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In uplink non-orthogonal multiple access (NOMA) channels, the existing cooperative successive interference cancellation (SIC) and power control (PC) schemes lack the capability of achieving the full capacity region, which restricts the outage performance of uplink NOMA users. For the uplink cognitive radio inspired NOMA system, we propose a new rate splitting (RS) strategy to maximize the achievable rate of the secondary user without deteriorating the primary user's outage performance. Based on the interference threshold and its own channel gain, the secondary user adaptively conducts RS, transmit power allocation and SIC, which utilizes the transmit power efficiently. The closed-form expression for the outage probability is derived for the secondary user. Numerical results show that the proposed RS scheme achieves the best outage performance for the secondary user among the existing cooperative SIC and PC schemes., Comment: 5 pages, 5 figures, accepted by IEEE Journal. arXiv admin note: substantial text overlap with arXiv:2110.02281

In this paper, we design a spatial modulation based orthogonal time frequency space (SMOTFS) system to achieve improved transmission reliability and meet the high transmission rate and high-speed demands of future mobile communications, which fully utilizes the characteristics of spatial modulation (SM) and orthogonal time frequency space (OTFS) transmission. The detailed system design and signal processing of the SM-OTFS system have been presented. The closed-form expressions of the average symbol error rate (ASER) and average bit error rate (ABER) of the SM-OTFS system have been derived over the delay-Doppler channel with the help of the union bounding technique and moment-generating function (MGF). Meanwhile, the system complexity has been evaluated. Numerical results verify the correctness of the theoretical ASER and ABER analysis of the SM-OTFS system in the high signal-to-noise ratio (SNR) regions and also show that the SM-OTFS system outperforms the traditional SM based orthogonal frequency division multiplexing (SM-OFDM) system with limited complexity increase under mobile conditions, especially in high mobility scenarios.

In this paper, a light emitting diode grouping based spatial modulation (LGSM) scheme is investigated for the indoor visible light communication (VLC) system for a better symbol error rate (SER) performance with the aid of characteristics of the spatial modulation. In consideration of the high channel correlation property of the visible light communication, the multiple transmitting LEDs are separated into different groups with the purpose of alleviating the channel correlation among each group. Owing to the proposed grouping scheme, the spatial information and channel correlation property can be perfectly utilized to improve the system performance of SER, which implies a higher transmission capability by the proposed LGSM scheme. Meanwhile, the mathematical derivation of SER for the proposed LGSM scheme is also provided by considering the maximal likelihood detection. Both of the simulated and theoretical results have proved that a better SER performance can be obtained via the proposed LGSM scheme compared with the common spatial modulation VLC system. Furthermore, the influence of the elevation angle of the receive photo detector in the LGSM VLC system is also investigated.

In this paper, we propose the quality-of-service (QoS) driven robust power allocation policy with channel uncertainty in the secure multicarrier full-duplex (FD) relay communication system, where the statistical delay QoS is given by the secure effective capacity (SEC). To maximize the SEC under the constraints of both the total system power and the residual loopback interference (LI) power of the FD relay, an optimization problem is formulated and the corresponding power allocation strategy has been presented in the case of perfect channel state information (CSI) and imperfect CSI. Specially, considering the imperfect CSI, we propose a robust power allocation scheme, where the channel uncertainty is modeled by a bounded region. Furthermore, the worst-case method and the Bernstein approximations are utilized to deal with the uncertainty. After the Taylor approximation based simplification of the formulated optimization problem, the optimal solution is obtained by subgradient descent algorithm based on Lagrangian dual method and Karush-Kuhn-Tucker (KKT) conditions. With known error range of CSI, numerical results and analysis illustrate that the proposed robust power allocation strategy can satisfy the statistical delay QoS requirement very well. Furthermore, the trade-off between the SEC and the robustness can be achieved with channel uncertainty.

A joint resource allocation policy for an underlay multi-user secure cognitive radio network (CRN) adopting the time-division multiple-access scheme with the guarantee of the statistical delay quality-of-service is proposed in this paper. Through the problem formulation of the resource allocation for the multi-user secure CRN with perfect channel state information (CSI), the energy-efficient joint power and time optimization scheme is proposed, which aims at minimizing the $\beta$ -fair cost functions subject to fairness, delay, and security constraints. Furthermore, considering the multi-user secure CRN with imperfect CSI, we also propose a robust resource allocation scheme and the tradeoff between the robustness and the achievable sum-power is analyzed. Numerical results show that the optimal resource allocation scheme with perfect CSI can effectively balance the tradeoff between the energy efficiency and the fairness and is superior to the other conventional resource allocation strategies. Moreover, the robust resource allocation policy with imperfect CSI makes the theoretical research much closer to the practical applications.

