U.S. patent application number 16/724836 was filed with the patent office on 2021-06-24 for hybrid unequal error protection (uep) for heterogeneous multi-service provisioning.
This patent application is currently assigned to United States of America as represented by Secretary of the Navy. The applicant listed for this patent is Naval Information Warfare Center, Pacific. Invention is credited to Michael P. Daly, Justin O. James.
Application Number | 20210194620 16/724836 |
Document ID | / |
Family ID | 1000005636478 |
Filed Date | 2021-06-24 |
United States Patent
Application |
20210194620 |
Kind Code |
A1 |
James; Justin O. ; et
al. |
June 24, 2021 |
Hybrid Unequal Error Protection (UEP) for Heterogeneous
Multi-Service Provisioning
Abstract
A method and system are discussed for providing Unequal Error
Protection (UEP) for heterogeneous multi-service provisioning. A
transmitter in a network may determine a current status of the
network. The transmitter may adaptively adjust a current asymmetric
signal constellation and a current channel Forward Error Correction
(FEC) coding rate based on the determined current status of the
network, and initiate transmission of multi-service data, using the
adaptively adjusted asymmetric signal constellation and the
adaptively adjusted FEC coding rate for transmission of the
multi-service data, based on hybrid Unequal Error Protection (UEP)
transmission.
Inventors: |
James; Justin O.; (San
Diego, CA) ; Daly; Michael P.; (San Diego,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Naval Information Warfare Center, Pacific |
San Diego |
CA |
US |
|
|
Assignee: |
United States of America as
represented by Secretary of the Navy
San Diego
CA
|
Family ID: |
1000005636478 |
Appl. No.: |
16/724836 |
Filed: |
December 23, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 1/0026 20130101;
H04L 2001/0098 20130101; H04L 27/3405 20130101; H04L 1/007
20130101; H04L 1/0003 20130101 |
International
Class: |
H04L 1/00 20060101
H04L001/00; H04L 27/34 20060101 H04L027/34 |
Goverment Interests
FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT
[0001] The United States Government has ownership rights in this
invention. Licensing inquiries may be directed to Office of
Research and Technical Applications, Naval Information Warfare
Center, Pacific, Code 72120, San Diego, Calif., 92152; telephone
(619) 553-5118; email: ssc_pac_t2@navy.mil. Reference Navy Case No.
104069.
Claims
1. A method of providing Unequal Error Protection (UEP) for
heterogeneous multi-service provisioning, the method comprising:
determining, at a transmitter in a network, a current status of the
network; adaptively adjusting a current asymmetric signal
constellation and a current channel Forward Error Correction (FEC)
coding rate based on the determined current status of the network;
and initiating transmission of multi-service data, using the
adaptively adjusted asymmetric signal constellation and the
adaptively adjusted FEC coding rate for transmission of the
multi-service data, based on hybrid Unequal Error Protection UEP
transmission.
2. The method of claim 1, further comprising: determining a hybrid
mode switch threshold point value based on a carrier-to-noise ratio
(CNR); initiating the transmission of a first portion of the
multi-service data using Unequal Error Protection (UEP) by channel
coding in an area lower than the hybrid mode switch threshold point
value, based on a current value of the CNR; and initiating the
transmission of a second portion of the multi-service data using
Unequal Error Protection (UEP) by Adaptive Multiresolution
Modulation (AMM) in an area above the hybrid mode switch threshold
point value.
3. The method of claim 1, wherein determining the current status of
the network includes determining a channel impairment in the
network.
4. The method of claim 1, wherein determining the current status of
the network includes determining an improvement in a condition of
the network following a channel impairment in the network.
5. The method of claim 1, wherein adaptively adjusting the current
asymmetric signal constellation includes modifying a size of the
current asymmetric signal constellation in use for transmitting at
the transmitter.
6. The method of claim 1, wherein adaptively adjusting the current
asymmetric signal constellation includes modifying a shape of the
current asymmetric signal constellation in use for transmitting at
the transmitter.
7. The method of claim 1, wherein initiating transmission of the
multi-service data includes improving spectral utilization
efficiency by transmitting the multi-service data, using the
adaptively adjusted asymmetric signal constellation and the
adaptively adjusted FEC coding rate for transmission of the
multi-service data, based on hybrid UEP.
8. A non-transitory computer-readable storage medium storing
instructions that are executable by at least one hardware device
processor to provide Unequal Error Protection (UEP) for
heterogeneous multi-service provisioning by: determining, at a
transmitter in a network, a current status of the network;
adaptively adjusting a current asymmetric signal constellation and
a current channel Forward Error Correction (FEC) coding rate based
on the determined current status of the network; and initiating
transmission of multi-service data, using the adaptively adjusted
asymmetric signal constellation and the adaptively adjusted FEC
coding rate for transmission of the multi-service data, based on
hybrid Unequal Error Protection (UEP) transmission.
