Communicating A Feedback Data Structure Containing Information
Identifying Coding To Be Applied On Wirelesslv Communicated Signaling
Technical Field
[0001] The invention relates generally to communicating a feedback data structure
containing information identifying coding to be applied on wirelessly transmitted signaling.
Background
[0002] Various wireless access technologies have been proposed or implemented to
enable mobile stations to communicate with other mobile stations or with wired terminals
coupled to wired networks. Examples of wireless access technologies include GSM (Global
System for Mobile communications) or UMTS (Universal Mobile Telecommunications
System) technologies, defined by the Third Generation Partnership Project (3GPP); CDMA
2000 (Code Division Multiple Access 2000) technologies, defined by 3GPP2; or other
wireless access technologies.
[0003] Another type of wireless access technology is the WiMAX (Worldwide
Interoperability for Microwave Access) technology. WiMAX is based on the IEEE (Institute
of Electrical and Electronics Engineers) 802.16 standards. The WiMAX wireless access
technology is designed to provide wireless broadband access.
[0004] One of the features provided by the WiMAX technology is support for MIMO
(multiple input, multiple output). MIMO refers to use of multiple antennas at the transmit
site and at the receive site, such that data can be transmitted from multiple antennas of a
transmitter over multiple paths for receipt by antennas of a receiver. Usage of the MIMO
technology enhances capacity, scalability, and flexibility of wireless networks. By using the
MIMO technology, multiple parallel channels (in the form of multiple spatial beams or
streams) can be provided to achieve increased capacity.
[0005] Closed loop MIMO (CL-MIMO) refers to a MIMO mode that uses information
about the transmission channel that is fed back from the mobile station to a serving base
station, where the base station uses the feedback information to select resources for use in
wireless communications between the base station and the mobile station and to compensate
for effects of the transmission channel. Conventionally, efficient feedback mechanisms have
not been provided to enable closed loop MIMO operations.
Summary
[0006] In general, according to a preferred embodiment, a method of wireless
communication in a closed loop muhiple input, multiple output (MIMO) system includes
communicating, over a wireless channel between a first wireless node and a second wireless
node, a feedback data structure containing information identifying coding to be applied on
signaling communicated wirelessly between the second wireless node and the first wireless
node.
[0007] Other or alternative features will become apparent from the following
description, from the drawings, and from the claims.
Brief Description Of The Drawings
[0008] Fig. 1 is a block diagram of an exemplary arrangement that includes a preferred
embodiment of the invention.
[0009] Fig. 2 is a schematic diagram illustrating feedback of information from a mobile
station to a base station, where the information that is fed back includes a precoding matrix
index (PMI), channel quality indicator (CQI), and rank information in a feedback header
structure, according to a preferred embodiment.
[0010] Figs. 3 and 5 illustrate feedback headers used for communicating feedback
information from a mobile station to a base station, according to some preferred
embodiments.
[0011] Fig. 4 illustrates an orthogonal frequency division multiplexing (OFDM) radio
resource structure that is used by some preferred embodiments.
[0012] Figs. 6-10 arc message flow diagrams of message exchanges between a mobile
station and base station, according to some preferred embodiments.
Detailed Description
[0013] In accordance with preferred embodiments, an improved feedback mechanism is
provided to allow a mobile station to send feedback information in a feedback data structure
to the serving base station, where the feedback information identifies coding to be applied by
the base station on downlink signaling (traffic data and/or control signaling and/or reference
signal) transmitted by the base station over a wireless channel to the mobile station. The
feedback information contained in the feedback data stmcture is based on detected wireless
channel conditions at the mobile station. The feedback information includes at least an
indicator that is used to select coding to be applied on signaling wirclessly conrununicated
between the base station and mobile station. As explained in further detail below, this
indicator includes a preceding matrix index (PMI) in some embodiments that is used to apply
preceding. Other feedback information can include a channel quality indicator (CQI) and
rank information. Coding based on CQI can include selection of the coding and modulation
scheme, while coding based on rank information refers to selection of a number of data
streams.
