My Project | Low Rate Wireless Personal Area Networks in NS2

Compared with wired networks, wireless networks provide advantages in deployment, cost, size, and distributed intelligence. Wireless technology not only enables users to set up a network quickly, but also enables them to set up a network where it is in-convenient or impossible to wire cables. The “care free” feature and convenience of deployment make a wireless network more cost-efficient than a wired network in general.
The release of IEEE 802.15.4 (referred to as 802.15.4 hereinafter), "Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Low Rate Wireless Personal Area Networks (LR-WPANs)”, represents a milestone in wireless personal area networks and wireless sensor networks.
AW ireless personal area network conforming to the IEEE 802.15.4 standard is composed of several devices and its functionality and features can be illustrated by several terms. Some of them are listed here.
Co-ordinator: It is a device which is authorized to provide synchronization services in an established network. There can be two different kinds of co-ordinators based on their operation scope. First is the PAN-Coordinator, which acts as a coordinator for the entire PAN. Where as an ordinary co-ordinator can only function within the scope of a cluster.
Cluster: A cluster is a small section of a bigger network, which has its own co-ordinator. Groups of clusters communicate with a central PAN-Coordinator to form the PAN in a mesh topology.
Device/End Node: A device is either a reduced/full function device that can be visualized as a leaf of a tree structure. Any device that is not a co-ordinator is an end node (device).
Personal Operating Space (POS): It is the operating range of a node in all directions, and is a constant irrespective of being in motion or stationary.
There are 14 PHY and 35 MAC Primitives defined by the IEEE 802.15.4 standard. The LR-WPAN supports two types of devices called the Full Function Device and the Reduced Function Device.
Full Function Device It is a device which supports all the 49 primitives supported by the technology. It is a fully functional device which is capable of assuming the role of either a PAN Coordinator, a Coordinator, or just as an end node (device). Also an FFD can function as a routing device in certain network topologies where data transfer among FFD is allowed (EX: peer-to-peer communication).
Reduced Function Device It is a device with reduced functionality which can only function as an end device or node. It cannot communicate with any other device other than the coordinator. Given their extremely low functionality, these devices are normally intended for simple applications like a light switch, etc. They merely send information to the coordinator at regular intervals about the status of the device it is monitoring. It can only support a maximum of 38 primitives.
A basic LR-WPAN comprises of a mixture of these devices, an FFD being the most common device used in a PAN. But any PAN network should have at least one FFD, to act as the PAN-Coordinator. However, depending on the application when a RFD is not feasible, to fulfill the needs of the application, an FFD can be applied. The devices of a network monitor the applications and reply back to the coordinator. The devices within the pan should be around the operating space of the coordinator. But given the dynamic propagation characteristics of the channel a definite operating space for each device cannot be defined.

Operating Frequencies and Datarates
Any technology cannot achieve wide ranging popularity if it not flexible enough to be used worldwide. This is also one of the primary reasons for the failure of several proprietary technologies. However, IEEE 802.15.4 has been designed to be applied worldwide. This allows manufactures to concentrate on devices that can work in any of the available channels based on channel characteristics, bandwidth requirements, local regulations, etc. It supports three different operating frequency bands, with different number of supporting channels and datarates.