30742448
Exact Distribution of the Amplitude of Adaptively Selected OFDM Signal Samples
The combination of deliberate clipping and an adaptive symbol selection scheme (ASSS) can be used to reduce the peak to average power ratio (PAPR) for Orthogonal Frequency Division Multiplexing (OFDM) signals. The probability density function (pdf) of a sample's amplitude of an adaptively selected OFDM signal without over-sampling has been considered to be approximately equal to the Rayleigh pdf. In this letter, we derive the exact pdf showing the relationship between the probability distribution of the sample's amplitude and the number of candidate OFDM symbols for ASSS. The use of the newly derived pdf can measure the effect of deliberate clipping on the adaptively selected OFDM signal more accurately.
46712099
Side Information Inserted Pilot Tone Transmission for PAPR Reduction in OFDM
In order to reduce the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals over fading channels, the selected mapping (SLM) scheme and channel estimation technique can be used. Because of the side information of SLM, however, the data rate decreases in the conventional transmission method. In this letter, to overcome this impairment, we propose a technique which transmits side information by using pilot tones. Numerical analysis and computer simulations show that this method can maintain the PAPR reduction ability of SLM while improving error performance.
28474910
Low voltage 2-path SC bandpass /spl Delta//spl Sigma/ modulator without bootstrapper
A 1.5V fully differential, 2-path fourth order switched capacitor bandpass /spl Delta/-/spl Sigma/ modulator was designed and fabricated in 1.2/spl mu/m CMOS without using any on-chip voltage multiplier. The effective clock frequency is 10 MHz. The Basic building blocks of the modulator are auto-zeroed differentiators. The signal bandwidth is 50kHz centered at the intermediate frequency of 2.5MHz. Tested results demonstrated that SNR=65dB for the full-scale input of 1.1V/sub p/. IM3=-75dB. The common mode input voltage is from rail to rail.
3921961
Call admission control for integrated on/off voice and best-effort data services in mobile cellular communications
This paper proposes a call admission control (CAC) policy for a cellular system supporting voice and data services, and providing a higher priority to handoff calls than to new calls. A procedure for searching the optimal admission region is given. The traffic flow is characterized by a three-dimensional (3-D) birth-death model, which captures the complex interaction between the on/off voice and best-effort data traffic sharing the total resources without partition. To reduce complexity, the 3-D model is simplified to an exact (approximate) 2-D model for voice (data). The mathematical expressions are then derived for the performance measures and for the minimal amount of resources required for quality-of-service (QoS) provisioning. Numerical results demonstrate that: 1) the proposed CAC policy performs well in terms of QoS satisfaction and resource utilization; 2) the approximate 2-D model for data traffic can achieve a high accuracy in the traffic flow characterization; and 3) the admission regions obtained by the proposed search method agree very well with those obtained by numerically solving the mathematical equations. Furthermore, computer simulation results demonstrate that the impact of lognormal distributed data file size is not significant, and may be compensated by conservatively applying the Markovian analysis results.
14777107
Cooperative OFDM for energy-efficient wireless sensor networks
This paper presents a new energy-efficient cooperative sensor network scheme. Cooperative nodes shift the carrier frequency of the source node, and the destination node receives the signal from the source node and the cooperative nodes as a standard orthogonal frequency division multiplexing (OFDM) receiver. The maximal ratio combining (MRC) approach is applied to achieve full diversity with low complexity. The proposed scheme is scalable with respect to the number of nodes and is robust to time synchronization. A clustered network topology and cooperation protocol are proposed to realize multi-hop long haul signal transmission. The effect of the cluster scale is studied thoroughly to obtain the optimal size of clusters subject to the cooperation overhead. Simulation results show that the proposed cooperation scheme can consistently reduce the transmission power with the increase of cooperation scale. However, there is an optimal cluster scale where a good tradeoff between the diversity gain and cooperation cost can be established to minimize the total power consumption of the whole network.
30689090
Modeling and simulation for crosstalk aggravated by weak-bridge defects between on-chip interconnects
This paper presents comprehensive analytic models that consider both the case of a weak bridge, and the combination of a weak bridge and crosstalk between two interconnects. Our models capture the induced signal delay and pulse as a function of the parameters of the circuit and input signals. Our results are compared with HSPICE and shown to be accurate. A simulator is developed that implements our models and accurately captures timing (delay) characteristics of a circuit. We contrast our results with others, and show the benefits of this new model as well as the ability to predict the range of resistance that leads to delay errors.
15085849
A novel framework for SVM-based image retrieval on large databases
In this paper, a novel framework is proposed to deliver a fast, robust, and generally applicable SVM-based image retrieval for large databases. A quick test scheme is developed, and on-line kernel learning is employed to realize it after analyzing the relationship between them. Then an upper bound on maximum test scope is derived to speed up testing further. Also, the general applicability is well maintained because this framework does not need a kernel function and index structure to be pre-defined. Taking the advantages of this framework, more sophisticated SVM can be used to improve retrieval performance while keeping short response time. Experimental results on large image databases verify the effectiveness and efficiency of the proposed framework.