U.S. patent application number 14/090726 was filed with the patent office on 2014-03-20 for apparatus and method for transmitting and receiving data streams in wireless system.
This patent application is currently assigned to Samsung Electronics Co., Ltd.. The applicant listed for this patent is Samsung Electronics Co., Ltd.. Invention is credited to Ismael Gutierrez, Alain MOURAD.
Application Number | 20140079004 14/090726 |
Document ID | / |
Family ID | 43736660 |
Filed Date | 2014-03-20 |
United States Patent
Application |
20140079004 |
Kind Code |
A1 |
MOURAD; Alain ; et
al. |
March 20, 2014 |
APPARATUS AND METHOD FOR TRANSMITTING AND RECEIVING DATA STREAMS IN
WIRELESS SYSTEM
Abstract
A method for transmitting data including a plurality of data
streams in a wireless system is described. The method includes
receiving one or more data streams; mapping the received data
streams to at least one logical frame; mapping the logical frame to
more than one additional physical slot; configuring each of the
more than one additional physical slot includes signaling
information for receiving the data streams; and transmitting at
least one superframe including the more than one additional
physical slot.
Inventors: |
MOURAD; Alain; (Middlesex,
GB) ; Gutierrez; Ismael; (Middlesex, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd. |
Gyeonggi-do |
|
KR |
|
|
Assignee: |
Samsung Electronics Co.,
Ltd.
Gyeonggi-do
KR
|
Family ID: |
43736660 |
Appl. No.: |
14/090726 |
Filed: |
November 26, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13353857 |
Jan 19, 2012 |
|
|
|
14090726 |
|
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Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04L 5/0037 20130101;
H04N 21/236 20130101; H04L 27/2605 20130101; H04L 5/0091 20130101;
H04W 28/06 20130101; H04L 27/2656 20130101; H04L 5/0048 20130101;
H04L 5/0007 20130101 |
Class at
Publication: |
370/329 |
International
Class: |
H04L 5/00 20060101
H04L005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 19, 2011 |
GB |
1100901.6 |
Oct 26, 2011 |
GB |
1118537.8 |
Claims
1. A method for transmitting data including a plurality of data
streams in a wireless system, comprising: receiving one or more
data streams; mapping the received data streams to at least one
logical frame; mapping the logical frame to more than one
additional physical slot; configuring each of the more than one
additional physical slot includes signaling information for
receiving the data streams; and transmitting at least one
superframe including the more than one additional physical
slot.
2. The method of claim 1, wherein the data streams are broadcast
data streams for a handheld terminal.
3. The method of claim 1, wherein the signaling information
includes P1, L1-pre and L1-post information, and the L1-post
information includes L1-config and L1-dynamic information.
4. The method of claim 3, wherein the P1 and L1-pre information is
allocated in every additional physical slot.
5. The method of claim 3, wherein when the logical frame is
transmitted at one radio frequency, the L1-config and L1-dynamic
information is arranged at a head of each of the logical
frames.
6. The method of claim 3, wherein when consecutive logical frames
form a logical channel, the logical frame is transmitted at more
than one radio frequency, and there is more than one logical
channel, one logical channel is set as a primary logical channel,
the remaining logical channel is set as a secondary logical
channel, the L1-config and L1-dynamic information is arranged at a
head of each of logical frames of the primary logical channel, and
the L1-dynamic information is arranged at a head of each of logical
frames of the secondary logical channel.
7. The method of claim 6, wherein the logical channel includes the
superframe, the superframe includes a plurality of logical frames,
and the L1-config information is additionally arranged at a head of
each of superframes of the secondary logical channel.
8. The method of claim 3, wherein the L1-pre information includes
any one of L1_OFFSET_TIME indicating the number of cells between
L1-pre and L1-post, NGH_SLOT_INTERVAL indicating an interval
between two consecutive Next Generation Handheld (NGH) slots,
L1_OFFSET_FREQ indicating a Radio Frequency (RF) frequency of a
next slot carrying a logical frame of a Logical NGH Channel (LNC)
transmitted in a current slot, and LNC_OFFSET_DELTA indicating a
gap between the current slot and the next slot carrying a logical
frame of the current LNC.
9. An apparatus for transmitting data including a plurality of data
streams in a wireless system, comprising: a first gateway for
mapping data streams to one or more logical channels each including
at least one logical frame and mapping the logical frame to more
than one additional physical slot; one or more first modulators for
generating data to be included in the additional physical slot
based on the logical channels; a physical slot agent for
distributing the data to be included in the additional physical
slot to one or more second modulators; and the one or more second
modulators for modulating and transmitting at least one superframe
including the additional physical slot, wherein the physical slot
includes signaling information for receiving the data streams.
10. The apparatus of claim 9, wherein the data streams are
broadcast data streams for a handheld terminal.
11. The apparatus of claim 9, wherein the signaling information
includes P1, L1-pre and L1-post information, and the L1-post
information includes L1-config and L1-dynamic information.
12. The apparatus of claim 11, wherein the P1 and L1-pre
information is allocated in every additional physical slot.
13. The apparatus of claim 11, wherein when the frame is
transmitted at one radio frequency, the L1-config and L1-dynamic
information is arranged at a head of each of the logical frame.
14. The apparatus of claim 11, wherein when consecutive logical
frames form a logical channel, the logical frame is transmitted at
more than one radio frequency, and there is more than one logical
channel, one logical channel is set as a primary logical channel,
the remaining logical channel is set as a secondary logical
channel, the L1-config and L1-dynamic information is arranged at a
head of each of logical frames of the primary logical channel, and
the L1-dynamic information is arranged at a head of each of logical
frames of the secondary logical channel.
15. The apparatus of claim 11, wherein the L1-pre information
includes any one of L1_OFFSET_TIME indicating the number of cells
between L1-pre and L1-post, NGH_SLOT_INTERVAL indicating an
interval between two consecutive Next Generation Handheld (NGH)
slots, L1_OFFSET_FREQ indicating a Radio Frequency (RF) frequency
of a next slot carrying a logical frame of a Logical NGH Channel
(LNC) transmitted in a current slot, and LNC_OFFSET_DELTA
indicating a gap between the current slot and the next slot
carrying a logical frame of the current LNC.
16. A method for receiving data including a plurality of data
streams in a wireless system, comprising: receiving at least one
superframe including more than one additional physical slot;
forming at least one logical frame using data allocated to the
additional physical slot; obtaining a location of the additional
physical slot of each of the logical frame; obtaining signaling
information for receiving data stream included in the additional
physical slot; and receiving data streams allocated to the
additional physical slot using the signaling information.
17. The method of claim 16, wherein the data streams are broadcast
data streams for a handheld terminal.
18. The method of claim 16, wherein the forming the logical frame
further comprises: extracting data streams from the logical
frame.
19. The method of claim 16, wherein the signaling information
includes P1, L1-pre and L1-post information, and the L1-post
information includes L1-config and L1-dynamic information.
20. The method of claim 19, wherein the P1 and L1-pre information
is allocated in every additional physical slot.
21. The method of claim 19, wherein when the logical frame is
transmitted at one radio frequency, the L1-config and L1-dynamic
information is arranged at a head of each of the logical frame.
22. The method of claim 19, wherein when consecutive logical frames
form a logical channel, the logical frame is transmitted at more
than one radio frequency, and there is more than one logical
channel, one logical channel is set as a primary logical channel,
the remaining logical channel is set as a secondary logical
channel, the L1-config and L1-dynamic information is arranged at a
head of each of logical frames of the primary logical channel, and
the L1-dynamic information is arranged at a head of each of logical
frames of the secondary logical channel.
23. The method of claim 22, wherein the logical channel includes
the superframe, the superframe includes a plurality of logical
frames, and the L1-config information is additionally arranged at a
head of each of superframes of the secondary logical channel.
24. The method of claim 22, wherein the L1-pre information includes
any one of L1_OFFSET_TIME indicating the number of cells between
L1-pre and L1-post, NGH_SLOT_INTERVAL indicating an interval
between two consecutive Next Generation Handheld (NGH) slots,
L1_OFFSET_FREQ indicating a Radio Frequency (RF) frequency of a
next slot carrying a logical frame of a Logical NGH Channel (LNC)
transmitted in a current slot, and LNC_OFFSET_DELTA indicating a
gap between the current slot and the next slot carrying a logical
frame of the current LNC.
