Millimetre‐wave propagation is a promising broadband transmission technology for future fifth generation mobile communication systems. For a vector orthogonal frequency division multiplexing system, the authors investigate the millimetre‐wave propagation through a sparse multipath channel in a sense that it has a large time delay spread but with only a few non‐zero taps. By exploiting the sparse nature of millimetre‐wave channel, any sparse multipath channel can be characterised by the multipath delays and their corresponding channel coefficients. They first study an ideal case that the pilot signals are transmitted through a sparse channel without noise, and an exactly sparse inverse fast Fourier transform (SIFFT) algorithm is performed to estimate the non‐zero channel taps with reduced complexity. Then, they consider a more practical scenario that the pilot signals through a sparse channel with noise interference, and an approximately SIFFT algorithm is employed to estimate the effective channel taps, while the remaining small coefficients interfered by noise can be wiped out. Through numerical analysis, they demonstrate that the proposed SIFFT algorithms can reduce the computational complexity while keeping the root mean squared error of channel estimation at a low level.

Generalised frequency division multiplexing (GFDM) as a non‐orthogonal waveform candidate is posed to reduce the high out of band radiation of orthogonal frequency division multiplexing system via pulse shaping. In this study, an analytical model of introduced interference from neighbouring subcarriers caused by pulse shaping is firstly proposed. Signal‐to‐interference‐plus‐noise ratio (SINR) is calculated according to related GFDM models with different weighted‐type fractional Fourier transform (WFRFT) precoding orders. Approximated bit error rate (BER) expressions are derived for the low complexity GFDM system over additive white Gaussian noise and fading channels based on the analysis of SINR. Particularly, the BER superiority of WFRFT precoding is highlighted over the fading channels. Furthermore, peak‐to‐average power ratio and out of band power suppression performances are simulated at different WFRFT orders to illustrate the advantages of WFRFT precoding.

The increasingly extensive availability of location- acquisition technologies (such as GPS and GSM networks) and mobile computing techniques have generated a lot of spatial-temporal trajectory data which represents the mobility of diversification of moving objects such as people, vehicles, and animals. This brings new opportunities to understand the movement behaviors of moving objects in mobile social networks, which can become valuable for location-based services (LBS). However, the explosive growth of users' trajectory data has brought a lot of troubles to online real-time processing. In this paper, we focus on this direction and develop a complete data-driven framework involving real-time user mobility pattern modeling and a novel user similarity measurement based on both spatial and temporal information. Through experimental evaluation, it is verified that the proposed mobility pattern modeling method and similarity measurement can deliver excellent performance.

This paper presents a generalized frequency division multiplexing (GFDM) communication scheme based on 4-weighted fractional Fourier transform (WFRFT) precoding. The proposed scheme as well as its low complexity version achieves flexible multi-object optimization of system performance such as bit error rate (BER) and peak to average power ratio (PAPR). Compared to traditional GFDM scheme, the improved system based on weighted parameter selection brings about combined performance advantages.

This study proposes a quality‐driven approach that jointly selects the frequency reuse mode of device‐to‐device (D2D) links at lower layers, the video coding mode of frames, and multiple paths at higher layers for multimedia transmission in a cellular network with multi‐antenna relays placed at the intersection of adjacent cells. Based on power control of the shared relay, the user‐centered mode selection problem is formulated by maximising the quality of service (QoS) with total energy consumption constrained. Underlay mode and overlay mode are both considered. For each frame, one coding mode (I, P, or B) and multiple paths (cellular links and/or D2D links with/without relays) are selected to optimise the received video quality expectation. Different retransmission polices are considered to give higher protection levels to paths with higher transmission rates. The authors’ evaluation shows that the proposed unified power allocation and mode control scheme could enhance the perceived QoS as changing the energy constraint and the distances of different paths. The underlay mode is optimal in most cases. It provides evidences that it is not always the best to code all frames as I‐frames, to initialise the relay transmission power as the maximum, or to select one single path for video transmission.

