Distributed multichannel medium access control protocol without common control channel for single-hop cognitive radio networks

A novel distributed cognitive radio multichannel medium access protocol without common control channel was proposed.The protocol divided a transmission interval into two parts for exchanging control information and data,respectively.In addition to evaluating system saturation throughput of the proposed protocol,a three-dimensional multi channel Markov chain model to describe the sate of the cognitive users (CUs) in dynamic spectrum access was presented.The proposed analysis was applied to the packet transmission schemes employed by the basic,RTS/CTS access mechanism adopted in the normal IEEE 802.11.Analyzing the advantage of the two methods,a hybrid access mechanism was proposed to improve the system throughput.The simulation results show that the experiment results are close to the value computed by the model (less than 5%),and the proposed protocol significantly improves the performance of the system throughput by borrowing the licensed spectrum.By analyzing the dependence of throughput on system parameters,hybrid mechanism dynamically selecting access mechanism can maintain high throughput.

DQCA:a New Medium Access Control Protocol for MANs

A new medium access control protocol for MANs named DQCA(Distributed QueueCyclic Access)is presented in this paper.When the users of DQCA MAN transfer long files,the network will reach a steady state which is fair after a transient period.The transient pe-riod is shorter than that of DQDB.DQCA MAN has the flexibility in bandwidth allocation:the users can achieve different throughputs if the parameters,Pmax(i),are set to be differ-ent.The implementation of priority mechanism is simpler than that of DQDB.

Modeling and Simulation of P-Aloha,CSMA /CA and MACAW Protocols for Underwater Acoustic Channel

Medium access control( MAC) protocol of underwater acoustic communication network is a key technology for underwater acoustic networks( UANs). Most of the MAC protocols for wireless terrestrial communication networks have been designed with negligible propagation delay. If it is deployed directly in an underwater environment,the UANs will perform inefficiently. In this paper,the characteristics of underwater acoustic channel are modeled and simulated by using the OPNET simulation tool,which are the speed of sound, propagation loss, and four sources for ambient noise: the turbulence,shipping,wind driven waves and thermal noise. The performance of pure Aloha( P-Aloha),carrier sense multiple access with collision avoidance( CSMA / CA) and multiple access collision avoidance for wireless local area network( MACAW) protocols in underwater acoustic channel environment are evaluated. The different performance of protocols in underwater environment is compared in the simulation.

A DUAL RESERVATION CDMA-BASED MAC PROTOCOL WITH POWER CONTROL FOR AD HOC NETWORKS

This paper proposes a new multi-channel Medium Access Control (MAC) protocol named as Dual Reservation Code Division Multiple Access (CDMA) based MAC protocol with Power Control (DRCPC). The code channel is divided into common channel,broadcast channel and several data chan-nels. And dynamic power control mechanism is implemented to reduce near-far interference. Compared with IEEE 802.11 Distributed Coordination Function (DCF) protocol,the results show that the pro-posed mechanism improves the average throughput and limits the transmission delay efficiently.

AN MAC PROTOCOL SUPPORTING MULTIPLE TRAFFIC OVER MOBILE AD HOC NETWORKS

This letter presents the design and performance of a multi-channel MAC protocol that supports multiple traffics for IEEE 802.11 mobile ad-hoc networks. The dynamic channel selection scheme by receiver decision is implemented and the number of the data channel is independent of the network topology. The priority for real-time traffic is assured by the proposed adaptive back off algorithm and different IFS. The protocol is evaluated by simulation and the results have shown that it can support multiple traffics and the performance is better than the performance that IEEE 802.11 standard provides.

Enabling Technologies for Green Radio-over-Fiber Distributed Anten na System Based Wireless Sensor Network

Novel enabling technologies from physical layer to Medium Access Control (MAC) layer are proposed to provide energy efficient Radio-over-Fiber (RoF) Distributed Antenna System (DAS) based Wireless Sensor Networks (WSN). The power consumption performance of the network is evaluated in terms of the total network power consumption based on the proposed power consumption models from the physical layer. The results illustrate that for a given power consumption value, the tradeoff among the number of Remote Access Units (RAUs), the number of Multiple-Input Multiple-Output (MIMO) antennas and the number of hops must be taken into account. In order to efficiently reduce the total network power consumption, we also proposed a solution from the MAC layer using a sleep-aware MAC protocol, which can dynamically centralized control MIMO antennas to operate in a sleep mode. The proposed enabling technologies provide basis for selecting suitable RoF DAS based WSN and effectively reduce the power consumption.

A new multi-channel MAC protocol based on CDMA for ad hoc networks

This paper proposes a novel multichannel medium access control （MAC） protocol based on CDMA that improves network performance and reduces collision probability in wireless ad hoc networks. In the scheme, the code channel is divided into common channel, broadcast channel and several data channels. Simulation results show that the proposed protocol can achieve significantly better performance than the IEEE 802.11 standard.

