JOINT POWER WAVEFORMING
AND BEAMFORMING FOR
WIRELESS POWER TRANSFER
Presented By:
Ehtisham Ul Haq (FA15-BEE-005)
Maria Shehzadi (FA15-BEE-023)
Saira Batool
(FA15-BEE-042)
OUTLINE OF PRESENTATION

Why We Need This Research

Overview Of research paper

Concept Building Keywords

Introduction To Topic

Energy Harvesting

Block Diagram

Mathematical Design

Simulation Results And Discussion

Major Concerns For Designing

Main Contributions Of This Paper

Conclusion

References
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NEED OF RESEARCH
We are living in the era of Technology
and we enjoy internet. It can be a mobile
data or a connectivity by means of WiFi.
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PROBLEM THAT WE FACE DAILY
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OVERVIEW OF RESEARCH PAPER
In the IoT, wireless devices need more easily accessible energy resources,
which motivates the development of wireless power transfer (WPT) using radio
frequency signals.
Beamforming technique has been widely adopted by using multiple transmit
antennas to form a sharp energy beam toward an intended receiver.
In this paper, they propose a joint power waveforming and beamforming in
the time domain for WPT, in which the waveforms on multiple transmit antennas
driven by a common reference signal are designed to maximize the gain of
energy delivery efficiency.
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OVERVIEW OF RESEARCH PAPER
They considered both nonperiodic and periodic reference signals and
propose low-complexity waveforms that can achieve near-optimal
performance.
It is found that the energy delivery efficiency gain of the proposed approach
increases with the waveform length until saturation.
We theoretically analyze the outage probability of the proposed approach
under a uniform power delay channel profile, which quantifies the impact of
the number of antennas and multipaths.
Simulations are performed to validate the theoretic analysis and the
effectiveness of the proposed joint power waveforming and beamforming
approach.
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CONCEPT BUILDING KEYWORDS
Internet of Things (IoT)
Quality of Service (QoS)
Channel Impulse Response (CIR)
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INTERNET OF THINGS (IOT)
The internet of things, or IoT, is a
system of interrelated computing
devices, mechanical and digital
machines, objects, animals or people
that are provided with unique
identifiers (UIDs) and the ability to
transfer data over a network without
requiring human-to-human or humanto-computer interaction. [1]
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QUALITY OF SERVICE (QOS)
Quality of service (QoS) refers to a network’s ability to achieve maximum
bandwidth and deal with other network performance elements like latency,
error rate and uptime.
QoS involves controlling and managing
network resources by setting priorities
for specific types of data (video, audio,
files) on the network.
QoS is exclusively applied to network
traffic generated for video on demand,
VoIP, streaming media, videoconferencing
and online gaming. [2]
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CHANNEL IMPULSE RESPONSE (CIR)
The impulse response is a wideband
channel characterization and contains
all information necessary to simulate or
analyze any type of radio transmission
through the channel. [3]
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INTRODUCTION TO TOPIC
Topic is “Joint Power Waveforming and Beamforming for Wireless
Power Transfer”
Decomposition of topic:
 Power Waveforming and Beamforming
 Wireless Power Transfer
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WAVEFORMING AND BEAMFORMING
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PRACTICAL EXAMPLE
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WIRELESS POWER TRANSFER
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ENERGY HARVESTING
Energy harvesting is the process by which
energy is derived from external sources (e.g.,
solar power, thermal energy, wind energy etc),
captured, and stored for small, wireless
autonomous devices, like those used in
wearable electronics and wireless sensor
networks.
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ENERGY HARVESTING USING RF
