Multi-channel Access Scheme Research Articles

A Delay-Sensitive Multibase-Station Multichannel Access System for Smart Factory

The intelligence of industrial production depends on real-time and reliable transmission and timely feedback of information in the Industrial Internet of Things (IIoT) systems. However, the scarcity of spectrum resources, a harsh industrial electromagnetic environment, and a need for real-time processing of massive traffic have posed severe challenges to the real-time and reliable access of the MAC layer. Aiming to solve the real-time transmission problem in the IIoT system, a delay-sensitive multibase-station multichannel access scheme is proposed. First, a multibase-station multichannel access model for real-time transmission is developed. The way to match sensing nodes with base stations and channels is formulated as a delay-sensitive multibase-station multichannel access (DMMA) problem. Moreover, it is theoretically proved that the DMMA problem is NP-Hard. Finally, a delay-sensitive greedy schedule (DG-Schedule) scheme based on the minimum deadline priority is proposed to obtain a feasible solution to the DMMA problem. According to experiments on the TI CC2530, DG-Schedule can reduce packet loss by 11% and average latency by 88% compared to CSMA/CA. Therefore, the DG-Schedule scheme is more suitable for IIoT scenarios.

Resource Allocation in Multi-Cluster Cognitive Radio Networks With Energy Harvesting for Hybrid Multi-Channel Access

Cognitive radio and energy harvesting techniques have been able to provide insight for solutions to the inefficiency in spectrum utilization and the effects of the limited storage capacity of energy batteries. Nevertheless, the requirement for interference constraint for primary user (PU) protection, the quality of service (QoS) requirements of the SUs, and the low power density of the ambient electromagnetic waves have restricted the performance of the radio frequency powered cognitive radio networks (RF-CRNs) in terms of the achievable data rate for specific energy budget or sufficient energy budget for target data rate. We are therefore motivated to investigate a radio frequency powered cognitive radio (RF-CR) with the capacity for improved achievable throughput and energy harvesting. Our model consists of multiple PUs and SUs coexisting in a practical overlapping clustered network. In each time frame for the adopted time division multiple access (TDMA) technique, SUs can exploit the multi-user benefit to harvest energy from both the PU and SUs transmissions for improved active probability. Therefore, taken into consideration the heterogeneity of each SUs in terms of their signal-to-noise (SNR), the energy harvesting rates and the inter- and intra-cluster interference, the problem is formulated into a fractional nonlinear optimization to determine the sensing duration, and power allocations that maximize the average energy efficiency of the RF-CRN subject, to constraints on energy causality, and PU protection. The performance of the proposed hybrid multi-channel access scheme is studied in terms of the trade-off between the total achievable throughput by the secondary users and the interference generated among others. Simulation results show that a trade-off exists between achieving optimal spectral efficiency and energy efficiency and, the optimal transmit power therefore depends on the primary design objective. Results equally show that the proposed hybrid multi-channel access scheme outperforms the existing scheme in literature.

A Platoon-Centric Multi-Channel Access Scheme for Hybrid Traffic

Self-driving technology has made great advancements with the help of artificial intelligence and intelligent transportation system. Recent studies have shown that traffic efficiency and safety of autonomous vehicles can be further improved by autonomous platooning based on vehicular ad hoc networks (VANETs). However, hybrid traffic where autonomous platoons (APs) and individual human driven-vehicles (HDVs) co-exists is seldom considered. Wireless Access in the Vehicular Environment (WAVE) is the de facto wireless protocol for VANETs. WAVE has provided one control channel (CCH) and six service channels (SCHs). The multi-channel access scheme should be jointly designed along with the CCH communication protocol. To design a reliable and efficient communication protocol for hybrid traffic, we propose a platoon-centric multi-channel access scheme based on the reliable broadcast. The reliable broadcast scheme utilizes an enhanced RTS/CTS mechanism designed for multicast communications. A broadcast frequency control mechanism is proposed to balance CCH access intervals. Our scheme can improve the reliability of CCH communication and increase SCH utilization with minimal overhead. Analysis and simulation results demonstrate the superiority of the proposed mechanism.

Hybrid ORA and NORA schemes for machine‐to‐machine communication in long‐term evolution networks

Massive machine-type communication (MTC) devices will be deployed in the fifth-generation wireless communication networks, which will inevitably result in access collision problems. To alleviate this issue, the authors propose a hybrid orthogonal random access (ORA) and non-orthogonal random access (NORA) scheme to improve the throughput. In the proposed scheme, an expanded physical random access channel is employed to transmit preambles and MTC devices identity information simultaneously, which can help the base station (BS) to determine whether the MTC device can successfully transmit preamble. Subsequently, the MTC devices whose transmitted preambles are detected successfully by BS are statistically grouped, and then the devices in the same group transmit their data messages in a non-orthogonal multiple access manner. Meanwhile, to further improve the access throughput, the MTC devices that did not pass access class barring check are permitted to compete for the remained unscheduled resources with orthogonal multiple access manner. They also analyse the access throughput of the proposed scheme. Simulation results show that to serve all MTC devices distributed in a cell, their proposed scheme outperforms the traditional multichannel ALOHA and two-stage random access scheme in terms of access throughput and required number of random access slots.

