Conventional Carrier Sense Multiple Access Research Articles

Full duplex wireless communiation with dynamic buffer aided MAC protocol

This paper presents a dynamic buffer aided medium access control protocol for asymmetric traffic conditions in an IoT network, where the IoT devices send data to a wireless access point (WAP) which then forwards the data to the network fusion center. Specifically, the control frame structures of conventional carrier sense multiple access with collision detection (CSMA/CD) protocol are modified for incorporating the traffic asymmetry of the network. The devices and WAP are assumed to have full duplex abilities to support continuous sensing of the channel. The sensing performance of the considered system is derived for arbitrary number of devices in terms of probabilities of false alarm and miss detection. Moreover, the throughput of the network is also obtained. Simulation results show that the proposed cross-layer design achieves significant throughput improvement while incorporating traffic asymmetry of the network.

Energy Efficient and Throughput Optimal CSMA Scheme

Carrier sense multiple access (CSMA) is widely used as a medium access control (MAC) in wireless networks due to its simplicity and distributed nature. This motivated researchers to find CSMA schemes that achieve throughput optimality. In 2008, it has been shown that a simple CSMA-type algorithm is able to achieve optimality in terms of throughput and has been given the name “adaptive” CSMA. Later, new technologies emerged where a prolonged battery life is crucial such as environment and industrial monitoring. This inspired the foundation of new CSMA-based MAC schemes, where links are allowed to transition into a sleep mode to reduce the power consumption. However, the throughput optimality of these schemes was not established. This paper, therefore, aims to find a new CSMA scheme that combines both throughput optimality and energy efficiency by adapting to the throughput and power consumption needs of each link. This is done by controlling operational parameters, such as back-off and sleeping timers, with the aim of optimizing a certain objective function. The resulting CSMA scheme is characterized by being asynchronous, completely distributed and being able to adapt to different power consumption profiles required by each link while still ensuring throughput optimality. The performance gain in terms of energy efficiency compared with the conventional adaptive CSMA scheme is demonstrated through computer simulations.

Compute-and-Forward for Random-Access: The Case of Multiple Access Points

Compute-and-forward (C&F) recently finds new applications in random-access networks focusing on the single access point (AP) scenario. In this paper, we extend the use of C&F from the single AP scenario to the multi-AP scenario. To achieve this, we identify two major challenges and propose two novel solutions. First, we introduce an AP cooperation problem and develop an efficient distributed algorithm. Second, we introduce a joint channel estimation and active user recovery problem and propose a solution based on spare recovery techniques. In addition, we provide accurate throughput and delay expressions for C&F-based carrier-sense multiple access (CSMA) protocols. These expressions, together with our trace-driven simulations, demonstrate the significant advantages of C&F-based CSMA over conventional CSMA in the multi-AP scenario.

Node-Based Distributed Channel Access With Enhanced Delay Characteristics

Recent studies in wireless scheduling have shown that carrier-sense multiple access (CSMA) can be made throughput optimal by optimizing over activation rates. However, those throughput optimal CSMA algorithms were found to suffer from poor delay performance, especially at high throughputs where the delay can potentially grow exponentially in the size of the network. Motivated by these shortcomings, in this paper we propose a node-based version of the throughput optimal CSMA (NB-CSMA) as opposed to traditional link-based CSMA algorithms, where links were treated as separate entities. Our algorithm is fully distributed and corresponds to Glauber dynamics with “Block updates”. We show analytically and via simulations that NB-CSMA outperforms conventional link-based CSMA in terms of delay for any fixed-size network. We also characterize the fraction of the capacity region for which the average queue lengths (and the average delay) grow polynomially in the size of the network, for networks with bounded-degree conflict graphs. This fraction is no smaller than the fraction known for link-based CSMA, and is significantly larger for many instances of practical wireless ad-hoc networks. Finally, we restrict our focus to the special case of collocated networks, analyze the mean starvation time using a Markov chain with rewards framework and use the results to quantitatively demonstrate the improvement of NB-CSMA over the baseline link-based algorithm.

Post-CCA and Reinforcement Learning Based Bandwidth Adaptation in 802.11ac Networks

The new 802.11ac standard aims at achieving Gbps data throughput for individual users by exploiting enhanced physical-layer features, such as higher modulation levels, Multiple Input Multiple Output (MIMO), and wider bandwidths. However, the heterogeneity of bandwidth in a network can cause asymmetric interferences in which certain transmissions cannot be sensed by some other nodes. As a result, the conventional Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) may not work well in 802.11ac networks. We call this the Hidden Channel (HC) problem, which is shown to be real via experiments with USRP and WARP boards. To solve this problem, we propose bandwidth adaptation based on post-CCA , which is a clear channel assessment (CCA) procedure performed after completing a transmission. Post-CCA in wireless networks helps mimic the CSMA with Collision Detection (CSMA/CD) mechanism in the wired Ethernet, thus enhancing channel assessment capability. Using post-CCA, we propose Post-CCA based Bandwidth Adaptation (PoBA) that alters bandwidth and channel configuration dynamically by applying a reinforcement learning mechanism. Post-CCA and PoBA do not require any hardware modification and are also compliant with the 802.11 standards. PoBA is shown via simulation to increase network-wide throughput, channel utilization and fairness, and also lower packet error probability.

