UNIT I

1. Give the challenges of wireless sensor networks

a. Limited Resources (memory,computation,power)
b. Fewer infrastructures and also maintenance is very difficult.
c. Unreliable communication
d. Sensor node relies only on battery and it cannot be recharged or replaced.
e. Needs to be time synchronized between nodes .
f. Node failure, topology changes and adding of nodes and deletion of nodes
2. List out the requirements for WSN design.

Type of service
Quality of Service
Fault tolerance
Lifetime
Scalability
Wide range of densities
Programmability
Maintainability

3. Brief about the trade off between network lifetime and quality of service.
Data quality and network lifetime are often conflicting objectives in WSNs, as
improving one can degrade the other. For example, increasing the sampling rate can
improve the data quality, but it can also increase the energy consumption and shorten
the network lifetime. Similarly, reducing the data transmission can save energy and
extend the network lifetime, but it can also reduce the data quality by introducing
delays, losses, or errors. Therefore, managing the trade-off between data quality and
network lifetime requires a careful balance between the benefits and the costs of each
factor.

4. List out the modulation schemes involved in simple spectrum transceiver?

1. Amplitude Shift Keying
2. Frequency Shift Keying

5. Define hidden terminal problem.

It refers to the collision of packets at a receiving node due to the concurrent
transmission of those nodes that are not within the direct communication range of the
sender, but are within the transmission range of the receiver.

6. Compare single hop and multihop networks.

Single-hop routing:-
1. The network in which the devices (i.e. citation and location) are the only stations on
the system.
2. If a packet moves from origin to target using a single node unit, it is known as a
single hop method.
3. Single hop network is a growing network within a 192.168.0.1 to 255 IP router.
 Multi-hop network:-
1. A network that, apart from the two nodes, there is at least 1 other platform in the
route between source and the target.
2. Multi-hop routing is a form of communication in radio networks where the area of
the system is greater than the radar range of individual points.
3. In the multi-hop routing system, nodes positioned farther away from the node use
other intermediary points forwarding data to the node.

7. Define QoS.
Quality-of-Service is a set of service requirements to be met by the network while
transporting a flow. “Here a flow is” a packet stream from source to a destination
(unicast or multicast) with an associated Quality of Service (QoS).

8. What are the three types of mobility?

1. Node mobility, 2. Sink mobility, 3. Event mobility

9. Write the applications of wireless sensor networks.

1. Military Applications, 2. Medicine and health care, 3. Intelligent buildings (or
bridges) 4. Machine surveillance and preventive maintenance, 5. Precision agriculture

10. What do you understand about the characteristic requirements for WSN?
1. Types of service, 2. QoS, 3. Fault tolerance, 4. Life time, 5. Scalability, 6. Wide
range of densities, 7.Programmability
11. Define network life time.

Network lifetime which is defined as the time until the first sensor's energy runs out is an
important performance etric in WSNs. In traditional WSNs, all the sensor nodes are
configured to forward collect data to the sink through multihop communication
UNIT II
1. Brief about the RTS-CTS exchange for collision avoidance.
The RTS/CTS handshake It uses only a single channel and two special control
packets.Suppose that node B wants to transmit a data packet to node C. After B has
obtained channel access, it sends a Request To Send (RTS) packet to C, which includes
a duration field indicating the remaining length of the overall transaction. If C has
properly received the RTS packet, it sends a Clear To Send (CTS) packet, which again
contains a duration field. When B receives the CTS packet, it starts transmission of the
data packet and finally C answers with an acknowledgment packet.
 2. Give the factors( crucial points) influencing PHY design in WSN
a. Low power consumption.
b. • As one consequence: small transmit power and thus a small transmission
range.
c. • As a further consequence: low duty cycle. Most hardware should be switched
off or operated in
d. a low-power standby mode most of the time.
e. • Comparably low data rates, on the order of tens to hundreds kilobits per
second, required.
f. • Low implementation complexity and costs.
g. • Low degree of mobility.
h. • A small form factor for the overall node.

