U.S. patent application number 13/684425 was filed with the patent office on 2013-06-06 for channel state information feedback.
The applicant listed for this patent is Esmael Hejazi Dinan. Invention is credited to Esmael Hejazi Dinan.
Application Number | 20130142062 13/684425 |
Document ID | / |
Family ID | 48523938 |
Filed Date | 2013-06-06 |
United States Patent
Application |
20130142062 |
Kind Code |
A1 |
Dinan; Esmael Hejazi |
June 6, 2013 |
Channel State Information Feedback
Abstract
A wireless device receives a first reference signal from a first
base station and estimates a first signal strength based on the
received first reference signal. The wireless device receives a
second reference signal from a second base station and estimates a
second signal strength based on the received second reference
signal. The wireless device estimates an interference value based,
at least in part, on the second reference signal. The wireless
device estimates a signal to interference ratio value based on the
second signal strength and a total interference value. The total
interference value is computed based upon the interference value or
the interference value plus the first signal strength.
Inventors: |
Dinan; Esmael Hejazi;
(Herndon, VA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dinan; Esmael Hejazi |
Herndon |
VA |
US |
|
|
Family ID: |
48523938 |
Appl. No.: |
13/684425 |
Filed: |
November 23, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61567097 |
Dec 5, 2011 |
|
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Current U.S.
Class: |
370/252 |
Current CPC
Class: |
H04W 24/02 20130101;
H04L 5/0048 20130101; H04W 24/00 20130101; H04W 84/045 20130101;
H04W 24/10 20130101; H04L 27/2601 20130101 |
Class at
Publication: |
370/252 |
International
Class: |
H04W 24/00 20060101
H04W024/00 |
Claims
1. A method comprising: a) receiving, by a wireless device, a first
reference signal from a first base station on a first plurality of
OFDM resources in a first subframe in a plurality of subframes,
said first plurality of OFDM resources depending at least in part
on a first base station identifier of said first base station; b)
estimating, by said wireless device, a first signal strength
corresponding to said first base station based on said received
first reference signal; c) receiving, by said wireless device, a
second reference signal from a second base station, on a second
plurality of OFDM resources in said first subframe, said second
plurality of OFDM resources depending at least in part on a second
base station identifier of said second base station; d) estimating,
by said wireless device, a second signal strength corresponding to
said second base station based on said received second reference
signal; e) estimating, by said wireless device, an interference
value on said second plurality of OFDM resources based at least in
part on said second reference signal; and f) calculating, by said
wireless device, a signal to interference ratio value based on said
second signal strength and a total interference value, wherein: i)
if said first plurality of OFDM resources overlap with said second
plurality of OFDM resources, said total interference value is
computed based upon said interference value; and ii) if said first
plurality of OFDM resources do not overlap with said second
plurality of OFDM resources, said total interference value is
computed based upon said interference value plus said first signal
strength.
2. The method of claim 1, wherein radio signals are received from
said first base station at a substantially higher power than radio
signals received from said second base station.
3. The method of claim 1, wherein said second base station
transmits radio signals at a substantially higher power than said
first base station.
4. The method of any of claim 1, wherein said first base station
type is one of the following: a) a macro base station type; b) a
pico base station type; c) a femto base station type with open
access; and d) a femto base station type with close subscriber
group access.
5. The method of claim 1, wherein said second base station type is
one of the following: a) a macro base station type; b) a pico base
station type; c) a femto base station type with open access; and d)
a femto base station type with close subscriber group access.
6. The method of claim 1, wherein said first reference signal is
one of the following: a) a common reference signal; and b) a
channel state information reference signal.
7. The method of claim 1, wherein said second reference signal is
one of the following: a) a common reference signal; and b) a
channel state information reference signal.
8. The method of claim 1, wherein said first signal strength is
represented by one of the following: a) a short term signal
strength value obtained from a most recent observation; and b) a
long term signal strength value obtained by averaging a plurality
of recent observations.
9. The method of claim 1, wherein said second signal strength is
represented by one of the following: a) a short term signal
strength value obtained from a most recent observation; and b) a
long term signal strength value obtained by averaging a plurality
of recent observations.
10. The method of claim 1, wherein said interference value is one
of the following: a) a short term interference value obtained from
a most recent observation; and b) a long term interference value
obtained by averaging a plurality of recent observations.
11. A method comprising: a) receiving, by a wireless device, a
first reference signal from a first base station on a first
plurality of OFDM resources in a first subframe in a plurality of
subframes, said first plurality of OFDM resources depending at
least in part on a first base station identifier of said first base
station; b) estimating, by said wireless device, a first signal
strength corresponding to said first base station based on said
received first reference signal; c) receiving, by said wireless
device, a second reference signal from a second base station, on a
second plurality of OFDM resources in said first subframe, said
second plurality of OFDM resources depending at least in part on a
second base station identifier of said second base station; d)
estimating, by said wireless device, a second signal strength
corresponding to said second base station based on said received
second reference signal; e) estimating, by said wireless device, an
interference value on said second plurality of OFDM resources based
at least in part on said second reference signal; and f)
calculating, by said wireless device, a signal to interference
ratio value based on said second signal strength and a total
interference value, wherein: i) if said first plurality of OFDM
resources do not overlap with said second plurality of OFDM
resources, said total interference value is computed based upon
said interference value; and ii) if said first plurality of OFDM
resources overlap with said second plurality of OFDM resources,
said total interference value is computed based upon said
interference value minus said first signal strength.
12. The method of claim 11, wherein radio signals are received from
said first base station at a substantially higher power than radio
signals received from said second base station.
13. The method of claim 11, wherein said second base station
transmits radio signals at a substantially higher power than said
first base station.
14. The method of claim 11, wherein said first base station type is
one of the following: a) a macro base station type; b) a pico base
station type; c) a femto base station type with open access; and d)
a femto base station type with close subscriber group access.
15. The method of claim 11, wherein said first reference signal is
one of the following: a) a common reference signal; and b) a
channel state information reference signal.
16. The method of claim 11, wherein said second reference signal is
one of the following: a) a common reference signal; and b) a
channel state information reference signal.
17. A wireless device comprising: a) one or more communication
interfaces; b) one or more processors; and c) memory storing
instructions that, when executed, cause the wireless device to: i)
receive a first reference signal from a first base station on a
first plurality of OFDM resources in a first subframe in a
plurality of subframes, said first plurality of OFDM resources
depending at least in part on a first base station identifier of
said first base station; ii) estimate a first signal strength
corresponding to said first base station based on said received
first reference signal; iii) receive a second reference signal from
a second base station, on a second plurality of OFDM resources in
said first subframe, said second plurality of OFDM resources
depending at least in part on a second base station identifier of
said second base station; iv) estimate a second signal strength
corresponding to said second base station based on said received
second reference signal; v) estimate an interference value on said
second plurality of OFDM resources based at least in part on said
second reference signal; and vi) calculate a signal to interference
ratio value based on said second signal strength and a total
interference value, wherein: (1) if said first plurality of OFDM
resources overlap with said second plurality of OFDM resources,
said total interference value is computed based upon said
interference value; and (2) if said first plurality of OFDM
resources do not overlap with said second plurality of OFDM
resources, said total interference value is computed based upon
said interference value plus said first signal strength.
18. The wireless device of claim 17, wherein said first signal
strength is represented by one of the following: a) a short term
signal strength value obtained from a most recent observation; and
b) a long term signal strength value obtained by averaging a
plurality of recent observations.
19. The wireless device of claim 17, wherein said second signal
strength is represented one of the following: a) a short term
signal strength value obtained from a most recent observation; and
b) a long term signal strength value obtained by averaging a
plurality of recent observations.
20. The wireless device of claim 17, wherein said interference
value is one of the following: a) a short term interference value
obtained from a most recent observation; and b) a long term
interference value obtained by averaging a plurality of recent
observations.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/567,097, filed Dec. 5, 2011, entitled "Channel
State Information Feedback," which is hereby incorporated by
reference in its entirety.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0002] Examples of several of the various embodiments of the
present invention are described herein with reference to the
drawings, in which:
[0003] FIG. 1 is a diagram depicting example sets of OFDM
subcarriers as per an aspect of an embodiment of the present
invention;
[0004] FIG. 2 is a diagram depicting an example transmission time
and reception time for two carriers as per an aspect of an
embodiment of the present invention;
[0005] FIG. 3 is a diagram depicting OFDM radio resources as per an
aspect of an embodiment of the present invention;
[0006] FIG. 4 is a block diagram of a base station and a wireless
device as per an aspect of an embodiment of the present
invention;
[0007] FIG. 5 is a block diagram depicting a system for
transmitting data traffic over an OFDM radio system as per an
aspect of an embodiment of the present invention;
[0008] FIG. 6 is a diagram depicting an example heterogeneous
network as per an aspect of an embodiment of the present
invention;
[0009] FIG. 7 is a diagram illustrating a few example interference
scenarios as per an aspect of an embodiment of the present
invention;
[0010] FIG. 8 is a diagram depicting an example almost blank
subframe as per an aspect of an embodiment of the present
invention;
[0011] FIG. 9 is an example almost blank subframe configuration as
per an aspect of an embodiment of the present invention;
[0012] FIG. 10 is a diagram depicting an example wireless device
configuration as per an aspect of an embodiment of the present
invention;
[0013] FIG. 11 is a flow chart illustrating an example processing
of control format indicator signal as per an aspect of an
embodiment of the present invention;
[0014] FIG. 12 is a flow chart illustrating an example processing
of physical broadcast signal as per an aspect of an embodiment of
the present invention;
[0015] FIG. 13 is a flow chart illustrating an example processing
of synchronization signal as per an aspect of an embodiment of the
present invention;
[0016] FIG. 14 is a flow chart illustrating an example processing
of reference signals as per an aspect of an embodiment of the
present invention; and
[0017] FIG. 15 is a flow chart illustrating transmission of control
messages as per an aspect of an embodiment of the present
invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0018] Example embodiments of the present invention enable channel
state information feedback in wireless communication systems.
Embodiments of the technology disclosed herein may be employed in
the technical field of wireless communication systems. More
particularly, the embodiments of the technology disclosed herein
may relate to channel state information feedback in wireless
communication systems.
[0019] Example embodiments of the invention may be implemented
using various physical layer modulation and transmission
mechanisms. Example transmission mechanisms may include, but are
not limited to: CDMA (code division multiple access), OFDM
(orthogonal frequency division multiplexing), TDMA (time division
multiple access), Wavelet technologies, and/or the like. Hybrid
transmission mechanisms such as TDMA/CDMA, and OFDM/CDMA may also
be employed. Various modulation schemes may be applied for signal
transmission in the physical layer. Examples of modulation schemes
include, but are not limited to: phase, amplitude, code, a
combination of these, and/or the like. An example radio
transmission method may implement QAM (quadrature amplitude
modulation) using BPSK (binary phase shift keying), QPSK
(quadrature phase shift keying), 16-QAM, 64-QAM, 256-QAM, and/or
the like. Physical radio transmission may be enhanced by
dynamically or semi-dynamically changing the modulation and coding
scheme depending on transmission requirements and radio
conditions.
[0020] FIG. 1 is a diagram depicting example sets of OFDM
subcarriers as per an aspect of an embodiment of the present
invention. As illustrated in this example, arrow(s) in the diagram
may depict a subcarrier in a multicarrier OFDM system. The OFDM
system may use technology such as OFDM technology, SC-OFDM (single
carrier-OFDM) technology, or the like. For example, arrow 101 shows
a subcarrier transmitting information symbols. FIG. 1 is for
illustration purposes, and a typical multicarrier OFDM system may
include more subcarriers in a carrier. For example, the number of
subcarriers in a carrier may be in the range of 10 to 10,000
subcarriers. FIG. 1 shows two guard bands 106 and 107 in a
transmission band. As illustrated in FIG. 1, guard band 106 is
between subcarriers 103 and subcarriers 104. The example set of
subcarriers A 102 includes subcarriers 103 and subcarriers 104.
FIG. 1 also illustrates an example set of subcarriers B 105. As
illustrated, there is no guard band between any two subcarriers in
the example set of subcarriers B 105. Carriers in a multicarrier
OFDM communication system may be contiguous carriers,
non-contiguous carriers, or a combination of both contiguous and
non-contiguous carriers.
[0021] FIG. 2 is a diagram depicting an example transmission time
and reception time for two carriers as per an aspect of an
embodiment of the present invention. A multicarrier OFDM
communication system may include one or more carriers, for example,
ranging from 1 to 10 carriers. Carrier A 204 and carrier B 205 may
have the same or different timing structures. Although FIG. 2 shows
two synchronized carriers, carrier A 204 and carrier B 205 may or
may not be synchronized with each other. Different radio frame
structures may be supported for FDD (frequency division duplex) and
TDD (time division duplex) duplex mechanisms. FIG. 2 shows an
example FDD frame timing. Downlink and uplink transmissions may be
organized into radio frames 201. In this example, radio frame
duration is 10 msec. Other frame durations, for example, in the
range of 1 to 100 msec may also be supported. In this example, each
10 ms radio frame 201 may be divided into ten equally sized
sub-frames 202. Other subframe durations such as including 0.5
msec, 1 msec, 2 msec, and 5 msec may also be supported.
Sub-frame(s) may consist of two or more slots 206. For the example
of FDD, 10 subframes may be available for downlink transmission and
10 subframes may be available for uplink transmissions in each 10
ms interval. Uplink and downlink transmissions may be separated in
the frequency domain. Slot(s) may include a plurality of OFDM
symbols 203. The number of OFDM symbols 203 in a slot 206 may
depend on the cyclic prefix length and subcarrier spacing.
