U.S. patent application number 10/968702 was filed with the patent office on 2013-07-11 for transmission of overhead information for reception of multiple data streams.
This patent application is currently assigned to QUALCOMM Incorporated. The applicant listed for this patent is Bruce Collins, Ramaswamy Murali, Dhinakar Radhakrishnan, Rajiv Vijayan, Gordon Kent Walker. Invention is credited to Bruce Collins, Ramaswamy Murali, Dhinakar Radhakrishnan, Rajiv Vijayan, Gordon Kent Walker.
Application Number | 20130177010 10/968702 |
Document ID | / |
Family ID | 38960041 |
Filed Date | 2013-07-11 |
United States Patent
Application |
20130177010 |
Kind Code |
A9 |
Vijayan; Rajiv ; et
al. |
July 11, 2013 |
TRANSMISSION OF OVERHEAD INFORMATION FOR RECEPTION OF MULTIPLE DATA
STREAMS
Abstract
Techniques for transmitting overhead information to facilitate
efficient reception of individual data streams are described. A
base station may transmit multiple data streams on multiple data
channels (or MLCs). The MLCs may be transmitted at different times
and on different frequency subbands. The time-frequency location of
each MLC may change over time. The overhead information indicates
the time-frequency location of each MLC and may be sent as
"composite" and "embedded" overhead information. The composite
overhead information indicates the time-frequency locations of all
MLCs and is sent periodically in each super-frame. A wireless
device receives the composite overhead information, determines the
time-frequency location of each MLC of interest, and receives each
MLC at the indicated time-frequency location. The embedded overhead
information for each MLC indicates the time-frequency location of
that MLC in the next super-frame and is transmitted along with the
payload of the MLC in the current super-frame.
Inventors: |
Vijayan; Rajiv; (San Diego,
CA) ; Walker; Gordon Kent; (Poway, CA) ;
Collins; Bruce; (San Diego, CA) ; Radhakrishnan;
Dhinakar; (San Diego, CA) ; Murali; Ramaswamy;
(San Diego, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Vijayan; Rajiv
Walker; Gordon Kent
Collins; Bruce
Radhakrishnan; Dhinakar
Murali; Ramaswamy |
San Diego
Poway
San Diego
San Diego
San Diego |
CA
CA
CA
CA
CA |
US
US
US
US
US |
|
|
Assignee: |
QUALCOMM Incorporated
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20050141475 A1 |
June 30, 2005 |
|
|
Family ID: |
38960041 |
Appl. No.: |
10/968702 |
Filed: |
October 18, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10932586 |
Sep 1, 2004 |
7221680 |
|
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10968702 |
|
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60499741 |
Sep 2, 2003 |
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60559740 |
Apr 5, 2004 |
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60559740 |
Apr 5, 2004 |
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60514320 |
Oct 24, 2003 |
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Current U.S.
Class: |
370/345 |
Current CPC
Class: |
H04W 72/005 20130101;
H04W 52/0216 20130101; Y02D 30/70 20200801; Y02D 70/10 20180101;
H04W 4/06 20130101 |
Class at
Publication: |
370/345 |
Claims
1. A method of transmitting overhead information in a communication
system, comprising: determining location information for each of a
plurality of data channels, the location information for each data
channel indicating time location, frequency location, or both time
and frequency location where the data channel is transmitted;
generating overhead information with the location information for
the plurality of data channels; and transmitting the overhead
information in a time division multiplexed (TDM) manner with data
for the plurality of data channels.
2. The method of claim 1, further comprising: transmitting at least
one data stream on each of the plurality of data channels.
3. The method of claim 2, wherein the location information for each
data channel indicates the number of data streams transmitted on
the data channel.
4. The method of claim 2, wherein the location information for each
data channel indicates size of each data stream being transmitted
on the data channel.
5. The method of claim 1, further comprising: transmitting the
plurality of data channels in super-frames, each super-frame having
a predetermined time duration, and wherein the transmitting the
overhead information in a TDM manner comprises transmitting the
overhead information in each super-frame in a TDM manner with the
data for the plurality of data channels.
6. The method of claim 5, wherein the overhead information
transmitted in each super-frame comprises location information for
the plurality of data channels for the super-frame.
7. The method of claim 5, wherein the determining the location
information for each of the plurality of data channels comprises
generating location information for each data channel for a current
super-frame to indicate whether or not the data channel is
transmitted in the current super-frame.
8. The method of claim 5, wherein the determining the location
information for each of the plurality of data channels comprises
for each data channel transmitted in a current super-frame,
generating location information for the data channel to indicate a
starting time in which the data channel is transmitted in the
current super-frame.
9. The method of claim 5, wherein the determining the location
information for each of the plurality of data channels comprises
for each data channel not transmitted in a current super-frame,
generating location information for the data channel to indicate a
next earliest super-frame in which the data channel is potentially
transmitted.
10. The method of claim 1, further comprising: transmitting the
plurality of data channels in a plurality of slots, each slot being
associated with a respective set of frequency subbands.
11. The method of claim 10, wherein the plurality of slots are
assigned a plurality of slot indices, and wherein the determining
the location information for each of the plurality of data channels
comprises generating location information for each channel to
indicate a lowest slot index, a starting slot index, and a highest
slot index used for the data channel.
12. The method of claim 11, wherein the determining the location
information for each of the plurality of data channels further
comprises mapping the lowest slot index, the starting slot index,
and the highest slot index for each data channel to a code value
based on a mapping scheme.
13. The method of claim 10, wherein the plurality of slots are
assigned a plurality of slot indices, and wherein the determining
the location information for each of the plurality of data channels
further comprises generating location information for each data
channel to indicate a lowest slot index and a highest slot index
used for the data channel.
14. The method of claim 5, wherein the determining the location
information for each of the plurality of data channels further
comprises generating location information for each data channel for
a current super-frame to indicate a length of each data packet
being sent on the data channel in the current super-frame.
15. The method of claim 1, wherein the generating the overhead
information comprises generating a first portion of overhead
information with location information for data channels with a
first coverage area, and generating a second portion of overhead
information with location information for data channels with a
second coverage area.
16. The method of claim 15, wherein the first coverage area is a
wide coverage area and the second coverage area is a local coverage
area.
17. The method of claim 15, wherein the transmitting the overhead
information comprises transmitting the first and second portions of
the overhead information in first and second time intervals,
respectively.
18. The method of claim 15, further comprising: processing the
first portion of the overhead information in accordance with a
first mode; and processing the second portion of the overhead
information in accordance with a second mode, wherein each of the
first and second modes indicates a particular code rate and a
particular modulation scheme to use for the overhead
information.
19. The method of claim 1, further comprising: forming at least one
overhead message for the overhead information for the plurality of
data channels, each overhead message including at least one
location record, and each location record including location
information for an associated data channel.
20. The method of claim 19, wherein the plurality of data channels
are assigned different identifiers, and wherein the forming the at
least one overhead message comprises arranging the at least one
location record for each overhead message in sequential order based
on identifiers of at least one associated data channel.
21. The method of claim 19, wherein each location record has a
fixed length.
22. The method of claim 5, further comprising: determining location
information for each data channel for a future super-frame, the
location information for each data channel for the future
super-frame indicating time location, frequency location, or both
time and frequency location where the data channel is transmitted
in the future super-frame; and transmitting the location
information for each data channel for the future super-frame along
with data for the data channel in a current super-frame.