9. The non-transitory computer-readable storage medium of claim 7,
wherein the instructions are executable by the at least one
hardware device processor to: determine a hybrid mode switch
threshold point value based on a carrier-to-noise ratio (CNR);
initiate the transmission of a first portion of the multi-service
data using Unequal Error Protection (UEP) by channel coding in an
area lower than the hybrid mode switch threshold point value, based
on a current value of the CNR; and initiate the transmission of a
second portion of the multi-service data using Unequal Error
Protection (UEP) by Adaptive Multiresolution Modulation (AMM) in an
area above the hybrid mode switch threshold point value.
10. The non-transitory computer-readable storage medium of claim 7,
wherein determining the current status of the network includes
determining a channel impairment in the network.
11. The non-transitory computer-readable storage medium of claim 7,
wherein determining the current status of the network includes
determining an improvement in a condition of the network following
a channel impairment in the network.
12. The non-transitory computer-readable storage medium of claim 7,
wherein adaptively adjusting the current asymmetric signal
constellation includes modifying a size of the current asymmetric
signal constellation in use for transmitting at the
transmitter.
13. The non-transitory computer-readable storage medium of claim 7,
wherein adaptively adjusting the current asymmetric signal
constellation includes modifying a shape of the current asymmetric
signal constellation in use for transmitting at the
transmitter.
14. The non-transitory computer-readable storage medium of claim 7,
wherein initiating transmission of the multi-service data includes
improving spectral utilization efficiency by transmitting the
multi-service data, using the adaptively adjusted asymmetric signal
constellation and the adaptively adjusted FEC coding rate for
transmission of the multi-service data, based on hybrid UEP.
15. A system for providing Unequal Error Protection (UEP) for
heterogeneous multi-service provisioning, the system comprising: a
transmitter in a network, the transmitter including: at least one
hardware device processor; and a non-transitory computer-readable
storage medium storing instructions that are executable by the at
least one hardware device processor to: determine a current status
of the network; adaptively adjust a current asymmetric signal
constellation and a current channel Forward Error Correction (FEC)
coding rate based on the determined current status of the network;
and initiate transmission of multi-service data, using the
adaptively adjusted asymmetric signal constellation and the
adaptively adjusted FEC coding rate for transmission of the
multi-service data, based on hybrid UEP transmission.
16. The system of claim 15, wherein the instructions are executable
by the at least one hardware device processor to: determine a
hybrid mode switch threshold point value based on a
carrier-to-noise ratio (CNR); initiate the transmission of a first
portion of the multi-service data using Unequal Error Protection
(UEP) by channel coding in an area lower than the hybrid mode
switch threshold point value, based on a current value of the CNR;
and initiate the transmission of a second portion of the
multi-service data using Unequal Error Protection (UEP) by Adaptive
Multiresolution Modulation (AMM) in an area above the hybrid mode
switch threshold point value.
17. The system of claim 15, wherein determining the current status
of the network includes determining a channel impairment in the
network.
18. The system of claim 15, wherein determining the current status
of the network includes determining an improvement in a condition
of the network following a channel impairment in the network.
19. The system of claim 15, wherein adaptively adjusting the
current asymmetric signal constellation includes modifying a size
of the current asymmetric signal constellation in use for
transmitting at the transmitter.
20. The system of claim 15, wherein initiating transmission of the
multi-service data includes improving spectral utilization
efficiency by transmitting the multi-service data, using the
adaptively adjusted asymmetric signal constellation and the
adaptively adjusted FEC coding rate for transmission of the
multi-service data, based on hybrid UEP.
Description
BACKGROUND
[0002] Multiservice applications are projected to become a central
theme of the next-generation of wireless communications systems.
Thus, heterogeneous multiservice provisioning may become a
significant component of the systems. Future generations of
communications systems may need to support a multitude of services
with a wide variety of reliability requirements and data rates. For
example, some errors may be tolerable for certain applications,
such as video processing. However, these same errors may be
unacceptable for other applications (e.g., mission critical data).
Additionally complicating this issue, the quality of a wireless
link in a contested mobile environment may be highly variable (due
to node mobility, fluctuations in the propagation characteristics
and interference levels, and limited battery resources) which may
cause noteworthy variations in data delivery delays and packet
losses (e.g., due to network flow congestion and finite length
queues).
[0003] Conventionally, practical communications systems employ
symmetric modulation. In symmetric modulation signal
constellations, the minimum distance between any one symbol and all
others is the same. This constellation design gives each bit within
a modulated symbol approximately the same level of protection.