[0014] The feedback data structure according to some preferred embodiments also
allows for identification of the M(M> 1) best bands of the wireless channel (e.g., the M best
bands based on detected channel conditions). Since M bands are identified in the feedback
data structure, M indicators, such as M PMI values, corresponding to the M bands are
provided in the feedback data structure. Once the base station obtains the feedback data
structure, the base station can select one or more of the M best bands to use for
communicating data between the base station and mobile station.
[0015] A "base station" refers to any node that is able to communicate wirelessly with
one or more mobile stations within a cell or cell sector. In some embodiments, the base
station is according to WiMAX (Worldwide Interoperability for Microwave Access), as
defined by the IEEE (Institute of Electrical and Electronics Engineers) 802.16 specifications.
Although reference is made to WiMAX in the preferred embodiments, it is noted that the
same or similar techniques can be applied to other technologies, including UMTS (Universal
Mobile Telecommunications System) technologies as defined by the Third Generation
Partnership Project (3GPP), and the CDMA 2000 (Code Division Multiple Access 2000)
technology, as defined by 3GPP2, Reference to UMTS covers the Long-Term Evolution
(LTE) technology.
[0016] A wireless channel between a base station and a mobile station refers to a
collection of resources (one or more carriers of different frequencies, one or more time slots,
etc.). In the WiMAX context, a wireless channel includes a collection of sub-carriers (of
different frequencies) in the frequency dimension and time slots in the time dimension. A
wireless channel can include multiple bands (described further below).
[0017] Although reference is made to various exemplary wireless access technologies,
it is noted that techniques according to some embodiments can also be applied to other types
of wireless access technologies.
[0018] Fig. I illustrates an exemplary wireless access network 101 that includes a base
station 100 that is able to wirclcssly communicate with a mobile station 102 over a wireless
channel 104. The base station 100 can be a WiMAX base station or another type of base
station.
[0019] The mobile station 102 includes a wireless interface 106 to communicate
wirelessly over the wireless channel 104. The mobile station 106 also includes software 108
that is executable on one or more central processing units (CPUs) 110 to perform various
tasks associated with a mobile station 102. The CPUs 110 is (are) connected to a storage 112
to store data and software instructions.
[0020] Similarly, the base station 100 includes a wireless interface 114 to communicate
wirelessly over the wireless channel 104. The base station 100 also includes software 116
executable on one or more CPUs 118 in the base station 100, which is (are) connected to a
storage 120 to store data and software instructions. The storage 120 also includes a codebook
130 that includes various entries containing corresponding preceding matrices for applying
preceding on downlink signaling communicated between the base station 100 and the mobile
station 102. Note that the storage 112 of the mobile station 102 also contains a codebook 131
that is the same as codebook 130.
[0021 ] Although just one base station 100 and mobile station 102 are depicted in Fig. 1,
it is noted that a typical wireless access network would include multiple base stations for
communication with multiple mobile stations located within a respective cell or cell sector.
[0022] The wireless access network 101 also includes a control node 122 to which the
base station 100 is connected. The control node 122 can be a system controller such as an
access service network (ASN) gateway in the WiMAX context. The control node 122 is in
turn connected to a gateway node 124, which cormects the wireless access network to an
external network 126, such as the Internet. The gateway node 110 can be a connectivity
service network (CSN) node in the WiMAX context.
[0023] According to some preferred embodiments, the wireless access network 101
depicted in Fig. 1 provides codebook-based closed loop MIMO (CL-MIMO) operations, in
which feedback information is provided from the mobile station 102 to the base station 100 to
allow the base station 100 to apply a selected precoding to downlink signaling communicated
between the base station and the mobile station. Although reference is made to applying
codebook-based precoding to downlink signaling, note that codebook-based precoding can
also be applied to uplink signaling transmitted wirelessly from the mobile station 102 to the
base station 100. Techniques according to preferred embodiments are also applicable to
precoding of uplink signaling.