25. An apparatus for receiving a broadcast frame in a wireless
system, comprising: a logical channel selector for receiving at
least one logical frame mapped to more than one additional physical
slot and extracting signaling information included in the
additional physical slot; and one or more Radio Frequency (RF)
selector for receiving an RF signal and obtaining data streams
allocated to the additional physical slot using the signaling
information extracted by the logical channel selector.
26. The apparatus of claim 25, further comprising one or more
decoding unit for decoding data that is transmitted in a physical
slot.
27. The apparatus of claim 25, wherein the signaling information
includes P1, L1-pre and L1-post information, and the L1-post
information includes L1-config and L1-dynamic information.
28. The apparatus of claim 27, wherein the P1 and L1-pre
information is allocated in every additional physical slot.
29. The apparatus of claim 27, wherein when the logical frame is
transmitted at one radio frequency, the L1-config and L1-dynamic
information is arranged at a head of each of the logical frame.
30. The apparatus of claim 27, wherein when consecutive logical
frames form a logical channel, the frame is transmitted at more
than one radio frequency, and there is more than one logical
channel, one logical channel is set as a primary logical channel,
the remaining logical channel is set as a secondary logical
channel, the L1-config and L1-dynamic information is arranged at a
head of each of logical frames of the primary logical channel, and
the L1-dynamic information is arranged at a head of each of logical
frames of the secondary logical channel.
31. The apparatus of claim 27, wherein the L1-pre information
includes any one of L1_OFFSET_TIME indicating the number of cells
between L1-pre and L1-post, NGH_SLOT_INTERVAL indicating an
interval between two consecutive Next Generation Handheld (NGH)
slots, L1_OFFSET_FREQ indicating a Radio Frequency (RF) frequency
of a next slot carrying a logical frame of a Logical NGH Channel
(LNC) transmitted in a current slot, and LNC_OFFSET_DELTA
indicating a gap between the current slot and the next slot
carrying a logical frame of the current LNC.
Description
PRIORITY
[0001] This application is a Continuation Application of U.S.
patent application Ser. No. 13/353,857, which was filed in the U.S.
Patent and Trademark Office on Jan. 19, 2012, and claims priority
under 35 U.S.C. .sctn.119(a) to Patent Applications filed in the
United Kingdom Intellectual Property Office on Jan. 19, 2011 and
assigned Serial No. GB 1100901.6, and Oct. 26, 2011 and assigned
Serial No. GB 1118537.8, the content of each of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to wireless systems,
and more specifically, but not exclusively, to a method and
apparatus relating to transmission and reception of data streams in
digital video broadcast systems.
[0004] 2. Description of the Related Art
[0005] A wireless system, such as a digital video broadcasting
system, may transmit data in the form of a sequence of frames
arranged in a frame structure. A digital video broadcasting system
generally complies with digital video broadcasting standard, and
the digital broadcasting standard may include, for example, Digital
Video Broadcasting (DVB), Advanced Televisions Systems Committee
(ATSC), Integrated Services Digital Broadcasting (ISDB) or Digital
Multimedia Broadcasting (DMB). Each frame typically comprises a
preamble section and a data section, the preamble section and the
data section being time-multiplexed. The data section may include
data that is arranged in the form of a number of data streams that
may be referred to as physical layer pipes (PLP). A physical layer
pipe may carry, for example, a service such as a video channel
provided to a user. Data or data streams from the frames may be
received using signaling information. The signaling may be referred
to as physical layer signaling, or Layer 1 (L1) signaling. The
signaling may indicate a modulation or coding scheme to be used for
receiving data, and it may indicate sections of a data field to be
decoded, or indicate information needed for data reception such as
the location of a data stream within the data section.
[0006] Referring to the Digital Video Broadcasting (DVB) standard,
Digital Video Broadcast standard frame structures may provide
physical slots within the DVB physical frame structure, which are
reserved for future use. For example, Digital Video Broadcasting
Terrestrial 2.sup.nd generation (DVB-T2), the terrestrial
broadcasting standard, has a superframe structure including
multiple frames, and includes slots that do not carry DVB-T2
signals, in the superframe or each frame. It is referred to as
Future Extension Frame (FEF) slots. In other words, FEF slots may
be provided in addition to the parts of the frame structure which
are for transmission of signals intended for reception by
conventional fixed Digital Video Broadcast receivers.
[0007] Referring to Digital Video Broadcasting Next Generation
Handheld (DVB-NGH) for reception of mobile broadcasting, which is
currently being established, digital video broadcasting systems may
provide for the transmission of signals specifically intended for
reception by mobile broadcasting receivers and hand held devices.
Such signals may be, for example, of lower bandwidth and have more
robust modulation and coding than signals intended for reception by
fixed receivers.
[0008] There have been proposals to use the additional physical
slots, such as the FEF slots, for the transmission of signals
intended for reception by handheld receivers. Typically, the
additional physical slot includes signaling information for
reception of data transmitted on the physical slots or frames.
[0009] However, such a scheme, in which the signaling information
is arranged in each of the physical slots, may suffer from limited
capacity, due to short physical slot duration and high signaling
overhead. Furthermore, such a scheme may be limited in terms of
achievable statistical multiplexing gain, due to the limited
capacity that may be achieved.
SUMMARY OF THE INVENTION
[0010] An aspect of the present invention provides an apparatus and
method for transmitting and receiving data streams in a wireless
system, to mitigate the problems with the prior art systems.
[0011] Another aspect of the present invention provides an
apparatus and method for transmitting and receiving data streams in
a wireless system, to solve the problems that the conventional
scheme may suffer from limited capacity, due to short physical slot
duration and high signaling overhead, and may be limited in terms
of multiplexing gain, due to the limited capacity.
[0012] In accordance with one aspect of the present invention,
there is provided a method for transmitting data including a
plurality of data streams in a wireless system. The method includes
receiving one or more data streams; mapping the received data
streams to at least one logical frame; mapping the logical frame to
more than one additional physical slot; configuring each of the
more than one additional physical slot includes signaling
information for receiving the data streams; and transmitting at
least one superframe including the more than one additional
physical slot.
[0013] In accordance with another aspect of the present invention,
there is provided an apparatus for transmitting data including a
plurality of data streams in a wireless system. The apparatus
includes a first gateway for mapping data streams to one or more
logical channels each including at least one logical frame and
mapping the logical frame to more than one additional physical
slot; one or more first modulators for generating data to be
included in the additional physical slot based on the logical
channels; a physical slot agent for distributing the data to be
included in the additional physical slot to one or more second
modulators; and the one or more second modulators for modulating
and transmitting at least one superframe including the additional
physical slot, wherein the physical slot includes signaling
information for receiving the data streams.
[0014] In accordance with further another aspect of the present
invention, there is provided a method for receiving data including
a plurality of data streams in a wireless system. The method
includes receiving at least one superframe including more than one
additional physical slot; forming at least one logical frame using
data allocated to the additional physical slot; obtaining a
location of the additional physical slot of each of the logical
frame; obtaining signaling information for receiving data stream
included in the additional physical slot; and receiving data
streams allocated to the additional physical slot using the
signaling information.
[0015] In accordance with yet another aspect of the present
invention, there is provided an apparatus for receiving a broadcast
frame in a wireless system. The apparatus includes a logical
channel selector for receiving at least one logical frame mapped to
more than one additional physical slot and extracting signaling
information included in the additional physical slot; and one or
more Radio Frequency (RF) selector for receiving an RF signal and
obtaining data streams allocated to the additional physical slot
using the signaling information extracted by the logical channel
selector.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The above and other aspects, features and advantages of
certain exemplary embodiments of the present invention will be more
apparent from the following description taken in conjunction with
the accompanying drawings, in which:
[0017] FIG. 1 is a schematic diagram showing physical slots
according to an embodiment of the present invention;
[0018] FIG. 2 is a schematic diagram showing mapping of a logical
frame to physical slots in an embodiment of the present
invention;
[0019] FIG. 3 is a schematic diagram showing logical channels
according to an embodiment of the present invention;
[0020] FIG. 4 is a schematic diagram showing mapping of signaling
information to logical channels according to an embodiment of the
present invention;
[0021] FIG. 5 is a schematic diagram showing mapping of a primary
channel and a secondary logical channel to physical slots in an
embodiment of the present invention;
[0022] FIG. 6 is a schematic diagram showing FEF slots on three RF
channels in an embodiment of the present invention;
[0023] FIG. 7 is a schematic diagram showing an arrangement of
three logical channels according to an embodiment of the present
invention;
[0024] FIG. 8 is a schematic diagram showing shifting of physical
slots according to an embodiment of the present invention;
[0025] FIG. 9 is a schematic diagram showing an arrangement of two
logical channels according to an embodiment of the present
invention;
[0026] FIG. 10 is a schematic diagram showing NGH frames in an
embodiment of the present invention;
[0027] FIG. 11 is a schematic diagram showing the alignment of NGH
superframe configuration and T2 superframe configuration in an
embodiment of the present invention;
[0028] FIG. 12 is a table showing the L1-Pre signaling field in an
embodiment of the present invention;
[0029] FIG. 13 is a table showing the L1-config signaling field in
an embodiment of the present invention;
[0030] FIG. 14 is a table showing the L1-dynamic and Inband
signaling fields in an embodiment of the present invention;
[0031] FIG. 15 is a flow diagram showing a receiver in an
embodiment of the present invention;
[0032] FIG. 16 is a schematic diagram showing a network and
transmitter architecture in an embodiment of the present
invention;
[0033] FIG. 17 is a schematic diagram showing a repeater in an
embodiment of the present invention; and
[0034] FIG. 18 is a schematic diagram showing a repeater in an
embodiment of the present invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0035] Embodiments of the present invention will be described in
connection with the Digital Video Broadcasting Terrestrial 2.sup.nd
generation (DVB-T2) system or the Digital Video Broadcasting Next
Generation Handheld (DVB-NGH) system now under establishment, by
way of example. However, it will be understood that this is by way
of example only and that other embodiments may involve other
wireless broadcast systems or unicast/mulitcast systems;
embodiments of the present invention are not limited to the use for
transmission of digital video signals.