3. Give the significance of addressing and naming.

In WSN,the address assignment can happen a priori or on demand, by using an

address assignment protocol. Such an on-demand address assignment protocol can be either
centralized or distributed. since the scope of a MAC protocol is communication between
neighboring nodes and it is sufficient that addresses are locally unique within a two-hop
neighborhood. This requirement ensures that no two neighbors of a selected node have the
same MAC address.
4. What is mediation device protocol?
It is compatible with the peer-to-peer communication mode of IEEE 802.15.4 low-
rate WPAN standard. It allows each node in a WSN to go into sleep mode
periodically and to wake up only for short times to receive packets from neighbor
nodes.
5. Define wakeup radio.
Wake up Radios are the basic circuits for the on-demand communications scheme.
The WuR handles the sending and receiving of wake up messages that switch on the
main processing unit or the main radio of the required node. at least the same as the
periodic listening schemes based networks.

6. Define energy efficient unicast protocol.

It is simple that take the network graph, assign to each link a cost value that reflects
the energy consumption across this link, and pick any algorithm that computes least-
cost path in a graph.

7. What is an exposed- terminal problem?

The exposed terminal problem refers to the lack of ability of a node, which is blocked
due to transmission by a nearby transmitting node, to transmit to another node.

8. What are the classes of MAC protocols?

1. Fixed assignment protocols
2. Demand assignment protocols
3. Random access protocols

9. Define slotted ALOHA.

 The time is subdivided into time slot and a node is allowed to start packet
transmission only at the beginning of a slot.

10. Explain the principle of S-MAC Protocol.

The main concept in SMAC is that, all the neighboring nodes form virtual clusters
and synchronize their sleep and listen periods. They communicate during their listen
periods and sleep rest of the time. The immediate neighbors of nodes which are
transmitting and receiving, sleep until the communication is completed.

UNIT III
1. List out the network management requirements
 WSN is a special type of wireless network:
 Possibly with ad hoc structure and
 With limited resources
 Due to these WSN constraints: networking protocols, the application model, middleware
and sensor node OS should be s=designed very carefully
 So here, network management for WSNs is requires to use those limited resources
effectively and efficiently.
2. List out the SNMP management function
SNMP provides a common mechanism for network devices to relay management
information within single and multi-vendor LAN or WAN environments. It is an
application layer protocol in the OSI model framework. Typically, the SNMP protocol
is implemented using the User Datagram Protocol (UDP).

3. Define Get Request

A GET request, in simple terms, is a way for you to grab data from a data source with
the help of the internet. It's done using the GET request method, which is a very
common HTTP request method (like POST, PUT, or DELETE).

4. List the different types of SNMP messages

 TRAP
 GET
 GET-NEXT
 GET-RESPONSE
 SET
5. What are the three vertical layers of service management ?
 Networks and System Management
 Service development operations
 Customer care process

6. Define the functions of manager and agent

SNMPManager–It is a centralized system used to monitor network. It is also known as
Network Management Station (NMS)
SNMP agent – It is a software management software module installed on a managed
device. Managed devices can be network devices like PC, routers, switches, servers,
etc.

7. Define naming
Naming is a scheme is used to identify the sensor node. An efficient naming scheme
Lower computational overhead Making routing protocol more efficient

8. List the properties of localization and positioning.

 Physical position and Symbolic location
 Absolute versus relative coordinates
 Localized versus centralized computation
 Accuracy and Precision
 Scale
 Limitation
 Costs

9. Define SMI & MIB.

SMI stands for Structure of Management Information. It defines the rules for describing
managed objects. In the SNMP framework, managed objects reside in a virtual database
called the management information base (MIB). Collection of related objects are
defined in MIB modules.

UNIT IV

1. Write about the topology control

Topology control is an idea is to deliberately restrict the set of nodes that are considered
neighbors of a given node. This can be done by controlling transmission power, by
introducing hierarchies in the network and signaling out some nodes to take over certain
coordination tasks, or by simply turning off some nodes for a certain time.