In this paper, the mode selection (underlay or overlay) for device-to-device (D2D) links at low layers is jointly analyzed with the video coding mode selection and multiple transmission path selection at high layers. For each packet, three video coding modes (I, P, and B) and three transmission paths (cellular link with/without the shared relay and D2D link) are considered to optimize the received video quality expectation. The cross-layer mode selection problem is formulated by maximizing the Quality of Service (QoS) with total energy consumption constrained. Our evaluation shows that the proposed joint mode selection strategy could enhance the perceived QoS with less energy consumption as changing the channel conditions and transmitting power of different paths in a single sector. The coding mode selection is mainly decided by the energy constraint and the path selection mostly depends on the channel conditions.

This study investigates the outage probability of device‐to‐device communication assisted by a relay node utilising a one‐way amplify‐and‐forward relaying strategy. The authors assume that all the terminals are equipped with a single antenna and all the users know perfect channel state information. They first derive the exact closed‐form expression for characterising the outage probability performance of the system. They subsequently discuss several special scenarios and obtain the asymptotic results for each of the considered scenarios. The results can be easily computed with only the channel statistics. Based on the analysis in the high signal‐to‐noise ratio regime, closed‐form power allocation policies are developed to improve the outage probability performance. The author's analytical results are validated via Monte Carlo computer simulations.

This paper addresses the problem that devices are reluctant to participate in local device-to-device (D2D) communications in the purpose of improving the data transmission quality. We propose a novel game-theoretic approach of joint source selection and power control, which enhances the multimedia transmission quality with latency constraint. The proposed approach first analyzes the interactions between the base station (BS) and the devices using a Stackelberg game model. The optimal transmission power and price are obtained for each source device through deriving Stackelberg equilibrium off-line, in which the BS and the device both achieve maximum utilities. Second, the BS schedules the devices according to its equilibrium of signal-to-interference-and-noise ratios in D2D links. Finally, the selected best source devices complete the multimedia transmission with their power controlled. Simulations demonstrate that our proposed scheme can significantly improve multimedia transmission quality with low complexity.

The Spatial Modulation (SM) transmission scheme boosts the spectral efficiency and achieves the multiplexing gain by activating a single transmit antenna in each time slot. Radio wave propagation characteristics determined by the environment is a decisive factor for the SM system. In this paper, we investigate the performance of the SM scheme over real-world 4x4 Multi-Input Multi-Output (MIMO) channels measured in typical indoor scenarios. Firstly, a MIMO channel sounder is established. Based on the sounder, 15150 complex 4x4 MIMO channel matrices are measured inside a typical teaching building under both Line of Sight (LOS) and None Line of Sight (NLOS) scenarios. Secondly, by comparing the SM system over the measured channel and commonly-used channel models, we prove that both the Independently and Identically Distribute (i.i.d.) Rayleigh and the Spatial Correlation (SC) channel model are oversimplified, and that only practical experiences can yield definitive answers to the achievable real-world system performance. Thirdly, the Average Bit Error Probability (ABEP) performance of the SM system is studied based on the measured data under a variety of system configurations. The study of different receive antenna array settings (4x4, 4x2 and 4x1 MIMO setups) approves the significance of combining scheme at the receiver. SM systems employing different signal constellations (Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK) and 16 Quadrature Amplitude Modulation (16QAM)) are also investigated and some interesting results are revealed. Lastly, performance assessment of SM against State-Of-The-Art (SOTA) MIMO schemes (Space-Time Block Code (STBC) and Vertical Bell Labs Layered Space-Time (V-BLAST) code) is conducted. Results show that for a 4x4 MIMO, the low-complexity SM scheme outperforms both STBC and V-BLAST.