23. An apparatus in a communication system, comprising: a
controller operative to determine location information for each of
a plurality of data channels and to generate overhead information
with the location information for the plurality of data channels,
the location information for each data channel indicating time
location, frequency location, or both time and frequency location
where the data channel is transmitted; and a data processor
operative to process the overhead information for transmission in a
time division multiplexed (TDM) manner with data for the plurality
of data channels.
24. The apparatus of claim 23, further comprising: a transmitter
unit operable to transmit the plurality of data channels in
super-frames, each super-frame having a predetermined time
duration, and to further transmit the overhead information in each
super-frame.
25. The apparatus of claim 24, wherein the controller is further
operative to determine location information for each data channel
for a future super-frame, the location information for each data
channel for the future super-frame indicating time location,
frequency location, or both time and frequency location where the
data channel is transmitted in the future super-frame, and wherein
the data processor is further operative to process the location
information for each data channel for the future super-frame for
transmission along with data for the data channel in a current
super-frame.
26. The apparatus of claim 23, wherein the communication system is
a wireless broadcast system utilizing orthogonal frequency division
multiplexing (OFDM).
27. An apparatus in a communication system, comprising: means for
determining location information for each of a plurality of data
channels, the location information for each data channel indicating
time location, frequency location, or both time and frequency
location where the data channel is transmitted; means for
generating overhead information with the location information for
the plurality of data channels; and means for transmitting the
overhead information in a time division multiplexed (TDM) manner
with data for the plurality of data channels.
28. The apparatus of claim 27, further comprising: means for
transmitting the plurality of data channels in super-frames, each
super-frame having a predetermined time duration, and wherein the
overhead information is transmitted in each super-frame.
29. The apparatus of claim 28, further comprising: means for
determining location information for each data channel for a future
super-frame, the location information for each data channel for the
future super-frame indicating time location, frequency location, or
both time and frequency location where the data channel is
transmitted in the future super-frame; and means for transmitting
the location information for each data channel for the future
super-frame along with data for the data channel in a current
super-frame.
30. A method of transmitting overhead information in a
communication system, comprising: transmitting a plurality of data
channels in super-frames, each super-frame having a predetermined
time duration, and each data channel carrying at least one data
stream; determining location information for each of the plurality
of data channels, the location information for each data channel
indicating time location, frequency location, or both time and
frequency location where the data channel is transmitted in a
future super-frame; and transmitting the location information for
each data channel along with data for the data channel in a current
super-frame.
31. The method of claim 30, wherein the future super-frame is a
next super-frame immediately following the current super-frame.
32. The method of claim 30, wherein the future super-frame is more
than one super-frame from the current super-frame.
33. The method of claim 30, wherein the determining the location
information for each of the plurality of data channels comprises
generating location information for each data channel to indicate
whether or not the data channel is transmitted in the future
super-frame.
34. The method of claim 30, wherein the determining the location
information for each of the plurality of data channels comprises
for each data channel to be transmitted in the future super-frame,
generating location information for the data channel to indicate a
starting time in which the data channel is transmitted in the
future super-frame.
35. The method of claim 30, wherein the determining the location
information for each of the plurality of data channels comprises
for each data channel not transmitted in the future super-frame,
generating location information for the data channel to indicate a
next earliest super-frame in which the data channel is potentially
transmitted.
36. The method of claim 30, wherein the transmitting the plurality
of data channels comprises transmitting the plurality of data
channels in a plurality of slots, each slot being associated with a
particular set of frequency subbands.
37. The method of claim 36, wherein the plurality of slots are
assigned a plurality of slot indices, and wherein the determining
the location information for each of the plurality of data channels
comprises for each data channel to be transmitted in the future
super-frame, generating location information for the data channel
to indicate a lowest slot index, a starting slot index, and a
highest slot index used for the data channel in the future
super-frame.
38. The method of claim 30, wherein the determining the location
information for each of the plurality of data channels comprises
for each data channel to be transmitted in the future super-frame,
generating location information for the data channel to indicate a
length of each data packet to be sent on the data channel in the
future super-frame.
39. An apparatus in a communication system, comprising: a
transmitter unit operable to transmit a plurality of data channels
in super-frames, each super-frame having a predetermined time
duration, and each data channel carrying at least one data stream;
a controller operative to determine location information for each
of the plurality of data channels, the location information for
each data channel indicating time location, frequency location, or
both time and frequency location where the data channel is
transmitted in a future super-frame; and a data processor operative
to process the location information for each data channel for
transmission along with data for the data channel in a current
super-frame.
40. An apparatus in a communication system, comprising: means for
transmitting a plurality of data channels in super-frames, each
super-frame having a predetermined time duration, and each data
channel carrying at least one data stream; means for determining
location information for each of the plurality of data channels,
the location information for each data channel indicating time
location, frequency location, or both time and frequency location
where the data channel is transmitted in a future super-frame; and
means for transmitting the location information for each data
channel along with data for the data channel in a current
super-frame.
41. A method of receiving data in a communication system,
comprising: receiving overhead information for a plurality of data
channels transmitted in super-frames, each super-frame having a
predetermined time duration, wherein the overhead information for a
current super-frame is transmitted in a time division multiplexed
(TDM) manner with data sent in the current super-frame for the
plurality of data channels; obtaining first location information
for a selected data channel from the overhead information received
in the current super-frame, the first location information
indicating time location, frequency location, or both time and
frequency location where the selected data channel is transmitted
in the current super-frame; and receiving the selected data channel
in the current super-frame based on the first location
information.
42. The method of claim 41, further comprising: processing the
selected data channel to obtain second location information for the
selected data channel, second the location information being
transmitted along with data for the selected data channel in the
current super-frame and indicating time location, frequency
location, or both time and frequency location where the selected
data channel is transmitted in a future super-frame; and receiving
the selected data channel in the future super-frame based on the
second location information.
43. An apparatus in a communication system, comprising: a
controller operative to receive overhead information for a
plurality of data channels transmitted in super-frames, and to
obtain first location information for a selected data channel from
the overhead information received in a current super-frame, each
super-frame having a predetermined time duration, the overhead
information for a current super-frame being transmitted in a time
division multiplexed (TDM) manner with data sent in the current
super-frame for the plurality of data channels, and the first
location information indicating time location, frequency location,
or both time and frequency location where the selected data channel
is transmitted in the current super-frame; and a data processor
operative to receive the selected data channel in the current
super-frame based on the first location information.
44. The apparatus of claim 43, wherein the data processor is
further operable to process the selected data channel to obtain
second location information for the selected data channel, the
second location information being transmitted along with data for
the selected data channel in the current super-frame and indicating
time location, frequency location, or both time and frequency
location where the selected data channel is transmitted in a future
super-frame, and wherein the data processor is further operative to
receive the selected data channel in the future super-frame based
on the second location information.
45. An apparatus in a communication system, comprising: means for
receiving overhead information for a plurality of data channels
transmitted in super-frames, each super-frame having a
predetermined time duration, wherein the overhead information for a
current super-frame is transmitted in a time division multiplexed
(TDM) manner with data sent in the current super-frame for the
plurality of data channels; means for obtaining first location
information for a selected data channel from the overhead
information received in the current super-frame, the first location
information indicating time location, frequency location, or both
time and frequency location where the selected data channel is
transmitted in the current super-frame; and means for receiving the
selected data channel in the current super-frame based on the first
location information.
