Carrier Sense Multiple Access Research Articles

Learning-Based Autonomous Channel Access in the Presence of Hidden Terminals

We consider the problem of autonomous channel access (AutoCA), where a group of terminals tries to discover a communication strategy with an access point (AP) via a common wireless channel in a distributed fashion. Due to the irregular topology and the limited communication range of terminals, a practical challenge for AutoCA is the hidden terminal problem, which is notorious in wireless networks for deteriorating throughput and delay performances. To meet the challenge, this paper presents a new multi-agent deep reinforcement learning paradigm, dubbed MADRL-HT, tailored for AutoCA in the presence of hidden terminals. MADRL-HT exploits topological insights and transforms the observation space of each terminal into a scalable form independent of the number of terminals. To compensate for the partial observability, we put forth a look-back mechanism such that the terminals can infer behaviors of their hidden terminals from the carrier-sensed channel states as well as feedback from the AP. A window-based global reward function is proposed, whereby the terminals are instructed to maximize the system throughput while balancing the terminals' transmission opportunities over the course of learning. Considering short-packet machine-type communications, extensive numerical experiments verified the superior performance of our solution benchmarked against the legacy carrier-sense multiple access with collision avoidance (CSMA/CA) protocol.

“Hybrid MAC Methodology for Improving the QOS in Fiber Wireless Network”

The Fi-Wi (Fiber-Wireless) approach stands out as a crucial element in the realm of networks, demonstrating superiority over various technologies. With the exponential growth in Internet users, significant strides have been made in the evolution of Fi-Wi networking systems in recent years. This mechanism offers broader bandwidth and network stability, ensuring high-speed connectivity with "Anytime Anywhere" availability for end users. However, the escalating energy demand in networking systems poses a constraint on the network's lifespan, impacting transmission.
 Over the years, researchers have proposed and tested various Media Access Control (MAC) protocols to address transmission and energy consumption issues. Despite these efforts, existing protocols have encountered challenges such as overheating, delays, throughput issues, and collisions. This research paper introduces a combination of Time Division Multiple Access (TDMA) and Carrier Sense Multiple Access (CSMA) to tackle associated challenges. The primary objective is to enhance throughput and reduce delays in Fi-Wi networks.
 To achieve this goal, the study employs techniques that involve and Utilizing an Orthogonal Frequency Division Multiplexing (OFDM) modulator, a free-space optical (FSO) communication channel, an OFDM demodulator, and Opti-system for the analysis and enhancement of received signals, our study demonstrates that the proposed MAC protocol surpasses conventional MAC protocols in terms of delay, data throughput, and transmission efficiency.

Applying Carrier Sense Multiple Access to Industrial IoT at Terahertz Frequencies

Applying Carrier Sense Multiple Access to Industrial IoT at Terahertz Frequencies

A Torpor-based Enhanced Security Model for CSMA/CA Protocol in Wireless Networks

Mobile wireless networks enable the connection of devices to a network with minimal or no infrastructure. This comes with the advantages of ease and cost-effectiveness, thus largely popularizing the network. Notwithstanding these merits, the open physical media, infrastructural-less attributes, and pervasive deployment of wireless networks make the channel of communication (media access) vulnerable to attacks such as traffic analysis, monitoring, and jamming. This study designed a virtual local area network (VLAN) model to circumvent virtual jamming attacks and other intrusions at the Media Access Control (MAC) layer of the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol. A Torpor VLAN (TVLAN) Data Frame Encapsulation and the algorithm for T-VLAN security in CSMA/CA were formulated and presented. A simulation experiment was conducted on the model using OMNeT++ software. The performance metrics used to evaluate the model were packet delivery ratio, network throughput, end-to-end channel delay, and channel load. The simulation results show that the TVLAN defence mechanism did not increase the channel load arbitrarily during TVLAN defence. similarly, the system throughput was shown to be 82% during TVLAN defence. Nevertheless, the network delay of the system during TVLAN defence was significantly high but the channel load was 297 when the TVLAN security mechanism was launched. These results demonstrate the model’s ability to provide a survivability mechanism for critical systems when under attack and add a security layer to the CSMA/CA protocol in wireless networks. Such a remarkable performance is required of a CSMA/CA infrastructure for improving the cybersecurity posture of a wireless network.

