Wang, TQ, Li, H & Huang, X 2019, 'Analysis and Mitigation of Clipping Noise in Layered ACO-OFDM Based Visible Light Communication Systems', IEEE Transactions on Communications.View/Download from: UTS OPUS or Publisher's site
IEEE Due to the limited dynamic range of the off-theshelf electrical and optical components, deliberate digital clipping (DDC) is widely applied to optical orthogonal frequency division multiplexing (OFDM) based visible light communication systems. In this paper, we present a theoretical characterization of the layered asymmetrically clipped optical OFDM (ACO-OFDM) signals subject to peak clipping. We decouple a clipped L-layer ACO-OFDM symbol to L single-layer ACO-OFDM symbols, each corresponding to a layer, and show that these symbols are subject to symmetrical peak clippings at random levels. Using the Bussgang’s theorem, the resulting attenuation factors and variances of the additive noise associated with each layer are derived. It is shown that the clipping noise caused by the DDC mainly falls onto the first layer, and its impact is gradually reduced in the subsequent layers. In order to combat the clipping noise, a novel receiver based on decision aided reconstruction is proposed. Simulation results show that the proposed receiver can effectively mitigate the clipping noise, leading to significant improvement of bit error rates over the conventional receiver.
Li, H, Wang, TQ & Huang, X 2019, 'Joint Adaptive AoA and Polarization Estimation Using Hybrid Dual-Polarized Antenna Arrays', IEEE Access, vol. 7, pp. 76353-76366.View/Download from: UTS OPUS or Publisher's site
© 2013 IEEE. The propagation of a millimeter wave (mmWave) signal is dominated by its line-of-sight component. Therefore, the knowledge of angle-of-arrival and polarization state of the wave is of great importance for its reception at the receiver. In this paper, we estimate these parameters for an information-bearing signal in mmWave systems using hybrid antenna arrays with dual-polarized dipoles. The estimation is studied in the context of both the interleaved and localized arrays. Two blind adaptive algorithms, namely, the joint differential beam tracking and cross-correlation-to-power ratio polarization tracking, and the differential beam and polarization search, are developed, each tailored for an array. It is shown that the use of dual-polarized dipoles in combination with the developed algorithms effectively lead to polarization diversity which significantly enhances the signal-to-noise ratio at the decoder. The simulation results also show that the antennas with dual dipoles provide improved accuracy and convergence rate for the estimations compared with the conventional arrays.
Li, H, Wang, TQ, Huang, X & Guo, YJ 2019, 'Adaptive AoA and Polarization Estimation for Receiving Polarized mmWave Signals', IEEE Wireless Communications Letters.View/Download from: UTS OPUS or Publisher's site
IEEE This paper proposes a novel hybrid dual-polarized antenna array which exploits two orthogonally-collocated dipoles to capture the full power of a polarized millimeter wave signal. To maximize the received signal-to-noise ratio (SNR), we study the adaptive angle-of-arrival and polarization state estimation, and develop a differential beam tracking algorithm and a cross-correlation-to-power ratio polarization tracking algorithm for interleaved hybrid dual-polarized arrays. Simulation results verify the superior performance of the proposed algorithms, and confirm the significant improvement of SNR obtained by using the proposed array and algorithms.