In this paper, an orthogonal complementary code (OCC)-selection-based high-efficient ultrawideband (UWB) spatial modulation (SM) system has been proposed to achieve higher transmission rate and better system performance. The OCC is employed to spread the spectrum, carry extra information bits, and alleviate the multipath interference simultaneously. Meanwhile, the SM technique is adopted to further increase the system bit rate and overcome the synchronization and interference issues of a multiantenna system. In the proposed UWB SM system, the information bits are conveyed through three ways: direct bipolar pulse amplitude modulation, indirect spread spectrum code selection, and transmit antenna selection. To further enhance the system performance over a multipath fading channel, the selective Rake receiver and maximum ratio combining detection are utilized. A closed-form expression of the system bit error rate is derived through the moment-generating function. Numerical results are provided to verify the theoretical analysis and show the efficiency and performance improvement of the proposed OCC-selection-based UWB SM system.

In this paper, a deep learning-based traffic state discrimination method is proposed to detect traffic congestion at urban intersections. The detection algorithm includes two parts, global speed detection and a traffic state discrimination algorithm. Firstly, the region of interest (ROI) is selected as the road intersection from the input image of the You Only Look Once (YOLO) v3 object detection algorithm for vehicle target detection. The Lucas-Kanade (LK) optical flow method is employed to calculate the vehicle speed. Then, the corresponding intersection state can be obtained based on the vehicle speed and the discrimination algorithm. The detection of the vehicle takes the position information obtained by YOLOv3 as the input of the LK optical flow algorithm and forms an optical flow vector to complete the vehicle speed detection. Experimental results show that the detection algorithm can detect the vehicle speed and traffic state discrimination method can judge the traffic state accurately, which has a strong anti-interference ability and meets the practical application requirements.

To improve the performance of the ultra-wideband (UWB) system against multiple interferences existed in wireless personal area network (WPAN), such as narrowband interference (NBI), multiple-access interference (MAI), and multipath interference (MI), we present an orthogonal complementary code (OCC)-based UWB system with modified chirp waveforms. Considering the time–frequency characteristics of the chirp functions and the principle of NBI suppression, we first propose the modified linear and nonlinear chirp function-based flexible UWB pulses to suppress the multiple NBIs. Furthermore, with the implementation of OCC spread modulation, the modified chirp waveform-based UWB system is presented to effectively alleviate the influence of the MAI and MI. Simulation results and analysis validate the efficiency of the modified chirp pulse-based OCC-UWB system in the suppression of NBIs, MAI, and MI.

Spatial modulation (SM) has been employed in indoor visible light communication (VLC) systems because of its high data rate and low complexity transmission. However, the activated LED may have poor channel conditions in conventional SM VLC systems, which leads to significant performance degradation. In this paper, a cooperative incremental hybrid decode-amplify-forward (IHDAF) protocol-based SM-index modulation (SM-IM) VLC system is proposed. For the SM-IM scheme, the spatial information and the modulated information are jointly transmitted in one symbol via the optimal VLC channel. The system model and the theoretical outage probability of the proposed IHDAF protocol-based SM-IM VLC system are presented. Numerical results show that the outage probability of the IHDAF protocol-based SM-IM VLC system can be significantly improved compared with the traditional amplify-and-forward and decode-and-forward protocol-based SM VLC systems. Additionally, the power allocation of the proposed scheme is also studied.

We investigate a secure multiuser time division multiple access (TDMA) system with statistical delay quality of service (QoS) guarantee in terms of secure effective capacity. An optimal resource allocation policy is proposed to minimize the β-fair cost function of the average user power under the individual QoS constraint, which also balances the energy efficiency and fairness among the users. First, convex optimization problems associated with the resource allocation policy are formulated. Then, a subgradient iteration algorithm based on the Lagrangian duality theory and the dual decomposition theory is employed to approach the global optimal solutions. Furthermore, considering the practical channel conditions, we develop a stochastic subgradient iteration algorithm which is capable of dynamically learning the intended wireless channels and acquiring the global optimal solution. It is shown that the proposed optimal resource allocation policy depends on the delay QoS requirement and the channel conditions. The optimal policy can save more power and achieve the balance of the energy efficiency and the fairness compared with the other resource allocation policies.

