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A lattice reduction aided MMSE detection combined with successive interference cancellation (SIC) scheme is proposed in this paper to suppress the noise amplification in the commonly used MMSE detection of non-orthogonal frequency division multiplexing (NFDM) signals. By adopting Lenstra-Lenstra-Lovasz (LLL) algorithm to reduce condition number of the nearly singular modulation matrix in NFDM, the...
An enhanced medium access control (MAC) protocol for wireless networks with multi-packet reception (MPR) capability is proposed. The proposed protocol is based on the dynamic multi-group priority queueing protocol recently introduced to exploit the cooperative diversity for improving the system throughput. Two kinds of throughput losses, i.e., over-loaded loss and under-loaded loss, are defined first...
The worldwide interoperability for microwave access (WiMAX) can use frequency reuse factor 1 as its network deployment, but it may suffer from serious inter-cell interference (ICI) near the cell edge. Fractional frequency reuse (FFR) is introduced to deal with this problem. In this paper, we investigate the application of Fractional frequency reuse in mobile WiMAX system. Characteristics of frequency...
A cross-layer resource allocation algorithm with fractional frequency reuse and guaranteed diverse QoS is proposed for WiMAX system, where dynamic resource allocation is implemented at both radio network controller (RNC) and base stations (BSs). In order to maximize system frequency reuse ratio to reach the diverse QoS requirements, several novel subchannel allocation schemes are proposed. An RNC...
In this paper, the Doppler shift of the time-varying multi-path channel is estimated by calculating the rate of minimum (ROM) of the signal envelope of the channel coefficient estimates at the strongest path. Then followed by an analysis of the effect of noise, we proposed a modification to make the estimation performance robust to signal-to-noise ratio (SNR), and simulations show a great performance...
Cognitive radio (CR) is a novel concept for improving spectrum utilization in wireless communication systems by permitting secondary (unlicensed) users to access those frequency bands which are not currently being used by primary (licensed) users. A CR user has the ability to change its transmit parameters rapidly according to the environment it senses. Orthogonal frequency division multiplexing (OFDM)...
The emerging vehicular networks in the forms of intra-car, car-to-car, and car-to-infrastructure communications will enable a variety of applications for safety, traffic efficiency, driver assistance, as well as infotainment to be incorporated into future automotive designs. However, the availability of these exciting automotive applications can also lead to formidable set of exploits and vulnerable...
Owing to retransmission of lost packets and bursty nature of source data, even an ad hoc network with low average traffic may suffer heavy traffic in some certain periods, which in further may degrade system performance, particularly in multi-hop wireless communication. Aiming to provide a solution to above problem, in this paper, we construct a hybrid system based on plural ad hoc networks, which...
A novel steganographic scheme based on a mechanism of data decomposition is proposed. In this scheme, a secret message is represented as a sequence of digits in a notational system with a prime base. Each digit block is decomposed into a number of shares. These shares are then embedded in different cover images respectively. In each cover, a share is carried by a group of cover pixels and, at most,...
This study has proposed a new detection method for DDoS attack traffic based on statistical test. We first investigate the statistics of SYN arrival rate and find that SYN arrival rate can be can be modeled by normal distribution. We set up a threshold for maximum arrival rate to detect DDoS flood traffic. We also establish a threshold for incomplete three-way handshaking packet ratio to detect possible...
We study a cognitive radio (CR) network with cognitive users communicating in the presence of a primary user. All users are uniformly distributed within a circle. Each user is equipped with a single ideal isotropic antenna. We propose a scheme in which all users collaboratively transmit the signal by adjusting the carrier phase of each transmitter such that the interference caused by the cognitive...
A novel suboptimal technique called extended iterative flipping (E-Flipping) algorithm has been proposed to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. The key idea of the proposed technique is to partition the partial transmit sequences (PTSs) into several groups and then to perform the "flipping" operation on each group. It...
Radio frequency identification (RFID) provides a more convenient and automatic approach for object identification than traditional universal product code-based barcode technology. However radio communications are naturally unreliable and inevitably lead to unreliable object identification, which in turn encumber some special applications demanding large-scale deployment of RFID, even though many RFID...
A word-oriented stream cipher named TAIYI for confidentiality and integrity algorithms of 3G is presented, together with preliminary security analysis and implementation results. The proposal is a clock-controlled filter generator using sigma-LFSR as source part and inverse function to generate key stream. The design is based on simple and well-studied concepts, and it can be easily implemented in...
This paper introduces a distributed spectrum sharing scheme in the context of cognitive radio which enables efficient usage of spectrum. This is achieved by using the past experience based on reinforcement learning. It shows that reinforcement spectrum sharing provides a good solution and has the potential to significantly improve the system performance. Several learning strategies based on different...
Dynamics of sensor networks make security one of the top issues we should pay attention to. Sensor networks can be deployed in hostile environments where their nodes are easy to be captured or re-programmed for deleterious use by an adversary. Therefore, it is necessary to protect communications between sensor nodes through cryptographic methods. To address this, symmetric key management in wireless...
In this article, we first review the evolution of peer-to-peer (P2P) file sharing and media streaming systems, and then focus on one of the most popular P2P-based media streaming services - PPStream. We describe the PPStream protocol discovered through reverse engineering efforts and discuss our measurement study conducted to evaluate three aspects of the system: privacy, locality, and availability...
L-diversity model is an effective model to thwart homogeneity attack and background knowledge attack for microdata, but it has some defects on handling numerical sensitive attributes. The paper proposes an improved l-diversity model to address the problem. The model divides numerical sensitive values into several levels, and realizes sensitive attribute l-diversity based on these levels. Distinct...
The iterative message passing algorithm (MPA) for low-density parity-check (LDPC) codes is effective in the additive white Gaussian noise (AWGN) channels. However, the impulse interference is not negligible in many communication channels, such as power line channels, where the impulse interference greatly deteriorates the performance of MPA based on Gauss optimization. It is necessary to restudy the...
In this paper, we propose an adaptive scheduling method for unitary precoded downlink multiuser MIMO transmission based upon limited feedback. To alleviate the conflict between the scheduling gain and the quantization precision, the proposed method allocates a set of weights to each of the matrices within the codebook. These weights are selected adaptively according to the number of active users and...
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