[0022] In an example case of TDD, uplink and downlink transmissions
may be separated in the time domain. According to some of the
various aspects of embodiments, each 10 ms radio frame may include
two half-frames of 5 ms each. Half-frame(s) may include eight slots
of length 0.5 ms and three special fields: DwPTS (Downlink Pilot
Time Slot), GP (Guard Period) and UpPTS (Uplink Pilot Time Slot).
The length of DwPTS and UpPTS may be configurable subject to the
total length of DwPTS, GP and UpPTS being equal to 1 ms. Both 5 ms
and 10 ms switch-point periodicity may be supported. In an example,
subframe 1 in all configurations and subframe 6 in configurations
with 5 ms switch-point periodicity may include DwPTS, GP and UpPTS.
Subframe 6 in configurations with 10 ms switch-point periodicity
may include DwPTS. Other subframes may include two equally sized
slots. For this TDD example, GP may be employed for downlink to
uplink transition. Other subframes/fields may be assigned for
either downlink or uplink transmission. Other frame structures in
addition to the above two frame structures may also be supported,
for example in one example embodiment the frame duration may be
selected dynamically based on the packet sizes.
[0023] FIG. 3 is a diagram depicting OFDM radio resources as per an
aspect of an embodiment of the present invention. The resource grid
structure in time 304 and frequency 305 is illustrated in FIG. 3.
The quantity of downlink subcarriers or resource blocks (RB) (in
this example 6 to 100 RBs) may depend, at least in part, on the
downlink transmission bandwidth 306 configured in the cell. The
smallest radio resource unit may be called a resource element (e.g.
301). Resource elements may be grouped into resource blocks (e.g.
302). Resource blocks may be grouped into larger radio resources
called Resource Block Groups (RBG) (e.g. 303). The transmitted
signal in slot 206 may be described by one or several resource
grids of a plurality of subcarriers and a plurality of OFDM
symbols. Resource blocks may be used to describe the mapping of
certain physical channels to resource elements. Other pre-defined
groupings of physical resource elements may be implemented in the
system depending on the radio technology. For example, 24
subcarriers may be grouped as a radio block for a duration of 5
msec.
[0024] Physical and virtual resource blocks may be defined. A
physical resource block may be defined as N consecutive OFDM
symbols in the time domain and M consecutive subcarriers in the
frequency domain, wherein M and N are integers. A physical resource
block may include M.times.N resource elements. In an illustrative
example, a resource block may correspond to one slot in the time
domain and 180 kHz in the frequency domain (for 15 KHz subcarrier
bandwidth and 12 subcarriers). A virtual resource block may be of
the same size as a physical resource block. Various types of
virtual resource blocks may be defined (e.g. virtual resource
blocks of localized type and virtual resource blocks of distributed
type). For various types of virtual resource blocks, a pair of
virtual resource blocks over two slots in a subframe may be
assigned together by a single virtual resource block number.
Virtual resource blocks of localized type may be mapped directly to
physical resource blocks such that sequential virtual resource
block k corresponds to physical resource block k. Alternatively,
virtual resource blocks of distributed type may be mapped to
physical resource blocks according to a predefined table or a
predefined formula. Various configurations for radio resources may
be supported under an OFDM framework, for example, a resource block
may be defined as including the subcarriers in the entire band for
an allocated time duration.
[0025] According to some of the various aspects of embodiments, an
antenna port may be defined such that the channel over which a
symbol on the antenna port is conveyed may be inferred from the
channel over which another symbol on the same antenna port is
conveyed. In some embodiments, there may be one resource grid per
antenna port. The set of antenna port(s) supported may depend on
the reference signal configuration in the cell. Cell-specific
reference signals may support a configuration of one, two, or four
antenna port(s) and may be transmitted on antenna port(s) {0}, {0,
1}, and {0, 1, 2, 3}, respectively. Multicast-broadcast reference
signals may be transmitted on antenna port 4. Wireless
device-specific reference signals may be transmitted on antenna
port(s) 5, 7, 8, or one or several of ports {7, 8, 9, 10, 11, 12,
13, 14}. Positioning reference signals may be transmitted on
antenna port 6. Channel state information (CSI) reference signals
may support a configuration of one, two, four or eight antenna
port(s) and may be transmitted on antenna port(s) 15, {15, 16},
{15, . . . , 18} and {15, . . . , 22}, respectively. Various
configurations for antenna configuration may be supported depending
on the number of antennas and the capability of the wireless
devices and wireless base stations.
[0026] According to some embodiments, a radio resource framework
using OFDM technology may be employed. Alternative embodiments may
be implemented employing other radio technologies. Example
transmission mechanisms include, but are not limited to: CDMA,
OFDM, TDMA, Wavelet technologies, and/or the like. Hybrid
transmission mechanisms such as TDMA/CDMA, and OFDM/CDMA may also
be employed.
[0027] FIG. 4 is an example block diagram of a base station 401 and
a wireless device 406, as per an aspect of an embodiment of the
present invention. A communication network 400 may include at least
one base station 401 and at least one wireless device 406. The base
station 401 may include at least one communication interface 402,
at least one processor 403, and at least one set of program code
instructions 405 stored in non-transitory memory 404 and executable
by the at least one processor 403. The wireless device 406 may
include at least one communication interface 407, at least one
processor 408, and at least one set of program code instructions
410 stored in non-transitory memory 409 and executable by the at
least one processor 408. Communication interface 402 in base
station 401 may be configured to engage in communication with
communication interface 407 in wireless device 406 via a
communication path that includes at least one wireless link 411.
Wireless link 411 may be a bi-directional link. Communication
interface 407 in wireless device 406 may also be configured to
engage in a communication with communication interface 402 in base
station 401. Base station 401 and wireless device 406 may be
configured to send and receive data over wireless link 411 using
multiple frequency carriers. According to some of the various
aspects of embodiments, transceiver(s) may be employed. A
transceiver is a device that includes both a transmitter and
receiver. Transceivers may be employed in devices such as wireless
devices, base stations, relay nodes, and/or the like. Example
embodiments for radio technology implemented in communication
interface 402, 407 and wireless link 411 are illustrated are FIG.
1, FIG. 2, and FIG. 3. and associated text.
[0028] FIG. 5 is a block diagram depicting a system 500 for
transmitting data traffic generated by a wireless device 502 to a
server 508 over a multicarrier OFDM radio according to one aspect
of the illustrative embodiments. The system 500 may include a
Wireless Cellular Network/Internet Network 507, which may function
to provide connectivity between one or more wireless devices 502
(e.g., a cell phone, PDA (personal digital assistant), other
wirelessly-equipped device, and/or the like), one or more servers
508 (e.g. multimedia server, application servers, email servers, or
database servers) and/or the like.
[0029] It should be understood, however, that this and other
arrangements described herein are set forth for purposes of example
only. As such, those skilled in the art will appreciate that other
arrangements and other elements (e.g., machines, interfaces,
functions, orders of functions, etc.) may be used instead, some
elements may be added, and some elements may be omitted altogether.
Further, as in most telecommunications applications, those skilled
in the art will appreciate that many of the elements described
herein are functional entities that may be implemented as discrete
or distributed components or in conjunction with other components,
and in any suitable combination and location. Still further,
various functions described herein as being performed by one or
more entities may be carried out by hardware, firmware and/or
software logic in combination with hardware. For instance, various
functions may be carried out by a processor executing a set of
machine language instructions stored in memory.
[0030] As shown, the access network may include a plurality of base
stations 503 . . . 504. Base station 503 . . . 504 of the access
network may function to transmit and receive RF (radio frequency)
radiation 505 . . . 506 at one or more carrier frequencies, and the
RF radiation may provide one or more air interfaces over which the
wireless device 502 may communicate with the base stations 503 . .
. 504. The user 501 may use the wireless device (or UE: user
equipment) to receive data traffic, such as one or more multimedia
files, data files, pictures, video files, or voice mails, etc. The
wireless device 502 may include applications such as web email,
email applications, upload and ftp applications, MMS (multimedia
messaging system) applications, or file sharing applications. In
another example embodiment, the wireless device 502 may
automatically send traffic to a server 508 without direct
involvement of a user. For example, consider a wireless camera with
automatic upload feature, or a video camera uploading videos to the
remote server 508, or a personal computer equipped with an
application transmitting traffic to a remote server.
[0031] One or more base stations 503 . . . 504 may define a
corresponding wireless coverage area. The RF radiation 505 . . .
506 of the base stations 503 . . . 504 may carry communications
between the Wireless Cellular Network/Internet Network 507 and
access device 502 according to any of a variety of protocols. For
example, RF radiation 505 . . . 506 may carry communications
according to WiMAX (Worldwide Interoperability for Microwave Access
e.g., IEEE 802.16), LTE (long term evolution), microwave,
satellite, MMDS (Multichannel Multipoint Distribution Service),
Wi-Fi (e.g., IEEE 802.11), Bluetooth, infrared, and other protocols
now known or later developed. The communication between the
wireless device 502 and the server 508 may be enabled by any
networking and transport technology for example TCP/IP (transport
control protocol/Internet protocol), RTP (real time protocol), RTCP
(real time control protocol), HTTP (Hypertext Transfer Protocol) or
any other networking protocol.
[0032] According to some of the various aspects of embodiments, an
LTE network may include many base stations, providing a user plane
(PDCP: packet data convergence protocol/RLC: radio link
control/MAC: media access control/PHY: physical) and control plane
(RRC: radio resource control) protocol terminations towards the
wireless device. The base station(s) may be interconnected with
other base station(s) by means of an X2 interface. The base
stations may also be connected by means of an S1 interface to an
EPC (Evolved Packet Core). For example, the base stations may be
interconnected to the MME (Mobility Management Entity) by means of
the S1-MME interface and to the Serving Gateway (S-GW) by means of
the S1-U interface. The S1 interface may support a many-to-many
relation between MMEs/Serving Gateways and base stations. A base
station may include many sectors for example: 1, 2, 3, 4, or 6
sectors. A base station may include many cells, for example,
ranging from 1 to 50 cells or more. A cell may be categorized, for
example, as a primary cell or secondary cell. When carrier
aggregation is configured, a wireless device may have one RRC
connection with the network. At RRC connection
establishment/re-establishment/handover, one serving cell may
provide the NAS (non-access stratum) mobility information (e.g.
TAI-tracking area identifier), and at RRC connection
re-establishment/handover, one serving cell may provide the
security input. This cell may be referred to as the Primary Cell
(PCell). In the downlink, the carrier corresponding to the PCell
may be the Downlink Primary Component Carrier (DL PCC), while in
the uplink, it may be the Uplink Primary Component Carrier (UL
PCC). Depending on wireless device capabilities, Secondary Cells
(SCells) may be configured to form together with the PCell a set of
serving cells. In the downlink, the carrier corresponding to an
SCell may be a Downlink Secondary Component Carrier (DL SCC), while
in the uplink, it may be an Uplink Secondary Component Carrier (UL
SCC). An SCell may or may not have an uplink carrier.
[0033] A cell, comprising a downlink carrier and optionally an
uplink carrier, is assigned a physical cell ID and a cell index. A
carrier (downlink or uplink) belongs to only one cell, the cell ID
or Cell index may also identify the downlink carrier or uplink
carrier of the cell (depending on the context it is used). In the
specification, cell ID may be equally referred to a carrier ID, and
cell index may be referred to carrier index. In implementation, the
physical cell ID or cell index may be assigned to a cell. Cell ID
may be determined using the synchronization signal transmitted on a
downlink carrier. Cell index may be determined using RRC messages.
For example, when the specification refers to a first physical cell
ID for a first downlink carrier, it may mean the first physical
cell ID is for a cell comprising the first downlink carrier. The
same concept may apply to, for example, carrier activation. When
the specification indicates that a first carrier is activated, it
equally means that the cell comprising the first carrier is
activated.
[0034] Embodiments may be configured to operate as needed. The
disclosed mechanism may be performed when certain criteria are met,
for example, in wireless device, base station, radio environment,
network, a combination of the above, and/or the like. Example
criteria may be based, at least in part, on for example, traffic
load, initial system set up, packet sizes, traffic characteristics,
a combination of the above, and/or the like. When the one or more
criteria are met, the example embodiments may be applied.
Therefore, it may be possible to implement example embodiments that
selectively implement disclosed protocols.
[0035] FIG. 6 shows an example heterogeneous network in an example
embodiment. The coverage and capacity of macro base station 601 may
be extended by the utilization of base stations with lower transmit
power. Micro, Pico, femto and relay nodes are examples of low power
base stations. In an example embodiment, pico base stations (or
pico-cell) 602, 603, and 607 may have transmit power ranges from
approximately 200 mW to approximately 5 W. Macro base stations may
have a transmit power that typically varies between 5 and 100 W.
Femto base stations (or femto-cells) may be used for local services
such as in indoor services, and their transmit power may be
approximately 200 mW or less. These are just some example power
ranges, and as such, should not be considered as a hard limit on
the transmit power of a base station type. For example, some
femto-cell product may transmit at a power greater than 200 mW.
Femto or pico base stations 605, 606 may be configured with a
restricted subscriber group that may allow access only to its
closed subscriber group (CSG) members. Such femto or pico base
stations may be referred to as closed femtos or picos. Femto or
pico base stations may also be configured as open femtos 604 or
picos 602, 603. Relay Nodes (e.g. 608) may employ the macro base
stations air interface as a backhaul and may increase coverage and
capacity of the macro base station. A network that comprises of a
mix of macro base stations and low-power nodes such as pico or
femto base stations, where some base stations may be configured
with restricted access and some may lack a wired backhaul, is
referred to as a heterogeneous network.