46. The apparatus of claim 45, further comprising: means for
processing the selected data channel to obtain second location
information for the selected data channel, the second location
information being transmitted along with data for the selected data
channel in the current super-frame and indicating time location,
frequency location, or both time and frequency location where the
selected data channel is transmitted in a future super-frame; and
means for receiving the selected data channel in the future
super-frame based on the second location information.
Description
[0001] This application claims the benefit of provisional U.S.
application Ser. No. 10/932,586, entitled "Method for Adding
Overhead Information to Receive Multiple Multimedia Streams over
Mobile Wireless Radio Links" filed Sep. 1, 2004, provisional U.S.
Application Ser. No. 60/499,741, entitled "A Method for
Multiplexing and Transmitting Multiple Multimedia Streams to Mobile
Terminals over Terrestrial Radio," filed Sep. 2, 2003, and
provisional U.S. Application Ser. No. 60/559,740 entitled
"Multiplexing and Transmission of Multiple Data Streams in a
Wireless Multi-Carrier Communication System," filed Apr. 5,
2004.
BACKGROUND
[0002] I. Field
[0003] The present invention relates generally to communication,
and more specifically to techniques for transmitting overhead
information for reception of multiple data streams in a
communication system.
[0004] II. Background
[0005] A base station in a wireless communication system may
simultaneously transmit multiple data streams for broadcast,
multicast, and/or unicast services. A broadcast transmission is
sent to all wireless devices within a designated coverage area, a
multicast transmission is sent to a group of wireless devices, and
a unicast transmission is sent to a specific wireless device. For
example, the base station may broadcast a number of data streams
for multimedia (e.g., television) programs via a terrestrial radio
link for reception by wireless devices. In general, the base
station may transmit any number of data streams, which may change
over time, and each data stream may have a fixed or variable data
rate.
[0006] A wireless device within the coverage area of the base
station may be interested in receiving only one or few specific
data streams among the multiple data streams transmitted by the
base station. If the base station multiplexes all data streams onto
one composite stream prior to transmission, then the wireless
device may need to receive the signal transmitted by the base
station, process (e.g., downconvert, demodulate, and decode) the
received signal to obtain the composite stream sent by the base
station, and perform demultiplexing to extract the one or few
specific data streams of interest. This type of processing may not
be problematic for receiver units intended to be powered on all the
time. However, many wireless devices are portable and powered by
internal batteries. Continual demodulation and decoding of the
received signal to recover just one or few data streams of interest
may consume significant amounts of battery power, which may greatly
shorten the "ON" time for the wireless device.
[0007] If the multiple data streams are transmitted separately,
then the base station may also transmit control information on a
dedicated control channel to indicate when and where each data
stream will be transmitted. In this case, the wireless device may
need to continuously decode the dedicated control channel to obtain
control information for each data stream of interest, which can
deplete battery power. The wireless device may also need to
simultaneously decode each data stream of interest along with the
dedicated control channel, which can increase the complexity of the
wireless device.
[0008] There is therefore a need in the art for techniques to send
overhead information such that individual data streams of interest
to wireless devices may be efficiently received with reduced power
consumption.
SUMMARY
[0009] Techniques for transmitting overhead information to
facilitate efficient reception of individual data streams are
described herein. A base station may transmit multiple data streams
on multiple data channels. A data channel is also called a
multiplexed logical channel (MLC) in the following description but
may also be referred to by some other terminology. Each MLC may
carry one or more data streams and may be transmitted at different
times, on different frequency subbands, and so on. The
time-frequency location of each MLC may change over time. The
overhead information indicates the time-frequency location where
each MLC is transmitted. The overhead information for all of the
MLCs may be sent in two parts called "composite" overhead
information and "embedded" overhead information.
[0010] In an embodiment, the composite overhead information
includes location information for all MLCs and is sent periodically
at the start of each super-frame of a predetermined time duration,
as described below. The composite overhead information for each
super-frame contains location information for each MLC for that
super-frame, and this location information indicates the
time-frequency location where the MLC will be transmitted in the
super-frame. A wireless device may receive the composite overhead
information for a current super-frame, determine the time-frequency
location of each MLC of interest based on the location information
for the MLC, and receive each MLC of interest in the current
super-frame at the indicated time-frequency location. The periodic
and known transmission of the composite overhead information allows
the wireless devices in the system to rapidly acquire each MLC of
interest, decode each desired MLC with minimal "ON" time, and
quickly switch between MLCs.
[0011] The composite overhead information may be partitioned into a
wide-area portion and a local-area portion. The wide-area portion
may contain location information for all MLCs with a wide coverage
area (e.g., nationwide). The local-area portion may contain
location information for all MLCs with a local coverage area (e.g.,
citywide). The wide-area and local-area portions may be processed
differently by both the base station and the wireless devices for
robust reception performance.
[0012] In an embodiment, the embedded overhead information for each
MLC in each super-frame contains location information for that MLC
for a future (e.g., next) super-frame and is transmitted along with
the payload of the MLC in the current super-frame. A wireless
device receiving a given MLC can obtain the embedded overhead
information for that MLC as part of the processing for the MLC in
the current super-frame. The wireless device may then use this
information to receive the MLC in the next super-frame, without
having to "wake up" and receive the composite overhead information
sent in the next super-frame.
[0013] Various aspects and embodiments of the invention are
described in further detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The features and nature of the present invention will become
more apparent from the detailed description set forth below when
taken in conjunction with the drawings in which like reference
characters identify correspondingly throughout and wherein:
[0015] FIG. 1 shows a wireless multi-carrier broadcast system;
[0016] FIG. 2 shows an exemplary super-frame structure;
[0017] FIG. 3 shows exemplary packet processing for one MLC;
[0018] FIG. 4 shows assignment of slots to an MLC using a "zigzag"
pattern;
[0019] FIG. 5 shows an exemplary message for carrying location
information for multiple MLCs;
[0020] FIG. 6 shows transmission of composite and embedded overhead
information;
[0021] FIG. 7 shows a process for transmitting overhead
information;
[0022] FIG. 8 shows a block diagram of a base station; and
[0023] FIG. 9 shows a block diagram of a wireless device.
DETAILED DESCRIPTION
[0024] The word "exemplary" is used herein to mean "serving as an
example, instance, or illustration." Any embodiment or design
described herein as "exemplary" is not necessarily to be construed
as preferred or advantageous over other embodiments or designs.
[0025] The techniques described herein for transmitting overhead
information may be used for wireless and wireline communication
systems, for time division multiplexed (TDM), frequency division
multiplexed (FDM), and code division multiplexed (CDM) systems, for
single-input single-output (SISO) and multiple-input
multiple-output (MIMO) systems, for single-carrier and
multi-carrier systems, and so on. Multiple carriers may be provided
by orthogonal frequency division multiplexing (OFDM), some other
multi-carrier modulation techniques, or some other construct. OFDM
effectively partitions the overall system bandwidth into multiple
(N) orthogonal subbands. These subbands are also referred to as
tones, carriers, subcarriers, bins, and frequency channels. With
OFDM, each subband is associated with a respective subcarrier that
may be modulated with data. The techniques described herein may
also be used for broadcast, multicast, and unicast services. For
clarity, these techniques are described below for an exemplary
wireless multi-carrier broadcast system.
