the VoLTE data to the
eNodeB 554. Accordingly, in a time period 649, the eNodeB 554 may
receive SO packets but may not have any ROHC context that can be
used to decompress the SO packets. Thus, the eNodeB 554 discards
the SO packets received from the UE 502 in the time period 649.
Further, because the ROHC compressor 510 of the UE 502 is operating
in the U-mode, the ROHC compressor 510 may not have established or
may not utilize the feedback channel 590 with the ROHC decompressor
560 of the eNodeB 554. Therefore, the ROHC compressor 510 may not
receive feedback from the ROHC decompressor 560 that the ROHC
decompressor 560 has not established the context and is not able to
decompress the SO packets. Consequently, without any feedback, the
ROHC compressor 510 of the UE 502 may continue generating SO
packets, which are subsequently received and dropped at the ROHC
decompressor 560 of the eNodeB 554.
[0071] From the start of the RLF interruption period 629, the
eNodeB 554 is not be able to send VoLTE data to the UE 504 via the
EPC 110 and the E-UTRAN 104. Accordingly, the UE 504 may not
receive any downlink RTP packets carrying the VoLTE data. If the UE
504 does not receive any downlink RTP packets in a wait period 631
(e.g., 10 seconds), the UE 504, at operation 653, send a time out
(e.g., SIP BYE) message to the IMS service 606 and terminates the
VoLTE call with the UE 504. Upon receiving the time out message,
the IMS service 606 accordingly sends, at operation 656, a time out
message (e.g., SIP BYE) to the UE 502. Subsequently, at operation
659, the UE 502 may terminate the VoLTE call with the UE 504. As
such, the mismatch of the ROHC states at the ROHC compressor 510
and the ROHC decompressor 560 may result in the VoLTE call being
dropped.
[0072] FIG. 7 is a diagram 700 illustrating adaptive ROHC state
transition operations at a device. A device 702 has, among other
components, a media plane 712, a voice encoder 716, an RTP/RTP
control protocol (RTCP) layer 722, a user datagram protocol (UDP)
layer 726, an IP layer 728, a PDCP layer 732, an RLC layer 736, a
MAC layer 740, and a PHY layer 744. The PDCP layer 732 includes the
ROHC compressor 510, which may have a compressor interface 733. The
PDCP layer 732 further may include a PDCP buffer 734. The RLC layer
736 may operate in an unacknowledged mode 738 or an acknowledged
mode.
[0073] In certain configurations, when the device 702 employs a
ROHC sublayer (e.g., the ROHC compressor 510) to compress data
packets to be transmitted to another device, the sublayers or
layers below the ROHC sublayer may be configured to implement the
techniques described infra to address the mismatch issues described
supra. In this example, the UE 502 is used as an exemplary device
702. The UE 502 operates the ROHC compressor 510 to compress
packets to be sent to the eNodeB 552 or the eNodeB 554.
Accordingly, the description infra may use the PDCP layer 732, the
RLC layer 736, the MAC layer 740, and the PHY layer 744 at the UE
502 as examples to describe the techniques. Nonetheless, the
techniques described infra may be equally applied to the eNodeB 552
or the eNodeB 554 when the eNodeB 552 or the eNodeB 554 operates a
ROHC compressor 510 to compress packets to be transmitted to the UE
502 or the UE 504. Further, the techniques described infra may use
the U-mode of the ROHC compressor 510 as an example. Nonetheless,
the techniques described infra may be similarly applied to the
O-mode and the R-mode of the ROHC compressor 510.
[0074] Particularly, with reference to FIGS. 6 and 7, in certain
configurations, the media plane 712 of the UE 502 sends the voice
data to the voice encoder 716 to generate encoded voice data in the
IR time period 636. In this example, the UE 502 utilizes the
RTP/RTCP layer 722, the UDP layer 726, and the IP layer 728 to
generate RTP packets carrying the encoded voice data. The RTP
packets are then sent to the PDCP layer 732. The PDCP layer 732
includes the ROHC compressor 510 in a ROHC sublayer. As described
supra, in the IR time period 636, the ROHC compressor 510,
operating in the IR state 524 of the U-mode, processes the RTP
packets to generate IR packets. The IR packets are packaged into
PDCP protocol data units (PDUs), which may be buffered at the PDCP
buffer 734. In this technique, the ROHC compressor 510 does not
switch to the higher states (e.g., the SO state 528) after sending
a number of IR packets (e.g., 4 IR packets) to the PDCP layer 732.
