Performance comparison
between slotted IEEE
802.15.4 and IEEE 802.11ah
in IoT based applications
Speaker: Po-Hung Chen
Advisor: Dr. Ho-Ting Wu
2016/01/21
Outline
• Introduction
• IEEE 802.15.4
• IEEE 802.11ah
• Simulation Setting
• Simulation Result
• Conclusion
• Reference
1
Introduction
• In this paper, we present a performance comparison between IEEE
802.15.4 and IEEE 802.11ah standards by evaluating the network
throughput and energy consumption.
• IoT requirements, such as lower complexity, reduced implementation
and operation costs, broader coverage range and higher energy
efficiency.
2
Introduction(Cont.)
• The IEEE 802.15.4 standard is presently being used for wireless sensor
networks and ZigBee applications.
• IEEE 802.11ah is a new global WLAN standard using sub-1 GHz
frequency band.
Transmission range
Bit rate
Bandwidth
IEEE 802.15.4
10-100 m
20 kbps
40 kbps
250 kbps
868 MHz (Europe)
915 MHz (America)
2.4 GHz (Global)
IEEE 802.11ah
1000 m
least 100 kbps
Sub 1 GHz
3
IEEE 802.15.4
• IEEE 802.15.4 is a standard which specifies the physical layer and mac
layer for low-rate wireless personal area networks (LR-WPANs).
• It’s defined in 2003.
• The ZigBee technology is based on the IEEE 802.15.4 standard.
4
IEEE 802.15.4(Cont.)
• IEEE 802.15.4 standard has two types of devices a Full-Function
device (FFD) and a Reduced-Function device (RFD).
• The FFD is capable of all network functionalities and can operate in
three different modes: it can operate as a PAN coordinator, a
coordinator or it can serve simply as a device.
• An RFD device is low on resources and memory capacity and is
capable only of very simple applications such as a node which senses
light or temperature.
5
IEEE 802.15.4(Cont.)
6
IEEE 802.15.4(Cont.)
• The IEEE 802.15.4 standard defines two different channel access
modalities:
• Beacon-enabled  slotted CSMA/CA
• Beacon-less  unslotted CSMA/CA
7
IEEE 802.15.4(Cont.)
• Communication to a coordinator in a beacon-enabled network
8
IEEE 802.15.4(Cont.)
• Communication to a coordinator in a beacon-less network
9
IEEE 802.15.4(Cont.)
• Slotted CSMA/CA
Slotted CSMA/CA
Delay for
random(2^BE-1)
unit backoff periods
NB=0, CW=2
BE=min(2,macMinBE)
Y
Perform CCA on
backoff period
boundary
Batterylife
Extension ?
N
BE=macMinBE
Channel Idle?
Y
N
CWcontention window
NBnumber of backoffs
BEbackoff exponent
RTnumber of retransmissions
CCAclear channel assessment
CW=2, NB=NB+1
BE=min(BE+1,aMaxBE)
Locate Backoff
Period Boundary
N
CW=CW-1
N
NB>macMaxCSMABackoffs?
Y
Failure
CW=0
Y
Success
10
IEEE 802.15.4(Cont.)
• Unslotted CSMA/CA
UnSlotted CSMA/CA
Channel Idle?
NB=0,
BE=macMinBE
N
NB=NB+1
BE=min(BE+1,aMaxBE)
Delay for
random(2^BE-1)
unit backoff periods
Perform CCA
Y
N
NB>macMaxCSMABackoffs?
Y
Failure
Success
11
IEEE 802.11ah
• The IEEE 802.11ah standard is one of the candidate standards for IoT
and Machine to Machine (M2M) applications which is still in its
preliminary stage of development.
• IEEE 802.11ah draft 1.0 was conducted in September 2013.
• The standardization should be completed approximately by March
2016.
12
IEEE 802.11ah(Cont.)
• IEEE 802.11ah using sub 1-GHz frequency to transfer data.
• It’s a new standard for IoT, because it can transfer a long range more
than 1000 meter, least 100 kbps data rate, and compatible with
802.11 WLAN legacies.
The common standards we use everyday:
• IEEE 802.11n  2.4GHz
• IEEE 802.11ac  5GHz
13
IEEE 802.11ah(Cont.)
IEEE 802.11ah advantages:
• Low power consumption
• Long battery life
• Burst data transmission
• Easy Setup
• High Transmission range
• On-Hop reach
• Reliability
14
IEEE 802.11ah(Cont.)
