AT and T Laboratories

Middletown, United States

AT and T Laboratories

Middletown, United States
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Novlan T.D.,University of Texas at Austin | Ganti R.K.,University of Texas at Austin | Andrews J.G.,University of Texas at Austin | Ghosh A.,AT and T Laboratories
GLOBECOM - IEEE Global Telecommunications Conference | Year: 2011

Fractional frequency reuse (FFR) is an interference management technique well-suited to OFDMA-based cellular networks wherein the cells are partitioned into spatial regions with different frequency reuse factors. To date, FFR techniques have been typically been evaluated through system-level simulations using a hexagonal grid for the base station locations. This paper instead focuses on analytically evaluating the two main types of FFR deployments - Strict FFR and Soft Frequency Reuse (SFR) - using a Poisson point process to model the base station locations. The results are compared with the standard grid model and an actual urban deployment. Under reasonable special cases for modern cellular networks, our results reduce to simple closed-form expressions, which provide insight into system design guidelines and the relative merits of Strict FFR, SFR, universal reuse, and fixed frequency reuse. © 2011 IEEE.


Ramachandran G.,AT and T Laboratories | Ciavattone L.,AT and T Laboratories | Morton A.,AT and T Laboratories
IEEE International Workshop on Quality of Service, IWQoS | Year: 2011

In this paper we show data plane restoration measurements for restoration under backbone link failures for a large network with IP/MPLS OSPF routing and also for the same backbone with Traffic Engineering (TE) and Fast Reroute (FRR) deployed. Our study is unique as we analyzed a significant quantity of measurements obtained from a production network over a 14-month period encompassing many link failures. The results show that TE/FRR restoration reduces outage-induced loss-duration substantially as compared to OSPF restoration. We also note that for both OSPF and FRR the course of restoration is not as simple as is commonly believed. A detailed study of the data shows that while loss-duration and overall duration is much reduced, TE/FRR results in path changes with no detectable loss over a period of seconds. Thus implementation of TE/FRR in a network results in a vast improvement in behavior for all data flows. © 2011 IEEE.


Novlan T.D.,University of Texas at Austin | Ganti R.K.,Indian Institute of Technology Madras | Ghosh A.,AT and T Laboratories | Andrews J.G.,University of Texas at Austin
IEEE Transactions on Wireless Communications | Year: 2011

Fractional frequency reuse (FFR) is an interference management technique well-suited to OFDMA-based cellular networks wherein the bandwidth of the cells is partitioned into regions with different frequency reuse factors. To date, FFR techniques have been typically been evaluated through system-level simulations using a hexagonal grid for the base station locations. This paper instead focuses on analytically evaluating the two main types of FFR deployments-Strict FFR and Soft Frequency Reuse (SFR)-using a Poisson point process to model the base station locations. The results are compared with the standard grid model and an actual urban deployment. Under reasonable special cases for modern cellular networks, our results reduce to simple closed-form expressions, which provide insight into system design guidelines and the relative merits of Strict FFR, SFR, universal reuse, and fixed frequency reuse. Finally, a SINR-proportional resource allocation strategy is proposed based on the analytical expressions and we observe that FFR provides an increase in the sum-rate as well as the well-known benefit of improved coverage for cell-edge users. © 2011 IEEE.


Liou J.-C.,AT and T Laboratories
Proceedings of the 6th IASTED International Conference on Software Engineering and Applications, SEA 2002 | Year: 2012

During the last decade, software engineering researchers have tried to identify the success and obstacle factors to the software development. Conclusions from most of the researches related to the issue show that software process is one of the most important subjects contributing into the success or failure to the software development. The Capability Maturity Model (CMM), the ISO9000 series, and best practices are some well known parts of the process management and improvement standards or guidelines. Among them, the CMM is the one specially focusing on the software development. In this paper, we demonstrate that leadership and other human factors can negatively affect the process maturity of software development organizations. Even for those organizations that are assessed for certain levels of process maturity, with no periodical audit from CMM assessors, their process maturity still under influence of these factors. These human factors, based on the industry experience, are identified and possible resolutions are discussed.