[0026] FIG. 1 shows a wireless multi-carrier broadcast system 100.
System 100 includes a number of base stations 110 that are
distributed throughout the system. A base station is generally a
fixed station and may also be called an access point, a
transmitter, or some other terminology. Wireless devices 120 are
located throughout the coverage area of the system. A wireless
device may be fixed or mobile and may also be called a user
terminal, a mobile station, user equipment, or some other
terminology. A wireless device may also be a portable unit such as
a cellular phone, a handheld device, a wireless module, a personal
digital assistant (PDA), and so on.
[0027] Each base station may transmit wide-area content, local-area
content, or a combination of both. Wide-area content is content
sent over a large coverage area (e.g., nationwide), and local-area
content is content sent over a smaller coverage area (e.g.,
citywide). Neighboring base stations may transmit the same or
different contents. Each base station may also transmit multiple
data streams for wide-area and/or local-area contents to wireless
devices within its coverage area. These data streams may carry
multimedia content such as video, audio, teletext, data,
video/audio clips, and so on. The data streams are sent on data
channels or MLCs.
[0028] In a specific embodiment that is described in detail below,
each MLC may carry up to three data streams, e.g., one data stream
for signaling and up to two data streams for packet/traffic data.
Each multimedia program may be sent as one or more data streams,
e.g., different data streams for different multimedia contents such
as video, audio, data, and so on. The one or more data streams for
each multimedia program may be sent on one or more MLCs. For
example, one MLC may carry two data streams for a given
program--one data stream for real-time content and another data
stream for a video clip to be played along with the real-time
content at designated times. As another example, two MLCs may carry
three data streams for a single multimedia (e.g., television)
program--one MLC may carry one data stream for video and another
data stream for data, and a second MLC may carry one data stream
for audio. Transmitting the video and audio portions of the program
on separate MLCs allows the wireless devices to independently
receive the video and audio. In general, each MLC may carry any
number of data streams, and each multimedia program may be sent in
any number of data streams and on any number of MLCs.
[0029] FIG. 2 shows an exemplary super-frame structure that may be
used for system 100. Data transmission occurs in units of
super-frames 210. Each super-frame spans a predetermined time
duration, which may be selected based on various factors such as,
for example, the desired statistical multiplexing for the data
streams, the amount of time diversity desired for the data streams,
the acquisition time for the data streams, buffer requirements for
the wireless devices, and so on. A super-frame size of
approximately one second may provide a good tradeoff between the
various factors noted above. However, other super-frame sizes may
also be used. A super-frame may also be called a frame, a time
slot, or some other terminology.
[0030] For the embodiment shown in FIG. 2, each super-frame
includes a field 212 for a TDM pilot, a field 214 for overhead
information, and four equal-sized frames 216a through 216d. The TDM
pilot may be used by the wireless devices for synchronization
(e.g., frame detection, frequency error estimation, timing
acquisition, and so on) and possibly for channel estimation. The
overhead information indicates the specific location of each data
channel within the super-frame and may be sent as described below.
The data streams are multiplexed and sent in the four frames.
[0031] FIG. 2 shows a specific super-frame structure. In general, a
super-frame may span any time duration, include any number and any
type of fields, and have any number of frames. The system may also
use other frame structures for transmission.
[0032] In an embodiment, the protocol stack for the system includes
upper layers that reside on top of a stream layer, which resides on
top of a medium access control (MAC) layer, which further resides
on top of a physical layer. The upper layers control transmission
of multimedia contents, access to the contents, and so on. The
stream layer provides binding of upper layers packets to data
streams on an MLC-by-MLC basis. The MAC layer performs multiplexing
of packets for different data streams associated with each MLC. The
physical layer provides a mechanism to transmit the multiple data
streams via a communication channel.
[0033] FIG. 3 shows an embodiment of the packet formats used for
the stream layer, the MAC layer, and the physical layer. FIG. 3
also shows the processing for one MLC in one super-frame. The MLC
may carry up to three data streams, which are designated as streams
0, 1, and 2. Stream 0 may be used to send signaling for the MLC,
and streams 1 and 2 may be used to send different multimedia
contents (e.g., video, audio, datacast, multicast, and so on). The
signaling may be for various items such as, e.g., a decryption key
used to decrypt the other data streams being sent on the MLC. (The
decryption key may be decrypted by a wireless device having a
proper subscription key, which may be obtained upon activation of a
service.) Other types of signaling may also be sent on stream 0.
For example, stream 0 may carry a presentation record that defines
the characteristics of the media carried by the MLC, the location
of the same MLC in the next super-frame, text components and/or
media, and so on. In general, each stream may carry more than one
type of media, although it may be more convenient to carry a single
media type in each stream. For each super-frame, the stream layer
provides one stream layer packet for each data stream sent on the
MLC in that super-frame. For clarity, the following description
assumes that three data streams are being sent on the MLC.
[0034] The MAC layer forms a MAC capsule for the MLC for each
super-frame in which the MLC is transmitted. The MAC capsule
includes a MAC capsule header and a MAC capsule payload. The MAC
capsule header carries embedded overhead information for the MLC,
which may be used to receive the MLC in a future (e.g., the next)
super-frame. The MAC capsule payload carries the stream layer
packets to be sent in the current super-frame for the data streams
carried by the MLC. The MAC layer forms No MAC layer packets (or
simply, MAC packets) for the MAC capsule header and stream 0
packet, N.sub.1 MAC packets for stream 1 packet, and N.sub.2 MAC
packets for stream 2 packet, where N.sub.0.gtoreq.1,
N.sub.1.gtoreq.1, and N.sub.2.gtoreq.1 if all three data streams
are being sent. To facilitate independent reception of the data
streams, each stream layer packet is sent in an integer number of
MAC packets, and the length of each stream layer packet is included
in the overhead information. The MAC layer also performs block
encoding on the (N.sub.1+N.sub.1+N.sub.2) MAC packets for the MLC
and generates N.sub.p parity MAC packets, where N.sub.p.gtoreq.0
and is dependent on whether or not block encoding is enabled and,
if enabled, the block encoding mode selected for the MLC. For each
super-frame in which the MLC is transmitted, the MAC layer provides
an encoded MAC capsule that contains
(N.sub.0+N.sub.1+N.sub.2+N.sub.p) data and parity MAC packets.
[0035] The physical layer receives the encoded MAC capsule and
processes (e.g., encodes, interleaves, and symbol maps) each MAC
packet to generate a corresponding physical layer (PL) packet. In
an embodiment, the MAC packets are of a fixed size (e.g.,
approximately 1K bytes), the PL packets for the MLC are of equal
size, and the PL packet size is determined by the code rate and
modulation scheme used for the MLC. The one-to-one mapping between
MAC packets and PL packets simplifies the processing at the base
station and wireless devices.
[0036] Data may be transmitted in various manners in system 100. In
an embodiment, M slots are formed in each symbol period and are
mapped to M disjoint or non-overlapping sets of subbands, where
M.gtoreq.1. To obtain frequency diversity, the subbands in each set
may be uniformly distributed across the N total subbands in the
system. The subbands in each set are then interlaced with the
subbands in each of the other M-1 sets. Each subband set may thus
be called an "interlace". Each slot may be mapped to different
interlaces in different symbol periods (e.g., based on a
predetermined mapping scheme) to improve frequency diversity and
obtain other benefits. For clarity, the following description is
for data transmission in slots, and the slot-to-interlace mapping
is not described.