Li, H, Wang, TQ, Huang, X, Zhang, JA & Guo, YJ 2019, 'Low-Complexity Multiuser Receiver for Massive Hybrid Array mmWave Communications', IEEE TRANSACTIONS ON COMMUNICATIONS, vol. 67, no. 5, pp. 3512-3524.View/Download from: UTS OPUS or Publisher's site
Wang, TQ, Li, H & Huang, X 2018, 'Interference Cancellation for Layered Asymmetrically Clipped Optical OFDM With Application to Optical Receiver Design', JOURNAL OF LIGHTWAVE TECHNOLOGY, vol. 36, no. 11, pp. 2100-2113.View/Download from: UTS OPUS or Publisher's site
Wang, TQ & Huang, X 2018, 'Fractional Reverse Polarity Optical OFDM for High Speed Dimmable Visible Light Communications', IEEE Transactions on Communications, vol. 66, no. 4, pp. 1565-1578.View/Download from: UTS OPUS or Publisher's site
© 1972-2012 IEEE. In this paper, fractional reverse polarity optical orthogonal frequency division multiplexing (FRPO-OFDM) is studied to enable dimming compatible visible light communications. The scheme combines a layered asymmetrically clipped optical OFDM (ACO-OFDM) sequence with an information-carrying brightness control sequence (BCS) in the form of M -ary pulse position modulation. We derive the expressions of the FRPO-OFDM signal and its achievable brightness level, and develop an effective detector which can recover information from both sequences based on maximum likelihood detection. We show that when the detector is to be implemented, the use of multi-layer ACO-OFDM imposes strong periodicity on the BCS, which leads to a trade-off between spectral efficiency and brightness resolution for dimming control. It is shown that high spectral efficiency can be achieved with practical dimming requirements. Simulation results show that the extra information carried by the BCS can be decoded with extremely low bit error rate and thus has negligible impacts on the demodulation of the ACO-OFDM signal, when the system nonlinearity is not dominating.
Steendam, H, Wang, TQ & Armstrong, J 2017, 'Theoretical lower bound for indoor visible light positioning using received signal strength measurements and an aperture-based receiver', Journal of Lightwave Technology, vol. 35, no. 2, pp. 309-319.View/Download from: UTS OPUS or Publisher's site
© 1983-2012 IEEE. Indoor visible light positioning (VLP) using signals transmitted by lighting LEDs is a topic attracting increasing interest within the research community. In the recent years, VLP techniques using a range of receiver structures and positioning algorithms have been described. In this paper, we analyze the performance of a VLP system, which uses an aperture-based receiver and measurements of received signal strength. An aperture-based receiver has a number of receiving elements, each consisting of a photodiode and an associated aperture. It has been shown that receivers of this form can be designed which are compact and provide both a wide overall field-of-view and good angular diversity. As a result, they can efficiently extract position-related information from light transmitted by nondirectional LEDs. In our approach, we correlate the signals at the outputs of the photodiodes with a set of reference signals. The resulting observations include information on the received signal strength as well as the angle-of-arrival, and are used to directly estimate the receiver's position. In order to assess the performance of positioning algorithms based on this approach, we derive the Cramer-Rao lower bound on the position estimate. We show that the Cramer-Rao bound depends on the selected reference signal, and that subcentimetre to centimetre accuracy can be obtained, using only a limited number of nondirectional LEDs.
Wang, TQ, Li, H & Huang, X 2017, 'Diversity Combining for Layered Asymmetrically Clipped Optical OFDM Using Soft Successive Interference Cancellation', IEEE Communications Letters, vol. 21, no. 6, pp. 1309-1312.View/Download from: UTS OPUS or Publisher's site
© 1997-2012 IEEE. In this letter, we present a novel diversity combining receiver for demodulating layered asymmetrically clipped optical orthogonal frequency division multiplexing. The receiver consists of a soft successive interference cancellation (SIC) module which cancels the inter-layer interference (ILI) using the minimum mean square error (MMSE) estimates of the information symbols, and a diversity combining module which extracts the diversity components from the clipping noise. We show that the soft SIC module alone can effectively suppress the ILI, leading to bit error rates (BERs) resembling those of a genie receiver which is free of error propagation. It is also shown that the diversity combining receiver which combines the MMSE estimates with their diversity components outperforms the genie receiver by up to 2 dB at the BER of 10 -6 .
