Spatial Reuse Research Articles

Network Densification in 5G: From the Short-Range Communications Perspective

Besides advanced telecommunications techniques, the most prominent evolution of wireless networks is the densification of network deployment. In particular, the increasing access point/ user density and reduced cell size significantly enhance spatial reuse, thereby improving network capacity. Nevertheless, does network ultra-densification and over-deployment always boost the performance of wireless networks? Since the distance from transmitters to receivers is greatly reduced in dense networks, signal is more likely to be propagated from long- to short-range distance. Without considering short-range propagation features, conventional understanding of network densification becomes doubtful. In this regard, it is imperative to reconsider the pros and cons brought by network densification. In this article, we first discuss the short-range propagation features in densely deployed networks and verify through experimental results the validity of the proposed short-range propagation model. Considering short-range propagation, we further explore the fundamental impact of network densification on network capacity, aided by which a concrete interpretation of ultra-densification is presented from the network capacity perspective. Meanwhile, as short-range propagation makes interference more complicated and difficult to handle, we discuss possible approaches to further enhance network capacity in ultra-dense wireless networks. Moreover, key challenges are presented to suggest future directions.

A novel strategy for LED re-utilization for visible light communications

A resource allocation optimization model for downlink indoor Optical Wireless Communications networks (OWC) is proposed in this paper. The optimization problem is formulated as a mixed integer binary problem. A centralized smart coordinator solves the problem in order to assign efficiently Visible Light Communications (VLC) channels to users. The optimization problem is solved with two different approaches based on Cuckoo Search algorithm (CS). The first one solves the complete network problem considering all users and access points simultaneously with a random initialization procedure. Whilst the second approach is a CS based decomposition procedure, which obtains feasible solutions with the help of a spatial reuse aided algorithm. Both procedures were tested for different receivers Fields of View (FOV), e.g., FOV=30° and 60° which are placed randomly on the coverage area and for different transmitter's power levels. Results show that the solutions obtained with spatial reuse aided procedure outperforms the first approach in terms of total network throughput for different power levels, i.e., 1 and 10W, and different number of users. Finally, results obtained with the second approach allow the usage of a wider FOV.

Directional MAC protocol for IEEE 802.11ad based wireless local area networks

IEEE 802.11ad defines a new physical and medium access control layer for IEEE 802.11 networks to operate in the unlicensed 60 GHz millimeter wave spectrum for multi-gigabit wireless communications. Higher frequency waves have higher propagation loss but smaller antenna size. Hence, for millimeter wave networks, higher number of antennas can be packed together, enabling beamforming with very large gains. In this paper, we propose a novel Directional MAC protocol for Basic Stations (DMBS) with the goal of fully leveraging spatial reusability, and limiting deafness and hidden terminal problems with minimal overhead, and without using any complicated hardware for localization. The distinguishing features of DMBS are threefold. First, DMBS extends the association beamforming training time (A-BFT) of IEEE 802.11ad, during which the stations perform initial beamforming training with the access point (AP), by an intelligent listening mechanism. This mechanism allows the stations to passively learn about the best direction of the neighboring stations, decreasing the associated beamforming training overhead. Second, DMBS determines the best transmission direction by using multi-directional sequential (circular) RTS/CTS (Request To Send/ Clear To Send) (CRTS/CCTS) packets, and tracks the best direction by updating its beamforming table upon reception of every RTS/CTS packet, without requiring any additional hardware for localization. If the location information of the destination is up-to-date, the source station only transmits directional RTS/CTS (DRTS/DCTS) in the known direction. Third, DMBS uses two network allocation vectors (NAVs). The first NAV, denoted by NAV1, is used to reduce deafness by determining the busy nodes upon the reception of every RTS/CTS packet. The second NAV, called NAV2, is used to limit hidden terminal problem while maximizing spatial reusability by determining whether a transmission can interfere with active communication links. If NAV2 is set, then the node defers its multi-directional communication but still communicates directionally. We provide a novel Markov chain based analytical model to calculate the aggregate network throughput of DMBS. We demonstrate via extensive simulations that DMBS performs better than existing directional communication protocols in terms of throughput for different network sizes, mobilities and number of receivers.

