1. System-Level Power Management: An Overview,
Ali Iranli and Massoud Pedram,
In The VLSI Handbook, Edited by W-K. Chen, Taylor and Francis, 2006.
Abstract: One of the key challenges of computer system design is the management and conservation of energy. This challenge is evident in a number of ways. The goal may be to extend the battery lifetime of a portable, battery-powered device. The processing power, memory, and network bandwidth of such devices are increasing quickly, resulting in an increase in demand for higher power dissipation, while the battery capacity is improving at a much slower pace. Other goals may be to limit the cooling requirements of a computer system or to reduce the financial cost of operating a large computing facility with a high energy bill. This chapter focuses on techniques which dynamically manage electronic systems in order to minimize its energy consumption. Ideally, the problem of managing the energy consumed by electronic systems should be addressed at all levels of design, ranging from low-power circuits and architectures to application and system software capable of adapting to the available energy source. Many research and industrial efforts are currently underway to develop low-power hardware as well as energyaware application software in the design of energy-efficient computing systems. Our objective in this chapter is to explore what the system software, vis-ŕis the operating system (OS), can do within its own resource management functions to improve the energy efficiency of the computinng system without requiring any specialized, low-power hardware or any explicit assistance from application software and compilers. There are two approaches to consider at the OS-level for attacking most of the specific energy-related goals described above. The first is to develop resource management policies that eliminate waste or overhead and allow energy-efficient use of the devices. The second is to change the system workload so as to reduce the amount of work to be done, often by changing the fidelity of objects accessed, in a manner which will be acceptable to the user of the application. This chapter provides a first introduction to these two approaches with appropriate review of related works.
1. Cycle-based Decomposition of Markov Chains with Applications to Low Power Synthesis and Sequence Compaction for Finite State Machines,
Ali Iranli and Massoud Pedram,
To appear in IEEE Trans. on Computer Aided Design, 2006.
Abstract: This paper advances the state-of-the-art by presenting a well-founded mathematical framework for modeling and manipulating Markov processes. The key idea is based on the fact that a Markov process can be decomposed into a collection of directed cycles with positive weights, which are proportional to the probability of the cycle traversals in a random walk. Two applications of this new formalism in the computer aided design area are studied. In the first application, we present a new state assignment technique to reduce dynamic power consumption in finite state machines. The technique comprises of first decomposing the state machine into a set of cycles and then performing a state assignment by using Gray codes. The proposed encoding algorithm reduces power consumption by an average of 15%. The second application is sequence compaction for improving the efficiency of dynamic power simulators. The proposed method is based on the cycle decomposition of the Markov process representing the given input sequence and then selecting a subset of these cycles to construct the compacted sequence.
10. Crosstalk Analysis in nanometer technologies,
Shahin Nazarian, Ali Iranli, and Massoud Pedram,
to appear in Proc. of Great Lakes Symposium on VLSI (GLSVLSI), Apr. 2006.
Abstract:
Process variations have become a key concern of circuit designers because of their significant, yet hard to predict impact on performance and signal integrity of VLSI circuits. Statistical approaches have been suggested as the most effective substitute for corner-based approaches to deal with the variability of present process technology nodes. This paper introduces a statistical analysis of the crosstalk-aware delay of coupled interconnects considering process variations. The few existing works that have studied this problem suffer not only from shortcomings in their statistical models, but also from inaccurate crosstalk circuit models. We utilize an accurate distributed RC-(pi) model of the interconnections to be able to model process variations close to reality. The considerable effect of correlation among the parameters of neighboring wire segments is also indicated. Statistical properties of the crosstalk-aware output delay are characterized and presented as closed-formed expressions. Monte Carlo Spice-based experimental results demonstrate the effectiveness of the proposed approach in accurately modeling the correlation-aware process variations and their impact on interconnect delay when crosstalk is present.
9. Energy Efficient Strategies for deployment of a Two-level Wireless Sensor Network ,
Ali Iranli, Morteza Maleki, and Massoud Pedram,
Proc. of International Symposium on Low Power Electronics and Design, Aug. 2005.
Abstract: We investigate and develop energy-efficient strategies for deployment of wireless sensor networks (WSN) for the purpose of monitoring some phenomenon of interest in a coverage region. We first describe a two-level WSN structure where the sensors in the lower level monitor their surrounding environment and the micro-servers in the top level provide connectivity between the sensors and a base station. We then formulate and solve the problem of assigning positions and initial energy levels to the micro-servers and concurrently partitioning the sensors into clusters assigned to individual micro-servers so as to maximize the monitoring lifetime of the two-level WSN subject to a total energy budget. This problem, called MDEA, is solved for both collinear deployment and planar deployment situations. Our experimental results show that the design and deployment of such a two-level WSN increase the network lifetime by a factor of two or more compared to a flat WSN with the same total initial energy and quality of monitoring.
8. DTM: Dynamic Tone Mapping for Backlight Scaling ,
Ali Iranli, and Massoud Pedram,
Proc. of Design Automation Conference, Jun. 2005.
Abstract: This paper proposes an approach for pixel transformation of
the displayed image to increase the potential energy saving of the
backlight scaling method. The proposed approach takes advantage of
human visual system characteristics and tries to minimize the incurred
distortion between the perceived brightness values of the individual
pixels in the original image and those of the backlight scaled image.
This is in contrast to previous backlight scaling approaches where the
luminance values of the individual pixels are matched. Moreover, the
proposed approach based on tone mapping is amenable to highly
efficient hardware realization and does not require any information
about the histogram of the displayed image, which makes it desirable for
video applications. Experimental results show that the dynamic tone
mapping for backlight scaling method results in about 35% power
saving with an effective distortion rate of 5% and 55% power saving for
a 20% distortion rate. This is significantly higher power savings
compared to previously reported backlight dimming approaches.