Consequently, data encoded to each bit within a modulated symbol
has approximately the same bit error rate (BER)
characteristics.
[0004] Symmetric modulations are adequate for conventional
stove-piped communications systems dedicated to only one function
and QoS requirement. In such a system, symmetric modulation
constellations are optimal, because the QoS requirement for all
transmitted data is homogenous. For newer communications systems
with a multitude of different services with heterogeneous QoS
requirements, symmetric modulation may be sub-optimal. When
transmitting heterogeneous data using a symmetric modulation, the
modulation and requisite SNR need to meet the more stringent QoS.
This over-compensation may result in inefficient wasteful resource
utilization, in the form of energy and/or spectral efficiency.
[0005] In network transmissions, Adaptive Multiresolution
Modulation (AMM) permits adaptation of both the shape (.beta.) and
the size of an asymmetric signal constellation. The spectral
efficiency gain achieved through the employment of AMM at the
physical (PHY) layer (of the Open Systems Interconnection (OSI)
model) may be substantial (e.g., up to fifty percent (50%)
increase), especially at low and moderate carrier-to-noise ratio
(CNR) (see, e.g., J. James et al., "Adaptive Multiresolution
Modulation for Multimedia Traffic over Nakagami Fading Channels,"
International Journal of Wireless & Mobile Networks (April
2012), pp. 1-20 ("James 1" hereinafter) and J. James et al.,
"Adaptive Multiresolution Modulation for Multimedia Traffic," IEEE
Consumer Communications and Networking Conference (CCNC) (Jan.
9-12, 2012), pp. 697-698 ("James 2" hereinafter)).
[0006] As further explanation of constellations, a constellation
diagram is a representation of a signal modulated by a digital
modulation scheme such as quadrature amplitude modulation or
phase-shift keying. The diagram represents the signal as a
two-dimensional xy-plane scatter diagram in the complex plane at
symbol sampling instants. The angle of a point, measured
counterclockwise from the horizontal axis, represents the phase
shift of the carrier wave from a reference phase. The distance of a
point from the origin represents a measure of the amplitude or
power of the signal.
[0007] In a digital modulation system, information may be
transmitted as a series of samples, each occupying a uniform time
slot. During each sample, the carrier wave has a constant amplitude
and phase which may be restricted to one of a finite number of
values, so each sample encodes one of a finite number of "symbols",
which in turn represent one or more binary digits (bits) of
information. Each symbol may be encoded as a different combination
of amplitude and phase of the carrier, so each symbol may be
represented by a point on the constellation diagram. The
constellation diagram may represent all the possible symbols that
can be transmitted by the system as a collection of points. In a
frequency or phase modulated signal, the signal amplitude is
constant, so the points lie on a circle around the origin.
[0008] The carrier representing each symbol can be created by
adding together different amounts of a cosine wave representing the
"I" or in-phase carrier, and a sine wave, shifted by 90.degree.
from the I carrier called the "Q" or quadrature carrier. Thus, each
symbol may be represented by a complex number, and the
constellation diagram may be regarded as a complex plane, with the
horizontal real axis representing the I component and the vertical
imaginary axis representing the Q component. A coherent detector
may independently demodulate these carriers. The principle of using
two independently modulated carriers is the foundation of
quadrature modulation. In pure phase modulation, the phase of the
modulating symbol is the phase of the carrier itself.
[0009] A "signal space diagram" refers to an ideal constellation
diagram showing the correct position of the point representing each
symbol. After passing through a communication channel, due to
electronic noise or distortion added to the signal, the amplitude
and phase received by the demodulator may differ from the correct
value for the symbol. When plotted on a constellation diagram, the
point representing that received sample may be offset from the
correct position for that symbol. For example, a vector signal
analyzer can display the constellation diagram of a digital signal
by sampling the signal and plotting each received symbol as a
point. The result is a "ball" or "cloud" of points surrounding each
symbol position. For example, measured constellation diagrams may
be used to recognize the type of interference and distortion in a
signal.
[0010] With regard to error protection, at the PHY layer, there are
three techniques that may facilitate Unequal Error Protection
(UEP): 1) increase the transmission power while sending high
priority bits; 2) use channel coding with varying levels of error
protection; and/or 3) employ a suitable multiresolution
(hierarchical) modulation scheme.
[0011] An example technique using UEP is discussed in K. Yang, et
al., "Unequal Error Protection for Streaming Media Based on
Rateless Codes," IEEE Transactions on Computers, vol. 61 no. 5, pp.
666-675, May 2012 ("Yang" hereinafter).
[0012] Based on the discussion above, there is clearly a need for
improved techniques for improving efficiency of heterogeneous
multiservice content distribution across disadvantaged and/or
contested wireless communications channels.
