Author
Sampath Rangarajan
Other affiliations: NEC, University of Science and Technology of China, University of Illinois at Urbana–Champaign
Bio: Sampath Rangarajan is an academic researcher from Princeton University. The author has contributed to research in topics: Scheduling (computing) & Wireless network. The author has an hindex of 40, co-authored 228 publications receiving 8165 citations. Previous affiliations of Sampath Rangarajan include NEC & University of Science and Technology of China.
Papers
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TL;DR: In this article, the authors present a survey of self-interference mitigation techniques for in-band full-duplex (IBFD) wireless systems and discuss the challenges and opportunities in the design and analysis of IBFD wireless systems.
Abstract: In-band full-duplex (IBFD) operation has emerged as an attractive solution for increasing the throughput of wireless communication systems and networks. With IBFD, a wireless terminal is allowed to transmit and receive simultaneously in the same frequency band. This tutorial paper reviews the main concepts of IBFD wireless. One of the biggest practical impediments to IBFD operation is the presence of self-interference, i.e., the interference that the modem's transmitter causes to its own receiver. This tutorial surveys a wide range of IBFD self-interference mitigation techniques. Also discussed are numerous other research challenges and opportunities in the design and analysis of IBFD wireless systems.
1,752 citations
Posted Content•
TL;DR: This tutorial surveys a wide range of IBFD self-interference mitigation techniques and discusses numerous other research challenges and opportunities in the design and analysis of IB FD wireless systems.
Abstract: In-band full-duplex (IBFD) operation has emerged as an attractive solution for increasing the throughput of wireless communication systems and networks. With IBFD, a wireless terminal is allowed to transmit and receive simultaneously in the same frequency band. This tutorial paper reviews the main concepts of IBFD wireless. Because one the biggest practical impediments to IBFD operation is the presence of self-interference, i.e., the interference caused by an IBFD node's own transmissions to its desired receptions, this tutorial surveys a wide range of IBFD self-interference mitigation techniques. Also discussed are numerous other research challenges and opportunities in the design and analysis of IBFD wireless systems.
1,549 citations
22 Aug 2012
TL;DR: The design and implementation of MIDU is presented, the first MIMO full duplex system for wireless networks, and it is shown that MIDU's design provides large amounts of self-interference cancellation with several key advantages.
Abstract: Given that full duplex (FD) and MIMO both employ multiple antenna resources, an important question that arises is how to make the choice between MIMO and FD? We show that optimal performance requires a combination of both to be used. Hence, we present the design and implementation of MIDU, the first MIMO full duplex system for wireless networks. MIDU employs antenna cancellation with symmetric placement of transmit and receive antennas as its primary RF cancellation technique. We show that MIDU's design provides large amounts of self-interference cancellation with several key advantages: (i) It allows for two stages of additive antenna cancellation in tandem, to yield as high as 45 dB self-interference suppression; (ii) It can potentially eliminate the need for other forms of analog cancellation, thereby avoiding the need for variable attenuator and delays; (iii) It easily scales to MIMO systems, therefore enabling the coexistence of MIMO and full duplex. We implemented MIDU on the WARP FPGA platform, and evaluated its performance against half duplex (HD)-MIMO. Our results reveal that, with the same number of RF chains, MIDU can potentially double the throughput achieved by half duplex MIMO in a single link; and provide median gains of at least 20% even in single cell scenarios, where full duplex encounters inter-client interference. Based on key insights from our results, we also highlight how to efficiently enable scheduling for a MIDU node.
351 citations
TL;DR: In virtualizing a base station's uplink and downlink resources into slices, NVS meets three key requirements-isolation, customization, and efficient resource utilization-using two novel features: a provably optimal slice scheduler and a generic framework for efficiently enabling customized flow scheduling within the base station on a per-slice basis.
Abstract: This paper describes the design and implementation of a network virtualization substrate (NVS ) for effective virtualization of wireless resources in cellular networks. Virtualization fosters the realization of several interesting deployment scenarios such as customized virtual networks, virtual services, and wide-area corporate networks, with diverse performance objectives. In virtualizing a base station's uplink and downlink resources into slices, \ssr NVS meets three key requirements-isolation, customization, and efficient resource utilization-using two novel features: 1) NVS introduces a provably optimal slice scheduler that allows existence of slices with bandwidth-based and resource-based reservations simultaneously; and 2) NVS includes a generic framework for efficiently enabling customized flow scheduling within the base station on a per-slice basis. Through a prototype implementation and detailed evaluation on a WiMAX testbed, we demonstrate the efficacy of \ssr NVS. For instance, we show for both downlink and uplink directions that \ssr NVS can run different flow schedulers in different slices, run different slices simultaneously with different types of reservations, and perform slice-specific application optimizations for providing customized services.
339 citations
18 May 2009
TL;DR: Comprehensive evaluations indicate that in addition to providing improved coverage indoors, with carefully designed resource management solutions that leverage spatial reuse, femto cells have a great potential to increase the system performance by two folds.