[0036] As illustrated in FIG. 1, existing Digital Video Broadcast
frame structures, e.g., DVB-T2 system, may provide for FEF slots
2a, 2b, 2c within a transmission sequence 1 of a radio frequency
channel. The FEF slots may also be referred to as FEF parts or FEF
sections. The FEF slots are physical slots, which are not used for
transmission of DVB-T2 signals and may be reserved for future use.
In FIG. 1, DVB-T2 data is transmitted in T2-frames 8, and the FEF
slots may be provided in addition to the parts of the frame
structure which are for transmission of signals intended for
reception by conventional DVB-T2 receivers.
[0037] There have been proposals to use the FEF slots, in which the
existing DVB-T2 data may not be transmitted, for the transmission
of signals intended for reception by handheld receivers, e.g.,
DVB-NGH receivers. In this case, all or some of the FEF slots are
used for transmission of NGH signals, and these are called NGH
slots 4. The NGH slots may also be referred to as NGH parts and NGH
sections. Although the following description will be made in
conjunction with FEF slots, NGH signals will be transmitted
actually in NGH slots which are all or some of the FEF slots. The
simplest example of such a scheme is illustrated as "Option 1" 3 in
FIG. 1. It can be seen that the NGH signals are divided and
transmitted as a series of logical NGH frames (6a to 6e) on a
logical NGH channel 3, each logical frame 6a, 6b, 6c being
transmitted within a separate FEF slot 2a, 2b, 2c. In other words,
one logical NGH frame is allocated to every FEF slot. NGH frame
including NGH data is called logical NGH frame (LNF) because it is
physically transmitted in FEF slot or NGH slot which is not greater
than the FEF slot. The logical NGH frame, NGH frame and LNF will be
used in the same meanings. In addition, a channel over which the
NGH frames are continuously transmitted is referred to as a logical
NGH channel (LNC). The logical NGH channel, NGH channel and LNC
will be used in the same meanings. Physically, the logical NGH
channel may be arranged and transmitted in a plurality of
frequencies and times, and will be described in detail in
conjunction with embodiments of the present invention. As shown in
FIG. 1, the logical NGH frame 6a may occupy a NGH slot 4 that may
be smaller, but no larger, than the FEF slot 2a. Each logical NGH
frame has associated signaling information; this would be typically
transmitted as a preamble 7a, 7b, 7c in each FEF slot. However,
such a scheme, i.e., a scheme of transmitting each logical NGH
frame in each FEF slot and arranges signaling information in each
logical NGH frame, may suffer from limited capacity, due to high
signaling overhead.
[0038] In a first embodiment of the present invention, as
illustrated by FIG. 1 as "Option 2" 5 and by FIG. 2, a logical NGH
frame 27 is configured in two or more FEF slots 2a, 2b and 2c, so
that the length of the logical NGH frame 27 may be greater than the
length of a FEF slot 2a, 2b. In other words, one logical NGH frame
may be configured by combining the data transmitted in two or more
FEF slots, and this may be expressed as FEF bundling. In this case,
the ratio of signaling information for signaling overhead and data
capacity may be reduced compared to the case where the length of
logical NGH frame is limited to the length of FEF slot, like
"Option 1" 3. In the case where they are transmitted over multiple
Radio Frequency (RF) channels, the two or more FEF slots may be
within a transmission sequence for different radio frequency
channels and the logical frames may be arranged to have a constant
length, even though the length of FEF slots may vary between the
radio frequency channels. The length of the logical NGH frames may
be set to an optimum value in terms of a tradeoff between signaling
overhead and data acquisition time for a receiver requesting access
to the additional data.
[0039] The signals intended for reception by NGH receivers
typically comprise several data streams, that may be physical layer
pipes (PLPs), and a first set of these data streams may be mapped
onto a series of logical NGH frames typically. As illustrated in
FIG. 1, in an embodiment of the invention, a given logical NGH
frame 27 may be transmitted in at least parts of two or more FEF
slots, also referred to as FEF parts. In the case of logical NGH
frame j of FIG. 1, it can be seen that this logical NGH frame j is
transmitted in three FEF slots, which may be referred to as
additional physical slots 12a, 12b, and 12c. The length of a
logical NGH frame may accordingly be independent of the length of
an FEF slot, so that the logical NGH frame may be arranged to have
a lower proportion of signaling information to data capacity than
would be the case (Option 1) if the length of the logical NGH frame
were limited by the length of an additional Physical slot (FEF
slot). As illustrated by FIG. 2, a given logical NGH frame 27,
typically comprises signaling information and data, the signaling
information typically comprising "P1" 20a, 20b and "L1-pre" 22a,
22b, "L1-config" 24, and "L1-dynamic" 25. The "P1", "L1-pre",
"L1-config", and "L1-dynamic" will be understood with reference to
details of "ETSI EN 302 755" (DVB-T2 standard document) unless
stated otherwise in the specification. The "L1-config" and
"L1-dynamic" in all will be referred to as "L1-post". The data
sections 23, 26 and 28 comprise physical layer pipes. The physical
layer pipes may overlap in the time domain and be multiplexed in
the frequency domain, for example.
[0040] In the first embodiment of the present invention, P1 and
L1-pre signaling information 20a, 22a, 20b, 22b, etc. may be
transmitted in every additional physical slot 2a, 2b, etc. which
may be FEF slot, and the signaling information indicates a start of
the slot and includes physical layer parameters to be used when the
transmission in each additional physical slot is received. L1-post
signaling information 24, 25, etc. such as L1-dynamic and L1-config
may not be transmitted in every additional physical slot, because
basically it is transmitted on an NGH frame basis. Data 18a, 18b,
18c, 18d, 18e, and 18f such as payload data may be transmitted
within each additional physical slot.
[0041] The L1 config is a section in which L1-config signaling
information is transmitted, and the L1-config signaling information
typically includes information that is valid for each frame of the
superframe including multiple frames, and is the same for each
logical NGH frame of the superframe. The L1-dynamic information
typically varies from logical NGH frame to logical NGH frame, and
includes information for decoding the physical layer pipe within
the logical NGH frame. Typically, L1-dynamic information may
include a start address of the physical layer pipe, for
example.
[0042] The signaling information is arranged taking into account
the compatibility and signaling overhead with the existing system,
and the content of the signaling information. For example,
referring to FIG. 2, P1 and L1-pre information is transmitted in
every NGH slot. This is to take into account the compatibility with
the existing DVB-T2 system. On the other hand, the L1-config
information and the L1-dynamic information are arranged in the
location of a relevant symbol in NGH slot, taking into account the
start or end of the logical NGH frame. Although not shown, if the
signaling information of L1-config information is small in
quantity, the L1-config information may be transmitted in every NGH
slot together with P1 and L1-pre information. L1-pre information
may be arranged in the location corresponding to the start or end
of the logical NGH frame if the existing system (T2) receivers and
the NGH receivers have no problem in receiving existing signal (T2
signals) and NGH signals, respectively, even though the L1-pre
information is not arranged in every NGH slot. Each of the
L1-config information and the L1-dynamic information may be deleted
depending on the content of its signaling information.
