Efficient CSMA/CA Packet Relay-Assisted Scheme with Payload Combining for ITS V2V Communication

WBAN을 위한 MAC 프로토콜은 의료용 센서 노드의 가변적인 데이터를 효율적으로 처리하기 위해서 응급상황에서 발생하는 트래픽을 가장 높은 우선순위로 처리하는 CSMA/CA(: Carrier Sense Multiple Access with Collision Avoidance) 알고리즘을 수행하게 된다. 노드가 전송하는 응급 메시지는 충돌이 발생하게 되고 응급 메시지 재전송으로 인한 전송 지연이 발생할 수 있으며 재전송으로 인한 에너지 낭비를 가져올 수 있다. 본 논문에서는 이러한 문제점들을 개선하기 위해서 우선순위 큐잉을 적용한 CSMA/CA 알고리즘의 경우 MAC 명령어 프레임과 데이터 프레임의 우선순위를 정하여 서로 다른 백오프 파라미터를 적용하고 충돌로 인한 프레임 손실을 최소화하는 알고리즘을 제안하였다. 성능평가 결과 제안한 MAC 프로토콜을 사용했을 때가 IEEE 802.15.6을 사용했을때 보다 충돌 확률이 감소하여 패킷 전송 처리율이 증가하고 패킷 손실량이 감소함을 보였다. MAC protocol for WBAN performs CSMA/CA(:Carrier Sense Multiple Access with Collision Avoidance)algorithm that handles traffic which occurs in emergency with top priority in order to deal with variable data of sensor node for medicine. Emergency message that node sends undergoes collision and delay of transmission by retransmission of emergency message and waste of energy by retransmission. This paper suggests algorithm that minimizes loss of frame caused by collision and applies different backoff parameters by setting order of priority between MAC instruction frame and data frame in CSMA/CA algorithm case which applies order of priority queuing to improve aforementioned problem. According to performance evaluation, it has been found that using suggested MAC protocol showed lower collision probability, higher packet transmission processing ratio and lower packet loss compared with using IEEE 802.15.6.

The current stage of telecommunication technologies development is characterized by the rapid growth use of wireless technologies in access networks and the growth requirements for its quality. The bottleneck that significantly reduces the bandwidth of each subscriber connection is that the total bandwidth of the wireless local network is shared among its active members by the shared technology used. The access management sub-layer to the shared physical environment is responsible for this in the network architecture. The main method used at this sub-layer is the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) scheme. This work is devoted to the analysis of CSMA/CA scheme and the development of an analytical model for its further study and use for the improvement of wireless local networks. The input data is a transition state diagram of a local area wireless network station in data transmission mode. According to the CSMA/CA scheme, stations cannot change their state after starting frame transmission until a confirmation frame of successful reception arrives from the addressee or until the time to wait for it expires. Considering this, it is proposed to use a simplified transition state diagram for the analysis. The operation of the station by the simplified transition state diagram is described using a system of differential equations. As a result of the solution of this system, expressions representing the probability of the station being in each of its states as a function of the intensities of the station’s transitions from each state to another are derived. The values of these intensities depend on both the outgoing traffic of the station and the traffic in the network. The resulting expressions can be used in further work on the analysis of the CSMA/CA scheme, as they make it possible to estimate the operation of the station at different ratios of the station’s output traffic and external traffic generated by other stations of the network. This can be used to develop an enhanced algorithm station operation of wireless local area networks by adapting the parameters of the CSMA/CA scheme to specific current loads of both the station and the network.

In this paper we present a two-dimensional medium access control (MAC) protocol. Orthogonal frequency division multiple access (OFDMA) can make multiple stations (STA) transmit simultaneously on different sub-channels. On the other hand, carrier sense multiple access with collision avoidance (CSMA/CA) could make different stations contend the available channel from the time domain to avoid collision with each other. We propose a two-dimensional MAC protocol based on OFDMA and CSMA/CA in broadband systems. With the new designed MAC protocol different stations will access the channel from the time-frequency domain without interference and collision. The combination of OFDMA with CSMA/CA will improve the system throughput with efficient MAC and decrease the collision probability. We design that different stations will contend the available time-frequency resources dynamically under fairness. The system throughput of the designed protocol is analyzed and simulation results are presented to show the performance under our designed protocol far better than the conventional CSMA/CA protocol.

The effectiveness of wireless local area networks significantly depends on the method of access to the common physical environment. The main access method that is used today in wireless local area networks is carrier sense multiple access with collision avoidance (CSMA/CA), managing the efficient distribution of the common environment between active stations. In this paper, as a topic of research we consider the state transition diagram of a CSMA/CA - based network, and we describe it by a system of differential equations. Analytical expressions for the probabilities of being in one of the possible states of a network station are derived.KeywordsWireless local computer networkCarrier sense multiple access with collision avoidance (CSMA/CA)State transition diagram