SUMMARY
[0013] A method and system are discussed that provide Unequal Error
Protection (UEP) for heterogeneous multi-service provisioning. A
transmitter in a network may determine a current status of the
network. The transmitter may adaptively adjust a current asymmetric
signal constellation and a current channel Forward Error Correction
(FEC) coding rate based on the determined current status of the
network, and initiate transmission of multi-service data, using the
adaptively adjusted asymmetric signal constellation and the
adaptively adjusted FEC coding rate for transmission of the
multi-service data, based on hybrid UEP transmission.
[0014] This Summary is not intended to identify key features or
essential features of the claimed subject matter, nor is it
intended to be used to limit the scope of the claimed subject
matter. The details of one or more implementations are set forth in
the accompanying drawings and the description below. Other features
will be apparent from the description and drawings, and from the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a block diagram of an example system having a
distributed network architecture.
[0016] FIG. 2 is a block diagram of an example node in the
distributed network architecture shown in FIG. 1.
[0017] FIG. 3 illustrates a comparison of Symmetric 8-PSK and
Asymmetric 8-PSK.
[0018] FIG. 4 illustrates an average spectral efficiency for AMM
and AFECC.
[0019] FIG. 5 illustrates an Average Spectral Efficiency for
Hybrid-UEP, AMM, and AFECC.
[0020] FIG. 6 illustrates average spectral efficiency for example
Hybrid-UEP and symmetric (SYM) schemes.
[0021] FIG. 7 illustrates a received I-Q constellation graph.
[0022] FIG. 8 is a flowchart illustrating example operations of the
system of FIG. 2, according to example embodiments.
DETAILED DESCRIPTION
[0023] A method and system are disclosed herein for providing
Unequal Error Protection (UEP) for heterogeneous multi-service
provisioning. The method and system each provide for determining,
at a transmitter in a network, a current status of the network;
adaptively adjusting a current asymmetric signal constellation and
a current channel Forward Error Correction (FEC) coding rate based
on the determined current status of the network; and initiating
transmission of multi-service data, using the adaptively adjusted
asymmetric signal constellation and the adaptively adjusted FEC
coding rate for transmission of the multi-service data, based on
hybrid-UEP transmission.
[0024] Example techniques discussed herein provide hybrid-UEP,
based on a network link adaptation strategy, for efficient
heterogeneous multiservice content distribution across
disadvantaged and/or contested wireless communications channels.
Hybrid-UEP permits adaptation of both the shape and the size of the
asymmetric signal constellation, as well as channel Forward Error
Correction (FEC) coding rate, with a goal of improving the
throughput for multi-service data while fulfilling the distinct
Quality of Service (QoS) packet error rate (PER) requirements for
each traffic type under different channel conditions. For example,
a hybrid-UEP scheme may employ Unequal Error Protection by channel
coding (ADC) in a low carrier-to-noise ratio (CNR) region to
provide increased robustness, and may employ UEP by Adaptive
Multiresolution Modulation (AMM) in the moderate to high CNR
regions to increase spectral efficiency.
[0025] The spectral efficiency gain achieved through the employment
at the PHY layer may be substantial, particularly at low and
moderate signal-to-noise ratio (SNR). In some cases, hybrid-UEP may
also double the battery life compared to current symmetric
modulations for the same bit rate. Example techniques discussed
herein may be used to increase the spectral efficiency of any
communications system which transmits heterogeneous (multi-service)
data. Unlike conventional stove-pipe systems, many current
communications and network systems carry a variety of information
(e.g., video, imagery, voice, and data). Example techniques
discussed herein may meet the QoS requirements of the heterogeneous
and multiservice data while not wasting energy or sacrificing
performance. Hybrid-UEP may avoid the "cliff effect" in which all
data transmission cuts out when the channel becomes very poor.
Instead, there may be a graceful degradation and the most important
data may still be sent through all but the worst channel
outages.
[0026] Example techniques discussed herein may provide efficient
resource utilization techniques for managing heterogeneous
multiservice provisioning over wireless channels and networks. To
accomplish this goal, cross-layer design may be leveraged. In
cross-layer design, the inter-dependencies between various protocol
layers may be characterized and exploited while cooperatively
optimizing the end-to-end (E2E) performance metrics. In contrast to
wired networks, wherein QoS may be assured by separately optimizing
each layer in the Open Systems Interconnection (OSI) model, in
wireless systems, there may exist a strong interconnection between
layers which may yield the layered design approach inefficient.
Furthermore, many conventional techniques may only consider a
subset of layers of the protocol stack and may not fully utilize
techniques available at the lower layers.