ABSTRACT The fractional Fourier transform (FRFT)—a generalization of the well‐known Fourier transform (FT)—is a comparatively new and powerful mathematical tool for signal processing. Many results in Fourier analysis have currently been extended to the FRFT, including the ordinary convolution theorem. However, the extension of the ordinary convolution theorem associated with the FRFT has been developed differently and is still not having a widely accepted closed‐form expression. In this paper, a generalized convolution theorem for the FRFT is proposed, and the dual of it is also presented. The ordinary convolution theorem and some of its existing extensions related to the FRFT are shown to be special cases of the derived results. Moreover, some applications of the derived results are presented. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we propose an opportunistic spectrum sharing protocol that exploits the situation when the primary system experiences weak channel conditions. Specifically, when the outage rate of the primary systeme falls below the target rate, the secondary system tries to help the primary system achieve its target rate by acting as a decode-and-forward relay for the primary system, and allocating a fraction of its subcarriers to forward the primary signal. As a reward, the secondary system gains spectrum access by using the remaining subcarriers to transmit its own signal. We study the joint optimization of the set of subcarriers used for cooperation and the secondary subcarrier power allocation such that the transmission rate of the secondary system is maximized, while guaranteeing the primary system to achieve its target rate. Simulation results demonstrate that both primary and secondary systems can benefit from the proposed secondary spectrum access scheme.

To suppress the effects of ultra-wideband receiver caused by non-Gaussian noise and difference of channel profile, an adjustable observation window length equalisation receiver based on H∞ criterion is proposed. In contrast to the existing fixed observation window length (FOWL) equalisation receivers based on the minimum mean square error (MMSE) criterion, the proposed receiver is found on H∞ criterion and can adaptively adjust the observation window length according to the specific channel profile. The proposed receiver so designed is shown to outperform the FOWL equalisation receivers based on the conventional MMSE criterion in a non-Gaussian noise environment.

The classical multichannel sampling theorem for common bandlimited signals has been extended differently to fractional bandlimited signals associated with the fractional Fourier transform (FRFT). However, the implementation of those existing extensions is inefficient because of the effect of spectral leakage and hardware complexity. The purpose of this letter is to introduce a practical multichannel sampling theorem for fractional bandlimited signals. The theorem which is constructed by the ordinary convolution in the time domain can reduce the effect of spectral leakage and is easy to implement. The classical multichannel sampling theorem and the well-known sampling theorem for the FRFT are shown to be special cases of it. Some potential applications of this theorem are also presented. The validity of the theoretical derivations is demonstrated via simulations.

Abstract Cognitive ultra‐wideband (C‐UWB) systems have recently received much attention because the huge bandwidth of ultra‐wideband (UWB) systems can better exploit the advantages of cognitive radio (CR) systems. Dynamic spectrum access (DSA) is a key technique in CR systems to implement dynamic spectrum change and can be easily implemented by changing the transmitted pulse shape in a C‐UWB communication system. In this paper, we propose an orthogonal expansion based pulse shaping method to implement DSA and to compensate for antenna distortion, which uses the orthogonal Hermite functions as the orthogonal basis. In order to eliminate the direct current (DC) component existing in even orthogonal Hermite functions and to reduce the computational complexity, two modified methods and a simplification procedure are also proposed. Our results indicate that the proposed orthogonal expansion based pulse shaping methods have a much lower computational complexity than the semi‐definite programming (SDP) method, while achieving a high power efficiency. Furthermore, we demonstrate that the distortion caused by the antenna effects can also be compensated during the pulse shaping process and a better signal‐to‐noise ratio (SNR) can thus be achieved. Therefore, the proposed method is very suitable for practical application in C‐UWB communications, in which the spectrum environment changes rapidly. Copyright © 2009 John Wiley & Sons, Ltd.

According to the low cost and complexity demands in most sensor applications, a new ultra wideband (UWB) time of arrival (TOA) estimation method based on weighted energy detection is proposed in this paper. Firstly, the energy block that contains the direct path (DP) component is detected by generalized likelihood ratio test (GLRT). Then the precise position of DP within the detected energy block is obtained by channel statistics. Key parameters of performance are studied and optimized. The results compared with traditional TOA estimation algorithms also show that this method can achieve a relative high performance under low sampling rate conditions.

