ROBOTIC INNER SIGNAL PROPAGATION AND RANDOM ACCESS OVER HYBRID ACCESS SCHEME

International Journal of Computer Networks & Communications (IJCNC) Vol.12, No.4, July 2020
DOI: 10.5121/ijcnc.2020.12405 71
ROBOTIC INNER SIGNAL PROPAGATION AND
RANDOM ACCESS OVER HYBRID ACCESS SCHEME
Abir Hossain, Zhenni Pan, Megumi Saito, Jiang Liu and Shigeru Shimamoto
Department of Computer Science and Communications Engineering,
Waseda University, Tokyo 169-0072, Japan
ABSTRACT
This paper proposes a Hybrid Access Scheme (HAS) aiming to convert a future robot’s backend
communication system by a finite number of sensors instead of using a lot of wires. To replace this
communication, the HAS needs to assure higher reliability within stringent low latency packet
transmission. In this paper, the HAS utilizes the packet diversity principle and forward multiple copies of
the same packet over the massive number of subcarrier channels. The HAS assigns the random accessing
to select a subcarrier channel for general packet transmitting sensors. The audio and video sensors
transmit packets over the dedicated channels to avoid collisions. The HAS system allows transmitting
audio, video and general sensors simultaneously. The minimum number of subcarriers to satisfy the
URLLC reliability requirement of 99.999% is evaluated for different packet duplications over different
arrival condition.The HAS system’s reliability and collision probability are evaluated in MATLAB
simulator for different packet duplication over different arrival condition. Moreover, the signal
propagation expressions are captured using ANSYS HFSS software for rectangular and circular
transmission medium over the 900 MHz, 2.4 GHz, 24 GHz, and 55 GHz frequency bands for different
structural configurations.
KEYWORDS
Hybrid Access Scheme, Signal Propagation, Random Access, reliability, URLLC
1. INTRODUCTION
In the state-of-the-art technology, wireless sensor converted system is getting more attention day
by day. A wireless sensor converted system being demanded due to its mobility, scalability,
ﬂexibility, cost-efﬁciency, and faster deployment. However, a robot consists of multiple
elements, and many wires are usually required as the communication backbone among attached
different elements [1]. A wire connected robot gain more weight and consume more power for its
usual movement. Moreover, the maintenance become complex when any internal wires get
disconnected during operation. By increasing the demands of wireless sensor connected system
and to resolve the defined problems, we intend to convert a wire system into a wireless one by a
Hybrid Access Scheme (HAS). A typical wireless sensor connected robot is presented in Figure 1.
As illustrated in Figure 1, there are three types of sensors (Audio, video and general sensor)
deployed ubiquity over the robotic structure and utilize hybrid access scheme to ensure ultra -
reliable low latency communication. The 3GPP sets the standard for Ultra-Reliable Low Latency
Communication (URLLC) reliability requirement for a single packet transmission having size of
32 bytes is 1-10-5
(alternatively 99.999%) with an interface latency of 1ms [2,3]. Due to ensure
this higher reliability and latency, the HAS adopts packet diversity principle and transmits over
massive number of subcarrier channels in almost error-free and interference-free manner.

72
Figure 1. Wireless sensor connected robot.
The HAS system assumed to assign a massive number of orthogonal subcarrier channels to
transmit packets from sensor to receiver site. Due to consider small area inside a robotic
structure, we assumed that the assign massive number of channels will not interfere with the
central mobile bandwidth assignment.
1.1. Related works
A several number of research works conducted to convert an established into a wireless system
by a finite number of sensors. Under the 5G communication domain, a sensor communication
based structural health monitoring and early earthquake warning system is presented in [4] that
give a proposal of monitoring and warning generation system in presence of seismic events. A
wireless sensor connected structural health monitoring system proposed for an airplane is studied
in [5] where sensor nodes observing the health conditions of an airplane deployed and covered
the entire area of an aircraft. These nodes evaluate throughput, the data dropped rate and the
delay for a maximum of 7 nodes as approximately 12000 bps, 180 bps, and115ms, respectively.
A real time elderly health care monitoring system is proposed in[6] that utilize a wireless sensor
network where bracelet-type devices are equipped with sensors applied to each patient under the
monitoring system of the healthcare that received data in real time and stored in a central
monitoring server. A spacecraft automation and communication based on sensor is studied in [7],
that transmit 988 B payload of sensor data in UWB in spacecraft networks over the different
frequency bands using a TDMA protocol having a short 5ms time slot. A wireless sensor-
connected robot’s OFSMA MAC protocol is accepted in [8], which considered only a single
frequency band. The main objectives of that proposed work are to determine the minimum
number of channels to satisfy 99.999% reliability and air-interface latency for single-packet
uplink communication.
The URLLC is a challenging service launched by 5G communication due to its higher reliability
requirement and lower latency bound. The URLLC is specially designed to overcome the
mission-critical system [9,10] where the link reliability is highly expected in a strict latency
requirement. The URLLC service is highly demanded and attracts attention a lot of researcher