[0036] Femto cells may be classified as open or closed depending on
whether the femto cells allow access to all, or to a restricted set
of wireless devices. Closed femtos may restrict the access to a
closed subscriber group (CSG). Open femtos may be similar to
pico-cells, but may use the network backhaul provided by the home
network. A femto cell may also be a hybrid, whereby many wireless
devices may have access, but with lower priority for the wireless
devices that do not belong to the femto's subscriber group. Closed
femtos may not allow access to wireless devices, and may become a
source of interference to those wireless devices. Co-channel
deployments of closed femtos may cause coverage holes and hence
outage of a size proportional to the transmit power of the
femto-cell. Femto-cells may or may not have an X2 interface.
OAM-based or X2 based techniques in conjunction with possibly
autonomous power control techniques may be used for interference
management with femto cells depending on the existence of a femto
X2 interface. These techniques may reduce the outage and/or
interference that these network nodes cause around them and enable
reception of the signal from the macro-cell in close proximity to
the closed femto.
[0037] Co-channel deployment of low-power nodes and high power
nodes may introduce new challenges. The introduction of low-power
nodes in a macro network may create an imbalance between uplink and
downlink coverage. Due to the larger transmit power of the macro
base station, the handover boundary may be shifted closer to the
low-power node. This shift may lead to severe uplink interference
problems as wireless devices served by macro base stations create
strong interference to the low-power nodes. Given the relatively
small footprint of low-power nodes, low-power nodes may become
underutilized due to geographic changes in data traffic demand. The
limited coverage of low-power nodes may be a reason for limited
performance gain in heterogeneous networks. Some of the deployed
femto cells may have enforced restricted associations, which may
create a coverage hole and may exacerbate the interference
problem.
[0038] FIG. 7 illustrates a few example interference scenarios in
an example embodiment. The solid arrow shows the desired signal,
and the arrow with the dashed line shows the unwanted interference.
Wireless device 701 may not be a member of CSG cell 705 and may be
roaming in the coverage area of femto-cell 705. It may receive the
signal from macro base station 708, and may receive high
interference from CSG pico-cell 705. In another example, wireless
device 702 may not be a member of CSG cell 706 and may be roaming
in the coverage area of femto-cell 706. The wireless device 702 may
transmit a signal to base station 708 in the macro base station
uplink channel. The wireless device 702 may create high
interference for femto-cell 706. The wireless device 703 may not be
a member of CSG cell 707 and may be roaming in the coverage area of
femto-cell 707. The wireless device 703 may be a member of CSG
femto-cell 706 and may a transmit signal to femto-cell 706. The
wireless device 703 may create high interference for femto-cell
707. In another example scenario, the wireless device 704 may be in
the cell coverage edge of pico-cell 709. The wireless device 704
may receive a signal from pico-cell 709. The wireless device 704
may also receive high interference from macro base station 708. As
shown in these examples, in order to cope with the interference, it
may be required to introduce techniques that may adequately address
these issues.
[0039] A new physical layer design in LTE networks may allow for
flexible time and frequency resource partitioning. This added
flexibility may enable macro- and femto/picocells to assign
different time-frequency resource blocks within a carrier or
different carriers (if available) to their respective wireless
devices. This is one of the inter-cell interference coordination
(ICIC) techniques and may be used on a downlink or an uplink to
mitigate interference. With additional complexity, joint processing
of serving and interfering base station signals may further improve
the performance of heterogeneous networks.
[0040] According to some of the various aspects of embodiments,
cell range expansion through handover biasing and resource
partitioning among different node power classes may decrease
interference. The biasing mechanism may allow for load balancing.
Depending on the bias value, the network may control the number of
wireless devices associated with the low-power nodes and therefore
control traffic demand at those nodes. Resource partitioning, which
may be adaptive, may allow configuration and adjustment of
interference protected resources, enabling wireless devices in a
cell's expanded area to receive data. Resource partitioning
techniques may mitigate uplink and downlink interference and allow
non-CSG member wireless devices to receive service when in
proximity of closed femto-base stations.
[0041] In a heterogeneous network, the network nodes may be
deployed in the same frequency layer. Deploying low-power nodes at
the same frequency layer as the (high-power) macro-cells may
present interference problems in the case of closed femtos. Also,
for the case of open access nodes (open femtos, pico-cells, and
RNs), the coverage of the low-power nodes may be overshadowed by
the transmissions of the high-power nodes. Interference
coordination techniques may solve these problems. A reduction of
closed femto interference to the macro layer and a performance
increase from the introduction of open access low-power nodes may
be achieved by interference control techniques. To enable efficient
support of co-channel deployment of heterogeneous networks, an
interference management scheme may adapt to different traffic loads
and different numbers of low-power nodes at various geographical
areas.
[0042] According to some of the various aspects of embodiments,
resource partitioning may be employed for interference management
in co-channel deployments. To reach its full potential, resource
partitioning may be paired with interference-cancellation-capable
wireless devices. Similar approaches may be applied to micro, pico,
femto, and relay nodes. Each node may have its own caveats. For
example, the X2 backhaul link between the macro and relay base
stations may be over an LTE air interface. In another example,
closed femto cells may create their own interference challenges.
Femto base stations may lack an X2 interface and employ static or
dynamic interference management methods using OAM-based or similar
solutions.
[0043] According to some of the various aspects of embodiments,
adaptive interference management in LTE may be enabled through X2
backhaul coordination of resources used for scheduling data
traffic. The granularity of the negotiated resource may be a
subframe. One of the various motivations behind resource
partitioning may be to control interference and/or enable cell
range expansion through cell biasing. In a typical case, cell range
expansion may be enabled to improve system capacity, and a cell
bias may be applied to low-power nodes. The bias value may refer to
a threshold that triggers a handover between two cells. A positive
bias may enable a wireless device to be handed over to a pico-cell
when the difference in the signal strength from the macro- and
pico-cells drop below a bias value. The high-power node (macro base
station) may inform the low-power node (pico base station) of which
resources may be utilized for scheduling macro wireless device and
which subframes would remain unutilized (almost blank subframes).
Low-power nodes may be made aware of the interference pattern from
a high-power base station and may schedule a wireless device in the
cell extended areas on subframes protected from high-power
interference. That is, subframes corresponding to almost blank
subframes at the high-power base station.
[0044] According to some of the various aspects of embodiments, the
X2 interface may enable direct base station to base station
interface for inter-cell interference coordination (ICIC).
Co-channel deployments of heterogeneous networks may require
coordination of almost blank subframes. Almost blank subframes may
reduce the interference created by the transmitting node while
providing full legacy support. On almost blank subframes, base
station may not schedule unicast traffic while it may transmit
acquisition channels and common reference signal to provide legacy
support. FIG. 8 shows an example almost blank subframe. In this
example CRS (R0, R1, R2, R3 signals) are transmitted only in the
control region and are not transmitted in the data region. The
interfering base station may still transmit PSS, SSS, PBCH, and RSs
to support legacy terminals. Some interference still may exist. In
this example, no data may be transmitted in almost blank subframes
or data may be transmitted at a substantially lower power in almost
blank subframes.
[0045] Interference coordination using almost blank subframes may
be performed by means of a bitmap. Each bit in the bitmap may be
mapped to a single subframe. The size of the bitmap may be, for
example, 40 bits, resulting in the interference pattern repeating
itself after 40 ms. FIG. 9 shows an example almost blank subframe
configuration in an example embodiment. In this example embodiment,
no data may be scheduled in almost blank subframes (ABS). In
another embodiment, data may be scheduled in almost blank subframes
at a substantially lower power. Subframes 901, 902, 903, and 904
may be configured as ABS in the macro base station. When a macro
base station transmits an almost blank subframe, data may not be
scheduled in that subframe (or data may be transmitted at a
substantially lower power). This may increase the coverage of the
femto or pico base stations close to that macro base station.
Subframes 905 and 906 may be configured as ABS in the femto base
station. When the femto base station transmits an almost blank
subframe, data may not be scheduled in that subframe (or data may
be transmitted at a substantially lower power). This may increase
coverage allowed for the macro base station or the neighboring
femto base stations. In the example of FIG. 9, the almost blank
subframe pattern may be repeated every 10 msec. This is just an
example and various configurations may be possible. The almost
blank subframe configuration may be changed dynamically according
to load and traffic, time of the day, or many other parameters. In
an example embodiment, based on the data traffic demand, the
pattern may change as often as every 40 ms. The communication
between nodes may be peer to peer. Or it may be in a master-slave
relationship. The node creating dominant interference conditions
may control which resources may be used to serve wireless devices
in the cell range extension area. In an example scenario, a macro
base station may be a master, and a pico base station may be a
slave since cell range expansion would most frequently be
established for pico base stations. The cell range expansion may be
desirable for a macro base station as well. A use case for cell
range expansion at the macro base station may be to reduce the
number of handovers. In a scenario with a large number of
high-mobility users, the number of handovers in the network may
become a problem, for example when in the deployment of pico base
stations the cells become small. The same resource partitioning
schemes may then be utilized to allow high mobility macro wireless
devices to remain attached to a macro-cell while deep inside
coverage of a pico-cell. In this case, the pico base station may
restrict scheduling data traffic on some resources, allowing
coverage for high-mobility macro wireless devices.
[0046] According to some of the various aspects of embodiments,
subframe resource partitioning may create an interference pattern
that may require a new radio resource measurement paradigm. As
dominant interference may potentially vary from one subframe to the
other, in order to ensure radio resource management measurement
accuracy, it may be needed to restrict measurements to a desired
set of subframes. In an example embodiment, it may be desirable to
define anchor interference-protected resources that may be utilized
for radio resource measurement. The 40-bit bitmap may include
indications of which subframes may have static protection from
interference and therefore may be suitable for measurements. The
remaining resources may change more often.
[0047] According to some of the various aspects of embodiments, the
serving base station may inform a wireless device of the set of
subframes to which the wireless device measurement may be
restricted. A set of subframes may be configured for radio link
monitoring and to check if the current connection is reliable
enough. The same or a different set of subframes may be introduced
for radio resource management, for example, a handover decision. An
additional set of subframes may be signaled for the measurement for
some neighboring base stations. This configuration may be
relatively static and may not change rapidly. Another set of
subframes may be configured in the wireless device for channel
state information reporting and link adaptation. Two sets of
subframes may be signaled to a wireless device for two different
channel state information types. For example, one may be for almost
blank subframes, and the other may be for normal subframes. This
configuration may change dynamically depending on the network
configuration.
[0048] FIG. 10 illustrates example channel state information
bitmaps and an example radio link management bitmap. Subframe 1001
(subframe 3) is semi-statically configured as ABS and therefore it
is used for radio link management in a wireless device in a victim
base station. Subframes 1002, 1003, and 1004 (subframes 1, 6, and
8) are dynamically configured as ABS subframes. CSI bitmap 1 is
used for a first channel state information measurement and CSI
bitmap 2 is used for a second channel state information
measurement. This is an example, and various configurations and
bitmap lengths, such as 40 bits or 70 bits, may also be supported.
When there is no X2 interface, a static OAM-based or similar
solution may be employed. The same principle of extending coverage
of one cell into the area covered by the other may be achieved. In
this case, it may be the macro-cell service that needs to be
extended into an area covered by the closed femto-cell.
[0049] The resource partitioning may reduce interference from the
data channel. Interference from the acquisition channels and CRS
signal may remain, since these signals may be transmitted for
backward compatibility reasons. Subframe time shifting may be
utilized in FDD systems to reduce collision of the acquisition
channels between base stations of different power classes that
require partitioning, but may not be employed in TDD systems.
Interference mitigation for the acquisition channels may be needed
for cell range expansion to enable the wireless device to detect
and acquire a weak cell and then measure and feedback the
measurement report to the network, which may be needed for handover
and cell range expansion.
[0050] CRS interference mitigation may improve system performance.
CRS interference may degrade turbo code performance and the overall
signal-to-interference-plus-noise radio (SINR). Therefore, the
potential gains of cell range expansion may be reduced. Given that
acquisition channels and CRS may be broadcast at high power
targeting wireless devices at the cell edge, a robust wireless
device solution is feasible.
[0051] One of the various rationales for the wireless device
solution for the acquisition signals and CRS interference
mitigation is that interference may be estimated and subtracted so
that in the end it may not represent significant interference.
Acquisition channels may be transmitted at the same location in
cells, which means that the acquisition channels interference may
comprise acquisition channels from neighboring interfering cells.
This structure may lend itself to a design of an interference
canceller. A wireless device receiver first may decode the
strongest signal, may perform channel gain estimation toward the
interfering cell, may cancel the interfering signal, and may
continue the procedure until acquisition channels of the serving
cell are acquired.
[0052] A similar procedure may be performed to remove CRS
interference. The difference may be that CRS tones may also
interfere with data tones since interference between CRS tones
between high-power and low-power nodes may be reduced by CRS tone
shifting. The procedure may be similar. If strong CRS interference
is detected, and after the channel gain toward the interfering cell
is estimated, the CRS signal may be cancelled. The procedure may be
repeated until interfering signals are subtracted.