[0024] A schematic diagram of components involved in a downlink CL-MIMO
operation is depicted in Fig. 2. A wireless link is represented as H in Fig. 2, where H is a
channel matrix (or transfer function) that affects a signal sent from the base station to the
mobile station (on the downlink). In the mobile station 102, a block 202 represents tasks of
the mobile station 102 relating to estimating channel capacities. In one implementation,
based on the channel capacity estimation, the mobile station 102 calculates a PMI (precoding
matrix index), a channel quality indicator (CQI), and a rank mode, which are fed back (at
210) in a feedback data structure in the uplink from the mobile station 102 to the base station
100. Other mechanisms of calculating PMI, CQI, and/or rank mode can be employed in other
implementations.
[0025] The channel estimation performed by the mobile station is an estimation of the
channel matrix H. The mobile station also has knowledge of the precoding matrices that are
kept in the codebook 131 that is also stored as 130 in the base station 100. In one example,
the channel estimation performed in block 202 is according to a submission by
Kathiravetpillai Sivanesan et al., entitled "Post Processing SINR Calculation Based on
Midamble for Band AMC," dated March 19, 2008. In other examples, other types of channel
estimation techniques can be used.
[0026] From the estimated channel matrix H, the mobile station is able to calculate
channel capacity values for all available preceding matrices and MIMO modes (e.g., rank 1
and rank 2), and chooses the preceding matrix and the MIMO mode (rank) that gives the
largest AWGN (additive white Gaussian noise) capacity value. Note that there can be
additional rank modes in other implementations. If M best bands are selected, the respective
preceding matrix and MIMO rank for each of the M best bands is selected. Each preceding
matrix is associated with a respective PMI. The M best bands are identified based on
respective AWGN capacities of the bands. Alternatively, the M best bands can be identified
based en other criteria.
[0027] The CQIs for the respective M best bands are also calculated. Each CQI
provides information regarding the quality of a respective band between the base station and
mobile station.
[0028] The rank mode that can be used in some implementations includes rank 1 or
rank 2. Note that the rank mode indicated by the mobile station in the feedback data structure
can be overridden by the base station under certain conditions. Additional ranks can be used
in other embodiments. "Rank 2" indicates that a particular wireless channel used to
communicate data between a base station and a mobile station is able to use two layers such
that two spatial beams can be used simultaneously to allow simultaneous transmission of data
to the mobile station to double the frequent data communication. On the other hand, "rank 1"
means that just a single layer can be used for the wireless chaimel, which means that just one
of multiple spatial beams are used for transmitting data.
[0029] The codebook 130 that is stored at the base station 100 is arranged as a matrix
having rows corresponding to multiple PMI values, and two columns corresponding to the
two possible ranks (1, 2). Each PMI value that is fed back from the mobile station 102 to the
base station 100 indexes to a row in the codebook 130, while each corresponding rank mode
selects one of the two columns of the codcbook 130. Together, a pair of a PMI value and the
rank mode selects one of the entries of the codebook 130, from which a corresponding
preceding matrix is extracted. The selected precoding matrix is represented as "W" in Fig. 2.
[0030] The selected precoding matrix W is applied by a precoder 204 to an input signal
(x) in the base station 100. The preceded signal is transmitted as signal z from the base
station 100. The transmitted signal z is communicated over the wireless channel (represented
by H), which is combined (at 206) with noise (n) to provide received signal y at the mobile
station 102. The received signal y is decoded by a decoder 208 in the mobile station 102 to
extract the original signal x. The decoding performed by the decoder 208 involves reversing
the precoding applied by the precoder 204 in the base station 100.