Rather, the ROHC compressor 510 waits an indication from a lower
layer or sublayer before transitioning to the higher states. For
example, the ROHC compressor 510 may provide the compressor
interface 733 through which the lower layers or sublayers can
communicate with the ROHC compressor 510. The indication may
indicate that the ROHC compressor 510 may transition to a higher
state or that an IR packet has been correctly received at the
eNodeB 554. The indication may alternatively indicate that the ROHC
compressor 510 should stay in the IR state 524, as a configurable
number of IR packets have not been correctly received at the eNodeB
554.
[0075] In particular, the PDCP layer 732 monitors whether any PDCP
PDU containing an IR packet has been dropped at the PDCP layer 732
due to expiration of the PDCP discard timer. If one or more PDCP
PDUs have been dropped at the PDCP layer 732, the PDCP layer 732
may send an indication 772 to the ROHC compressor 510 to instruct
the ROHC compressor 510 to stay in the IR state 524 and to delay
transitioning to the higher states, as the eNodeB 554 will not
receive the IR packet contained in the PDCP PDU that has been
dropped.
[0076] Further, when a PDCP PDU containing an IR packet is
delivered to the RLC layer 736, the RLC layer 736 continues
monitoring the handling of the PDCP PDU. In this example, the RLC
layer 736 operates in the unacknowledged mode 738. The RLC layer
736 monitors whether the PDCP PDU has been packaged into an RLC PDU
and then successfully delivered to the MAC layer 740. If the PDCP
PDU is not delivered to the MAC layer 740 via an RLC PDU, the RLC
layer 736 may send an indication 774 to the ROHC compressor 510 to
instruct the ROHC compressor 510 to stay in the IR state 524 and to
delay transitioning to the higher states, as the eNodeB 554 will
not receive the IR packet contained in the PDCP PDU.
[0077] Further, when an RLC PDU containing an IR packet is
delivered to the MAC layer 740, the MAC layer 740 continues
monitoring the handling of the RLC PDU. The MAC layer 740 monitors
whether the RLC PDU has been packaged into a MAC PDU (MPDU) at the
MAC layer 740 and then delivered to the PHY layer 744 and whether
the MPDU has been packaged into a PHY PDU (PPDU) that is to be
transmitted to the eNodeB 554. Once the PPDU has been transmitted
to the eNodeB 554 at the PHY layer 744, the MAC layer 740 continues
monitoring the ACK or NACK received in the HARQ procedure. When the
MAC layer 740 detects that the RLC PDU was not packaged into a PPDU
or the PPDU was not transmitted at the PHY layer 744, or
determines, e.g., based on a NACK, that the MPDU carrying an IR
packet was not successfully received at the eNodeB 554, the MAC
layer 740 may send an indication 776 to the ROHC compressor 510 to
instruct the ROHC compressor 510 to stay in the IR state 524 and to
delay transitioning to the higher states, as the eNodeB 554 did not
successfully receive the IR packet via the PPDU.
[0078] When the MAC layer 740 of the UE 502 receives an ACK from
the eNodeB 554 through the HARQ procedure for an MPDU carrying an
IR packet, the MAC layer 740 may send an indication 776 to the ROHC
compressor 510 to indicate that the IR packet has been successfully
received at the eNodeB 554. Accordingly, the ROHC compressor 510
may gain more confidence that the eNodeB 554 may be able to
establish the ROHC context. After the ROHC compressor 510 has
received a configurable number of indications 776 (e.g., 4
indications) collectively indicating that a configurable number of
IR packets (e.g., 4 IR packets) have been successfully received at
the eNodeB 552, the ROHC compressor 510 may be confident to
transition to a higher state (e.g., the SO state 528 or the FO
state 526). Alternatively, the MAC layer 740 may send an indication
776 to the ROHC compressor 510 to indicate that the ROHC compressor
510 may transition to a higher state. In this example, at the end
of the in the IR time period 636, the ROHC compressor 510
determines that the number of the IR packets have been successfully
received at the eNodeB 554. Subsequently, the ROHC compressor 510
transitions to the SO state 528 and enters the SO time period 639.
