U.S. patent application number 12/473399 was filed with the patent office on 2010-03-04 for contention-based feedback for multicast and broadcast service.
Invention is credited to Jeong Eun Lee.
Application Number | 20100058133 12/473399 |
Document ID | / |
Family ID | 41725328 |
Filed Date | 2010-03-04 |
United States Patent
Application |
20100058133 |
Kind Code |
A1 |
Lee; Jeong Eun |
March 4, 2010 |
CONTENTION-BASED FEEDBACK FOR MULTICAST AND BROADCAST SERVICE
Abstract
In some embodiments, a mobile device includes interface to
receive multicast and broadcast service (MBS) signals and to
transmit uplink signals, The mobile device also includes logic to
detect errors in the transmission of the received MBS signals and
provide negative acknowledge (NACK) signals indicating at least
some of the errors in a contention-based MBS feedback channel in at
least some of the uplink signals. Other embodiments are
described.
Inventors: |
Lee; Jeong Eun; (Portland,
OR) |
Correspondence
Address: |
Alan K. Aldous;c/o Intellevate, LLC
P.O.Box 52050
Minneapolis
MN
55402
US
|
Family ID: |
41725328 |
Appl. No.: |
12/473399 |
Filed: |
May 28, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61094357 |
Sep 4, 2008 |
|
|
|
Current U.S.
Class: |
714/748 ;
370/312; 714/799; 714/E11.024; 714/E11.131 |
Current CPC
Class: |
H04L 1/0001 20130101;
H04W 72/0453 20130101; H04W 72/046 20130101; H04L 1/1861 20130101;
H04L 1/1854 20130101; H04L 1/1877 20130101; H04B 7/2656 20130101;
H04W 84/047 20130101; H04B 7/2606 20130101; H04L 2001/0093
20130101 |
Class at
Publication: |
714/748 ;
714/799; 370/312; 714/E11.131; 714/E11.024 |
International
Class: |
H04L 1/08 20060101
H04L001/08; G06F 11/07 20060101 G06F011/07; G06F 11/14 20060101
G06F011/14 |
Claims
1. A mobile device comprising: an interface to receive multicast
and broadcast service (MBS) signals and to transmit uplink signals;
and logic to detect errors in the transmission of the received MBS
signals and provide negative acknowledge (NACK) signals indicating
at least some of the errors in a contention-based MBS feedback
channel in at least some of the uplink signals.
2. The mobile device of claim 1, wherein the logic selectively
provides the NACK signals.
3. The mobile device of claim 2, wherein the logic selectively
provides the NACK signals by performing a probability function in
response to the detected errors and provides at least one of the
NACK signals when the probability function yields one state and to
not provides the NACK signals when the probability function yields
another state.
4. The mobile device of claim 1, wherein the interface does not
also provide ACK feedback in uplinks signals.
5. The mobile device of claim 1, wherein the feedback channel
provides the NACK signals in short codewords which are subsets of a
larger number of bits.
6. The mobile device of claim 1, wherein the feedback channel
provides the NACK signals in long codewords.
7. The mobile device of claim 1, wherein the logic detects signal
strength of the MBS signals and chooses a particular feedback
channel based on the detected signal strength.
8. The mobile device of claim 1, wherein the MBS feedback channel
is a first MBS feedback channel, and wherein the logic provides
additional NACK signals on additional MBS feedback channels for
different sources, wherein the sources are at least one of MBS
services and MBS base station zones.
9. The mobile device of claim 8, further comprising memory to hold
instructions and wherein the logic uses the instructions to detect
the errors and selectively provide the NACK.
10. The mobile device of claim 1, wherein the errors relate to
quality of service.
11. A base station comprising: an interface to transmit multicast
and broadcast service (MBS) signals and to receive uplink signals;
and logic to control transmission and some content of the MBS
signals and to detect negative acknowledge (NACK) signals in
contention-based MBS feedback channels of the uplink signals and to
react to at least some of the NACK signals.
12. The base station of claim 11, wherein the NACK signals have
contents and depending on how many NACK signals are received in a
particular time and on the contents of the NACK signals, the logic
may respond by doing at least one of the following (1) making no
change in the MBS signals, (2) re-transmit some of the MBS signals,
and (3) causing link adaptation.
13. The base station of claim 12, wherein the logic selectively
responds either autonomously to the received NACK signals or by
first communicating with an MBS controller.