RF energy is currently broadcasted from billions of radio transmitters
around the world, including mobile telephones, handheld radios, mobile
base stations, and television/ radio broadcast stations.
The ability to harvest RF energy, enables wireless charging of lowpower devices and has resulting benefits to product design, usability,
and reliability.
Battery-based systems can be trickled charged to eliminate battery
replacement or extend the operating life of systems using disposable
batteries.
Battery-free devices can be designed ,free of connectors, cables, and
battery access panels, and have freedom of placement and mobility
during charging and usage.
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BLOCK DIAGRAM
Waveform
𝑔0 [𝑛]
V[n]
Waveform
𝑔1 [𝑛]
Channel
Receiver
Waveform
𝑔𝑀−1 [𝑛]
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PHASES WHILE TRANSMISSION
There are two phases
Phase 1: Channel Probing
Phase 2: Power Transfer
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CHANNEL PROBING
During the first phase, the receiver first sends a pilot
sounding signal with a delta-like autocorrelation function to
each transmit antenna for estimating the corresponding
CIR.
The CIR can be estimated very accurately through Golay
sequences and the correlation method.
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POWER TRANSFER
The transmitter computes a waveform 𝑔𝑚 [𝑛] for each
transmit antenna based on the estimated CIR during the
second phase for the WPT purpose, for 𝑚 = 0, . . . , 𝑀 −
1 and 𝑛 = 0, . . . , 𝑁𝑔 − 1, and 𝑁𝑔 is the length of the
waveform.
Let 𝑣[𝑛] be a reference signal of length 𝑁𝑣 , for 𝑛 =
0, . . . , 𝑁𝑣 − 1, which acts as the energy-bearing signal
for continuously supplying energy.
The multipath channels will disperse the radiated power
to multiple copies of the transmitted signals.
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MATHEMATICAL DESIGN
The channel impulse response (CIR) between the 𝑚𝑡ℎ transmit antenna
and the receiver is modeled as
𝐿−1
ℎ𝑚 𝑛 =
𝑙=0
ℎ𝑚,𝑙 𝛿 𝑛 − 𝑙 ,
𝑛 = 0, … , 𝐿 − 1
The reference signal after the waveform embedding at the
𝑚𝑡ℎ transmit antenna can be formulated as
𝑠𝑚 𝑛 = 𝑃𝑣 𝑣 ⋆ 𝑔𝑚 𝑛 ,
𝑛 = 0, … , 𝑁𝑔 + 𝑁𝑣 − 2
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MATHEMATICAL DESIGN
Where we assume that the total waveform power is equal to one,
i.e.
𝑀−1
𝑚=0
𝑁𝑔 −1
𝑛=0
𝑔𝑚 𝑛
2
=1
The average reference signal power is given by
𝑁𝑣 −1
1
𝑣 𝑛 2 =1
𝑁𝑣
𝑛=0
𝑃𝑣 is the average transmit power.
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MATHEMATICAL DESIGN
the received signal at the receiver side is given as
𝑀−1
𝑦𝑛 =
𝑚=0
𝑀−1
=
𝑃𝑣
𝑚=0
𝑠𝑚 ⋆ ℎ𝑚 𝑛 + 𝑧 𝑛
𝑣 ⋆ 𝑔𝑚 ⋆ ℎ𝑚 𝑛 + 𝑧 𝑛
𝑛 = 0, … , 𝑁𝑔 + 𝑁𝑣 + 𝐿 − 3
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SIMULATION RESULTS AND DISCUSSION
1. Average Energy Delivery Efficiency Gain (dB) vs Iteration Number
2. Average Energy Delivery Efficiency Gain (dB) vs Waveform Length ( 𝑁𝑔 ) –
(With Non-Periodic Transmission of Reference Signals)
3. Average Energy Delivery Efficiency Gain (dB) vs Waveform Length ( 𝑁𝑔 ) –
(With Periodic Transmission of Reference Signals)
4. Average Energy Delivery Efficiency Gain (dB) vs Number of Transmit Antennas
5. Outage Performance Of The Average Harvested Energy And The Analytical
Upper Bound For The Multi-antenna PW Systems
6. Outage Performance Of The Average Harvested Energy And The Analytical
Upper Bound For Different Lengths Of Waveforms
7. Average Energy Delivery Efficiency Gain And The Analytical Lower Bound
For The Multi-antenna PW Systems
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AVERAGE ENERGY DELIVERY EFFICIENCY GAIN (DB) VS
ITERATION NUMBER
Observations:
1. Better Converged Performance of
periodic transmission of reference
signals than non-periodic transmission.
Because periodic transmission allows
fully concentrated power on best
selected frequency
2. The proposed system with the
designed initialization beats that with
the random initialization, and its
performance
can
quickly
get
converged within two iterations.
𝑀 = 4 , 𝑁𝑣 = 100, 𝑁𝑔 → 𝑙𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑡ℎ𝑒 𝑤𝑎𝑣𝑒𝑓𝑜𝑟𝑚
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AVERAGE ENERGY DELIVERY EFFICIENCY GAIN (DB) VS WAVEFORM
LENGTH (𝑁𝑔 ) – (WITH NON-PERIODIC TRANSMISSION OF REFERENCE SIGNALS)
Observation:
1. For non-periodic transmission, it is