7. Lifetime-Aware Intrusion Detection
under Safegaurding Constraints ,
Ali Iranli, Hanif Fatemi, and Massoud Pedram,
Proc. of International Conference on Information Processing in Sensor Networks, Apr. 2005.
Abstract: This paper addresses the problem of maximizing the
service lifetime of a distributed battery-powered sensor
network in the context of the network interdiction problem
under user-specified initial energy and probability of detection
constraints. We consider a version of this problem where the
probability distribution of selecting paths by the intruder is
known to the interdictor. A two-step solution technique is
proposed in which in the first step the safeguarding constraints
are satisfied and in the latter step the scheduling problem is
solved. Experimental results show speedups up to orders of
magnitudes with only 10% degradation in network lifetime for
scheduling algorithm.
6. HEBS: Histogram
Equalization for Backlight Scaling,
Ali Iranli, Hanif Fatemi, and Massoud Pedram,
Proc. of Design Automation and Test in Europe, Feb. 2005.
Abstract: In this paper, a method is
proposed for finding a pixel transformation function that maximizes backlight
dimming while maintaining a pre-specified image distortion level for a liquid
crystal display. This is achieved by finding a pixel transformation function,
which maps the original image histogram to a new histogram with lower dynamic
range. Next the contrast of the transformed image is enhanced so as to
compensate for brightness loss that would arise from backlight dimming. The
proposed approach relies on an accurate definition of the image distortion which
takes into account both the pixel value differences and a model of the human
visual system and is amenable to highly efficient hardware realization.
Experimental results show that the histogram equalization for backlight scaling
method results in about 45% power saving with an effective distortion rate of 5%
and 65% power saving for a 20% distortion rate. This is significantly higher
power savings compared to previously reported backlight dimming approaches.
5.
A Game Theoretic Approach to Low Energy Wireless Video Streaming,
Ali Iranli, Kihwan Choi, and Massoud Pedram,
Proc. of Design Automation and Test in Europe, Feb. 2004.
Abstract: This paper presents a
dynamic energy management policy for a wireless video streaming system,
consisting of battery powered client and server. The paper starts from the
observation that the video quality in wireless streaming is a function of three
factors: encoding aptitude of the server, decoding aptitude of the client, and
the wireless channel. Based on this observation, the energy consumption of a
wireless video streaming system is modeled and analyzed. Using the proposed
model, the optimal energy assignment to each video frame is done such that the
maximum system lifetime is achieved while satisfying a given minimum video
quality requirement. Experimental results show that the proposed policy
increases the system lifetime by 20%.
4.
Technology Mapping and Packing for Coarse-Grained, Anti-Fuse Based FPGAs,
Chang Woo Kang, Ali Iranli, and Massoud Pedram,
Proc. of Asia and South Pacific Design Automation Conference, Jan. 2004.
Abstract: We present a new
synthesis flow for anti-fuse based FPGAs with multiple-output logic cells. The
flow consists of two steps: mapping and packing. The mapper finds mapping
solutions using a dynamic programming-based approach that finds the best match
at each node of the decomposed target circuit. After this mapping step is
completed, the resulting netlist of cells is optimally packed into net list of
logic cells by using a multi-dimensional coin change problem formulation which
is again solved by a dynamic programming based approach. Experimental results
for Quicklogic’s pASIC3 logic family are provided to assess the effectiveness of
the proposed mapping and packing techniques.
3. A Game
Theoretic Approach to Dynamic Energy Minimization in Wireless Transceivers
,
Ali Iranli, Hanif Fatemi and Massoud Pedram,
Proc. of International
Conference on Computer Aided Design (ICCAD), Nov. 2003. Nominated
for best paper award
Abstract: Adaptive transceivers can significantly reduce the
energy consumption of a mobile, battery-powered node by
capturing realtime changes in the communication channel.
This paper proposes a game-theoretic solution to the
optimization of the energy consumption in wireless
transceivers. This is accomplished by dynamically adapting
the modulation level of the transmitter modulator and the error
correction aptitude of the receiver decoder with respect to channel
conditions subject to specified average bit-error-rate and throughput
constraints. Experimental results demonstrate energy savings
of up to 15%.
2. Energy-Aware
Wireless Video Streaming,
Ali Iranli, Kihwan Choi, and Massoud Pedram,
Proc. of Workshop on Embedded Systems for
Real-Time Multimedia, Oct. 2003.
Abstract: This paper
presents a dynamic energy management policy for a wireless video streaming
system, consisting of battery-powered client and server. The paper starts from
the observation that the video quality in wireless streaming is a function of
three factors: encoding aptitude of the server, decoding aptitude of the client,
and the wireless channel. Based on this observation, the energy consumption of a
wireless video streaming system is modeled and analyzed. Using the proposed
model, the optimal energy assignment to each video frame is done such that the
maximum system lifetime is achieved while satisfying a given minimum video
quality requirement. Experimental results show that the proposed policy
increases the system lifetime by 20%.
1. Low Power Synthesis of Finite State Machines
with Mixed D and T Flip-Flops,
Ali Iranli, Peyman Rezvani, and Massoud Pedram,
Proc. of Asia
and South Pacific Design Automation Conference, Jan. 2003.
Abstract: This paper
presents a state assignment technique to reduce dynamic power consumption in
finite state machines (FSM). The key idea is to decompose the state machine into
a set of cycles that are collectively equivalent to the original FSM, and
perform state assignment based on the cycle realization of the state machine
using Gray codes. A new implementation of state machines by using a combination
of D and T flip-flops is thereby proposed, which in conjunction with the
proposed encoding algorithm, reduces power consumption by an aver-age of 15%.