[0043] In embodiments of the present invention, NGH slots within a
sequence of additional physical slots (FEF slots) are bundled
together as described above to form a logical NGH channel for
transmitting a set of data streams, and a series of logical NGH
logical frames within a logical channel are mapped to the sequence
of additional physical slots, for example, FEF slots. The sequence
of logical NGH frames may be transmitted over one or more RF
channels. If the sequence is transmitted over a single RF channel,
then a tuner needs not to re-tune between additional physical slots
in order to receive the sequence of logical NGH frames. However, if
the sequence 30a . . . 30h of a logical NGH channel or a series of
logical NGH frames is transmitted over multiple radio frequencies
RF1, RF2, RF3 and RF4, i.e., is chosen to fall on several radio
frequency channels, as in a second embodiment illustrated by FIG.
3, then a logical channel with a larger capacity may be formed, and
also the logical channel may benefit from frequency diversity. A
single channel may be formed having a large data capacity resulting
from the data capacity of the sequence of additional physical
slots, rather than multiple channels each with a smaller data
capacity, so that services may be multiplexed onto the single
channel with a resulting gain in terms of statistical
multiplexing.
[0044] As shown in FIG. 3, a guard interval is provided between
each additional physical slot and each preceding additional
physical slot of the sequence 30a . . . 30h, to allow re-tuning of
a tuner between the reception of each of the additional physical
slots, so that a single tuner may be used to receive the sequence.
For example, after receiving 30a over RF1 using a single tuner, it
is possible to tune to RF2 before receiving 30b.
[0045] As also shown by FIG. 3, a second logical NGH channel can be
formed by mapping a second set of data streams onto a second series
of logical NGH frames and mapping the second sequence of logical
NGH frames to a second sequence of additional physical slots, for
example FEF slots 32a . . . 32h. As shown in FIG. 3, the second
sequence of additional physical slots 32a . . . 32h may not include
any of the first sequence of said additional physical slots 30a . .
. 30h, so that the second logical channel may make use of further
additional physical slots beyond those that may be received using a
single tuner. Further logical channels may be provided by further
sequences of additional physical slots.
[0046] In cases where more than one logical channel is provided,
one of the logical channels may be designated as a primary logical
channel, which may be referred to as a Primary NGH Channel (PNC)
and the others as secondary logical channels, which may be referred
to as Secondary NGH Channels (SNC). The primary logical channel may
be formed from physical slots that are selected for greater
robustness, greater capacity, shorter intervals between physical
slots, and/or lower overhead, and the primary logical channel may
be used for first acquisition of a signal by a receiver or for fast
zapping. The primary logical channel may convey L1-config
information to enable acquisition of a service provided by a
secondary logical channel. In other words, the primary logical
channel serves as an entry point to a service provided by a
secondary logical channel. Thus, a receiver requiring access to
services carried on a secondary logical channel may first receive
the primary logical channel, which will provide L1-config
information to enable acquisition of a service provided by a
secondary logical channel or further logical channels. As a result,
it may only be necessary to convey L1-config information in every
frame of the primary logical channel, and not in every frame of a
secondary logical channel, reducing signaling overhead and
increasing data capacity of the second and further channels.
[0047] The L1-config information may indicate a configuration of
one or more of said plurality of data streams, and may be carried
by each logical frame that is mapped to the primary logical
channel, to reduce the delay in accessing a data stream. The
L1-config information may also be carried by the first logical
frame in a superframe of a secondary logical channel, because there
may be system parameters that may be changed in units of a
superframe which is a set of multiple frames. Even in this case, it
is not necessary to be carried by other logical frames in the
secondary logical channel except for the primary logical channel,
to reduce the signaling overhead.
[0048] In an embodiment of the invention, the L1-config information
may include information relating to the sequences of additional
physical slots forming the primary and secondary logical
channels.
[0049] By contrast, L1-dynamic information may be included in each
logical frame of the primary and secondary logical channels, but
the L1-dynamic information may only carry information relating to
the respective logical channel, reducing signaling overhead.
[0050] The arrangement of configuration information (for example
L1-config) and dynamic signaling information (for example
L1-dynamic) within primary and secondary channels is illustrated by
FIG. 4. It can be seen that the L1-dynamic signaling is carried by
each of all logical channels including the PNC and SNC, whereas the
L1-config signaling is carried primarily by the PNC logical
channel, and the dashed lines indicate that the L1-config signaling
is carried by only a subset of the frames (e.g., the first frame of
the superframe of SNC) of the SNC logical channels. FIG. 4 also
illustrates that the PNC and SNC logical channels each include FEF
slots on a number of RF channels.
[0051] A third embodiment corresponds to a method of generating
multiple logical channels, unlike the second embodiment of
generating one logical channel. FIG. 5 illustrates how a sequence
of data frames 52 forming a primary logical channel and a sequence
of data frames 54 forming a secondary logical channel may be mapped
to within FEF slots on a three RF channels 56, 57, 58.
[0052] In the case of a primary logical channel 52, L1-config
information and L1-dynamic information are arranged in the location
of a symbol in an NGH slot related to the location of the start or
end of each logical NGH frame. On the other hand, in the case of a
secondary logical channel 54, only L1-dynamic information is
arranged in the location of a symbol in an NGH slot related to the
location of the start or end of each logical NGH frame. In the
example of FIG. 5, first, second and third NGH slots of the primary
logical channel 52 are transmitted at RF1 56, RF2 57 and RF3 58,
respectively, and the first, second and third NGH slots include
part of an (i-1)-th logical frame, all of an (i)-th logical frame,
and part of an (i+1)-th logical frame. Boundaries among the
(i-1)-th, (i)-th and ((i+1)-th logical frames may be determined
from the location of L1-config information and L1-dynamic
information. In addition, first, second and third NGH slots of the
secondary logical channel 54 are transmitted at RF3 58, RF1 56 and
RF2 57, respectively, and the first, second and third NGH slots
include part of an (i-1)-th logical frame of the secondary logical
channel and part of an (i)-th logical frame thereof. The boundary
between the (i-1)-th and (i)-th logical frames may be determined
from the location of the L1-dynamic information.
[0053] Typically, each logical frame for a given superframe has the
same number of Orthogonal Frequency Division Multiplexing
Symbols.
[0054] Digital video broadcast systems may include repeaters or gap
fillers to provide coverage in regions where propagation from a
main transmitter antenna is poor. In an embodiment of the
invention, physical slots forming at least one logical channel are
selected for retransmission at a repeater or gap filler in
preference to the other received data, such as Digital Video
Broadcasting signals intended for reception by fixed receivers.
This may improve the efficiency of the repeater, since only data
received within the additional physical slots may need to be
re-transmitted, as the additional data may be intended for
reception by handheld devices. The handheld devices may require a
stronger signal than is required for reception of the first data
transmitted within the physical frame structure which may be
intended for reception by fixed receivers that may have rooftop
antennas. Furthermore, only a single tuner may be required at the
repeater for each logical channel.
[0055] The number of transmitted logical channels may depend on the
maximum number of additional physical slots, e.g. FEF slots, that
are transmitted simultaneously. This is illustrated by FIG. 6 and
FIG. 7. In FIG. 6, it can be seen that sequences of FEF slots may
be available on three RF channels 60, 62, 64 and it can be seen
from the lower time line 66 that there may be between 0 and a
maximum `3` of FEF slots transmitted simultaneously. In other
words, although the structure of the superframe used at each RF was
the same in the embodiments which have been described so far, each
RF has a different structure of superframe in an embodiment of FIG.
6. Under this structure, each RF may be different in the number,
length and location of FEF slots allocated thereto, and each RF may
be different even in the ratio of data (e.g., DVB-T2 data and
DVB-NGH data) transmitted at the entire RF to data (e.g., DVB-NGH
data) transmitted in FEF slots, or the ratio of DVB-T2 data to
DVB-NGH data. In FIG. 7, it can be seen that three logical channels
70, 72, 74 may be formed from these FEF slots, in the frequency
hopping manner illustrated. As can be seen in FIG. 7, the maximum
number of logical channels is related to the number of overlapping
FEF slots. Each logical channel, as described before, may form PNC
and SNC.
[0056] As illustrated by FIG. 8, timing offsets of the FEF slots on
a set of RF channels 80, 82, 84, 86 may be arranged to reduce the
overlap between FEF slots, so that the FEF slots are distributed
more evenly in time domain, so that the capacity of each logical
channel may be increased, while the number of logical channels
required to make use of available additional slots may be reduced.
