Filters








911 Hits in 1.6 sec

Super-Regenerative Receiver

U. L. Rohde, A. K. Poddar
2008 2008 IEEE Sarnoff Symposium  
This article describes the super-regenerative receiver (SRR), a device widely used in short distance telemetry and remote control applications. The difficulty in modeling the regenerative behavior served as the basis for "cut and try" methodology based on results obtained from the simplified model using a conventional approach. This work presents the SRR behavior to practical implementations by dynamically controlling the injection-mode levels of the super-regenerative oscillator (SRO) for
more » ... um sensitivity and dynamic ranges. Integrated Circuit (IC) designers have the luxury of taking for granted that the incremental cost of a transistor is essentially zero, which has given liberty to the large device count circuits that are prevailing today. This is a recent development, but it really was not all that long ago when the economics of circuit design were fundamentally based on the number of device counts, and often the designer was restricted by the relatively expensive active device to try to get blood (or at least rectification) from a stone. 1-13 It is amazing that in the early 1920s, Edwin Armstrong devised a super-regenerative receiver circuit using few components that trade log of gain for bandwidth, contrary to the conventional wisdom that gain and bandwidth should trade off more or less directly. The reduction of the number of the device components is not only cost-effective, but also improves reliability. The characteristics of the super-regenerative receiver to generate large-signal gain at very low bias currents and the ability to operate above the cut-off frequency (f T ) of the RF device make it attractive and the preferred architecture for integrated ultra-low power wireless receivers. Figure 1 depicts a 1940's 500 MHz SRR, which is bulky and require manual calibration, but the circuit operates above the device f T, which was an astonishing accomplishments in those days. 12-13 Fig.1. A 1940's 500 MHz Super-regenerative Receiver (vintage two-tube superregenerative detector) 12 The phenomenon of super-regenerative detection has been the main focus of the research, and it is still an open issue despite significant gains in practical experience and modern CAD tools for design. The SRR circuit uses just a few components, and its basic design is simple, but detailed analysis is complex, due to the time varying and nonlinear characteristics of the receiver circuit. Super-regenerative receivers have been used for many decades, and are still manufactured in large quantities for short-distance data exchanges. Although an SRR has advantages of high gain, simplicity, low cost, low power consumption and constant demodulated output over a wide range of input signal levels, it has also drawbacks of inherent frequency instability. Figure 2 shows the typical block diagram of a super-regenerative receiver, which consists of a matching network, an isolation amplifier, an amplifier with time varying loop gain and a bandpass feedback network forming a regenerative oscillator. 13 Ante nna Passi ve Matching Ne twork Buffe r Ampl ifie r A(t) Ti me varying loop gain Band Pass Positive Fee dback Ne twork S RO Figure 2. A typical bloc diagram of super-regenerative receiver (SRR) The buffer amplifier between the antenna and the SRO (super-regenerative oscillator) performs the following functions: It reduces the RF leakage of the oscillation signal to the antenna, it provides an input match to the antenna via the passive matching network, and it injects the RF input signal current into the oscillator tank without adding significant loading to the SRO. The time varying nature of the loop gain is designed such that the SRO transconductance periodically exceeds the critical values of the transistor transconductance g m necessary to induce instability. Consequently, the SRO periodically starts up and shuts off. The periodic shutdown of the SRO is called "quenching". The start-up time of a SRO (the time from enabling the oscillator until it reaches its saturation voltage V SRO,) can be described by:         = 2 log n SRO rise rise v V t τ (1) where τ rise is the time constant of the exponentially increasing oscillation envelope,
doi:10.1109/sarnof.2008.4520077 fatcat:ftvoawzfybbm5o7ts52242axhi

