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Wireless sensor network is becoming increasingly important in applications such as environmental monitoring and traffic control. They collect a large amount of sensor data, e.g., temperature and pressure. Nearby sensor nodes monitoring an environmental feature typically measure correlated values. In this paper, we propose a new location-aware-based data clustering (LABDC) algorithm to analyze the...
According to the widely used IEEE 802.15.4, one of the most effective ways to reduce the power consumption of sensor nodes is to enable the optional sleep mode by radio shutdown. In this paper, we propose an extended Markov-based analytical model for IEEE 802.15.4 slotted carrier sense multiple access/collision avoidance (CSMA/CA) algorithm considering the newly enabled sleep mode. For taking account...
IEEE 802.15.4 is one of the most important protocols for wireless sensor networks. To improve the performance of this protocol in consideration of the trade-off between power consumption and end-to-end delay, duty cycle adaptation algorithms are effective solutions. In this paper, we propose an individual beacon order adaptation (IBOA) algorithm for IEEE 802.15.4 networks, which can individually adapt...
We propose a novel routing scheme for providing Quality of Service (QoS) for multi-target tracking in multi-sink wireless sensor networks (WSNs). We first introduce the concept of event ordering, by virtue of which a priority-based buffer management scheme is applied to achieve QoS. We also propose a directional QoS-aware routing protocol (DQRP) for the dissemination of the event ordering list. The...
The region coverage is an important affecting factor of target detection performance in wireless video sensor networks (WVSN). However, the traditional region coverage can not estimate the target detection performance properly, so the concept of effective coverage is introduced in this paper, which can be considered as the equivalent of target detection performance. Moreover, we propose an effective...
Wireless sensor networks are widely used for condition monitoring applications. Much effort has been invested in improving the performance of such networks. Diversity is a well-proven technique in this context. Here, we present the practical application of base station and antenna diversity. Empirical measurements of performance in a realistic environment are reported and a statistical analysis of...
Orthogonal frequency division multiplexing (OFDM) systems are sensitive to time and frequency offset errors. In this paper, a method of joint timing and frequency synchronization for OFDM systems has been proposed based on preamble structure defined in IEEE 802.16 standard. The proposed method in coarse frame detection has good robustness and anti-noise ability. The coarse and fine frequency offset...
Synchronization at receiver, including mode detection, frame synchronization, sampling time recovery (STR) and carrier frequency synchronization four parts, is crucial for digital communication systems. Time domain synchronous (TDS) block transmission system, in which pseudo noise (PN) sequences are padded between two adjacent data blocks as guard intervals (GI), is widely used in wireless communication...
This paper proposes a new frequency synchronization algorithm based on alternating guard intervals in the TDS-OFDM system. It utilizes the following two facts: the maximum length of identical sequences exist in the alternating guard intervals in the TDS-OFDM system and high precise frequency estimation can be achieved by extending the equivalent length of the delay for autocorrelation in the conventional...
This paper develops a new hidden pilots based algorithm for the carrier frequency offset (CFO) estimation of multicarrier DS-CDMA (MC-DS-CDMA) systems. Multiple CFO of different users in the uplink of MC-DS-CDMA systems may violate the orthogonality among subcarriers and induce both inter-carrier interference (ICI) and inter-user interference (IUI). This algorithm utilizes mutually orthogonal hidden...
This paper proposes a novel hyperchaotic PN (pseudo-noise) sequence, which is generated by a novel Rossler hyperchaotic system. Its correlation characteristics are analyzed via numerical simulations. Then the PN sequence is applied to the direct sequence ultra-wideband (DS-UWB) system to enhance its antinoise performance. The model of chaos-based DS-UWB communication system is established in the purpose...
In the cooperative spatial multiplexing MIMO-OFDM systems in multipath fading environments, the streams from different transmit antennas are not aligned in the time domain, and have different frequency offsets. The preambles and synchronization algorithms in the centralized MIMO-OFDM systems can no longer apply. A new preamble structure is proposed for this system, and the corresponding timing and...
An improved space-time-frequency (STF) code using digital phase sweeping (DPS) is proposed for multi-input multi-output-orthogonal frequency division multiplexing (MIMO-OFDM) systems. It achieves full diversity attainable over frequency-selective channels and works for arbitrary power delay profile. The maximum transmission rate of the proposed code is one symbol per channel use independently of the...
A new space-time block code (STBC) achieving full rate and full diversity for general QAM and four transmit antennas is proposed. This code also possesses a quasi-orthogonal (QO) property like the conventional minimum decoding complexity QO-STBC (MDC-QO-STBC), leading to joint ML detection of only two real symbols. The proposed code is shown to exhibit the identical error performance with the existing...
In this paper, we propose a numerical formulation of decoupling matrix with rate one quasi-orthogonal space-time block code (QOSTBC) for eight transmit antennas. Tirkkonen et al. provided zero-forcing decoupling matrix for eliminating inter-symbol interference (ISI) in QOSTBC with 4 transmit antennas. We expand zero-forcing decoupling matrix with 8 transmit antennas, and also MMSE decoupling matrix...
In this paper, the new detection scheme proposed by Tarokh and Alamouti is investigated and expanded to two schemes of two transmit two receive antennas and four transmit one receive antennas. Previously, Tarokh and Alamouti, based on the simple transmit diversity scheme proposed by Alamouti, have provided two new detection methods to decode signals at the receiver without channel information. We...
A close-form expression of the exact pair-wise error probability (PEP) for space-time (S-T) codes in Rayleigh fading channel is derived using the probability-density function (PDF) of a sum of independent exponential distributed random variables. Since the expression requires evaluating the coefficients for partial fraction expansion, an easy analytical way is proposed for doing this. The exact PEP...
Space time coding in the case where the channel state information is unknown has received only limited attention, although a signaling scheme called unitary space-time modulation (USTM) has already been proposed. An important reason for the impracticability of USTM is its too large calculation amount when meeting with a large size constellation. We propose a size-reduced method for constellation of...
In this paper, a joint power and subcarrier allocation scheme in single-cell uplink OFDMA systems is proposed based on game theory. Our goal is to maximize the power efficiency of each user under peak power constraint. For the purpose, a utility function is designed which can enhance the rate per joule of energy consumed greatly, and the existence and uniqueness of the Nash equilibrium of the function...
This paper proposes a cooperative game theoretic resource allocation scheme for downlink OFDMA wireless networks. We define a user??s payoff as a function of his data throughput. Then the source allocation can be modeled as a cooperative game to maximize the aggregate payoff of the users. To achieve the Nash bargaining solution (NBS) of the game, a suboptimal subcarrier allocation is first performed...
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