Performance Evaluation of Collision Avoidance for Multi-node LoRa Networks based on TDMA and CSMA Algorithm

LoRa can be used as the communication technology for the intelligent monitoring system. However, LoRa is usually used for outdoor communication. The usage of LoRa as indoor communication has many challenges. One of the challenges is that collision happens when using standard LoRa devices with only one channel. The algorithms based on TDMA (Time-division Multiple Access) and CSMA (Carrier-sense Multiple Access) protocols can be used to address this challenge. These two algorithms can be modified by applying the device that is the center of the network (gateway) as a central control and the data transmitter (sensor node) as a passive device. The test was conducted on the Intelligent Laboratory Monitoring System to evaluate this design on a multi-node LoRa network. RSSI testing proves that the distance and building interference affect the signal strength or RSSI of sensor nodes, so the average RSSI value is -73.75 with an RSSI threshold of value -106. The gateway successfully collected each sensor node data with an average success of about 64.953%. The experiment results show the success rate of the CSMA-based algorithm is 10% versus 100% in TDMA-based algorithm; the delay is 4125 ms for CSMA-based and 428.3 ms for TDMA-based. This result means that the CSMA-based algorithm is more complex, takes more time to process the data than the TDMA-based algorithm, has a low success rate, and is more prone to collisions.

“Hybrid MAC Methodology for Improving the Qos in Fiber Wireless Network”

The Fi-Wi (Fiber-Wireless) approach stands out as a crucial element in the realm of networks, demonstrating superiority over various technologies. With the exponential growth in Internet users, significant strides have been made in the evolution of Fi-Wi networking systems in recent years. This mechanism offers broader bandwidth and network stability, ensuring high-speed connectivity with "Anytime Anywhere" availability for end users. However, the escalating energy demand in networking systems poses a constraint on the network's lifespan, impacting transmission.
 Over the years, researchers have proposed and tested various Media Access Control (MAC) protocols to address transmission and energy consumption issues. Despite these efforts, existing protocols have encountered challenges such as overheating, delays, throughput issues, and collisions. This research paper introduces a combination of Time Division Multiple Access (TDMA) and Carrier Sense Multiple Access (CSMA) to tackle associated challenges. The primary objective is to enhance throughput and reduce delays in Fi-Wi networks.
 To achieve this goal, the study employs techniques that involve and Utilizing an Orthogonal Frequency Division Multiplexing (OFDM) modulator, a free-space optical (FSO) communication channel, an OFDM demodulator, and Opti-system for the analysis and enhancement of received signals, our study demonstrates that the proposed MAC protocol surpasses conventional MAC protocols in terms of delay, data throughput, and transmission efficiency.

Low-Latency Wireless Network Extension for Industrial Internet of Things.

The timely delivery of critical messages in real-time environments is an increasing requirement for industrial Internet of Things (IIoT) networks. Similar to wired time-sensitive networking (TSN) techniques, which bifurcate traffic flows based on priority, the proposed wireless method aims to ensure that critical traffic arrives rapidly across multiple hops to enable numerous IIoT use cases. IIoT architectures are migrating toward wirelessly connected edges, creating a desire to extend TSN-like functionality to a wireless format. Existing protocols possess inherent challenges to achieving this prioritized low-latency communication, ranging from rigidly scheduled time division transmissions, scalability/jitter of carrier-sense multiple access (CSMA) protocols, and encryption-induced latency. This paper presents a hardware-validated low-latency technique built upon receiver-assigned code division multiple access (RA-CDMA) techniques to implement a secure wireless TSN-like extension suitable for the IIoT. Results from our hardware prototype, constructed on the IntelFPGA Arria 10 platform, show that (sub-)millisecond single-hop latencies can be achieved for each of the available message types, ranging from 12 bits up to 224 bits of payload. By achieving one-way transmission of under 1 ms, a reliable wireless TSN extension with comparable timelines to 802.1Q and/or 5G is achievable and proven in concept through our hardware prototype.