In this paper, we propose and analyze a new relaying scheme for the three-node cooperative relaying system, named as incremental hybrid decode-amplify-forward relaying (IHDAF), where the relay may choose to keep silent or transmit message in decode-and-forward (DF) or amplify-and-forward (AF) mode based on the qualities of the channels among the source, relay, and destination. Closed-form expressions of the outage probability and bit error rate (BER) of the proposed IHDAF protocol are derived. The optimal relationship of the two important signal-to-noise ratio (SNR) thresholds at the relay and destination to decide whether cooperation is necessary and the cooperative mode has been achieved. Moreover, the effects of the power allocation schemes, SNR thresholds, and relay locations on the outage probability and BER of the IHDAF protocol are studied. Theoretical analysis and simulation results show that the IHDAF relaying scheme outperforms the incremental-selective DF (ISDF), incremental DF (IDF), and cooperative STBC schemes, especially when the relay is close to the destination.

In this paper, aiming to minimize the system outage probability in the condition of limited total power consumption, we study the optimal power allocation and relay positioning of the opportunistic incremental Amplify-and-Forward (OIAF) cooperative system over Rayleigh fading channels with the utilization of convex optimization theory. The analysis of the outage probability and bit error rate (BER) performance is provided. Moreover, we also provide the analysis about the impact of information rate R on the BER performance under certain conditions when the number of the relays, the relay position and also the total power vary. Simulation results show that the proposed joint power optimization and best relay positioning scheme has advantages over other schemes in outage performance.

In order to alleviate multiple access interference and multipath interference of ultra-wideband UWB system, we propose the orthogonal complementary code OCC-based direct-sequence UWB system and offset-stacking OS-UWB system. OCC has perfect partial autocorrelation and cross-correlation characteristics. With the application of OCC in UWB system, we can obtain better performance in multiple access interference and multipath interference. The proposed OS-UWB structure can also achieve variable data rate transmission because of its innovative OS spreading technique. Theoretical analysis and simulation results show that the proposed UWB system can achieve excellent performance and outperform the unitary code-based direct-sequence UWB system. Copyright © 2013 John Wiley & Sons, Ltd.

In this study, the authors propose a new pulse waveform design methodology for ultra-wideband (UWB) applications, namely spectrum shifted Gaussian waveform (SSGW) approach. Specifically, UWB pulses can be generated by superposition of Gaussian sub-carriers, which can be used to fit Federal Communication Commission (FCC) spectrum masks specified for UWB applications. In this way, it can match with the FCC masks much better than those generated using the traditional methods based on Gaussian or Hermite pulses and their higher order derivatives. The SSGW works with a low computational complexity and offers a unique agility in design of time-domain pulse shapes to fit different power spectrum density masks. In principle, the SSGW approach can also be used for pulse waveform design in many other bandwidth efficient communication systems, not necessarily limited only to UWB systems.

To meet the ever-growing demand for a higher communicating rate and better communication quality, more and more small cells are overlaid under the macro base station (MBS) tier, thus forming the heterogeneous networks. Small cells can ease the load pressure of MBS but lack of the guarantee of performance. On the other hand, cooperation draws more and more attention because of the great potential of small cell densification. Some technologies matured in wired network can also be applied to cellular networks, such as Software-defined networking (SDN). SDN helps simplify the structure of multi-tier networks. And it's more reasonable for the SDN controller to implement cell coordination. In this paper, we propose a method to offload users from MBSs through small cell cooperation in heterogeneous networks. Association probability is the main indicator of offloading. By using the tools from stochastic geometry, we then obtain the coverage probabilities when users are associated with different types of base stations (BSs). All the cell association and cooperation are conducted by the SDN controller. Then on this basis, we compare the overall coverage probabilities, achievable rate and energy efficiency with and without cooperation. Numerical results show that small cell cooperation can offload more users from MBS tier. It can also increase the system's coverage performance. As small cells become denser, cooperation can bring more gains to the energy efficiency of the network., 12 pages, 7 figures