14. The base station of claim 13, wherein when the logic
communicates with an MBS controller, the BS forwards the collected
feedback information from the uplink signals to the MBS controller
and receives instructions from the MBS controller regarding how to
respond.
15. The base station of claim 14, wherein the MBS controller is not
included in base station.
16. The base station of claim 11, wherein the logic provides
signals to remote mobile stations and indicates to the remote
mobile stations whether they are to provide MBS feedback signals in
response to all detected errors or only in response to a portion of
detected errors.
17. A method comprising: receiving multicast and broadcast service
(MBS) signals; and detecting errors in the transmission of the
received MBS signals; providing negative acknowledge (NACK) signals
indicating at least some of the errors in a contention-based MBS
feedback channel in at least some of uplink signals; and
transmitting the uplink signals.
18. The method of claim 17, wherein the logic selectively provides
the NACK signals by performing a probability function in response
to the detected errors and provides at least one of the NACK
signals when the probability function yields one state and to not
provides the NACK signals when the probability function yields
another state.
19. The method of claim 17, wherein the MBS feedback channel is a
first MBS feedback channel, and wherein additional NACK signals are
provided on additional MBS feedback channels.
20. The method of claim 17, wherein the feedback channel provides
the NACK signals in short codewords.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
application 61/094,357, filed Sep. 4, 2008.
BACKGROUND
[0002] 1. Technical Field
[0003] Embodiments of the invention relate generally to providing
feedback for multicast and broadcast services.
[0004] 2. Background Art
[0005] In wireless communication systems, multicast and broadcast
service (MBS) refers to a multicast and broadcast service that
delivers services to subscriber stations (SS) and/or mobile
stations (MS). A benefit of MBS is that a fixed amount of resources
can be used to support a very large number of users, as does the TV
broadcast system. In single-base station (BS) access, the access to
a MBS service is provided by a BS, and in Multi-BS access, the
access is provided by multiple BSs which belong to a MBS Zone. BSs
within the MBS Zone may transmit synchronized signals to improve
the reliability of reception. The synchronized transmission may
require a MBS controller that coordinates multiple BSs.
[0006] There is currently not an acknowledge
(ACK)/negative-acknowledge (NACK) or channel quality indicator
(CQI) feedback mechanism in place for MBS since feedback overhead
may increase linearly with an increasing number of users. This is a
common problem with broadcast systems. MBS is mainly a downlink
(DL) service without any uplink (UL) allocation or with a
relatively small amount of UL used for such things as ranging,
registration, and handover. Current MBS systems do not take
advantage of link adaptation and hybrid automatic repeat request
(HARQ) gains. Rather, in a robust MBS system, packets are
transmitted blindly, and individual packet reception is not
monitored by the MBS system. A study suggests an 8-15% throughput
gain when link adaptation is used. A 3GPP long-term evolution (LTE)
standard included a description of using multimedia
broadcast/multicast service (MBMS) feedback for single-BS access,
but to the inventors' knowledge did not give details on how this
was to be accomplished.
[0007] The following are ways in which feedback can be sent in a
broadband wireless network.
[0008] 1. Contention-free dedicated feedback: HARQ feedback or CQI
feedback for unicast can be sent contention-free over a dedicated
channel. However, this does not provide a scalable solution for
MBS.
[0009] 2. Contention-free shared feedback (Power-based): Users send
feedback over the shared channel by sending the same code or bit
sequence, thus it is contention-free. Combined received power is
measured to tell if there was any feedback. This has been proposed
for MBS, but the contention-free shared feedback approach is not
appropriate for MBS feedback which is expected to have a large
number of feedbacks. In the proposal, both ACKs and NACKs are sent
in feedbacks. Energy detection is then used to determine an ACK to
NACK ratio to decide whether re-transmission or power/data-rate
adjustment is to be done.