Performance enhancement of IPv6 low power wireless personal area networks (6LoWPAN) by Lamport’s algorithm

The internet of things (IoT) requires connecting various physical devices, including computing and mechanical devices to the internet. IPv6 over low power wireless personal area networks (6LoWPAN) is the great option for realizing IoT. IEEE 802.15.4 defines the physical and medium access control (MAC) layers of 6LoWPAN. MAC layer of 6LoWPAN plays an important role in the efficient utilization of resources and energy consumption of 6LoWPAN devices. The contribution of this paper is the improvement of resource utilization of 6LoWPAN devices including energy consumption and delay using Lamport’s algorithm in the MAC layer instead of the conventional carrier sense multiple access with collision avoidance approach. The proposed Lamport’s algorithm protocol shows a significant improvement in energy consumption and throughput of 6LoWPAN devices.

Distributed medium access control protocol based on successive collision detection for dense wireless sensor networks

The medium access control protocol plays an important role to decrease access collisions in dense wireless sensor networks where multiple sensors in the same vicinity attempt to transmit a packet simultaneously. In this article, we propose a distributed medium access control protocol that uses successive multiple collision detection phases for dense wireless sensor network environments by enhancing the typical carrier sense multiple access with collision resolution protocol that uses only a single collision detection phase. In the proposed medium access control protocol, colliding stations are filtered in each collision detection phase and only surviving stations compete again in the next collision detection phase. Therefore, the collision detection probability becomes higher as the collision detection phases proceed. Utilizing the successive multiple collision detection phases, we analyze the throughput numerically and find optimal operating parameters—such as the number of collision detection phases and the number of collision detection slots per phase—that maximize the throughput. Analysis and simulation results show that the proposed medium access control protocol using the successive collision detection technique significantly outperforms the conventional carrier sense multiple access with collision resolution protocol.

SIR-based multiple access with cascade yielding avoidance for distributed device-to-device communications

As the demands for efficient distributed device-to-device (D2D) communications increase, signal-to-interference ratio (SIR)-based multiple access (SBMA) technique has been proposed. By enabling SIR-aware multiple access control in distributed D2D communication, SBMA can improve utilization of the shared wireless medium in comparison with the conventional carrier sense multiple access technique. However, SBMA suffers from the cascade yielding problem which adversely affects the performance gain expected from SBMA. Cascade yielding is caused due to the limited knowledge available to each device about the medium access decisions of the neighboring devices. In order to reduce this problem, this paper enhances SBMA by taking into account the yielding relationships between neighboring devices during medium access decisions. The yielding relationships enable each device to more precisely estimate the SIRs and hence more effectively determine medium accessibility. Our simulation results show that the enhanced SBMA can allow more devices to simultaneously access the shared medium and improve the overall performance of D2D communications.

Safety-Message Broadcast in Vehicular Ad Hoc Networks Based on Protocol Sequences

In vehicular collision avoidance systems, safety messages are broadcast by mobile users periodically on the highway to all of their neighbors within hearing range. These safety messages are time sensitive and have stringent delay requirements. Conventional carrier-sense multiple access, where users must content with channel access, is not suitable for this kind of application. In this paper, we propose using protocol sequences to broadcast safety messages. Protocol sequences are deterministic 0-1 sequences. Each user reads out the 0's and 1's of the assigned protocol sequence periodically and transmits a packet in a time slot if and only if the sequence value is equal to 1. It requires no time synchronization among the users. We compare the delay performance with an ALOHA-type random access scheme and show that the delay can, in fact, be reduced by employing protocol sequences instead.

Z-MAC: Performance Evaluation and Enhancements

Most of the hybrid wireless sensor networks MAC protocols are based on conventional Carrier Sense Multiple Access (CSMA) wireless protocols. Z-MAC is an efficient hybrid protocol which alternates between CSMA and TDMA. It utilizes CSMA in low channel contention and switch to TDMA mode in high channel contention. In this paper, we show that Z-MAC does not perform well under high traffic load. It also proposes few enhancements to achieve better performance.

