Time Slotted Channel Hopping or Time Synchronized Channel Hopping (TSCH) is a

channel access method In telecommunications and computer networks, a channel access method or multiple access method allows more than two terminals connected to the same transmission medium to transmit over it and to share its capacity. Examples of shared physical med ...

for

shared-medium network In telecommunication, a shared medium is a transmission medium, medium or channel (communications), channel of information transfer that serves more than one user at the same time. In order for most channels to function correctly, no more than on ...

s. TSCH is used by Low-Power devices to communicate using a wireless link. It is designed for low-power and lossy networks (LLNs) and aims at providing a reliable

Media access control In IEEE 802 LAN/MAN standards, the medium access control (MAC, also called media access control) sublayer is the layer that controls the hardware responsible for interaction with the wired, optical or wireless transmission medium. The MAC sublay ...

layer. TSCH can be seen as a combination of

Time division multiple access Time-division multiple access (TDMA) is a channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, o ...

and

Frequency-division multiple access Frequency-division multiple access (FDMA) is a channel access method used in some multiple-access protocols. FDMA allows multiple users to send data through a single communication channel, such as a coaxial cable or microwave beam, by dividing ...

mechanisms as it uses diversity in time and frequency to provide reliability to the upper network layers. The TSCH mode was introduced in 2012 as an amendment (IEEE 802.15.4e) to the Medium Access Control (MAC) portion of the

IEEE 802.15.4 IEEE 802.15.4 is a technical standard which defines the operation of a low-rate wireless personal area network (LR-WPAN). It specifies the physical layer and media access control for LR-WPANs, and is maintained by the IEEE 802.15 working group, ...

standard. The amendment was rolled into the

in 2015.

Description

Wireless communications are often referred as unreliable due to the unpredictability of the wireless medium. While wireless communications bring many advantages (e.g no wires maintenance, costs reduction ...), the lack of reliability slows down the adoption of wireless networks technologies. TSCH aims at reducing the impact of the wireless medium unpredictability to enable the use of reliable low-power wireless networks. It is very good at saving the nodes' energy because each node shares a schedule, allowing it to know in advance when to turn on or off its radio. The

standard uses different frequency bands, and each frequency band is separated in channels. In TSCH, communications are done using those different channels and at different times. However, this standard does not define how to build and maintain the communication schedule. Many works have been proposed to organize the schedule in a centralized or distributed way.

Channel Hopping

Let ''chOf'' be the channel offset, assigned to a given link. The channel offset, chOf, is translated to a frequency f (i.e. a real channel) using:

f = F

where ASN is the Absolute Slot Number, i.e. the total number of slots that elapsed since the network was deployed. The ASN is incremented at each slot and shared by all devices in the network.

Multipath-Fading Mitigation

Multipath propagation In radio communication, multipath is the propagation phenomenon that results in radio signals reaching the receiving antenna by two or more paths. Causes of multipath include atmospheric ducting, ionospheric reflection and refraction, and reflec ...

can create internal destructive interferences of a wireless signal known as multipath fading. This phenomenon can be overcome by shifting the location of the communicating nodes or by switching the communication carrier frequency. The channel hopping mechanism of TSCH allows to overcome the impact of multipath fading by changing the communication carrier frequency for every transmission

Implementations

TSCH is implemented in simulation or on real hardware. Simulation:
NS2
*

OpenWSN OpenWSN is a project created at the University of California Berkeley and extended at the INRIA and at the Open University of Catalonia (UOC) which aims to build an open standard-based and open source implementation of a complete constrained networ ...

Firmware: *

RIoT A riot is a form of civil disorder commonly characterized by a group lashing out in a violent public disturbance against authority, property, or people. Riots typically involve destruction of property, public or private. The property targete ...

Contiki Contiki is an operating system for networked, memory-constrained systems with a focus on low-power wireless Internet of Things (IoT) devices. Extant uses for Contiki include systems for street lighting, sound monitoring for smart cities, radiati ...

6TiSCH

TSCH is one of the key elements of the 6TiSCH stack as part of the IEEE802.15.4-2015 standard.

Uses

Due to its low power consumption and reliability, TSCH (or its previous versions) is mainly used in Low-Power

Wireless Sensor Networks Wireless sensor networks (WSNs) refer to networks of spatially dispersed and dedicated sensors that monitor and record the physical conditions of the environment and forward the collected data to a central location. WSNs can measure environmental c ...

. Companies are using it in their wireless sensor networks such as

Linear Technology Linear Technology Corporation was an American semiconductor company that designed, manufactured and marketed high performance analog integrated circuits. Applications for the company's products included telecommunications, cellular telephones, ne ...

and Emerson

Description

Channel Hopping

Multipath-Fading Mitigation

Implementations

6TiSCH

Uses

See also

References

Further reading