[0037] For a given super-frame structure, a fixed number of slots
is available for transmission in each super-frame. Some of the
available slots may be used to transmit an FDM pilot, which may be
used by the wireless devices for channel estimation and other
purposes. Some slots may also be allocated for a control channel
used to transmit signaling for the MLCs, as described below. The
remaining slots are then available for allocation to the MLCs.
[0038] Each MLC may be "allocated" a fixed or variable number of
slots in each super-frame depending on the MLC's payload, the
availability of slots in the super-frame, and possibly other
factors. Each "inactive" MLC, which is an MLC that is not
transmitted in a given super-frame, is allocated zero slots. Each
"active" MLC, which is an MLC to be transmitted in a given
super-frame, is allocated at least one slot. Each active MLC is
also "assigned" specific slots within the super-frame based on an
assignment scheme that attempts to (1) pack the slots for all
active MLCs as efficiently as possible, (2) reduce the transmission
time for each MLC, (3) provide adequate time-diversity for each
MLC, and (4) minimize the amount of signaling needed to indicate
the slots assigned to each MLC. Various schemes may be used to
assign slots to MLCs. In general, there is a tradeoff between time
diversity and power savings. The system may provide flexibility to
allow power consumption to be favored over time diversity, or vice
versa, for different MLCs. For example, some MLCs may be optimized
for time diversity while other MLCs may be optimized for power
consumption. MLCs containing many turbo code blocks inherently
achieve more time diversity, while lower data rate MLCs can benefit
from additional time diversity.
[0039] FIG. 4 shows an exemplary slot assignment scheme that
assigns slots to MLCs using a "sinusoidal" or "zigzag" pattern. For
this scheme, a frame is divided into one or more "strips", and each
strip spans at least one slot index and further spans a contiguous
number of (e.g., all) symbol periods in the frame. Each active MLC
is mapped to one strip and is assigned slots in that strip. The
slots in each strip may be assigned to the MLCs mapped to that
strip in a specific order using a vertical zigzag pattern. This
zigzag pattern selects slots from the lowest slot index for the
strip to the highest slot index for the strip, one symbol period at
a time, starting with the first symbol period for the strip.
[0040] FIG. 4 also shows the assignment of slots to a given MLC x
for one frame 216. MLC x is assigned slots starting from a start
slot index (Start Slot) at a designated symbol period index (Start
Offset) and going to a highest slot index (Max Slot), then starting
from a lowest slot index (Min Slot) in the next symbol period index
and going to the highest slot index, and so on, until the number of
slots allocated to MLC x has been reached. For the example shown in
FIG. 4, MLC x is assigned 16 slots starting at slot index 4 in
symbol period index 3, zigzaging between the lowest slot index 2
and the highest slot index 5, and concluding at slot index 3 in
symbol period index 7.
[0041] An exemplary slot assignment scheme has been described
above. The MLCs may also be assigned slots in other manners using
other schemes. For example, each MLC may be assigned slots in a
rectangular pattern on the two-dimensional (2-D) plane for slot
versus symbol period, as shown in FIG. 4. The active MLCs may be
assigned rectangular patterns such that these patterns are packed
as efficiently as possible in the frame.
[0042] The slots assigned to each active MLC for each super-frame
may be conveyed in the location information sent for the MLC. The
parameters used to describe the slots assigned to each active MLC
are typically dependent on the scheme used to assign the slots. For
example, if each active MLC is assigned a rectangular pattern, then
this pattern may be described by two corners, e.g., the slot index
and symbol period index for the lower left corner of the pattern
and the slot index and symbol period index for the upper right
corner of the pattern. If each active MLC is assigned slots using
the zigzag pattern, then the assigned slots for the MLC may be
described by the Start Slot, the Min Slot, the Max Slot, and the
number of slots allocated to the MLC, as shown in FIG. 4.
[0043] FIG. 5 shows an embodiment of a System Parameters Message
used to carry location information for the MLCs. In general, the
location information for each MLC includes all parameters used to
describe the time-frequency location for the MLC, e.g., the
specific slots assigned to the MLC. For the embodiment shown in
FIG. 5, the System Parameters Message contains a message header and
one or more location records. The message header may carry
information such as, for example, (1) the system time for the
beginning of the current super-frame, (2) a network identifier, (3)
the source of the message, (4) a protocol version supported by the
system, (5) transmission parameters for a control channel
(described below), (6) the MLC for the first location record sent
in the message right after the header, (7) the number of location
records (N.sub.rec) being sent in the message, and so on. In
general, the message header may contain any pertinent information
for the wireless devices.
[0044] The message carries N.sub.rec location records for N.sub.rec
MLCs after the message header, one location record for each MLC,
where N.sub.rec.gtoreq.1. In an embodiment, each location record
has a fixed length or size of L bits, and the N.sub.rec location
records are sent in sequential order based on the identifiers (IDs)
for the MLCs. For example, if the first location record is for MLC
x, then the second location record is for MLC x+1, the third
location record is for MLC x+2, and so on, and the last location
record is for MLC x+N.sub.rec-1. This allows the wireless devices
to quickly find and extract the location record for each MLC of
interest.
[0045] For the embodiment shown in FIG. 5, each location record
contains an MLC Present bit that is set to `1` if the associated
MLC is being sent in the current super-frame and is set to `0`
otherwise. If the MLC Present bit is set to `1`, then the location
record carries a Start Offset field, a Slot Info field, and a
Stream Lengths field. The Start Offset field indicates the first or
starting symbol period index for the slots assigned to the MLC. The
Slot Info field contains slot information, which conveys all
parameters used to describe the assigned slots (e.g., the Min Slot,
Start Slot, and Max Slot). The Stream Lengths field carries the
length of each stream layer packet carried by the MLC in the
current super-frame (e.g., N.sub.0, N.sub.1, and N.sub.2 for the
three stream layer packets in FIG. 3). The number of slots
allocated to the MLC may be determined based on the stream lengths
and the transmission parameters (e.g., the code rate and modulation
scheme) used for the MLC. If the MLC Present bit is set to `0`,
then the location record carries a Next Super-frame Offset field
and a Reserved field. The Next Super-frame Offset field indicates
the next super-frame in which the MLC may be sent. If this field is
set to `0`, then the MLC may be sent in any upcoming super-frame.
If this field is set to a non-zero value, then this value indicates
the minimum number of super-frames from the next super-frame where
the MLC may continue. For example, if the Next Super-frame Offset
field is set to four, then the MLC will not be sent until at least
five super-frames from the current super-frame. The wireless
devices may start searching for the next occurrence of the MLC
starting at this future super-frame. Table 1 summarizes the various
fields of the location record for one MLC.
TABLE-US-00001 TABLE 1 MLC Present = `1` (active MLC) Start Offset
Indicate the starting symbol period index for the slots assigned to
the MLC. Slot Info Contain parameters describing the slots assigned
to the MLC. Stream Contain the length of each stream layer Lengths
packet carried by the MLC in the current super-frame. MLC Present =
`0` (inactive MLC) Next Super- Indicate the next super-frame in
which the MLC frame Offset may be sent. Reserved Padding to make
the location record a fixed size.