found that the average energy
delivery efficiency gain can be
dramatically improved by increasing
the lengths of waveforms or
reference signals. If 𝑁𝑔 = 280 , the
performance improvement is as large
as 22 dB when 𝑁𝑣 is increased from
1 to 150.
2. The
performance
improvement
becomes moderate as the values of
𝑁𝑣
and
𝑁𝑔
increase.
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AVERAGE ENERGY DELIVERY EFFICIENCY GAIN (DB) VS WAVEFORM
LENGTH (𝑁𝑔 ) – (WITH PERIODIC TRANSMISSION OF REFERENCE SIGNALS)
Observation:
1. Similar
performance
trends
can be observed for the case of
periodic transmission. For 𝑁𝑣 = 150
and 𝑁𝑔 = 280, the average energy
delivery efficiency gain of the
proposed multi-antenna PW system is
around 34 dB.
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AVERAGE ENERGY DELIVERY EFFICIENCY GAIN (DB) VS
NUMBER OF TRANSMIT ANTENNAS
Observations:
1. It compares the performances of the multiantenna PW system and the frequencydomain beamforming system, in terms of the
average energy delivery efficiency gain.
2. The energy delivery efficiency gain of the
multi-antenna PW system with the periodic
transmission of reference signals is 5 dB
better than that with the non-periodic
transmission for various numbers of transmit
antennas.
3. When B is increased from 10 MHz to 125
MHz, the performance gap between the
frequency-domain approach and our
proposed time-domain becomes narrow in the
UWB SV channel.
𝑁𝑔 = 𝑁𝑣 = 100, 𝑀𝑢𝑙𝑡𝑖𝑝𝑎𝑡ℎ𝑠 𝐿 = 20
𝑈𝑊𝐵 𝑆𝑉 → 𝑈𝑙𝑡𝑟𝑎 𝑊𝑖𝑑𝑒 𝐵𝑎𝑛𝑑 𝑆𝑎𝑙𝑒ℎ − 𝑉𝑎𝑙𝑒𝑛𝑧𝑢𝑒𝑙𝑎
(𝑆𝑉, 𝐼𝐸𝐸𝐸 802.15.3𝑎)
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Observations:
1. It shows the exact outage probability of
the average harvested energy and the
derived upper bound given under the
UPD channel profile for various numbers
of transmit antennas and multipaths.
2.
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MAJOR CONCERNS FOR DESIGNING
Low Power Transfer Efficiency:
RF signal-based power transfer systems are the low
power transfer efficiency due to the severe radio wave propagation
loss, including multipath, shadowing and large-scale path loss over
distance.
Law of energy conservation:
According to the law of energy conservation, only a
small portion of energy radiated from a transmitter can be harvested
at a receiver in reality, yielding an energy scarcity problem.
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MAJOR CONCERNS FOR DESIGNING (CONT.…)
Higher receiver sensitivity:
Unlike the conventional information receivers, energy
receivers require much higher receiver sensitivity to convert RF
signals into DC power via rectifier circuits, which makes the design
even more challenging, e.g., −50 dBm for information receivers
and −10 dBm for energy receivers.
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MAIN CONTRIBUTIONS OF THIS PAPER
1. This work is the first attempt to formulate the WPT problem by
combining power waveforming and beamforming and jointly
optimize the reference signal and the waveforms to maximize
the energy delivery efficiency gain. Two kinds of reference
signals are considered in our study: non-periodic and periodic.
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CONCLUSION
1. In this paper, they investigated a joint power waveforming and beamforming
design for WPT, in which the waveforms on multiple transmit antennas driven by a
common reference signal are optimized to maximize the gain of energy delivery
efficiency.
2. Analytic upper and lower bound expressions for the outage performance of the
average harvested energy and the energy delivery efficiency gain were derived
in closed forms under the UPD channel profile.
3. The analytic results allowed us to quantify the influence of several system
parameters, e.g., the number of transmit antennas, the channel length, the
waveform length, on the WPT performance.
4. Simulation results revealed that a 20–30dB improvement can be achieved by
employing the proposed scheme compared to the conventional narrow-band
beamforming scheme
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REFERENCES
No
Reference
1
"IoT analytics guide: Understanding Internet of Things data," [Online]. Available:
https://internetofthingsagenda.techtarget.com/definition/Internet-of-Things-IoT.
[Accessed
16
December 2018].
2
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