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ABSTRACT: In this paper, we present a simple algorithm for extraction of laser rate equation parameters based on a set of simple laboratory measurements. Commercial semiconductor DFB laser (Fujitsu FLD3F7CZ) with central wavelength 1310 nm is used to obtain the P-I and frequency response curves. Simulation results using the extracted parameters are in good agreement with the experimental results in both small and large signal modulation.
Radio Science Conference, 2009. NRSC 2009. National; 04/2009
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ABSTRACT: Enhanced analytical equations are derived to predict the inductance and series resistance of a common active inductor configuration. The equations, based on MOSFET small-signal parameters, are used to predict the inductance and series resistance of an active inductor implemented in a 0.18 ¿m CMOS process. The inductor's characteristics are presented, demonstrating analytical equation accuracy and circuit functionality between 70 MHz and 700 MHz.
Microelectronics, 2008. ICM 2008. International Conference on; 01/2009
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ABSTRACT: An 8-bit successive approximation analog-to-digital converter (ADC) with offset correction circuitry and a tunable capacitor is presented for biomedical applications. The ADC is designed in a standard 0.13 mum CMOS process technology and operates with voltage supplies down to 0.30 V using MOSFETs operating in their sub-threshold region of operation to achieve ultra low power dissipation. Post layout simulations were used to determine that the ADC achieves 8.5 pJ/cycle energy dissipation operating at 20 kS/s with a 0.4 V supply. An offset correction circuit is included for the comparator which significantly reduces the offset voltage as a result of process and mismatch variation. The attenuation capacitor is digitally tuned and post layout simulation results show the advantage of tuning to adjust linearity and dynamic performance for the ADC.
Circuits and Systems, 2007. MWSCAS 2007. 50th Midwest Symposium on; 09/2007
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ABSTRACT: A ring oscillator with two control signals is presented. It is used in the design of a low power multi-band voltage- controlled ring oscillator. Fabricated in CMOS 0.18 mum technology, a single VCO can support operation in six frequency bands including 450 MHz, 700 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2400 MHz. The VCO occupies 2461 mum<sup>2</sup> chip area and consumes from 2.2 mW to 5.6 mW from a 1.8 V supply.
Circuits and Systems, 2007. NEWCAS 2007. IEEE Northeast Workshop on; 09/2007
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ABSTRACT: An 8-bit successive approximation analog-to-digital converter (ADC) with offset correction circuitry is presented for implantable sensor applications. The ADC is designed in a 0.13mum CMOS process technology and operates with voltage supplies down to 0.35 V using MOSFETs operating in their sub-threshold region of operation. Sample rates of 60kS/s are achieved with an INL and DNL of approximately 0.26LSB and 0.35LSB respectively. The SAR ADC achieves 10.7pJ/cycle operating at 20 kS/s with a 0.4 V supply. An offset correction circuit is included to dynamically minimize the offset voltage on the comparator.
Circuits and Systems, 2007. ISCAS 2007. IEEE International Symposium on; 06/2007
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ABSTRACT: An 8-bit successive approximation analog-to-digital converter (ADC) for ultra low power applications is presented. It is designed in a standard 0.13mum CMOS process technology. The design can operate with low voltage supplies down to 0.45 V. It makes use of sub-threshold transistor operation to achieve nanowatts of power consumption at sample rates exceeding 60kS/s. A specially designed switch allows large input swings. Post layout simulations show an INL and DNL of approximately 0.3LSB and 0.45LSB respectively
Circuits and Systems, 2006. ISCAS 2006. Proceedings. 2006 IEEE International Symposium on; 06/2006
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ABSTRACT: In this paper, we present a novel transmission scheduling scheme for fixed broadband wireless access (FBWA) networks. In order to mitigate high co-channel interference resulting from dense reuse of frequency, scheduling schemes often consider interference management issues as an essential part. To that end, a series of literature has been published recently, where a group of base stations form an interference group, and scheduling scheme deployed in the group allows only one base station to transmit at a time. As a result of time orthogonality in transmissions, the co-channel interference and hence the packet error rate can be reduced. However, prohibiting concurrent transmissions in these orthogonal schemes introduces higher end-to-end packet delay which might not be desirable for real-time traffic such as voice and video. Our proposed scheme aims to improve delay performance as well as to ensure better resource utilization in such schemes in several ways, most notably by introducing opportunistic non-orthogonality in transmissions, incorporating channel state based scheduling decisions, and employing adaptive modulation and coding.
Communications, 2005. ICC 2005. 2005 IEEE International Conference on; 06/2005
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ABSTRACT: Link adaptation techniques, such as power control and adaptive coding and modulation, aim at maximizing the resource utilization in wireless networks. However, fair resource allocation must be taken into consideration, particularly in fixed broadband wireless access networks. The low/no mobility of users in such networks leads to location-dependent resource utilization, which can cause a significant variation in the performance from one user to another. For instance, adaptive coding and modulation schemes increase the average throughput in the network; however, they also increase the variation of the throughput. This is because users with good link quality always have high throughput, while users with bad link quality always have low throughput. The fairness and efficiency of various link adaptation techniques are analyzed. The analyzed algorithms are selected as a representative set of different link adaptation techniques with various fairness and efficiency characteristics.
Vehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59th; 06/2004
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ABSTRACT: This work analyzes the impact of having more than one frequency channel on outage probability and node throughput in TDMA-based broadband fixed cellular multihop networks. The scenario considered is a low node density, start-up network with inadequate single-hop coverage. In this scenario the user terminals themselves act as relays, therefore, there are no additional relays deployed by the service provider: besides, no separate relaying channels are used (this scenario ensures a fair comparison between the multihop cellular network considered here and the traditional single-hop cellular network). In a situation where there is outage with a single-hop due to poor coverage, a suitable multihop route with minimum number of hops is sought. It is observed that as the number of available channels increases the coverage is enhanced remarkably; in addition, the average node throughput is increased as well although no explicit attempt for throughput maximization is made during the search for the multihop routes.
Wireless Communications and Networking Conference, 2004. WCNC. 2004 IEEE; 04/2004
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ABSTRACT: We present a pre-distorter model derived from a modified semiconductor user model that reduces the nonlinear distortion in directly modulated semiconductor lasers. Simulation results showing improvements greater than 40dB for the second harmonic and the second and third order intermodulation distortion components over a wide frequency range are given. Performance and capability of the pre-distorter are examined for two different lasers (Ortel 1510B and Fujitsu FLD3F7CZ) under different operating conditions.
Circuits and Systems, 2003. MWSCAS '03. Proceedings of the 46th IEEE International Midwest Symposium on; 01/2004
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ABSTRACT: In this paper, we present a semiconductor laser model to accurately predict the dynamic operations and the nonlinear distortion in a directly modulated semiconductor lasers. We introduce a new implementation technique for the proposed model that provides a compelling incentive for the performance assessment and enhancement of the analog wireless/optical transceivers using Agilent Advanced Design System (ADS) CAD tool. A detailed comparative experimental and simulation study of the dynamic operation and the nonlinear distortion in laser diodes are used to verify the accuracy of the proposed model for analyzing the performance of the analog optical transmitters. The measured results, such as harmonic and intermodulation distortion levels, are in good agreement with the simulation results.
Electronics, Circuits and Systems, 2003. ICECS 2003. Proceedings of the 2003 10th IEEE International Conference on; 01/2004
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ABSTRACT: Link adaptation techniques, such as power control and adaptive coding and modulation, aim at maximizing the throughput in wireless networks while maintaining the signal quality in terms of the signal to interference ratio. However, fair resource allocation among different users must be taken into consideration, particularly in fixed broadband wireless access networks. The low/no mobility of users in such networks can lead to location-dependent resource utilization, which causes a significant variation in the performance from a user to another. For instance, adaptive coding and modulation schemes increase the aggregate throughput in the network; however, they also increase the variation of the throughput among users. In this paper, we propose, and analyze the performance of, three fairness enhancement schemes that can be integrated with link adaptation techniques. Results show that the three proposed scheme can enhance the fairness of link adaptation techniques with different degrees without causing (or with minor) degradation to the total network throughput.
Vehicular Technology Conference, 2003. VTC 2003-Fall. 2003 IEEE 58th; 11/2003
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ABSTRACT: In this paper the integration of wireless and optical networks has been presented. Analog link design calculations and analysis are discussed. A detailed comparative experimental and simulation study of the dynamic operation and the nonlinear distortion in laser diodes is used to verify the accuracy of the proposed model for analyzing the performance of the analog optical interface. The measured results, such as harmonic and intermodulation distortion levels, are in good agreement with the simulation results. Second and third order intermodulation improvements attained using a proposed predistorter are presented.
Advanced Optoelectronics and Lasers, 2003. Proceedings of CAOL 2003. First International Conference on; 10/2003
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ABSTRACT: Protocols, currently used for ad-hoc wireless networks, are designed and tested for networks, which are different in characteristics than ad-hoc networks. Hence, the challenge is to improve current protocols or design new protocols to meet the demands for such new type of networks. Although the research challenge covers all layers of ad-hoc network stack, the current research focus is on network and data link layer mainly to obtain optimum routing algorithm and overcome the problem of applying IEEE802.11 to multihop, ad-hoc, networks. There are two common approaches to analyze the proposed solutions; analytical approach and simulation approach which is most commonly used. In this paper, a simulation framework is developed as a tool for the analysis of new protocols and algorithms. This framework is designed to be, reusable in the sense that it can be integrated with new protocols/current protocols for evaluation purposes. The results from the framework include the network throughput and the packet delay for end-to-end links. The output is given as runtime visual presentation, which may give some hints about the problem type. Moreover, the output presentation may be customized according to user objectives.