73
due to its exciting and interesting applications. Among the different applications, the URLLC is
applicable in reliable remote action with robots and coordination among vehicles [11], tactile
internet [12], augmented or virtual reality (AR/VR) [13] and many more. This research work
[14] presents an emerging system of URLLC and eMBB where the time is divided into slots and
the time slot is further subdivided into minislots. The URLLC data is overlapped with eMBB
traffic and transmitted over the channel using superposition/puncturing and received successfully
using successive interference cancellation method. The URLLC is sensitive to its latency of the
packet transmission. This research [15] covers URLLC and eMBB resource slicing over minislots
in a risk-sensitive approach considering Conditional Value at Risk (CVaR) by managing properly
both eMBB users scheduling and URLLC slot placement for the downlink communication. An
unmanned aerial vehicle (UAV) based relay system is analyzed in [16] where the data is
transmitted under the URLLC requirements. This research work subjected to optimize the
blocklength allocation and minimize the decoding error probability under the latency
requirement.
There are several random accessing protocols studied in the slotted ALOHA system to
achieve the expected reliability and latency defined in URLLC. A contention-based slotted
ALOHA system has been proposed in [17] that adopts multichannel, multipacket diversity and
transmit multiple copies of the same packets in consecutive slots to improve system reliability,
and to reduce latency to satisfy URLLC’s conditions. Multichannel random accessing using
OFDMA is analyzed in [18], which proposed a fast retrial algorithm to forward a packet into a
frequency diversity system after a collision in a slotted ALOHA system. A multi-packet
messaging system in a cluster-based environment analysed in [19] where the multiple packets
forwarded into different slots and having an independent frequency is to improve the system
throughput.
1.2. Contributions
The existing research work is not suitable to convert our proposed objective to convert a future
robot’s internal communication developed by sensors. To implement our proposed aim, we
propose a hybrid access scheme. The main contributions of the paper are listed below:
 We propose a new hybrid access scheme (HAS) for a future robot’s internal communication
system. The HAS scheme ensures the higher packet transmission reliability of the audio,
video, and randomly transmitted general sensors over the differently allocated subcarrier
channels.
 We introduce a system model to represent the hybrid access scheme’s total transmitted
packet signal for a single Transmission Time Interval (TTI) slot, introduced AWGN noise
into the channel and finally the received packet signal at the receiver site.
 We determine the minimum number of subcarriers required to satisfy the reliability of
99.999% defined by URLLC for different packet duplication over variable arrival
conditions.
 We evaluate the HAS system’s packet transmission reliability and collision probability for
fixed channel conditions by assigning sensor and subcarrier channel ratio as 1:1 with the
variation of different packet duplications and low to higher arrival conditions.

74
 We capture the signal propagation expression for rectangular and circular transmission
medium as part of a robotic body structure for different structural configurations over
diverse frequency bands and determine the success or failure transmission for various
structural configurations.
The rest of this paper is organized as follows: Section 2 explains the details of the hybrid access
scheme. In Section 3 represents the system model of the hybrid access scheme, presents the
signal expression of the transmitted and received signals. Moreover, in section 3 presents a
detailed explanation about the structure and properties of the rectangular and circular
transmission medium. The simulation results are presented in Section 4. Finally, this paper is
summarized in Section 5.
2. HYBRID ACCESS SCHEME
A Hybrid Access Scheme (HAS) is a combination of the Orthogonal Frequency Subcarrier-based
Multiple Access Scheme (OFSMA) [7] and Dedicated Channel Access (DCA) presented in
Figure 2. The general sensors transmit signal based on the OFSMA access scheme over the
randomly selected subcarriers and the audio and video sensors transmit over the dedicated
subcarriers assigned for transmission. The OFSMA access scheme presented in Figure 3. The
OFSMA access scheme adopts a packet diversity principle and transmits multiple copies of the
same packet over a different numbers of subcarrier channels in order to improve the reliability of
the transmission. The system assumed that, there is no internal or self-packet collision among the
transmitted duplicated packets emitted from a sensor for a single specific TTI. According to the
OFSMA scheme, first a packet equivalent bit is created and copied for the number of duplicated
packets. Each duplicated packet bits select an independent orthogonal subcarrier frequency
randomly and perform modulation and mapping for transmission. After performing Inverse First
Fourier Transform (IFFT), the signal of the packet bits is transmitted over Additive White
Gaussian Noise (AWGN) channels to receiver. Due to multiple sensors transmission, there is a
probability of collision, but it is minimized by introducing a massive number of subcarrier
channels. Among the multiple transmission of a single packet, if at least one packet is
successfully received by the receiver then it marked as a success and receiver ignores the other
copies of the same duplicated packets. At the receiver side, uses a band pass filter to detect and
collect the signal frequency. The receiver then started performing the reverse operation and
decoded the signal bits from independent orthogonal subcarrier frequency and retrieve the
original bit sequence. The audio and video sensors transmit packet over the dedicated channel.
Due to the exclusive assignment of the channel, there is no probability of the collision, but a
minor number of packets might be lost due to having low signal power at the receiver end.