Effects Investigation of MAC and PHY Layer Parameters on the Performance of IEEE 802.15.6 CSMA/CA

The recently released IEEE 802.15.6 standard specifies several physical (PHY) layer and medium access control (MAC) layer protocols for variety of medical and non-medical applications of Wireless Body Area Networks (WBAN). The most suitable way for enhancing network performance is to be the choice of different MAC and PHY parameters based on quality of service (QoS) requirements of different applications. The impact of different MAC and PHY parameters on the network performance and the tradeoff relationship between the parameters are essential to overcome the limitations of exiting carrier sense multiple access with collision avoidance (CSMA/CA) scheme of IEEE 802.15.6 standard. To address this issue, we develop a Markov chain-based analytical model of IEEE 802.15.6 CSMA/CA for all user priorities (UPs) and apply this general model to different network scenarios to investigate the effects of the packet arrival rate, channel condition, payload size, access phase length, access mechanism and number of nodes on the performance parameters viz. reliability, normalized throughput, energy consumption and average access delay. Moreover, we conclude the effectiveness of different access phases, access mechanisms and user priorities of intra-WBAN.

Reinforcement learning based multi-parameter joint optimization in dense multi-hop wireless networks

Carrier Sense Multiple Access with Collision Avoid (CSMA/CA) restricts the channel utilization efficiency although it always is regarded as a promising distributed channel access scheme, especially in dynamic dense wireless network scenarios. This paper investigates a Reinforcement Learning (RL) based multi-parameter joint optimization mechanism to build suitable access configuration for dense wireless multi-hop networks. Specifically, we propose a light-weight CSMA/CA mechanism based on Q-Learning (QL), namely QL-CSMA/CA, which jointly optimizes multiple channel access parameters, including Contention Window (CW), Maximum Backoff Exponent (MaxBE), and Maximum CSMA Backoffs (MaxCSMABackoffs), by setting mixed rewards and thus leading to higher network performance. Due to the limitation of the QL-CSMA/CA in large-scale state-space scenarios, we further present an enhanced CSMA/CA mechanism based on Deep Q-Network (DQN), namely DQN-CSMA/CA. Despite introducing a little complexity, the DQN-CSMA/CA can significantly improve transmission performance by utilizing more comprehensive network state information in complex dynamic network scenarios. Simulation results demonstrate the effectiveness of the proposed algorithms in terms of throughput, packet loss rate, delay, and collision rate, especially in high-density scenarios. Specifically, compared to SCAMA and traditional CSMA/CA algorithms, the QL-CSMA/CA algorithm achieves 9% and 5% performance improvements in terms of throughput, while DQN-CSMA/CA algorithm achieves 14% and 10% improvements in terms of throughput, respectively.

Distributed Physical-layer Network Coding MAC protocol

Physical-layer Network Coding (PNC) was first proposed for a Two-Way Relay Channel (TWRC) to improve the spectrum efficiency since it allows nodes to transmit simultaneously via a relay node. This technique requires multiple nodes to transmit their packets with accurate synchronization. Therefore, in many works of literature, centralized scheduling with perfect synchronization has been assumed to be employed on top of PNC.Such assumptions are not applicable in general random access multi-hop wireless networks. Therefore, this paper proposes a distributed MAC protocol that supports PNC in static multi-hop wireless networks. The proposed MAC protocol is based on the Carrier Sense Multiple Access (CSMA) strategy, where RTS/CTS frames are used to detect PNC opportunities and to offer the appropriate scheduling of the involved transmissions that should occur simultaneously. This packet exchange process is coordinated by the relay node and was designed to guarantee compatibility with other conventional relaying schemes with specific concerns for the hidden node issues. Our solution was practically tested on a real testbed with different static wireless topologies and several physical settings.With numerical results, we investigate the effectiveness of PNC in distributed wireless multi-hop networks. Compared to the conventional CSMA/CA and the PNC opportunistic (PNCOPP) MAC protocols, the proposed protocol’s performances are advantageous in various scenarios, especially in large networks.

