Distributed Inter-frame Space Research Articles

Analysis of the efficiency of block frame transmission in IEEE 802.11 computer networks

In infrastructure schemes of WLANs wireless computer networks, which are based on the use of the DSF (distributed coordination function) function and the CSMA/CA mechanism, the station STA (STAtion) sends a frame if the transmission channel is released after waiting for the end of the DIFS (distributed interframe space) interval and operation of the slot selec-tion mechanism for transmission (backoff mechanism). In case of collisions or damage to the frame by interference, the AP cannot decode the frame and does not send it back to the ACS station. The sending station STA waits for the re-ceipt of a potential ASK before the expiration of the corresponding timeout, and in case of receipt, starts the backoff procedure before transmission. The duration of the slot used in the backoff process depends on the speed of the physical layer technology. To reduce overhead, a transmission mechanism using frame blocks was proposed. This mechanism assumes that a block of frames intended for one recipient can be sent without con-firming the fact of correct reception by the AP access point of each frame separately. In this case, the sender (STA) competes for access to the channel for the first frame of the block. If it wins the access competition, the transmission of the first frame begins, and after receiving the ACK acknowledgment for it and a short SIFS separation interval, the STA transmits a whole block of frames, which is accompanied by a BAR service frame. The mechanism of frames block transmission in wireless computer networks IEEE 802.11 DCF with infrastructure topology has been analyzed. In protected mode, the depend-encies of network throughput on data transmission rate and the number of frames in a block are determined. It is shown that the mechanism of block transmission significantly increases the network throughput, especially in the range of higher transmission rates. With a marked increase in the intensity of interference the transmission of blocks becomes more complicated. Already with BER=10^-6 and the frames number of the order of 10 and more, in some cases there is a need to retransmit distorted in a block frames, and at BER=10^-5 there are many re-transmissions, so the resulting network throughput becomes small.

Contention Resolution in Wi-Fi 6-Enabled Internet of Things Based on Deep Learning

Internet of Things (IoT) is expected to vastly increase the number of connected devices. As a result, a multitude of IoT devices transmit various information through wireless communication technology, such as the Wi-Fi technology, cellular mobile communication technology, low-power wide-area network (LPWAN) technology. However, even the latest Wi-Fi technology is still ready to accommodate these large amounts of data. Accurately setting the contention window (CW) value significantly affects the efficiency of the Wi-Fi network. Unfortunately, the standard collision resolution used by IEEE 802.11ax networks is nonscalable; thus, it cannot maintain stable throughput for an increasing number of stations, even when Wi-Fi 6 has been designed to improve performance in dense scenarios. To this end, we propose a CW control strategy for Wi-Fi 6 systems. This strategy leverages deep learning to search for optimal configuration of CW under different network conditions. Our deep neural network is trained by data generated from a Wi-Fi 6 simulation system with some varying key parameters, e.g., the number of nodes, short interframe space (SIFS), distributed interframe space (DIFS), and data transmission rate. Numerical results demonstrated that our deep learning scheme could always find the optimal CW adjustment multiple by adaptively perceiving the channel competition status. The finalized performance of our model has been significantly improved in terms of system throughput, average transmission delay, and packet retransmission rate. This makes Wi-Fi 6 better adapted to the access of a large number of IoT devices.

A Novel Adaptive Contention Window and Distributed Inter Frame Space for IEEE 802.11

The networks nodes in IEEE 802.11 standard need a strategy to enhance the system performance. The network performance can be evaluated in view of Quality of Service (QoS) parameters, for example, delay, throughput, packet loss, jitter and collision which are strict prerequisites for multimedia applications. This paper exhibits an element component to modify the contention window (CW) and distributed inter frame space (DIFS) parameters to the IEEE 802.11 Medium Access Control (MAC) convention to improve QoS. The proposed plan is in light of the Collision Rate (CR), Collision Rate Variation (CRV) and packet loss rate for every bundle activity class to modify the CW and DIFS at runtime in single-hop networks. The simulation results demonstrate that the proposed plan upgrades the normal QoS for high priority traffic by 34% and 33.9% for the 5 and 10 connections, respectively. While the normal QoS for the low priority traffic is enhanced by 17.3% and 33.6% for the 5 and 10 connections, respectively. The outcomes demonstrate that, the proposed methodology support the QoS in wireless networks.

ZigBeeと無線LANの共存のためのAIFSN適応制御

This paper proposes an adaptive arbitration interframe space number (AIFSN) control for ZigBee and wireless LAN (WLAN) coexistence. The authors have been proposed the coexistence method which is utilizing the AIFS specified in the IEEE802.11e standard greater than the distributed interframe space (DIFS). Because the AIFS value is always high in the conventional method, the ZigBee success ratio is improved but the WLAN throughput is degraded. To overcome this problem, the AIFS is changed adaptively according to the reception of ZigBee Data frames. The adaptive AIFSN control is applied to the conventional method. Compared with the conventional method, simulation results show the degradation of ZigBee success ratio is small and the WLAN throughput is improved.

Trinary Partitioned Black-Burst-Based Broadcast Protocol for Time-Critical Emergency Message Dissemination in VANETs

In this paper, we propose a multihop broadcast protocol for dissemination of time-critical emergency messages (EMs) in vehicular ad hoc networks (VANETs), where the IEEE 802.11p technology is used for communication among the nodes. The proposed trinary partitioned black-burst-based broadcast protocol (3P3B) consists of two primary mechanisms. First, a mini distributed interframe space (DIFS) in a medium access control (MAC) sublayer is introduced to give the time-critical EMs a higher access priority to the communication channel compared with other messages. Second, a trinary partitioning is designed to iteratively partition the communication range into small sectors. The trinary partitioning mechanism allows the farthest possible vehicle in the farthest sector from the sender node to perform forwarding to increase the dissemination speed by reducing the number of forwarding hops. In addition, 3P3B reduces the contention period jitter, which is independent of the density of vehicles, resulting in a more stable contention period. Analytical models are proposed for performance evaluation in conjunction with simulation-based performance analysis. The results demonstrate that 3P3B outperforms benchmarks of the existing broadcast protocols in VANETs in terms of the average message dissemination speed, message progress, communication delay, and packet delivery ratio.