[0053] RRC messages are used to configure wireless device
configuration parameters related to almost blank configuration and
measurements. An example RRC message configuration in an example
embodiment is described in the following paragraphs. A subframe
pattern bitmap may indicate the time domain measurement resource
restriction pattern for primary or secondary carrier measurements
(RSRP, RSRQ and the radio link monitoring). The bitmap length may
be, for example, 40 bits. Another subframe bitmap may configure
neighbor measurement patterns. A neighbor measurement bitmap along
with the list of cells for which the neighbor measurement bitmap is
applied may be transmitted to the wireless device. If the list of
cells is not included, the wireless device may apply time domain
measurement resource restrictions for neighbor cells. Time domain
measurement resource restriction patterns may be applicable to
neighbor cell RSRP and RSRQ measurements on a carrier frequency
indicated by RRC. In an example embodiment, two CSI subframe
pattern configuration bitmaps may be transmitted to the wireless
device. Each bit map may be 40 bits long. The CSI configuration may
include a channel quality index, a rank indicator, a precoding
matrix indicator, a combination thereof, or the like.
[0054] A base station may broadcast an ABS subframe configuration
employing MBSFN (multi-cast, broadcast, single frequency network)
subframe configuration broadcast or unicast messages. An example
broadcast message is an RRC system information block. MBSFN or ABS
subframe configurations may include a radio frame allocation
period, a radio frame allocation offset, a subframe allocation
bitmap, any combination of these parameters, or the like. A radio
frame allocation period may be 1, 2, 4, 8, 16 or 32 frames. A radio
frame allocation offset may be a number between 1 to 7 subframes. A
subframe allocation bitmap may be for one frame or four frames.
Radio frames that contain MBSFN/ABS subframes may occur when
equation (SFN mod radio Frame Allocation Period=radio Frame
Allocation Offset) is satisfied. Values 1 and 2 may not be
applicable to radio frame allocation period when four Frames are
used.
[0055] According to some of the various aspects of embodiments, a
subframe allocation bitmap may define the subframes that are
allocated for MBSFN within the radio frame allocation period
defined by the radio frame allocation period and the radio frame
allocation offset. A subframe allocation bitmap for one frame may
be six bits long and for four frames may be 24 bits long. In a
bit-map indicating MBSFN/ABS subframe allocation in four
consecutive radio frames, a "1" may denote that the corresponding
subframe is allocated for MBSFN/ABS. The bitmap may be interpreted
as follows: For FDD: Starting from the first radio frame and from
the first/leftmost bit in the bitmap, the allocation may apply to
subframes #1, #2, #3, #6, #7, and #8 in the sequence of the four
radio-frames. For TDD: Starting from the first radio frame and from
the first/leftmost bit in the bitmap, the allocation applies to
subframes #3, #4, #7, #8, and #9 in the sequence of the four
radio-frames. The last four bits may not be used. Uplink subframes
may not be allocated.
[0056] Other example configurations may be implemented. For
example, an MBSFN subframe configuration may be used to introduce
ABS subframes and subframes used for scheduling release 10 or above
wireless devices. For example, an MBSFN configuration may introduce
subframe 1, 3, 6 and 8 as MBSFN subframes in a frame. Then MBSFN
subframe 1 may be used for scheduling release 10 or above wireless
devices, and MBSFN subframe 3, 6, and 8 may be used as almost blank
subframes. Therefore, as seen in this example, MBSFN configuration
may indicate other types of subframes in addition to almost blank
subframes. In another configuration, a base station may use one or
many of MBSFN subframes for broadcasting or multicasting services.
In a typical scenario, in which MBSFN may be configured, for
example, for four frames, with a period of 40 msec, various
configurations for combining ABS, MBSFN, and release 10 or above
subframes may be possible. In this specification, ABS subframes may
be called special subframes.
[0057] According to some of the various aspects of embodiments,
special subframes may be configured for the primary carrier (cell)
as well as one or more secondary carriers (cells). The
configuration parameters for the measurement parameters of the
secondary carrier(s) may employ the bitmaps with the same length
and format of the configuration parameters of the primary carrier.
In an example embodiment, the configuration parameters of special
subframes for one or more secondary carriers may be the same as the
configuration parameters for the special subframe configuration of
the primary carrier.
[0058] According to some of the various aspects of embodiments,
non-backward compatible carriers may be configured with special
subframes. In a non-backward compatible carrier special subframe,
no common reference signal may be transmitted during the special
subframe. Or, data and reference signals in a non-backward
compatible carrier special subframe may be transmitted at a
substantially lower power to ensure that no interference (to other
cells) is observed during the special subframe.
[0059] Example embodiments of the invention may enable channel
state information feedback in wireless communication systems. Other
example embodiments may comprise a non-transitory tangible computer
readable media comprising instructions executable by one or more
processors to cause channel state information feedback in wireless
communication systems. Yet other example embodiments may comprise
an article of manufacture that comprises a non-transitory tangible
computer readable machine-accessible medium having instructions
encoded thereon for enabling programmable hardware to cause a
device (e.g. wireless communicator, UE, base station, etc.) to
enable channel state information feedback. The device may include
processors, memory, interfaces, and/or the like. Other example
embodiments may comprise communication networks comprising devices
such as base stations, wireless devices (or user equipment: UE),
servers, switches, antennas, and/or the like.
[0060] Co-channel deployments may be of interest due to cost
effectiveness and high spectral efficiency. Resource partitioning
may effectively mitigate interference from the data channel.
However, interference from the acquisition channels, CRS signal,
and control channels (including a control format indicator channel)
may remain, since these signals may be needed to be transmitted for
backward compatibility reasons. Subframe time shifting may be
utilized in FDD systems to avoid collision of the acquisition
channels between base stations of different power classes that
require partitioning. Subframe time shifting may not be necessary
in TDD systems. There may be limited network solutions for CRS
interference mitigation for either FDD or TDD systems. Without
additional interference mitigation of the acquisition channels,
CRS, and control channels (including the control format indicator
channel), limited medium bias values (for example, 6-10 dB) for
handover may be supported. This may limit the potential for cell
range expansion.
[0061] Interference mitigation for the acquisition channels may be
needed for cell range expansion. Interference mitigation may enable
wireless devices to detect and acquire a weak cell and then measure
and feedback the measurement report to the network.
[0062] CRS interference mitigation may have a role in system
performance. Strong CRS interference, even though present on a
relatively small fraction of resource elements, may degrade turbo
code performance and the overall signal-to-interference-plus-noise
ratio (SINR). The potential gains of cell range expansion may be
reduced. The control format indicator channel may carry important
information without which the wireless device may not be able to
decode the control information. Strong interference on the control
format indicator channel may result in loss of information carried
on this channel and may cause a wireless device to lose the ability
to decode other control channels carrying scheduling and other
related information.
[0063] According to some of the various aspects of embodiments, a
wireless device solution may be feasible given that acquisition
channels, CRS, and/or the control format indicator channel may be
broadcast at a high power targeting wireless devices at the cell
edge. Interference may be estimated and subtracted so that it may
not represent significant interference for the acquisition signals,
CRS, and the control format indicator channel. Acquisition channels
may be transmitted at the same radio resource location in cells.
The acquisition channels interference may comprise the acquisition
channels from the neighboring interfering cells. This structure may
lend itself to a design of an interference canceller. A wireless
device receiver may first decode one of the strongest signals, may
perform channel gain estimation toward the interfering cell, may
cancel the interfering signal, and may continue the procedure until
acquisition channels of the serving cell are acquired.
[0064] A similar procedure may be performed to remove CRS
interference. The CRS tones may also interfere with data tones
since interference between CRS tones between high- and low-power
nodes may be avoided/reduced by CRS tone shifting. If strong CRS
interference is detected, and after the channel gain toward the
interfering cell is estimated, the CRS signal may be cancelled. The
procedure may be repeated until interfering signals are
subtracted.
[0065] According to some of the various aspects of embodiments, the
control format indicator channel may be transmitted at the same
location in cells. The control format indicator channel's
interference may comprise the control format indicator channel from
the neighboring interfering cells. This structure may lend itself
to a design of an interference canceller. A wireless device
receiver may first decode one of the strongest signals, may perform
channel gain estimation toward the interfering cell, may cancel the
interfering signal, and may continue the procedure until the
control format indicator channel of the serving cell is decoded.
There is a need to develop mechanisms for processing broadcast
channels, for example, in hierarchical networks. A different signal
processing mechanism may be needed compared with traditional
methods when there is strong co-channel interference among base
stations. The mechanisms may be different than traditional methods
since the signal patterns may be known or the wireless device may
able to determine interference patterns before an interference
cancellation process starts. Embodiments of the present invention
provide mechanisms to process received signals and to obtain
broadcast messages and signals.
[0066] In an example embodiment, resource partitioning mechanisms
such as ABS subframe configurations may be used for data channels.
Different interfering signals may be transmitted at different times
employing an ABS configuration among interfering base stations. In
an example embodiment, resource partitioning may be performed in
frequency domains, for example different interfering ePDCCH and/or
PDCCH may be transmitted in different frequency bands. Simulation
results show that advanced interference cancellation may be
effective on control format indicator channel and/or physical
broadcast channels, while the same techniques may not be applicable
to other channels such as (e)PDCCH and/or PDSCH. Signal pattern may
have more limited possibilities for control format indicator
channel and/or physical broadcast channels. The number of
iterations required for interference cancellation for control
format indicator channel and physical broadcast channels may be
limited. At least for the above reasons, interference cancellation
is applied to control format indicator channel and/or physical
broadcast channels.
[0067] The same or similar approaches may not be appropriate for
all control channels, (e.g., control channels carrying scheduling
information) and/or data channels. The reason may be that such
control and/or data channels may be scrambled with the identity of
a target wireless device, and in order for a wireless device to
cancel the interference of such channels, the wireless device may
need to try a very large number of hypotheses considering the
information being transmitted to potential wireless identifiers in
the neighboring cell. This may require a large amount of
computational complexity, and may not be practical. The
interference cancellation for synchronization signals may require a
limited number of correlations to detect interfering
synchronization signal. This process may be simpler than
interference cancellation for (e)PDCCH and/or PDSCH. I mechanism is
introduced for interference cancellation of synchronization
signal.
[0068] FIG. 11 is a flow chart illustrating an example processing
of control format indicator signal as per an aspect of an
embodiment of the present invention. According to some of the
various aspects of embodiments, a wireless device may demodulate,
descramble and decode a first control format indicator signal to
generate a first signal as shown in 1102. The first control format
indicator signal may be received from a first base station on a
plurality of OFDM subcarriers in a first OFDM symbol of a first
subframe in a plurality of subframes. The wireless device may
process the first signal. The processing of the first signal may
comprise encoding, scrambling, modulating and scaling the first
signal as shown in 1104. The wireless device may subtract the
processed first signal from received signals on the plurality of
OFDM subcarriers in the first OFDM symbol of the first subframe to
generate a second signal as shown in 1106. The wireless device may
process the second signal. The processing of the second signal may
comprise demodulating, descrambling and decoding a second control
format indicator signal to generate a second control format
indicator as shown in 1108. The second control format indicator
signal may be received from a second base station in the first OFDM
symbol of the first subframe. The wireless device may determine the
number of OFDM symbols of a control region of the second base
station based on the second control format indicator as shown in
1110.
[0069] According to some of the various aspects of embodiments, the
second base station may be of a different base station type than
the first base station. The first base station type may be one of
the following: a macro base station type, a pico base station type,
a femto base station type with open access, and a femto base
station type with close subscriber group access. The second base
station type may be one of the following: a macro base station
type, a pico base station type, a femto base station type with open
access, and a femto base station type with close subscriber group
access. The second control format indicator may comprise two bits
of information. The second control format indicator signal may be
encoded, by the second base station, employing a repetition code.
The first control format indicator signal may be received over
sixteen modulation symbols. Those skilled in the art will recognize
that the first control format indicator signal may be received over
different amount of modulation symbols in accordance with various
systems.
[0070] FIG. 12 is a flow chart illustrating an example processing
of physical broadcast signal as per an aspect of an embodiment of
the present invention. According to some of the various aspects of
embodiments, a wireless device may demodulate, descramble and
decode a first physical broadcast signal to generate a first signal
as shown in 1202. The first physical broadcast signal may be
received from a first base station on a plurality of OFDM
subcarriers substantially in the center of a frequency band of a
carrier in a plurality of OFDM symbols of a subset of subframes in
a plurality of subframes. The term substantially is used to
indicate possible inaccuracies in the frequency of frequency
synthesizers. The signal is practically considered in the center of
the frequency band. The wireless device may process the first
signal. The processing of the first signal may comprise encoding,
scrambling, modulating and scaling the first signal as shown in
1204. The wireless device may subtract the processed first signal
from received signals on the plurality of OFDM subcarriers in the
plurality of OFDM symbols of the subset of subframes to generate a
second signal as shown in 1206. The wireless device may process the
second signal. The processing of the second signal comprising
demodulating, descrambling and decoding a second physical broadcast
signal to generate a second physical broadcast message as shown in
1208. The second physical broadcast signal may be received from a
second base station in the plurality of OFDM symbols of the subset
of subframes. The wireless device may determine a plurality of
system parameters of the second base station based on the second
physical broadcast message as shown in 1210.
[0071] According to some of the various aspects of embodiments, the
second base station may be of a different base station type than
the first base station. The first base station type may be one of
the following: a macro base station type, a pico base station type,
a femto base station type with open access, and a femto base
station type with close subscriber group access. The second base
station type may be one of the following: a macro base station
type, a pico base station type, a femto base station type with open
access, and a femto base station type with close subscriber group
access. The first physical broadcast signal reception may reoccur
periodically with a fix period, for example every 40 msec. The
first physical broadcast signal may be received over seventy two
OFDM subcarriers substantially in the center of a carrier. The
plurality of system parameters may comprise at least one of: system
bandwidth information, HARQ indicator channel structure
information, and eight most significant bits of system frame
number. The second physical broadcast signal may be encoded, by the
second base station, employing a convolutional code and a
repetition code. Those skilled in the art will recognize that
physical broadcast signal(s) may be encoded using other techniques.
