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Cognitive radios have enabled the users to utilize licensed bands opportunistically without causing harmful interference to licensed users. Spectrum analysis is an important technique in cognitive radio networks. And it helps ranking available channels using spectrum sensing results. Appropriate channel assignment decisions will be made according to the ranking results and user requirements. Here...
In order to achieve better spectral efficiency, several prototypes have been suggested as physical layer candidates for cognitive radio systems as OFDM (Orthogonal Frequency Division Multiplexing), SRRC (Square Root Raised Cosine) and others. In such models, we are confronted to problems of interference between the cognitive users and licensed users which degrade the performances of using models....
In cognitive radio networks, the process of sensing the potential channels and choosing free ones to access in is called spectrum access. In this paper, three spectrum access schemes are compared. They are sensing-all before accessing scheme, Partially Observable Markov Decision Process (POMDP) based scheme and sequential channel sensing scheme. The efficacy of these schemes is studied by both theoretical...
The information about channel statistics is sometimes not available for cognitive users a priori. The need to learn this information online creates a fundamental trade-off between exploitation and exploration. This can be formulated as a Multi-Armed Bandit (MAB) problem. In this work the channel sensing-order setting problem is studied under this scenario. It is shown that the regret of classic UCB1...
Modern mobile communication increasingly tends to provide high speed transmission multimedia services, therefore the deployment of 4G cellular networks is expected to provide the high speed transmission multimedia services that rely on heterogeneous radio access architectures, whereby cells of different coverage and capacity coexist in the same geographical areas. In this paper, we researched the...
In Satellite Communication System, system lifetime drops drastically in energy consumption of the payload. MIMO has been done in order to take advantage of the correlation among satellites' data for increasing the capacity of channel and decreasing the transmission power. This paper studies a dual-satellite scenario based upon synchronization-deriving and gateway-processing schemes, aimed at overcoming...
Centralized, cooperative, cloud radio access network (C-RAN) is a novel wireless access network architecture which can provide low cost and high performance. Applying C-RAN on broadband wireless access system for high-speed railway (HSR) may improve the quality of existing network architecture. In this paper, we describe the current research status and some difficulties of broadband wireless access...
Femtocell is a promising solution to improve indoor coverage and system capacity with lower transmit power and enhanced user Quality of Service in LTE network. Moreover, the integration of femtocells into cellular networks makes the inter-cell handover process more frequent and time sensitive. Because femtocell base station uses public Internet to connect with mobile core network, the legacy handover...
The massive random accesses of machine type communication (MTC) in current wireless networks (e.g. LTE-A, WiMAX) are a challenging and urgent issue. In this paper, the random access performances in LTE-A networks are first analyzed in terms of success probability, access delay, physical random access channel efficiency, and the number of retransmissions. Based on the analysis, two QoS-based optimization...
Conduction current field communication technology is a radio-communication mode, which penetrates the formation by means of radio waves, and uses the layered earth as electromagnetic wave propagation medium. On the propagation in crust, traditional wireless communication mode has the disadvantages of the serious signal attenuation and the low antenna radiation efficiency. In addition, the arrangement...
Distributed antenna systems (DAS) have been studied in cellular communication systems to improve system performance and enhance system capacity. This paper studies the system outage performance of downlink DAS with beamforming at antennas ports (AP). Firstly, a composite channel including Rayleigh fading, shadowing and path loss is established. Then, the mathematical expression of system outage probability...
Energy efficiency and spectral efficiency are two important aspects of wireless system. In this paper, a distributed scheme of energy-efficient power control is addressed jointly with 3D-beamforming (3D-BF), named as energy-efficient 3D-beamforming (EE-3DBF). In consideration of the high complexity to deal with power control and 3D-BF simultaneously, EE-3DBF is divided into limited coordination downtilt...
In [1] and [2], we have proposed a novel metric for evaluating the capacity to the total energy consumption ratio of Multiple Input Multiple Output (MIMO) systems. We have considered the context of Wireless Sensor Networks (WSNs) and we have evaluated the proposed metric over the distance between the transmitting and the receiving sides. We have identified the optimal MIMO system configuration for...
For the problem of increasingly scarce spectrum resources, improving bandwidth efficiency is to be solved. Drawing on traditional techniques based on CDMA (Code Division Multiple Access, CDMA) communication, this paper puts forward a transmission system in the same bandwidth of LFM and voice SSB signal. Theoretical analysis and simulation results showed that LFM and voice SSB signal can be transmitted...
OvTDM is a new transmission scheme that can obtain high spectral efficiency with very low threshold signal noise ratio (SNR) by using the inter symbol interference (ISI). Fano algorithm (FA) is researched in this paper to implement fast ML decoding at high spectral efficiency for OvTDM. Numerical results show that the complexity of OvTDM with FA has no relationship with the number of state which is...
A reconfigurable ultra-wideband (UWB) bandpass filter (BPF) with tunable notch band for UWB system is presented in this paper. The UWB BPF adopts the proposed stub-loaded multiple-mode resonator (MMR) structure and RF-MEMS switched capacitor network which is used for electronic tuning. The filter is printed on a Roger's RT/Duriod 6010 substrate with the dimensions of 10 mm × 10 mm × 1.2 mm and relative...
A novel compact multi-band Electromagnetic Band Gap (EBG) structure is introduced in this paper. Through etching four identical F-shaped slots on the surface of conventional mushroom-shaped EBG (CMT-EBG) structure, which is spiral and symmetrically distributed about the centre of EBG surface, the equivalent current path is extended while producing four resonant circuits. The simulated results present...
This paper presents a dual-band bandpass filter with tunable centre frequencies. The proposed filter is mainly implemented by two λ / 2 resonator and three varactor diodes. By adjusting all varactors can adjust the centre frequency of the two passband, if Cv1 is fixed, only tuned Cv2 can achieve first pass band fixed while the second passband could be adjusted. When adjusted the frequency of both...
The number of mobile subscribers has increased by 399 million in 2013, of which WCDMA/HSPA subscribers account for 68%. Meanwhile, various short-size packet services, such as web browsing, instant messaging and social network applications, are growing rapidly, leading to a sharp increase in signaling load and limit the network capacity to allocate resources efficiently in High Speed Uplink Packet...
Low power wide area (LPWA) networks are power-constrained and work on industrial, scientific, medical (ISM) bands. The scheme of clear channel assessment (CCA) has a great influence on network performance, and the most important characteristics of CCA methods for LPWA networks are high detection probability and power saving. For different wireless networks, carrier sensing (CS), one of the CCA methods,...
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