R. Ford, M. Zhang, M. Mezzavilla, S. Dutta, S. Rangan, M. Zorzi, Achieving Ultra-Low Latency in 5G Millimeter Wave Cellular Networks, arXiv:1602.06925 [cs.NI]
The mmWave bands offer the possibility of a new generation of wide-area cellular networks with massive bandwidths and very low latencies. However, translating the exciting possibilities of the mmWave spectrum for the physical layer to corresponding benefits for end-to-end (E2E) services will require significant changes at multiple layers of the protocol stack. In this article, we identify three particular design issues that need consideration: (i) changes in the architecture of the core network to bring data and network functions physically closer to the end user, (ii) a flexible MAC layer to enable low-latency scheduling while still allowing efficient use of the air-link resources and (iii) fast adaptive congestion control that handles the rapidly varying nature of the mmWave channel. For each of these areas, we survey current solutions, discuss possible directions of innovation and present some novel results from our own research that show the potential of the various techniques in contributing to the reduction of the overall latency to approach the very challenging requirements set forth by the more demanding 5G applications.
F. Boccardi et al., “Spectrum Pooling in MmWave Networks: Opportunities, Challenges, and Enablers,” in IEEE Communications Magazine, vol. 54, no. 11, pp. 33-39, November 2016.
Motivated by the specific characteristics of mmWave technologies, we discuss the possibility of an authorization regime that allows spectrum sharing between multiple operators, also referred to as spectrum pooling. In particular, considering user rate as the performance measure, we assess the benefit of coordination among networks of different operators, study the impact of beamforming at both base stations and user terminals, and analyze the pooling performance at different frequency carriers. We also discuss the enabling spectrum mechanisms, architectures, and protocols required to make spectrum pooling work in real networks. Our initial results show that, from a technical perspective, spectrum pooling at mmWave has the potential to use the resources more efficiently than traditional exclusive spectrum allocation to a single operator. However, further studies are needed in order to reach a thorough understanding of this matter, and we hope that this article will help stimulate further research in this area.
F. Fund, S. Shahsavari, S. Panwar, E. Erkip, S. Rangan, “Do open resources encourage entry into the millimeter wave cellular service market?” In Proceedings of the Eighth Wireless of the Students, by the Students, and for the Students Workshop (S3). ACM, New York, NY, USA, 12-14. October 03 – 07, 2016
Resources that are “open”, such as unlicensed spectrum or a deployment of base stations open to all service providers, may offer greater gains in mmWave bands than at conventional cellular frequencies. However, even when sharing is technically beneficial, it may not be profitable. In this paper, both the technical and economic implications of resource sharing in millimeter wave networks are studied. The results suggest that “open” deployments of neutral small cells that serve subscribers of any service provider encourage market entry by making it easier for networks to reach critical mass, more than “open” (unlicensed) spectrum would. A poster version of this work won first prize at the 2016 IEEE Sarnoff Symposium.
R. Ford, M. Zhang, S. Dutta, M. Mezzavilla, S. Rangan “A Framework for End-to-End Evaluation of 5G mmWaveCellular Networks in ns-3,” Proceedings of the Workshop on ns-3, Pages 85-92, June 15 – 16, 2016, Seattle, WA, USA
The growing demand for ubiquitous mobile data services along with the scarcity of spectrum in the sub-6 GHz bands has given rise to the recent interest in developing wireless systems that can exploit the large amount of spectrum available in the millimeter wave (mmWave) frequency range. Due to its potential for multi-gigabit and ultra-low latency links, mmWave technology is expected to play a central role in 5th Generation (5G) cellular networks. Overcoming the poor radio propagation and sensitivity to blockages at higher frequencies presents major challenges, which is why much of the current research is focused at the physical layer. However, innovations will be required at all layers of the protocol stack to effectively utilize the large air link capacity and provide the end-to-end performance required by future networks. Discrete-event network simulation will be an invaluable tool for researchers to evaluate novel 5G protocols and systems from an end-to-end perspective. In this work, we present the first-of-its-kind, open-source framework for modeling mmWave cellular networks in the ns-3 simulator. Channel models are provided along with a configurable physical and MAC-layer implementation, which can be interfaced with the higher-layer protocols and core network model from the ns-3 LTE module to simulate end-to-end connectivity. The framework is demonstrated through several example simulations showing the performance of our custom mmWave stack.
E. Kurdoglu, Y. Liu, Y. Wang, Y. Shi, C. Gu, J. Lyu, “Real-time Bandwidth Prediction and Rate Estimation for Video Calls over Cellular Networks,” in Proceedings of the 7th International Conference on Multimedia Systems, ACM, 2016 / Klagenfurt, Austria
Cellular links often present highly-varying network bandwidth and packet delays that can cause the video frames to be excessively delayed, destroying the interactivity of the video call. This paper presents Rebera, a cross-layer design of proactive congestion control, video encoding and rate adaptation. Rebera actively measures the available bandwidth in real-time by employing the video frames as packet trains. Using an online linear adaptive filter, Rebera makes a history-based prediction of the future capacity, and determines a bit budget for the video rate adaptation. Our experiments with real cellular link traces demonstrate Rebera can deliver higher bandwidth utilization and shorter packet delays than Apple’s FaceTime. Our work has been adopted in recent release of WeChat, #1 social media app in China, improving video call quality.