[0027] Example techniques discussed herein may employ AMM that
takes advantage of the differences in the QOS requirements between
different types of heterogeneous multiservices (imposed by the
upper layers) for improving the spectral utilization efficiency by
exploiting the abstraction of the established channel conditions at
the PHY layer.
[0028] FIG. 1 is a block diagram of an example system 10 having a
distributed network architecture that may be used to implement
techniques discussed herein. System 10 may include a plurality of
nodes 20 that are each configured to send signals 30 to each of the
other nodes 20 and receive signals 30 from each of the other nodes
20. Nodes 20 may be organized in any type of distributed network
configuration. In some embodiments, nodes 20 are fixed in their
location within the network. In some embodiments, nodes 20 are
mobile and are able to move about within the network. In some
embodiments, system 10 may include both fixed and mobile nodes. In
some embodiments, nodes 20 comprise sensors that may be used to
detect objects within an environment.
[0029] FIG. 2 is a block diagram of an example of a node 20. As
shown, node 20 includes a processor 22 operatively connected to a
memory unit 24 and a transceiver 26. In some embodiments, processor
22 is a general purpose processor. In some embodiments, processor
22 is a processor that is specifically programmed to contain
instructions therein, readable by the processor, that allow the
processor to send/receive information to/from memory unit 24 and
transceiver 26, as well as to cause transceiver 26 to send/receive
signals in accordance with embodiments discussed herein. Further,
depending on the particular application of the node, e.g., a
sensor, node 20 may include more components therein to allow the
node to perform functions required by the specific application.
[0030] In asymmetric modulation, the signal constellation is
pre-distorted to increase resource utilization efficiency when
transmitting multi-service, heterogeneous data. By pre-distorting
the signal constellation, heterogeneous QoS requirements can be
satisfied while not wasting resources. In asymmetric modulation,
the shape of the signal constellation may be dictated by the QoS
requirements at the APP layer. For cases where the QoS BER or PER
requirements are closer to each other, the optimal signal
constellation shape is more symmetric. For cases where the QoS BER
or PER requirements are farther apart from each other, the optimal
signal constellation shape is more asymmetric.
[0031] At a receiver, demodulation, symbol-to-bit translation, may
be based on pre-defined decision regions. FIG. 3 illustrates a
comparison of Symmetric 8-PSK (phase-shift keying) (302) and
Asymmetric 8-PSK (304), as shown by constellation diagrams. In FIG.
3, the decision regions for bit 1, bit 2, and bit 3 for both
symmetric and asymmetric 8-PSK (phase-shift keying) are shown. As
shown, decision region 306 illustrates the decision region for bit
1 for symmetric 8-PSK, decision region 308 illustrates the decision
region for bit 2 for symmetric 8-PSK, and decision region 310
illustrates the decision region for bit 3 for symmetric 8-PSK. As
shown, decision region 312 illustrates the decision region for bit
1 for asymmetric 8-PSK, decision region 314 illustrates the
decision region for bit 2 for asymmetric 8-PSK, and decision region
316 illustrates the decision region for bit 3 for asymmetric 8-PSK.
If the transmitted symbol is received in the correct decision
region, the symbol may be demodulated correctly. If the transmitted
symbol is received in the incorrect decision region due to
attenuation, noise, interference, or some other phenomena, the
symbol may be demodulated erroneously. Consequently, transmitted
symbols closer to the decision region boundary may need less
corruption to be received in the incorrect decision region and are
more likely to be received in error.
[0032] An adaptive demodulation scheme is based on a maximum
likelihood (ML) detection rule for each bit. As shown in FIG. 3,
for the 8-PSK constellations, the first bit, also known as the most
significant bit (MSB), is "0" in the right half plane and "1" in
the left half plane. Moreover, if the phase angle between the
symbol and the positive x-axis (.PHI.) is between
-(.pi./2)<.PHI.<(.pi./2), "0" may be assigned to the first
bit. Similarly, the second bit which represents the next most
significant bit is "0" in the upper half plane and "1" in the lower
half plane. It may be noted that the second bit may be considered
"less important" than the first bit (i.e., the MSB). The complete
set of decision rules employed by the demodulator for asymmetric
8-PSK modulation may be denoted as:
[0033] (a) For 1.sup.st bit: If -(.pi./2)<.PHI.<(.pi./2),
i.sub.1=0; else i.sub.1=1.
[0034] (b) For 2.sup.nd bit: If 0<.PHI.<.pi., i.sub.2=0; else
i.sub.2=1.
[0035] (c) For 3.sup.rd bit: If
(.pi./2).beta.<.PHI.<.pi.-(.pi./2).beta. or
-.pi.+(.pi./2).beta.<.PHI.<-(.pi./2).beta., i.sub.3=0; else
i.sub.3=1.
