Advantages of TSMPBy Kiana Karimpour

ScopeToday there are plenty of protocols available which could be useful for

a wireless data transmission such as:• WiFi• Bluetooth• ZigBee• Z-Wave• 6LoWPAN• ANT• ONE-NET• wirelessHART• MiFi• …

The scope of this presentation is to review the advantages of TSMP and connection methods which deploy such advantages.

What Is TSMP

TSMP (Time Synchronized Mesh Protocol) is a networking protocol that forms the foundation of reliable, ultra low-power wireless sensor networking. TSMP provides redundancy and fail-over in time, frequency and space to ensure very high reliability even in the most challenging radio environments. TSMP also provides the intelligence required for self-organizing, self-healing mesh routing.

TSMP OverviewTSMP is a media access and networking protocol that is designed

specifically for low power, low-bandwidth reliable networking. Current TSMP implementations operate in the 2.4 GHz ISM band on IEEE 802.15.4 radios and in the 900 MHz ISM band on proprietary radios. Figure 1 shows the elements of TSMP in the standard wireless network stack and the OSI network stack.

Challenges in WSNs • RF interference : The small portion of the electromagnetic spectrum

devoted to general-purpose wireless communication devices is crowded with traffic from Wi-Fi networks, cordless telephones, bar-code scanners, and innumerable other devices that can interfere with communications

• Blocked Paths: Unlike wired networks, wireless paths often change; paths may later be blocked by new equipment. Assuring reliability for the life of the network, not just the first few weeks after installation, requires continually working around these blockages in a transparent, automatic fashion.

• Node Loss: Nodes may be damaged, destroyed or removed during the life of the network. Additionally, power surges, blackouts, or brownouts can cause nodes to fail unless they have an independent power source.

WSN Solution• A well-designed wireless network architecture will transparently adapt to

changing environments, allowing long-term operation with zero-touch maintenance.

• Applying self-organizing and self-healing intelligence to continuously adapt to unpredictable conditions without constant tuning by wireless experts.

• Time Synchronized Mesh Protocol (TSMP) provides a mechanism for WSN intelligence. By defining how a wireless node utilizes radio spectra, joins a network, establishes redundancy and communicates with neighbors, TSMP forms a solid foundation for WSN applications.

TSMP Key Components

• There are five key components of TSMP that contribute to end-to-end network reliability, simple installation and power efficiency.

• Time synchronized communication • Frequency hopping • Automatic node joining and network formation • Fully-redundant mesh routing • Secure message transfer

Time Synchronized Communication

All node-to-node communication in a TSMP network is transacted in a specific time window. Commonly referred to as Time Division Multiple Access (TDMA), synchronized communication is a proven technique that provides reliable and efficient transport of wireless data. In a wireless system all devices within range of each other must share the same media. Several other Media Access Control (MAC) mechanisms are available including CSMA, CDMA and TDMA. TSMP is based on TDMA.

Frequency hopping • addition to slicing the wireless media across time, TSMP also slices it across

frequency. This provides robust fault tolerance in the face of common RF interferers as well as providing a tremendous increase in effective bandwidth. Commonly referred to as Frequency Hopping Spread Spectrum (FHSS).

• Another technique to overcome RF challenges is Direct Sequence Spread Spectrum (DSSS). DSSS provides a few dB of coding gain and some improvement in multi-path fading(see figure 4 below).

• It should be noted that a combination of FHSS and DSSS provides both interference rejection (FHSS) and the coding gain (DSSS).

• The other technique for overcoming interference is increasing the radio power effectively “turning up the volume”. Although often effective, turning up the volume on 802.15.4 radios kills battery life and is not an ideal solution for low-power WSNs.

Frequency Hopping

Automatic Node Joining and Network

Formation• Every TSMP node has the intelligence to discover neighbors, measure RF

signal strength, acquire synchronization and frequency hopping information, and then establish paths and links with neighbors.

• All TSMP nodes are fully capable mesh networking nodes. Every TSMP node has the ability to route traffic from neighbors as dictated by RF connectivity and/or network performance requirements. During the life of an installation it may be the case that a node joins as an end node, becomes a routing node due to changing RF conditions and then reverts back to an end node.

• All TSMP messages are encrypted and include a network ID. The network ID is used to bind nodes together into a network, allowing multiple TSMP networks to operate in the same radio space without the risk of sharing data or misrouting messages

Fully-Redundant Mesh Routing

• A full mesh topology with automatic node joining and healing lets the network maintain long-term reliability. Only self-organizing full mesh networks can find and utilize the most stable routes through the available node topology.

