Abstract — We consider wireless systems where the nodes operate on batteries so that energy consumption must be minimized while satisfying given throughput and delay requirements. In this context, we analyze the best modulation strategy to minimize the total energy consumption required to send a given number of bits. The total energy consumption includes both the transmission energy and the circuit energy consumption. For uncoded systems, by optimizing the transmission time and the modulation parameters we show that up to 80 % energy savings is achievable over non-optimized systems. For coded systems, we show that the benefit of coding varies with the transmission distance and the underlying modulation schemes. Index Terms — Energy efficiency, modulation optimization, MQAM, MFSK.

We consider the joint optimal design of the physical, medium access control (MAC), and routing layers to maximize the lifetime of energy-constrained wireless sensor networks. The problem of computing lifetime-optimal routing flow, link schedule, and link transmission powers for all active time slots is formulated as a non-linear optimization problem. We first restrict the link schedules to the class of interference-free time division multiple access (TDMA) schedules. In this special case, we formulate the optimization problem as a mixed integerconvex program, which can be solved using standard techniques. Moreover, when the slots lengths are variable, the optimization problem is convex and can be solved efficiently and exactly using interior point methods. For general non-orthogonal link schedules, we propose an iterative algorithm that alternates between adaptive link scheduling and computation of optimal link rates and transmission powers for a fixed link schedule. The performance of this algorithm is compared to other design approaches for several network topologies. The results illustrate the advantages of load balancing, multihop routing, frequency reuse, and interference mitigation in increasing the lifetime of energy-constrained networks. We also briefly discuss computational approaches to extend this algorithm to large networks.

this paper, we review the Bluetooth technology, a new universal radio interface enabling electronic devices to connect and communicate wirelessly via short-range connections. Motivations for the air interface design and radio requirement decisions are discussed. Frequency hopping, interference resistance, and the concepts of ad hoc connectivity and scatternets are explained in detail. Furthermore, Bluetooth characteristics enabling low-cost single-chip implementations and supporting low power consumption are discussed

Linear time-invariant (LTI) phase noise theories provide important qualitative design insights but are limited in their quantitative predictive power. Part of the difficulty is that device noise undergoes multiple frequency translations to become oscillator phase noise. A quantitative understanding of this process requires abandoning the principle of time invariance assumed in most older theories of phase noise. Fortunately, the noise-to-phase transfer function of oscillators is still linear, despite the existence of the nonlinearities necessary for amplitude stabilization. In addition to providing a quantitative reconciliation between theory and measurement, the time-varying phase-noise model presented in this tutorial identifies the importance of symmetry in suppressing the upconversion of 1 noise into close-in phase noise, and provides an explicit appreciation of cyclostationary effects and AM--PM conversion. These insights allow a reinterpretation of why the Colpitts oscillator exh...

Abstract—This paper presents a physical model for planar spiral inductors on silicon, which accounts for eddy current effect in the conductor, crossover capacitance between the spiral and center-tap, capacitance between the spiral and substrate, substrate ohmic loss, and substrate capacitance. The model has been confirmed with measured results of inductors having a wide range of layout and process parameters. This scalable inductor model enables the prediction and optimization of inductor performance. Index Terms—Eddy currents, inductor model, on-chip inductors, quality factor, self resonance, substrate loss. I.

We present an efficient method for optimal design and synthesis of CMOS inductors for use in RF circuits. This method uses the the physical dimensions of the inductor as the design parameters and handles a variety of specifications including fixed value of inductance, minimum self-resonant frequency, minimum quality factor, etc. Geometric constraints that can be handled include maximum and minimum values for every design parameter and a limit on total area. Our method is based on formulating the design problem as a special type of optimization problem called geometric programming, for which powerful efficient interior-point methods have recently been developed. This allows us to solve the inductor synthesis problem globally and extremely efficiently. Also,we can rapidly compute globally optimal trade-off curves between competing objectives such as quality factor and total inductor area. We have fabricated a number of inductors designed by the method, and found good agreement between the experimental data and the specifications predicted by our method. 1

Abstract — We consider radio applications in sensor networks where energy is a limited resource so that energy consumption must be minimized while satisfying given delay and throughput requirements. In this context, we analyze energy-efficient data collection strategies where we minimize the total energy consumption necessary for collecting a certain amount of data from multiple sensors. The total energy consumption includes both the transmission energy and the circuit energy consumption. We propose a variable-length TDMA scheme where the slot length is adaptively assigned according to the number of bits in the transmitting queues and the distance between the transmitting nodes and the collecting node. The underlying goal is to finish the collection of information bits from the multiple sensor nodes before a deadline T with minimum energy cost. We show that the problem can be efficiently solved by convex relaxation methods, and in some special cases simple analytical solutions can be derived. Index Terms — Energy efficiency, modulation optimization, Multiple access, Cross-layer.

Abstract—This paper presents the basis of the modeling of the MOS transistor for circuit simulation at RF. A physical equivalent circuit that can easily be implemented as a Spice subcircuit is first derived. The subcircuit includes a substrate network that accounts for the signal coupling occurring at HF from the drain to the source and the bulk. It is shown that the latter mainly affects the output admittance PP. The bias and geometry dependence of the subcircuit components, leading to a scalable model, are then discussed with emphasis on the substrate resistances. Analytical expressions of the parameters are established and compared to measurements made on a 0.25- m CMOS process. The parameters and transit frequency simulated with this scalable model versus frequency, geometry, and bias are in good agreement with measured data. The nonquasi-static effects and their practical implementation in the Spice subcircuit are then briefly discussed. Finally, a new thermal noise model is introduced. The parameters used to characterize the noise at HF are then presented and the scalable model is favorably compared to measurements made on the same devices used for the-parameter measurement. Index Terms—Modeling, MOS devices, MOSFET’s, RF CMOS IC, semiconductor device modeling, semiconductor device noise,

Abstract—We consider radio applications where the nodes operate on batteries so that energy consumption must be minimized while satisfying given throughput and delay requirements. In this context, we analyze the best modulation strategy to minimize the total energy consumption required to send a given number of bits when error-control codes are used. The total energy consumption includes both the transmission energy and the circuit energy consumption. We show that for both MQAM and MFSK the total energy consumption may be reduced significantly if the transmission time Ton is optimized to reduce the sum of transmission energy and circuit energy consumption. Our optimization considers both delay and peak-power constraints. Numerical examples are given, where we exhibit up to 90 % energy savings over modulation strategies that minimize the transmission energy alone. We also show that the benefit of coding varies with the transmission distance and the underlying modulation schemes. I.

We present a technique for enhancing the bandwidth of gigahertz broad-band circuitry by using optimized on-chip spiral inductors as shunt-peaking elements. The series resistance of the on-chip inductor is incorporated as part of the load resistance to permit a large inductance to be realized with minimum area and capacitance. Simple, accurate inductance expressions are used in a lumped circuit inductor model to allow the passive and active components in the circuit to be simultaneously optimized. A quick and efficient global optimization method, based on geometric programming, is discussed. The bandwidth extension technique is applied in the implementation of a 2.125-Gbaud preamplifier that employs a common-gate input stage followed by a cascoded common-source stage. On-chip shunt peaking is introduced at the dominant pole to improve the overall system performance, including a 40% increase in the transimpedance. This implementation achieves a 1.6-k\Omega transimpedance and a 0.6- A i...