75
Figure 2. Hybrid Access Scheme
Figure 3. OFSMA Access Scheme
3. SYSTEM MODEL
We consider signal transmission and propagation in our system model. The first part of our
system models presents the HAS system design. The system design covers in a short range of the
signal over the randomly selected subcarrier’s transmitted packets for a single TTI, dedicated
channels signal for a single TTI, considers AWGN noisy channels and finally the total received
signal from all sensors in a single TTI. The second part of the system considers different

76
structures as part of a robotic structure and captures the signal propagation expression for
different frequency bands. The HAS system design and robotic signal propagation explain below.
3.1. HAS System Design
An uplink transmission system is considered in our system present as shown in Figure 4. A finite
number of sensors ubiquitously plotted around the centralized receiver. In our system, three types
of sensors are considered as a) General sensor, b) Audio sensor and, c) Video sensor. The sensors
transmit signal over the finite number of subcarrier channels. The subcarrier channels are also
divided into two categories as random accessible channels and dedicated channels. The general
sensors transmit signal data over the randomly selected channel and there might be a probability
of a collision. To avoid the collision over the transmission, the system adopts the packet diversity
principle. According to the packet diversity principle, each general sensor transmits multiple
copies of the same packet over the randomly selected subcarrier channels. Among the multiple
copies of the packet, if at least one packet is successfully received by the receiver, then the
transmission is determined as a successful transmission. The system assigned a massive number
of subcarrier channels in order to lower the probability of the collision. The general sensors are
responsible for transmitting regular small payload data for communication. The dedicated
subcarrier channels are allocated for audio and video sensors. There is no probability of collision
in the dedicated channels for audio and video sensors.
Figure 4. HAS system design
The system assumes a total K number of sensors transmitting over the randomly accessible
subcarrier channels defined as RK. The general sensors represented as sensor1,
sensor2,...,sensorRK. The general sensors are assigned a set of subcarrier channels as fs= f1, f2, ….,
fc . Each subcarrier channel fi can be selected randomly as

77
𝑓𝑠
ℝ
← 𝑓𝑖 (1)
Each general sensor transmitting x=1, 2, …, d duplicated packets over the randomly selected
subcarrier channels fi. The d duplicated packet signal sd(t) can be expressed [7] as
𝑆 𝑑( 𝑡) = ∑ 𝑢 𝑥( 𝑡) 𝑒 𝑗2𝜋𝑓 𝑖𝑥 𝑡
𝑑
𝑥=1
where ux(t) is a complex baseband signal for x number of duplicated packets with an in-phase and
quadrature component and fix is the randomly selected frequency fi for x duplicated packets. The
slotted-ALOHA protocol assigns sensors different slot to transmit data packets. For a total of
y=1, 2, …, RK number of general sensors transmit d duplicated equals to RK x d possible packet
can be transmit in a single slot that can be presents as
𝑆 𝑅𝐾( 𝑡) = ∑ ∑ 𝑢 𝑥,𝑦( 𝑡) 𝑒 𝑗2𝜋𝑓 𝑖𝑥 𝑡
𝑑
𝑥=1
𝑅𝐾
𝑦=1
where ux,y(t) is a complex baseband signal for x number of duplicated packets from y number of
sensors having an in-phase and quadrature component. The system also considers a set of audio
and video sensors which transmit audio and video packets over the dedicated channels. For a
single TTI slot, let’s consider a maximum of DK audio or video frames are transmitted over the
dedicated subcarrier channel can be expressed as
𝑆 𝐷𝐾( 𝑡) = ∑ 𝑢( 𝑡) 𝑒 𝑗2𝜋𝑓 𝑚 𝑡
𝐷𝐾
𝑚=1
Where u(t) is a complex baseband signal expression for audio or video frame with an in-phase
and quadrature component, fm is the dedicated subcarrier frequency channel for the frame and t
determines the duration of the frame. So, the total data transmitted in a single slot over the hybrid
access scheme can be represented as
𝑆𝑡𝑜𝑡𝑎𝑙( 𝑡) = 𝑆 𝑅𝐾(𝑡) + 𝑆 𝐷𝐾( 𝑡)
𝑆𝑡𝑜𝑡𝑎𝑙( 𝑡) = ∑ ∑ 𝑢 𝑥,𝑦( 𝑡) 𝑒𝑗2𝜋𝑓𝑖𝑥 𝑡
𝑑
𝑥=1
𝑅𝐾
𝑦=1
+ ∑ 𝑢( 𝑡) 𝑒𝑗2𝜋𝑓 𝑚 𝑡
𝐷𝐾
𝑚=1
Equation (5) presents the signal expression for total transmitted packet by the audio, video and
general sensors in a single transmission slot. The total signal Stotal(t) is transmitted over the
AWGN channel, and noise n(t) ∼CN (0, σ2) is added to the signal. For any single TTI slot, the
received signal rtotal(t) can be deﬁned as
𝑟𝑡𝑜𝑡𝑎𝑙( 𝑡) = ∑ ∑ 𝑢 𝑥,𝑦( 𝑡) 𝑒𝑗2𝜋𝑓𝑖𝑥 𝑡
𝑑
𝑥=1
𝑅𝐾
𝑦=1
+ ∑ 𝑢( 𝑡) 𝑒𝑗2𝜋𝑓 𝑚 𝑡
𝐷𝐾
𝑚=1
+ 𝑛( 𝑡).
(2)
(3)
(4)
(5)
(6)

