CSMA based inter-vehicle communication using distributed and polling coordination

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.

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In the overlay medium access control (MAC) of cognitive radio networks, secondary user (SU) uses the spectrum portion which is assigned to primary user (PU), when PU is not using this spectrum at that time. In this article, a multiuser overlay MAC protocol is considered in which PUs and SUs are using time division multiple access and carrier sense multiple access (CSMA) MAC schemes, respectively. Firstly, new frame format and algorithm for the proposed MAC protocol are described, then the analytical modelling of this protocol is explained. In the SU network, Markov chain model along with the CSMA protocol is used for better utilization of the opportunity from the PU network (PUN). Channel utilization and probability of success are also derived and analyzed for this protocol with respect to idle time, collision (failure) time, various spectrum opportunities from PUN, number of SUs, and their fairness. This MAC scheme provides the optimal solution for channel utilization under a constraint on the probability of collisions. Numerical results are also provided to validate analysis of proposed MAC protocol and to investigate the performance behaviour of the optimal solution.

Machine-to-Machine (M2M) networks require more elaborate design of medium access control (MAC) due to their higher complexity in system management. In many applications of M2M networking, the major traffic pattern consists of data collected from several source nodes to a sink through a unidirectional tree. Earlier prevalence of Carrier-Sense Multiple Access (CSMA) has continuously been being switched to Time-Division Multiple Access (TDMA). The main drawback of CSMA is idle listening, which refers to the fact that the nodes have to unnecessarily wake up due to lack of schedule. Energy inefficiency of a network gets higher as the number of nodes committed to idle listening, which seriously limits the scalability of a network. Recent enhancement of hardware has been enabling sufficiently accurate synchronization while keeping energy consumption low enough, which mitigates the main drawback of TDMA. This paper proposes a TDMA-based MAC protocol that achieves higher energy efficiency in centralized M2M communications. As a TDMA-based protocol, the proposed protocol is fully scheduled and hence no idle listening occurs. Moreover, the protocol reduces the length of a multi-hop transaction which results in higher energy efficiency as well as lower latency. Simulation results show that the proposed MAC protocol outperforms the conventional CSMA and other popular MAC schemes, in terms of energy consumption, delay, and packet delivery ratio (PDR).

In this paper, we consider medium access control (MAC) protocol design for random-access cognitive radio (CR) networks. A two-level opportunistic spectrum access strategy is proposed to optimize the system performance of the secondary network and to adequately protect the operation of the primary network. At the first level, secondary users (SUs) maintain a sufficient detection probability to avoid interference with primary users (PUs), and the spectrum sensing time is optimized to control the total traffic rate of the secondary network allowed for random access when the channel is detected to be available. At the second level, two MAC protocols called the slotted cognitive radio ALOHA (CR-ALOHA) and cognitive-radio-based carrier-sensing multiple access (CR-CSMA) are developed to deal with the packet scheduling of the secondary network. We employ normalized throughput and average packet delay as the network metrics and derive closed-form expressions to evaluate the performance of the secondary network for our proposed protocols. Moreover, we use the interference and agility factors as the performance parameters to measure the protection effects on the primary network. For various frame lengths and numbers of SUs, the optimal performance of throughput and delay can be achieved at the same spectrum sensing time, and there also exists a tradeoff between the achievable performance of the secondary network and the effects of protection on the primary network. Simulation results show that the CR-CSMA protocol outperforms the slotted CR-ALOHA protocol and that the PUs' activities have an influence on the performance of SUs for both the slotted CR-ALOHA and CR-CSMA.

Optical camera communication (OCC), a branch of optical wireless communication (OWC), enables data transmission using LEDs and reception via cameras. This technology offers benefits such as a broad spectrum, low cost, high efficiency, and resistance to electromagnetic interference. However, OCC faces challenges in medium access management, which necessitates the development of effective medium access control (MAC) protocols. The IEEE 802.15.7 standard proposes MAC protocols tailored for various OCC modes and simplifies frame structures. In this study, we develop and test a MAC protocol based on carrier sense multiple access with collision avoidance (CSMA/CA) and integrate a novel transform alignment technique aimed at optimizing the bit error rate (BER) performance. By addressing the inherent medium access challenges in OCC, such as signal interference and access contention, the new protocol significantly boosts data transmission efficiency and enhances communication reliability.