Throughput Optimal Switching in Multichannel WLANs

We observe that in a multichannel wireless system, an opportunistic channel/spectrum access scheme that solely focuses on channel quality sensing measured by received SNR may induce users to use channels that, while providing better signals, are more congested. Ultimately the notion of channel quality should include both the signal quality and the level of congestion, and a good multichannel access scheme should take both into account in deciding which channel to use and when. Motivated by this, we focus on the congestion aspect and examine what type of dynamic channel switching schemes may result in the best system throughput performance. Specifically, we derive the stability region of a multiuser multichannel WLAN system and determine the throughput optimal channel switching scheme within a certain class of schemes. We also empirically examine the impact of considering congestion in addition to signal quality in making channel selection decisions.

Adaptive and Distributed Access to Spectrum Holes in Cognitive Radio System

Cognitive radio technology enables Secondary Users (SUs) to access the frequency channels licensed to Primary Users. In this paper, we propose a novel dynamic multichannel access scheme for cognitive radio systems, which are based on a multichannel variation of a p-persistent Carrier Sensing Multiple Access scheme. To optimize the system-wide performance, the proposed scheme exploits different gains of frequency channels due to frequency-selective fading. With the proposed scheme, SUs share frequency channels in a fully distributed way, without any explicit control information exchange. To design the proposed scheme, we formulate the whole system as a "channel access game," according to game-theoretic framework. In the channel access game, the utility function should reflect the system-wide performance. We derive closed-form performance measures by modelling the system as a continuous time Markov chain, and use them to construct a proper utility function. Then, each SU independently decides its own channel access strategy (i.e., the distribution of the random backoff time) which optimizes the utility function. The simulation results show that the proposed scheme promotes SUs to compete and cooperate with each other to a suitable level and, as a result, performs well in all range of SU population.

Optimal channel access for TCP performance improvement in cognitive radio networks

Cognitive radio (CR) is a promising technology to improve spectrum utilization. Most of previous work on CR networks concentrates on maximizing transmission rate in the physical layer. However, the end-to-end transmission control protocol (TCP) performance perceived by secondary users is also a very important factor in CR networks. In this paper, we propose a novel multi-channel access scheme in CR networks, where the channel access is based on the TCP throughput in the transport layer. Specifically, we formulate the channel access process in CR network as a restless bandit system. With this stochastic optimization formulation, the optimal channel access policy is indexable, meaning that the channels with highest indices should be selected to transmit TCP traffic. In addition, we exploit cross-layer design methodology to improve TCP throughput, where modulation and coding at the physical layer and frame size at the data-link layer are considered together with TCP throughput in the transport layer to improve TCP performance. Simulation results show the effectiveness of the proposed scheme.

Performance Study for Two-Tier CDMA Cellular Systems with Multi-Channel Access

The CDMA cellular system can provide more capacity than AMPS systems and the hierarchical layer of cells is required for system design. However, system performance and capacity is degraded due to the cochannel interference between microcell and macrocell if a single frequency channel is shared. This paper proposes three multi-channel access schemes where various frequency channels are assigned for microcell and macrocell. Performances of channel capacity, blocking probability and blocking ratio in uplink and downlink are evaluated. Due to channel segregation and thus the cochannel interference among macrocell and microcell are minimized, the proposed scheme 3 where all channels are accessible sequentially in macrocell and microcell performs the best in system capacity and blocking probability than the other schemes.

New Channel Assignment Methods for Hot-Spot Overlaying CDMA Cellular Systems

The CDMA cellular system can provide more capacity than AMPS systems. To deploy microcells overlaying in macrocells to provide more capacity is also attractive. However, system performance and capacity degrade due to the co-channel interference among microcells and macrocells if a single channel is used. Based on a hot-spot overlaying environment, we propose three multi-channel schemes where different channels can be assigned for hot spot and macrocell. Performance measures in terms of capacity, service hole, blocking probability and blocking ratio in uplink and downlink are evaluated. It shows that the schemes with channel selection based on SIR and active users gain more benefits than the scheme with separate channels assigned for macrocells and hot-spot. Using the proposed multi-channel access schemes, we can avoid the co-channel interference among macrocells and hot-spot and provide more capacities than Baier's suggestion [1]. In addition, the proposed schemes make soft handoff workable and improve the system performance.

Performance evaluation for multichannel access schemes in CDMA cellular systems

The CDMA system promisingly provides more capacity than AMPS. However, providing multichannels for a CDMA system is a requisite to satisfy the demanded capacity. In this paper, five schemes of multichannel assignment are proposed. Based on computer simulation, performance measures such as blocking probabilities, the overall capacity, the capacity of each channel and the number of retrials are obtained. Simulation results indicate that the SIR-based selection scheme is preferable to the other schemes. © 1998 John Wiley & Sons, Ltd.

Performance investigation of a token passing access protocol for a multichannel optical fibre LAN

An alternative approach to multichannel local area network access is described. The new multichannel access scheme or protocol is based on a token passing arbitration policy. It is specifically intended for use with a starconfigured optical fibre LAN employing wavelength division multiplexing technology in order to provide a multichannel transmission medium. The multichannel network architecture comprises a single reservation channel and several equivalent speed data channels. Delay versus throughput performance characteristics for the network obtained by both analysis and discrete event simulation are shown. The multichannel token passing protocol is found to significantly improve these characteristics in comparison with a conventional single channel token passing approach using the same overall network transmission rate (i.e. the sum of the individual channel bit rates in the multichannel case). Furthermore, when the end-to-end propagation delay for an individual channel on the network becomes large, the multichannel token passing protocol is shown to exhibit an improved delay versus throughput performance over a multichannel protocol employing carrier sense multiple access with collision detection.