Xiaoya Zuo

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.

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.

A reliable channel reservation based multi-channel MAC protocol with a single transceiver

The multi-channel MAC protocols have been proposed recently to improve the network capacity by accommodating more concurrent transmissions. In this paper, we propose a distributed multi-channel MAC protocol using reliable multiple channel reservation with only a single transceiver. Specifically, the control handshake information is reserved to be re-broadcasted over the control channel to address the multi-channel hidden terminal problem. Besides, by reserving multiple data transmission opportunities on the selected data channel, the control channel congestion is further relieved. Then we prove that the multi-channel hidden terminal problem can be addressed using reservation on the control channel, and analyze the effectiveness of the proposed protocol in the aspect of the average number of data channels simultaneously utilized. Extensive simulation results show that the proposed protocol is able to achieve nearly 2.5 times the saturation throughput of DCA protocol [15] when five-step channel reservation is adopted.

Cell capacity for 5G cellular network with inter-beam interference

The emerging 5G cellular networks will operate at millimeter wave (mmWave) frequency bands to enhance the cell capacity. Massive MIMO antenna array and beamforming technology are used in order to overcome propagation limitations of mmWave band. Multi-beam based communication system is considered as the basic structure for 5G mobile network. However, to optimize the cell capacity, the question of how many beams are required remains unclear. In this paper, considering 5G mmWave cellular system with massive MIMO and beamforming technologies, we accurately model the inter-beam interference and evaluate the cell capacity and outage probability of the system. The simulation results give the optimal number of beams to maximize the cell capacity. Our research provides a possible guidance for the design of 5G cellular system.

A heuristic clique based STDMA scheduling algorithm for spatial concurrent transmission in mmWave networks

In this paper, a heuristic clique based spatial time division multiplexing access (STDMA) scheduling algorithm is proposed for concurrent transmission in millimeter wave networks. Firstly, based on the physical interference model an interference level caused by one transmission request to another is defined, which transforms the SINR condition to a summation form. Then, an un-directional conflict graph is constructed, a feasible clique of which is proved corresponding to a feasible concurrent transmission requests group in one timeslot. Finally, a heuristic clique based STDMA scheduling algorithm is proposed to find the maximum feasible concurrent scheduled transmission requests in one timeslot. Extensive simulations are conducted, and the simulation results show that compared to the existing blind scheduling algorithm, the spatial sharing gain is improved by 11%-36%.

Fair downlink traffic scheduling for energy sustainable vehicular roadside infrastructure

In this paper, the timeslot based traffic scheduling problem is considered with the objectives to fairly and energy efficiently serve the vehicles. The contact durations between the vehicles and the RSU are slotted into timeslots, during each of which one unit of the traffic can be transmitted from the RSU to one vehicle, and then one unit of vehicles requirement can be satisfied. The downlink traffic scheduling cost is defined as the transmission energy cost to deliver the traffic. The fairness of the traffic scheduling strategy is evaluated by the Jains fairness index of the unsatisfied vehicle requirements. The proposed problem is formulated as a three-step optimization problem. To address the difficulty of the three-step optimization problem, a flow network based algorithm is proposed. Both the offline and the online traffic schedule strategies are derived. Simulation results show that the derived offline traffic scheduling strategy outperforms the original energy optimal traffic scheduling strategy in terms of fairness, while the transmitted traffic and the transmission energy cost remains almost the same. The derived online traffic scheduling strategy outperforms the existing GMCF algorithms in terms of fairness, at the expense of larger transmission energy, and with the same total transmission traffic.

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.