78
The equation (6) presents the total received signal with noise added by the receiver. We assumed
that, the system has the advanced receiving and decoding capability to receive and decode
multiple copies of the data packet at the same time.
3.2. Signal Propagation
We consider a short-range signal propagation inside a robot`s body. The signal needs to
propagation 0.1m~1m distance based on sensor deployment over the robot. We consider two
types of the signal transmission medium as part of the robotic inner structure in our proposed
system, rectangular transmission medium and circular transmission medium presented in Figure
5. The rectangular and circular shaped transmission medium design with IRON metal and outside
coated with silver. The inner long tunnel-shaped area of both rectangular and circular shaped
transmission medium towards Z- direction is full of air. We assume that the signal transmits from
the transmitting point indicated in the Figure and receives at the receiving point defined at the
end of the Z- direction. The signal propagates towards Z- direction both for rectangular and
circularmedium. The rectangular transmission medium considers three type of width and height
configuration as (190,95) mm, (100,50) mm, and (25,15) mm. The circular transmission medium
considers three radius configurations as 100 mm, 50 mm, and 5 mm. We consider the following
parameters listed in Table 1 for evaluating the signal propagation expression of the rectangular
and circular shaped transmission medium.
Figure 5. Signal transmission medium, a) Rectangular shaped transmission medium, b) Circular shaped
transmission medium.

79
Table 1. Rectangular and circular transmission medium properties
Parameters
Rectangular transmission
medium
Circular transmission medium
Transmit power 20 dBm 20 dBm
Operating frequency
900MHz, 2.4GHz, 24GHz, and
55GHz
900MHz, 2.4GHz, 24GHz, and
55GHz
Structure
width Height Radius
190mm 95mm 100mm
100mm 50mm 50mm
25mm 15mm 5mm
Length 1000mm 1000mm
Delta S 0.02 0.02
Relative permittivity, air 1.0006 1.0006
Relative permittivity, iron 1 1
Relative permittivity, silver 1 1
Relative permeability, air 1.0000004 1.0000004
Relative permeability, iron 4000 4000
Relative permeability, silver 0.99998 0.99998
4. SIMULATION RESULTS
This section covers the details of our proposed HAS system simulation and performance
evaluation. We simulate our HAS system in a system-level simulation generating in the
MATLAB simulator to evaluate the performance of our hybrid access scheme. The signal
propagation expression is captured using ANSYS HFSS software. The 90 sensors transmitted 3-
packet, 5-, and 7- packet duplication over a different number of subcarrier channels where the
subcarrier selection is random and determine the minimum number of subcarriers, reliability and
collision probability of the system. We consider random subcarrier selection in order to minimize
the scheduling latency of the system. The packet generation and transmission follow the poison
arrival process. The sensors transmit packets over a slotted ALOHA system and each slot
duration is 0.1ms. The HAS system considers BPSK modulation scheme to ensure low bit error of
the transmitted packets. The simulation runs for 1000s and presented in the figure. The details
simulation parameters are presented in Table 2.
4.1. Reliability and Collision Probability
The 90 sensors transmit 3-, 5-, and 7-packet duplication over 2.4 GHz frequency band and
determine the minimum number of subcarriers to satisfy the URLLC defined reliability of
99.999% for different arrival conditions presented in Figure 6. The 3-packet duplication secured
reliability of 99.999% having a higher number of subcarriers included in the system compared to
all other packet duplications. At an arrival rate of 5000 pk/sec, the 3-packet duplications
demanded 440 subcarriers to satisfy the reliability of 99.999% for packet transmission. This
happens due to the smaller number of packet duplications and a higher number of intra-packet