As shown in FIG. 8, the maximum number of FEF slots transmitted
simultaneously may be reduced to two by appropriate timing
offsetting between the four RF channels shown, so that two logical
channels 90, 92 may be formed as shown in FIG. 9, as primary 94 and
secondary 96 logical channels.
[0057] Embodiments of the invention will now be described in more
detail.
[0058] In prior art systems, due to the high capacity requirements
of conventional DVB-T2 services intended primarily for reception by
fixed receivers, including High Definition (HD) and three
dimensional (3D) services, the amount of bandwidth per RF channel
used for NGH is typically quite low (FEF_length<20% in most
cases). In other words, the more the T2 frames to be transmitted,
the less the FEFs available for transmission of DVB-NGH data,
because of the large amount of data used in the conventional
DVB-T2. As a result, the number of NGH services per T2 RF channel
may be very low (3-5 TV and radio programs), limiting the gain
achievable by Statistical Multiplexing. Additionally, the padding
overhead that is introduced at the end of each frame may become
more significant the shorter the frame is. In order not to affect
the zapping time (time to receive a new service) of T2 services,
short FEFs may be used (FEF_INTERVAL.ltoreq.2). In this case, the
NGH L1 signaling overhead may become quite significant. When the
number of PLPs is increased, the main overhead may be caused by
L1-Post signaling information (L1-config and L1-dynamic).
[0059] Embodiments of the invention address these problems by
bundling data transmitted in FEF slots to provide one or more
logical NGH channels. A first embodiment of the invention
introduces a new frame format, as illustrated by as "Option 2" 5 in
FIG. 1. A P1 symbol indicates the start of the NGH slot. Otherwise,
the conventional T2 receivers may not receive T2 signals.
[0060] "Option 1" 3 in FIG. 1 represents the situation in the prior
art, in which a NGH frame is transmitted within a FEF slot. In this
case, a DVB-T2 frame is encapsulated within the FEF.
[0061] In an embodiment of the invention, a NGH frame is not
equivalent to a FEF and is not equivalent to a DVB-T2 frame. In
this arrangement, an NGH frame is not aligned with the FEF part,
also referred to as a FEF slot, and the NGH signal does not have to
use the full FEF; the portion where NGH signals are transmitted in
the FEF part is referred to in FIG. 1 as the NGH slot. Data in FEF
parts are then bundled (time-domain bundling) to form the NGH
frames as shown in FIG. 1. Typically, all NGH frames may have the
same number of OFDM symbols, and all frames may have the same
capacity. Typically, L1-Pre is transmitted immediately after the P1
symbol. P2 symbols (which may have special pilot patterns) may be
used to carry the L1-Pre information. Typically only one P2 symbol
may be enough for this. As in DVB-T2, L1-Pre information may carry
minimum information about the frame format, resulting in a decrease
in signaling overhead of L1-Pre information. With L1-Pre
information, the NGH receiver knows the start/end of the NGH
physical slot, as well as when the next NGH frame is scheduled and
its duration. This may simplify the detection of L1-config and
L1-dynamic (L1-Pre contains a pointer to the next L1-config and
L1-dynamic). Typically, L1-config and L1-dynamic may be transmitted
starting at any OFDM symbol of the FEF part or NGH slot, but may
not be present in the FEF part or NGH slot.
[0062] As illustrated by FIG. 3, data included in FEF parts on
different T2 RF channels can be bundled (frequency domain bundling)
increasing the capacity of the logical NGH channel. However, in
case of overlapping FEFs, i.e., if FEF is present on multiple RFs
at a certain time, only the signal included in one FEF part among
the FEFs on multiple RFs may be recovered when a single tuner is
used for reception. Each data service is provided by a single
logical NGH channel, so that only one tuner is required to recover
the service. Next, the concept of multiple logical NGH channels
will be described. If there are multiple logical NGH channels,
instead of signaling all the services as proposed with Time
Frequency Slicing (TFS), which may cause excessive overhead, one
logical NGH channel may be selected as Primary NGH Channel (PNC)
and the rest as Secondary NGH Channel (SNC). In an embodiment of
the invention, L1-Pre contains information about in which RF the
primary NGH channel is carried. L1-config is mapped onto to the
primary channel and at the beginning of each superframe in each
secondary channel. L1-dynamic may be mapped to all logical channels
but may contain only the signaling for the services carried by such
logical NGH channel. The primary NGH channel may then be
responsible for providing the fast zapping and acquisition, and may
be considered the entry point to any service transmitted in any of
the secondary NGH channels. If only one tuner is required at the
receiver side, the bandwidth assigned to one logical NGH channel is
typically not higher than that of a T2 RF channel.
[0063] In embodiments of the invention, the FEFs may be bundled,
and this may be signalled in various scenarios as follows.
[0064] (1) Firstly, a single T2 RF channel may be used, and any T2
superframe structure may be used (FIG. 2). Alternatively, multiple
T2 RF channels may be used. In this case, there may be several
options as follows. (2) All RF channels of multiple T2 RF channels
may have the same T2 superframe structure, and a single logical NGH
channel may be provided (FIG. 3). (3) All RF channels of multiple
T2 RF channels may have the same T2 superframe structure, and
multiple logical NGH channels may be provided (FIG. 4). In each of
the above cases, the T2 frame length and FEF interval may be
flexible and may be adapted to provide an optimum configuration of
the NGH channel.
[0065] As a further alternative, (4) different T2 superframes
structures may be provided among multiple T2 RF channels and
multiple logical NGH channels (FIGS. 6 to 9). In this case, the
degree of freedom for logical channels may be acquired by time
shift in the T2 superframes. If only the NGH signal independent of
T2 transmission is transmitted, the NGH slots can be chosen freely,
also introducing FEF parts within the NGH signal.
[0066] FIG. 2 illustrates the case of a single T2 RF channel. In
this case, FEF bundling operates only in the time domain. In this
case, no constraints may be required on the existing T2 signal.
[0067] In the case of multiple T2 RF channels as in FIG. 3, with
the same T2 superframes structures in all T2 RFs and single logical
NGH channel, the case may represent the simplest scenario for
frequency domain-considered FEF bundling over multiple T2 RF
channels. In order to bundle all T2 RF channels in a single logical
NGH channel, the condition of following Equation (1) should be
met:
N.sub.RF(T.sub.SLOT+T.sub.SW).ltoreq.(T.sub.FEF+FEF_INTERVAL.times.T.sub-
.F) (1)
where T.sub.SW is the time required by the receiver to tune to a
new frequency. N.sub.RF is the number of RFs, and T.sub.SLOT and
T.sub.FEF are a length (time) of SLOT and a length (time) of FEF,
respectively. FEF_INTERVAL is the number of T2 frames between two
FEFs, and TF is a length (time) of a T2 frame. The maximum logical
NGH channel capacity (bit rate) may be achieved when both sides of
the expression are equal.
[0068] In the case of multiple T2 RF channels, with the same T2
superframes structures in all T2 RFs and multiple logical NGH
channels, when previous condition is not met, it may be inferred
that during some intervals two NGH slots are simultaneously
allocated to T2 RF channels or not enough time is available to
switch between frequencies. In order to require only one tuner at
the receiver, embodiments of the invention may employ multiple
logical NGH channels. In the case of multiple logical channels, the
previous condition may be updated to Equation (2) below:
N.sub.RF(T.sub.FEF+T.sub.SW).ltoreq.N.sub.LNC(T.sub.FEF+FEF_INTERVAL.tim-
es.T.sub.F) (2)
where N.sub.LNC is the number of logical NGH channels
(1.ltoreq.N.sub.LNC.ltoreq.N.sub.RF).
[0069] FIG. 5 illustrates the case of multiple T2 RF channels, with
the same T2 superframes structures in all T2 RFs and multiple
Logical NGH channels.
[0070] FIG. 6 illustrates the case of Multiple T2 RF channels, with
different T2 superframes structures among T2 RFs and multiple
logical NGH channels.
[0071] In this more general case, NGH percentage bandwidth (BW %)
may be different across T2 RF channels, with different superframe
structures (i.e. T2 frame length, FEF interval and FEF length) and
non-synchronized T2 RFs. In this case, as illustrated by FIG. 6,
the number of multiple logical NGH channels N.sub.LNC may be
computed as the maximum number of overlapping FEFs, for example
N.sub.LNC=3 in FIG. 6.
