Probability and Measure

Millimeter wave (mmWave) communications have recently attracted large research interest, since the huge available bandwidth can potentially lead to the rates of multiple gigabit per second per user Though mmWave can be readily used in stationary scenarios, such as indoor hotspots or backhaul, it is challenging to use mmWave in mobile networks, where the transmitting/receiving nodes may be moving, channels may have a complicated structure, and the coordination among multiple nodes is difficult To fully exploit the high potential rates of mmWave in mobile networks, lots of technical problems must be addressed This paper presents a comprehensive survey of mmWave communications for future mobile networks (5G and beyond) We first summarize the recent channel measurement campaigns and modeling results Then, we discuss in detail recent progresses in multiple input multiple output transceiver design for mmWave communications After that, we provide an overview of the solution for multiple access and backhauling, followed by the analysis of coverage and connectivity Finally, the progresses in the standardization and deployment of mmWave for mobile networks are discussed

Millimeter Wave Communications for Future Mobile Networks

Diverse proprietary network appliances increase both the capital and operational expense of service providers, meanwhile causing problems of network ossification. Network function virtualization (NFV) is proposed to address these issues by implementing network functions as pure software on commodity and general hardware. NFV allows flexible provisioning, deployment, and centralized management of virtual network functions. Integrated with SDN, the software-defined NFV architecture further offers agile traffic steering and joint optimization of network functions and resources. This architecture benefits a wide range of applications (e.g., service chaining) and is becoming the dominant form of NFV. In this survey, we present a thorough investigation of the development of NFV under the software-defined NFV architecture, with an emphasis on service chaining as its application. We first introduce the software-defined NFV architecture as the state of the art of NFV and present relationships between NFV and SDN. Then, we provide a historic view of the involvement from middlebox to NFV. Finally, we introduce significant challenges and relevant solutions of NFV, and discuss its future research directions by different application domains.

Software-Defined Network Function Virtualization: A Survey

The fifth generation (5G) mobile communication systems will be in use around 2020. The aim of 5G systems is to provide anywhere and anytime connectivity for anyone and anything. Several new technologies are being researched for 5G systems, such as massive multiple-input multiple-output communications, vehicle-to-vehicle communications, high-speed train communications, and millimeter wave communications. Each of these technologies introduces new propagation properties and sets specific requirements on 5G channel modeling. Considering the fact that channel models are indispensable for system design and performance evaluation, accurate and efficient channel models covering various 5G technologies and scenarios are urgently needed. This paper first summarizes the requirements of the 5G channel modeling, and then provides an extensive review of the recent channel measurements and models. Finally, future research directions for channel measurements and modeling are provided.

A Survey of 5G Channel Measurements and Models

While celebrating the 21st year since the very first IEEE 802.11 “legacy” 2 Mbit/s wireless local area network standard, the latest Wi-Fi newborn is today reaching the finish line, topping the remarkable speed of 10 Gbit/s. IEEE 802.11ax was launched in May 2014 with the goal of enhancing throughput-per-area in high-density scenarios. The first 802.11ax draft versions, namely, D1.0 and D2.0, were released at the end of 2016 and 2017. Focusing on a more mature version D3.0, in this tutorial paper, we help the reader to smoothly enter into the several major 802.11ax breakthroughs, including a brand new orthogonal frequency-division multiple access-based random access approach as well as novel spatial frequency reuse techniques. In addition, this tutorial will highlight selected significant improvements (including physical layer enhancements, multi-user multiple input multiple output extensions, power saving advances, and so on) which make this standard a very significant step forward with respect to its predecessor 802.11ac.

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A Tutorial on IEEE 802.11ax High Efficiency WLANs

Internet of Things (IoT) is a kind of information carrier, which enables for all ordinary objects that can perform independent functions to realize interconnection. The standardization process of wireless local area networks (WLANs) which is an important network system of IoT is gradually advancing. IEEE 802.11ax will replace IEEE 802.11a/b/g/n/ac as the latest WLANs standard. The uplink transmission of IEEE 802.11ax adopts a hybrid access mode. The mode means that the stations (STAs) can access the network adopting either scheduling access mode or random access mode. Since the hybrid access mode supports both the scheduling and random access, how to allocate the resources among the STAs which adopt the two access modes is the first problem to be solved. In particular, IEEE 802.11ax focuses more on the network performance of the high-dense deployment scenarios. The characteristic of the interference of the overlapping basic service set (OBSS) situation is the key factor of the efficiency of resource allocation algorithm. Therefore, firstly, this paper combines capacity entropy multi-user access (CEM) with utility function, and defines a metric value to measure the utility of two kinds of users. Secondly, the simulation-assisted method is used to obtain the probability distribution characteristic of the interference power random variables from dense multi-cell scenarios of IEEE 802.11ax. Then, based on interference power random variables which generated by the probability density curve obtained by simulation, we propose an algorithm which can maximizetotal utility of scheduling and random access STAs, i.e., to maximize the total satisfaction of all STAs. The authors believe that the research can enhance the quality of experience (QoE) of users in dense multi-cell scenarios for the next generation WLANs.

