IEEE 802.15.4 is the standard for data communications with business and consumer devices and is designed with low power consumption, meaning batteries essentially last forever. The ZigBee standard provides network, security and application support services on top of the wireless standard IEEE 802.15.4 Medium Access Control (MAC) and Physical Layer (PHY). ZigBee (IEEE standard) is a category in the IEEE 802 family, along with some well-known protocols such as Wi-Fi and Bluetooth that use the 2.4 GHz industrial and scientific and medical (ISM) radio band.
This thesis focuses on the performance analysis of different routing protocol, emphasis on the definitions of different routing protocols defined by IEEE 802.15.4. To analyze the performance, Network Simulator (NS-2) simulations are used for better results. IEEE 802.15 is a working group of the Institute of Electrical and Electronics Engineers (IEEE) IEEE 802 standards committee that specifies wireless personal area network (WPAN) standards. IEEE 802.15.4 is a standard that specifies the physical layer and media access control for low-rate wireless personal area networks (LR-WPANs).
As already mentioned, the main identifying feature of IEEE 802.15.4 among WPANs is the importance of achieving extremely low manufacturing and operating costs and technological simplicity, without sacrificing flexibility or generality. Zigbee is the IEEE 802.15.4 Low Rate Wireless Personal Area Network (LR-WPAN) in a large-scale Wireless Sensor Network (WSN) application.
ZigBee Specifications
ZigBee Layers
- Application Layer
- ZigBee Device Object (ZDO)
- Network Layer
- Security Plane ………………………………………..………………………………………………………………..….9-10
- Physical Layer
Applications to monitor temperature, humidity or any other desirable atmospheric parameters can be placed on this layer for agricultural use. A special application is on every ZigBee device, and it is the ZigBee Device Object, or ZDO. This application provides key functions such as defining the type of ZigBee device (end device, router and coordinator) that a specific node is, initializing the network, and also participating in the formation of a network.
As Figure 1 shows, this layer provides network management, routing management, network message brokering, and network security management. This layer is defined by the ZigBee Alliance, which is an association of companies united to work for a better ZigBee standard. Using this frame counter, the device can determine and track the age of the message it receives.
This layer extracted from the IEEE 802.15.4 standard provides services to the network layer above, which is part of the ZigBee stack layer. The MAC layer is responsible for addressing data to determine where the frame is going, or coming from. It is also this layer that provides multiple access control, such as CSMA/CA, which enables reliable transmission of data.
Finally, the MAC sublayer can be exploited by higher layers to achieve secure communications (through measures such as an ACL). This standard manages the physical transmission of radio waves in different unlicensed frequency bands around the world to enable communication between devices within a WPAN. The tires are specified in the table below, linking them to the area in which the tire is used.
This layer allows channel selection to avoid radio interference, as well as data exchange with the upper layer (MAC sublayer) to which it provides the service.
Network Topologies…………………………………………………….……………………………………………..….11-12
Star Topology……………………………………………………………..………………………………………………12-13
In this simple topology, a coordinator is surrounded by a group of end devices or routers. Even if routers are connected to the coordinator, their message passing functions are not used. This type of topology is attractive because of its simplicity, but at the same time presents some important disadvantages.
In the event that the coordinator stops working, the entire network is dysfunctional because all traffic must travel through the center of the star. For the same reason, the coordinator can easily be a bottleneck for traffic within the network, especially since a ZigBee network can have more than 60,000 nodes. In a tree network, a coordinator initializes the network and is the top (root) of the tree.
Child nodes cannot connect to an end device because it does not have the ability to transfer messages. This topology allows for different levels of nodes, with the coordinator at the highest level. For messages to be forwarded to other nodes in the same network, the source node must forward the message to its parent, which is the node one level up from the source node, and the message is continually routed up the tree until it can sent back to the destination node.
Since the number of potential paths a message can take is only one, this type of topology is not the most reliable topology. If a router fails, all of that router's children are cut off from communicating with the rest of the network. If a particular router fails, ZigBee's self-healing (or path discovery) mechanism will allow the network to find an alternative path for the message to take.