The carrier-sensing multiple access with collision avoidance (CSMA/CA) protocol is the most well-known medium access control (MAC) protocol for wireless networks. Both the distributed coordination function (DCF) defined in IEEE 802.11 and the MAC layer defined in IEEE 802.15.4 are based on the CSMA/CA protocol. Nevertheless, these two standards have quite different carrier-sensing mechanisms. Different to continuous carrier sensing in DCF, an IEEE 802.15.4 node only senses the channel once just after a backoff. Sensing-once mechanism can reduce the computation loading on the CPU. However, it significantly increases the probability of failure transmission because a node is not fully aware of channel activity. This paper first proposes a software architecture integrating proper hardware features for designing a DCF-based MAC protocol and then successfully implements it on a low-power transceiver. In addition, this paper conducts experiments in a star topology network to compare the performance of the above DCF-MAC protocol with the IEEE 802.15.4 MAC protocol. Experimental results show that, without continuous sensing, the IEEE 802.15.4 network suffers a high transmission failure probability as the network size increases. Consequently, the proposed DCF-based MAC protocol outperforms the IEEE 802.15.4 MAC protocol in terms of packet loss probability and throughput.

The IEEE 802.11 Distributed Coordination Function (DCF) Medium Access Control (MAC) protocol is designed to efficiently facilitate the limited communication bandwidth of wireless channel. This protocol uses Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) mechanism. This mechanism continues suffer from throughput degradation when directly applied in multihop Wireless Mesh Network (WMN). The major reason for this poor performance is due to larger signaling overheads (RTS and CTS signaling packet) introduced in order to forward a single data packet in multihop WMN. This inefficient forwarding operation caused the throughput degradation signifficantly. Therefore, an efficient forwarding operation is proposed in this paper to reduce the amount of signaling overheads which are needed to forward a single packet in multihop WMN. The proposed protocol uses the capability of overhearing in order to forward the data packet from one hop to another hop. This process will continue until the data packet reaches the respective destination. As a result, the enhanced protocol reduces the latency caused by signaling thus improve its throughput in multihop WMN. The multihop network performances are evaluated analytically in terms of throughput and delay. Through the simulation, it is proven that the proposed protocol provides significant improvement in throughput and delay. The results show that the proposed protocol outperforms the existing IEEE DCF MAC protocol when it is evaluated in multihop WMN.

Power consumption, latency, and complexity are considered to be a benchmark for comparing Medium Access Control (MAC) protocols in Wireless Sensor Networks (WSN). However, the importance of these elements varies according to the application. In this paper, three MAC protocols are proposed for forest fire detection. Basically, two of these protocols are based on the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol with some modification to suit the forest fire detection application. These protocols are called Persistent CSMA (P-CSMA) and Per Hope Synchronization CSMA (PHS-CSMA). The third one is a Time Division Multiple Access (TDMA)-based protocol, called Sensor TDMA (S-TDMA). These three protocols are investigated and analyzed by simulation. Results show that there is no superior protocol which outperforms others in terms of power consumption, delay and complexity. However, a trade-off does exist. In terms of power consumption, S-TDMA outperforms other protocols but it has the worst performance in terms of delay. On the other hand, considering the design complexity, S-TDMA is the most complex as it needs time synchronization over the entire cluster while PCSMA and PHS-CSMA don't require time synchronization between nodes.

Impulse-based ultrawideband (I-UWB) is an attractive radio technology for large ad hoc and sensor networks due to its robustness to multipath effects, subcentimeter ranging ability, simple hardware, and low radiated power. Large distributed networks, such as ad hoc and sensor networks, often implement distributed medium access control (MAC) protocols based on carrier sense multiple access (CSMA). In CSMA, narrowband systems check for medium activity before transmitting by checking for in-band energy around a carrier frequency. I-UWB systems lack a carrier, and the narrow pulses, low radiated power, harsh channel conditions, and strict Federal Communications Commission power limits present challenges in detecting medium activity. We propose a pulse sensor for I-UWB systems that overcomes the challenges of quickly, reliably, and efficiently identifying medium activity. The pulse sensor enables distributed MAC protocols for I-UWB radios that are analogous to CSMA for narrowband radios. Simulations show that the proposed pulse sensor architecture is practical for I-UWB radios

