University:
College
Course:
College Engineering
Academic year:

2023
Views:

357

Pages:

2
Author:

Dipin K.

Performance Metrics Given the wide range of protocols that have been proposed, it is necessary to understand the metrics that are used to compare the MAC protocols. Delay, throughput, fairness, support for multimedia, and stability are the widely used metrics to compare MAC protocols. Robustness against fading and battery power consumption are additional metrics used to compare wireless MAC protocols. Following is a brief discussion of these metrics.        Delay Throughput Fairness Stability Robustness against Channel Fading Power Consumption Support for Multimedia Delay: Delay is defined as the average time spent by a packet in the MAC queue, i.e., from the instant it is enqueued till its transmission is complete. Delay is a function of protocol and traffic characteristics. Therefore, when comparing protocols, it is necessary to compare them based on the same traffic parameters. Throughput: Throughput is the fraction of the channel capacity used for data transmission. A MAC protocol's objective is to maximize the throughput while minimizing the access delay. If the average message size is P bits, the average time to transfer a single packet is T secs, and C b/s is the capacity of the channel, then the throughput γ given by γ =P/ TC. Fairness: A MAC protocol is fair if it does not exhibit preference to any single node when multiple nodes are trying to access the channel. This results in fair sharing of the bandwidth. This definition can be biased when traffic with different priorities is handled. When multimedia traffic is supported, fairness is defined as be enable to distribute bandwidth in proportion to their allocation. Stability: Due to overhead in the protocol, the system may be able to handle sustained source loads that are much smaller than the maximum transmission capacity of the channel. A stable system can handle instantaneous loads that are greater than the maximum sustained load when the long-term offered load is less than the maximum. Robustness against Channel Fading: The wireless channel is time-varying and error-prone. Channel fading can make the link between two nodes unusable for short periods of time. Such link failures should not result in unstable behavior. Power Consumption: Most wireless devices have limited battery power. Hence, it is important for MAC protocols to conserve power and provide some power saving features. Support for Multimedia: With the convergence of voice, video, and data networks, it is now necessary for MAC protocols to support multimedia traffic Protocols require mechanisms to treat packets from various applications based on their delay constraints. Two common methods are access priorities and scheduling- Access priorities provide differentiated service by allowing certain nodes to get access to the network services with a higher probability than others. Scheduling can give delay and jitter guarantees.