[0010] 3. Contention-based shared channel: Users send feedback
contending over the shared channel. Time-domain, frequency-domain,
or spreading-code contention can be used. The design and operation
of contention-based channels such as code division multiplex access
(CDMA) type channels are well known. [0011] a. "Long-spreading"
(sometimes called long coding) contention channel: many users share
all frequencies. A pseudorandom code of a large length uses entire
channel allocated. As an example, long code-words may have 144
frequencies. WiMax and LTE standards include long spreading. [0012]
b. "Short-spreading" (sometimes called short coding) slotted
contention channel: A contention channel is divided into multiple
small slots with short codes within each slot. Upon contention,
each contender chooses a slot and a code within the slot. For
example, if a long codeword use 144 frequencies (sometimes called
tones), corresponding short pseudo noise code-words approach may
use 9 slots of 16 frequencies (sometime called tones). Using short
pseudo noise code-words results in a higher percentage of MSs being
detected as compared with using long code-words by reducing
interference among codewords. For example, if X MSs use long codes
using 144 tones, a certain percentage are likely to be accurately
detected by a base station. By contrast, if a first group of X/9
MSs use a first slot of 16 tones, and a second group of X/9 MSs use
a second slot of 16 tones, etc., the total percentage of accurately
detected MSs will be higher than in the long-spreading
situation.
[0013] As used herein, the term MBS is intended to be interpreted
broadly to include various multiple broadcast services including
MBMS (multimedia broadcast/multicast service), which is a term
sometime used in connection with LTE.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The invention will be understood more fully from the
detailed description given below and from the accompanying drawings
of embodiments of the invention which, however, should not be taken
to limit the invention to the specific embodiments described, but
are for explanation and understanding only.
[0015] FIG. 1 is a block diagram representation of an MBS system
including a WiMax network including a BS and several MSs according
to some embodiments of the invention.
[0016] FIG. 2 is a block diagram representation of a BS of FIG. 1,
according to some embodiments of the invention.
[0017] FIG. 3 is a block diagram representation of an MS of FIG. 1,
according to some embodiments of the invention.
[0018] FIG. 4 is a graphical representation of a long spreading
approach using an M tone code on frequency and time domains in
connection with some embodiments of the invention.
[0019] FIG. 5 is a graphical representation of a short spreading
approach using an M/N tone code on frequency and time domains in
connection with some embodiments of the invention.
[0020] FIG. 6 is a graphical representation of a downlink (DL)
subframe and an uplink (UL) subframe that may be used in some
embodiments of the invention.
[0021] FIG. 7 is a graphical representation of several base
stations and mobile stations used in illustrating some aspects of
some embodiments of the invention.
[0022] FIG. 8 is a graphical representation of mobile stations
receiving signals of different signal SINR/MCS levels from a base
station used in illustrating some aspects of some embodiments of
the invention.
[0023] FIG. 9 is block diagram representation of the mobile station
of FIG. 3 according to some embodiments of the invention.
DETAILED DESCRIPTION
[0024] The following disclosure describes scalable feedback
mechanisms for MBS. In some embodiments, these mechanisms are
contention-based and may be used to advance the state of the art in
link adaptation and HARQ and significantly improve coverage and
spectral efficiency for MBS. In some embodiments, these mechanisms
may be used in supporting more cell edge users, supporting more
video streams by using higher data rate modulation and coding
schemes (MCSs), and improving service quality by lowering packet
error rate (PER) through HARQ. By allowing the MBS link adaptation
and HARQ to work with NACK only feedback, the number of actually
transmitted feedbacks may be reduced.
[0025] The concept of contention-based feedback is not new in
uni-cast, but it has not been used for MBS feedback. Perhaps a
reason why contention-based MBS feedback has not been used is
because there is a conceptual mismatch between MBS and
contention-based feedback. The conceptual mismatch is that MBS is
directed to overall network system performance in contrast to
nominal contention-based feedback which distinguishes feedbacks
from each transmitting MS. Another possible reason for not
providing MBS feedback is that to the extent anyone thought about
it, the potentially very large number of ACKs from a large number
of MSs (the ACK explosion problem) may have seemed unworkable.
[0026] FIG. 1 illustrates an MBS system 10 in which
contention-based feedback channels are used to provide feedback for
MBS signals from MSs 56 to a BS 50. System 10 includes MBS content
providers 20 that provides MBS contents 24, which is provided to a
WiMax network 36. As an example, MBS contents 24 includes an
interactive service 26 (such as video conferencing), local
streaming 28 (such as television and associated advertisements),
and alert information 30 (such as emergency traffic information).
Of course, in other examples, not each of these is required and
other content sources could be included.
[0027] WiMax network 36 includes a network service provider (NSP)
38 having a connectivity service network (CSN) 40, and network
access provider (NAP) 46 having an access service network (ASN) 48.