Wang, TQ, He, C & Armstrong, J 2017, 'Performance analysis of aperture-based receivers for MIMO IM/DD visible light communications', Journal of Lightwave Technology, vol. 35, no. 9, pp. 1513-1523.View/Download from: UTS OPUS or Publisher's site
© 2016 IEEE. Aperture-based receivers are a new form of receiver for multiple-input multiple-output (MIMO) intensity-modulated direct-detection visible light communication (VLC). These receivers provide a wide field of view and excellent angular diversity using a compact planar structure and so are ideally suited for integration in hand-held devices such as smartphones. It is shown that in typical scenarios to achieve similar performance the photodiodes in a conventional receiver based on spatial diversity would have to be separated by distances greater than 30 cm. An in-depth analysis of the performance of aperture-based receivers is presented. Expressions are derived for the channel gain between an optical transmitter and each receiving element (RE) as a function of the transmission pattern of the transmitter, the design of the RE, and the relative positions of the transmitter and receiver. It is shown that a well-designed receiver consisting of multiple REs can separate signals received from different directions with low-multistream interference and that the associated MIMO channel matrices are well conditioned. Simulations are performed for a typical indoor VLC scenario in which light-emitting diode luminaires transmit information using asymmetrically clipped optical orthogonal frequency division multiplexing. Results are presented for receivers using both linear and nonlinear equalizers and for both line of sight (LOS) and LOS plus diffuse reception. The diffuse component is shown to improve the bit error rate (BER) performance slightly. It is shown that the BER depends on the receiver position. When a zero-forcing (ZF) linear receiver is used, the BER is dominated by the most attenuated signal, so the performance degrades at the corners of the room. In contrast, the receivers with nonlinear equalizers based on ZF followed by successive interference cancelation achieve low BER throughout the scenario.
Tahar, M, Wang, TQ, Guerra Medina, MF, Gonzalez, O & Armstrong, J 2016, 'Experimental Demonstration of Diversity Combining for Asymmetrically Clipped Optical OFDM', IEEE COMMUNICATIONS LETTERS, vol. 20, no. 5, pp. 906-909.View/Download from: Publisher's site
Yue, DW, Lau, FCM & Wang, Q 2016, 'Log-average-SNR ratio and cooperative spectrum sensing', Journal of Communications and Networks, vol. 18, no. 3, pp. 311-319.View/Download from: UTS OPUS or Publisher's site
© 2011 KICS. In this paper, we analyze the spectrum-sensing performance of a cooperative cognitive radio (CR) network consisting of a number of CR nodes and a fusion center (FC). We introduce the «log-average-SNR ratio» that relates the average SNR of the CRnode- FC link and that of the primary-user-CR-node link. Assuming that the FC utilizes theK-out-of-N rule as its decision rule, we derive exact expressions for the sensing gain and the coding gain - parameters used to characterize the CR network performance at the high SNR region. Based on these results, we determine ways to optimize the performance of the CR network.
Wang, TQ, Green, RJ & Armstrong, J 2015, 'MIMO Optical Wireless Communications Using ACO-OFDM and a Prism-Array Receiver', IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, vol. 33, no. 9, pp. 1959-1971.View/Download from: UTS OPUS or Publisher's site
He, C, Wang, TQ & Armstrong, J 2015, 'Performance of Optical Receivers Using Photodetectors With Different Fields of View in a MIMO ACO-OFDM System', JOURNAL OF LIGHTWAVE TECHNOLOGY, vol. 33, no. 23, pp. 4957-4967.View/Download from: Publisher's site
Yue, DW, Lau, FCM & Wang, Q 2014, 'On the diversity order of a general cooperative relaying communication system', Wireless Personal Communications, vol. 77, no. 1, pp. 605-631.View/Download from: UTS OPUS or Publisher's site
Cooperative communication technology exploiting distributed spatial diversity is a promising solution for the future high data-rate cellular and ad-hoc wireless communications. To characterize the performance of a cooperative network, the cooperative diversity is commonly used. In this paper, we revisit the concept of diversity and look into the essence of cooperative diversity. We analyze the diversity performance of a general cooperative relaying system with multiple branches. Moreover, each branch consists of one or more hops. Unlike in other analyses, the assumptions that each node being only equipped with a single antenna and that all channel characteristics belonging to the same family are NOT required in our study. Using the decode-and-forward (DF) relaying protocol as an illustration, we provide analytical results on the diversity gain and the coding gain. The results also encompass most of the existing results as special cases. We further show the relationship between the diversity order of a branch and those of the constituent links; and the relationship between the diversity order of the network and those of the constituent branches. In particular, we show that for the uncoded DF protocol, the full diversity order can be achieved by using simple hard-decision detection at the destination. The requirement is to set appropriate signal-to-noise-ratio (SNR) thresholds for the multi-hop branches. To improve the bandwidth efficiency, we also randomly select one branch, among those branches satisfying the SNR-threshold requirement, for the transmission. We show that such a scheme accomplishes the full diversity order and produces a good error performance. © 2013 Springer Science+Business Media New York.