Abstract Localization is essential for wireless sensor networks (WSNs). It is to determine the positions of sensor nodes based on incomplete mutual distance measurements. In this paper, to measure the accuracy of localization algorithms, a ranging error model for time of arrival (TOA) estimation is given, and the Cramer—Rao Bound (CRB) for the model is derived. Then an algorithm is proposed to deal with the case where (1) ranging error accumulation exists, and (2) some anchor nodes broadcast inaccurate/wrong location information. Specifically, we first present a ranging error‐tolerable topology reconstruction method without knowledge of anchor node locations. Then we propose a method to detect anchor nodes whose location information is inaccurate/wrong. Simulations demonstrate the effectiveness of our algorithm. Copyright © 2008 John Wiley & Sons, Ltd.

Abstract In this paper, based on the analysis of the experimental data using a new post‐processing method for time‐domain channel measurements, a new double‐cluster statistical model for UWB systems with a bandwidth lower than 1 GHz in non‐line‐of‐sight (NLOS) indoor propagation environment is proposed. By using the proposed model, both the model itself and the parameter estimation of the corresponding model are simplified. By defining the polarity of a particular model parameter, the model has the flexibility to deal with both ‘soft NLOS’ and ‘hard NLOS’ indoor propagation environments. Therefore, the channel impulse responses (CIRs) generated by the proposed model ‘resemble’ the measured CIR better than the SV (Saleh‐‐Valenzuela)/IEEE 802.15.3a model not only in terms of the average values, but also in terms of the cumulative distribution functions (CDFs) of the small‐scale statistics. Copyright © 2008 John Wiley & Sons, Ltd.

In order to achieve efficient dynamic spectrum access (DSA) in Cognitive Ultra-Wideband (C-UWB) systems, an orthogonal wavelets based dynamic pulse shaping method is proposed to obtain pulses which can adapt to any given spectral requirements. Using Meyer wavelet set as the orthogonal basis, pulses with high power efficiency can be achieved. The compact support property of Meyer wavelets enables us to efficiently reduce the computational complexity in dynamic pulse shaping calculation. Moreover, we demonstrate that the proposed method is easy to implement and can achieve a good balance between power efficiency and system complexity.

Localization is essential for wireless sensor networks (WSNs). It is to determine the positions of sensor nodes based on incomplete mutual distance measurements. In this paper, to measure the accuracy of localization algorithms, a ranging error model for time of arrival (TOA) estimation is given, and the Cramer-Rao bound (CRB) for the model is derived. Then an algorithm is proposed to deal with the case where 1) ranging error accumulation exists, and 2) some anchor nodes broadcast inaccurate/wrong location information. Specifically, we first present a ranging error-tolerable topology reconstruction method without knowledge of anchor node locations. Then we propose a method to detect anchor nodes that have inaccurate/wrong position information. Simulations demonstrate the improvement of our algorithm compared to others.

In impulse radio (IR) type Ultra-Wideband (UWB) communications, orthogonal waveforms confirm to given spectral mask are desired to improve system capacity. Therefore, in this paper, an orthogonal wavelet based pulse shaping algorithm is proposed and compactly supported Meyer wavelet is used as an example to show how to obtain orthogonal pulses. Simulation results show that the proposed algorithm can obtain orthogonal pulses with high power efficiency and the pulse generator can be implemented simply as well.

We present a video object extraction algorithm combining image partition with motion detection. It consists of three stages: spatial image partition (SIP), temporal motion detection (TMD) and spatiotemporal projection (STP). Firstly, we partition the current video frame into a series of image regions by a modified watershed transform with double open-closing reconstruction and non-linear pixel classification, and the corresponding region boundaries are achieved. In the next stage, global motion estimation and compensation (GME & GMC) are performed, then motion detection based on Gaussianity test is applied to pixels on region boundaries, not to all pixels belonging to regions. In final stage, motion mask is projected to the current frame to segmenting video objects. Preliminary simulation results demonstrate the performance of the proposed algorithm.

