TCP over 6LoWPAN for Industrial Applications

SHORT PAPER: TCP over 6LoWPAN for IndustrialApplications

Tiancong Zheng, Ahmed Ayadi, Xiaoran Jiang

IT/TELECOM BretagneRennes, France

8-9 February 2011

Ahmed Ayadi (IT/TELECOM Bretagne) NTMS Wireless Sensor Networks 2011 Paris, 8-9 February 2011 1 / 23

Outline

1 IPv6 over Low-power Wireless Personal Area Networks: Overview

2 Reliable transport protocols for 6LoWPANs: Why TCP??

3 TCP over 6LoWPANs for Industrial Applications

4 Experimental SetupHardware SetupSoftware SetupPhysical SetupEnergy Parameters

5 Results and DiscussionOne hop ScenarioMulti-hop Results

6 Conclusion and perspectives


IPv6 Low-power Wireless Personal Area Networks:Overview

6LoWPAN is the name of a working group in the internet area of the IETF,

The IETF Working Group 6LoWPAN has recently introduced an adaptationlayer that provides header compression and fragmentation/reassemblymechanisms to allow sending/receiving IPv6 packets over LLNs (e.g., IEEE802.15.4).

Internet

IPv4/IPv6

Edgerouters

LoWPAN nodes


The 6LoWPAN layer in TCP/IP model

Figure: The 6LoWPAN architecture


Reliable transport protocols for 6LoWPANs: Why TCP??

Currently, the 6LoWPAN WG has defined only UDP header compressionalgorithm named NHC,

UDP does not assure reliable communication between wireless divines,

If some industrial applications are loss tolerant, many others applications aresensitive to losses and their performance decrease when the loss ratioincreases.

TCP is the most reliable transport protocol used in IP-based networks,

TCP ensures reliability of data transmission from a sensor to a host externalIP and vice versa,

TCP could be a good choice for Machine-To-Machine reliable connection,

With TCP, we are able open SSH connection to log into wireless devices(sensors, actors, etc.) and execute commands.

TCP allows also remotely programming/retasking wireless devicesover-the-air.


Reliable transport protocols for 6LoWPANs: Why TCP??

Currently, the 6LoWPAN WG has defined only UDP header compressionalgorithm named NHC,

UDP does not assure reliable communication between wireless divines,

If some industrial applications are loss tolerant, many others applications aresensitive to losses and their performance decrease when the loss ratioincreases.

TCP is the most reliable transport protocol used in IP-based networks,

TCP ensures reliability of data transmission from a sensor to a host externalIP and vice versa,

TCP could be a good choice for Machine-To-Machine reliable connection,

With TCP, we are able open SSH connection to log into wireless devices(sensors, actors, etc.) and execute commands.

TCP allows also remotely programming/retasking wireless devicesover-the-air.


Outline








TCP over 6LoWPANs for Industrial Applications

Reduces wired links between machines,

I Replace cables by reliable wireless Machine-to-Machine (M2M) links:low-cost, easy installation, easy move and removal, etc.

1

1larousse.frAhmed Ayadi (IT/TELECOM Bretagne) NTMS Wireless Sensor Networks 2011 Paris, 8-9 February 2011 7 / 23


Renewable energy: Solar energy2, Wind power 3, etc.

I Reduce maintenance, integration and operation costs

2ecofriend.org3wordpress.com



Environment: Waste control, 45, Air quality, etc.

4evoc.com5waste.epa.gov.tw


Outline








Hardware Setup

In our testbed, all wireless devices are connected to the standard laptop byUSB port. This solution allows us to log the output messages from the motsto the standard laptop,

The embedded device used in our testbed: the Crossbow TelosB mote. Ituses TI MSP430 microcontroller, which offers a 10kB RAM, and a 48 kBprogram flash memory. Its radio is CC2420,which uses ISM frequency bandand offers 250 kbps data rate.

We used the last channel (No. 26) of IEEE 802.15.4 to reduce theinterference with IEEE 802.11.


Software Setup

Contiki OS 6 as the operating system for our wireless devices.

Contiki OSis a memory-constraint open source operating system fornetworked embedded devices that includes the uIPv6 stack.

We have chosen Contiki OS because 6LowPAN, UDP and TCP are alreadyimplemented on this OS.