[0046] The slot information may be encoded to reduce the number of
bits needed to convey this information. An exemplary encoding
scheme for the slot information is described below. This encoding
scheme is for slot assignment using the zigzag pattern shown in
FIG. 4 and further assumes that the lowest slot index for any MLC
is 1 and the highest slot index is 7. Slot index 0 may be used for
the FDM pilot, the control channel, and so on. With the above
assumption, the lowest slot index (Min Slot), the starting slot
index (Start Slot), and the highest slot index (Max Slot) for any
MLC are related as follows:
1.ltoreq.Min Slot.ltoreq.Start Slot.ltoreq.Max Slot.ltoreq.7. Eq
(1)
The delta or difference between the starting and lowest slot
indices and the delta between the highest and starting slot indices
may be computed as follows:
.DELTA.Start=Start Slot-Min Slot and Eq (2)
.DELTA.Max=Max Slot-Start Slot. Eq (3)
The slot information for each MLC may be given by a slot
information code value (Slot Info Code) that is determined based on
the Min Slot, .DELTA.Start, and .DELTA.Max for that MLC. Table 2
shows an exemplary mapping of Min Slot, .DELTA.Start, and
.DELTA.Max to Slot Info Code.
TABLE-US-00002 TABLE 2 Slot Min Info Slot .DELTA.Start .DELTA.Max
Code 1 0 0 0 1 0 1 1 1 0 2 2 1 0 3 3 1 0 4 4 1 0 5 5 1 0 6 6 1 1 0
7 1 1 1 8 1 1 2 9 1 1 3 10 1 1 4 11 1 1 5 12 1 2 0 13 1 2 1 14 1 2
2 15 1 2 3 16 1 2 4 17 1 3 0 18 1 3 1 19 1 3 2 20 1 3 3 21 1 4 0 22
1 4 1 23 1 4 2 24 1 5 0 25 1 5 1 26 1 6 0 27 2 0 0 28 2 0 1 29 2 0
2 30 2 0 3 31 2 0 4 32 2 0 5 33 2 1 0 34 2 1 1 35 2 1 2 36 2 1 3 37
2 1 4 38 2 2 0 39 2 2 1 40 2 2 2 41 2 2 3 42 2 3 0 43 2 3 1 44 2 3
2 45 2 4 0 46 2 4 1 47 2 5 0 48 3 0 0 49 3 0 1 50 3 0 2 51 3 0 3 52
3 0 4 53 3 1 0 54 3 1 1 55 3 1 2 56 3 1 3 57 3 2 0 58 3 2 1 59 3 2
2 60 3 3 0 61 3 3 1 62 3 4 0 63 4 0 0 64 4 0 1 65 4 0 2 66 4 0 3 67
4 1 0 68 4 1 1 69 4 1 2 70 4 2 0 71 4 2 1 72 4 3 0 73 5 0 0 74 5 0
1 75 5 0 2 76 5 1 0 77 5 1 1 78 5 2 0 79 6 0 0 80 6 0 1 81 6 1 0 82
7 0 0 83
[0047] If the maximum slot index is 7, then the parameters Min
Slot, Start Slot, and Max Slot may each be conveyed with 3 bits,
and the slot information for each MLC may be conveyed with 9 bits
for the three parameters. The Slot Info Code may be conveyed with 7
bits for the 84 possible code values shown in Table 2. The encoding
scheme described above thus reduces the number of bits needed to
convey the slot information for each MLC.
[0048] The stream layer packet lengths may also be encoded to
reduce the number of bits needed to convey this information. An
exemplary encoding scheme for the stream layer packet lengths is
described below. This encoding scheme is for the packet formats
shown in FIG. 3 and further assumes that (1) up to three stream
layer packets may be sent in any MLC in a super-frame and (2) the
three stream layer packets have small, medium, and large sizes.
[0049] For the embodiment shown in FIG. 5, the Stream Lengths field
contains a Stream Mode subfield, a Length Format subfield, a Small
Stream Length subfield, a Medium Stream Length subfield, and a
Large Stream Length subfield. The Stream Mode subfield is set to
`0` to indicate that two stream layer packets are sent in the MLC
and is set to `1` to indicate that three stream layer packets are
sent in the MLC. The Length Format subfield indicates the sizes of
the stream layer packets for the up to three data streams sent on
the MLC. Table 3 shows an exemplary definition of the Length Format
subfield for different stream layer packet sizes for the three data
streams.
TABLE-US-00003 TABLE 3 Mode = `0` (two stream layer Mode = `1`
(three stream layer packets) packets) Length Stream Stream Stream
Length Stream Stream Stream Format 0 1 2 Format 0 1 2 `000` Not
Sent Medium Large `000` Small Medium Large `001` Not Sent Large
Medium `001` Small Large Me- dium `010` Medium Not Sent Large `010`
Medium Small Large `011` Medium Large Not Sent `011` Medium Large
Small `100` Large Not Sent Medium `100` Large Small Me- dium `101`
Large Medium Not Sent `101` Large Medium Small `110` Not Sent Not
Sent Large `110` Reserved `111` Not Sent Large Not Sent `111`
Reserved
[0050] For the embodiment shown in Table 3, one data stream carried
by the MLC is designated as a "large" stream, one data stream is
designated as a "medium" stream, and a third data stream (if sent)
is designated as a "small" stream. The stream layer packets for the
large, medium, and small streams may carry up to N.sub.large,
N.sub.medium, and N.sub.small MAC packets, respectively. The Large
Stream Length subfield indicates the length of the stream layer
packet for the large stream sent on the MLC and contains
B.sub.large bits, where B.sub.large=log.sub.2 (N.sub.large). The
Medium Stream Length subfield indicates the stream layer packet
length for the medium stream sent on the MLC and contains
B.sub.medium bits, where B.sub.medium=log.sub.2(N.sub.medium). The
Small Stream Length subfield indicates the stream layer packet
length for the small stream (if any) sent on the MLC and contains
B.sub.small bits, where B.sub.small=log.sub.2 (N.sub.small).
[0051] FIG. 5 shows the case in which three data streams are sent
on the MLC, and three subfields are used to indicate the lengths of
the stream layer packets for these three data streams. If only two
data streams are sent on the MLC, then the B.sub.small bits for the
small stream may be used for the medium or large stream (not shown
in FIG. 5).
[0052] If each data stream sent in the MLC can carry up to 1024 MAC
packets in each super-frame, then a 10-bit stream length subfield
may be used for each data stream. In this case, 30 bits may be used
to convey the stream layer packet lengths for the three data
streams carried in the MLC. However, if the three data streams have
different lengths and if the large, medium, and small streams can
carry up to 1024, 256, and 2 MAC packets, respectively, then
B.sub.large=10, B.sub.medium=8, and B.sub.small=1 bits may be used
for the three streams. If one bit is used for the Stream Mode
subfield and three bits are used for the Length Format subfield,
then a total of 23 bits may be used to convey the stream layer
packet lengths for the three data streams carried by the MLC. The
encoding scheme described above can thus reduce the number of bits
needed to convey the stream lengths for each MLC.
[0053] A specific encoding scheme for slot information and a
specific encoding scheme for stream lengths have been described
above. Other encoding schemes may also be used, e.g., for different
slot assignment schemes, different packet formats, and so on.
Different encoding schemes may achieve different number of bit
savings. In any case, the bit savings achieved with encoding may be
significant for a large number of MLCs. Since overhead information
is sent periodically and since overhead bits are relatively
expensive, it is desirable to minimize the number of overhead bits
as much as possible for greater efficiency.