Feasibility Study of 60 GHz Millimeter-Wave Technologies for Hyperconnected Fog Computing Applications

This paper conducts the feasibility study for discussing about the interference impacts in advanced fog computing (FC) networks with 60 GHz millimeter-wave wireless technology. With the concept of FC, cloud computing services can be utilized with local computing devices ( FC devices ) those are located nearby user terminals [edge devices (EDs)] for low-latency communications. Since EDs can be densely deployed in urban areas, wireless hyperconnection should be supportable in FC networks. For the system, 60 GHz millimeter-wave technology can be used as one of wireless networking methods because it can provide: 1) high rates for visual information delivery and 2) high directionality for spatial reuse in hyperconnected FC networks. Therefore, this performance simulation study under the consideration of interference impacts determines whether utilizing 60 GHz millimeter-wave wireless technology for hyperconnected FC networks is feasible or not. Under the consideration of various interference scenarios, the interference impacts are calculated. As presented in simulation-based performance evaluation results, we verify that 1.5 Gb/s high rate can be supportable even though more than 1000 EDs are deployed in the 100 m-by-100 m size small-scale networks (upper bound). Therefore, we confirm that hyperconnection can be realized with 60 GHz millimeter-wave technology for FC networks.

SSAAR: Enhanced Spatial Reusability for Optimal Path Selection in Wireless Sensor Networks

The advancements made in the wireless sensor networks have enabled the research communities to delve into the study of spatial reusability concepts. Due to the restricted capacity in wireless links, it is a significant to select the optimal route for packet transmission. The achievement of optimal route selection is verified by the high end-to-end throughput rate. Routing in WSNs is very challenging due to the inherent characteristics that distinguish these networks from other wireless networks like mobile ad hoc networks or cellular networks. In this paper, we have proposed an improved spatial reusability process using Single Path and Anypath Routing Protocols (SSAAR). The task of single path routing is to minimize the cost of the nodes in wireless links, whereas the task of any path routing is to assists the intermediate node who overhears the packet to participate in packet forwarding. Experimental results have shown the efficacy of our proposed work in terms of cost minimization functionalities. Keywords: Cost Minimization, Packet Forwarding, Single Path and Anypath Routing Protocols, Wireless Sensor Networks, Wireless Links

Optimal Base Station Density of Dense Network: From the Viewpoint of Interference and Load.

Network densification is attracting increasing attention recently due to its ability to improve network capacity by spatial reuse and relieve congestion by offloading. However, excessive densification and aggressive offloading can also cause the degradation of network performance due to problems of interference and load. In this paper, with consideration of load issues, we study the optimal base station density that maximizes the throughput of the network. The expected link rate and the utilization ratio of the contention-based channel are derived as the functions of base station density using the Poisson Point Process (PPP) and Markov Chain. They reveal the rules of deployment. Based on these results, we obtain the throughput of the network and indicate the optimal deployment density under different network conditions. Extensive simulations are conducted to validate our analysis and show the substantial performance gain obtained by the proposed deployment scheme. These results can provide guidance for the network densification.

Negotiable Auction Based on Mixed Graph: A Novel Spectrum Sharing Framework

Auction-based spectrum sharing is a promising solution to improve the spectrum utilization in 5G networks. Along with the spatial reuse, we observe that the ability to adjust the coverage of a spectrum bidder can provide room to itself for further negotiation while auctioning. In this paper, we propose a novel economic tool, size-negotiable auction mechanism (SNAM), which provides a hybrid solution between auction and negotiation for multi-buyers sharing spectrum chunks from a common database. Unlike existing auction-based spectrum sharing models, each bidder of the SNAM submits its bid for using the spectrum per unit space and a set of coverage ranges over which the bidder is willing to pay for the spectrum. The auctioneer then coordinates the interference areas (or coverage negotiation) to ensure no two winners interfere with each other while aiming to maximize the auction’s total coverage area or revenue. In this scenario, the undirected graph used by existing auction mechanisms fails to model the interference among bidders. Instead, we construct a mixed interference graph and prove that SNAM’s auctioning on the mixed graph is truthful and individually rational. Simulation results show that, compared with existing auction approaches, the proposed SNAM dramatically improves the spatial efficiency, hence leads to significantly higher seller revenue and buyer satisfaction under various setups. Thanks to its low complexity and low overhead, SNAM can target fine timescale trading (in minutes or hours) with a large number of bidders and requested coverages.