The ROHC compressor 510, in operation 646, transmits SO packets to
the eNodeB 554.
[0079] In this example, the eNodeB 554 receives the IR packets in a
time period 637. After receiving one or more IR packets, at a time
point 644, the eNodeB 554 establishes full ROHC context and may
operate in the full-context state 578. Subsequently, in the time
period 649, the eNodeB 554 receives the SO packets carrying the RTP
packets. At operation 651, the eNodeB 554 sends the RTP packets to
the UE 504.
[0080] FIG. 8 is a flow chart 800 of a method (process) of adaptive
ROHC state transition performed by a first device. The first device
may be a UE or a base station (e.g., the UE 502, the UE 504, the
eNodeB 552, the eNodeB 554, the apparatus 902/902'). At operation
813, the first device operates a ROHC compressor in a first state
at a ROHC sublayer to compress a first packet to be transmitted to
a second device. The first packet includes information for a ROHC
decompressor to establish a ROHC context. The information enables
the ROHC decompressor to decompress a second packet compressed by
the ROHC compressor when operating in a second state. In certain
configurations, the ROHC compressor operates in the U-mode, the
O-mode, or the R-mode. For example, referring to FIGS. 5 and 6, in
the IR time period 636, the ROHC compressor 510 of the UE 502,
operating in the IR state 524 of the U-mode, processes the RTP
packets to generate IR packets.
[0081] At operation 816, the first device determines, at a sublayer
or a layer lower than the ROHC sublayer, whether the first packet
has been successfully received at the second device. When the first
packet has been successfully received at the second device, the
first device, at operation 819, operates the ROHC compressor in the
second state to compress the second packet to be transmitted to the
second device in response to a determination that the first packet
has been successfully received at the second device. For example,
referring to FIGS. 5 and 6, when the MAC layer 740 of the UE 502
receives an ACK from the eNodeB 554 through the HARQ procedure for
an MPDU carrying an IR packet, the MAC layer 740 may send an
indication to the ROHC compressor 510 to indicate that the IR
packet has been successfully received at the eNodeB 554. At the end
of the in the IR time period 636, the ROHC compressor 510
determines that the number of the IR packets have been successfully
received at the eNodeB 554. Subsequently, the ROHC compressor 510
transitions to the SO state 528 and enters the SO time period
639.
[0082] When the first packet has not been successfully received at
the second device, the first device, at operation 833, continues
operating the ROHC compressor in the first state. In certain
configurations, the first state is an IR state, and the second
state is a FO state or a SO state. In certain configurations, the
ROHC context is one of a static context or a full context.
[0083] In certain configurations, to determine whether the first
packet have been successfully received at the second device, the
first device, at operation 823, determines whether the first packet
has been discarded at a PDCP layer at the first device. When the
first packet has been discarded at the PDCP layer, the first device
proceeds to operation 833. For example, referring to FIGS. 5 and 6,
the PDCP layer 732 monitors whether any PDCP PDU containing an IR
packet has been dropped at the PDCP layer 732 due to expiry of the
PDCP discard timer. If one or more PDCP PDUs have been dropped at
the PDCP layer 732, the PDCP layer 732 may send an indication to
the ROHC compressor 510 to instruct the ROHC compressor 510 to stay
in the IR state 524 and to delay transitioning to the higher
states, as the eNodeB 554 will not receive the IR packet contained
in the PDCP PDU that have been dropped.