80
collisions. The 5-packet duplication secured 99.999% reliability with a lower number of
subcarriers demands compared to 3-packet duplications but higher than 7-packet duplications. At
5000 pk/sec arrival condition, the 5-packet duplications required 140 subcarriers to satisfy the
reliability of 99.999% for packet transmission. The 7-packet duplication achieved 99.999%
reliability having the lower number of subcarriers demands compared to all other packet
duplications. At 5000 pk/sec, the 7-packet duplications demanded 110 subcarriers to satisfy the
URLLC defined reliability of 99.999% for packet transmission.
Table 2. Simulation properties
Parameters Values
Total general sensor 90
Total random Subcarrier channel 60~450
Total audio Sensor 5
Total video sensor 5
Dedicated channel 10
Carrier frequency 2.4GHz
Operating frequency for signal
expression
900MHz, 2.4GHz, 24GHz, and 55GHz
Subcarrier bandwidth 10 KHz
Packet size 100 bits
Modulation BPSK
Transmit Power 20 dBm
Link speed 1 Mbps
Packet duplication 3, 5 and 7
Arrival rate, λ 1~10000 pk/sec
Slot duration 0.1 ms
Simulation time 1000 s

81
Figure 6. The minimum number of subcarriers determined for satisfying URLLC reliability of 99.999% for
different packet duplication over 2.4 GHz frequency band.
The reliability and collision probability is measured for all sensors. The 3-, 5-, and 7-packet
duplications transmitted packets over randomly selected 90 subcarrier channels. The audio and
video sensors transmitted a single packet over the 10 dedicated channels. At the receiver side, we
evaluated the reliability and collision probability for audio, video and general sensors. The
reliability for 3-, 5-, 7-packet duplication and dedicated channel assigned audio and video sensors
is presented in Figure 7.
As shown in Figure 7, the 3-packet duplication has lower reliability compared to all others in the
simulation results due to small number of duplicated packets and subcarrier channels. At an
arrival rate of 10000 pk/sec, the 3-packet duplication reliability is 99.9578%. The 3-packet
duplication could not achieve 99.999% reliability for any arrival conditions due to small number
of packet duplications. The 5-packet duplication has higher reliability compared to 3-packet
duplication but lower than 7-packet and dedicated channels accessible audio and video sensors.
At arrival of 1 pk/sec, the 5-packet has secured 99.9995% reliability and at the highest arrival rate
10000 pk/sec the reliability is 99.9867%. The 10 audio and video sensors reliability response are
closed to 7-packet duplication reliability up to 2500 pk/sec arrival rates after that the dedicated
channels improved its reliability response. The dedicated channels reliability response and 7-
packet reliability response are zoomed from 1000 pk/sec to 10000 pk/sec arrival rates. The 7-
packet secure 99.9994% reliability at an arrival rate of 2500 pk/sec but after that arrival rate its
reliability is decreased and lowers than 99.999%. At an arrival rate of 10000 pk/sec, the 7-packet
reliability response is 99.989%. The 10 audio and video sensors dedicated channel evaluated
99.999% reliability up to arrival rate 7500 pk/sec and at an arrival rate of 10000 pk/sec, the
estimated reliability is 99.9989%.

82
Figure 7. Reliability response for 3-packet, 5-packet, 7-packet and 10 audio and video sensors dedicated
channel.
The 90 general sensors transmit 3-, 5-, 7-packet duplication over the 90 subcarrier channels and
10 audio and video sensors forward a single packet over 10 dedicated channels. At the receiver
site, we evaluate the collision probability that presented in Figure 8. According to Figure 8, the 3-
packet duplication has a higher collision probability than 5-, and 7-packet duplications due to
lower number of packet duplications and a small number of subcarrier channels. At an arrival rate
of 10000 pk/sec, the 3-packet duplications collision probability is 0.0422%. The 5-packet
duplications collision probability is lower than 3 -packet duplications but higher than 7-packet
duplications. At the highest 10000 pk/sec arrival rate, the 5-packet collision probability is
0.0133%. The 7-packet duplications collision probability is higher than 3-, and 5-packet
duplications and at arrival rate of 10000 pk/sec it achieved 0.011%. Among the audio and video
sensors transmitted packets, there is no collision but very few packets lost due to low power at
the receiver. We set the minimum threshold power to receive at receiver is 39.798 dBm for single
2.4 GHz frequency band. The packets having lower power than that is dropped, and the collision
probability is presented along with 7-packet duplication inside the zoom section. The audio and
video sensors secured lower collision probability than all other comparisons and at an arrival rate
of 10000 pk/sec, it secured 0.0011%. The HAS system assumed that there is no collision among
the duplicated packets emitted from same source in the network. Moreover, in a sequence of
bitstreams, if there is a combination of success packets and collide packets bits, the receiver
assumed to decode and select one the success packets bit sequence from the total bit sequence.