Free space path loss equation
Pr
Pt
f
c
d
= Received signal strength [dBm]
= Transmitter output signal strength [dBm]
= frequency [Hz]
= speed of light
= distance from transmitter
15
IEEE 802.11ah(Cont.)
16
IEEE 802.11ah(Cont.)
• The basic access to the medium in IEEE 802.11ah is using the DCF
based on CSMA/CA scheme.
IEEE 802.11 MAC defined two Coordination Function :
• Distributed Coordination Function (DCF)
• Point Coordination Function (PCF)
17
IEEE 802.11ah(Cont.)
The DCF scheme can use two different mechanisms:
• two-way handshaking technique known as basic access mechanism.
• four-way handshaking technique known as RTS/CTS method.
Source
Distance
RTS
CTS
Source
Distance
DATA
ACK
DATA
ACK
Transmission With
RTS/CTS method
Transmission Without
RTS/CTS method
18
IEEE 802.11ah(Cont.)
• IEEE 802.11ah use cases,
backhaul networks for
sensor and meter
19
Simulation Setting
• Using OMNeT++ to simulate.
• OMNeT++ is an open-source simulator.
• C++
• It’s useful for simulating the communication networks, and other
distributed and parallel systems.
20
Simulation Setting(Cont.)
• Simulation Topology
• The AP is located in the middle of the playground.
• Other nodes are located in a uniformly distributed
manner.
• To increase the simulation accuracy, each
simulation scenario is randomly repeated 100
times and average of results is calculated by using
the Monte Carlo method.
21
Simulation Setting(Cont.)
• Common setting for both standards.
22
Simulation Setting(Cont.)
Setting for IEEE 802.15.4
Setting for IEEE 802.11ah
23
Simulation Setting(Cont.)
• For instance, the size of payload is chosen 256 Bytes in both
standards, even though the maximum payload in IEEE 802.15.4 is 127
Bytes.
• In simulate IEEE 802.15.4 standard, it’s removed the CFP period.
• In simulate IEEE 802.11ah standard, it’s using 2-way handshaking.
24
Simulation Setting(Cont.)
2 type for simulate
• Ideal channel
• Non-ideal channel
path loss [dB]
where d is the distance between transmitter and receiver in meter.
25
Simulation Setting(Cont.)
2 different traffic to simulate
• Saturated traffic
Each nodes always have a packet to send.
• Low traffic
Each node generates a packet with the inter arrival time of 100 ms
with random starting time.
26
Simulation Setting(Cont.)
• It’s using a fairness measure, because of in non-ideal channel the
signal is loss in the path, the closer nodes have higher probability to
send their packet.
• Fairness measure is calculated by Raj Jain's equation:
i
i
where n stands for the number of nodes and Xi is the throughput
of the ith node.
27
Simulation Result
28
Simulation Result(Cont.)
29
Simulation Result(Cont.)
30
Simulation Result(Cont.)
31
Conclusion
• The IEEE 802.11ah is better in term of throughput but in the case of
the energy consumption, the IEEE 802.15.4 still outperforms the IEEE
802.11ah specially in a dense network and non-saturated traffic.
32
Reference
• Behnam Badihi Olyaei; Juho Pirskanen; Orod Raeesi, “Performance comparison
between slotted IEEE 802.15.4 and IEEE 802.1 lah in IoT based applications” in
Wireless and Mobile Computing, Networking and Communications (WiMob), 2013
IEEE 9th International Conference, pp.332-337
• N. Salman; I. Rasool; A.H. Kemp, ” Overview of the IEEE 802.15.4 standards family for
Low Rate Wireless Personal Area Networks” in Wireless Communication Systems
(ISWCS), 2010 7th International Symposium, pp.701-705
• Weiping Sun; Munhwan Choi; Sunghyun Choi, “IEEE 802.11ah: A Long Range 802.11
WLAN at Sub 1 GHz” in Journal of ICT Standardization, Vol. 1, pp.83-108, doi:
10.13052/jicts2245-800X .125, July 2013
• IEEE Std 802.15.4™-2003
• Ozkan Katircioğlu; Hasan Isel; Osman Ceylan, ” Comparing ray tracing, free space
path loss and logarithmic distance path loss models in success of indoor localization
with RSSI” in Telecommunications Forum (TELFOR), 2011 19th, pp.313-316
(Just for the free space path loss equation)
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Thank you for listening.
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