Video streaming over wireless networks

Zohar Naor
2007 2007 IEEE Sarnoff Symposium  
Video streaming over wireless networks is compelling for many applications, ranging from home entertainment to surveillance to search-and-rescue operations. Interesting technical challenges arise when the unpredictable nature of the wireless radio channel meets the requirements of high data rate and low latency for video transport. This tutorial provides an overview of the technical challenges of video streaming over wireless networks, with a focus on novel cross-layer design solutions for
more » ... rce allocation. Performance comparison of various centralized and distributed schemes are presented, using video streaming over wireless home networks as an application example. INTRODUCTION Video streaming over wireless networks is compelling for many applications, and an increasing number of systems are being deployed. Video streaming of news and entertainment clips to mobile phones is now widely available. For surveillance applications, cameras can be flexibly and cheaply installed, if a wireless network provides connectivity. A wireless local area network (WLAN) might connect various audiovisual entertainment devices in a home. Last, but not least, in search-and-rescue operations, real-time audiovisual communication over wireless ad-hoc networks can save lives. While video streaming requires a steady flow of information and delivery of packets by a deadline, wireless radio networks have difficulties to provide such a service reliably. The problem is challenging due to contention from other network nodes, as well as intermittent interference from external radio sources such as microwave ovens or cordless phones. For mobile nodes, multi-path fading and shadowing might further increase the variability in link capacities and transmission error rate. For such systems to deliver the best end-to-end performance, video coding, reliable transport and wireless resource allocation must be considered jointly, thus moving from the traditional layered system architecture to a cross-layer design. This tutorial provides an overview of the design challenges for video streaming over wireless networks, and surveys recent research efforts in the field. The paper is organized by wireless streaming problems of increasing complexity, ranging from the simple scenario of delivering a single video stream over a single wireless link (Section 2), to sharing a wireless multi-access channel among multiple video streams (Section 3) to the general case of multiple streams sharing a mesh network (Section 4). While most of the issues discussed are general, we use high-definition (HD) video streaming over 802.11a home networks as a concrete example when presenting simulation results.
doi:10.1109/sarnof.2007.4567349 fatcat:un5k57eusffoxmum2rlpgnk6jm

Radio resource management for OFDMA uplinks

Patrick Hosein
2007 2007 IEEE Sarnoff Symposium  
The next generation of wireless networks (4G) will use OFDMA (Orthogonal Frequency Division Multiple Access) in the reverse link. In OFDMA, the reverse link resources assigned to a user are called tiles each of which consists of a subset of consecutive subcarriers. Since at most one user is assigned to each of these tiles then reverse link transmissions within a sector are orthogonal. However, the transmission is affected by intercell interference since users in adjacent sectors may also have
more » ... en assigned to the same tile. If those users in the adjacent sectors transmitted with high power then the intercell interference may severely limit the SINR achieved by the user. Therefore user transmission powers must be carefully managed to avoid excessive intercell interference. In this paper we propose a distributed algorithm for the problem and use numerical results to illustrate its performance.
doi:10.1109/sarnof.2007.4567344 fatcat:jsbijyts5za23kbeegrg7xwz5y

Safety issues in collaborative vehicle control

N. F. Maxemchuk
2009 2009 IEEE Sarnoff Symposium  
Collaborative driving systems are complex, distributed systems that control physical vehicles. They can reduce accidents, decrease fuel consumption, reduce commute times and increase the capacity of highways. However, errors in their implementation can cause unsafe conditions that result in the loss of human life. Our objective is to find ways to design, verify, and quantify safety in these systems. In this paper we describe a collaborative driving system that assists in safely and quickly
more » ... ng vehicles when highways merge, following tolls, and at construction or accident sites. We describe 1) an architecture that partitions the application into modules that can be tested and modified independently, 2) a communication protocol that provides an unconventional set of services that simplifies the implementation of the system, and 3) a strategy for cooperation between the human operator and the system.
doi:10.1109/sarnof.2009.4850377 fatcat:3aocbnerkfhxnpqftu2soy4iti

MoCCA: A mobile cellular cloud architecture

Amitabh Mishra, Gerald Masson
2012 2012 35th IEEE Sarnoff Symposium  
This paper presents MoCCA -a cellular cloud architecture for building mobile clouds using small-footprint micro-servers running on cell phones. We provide details of this architecture which is based on GSM standard, discuss several challenges, and include performance results to validate the assumptions that a mobile cellular cloud can indeed be in the realm of possibilities.
doi:10.1109/sarnof.2012.6222749 dblp:conf/sarnoff/MishraM12 fatcat:il3fdn2o3vfchmzau2ufbjmdfm

Mitigating Deafness in Multiple Beamforming Antennas

Vivek Jain, Dharma P. Agrawal
2006 2006 IEEE Sarnoff Symposium  
Deafness is considered as a major medium access problem arising due to directional communication in beamforming antennas. In this paper, we provide a novel algorithm for mitigating deafness (AMD) in such antennas. The algorithm extends the directional virtual carrier sensing mechanism by dynamically maintaining parameters for every beam. AMD can easily be implemented with the existing medium access control (MAC) protocols for multiple beamforming antennas. Simulation results show that
more » ... le performance gains can be achieved when the proposed algorithm is employed by the existing MAC schemes.
doi:10.1109/sarnof.2006.4534749 fatcat:f6ojdzpdg5gkpgve6t2eckq7k4

