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In mobile ad hoc networks (MANETs), the IEEE 802.11 CSMA/CA is deployed as the primary medium access control (MAC) layer protocol to schedule the access to the wireless medium. The IEEE 802.11 standard was designed with the assumption that nodes would never deviate from the protocol. However, MANET nodes may purposefully show misbehavior at the MAC layer to obtain more bandwidth or degrade the network performance and disrupt the network services. This paper reviews and classifies the most important strategies generating MAC layer misbehavior based on their objectives and operating principles. Then, it examines some of the recent proposed solutions and mechanisms for detecting and preventing MAC layer misbehavior. A comparison of the studied solutions is carried out using a set of critical evaluation metrics. Finally, the paper concludes with a brief summary of key ideas and a general direction that can provide a basis for future work. [ABSTRACT FROM AUTHOR]

In the IEEE 802.11 standard, network nodes experiencing collisions on the shared medium need a mechanism that can prevent collisions and improve the throughput. Furthermore, a backoff mechanism is used that uniformly selects a random period of time from the contention window (cw) that is dynamically controlled by the Binary Exponential Backoff (BEB) algorithm. Prior research has proved that the BEB scheme suffers from a fairness problem and low throughput, especially under high traffic load. In this paper, we present a new backoff control mechanism that is used with the IEEE 802.11 distributed coordination function (DCF). In particular, we propose a dynamic, deterministic contention window control (DDCWC) scheme, in which the backoff range is divided into several small backoff sub-ranges. In the proposed scheme, several network levels are introduced, based on an introduced channel state vector that keeps network history. After successful transmissions and collisions, network nodes change their cw based on their network levels. Our extensive simulation studies show that the DDCWC scheme outperforms four other well-known schemes: Multiplicative Increase and Linear Decrease, Double Increment Double Decrement, Exponential Increase Exponential Decrease, and Linear/Multiplicative Increase and Linear Decrease. Moreover, the proposed scheme, compared with the IEEE 802.11 DCF, gives 30.77% improvement in packet delivery ratio, 31.76% in delay, and 30.81% in throughput. [ABSTRACT FROM AUTHOR]

This article proposes a quantitative evaluation framework of all the dimensions provided by hotel websites. The proposed framework evaluates the richness of specific and comprehensive information. A proposed conceptual model that describes the hotel websites' features is used in order to summarize the data and consider how sound websites are in terms of technology and management. The model combines various dimensions (i.e., information attributes, website design attributes, reservation engine facilities, payment, provided services attributes, provided information attributes, quality of content, language support, website operating attributes, website structure, navigation, and search facilities). The proposed evaluation method is based on the websites evaluation by users/guests, hotel managers, and IT professionals, while it uses principal components analysis (PCA) to estimate the performance score from users/guests, hotel managers, and IT professionals as well the overall score of a website. Using this framework, we determine how each data dimension impacts on each performance indicator as well as on the overall performance. We applied our method and evaluated 30 chain hotel websites operating in Greece, and found interesting insights for the hotel chain industry in Greece. [ABSTRACT FROM PUBLISHER]