[0054] FIG. 6 shows an embodiment for transmitting composite and
embedded overhead information in a manner to facilitate efficient
reception of the data streams. The composite overhead information
is sent at the start of each super-frame in a TDM manner and
contains location information for all MLCs. For example, one System
Parameters Message may contain location information for all MLCs
carrying wide-area content, and another System Parameters Message
may contain location information for all MLCs carrying local-area
content. The System Parameters Message for each coverage type
(wide-area or local-area) contains one location record for each MLC
carrying content of that coverage type. Each location record in
each System Parameters Message contains location information (e.g.,
start offset, slot information, and stream lengths) for the
associated MLC for the current super-frame, if the MLC is
active.
[0055] An encoded MAC capsule is transmitted in the current
super-frame for each active MLC. In an embodiment, the encoded MAC
capsule is partitioned into four equal-sized portions, and each
portion is further processed and transmitted in one frame on the
slots assigned to the MLC. The transmission of the encoded MAC
capsule over four frames provides time diversity and robust
reception performance in a slowly time-varying fading channel. For
each MLC, the same slot assignment may be used for the four frames
of the super-frame, as shown in FIG. 6, and this slot assignment is
conveyed in the location record for that MLC.
[0056] In an embodiment, the MAC capsule header for the MAC capsule
for each MLC x contains location information for MLC x for the next
super-frame, if the MLC will be transmitted in that super-frame.
For the embodiment shown in FIG. 6, the MAC capsule header contains
an MLC ID field and a Cont Next SF field. The MLC ID field carries
the ID of MLC x. The Cont Next SF field is set to `1` if MLC x will
be transmitted in the next super-frame and is set to `0` otherwise.
If MLC x is transmitted in the next super-frame, then the MAC
capsule header further contains a Next SF Start Offset field, a
Next SF Slot Info field, and a Next SF Stream Lengths field, which
carry the same type of information as the Start Offset, Slot Info,
and Stream Lengths fields, respectively, in the location record.
However, the Start Offset, Slot Info, and Stream Lengths fields in
the location record carry "current" overhead information for MLC x
for the current super-frame. The Next SF Start Offset, Next SF Slot
Info, and Next SF Stream Lengths fields in the MAC capsule header
carry "future" overhead information for MLC x for the next
super-frame. In an embodiment, if MLC x is not transmitted in the
next super-frame, then the MAC capsule header further contains a
Next Super-frame Offset field and a Reserved field (not shown in
FIG. 6), which carry the same type of information as the Next
Super-frame Offset field and the Reserved field, respectively, in
the location record. In another embodiment, if MLC x is not
transmitted in the next super-frame, then the MAC capsule header
carries the location information (e.g., Next SF Start Offset field,
Next SF Slot Info field, and Next SF Stream Lengths field) for MLC
x for the next super-frame in which MLC x will be transmitted.
[0057] As shown in FIG. 6, a wireless device that has just powered
on or has just switched to a new MLC may receive the composite
overhead information sent at the start of each super-frame and
determine the location where the new MLC will be sent in the
current super-frame. The wireless device may then receive the MAC
capsule for this new MLC at the location indicated by the location
record for the MLC. The wireless device may obtain from the MAC
capsule header the embedded overhead information for this MLC for
the next super-frame. The wireless device may then use this
embedded overhead information to receive the MLC in the next
super-frame, without having to process the composite overhead
information sent at the start of the next super-frame. If the MLC
is transmitted continuously in each super-frame, which is often the
case for a multimedia program, then the wireless device may need to
receive the composite overhead information only once. The wireless
device may thereafter obtain the embedded overhead information for
the MLC for each future super-frame from the MAC capsule header. In
this way, the wireless device may be turned "ON" for a shorter time
duration and may be able to conserve more battery power. The MLC ID
is used to ensure that the wireless device is processing the MAC
capsule for the proper MLC, e.g., in case the MLC is decoded in
error.
[0058] FIG. 7 shows a process 700 for transmitting overhead
information for multiple data channels or MLCs. The location
information for each MLC for the current super-frame is determined
(e.g., block 712). The location information for each MLC indicates
the time-frequency location for the MLC and may have the format
shown in FIG. 5 or some other format. The location information for
each MLC for a future (e.g., next) super-frame is also determined
(e.g., block 714). Composite overhead information for the current
super-frame is formed with the location information for all MLCs
for the current super-frame (block 716) and is transmitted at the
start of the current super-frame in a TDM manner (block 718). The
location information for each MLC for the future super-frame is
transmitted along with the payload for the MLC in the current
super-frame (block 720).
[0059] For the embodiments described above, the overhead
information is sent in two parts. The composite overhead
information is sent periodically at the start of each super-frame
(which may be relatively infrequently, e.g., once every second) and
conveys the slot assignments for all MLCs sent in that super-frame.
A wireless device may use the composite overhead information if it
is requesting content for the first time (e.g., after powering on),
if an MLC of interest was decoded in error in a previous
super-frame, if the wireless device is receiving a new MLC, if the
wireless device switches reception from a current MLC to a new MLC,
and so on.
[0060] A wireless device may use the embedded overhead information
to determine when to wake up in the next super-frame. If the
wireless device has successfully decoded an MLC of interest in the
current super-frame, then the wireless device does not need to wake
up to receive the composite overhead information sent in the next
super-frame. This reduces the ON time for the wireless device to
receive data streams. The embedded overhead information is thus a
power-efficient way to provide the location where the MLC will be
sent in the next super-frame. The wireless device can obtain this
embedded overhead information as part of the processing for the
MLC. If each MLC carries embedded overhead information only for
itself and no other MLCs, as described above, then the embedded
overhead information only needs to point to a single location in
the next super-frame for this MLC. The embedded overhead
information is protected by the same error-correction coding used
for the payload of the MLC, which ensures robust reception of the
embedded overhead information.
[0061] The super-frame duration may be selected such that the
composite and embedded overhead information consumes a relatively
small percentage of the total system capacity while still allowing
for fast changes between data channels. The partitioning of the
composite overhead information into wide-area and local-area
portions also provides several benefits. The overhead data bits for
the wide-area portion may be sent in a manner to obtain the
benefits of using OFDM in a single-frequency network (SFN). For
example, a wireless device may receive and combine the overhead
data bits from multiple base stations to obtain greater reception
reliability. The overhead data bits for the local-area portion may
be transmitted differently than those for the wide-area portion,
e.g., using a different OFDM pilot structure, a lower code rate, a
lower order modulation scheme, and so on, in order to improve
reception of these bits at the boundaries of the local coverage
areas. In general, the wide-area and local-area portions may be
processed with the same or different coding and modulation schemes,
may have the same or different formats and lengths, and so on. The
overhead information is processed and transmitted to be as robust
as the traffic data.
[0062] The location information for each MLC may be sent once to
allow the wireless devices to receive the MLC. The location
information for all MLCs may be sent in the composite overhead
information at the start of each super-frame. The location
information for each active MLC may also be sent redundantly along
with the payload for the MLC to improve efficiency in receiving the
MLC. However, this redundant location information is optional and
may be omitted (i.e., not transmitted).
[0063] The overhead information for the data channels may also be
sent in other manners. For example, the stream lengths may be
included in the MAC capsule header instead of the location record.