Scheduling With Predictable Link Reliability for Wireless Networked Control

Predictable link reliability is required for wireless networked control, yet co-channel interference remains a major source of uncertainty in wireless link reliability. Formulated specifically for distributed predictable control of co-channel interference, the physical-ratio-K (PRK) interference model integrates the protocol model’s locality and the physical model’s high fidelity while addressing their weaknesses, and it transforms interference control in arbitrary networks to a problem involving coordination between close-by nodes only. To apply the PRK model in real-world settings, we design protocol PRKS that addresses the challenges of model instantiation and protocol signaling in PRK-based scheduling. In particular, PRKS uses a control-theoretic approach to instantiate the PRK model in dynamic uncertain networks, uses local signal maps to address the challenges of large interference range and anisotropic asymmetric wireless communication, and leverages the different timescales of PRK model adaptation and data transmission to decouple protocol signaling from data transmission. Through testbed-based measurement study, we show that, unlike existing scheduling protocols where link reliability is unpredictable and the ratio of links whose reliability meets application requirements can be as low as 0%, PRKS enables predictably high link reliability (e.g., 95%) for all the links in different network and environmental conditions without a priori knowledge of these conditions. Through local distributed coordination, PRKS also achieves a channel spatial reuse very close to what is enabled by the state-of-the-art centralized scheduler while ensuring the required link reliability. By ensuring the required link reliability in scheduling, PRKS also enables a lower communication delay and a higher network throughput than existing scheduling protocols.

Study on Routing Protocol in Airborne-Sea Ad Hoc Networks with Directional Antennas

In this paper, we propose a directional routing protocol for airborne-sea ad hoc networks (ASNETs). Directional antennas have the potential to provide a fundamental breakthrough in ad hoc network capacity, connectivity, and covertness because they have great advantages such as high spatial reuse and range extension. ASNETs is a special ad hoc network which include two kinds nodes, namely aircraft and ship. To fully exploit the benefits of directional antennas in ASNETs, a Node-Avoided Directional Routing (NADR) protocol is to be considered. The main feature of NADR is that route request packets is always transmitted by those less load nodes. That is why NADR can effectively balance the load of node. Preliminary simulation results are found to be very promising, the performance of NADR is better than DSR and DRP in terms of the packet delivery ratio and throughput.

Resource Allocation Based on Channel Sensing and Spatial Spectrum Reuse for Cognitive Femtocells

A cognitive femtocell is a new small cell based on a smart home base station to solve the spectrum-scarcity problem. Recently, dedicated resource allocation for cognitive femtocell to mitigate co-channel interference is extensively researched. However, the cognitive femtocell may suffer from the lack of frequency resource for its users due to high data traffic load of the macrocell. We propose a novel resource allocation and power control mechanism using spatial frequency reuse and spectrum sensing, which enables femto users in the cognitive femtocell to obtain more feasible resource. We analyze and evaluate the performance gain of the proposed scheme. Although data traffic load of the macrocell increases, the capacity of the cognitive femtocell can be maintained appropriately by the proposed resource allocation and power control scheme and it is shown that the performance is improved compared to that of the conventional scheme.

Efficient resource allocation algorithm for overlay D2D communication

Device-to-device (D2D) communication in cellular systems offers an economically viable means of improving the system capacity by allocating multiple D2D links within the same resource block (RB), under appropriate interference-control techniques. In this paper, we propose an efficient resource allocation algorithm that enables maximum spatial reuse in orthogonal frequency division multiple access (OFDMA) systems. Given a set of D2D requests, the proposed algorithm greedily determines the number of RBs required, following the reliability criteria. Simulation results show that, compared to the greedy algorithm (Lee, Choi, and Jeon, 2013), the proposed algorithm could save up to 18.6% RBs, improve the throughput per RB by up to 23.4%, and reduce the computation time by up to 67.9%.