A team of scientists led by Dr. Lakshminarayanan Subramanian from NYUWIRELESS and Dr. Umar Saif from ITU, Pakistan have developed a system that can forecast the outbreak of dengue fever by simply analyzing the calling behavior of citizens to a public-health hotline. This telephone-based disease surveillance system can forecast two to three weeks ahead of time, and with intra-city granularity, the outbreak of dengue fever, a mosquito-borne virus that infects up to 100 million people each year world-wide. Other researchers involved in this work include: Nabeel Abdur Rehman (NYU Tandon), Talal Ahmad (NYUWIRELESS and NYU Courant), Shankar Kalyanaraman (Postdoc at NYU Courant at the time of the study) and Fahad Pervaiz (University of Washington). The work is described in the journal Science Advances.
Shu Sun, et al, “Investigation of Prediction Accuracy, Sensitivity, and Parameter Stability of Large-Scale Propagation Path Loss Models for 5G Wireless Communications,” IEEE Trans. Vehicular Technology, 65:5, May 2016.
This paper provides the first rigorous sensitivity analysis to compare various channel models proposed for 5G mmWave standards. The analysis uses aggregate data collected by NYU and its affiliates over large numbers of frequencies and locations. It is demonstrated that physically-based close-in (CI) and close-in with frequency dependence (CIF) channel models provide more robust predictions of path loss when compared to standard alpha-beta-gamma (ABG) path loss models. Partially based on these results, the 3GPP has made the CI model the de facto standard for LOS scenarios and optional for NLOS.
M. Samimi, T. S. Rappaport, 3-D Millimeter-Wave Statistical Channel Model for 5G Wireless System Design, IEEE Transactions on Microwave Theory and Techniques, June 2016.
This paper provides the first complete statistical omni-directional wideband path loss model describing the statistics on the number of clusters and the angle of arrivals and departure, delays and power of the clusters. This model will be invaluable to design and evaluation of mmWave systems. MATLAB simulation code is available at NYU WIRELESS research page.
S. Goyal, Carlo Galiotto, Nicola Marchetti, Shivendra Panwar, Throughput and Coverage for a Mixed Full and Half Duplex Small Cell Network, Proc. IEEE ICC, 2016 (to appear).
This paper presents the throughput and coverage trade-offs for a multiple small cell network with full duplex capability, and shows the potential gains of mixing full and half duplex operations in a small cell network. The paper won the IEEE ICC Best Paper award.
Zhang, Menglei, Marco Mezzavilla, Russell Ford, Sundeep Rangan, Shivendra Panwar, Evangelos Mellios, Di Kong, Andrew Nix, and Michele Zorzi. “Transport Layer Performance in 5G mmWave Cellular.” IEEE/ACK INFOCOM MmNet Workshop, April 2016 (to appear).
While we have made much progress in characterizing mmWave links in isolation, the performance of cellular networks with these links has not been fully understood. The paper provides the first end-to-end complete evaluation of mmWave cellular systems including modeling of the mmWave channel, beamforming tracking, MAC, RLC layers, and congestion control. The analysis combines NYU WIRELESS’ open-source ns3 simulation framework with ray tracing data from Prof. Andy Nix’s lab at the University of Bristol.
C. Nicolas Barati; S. Amir Hosseini; Marco Mezzavilla; Parisa Amiri-Eliasi; Sundeep Rangan; Thanasis Korakis; Shivendra S. Panwar; Michele Zorzi, “Directional initial access for millimeter wave cellular systems,” Proc. Asilomar Conference on Signals, Systems and Computers, Pacific Grove, CA, 2015, pp. 307-311.
A key challenge in designing mmWave cellular systems is initial access: Since mmWave communication relies on highly directional transmissions, the base station and user equipment (UE) must search over a large angular space to find initial directions of communication which can greatly increase the access delay. Among other conclusions, the paper demonstrates that low-resolution fully digital architectures combined with new access protocols can offers order of magnitude faster access delay over conventional phased-array systems today.
F. Liu, E. Bala, E. Erkip, M. C. Beluri and R. Yang, “Small-Cell Traffic Balancing Over Licensed and Unlicensed Bands,” IEEE Transactions on Vehicular Technology, vol. 64, no. 12, pp. 5850-5865, Dec. 2015.
Standard bodies have been actively working on developing small cells with dual band licensed and unlicensed capabilities. The paper develops a practical algorithm for integrated WiFi cells and dual band femtocells to optimize load balancing based on the real-time channel, interference, and traffic conditions of both bands. It is also among the top downloaded papers of the journal.
S. Ulukus Aylin Yener; Elza Erkip; Osvaldo Simeone; Michele Zorzi; Pulkit Grover; Kaibin Huang, “Energy Harvesting Wireless Communications: A Review of Recent Advances,” in IEEE Journal on Selected Areas in Communications, vol. 33, no. 3, pp. 360-381, March 2015.
Energy harvesting is a new technology for wireless communications where devices capture energy from the environment or man-made phenomena. This technology can enable a new generation of ultra-low power devices with minimal need for batteries. This paper provides an overview of the state-of-the-art results in the field and is one of the top downloaded papers in this journal.