In this paper, we advocate implementing carrier sense multiple access with collision detection (CSMA/CD) in the broadband power line communication (BB-PLC) standard, G.hn, and show the gain in data rate obtained over carrier sense multiple access with collision avoidance (CSMA/CA). The use of CSMA/CD is made feasible due to the recent implementation of in-band full duplex operation in BB-PLC. We provide this implementation on a G.hn model using the NS-3 simulator, which we have made available as open-source. Our G.hn model implements physical and data link layers, including repeating function that makes it possible to simulate the long line network topologies (e.g., the network for electricity metering purpose). We also add IP/UDP layers to accomplish the higher layer protocol stack. We also provide analytical calculations of efficiency gains and validate them through our simulation results. We show that the highest achievable data rate with CSMA/CD is up to 5% higher than with CSMA/CA. Furthermore, we demonstrate that the protocol with CSMA/CD is less dependent on the number of active senders and has a smaller range of optimal contention window sizes (CW) for the same range of active senders, in comparison to CSMA/CA. This also simplifies the protocol implementation as the back-off algorithm for CSMA/CD does not vary CW as much as for CSMA/CA.

IEEE 802.15.4 employs a medium access control protocol based on carrier sense multiple access with collision avoidance (CSMA/CA). Channel sensing may have critical impact on the system throughput and energy consumption as well. In this paper, we investigate the effect of channel sensing on the CSMA/CA performance in IEEE 802.15.4 star-topology configured networks. We show that the hidden node ratio (i.e., the probability that any two child nodes cannot hear each other in a star-topology configured network) is highly associated with the target false-alarm probability of the channel sensing detector. We show that the CSMA/CA performance of IEEE 802.15.4 network can significantly be improved by adjusting the hidden node ratio.

This paper presents a theoretical analysis of the maximum throughput of a wireless mesh backhaul network that is achievable over a practical carrier sense multiple access with collision avoidance (CSMA/CA) medium access control (MAC) protocol. We resort to the multicommodity flow (MCF) formulation augmented with the conflict-graph constraints, whereas we use a novel approach to take into account the collision overhead in the distributed CSMA/CA MAC. Such overhead due to random access has been ignored by existing MCF-based capacity studies, which assume impractical centralized scheduling and result in aggressive capacity planning, which is unachievable over the CSMA/CA MAC. This paper makes the following three main contributions: 1) we develop a generic method of integrating the CSMA/CA MAC analysis with the MCF formulation for optimal network capacity analysis, which readily generates an upper bound of the network throughput; 2) we define a new concept of CSMA/CA clique and theoretically study its relationship to a CSMA/CA area in terms of throughput; and 3) using the CSMA/CA clique as a tool, we derive a lower bound of the network throughput achievable over the CSMA/CA MAC by clique-based MCF formulation. NS-2 simulation results are presented to demonstrate the tightness of the upper and lower bounds that are newly developed, compared to those based on the MCF formulation assuming a slotted system and centralized scheduling.

The importance of Wireless Sensor Network (WSN) increases due to deployment for geographical, environmental and surveillance purpose in war fields. WSN facing several challenges due to its complex nature including key problems, such as routing and medium access control protocols. Several approaches were proposed for the performance evaluation of WSN on the basis of these issues due to the fact that MAC layer access protocols have a great impact on the performance of WSN. In this paper, we investigated the performance evaluation of three well known MAC Access protocols, i.e. sensor medium access control protocol (SMAC), carrier sense multiple access with collision avoidance (CSMA/CA), and time division multiple access (TDMA) over adhoc on demand distance vector (AODV) routing protocol. The number of simulation scenarios were carried out by using NS- 2, the simulation metrics used are throughput, end-to-end delay and energy consumed. Simulation results showed that SMAC out perform CSMA/CA and TDMA by consuming less energy, less end to end delay and high throughput due to contention based approach to access the medium for transmission.

The IEEE 802.11 standards for wireless local area networks define how the stations of an ad-hoc wireless network coordinate in order to share the medium efficiently. This work investigates the performance of such a network by considering the two different access mechanisms proposed in these standards. The IEEE 802.11 access mechanisms are based on the carrier sense multiple access with collision avoidance (CSMA/CA) protocol using a binary slotted exponential backoff mechanism. The basic CSMA/CA mechanism uses an acknowledgment message at the end of each transmitted packet, whereas the request to send/clear to send (RTS/CTS) CSMA/CA mechanism also uses a RTS/CTS message exchange before transmitting a packet. In this work, we analyze these two access mechanisms in terms of throughput and delay. Extensive numerical results are presented to highlight the characteristics of each access mechanism and to define the dependence of each mechanism on the backoff procedure parameters.

Wireless networks have become a very attractive solution for soft real-time data transport in the industry. For such technologies to carry real-time traffic, reliable bounds on end-to-end communication delays have to be ascertained to warrant a proper system behavior. As for legacy wired embedded and real-time networks, two main wireless multiple access methods can be leveraged: one is time division multiple access (TDMA), which follows a time-triggered paradigm, and the other is carrier sense multiple access with collision avoidance (CSMA/CA), which follows an event-triggered paradigm. This paper proposes an analytical comparison of the time behavior of two representative TDMA and CSMA/CA protocols in terms of the worst-case end-to-end delay. This worst-case delay is expressed in a probabilistic manner because our analytical framework captures the versatility of the wireless medium. Analytical delay bounds are obtained from delay distributions, which are compared to fine-grained simulation results. Exhibited study cases show that TDMA can offer smaller or larger worst-case bounds than CSMA/CA depending on its settings.