[0084] When the first packet has not been discarded at the PDCP
layer, the first device, at operation 826, determines whether the
first packet has been packaged at an RLC layer into an RLC PDU and
then delivered to a MAC layer. In certain configurations, the RLC
layer is in an unacknowledged mode. When the first packet has not
been packaged at the RLC layer into an RLC PDU and then delivered
to the MAC layer, the first device proceeds to operation 833. For
example, referring to FIGS. 5 and 6, the RLC layer 736 continues
monitoring the handling of the PDCP PDU. The RLC layer 736 operates
in the unacknowledged mode 738. The RLC layer 736 monitors whether
the PDCP PDU has been packaged into an RLC PDU and then
successfully delivered to the MAC layer 740. If the PDCP PDU is not
delivered to the MAC layer 740 via an RLC PDU, the RLC layer 736
may send an indication to the ROHC compressor 510 to instruct the
ROHC compressor 510 to stay in the IR state 524 and to delay
transitioning to the higher states, as the eNodeB 554 will not
receive the IR packet contained in the PDCP PDU.
[0085] When the first packet has been packaged at the RLC layer
into an RLC PDU and then delivered to the MAC layer, the first
device transmits, at a PHY layer, the first packet in a PPDU to the
second device. Then at operation 829, the first device determines
whether an acknowledgement has been received from the second device
for the PPDU. When an acknowledgement has not been received from
the second device for the PPDU, the first device proceeds to
operation 833. When an acknowledgement has been received from the
second device for the PPDU, the first device proceeds to operation
810. For example, referring to FIGS. 5 and 6, the MAC layer 740
continues monitoring the ACK or NACK received in the HARQ
procedure. When the MAC layer 740 determines, e.g., based on a
NACK, that the MPDU carrying an IR packet was not successfully
received at the eNodeB 554, the MAC layer 740 may send an
indication to the ROHC compressor 510 to instruct the ROHC
compressor 510 to stay in the IR state 524 and to delay
transitioning to the higher states, as the eNodeB 554 did not
successfully receive the IR packet via the PPDU.
[0086] FIG. 9 is a conceptual data flow diagram 900 illustrating
the data flow between different modules/means/components in an
exemplary apparatus 902. The apparatus may be a UE or an eNodeB.
The apparatus is a first device and includes a reception module
904, a ROHC compressor 906, a ROHC management module 908, and a
transmission module 910.
[0087] In certain configurations, the ROHC management module 908
may be configured to operate the ROHC compressor 906 in a first
state at a ROHC sublayer to compress a first packet to be
transmitted to a second device 950. The first packet includes
information for a ROHC decompressor to establish a ROHC context.
The information enables the ROHC decompressor to decompress a
second packet compressed by the ROHC compressor 906 when operating
in a second state. The ROHC management module 908 may be configured
to determine, at a sublayer or a layer lower than the ROHC
sublayer, whether the first packet has been successfully received
at the second device 950. The ROHC management module 908 may be
configured to send indications 936 regarding whether the first
packet has been successfully received at the second device 950 to
the ROHC compressor 906. The ROHC management module 908 may be
configured to continue operating the ROHC compressor 906 in the
first state in response to a determination that the first packet
has not been successfully received at the second device 950. The
ROHC management module 908 may be configured to operate the ROHC
compressor 906 in the second state to compress the second packet to
be transmitted to the second device 950 in response to a
determination that the first packet has been successfully received
at the second device 950. The ROHC compressor 906 may be configured
to send compressed packets 938 to the transmission module 910. The
transmission module 910 may be configured to transmit compressed
packets 942 to the second device 950.
[0088] In certain configurations, the first state is an IR state,
and the second state is a FO state or a SO state. In certain
configurations, the ROHC context is one of a static context or a
full context. In certain configurations, the first packet is
determined to have not been successfully received at the second
device 950 when the first packet has been discarded at a PDCP layer
at the first device. In certain configurations, the first packet is
determined to have not been successfully received at the second
device 950 when the first packet has not been packaged at an RLC
layer into an RLC PDU and then delivered to a MAC layer.