ASN 50 includes at least one BS (typically many BSs) of which BS 50
is an example. Network 36 may include additional NSPs, CSNs, NAPs,
ASN, MSs, and BSs. These components of WiMax network 36 may be
compliant with WiMax standards such as IEEE 802.16e, 802.16Rev2,
and 802.16m and the WiMax Forum. Although the example of FIG. 1 is
illustrated with a WiMax network, it may be used with other
wireless systems using MBS signals. For example, it may be used
with LTE based systems.
[0028] Various mobile stations (MSs), for example, MSs 56-1, 56-2,
. . . 56-10, are attempting to receive wireless MBS signals from BS
50. In practice, there may be many more MSs interfacing with BS 50.
Over a particular range of time in the example, there is some error
in the transmission to MSs 56-1, 56-3, 56-5, and 56-10, while there
is not for the other MSs. As described in more detail below, MSs
that meet the feedback condition provide a feedback signal to
indicate an error to BS 50. In some embodiments, the feedback
signals include NACK signals, but not ACK signals. BS 50 may then
determine what, if any, changes should be made in response to the
feedback signal. For example, BS 50 could make no change,
retransmit signals, perform link adaptation, and/or do rate
shaping.
[0029] The system of FIG. 1, may be implemented as frequency domain
spreading, time domain spreading, or frequency-time domain
spreading or CQI based channel as described herein.
[0030] FIG. 2 illustrates details on of BS 50 according to some
embodiments, although various details of a BS are not illustrated
in FIG. 2. In other embodiments, the details may be different. FIG.
2 includes modules that may represent executing software and/or
firmware. BS 50 includes logic 62 that includes an MBS control
module 64 and feedback detecting and interpreting module 66. MBS
control 64 controls the providing of MBS signals to interface 68
and controls the transmission of signals by interface 68 through
antenna(s) 70. As examples, MBS control module 64 may provide
retransmission or link adaptation decisions. Feedback signals are
received by antenna(s) 70 and are provided to feedback interpreting
module 66. Various other signals are also received by antenna(s) 70
and provided to modules of BS 50 that are not specifically
illustrated in or discussed in connection with FIG. 2. As will be
explained in greater detail, feedback interpreting module 66
determines what, if any, changes should be made in response to the
feedback signal. Modules 64 and 66 may include hardware such as one
or more microprocessors, digital signal processors (DSPs) that
execute instructions from software and/or firmware stored in memory
74 or elsewhere. Modules 64 and 66 may share some or all hardware.
Interface 68 may include hardware that executes instructions.
[0031] FIG. 3 illustrates details of MS 56-1 according to some
embodiments, although various details of an MS are not illustrated
in FIG. 3. In other embodiments, the details may be different. FIG.
2 includes modules that may represent executing software and/or
firmware. An interface 84 receives MBS signals from antenna(s) 78
and provides feedback signals and other signals to a base station
such as BS 50 in FIGS. 1 and 2. In the example of FIG. 3, MS 56-1
includes logic 86 that includes an error detection module 88,
sample control module 90, and UL control module 94. Error detection
88 detects errors in the MBS signals. Merely as examples and not
requirements, an error may be detected by, for example, a checksum
being wrong, packets being out of order, or a delayed threshold
being exceeded. Sample control module 90 determines whether MS 56-1
will provide a feedback signal to a remote BS indicating
information about the error. For example, sample control module 90
could generate a random number and if the random number is less
than (or is less than or equals) a certain value, a feedback signal
may be provided and otherwise it would not be provided--or vice
versa (if the random number exceeds or equals to (or exceeds or
equals) a certain value, a feedback signal may be provided and
otherwise it would not be). The certain value can be pre-set or
dynamically updated from, for example, the base station. In some
embodiments, module 90 controls a type of feedback.
[0032] Feedback control module 94 controls the contents of an
uplink signal to be transmitted by interface 84 on antenna(s) 78.
The UL signal may include one or more feedback signals. Modules 88,
90, and 94 may include hardware such as one or more microprocessors
or digital signal processors that execute instructions of software
and/or firmware stored in memory 96 or elsewhere. Modules 88, 90,
and 94 may share some or all hardware. Interface 84 may include
hardware that executes instructions. Memory 74 and 96 may include
Flash memory and/or other types of memory.