In order to provide more accurate detection of the primary user's activity in cognitive radio CR systems, cooperative spectrum sensing is proposed. The transmit diversity can also be employed by cooperative spectrum sensing to improve the performance of decision reporting. Hence, in the reporting channels between the cognitive users and the base stationBS, space time block code STBC scheme is considered in each cluster with time division multiple access TMDA method. In this paper, to improve the time efficiency in the case that one cluster makes sensing report, whereas the others do nothing but wait for their orders, we set each cluster with different sensing durations and the clusters will not stop the spectrum sensing until their results are reported. Furthermore, we also adopt the flexible sensing durations to decrease unnecessary energy consumption based on the clusters' sensing sensitivities. Simulation results and analysis show the better detection performance and time efficiency of the proposed scheme. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, a dual-hop regenerative cooperative relaying UWB communication system with detect-and-forward (DTF) and decode-and-forward (DF) in multipath channels is studied. The average system bit error rate (BER) and the system performance with DTF and DF relaying schemes are provided. The DF relaying with convolutional coding is employed in this cooperative relaying UWB system. Gaussian quadrature numerical method is used to obtain the moment-generating function (MGF) of the received energy. Our simulation results show the advantages of the DF based cooperative IR-UWB system over IEEE 802.15.3a channels.

SUMMARY In this work, we investigate the closed loop extended orthogonal-space time block codes in decode- and-forward cooperative networks and propose an updatable automatic repeat request protocol with relay selection. In the system, the relays decoding correctly are incorporated into a relay set, the optimal relays within this relay set can be selected based on the channel information, and the extended orthogonal-space time block codes scheme is employed with the help of the feedback in automatic repeat request message. With the consideration of the relay selection, the system performance can be improved. Simulation and analysis results prove the efficiency of the proposed scheme, which achieves better performance than conventional relay schemes. Copyright © 2012 John Wiley & Sons, Ltd.

In order to alleviate the narrowband interference (NBI) to ultra wideband (UWB) systems, we propose two non-linear UWB chirp waveforms based on the arctrigonometric and archyperbolic function in this paper. The proposed UWB pulses can obtain good performance in NBI suppression. Both of the two chirp pulses require only the time domain processing because of the inherent relationship between the frequency domain and the time domain. Theoretical analysis and simulation results show that the direct sequence pulse binary amplitude modulation (DS-BPAM) UWB systems with the proposed chirp waveforms can achieve excellent NBI suppression performance and outperform the linear chirp waveform based UWB system significantly. Copyright © 2010 John Wiley & Sons, Ltd. (In this paper, we propose two novel non-linear chirp UWB waveforms, atan chirp and asinh chirp, based on the arctrigonometric and archyperbolic function. Theoretical analysis and simulation results show the efficiency of the proposed UWB waveforms in NBI suppression at any single frequency band.)

In this paper, we investigate the multiple input multiple output (MIMO) direct sequence bipolar pulse amplitude modulation (DS-BPAM) ultra wideband (UWB) system over indoor multipath fading channels based on the research of Alamouti space-time block codes (STBC) and DS-BPAM UWB system. Selective Rake (SRake) receiver is employed in this paper in order to deal with the multipath effects. Theoretical bit error probability of the MIMO DS-BPAM UWB system with SRake receiver is derived. Simulation results of the MIMO DS-BPAM UWB system with SRake receiver and conventional coherent receiver over multipath fading channels are provided. The results show the efficiency of the MIMO DS-BPAM UWB system with SRake receiver.

This work presents an M-ary multiple access code-selected direct sequence (DS) ultra wideband (UWB) communication system. A high data rate multiple access UWB system can be obtained by a code selection mechanism. In the proposed system, each user is assigned a DS code set with M/2 DS code sequence and a particular DS code sequence can be selected by the log2 (M/2) bits from the DS code set. More importantly for this M-ary UWB communication system, with the increase of the modulation level M, it allows to reduce the required transmitter power maintaining the number of users, the data transmission rate and the multiple access performance. In this paper, we also introduce the detailed algorithm to compute the bit error rate (BER) over the AWGN channel and correlation receivers.

Coexisting with many concurrent narrowband services, the performance of UWB systems will be affected considerably by them. Specifically, IEEE 802.11a systems which operate around 5 GHz and overlap the band of UWB signals will interfere with UWB systems significantly. In this paper, a novel narrow-band interferences (NBI) suppression technique based on singular value decomposition (SVD) algorithm for a direct sequence ultra-wideband (DS-UWB) communication system is presented. SVD is used to approximate the interferences which then are subtracted from the received signals. The proposed technique is simple and robust. Simulation results show that the proposed new technique is very effective.

A novel M-ary direct sequence ultra wideband (UWB) communication system based on the selection of the direct sequence code is studied in this paper. The proposed M-ary code selected direct sequence bipolar pulse amplitude modulation scheme can achieve high bit rate without increasing the system bandwidth or changing the pulse shape. With the increase of the modulation level M, the system bit error rate will be improved even at lower signal to noise ratio per bit. The exact bit error probability is derived over the AWGN channel and correlation receivers. Both Monte-Carlo simulation and the theoretical analysis prove the efficiency of this M-ary UWB system.