[0072] FIG. 7 illustrates the case of multiple T2 RF channels, with
different T2 superframes structures among T2 RF channels and
multiple logical NGH channels, as in FIG. 6. Typically, the first
logical NGH channel to be allocated is the PNC 72. A main function
of the PNC may be to enable fast zapping, therefore, the PNC may be
the logical channel with the largest capacity. This may also help
to compensate the additional overhead of the PNC. In the example of
FIG. 7, the FEFs are assigned to the PNC in a way that the
frequency diversity gain is maximized (PNC may use all RF
frequencies). In other embodiments, in order to allocate FEFs,
other criteria may be used. For example, increased robustness for
the PNC (e.g. allocating a lower frequency to PNC) may be other
criteria, and the PNC may be allocated to a single RF to avoid
switching between channels. A lower difference in frequency between
consecutive FEFs, overhead, etc. may be other criteria. In an
embodiment of the invention, after the PNC has been allocated,
remaining FEFs are allocated to the SNC(s). Multiple combinations
may be possible as long as the minimum switching time between RF
carriers is guaranteed. In the example of FIG. 7, FEFs are
connected in order to average the bit rate between logical NGH
channels and also to increase frequency diversity thanks to
frequency hopping, but other criteria could be introduced, in a
similarly manner as for the PNC allocation.
[0073] In the previous example, the FEFs on different RF channels
occur mostly simultaneously (i.e. N.sub.LNC.fwdarw.N.sub.RF). In an
embodiment of the invention, the T2 superframes may be shifted to
reduce the number of logical NGH channels, increasing the capacity
of each logical NGH channel. Increasing the capacity of each NGH
carrier may increase the potential gain of statistical multplexing.
Since the superframe format from each RF is known, the period of
the multiple logical NGH channel set may be computed. This period
T.sub.b is useful since optimisation algorithms may work with that
span.
[0074] FIG. 8 illustrates an algorithm to bundle the FEFs as an
embodiment of the invention. In this case, there are multiple T2 RF
channels and multiple logical NGH channels, and the multiple TF RF
channels have different T2 superframe structures. The following
algorithm may be employed to obtain the shift to be applied to each
RF.
[0075] (1) A guard time is inserted before each FEF. This guard
time is determined taking into account the tuning time, which is
time required for the tuner to start decoding of the data
transmitted on the switched RF channel after switching the RF
frequency. This guard time is represented by the black boxes in
FIG. 8.
[0076] (2) The RF channels may be sorted according to the FEF
length from the largest FEF to the shortest FEF. In case of equal
FEF length, the RF with the largest FEF_INTERVAL is placed
first.
[0077] (3) For a given FEF (e.g., the first FEF in the superframe),
each i.sup.th RF may be shifted so that the given FEF is
transmitted after the FEF of the (i-1)-th RF.
[0078] (4) The number of simultaneous FEFs N.sub.LNC(t) is
obtained. At a first point in the algorithm, for the highest value
of N.sub.LNC(t), it is referred as n.sub.LNC, and the overlapping
FEFs N.sub.OV are obtained. The N.sub.OV overlapping FEFs are
sorted from longer FEFs to shorter FEFs. The longest N.sub.OV-1
FEFs among the sorted FEFs are then evaluated for shifting. The
shifting will be carried out if the max(N.sub.LNc(t)) after
shifting is less than max(N.sub.LNC(t)) before shifting. If
n.sub.LNC is reduced, the next step is to go to said first point in
the algorithm. If not, then the end of the algorithm may be
reached. In other words, a process is repeated, which includes
calculating the number of FEFs overlapping in the time domain,
shifting the remaining FEFs except of the shortest FEF to reduce
the calculated number of overlapping FEFs, and shifting once again
the remaining FEFs except for the shortest FEF among the shifted
FEFs.
[0079] As a result, the FEFs may be mapped to the resulting logical
NGH cannels as illustrated in FIG. 9. It can be seen that, as
previously discussed, FEFs are mapped to a PNC and SNC(s). Due to
the shifts applied, several adjacent FEFs may be mapped to the same
PNC/SNC. This may be beneficial in terms of power consumption since
the FEF may be transmitted/received for each PNC/SNC as bursts. In
an embodiment of the invention, the FEFs are assigned to the
logical NGH channels such that the differences in bit rate between
the logical NGH channels are minimized while maximizing the number
of explored RF frequencies is maximized (i.e. higher frequency
diversity). The final FEF mapping may be signalled in the L1-config
transmitted in the PNC.
[0080] FIG. 10 illustrates how the NGH frames may be defined. In
this example, NGH frames are defined in terms of the number of OFDM
symbols in each NGH frame, which is constant for all the NGH frames
in one NGH superframe. The NGH frame capacity may be kept constant
from NGH frame to NGH frame, however, due to the bursty nature of
the transmission, there may be variations on the instantaneous
throughput. However, different logical NGH channels may have
different number of OFDM symbols per frame. In the PNC, L1-config
and L1-dynamic are typically transmitted at the beginning of each
NGH frame, whereas in the SNCs, typically L1-config and L1-dynamic
are transmitted at the beginning of a first NGH frame of the
superframe and only L1-dynamic is transmitted at the beginning of
the remaining NGH frame, except for the first NGH frame of the
superframe.
[0081] FIG. 11 illustrates how the NGH superframes and T2
superframes may be aligned. A change in NUM_T2_FRAMES,
NUM_DATA_SYMBOLS, FEF_LENGTH, or FEF_INTERVAL creates a new
superframe structure (hereinafter, the superframe structure may be
abbreviated as SuperFrame Structure (SFS)). Since FEF-bundling
operates based on the structures of the existing multiple T2 RF
channels, any change in the structure of the T2 RF channels causes
a change in NGH configuration, making it necessary to reconfigure
the NGH configuration. Each reconfiguration may need to be
signalled and propagated to all the receivers. For this fast
reconfiguration, L1-Pre may allow L1-config and L1-dynamic in any
logical NGH channel (PNC and SNC). This option may be used during
SFS reconfiguration avoiding possible micro-cuts in case the
receivers had to switch to PNC and then came back to the SNC.
However, these changes do not happen frequently, and are usually
scheduled during late hours to minimize the impact at the
receivers. Therefore, the extra signaling required may be
negligible. Apart from this possible limitation, NGH superframe may
be defined freely.
[0082] In existing T2 signaling, the signaling fields that
determine the frame structure (and the FEF length) are included
L1-Pre signaling and L1-Post signaling, and the L1-Post information
includes L1-config information and L1-dynamic information. The
signaling fields that determine the frame structure in the DVB-T2
transmission system include NUM_T2_FRAMES (the number of T2 frames
per superframe) and NUM_DATA_SYMBOLS (the number of OFDM symbols
per T2 frame), which are transmitted in L1-Pre, and include
FEF_LENGTH (length of FEF) and FEF_INTERVAL (the number of
T2-frames between two FEFs), which are transmitted in L1-Post. In
the present invention, to transmit NGH data in FEF, part or all of
the signaling fields should be changed, added or deleted.
[0083] FIG. 12 illustrates an example of signaling information
included in L1-pre in an embodiment of the invention. As
illustrated in FIG. 12 as an embodiment of the invention for NGH,
under the proposed frame structure in which the T2/NGH frame is
transmitted after being multiplexed on the same frame structure, it
may be efficient to signal the frame structure in a single field
(i.e., L1-Pre). This may be achieved by transmitting information
such as interval between FEFs, interval between NGH slots and the
number of OFDM symbols per NGH frame, in L1-Pre. For example,
NGH_SLOT_INTERVAL transmitted in L1-Pre indicates an interval
between two consecutive NGH slots. The longest interval may be
obtained when FEF_INTERVAL=256 and the longest frame length is used
(250 ms), and in this case, the longest NGH_SLOT_INTERVAL may be
given as 64 seconds. The NGH_SLOT may be limited to 250 ms. The
number of OFDM symbols per NGH frame may also be also signalled,
and information about the number of symbols may be transmitted in
the NUM_SYMBOLS_NGH_FRAME field of L1-Pre. L1-Pre may indicate the
position of the next L1-config and L1-dynamic (the start position
of next NGH frame). The position information may only be necessary
during the initial scanning or zapping. L1-Pre may also be used to
transmit information (PNC_RF_FREQUENCY) about the RF of the Primary
Logical NGH Channel (PNC) that is present closest. This may inform
a receiver of the position of L1-config during initial scanning or
zapping of the transmitter. The position of L1-config should be
informed for decoding of desired service mapped to PNC/SNC.