83
Figure 8. Collision probability for 3-packet, 5-packet, 7-packet and 10 audio and video sensors dedicated
channel.
4.2. Signal Propagation
The signal expressions are captured for rectangular and circular transmission medium at
maximum 1meter (1000mm) distance as the different internal structure of a future robot body.
The signal propagation is measured and captured for 900 MHz, 2.4 GHz, 24 GHz, and 55 GHz
frequency bands. The measurement properties are depicted in Table 1. The rectangular
transmission medium having width of 190 mm and height of 95 mm signal expression captured
for defined frequency bands that presented in Figure 9. The signal is transmitted through the air
medium to Z direction at about 1000 mm long. For the rectangular transmission medium having a
configuration of width 190 mm, and height 95 mm, the strong signal is transmitted over the 900
MHz and 2.4 GHz frequency bands. The received signal is comparatively weak for 24 GHz
frequency band and for 55 GHz the signal could not propagate at the end towards the receiver to
Z- direction.
The signal propagation expression for rectangular transmission medium with a width of 100 mm
and a height of 50 mm is presented in Figure 10. The signal could not propagate through 900
MHz, 24 GHz, and 55 GHz frequency bands at the end of the Z- direction to the receiver due to
half of the size of the rectangular medium. But only 2.4 GHz frequency bands successfully
propagated the signal at the receiving Z- direction. Moreover, the signal slightly propagated over
900 MHz is comparatively strong compared to 24 GHz frequency band and the signal propagated
over 24 GHz frequency band is also comparatively strong compared to 55 GHz frequency band.

84
Figure 9. Signal propagation over 1000mm long, 195 mm width and 95 mm height rectangular
transmission medium for, a) 900 MHz frequency band b) 2.4 GHz frequency band, c) 24 GHZ frequency
band, and d) 55 GHz frequency band.
For the width of 25 mm and a height of 15 mm of the rectangular transmission medium signal
expression is illustrated in Figure 11. The 900 MHz and 2.4 GHz frequency band shown a dim
signal expression, but 24 GHz and 55 GHz present a strong signal propagation compared to
previous rectangular configuration. By analyzing the signal propagation expression presented in
Figure 9-11, the higher size of width and height is better for lower frequency bands and the lower
width and height size shown a comparatively better signal propagation expression for higher
frequency bands.

85
The signal propagation for a circular transmission medium is illustrated in the figure 12-14. The
circular transmission medium having a radius of 100 mm is presented in the figure 12. As
presented in figure, the signal is successfully propagated over 900 MHz and 2.4 GHz frequency
bands to the receiver towards Z- direction and signal strength is strong enough. The signal could
not propagate to the receiver over 24 GHz and 55 GHz frequency bands and signal strength is
extremely low compared to 900 MHz and 2.4 GHz frequency bands.
The signal propagation for circular transmission medium having radius of 50 mm is presented in
Figure 13. The signal only propagated over 2.4 GHz frequency band and none of the other three
frequency band could not propagate the signal to the receiver towards Z- direction. Moreover, the
55 GHz frequency band’s propagate signal is the weakest signal compared to all others. So, for
the robotic internal transmission, the proposed circular structure performance is worse compare to
other similar structures.
The signal propagation expression illustrated in Figure 14 for 5 mm radius shown the signal is
transmitted to the receiver towards Z direction for 24 GHz and 55 GHz but a very poor signal
expression for 900 MHz and 2.4 GHz frequency bands. This circular structure shows better signal
strength for 24 GHz and 55 GHz frequency bands compared to the previous circular transmission
medium structure. That implies this structure is recommended as better for higher frequency
bands. The circular transmission medium is analyzed for three different radius configurations
over 900 MHz, 2.4 GHz, 24 GHz, and 55 GHz frequency bands. The higher radius configuration
of the circular transmission medium is more capable to transmit strong signals and able to
propagate signals to the receiver towards Z- direction for comparatively lower frequency bands.
On the other hands, the lower circular transmission medium structure viable for higher frequency
bands with strong signals.