Operating Massive MIMO in Unlicensed Bands for Enhanced Coexistence and Spatial Reuse

We propose to operate massive multiple-input multiple-output (MIMO) cellular base stations (BSs) in unlicensed bands. We denote such systems as massive MIMO unlicensed (mMIMO-U) ones. We design the key procedures required at a cellular BS to guarantee coexistence with nearby Wi-Fi devices operating in the same band. In particular, spatial reuse is enhanced by actively suppressing interference toward neighboring Wi-Fi devices. Wi-Fi interference rejection is also performed during an enhanced listen-before-talk phase. These operations enable Wi-Fi devices to access the channel as though no cellular BSs were transmitting, and vice versa. Under concurrent Wi-Fi and BS transmissions, the downlink rates attainable by cellular user equipment (UEs) are degraded by the Wi-Fi-generated interference. To mitigate this effect, we select a suitable set of UEs to be served in the unlicensed band accounting for a measure of the Wi-Fi/UE proximity. Our results show that the so-designed mMIMO-U allows simultaneous cellular and Wi-Fi transmissions by keeping their mutual interference below the regulatory threshold. Compared with a system without interference suppression, Wi-Fi devices enjoy a median interference power reduction of between 3 dB with 16 antennas and 18 dB with 128 antennas. With mMIMO-U, cellular BSs can also achieve large data rates without significantly degrading the performance of Wi-Fi networks deployed within their coverage area.

Fundamental Analysis of Full-Duplex Gains in Wireless Networks

Full-duplex radio technology is becoming mature and holds potential to boost the spectrum efficiency of a point-to-point wireless link. However, a fundamental understanding is still lacking, with respect to its advantages over half-duplex in multi-cell wireless networks with contending links. In this paper, we establish a spatial stochastic framework to analyze the mean network throughput gain from full duplex, and pinpoint the key factors that determine the gain. Our framework extends classical stochastic geometry analysis with a new tool set, which allows us to model a tradeoff between the benefit from concurrent full-duplex transmissions and the loss of spatial reuse, particularly for CSMA-based transmitters with random backoff. We analytically derive closed-form expressions for the full-duplex gain as a function of link distance, interference range, network density, and carrier sensing schemes. It can be easily applied to guide the deployment choices in the early stage of network planning.

Resource and Mobility Management in the Network Layer of 5G Cellular Ultra-Dense Networks

The provision of very high capacity is one of the big challenges of the 5G cellular technology. This challenge will not be met using traditional approaches like increasing spectral efficiency and bandwidth, as witnessed in previous technology generations. Cell densification will play a major role thanks to its ability to increase the spatial reuse of the available resources. However, this solution is accompanied by some additional management challenges. In this article, we analyze and present the most promising solutions identified in the METIS project for the most relevant network layer challenges of cell densification: resource, interference and mobility management.

Overhead Reduction by Spatial Reusability in Multi-Hop Wireless Networks

The issue of routing in multi-hop wireless networks, to achieve high end-to-end throughput, it is difficult to find the optimal path from the source node to the destination node. Although a large number of routing protocols have been implemented to find the path with minimum transmission time for sending a single packet, such transmission time reduces protocols cannot be guaranteed to achieve high end-to-end throughput. Spatial reusability aware routing in multi hop wireless network is featured by considering spatial reusability of the wireless communication media. Spatial reusability-aware single-path routes and any path routing protocols, and compare them with existing single-path routing and any path routing protocols, respectively. Our evaluation results demonstrate that our protocols significantly improve the end-to-end throughput compared with existing protocols. Resource allocation algorithm is inquired to maximize the energy efficiency (EE) in multiuser decode-and-forward (DF) relay interference networks.