[0036] It may be noted that for asymmetric modulation, ML decoding
may be performed on individual bits instead of the received symbol.
This may facilitate partial symbol recovery, which increases
spectral efficiency and throughput under disadvantaged channel
conditions. For symmetric modulation, ML decoding may be executed
on the received symbol. Consequently, there is no partial symbol
recovery (meaning that either all of the bits or none of the bits
are demodulated correctly). Thus, asymmetric modulations may be
decoded with lower uncoded BERs (Bit Error Rates) than can
symmetric modulations in the low to moderate SNR/CNR regions.
[0037] For symmetric 8-PSK, all of the constellation symbols are
equidistant in the signal space. Thus, for symmetric 8-PSK, the BER
and PER characteristics of each bit are roughly the same. For
asymmetric 8-PSK, as the constellation becomes more asymmetric, bit
1 is farther from the decision region and less vulnerable to
corruption. However, bit 2 and especially bit 3 may move closer to
the decision regions and may be more vulnerable to corruption. In
essence, asymmetric modulation provides more protection to the most
significant bits (MSBs) at the expense of less protection of the
least significant bits (LSBs). In many scenarios, MSBs may be
considered more "important" and/or more "significant" than LSBs.
Therefore, in accordance with example techniques discussed herein,
an asymmetric modulation implementation may need to determine the
optimal signal constellation shape at the PHY layer based on the
QoS requirements at the APP layer. In accordance with an example
embodiment herein, by harmonizing the distinctive QoS requirements
for multiservice sources to the shape of the multicast modulation,
a significant embedding gain may be produced.
[0038] To facilitate determining the optimum .beta. value for each
modulation scheme, the .beta. value that results in the minimum of
the maximum .gamma..sub.req.sup.i may be decided:
arg min .beta. { max i { .gamma. req i } } ##EQU00001##
[0039] For the particular case of 8-PSK, the QoS's may be defined
as:
[0040] P.sub.B.sup.(1).ltoreq.1.0239e-04
[0041] P.sub.B.sup.(2).ltoreq.1.02e-02
[0042] P.sub.B.sup.(3).ltoreq.6.41e-01
[0043] .beta..di-elect cons.(0,0.5],i.di-elect cons.{1,2,3}.
[0044] Acquiring an optimum .beta. value for different modulation
schemes may ensure that each modulation scheme maximizes its
capability based on the specified QoS requirements.
[0045] For adaptive FEC, the constellations symbols are equidistant
in the signal space. Unequal error protection may be facilitated by
using FEC of various strengths. More important data (i.e., data
determined as "more important," for example, based on a
predetermined importance threshold value, or based on a subjective
input, such as importance of high bits and low bits, or importance
of a particular type of data) is protected with stronger coding
with more redundancy, less important information (i.e., data
determined as "less important") is protected with weaker coding
with less redundancy. In accordance with an example embodiment
herein, for Adaptive Forward Error Correction Coding (AFECC), the
symbol rate adapts based on the prevailing channel conditions.
However, the symbol shape remains symmetric.
[0046] The coded BER is calculated using the uncoded BER for
symmetric M-PSK and FEC code parameters (n, k, and t):
B E R Coded = r = t + 1 n n ! k ! ( n - k ) ! ( B E R Uncoded ) r (
1 - B E R Uncoded ) n - r ##EQU00002##
[0047] where n represents the block size of FEC, k represents the
number of information bits in the FEC block, and t represents the
number of correctable bits for the FEC block.
[0048] The coded PER is calculated using the coded BER:
PER.sub.Coded=1-(1-BER.sub.Coded).sup.N.sup.p, where N.sub.p is the
packet size.
[0049] AMM uses an asymmetric-shaped modulation constellation to
provide UEP for different bits within a single modulated symbol. As
the constellation becomes more asymmetric, the UEP disparity
between the bits becomes greater. More important information may be
mapped to the more protected bit positions (e.g., the MSBs) within
the modulated symbol, and less important information may be mapped
to the less protected bit positions (e.g., the LSBs) within the
modulation symbol. In an example embodiment herein, AFECC uses FEC
coding of varying code rates. More important information is
transmitted using stronger low rate codes with more coding
redundacy. Less important information is transmitted using weaker
high rate codes with less coding redundacy.
[0050] Given that AFECC may perform better in the low
carrier-to-noise ratio (CNR) region and AMM may perform better in
the moderate to high CNR regions, in an example embodiment herein,
a hybrid-UEP scheme employs UEP by AFECC in the low CNR region to
provide increased robustness and employs UEP by AMM in the moderate
to high CNR regions to increase spectral efficiency.