[0084] FIG. 13 illustrates an example of signaling in L1-config in
an embodiment of the invention. In L1-config, the number of
associated RF channels as well as the number of logical NGH
channels (NUM_LNC) is indicated. In L1-config, the T2 frame/NGH
slot structure for every T2 RF is signalled and transmitted. The
shift between first FEFs of each T2 superframe may be known in the
NGH_SLOT_OFFSET field existing in a loop for each RF. This loop
provides information to make it possible to know the T2 superframe
structures of all associated T2 RF channels. A second loop signals
how the FEFs are mapped to the logical NGH channels (only one cycle
is signalled, and the number of cycles per superframe is an integer
number). Each PLP is then assigned to one logical NGH channel. In
this example, since NGH frames are not aligned with the FEFs, the
FIRST_FRAME_IDX refers then to the first NGH frame, not to the
first NGH slot. In the case that FEF bundling is not used,
L1-config remains close to prior art (DVB-T2, etc.) signaling, so
that there may be little or no overhead.
[0085] FIG. 14 illustrates an example of signaling in L1-dynamic
and Inband Signaling in an embodiment of the invention. RF_IDX
field is no longer needed in L1-dynamic. This is because reach
Physical Layer Pipe (PLP) is allocated to one logical NGH channel,
and this information has already been transmitted in L1-config
information. Note that RF_IDX field is replaced by SLOT_IDX.
SLOT_IDX may allow the receiver to know in which position of the
FEF_bundling sequence is, and therefore, knowing the SLOT(s) that
will be used by each logical NGH channel in the future. In the case
of SNC with the different components mapped into different PLPs,
the whole set of PLPs should be mapped to the same logical NGH
channel so that only one tuner may be required.
[0086] FIG. 15 is a flow chart showing the operation of a receiver
in an embodiment of the invention, showing steps at the receiver to
discover the logical NGH channels and their structure. This process
may be carried during initial scanning or zapping when the
structure of the target logical NGH channel is unknown or during
changes in the superframe structure.
[0087] Referring to FIG. 15, a receiver searches a received signal
for a P1 symbol and decodes the P1 symbol in step 1501, making it
possible to determine if the frame is an NGH signal. For example,
if an S1 field made of 3 bits of a P1 symbol has a specific value,
it is possible to determine whether an FEF, to which the P1
presently belongs, is transmitting an NGH signal. Time and
frequency synchronization of the receiver and synchronizations for
the frame boundary are obtained in the P1. If it is determined that
the P1 is not an NGH signal, the receiver returns to step 1501.
However, if it is determined that the P1 is an NGH signal, the
receiver determines in step 1505 whether the NGH signal is an
NGH-only channel. If it is an NGH-only channel on which the T2
signal and the NGH signal are not transmitted together but only the
NGH signal is transmitted, the receiver finds a logical NGH channel
in step 1521. In the case of the NGH-only channel, all of its
channels have NGH data because T2 signals are not transmitted
together. So, this channel is not expressed as a logical NGH
channel, but may be expressed as an NGH channel only. However, if
it is not an NGH-only channel, the receiver decodes L1-Pre in step
1507, and determines in step 1509 whether the RF position
PNC_RF_FREQ where PNC exists is the current frequency. In other
words, the receiver determines whether PNC exists in the current
frequency. If PNC_RF_FREQ is not the current frequency, the
receiver sets the current frequency to PNC_RF_FREQ in step 1511,
and returns to step 1501. In other words, to receive an RF signal
where PNC exists, the receiver sets the current frequency to
PNC_RF_FREQ, and receives the RF signal.
[0088] However, if PNC_RF_FREQ is the current frequency in step
1509, the receiver waits L1-config to start in step 1513. If
L1-config starts, the receiver decodes L1-config and L1-dynamic in
sequence in steps 1515 and 1517, obtains information (e.g.,
NGH_SLOT_INTERVAL, NUM_SYMBOLS_SLOT, NGH_SLOT_OFFSET,
LNC_SLOT_PERIOD, RF_IDX, etc.) about a configuration of the logical
NGH channel in step 1519, and then finds a (logical) NGH channel on
which the desired service is transmitted, in step 1521.
[0089] FIG. 16 illustrates a network and transmitter architecture
as an embodiment of the invention. The network and transmitter
architecture in FIG. 16 includes a T2 network 1610, an FEF agent
1620, and an NGH network 1630. In realization, the FEF agent may be
included in a separate processor or an existing processor on the
NGH network or the T2 network. Physically, the NGH network may be
configured as one physical entity by being combined with the
existing T2 network. The T2 network 1610 in FIG. 16 is not so
different in architecture from the existing T2 network and
transmitter, so its description will be omitted.
[0090] In this embodiment, at least two new elements are
introduced: the FEF bundler 1622 and FEF distributor 1624. The FEF
bundler 1622 may be in charge of creating the logical NGH channels
and assign the FEFs to the logical NGH channels. The FEF bundler
1622 may assign the physical slots to the logical channels
according to an embodiment of the present invention. An input of
the FEF bundler 1622 may be the superframe configuration used in T2
RF channels of the T2 network 1610. The FEF bundler 1622 may be
connected to at least one NGH network 1630, but it could be
connected to multiple NGH networks since the bandwidth allocation
may be done by the FEF agent 1620. Once the logical channels are
defined, the FEF bundler 1622 may inform the NGH gateway 1632 of
the number of logical channels, the bit rate of each, the frame
duration in each, which physical slots are assigned to each logical
channel and the timing of each, etc. In other words, the FEF
bundler is in charge of collecting information for creating logical
NGH channels, and creating logical NGH channels based on the
collected information.
[0091] As illustrated in FIG. 16 in an embodiment of the invention,
the FEF distributor 1624 typically receives all NGH slots, and then
may pad the rest of the FEF part with null data, and may send each
NGH slot to the T2 modulator 1612-1, . . . , 1612-n. The FEF
distributor may change packets to send each NGH slot to the T2
modulator, and in this case, may create T2-Modulator Interface
(T2-MI) packets. The input to the FEF distributor 1624, in this
example, is the IQ samples corresponding to every physical slot,
and the NGH logical channel configuration defined by the FEF
bundler 1622. The output of the FEF distributor 1624 may be a T2-MI
packet containing the input IQ samples and adding the signaling
required to address the modulator that should transmit the
modulated physical slot, and the padding cells (the basic unit of
OFDM resources in which the frequency and time domains are
considered) in case the FEF is not fully used. The T2-MI packet may
then be transmitted into the T2 distribution network 1614. In this
example, NGH BB modulators 1634-1, . . . , 1634-n generate a BB NGH
signal and NGH modulators 1636-1, . . . , 1636-n generate a RF NGH
signal transmitted in NGH-only RF channels. This allows reusing a
part of the T2 modulator 1612-1, . . . , 1612-n in charge of
upconverting the FEF IQ cells to the corresponding frequency. This
may help decreasing the cost of the NGH network, in particular when
the NGH signal is transmitted in the FEF part.
[0092] FIG. 17 and FIG. 18 illustrate examples of repeaters, gap
fillers or receivers in an embodiment of the invention. Amplifying
the T2 signal may be a waste of power in situations where it is
primarily the NGH coverage that need to be improved (e.g. in
indoors, tunnels, public transport, etc.), since for conventional
fixed receivers, the T2 signal may typically be received from
roof-top antennas with much better reception conditions. In an
embodiment of the invention, a potentially much more efficient
scheme is provided where the signal that is repeated is only the
NGH signal. This may be achieved if the repeaters operate on a
logical NGH channel basis. Since NGH slots of a logical channel may
occur more frequently than FEF parts of a single T2 signal, the
repeater may operate more continuously (less gaps between bursts).
The number of tuners required by each repeater may be reduced since
1.ltoreq.N.sub.LNC.ltoreq.N.sub.RF (i.e. one tuner per logical NGH
channel). As illustrated by FIG. 17, an additional module (logical
NGH channel selector) may be in charge of retrieving the L1
signaling related to each logical NGH channel that needs to be
repeated. The L1 signaling is then used to switch between the FEFs
forming the logical NGH channel. An independent amplify and forward
RF chain may be required for each logical NGH channel that is
repeated. As illustrated by FIG. 18, in case of a more advanced
repeater, the NGH signal may be decoded before forwarding it to the
receivers (a so-called Decode-Amplify-Forward scheme). However,
since decoding the signal may introduce a greater delay, the
restored NGH signal may be transmitted in a different frequency to
avoid interference to the original RF channel. For the same reasons
previously explained in relation to the temporal overlapping of the
logical NGH channel, each NGH channel should be transposed to a
different frequency. If FEFs in which NGH signals are transmitted
are transmitted only on one RF, a single RF channel selector
instead of multiple RF channel selectors may be sufficient.
