Qiao Qu

Survey on OFDMA based MAC protocols for the next generation WLAN

The physical (PHY) layer peak rate of the wireless local area network (WLAN) has been almost exponentially improved over the past 15 years since 1999. However, it is proved that the throughput is very low comparing to the PHY peak rate, and the media access control (MAC) efficiency is very low in the current WLANs specification, especially in dense deployment scenarios. Therefore, to achieve high MAC efficiency the IEEE Standards Association Standards Board (IEEE-SA) approves IEEE 802.11ax in March 2014, to draw up a brand new amendment for the next generation WLAN. One of the promising technologies to improve MAC efficiency is Orthogonal Frequency Division Multiple Access (OFDMA). In this paper, we firstly investigate the existing OFDMA based MAC protocols in the literature. Then, a framework of OFDMA based MAC protocol for the next generation WLAN is proposed. Finally, all of the existing OFDMA based MAC protocols listed in this paper are compared according to the proposed design issues. To the best of our knowledge this paper is the first survey focusing on OFDMA based MAC protocols for the next generation WLAN.

An OFDMA based concurrent multiuser MAC for upcoming IEEE 802.11ax

Recently, IEEE drew up a new task group named TGax to draft out the standard IEEE 802.11ax for next generation WLANs. However, the average throughput is very low due to the current medium access control (MAC) protocol. A promising solution for this problem is to draw Orthogonal Frequency Division Multiple Access (OFDMA) into IEEE 802.11ax to enable multiuser access. The key challenges of adopting OFDMA are synchronization and overhead reduction. In this paper, we propose an OFDMA based Multiple Access for IEEE 802.11ax (OMAX) protocol to solve both two challenges above. The whole channel physical channel sensing and fast backoff are adopted to ensure synchronization, while enhanced RTS/CTS mechanism and new frame structure are designed to reduce overhead. Moreover, the mathematic model of OMAX is formulated, and the performance of OMAX is analyzed. The analysis and simulation result indicate that the proposed OMAX protocol increases the throughput to 160%.

An OFDMA based multiple access protocol with QoS guarantee for next generation WLAN

To provide better QoS guarantee for the next generation WLAN, IEEE 802.11ax task group is founded in March 2014. As a promising technology to accommodate multiple nodes concurrent transmissions in dense deployment scenario, orthogonal frequency division multiple access (OFDMA) will be adopted in IEEE 802.11ax with great possibility. In this paper, an OFDMA based multiple access protocol with QoS guarantee is proposed for the next generation WLAN. Firstly, a redundant access mechanism is given to increase the access success probability of the video traffic where the video stations can concurrently send multiple RTS packets in multiple subchannels. Secondly, a priority based resource allocation scheme is presented to let AP allocate more resources to the video stations. Simulation results show that our protocol outperforms the existing OFDMA based multiple access for IEEE 802.11ax (OMAX) protocol in terms of delay and delay jitter of video traffic in dense deployment scenario.

FuPlex: A full duplex MAC for the next generation WLAN

IEEE 802.11 wireless local area network (WLAN) has been increasingly developed over several decades. It requires four times throughput improvement in the next generation WLAN. Thus, researchers focus on the co-frequency co-time full duplex technology, which makes the devices transmit and receive packets simultaneously and theoretically doubles the throughput. Some existing works proposed several media access control (MAC) protocols on the assumption that all nodes have full duplex capability. However, it is more practicable that only AP possesses full duplex capability whereas STAs have no full duplex capability in the early stage of introducing full duplex technology into the next generation WLAN. In this paper, a simple and compatible full duplex MAC protocol named FuPlex is proposed. The design details of FuPlex, including primary access, secondary access and data transmission, are introduced. Simulation results show that FuPlex improves the throughput to 150% compared with legacy IEEE 802.11 MAC protocol.

Integrated Link-System Level Simulation Platform for the Next Generation WLAN - IEEE 802.11ax

As the most widely used standards for wireless local area network (WLAN), IEEE 802.11 standards are continuously amended by introducing new techniques so as to meet the increasing demands. In order to verify the performance of amended protocols, network simulation is considered as a significant method. However, as far as we know, current simulation tools are only for either media access control layer (MAC) or physical layer (PHY). The separate simulation of MAC and PHY can hardly evaluate the performance of IEEE 802.11ax in whole system level for authenticity and objectivity. Hence, the next generation WLAN (IEEE 802.11ax) requires integrated system simulation to take impacts of both MAC and PHY techniques into account. Moreover, IEEE 802.11ax introduces some new techniques, such as orthogonal frequency division multiple access (OFDMA), multi-user multiple input multiple output (MU- MIMO) and non-continuous channel bonding. In this paper, we design and further implement the integrated link-system level simulation platform, which makes it possible to evaluate the new technologies for IEEE 802.11ax. Moreover, we propose a MAC protocol combining OFDMA, MU-MIMO, non-continuous channel bonding and link adaptation and further evaluate its performance. Finally, we validate performance gains of IEEE 802.11ax through simulation, and the simulation results show that IEEE 802.11ax has obviously higher throughput, better quality of service (QoS) and higher multi- channel efficiency. To the best of our knowledge, this is the first work to design and implement simulation platform for IEEE 802.11ax with an integrated link- system level framework.