Any medium access control (MAC) protocol designed for underwater acoustic networks (UANs) must take some unique characteristics of underwater channels into consideration for apt functioning, such as long propagation delay, high bit-error rate, limited bandwidth and so forth. Already, many MAC protocols are designed for UANs, which have fully or partially taken these characteristics into account and could be classified as handshake-free and handshake-based protocols. In this paper, these two classes are investigated through a comprehensive simulation campaign by employing their prominent representative protocols, namely ALOHA, carrier sense multiple access (CSMA) and multiple access with collision avoidance based adaptive packet train (MACA-APT) protocol. The contribution of this paper lies as follows: (i) unearthing the optimum values of various parameters on which the performance of a protocol relies; (ii) investigating the performance of all three protocols through a realistic channel model simulator by varying a couple of network parameters, and iii) discovering their effectiveness on various applications.

In this paper, a new medium access control (MAC) protocol entitled three-phase multiple access with continual contention resolution (TPMA-CCR) is proposed for wireless multi-hop ad hoc networks. This work is motivated by the previously known threephase multiple access (TPMA) scheme of Hou and Tsai [2] which is the suitable MAC protocol for clustering multi-hop ad hoc net- works owing to its beneficial attributes such as easy collision detectible, anonymous acknowledgment (ACK), and simple signaling format for the broadcast-natured networks. The new TPMA-CCR is designed to let all contending nodes participate in contentions for a medium access more aggressively than the original TPMA and with continual resolving procedures as well. Through the systematical performance analysis of the suggested protocol, it is also shown that the maximum throughput of the new protocol is not only superior to the original TPMA, but also improves on the conventional slotted carrier sense multiple access (CSMA) under certain circumstances. Thus, in terms of performance, TPMA-CCR can provide an attractive alternative to other contention-based MAC protocols for multi-hop ad hoc networks.

Power efficient ultra-wideband based wireless communication for wireless body area network applications

In this paper we propose a simple relay enabled medium access (SRMAC) protocol that enables cooperative relay transmissions. Due to the wireless signal power attenuation with distance, using a relay in a wireless network can make wireless networking more bandwidth efficient at the expense of requiring multiple transmissions for a single packet. Standard MAC protocols such as the IEEE 802.11 MAC protocol, while useable with relaying, however are not designed explicitly for relay communication. When IEEE 802.11 MAC protocol is used for cooperative communication such a relaying, each packet transmission would need to separately contend for the channel via a channel access procedure which can use significant resources (both energy and bandwidth). Because using a single relay requires two transmissions, an efficient medium access control (MAC) protocol that supports two hop transmission is needed. We introduce a protocol, SRMAC, which is a simple cooperative MAC protocol that utilizes information from the physical layer for the MAC operation of relay networks. We consider the bandwidth efficiency of SRMAC protocol considering both the physical layer and MAC layer. The SRMAC protocol includes the possibility of both cooperative transmission and direct transmission. With SRMAC, cooperative transmission (relaying) can be dynamically chosen when it is more beneficial than direct transmission. The SRMAC protocol can improve the throughput by up to 20% compared to conventional MAC protocols.

Since cognitive wireless network (CRN) has the characteristic of secondary use, it can enable the device to dynamically access available spectrum without interference to primary users (PUs), which can effectively alleviate contradiction between the lack of spectrum resources and the growing demand for wireless access. However, Medium Access Control (MAC) protocol as CRN core components, can achieve competition access of the licensed spectrum and coordination control, which will maximize spectrum utilization efficiency and network throughput. The contribution of this survey is threefold. First, we analyze the characteristics of the existed multi- channel MAC protocol in CRN; Second, according to the different ways of spectrum access in CRNs, the multi-channel MAC protocols are classified into time-slotted based MAC protocol, control channel based MAC protocol and hybrid MAC protocol, and the paper emphatically analyzed the advantages and disadvantages of these multi-channel MAC protocols; Finally, the paper explores the difficulties and the challenges of multi-channel MAC protocols design in cognitive wireless network.