[0093] Although not illustrated, if the amplifying and forwarding
units, the RF combiner, and the antenna are excluded from the
structure of the repeater and gap filler shown in FIGS. 17 and 18,
it is a structure of a receiver for receiving signals transmitted
under the structure of the present invention. In other words, the
receiver obtains information about FEFs in which NGH signals are
transmitted, by means of the logical NGH channel selector, selects
an RF channel on which the FEFs are transmitted, by controlling the
RF channel selector based on the information, and decodes NGH
signals transmitted in FEFs by means of the decoding unit partially
shown in FIG. 18, finally obtaining NGH signals. Also, although not
illustrated, if the FEFs, in which the NGH signals are transmitted,
are transmitted only on one RF, a single RF channel selector
instead of multiple RF channel selectors may be sufficient.
[0094] As has been described, FEF bundling may tie together FEFs
both in time and frequency domains, and this may have benefits
including the following. In case of a single RF, FEF bundling may
help to reduce the L1 overhead since FEF length and NGH frame
duration independent, and may provide a gain in terms of time
diversity. In case of multiple RF, FEF bundling may also help to
reduce the L1 overhead since FEF length and NGH frame duration may
be independent since L1 Config may only be transmitted in the PNC
(SNC only on the first frame of the superframe). FEF bundling may
reduce the zapping time and FEF bundling may simplify the mapping
of the services since a single large capacity NGH channel is seen,
so that more services may be multiplexed increasing the statistical
multiplexing gain. If FEF bundling works over multiple RF carriers,
frequency hopping may bring additional frequency diversity, with
gains up to 4 dB or more in case of indoor or low mobility
scenarios. FEF bundling of the invention may not impose any
constraint to the T2 signal (e.g. minimum FEF length/NGH
bandwidth), nor degrade the T2 receiver's performance (e.g. zapping
time). Since no synchronization is required between the T2 RF
signals, FEF bundling may be used even when the T2 RFs are operated
by different broadcasters and the T2 RF could be transmitted from
different sites.
[0095] In an embodiment of the present invention, a different
approach to different signaling from some aspects of embodiments
described already will be described.
[0096] The concept of logical NGH channels typically defines
logical NGH channels (LNCs) including logical frames that are
mapped onto physical resources available in DVB system multiplex.
The physical resources may be referred to as additional physical
slots, each of which is a time slot in RF frequencies and has its
own bandwidth. So, one RF frequency will have its own configuration
in terms of the time slot and a period of the bandwidth. Different
configurations may be applied to different RF frequencies at one RF
frequency. LNCs may be mapped to physical resources, and a process
thereof is known as scheduling. This mapping is typically dynamic,
though it may be static in certain cases. The static case may
correspond to, for example, a case where the same configuration of
the time slot period and bandwidth is applied to all RF frequencies
and slots of the RF frequencies are synchronized, i.e., aligned in
time.
[0097] This dynamic mapping to the additional physical slots (e.g.,
physical resources) of the LNCs may be signalled by information
about LNC that may include physical slots of a first sequence, in
L1 signaling. The L1 signaling typically includes two parts: L1-Pre
(typically with a fixed length, i.e., fixed field size) and L1-post
(typically with a variable length), and may be transmitted in a
separate signaling section. In this case, it may be called
out-of-band signaling or out-of-band type signaling. In addition,
only the dynamic information about signaling of a desired PLP in
the next frame may be transmitted based on the in-band signaling,
i.e., the signaling information included in the data PLP of the
current frame. Typically, sending signaling data together with data
is called in-band signaling or in-band type signaling.
[0098] The L1-Pre part is fixed in length and value, for a given
superframe. In an embodiment of the present invention, logical
frames may be dynamically mapped to slots and the fixed length of
L1-pre may be preserved, but values of some mapping-related fields
are subject to change. In an embodiment of the present invention, a
receiver determines that some fields may vary, without considering
that L1-pre is a mere repetition from one frame of a superframe to
another frame. As to decoding for firmly maintaining L1-pre, in an
embodiment of the present invention, a soft decoding input may be
set as a value indicating that the fixed part has been known for
the sequence and/or superframe of physical layer slots. For
example, the fixed part, if necessary, may have Log Likelihood
Ratio (LLR) values which are set to infinity to ensure the better
decoding performance of the variable part.
[0099] In an embodiment of the present invention, another approach
to signaling is to signal the start of logical frame that may be a
Logical NGH Frame (LNF). As mentioned before, L1-pre part may have
a variable value for some fields, and in an embodiment of the
present invention, mapping-related signaling may be done in L1-pre
rather than partially in L1-pre and partially in L1-dynamic as done
in other embodiments of the present invention. The signaling
conveyed in in data streams that may be a data section (i.e.,
Physical Layer Pipes (PLPs) rather than a separate signaling
section, is called in-band signaling, and the in-band signaling may
be used by copying the L1-pre signaling. In addition, signaling for
PLP carrying in-band signaling may not be limited.
[0100] For example, signaling including information about physical
slots of a first sequence such as a logical channel may include the
following signaling in an embodiment of the present invention,
which is typically carried in both a first part of a preamble of
each additional physical slot such as L1-Pre and an L1-Post part
such as L1-dynamic. A signaling element L1_OFFSET_TIME for
signaling the number of cells between L1-pre (a) and L1-post (b)
exists in L1-Pre signaling. The L1-post (b) may be one associated
with the next logical frame, if no L1-post signaling exists in an
NGH slot where the L1-pre (a) exists. In this signaling element,
for example, 0xFFFF may mean that L1-post does not exist in the
current slot. L1-Pre signaling may have L1_OFFSET_FREQ that
indicates the current LNC as frequency of the possible next slot.
In other words, this indicates an RF frequency of the next slot
carrying a frame of LNC transmitted in the current slot. L1-dynamic
signaling has LNC_WINDOW indicating the number of slots mapped to
LNC before being signalled. Typically, this is for all LNCs in the
system. L1-dynamic signaling may also have a signaling element
T_DELTA indicating a slot allocated to the last/previous slot that
is signalled again for all LNCs in the system. In-band signaling
may include a signaling element PLP_LNC_WINDOW for signaling the
number of slots that are mapped to LNC and signalled. The in-band
signaling may include a signaling element PLP_T_DELTA indicating a
slot allocated to the signalled last/previous slot. These in-band
signaling elements are typically about LNC(s) related to a given
PLP.
[0101] In an embodiment of the present invention that uses another
access to signaling, an L1-Pre part may have an information element
similar to L1_OFFSET_TIME as described in connection with the
previous embodiment, and this may be re-named as
L1-OFFSET_NOF_CELLS, which signals the number of cells between
L1-pre and L1-post. Again, 0xFFFF may mean that L1-post does not
exist in the current slot. L1-Pre part may also have an information
element similar to L1_OFFSET_FREQ, which may be re-named as
LNC_OFFSET_FREQ, which signals a frequency of the next slot that
will carry the current LNC. In addition, an L1-Pre part may have an
information element LNC_OFFSET_DELTA indicating a gap between the
current slot and the next slot carrying a frame of the current LNC.
In an embodiment of the present invention, LNC_WINDOW and T_DELTA
signals are not included in L1-dyn as mentioned in connection with
the previous embodiments. This is because these are not typically
required. In an L1-Pre part of a physical slot, signaling elements,
e.g., signaling fields, give the receiver an access to the time and
frequency coordinates of the next slot carrying the start of the
same current and next LNCs. So, dynamic mapping of the current LNC
will be signalled slot by slot in L1-Pre, and typically specific
signaling is not required in L1-dynamic. In-band signaling may
include an information element PLP_LNC_OFFSET_FREQ for signaling
frequency of the next slot that will carry the current PLP in the
current LNC, and an information element PLP_LNC_OFFSET_DELTA for
signaling the relative time in the T periods as the next slot that
will carry the current PLP in the current LNC. The signaling
information elements of the in-band signaling fields may be
typically identical to the equivalent elements in L1-pre, and are
typically related only to each PLP in the current LNC. Typically,
in the in-band signaling mode, a receiver does not continuously
receive signaling in an L1-pre part.
[0102] The above embodiments are to be understood as illustrative
examples of the invention. It is to be understood that any feature
described in relation to any one embodiment may be used alone, or
in combination with other features described, and may also be used
in combination with one or more features of any other of the
embodiments, or any combination of any other of the embodiments.
Furthermore, equivalents and modifications not described above may
also be employed without departing from the scope of the invention,
which is defined in the accompanying claims.
* * * * *