Novlan T.,University of Texas at Austin | Andrews J.G.,University of Texas at Austin | Sohn I.,University of Texas at Austin | Ganti R.K.,University of Texas at Austin | Ghosh A.,AT and T Laboratories
GLOBECOM - IEEE Global Telecommunications Conference | Year: 2010

Fractional frequency reuse (FFR) is an interference coordination technique well-suited to OFDMA based wireless networks wherein cells are partitioned into spatial regions with different frequency reuse factors. This work focuses on evaluating the two main types of FFR deployments: Strict FFR and Soft Frequency Reuse (SFR). Relevant metrics are discussed, including outage probability, network throughput, spectral efficiency, and average cell-edge user SINR. In addition to analytical expressions for outage probability, system simulations are used to compare Strict FFR and SFR with universal frequency reuse based on a typical OFDMA deployment and uniformly distributed users. Based on the analysis and numerical results, system design guidelines and a detailed picture of the tradeoffs associated with the FFR systems are presented, showing that Strict FFR provides the greatest overall network throughput and highest cell-edge user SINR, while SFR balances the requirements of interference reduction and resource efficiency. ©2010 IEEE.


Quackenbush S.R.,AT and T Laboratories
143rd Technical Conference and Exhibition | Year: 2016

MPEG-4 standardizes natural audio coding at bitrates ranging from 2 kbit/s, suitable for intelligible speech coding, to 64 kbit/s per channel, suitable for high-quality audio coding. Within this range, three categories of coding are defined: parametric coding, Code Excited Linear Predictive coding (CELP) and time/frequency (T/F) coding. The unique contribution of MPEG-4 audio is that not only does it scale across a wide range of bitrates, but it also scales across a broad set of other parameters, such as sampling rate, bandwidth, voice pitch and complexity. This paper presents an overview of the MPEG-4 natural audio coding framework and each of its component coding techniques. © 2001 Society of Motion Picture and Television Engineers, Inc.


Novlan T.D.,University of Texas at Austin | Ganti R.K.,Indian Institute of Technology Madras | Ghosh A.,AT and T Laboratories | Andrews J.G.,University of Texas at Austin
IEEE Transactions on Communications | Year: 2012

Interference management techniques are critical to the performance of heterogeneous cellular networks, which will have dense and overlapping coverage areas, and experience high levels of interference. Fractional frequency reuse (FFR) is an attractive interference management technique due to its low complexity and overhead, and significant coverage improvement for low-percentile (cell-edge) users. Instead of relying on system simulations based on deterministic access point locations, this paper instead proposes an analytical model for evaluating Strict FFR and Soft Frequency Reuse (SFR) deployments based on the spatial Poisson point process. Our results both capture the non-uniformity of heterogeneous deployments and produce tractable expressions which can be used for system design with Strict FFR and SFR. We observe that the use of Strict FFR bands reserved for the users of each tier with the lowest average \sinr provides the highest gains in terms of coverage and rate, while the use of SFR allows for more efficient use of shared spectrum between the tiers, while still mitigating much of the interference. Additionally, in the context of multi-tier networks with closed access in some tiers, the proposed framework shows the impact of cross-tier interference on closed access FFR, and informs the selection of key FFR parameters in open access. © 1972-2012 IEEE.


Oda S.,Fujitsu Limited | Miyabe M.,Fujitsu Limited | Yoshida S.,Fujitsu Limited | Katagiri T.,Fujitsu Limited | And 4 more authors.
2016 Optical Fiber Communications Conference and Exhibition, OFC 2016 | Year: 2016

A living network is demonstrated, that, unlike today's static planning, adapts to varying network conditions, and allows operation close to performance limits. An autonomously operating test-bed shows feasibility with an allocated margin of only 1.5 dB. © 2016 OSA.


Chiu A.L.,AT and T Laboratories | Choudhury G.,AT and T Laboratories | Clapp G.,Applied Research | Doverspike R.,AT and T Laboratories | And 15 more authors.
Journal of Optical Communications and Networking | Year: 2012

The Core Optical Networks (CORONET) program addresses the development of architectures, protocols, and network control and management to support the future advanced requirements of both commercial and government networks, with a focus on highly dynamic and highly resilient multi-terabit core networks. CORONET encompasses a global network supporting a combination of IP and wavelength services. Satisfying the aggressive requirements of the program required a comprehensive approach addressing connection setup, restoration, quality of service, network design, and nodal architecture. This paper addresses the major innovations developed in Phase 1 of the program by the team led by Telcordia and AT&T. The ultimate goal is to transfer the technology to commercial and government networks for deployment in the next few years. © 2011 Optical Society of America.

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