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HCF controlled channel access (HCCA), defined in the IEEE 802.11e document, provides a sample scheduler to allocate transmission opportunity (TXOP) to QoS-aware stations (QSTAs). Since the calculation of TXOP duration is based on mean data rate, it is efficient for constant bit rate (CBR) traffic. For variable bit rate (VBR) traffic, however, delay bound of some admitted traffic flows may be violated...
It is necessary that the satellite transponder has ability to suppress interferences for reliable communications in real applications, specially military areas. Adaptive interference suppression methods using transform domain approach are presented for an on-board filter bank in this paper. The three kinds of algorithms to compute the threshold level are jointly evaluated with the notch filter or...
We propose a transceiver structure that can effectively improve BER (bit error rate) performance for TR-UWB (transmitted reference-ultra wide band) systems based on impulse radios. Unlike coherent UWB systems that are too complex for practical implementation while having good BER performances, the complexity of the TR-UWB systems is quite low since they transmit data with the corresponding reference...
Bidirectional optical cross connects (BOXCs) using a fiber Bragg gratings (FBGs) and optical circulators (OCs) have been considered for bidirectional WDM ring networks. Theoretical analysis is carried out to evaluate the performance of a bidirectional optical cross connects (BOXCs) in a wave length division multiplexing (WDM) transmission system in the presence of homodyne crosstalk due to fiber Bragg...
The paper evaluates the performance of a CDMA based wireless sensor networks (WSN) in terms of outage probability and BER, considering correlation among interferers in shadowed environment. An appropriate model for the interference power, outage and BER are presented for a single hop communication. Detection probability is also evaluated in shadowed environment. The effects of node density, minimum...
In this paper, we propose a method to enhance the application of importance sampling (IS) technique for efficient simulation of Viterbi decoded terminated convolutional codes. The proposed method exploits the weight enumerators of terminated convolutional codes to enhance the performance of the IS technique known as error event simulation (EES). The essence of the proposed technique is to simulate...
OFDM is one of the most promising techniques for the high speed next generation mobile communication. However, it has a high peak to average power ratio. In this paper, we propose spread spectrum (SS)-OFDM for PAPR reduction. In this method, each subcarrier forms Nyquist pulse the same way to OSSR-OFDM which we proposed in. The results of computer simulation show that our proposal with a large roll-off...
A cognitive radio wireless network is investigated, in which a number of primary users (PUs) transmit in orthogonal frequency bands. There are also a number of secondary users (SUs) in the network, which monitor transmission opportunities in these frequency bands by collaboratively detecting whether each PU is transmitting. Each SU can participate in detecting only one PU's transmission at a time...
We consider the digital fingerprinting problem where colluders apply uniform linear averaging followed by AWGN. For each user, the receiver computes the correlation between the attacked signal and that user's fingerprint, and performs thresholding (focused detection). We model the fingerprinting problem as a multi-user communications problem and develop a detection theoretic framework. Assuming independent...
Compressed sensing deals with the reconstruction of a high-dimensional signal from far fewer linear measurements, where the signal is known to admit a sparse representation in a certain linear space. The asymptotic scaling of the number of measurements needed for reconstruction as the dimension of the signal increases has been studied extensively. This work takes a fundamental perspective on the problem...
This paper describes a dual-band clock and data recovery circuit using a new half-rate linear phase detector. With the proposed sampling scheme, the phase detector produces UP/DN signals with equal pulsewidth and thus eliminates the demand of current scaling in the charge pump. The test chip fabricated by CMOS 0.18 ??m 1P6M process can operate at 2.7 and 1.62 Gbps which satisfies the DisplayPort standard...
In this paper, we analyze the performance of estimating the common support for jointly sparse signals based on their projections onto lower-dimensional space. We formulate support recovery as a multiple-hypothesis testing problem and derive both upper and lower bounds on the probability of error for general measurement matrices, by using Chernoff bound and Fano's inequality, respectively. When applied...
This paper presents an FPGA-based implementation of a tri-mode decoder for decoding the cyclic (4095,3367) Euclidean geometry LDPC code which has minimum distance 65 and no trapping set of size less than 65. The implementation integrates three compatible decoding algorithms in a single decoder. The three decoding algorithms are the one-step majority-logic decoding (OS-MLGD) algorithm and two iterative...
Given the possibility of communication systems failing catastrophically, we investigate limits to communicating over channels that fail at random times. These channels are finite-state semi-Markov channels. We show that communication with arbitrarily small probability of error is not possible. Making use of results in finite block-length channel coding, we determine sequences of block-lengths that...
When rate expectations of users in a wireless network cannot all be satisfied, one choice is to discard some users from the system, in a mechanism called admission control. However, in a data network, users have a certain tolerance to occasional rate outages. In this paper we argue that it may be preferable for users to reduce their rate objectives smoothly, by considering an outage probability tolerance,...
This paper examines linear beamforming methods for secure communications in a multiuser wiretap channel with a single transmitter, multiple legitimate receivers, and a single eavesdropper, where all nodes are equipped with multiple antennas. No information regarding the eavesdropper is presumed at the transmitter, and we examine both the broadcast MIMO downlink with independent information, and the...
In the present wireless scenario, transmit diversity has become one of the key contributing technologies. Analytical estimations of bit error rate (BER) can be obtained with space time transmit diversity (STTD). The desired user's BER performance improves as fading of interfering signal decreases. Nakagami-m fading is becoming more prevalent in performance analysis and other studies related to mobile...
The performance of Bluetooth under the interference of RFID is investigated. A mathematical model is proposed to quantify the performance degradation of Bluetooth. The proposed model carefully takes PHY (i.e., the channel model, the transmitted power, the distance and the modulation) and MAC (i.e., the frequency hopping, the packet format and the traffic load) into account. Packet error rate (PER),...
With the development of wireless and mobile Internet technology, people in everyday life and business hope for access to the Internet even while they are in movement. IEEE 802.20 technology is mobile and can effectively address high-speed network access. In this paper the PHY layer model for simulating 802.20 in SIMULINK and subsystems in MATLAB S-function files are presented. To evaluate the performance...
We report a wavelength conversion efficiency of -5.5 dB via four-wave-mixing in a low-loss 2.5 cm long sub-micron silicon-on-insulator rib waveguide. The impact of non-linear absorption and waveguide dimensions on the conversion efficiency is studied.
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