Data Dissemination In Wireless Sensor Network

Data Dissemination is a procedure where the server initiates and manages transfer of data as well as updates. It also helps in maintaining data consistency and cache management. It is defined as “Pushing data to mobile devices from a server or some other computer.” Mobile devices can select time and cache required data. In ad-hoc network, traffic is peer to peer. Multi-hop routing is used to communicate data. In wireless sensor network, other traffic models are possible which are as follows: 

• Data Collection Model: The source sends data to a collection periodically on demand
• Data Diffusion Model:  A sensor node that generates data based on its sensing mechanism’s observation.

 Data dissemination has two different entities:

• Source: Generating data.
• Event: Something that needs to be reported for example, in target detection, some abnormal activity.
• Sink: A node randomly located in the field, that is interested in events and seeks such information.

Event in the below diagram indicates the information to be reported or sent. After source receives an interest from the sink, the event is transferred from the source to the sink. Data dissemination is a two step process. First, the node that is interested in some events, broadcasts its interests to its neighbors periodically. Interests are then propagated through the whole sensor network. In the second step, nodes that have requested data, send back data after receiving the request. Intermediate nodes in the sensor network also keep a cache of received interests and data.

There exists several data dissemination methods:

Flooding: It is the simplest design. In this method, each node receiving data repeats it by broadcasting the data to every neighbor unless the maximum hop lifetime of the data has been reached.

Data dissemination is a critical function in wireless sensor networks (WSNs) that involves the transmission of sensor data from one or more nodes to a base station or other nodes in the network. 

The features of data dissemination in WSNs include:

Energy Efficiency: WSNs are typically powered by batteries or other low-power sources, and so energy efficiency is a crucial consideration in data dissemination. Techniques such as data aggregation, compression, and clustering can be used to reduce the amount of data transmitted and conserve energy.

Reliability: Data dissemination in WSNs must be reliable, meaning that all nodes in the network receive the necessary data without loss or duplication. Techniques such as error detection and correction can be used to ensure reliability.

Scalability: WSNs can range in size from a few nodes to thousands or even millions of nodes. Data dissemination techniques must be scalable to accommodate the number of nodes in the network.

Security: WSNs are vulnerable to security threats, such as eavesdropping, tampering, and denial of service attacks. Techniques such as encryption and authentication can be used to ensure the security of data dissemination.

Adaptability: WSNs must be adaptable to changing conditions in the environment, such as changes in the number and location of nodes, changes in data rates, and changes in network topology. Techniques such as dynamic routing and load balancing can be used to adapt to these changes.

QoS Requirements: In some applications, data dissemination may have Quality of Service (QoS) requirements such as delay, throughput, or reliability. Techniques such as priority scheduling and traffic shaping can be used to ensure that QoS requirements are met.

data dissemination in WSNs is a complex task that requires careful consideration of the above features to ensure efficient and reliable operation of the network.

Advantages

• Simple to setup and implement. 
• Data and queries reach all the nodes in the network.

Disadvantages of Flooding

• Implosion- No restriction on multiple nodes sending same packets to the same destination.
• Overlapping- Neighbor nodes may receive the same message if the nodes access the same event.
• Resource Blindness- Flooding does not care about energy efficiency of the nodes. 

Gossiping: It is the enhancement of Flooding. In this, when a node receives data, it randomly chooses a neighbor and sends the data to it. Unlike Flooding, we does not need to bother about duplicate data packets being sent to the same location. It also contributes to the latency of network. 

Advantages

• This protocol is easily scalable.
• It eliminates some of the shortcomings of Flooding.
• This protocol sends data in autonomous and decentralized manner

Disadvantages of Gossiping

• The destination is selected randomly so it may lead to starvation for some nodes as they may not be selected to send data at all.

SPIN: Sensor Protocols for Information via Negotiation (SPIN) has the required features which can overcome the shortcomings of flooding. When interested nodes send a request, SPIN will send the data to the corresponding node otherwise it will not on its own. SPIN messages can be distinguished into three types: 

• ADV- ADV message is used to signal that the sensor has data to send and describes the data by the help of a sensor
• REQ- REQ message is used when a node is ready to receive data from neighboring node
• DATA- The information to be sent is contained here 

Advantages

• SPIN is more efficient than flooding since the negotiation reduces the implosion and overlap.

Disadvantages

• SPIN-2 is more effective than SPIN-1 as it uses energy or resource threshold so that limited number of nodes can participate in data transmission.

Cost- field Approach: The goal of the cost-field approach is the efficient flow of data from source to sink through a path which is free of obstacles. It’s job is to keep the path obstacle free. The cost-field approach relies upon two steps to work properly. The first step is that all sensor nodes should have a cost field, based on parameters like delay. In the second step, data is distributed based on the parameter of costs. It is imperative that the lower the cost at each node from the source to the sink, the more optimal the path is. This approach does not require to maintain information about the path of the nodes arranged in the configuration sequence. 

Advantages

• Makes sure sensor path is problem free
• Does not need to maintain explicit path information
• The cost at each node is the minimum cost from the node to the sink, which occurs on the optimal path

Disadvantages

• Time consuming. As it uses back-off timers for forwarding data to other nodes.