Improving power efficiency of CSMA wireless networks using multi-user diversity - [transaction letters

This paper proposes a method that reduces transmit-power consumption of carrier-sense multiple-access (CSMA) networks by utilizing multiuser diversity and power control. Using this method, a terminal sends a packet at a slot if the terminal's signal-to-noise ratio (SNR) is above the threshold associated with the slot. Since the threshold value decreases as time advances, this method will make the user with the largest SNR access the shared channel; thus, a packet can be transmitted with less transmit power. The analysis under the infinite-user model shows that, as traffic load grows, the expected sum-power of the conventional CSMA network increases whereas that of the proposed method decreases.

Average Channel Utilization of CSMA With Geometric Distribution Under Varying Workload

Performance analysis of fixed-size contention window carrier sense multiple-access (CSMA) protocol with geometric distribution for slot selection probability is addressed in the paper. This MAC scheme, called Sift, was initially proposed for large-scale event-driven wireless sensor networks. The goal of the present paper is to evaluate the standard performance measures (throughput, protocol capacity, collision rate, and mean access delay) for geometrically distributed CSMA both in the context of data-centric dense sensor networks and node-centric industrial automation systems. The analytical approach based on the stochastic analysis has been applied. To demonstrate how the protocol is able to cope with bursty traffic, the average throughput defined over a specified workload range has been introduced and examined. Using the average throughput as the performance criterion, the geometric CSMA has been compared to conventional CSMA schemes with uniform distribution. The latter are represented by the classical p-persistent CSMA and the predictive p-persistent CSMA used in LonWorks control networks. It is shown that G-CSMA is overload-tolerant event-driven MAC protocol since the average throughput may be kept on high level in wide range of workload if the shape of geometric distribution is well chosen.

Throughput maximization by utilizing multi-user diversity in slow-fading random access channels

In slow-fading uplink channels, carrier-sense multiple-access (CSMA) has been a popular random-access method, although it can have increased the throughput by using channel state information (CSI) acquired from a downlink training signal and electromagnetic reciprocity. To improve the throughput by using the CSI, this paper presents a random- access scheme that achieves multi-user diversity, called opportunistic p-persistent CSMA (OpCSMA). A user using OpCSMA sends a packet in a slot if the user's CSI exceeds the threshold assigned to the slot. The thresholds diminish with time to prioritize users having good CSI, while being designed to maintain the same persistency as the conventional CSMA, thus enabling backward compatibility. OpCSMA is mathematically shown to significantly increase the throughput compared with conventional CSMA, when the infinite-user model is used to model the variation of the number of users. As the expected number of users increases, the expected sum-rate of the OpCSMA approaches that using a centralized scheduler, which is the theoretical upper bound.

A Power Adapted MAC (PAMAC) Scheme for Energy Saving in Wireless Ad Hoc Networks

Nowadays, numerous Medium Access Control (MAC) contention protocols for ad hoc networks typically use a fixed transmit power level without using any transmit power control. In this paper, we present an enhancement scheme, called Power Adapted Medium Access Control (PAMAC) scheme for achieving energy conservation, which allows a node to vary its own transmit power on a packet basis. The primary objective of this scheme is to use suitable transmit power level for Clear-To-Send (CTS), DATA, and Acknowledgement (ACK) that still allows to achieve a correct reception of a packet despite intervening path loss, noise and interference. The evaluation of the throughput efficiency per node, energy consumption per node and energy per successfully transmitted bit is performed by a computer simulation. Simulation results indicate that the proposed PAMAC scheme can achieve a high reduction of the energy consumption and energy per successfully transmitted bit and also an improvement in the throughput efficiency per node compared to the conventional Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol.

A multichannel media access control protocol for multihop wireless networks with guaranteed functions

AbstractIn this paper, we propose a multichannel Medium Access Control (MAC) protocol based on the Point Coordination Function (PCF) stipulated in the IEEE 802.11 standard in order to guarantee the end‐to‐end bandwidth in a multihop wireless network. In the proposed protocol, each wireless terminal is equipped with multiple wireless interfaces and assigns a wireless channel to each wireless interface. Each wireless interface autonomously determines whether to operate in the master mode as the parent terminal, in the slave mode as a child terminal, or in the silent mode as a transmission disabled terminal, and builds a parent‐child relationship with each wireless link. Since this enables the use of the PCF at each wireless link and guarantees the bandwidth, the end‐to‐end bandwidth can be guaranteed in a multihop wireless network. We evaluate the performance of the proposed protocol in computer simulations and demonstrate improved throughput, delay, and packet loss rate compared to the conventional Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol. We also demonstrate that the bandwidths for bandwidth‐guaranteed packets are guaranteed even when traffic mixing conventional bandwidth‐guaranteed packets and best‐effort packets are present on the network. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(4): 16–25, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10139