Simulation of a WiMAX network to evaluate the performance of MAC IEEE 802.16 during the IR phase of Network Entry and Initialization

Pervasive Computing is also called as Ubiquitous Computing, which means "being present everywhere at once" or "constantly encountered". The main idea behind making these pervasive computing systems is that these systems improve living by performing computations on their own, without having to be monitored by anyone. These systems are targeted to become invisible to the user i.e., they perform their tasks without the user's knowledge. To achieve this environment, the underlying requirement is a Network. One of the biggest constraints in achieving this environment is the "Last Mile" problem. It refers to the last leg of delivering connectivity from a communications provider to a customer. In recent years there has been increasing interest shown in wireless technologies for subscriber access, as an alternative to traditional twisted-pair local loop. WiMAX, Worldwide Interoperability for Microwave Access, is a Telecommunications technology that provides wireless transmission of data and is based on the IEEE 802.16 standard (also called Broadband Wireless Access). 802.16 uses paired radio channels Up Link Channel (UL) and Down Link Channel (DL) for establishing a communication between Base Station (BS) and Subscriber Station (SS). When a SS wants to establish connectivity with a BS it goes through the Network Entry and Initialization procedure of which Initial Ranging (IR) is a very important part. IR is the process of acquiring the correct timing offset and power adjustments such that the SS's transmissions are aligned to maintain the UL connection with the BS. All the SS's of a BS will compete for the contention slots for their network entry. Whenever the SS has to transmit the request packets it performs the Truncated Binary Exponential Backoff procedure. This method is the contention resolution procedure used in IEEE 802.16 networks. Our focus here was to simulate a WiMAX network so as to evaluate the performance of MAC IEEE 802.16 during the IR phase of Network Entry and Initialization. We have used Network Simulator-2 (NS-2) for our simulation purposes. We are using WiMAX "patch" which simulates the PHY and the MAC features of a WiMAX network. We have evaluated the performance of MAC IEEE 802.16 for various topologies.