An accurate power analysis model based on MAC layer for the DCF of 802.11n

The 802.11 wireless local area network technology is popular in power-sensitive devices such as smart phones and personal digital assistants. In this article, we present an accurate power consumption model based on the Bianchi model and power measurement in the physical layer to predict the power consumption of 802.11n and multiple-input–multiple-output mode of 802.11n. In this model, we calculate the total energy consumption by summing up several components: the idle listening energy consumed in the distributed inter-frame space period and backoff stages, the energy consumed in transmitting a frame, the idle listening energy consumed in the short inter-frame space turnaround time, the energy consumed in receiving an acknowledgment frame from the access point, and the energy consumed in collisions for one frame transmission. The probability of successful frame transmission and medium access control (MAC) efficiency of 802.11n are also analyzed as a function of the number of active stations and different choices of frame transmission probability by each active station. Finally, the impact of imperfect channels on energy consumption and MAC efficiency is explored.

A Novel Delay Model for IEEE 802.11

With the popularity of the IEEE 802.11 standards, many analytical delay studies for the Distributed Coordination Function (DCF) have been reported. In this paper, we analyze the additional idle durations that a tagged node needs to wait due to other nodes transmissions. Separating the distributed inter-frame space (DIFS) and extended inter-frame space (EIFS) durations from the full time of a successful transmission, we provide a correct function analysis of the DIFS and EIFS durations and build a more accurate delay model for the IEEE 802.11 DCF. The theoretical analysis and simulation results prove that the proposed delay model is coincident with the real performance when the node number increases.

Design and Analysis of a Robust Broadcast Scheme for VANET Safety-Related Services

IEEE- and ASTM-adopted dedicated short-range communications (DSRC) standards are key enabling technologies for the next generation of vehicular safety communications. Vehicle-safety-related communication services, which require reliable and fast message delivery, usually demand broadcast communications in vehicular ad hoc networks (VANETs). In this paper, we propose and justify a distributive cross-layer scheme for the design of the control channel in DSRC with three levels of broadcast services that are critical to most potential vehicle-safety-related applications. The new scheme for enhancing broadcast reliability includes preemptive priority in safety services, dynamic receiver-oriented packet repetitions for one-hop emergency warning message dissemination, a multifrequency busy tone and minislot within the distributed interframe space (DIFS) in IEEE 802.11, and robust distance-based relay selection for multihop broadcast of emergency notification messages. Compared with a current draft of IEEE 802.11p and other schemes for DSRC safety-related services, the scheme proposed in this paper is more robust and scalable and easy to implement. Additionally, we investigate the reliability and performance of the proposed broadcast scheme for DSRC VANET safety-related services on the highway analytically and by simulations. The analytic model accounts for the impact of the hidden terminal problem, the fading channel conditions, varied message arrival intervals, and the backoff counter process on reliability and performance.

An idle listening-aware energy efficient scheme for the DCF of 802.11n

802.11 wireless local area network (WLAN) technology is now common in power sensitive devices like smart phones and personal digital assistants (PDAs). However, the energy efficiency of such devices will be very low, especially for next generation WLAN technology. The reasons for this include the existence of a large number of active stations, short data time and ultra high physical layer (PHY) data rate, which are the characteristics of next generation WLAN technology. This poor energy efficiency will be due to the fact that the device will consume a lot of idle-listening energy during the Distributed InterFrame Space (DIFS) and back-off time, and that the energy consumed for idle listening is similar to the energy consumed while receiving data. In this article, we propose an intelligent scheme for reducing the energy consumed in idle listening. Our analysis and simulation programs show that our scheme can lengthen the battery endurance due to the shortening in idle-listening time effectively especially when the number of active stations is large. An important characteristic of our scheme is that it is fully compatible with legacy Distributed Coordinated Function (DCF), and there will be no throughput reduction if this power saving scheme is applied to the DCF of 802.11. We also propose an accurate power consumption model in the MAC layer which to the best of our knowledge has not been presented in any earlier research.

Performance Enhancement of IEEE 802.11 WLAN with a Cognitive Radio Technique

Cognitive Radio (CR) is expected to bring about a more flexible wireless communication environment by the efficient utilization of spectrum resources. In this paper, a CR coexisting with IEEE 802.11 Wireless Local Area Networks (WLANs) is proposed. In the Distributed Coordination Function (DCF) access scheme in IEEE 802.11 WLAN, a station (STA) transmits a data frame by executing a random backoff procedure after Distributed Inter Frame Space (DIFS) period, and the destination STA of the data frame responds with Ack frame to the source STA after Short Inter Frame Space (SIFS) period. After the Ack frame is transmitted, the same procedures are repeated. The proposed CR terminal recognizes the DIFS period and the SIFS period, and then it transmits CR signals during these periods with the transmission power that does not affect the IEEE 802.11 WLAN protocol. Thus, the proposed CR terminals recognize the periods during which IEEE 802.11 STAs do not transmit any frames and they use the periods to transmit CR signals. In this paper, IEEE 802.11 WLAN STA that has the capability for the proposed CR technique in addition to the normal 802.11 WLAN capability is considered and the improved average throughputs by the CR communications are evaluated in the computer simulation, and then the effectiveness of the proposed method is clarified.