Securing resource-constrained wireless ad hoc networks

Yuguang Fang, Yanchao Zhang
2007 2007 IEEE Sarnoff Symposium  
Wireless ad-hoc networks have seen widespread usage due to their ease of implementation. Most of these devices are battery operated devices and therefore suffer from serious limitations in terms of power consumption. It becomes desirable to implement power aware routing schemes that minimises the power consumption and at the same time improves the traffic capacity of the network. The broadcast nature and the spatial diversity of the wireless communication is utilised efficiently in the
more » ... stic routing scheme and achieves improvement in the performance of the wireless networks. In contrast to the traditional routing scheme which makes use of a predetermined route for packet transmission, the opportunistic routing scheme defines a predefined forwarding candidate list formed by using single network metrics. In this paper, a protocol is proposed which uses multiple metrics such as residual energy and link quality for route selection. A variable power control algorithm is also implemented to transmit the packets at the optimal power level and therefore achieves considerable power saving in the resource constrained wireless ad-hoc environment. Using extensive simulations, we study the impact of variable power control on the network capacity, power saving and connectivity of the network.
doi:10.1109/sarnof.2007.4567365 fatcat:2qjd2rqmrjdfza62j4vkl26p6y

New Directions in Peer-to-Peer Malware

David Dittrich, Sven Dietrich
2008 2008 IEEE Sarnoff Symposium  
doi:10.1109/sarnof.2008.4520101 fatcat:nvxzinprwjc5plw64rkpwovh7i

Making the case for EAP channel bindings

T. Charles Clancy, Katrin Hoeper
2009 2009 IEEE Sarnoff Symposium  
In current networks that use EAP and AAA for authenticated admission control, such as WiFi, WiMAX, and various 3G internetworking protocols, a malicious base station can advertise false information to prospective users in an effort to manipulate network access in some way. This paper identifies and discusses the resulting threats (e.g. the lying NAS problem in enterprise networks and the newly identified lying provider problem in roaming environments) and shows how these threats can be
more » ... for a number of attacks, including traffic herding, denial of service, cryptographic downgrade attacks, and forced roaming. Finally, the paper presents how an EAP channel binding protocol can thwart the identified attacks by allowing a client to inform the EAP server about the unauthenticated information it received during the network selection process. The back-end server can then ensure the consistency of the advertised information with its configured policy. As a result, EAP channel bindings enable an end-to-end validation of network properties, which is otherwise infeasible in existing AAA infrastructures. Standardization activities currently exist within the IETF to implement this technique.
doi:10.1109/sarnof.2009.4850319 fatcat:yqfktzbwibcvxb7t4cgqqmbn3e

Security vulnerabilities and solutions for packet sampling

Sharon Goldberg, Jennifer Rexford
2007 2007 IEEE Sarnoff Symposium  
Packet sampling supports a range of Internet measurement applications including characterizing the spatial flow of traffic through a network for traffic engineering purposes, identifying the flows utilizing a link for billing purposes or for intrusion detection, and monitoring end-to-end data-path quality. However, packet-sampling mechanisms must be robust to adversarial hosts that craft packet streams that are disproportionately selected by a packet sampler. For example, a botnet flooding a
more » ... work with packets in a denial-of-service attack, or a greedy customer trying to avoid being billed for network utilization, each have a strong incentive to craft packet streams that evade selection by the packet sampler. In this paper, we focus on securing the passive packet sampling mechanisms recommended by PSAMP (the IETF Packet Sampling working group [1]) against adversarial hosts. We show that (1) some of the packet sampling techniques suggested in current drafts of the PSAMP charter have security vulnerabilities, (2) secure uncoordinated sampling can be achieved using random sampling with a cryptographic random number generator, and (3) secure coordinated sampling requires a cryptographic pseudorandom function, keyed with a secret key that should be changed each time the sampler leaks information to the hosts. • Greedy customers have an incentive to generate packet streams that evade selection by the Sampler in order to avoid being billed by providers for network utilization. • Malicious users or botnets performing a denial of service (DoS) attack have an incentive to generate packets that evade selection by the Sampler in order to avoid an intrusion detection system. • Malicious users or botnets may attempt to flood the
doi:10.1109/sarnof.2007.4567339 fatcat:oe6s5n47azcaxeakmyp5w6yu3y