[0031] Feeding back the PMI, CQI, and rank information can be performed using a
feedback header structure sent (at 210) on the uplink from the mobile station 102 to the base
station 100. Use of the feedback data structure is relatively efficient since the feedback data
structure can be provided with data frames sent from the mobile station 102 to the base
station 100. "Providing" the feedback header structure with data frames includes inserting
the feedback header structure into the data frames (header or body of data frames) or
appending the feedback header structure to the data frames. Using the feedback data
structure also provides enhanced flexibility, since a feedback data structure can be sent
multiple times to ensure receipt by the base station.
[0032] Note that the base station is able to override any recommendation (PMI, CQI,
and/or rank information) from the mobile station under certain conditions. If a PMI is
overridden, then the base station can signal the different PMI to the mobile station.
[0033] The feedback header structure according to the WiMAX protocol includes
multiple portions; in one embodiment, the multiple portions of the feedback header stmcture
includes a feedback header of a first type and a feedback header of a second type. In one
example, the two types of feedback headers are feedback header type 0110 and feedback
header type 1101 according to the WiMAX standards. The feedback header type 0110 is sent
less frequently than feedback header type 1101. In some implementations, feedback header
type 1101 is sent with every data frame, whereas feedback header type 0110 is sent every N
data firames, where AN> 1. In one example, N is equal to six.
[0034] A "frame" of data refers to some predefined collection of data bits (and control
information) that can be exchanged over a wireless channel between a base station and a
mobile station. In some cases, frames are concatenated into a superframe that is carried in the
uplink or downlink. More generally, the feedback header structure has multiple portions,
where a first portion is sent more frequently than at least a second portion of the feedback
header structure.
[0035] Fig. 3 shows a portion of the content of a feedback header (300) of type 0110.
The content of the feedback header 300 (of type OHO) contains a first element 302 that
indicates the M best bands in the wireless channel between the base station and mobile
station, where M> 1. in one example implementation, the element 302 that identifies the M
best bands is a bitmap, such as a 12-bit bitmap. In one example, M is equal to 3 (although
other values can be used in other implementations).
[0036] A "band" used in the WiMAX context refers to an AMC (adaptive modulation
and coding) logical band that is formed of 8 bins (in the frequency domain) and all the
downlink data OFDM (orthogonal frequency division multiplexing) symbols (in the time
domain). According to OFDM, different users can be assigned different sets of sub-carriers
(at different frequencies) and in different time slots (which includes a set of the OFDM
symbols). In one implementation, a bin is defined as 9 consecutive sub-carriers of different
corresponding frequencies. Such a bin is shown in Fig. 4 as bin 400. The bin 400 includes 9
sub-carriers and one OFDM symbol (in the time domain). An AMC logical band includes 8
bins 400 (along the frequency dimension) and all the OFDM symbols along the time
dimension. In one implementation, there can be 12 bands in each wireless channel between
the base station and mobile station.
[0037] More generally, a "band" refers to some predefined portion of a wireless radio
resource, which can have multiple such predefined portions to use for communicating data
between the base station and mobile station.
[0038] The feedback header 300 of Fig. 3 also includes element 304 containing CQIs
for the M best bands. Thus, the element 304 includes a first CQI for the best band, a second
CQI for the second best band, and a third CQI for the third best band. In one implementation,
each CQI contains 5 bits, such that the number of bits to store the M CQIs is M x 5.
[0039] Another element 306 of the feedback header 300 contains rank information, to
identify the rank modes for the M bands. In other words, the rank mode for the best band, the
rank mode for the next best band, and so forth, are included in the element 306. Each rank
mode is represented as one bit (to indicate rank 1 or rank 2), such that the element 306 is
made up of M bits.
[0040] Although specific numbers of bits are noted above for elements 302, 304, and
306 of the feedback header 300, these numbers are provided for purposes of example. In
different implementations, different sizes of the elements 302, 304, and 306 can be employed.
Moreover, the feedback header 300 also contains other information (not shown).
[0041] Fig. 5 shows a feedback header 500 according to type 1101. The feedback
header 500 contains an element 502 containing the PMI values for the M best bands. If the
PMI value is 3 bits in length, then the number of bits for element 502 is M x 3. However, if
the length of a PMI is 6 bits, then the number of bits of element 502 is M x 6.