[0089] In certain configurations, the transmission module 910 may
be configured to transmit, at a PHY layer, the first packet in a
PPDU to the second device 950. The reception module 904 may be
configured to receive ROHC feedback 932 and HARQ ACKs/NACKs 934
from the second device 950. The reception module 904 then may send
the ROHC feedback 932 to the ROHC compressor 906 and may send the
HARQ ACKs/NACKs 934 to the ROHC management module 908. The ROHC
management module 908 may be configured to determine whether an
acknowledgement has been received from the second device 950 for
the PPDU. The first packet is determined to have not been
successfully received at the second device 950 in response to a
determination that an acknowledgement has not been received from
the second device 950 for the PPDU. The first packet is determined
to have been successfully received at the second device 950 in
response to a determination that an acknowledgement has been
received from the second device 950 for the PPDU.
[0090] In certain configurations, the RLC layer is in an
unacknowledged mode. In certain configurations, the ROHC compressor
906 operates in a unidirectional mode, a bidirectional optimistic
mode, or a bidirectional reliable mode. In certain configurations,
the first device is a UE or a base station.
[0091] In certain configurations, the reception module 904 may be
configured to receive ROHC feedback from the second device 950 and
may be configured to send the ROHC feedback to the ROHC compressor
906.
[0092] The apparatus may include additional modules that perform
each of the blocks of the algorithm in the aforementioned
flowcharts of FIG. 8. As such, each block in the aforementioned
flowcharts of FIG. 8 may be performed by a module and the apparatus
may include one or more of those modules. The modules may be one or
more hardware components specifically configured to carry out the
stated processes/algorithm, implemented by a processor configured
to perform the stated processes/algorithm, stored within a
computer-readable medium for implementation by a processor, or some
combination thereof.
[0093] FIG. 10 is a diagram 1000 illustrating an example of a
hardware implementation for an apparatus 902' employing a
processing system 1014. The processing system 1014 may be
implemented with a bus architecture, represented generally by the
bus 1024. The bus 1024 may include any number of interconnecting
buses and bridges depending on the specific application of the
processing system 1014 and the overall design constraints. The bus
1024 links together various circuits including one or more
processors and/or hardware modules, represented by the processor
1004, the modules 904, 906, 908, 910, and the computer-readable
medium/memory 1006. The bus 1024 may also link various other
circuits such as timing sources, peripherals, voltage regulators,
and power management circuits, which are well known in the art, and
therefore, will not be described any further.
[0094] The processing system 1014 may be coupled to a transceiver
1010. The transceiver 1010 is coupled to one or more antennas 1020.
The transceiver 1010 provides a means for communicating with
various other apparatus over a transmission medium. The transceiver
1010 receives a signal from the one or more antennas 1020, extracts
information from the received signal, and provides the extracted
information to the processing system 1014, specifically the
reception module 904. In addition, the transceiver 1010 receives
information from the processing system 1014, specifically the
transmission module 910, and based on the received information,
generates a signal to be applied to the one or more antennas 1020.
The processing system 1014 includes a processor 1004 coupled to a
computer-readable medium/memory 1006. The processor 1004 is
responsible for general processing, including the execution of
software stored on the computer-readable medium/memory 1006. The
software, when executed by the processor 1004, causes the
processing system 1014 to perform the various functions described
supra for any particular apparatus. The computer-readable
medium/memory 1006 may also be used for storing data that is
manipulated by the processor 1004 when executing software. The
processing system further includes at least one of the modules 904,
906, 908, and 910. The modules may be software modules running in
the processor 1004, resident/stored in the computer readable
medium/memory 1006, one or more hardware modules coupled to the
processor 1004, or some combination thereof. Where the first device
is an eNodeB, the processing system 1014 may be a component of the
eNB 410 and may include the memory 476 and/or at least one of the
TX processor 416, the RX processor 470, and the
controller/processor 475. Where the first device is a UE, the
processing system 1014 may be a component of the UE 450 and may
include the memory 460 and/or at least one of the TX processor 468,
the RX processor 456, and the controller/processor 459.
[0095] In one configuration, the apparatus 902/902' includes means
for operating a ROHC compressor in a first state at a ROHC sublayer
to compress a first packet to be transmitted to a second device.