[0033] FIG. 4 illustrates a M tone code long spreading approach on
frequency and time domains. Slots may be formed of a particular
number of frequencies f1, f2 . . . fM frequencies and time symbols.
FIG. 5 illustrates a short spreading approach on frequency and time
domain resources of N M/N tone codes each having M/N frequencies.
Slots 1, 2, . . . N correspond to different M/N tone codes.
[0034] In long spreading, users share the same channel. In short
spreading, users may select a particular channel randomly or
through another method. An advantage of a short spreading approach
is that there is a higher probability of detection. Although the
total number of MSs in the system may be the same with long
spreading, there are fewer MSs contenting in the slot used and more
MSs are detected than with long spreading, which may have a very
low detection rate with a high number of contending MSs.
[0035] FIG. 6 illustrates a DL subframe 112 and an UL subframe 114,
which are examples of WiMax frames. As an example, DL subframe 112
is used to transmit signals from a BS to an MS (such as BS 50 to MS
56-1). UL subframe 114 is used to transmit signals from an MS to a
BS (such as MS 56-1 and BS 50). The embodiments of the invention
are not restricted to the particular details of DL subframe 112
shown in FIG. 6. DL subframe 112 shows a preamble, UL map, DL map,
FCH, and MBS OFDMA region as possibilities. UL subframe 114 may be
used to carry various signals including fields MBS 1 . . . MBS n-1,
MBS n, which may represent different feedback channels. The
different feedback channels may correspond to different MBS
services. For example, one feedback channel may correspond to
sending feedback to service 26 of FIG. 1 and another channel may
correspond to sending feedback a particular one of local streaming
28. As shown in FIG. 6, MBS n further comprising slots 1, 2, . . .
N 116, which in some embodiments correspond to slots 1, 2, . . . N
of the short coding approach of FIG. 5. Thus, in the example of
FIG. 6, short coding is used for the feedback channel MBS n. As
discussed therein, other coding choice could be used. Other
messages may be included in the DL and UL subframes.
[0036] In some embodiments, different feedback channels are used
for providing feedback for different services. In other
embodiments, feedback for different services can be provided over
the same channel. In some embodiments, groups of base stations are
in a zone of base stations, and different channels can be used for
different zones. In some embodiments, some channels are used for
different services and other channels are used for different
zones.
[0037] A scalable and efficient feedback solution is desirable
because of the large number of potential MSs in MBS systems. By
using contention-based feedback for an MBS system, the number of
feedbacks may be estimated by resolving contending code-words. In
order to further enhance the detection performance, false detection
probability may be reduced because in some situations, what matters
is `how many`, not `who sent what`. Further, allowing MBS link
adaptation and HARQ to work with NACK only feedback reduces the
number feedbacks compared with ACK. In some embodiments, the NACK
signals are provided by only a portion of the MSs because if there
is too much contention, the probability of detection is reduced.
Sampling may be used in which an MS sends NACK based on a network
configured feedback transmission probability. For example, the
receiver sends feedback only when its drawn random number is less
than the feedback transmission probability.
[0038] In some embodiments, the contention-based MBS feedback works
as follows. An MBS feedback contention channel may be allocated
using either the "long-spreading" or the "short-spreading"
approach. Still other coding approaches are discussed below. The
invention is not restricted to allocating a different feedback
channel for each MBS service or allocating a feedback channel for
all services. In the case of Multi-BS access, feedback channel
allocation across BSs may be either identical or non-overlapping in
terms of time-frequency allocation. Identical channel allocation
could allow user's movement between cells without signaling.
[0039] Upon detection of a packet reception failure (such as
through error detection module 88 in FIG. 3), a receiver (such as
MS 56-1) sends NACK-only feedback over the contention channel (in
long-spreading) or over a slot in the contention channel (in
short-spreading). The receiver might choose to not send a NACK
based on a NACK feedback reduction policy. The feedback reduction
policy may be either pre-configured or dynamically configured, and
transmitted either by unicast or multicast/broadcast. This policy
may be set on a per BS basis or shared among multiple BSs. The
invention is not restricted to any particular way to select the
slot for short-spreading. Some examples of slot selection include
random selection and "sticky contention."