86
Figure 12. Signal propagation over 1000mm long, and 100 mm radius circular transmission medium for, a)
900 MHz frequency band b) 2.4 GHz frequency band, c) 24 GHZ frequency band, and d) 55 GHz
frequency band.
frequency band.

87
frequency band.
The signal propagation expression results for different frequency bands and different structural
configuration is summarized in Table 3 with an overview defining either the signal is strong,
average or bad over 900 MHz, 2.4 GHz, 24 GHz, and 55 GHz frequency bands both for the
rectangular and circular transmission medium. Moreover, the result presented in Table 3 also
defines either the signal is propagated to the receiving point towards Z for different frequency
bands and different structural configurations or not.
5. CONCLUSION
In this paper, a hybrid access scheme is proposed for future robot’s internal communication by
sensors instead of wire. The audio, video and general sensors able to transmit signals
simultaneously over the hybrid access scheme. The audio and video sensors transmit signals over
the dedicated subcarrier channels and the general sensors transmit signals over the randomly
selected subcarrier channels. The OFSMA system’s reliability is evaluated for 99.999% as
URLLC reliability requirement and determine the minimum number of subcarriers demanded to
achieve this reliability level for different packet duplications. The 3-packet duplication needed
440 subcarriers, 5-packet duplication demanded 140 subcarriers, and finally the 7-packet
duplications required 110 subcarriers to satisfy the URLLC recommended reliability of 99.999%
at 5000 pk/sec arrival conditions. The HAS system’s reliability and collision probability is
evaluated for fixed channel conditions and determine either different arrival conditions the
reliability satisfies the URLLC specified reliability requirement or not. For fixed channel
assignment, the URLLC reliability requirement of 99.999%, 3-packet duplication not satisfied for

88
Table 3. Signal propagation results for different structural configuration over different frequency bands
Parameters 900 MHz 2.4 GHz 24 GHz 55 GHz
Rectangulartransmission
medium
Width Height Strength
Propaga
te?
Strength
Propagate
?
Strength
Propaga
te?
Strength
Propagate
?
190mm 95mm Strong Yes Strong Yes Average Yes Bad No
100mm 50mm Bad No Strong Yes Bad No Bad No
25mm 15mm Bad No Bad No Strong Yes Average yes
Circular
transmissionmedium
Radius
100mm Strong Yes Strong Yes Bad No Bad No
50mm Bad No Strong Yes Bad No Bad No
5mm Bad No Bad No Strong Yes Average Yes
any arrival condition, 5-packet duplication satisfied for 1 pk/sec, 7-packet duplication satisfied
for up to 2500 pk/sec, and finally dedicated channel assignment satisfied for 7500 pk/sec arrival
condition. Moreover, the signal propagation initiated by different sensors is also simulated over
ANSYS HFSS software for 900 MHz, 2.4 GHz, 24 GHz and 55 GHz frequency bands. The
transmission medium having size (width, height and radius) of higher number is shown better
performance for comparatively lower frequency bands and vice-versa. For signal measurement,
we cannot determine a fixed value of received power in dBm in the receiving point. In future, we
try to resolve the problem. The system is simulated over two different simulation platform but in
real field the result might have more interference and the result might be affected by different
factors.
We investigate our system for a short-range robotic communication system. The HAS scheme
might also applicable for any short-range, mission-critical, higher reliable system. The HAS
system might also consider automation of vehicles and other types of robotic or automated
communication domains.
CONFLICTS OF INTEREST
The authors declare no conflict of interest.
ACKNOWLEDGMENT
This research work is supported by JICA INNOVATIVE ASIA program. We grateful to JICA.