The second physical broadcast message may comprise fourteen bits of
information. The second physical broadcast message may comprise a
master information block.
[0072] According to some of the various aspects of embodiments, a
wireless device may correlate received signals on a first plurality
of OFDM subcarriers substantially in the center of a frequency band
of a carrier in a first subset of OFDM symbols with a first
plurality of predetermined primary synchronization signals to
produce a first plurality of correlation values. In one example
embodiment, the correlation process may comprise a summation of a
plurality of multiplications. In another example implementation,
correlation may be performed by hardware, firmware, software in
combination with hardware, and/or an electronic circuit, for
example, by a matched filter, DSP processor and/or the like. Other
examples of correlation mechanisms may be implemented. Correlation
may be of any type of correlation and may not be limited to above
embodiments. Correlation process may be any type of mechanisms that
detects association, similarity, connection, and/or relationship
between two signals.
[0073] The wireless device may identify based at least in part on
the first plurality of correlation values, a first primary
synchronization signal in the first plurality of predetermined
primary synchronization signals as a primary synchronization signal
transmitted by a first base station. The wireless device may
process the first primary synchronization signal. The processing of
the first primary synchronization signal may comprise scaling the
first primary synchronization signal by a scaling factor that
depends, at least in part, on a correlation value corresponding to
the first primary synchronization signal. The wireless device may
subtract the processed first primary synchronization signal from
received signals on the first plurality of OFDM subcarriers in the
first subset of OFDM symbols to generate a first updated received
signal. The wireless device may correlate the first updated
received signal with a second plurality of predetermined primary
synchronization signals to produce a second plurality of
correlation values. The wireless device may identify based at least
in part on the second plurality of correlation values, a second
primary synchronization signal as a primary synchronization signal
transmitted by a second base station.
[0074] The wireless device may correlate received signals on a
second plurality of OFDM subcarriers substantially in the center of
the frequency band of the carrier in a second subset of OFDM
symbols with a first plurality of predetermined secondary
synchronization signals to produce a third plurality of correlation
values. The wireless device may identify based at least in part on
the third plurality of correlation values, a first secondary
synchronization signal in the first plurality of predetermined
secondary synchronization signals as a secondary synchronization
signal transmitted by the first base station. The wireless device
may process the first secondary synchronization signal. The
processing of the first secondary synchronization signal may
comprise scaling by a scaling factor that depends, at least in
part, on a correlation value corresponding to the first secondary
synchronization signal.
[0075] The wireless device may subtract the processed first
secondary synchronization signal from received signals on the
second plurality of OFDM subcarriers in the second subset of OFDM
symbols to generate a second updated received signal. The wireless
device may correlate the second updated received signal with a
second plurality of predetermined secondary synchronization signals
to produce a fourth plurality of correlation values. The wireless
device may identify based at least in part on the fourth plurality
of correlation values, a second secondary synchronization signal in
the second plurality of predetermined secondary synchronization
signals as a secondary synchronization signal transmitted by the
second base station. The wireless device may obtain frame and
subframe timing information of the second base station employing
the second primary synchronization signal and the second secondary
synchronization signal.
[0076] According to some of the various aspects of embodiments, the
first primary synchronization signal may have a highest correlation
value among the first plurality of correlation values. The second
primary synchronization signal may have a highest correlation value
among the second plurality of correlation values. The first
secondary synchronization signal may have a highest correlation
value among the third plurality of correlation values. The second
secondary synchronization signal may have a highest correlation
value among the fourth plurality of correlation values. The first
plurality of predetermined secondary synchronization signals may
depend, at least in part, on the first primary synchronization
signal. The second plurality of predetermined secondary
synchronization signals may depend, at least in part, on the second
primary synchronization signal.
[0077] FIG. 13 is a flow chart illustrating an example processing
of synchronization signal as per an aspect of an embodiment of the
present invention. According to some of the various aspects of
embodiments, a wireless device may correlate received signals on a
plurality of OFDM subcarriers substantially in the center of a
frequency band of a carrier in a subset of OFDM symbols with a
first plurality of predetermined synchronization signals to produce
a first plurality of correlation values as shown in 1302. The
wireless device may identify based at least in part on the first
plurality of correlation values, a first synchronization signal in
the first plurality of predetermined synchronization signals as a
synchronization signal transmitted by a first base station as shown
in 1304. The wireless device may process the first synchronization
signal. The processing of the first synchronization signal may
comprise scaling the first synchronization signal by a scaling
factor that depends, at least in part, on a correlation value
corresponding to the first synchronization signal as shown in 1306.
The wireless device may subtract the processed first
synchronization signal from received signals on the plurality of
OFDM subcarriers in the subset of OFDM symbols to generate an
updated received signal as shown in 1308. The wireless device may
correlate the updated received signal with a second plurality of
predetermined synchronization signals to produce a second plurality
of correlation values as shown in 1310. The wireless device may
identify based at least in part on the second plurality of
correlation values, a second synchronization signal as a
synchronization signal transmitted by a second base station as
shown in 1312. The wireless device may obtain frame and subframe
timing information of the second base station employing the second
synchronization signal as shown in 1314.
[0078] The first base station type may be of a different type than
the second base station type. The first base station type may be
one of the following: a macro base station type, a pico base
station type, a femto base station type with open access, and a
femto base station type with close subscriber group access. The
second base station type may be one of the following: macro base
station type, a pico base station type, a femto base station type
with open access, and a femto base station type with close
subscriber group access.
[0079] The first synchronization signal may have a highest
correlation value among the first plurality of correlation values.
The second synchronization signal may have a highest correlation
value among the second plurality of correlation values. The
plurality of synchronization signals may be transmitted over
seventy-two OFDM subcarriers substantially in the center of the
carrier. The plurality of synchronization signals may determine a
physical identifier of a carrier on which the plurality of
synchronization signals are transmitted. The scaling factor may be
a function of characteristics of a wireless channel over which the
plurality of synchronization signals are transmitted.
[0080] A similar procedure may be performed to remove CRS
interference. The CRS tones may also interfere with data tones
since interference between CRS tones between high- and low-power
nodes may be avoided by CRS tone shifting. If strong CRS
interference is detected, and after the channel gain toward the
interfering cell is estimated, the CRS signal may be cancelled. The
procedure may be repeated until most of the interfering signals are
subtracted. However, the problem of reliable channel quality
information (CQI) feedback for data transmission may remain,
depending on whether CRS tones interfere with data tones or not,
and whether the interfering base station transmits or does not
transmit data on the corresponding subframe (e.g., whether the
corresponding subframe is an almost blank subframe for the
interfering base station or not). Based on these alternatives, at
least four different cases may be considered for CQI
computation:
[0081] 1. CRS tones of the interfering base station may overlap
with the CRS tones of the interfered base station, and the
interfering base station transmits data on the corresponding
subframe. In this case, there may be no need for post processing of
the interference values estimated on the CRS tones. The
interference seen on the data tones may most likely be similar to
the interference seen on the CRS tones. The wireless device may use
the interference estimate obtained from the CRS tones directly with
the channel estimates obtained for the serving base station from
the CRS tones to compute the CQI value and may feed it back to its
serving base station.
[0082] 2. CRS tones of the interfering base station may overlap
with CRS tones of the interfered base station, but the interfering
base station may not transmit data on the corresponding subframe
(e.g., the corresponding subframe is an almost blank subframe of
the interfering base station). In this case, the interference
estimated on the CRS tones may include interference from the
interfering base station, but this interference may not be present
on the data tones. So the interference value may be overestimated.
The wireless device may separately estimate the interference
contribution of the interfering base station, and may subtract it
from the total interference measured on the CRS tones to obtain a
more accurate estimate of the interference observed on the data
tones. This more accurate interference estimate may be used along
with the channel estimate of the serving base station obtained from
the CRS tones to compute the CQI value.
[0083] 3. CRS tones of the interfering base station may not overlap
with CRS tones of the interfered base station, and the interfering
base station transmits data on the corresponding subframe. In this
case, depending on the signals transmitted by the interfering base
station on the CRS tones of the interfered base station, there may
be at least two options. If the interfering base station punctures
these tones and does not transmit a signal on these tones (to allow
for more accurate channel estimation at the interfered base
station), then the interference value estimated on the CRS tones
may be an underestimate and may need to be adjusted before using
the interference value estimate in a CQI computation. This
adjustment may involve separate estimation of the potential
interference from the interfering base station and adding the
separate estimation to the total interference estimated on the CRS
tones of the interfered base station. If on the other hand, the
interfering base station transmits data on the CRS tones of the
interfered base station, then the interference estimate on the CRS
tones of the interfered base station may be accurate and there may
be no need for further adjustment for the CQI computation.
[0084] 4. CRS tones of the interfering base station may not overlap
with CRS tones of the interfered base station, and the interfering
base station may not transmit data on the corresponding subframe.
In this case, there may be no underestimation or overestimation of
the interference on the CRS tones of the interfered base station.
Therefore, there may be no need for further adjustment for the CQI
computation.
[0085] FIG. 14 is a flow chart illustrating an example processing
of reference signals as per an aspect of an embodiment of the
present invention. A wireless device may receive a first reference
signal from a first base station in the plurality of base stations
on a first plurality of OFDM resources in a first subframe in the
plurality of subframes as shown in 1402. The first plurality of
OFDM resources may depend, at least in part, on a first base
station identifier of the first base station. The wireless device
may estimate a first signal strength corresponding to the first
base station based on the received first reference signal as shown
in 1404.
[0086] The wireless device may receive a second reference signal
from a second base station, on a second plurality of OFDM resources
in the first subframe as shown in 1406. The second plurality of
OFDM resources may depend, at least in part, on a second base
station identifier of the second base station. The wireless device
may estimate a second signal strength corresponding to the second
base station based on the received second reference signal as shown
in 1408. The wireless device may estimate an interference value on
the second plurality of OFDM resources based, at least in part, on
the second reference signal as shown in 1410. The wireless device
may calculate a signal to interference ratio value based on the
second signal strength and a total interference value as shown in
1412. If the first plurality of OFDM resources overlap with the
second plurality of OFDM resources, the total interference value
may be computed based upon the interference value. If the first
plurality of OFDM resources do not overlap with the second
plurality of OFDM resources, the total interference value may be
computed based upon the interference value plus the first signal
strength.
[0087] According to some of the various aspects of embodiments, the
wireless device may receive a first reference signal from a first
base station in the plurality of base stations on a first plurality
of OFDM resources in a first subframe in the plurality of
subframes. The first plurality of OFDM resources may depend, at
least in part, on a first base station identifier of the first base
station. The wireless device may estimate a first signal strength
corresponding to the first base station based on the received first
reference signal. The wireless device may receive a second
reference signal from a second base station in the plurality of
base stations, on a second plurality of OFDM resources in the first
subframe. The second plurality of OFDM resources depend, at least
in part, on a second base station identifier of the second base
station. The wireless device may estimate a second signal strength
corresponding to the second base station based on the received
second reference signal.
[0088] The wireless device may estimate an interference value on
the second plurality of OFDM resources based, at least in part, on
the second reference signal. The wireless device may estimate a
signal to interference ratio value based on the second signal
strength and a total interference value. If the first plurality of
OFDM resources do not overlap with the second plurality of OFDM
resources, the total interference value may be computed based upon
the interference value. If the first plurality of OFDM resources
overlap with the second plurality of OFDM resources, the total
interference value may be computed based upon the interference
value minus the first signal strength.
[0089] According to some of the various aspects of embodiments, the
first base station may transmit data to a plurality of wireless
devices on the first subframe. The first base station may not
transmit data on the first subframe. The first base station may
transmit radio signals at a substantially higher power than the
second base station. The second base station may transmit radio
signals at a substantially higher power than the first base
station. The first base station may be a macro base station. The
first base station may be a pico base station. The first base
station may be a femto base station with open access. The first
base station may be a femto base station with close subscriber
group access. The second base station may be a macro base station.
The second base station may be a pico base station. The second base
station may be a femto base station with open access. The second
base station may be a femto base station with close subscriber
group access.
[0090] The first reference signal may be a common reference signal.
The second reference signal may be a common reference signal. The
first reference signal may be a channel state information reference
signal. The second reference signal may be a channel state
information reference signal. The first signal strength may be a
short term signal strength value obtained from the most recent
observation. The first signal strength may be a long term signal
strength value obtained from averaging a plurality of recent
observations. The second signal strength may be a short term signal
strength value obtained from the most recent observation. The
second signal strength may be a long term signal strength value
obtained from averaging a plurality of recent observations. The
interference value may be a short term interference value obtained
from the most recent observation. The interference value may be a
long term interference value obtained from averaging a plurality of
recent observations.
[0091] The control format indicator channel may be transmitted at
the same location in cells, which means that the control format
indicator channel's interference may comprise the control format
indicator channel from the neighboring interfering cells. This
structure may lend itself to a design of an interference canceller.
A wireless device receiver may first decode one of the strongest
signals, may perform channel gain estimation toward the interfering
cell, may cancel the interfering signal, and may continue the
procedure until control format indicator channel of the serving
cell is decoded.