Contiki OS provides standard operating system features like threads, timers,random number generator, clocks, a file system, and a command line shell.

TCP is partially implemented on Contiki OS because of thememory-constraint of the wireless devices.

6www.sics.se/contikiAhmed Ayadi (IT/TELECOM Bretagne) NTMS Wireless Sensor Networks 2011 Paris, 8-9 February 2011 12 / 23

Physical Setup

ERN1

N2

N3 N4

N5

EN

Laptop Station

Wireless Devices

1m 3m 3m

1.5m

1.5m

3m

Seven wireless nodes are distributed with the same distance (between threeand four meters) between each neighbor.We can distinguish four types ofwireless devices based on their functionalities:

1 The Edge Router is the border router that connects the wirelessnetwork to the IP-based wired network.

2 Wireless nodes (N1, N2, N3, N4, and N5) play two functions: a sensornode where TCP client application is running called Ternminal Node,or relay of data frames from the ER to the TN and vice-versa.

3 The External Node generates a concurrent CBR traffic.


Outline








Energy Parameters

Contiki OS provides a tool to compute the running time spent by a node onone of the flowing radio states: Transmit and Listen.

Contiki OS provides also an estimation of its CPU consumption.

For example to compute the consumed energy due the channel listeningEListen

EListen = TListen × Voltage × IListen

where TListen and IListen are respectively the time spent by a mote in listen modeand the listen current.

Table: Energy Parameters

Parameter ValueVoltage 3 VCPU 0.5 mATransmit 17.4 mAListen 19.7 mA


One hop Results

Compare three scenarios:

I Only TCP,I TCP with UDP (364bps),I TCP with UDP (1546bps).

Table: Energy consumption distribution

Mac Protocol CPU Transmit ListenCX-MAC 7.5% 14.3% 78.1%

Table: TCP with CX-MAC: One hop performance

Cons. Ener.(mj) Segm. Retrans. Trans. Dur.(s)No CBR 2755.7 0.1 267.1CBR=364bps 2886.7 10.3 295.2CBR=1.5kbps 3393.1 52.1 408.7


Multi-hops scenario

Compare three scenarios:

I Only TCP,I TCP with UDP (364bps),I TCP with UDP (1546bps).

ERN1

N2

N3 N4

N5

EN

Laptop Station

Wireless Devices

1m 3m 3m

1.5m

1.5m

3m


Multi-hop: Retranmissions

1 2 3 4 5

0

50

100

150

200

250

Number of hops

Ret

ran

smis

sion

tim

es

No CBRCBR=364bps

CBR=1546bps

Figure: Experimental results of multi-hop TCP over 6LoWPAN end-to-endretransmissions times with and without a concurrent CBR traffic


Multi-hop: Transfer Duration

1 2 3 4 5

500

1,000

1,500

2,000

Number of hops

Tra

nsf

erD

ura

tion

(s)

No CBRCBR=364bps

CBR=1546bps

Figure: Experimental results of multi-hop TCP over 6LoWPAN transferdurationwith and without a concurrent CBR traffic


Multi-hop: Throughput

1 2 3 4 5

500

1,000

1,500

Number of hops

Th

rou

ghp

ut

(bp

s)

No CBRCBR=364bps

CBR=1546bps

Figure: Experimental results of multi-hop TCP over 6LoWPAN throughput withand without a concurrent CBR traffic


Multi-hop: Consumed energy

1 2 3 4 50.2

0.4

0.6

0.8

1

·104

Number of hops

Con

sum

edE

ner

gy(m

J)

No CBRCBR=364bps

CBR=1546bps

Figure: Experimental results of multi-hop TCP over 6LoWPAN total consumedenergy with and without a concurrent CBR traffic


Conclusion and perspectives

ConclusionI The IEEE 802.15.4 radios are very sensitive (interference with WiFi,

Air-conditioner Movement of persons, etc.).I TCP offers a reliable data communication between anywhere IP host to

a low-power wireless device,

PerspectivesI The TCP performance could be improved by reducing the header size

(TCPHC),I A cross-layer mechanisms could also optimize the energy consumption

by reducing the radio passive listening.

AcknowledgmentI This work has been funded by the Pole de Recherche Avancee en

Communications.


Thank you


Documents

TCP over 6LoWPAN for Industrial Applications