89
REFERENCES
[1] Shimojo, M., Araki, T., Teshigawara, S., Ming, A., & Ishikawa, M. (2007, October). A net-structure
tactile sensor covering free-form surface and ensuring high-speed response. In 2007 IEEE/RSJ
International Conference on Intelligent Robots and Systems (pp. 670-675). IEEE.
[2] Ganjalizadeh, M., Di Marco, P., Kronander, J., Sachs, J., &Petrova, M. (2019, December). Impact of
correlated failures in 5G dual connectivity architectures for URLLC applications. In 2019 IEEE
Globecom Workshops (GC Wkshps) (pp. 1-6). IEEE. [3]3GPP, “5G; Study on Scenarios and
Requirements for Next Generation Access Technologies,” Tech. Rep., 38.913,14.3.0, 2017.
[4] D’Errico, L., Franchi, F., Graziosi, F., Marotta, A., Rinaldi, C., Boschi, M., &Colarieti, A. (2019,
April). Structural Health Monitoring and Earthquake Early Warning on 5G uRLLC Network. In 2019
IEEE 5th World Forum on Internet of Things (WF-IoT) (pp. 783-786). IEEE.
[5] Notay, J. K., & Safdar, G. A. (2011, September). A wireless sensor network based structural health
monitoring system for an airplane. In The 17th International Conference on Automation and
Computing (pp. 240-245). IEEE.
[6] Almarashdeh, I., Alsmadi, M., Hanafy, T., Albahussain, A., Altuwaijri, N., Almaimoni, H., ... & Al
Fraihet, A. (2018). Real-time elderly healthcare monitoring expert system using wireless sensor
network. International Journal of Applied Engineering Research ISSN, 0973-4562.
[7] Ratiu, O., Panagiotopoulos, N., Vos, S., & Puschita, E. (2018, December). Wireless Transmission of
Sensor Data over UWB in Spacecraft Payload Networks. In 2018 6th IEEE International Conference
on Wireless for Space and Extreme Environments (WiSEE) (pp. 131-136). IEEE.
[8] M. A. Hossain, M. Saitou, Z. Pan, J. Liu, and S. Shimamoto. (2020) “Orthogonal Frequency
Subcarrier-based Multiple Random Access in Ultra Reliability and Low Latency Communication,” in
IEEE Consumer Communications Networking Conference, ser. 2nd IEEE Workshop on Cyber-
Physical Networking (CPN’20), In press
[9] Islam, A., Musavian, L., & Thomos, N. (2019, December). Performance Analysis of Vehicular
Optical Camera Communications: Roadmap to uRLLC. In 2019 IEEE Global Communications
Conference (GLOBECOM) (pp. 1-6). IEEE.
[10] Yoshizawa, T., Baskaran, S. B. M., & Kunz, A. (2019, October). Overview of 5G URLLC System
and Security Aspects in 3GPP. In 2019 IEEE Conference on Standards for Communications and
Networking (CSCN) (pp. 1-5). IEEE.
[11] Park, J., Samarakoon, S., Shiri, H., Abdel-Aziz, M. K., Nishio, T., Elgabli, A., & Bennis, M. (2020).
Extreme URLLC: Vision, Challenges, and Key Enablers. arXiv preprint arXiv:2001.09683.
[12] Chang, B., Zhao, G., Chen, Z., Li, P., & Li, L. (2019, December). D2D Transmission Scheme in
URLLC Enabled Real-Time Wireless Control Systems for Tactile Internet. In 2019 IEEE Global
Communications Conference (GLOBECOM) (pp. 1-6). IEEE.
[13] Baratè, A., Haus, G., Ludovico, L. A., Pagani, E., & Scarabottolo, N. (2019). 5G Technology for
Augmented and Virtual Reality in Education. In Proceedings of the International Conference on
Education and New Developments 2019 (END 2019) (pp. 512-516).
[14] Anand, A., De Veciana, G., & Shakkottai, S. (2020). Joint scheduling of URLLC and eMBB traffic in
5G wireless networks. IEEE/ACM Transactions on Networking.
[15] Alsenwi, M., Tran, N. H., Bennis, M., Bairagi, A. K., & Hong, C. S. (2019). eMBB-URLLC resource
slicing: A risk-sensitive approach. IEEE Communications Letters, 23(4), 740-743.
[16] Pan, C., Ren, H., Deng, Y., Elkashlan, M., & Nallanathan, A. (2019). Joint blocklength and location
optimization for URLLC-enabled UAV relay systems. IEEE Communications Letters, 23(3), 498-
501.
[17] Singh, B., Tirkkonen, O., Li, Z., & Uusitalo, M. A. (2017). Contention-based access for ultra-reliable
low latency uplink transmissions. IEEE Wireless Communications Letters, 7(2), 182-185.
[18] Choi, Y. J., Park, S., & Bahk, S. (2006). Multichannel random access in OFDMA wireless
networks. IEEE Journal on Selected Areas in Communications, 24(3), 603-613.
[19] Sen, S., Dorsey, D. J., Guérin, R., & Chiang, M. (2012, October). Analysis of slotted ALOHA with
multipacket messages in clustered surveillance networks. In MILCOM 2012-2012 IEEE Military
Communications Conference (pp. 1-6). IEEE.

ROBOTIC INNER SIGNAL PROPAGATION AND RANDOM ACCESS OVER HYBRID ACCESS SCHEME

More Related Content

What's hot

Similar to ROBOTIC INNER SIGNAL PROPAGATION AND RANDOM ACCESS OVER HYBRID ACCESS SCHEME

More from IJCNCJournal

Recently uploaded

ROBOTIC INNER SIGNAL PROPAGATION AND RANDOM ACCESS OVER HYBRID ACCESS SCHEME