[0092] The same or similar approaches may not be appropriate for
other control channels, (e.g., control channels carrying scheduling
information). The reason may be that such control channels may be
scrambled with the identity of a target wireless device, and in
order for a wireless device to cancel the interference of such
channels, the wireless device may need to try a very large number
of hypotheses considering the information being transmitted to
potential wireless identifiers in the neighboring cell. This may
require a large amount of computational complexity, and may not be
practical.
[0093] The control region of most packet switched technologies may
be a shared region in the sense that control information for many
different wireless devices may be transmitted on the same
resources. This may reduce the amount of overhead for such systems,
especially with dynamic scheduling of the wireless devices, in
which, in a given subframe, a small number of active wireless
devices may be scheduled. Each wireless device may monitor a
portion or the entire control region for potential control channel
transmissions targeting that particular wireless device. On the
other hand, many technologies may use a mechanism such as a hashing
mechanism to limit the number of the decode hypotheses of the
wireless devices. As a very simple example, it may be specified
that wireless devices with the wireless device identifier from the
first half of the entire wireless device identifiers space may
expect control information on the first half of the resources of
entire the control region, and wireless devices with the wireless
device identifier from the second half of the entire wireless
device identifiers space may expect control information on the
second half of the resources of entire the control region. With
this rule, the number of decode hypotheses of any wireless device
in the system may be reduced by half. Practical systems and
technologies may use more sophisticated hashing mechanisms to
further reduce the number of decode hypotheses of the wireless
devices.
[0094] Following the example given above, an alternate method of
mitigating control channel information which is based on base
station coordination and may not require wireless device
involvement or may reduce wireless device involvement may be
considered. In this alternate method, base stations that are
potential interferers to each other may decide to coordinate the
wireless device identifiers that they assigned to their served
wireless devices such that the corresponding control transmissions
of the two base stations may not overlap in time frequency
resources or may have a reduced overlap in time frequency
resources. For the simple example provided above, it may be
necessary for the two base stations to agree that one of them uses
the first half of the wireless identifiers space and the other base
station uses the second half of the wireless identifiers space.
With this agreement, the control transmissions of the first base
station may take place on the first half of the resources of the
control region and the control transmissions of the second base
station may take place on the second half of the resources of the
control region. This may avoid or reduce overlap and thus reduce
interference between each of the base stations.
[0095] Practical systems may use more sophisticated hashing
algorithms for the mapping between wireless device identifiers and
control region resources. Nevertheless, wireless device identifier
partitioning algorithms similar to the scheme described above may
be devised so that wireless device identifier space may be
partitioned such that the amount of interfering control resources
between base stations may be reduced.
[0096] FIG. 15 is a flow chart illustrating transmission of control
messages as per an aspect of an embodiment of the present
invention. A first base station may be configured with a first
plurality of wireless device identifiers. A second base station may
be configured with a second plurality of wireless device
identifiers. For example, a first plurality of wireless device
identifiers may be selected and then assigned to a first base
station, and a second plurality of wireless device identifiers may
be selected and then assigned to a second base station. In an
example implementation, the selection and/or assignment of wireless
device identifiers to the base stations may be done by a network
administrator, network management system, and/or the like. The list
of selected wireless device identifiers may be communicated to the
base station via a management interface. A base station assigns a
wireless device identifier from the pool of wireless device
identifiers configured in that base station to wireless device
identifiers connected to the base station.
[0097] A first base station may assign a first plurality of
wireless device identifiers to a first plurality of wireless
devices in connected mode as shown in 1502. The first base station
may transmit a plurality of first unicast and/or broadcast control
messages to a first subset of the first plurality of wireless
devices employing a first plurality of OFDM resources in a first
subframe of the first base station as shown in 1504. The first
plurality of OFDM resources may depend, at least in part, on
wireless device identifiers of the first subset of the first
plurality of wireless devices.
[0098] A second base station may assign a second plurality of
wireless device identifiers to a second plurality of wireless
devices in connected mode as shown in 1506. The second base station
may transmit a second plurality of unicast and/or broadcast control
messages to a second subset of the second plurality of wireless
devices employing a second plurality of OFDM resources in a second
subframe of the second base station as shown in 1508. The second
subframe being transmitted substantially simultaneously with the
first subframe. The base stations frame and subframe transmission
may be synchronized by GPS, packet based synchronization
mechanisms, and/or the like. Synchronization errors may be
inevitable due to inaccuracy in the synchronization techniques used
to achieve synchronization among base stations. Synchronization
errors may be below a small fraction of subframe duration. The
second plurality of OFDM resources may depend, at least in part, on
wireless device identifiers of the second subset of the second
plurality of wireless devices. The first plurality of wireless
device identifiers and the second plurality of wireless device
identifiers may be configured to maintain overlap between the first
plurality of OFDM resources and the second plurality of OFDM
resources is at or below a pre-determined threshold as shown in
1510. In an example embodiment, average overlap over a plurality of
subframes may be at or below a threshold. In another example
embodiment for most (for example above a pre-determined percentage)
of subframes, the overlap may be at or below a threshold. In an
example embodiment, overall overlap between OFDM resources of the
control regions of the base stations may be reduced to reduce
interference in the control region. For example, the reduction in
overlap could be on each individual frame, or could be a
statistical reduction of overlap over a plurality of frames. Other
embodiments to reduce overall overlap may be implemented.
[0099] The first base station may be of a different base station
type than the second base station. The pre-determined threshold is
zero or larger. In some example embodiments, the pre-determined
threshold could be one of the following: below ten percent of the
smaller of the first plurality of OFDM resources and the second
plurality of OFDM resources, below twenty percent of the smaller of
the first plurality of OFDM resources and the second plurality of
OFDM resources, or below fifty percent of the smaller of the first
plurality of OFDM resources and the second plurality of OFDM
resources. In other words, the pre-determined threshold may be
between ten to fifty percent of the smaller of said first plurality
of OFDM resources and said second plurality of OFDM resources.
However, those skilled in the art will recognize that other
threshold values may be employed accordingly depending upon the
constraints of any particular embodiment.
[0100] At least one unicast message in the first plurality of
unicast control messages and the second plurality of unicast
control messages may comprise at least one of the following: a
resource identifier, a modulation and coding format indicator, a
HARQ process identifier, a redundancy version, a transmission mode
indicator, and an uplink power control indicator. The transmission
mode indicator may be employed, by a wireless device, to determine
a transmission mode from a plurality of transmission modes. The
plurality of transmission modes may be one of: a transmit diversity
mode, a cyclic delay diversity mode, a spatial multiplexing mode, a
beamforming mode, and a precoding mode. The uplink power control
command may be an absolute power control command and a relative
power control command. The uplink power control indicator may be a
single power control command for a single wireless device. The
uplink power control indicator may comprise a plurality of power
control commands for a plurality of wireless devices. At least one
power control command in the plurality of power control commands
may be an absolute power control command or a relative power
control command.
[0101] According to some of the various aspects of embodiments, the
packets in the downlink may be transmitted via downlink physical
channels. The carrying packets in the uplink may be transmitted via
uplink physical channels. The baseband data representing a downlink
physical channel may be defined in terms of at least one of the
following actions: scrambling of coded bits in codewords to be
transmitted on a physical channel; modulation of scrambled bits to
generate complex-valued modulation symbols; mapping of the
complex-valued modulation symbols onto one or several transmission
layers; precoding of the complex-valued modulation symbols on
layer(s) for transmission on the antenna port(s); mapping of
complex-valued modulation symbols for antenna port(s) to resource
elements; and/or generation of complex-valued time-domain OFDM
signal(s) for antenna port(s).
[0102] Codeword, transmitted on the physical channel in one
subframe, may be scrambled prior to modulation, resulting in a
block of scrambled bits. The scrambling sequence generator may be
initialized at the start of subframe(s). Codeword(s) may be
modulated using QPSK, 16QAM, 64QAM, 128QAM, and/or the like
resulting in a block of complex-valued modulation symbols. The
complex-valued modulation symbols for codewords to be transmitted
may be mapped onto one or several layers. For transmission on a
single antenna port, a single layer may be used. For spatial
multiplexing, the number of layers may be less than or equal to the
number of antenna port(s) used for transmission of the physical
channel. The case of a single codeword mapped to multiple layers
may be applicable when the number of cell-specific reference
signals is four or when the number of UE-specific reference signals
is two or larger. For transmit diversity, there may be one codeword
and the number of layers may be equal to the number of antenna
port(s) used for transmission of the physical channel.
[0103] The precoder may receive a block of vectors from the layer
mapping and generate a block of vectors to be mapped onto resources
on the antenna port(s). Precoding for spatial multiplexing using
antenna port(s) with cell-specific reference signals may be used in
combination with layer mapping for spatial multiplexing. Spatial
multiplexing may support two or four antenna ports and the set of
antenna ports used may be {0, 1} or {0, 1, 2, 3}. Precoding for
transmit diversity may be used in combination with layer mapping
for transmit diversity. The precoding operation for transmit
diversity may be defined for two and four antenna ports. Precoding
for spatial multiplexing using antenna ports with UE-specific
reference signals may also, for example, be used in combination
with layer mapping for spatial multiplexing. Spatial multiplexing
using antenna ports with UE-specific reference signals may support
up to eight antenna ports. Reference signals may be pre-defined
signals that may be used by the receiver for decoding the received
physical signal, estimating the channel state, and/or other
purposes.
[0104] For antenna port(s) used for transmission of the physical
channel, the block of complex-valued symbols may be mapped in
sequence to resource elements. In resource blocks in which
UE-specific reference signals are not transmitted the PDSCH may be
transmitted on the same set of antenna ports as the physical
broadcast channel in the downlink (PBCH). In resource blocks in
which UE-specific reference signals are transmitted, the PDSCH may
be transmitted, for example, on antenna port(s) {5, {7}, {8}, or
{7, 8, . . . , v+6}, where v is the number of layers used for
transmission of the PDSCH.
[0105] Common reference signal(s) may be transmitted in physical
antenna port(s). Common reference signal(s) may be cell-specific
reference signal(s) (RS) used for demodulation and/or measurement
purposes. Channel estimation accuracy using common reference
signal(s) may be reasonable for demodulation (high RS density).
Common reference signal(s) may be defined for LTE technologies,
LTE-advanced technologies, and/or the like. Demodulation reference
signal(s) may be transmitted in virtual antenna port(s) (i.e.,
layer or stream). Channel estimation accuracy using demodulation
reference signal(s) may be reasonable within allocated
time/frequency resources. Demodulation reference signal(s) may be
defined for LTE-advanced technology and may not be applicable to
LTE technology. Measurement reference signal(s), may also called
CSI (channel state information) reference signal(s), may be
transmitted in physical antenna port(s) or virtualized antenna
port(s). Measurement reference signal(s) may be Cell-specific RS
used for measurement purposes. Channel estimation accuracy may be
relatively lower than demodulation RS. CSI reference signal(s) may
be defined for LTE-advanced technology and may not be applicable to
LTE technology.
[0106] In at least one of the various embodiments, uplink physical
channel(s) may correspond to a set of resource elements carrying
information originating from higher layers. The following example
uplink physical channel(s) may be defined for uplink: a) Physical
Uplink Shared Channel (PUSCH), b) Physical Uplink Control Channel
(PUCCH), c) Physical Random Access Channel (PRACH), and/or the
like. Uplink physical signal(s) may be used by the physical layer
and may not carry information originating from higher layers. For
example, reference signal(s) may be considered as uplink physical
signal(s). Transmitted signal(s) in slot(s) may be described by one
or several resource grids including, for example, subcarriers and
SC-FDMA or OFDMA symbols. Antenna port(s) may be defined such that
the channel over which symbol(s) on antenna port(s) may be conveyed
and/or inferred from the channel over which other symbol(s) on the
same antenna port(s) is/are conveyed. There may be one resource
grid per antenna port. The antenna port(s) used for transmission of
physical channel(s) or signal(s) may depend on the number of
antenna port(s) configured for the physical channel(s) or
signal(s).
[0107] Element(s) in a resource grid may be called a resource
element. A physical resource block may be defined as N consecutive
SC-FDMA symbols in the time domain and/or M consecutive subcarriers
in the frequency domain, wherein M and N may be pre-defined integer
values. Physical resource block(s) in uplink(s) may comprise of
M.times.N resource elements. For example, a physical resource block
may correspond to one slot in the time domain and 180 kHz in the
frequency domain. Baseband signal(s) representing the physical
uplink shared channel may be defined in terms of: a) scrambling, b)
modulation of scrambled bits to generate complex-valued symbols, c)
mapping of complex-valued modulation symbols onto one or several
transmission layers, d) transform precoding to generate
complex-valued symbols, e) precoding of complex-valued symbols, f)
mapping of precoded complex-valued symbols to resource elements, g)
generation of complex-valued time-domain SC-FDMA signal(s) for
antenna port(s), and/or the like.
[0108] For codeword(s), block(s) of bits may be scrambled with
UE-specific scrambling sequence(s) prior to modulation, resulting
in block(s) of scrambled bits. Complex-valued modulation symbols
for codeword(s) to be transmitted may be mapped onto one, two, or
more layers. For spatial multiplexing, layer mapping(s) may be
performed according to pre-defined formula (s). The number of
layers may be less than or equal to the number of antenna port(s)
used for transmission of physical uplink shared channel(s). The
example of a single codeword mapped to multiple layers may be
applicable when the number of antenna port(s) used for PUSCH is,
for example, four. For layer(s), the block of complex-valued
symbols may be divided into multiple sets, each corresponding to
one SC-FDMA symbol. Transform precoding may be applied. For antenna
port(s) used for transmission of the PUSCH in a subframe, block(s)
of complex-valued symbols may be multiplied with an amplitude
scaling factor in order to conform to a required transmit power,
and mapped in sequence to physical resource block(s) on antenna
port(s) and assigned for transmission of PUSCH.
