Optimal Bandwidth Utilization in Wireless Token Ring Networks

Wireless Token Ring Protocol (WTRP) is the medium access protocol that enables the mobile nodes to communicate in Ad-hoc networks. The major focus of Wireless Token Ring Protocol is to support mobility of nodes in ad-hoc networks. This implies the bandwidth is limited and the channel is shared among many stations. Under normal operating conditions, MAC protocol provides guarantees to achieve Quality of Service (QOS). This is achieved by Minimum throughput for each station and Medium access time for each station is bounded. To improve the performance of WTRP three different secondary message-passing techniques are proposed. These are: 1). a data packet can be sent in a reverse direction, 2). a data packet can jump to the farthest node and 3). a condition under which a secondary communication is possible within the ring.Computer Science Departmen

A Control Plane For Prioritized Real-time Communications In Wireless Token Ring Networks

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2008Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2008Kablosuz ağlarda gerçek zaman kısıtlarını sağlamak zor bir araştırma problemidir. Jetonlu halka mimarisine sahip ağlar yanıt süreleri deterministik olduğundan ve gecikmelerin üst sınırının tahmin edilebilir olmalarından dolayı gerçek zaman kısıtlarını sağlamak için daha elverişlidir. Bu tezde kablosuz jetonlu halka ağları için katı gerçek zaman kısıtlarını sağlamak üzere MAC katmanında zamanlı jeton protokolünü içeren merkezi bir denetim düzlemi önerilmektedir. Bu denetim düzleminde üç tane fonksiyon gerçeklenmiştir. Bunlar kabul denetimi, istasyon çıkarma ve trafik ayrımı fonksiyonlarıdır. Böylece dinamik bir halka yapısı oluşturulmuş ve yüksek öncelikli trafiğin ağa girme şansı artmış ve düşük öncelikli trafik taşıyan istasyonların gerektiğinde yüksek öncelikli trafiğe yer vermeleri için ağdan çıkarılmaları sağlanmıştır. Simülasyon sonuçlarına göre önerilen denetim düzlemi sayesinde yüksek öncelikli trafiğin düşük öncelikli trafiğe göre ağda daha fazla bant genişliğine sahip olduğu ve katı gerçek zaman kısıtlarının sağlandığı görülmüştür.Providing real-time guarantees in wireless networks is a challenging research problem. Token ring networks are more suitable for real-time communications due to the fact that the response time is highly deterministic and also the upper bound of the latency in these networks is predictable. This thesis proposes a centralized control plane incorporating the timed token protocol in the MAC layer for providing hard real-time guarantees in wireless token ring networks which implements three important functions, namely the admission control procedure, the station eviction procedure and a traffic differentiation mechanism. In this approach a dynamic ring structure is built, where high priority stations have more chance of admittance and stations with low priority can be removed from the ring. Simulation results show that the proposed control plane ensures higher priority traffic more bandwidth than lower priority traffic and guarantees that deadline constraints of hard real-time traffic are satisfied.Yüksek LisansM.Sc

Overlay Token Ring Protocol for Vehicular Communication Networks

Vehicular communication has been an emerging topic among current wireless research. The vehicular communication can be classified to Inter-Vehicle Communication (IVC) and Road-to-Vehicle Communication (RVC). IVC and RVC support applications mainly on two aspects: safety applications aiming to reduce dangers on the road, and data applications aiming to provide information and entertainment to people on traveling. Vehicles nearby form Vehicular Ad hoc Networks (VANETs) without any fixed infrastructures. Due to the characteristics of vehicular networks such as quickly changing and unstable network topology, IVC has special requirements to the network protocols. Several MAC protocols have been appeared or improved based on previous work for IVC. But these protocols are designed either for QoS guaranteed data service or for reliable message broadcast. There is not a protocol including both application requirements and inexpensive to implement as well. MAC protocol for vehicular communication hasn’t been finalized. In this thesis, an overlay token ring protocol (OTRP) is proposed which can work on MAC layer with broadcast function and taking into the IVC features into consideration. In OTRP, vehicles are grouped to overlapped rings with a token passed in each ring as the sole right for transmission. The ring is dynamically updated in a distributed manner based on smart algorithm at each node. OTRP provides bounded delay by assigning maximum token holding time for each node. It also reduces collisions by decreasing the number of contention nodes by times of ring size. Fair and high throughput is obtained as well. Furthermore, it provides reliable and prompt broadcast of emergency messages by pre-emptively transmitting while applying the token as an acknowledgement. The time nodes reliably receive the message is within limit. Theoretical analysis is provided and simulation results are given to evaluate the performance of OTRP under saturated traffic conditions both in safety and data applications

Hybrid token-CDMA MAC protocol for wireless networks.

Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2009.Ad hoc networks are commonly known to implement IEEE 802.11 standard as their medium access control (MAC) protocol. It is well known that token passing MAC schemes outperform carrier-sense-multiple-access (CSMA) schemes, therefore, token passing MAC protocols have gained popularity in recent years. In recent years, the research extends the concept of token passing ' scheme to wireless settings since they have the potential of achieving higher channel utilization than CSMA type schemes. In this thesis, a hybrid Token-CDMA MAC protocol that is based on a token passing scheme with the incorporation of code division multiple access (CDMA) is introduced. Using a dynamic code distribution algorithm and a modified leaky-bucket policing system, the hybrid protocol is able to provide both Quality of Service (QoS) and high network resource utilization, while ensuring the stability of a network. This thesis begins with the introduction of a new MAC protocol based on a token-passing strategy. The input traffic model used in the simulation is a two-state Markov Modulated Poisson Process (MMPP). The data rate QoS is enforced by implementing a modified leaky bucket mechanism in the proposed MAC scheme. The simulation also takes into account channel link errors caused by the wireless link by implementing a multi-layered Gilbert-Elliot model. The performance of the proposed MAC scheme is examined by simulation, and compared to the performance of other MAC protocols published in the literature. Simulation results demonstrate that the proposed hybrid MAC scheme is effective in decreasing packet delay and significantly shortens the length of the queue. The thesis continues with the discussion of the analytical model for the hybrid Token CDMA protocol. The proposed MAC scheme is analytically modelled as a multiserver multiqueue (MSMQ) system with a gated service discipline. The analytical model is categorized into three sections viz. the vacation model, the input model and the buffer model. The throughput and delay performance are then computed and shown to closely match the simulation results. Lastly, cross-layer optimization between the physical (PHY) and MAC layers for the hybrid token-CDMA scheme is discussed. The proposed joint PHY -MAC approach is based on the interaction between the two layers in order to enable the stations to dynamically adjust the transmission parameters resulting in reduced mutual interference and optimum system performance

A Survey of Medium Access Mechanisms for Providing QoS in Ad-Hoc Networks

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DTB-MAC: Dynamic Token-Based MAC Protocol for reliable and efficient beacon broadcasting in VANETs

© 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Most applications developed for vehicular environments rely on broadcasting as the main mechanism to disseminate their messages. However, in IEEE 802.11p, which is the most widely accepted MAC protocol for vehicular communications, all transmissions remain unacknowledged if broadcasting is used. Furthermore, safety message transmission requires a strict delay limit and a high reliability, which is an issue for random access MAC protocols like IEEE 802.11p. Therefore, transmission reliability becomes the most important issue for broadcast-based services in vehicular environments. In this paper, we propose a hybrid MAC protocol, referred as Dynamic Token-Based MAC Protocol (DTB-MAC). DTB-MAC uses both a token passing mechanism and a random access MAC protocol to prevent channel contention as much as possible, and to improve the reliability of safety message transmissions. Our proposed protocol tries to select the best neighbouring node as the next transmitter, and when it is not possible, or when it causes a high overhead, the random access MAC protocol is used instead. Based on simulation experiments, we show that the DTB-MAC protocol can achieve better performance compared with IEEE802.11p in terms of channel utilization and beacon delivery ratio.This work was partially supported by the Ministerio de Ciencia e Innovación, Spain, under Grant TIN2011-27543-C03-01.Balador, A.; Tavares De Araujo Cesariny Calafate, CM.; Cano Escribá, JC.; Manzoni, P. (2015). DTB-MAC: Dynamic Token-Based MAC Protocol for reliable and efficient beacon broadcasting in VANETs. IEEE. https://doi.org/10.1109/CCNC.2015.7157955