2. Brief about the requirements for time synchronization in WSN

• An algorithm must scale to large multihop networks of unreliable and severely
energy-constrained nodes. The scalability requirement refers to both the number of
nodes as well as to the average node degree/node density.
• The precision requirements can be quite diverse, ranging from microseconds to
seconds.
• The use of extra hardware only for time synchronization purposes is mostly ruled
out because of the extra cost and energy penalties incurred by dedicated circuitry.
• The degree of mobility is low. An important consequence is that a node can reach its
neighbors at any time, whereas in networks with high degree of mobility, intermittent
connectivity and sporadic communication dominates
 3. What are the advantages of rotating cluster heads?
Rotation is a widely used technique that aims at reducing the number of cluster head
elections and cluster formation phases thus reducing the amount of control messages.
Rotation is used to balance energy in static clustering where the network is clustered
once at the beginning or in combination with well known dynamic clustering strategies
in order to reduce the amount of re-clustering phases

4. Compare RBS and HRTS

Both protocols timestamp received packets already in the receiver interrupt. As compared to
other sender/receiver based protocols, TPSN removes much of the uncertainty at the sender
(operating system and networking stack, medium access delay) by timestamping an outgoing
packet immediately before transmission. For neither TPSN nor RBS, the possible clock drift
during exchange of the synchronization
packets has been considered.

5. What are the advantages of LEACH ?

LEACH is a MAC protocol, it contains many advantages like it does not need any
control information, it saves energy, it is completely distributed and also contain many
disadvantages like if cluster head dies then cluster become useless, clusters are divided
randomly etc.

6. Define data aggregation.

A sensor node sends and receives the number of packets directly proportional to the
sensor's energy consumption. The data detected by nearby sensors is highly correlated
in space. Data aggregation aggregates data from nearby sensors, eliminating redundant
transmission of data. It reduces the network's use of bandwidth and energy consumption
by eliminating redundant transmission.

7. What is phase transistion?

The optimization goal of topology control can be defined as the probability of connected
network versus average size of the largest component.Both these metrics increase sharply
from zero to their maximum values once a certain critical threshold for the transmission
range is exceeded. This effect is known for a large number of aspects of (random) graphs
in general and called a phase transition.

8. Define Disk graph and unit disk graph

 The transmission range of each node can be set to a precise radius of r m (i.e. all nodes at
most r m apart can communicate directly, and no other nodes can). This model is known
as the disk graph model; the special case of r = 1 is called the Unit disk graph.

9. What is data compression?

Data compression has been used to reduce energy consumption and improve network
lifetime, as it reduces data size before it can be forwarded from the sensing node to the
sink node in the network.

UNIT V
1. What are the three categories of hardware defined for sensors.
Sensor node hardware can be grouped into three categories
 Augmented general-purpose computers
 Dedicated embedded sensor nodes
 System-on-chip (SoC)

2. List out the characteristics affect the design of sensor network programming tools

The following characteristics affect the design of sensor network programming tools:

 Reliability
 Resource Utilization
 Scalability
 Data Centric Networks

3. What is TinyOS?
TinyOS is an embedded component-based operating system and platform for low-power wireless
devices in wireless sensor networks (WSNs), ubiquitous computing, personal area networks, building
automation and smart meters. It is written in the programming language nesC, as a set of cooperating
tasks and processes

4. Define SoC.
Build extremely low power and small footprint sensor nodes that still provide certain sensing,
computation, and communication capabilities. z Currently in the research pipeline with no predefined
instruction set, there is no software platform support available

5. How a TinyOS program can be executed?

A program executed in TinyOS has two contexts, tasks and events.
Tasks are posted by components to a task scheduler. Without preempting or being
preempted by other tasks
Triggered events can be preempted by other events and preempt tasks

6. Define Augmented general purpose computers.

Off-the-shelf operating systems such as WinCE, Linux and with standard wireless
communication protocols such as 802.11 or Bluetooth.
 Relatively higher processing capability
More power hungry
Fully supported popular programming languages
Ex: PDAs

7. What do you understand by the term components in TinyOS.

NesC programs are built out of components assembled to form whole programs. Components
have internal concurrency in the form of tasks. Threads of control may pass into a component
through its interfaces. These threads are rooted either in a task or a hardware interrupt.
Interfaces may be provided or used by components

8. Give few applications of WSN

Habitat monitoring
Target detection