[0109] According to some of the various embodiments, data may
arrive to the coding unit in the form of two transport blocks every
transmission time interval (TTI) per UL cell. The following coding
actions may be identified for transport block(s) of an uplink
carrier: a) Add CRC to the transport block, b) Code block
segmentation and code block CRC attachment, c) Channel coding of
data and control information, d) Rate matching, e) Code block
concatenation. f) Multiplexing of data and control information, g)
Channel interleaver, h) Error detection may be provided on UL-SCH
(uplink shared channel) transport block(s) through a Cyclic
Redundancy Check (CRC), and/or the like. Transport block(s) may be
used to calculate CRC parity bits. Code block(s) may be delivered
to channel coding block(s). Code block(s) may be individually turbo
encoded. Turbo coded block(s) may be delivered to rate matching
block(s).
[0110] Physical uplink control channel(s) (PUCCH) may carry uplink
control information. Simultaneous transmission of PUCCH and PUSCH
from the same UE may be supported if enabled by higher layers. For
a type 2 frame structure, the PUCCH may not be transmitted in the
UpPTS field. PUCCH may use one resource block in each of the two
slots in a subframe. Resources allocated to UE and PUCCH
configuration(s) may be transmitted via control messages. PUCCH may
comprise: a) positive and negative acknowledgements for data
packets transmitted at least one downlink carrier, b) channel state
information for at least one downlink carrier, c) scheduling
request, and/or the like.
[0111] According to some of the various aspects of embodiments,
cell search may be the procedure by which a wireless device may
acquire time and frequency synchronization with a cell and may
detect the physical layer Cell ID of that cell (transmitter). An
example embodiment for synchronization signal and cell search is
presented below. A cell search may support a scalable overall
transmission bandwidth corresponding to 6 resource blocks and
upwards. Primary and secondary synchronization signals may be
transmitted in the downlink and may facilitate cell search. For
example, 504 unique physical-layer cell identities may be defined
using synchronization signals. The physical-layer cell identities
may be grouped into 168 unique physical-layer cell-identity groups,
group(s) containing three unique identities. The grouping may be
such that physical-layer cell identit(ies) is part of a
physical-layer cell-identity group. A physical-layer cell identity
may be defined by a number in the range of 0 to 167, representing
the physical-layer cell-identity group, and a number in the range
of 0 to 2, representing the physical-layer identity within the
physical-layer cell-identity group. The synchronization signal may
include a primary synchronization signal and a secondary
synchronization signal.
[0112] According to some of the various aspects of embodiments, the
sequence used for a primary synchronization signal may be generated
from a frequency-domain Zadoff-Chu sequence according to a
pre-defined formula. A Zadoff-Chu root sequence index may also be
predefined in a specification. The mapping of the sequence to
resource elements may depend on a frame structure. The wireless
device may not assume that the primary synchronization signal is
transmitted on the same antenna port as any of the downlink
reference signals. The wireless device may not assume that any
transmission instance of the primary synchronization signal is
transmitted on the same antenna port, or ports, used for any other
transmission instance of the primary synchronization signal. The
sequence may be mapped to the resource elements according to a
predefined formula.
[0113] For FDD frame structure, a primary synchronization signal
may be mapped to the last OFDM symbol in slots 0 and 10. For TDD
frame structure, the primary synchronization signal may be mapped
to the third OFDM symbol in subframes 1 and 6. Some of the resource
elements allocated to primary or secondary synchronization signals
may be reserved and not used for transmission of the primary
synchronization signal.
[0114] According to some of the various aspects of embodiments, the
sequence used for a secondary synchronization signal may be an
interleaved concatenation of two length-31 binary sequences. The
concatenated sequence may be scrambled with a scrambling sequence
given by a primary synchronization signal. The combination of two
length-31 sequences defining the secondary synchronization signal
may differ between subframe 0 and subframe 5 according to
predefined formula (s). The mapping of the sequence to resource
elements may depend on the frame structure. In a subframe for FDD
frame structure and in a half-frame for TDD frame structure, the
same antenna port as for the primary synchronization signal may be
used for the secondary synchronization signal. The sequence may be
mapped to resource elements according to a predefined formula.
[0115] Example embodiments for the physical channels configuration
will now be presented. Other examples may also be possible. A
physical broadcast channel may be scrambled with a cell-specific
sequence prior to modulation, resulting in a block of scrambled
bits. PBCH may be modulated using QPSK, and/or the like. The block
of complex-valued symbols for antenna port(s) may be transmitted
during consecutive radio frames, for example, four consecutive
radio frames. In some embodiments the PBCH data may arrive to the
coding unit in the form of a one transport block every transmission
time interval (TTI) of 40 ms. The following coding actions may be
identified. Add CRC to the transport block, channel coding, and
rate matching. Error detection may be provided on PBCH transport
blocks through a Cyclic Redundancy Check (CRC). The transport block
may be used to calculate the CRC parity bits. The parity bits may
be computed and attached to the BCH (broadcast channel) transport
block. After the attachment, the CRC bits may be scrambled
according to the transmitter transmit antenna configuration.
Information bits may be delivered to the channel coding block and
they may be tail biting convolutionally encoded. A tail biting
convolutionally coded block may be delivered to the rate matching
block. The coded block may be rate matched before transmission.
[0116] A master information block may be transmitted in PBCH and
may include system information transmitted on broadcast channel(s).
The master information block may include downlink bandwidth, system
frame number(s), and PHICH (physical hybrid-ARQ indicator channel)
configuration. Downlink bandwidth may be the transmission bandwidth
configuration, in terms of resource blocks in a downlink, for
example 6 may correspond to 6 resource blocks, 15 may correspond to
15 resource blocks and so on. System frame number(s) may define the
N (for example N=8) most significant bits of the system frame
number. The M (for example M=2) least significant bits of the SFN
may be acquired implicitly in the PBCH decoding. For example,
timing of a 40 ms PBCH TTI may indicate 2 least significant bits
(within 40 ms PBCH TTI, the first radio frame: 00, the second radio
frame: 01, the third radio frame: 10, the last radio frame: 11).
One value may apply for other carriers in the same sector of a base
station (the associated functionality is common (e.g. not performed
independently for each cell). PHICH configuration(s) may include
PHICH duration, which may be normal (e.g. one symbol duration) or
extended (e.g. 3 symbol duration).
[0117] Physical control format indicator channel(s) (PCFICH) may
carry information about the number of OFDM symbols used for
transmission of PDCCHs (physical downlink control channel) in a
subframe. The set of OFDM symbols possible to use for PDCCH in a
subframe may depend on many parameters including, for example,
downlink carrier bandwidth, in terms of downlink resource blocks.
PCFICH transmitted in one subframe may be scrambled with
cell-specific sequence(s) prior to modulation, resulting in a block
of scrambled bits. A scrambling sequence generator(s) may be
initialized at the start of subframe(s). Block (s) of scrambled
bits may be modulated using QPSK. Block(s) of modulation symbols
may be mapped to at least one layer and precoded resulting in a
block of vectors representing the signal for at least one antenna
port. Instances of PCFICH control channel(s) may indicate one of
several (e.g. 3) possible values after being decoded. The range of
possible values of instance(s) of the first control channel may
depend on the first carrier bandwidth.
[0118] According to some of the various embodiments, physical
downlink control channel(s) may carry scheduling assignments and
other control information. The number of resource-elements not
assigned to PCFICH or PHICH may be assigned to PDCCH. PDCCH may
support multiple formats. Multiple PDCCH packets may be transmitted
in a subframe. PDCCH may be coded by tail biting convolutionally
encoder before transmission. PDCCH bits may be scrambled with a
cell-specific sequence prior to modulation, resulting in block(s)
of scrambled bits. Scrambling sequence generator(s) may be
initialized at the start of subframe(s). Block(s) of scrambled bits
may be modulated using QPSK. Block(s) of modulation symbols may be
mapped to at least one layer and precoded resulting in a block of
vectors representing the signal for at least one antenna port.
PDCCH may be transmitted on the same set of antenna ports as the
PBCH, wherein PBCH is a physical broadcast channel broadcasting at
least one basic system information field.
[0119] According to some of the various embodiments, scheduling
control packet(s) may be transmitted for packet(s) or group(s) of
packets transmitted in downlink shared channel(s). Scheduling
control packet(s) may include information about subcarriers used
for packet transmission(s). PDCCH may also provide power control
commands for uplink channels. OFDM subcarriers that are allocated
for transmission of PDCCH may occupy the bandwidth of downlink
carrier(s). PDCCH channel(s) may carry a plurality of downlink
control packets in subframe(s). PDCCH may be transmitted on
downlink carrier(s) starting from the first OFDM symbol of
subframe(s), and may occupy up to multiple symbol duration(s) (e.g.
3 or 4).
[0120] According to some of the various embodiments, PHICH may
carry the hybrid-ARQ (automatic repeat request) ACK/NACK. Multiple
PHICHs mapped to the same set of resource elements may constitute a
PHICH group, where PHICHs within the same PHICH group may be
separated through different orthogonal sequences. PHICH resource(s)
may be identified by the index pair (group, sequence), where
group(s) may be the PHICH group number(s) and sequence(s) may be
the orthogonal sequence index within the group(s). For frame
structure type 1, the number of PHICH groups may depend on
parameters from higher layers (RRC). For frame structure type 2,
the number of PHICH groups may vary between downlink subframes
according to a pre-defined arrangement. Block(s) of bits
transmitted on one PHICH in one subframe may be modulated using
BPSK or QPSK, resulting in a block(s) of complex-valued modulation
symbols. Block(s) of modulation symbols may be symbol-wise
multiplied with an orthogonal sequence and scrambled, resulting in
a sequence of modulation symbols
[0121] Other arrangements for PCFICH, PHICH, PDCCH, and/or PDSCH
may be supported. The configurations presented here are for example
purposes. In another example, resources PCFICH, PHICH, and/or PDCCH
radio resources may be transmitted in radio resources including a
subset of subcarriers and pre-defined time duration in each or some
of the subframes. In an example, PUSCH resource(s) may start from
the first symbol. In another example embodiment, radio resource
configuration(s) for PUSCH, PUCCH, and/or PRACH (physical random
access channel) may use a different configuration. For example,
channels may be time multiplexed, or time/frequency multiplexed
when mapped to uplink radio resources.
[0122] According to some of the various aspects of embodiments,
control message(s) or control packet(s) may be scheduled for
transmission in a physical downlink shared channel (PDSCH) and/or
physical uplink shared channel PUSCH. PDSCH and PUSCH may carry
control and data message(s)/packet(s). Control message(s) and/or
packet(s) may be processed before transmission. For example, the
control message(s) and/or packet(s) may be fragmented or
multiplexed before transmission. A control message in an upper
layer may be processed as a data packet in the MAC or physical
layer. For example, system information block(s) as well as data
traffic may be scheduled for transmission in PDSCH. Data packet(s)
may be encrypted packets.
[0123] According to some of the various aspects of embodiments,
data packet(s) may be encrypted before transmission to secure
packet(s) from unwanted receiver(s). Desired recipient(s) may be
able to decrypt the packet(s). A first plurality of data packet(s)
and/or a second plurality of data packet(s) may be encrypted using
an encryption key and at least one parameter that may change
substantially rapidly over time. The encryption mechanism may
provide a transmission that may not be easily eavesdropped by
unwanted receivers. The encryption mechanism may include additional
parameter(s) in an encryption module that changes substantially
rapidly in time to enhance the security mechanism. Example varying
parameter(s) may comprise various types of system counter(s), such
as system frame number. Substantially rapidly may for example imply
changing on a per subframe, frame, or group of subframes basis.
Encryption may be provided by a PDCP layer between the transmitter
and receiver, and/or may be provided by the application layer.
Additional overhead added to packet(s) by lower layers such as RLC,
MAC, and/or Physical layer may not be encrypted before
transmission. In the receiver, the plurality of encrypted data
packet(s) may be decrypted using a first decryption key and at
least one first parameter. The plurality of data packet(s) may be
decrypted using an additional parameter that changes substantially
rapidly over time.
[0124] According to some of the various aspects of embodiments, a
wireless device may be preconfigured with one or more carriers.
When the wireless device is configured with more than one carrier,
the base station and/or wireless device may activate and/or
deactivate the configured carriers. One of the carriers (the
primary carrier) may always be activated. Other carriers may be
deactivated by default and/or may be activated by a base station
when needed. A base station may activate and deactivate carriers by
sending an activation/deactivation MAC control element.
Furthermore, the UE may maintain a carrier deactivation timer per
configured carrier and deactivate the associated carrier upon its
expiry. The same initial timer value may apply to instance(s) of
the carrier deactivation timer. The initial value of the timer may
be configured by a network. The configured carriers (unless the
primary carrier) may be initially deactivated upon addition and
after a handover.
[0125] According to some of the various aspects of embodiments, if
a wireless device receives an activation/deactivation MAC control
element activating the carrier, the wireless device may activate
the carrier, and/or may apply normal carrier operation including:
sounding reference signal transmissions on the carrier, CQI
(channel quality indicator)/PMI(precoding matrix
indicator)/RI(ranking indicator) reporting for the carrier, PDCCH
monitoring on the carrier, PDCCH monitoring for the carrier, start
or restart the carrier deactivation timer associated with the
carrier, and/or the like. If the device receives an
activation/deactivation MAC control element deactivating the
carrier, and/or if the carrier deactivation timer associated with
the activated carrier expires, the base station or device may
deactivate the carrier, and may stop the carrier deactivation timer
associated with the carrier, and/or may flush HARQ buffers
associated with the carrier.