Power Aware MAC Protocol for Mobile Ad Hoc Networks Using Directional Antennas

Several power control schemes provide lower power consumption and increase network throughput. Some of these protocol use maximum energy and some adjustable energy to transmit data. Some schemes use directional antenna transmission technique without using any power control scheme. Therefore, in this paper, we proposed a power control scheme that uses directional antenna and takes interference into account. This Power control scheme uses different power levels to transmit RTS–CTS, DATA–ACK using directional antenna. The use of directional antenna increases spatial reuse in the network. Experiment result shows that proposed scheme enhances the throughput of the network and decreases energy consumption. This power control scheme has been compared with existing IEEE 802.11, DMAC, and DBASIC schemes. Our scheme outperforms the above existing schemes in terms of throughput and energy consumption. The throughput of this scheme improves from 9 to 19% for denser to sparse networks. However, as the network density increases the performance of the proposed scheme decreases marginally, but still remains better.

Power Control Directional MAC Protocol for Mobile Ad Hoc Networks

Since use of directional antennas in mobile ad hoc networks gaining popularity day by day because of its properties. Although MAC protocol using directional antenna enhances the network performance as it increases spatial reuse and minimizes energy consumption, in comparison of MAC protocols using omnidirectional antennas. But directional MAC protocol still have some well known problem, namely hidden terminal, exposed terminal problem, and deafness. Therefore, in this paper we proposed a MAC protocol that will attempt to minimize these problems without degrading network performance. Simulation results show that the performance of proposed work is better as compared to existing protocols.

Improving DL-MU-MIMO performance in IEEE 802.11ac networks through decoupled scheduling

The IEEE 802.11ac standard introduces new downlink multi-user MIMO (DL-MU-MIMO) transmissions to up to four users in order to increase spatial reuse in wireless local area networks (WLANs). We argue that even better WLAN per- formance can be achieved by slightly modifying the DL-MU-MIMO scheduling. To this end we propose a new queuing mechanism based on the decoupling of EDCA and DL-MU-MIMO scheduling (DEMS) to avoid head-of-line blocking. We show that DEMS outperforms traditional 802.11ac scheduling based on first in, first out transmission queues. The improvement is shown in terms throughput achieved with: (a) more efficient channel usage, (b) increased probability of transmission of high priority traffic, and (c) decreased competition between frames destined to distinct users.

Directional received medium access control protocol for underwater sensor networks

Aiming at handshake protocols in the presence of hidden terminal and exposed terminal problems in underwater sensor networks of single-channel, this paper has presented the communication protocol of directional received slotted floor acquisition multiple access based on single vector sensor orientation. This protocol uses the characteristics of single vector sensor to directional receive, solves the problem of the hidden and exposed terminal problem in the single channel condition through the directional handshake mechanism. For the problem of near-far effect, each node maintains the neighbor node information table in one-hop range, calculates the power of transmitting RTS and CTS packets according to the current neighbor information, and then calculates the transmission power that satisfies the signal-to-noise ratio requirement of the destination node according to the obtained information. Compared with the single channel protocol based on omnidirectional antenna, this protocol can make full use of the resources of idle channel and the degree of network spatial reuse. Simulation experiments show that under the two different business, compared with the classical Slotted FAMA protocol and MACAW, the throughput of network has improved by 40%~60% and 30%~40%, respectively, which proves that the directional protocol can improve the network throughput effectively.

Performance Limits of Network Densification

Network densification is a promising cellular deployment technique that leverages spatial reuse to enhance coverage and throughput. Recent work has identified that at some point ultra-densification will no longer be able to deliver significant throughput gains. In this paper, we provide a unified treatment of the performance limits of network densification. We develop a general framework, which incorporates multi-slope pathloss and the entire space of shadowing and small scale fading distributions, under strongest cell association in a Poisson field of interferers. First, our results show that there are three scaling regimes for the downlink signal-to-interference-plus-noise ratio (SINR), coverage probability, and average per-user rate. Specifically, depending on the near-field pathloss and the fading distribution, the user performance of 5G ultra dense networks (UDNs) would either monotonically increase, saturate, or decay with increasing network density. Second, we show that network performance in terms of coverage density and area spectral efficiency can scale with the network density better than the user performance does. Furthermore, we provide ordering results for both coverage and average rate as a means to qualitatively compare different transmission techniques that may exhibit the same performance scaling. Our results, which are verified by simulations, provide succinct insights and valuable design guidelines for the deployment of 5G UDNs.