A Hierarchical Deep Learning Approach for Optimizing CCA Threshold and Transmit Power in Wi-Fi Networks

The nodes, e.g., access points and clients, in current WiFi networks rely on carrier sense multiple access (CSMA) for channel access. This means they rely on a clear channel assessment (CCA) threshold to determine when it is safe to transmit a packet. In practice, this threshold is fixed, and nodes do not adapt their CCA threshold given varying channel conditions. To this end, this paper proposes and studies the use of deep reinforcement learning (DRL) to optimize the CCA threshold and transmit power of an AP. It allows an AP to learn the optimal policy for setting its CCA threshold and transmit power given its queue length and interference level. We outline a semi-Markov decision process (Semi-MDP) for the problem at hand and solve it using a decentralized deep hierarchical reinforcement learning (HRL) approach. We then evaluate its performance using traffic generated via a Poisson distribution and also from a trace file. The results show that when compared to two competing solutions, an AP with HRL reduces its average queue length by 24.4% and 52.4%, respectively.

On Flow Control and Optimized Back-Off in Non-Saturated CSMA

Medium Access Control (MAC) main functions encompass contention for channel access, packet scheduling, error control, and data integrity. Channel contention is a collective function involving all stations in the network, while data integrity pertains to data flows of each individual station. We propose a design where contention related functions are separated from other data management functions. The hinge connecting contention and other data management functions is a flow control algorithm, aiming at guaranteeing stability of contention queues and load on the MAC channel. With reference to Carrier-Sense Multiple Access (CSMA), we define an analytical model of contention queues under non saturated traffic. An asymptotic analysis of the model for large number of stations yields a closed form of the optimal flow control rate. The insight gained from the model is used to design an adaptive flow control algorithm that guarantees throughput optimality for all values of the number of stations.

Performance analysis of distributed coordination function with early collision detection in In-band Full-duplex wireless networks

In-band Full-duplex (IB-FD) wireless has the potential to double the spectral efficiency offering its innate capability to resolve conventional problems emerge owing to the imperfect medium access control (MAC) in In-band half-duplex (IB-HD) wireless networks. IEEE 802.11 distributed coordination function (DCF), a binary slotted exponential back-off with carrier sense multiple access scheme, has been used extensively in literature as the fundamental contention resolution technique to devise MAC protocols for IB-FD wireless networks. Unlike IB-HD, an IB-FD network can contain two simultaneously active transmission links within a single collision domain. This phenomenon invalidates the applicability of existing IB-HD models of the DCF to compute its performance (i.e., saturation throughput) accurately in IB-FD wireless networks. We have proposed two MAC protocols for two types of network scenarios taking early collision detection capability of an IB-FD wireless transceiver into consideration. This paper also presents a distinct analytical model to quantify the performance of the DCF in the context of IB-FD wireless assuming finite number of stations and idle channel conditions. We have applied the concept of primary–secondary transmission links and, thoroughly derived the probability that a station transmits either as primary or secondary in a randomly chosen time-slot taking secondary transmitter’s back-off counter into account. We have also investigated the effect of inter-station interference free IB-FD link on the performance of the DCF. Our protocol, when applied to network without hidden stations, has obtained the highest throughput gain of 1.59, 1.61, 1.68 while the DCF is configured with CWmin of 16, 32, 64, respectively than IEEE 802.11 basic access scheme. We have observed increased throughput gain with hidden stations, thanks to inter-station interference free transmission region, and achieved 2.12, 2.14, 2.16 times higher throughput, respectively than that of IEEE rts-cts access scheme.

Inter-Frame-Relationship Protected Signal: A New Design for Radio Frequency Fingerprint Authentication.