In our project, one of the scenarios is to investigate this feature by removing a router from the network during operation and watching the end devices find an alternate route to communicate with the coordinator.
Power system for Zigbee
Characteristics of ZigBee …………………………………………………………………………………………….….15-16
ZigBee networks consist of multiple traffic types with their own unique characteristics, including periodic data, intermittent data, and low-latency repetitive data. In offline mode, the device will only connect to the network when communication is required, saving significant energy. The RFD (Reduced Function Device) wakes up and listens for the beacon from the PAN coordinator, if received, requests the RFD to join the network.
Intermittent types of traffic, such as wireless light switches, connect to the network when needed to communicate (ie turn on a light). For low-latency repetitive applications, a guaranteed timeslot option provides Quality of Service with a dedicated contention-free timeslot in each superframe that reduces contention and latency. ZigBee applications benefit from the ability to quickly attach information, disconnect, and deep sleep, which results in low power consumption and extended battery life.
There are two approaches to wireless communication between two hosts. The first is the centralized cellular network, where each mobile is connected to some fixed base station (each base station is responsible for a different cell), so that a communication between two mobile stations requires them to involve one or more base stations. Another decentralized approach consists of an ad hoc network between users who want to communicate with each other. Due to the more limited range of a mobile terminal (with respect to a fixed base station), this approach requires that mobile nodes not only source or destination odd packets, but also forward packets between other mobiles.
However, ad hoc networks have the advantage that they can be quickly implemented, as they do not require an existing infrastructure. In cellular networks, the wireless part is limited only to the access or a network, and within this network, classic routing protocols can be used. Ad-hoc networks, on the other hand, rely on special routing protocols that must be adapted to frequent topology changes.
The Ns do not have an advanced physical layer module (although it does contain some radio channel modeling features). In ad-hoc networks in contrast routing protocols are centralized. those.
The routing Algorithms
Destination Sequenced Distance Vector-DSDV………………………………………………………….…20-21
If a node detects that a route to a destination has broken, then its hop number is set to infinity and its sequence number is uploaded (increased) but assigned an odd number: even numbers correspond to sequence numbers of connected paths. AODV is a distance vector type of routing. It does not require nodes to maintain routes to destinations that are not actively used. The destination sequence number is created for any routing information it sends to requesting nodes.
Using destination sequence numbers provides loop freedom and allows knowing which of several routes is the "freshest". Given the choice between two routes to a destination, a requesting node always chooses the one with the higher sequence number. When a node wants to find a route to another owner, it broadcasts a RREQ throughout the network until the destination is reached or another node is found with a "fresh enough" route to the destination (A "fresh enough" route is a valid route entry for the destination whose associated sequence number id is at least as large as that contained in RREQ). An RREP is then sent back to the source and the discovered route is made available.
Nodes that are part of an active route can offer connectivity information by broadcasting periodic local Hello messages (Special RREP messages) to its immediate neighbors. If Hello messages stop arriving from a neighbor beyond a given time limit, the connection is assumed to be lost. When a node detects that a route to a neighboring node is not valid, it removes the routing entry and sends a RERR message to neighbors that are active and using the route: this is possible by maintaining active neighbor lists.
Dynamic Source Routing-DSR
Route maintenance
ZIGBEE SIMULATION USING NS-2 23-28
- A 3 node example for ad-hoc simulation with DSR………………………………………………………….23-24
- General Figure
- DSDV Graph
- AODV Graph
- DSR Graph
The first TCP signaling packet is sent at time 10, but the connection cannot be opened.
RESULT ANALYSIS 29-32
- DSDV Total Sender Packet Figure
- DSDV Total Received Packet Figure
- Comparison on DSDV, AODV and DSR
- Analysis
DSR is suitable for the network with the least packet loss, but AODV has the most packet loss in the network and is not moderate to use.
CONCLUSION 33-34
For the future work, this area will investigate not only the comparison between AODV, DSR and DSDV routing protocols, but more in the large areas, extensive complex simulations could be performed using other existing performance metrics to get a more in-depth performance analysis of the ad hoc routing protocols.