[0051] Experimental results have shown that the gain achieved using
adaptive multiresolution modulation (AMM), a form of hierarchical
modulation at the physical (PHY) layer is significant, especially
at low and moderate carrier-to-noise ratio (CNR). This performance
gain is achieved by mapping higher priority buffer bits to higher
protected bit positions within the symbol and other bits to less
protected bit positions, enabling partial modulated symbol
recovery. Because of the partial modulated symbol recovery
facilitated by AMM, there is a graceful degradation and the most
important data is still able to be sent through all but the worst
channel outages.
[0052] Simulation results have shown, using the hybrid-UEP scheme
discussed herein, significant energy and spectral efficiency gains
may be achieved across the entire SNR range. For example, a
prototype radio demonstrated the UEP by multiresolution modulation
portion. Emulated over-the-air tests confirmed benefits highlighted
through simulations.
[0053] FIGS. 4 and 5 illustrate the experimental results. For
example, FIG. 4 illustrates an average spectral efficiency for AMM
and AFECC, r.gtoreq.1/2, using QoS's 1.0239e-04, 1.02e-02, and
6.41e-01 (Nakagami-m=3). FIG. 5 illustrates an Average Spectral
Efficiency for Hybrid-UEP, AMM, and ADC using QoS's 1.0239e-04,
1.02e-02, and 6.41e-01 (Nakagami-m=3).
[0054] From FIGS. 4 and 5, it may be noted that UEP by means of
AFECC, discussed herein, performs better than multiresolution
modulation (AMM) in the low SNR region. However, UEP by means of
AMM works better than AFECC in the moderate to high CNR regions.
AFECC coding works well in the low CNR region, but it is limited in
spectral efficiency in the moderate to high CNR range due to the
redundancy of the FEC. Conversely, AMM is limited in the low CNR
region due to the lack of coding redundancy. However, as the CNR
increases, AMM is able to maximize the spectral efficiency in the
moderate to high CNR regions. Given that AFECC performs better in
the low CNR region and AMM performs better in the moderate to high
CNR regions, the hybrid-UEP scheme discussed herein was created
which employs UEP by AFECC in the low CNR region to provide
increased robustness and UEP by AMM in the moderate to high CNR
regions to increase spectral efficiency.
[0055] As shown in FIG. 5, a hybrid mode switch threshold point
(504) may be used to determine when to switch modes, based on a
determination of a location (e.g., low or moderate to high region)
in values of CNR, according to an example embodiment.
[0056] FIG. 6 illustrates average spectral efficiency for the
Hybrid-UEP and symmetric (SYM) schemes using QoS's 1.0239e-04,
1.02e-02, and 6.41e-01 (Nakagami-m=3). As illustrated in FIG. 6,
using the hybrid-UEP scheme discussed herein, significant energy
and spectral efficiency gains may be achieved across the entire SNR
range. As shown in FIG. 6, the spectral efficiency improvements are
largest in the low SNR region and increased as much as one hundred
eighty percent (180%). The spectral efficiency gain in the high SNR
region is roughly twenty percent (20%). The energy savings offered
by the hybrid-UEP scheme discussed herein is as large as
sixty-eight percent (68%) in both the low and high SNR regions.
However, in general, the spectral efficiency gains are greatest in
the low SNR region and the energy efficiency gains are greatest in
the high SNR region.
[0057] FIG. 7 illustrates the received I-Q constellation graph and
thumbnail images at SNR=6 decibels (dB) for 8-PSK. As shown, FIG. 7
illustrates a received I-Q constellation graph and thumbnail image
for a) symmetric 8-PSK, .beta.=0.5 (702), and b) Asymmetric 8-PSK,
.beta.=0.3 (SNR=6 dB) (704). In FIG. 8, from the I-Q constellation
graph, it may be noted that the received constellation using
asymmetric modulation (.beta.=0.3) (704) is less affected by the
attenuation than the symmetric modulation (.beta.=0.5) (702).
Consequently, the thumbnail images received using asymmetric
modulation may have better perceived quality than those of the
symmetric modulation. While apparent for bit 1, the improvement is
evident for thumbnails representing bit 2 (706) and bit 3 (708).
For the symmetric constellation, the receiver method of failure is
an inability to maintain frequency and phase lock. For the
asymmetric modulation, in all but the most unacceptable
circumstances, frequency and phase lock is preserved because the
most protected bit stream is easily demodulated.
[0058] Using the hybrid-UEP approach discussed herein, the spectral
efficiency may improve across the entire CNR range. Using AFECC in
the low CNR region provides additional robustness, while AMM in the
moderate to high CNR regions may provide enhanced spectral
efficiency. The hybrid-UEP also outperforms either AFECC or AMM
alone.