Band-segment protection in multi-granular optical networks

Yang Wang, Xiaojun Cao
2009 2009 IEEE Sarnoff Symposium  
Protections are traditionally realized at fiber level (e.g., link protection) or wavelength level (e.g., path protection) in wavelength routing networks. With the advancing of waveband switching (WBS) techniques, these schemes may fail to efficiently accommodate the major goal of minimizing the node size (i.e., port count) in WBS networks. To achieve both the survivability and port reduction, we introduce the band-segment (BS) concept in WBS networks by which we can operate the protection at
more » ... eband level thus saving ports. Accordingly, we propose shared and dedicated protection schemes using band-segments, namely shared band-segment protection (SBSP) and dedicated bandsegment protection (DBSP) for WBS networks. Our simulation shows DBSP outperforms dedicated path protection dramatically in terms of port count, while SBSP can achieve both resource sharing and port reduction.
doi:10.1109/sarnof.2009.4850305 fatcat:uxwrgrrhlzetdatlti6qhhraam

Information Assurance in the SQoS Network

Pitipatana Sakarindr, Nirwan Ansari, Roberto Rojas-Cessa
2006 2006 IEEE Sarnoff Symposium  
In the SQoS network as introduced in [1] and [2], the border router in every autonomous system (AS) provides customized security mechanisms to the incoming packets. Some serious problems have been recently raised particularly when there are one or more compromised routers that attempt to modify, delete, or fabricate any part or the whole packet into the SQoS network. The compromised router can either passively or actively perform the malicious activities against the forwarding packets. The SQoS
more » ... network does not explicitly specify the method to detect whether the data contained in the packets have been abused by the compromised routers or by the end host itself. We deliberate the threats and later propose several methods to detect both the malicious routers and end hosts such that SQoS information and payload is authentic and integrity-protected.
doi:10.1109/sarnof.2006.4534794 fatcat:rfkmuoer4vamhiu3mhat3sf6dm

Challenges and Applications for Network-Processor-Based Programmable Routers

Tilman Wolf
2006 2006 IEEE Sarnoff Symposium  
The growth in ubiquity, performance, and commercial and academic use of computer networks continues to demand more performance and flexibility from the underlying network infrastructure. The lack of security, quality of service, and manageability in the current Internet poses a significant challenge and highlights the importance of considering other network designs. Programmable routers provide a vehicle for experimenting with new architectures that allow the dynamic deployment of new protocols
more » ... and services. To achieve the necessary throughput performance, programmable routers employ network processors, which are embedded system-on-a-chip multiprocessors. This paper discusses the challenges that such systems pose in terms of system architecture, programming abstraction, and deployment. The potential applications highlight the benefits of making router programmability a first-class networking function.
doi:10.1109/sarnof.2006.4534802 fatcat:mabeoiq4tzapljvddxlndnlbvm

Comparison of bi-directional relaying protocols

Sang Joon Kim, Natasha Devroye, Patrick Mitran, Vahid Tarokh
2008 2008 IEEE Sarnoff Symposium  
In a bi-directional relay channel, two nodes wish to exchange independent messages over a shared wireless channel with the help of a relay. In this paper, we derive achievable rate regions for four new half-duplex protocols and compare these to four existing half-duplex protocols and outer bounds. In time, our protocols consist of either two or three phases. In the two phase protocols, both users simultaneously transmit during the first phase and the relay alone transmits during the second
more » ... , while in the three phase protocol the two users sequentially transmit followed by a transmission from the relay. The relay may forward information in one of four manners; we outline existing Amplify and Forward (AF) and Decode and Forward (DF) relaying schemes and introduce novel Compress and Forward (CF), and Mixed Forward schemes. We derive achievable rate regions for the CF and Mixed relaying schemes for the two and three phase protocols. Finally, we provide a comprehensive treatment of 8 possible half-duplex bi-directional relaying protocols in Gaussian noise, obtaining their respective achievable rate regions, outer bounds, and their relative performance under different SNR and relay geometries. Index Termsbi-directional communication, achievable rate regions, compress and forward, relaying
doi:10.1109/sarnof.2008.4520117 fatcat:z4vy3i25zreyxn463u4l6jtdue

Energy-efficient schemes for on-demand relaying

Fanny Parzysz, Mai H. Vu, Francois Gagnon
2011 34th IEEE Sarnoff Symposium  
This paper approaches the fading relay channel from an energy consumption perspective and proposes an ondemand scheme based on superposition coding and incremental redundancy (IR). It aims at minimizing the relay's energy consumption, while maintaining a rate desired by the source. The source divides its message into two parts, which allows the destination to request only the missing part(s) from the relay. We derive the set of joint power and rate allocation optimal for energy. The proposed
more » ... eme only requires local SNR knowledge and is robust to feedback delay. Compared to classical IR, this scheme always provides energy gain, which can attain 50% (at each instant and on average), and helps decrease the outage probability.
doi:10.1109/sarnof.2011.5876473 fatcat:jec45sd4izbvdgcy5j624mlfja
« Previous Showing results 1 — 15 out of 911 results