[0042] Another element 504 in the feedback header 500 includes the differential CQIs
for the M best bands. A differential CQI is a shortened CQI (e.g., 2 bits instead of 5 bits) that
indicates a difference between the CQI of the current frame and the CQI reported in feedback
header 300. Note that the full CQI value is reported in the feedback header 300 that is sent
less frequently than feedback header 500. The feedback header 300 may be sent every N
frames. However, for each subsequent frame after the frame corresponding to feedback
header 300, a CQI may have changed, such that the differential CQIs provided in the element
504 of the feedback header 500 provides an indication of the extent of such change, if any.
[0043] Instead of reporting the PMI and the differential CQI in the feedback header
structure type 1101 as discussed above, the PMI, and differential CQI can alternatively be
communicated in the CQICH (CQI channel) sent on the uplink. The CQICH includes a
primary CQICH and a secondary CQICH. The primary CQICH is used to carry the PMI for
the M best bands. There is just one PMI value for all M best bands. The secondary CQICH
is used to carry the 1-bit differential CQI per band for the M best bands. The 1-bit
differential CQI represents the difference between the CQI of the current data frame and the
CQI reported in the feedback header 300. (Note that according to some embodiments, when
the CQICH is selected for providing feedback information to the base station, the feedback
header of type 0110 is still used; however, the feedback header of type 1101 is not used when
CQICH is selected).
[0044] CQICH is a more reliable mechanism for communicating information from the
mobile station to the base station, particularly for mobile stations that are located at the cell
edge or located in locations of high obstruction or reduced signal quality.
[0045] Based on detected channel conditions, the base station can provide an indication
to a mobile station regarding which mechanism to use to report the PMI and differential
CQIs. Under relatively good channel conditions, the base station can instruct the mobile
station to use the feedback header structure (type 1101) to report the PMI and differential
CQI. The feedback header of type 1101 is able to communicate more information than the
CQICH. For example, with the feedback header of type 1101, different PMI values can be
provided for corresponding M best bands, whereas the CQICH is limited to providing just
one PMI for the M best bands. Also, the CQICH is limited to using a 1-bit differential CQI
instead of the 2-bit differential CQI that can be communicated in the feedback header of type
1101.
[0046] Fig. 6 shows an exemplary flow diagram of exchanges of messages between the
base station and a mobile station. To enable the mobile station to send feedback information
to the base station for performing CL-MIMO operation, the base station 100 sends (at 602) a
polling information element, refened to as a Feedback_Polling_IE, to the mobile station 102.
The FeedbackPoUinglE indicates the feedback header type, feedback periodicity and the
duration of the feedback. The polling information element can be sent in a down link control
channel. More generally, the base station is able to send some type of an indication that a
feedback mechanism is to be activated.
[0047] The CL-MIMO operation could be started after the base station 100 issues two
polling IBs for feedback types 0110 and 1101, respectively, or only one polling IE for type
1101. When the mobile station 102 receives only one polling IE for type 1101 it overrides the
feedback header type to type 0110 in the first feedback, Nth feedback, 2Nth feedback and so
on. When the feedback type is overridden to type 0110 in a particular frame, the PMI and
differential CQI values will not be available. In that situation the PMI and differential CQIs
received in the previous frame can be used. In response to receiving the
Feedback_Polling_IEs for types 0110 and 1101, the mobile station begins to send the
feedback headers of types 1101 and OHO. The mobile station 102 first sends the feedback
header of type 0110 (at 604). Note that the feedback header of type 0110 is sent less
frequently than the feedback header of type 1101. Following transmission of the feedback
header of type 0110 (at 604), the mobile station sends (at 606, 608) feedback headers of type
1101, which can be performed every frame, for example.
[0048] Next, after N data frames have been sent, the mobile station 102 again sends (at
610) the feedback header of type 0110, followed by another feedback header of type 1101 (at
612).
