Zhongjiang Yan

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%.

Capacity analysis of wireless ad hoc networks with improved channel reservation

In ad hoc networks, interference is an important factor limiting the network capacity. Imposing a reservation zone around each receiver has been widely considered to mitigate the interference. A larger reservation zone can decrease the interference, but it also lowers the spatial reuse for reduced simultaneous transmissions. Therefore, there exists an optimal reservation zone to maximize the network capacity. In this paper, rate adaptation is brought to improve the channel reservation scheme, and network capacity achieved by jointly optimizing the data rate and reservation zone is investigated for spread-spectrum (SS) ad hoc networks. Compared to the transmission capacity with fixed data rate assumption, analytical and numerical results show that network capacity can be significantly improved, and the capacity gain remains constant in the order of 300% for direct sequence (DS) SS networks and increases with the growing spreading factors in the range of 300-800% for frequency hopping (FH) SS networks.

QoE-aware admission control and MAC layer parameter configuration algorithm in WLAN

In IEEE 802.11 wireless local area network (WLAN), the quality of the experience (QoE) of HTTP video streaming is seriously influenced by the restricted bandwidth and shared resources. However, to the best of our knowledge, the assessment and optimization of QoE of HTTP video streaming in WLAN have not been fully studied yet. In this paper, we propose an objective metric to assess the QoE and obtain the relationship between this metric and the achieved MAC layer throughput, which makes the MAC layer be aware of the QoE performance directly. Then, a novel admission control and MAC layer parameter configuration algorithm is proposed, which optimizes the QoE of HTTP video streaming and guarantees the throughput requirement of background traffic. Simulation results show that the proposed algorithm outperforms legacy IEEE 802.11 DCF in QoE optimization by a factor of six or more when the number of background stations is large.

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.

A 3D geometry-based stochastic model for 5G massive MIMO channels

Massive MIMO is one of the most promising technologies for the fifth generation (5G) mobile communication systems. In order to better assess the system performance, it is essential to build a corresponding channel model accurately. In this paper, a three-dimension (3D) two-cylinder regular-shaped geometry-based stochastic model (GBSM) for non-isotropic scattering massive MIMO channels is proposed. Based on geometric method, all the scatters are distributed on the surface of a cylinder as equivalent scatters. Non-stationary property is that one antenna has its own visible area of scatters by using a virtual sphere. The proposed channel model is evaluated by comparing with the 3GPP 3D channel model [1]. The statistical properties are investigated. Simulation results show that close agreements are achieved between the characteristics of the proposed channel model and those of the 3GPP channel model, which justify the correctness of the proposed model. The model has advantages such as good applicability.

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.

Cross-Layer Software-Defined 5G Network

In the past few decades, the world has witnessed a rapid growth in mobile communication and reaped great benefits from it. Even though the fourth generation (4G) mobile communication system is just being deployed worldwide, proliferating mobile demands call for newer wireless communication technologies with even better performance. Consequently, the fifth generation (5G) system is already emerging in the research field. However, simply evolving the current mobile networks can hardly meet such great expectations, because over the years the infrastructures have generally become ossified, closed, and vertically constructed. Aiming to establish a new paradigm for 5G mobile networks, in this article, we propose a cross-layer software-defined 5G network architecture. By jointly considering both the network layer and the physical layer together, we establish the two software-defined programmable components, the control plane and the cloud computing pool, which enable an effective control of the mobile network from the global perspective and benefit technological innovations. Specifically, by the cross-layer design for software-defining, the logically centralized and programmable control plane abstracts the control functions from the network layer down to the physical layer, through which we achieve the fine-grained controlling of mobile network, while the cloud computing pool provides powerful computing capability to implement the baseband data processing of multiple heterogeneous networks. The flexible programmability feature of our architecture makes it convenient to deploy cross-layer technological innovations and benefits the network evolution. We discuss the main challenges of our architecture, including the fine-grained control strategies, network virtualization, and programmability. The architecture significantly benefits the convergence towards heterogeneous networks and enables much more controllable, programmable and evolvable mobile networks. Simulations validate these performance advantages.

FH-SCMA: Frequency-Hopping Based Sparse Code Multiple Access for Next Generation Internet of Things

The next generation Internet of Things (IoT) is expected to support extremely diverse applications and terminals, which requires the massive connectivity. Unfortunately, current mobile communication systems with orthogonal multiple access technique can hardly satisfy this demand. On the other hand, the narrow band property has become the trend of the next generation IoT, however, the problem of interference alleviation in the narrow band system is difficult to be resolved. Recently, the sparse code multiple access (SCMA), a non- orthogonal multiple access technique for 5G, shows the obvious improvement in user connectivity and system capacity. After carrier aggregation brought into the future network, The IoT could offer the frequency hopping mechanism larger bandwidth resources. In this paper, by introducing frequency hopping mechanism to the SCMA, a frequency-hopping based sparse code multiple access (FH-SCMA) multiple access technique is proposed to meet the demand of both massive connectivity and the improvement in the interference alleviation. Simulation results show that the FH-SCMA obtains a spectrum efficiency gain of almost 300% compared with the frequency division multiple access (FDMA) based IoT system with frequency-hopping, and the performance of interference alleviation can also be significantly improved by about 2 to 5 times over the FDMA with frequency hopping.

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.