Abstract: Femto cells are a cost-effective means of providing ubiquitous connectivity in future broadband wireless networks. While their primary purpose has been to improve coverage in current solutions, their decreased cell sizes in turn also provide improved cell capacity through increased spatial reuse. The demand for bandwidth-intensive IP services will soon necessitate the need to tap into this improved capacity. However, the lack of direct coordination between the macro and femto cells, and the completely distributed nature of femto cells make this an extremely challenging task. In this work, we address this challenge by providing efficient resource management solutions for OFDMA-based femto cells along with performance guarantees. In the process, we consider two models that tradeoff performance and overhead. We also propose a novel location-based resource management solution for leveraging maximal spatial reuse from femto cells. Our comprehensive evaluations indicate that in addition to providing improved coverage indoors, with carefully designed resource management solutions that leverage spatial reuse, femto cells have a great potential to increase the system performance by two folds.
176 citations
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TL;DR: This article provides an overview of signal processing challenges in mmWave wireless systems, with an emphasis on those faced by using MIMO communication at higher carrier frequencies.
Abstract: Communication at millimeter wave (mmWave) frequencies is defining a new era of wireless communication. The mmWave band offers higher bandwidth communication channels versus those presently used in commercial wireless systems. The applications of mmWave are immense: wireless local and personal area networks in the unlicensed band, 5G cellular systems, not to mention vehicular area networks, ad hoc networks, and wearables. Signal processing is critical for enabling the next generation of mmWave communication. Due to the use of large antenna arrays at the transmitter and receiver, combined with radio frequency and mixed signal power constraints, new multiple-input multiple-output (MIMO) communication signal processing techniques are needed. Because of the wide bandwidths, low complexity transceiver algorithms become important. There are opportunities to exploit techniques like compressed sensing for channel estimation and beamforming. This article provides an overview of signal processing challenges in mmWave wireless systems, with an emphasis on those faced by using MIMO communication at higher carrier frequencies.
2,380 citations
TL;DR: In this article, the authors present a survey of self-interference mitigation techniques for in-band full-duplex (IBFD) wireless systems and discuss the challenges and opportunities in the design and analysis of IBFD wireless systems.
Abstract: In-band full-duplex (IBFD) operation has emerged as an attractive solution for increasing the throughput of wireless communication systems and networks. With IBFD, a wireless terminal is allowed to transmit and receive simultaneously in the same frequency band. This tutorial paper reviews the main concepts of IBFD wireless. One of the biggest practical impediments to IBFD operation is the presence of self-interference, i.e., the interference that the modem's transmitter causes to its own receiver. This tutorial surveys a wide range of IBFD self-interference mitigation techniques. Also discussed are numerous other research challenges and opportunities in the design and analysis of IBFD wireless systems.
1,752 citations
Posted Content•
TL;DR: This tutorial surveys a wide range of IBFD self-interference mitigation techniques and discusses numerous other research challenges and opportunities in the design and analysis of IB FD wireless systems.
Abstract: In-band full-duplex (IBFD) operation has emerged as an attractive solution for increasing the throughput of wireless communication systems and networks. With IBFD, a wireless terminal is allowed to transmit and receive simultaneously in the same frequency band. This tutorial paper reviews the main concepts of IBFD wireless. Because one the biggest practical impediments to IBFD operation is the presence of self-interference, i.e., the interference caused by an IBFD node's own transmissions to its desired receptions, this tutorial surveys a wide range of IBFD self-interference mitigation techniques. Also discussed are numerous other research challenges and opportunities in the design and analysis of IBFD wireless systems.
1,549 citations
TL;DR: This paper surveys the state-of-the-art literature on C-RAN and can serve as a starting point for anyone willing to understand C- RAN architecture and advance the research on the network.
Abstract: Cloud Radio Access Network (C-RAN) is a novel mobile network architecture which can address a number of challenges the operators face while trying to support growing end-user's needs. The main idea behind C-RAN is to pool the Baseband Units (BBUs) from multiple base stations into centralized BBU Pool for statistical multiplexing gain, while shifting the burden to the high-speed wireline transmission of In-phase and Quadrature (IQ) data. C-RAN enables energy efficient network operation and possible cost savings on baseband resources. Furthermore, it improves network capacity by performing load balancing and cooperative processing of signals originating from several base stations. This paper surveys the state-of-the-art literature on C-RAN. It can serve as a starting point for anyone willing to understand C-RAN architecture and advance the research on C-RAN.
1,516 citations
TL;DR: This paper analyzes the MEC reference architecture and main deployment scenarios, which offer multi-tenancy support for application developers, content providers, and third parties, and elaborates further on open research challenges.
Abstract: Multi-access edge computing (MEC) is an emerging ecosystem, which aims at converging telecommunication and IT services, providing a cloud computing platform at the edge of the radio access network MEC offers storage and computational resources at the edge, reducing latency for mobile end users and utilizing more efficiently the mobile backhaul and core networks This paper introduces a survey on MEC and focuses on the fundamental key enabling technologies It elaborates MEC orchestration considering both individual services and a network of MEC platforms supporting mobility, bringing light into the different orchestration deployment options In addition, this paper analyzes the MEC reference architecture and main deployment scenarios, which offer multi-tenancy support for application developers, content providers, and third parties Finally, this paper overviews the current standardization activities and elaborates further on open research challenges
1,351 citations