[0049] At some point, the base station 100 can send (at 614) another polling
information element, such as Feedback_Polling_IE, to the mobile station 102 to deactivate
the closed loop feedback, such that the mobile station 102 no longer sends feedback headers
to the base station 100.
[0050] Fig. 7 shows another exemplary flow diagram. In Fig. 7, the base station 100
initiates the feedback mechanism by sending (at 702) a first Feed_back_Polling_IE (type
0110) and sending (at 704) another FeedbackPoUinglE (type 1101) to the mobile station
102. In this example, two polling information elements are used instead of just one polling
information element in Fig. 6. In this example, in response to the two polling information
elements, the mobile station can send the two different types of feedback headers on separate
feedback channels.
[0051] A feedback header of type 0110 is sent (at 706) by the mobile station 102 to the
base station 100. Next, the mobile station 102 sends (at 708) the feedback header of type
1101 to the base station 100. The process continues until the base station 100 sends two
polling information elements (at 710, 712) to the mobile station 102 to deactivate the
feedback mechanism.
[0052] Fig. 8 shows an example of operation in which the base station has decided that
the mobile station should report feedback information in the CQICH (primary CQICH and
secondary CQICH) instead of using the feedback header of type 1101. In this example, the
base station sends (at 802) a Feedback_Polling_IE (type 0110) to the mobile station 102 to
instruct the mobile station 102 to send feedback headers of type 0110 on a periodic basis. In
addition, the base station 100 also sends (at 804) a CQICH_Enhanced_Alloc_IE to the mobile
station 102, where CQICH_Enhanced_Alloc_IE is a polling information element to notify the
mobile station to send feedback information in the CQICH instead of the feedback header
type 1101.
[0053] In response to the information elements, the mobile station sends (at 806) a
feedback header of type 0110 to the base station. Next, the mobile station sends (at 808, 810)
CQICHs to the base station 102. After N cycles, the mobile station sends (at 812) another
feedback header of type 0110, followed by another CQICH (at 814).
[0054] At some point, the base station can deactivate the feedback mechanism by
sending (at 816, 818) a FeedbackPollinglE and CQICH_Enhanced_Alloc_IE to the mobile
station 102.
[0055] Fig. 9 shows an example of switching between using a feedback header structure
of type 1101 and the CQICH to perform the feedback operation when the CL-MIMO
operation was started by feedback polling IE for type 1101 only. In the example in Fig. 9, the
mobile station sends (at 902) the feedback header of type 1101 to the base station, and next
sends (at 904) a feedback header of type 0110 to the base station. Next, the base station
sends a FeedbackPollinglE (type 0110) and CQICH_Enhanced_Alloc_IE (at 906) to the
mobile station, which are indications to the mobile station to switch to using CQICH instead
of using the feedback header of type 1101. For example, the base station may have detected
that the mobile station is in a low SINR (signal-to-interference-noise ratio) region.
[0056] Next, the mobile station sends (at 908) a feedback header of type 0110. Then,
the base station sends (at 910) a FeedbackPollinglE to the mobile station to deactivate
sending of the feedback header of type 1101. Following this, the mobile station again sends
(at 912) a feedback header of type 0110, followed by transmission of CQICH (at 914).
[0057] In a different embodiment, when the CL-MIMO operation was started using
Feedback_Polling_IEs_for types 0110 and 1101, the base station issues a
CQICHEnhancedAllocJE instead of sending (906) the Feedback_Polling_IE (type 0110)
to the mobile station to cause a switch to reporting using CQICH, Then
Feedback_Polling_IE for type 1101 to deactivate the transmission of feedback header type
1101.
