Performance comparison between slotted IEEE

802.15.4 and IEEE 802.11ah in IoT based applications

Speaker: Po-Hung ChenAdvisor: Dr. Ho-Ting Wu

2016/01/21

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Outline

• Introduction• IEEE 802.15.4• IEEE 802.11ah• Simulation Setting• Simulation Result• Conclusion• Reference

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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.

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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. IEEE 802.15.4 IEEE 802.11ahTransmission range 10-100 m 1000 m

Bit rate20 kbps40 kbps250 kbps

least 100 kbps

Bandwidth868 MHz (Europe)915 MHz (America)2.4 GHz (Global)

Sub 1 GHz

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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.

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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.

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IEEE 802.15.4(Cont.)

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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

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IEEE 802.15.4(Cont.)

• Communication to a coordinator in a beacon-enabled network

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IEEE 802.15.4(Cont.)

• Communication to a coordinator in a beacon-less network

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IEEE 802.15.4(Cont.)

• Slotted CSMA/CA

CWcontention window NBnumber of backoffsBEbackoff exponentRTnumber of retransmissionsCCAclear channel assessment

Slotted CSMA/CA

NB=0, CW=2

Batterylife Extension ?BE=min(2,macMinBE)

BE=macMinBE

Locate Backoff Period Boundary

Delay for random(2^BE-1)

unit backoff periods

Perform CCA on backoff period

boundary

Channel Idle?

CW=2, NB=NB+1BE=min(BE+1,aMaxBE) CW=CW-1

CW=0NB>macMaxCSMABackoffs?

Failure Success

Y

N

N

Y

Y

N

Y

N

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IEEE 802.15.4(Cont.)

• Unslotted CSMA/CA

UnSlotted CSMA/CA

NB=0, BE=macMinBE

Delay for random(2^BE-1)

unit backoff periods

Perform CCA

Channel Idle?

NB=NB+1BE=min(BE+1,aMaxBE)

NB>macMaxCSMABackoffs?

Failure Success

N

Y

Y

N

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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.

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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

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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

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IEEE 802.11ah(Cont.)

Free space path loss equation

= Received signal strength [dBm]= Transmitter output signal strength [dBm]= frequency [Hz]= speed of light= distance from transmitter

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IEEE 802.11ah(Cont.)

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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)

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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

DATA

ACK

Source Distance

DATA

ACK

Transmission With RTS/CTS method

Transmission Without RTS/CTS method

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IEEE 802.11ah(Cont.)

• IEEE 802.11ah use cases, backhaul networks for sensor and meter

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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.

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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.

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Simulation Setting(Cont.)

• Common setting for both standards.

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Simulation Setting(Cont.)

Setting for IEEE 802.15.4 Setting for IEEE 802.11ah

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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.

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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.

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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.

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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:

where n stands for the number of nodes and Xi is the throughput of the ith node.

i

i

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Simulation Result

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Simulation Result(Cont.)

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Simulation Result(Cont.)

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Simulation Result(Cont.)

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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.

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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.