Exploration of Energy Conservation MAC Protocol of WSNs for Ubiquitous Environment

According to analyze the facade phenomenon of wire-less sensor networks（WSNs）,this paper proposes a feasible method to state clearly and improve the power control efficiency of wire-less sensor networks（WSNs）. One of the crucial problems for WSNs is the design of medium access control （MAC） protocol. Our method want to adjust the activities of the MAC protocols control to achieve the enery conservation when the wireless communication module of sensor nodes is running, which is the major consumer of energy consumed by sensors energy. The energy efficiency of MAC protocol makes a strong impact on the network performance. To some extent,our research work describes and analyze the sources of energy consumption in MAC layer and simultaneously present an optimal method for the design of MAC protocol. Then we discusses some factors impacting on the performance of MAC protocol and metrics of performance evaluation. Eventually, the coming research direction is summarized.

An Analysis on Decentralized Adaptive MAC Protocols for Cognitive Radio Networks

The scarcity of bandwidth in the radio spectrum has become more vital since the demand for more and more wireless applications has increased. Most of the spectrum bands have been allocated although many studies have shown that these bands are significantly underutilized most of the time. The problem of unavailability of spectrum and inefficiency in its utilization has been smartly addressed by the cognitive radio （CR） technology which is an opportunistic network that senses the environment, observes the network changes, and then uses knowledge gained from the prior interaction with the network to make intelligent decisions by dynamically adapting their transmission characteristics. In this paper, some of the decentralized adaptive medium access control （MAC） protocols for CR networks have been critically analyzed, and a novel adaptive MAC protocol for CR networks, decentralized non-global MAC （DNG-MAC）, has been proposed. The results show the DNG-MAC outperforms other CR-MAC protocols in terms of time and energy efficiency.

Polling Strategy for Wireless Multimedia LANs

Wireless local area networks （WLANs） are a viable technology for multimedia traffic. One of the most common WLANs standards being adopted as a mature technology is the IEEE 802.11 standard. This paper presents a new polling strategy for wireless multimedia LANs with variable packet lengths, which synchronizes polling and transmission of the information packets. A mathematical model based on imbedded Markov chain theory and the generation function was used to predict the mean queue length and information packet waiting time. The efficiency of the new strategy was validated by mathematical analysis and simulations. The results show that parallel system＇s mean queue length, information packet waiting time and polling cycle time are all less than for the non-parallel system and that the improved system is more stable and has greater capacity.

SR-MAC: A Low Latency MAC Protocol for Multi-Packet Transmissions in Wireless Sensor Networks

Event detection is one of the major applications of wireless sensor networks （WSNs）. Most of existing medium access control （MAC） protocols are mainly optimized for the situation under which an event only generates one packet on a single sensor node. When an event generates multiple packets on a single node, the performance of these MAC protocols degrades rapidly. In this paper, we present a new synchronous duty-cycle MAC protocol called SR-MAC for the event detection applications in which multiple packets are generated on a single node. SR-MAC introduces a new scheduling mechanism that reserves few time slots during the SLEEP period for the nodes to transmit multiple packets. By this approach, SR-MAC can schedule multiple packets generated by an event on a single node to be forwarded over multiple hops in one operational cycle without collision. We use event delivery latency （EDL） and event delivery ratio （EDR） to measure the event detection capability of the SR-MAC protocol. Through detailed ns-2 simulation, the results show that SR-MAC can achieve lower EDL, higher EDR and higher network throughput with guaranteed energy efficiency compared with R-MAC, DW-MAC and PR-MAC.

A Dedicated MAC Protocol Package for Real-Time Ocean Current Field Estimation Using Distributed Underwater Acoustic Sensor Networks

Distributed underwater acoustic sensor networks(UASNs)are envisioned in real-time ocean current velocity estimation.However,UASNs at present are still dominated by post-processing partially due to the complexity of on-line detection for travel times and lack of dedicated medium access control(MAC)protocols.In this study,we propose a dedicated MAC protocol package for real-time ocean current velocity estimation using distributed UASNs.First,we introduce the process and requirements of ocean current velocity estimation.Then,we present a series of spatial reuse time division multiple access(TDMA)protocols for each phase of real-time ocean current field estimation using distributed UASNs,followed by numerical analysis.We divide UASNs into two categories according to their computing ability:feature-complete and feature-incomplete systems.The feature-complete systems that have abundant computing ability carry out the presented MAC protocol package in three phases,whereas the feature-incomplete ones do not have enough computing ability and the presented MAC protocol package is reduced to two phases plus an additional downloading phase.Numerical analysis shows that feature-complete systems using mini-slot TDMA have the best real-time performance,in comparison with feature-incomplete systems and other feature-complete counterparts.Feature-incomplete systems are more energy-saving than feature-complete ones,owing to the absence of in-network data exchange.