• Fully redundant routing requires both spatial diversity (try a different route) and temporal diversity (try again later). TSMP covers spatial diversity by enabling each node to discover multiple possible parent nodes and then establish links with two or more. Temporal diversity is handled by retry and failover mechanisms.

• Additionally, should an installed network need to be expanded, only a full mesh network can gracefully accommodate new nodes by relying on edge nodes to automatically assume routing duties

Secure Message Transfer

There are three pillars of secure message transfer:

• Encryption: TSMP uses industry-standard 128-bit symmetric key encryption for end-to-end confidentiality of packet payload

• Authentication : , TSMP uses packet source addresses protected by 32-bit Message Integrity Codes (MIC). Every packet carries two MIC codes to provide authentication: end-to-end source address authentication guaranteed by the network layer MIC, and node-to-node source address authentication, guaranteed by the MAC layer MIC. The MAC layer authentication is particularly important in protecting ACKs

• Integrity: The same 32-bit Message Integrity Codes (MICs) that authenticate the sending node’s address also serve to ensure content integrity

TSMP WSN Applications

Wireless Sensor networks based on TSMP are widely used in various applications including:

• Data Centers• Industrial Automation• Renewable Energy• Building Automation• Remote Monitoring• Transportation

Most Popular TSMP Standards

• WirelessHART:• Developed by HART communication• DigiMesh:• Developed by Digi International.[1].

Energy hole problemEnergy-hole means that nodes in the region near the sink have to

spend more energy and will be exhausted sooner than nodes in outer regions. Solution for this problem is

• When deploying the sensors, we simply need to increase the density of sensors While the distance from a node to the sink decreases.

• We can deploy the nodes with extra more energy in the energy-hole region.

System lifetime is the duration from the very beginning of the network until a certain proportion of nodes die. The energy consumption model that we use to analyze and simulate in this paper is Eq.

•

Assume that there are N hops along the route, then we can calculate the total energy consumption of transmitting the packet, and Eq. [3.1] is the formula, or it can be abbreviated as Eq. [3.2].• =N. .L + L +(N_2) • =(2N_2) + L

L.Bit data hardware energy consumption = the distance between two adjacent hops

SolutionCould adjust the transmission ranges of nodes in the outer region to reduce energy

consumption of nodes in the areas around the sink. Our solution to this problem is combining transmission range to the original routing graph of the TSMP network. Then algorithm operates as follows:

• a) Generate vectors that could contain all possible temporary transmitting trees whose vertexes‘ number equals their sub-region number;

• b) Let i denotes the concentric circles number, when i equals I, it means that the circle is the closest one to the sink, when i equals M it illustrates the outmost circle. The circulating will not stop until i is bigger than M. Set i=i+1 ;

• c) Compute the value of each tree according to Eq. [3.2], and take the minimal value as the major contribution to lifetime of the network;

• d) Each node in the temporary routing tree calculates its own energy consumption and renews its state. stands for the total energy of each node. And it's kept by each node. Set - - ;

• e) Find the minimal among all these temporary trees and assign it to in this loop;

• f) If i equals to M then stop the loop and select this transmission tree as the optimal routing graph; if not, then go back to step b) and keep on circulating.

Simulation and Evaluation

• We set each node has the initial state that battery contains 100 J energy, the maximal transmission range of the radio is 10 m, the distributive density of node is 3 nodes/m. Below table shows details about the parameters and its value.

Conclusion

This algorithm will be executed every time the TSMP synchronizes the whole network. By this way the routing graph can be renewed in time so that it could provide stable and reliable performance. Meanwhile nodes in different position of the network can choose their own transmission range and next hop relay. Thus the sensor nodes can maintain adjustable transmission range and preplanned routing graph and they can adjust their energy consumption and cooperate with other nodes. Finally the network can maintain and function for longer time to provide reliable, timely, secure delivery of data packets.[2].

Bibliography• [1]. DUST Networks, Inc., Technical Overview of Time Synchronized Mesh

Protocol (TSMP), Hayward, California.

• [2]. Yao Zhen; Duan Hui-chuan; Qi Lin, "Prolonging Time Synchronized Mesh Protocol network's lifetime by adjusting transmission range and routing graph," Information Technology in Medicine and Education (ITME), 2012 International Symposium on , vol.2, no., pp.910,913, 3-5 Aug. 2012

Discussion

• What is TSMP? It is a mesh protocol for transmitting wireless data.

• Why it is very reliable? Since it uses FHSS and DSSS together.

• Which nodes consume more energy? Nodes are near the sink.