[0126] If PDCCH on a carrier scheduling the activated carrier
indicates an uplink grant or a downlink assignment for the
activated carrier, the device may restart the carrier deactivation
timer associated with the carrier. When a carrier is deactivated,
the wireless device may not transmit SRS (sounding reference
signal) for the carrier, may not report CQI/PMI/RI for the carrier,
may not transmit on UL-SCH for the carrier, may not monitor the
PDCCH on the carrier, and/or may not monitor the PDCCH for the
carrier.
[0127] A process to assign subcarriers to data packets may be
executed by a MAC layer scheduler. The decision on assigning
subcarriers to a packet may be made based on data packet size,
resources required for transmission of data packets (number of
radio resource blocks), modulation and coding assigned to data
packet(s), QoS required by the data packets (i.e. QoS parameters
assigned to data packet bearer), the service class of a subscriber
receiving the data packet, or subscriber device capability, a
combination of the above, and/or the like.
[0128] According to some of the various aspects of embodiments,
packets may be referred to service data units and/or protocols data
units at Layer 1, Layer 2 and/or Layer 3 of the communications
network. Layer 2 in an LTE network may include three sub-layers:
PDCP sub-layer, RLC sub-layer, and MAC sub-layer. A layer 2 packet
may be a PDCP packet, an RLC packet or a MAC layer packet. Layer 3
in an LTE network may be Internet Protocol (IP) layer, and a layer
3 packet may be an IP data packet. Packets may be transmitted and
received via an air interface physical layer. A packet at the
physical layer may be called a transport block. Many of the various
embodiments may be implemented at one or many different
communication network layers. For example, some of the actions may
be executed by the PDCP layer and some others by the MAC layer.
[0129] According to some of the various aspects of embodiments,
subcarriers and/or resource blocks may comprise a plurality of
physical subcarriers and/or resource blocks. In another example
embodiment, subcarriers may be a plurality of virtual and/or
logical subcarriers and/or resource blocks.
[0130] According to some of the various aspects of embodiments, a
radio bearer may be a GBR (guaranteed bit rate) bearer and/or a
non-GBR bearer. A GBR and/or guaranteed bit rate bearer may be
employed for transfer of real-time packets, and/or a non-GBR bearer
may be used for transfer of non-real-time packets. The non-GBR
bearer may be assigned a plurality of attributes including: a
scheduling priority, an allocation and retention priority, a
portable device aggregate maximum bit rate, and/or the like. These
parameters may be used by the scheduler in scheduling non-GBR
packets. GBR bearers may be assigned attributes such as delay,
jitter, packet loss parameters, and/or the like.
[0131] According to some of the various aspects of embodiments,
subcarriers may include data subcarrier symbols and pilot
subcarrier symbols. Pilot symbols may not carry user data, and may
be included in the transmission to help the receiver to perform
synchronization, channel estimation and/or signal quality
detection. Base stations and wireless devices (wireless receiver)
may use different methods to generate and transmit pilot symbols
along with information symbols.
[0132] According to some of the various aspects of embodiments, the
transmitter in the disclosed embodiments of the present invention
may be a wireless device (also called user equipment), a base
station (also called eNodeB), a relay node transmitter, and/or the
like. The receiver in the disclosed embodiments of the present
invention may be a wireless device (also called user equipment-UE),
a base station (also called eNodeB), a relay node receiver, and/or
the like. According to some of the various aspects of embodiments
of the present invention, layer 1 (physical layer) may be based on
OFDMA or SC-FDMA. Time may be divided into frame(s) with fixed
duration. Frame(s) may be divided into substantially equally sized
subframes, and subframe(s) may be divided into substantially
equally sized slot(s). A plurality of OFDM or SC-FDMA symbol(s) may
be transmitted in slot(s). OFDMA or SC-FDMA symbol(s) may be
grouped into resource block(s). A scheduler may assign resource(s)
in resource block unit(s), and/or a group of resource block
unit(s). Physical resource block(s) may be resources in the
physical layer, and logical resource block(s) may be resource
block(s) used by the MAC layer. Similar to virtual and physical
subcarriers, resource block(s) may be mapped from logical to
physical resource block(s). Logical resource block(s) may be
contiguous, but corresponding physical resource block(s) may be
non-contiguous. Some of the various embodiments of the present
invention may be implemented at the physical or logical resource
block level(s).
[0133] According to some of the various aspects of embodiments,
layer 2 transmission may include PDCP (packet data convergence
protocol), RLC (radio link control), MAC (media access control)
sub-layers, and/or the like. MAC may be responsible for the
multiplexing and mapping of logical channels to transport channels
and vice versa. A MAC layer may perform channel mapping,
scheduling, random access channel procedures, uplink timing
maintenance, and/or the like.
[0134] According to some of the various aspects of embodiments, the
MAC layer may map logical channel(s) carrying RLC PDUs (packet data
unit) to transport channel(s). For transmission, multiple SDUs
(service data unit) from logical channel(s) may be mapped to the
Transport Block (TB) to be sent over transport channel(s). For
reception, TBs from transport channel(s) may be demultiplexed and
assigned to corresponding logical channel(s). The MAC layer may
perform scheduling related function(s) in both the uplink and
downlink and thus may be responsible for transport format selection
associated with transport channel(s). This may include HARQ
functionality. Since scheduling may be done at the base station,
the MAC layer may be responsible for reporting scheduling related
information such as UE (user equipment or wireless device) buffer
occupancy and power headroom. It may also handle prioritization
from both an inter-UE and intra-UE logical channel perspective. MAC
may also be responsible for random access procedure(s) for the
uplink that may be performed following either a contention and
non-contention based process. UE may need to maintain timing
synchronization with cell(s). The MAC layer may perform
procedure(s) for periodic synchronization.
[0135] According to some of the various aspects of embodiments, the
MAC layer may be responsible for the mapping of multiple logical
channel(s) to transport channel(s) during transmission(s), and
demultiplexing and mapping of transport channel data to logical
channel(s) during reception. A MAC PDU may include of a header that
describes the format of the PDU itself, which may include control
element(s), SDUs, Padding, and/or the like. The header may be
composed of multiple sub-headers, one for constituent part(s) of
the MAC PDU. The MAC may also operate in a transparent mode, where
no header may be pre-pended to the PDU. Activation command(s) may
be inserted into packet(s) using a MAC control element.
[0136] According to some of the various aspects of embodiments, the
MAC layer in some wireless device(s) may report buffer size(s) of
either a single Logical Channel Group (LCG) or a group of LCGs to a
base station. An LCG may be a group of logical channels identified
by an LCG ID. The mapping of logical channel(s) to LCG may be set
up during radio configuration. Buffer status report(s) may be used
by a MAC scheduler to assign radio resources for packet
transmission from wireless device(s). HARQ and ARQ processes may be
used for packet retransmission to enhance the reliability of radio
transmission and reduce the overall probability of packet loss.
[0137] According to some of the various aspects of embodiments, an
RLC sub-layer may control the applicability and functionality of
error correction, concatenation, segmentation, re-segmentation,
duplicate detection, in-sequence delivery, and/or the like. Other
functions of RLC may include protocol error detection and recovery,
and/or SDU discard. The RLC sub-layer may receive data from upper
layer radio bearer(s) (signaling and data) called service data
unit(s) (SDU). The transmission entities in the RLC layer may
convert RLC SDUs to RLC PDU after performing functions such as
segmentation, concatenation, adding RLC header(s), and/or the like.
In the other direction, receiving entities may receive RLC PDUs
from the MAC layer. After performing reordering, the PDUs may be
assembled back into RLC SDUs and delivered to the upper layer. RLC
interaction with a MAC layer may include: a) data transfer for
uplink and downlink through logical channel(s); b) MAC notifies RLC
when a transmission opportunity becomes available, including the
size of total number of RLC PDUs that may be transmitted in the
current transmission opportunity, and/or c) the MAC entity at the
transmitter may inform RLC at the transmitter of HARQ transmission
failure.
[0138] According to some of the various aspects of embodiments,
PDCP (packet data convergence protocol) may comprise a layer 2
sub-layer on top of RLC sub-layer. The PDCP may be responsible for
a multitude of functions. First, the PDCP layer may transfer user
plane and control plane data to and from upper layer(s). PDCP layer
may receive SDUs from upper layer(s) and may send PDUs to the lower
layer(s). In other direction, PDCP layer may receive PDUs from the
lower layer(s) and may send SDUs to upper layer(s). Second, the
PDCP may be responsible for security functions. It may apply
ciphering (encryption) for user and control plane bearers, if
configured. It may also perform integrity protection for control
plane bearer(s), if configured. Third, the PDCP may perform header
compression service(s) to improve the efficiency of over the air
transmission. The header compression may be based on robust header
compression (ROHC). ROHC may be performed on VOIP packets. Fourth,
the PDCP may be responsible for in-order delivery of packet(s) and
duplicate detection service(s) to upper layer(s) after handover(s).
After handover, the source base station may transfer unacknowledged
packet(s)s to target base station when operating in RLC
acknowledged mode (AM). The target base station may forward
packet(s)s received from the source base station to the UE (user
equipment).
[0139] In this specification, "a" and "an" and similar phrases are
to be interpreted as "at least one" and "one or more." In this
specification, the term "may" is to be interpreted as "may, for
example," In other words, the term "may" is indicative that the
phrase following the term "may" is an example of one of a multitude
of suitable possibilities that may, or may not, be employed to one
or more of the various embodiments. If A and B are sets and every
element of A is also an element of B, A is called a subset of B. In
this specification, only non-empty sets and subsets are considered.
For example, possible subsets of B={cell1, cell2} are: {cell1},
{cell2}, and {cell1, cell2}.
[0140] Many of the elements described in the disclosed embodiments
may be implemented as modules. A module is defined here as an
isolatable element that performs a defined function and has a
defined interface to other elements. The modules described in this
disclosure may be implemented in hardware, software in combination
with hardware, firmware, wetware (i.e hardware with a biological
element) or a combination thereof, all of which are behaviorally
equivalent. For example, modules may be implemented as a software
routine written in a computer language configured to be executed by
a hardware machine (such as C, C++, Fortran, Java, Basic, Matlab or
the like) or a modeling/simulation program such as Simulink,
Stateflow, GNU Octave, or Lab VIEWMathScript. Additionally, it may
be possible to implement modules using physical hardware that
incorporates discrete or programmable analog, digital and/or
quantum hardware. Examples of programmable hardware comprise:
computers, microcontrollers, microprocessors, application-specific
integrated circuits (ASICs); field programmable gate arrays
(FPGAs); and complex programmable logic devices (CPLDs). Computers,
microcontrollers and microprocessors are programmed using languages
such as assembly, C, C++ or the like. FPGAs, ASICs and CPLDs are
often programmed using hardware description languages (HDL) such as
VHSIC hardware description language (VHDL) or Verilog that
configure connections between internal hardware modules with lesser
functionality on a programmable device. Finally, it needs to be
emphasized that the above mentioned technologies are often used in
combination to achieve the result of a functional module.
[0141] The disclosure of this patent document incorporates material
which is subject to copyright protection. The copyright owner has
no objection to the facsimile reproduction by anyone of the patent
document or the patent disclosure, as it appears in the Patent and
Trademark Office patent file or records, for the limited purposes
required by law, but otherwise reserves all copyright rights
whatsoever.
[0142] While various embodiments have been described above, it
should be understood that they have been presented by way of
example, and not limitation. It will be apparent to persons skilled
in the relevant art(s) that various changes in form and detail can
be made therein without departing from the spirit and scope. In
fact, after reading the above description, it will be apparent to
one skilled in the relevant art(s) how to implement alternative
embodiments. Thus, the present embodiments should not be limited by
any of the above described exemplary embodiments. In particular, it
should be noted that, for example purposes, the above explanation
has focused on the example(s) using FDD communication systems.
However, one skilled in the art will recognize that embodiments of
the invention may also be implemented in TDD communication systems.
The disclosed methods and systems may be implemented in wireless or
wireline systems. The features of various embodiments presented in
this invention may be combined. One or many features (method or
system) of one embodiment may be implemented in other embodiments.
Only a limited number of example combinations are shown to indicate
to one skilled in the art the possibility of features that may be
combined in various embodiments to create enhanced transmission and
reception systems and methods.
[0143] In addition, it should be understood that any figures which
highlight the functionality and advantages, are presented for
example purposes only. The disclosed architecture is sufficiently
flexible and configurable, such that it may be utilized in ways
other than that shown. For example, the actions listed in any
flowchart may be re-ordered or only optionally used in some
embodiments.
[0144] Further, the purpose of the Abstract of the Disclosure is to
enable the U.S. Patent and Trademark Office and the public
generally, and especially the scientists, engineers and
practitioners in the art who are not familiar with patent or legal
terms or phraseology, to determine quickly from a cursory
inspection the nature and essence of the technical disclosure of
the application. The Abstract of the Disclosure is not intended to
be limiting as to the scope in any way.
[0145] Finally, it is the applicant's intent that only claims that
include the express language "means for" or "step for" be
interpreted under 35 U.S.C. 112, paragraph 6. Claims that do not
expressly include the phrase "means for" or "step for" are not to
be interpreted under 35 U.S.C. 112, paragraph 6.
* * * * *