By exploring the deterministic characteristics of the measurement data, a new propagation model with two deterministic clusters and stochastic arriving rays within each cluster is proposed. When considering cumulative distribution function (CDF) of the three key channel statistics, the proposed model fits the measurement data better than SV/IEEE 802.15.3a model which is seen as standard model for UWB indoor propagation channel. That means, with the additional knowledge of the specific environment geometry, the proposed model generating impulse responses "resemble" the measured channel impulse responses better than IEEE model. Moreover, the proposed model's parameters obtaining procedure is simplified by utilizing simple parameters of physical channel.

To mitigate the non-line-of-sight (NLOS) error of ultra-wideband (UWB) ranging caused by obstructions in dense multipath environments, this paper proposed a novel NLOS error mitigation method. The principles and characteristics of NLOS error are analyzed. Based on the signal propagation path loss model, the NLOS error estimation expression is deduced and further used to calibrate the ranging results. Low complexity path detection algorithms are proposed for implementation of the method. Test on measured data shows that the method can improve the ranging precision greatly.

For a single low earth orbit (LEO) satellite has limited capacity, the blocking probability of guaranteed handover (GH) algorithm increases rapidly in the case of high traffic load. So, when large amounts of multimedia services are transmitted via a single low earth orbit (LEO) satellite system, the PB of it is much higher. In order to solve this problem, a modified handover scheme defined by multi-tier optimal layer selection is proposed. The scheme sufficiently takes into account the characteristics of the low/medium earth orbit (LEO/MEO) double-layer satellite network and the multimedia transmitted by such network, so it can effectively reduce the traffic load in the LEO which perform GH algorithm. The simulation results show that this approach integrated with GH algorithm used in LEO/MEO satellite network achieves a significant improvement in the QoS performance and practicability of the algorithm as compared to the single LEO layer network. Also, the complexity of this algorithm was analyzed based on some numerical results.

In this paper, an onboard Asynchronous Transfer Mode (ATM) switching fabric based on Ant Algorithm with blocking avoidance is proposed in satellite ATM network. The onboard ATM switching fabric is an improved Benes network based on Ants Flooding Mechanism and Blocking Avoidance Mechanism to solve bandwidth-limited and delay-bounded problems in satellite communication network. Compared with traditional self-routing Benes network, better performances of proposed onboard ATM switching fabric are achieved.

In this paper, we address the scalable route problem of the large ad hoc network. The routing problem of ad hoc network is particularly challenging, especially for the large ad hoc networks, because the large number of mobile node and the high mobility of the mobile node. FSR (Fisheye state routing) scheme is proposed to resolve the routing problem in large ad hoc networks, but the this protocol use fixed route table update interval, so routing overhead of FSR is relative large while the mobility of node is high. This paper proposed DTUI (dynamic route table update interval) scheme to keep the routing overhead increasing linearly with the increasing number of the mobile hosts in the ad hoc networks. In our adaptive scheme, each node adaptive adjust own route table update interval according to the mobility of the mobile nodes. We study two types of execution: range-based DTUI adaptation and continuous function DTUI adaptation. The simulations prove that our scheme can reduce the routing overhead while guarantee certain route accuracy.

Mobility management is an important aspect in LEO systems. In terrestrial wireless networks, the movement of the user triggers location updating and determines the paging scheme, while in LEO satellite systems, location updating and paging is mainly based on the movement of satellites. Terrestrial location management techniques must be altered to fit LEO systems. The paper introduces a modified movement-based location update and paging scheme in LEO networks. We propose the meta-cell concept, which includes two spot-beams of one satellite. First, we present a location management scheme based on the architecture with a meta-cell location area. Then, an analytical model is applied to formulate the cost of location updating and location paging for the movement and meta-cell based dynamic location update scheme. The comparison of performance between the meta-cell architecture method and the conventional signal-spot-cell architecture method is provided to demonstrate the cost-effectiveness and robustness of the proposed scheme under various parameters. To reduce the impact of meta-cell architecture on location paging cost, we present a forced location update strategy which is used in the case that the meta-cell includes two spot-beams from different satellites.