[0058] Fig, 10 illustrates switching from using a CQICH to using a feedback header of
type 1101 for performing feedback. Initially, the mobile station sends (at 1002) a feedback
header of type 0110. Next, the base station detects that the mobile station is in a high SINR
region, such that the base station decides to switch the mobile station to feedback using
feedback header of type 1101. This is done by sending (at 1004) a Feedback_Polling_IE
(type 1101) to the mobile station. However, the mobile station still continues to send (at
1006) the feedback information using CQICH. It is not until the base station has sent (at
1008) the CQICH_Enhanced_Alloc_IE to deactivate the CQICH feedback that the mobile
station begins to transmit feedback information using feedback headers of type 1101 (e.g.,
1010,1012).
[0059] In the foregoing embodiments, instead of using the feedback header of type
0110, a REP-RSP (Report-Response) message can be used instead to carry to content
depicted in Fig. 3. In such an alternative embodiment, the flow diagrams of Figs. 6-10 would
be modified to replace each instance of feedback header of type 0110 with the REP-RSP
message.
[0060] The sending of polling information elements and feedback information
performed by the respective base station and mobile station can be controlled by software. If
controlled by software, instructions of such software are executed on a processor (such as
CPUs 110 and 118 in Fig. 1). The processor includes microprocessors, microcontrollers,
processor modules or subsystems (including one or more microprocessors or
microcontrollers), or other control or computing devices. A "processor" can refer to a single
component or to plural components (e.g., some CPU or multiple CPUs).
[0061] Data and instructions (of the software) are stored in respective storage devices,
which are implemented as one or more computer-readable or computer-usable storage media.
The storage media include different forms of memory including semiconductor memory
devices such as dynamic or static random access memories (DRAMs or SRAMs), erasable
and programmable read-only memories (EPROMs), electrically erasable and programmable
read-only memories (EEPROMs) and flash memories; magnetic disks such as fixed, floppy
and removable disks; other magnetic media including tape; and optical media such as
compact disks (CDs) or digital video disks (DVDs).
[0062] In the foregoing description, numerous details are set forth to provide an
understanding of the present invention. However, it will be understood by those skilled in the
art that the present invention may be practiced without these details. While the invention has
been disclosed with respect to a limited number of embodiments, those skilled in the art will
appreciate numerous modifications and variations therefrom. It is intended that the appended
claims cover such modifications and variations as fall within the true spirit and scope of the
invention.
What is claimed is:
1. A method of wireless communications in a closed loop multiple input, multiple output
(MIMO) system, comprising;
communicating, over a wireless channel between a first wireless node and a second
wireless node, a feedback data structure containing indicators identifying codings to be
applied on signaling communicated between the second wireless node and the first wireless
node,
wherein the indicators in the feedback data structure are based on wireless channel
conditions detected at the first wireless node, and
wherein the indicators correspond to plural bands in the wireless channel.
2. The method of claim 1, wherein communicating the feedback data structure between
the first and second wireless nodes comprises communicating the feedback data structure
between a mobile station and a base station.
3. The method of claim 1, wherein communicating the feedback data structure
containing the indicators comprises communicating the feedback data structure containing
precoding matrix index (PMI) values for the corresponding bands.
4. The method of claim 3, further comprising:
selecting, by the second wireless node, an entry of a codebook based on each of the
PMI values, wherein the codebook contains a plurality of entries containing respective
precoding matrices, wherein each precoding matrix is used to apply coding on signaling
transmitted by the second wireless node to the first wireless node.
5. The method of claim 3, wherein the feedback data structure further contains a channel
quality indicator and rank information, and wherein the method further comprises:
selecting, by the second wireless node, a modulation and coding scheme based on the
channel quality indicator; and
selecting, by the second wireless node, a number of data streams based on the rank
information..
6. The method of claim 1, further comprising:
the second wireless node overriding coding recommended by the mobile station based
on the indicators; and
the second wireless node sending an indication of changed coding to the mobile
station.
7. The method of claim 1, wherein communicating the feedback data structure comprises
communicating WiMAX (Worldwide Interoperability for Microwave Access) feedback
headers.