Electrical and Computer Engineering, 2003. IEEE CCECE 2003. Canadian Conference on; 06/2003
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ABSTRACT: An enhanced semiconductor laser model incorporating gain nonlinearities, gain saturation, index nonlinearities, leakage current, thermal effects, and noise effects is presented. Symbolically defined devices based on the proposed models are implemented in the Hewlett-Packard Advanced Design System computer-aided design tool. The laser model enables the simulation of the transient and steady-state dynamic characteristics of laser diodes such as carrier, photon concentration, optical power, and phase. Using the proposed model, important laser characteristics such as relaxation-oscillation peak frequency and modulation bandwidth are evaluated under different conditions and compared to published measurement results. Analog optical transmission performance limitations such as laser diode nonlinearity and noise are determined in both the time and frequency domains.
IEEE Journal of Selected Topics in Quantum Electronics 06/2003; · 3.78 Impact Factor
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ABSTRACT: This paper proposes a joint adaptive rate selection and power control algorithm for broadband TDMA/TDM wireless networks. The proposed algorithm is a modified, enhanced, and more robust version of the selective power control with active link protection (SPC-ALP) algorithm proposed for adaptive transmission rate and power control in CDMA networks [R.Jantti and S. Kim, 2000]. Unlike SPC-ALP, the proposed algorithm uses adaptive coding and modulation (instead of variable spreading gain) for transmission rate control. In addition, the proposed algorithm is different in two aspects; the first one is the inclusion of the cochannel interferer assistance mode, while the second one is the use of the signal quality as a criterion for user removal. Results show that the proposed algorithm outperforms SPC-ALP in terms of the net throughput and signal quality measures such as the outage probability and frame error rate. Channel reallocation is also studied and found to be very effective in enhancing the system performance particularly at low to medium loading.
Wireless Communications and Networking, 2003. WCNC 2003. 2003 IEEE; 04/2003
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ABSTRACT: The paper proposes a transmission scheduling algorithm for interference management in broadband wireless access networks. The algorithm aims at minimizing the cochannel interference using base station coordination while still maintaining the other quality of service (QoS) requirements, such as packet delay, throughput, and packet loss. The interference reduction is achieved by avoiding (or minimizing) concurrent transmission of potential dominant interferers. Dynamic slot allocation based on traffic information in other cells/sectors is employed. In order to implement the algorithm in a distributed manner, base stations have to exchange traffic information. Both real-time and non-real-time services are considered. Results show that significant enhancement in the signal-to-interference ratio can be achieved which decreases the packet error rate by almost one order of magnitude at the expense of a higher, but acceptable, packet delay at high loading.
Wireless Personal Multimedia Communications, 2002. The 5th International Symposium on; 11/2002
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ABSTRACT: Enhanced normalized laser rate equations suitable for large signal analyses and system level simulations are discussed. A large signal laser model including thermal effects and incorporating a modified laser gain formulation is presented. Symbolically defined devices (SDDs) implemented in the Hewlett Packard Advanced Design System (HP-ADS) are constructed using the proposed laser model. The effects of temperature on the transient response characteristics of 1.3 μm InGaAsP/InP Fabry-Perot lasers are predicted using the SDD implementation.
4thLaser and Fiber-Optical Networks Modeling, 2002. Proceedings of LFNM 2002. International Workshop on; 02/2002
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ABSTRACT: The transmission of MPEG-4 video over explicit rate networks
provides an opportunity for complete interaction between the application
and the network where the application can request the required bandwidth
from the network and then adapts its rate based on the network offered
rate. One method of rate adaptation is to encode video in multi layers,
were the basic layer is always transmitted and the enhanced layer is
only transmitted when enough resources are available. In this paper, we
propose a novel intelligent VOP discard algorithm (IVDA) that controls
the transmission of enhanced layer VOP The proposed algorithm depends on
the knowledge of the current network state, the encoding sequence,
nature of the various VOP types, and the buffer occupancy in order to
control the transmission of the enhanced layer VOP The proposed
algorithm was evaluated for various MPEG-4 test sequences with different
traffic characteristics under various network conditions
Global Telecommunications Conference, 2001. GLOBECOM '01. IEEE; 02/2001
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ABSTRACT: The use of smart antennas in frequency hopping (FH)-TDMA cellular
systems is one of the effective means of enhancing the capacity of
cellular radio systems. The capacity of such cellular systems is
interference limited and can be enhanced by reducing the cochannel
interference through exploiting the directivity of the smart antennas
and making use of spatial processing. This paper addresses the capacity
gain of smart antennas in FH-TDMA cellular system. We estimate the
system capacity analytically and by simulation as well. Multiple
switched beam smart antennas with sinc<sup>2</sup> antenna pattern are
utilized in the study. Perfect power control and discontinuous
transmission (using voice activity) are assumed in the simulation and in
theoretical analysis. The TDMA system is assumed to be GSM-like but the
analysis can be easily extended and applied to any other systems that
are based on TDMA such as IS-136
Vehicular Technology Conference Proceedings, 2000. VTC 2000-Spring Tokyo. 2000 IEEE 51st; 02/2000