Due to a poor understanding of the interactions among transmitters, wireless multihop networks have commonly been stigmatized as unpredictable in nature. Even elementary questions regarding the throughput limitations of these networks cannot be answered in general. In this paper we investigate the behavior of wireless multihop networks using carrier sense multiple access with collision avoidance (CSMA/CA). Our goal is to understand how the transmissions of a particular node affect the medium access, and ultimately the throughput, of other nodes in the network. We introduce a theory which accurately models the behavior of these networks and show that, contrary to popular belief, their performance is easily predictable and can be described by a system of equations. Using the proposed theory, we provide the analytical expressions necessary to fully characterize the capacity region of any wireless CSMA/CA multihop network. We show that this region is nonconvex in general and entirely agnostic to the probability distributions of all network parameters, depending only on their expected values.

The IEEE 802.15.3c/mmWave WPAN has been recently proposed as one of the most promising technologies that can allow broadband access in future 5G mobile networks. In this standard, the carrier sense multiple access with collision avoidance (CSMA/CA) technique was adopted to allow medium sharing between mobile devices co-located in the same small-cell. The performances of this access technique depend on two main parameters, the carrier sense threshold and the contention window derived from the persistence probability. One of the major limits of this method is that it can lead extensive contention and thus limited throughput. In this paper, we investigate the design of a contention based multiple access control technique for 5G wireless access networks where the carrier sense threshold and the persistence probability are dynamically adjusted according to the observed contention level observed by the device on the network. To this end, we model the multiple access paradigm in 5G networks using a non-cooperative game-theoretic framework, and we show that it admits an equilibrium. In addition, we propose a fully distributed multiple access control CSMA/CA based algorithm where the carrier sense threshold and the persistence probability are intelligently tuned according to the collision level gathered by the device on the shared wireless medium until reaching the equilibrium state. Through the simulations, we demonstrate that the proposed game theoretic based CSMA/CA outperforms the original version of the algorithm in terms of success transmission rate and delay.

Studies of the IEEE 802.15.4 Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) scheme have been received considerable attention recently, with most of these studies focusing on homogeneous or saturated traffic. Two novel transmission schemes—OSTS/BSTS (One Service a Time Scheme/Bulk Service a Time Scheme)—are proposed in this paper to improve the behaviors of time-critical buffered networks with heterogeneous unsaturated traffic. First, we propose a model which contains two modified semi-Markov chains and a macro-Markov chain combined with the theory of M/G/1/K queues to evaluate the characteristics of these two improved CSMA/CA schemes, in which traffic arrivals and accessing packets are bestowed with non-preemptive priority over each other, instead of prioritization. Then, throughput, packet delay and energy consumption of unsaturated, unacknowledged IEEE 802.15.4 beacon-enabled networks are predicted based on the overall point of view which takes the dependent interactions of different types of nodes into account. Moreover, performance comparisons of these two schemes with other non-priority schemes are also proposed. Analysis and simulation results show that delay and fairness of our schemes are superior to those of other schemes, while throughput and energy efficiency are superior to others in more heterogeneous situations. Comprehensive simulations demonstrate that the analysis results of these models match well with the simulation results.

In this work, we first study and then propose an optimal version on the medium access control mechanism known as carrier sense multiple access with collision avoidance (CSMA/CA). This protocol is adopted by many wireless communication standards, such as the IEEE 802.11 series and IEEE 802.15.4 (ZigBee). We first identify its drawbacks in a slow fading channel environment, and show that the CSMA/CA can be very energy-inefficient, especially in many wireless sensor network (WSN) applications where the traffic demand is low. In particular, we study communication over a Rayleigh fading channel, which we model by means of a time invariant Markov process. We then show that the decision regarding the optimal access time on such a channel can be formulated as an optimization problem, and that an optimal solution can be accurately derived. We also simulate a ZigBee node in a Rayleigh fading environment and the result shows that optimum channel access can save significant amount of energy compared to conventional CSMA/CA.

A vehicular ad hoc network (VANET) is designed to enable efficient and authentic node/infrastructure communication. The primary role of VANETs is to distribute time-sensitive safety messages (sm) regularly, which causes packet congestion and broadcast failure due to the network’s limited spectrum. For efficient and reliable delivery, the proposed paper uses a spatial hybrid division multiple access (SDMA) and time division multiple access (TDMA) over the control channel interval and hence termed a spatially distributed multichannel MAC (SDM-MAC) protocol. The frequency reuse approach is used to transfer data while efficiently utilising bandwidth, and throughput is considerably enhanced with carrier sense multiple access with collision avoidance (CSMA/CA) and with the help of TDMA. Moreover, an adaptive algorithm is proposed for an intelligent channel frame structure using this protocol to manage the highly dynamic scenario. The Markov chain defines the protocol, and the network simulator (NS2) analyses several performance metrics. Comparing the response with two existing MAC protocols, the proposed protocol reduces average latency compared to current MAC methods and improves the packet delivery ratio and throughput by an average of 26% and 28%, respectively.