If the MLCs are scheduled more than one super-frame in advance,
then the location record and/or MAC capsule header may also include
location information for a super-frame that is further out than the
next super-frame. The MAC capsule header may include a bit to
indicate whether the location information for the next super-frame
is the same as for the current super-frame, in which case the
location information may be omitted from the MAC capsule
header.
[0064] The overhead information indicates the location where each
MLC is transmitted. A control channel may be used to carry other
pertinent information for the MLCs. For example, the control
channel may carry, for each MLC, the code rate and modulation
scheme used for the MLC, the block coding used for the MLC, the
type of media being sent on each data stream carried by the MLC,
the upper layer entity that is bound to each data stream carried by
the MLC, and so on. The control channel may be sent in a manner
that is known a priori by the wireless devices, which may then be
able to receive the control without other signaling.
[0065] FIG. 8 shows a block diagram of a base station 110x, which
is one of the base stations in system 100. At base station 110x, a
transmit (TX) data processor 810 receives multiple (T) data streams
(denoted as {d.sub.1} through {d.sub.T}) from data sources 808,
where T.gtoreq.1. Each data stream may carry one stream layer
packet for each super-frame in which the data stream will be sent
(e.g., as shown in FIG. 3). TX data processor 810 also receives
embedded overhead data for each MLC and appends the overhead data
onto a proper stream layer packet being sent on the MLC (e.g., as
shown in FIG. 3). TX data processor 810 processes each data stream
in accordance with a "mode" used for that stream to generate a
corresponding data symbol stream. The mode for each data stream may
indicate, for example, the code rate, the modulation scheme, and so
on, to use for the data stream. TX data processor 810 provides T
data symbol streams (denoted as {s.sub.1} through {s.sub.T}) to a
symbol multiplexer (Mux)/channelizer 820. As used herein, a data
symbol is a modulation symbol for packet/traffic data, an overhead
symbol is a modulation symbol for overhead data, a pilot symbol is
a modulation symbol for pilot (which is data that is known a priori
by both the base station and wireless devices), a guard symbol is a
signal value of zero, and a modulation symbol is a complex value
for a point in a signal constellation used for a modulation scheme
(e.g., M-PSK, M-QAM, and so on).
[0066] TX data processor 810 also receives composite overhead data
to be sent at the start of each super-frame (which is denoted as
{d.sub.O}) from a controller 840. TX data processor 810 processes
the composite overhead data in accordance with a mode used for the
overhead data and provides an overhead symbol stream (denoted as
{s.sub.O}) to channelizer 820. The composite overhead data may be
partitioned into a wide-area portion and a local-area portion (as
shown in FIG. 6) and processed separately, e.g., based on the same
or different modes. The mode(s) used for the composite overhead
data are typically associated with a lower code rate and/or a lower
order modulation scheme than those used for the data streams to
ensure robust reception of the composite overhead data in
time-selective and/or frequency-selective terrestrial radio
channels.
[0067] Channelizer 820 multiplexes the data symbols in the T data
symbol streams onto their assigned slots. Channelizer 820 also
provides pilot symbols on slots used for pilot transmission and
guard symbols on subbands not used for transmission. Channelizer
820 further multiplexes pilot symbols and overhead symbols in the
pilot and overhead fields at the start of each super-frame, as
shown in FIG. 2. Channelizer 820 provides a composite symbol stream
(denoted as {S.sub.C}) that carries data, overhead, pilot, and
guard symbols on the proper subbands and symbol periods. An OFDM
modulator 830 performs OFDM modulation on the composite symbol
stream and provides a stream of OFDM symbols to a transmitter unit
(TMTR) 832. Transmitter unit 832 conditions (e.g., converts to
analog, filters, amplifies, and frequency upconverts) the OFDM
symbol stream and generates a modulated signal that is transmitted
from an antenna 834.
[0068] Controller 840 directs operation at base station 110x. A
memory unit 842 provides storage for program codes and data used by
controller 840. Controller 840 and/or a scheduler 844 allocate and
assign slots to the active MLCs.
[0069] FIG. 9 shows a block diagram of a wireless device 120x,
which is one of the wireless devices in system 100. An antenna 912
receives the modulated signal transmitted by base station 110x and
provides a received signal to a receiver unit (RCVR) 914. Receiver
unit 914 conditions, digitizes, and processes the received signal
and provides a sample stream to an OFDM demodulator 916. OFDM
demodulator 916 performs OFDM demodulation on the sample stream to
obtain received pilot symbols and received data and overhead
symbols. A controller 940 derives a channel response estimate for
the radio link between base station 110x and wireless device 120x
based on the received pilot symbols. OFDM demodulator 916 further
performs coherent detection (e.g., equalization or matched
filtering) on the received data and overhead symbols with the
channel response estimate and provides to a symbol demultiplexer
(Demux)/dechannelizer 920 "detected" data and overhead symbols,
which are estimates of the transmitted data and overhead symbols,
respectively.
[0070] Controller 940 obtains an indication of (e.g., user
selection for) one or more MLCs to be received by the wireless
device. Controller 940 then determines the slot assignment for each
selected MLC based on either (1) the composite overhead information
sent at the start of the current super-frame or (2) the embedded
overhead information sent in the MAC capsule header received in a
previous super-frame for the MLC. Controller 940 then provides a
control signal to dechannelizer 920. Dechannelizer 920 performs
demultiplexing of the detected data and overhead symbols for each
symbol period based on the control signal and provides one or more
detected data symbol streams and/or a detected overhead symbol
stream to RX data processor 930. RX data processor 930 processes
(e.g., symbol demaps, deinterleaves, and decodes) the detected
overhead symbol stream in accordance with the mode used for the
composite overhead data and provides decoded overhead data to
controller 940. RX data processor 930 also processes each detected
data symbol stream for each MLC of interest, in accordance with the
mode used for that stream, and provides a corresponding decoded
data stream to a data sink 932. In general, the processing at
wireless device 120x is complementary to the processing at base
station 110x.
[0071] Controller 940 also directs operation at wireless device
120x. A memory unit 942 provides storage for program codes and data
used by controller 940.
[0072] The techniques described herein for transmitting overhead
information may be implemented by various means. For example, these
techniques may be implemented in hardware, software, or a
combination thereof. For a hardware implementation, the processing
units at a base station may be implemented within one or more
application specific integrated circuits (ASICs), digital signal
processors (DSPs), digital signal processing devices (DSPDs),
programmable logic devices (PLDs), field programmable gate arrays
(FPGAs), processors, controllers, micro-controllers,
microprocessors, other electronic units designed to perform the
functions described herein, or a combination thereof. The
processing units at a wireless device may also be implemented
within one or more ASICs, DSPs, and so on.
[0073] For a software implementation, the techniques described
herein may be implemented with modules (e.g., procedures,
functions, and so on) that perform the functions described herein.
The software codes may be stored in a memory unit (e.g., memory
unit 842 and/or 942) and executed by a processor (e.g., controller
840 and/or 940). The memory unit may be implemented within the
processor or external to the processor.
[0074] The previous description of the disclosed embodiments is
provided to enable any person skilled in the art to make or use the
present invention. Various modifications to these embodiments will
be readily apparent to those skilled in the art, and the generic
principles defined herein may be applied to other embodiments
without departing from the spirit or scope of the invention. Thus,
the present invention is not intended to be limited to the
embodiments shown herein but is to be accorded the widest scope
consistent with the principles and novel features disclosed
herein.
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