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A new and efficient radio resource allocation and scheduling algorithm for SDMA/OFDMA systems with downlink zero-forcing beamforming is proposed to support the diverse quality of service (QoS) requirements of heterogeneous services. In particular, a unified urgent weight is given by taking into account QoS requirements (i.e., delay deadline, minimum data rate), queue length and user fairness. The...
In a cognitive radio cellular system, secondary users (SUs) are allowed to share the spectrum with primary users (PUs), and inevitably cause interference to PUs. To guarantee the interference to PUs under a predefined threshold, admission control has to be investigated. In addition, different SUs may require different levels of quality of service (QoS), and pay differently based on their services...
For several years now the industry is promising to mobile users high QoS seamless wireless access. This promise has been kept to some extent, but the cost for services is still high. Open spectrum access is expected to lead to lower cost of bit/Hz, encourage the development of new wireless technologies and increase their market penetration. Under an open spectrum access scenario where connectivity...
In this paper, a new antenna shuffling scheme which can improve both diversity and multiplexing gains for double space time transmit diversity (DSTTD) system is proposed. This scheme needs low computational complexity and limited feedback information. Based on the theoretical analysis, we can also know that achieving more diversity gain dose not opposite to achieve more multiplexing gain. The performance...
The problem of finding good linear codes for joint source-channel coding (JSCC) is investigated in this paper. By the code-spectrum approach, it has been proved in the authors' previous paper that a good linear code for the authors' JSCC scheme is a code with a good joint spectrum, so the main task in this paper is to construct linear codes with good joint spectra. First, the code-spectrum approach...
Sensor networks inherit unique technical challenges such as limited battery capacity and very primitive computing capabilities. To prolong the lifetime of the wireless sensor networks, energy efficiency is one of the most critical issues. Many routing protocols are developed to address this issue from different aspects. Related routing protocols can be classified into three categories: data-centric,...
For wideband Multiple Input And Multiple Output (MIMO) and orthogonal frequency division multiplexing (OFDM) wireless system, the fading selectivity in spatial-temporal-frequency domain and the variable network load and interference put a constraint on the system design. The traditional layered protocol design canpsilat adapt to these variance and results in low transmission efficiency. In this paper,...
In multi-cell orthogonal frequency division multiplexing cellular systems, the co-channel interference (CCI) from adjacent cells becomes the dominant interference. Considering the CCI in multiple cells, the optimal solution for data rate maximization is derived from the dual decomposition method. Based on the optimal solution, a simplified uplink distributed power allocation (UDPA) algorithm is proposed...
Asymptotic performance analysis of orthogonal frequency division multiple access (OFDMA) is conducted in this work. We take a cross-layer approach and analyze how the system performance scale with some important parameters such as number of user, CSIT quality and order of diversity. It is well studied that system goodput scale with number of user K in the order of O(log log K) due to multiuser diversity...
Regular expressions are increasingly used in network security applications. Multiple regular expressions matching is one of the most important performance bottlenecks in those systems. This paper proposes a new hardware-based multiple regular-expressions matching architecture, called MRM, for network intrusion detection system. It shows that traditional algorithm, such as AC, has to face the serious...
To enhance the structure of networks, some costly but more powerful relay nodes are usually placed in wireless sensor networks. These nodes can prolong network lifetime and preserve connectivity of networks. So it makes sense to place relay nodes to guarantee the connectivity and reliability of wireless sensor networks. In this paper, we focus on the reliable relay node placement problem. We take...
A key factor affecting the lifetime of wireless sensor networks(WSN) is its limited energy. Firstly, ratio of energy cost of different parts of a sensor node and time-dependent difference of data gathered is presented. Then, in order to prolong the lifetime of WSN under the limited energy, time-sensitivity of sensor is defined, sensors are classified based on it, scheduling for data gathering with...
This paper proposes a block spread orthogonal frequency division multiple access (BS-OFDMA) system with a combined space-time coded multiple-input multiple-out (STC-MIMO) scheme called STC-MIMO BS-OFDMA for transmission over frequency selective fading channels. In this system, a novel block spreading approach is firstly applied to effectively achieve precoding in the OFDMA system with lower complexity...
We explore the asymptotic performance of existing geographic routing with a utilization of k-hop neighborhood information. The reachability from source to sink improves as we integrate more information into the routing decision. It is observed that the average number of hops required decreases significantly from the 1-hop to 2-hop based searching. This indicates an attractive tradeoff between the...
For the purpose of reducing the effect of non-line-of-sight (NLOS) error that inhibits accurate location of mobile stations (MS), a novel approach based on the method of joint variance matching algorithm (JVMA) [1] is presented in our research. In order to improve location accuracy, scattering models are used to classify propagation environments and model the NLOS error effect to be incorporated into...
Cognitive Radio (CR) is considered as a promising approach for efficient utilization of precious radio spectrum resources. In this paper, we present a new approach that combine active interference cancellation (AIC) and vertical Bell Laboratories Layered Space-Time (V-BLAST) techniques to transmit data through a multiple-input and multiple-output (MIMO) system within protected band which has been...
The increasing demand for broadband wireless service in today's wireless communications, especially with WiMAX technology being one of the 3G standards, is causing cellular network providers to consider the integration of different heterogeneous networks. Consequently, network selection techniques play a vital role in ensuring quality of service in heterogeneous networks. In this article we develop...
Spectrum sensing is one of the key challenges in the cognitive radio network. Primary user signal must be detected reliably in the low signal-to-noise ratio (SNR) regime and in multipath fading environments. This paper analyzes effects of time-variant multipath Rayleigh fading channel on cyclostationary characteristics and derives the relationship between cyclostationary statistics of transmitted...
In order to improve the accuracy of the vertical handoff decision-making and efficient utilization of wireless network resources in radio heterogeneous network, this paper proposes a hierarchy multiple attribute decision with possibilities (HMADP) method based on service. This method uses analytic hierarchy process ( AHP ) and multi attribute decision making with possibility (MADMP). The AHP reflect...
Due to the limited energy supplies of nodes, in many applications like wireless sensor networks energy-efficiency is crucial for extending the lifetime of these networks. We study the routing problem for multihop wireless ad hoc networks based on cooperative transmission. The source node wants to transmit messages to a single destination. Other nodes in the network may operate as relay nodes. In this...
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