An analytical model for Quality of Experience of HTTP video streaming over wireless ad hoc networks

HTTP video streaming employs the TCP protocol as its transport protocol, which provides reliability on one hand, but delay or delay jitter on the other hand. IEEE 802.11 MAC protocol is assumed to support wireless networks, whose channel access efficiency impacts the performance of the upper layer, i.e., the data rate and the delay of TCP. In this paper, an analytical model for Quality of Experience (QoE) of HTTP video streaming over single-hop wireless networks is proposed. Particularly, two QoE performance metrics are evaluated, which are underflow times and fluency of playout, defined as the buffer empty times during playout, and the ratio of ideal watching time to the real watching time. The impacts of system parameters, such as the length of a video file, the playout threshold, the playout rate, and the arriving rate of a TCP streaming, on the system performance metrics are analyzed in detail. It is found that when both the TCP congestion window and the MAC contention window are set to one, the arriving rate of a TCP streaming can achieve its maximum, which results in the optimal QoE performance. Moreover, the optimal setting for the MAC contention window is also obtained for the case that the TCP congestion window is larger than one. The accuracy of the proposed analytical model is verified by extensive simulations.

AJRC-MAC: An ALOHA-Based Joint Reservation and Cooperation MAC for Dense Wireless Networks

The increase in collision and interference induced by the network densification poses the intractable challenge of improving network throughput. Channel reservation and cooperative transmission, two schemes improving the medium access control (MAC) efficiency and transmission reliability respectively, have drawn considerable attention. Joint optimization of reservation and cooperation is theoretically proved to be promising in improving the network throughput in our recent study. However, up to now no practical MAC protocol is proposed to evaluate its effectiveness. In this paper, we propose an ALOHA-based joint reservation and cooperation MAC (AJRC-MAC) protocol which adopts the reservation-based channel access and enables the cooperative transmission simultaneously for the dense wireless network. Simulation results evaluate the effectiveness of the joint reservation and cooperation, and show that a throughput gain of 330%, 250%, 130% can be achieved respectively for AJRC-MAC compared with the basic MAC, cooperation- only MAC and reservation-only MAC.

MU-FuPlex: A Multiuser Full-Duplex MAC Protocol for the Next Generation Wireless Networks

The ever-increasing data demands and the density of wireless nodes require higher data rate in wireless networks. To satisfy the requirement, it is necessary to propose novel medium access control (MAC) protocols to enhance multiuser channel access and multiuser data transmission in wireless network. The existing studies prove that full-duplex (FD) is able to improve the network capability without any extra bandwidth. However, there are few studies focusing on multiuser FD MAC protocol design for the next generation wireless networks. In this paper, a multiuser FD MAC protocol named as MU-FuPlex is introduced based on our proposed system model, and the interference information collection, FD transmit opportunity (FD-TXOP) mechanism, and frame format design for MU-FuPlex are discussed. To the best of our knowledge, this is the first work focusing on the combination of multiuser MAC and FD technology. The simulation results confirm that MU-FuPlex significantly improves the saturation throughput up to 200% compared with IEEE 802.11 DCF.

Power Control Based Multiuser Full-Duplex MAC Protocol for the Next Generation Wireless Networks

Continuously increasing the data rate in wireless networks is required to satisfy the ever-increasing service demands. Full-duplex (FD), a promising technology for wireless networks, is able to double the data rate theoretically. Although several researchers study the physical (PHY) and medium access control (MAC) protocols of FD technology, there are few study focusing on the multiuser MAC protocol design for the next generation wireless networks. In this paper, a power control (PC) based multiuser FD MAC protocol, named PC MU-FuPlex, is proposed. Moreover, the probability of establishing FD link is formulated specifically. The simulation results demonstrate that the proposed MAC protocol significantly improves the saturation throughput up to 200% compared to that without PC in higher modulation.

The neighbor channel sensing capability for wireless networks

In wireless networks, the capability of sensing the received power variation on wireless channel is named as channel sensing capability (CSC). However, as wireless networks become increasingly dense, it decreases the reliability of multiuser transmission if only CSC is simply used for indicating channel state. Thus, in this paper, a novel conception named as neighbor channel sensing capability (NCSC) is proposed to describe the capability of nodes for sensing the channel state of their neighbor nodes. We prove that the consistency of NCSC, defined as the variable of the difference of the received power of two neighboring nodes, obeys a Gaussian distribution when the location of all transmitting nodes obeys a homogeneous Poisson point process. Moreover, we derive the mean and variance of the consistency of NCSC, and give the expression of NCSC to accurately describe the capability of sensing the channel state of neighbor nodes. The simulation results show that NCSC can efficiently indicate and validate our analysis model and derivation.