http://www.cse.wustl.edu/~jain/cse567-06/ftp/mac_perf/index.html 1 of 9Survey on Performance Evaluation Techniques for MediumAccess Control ProtocolsRitun Patney, ritun.patney@gmailAbstractMedium Access Control (MAC) protocols, in data networks, are responsible for arbitrating access to a shared medium. This survey paper looks into the techniques and metrics used for evaluating these protocols. The most common performance metrics are delay and throughput, though in certain cases, like sensor networks, power consumption might also be an important metric. The paper focuses on three kinds of evaluation techniques: analytical modeling, simulation and practical experiments. The mostcommon technique seems to be analytical modeling. We discuss the methodologies used in some of the papers from theliterature.Keywords: MAC, performance, analytical modeling, simulation, experimentationTable of Contents1. Introduction 1.1 Open Systems Interconnection Model2. Medium Access Control 2.1 Aloha 2.2 CSMA 2.3 CSMA/CD 2.4 CSMA/CA 2.4.1 Hidden Node Problem 2.5 IEEE 802.11 2.6 MAC for sensor networks 2.7 IEEE 802.163. Analytical Modeling Techniques of MAC Protocols4. Simulation Studies5. Experimentation Studies6. ConclusionReferences1 IntroductionThe paper is organized as follows. In section 1, we discuss the various network layers. In section 2, we look at the common Medium Access Control (MAC) protocols used. The next three sections discuss some of the analytical, simulation, and experimentation techniques used for performance evaluation of MAC protocols. 1.1 Open Systems Interconnection ModelThe OSI model [11] is generally referred to as the OSI reference model (Figure 1). It presents an abstract model of network protocol layers and is helpful in the design of network protocols. Every layer provides some functions (interfaces) which are used by the layer above it. This structure is often referred to as a protocol stack.http://www.cse.wustl.edu/~jain/cse567-06/ftp/mac_perf/index.html 2 of 9 Fig. 1 - OSI protocol stack System designers working in one layer need not worry about the details of the layer below. This results in the stack being highly modular. The OSI standard consists of 7 layers: 7. Application Layer - This is where the user applications are run. Some common applications are FTP, HTTP, etc.6. Presentation Layer - Data in the network can be represented in many different formats. It can differ in the encryption used,MIME encoding, etc. This layer this presents the application layer a uniform interface by hiding these differences.5. Sessions Layer - It is responsible for creating, maintaining and terminating connections between the local host and a remotehost. It supports half-duplex or full duplex operation.4. Transport Layer - This layer is responsible for providing the transportation of data between the source and the destination.The service can be connection oriented or connectionless. It also performs fragmentation and error control.3. Network Layer - It is responsible for transferring packets between various networks. It provides for various routing decisions,as well as addressing and internetworking.2. Data Link Layer - This layer is responsible for delivery of frames to the next hop destination. It also tries to correct any errorsintroduced by the physical layer. This layer is often divided into two layers: Medium Access Control (MAC) and Logical Link Control (LLC). LLC is responsible for frame synchronization, flow control and error checking. The MAC decides which node gets access to the channel and who transmits when.1. Physical Layer - It deals with the actual transmission of bits over the medium in the form of electrical signals.TCP/IP reference model - This is also referred to as the Internet reference model. Compared to the OSI model, it has fewer layers, but it provides an easy fit for real World products. The model defines 4 layers: Application layer, Transport Layer, Internetworking Layer, and the Network Access Layer.2 Medium Access ControlAs discussed previously it is responsible for controlling access to the channel amongst various entities. Its role is important in networks where multiple users can transmit at the same time over the same channel (Ethernet segment, same radio channel, etc.), such as IEEE 802.11, Bluetooth, etc.Various MAC protocols have been defined in literature that employ different techniques to regulate access. They can begrouped into two categories: distributed and centralized. In the former, each node decides on its own when is the best time for itto transmit such that it is the only one which transmits to avoid collision. These are also referred to as random access protocols. If multiple nodes transmit, then these protocols provide mechanisms to resolve the collision. In the centralized version, a node is responsible for deciding who can access the channel, and the duration for which that node has control over the channel. The centralized node is generally referred to as a base station (BS). There are two ways to provide access to other nodes. One is in a round-robin fashion. Here the BS would poll every node periodically to find if it has data to transmit or not. The other can be a Request-Grant mechanism wherein the nodes contend to send channel access requests to the base station. The BS then allocates a time slot for every node from which it would have received the request. The next section details out some of the commonly used MAC protocols.http://www.cse.wustl.edu/~jain/cse567-06/ftp/mac_perf/index.html 3 of 92.1 AlohaAloha [1] [14] is based on the principle that if you have data to send, send it. If there is a collision then the protocol resends thedata at a latter time. This leads to degraded channel utilization since multiple nodes may transmit at the same time. An improvement of this protocol is the slotted Aloha, as discussed in the next section. The finite state machine for this protocol is given in figure 2. Fig. 2 - State Transition Diagram of AlohaSlotted Aloha [17] is an extension of basic Aloha in which time is divided into discrete time slots. A node can only transmit at the beginning of these time slots. This helps in reducing collisions.2.2 CSMAThis stands for Carrier Sense Multiple Access with Collision Detection. In CSMA, before transmitting, nodes listen for other traffic on the same shared medium. If they sense another node is transmitting, they withhold their transmission. Once the other node's transmission has
View Full Document
Unlocking...