Utility Maximization of Capacity Entropy for Dense IEEE 802.11ax WLANs based on Interference Characteristics

Most recently, an enhancement amendment named IEEE 802.11ax is proposed by the High-Efficiency WLAN (HEW) Task Group for the Next Generation WLAN (NGW), with a focus on improving spectrum efficiency as well as area throughput. However, collisions among stations (STAs) and Low-Rate-Links (LRLs) severely degrade the network performance, which have become a great matter of concern. In this paper, a channel reservation based multi-channel MAC protocol with serial cooperation is proposed for the next generation WLAN, called CRSC-MMAC, to explore the capabilities of both cooperative relay and channel reservation. In particular, with cooperative relay available, a LRL is divided into two wireless links that sequentially occur on the same data channel with higher data rate. Besides, by using multi-step channel reservation, multiple cooperative transmission opportunities can be reserved in advance with only one successful handshake on the control channel, and thus collisions are effectively alleviated. Extensive simulations are deployed using ns-2 simulator, simulation results show that saturation throughput of the proposed CRSC-MMAC protocol is nearly two times of that of the ‘Baseline’ scheme, and average packet delay of CRSC-MMAC is decreased by nearly 33%.

A channel reservation based multi-channel MAC protocol with serial cooperation for the next Generation WLAN

In the high-density deployment scenario of the next generation wireless local area network (WLAN), the intensification of conflict makes spectrum utilization low. In order to improve the spectrum efficiency, the academia and industry will introduce Co-frequency Co-time Full Duplex (CCFD) technology into MAC as a key technology. However, the existing full-duplex Medium Access Control (MAC) protocol based on access point (AP) scheduling has the problem of low success rate in establishing full-duplex links. In order to solve this problem, a dynamic full-duplex link matching algorithm based on Binary-Graph is proposed, which is based on the author’s earlier research on FD-OMAX [16]. This algorithm uses bipartite graph to establish the relationship model between full-duplex link and Resource Unit (RU). In each round of full-duplex transmission, AP establishes the optimal full-duplex link transmission based on the user’s dynamic interference information on RU resources. In order to improve the success probability of establishing full-duplex links and spectrum efficiency, an enhanced trigger-free full-duplex MAC protocol, EnFD-OMAX, is designed on the basis of FD-OMAX protocol. The simulation results show that compared with FD-OMAX protocol, MuFuPlex protocol, OMAX protocol and FuPlex protocol, the throughput distribution of EnFD-OMAX protocol increases by 26.5%, 56.60%, 88.37% and 118.4% under saturated traffic. In high-density deployment scenarios, the probability of full duplex link to successful transmission and MAC efficiency are increased by 88.98% and 149.9% respectively compared with OMAX protocol.

A Trigger-Free Multi-user Full Duplex User-Pairing Optimizing MAC Protocol

The next generation Wireless Local Area Network (WLAN) IEEE 802.11be regards Extremely High Throughput (EHT) as its core technology goal, among which multi-band capability and AP cooperation technology are regarded as its key technologies. However, the existing research on Orthogonal Frequency Division Multiple Access (OFDMA) protocol does not consider the multi-band capability and AP collaboration technology of IEEE 802.11be, so the improvement of system performance is limited and does not meet the EHT requirement. Especially when the nodes in overlapping coverage area have a large number of traffic, it is more important to improve the throughput of nodes in overlapping coverage area. In order to improve the throughput of nodes in overlapping coverage area, this paper proposes a spatial clustering group OFDMA protocol associated with multiple Basic Service Sets (BSSs). The protocol allows nodes in overlapping coverage area to be associated with multiple BSSs at the same time by using multi-band capability, that is, multi-association; Using AP collaboration technology allows nodes to perform parallel backoff with channels on multiple BSSs to improve access efficiency. Nodes in the overlapping coverage area are associated with the channels of multiple BSSs for parallel backoff. Node completed backoff and successfully accessed triggers a spatial clustering group (SCG) with close to its spatial location. OFDMA mode is used by SCG to access and transmit, thus increasing the access opportunities of nodes within overlapping coverage, thereby improving the throughput. The simulation results show that using the SCG-OFDMA protocol proposed in this paper associated with two BSSs, its throughput of nodes within overlapping coverage can achieve 353.41% higher than the IEEE 802.11ax protocol and 558.33% higher than the OMAX protocol respectively.

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Multiple BSSs Association Based Spatial Clustering Group Access Protocol for Next Generation WLAN

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.

Zhongjiang Yan

Papers

Utility Maximization of Capacity Entropy for Dense IEEE 802.11ax WLANs based on Interference Characteristics

A channel reservation based multi-channel MAC protocol with serial cooperation for the next Generation WLAN

A Trigger-Free Multi-user Full Duplex User-Pairing Optimizing MAC Protocol

Multiple BSSs Association Based Spatial Clustering Group Access Protocol for Next Generation WLAN

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