In this letter, a novel M-ary code-selected direct sequence (DS) ultra-wideband (UWB) communication system is presented. Our purpose is to achieve a high data rate by an M-ary code-selected direct sequence bipolar pulse amplitude modulation (MCSDS-BPAM) scheme. In this system, a particular DS code sequence is selected by the log2M/2 bits from the DS gold code set. This scheme can accomplish both a high data rate without increasing the system bandwidth or changing the pulse shape and improve the BER with an increase of modulation level M even at a lower signal-to-noise ratio (SNR). The receiver signal processing algorithm is given for an MCSDS-BPAM UWB system over an ideal AWGN channel and correlation receivers.

To improve the coexistence between ultrawideband (UWB) technology–based wireless personal area networks and other narrowband systems and efficiently suppress the multiple narrowband interferences (NBIs) and the multiuser interference (MUI) in UWB systems, we propose a multiband orthogonal complementary code–based UWB (OCC-UWB) system design in this paper, which utilizes the simple time-frequency relationship of the chirp waveforms. The system design is implemented in 2 ways, named the equant multiband scheme and the nonequant multiband scheme. The 2 implementation schemes can improve the spectrum utilization of UWB systems and have different principles of NBI suppression. The equant scheme adopts the nonlinear chirp waveforms to suppress multiple NBIs in the subbands with NBIs. In contrast, the nonequant scheme adopts the spectrum elusion method based on the division of the frequency band to exclude the NBIs' frequency bands. Combining the chirp UWB pulse design with the orthogonal complementary code spread modulation, we finally present the multiband chirp OCC-UWB system to suppress the MUI and the multipath interference simultaneously. Simulation results and theoretical analysis show that the proposed multiband chirp OCC-UWB system improves the system performance efficiently in the conditions of multiple NBIs, MUI, and multipath interference and increases the data transmission rate and the spectrum utilization simultaneously.

Due to the ultra low power spectral desity of the ultra-wide band (UWB), narrow band interference (NBI) with high-level emission power will degrade the accuracy of UWB ranging system. We propose a novel waveform to suppress the accuracy degradation by NBI with a given frequency. In addition, we compare the ranging error ratio (RER) of the proposed scheme with the traditional one with Gaussian monocycle in this letter.

In this letter, we propose an impulse series for an ultra-wideband-based cognitive radio system which can utilize the spectrum dynamically by controlling the impulse positions and thus reduce the system complexity.

Summary To improve the sensing performance and achieve higher throughput of the femtocells (FCs) while alleviating the influence to the macrocell in the cognitive massive multiple-input and multiple-output system (MIMO), we propose in this paper a hybrid time-division duplex (TDD) access scheme of the FCs with confidence factor–based weighted cooperative spectrum sensing (CSS). A first, we present an efficient hybrid TDD access scheme for better spectrum reuse of the FCs based on the typical TDD and reversed TDD schemes. Furthermore, confidence factor–based weighted CSS has been used for better spectrum sensing and interference alleviation. In the cognitive massive MIMO system, FC base stations will form dynamical clustering based on the channel conditions, sense the spectrum through cooperative scheme, and decide whether to access the spectrum or not. After information exchange within each FC cluster, the FC base stations can obtain and update their confidence factors and weight factors based on the sensing results and reliability. Numerical results and theoretical analysis show that the proposed scheme can get more accurate sensing results, increase the throughput and the spectrum access opportunity of the FCs, and efficiently alleviate the interference to the macrocell tier.

Summary In this paper, an opportunistic relaying-based incremental hybrid decode-amplify-forward (OR-IHDAF) scheme that combines robust protocol switch with efficient relay selection is proposed in multi-relay scenario to cope with the complex and variable channel environments. The proposed OR-IHDAF scheme can improve the system performance significantly compared with the incremental hybrid decode-amplify-forward protocol with the increase of the possible candidate relay nodes and opportunistic relay selection. The analytical expression of the system outage probability of the OR-IHDAF scheme is presented based on the probability density function and cumulative distribution function, which might be useful to avoid lengthy simulations. Numerical results show the correctness of our theoretical analysis and the performance improvement of the OR-IHDAF scheme compared with the other current hybrid cooperative protocols and OR-based cooperative schemes. The effects of the power allocation schemes on the outage probability are also provided. Copyright © 2015 John Wiley & Sons, Ltd.