8. The method of claim 7, wherein communicating the WiMAX feedback headers
comprises communicating a WiMAX feedback header of a first type and a WiMAX feedback
header of a second type, wherein the WiMAX feedback header of the first type is transmitted
every N frames, N greater than or equal to NI (NI > 1), and wherein the WiMAX feedback
header of the second type is transmitted every Nl frame.
9. The method of claim 7, wherein the feedback headers include a feedback header of a
first type and a feedback header of a second type, the feedback header of the first type
containing:
information identifying M best bands for transmitting data from the second
wireless node to the first wireless node, where M is greater than one,
channel quality indicators for the M best bands, and
rank information for the M best bands.
10. The method of claim 7, wherein the feedback header of the second type contains
precoding matrix index (PMI) values for the M best bands, and
wherein the feedback header of the second type is communicated more frequently
than the feedback header of the first type.
11. The method of claim 10, wherein the feedback header of the second type further
contains values indicating differential chaimel quality indicators for the M best bands,
wherein each differential channel quality indicator represents a difference in relation to the
corresponding channel quality indictor in the feedback header of the first type.
12. An article comprising at least one computer-readable storage medium containing
instructions that when executed cause a first wireless node to:
send, to the second wireless node, feedback information regarding coding to apply to
signaling to be transmitted by the second wireless node,
wherein the feedback information is sent in a feedback header under a first condition,
the feedback header being provided with a data frame, and
wherein the feedback information is sent in a control channel under a second
condition.
13. The article of claim 12, wherein the feedback header is of a first type, and wherein the
instructions upon execution causing the first wireless node to further send:
a feedback header of a second type to the second wireless node, wherein the feedback
header of the first type is sent at the same frequency or more frequently than the feedback
header of the second type.
14. The article of claim 13, wherein the control channel is a channel quality indicator
control channel (CQICH).
15. The article of claim 12, wherein the feedback information is sent in the feedback
header in response to a first indication from the second wireless node, and wherein the
feedback information is sent in the control chaimel in response to a second indication fi-om
the second wireless node.
16. The article of claim 12, wherein the feedback information includes at least one
preceding matrix index.
17. The article of claim 16, wherein the feedback information fiirther includes rank
information and at least one channel quality indicator.
18. The article of claim 16, wherein the feedback information includes multiple preceding
matrix indices for respective bands of a wireless channel between the first wireless node and
the second wireless node.
19. The article of claim 18, wherein each of the bands includes a set of sub-carriers of
different frequencies and a set of time slots.
20. A base station, comprising:
a wireless interface to communicate over a wireless channel with a mobile station;
a processor to:
receive, over the wireless channel, a feedback data structure containing
indicators identifying codings to be applied on signaling communicated between the base
station and the mobile station,
wherein the indicators in the feedback data structure are based on wireless
channel conditions detected at the mobile station, and
wherein the indicators correspond to plural bands in the wireless channel.
21. The base station of claim 20, wherein the plural bands comprise WiMAX (Worldwide
Interoperability for Microwave Access) bands.
22. A mobile station, comprismg;
a wireless interface to communicate over a wireless channel with a base station;
a processor to:
send, over the wireless channel, a feedback data structure containing indicators
identifying codings to be applied on signaling communicated between the base station and
the mobile station,
wherein the indicators in the feedback data structure are based on wireless
channel conditions detected at the mobile station, and
wherein the indicators correspond to plural bands in the wireless channel.
23. The mobile station of claim 22, wherein the plural bands comprise WiMAX
(Worldwide Interoperability for Microwave Access) bands.

To perform wireless communications in a closed loop multiple input, multiple output (MIMO) system, a feedback
data structure is communicated over a wireless channel between a first wireless node and a second wireless node, where the feedback
data structure contains indicators identifying coding to be applied by the second wireless node on signaling communicated
between the second wireless node and the first wireless node, where the information in the feedback data structure is based on
wireless channel conditions detected at the first wireless node. The indicators identify different codings to be used for different
corresponding bands in the wireless channel.