[0040] The number of feedbacks may be estimated by resolving
code-words received and a feedback reduction policy if any. The
total number of the receivers may be known in other means such as a
counting mechanism used in 3GPP (3.sup.rd Generation Partnership
Project). Feedbacks may be counted either at each BS or at the MBS
controller that coordinates MBS functions across BSs by forwarding
feedback responses from a BS in order to avoid double counting of
the same responses.
[0041] HARQ retransmission and modulation and coding scheme (MCS)
adaptation algorithms may be applied based on the feedback
estimation. For example, the first frame may be sent with a
particular MCS. Based on the percentage of the NACKs, the packet
may be retransmitted and/or sent using higher or lower MCS in the
next scheduled frame. The retransmission delay, maximum
retransmissions, the rate at which it adapts MCS level may
vary.
[0042] Contention-based systems allow better estimation of the
number of feedbacks than contention-free based approach by
resolving contention between received codewords.
[0043] In some embodiments, the above-described MBS feedback design
works for both Single_BS access and Multi-BS access. In Single-BS
access which is comprised of only one cell in FIG. 7, the access to
a MBS service is provided by a single BS, and in Multi-BS access
which is comprised of multiple cells in FIG. 7, the access is
provided by multiple BSs that transmit synchronized MBS signals to
MSs resulting in improved reception reliability. In Multi-BS
access, an MBS controller 130 coordinates the synchronized
transmission. Controller 130 may be in CSN 40, in ASN 48, or
elsewhere.
[0044] For successful decoding of feedbacks, UL synchronization may
be important. In general, UL synchronization may be achieved by
Unicast initial ranging or periodic ranging. For unicast and MBS
mixed scenario, MBS may benefit from the unicast ranging. On the
other hand, for a dedicated MBS scenario, ranging operation might
not be available to benefit from. The following are some possible
practices that may mitigate UL synchronization error. A longer
cyclic prefix (CP) may ensure that the signals from distant BSs do
not exceed CP period. MBS guard time with repetition coding may
also help. In order to take into account the delays of signals from
distant BSs, we may (1) insert empty guard time in the beginning
and/or at the end of MBS feedback channel and (2) use the
repetition coding (e.g. 2, 4, or 6).
[0045] CQI-based MBS feedback may also be used. Besides the random
selection of channel and code, NACK feedback may be sent based on
the user's channel quality. Feedback channel may be divided into
multiple slots according to SINR/MCS levels to be supported for
MBS. For example, FIG. 8 illustrates 5 different
signal-to-interference and noise ratio (SINR)/modulation and coding
scheme (MCS) (SINR/MCS) levels. The strongest is SINR/MCS level 1,
which is closest to the BS and the weakest is SINR/MCS level 1
farthest from the BS. MS1 has SINR/MCS level 4, MS2 has SINR/MCS
level 2, and MS3 has SINR/MCS level 5. The channel may be either
contention-free shared channel (power-based) or contention-based
shared channel, meaning feedbacks may be counted either by power
level or by resolving contending codes. Feedback may be sent over
the slot that corresponds to the user's SINR/MCS level. In some
embodiments, under this scheme, a total number of users in each
level is tracked.
[0046] There are various ways to implement an MS. FIG. 9
illustrates some details of one such implementation of MS 56-1,
although different details could be used. Referring to FIG. 9, an
RF interface 146 is coupled to antenna 78. RF section (mixers) 148
are coupled between analog front end 152 and RF interface 146.
Analog front end 152 is coupled to a baseband modem 154. Baseband
modem 154 includes an interface 156 that interfaces between analog
front end 152 and a hardware modem 160, DSP(s) 166, and ARM
device(s) 168. RAM 172 and nonvolatile memory 176 (such as flash
devices) provide memory and store instructions to be used by DSP(s)
166 and ARM device(s) 168. Addition hardware devices may be used.
The hardware may work with or without executing instructions.
[0047] For instructive purposes, Table 1 shows examples of the
number of feedbacks per video service under conditions of a total
of 2,400 MSs per BS, 3,600 MSs per BS, and 12,000 MSs per BS for 12
video services, assuming that the users for each service is evenly
distributed. Of course, that assumption is typically not true, but
Table 1 is still instructive. Of course, the inventions are not
limited to the details of Table 1.