Utilizing a multi-frame signal (MFS) rather than a single-frame signal (SFS) for radio frequency fingerprint authentication (RFFA) shows the advantage of higher accuracy. However, previous studies have often overlooked the associated security threats in MFS-based RFFA. In this paper, we focus on the carrier-sense multiple access with collision avoidance channel and identify a potential security threat, in that an attacker may inject a forged frame into valid traffic, making it more likely to be accepted alongside legitimate frames. To counter such a security threat, we propose an innovative design called the inter-frame-relationship protected signal (IfrPS), which enables the receiver to determine whether two consecutively received frames originate from the same transmitter to safeguard the MFS-based RFFA. To demonstrate the applicability of our proposition, we analyze and numerically evaluate two important properties: its impact on message demodulation and the accuracy gain in IfrPS-aided, MFS-based RFFA compared with the SFS-based RFFA. Our results show that the proposed scheme has a minimal impact of only -0.5 dB on message demodulation, while achieving up to 5 dB gain for RFFA accuracy.

A score based link delay aware routing protocol to improve energy optimization in wireless sensor network

The Wireless Sensor Network (WSN) is the most appearing expertise that has potential applications broad ranges that include environment examining, smart spaces, medical systems, and robotic study. Energy efficiency is a consideration of vital design for WSN. The collision is occurred owing to the transmission of data from the sensor nodes and the traffic at the SINK node is high because of the excess data transmission by the sensor nodes. An essential division of the consumption of resources in a WSN is managed by the mechanism of Medium Access Control (MAC). An existing MAC protocols initiated for the utilization of WSNs single channel for data transmission. The deployment of wireless sensor nodes is concerned in the harsh environment in which the drastic change of conditions suffers from sudden changes in the status of a node and the quality of a link. With limited energy, the sensor nodes are supplied and a major concern is towards improving the lifetime of a network. To deal with these issues, a novel and simple routing mechanism Score based Link Delay Aware Routing (SBLDAR) is proposed, which utilizes the multi-channel MAC procedure comprises of Carrier Sense Multiple Access/ Collision Avoidance (CSMA/CA), to exchange the data, the activity of Time Division Multiple Access (TDMA) sequencing nodes and also Frequency Division Multiple Access FDMA) to allow collision-free exchange simultaneously. Also, in order to overcome this issue, an approach has been put out in this work that involves leveraging a variety of trust variables to identify malicious nodes and then using fuzzy based Modified Sun Flower Optimization (FMSFO) algorithm to elect an effective cluster head. The score based route selection increases the network lifetime and improves network performance. By comparing with the other protocols, the proposed SBLDAR combined with the technique of multi-MAC protocol has shown that it increases the network’s overall performance based on the simulation studies.

Timeliness of wireless sensor networks with random multiple access

In this paper, we consider a wireless sensor network in which N sensor nodes deliver the observed information of interest to a remote receiver by competing for a sharing channel through the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol or the slotted ALOHA protocol. For this network, we evaluate the information freshness of the two random multiple access protocols using the age of information (AoI) metric. In order to explicitly express the average AoI of the CSMA/CA based network, we establish an equivalent and tractable transmission model for the network, in which the transmission probabilities and the collision probabilities are assumed to be identical over time and among sensor nodes. For the slotted ALOHA based network, we derive the average AoI by focusing on a randomly chosen reference node. Our theoretical results show that 1) the transmission probability and collision probability of the two networks increase with both the arrival rate and the number of sensor nodes; 2) with the same transmission probability, the average AoI of the CSMA/CA based network is always smaller than that of the slotted ALOHA based network, no matter how the arrival rate and the number of nodes change. Our Monte Carlo simulation results also validate the correctness of our theoretical calculations.

Performance analysis in overlay-based cognitive D2D communications in 5G networks

With the advent of fifth-generation 5G networks, mobile communication data rates are steadily rising. The existing base stations (BSs) must reduce the loads with minimal cost and effort. With traffic demands constantly rising, available spectrum resources must be utilized effectively. One of the most exciting developments in 5G networks, particularly cellular networks, is the potential for devices to communicate directly with one another through a technology called device-to-device communication (D2D). With the transmission split between D2D users on one side and cellular users and the BS on the other, it will be effective in the rapidly expanding capacity and offload traffic from the BS. With the dynamic spectrum access in mind, this article proposes using cognitive radio direct-to-device (CRD2D) communication in 5G networks to make use of the unused spectrum. Throughput and latency are examined, for a carrier sense multiple access (CSMA) based medium access control (MAC) protocol that uses a common control channel (CCC) for device users to negotiate the data channel and to address contention among device users. Device users can take advantage of cognitive radio to access multiple data channels simultaneously in a shared interference zone. Since this property has not been utilized, in prior works, we use it to measure the possible delay and throughput. Cognitive radio capability applied to D2D communication and the allocation of a common control channel for device users significantly increases aggregated network throughput by more than 60% compared to individual D2D throughput without causing any harmful interference to cellular users. The wait time can also be scale back using this method.

