mmWave Small Cell Networks Research Articles

Next-Generation mm-Wave Small-Cell Networks: Multiple Access, Caching, and Resource Management

Millimeter-wave (mm-wave) small cells have been considered an effective technique for significantly improving the data rates of future networks. More particularly, this article investigates the potential benefits of mm-wave small-cell networks from the perspective of nonorthogonal multiple access (NOMA) and wireless caching. We highlight a range of innovative resource management solutions conceived for mm-wave small-cell networks by invoking adaptive learning. Finally, several promising future research directions for these networks are identified.

Resource Management in Future Millimeter Wave Small-Cell Networks: Joint PHY-MAC Layer Design

The millimeter wave (mmWave) frequency band will become a key enabler for future wireless systems currently facing the explosive growth of data traffic and the sparsity of the traditional ultra-high frequency (UHF) band. Nevertheless, the challenges for mmWave communications lie in high propagation loss, sensitivity to blockage, high cost for equipping directional antennas, and so on. Furthermore, the traditional design for the UHF networks cannot be directly used for future mmWave networks, which needs to be reshaped from the perspectives of fundamental objectives, various constraints, and different degrees of freedom. This paper addresses the key functions and discusses the challenges for PHY layer and MAC layer design in mmWave small-cell networks, including mmWave antenna design, beamforming, initial access, radio resource allocation, power allocation, and so on. The novel resource management approach for the joint PHY-MAC layer design is proposed to find the trade-off among hardware cost of the mmWave antenna, beamforming overhead, and efficiency of the new resource block (RB) allocation in beam-frequency-time (B-T-F)-dimension. © 2013 IEEE.

Low-Complexity Channel Estimation and Cooperative Channel Allocation in Millimeter-Wave Small Cell Networks

In millimeter-wave massive multiple input multiple output (MIMO) antenna systems, channel estimation is a crucial component. In this paper, we propose a virtual channel representation channel estimation method using out-of-band spatial information to reduce training overheads. The proposed channel estimation method outperforms the exhaustive-search channel estimation method in terms of throughput performance. The proposed channel estimation also supports high throughput performance for high-speed user equipment environments unlike the existing channel estimation methods. Since the throughput performance degrades in multi-cell scenarios, we also propose a cooperative channel allocation method based on coalitional game framework. The proposed cooperative channel allocation method enhances throughput performance in mm-wave small cell networks.

5G MmWave Small Cell Networks: Architecture, Self-Organization, and Management

The nine articles in this special section focus on fifth generation (5G) millimeter-wave (mmWave) small cell networks (SCNs). To meet the demand of fast growing data rates, these networks have recently gained surging research interest worldwide. MmWave SCN is not a simple upgrade of its low-frequency predecessor by just adding additional spectrum or equipping advanced radio technologies. To fully release the potential, one has to rethink from the system and architecture levels down to the physical implementation level.

Evaluation Metrics and Simulation Tools for 5G Millimeter-Wave Networks

Recently, mmWave spectrum bands have attracted a lot of attention as they can be exploited by 5G to achieve high data rates and support ultrahigh traffic density. Since there are already systems allocated and operating in mmWave bands, it is critical to evaluate emerging spectrum sharing paradigms and enabling technologies for successful realization of 5G. One of the key challenges is the availability of evaluation metrics and tools to provide technical information enabling evidence-based policy discussions on the allocation and management of mmWave spectrum. In this article, we present and discuss evaluation metrics and simulation tools for 5G mmWave systems from a regulator's perspective. In particular, we propose a systematic approach to develop meaningful spectrum sharing metrics and demonstrate simulation tools suitable for assessing coverage in 5G mmWave small cell networks.

Performance Analysis of Cache-Enabled Millimeter Wave Small Cell Networks

Millimeter wave (mmWave) small-cell networks can provide high regional throughput, but the backhaul requirement has become a performance bottleneck. This paper proposes a hybrid system that combines traditional backhaul-connected small base stations (SBSs) and cache-enabled SBSs to achieve the maximum area spectral efficiency (ASE) while saving backhaul consumption in mmWave small cell networks. We derive and compare the ASE results for both the traditional and hybrid networks, and also show that the optimal content placement to maximize ASE is to cache the most popular contents. Numerical results demonstrate the performance improvement of deploying cache-enabled SBSs. Furthermore, given a total caching capacity, it is revealed that there is a tradeoff between the cache-enabled SBSs density and individual cache size to maximize the ASE.

Joint wavelet‐based spectrum sensing and FBMC modulation for cognitive mmWave small cell networks

Millimetre-wave (mmWave) 5G communications is an emerging technology to enhance the capacity of existing systems by thousand-fold improvement. Heterogeneous networks employing densely distributed small cells can optimise the available coverage and throughput of 5G systems. Efficiently utilising the spectrum bands by small cells is one of the approaches that will considerably increase the available data rate and capacity of the heterogeneous networks. This challenging task can be achieved by spectrum sensing capability of cognitive radios and new modulation techniques for data transmission. In this study, a wavelet-based filter bank is proposed for spectrum sensing and modulation in 5G heterogeneous networks. The proposed technique can mitigate the spectral leakage and interference by adapting the subcarriers according to cognitive information provided by wavelet packet based spectrum sensing (WPSS) and lowering sidelobes using wavelet-based filter bank multicarrier modulation. The performance improvement of WPSS compared with Fourier-based spectrum sensing is verified in terms of power spectral density comparison and probabilities of detection and false alarm. Meanwhile, the bit error rate performance demonstrates the superiority of the proposed wavelet-based system compared with its Fourier-based counterpart over the 60 GHz mmWave channel.