The first packet includes information for a ROHC decompressor to
establish a ROHC context. The information enables the ROHC
decompressor to decompress a second packet compressed by the ROHC
compressor when operating in a second state. The apparatus 902/902'
includes means for determining, at a sublayer or a layer lower than
the ROHC sublayer, whether the first packet has been successfully
received at the second device. The apparatus 902/902' includes
means for operating the ROHC compressor in the second state to
compress the second packet to be transmitted to the second device
in response to a determination that the first packet has been
successfully received at the second device.
[0096] In certain configurations, the apparatus 902/902' may be
configured to include means for continuing operating the ROHC
compressor in the first state in response to a determination that
the first packet has not been successfully received at the second
device. In certain configurations, the first state is an IR state,
and the second state is a FO state or a SO state. In certain
configurations, the ROHC context is one of a static context or a
full context.
[0097] In certain configurations, the first packet is determined to
have not been successfully received at the second device when the
first packet has been discarded at a PDCP layer at the first
device. In certain configurations, the first packet is determined
to have not been successfully received at the second device when
the first packet has not been packaged at an RLC layer into an RLC
PDU and then delivered to a MAC layer.
[0098] In certain configurations, the apparatus 902/902' may be
configured to include means for operating the RLC layer in an
unacknowledged mode. In certain configurations, the ROHC compressor
is configured to operate in a unidirectional mode, a bidirectional
optimistic mode, or a bidirectional reliable mode. In certain
configurations, the first device is a UE or a base station.
[0099] The aforementioned means may be one or more of the
aforementioned modules of the apparatus 902 and/or the processing
system 1014 of the apparatus 902' configured to perform the
functions recited by the aforementioned means. Where the first
device is an eNodeB, as described supra, the processing system 1014
may include the TX Processor 416, the RX Processor 470, and the
controller/processor 475. As such, in one configuration, the
aforementioned means may be the TX Processor 416, the RX Processor
470, and the controller/processor 475 configured to perform the
functions recited by the aforementioned means. Where the first
device is a UE, as described supra, the processing system 1014 may
include the TX Processor 468, the RX Processor 456, and the
controller/processor 459. As such, in one configuration, the
aforementioned means may be the TX Processor 468, the RX Processor
456, and the controller/processor 459 configured to perform the
functions recited by the aforementioned means.
[0100] It is understood that the specific order or hierarchy of
blocks in the processes/flowcharts disclosed is an illustration of
exemplary approaches. Based upon design preferences, it is
understood that the specific order or hierarchy of blocks in the
processes/flowcharts may be rearranged. Further, some blocks may be
combined or omitted. The accompanying method claims present
elements of the various blocks in a sample order, and are not meant
to be limited to the specific order or hierarchy presented.
[0101] The previous description is provided to enable any person
skilled in the art to practice the various aspects described
herein. Various modifications to these aspects will be readily
apparent to those skilled in the art, and the generic principles
defined herein may be applied to other aspects. Thus, the claims
are not intended to be limited to the aspects shown herein, but is
to be accorded the full scope consistent with the language claims,
wherein reference to an element in the singular is not intended to
mean "one and only one" unless specifically so stated, but rather
"one or more." The word "exemplary" is used herein to mean "serving
as an example, instance, or illustration." Any aspect described
herein as "exemplary" is not necessarily to be construed as
preferred or advantageous over other aspects. Unless specifically
stated otherwise, the term "some" refers to one or more.
Combinations such as "at least one of A, B, or C," "at least one of
A, B, and C," and "A, B, C, or any combination thereof" include any
combination of A, B, and/or C, and may include multiples of A,
multiples of B, or multiples of C. Specifically, combinations such
as "at least one of A, B, or C," "at least one of A, B, and C," and
"A, B, C, or any combination thereof" may be A only, B only, C
only, A and B, A and C, B and C, or A and B and C, where any such
combinations may contain one or more member or members of A, B, or
C. All structural and functional equivalents to the elements of the
various aspects described throughout this disclosure that are known
or later come to be known to those of ordinary skill in the art are
expressly incorporated herein by reference and are intended to be
encompassed by the claims. Moreover, nothing disclosed herein is
intended to be dedicated to the public regardless of whether such
disclosure is explicitly recited in the claims. No claim element is
to be construed as a means plus function unless the element is
expressly recited using the phrase "means for."
* * * * *