Adhoc Networks (MANETs)
Adhoc Networks (MANETs)
An Ad hoc Network is a self-configuring, infrastructure-less wireless network where mobile devices communicate directly.
Features:
- No central base station
- Nodes act as routers + hosts
- Dynamic topology (nodes move frequently)
- Multi-hop communication
Challenges:
- Frequent route changes
- Limited battery power
- Security issues
- Bandwidth constraints
Localization in Adhoc Network
Localization is the process of determining the geographical position of nodes.
Methods:
1. GPS-based Localization
- Uses satellites
- Accurate but costly & power-consuming
2. Range-based Methods
-
Based on:
- Signal strength (RSSI)
- Time of arrival (ToA)
3. Range-free Methods
- Uses connectivity information
- Less accurate but energy-efficient
Importance:
- Routing decisions
- Network management
- Tracking nodes
MAC Issues in Adhoc Networks
MAC = Medium Access Control
Controls how multiple nodes share the wireless channel.
Key Problems:
1. Hidden Terminal Problem
- Two nodes can’t see each other → collision occurs
2. Exposed Terminal Problem
- Node unnecessarily stops transmission
3. Limited Bandwidth
- Shared medium reduces efficiency
4. Energy Efficiency
- Nodes must conserve battery
Solutions:
- RTS/CTS (Request to Send / Clear to Send)
- Power control
- Scheduling
Routing Protocols in Adhoc Networks
Routing protocols find paths between nodes in a dynamic network.
Types:
1. Proactive (Table-driven)
- Maintain routing tables
- Example: DSDV
2. Reactive (On-demand)
- Find route only when needed
- Example: DSR, AODV
3. Hybrid
- Combination of both
Global State Routing (GSR)
Type:
Proactive routing protocol
Working:
-
Each node maintains:
- Neighbor list
- Topology table
- Routing table
- Periodically exchanges information
Advantages:
- Updated route information
Disadvantages:
- High overhead
- Not efficient in highly dynamic networks
Destination Sequenced Distance Vector (DSDV)
Type:
Proactive routing protocol
Key Idea:
- Based on Bellman-Ford algorithm
- Uses sequence numbers to avoid loops
Features:
- Periodic table updates
- Loop-free routing
Limitation:
- High bandwidth usage
Dynamic Source Routing (DSR)
Type
Reactive routing protocol
Working:
- Route is included in packet header
-
Uses:
- Route discovery
- Route maintenance
Advantages:
- No periodic updates
- Efficient for small networks
Disadvantages:
- Large packet size (full path included)
Adhoc On-Demand Distance Vector (AODV)
Type:
Reactive routing protocol
Working:
- Route created only when needed
-
Uses:
- Route Request (RREQ)
- Route Reply (RREP)
Advantages:
- Lower overhead than proactive
- Scalable
Disadvantages:
- Delay in route discovery
Temporary Ordered Routing Algorithm (TORA)
Type:
Reactive / Hybrid
Key Concept:
- Uses link reversal algorithm
- Maintains multiple routes
Features:
- Quick adaptation to topology changes
- Local route repair
Limitation:
- Complex implementation
QoS (Quality of Service) in Adhoc Networks
QoS ensures reliable and efficient data transmission.
QoS Parameters:
- Bandwidth
- Delay
- Packet loss
- Jitter
Challenges:
- Dynamic topology
- Limited resources
- Unstable links
Solutions:
- QoS-aware routing
- Resource reservation
- Traffic prioritization
Applications of Adhoc Networks
Real-world Uses:
1. Military Operations
- Battlefield communication
2. Disaster Recovery
- No infrastructure available
3. Vehicular Networks (VANETs)
- Communication between vehicles
4. Sensor Networks
- Environmental monitoring
5. Temporary Networks
- Conferences, events
Final Summary Table
| Protocol | Type | Key Feature |
|---|---|---|
| GSR | Proactive | Global topology |
| DSDV | Proactive | Sequence numbers |
| DSR | Reactive | Full path in packet |
| AODV | Reactive | On-demand routing |
| TORA | Hybrid | Link reversal |
Concept Connection
- Adhoc Networks → Base concept
- MAC + Localization → Support communication
- Routing Protocols → Enable data transfer
- QoS → Improves performance
- Applications → Real-world usage
Tags:
Mobile Computing