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As one of the significant reform methods to improve the management level of government investment project, agent-construction system has been applied in many places. During the process of agent construction, agent assumes considerable risk. This paper identifies the main risks of agent. Based on the analytic hierarchy process method, the main risk and relative influence factors are analyzed and evaluated...
Electronic marketplaces represent new places where supply and demand aggregate and negotiations take place. New opportunities and rapidly changing environment of electronic marketplaces lead to the need of more sophisticated negotiations to support various trades. Automated negotiation is one of the most popular and promising technologies to perform such task and will be a vital part of electronic...
In this paper, an innovative scheduling is designed for multi-hop multicast in wireless mesh networks, with utilization of concurrent transmission strategy. Since the performance of a multicast mechanism is constrained in a wireless setting due to the interference among local wireless transmissions, we analyze the interference relationships firstly among the transmissions by introducing a graph transformation...
The system of cdma2000 1x EV-DO is introduced to provide fast and efficient broadband wireless access. Up to now, there are three versions, mentioned as reversion 0, A and B. A great number of techniques, such as hybrid-ARQ, adaptive modulation and coding, as well as multi-user diversity, support the system to have higher spectral efficiency and better performance. In this paper, technical background...
Aiming at the effect of ultra wideband (UWB) system for the potential victim systems on UWB operating frequency band, using the entire physical layer model method, this paper studies the interference of direct-sequence ultra wideband (DS-UWB) and multi-band ultra wideband (MB-UWB) on these victim systems. Depended on the physical characteristics of UWB and these victim systems, the entire physical...
Considering ultra wide band (UWB) system which transmits data information using ultra-short pulses, a pulse shape modulation UWB system based on orthogonal UWB pulse is proposed, which is on the basis of the orthogonality and non- direct component of modified Hermite polynomial function. The simulation result shows that the method can not only improve the performance, but also decrease the bit error...
The time-hopping pulse position modulation (TH- PPM) is one of the most popular approaches for IR-UWB multiuser systems, and a lot of research efforts have been devoted on its performance analysis. In several latest literatures, a method of MAI modeling, as well as the numerical computation of the MAI characteristic function, had been carrid out to derive precision analytical bit error performance,...
This paper analyzes zero-forcing (ZF) code-aided narrow-band interference (NBI) rejection in synchronous direct-sequence code-division multiple access (DS-CDMA) systems of complex channel circumstance. The performance of decoding is badly affected based on general ZF code-aided techniques because of the phase of complex gain accounting for channel effects. The system based on modified ZF code-aided...
Some wideband wireless links such as unmanned aerial vehicle (UAV) and satellite links have much wider bandwidth than that of high power natural or artificial interference. An idea of adaptive narrow band interference (NBI) cancellation based on different algorithms and structures aiming at wideband wireless links where bandwidth of interference is relatively narrow is posed here. All these theoretically...
This paper presents three kinds of coverage rates, including the averaged coverage rate, the interference conditional coverage rate and the signal conditional coverage rate, to evaluate the performance of adaptive arrays. The coverage rate is the probability of the reception of the desired signal against certain interference scenarios. Numerical results demonstrate that coverage rates can describe...
In this paper, we investigate two space-time receivers based on zero forcing (ZF) and minimum mean square error (MMSE) criteria for space-time transmit diversity (STTD) system in time varying channel. The performances of these schemes are compared with conventional Alamouti's scheme under the condition of combining with/without ordered successive interference cancellation (OSIC) in terms of normalized...
A new kind of acknowledgment-type slotted-ALOHA-CDMA channel for multiple code spread spectrum, which can be used for uplink channel of VSAT systems, is studied for the first time in this paper. The channel model is developed firstly. Then the interference between subsystems is obtained and the transmission influence in subsystems is discussed. At last, detecting probability and throughput is calculated...
Against eliminating the multiple access interference (MAI) and sky-wave interference under multi-path channel in the radio navigation system, an improved hybrid interference cancellation (HIC) method that combines the advantages of both the successive interference canceller (SIC) and the parallel interference canceller (PIC) is proposed in this paper. It has the advantages of low complexity and easy...
Cognitive radios is emerging as a promising wireless paradigm, which will integrate benefits of software defined radio with a complete aware communication behavior. By detecting environments in real time and extracting interference characteristic in frequency spectrum, it can use flexible spectrum assign strategy for adaptive communications. To reach this goal many issues remain still open, such as...
In this paper, we compare the downlink performance of multiuser spatial multiplexing of centralized antenna system (CAS) and distributed antenna system (DAS) in interference-limited cellular scenario. We present the implementation of multiuser spatial multiplexing in a multicell system based on selection diversity. And two user scheduling strategies based on proportional fairness is proposed too....
The paper proposes an approach of optimizing transmit power in wireless sensor networks with random topology in order to prolong node lifetime. It defines optimal transmit power as the minimum transmit power used by all nodes necessary to guarantee end-to-end bit error rate (BER) requirement. Assuming Rayleigh fading channels and two- dimensional Poisson topology, we bring nearest with forward progress...
Based on analyzing the spectrum of narrowband interference, a method of suppressing narrow interference, which makes use of cyclostationary character of interference, is proposed in DSSS system in this thesis. The results of simulation indicate that this technique can suppress narrowband interference better than the estimator/subtracter filter in the time domain.
In this paper, a typical commercial short range wireless communication module which has weak immunity to interference has been tested and its performance has been evaluated with test bed. An adaptive frequency hopping scheme has been proposed to improve its immunity to interference and therefore enhance the wireless communication performance for reliability and delay-critical applications. Such scheme...
Single channel is a severe capacity bottleneck in wireless mesh networks (WMNs). Multiple channels enhance the wireless network capacity by simultaneous transmissions and decrease the interference among nodes. Due to the scarcity of non-overlapped channels, the way of assigning channels becomes extremely important for throughput optimization in WMNs. This article presents a channel assignment algorithm,...
Exact and general analysis of the capacity for multiple-input single-output (MISO) correlated Rayleigh fading channels in the presence of both correlated Rayleigh co-channel interference and additive Gaussian noise is not available in the literature, although its counterpart with Gaussian noise alone has been thoroughly investigated. The difficulty arises from the quadratic form of interference term...
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