[0059] Various storage media, such as magnetic computer disks,
optical disks, and electronic memories, as well as non-transitory
computer-readable storage media and computer program products, can
be prepared that can contain information that can direct a device,
such as a micro-controller, to implement the above-described
systems and/or methods. Once an appropriate device has access to
the information and programs contained on the storage media, the
storage media can provide the information and programs to the
device, enabling the device to perform the above-described systems
and/or methods.
[0060] For example, if a computer disk containing appropriate
materials, such as a source file, an object file, or an executable
file, were provided to a computer, the computer could receive the
information, appropriately configure itself and perform the
functions of the various systems and methods outlined in the
diagrams and flowcharts above to implement the various functions.
That is, the computer could receive various portions of information
from the disk relating to different elements of the above-described
systems and/or methods, implement the individual systems and/or
methods, and coordinate the functions of the individual systems
and/or methods.
[0061] Features discussed herein are provided as example techniques
that may be implemented in many different ways that may be
understood by one of skill in the art of computing, without
departing from the discussion herein. Such features are to be
construed only as example features, and are not intended to be
construed as limiting to only those detailed descriptions.
[0062] FIG. 8 is a flowchart illustrating example operations of the
system of FIG. 2, according to example embodiments. As shown in the
example of FIG. 8, at a transmitter in a network, a current status
of the network may be determined (802).
[0063] A current asymmetric signal constellation and a current
channel Forward Error Correction (FEC) coding rate may be
adaptively adjusted based on the determined current status of the
network (804). Transmission of multi-service data may be initiated,
using the adaptively adjusted asymmetric signal constellation and
the adaptively adjusted FEC coding rate for transmission of the
multi-service data, based on hybrid Unequal Error Protection (UEP)
transmission (806).
[0064] For example, a hybrid mode switch threshold point value
based on a carrier-to-noise ratio (CNR) may be determined. For
example, as shown in FIG. 5, the hybrid mode switch threshold point
(504) may be used to determine when to switch modes, based on a
determination of a location (e.g., low or moderate to high region)
in values of CNR.
[0065] For example, the transmission of a first portion of the
multi-service data may be initiated using Unequal Error Protection
(UEP) by channel coding in an area lower than the hybrid mode
switch threshold point value, based on a current value of the
CNR.
[0066] For example, the transmission of a second portion of the
multi-service data may be initiated using Unequal Error Protection
(UEP) by Adaptive Multiresolution Modulation (AMM) in an area above
the hybrid mode switch threshold point value.
[0067] For example, determining the current status of the network
may include determining a channel impairment in the network.
[0068] For example, determining the current status of the network
may include determining an improvement in a condition of the
network following a channel impairment in the network.
[0069] For example, adaptively adjusting the current asymmetric
signal constellation may include modifying a size of the current
asymmetric signal constellation in use for transmitting at the
transmitter.
[0070] For example, adaptively adjusting the current asymmetric
signal constellation may include modifying a shape of the current
asymmetric signal constellation in use for transmitting at the
transmitter.
[0071] For example, initiating transmission of the multi-service
data may include improving spectral utilization efficiency by
transmitting the multi-service data, using the adaptively adjusted
asymmetric signal constellation and the adaptively adjusted FEC
coding rate for transmission of the multi-service data, based on
hybrid UEP.
[0072] Features discussed herein are provided as example techniques
that may be implemented in many different ways that may be
understood by one of skill in the art of computing, without
departing from the discussion herein. Such features are to be
construed only as example features, and are not intended to be
construed as limiting to only those detailed descriptions.
[0073] For example, the one or more processors (e.g., hardware
device processors) may be included in at least one processing
apparatus. One skilled in the art of computing will understand that
there are many configurations of processors and processing
apparatuses that may be configured in accordance with the
discussion herein, without departing from such discussion.
[0074] In this context, a "component" or "module" may refer to
instructions or hardware that may be configured to perform certain
operations. Such instructions may be included within component
groups of instructions, or may be distributed over more than one
group. For example, some instructions associated with operations of
a first component may be included in a group of instructions
associated with operations of a second component (or more
components). For example, a "component" herein may refer to a type
of functionality that may be implemented by instructions that may
be located in a single entity, or may be spread or distributed over
multiple entities, and may overlap with instructions and/or
hardware associated with other components.
[0075] In this context, a "memory" may include a single memory
device or multiple memory devices configured to store data and/or
instructions. Further, the memory may span multiple distributed
storage devices. Further, the memory may be distributed among a
plurality of processors.
[0076] One skilled in the art of computing will understand that
there may be many ways of accomplishing the features discussed
herein.
[0077] It will be understood that many additional changes in the
details, materials, steps and arrangement of parts, which have been
herein described and illustrated to explain the nature of the
invention, may be made by those skilled in the art within the
principle and scope of the invention as expressed in the appended
claims.
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