TABLE-US-00001 TABLE 1 Per Service 12 Video # of # Reception #
Feedbacks Services Feedback MSs per failures (25% # of MSs per BS
allocation BS (20%) sampling) 2,400 144 tones 200 40 10 3,600 (9
slots * 16 300 60 15 12,000 tones in short- 1000 200 50
spreading)
Referring to Table 1, in the example of 200 MSs per BS per service,
there is an error (failure) in transmission for 40 MSs (or a 20%
failure rate) and a 25% sampling rate is used, then feedback is
provided by only 10 MSs. The BS knows that the 25% sampling rate is
used, so the BS assumes that there are failures for 40 MSs and uses
this assumption in determining what, if any, adjustments in MCS
level or re-transmissions to make. In Table 1, 12,000 user support
per BS with only 50 feedbacks per service is shown. Note that more
or less users may be supported by adjusting sampling rate and/or
the amount of channel allocation.
[0048] The invention is not restricted to use with any particular
wireless standard or protocol. Various wireless standards have been
proposed including WiMAX, IEEE 802.16e, 802.16m, 802.16Rev12, 3GPP,
3GPP2, CMMB, MediaFLO, DVB-H, IEEE 802.16m, WiMax Forum, 3 GPP
LTE.
[0049] In some embodiments, in addition to receiving NACK feedbacks
from some or all MSs that detect errors, there may be some ACK
feedbacks from some or all MSs that receive the MBS signals
correctly. In other embodiments, there are only NACK feedbacks, not
ACK feedbacks, to determine HARQ or link adaptation or other
responses.
ADDITIONAL INFORMATION AND EMBODIMENTS
[0050] The "logic" referred to herein may be implemented in
circuits, software, microcode, or a combination of them.
[0051] There are many details in which embodiments of the invention
may be implemented. The following are some details that may be used
in some embodiments (but not necessarily all the same embodiment),
but which are not required to be used in other embodiments:
[0052] Full resource usage for MBS.
[0053] 10 MHz bandwidth.
[0054] A WiMax frame of 900 subcarriers, 48 symbols, and 5 ms
frame.
[0055] Feedback every 200 ms MBS transmission period.
[0056] Frequency-domain spreading with 144 tones for long
spreading, and 9 slots of 16 tones (9*16=144 tones) for
short-spreading.
[0057] Feedback per MBS service and total of 12 IPTV services (for
example, 384 kbps video streams).
[0058] QPSK 1/2
[0059] Frequency-domain spreading with allocation of 144 tones for
contention channel.
[0060] 127 bit maximal PN codes for long-spreading.
[0061] 9 contention slots with 16 bit maximal PN codes for
short-spreading.
[0062] Random slot and code selection in short spreading.
[0063] Fading Channel and adjacent tone permutation. No path loss
and shadowing.
[0064] Simple correlation-based receiver for multi-user
detection.
[0065] Eased false detection probability since MBS feedback does
not require a strictly correct reception of codes.
[0066] Collisions and false detections are included as valid
feedback detection count.
[0067] Various other details may be used in other embodiments.
[0068] An embodiment is an implementation or example of the
invention. Reference in the specification to "an embodiment," "one
embodiment," "some embodiments," or "other embodiments" means that
a particular feature, structure, or characteristic described in
connection with the embodiments is included in at least some
embodiments, but not necessarily all embodiments. The various
appearances of "an embodiment," "one embodiment," or "some
embodiments" are not necessarily all referring to the same
embodiments.
[0069] When it is said the element "A" is coupled to element "B,"
element A may be directly coupled to element B or be indirectly
coupled through, for example, element C.
[0070] When the specification or claims state that a component,
feature, structure, process, or characteristic A "causes" a
component, feature, structure, process, or characteristic B, it
means that "A" is at least a partial cause of "B" but that there
may also be at least one other component, feature, structure,
process, or characteristic that assists in causing "B." Likewise,
that A is responsive to B, does not mean it is not also responsive
to C.
[0071] If the specification states a component, feature, structure,
process, or characteristic "may", "might", or "could" be included,
that particular component, feature, structure, process, or
characteristic is not required to be included. If the specification
or claim refers to "a" or "an" element, that does not mean there is
only one of the element.
[0072] The invention is not restricted to the particular details
described herein. Indeed, many other variations of the foregoing
description and drawings may be made within the scope of the
present invention. Accordingly, it is the following claims
including any amendments thereto that define the scope of the
invention.
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