CSMA Protocol performance with dynamic spreading factor in LPWAN networks with LoRa RF transceivers

Long Range (LoRa) is a spread spectrum modulation technology designed for Low-Power Wide-Area Networking (LPWAN) with a growing application in Internet of Things (IoT), which plays an important role in the global digitalization process. The expansion of LORAWAN networks demands careful circuit, system and network design to improve energy efficiency and quality of service. To support this task, advanced CAD tools can offer reliable network simulations results, where the effects of building blocks can be found. LoRaSim, one of the most popular simulators available for LoRa and LoraWan, had solely implemented an ALOHA access model protocol, which is not the most common protocol in real life scenarios. To mitigate this limitation and taking advantage of the open-source nature of both LoRaWAN and LoRaSim, it is proposed a Carrier Sense Multiple Access/ Collision Avoidance (CSMA/CA) protocol extension, as well as active adaptive parameters selection to cope with collisions. To demonstrate the effectiveness of these additions to the base solution, a comparison between both on different scenarios and their simulated performance key indicators will be presented.

Graph-based conflict-free MAC protocol and conflict analysis for a two-layer ultraviolet communication network

To efficiently exploit the space division multiplexing of ultraviolet (UV) communication, we apply link coverage characteristics to construct a conflict graph and design conflict-free protocols for a two-layer UV communication network. The network is divided into two layers: the first-layer network forms a backbone and the second-layer network serves as local access. We construct a routing model and medium-access control (MAC) model. Then we propose Routing-MAC joint scheduling for the first-layer network based on the conflict graph. We investigate the system throughput and delay of joint scheduling under different node intensities. For second-layer networks, we propose a multi-link conflict-free protocol adopting protocol frames of carrier sense multiple access with collision avoidance (CSMA/CA). Numerical results show that the multi-link conflict-free protocol can improve the system throughput by more than 100% compared with CSMA/CA. Moreover, we perform a conflict analysis on the proposed protocols to investigate the influence of conflict intensity. According to the conflict analysis, we optimize the path planning of Routing-MAC joint scheduling to reduce the average delay of the network. Numerical results show that the optimized Routing-MAC joint scheduling leads to larger system throughput and lower delay.

Embracing Channel Estimation in Multi-Packet Reception of ZigBee

As a low-power and low-cost wireless protocol, the promising ZigBee has been widely used in sensor networks and cyber-physical systems. Since ZigBee based networks usually adopt tree or cluster topology, the convergecast scenarios are common in which multiple transmitters send packets to one receiver, leading to the severe collision problem. The conventional ZigBee adopts carrier sense multiple access with collisions avoidance to avoid collisions, which introduces additional time/energy overhead. The state-of-the-art methods resolve collisions instead of avoidance, in which mZig decomposes a collision by the collision itself and reZig decodes a collision by comparing with reference waveforms. However, mZig falls into high decoding errors only exploiting the signal amplitudes while reZig incurs high computational complexity for waveform comparison. In this paper, we propose CmZig to embrace channel estimation in multiple-packet reception (MPR) of ZigBee, which effectively improves MPR via lightweight computing used for channel estimation and collision decomposition. First, CmZig enables accurate collision decomposition with low computation complexity, which uses the estimated channel parameters modeling both signal amplitude and phase. Second, CmZig adopts reference waveform comparison only for collisions without chip-level time offsets, instead of the complex machine learning based method. We implement CmZig on USRP-N210 and establish a six-node testbed.