Wang, Q, Yue, DW & Yuan, J 2014, 'An optimal cooperative spectrum sensing strategy with exponential primary link traffic', Wireless Communications and Mobile Computing, vol. 14, no. 8, pp. 789-802.View/Download from: UTS OPUS or Publisher's site
In this paper, we investigate the optimal sensing settings for a cognitive radio (CR) network consisting a number of CR users and a fusion center (FC). Our objective is to maximize the channel utilization under the constraint that the signals from the primary user (PU) are sufficiently protected. We focus on the utilization of the channel in which PUs dynamically enter the network with burst nature. Thus, we apply the average error probability (AEP) as the metric of channel utilization. Moreover, in order to protect the PU signal from being interfered, the missing detection probability is applied as the constraint function. Assuming that counting rules are utilized in the FC, we derive the false alarm probability, the missing detection probability, and the AEP in the maximum a posteriori (MAP) fashion. Then, after proving the monotonic properties of the objective function and the constraint function, we propose an efficient algorithm named Algorithm I that can derive the optimal settings for maximizing the channel utilization. Moreover, a simplified algorithm named Algorithm II is also proposed to minimize the AEP, supposing that perfect synchronization exists between the CR users and the PU. Finally, we show our numerical results and compare our optimal results with those found by exhaustive searches. We conclude that our Algorithm I produces optimal results very close to those found by exhaustive searches. Performance comparison between Algorithms I and II is also provided in terms of the AEP and the probability of missing detection. Copyright © 2012 John Wiley & Sons, Ltd.
Wang, Q, Yue, D & Yan, Q 2013, 'Channel capacity of multiple antenna systems with interference and covariance feedback', Dianbo Kexue Xuebao/Chinese Journal of Radio Science, vol. 28, no. 5, pp. 883-890.View/Download from: UTS OPUS or Publisher's site
The optimization of ergodic channel capacity is investigated for multiple-input multiple-output (MIMO) multiple antenna systems with co-channel interference when the covariance feedback is available at the transmitter. An equivalent form of the co-interference component is first derived. Then an optimal capacity estimation algorithm is proposed by performing gradient projection algorithm which is based on nonlinear programming theory. Finally, Monte-Carlo simulation is given. The numerical results show that the performance with the proposed algorithm is close to the optimal one which is obtained by water-filling algorithm when both the interference power and the correlation between antennas are strong. Copyright © 2013 by Editorial Department of Chinese Journal of Radio Science.
Wang, Q, Yue, D-W & Lau, FCM 2013, 'Outage Performance and Cooperative Diversity Under Amplify and Forward Relaying in Cognitive Radio Networks', WIRELESS PERSONAL COMMUNICATIONS, vol. 69, no. 2, pp. 891-914.View/Download from: UTS OPUS or Publisher's site
Wang, TQ, Sekercioglu, YA, Neild, A & Armstrong, J 2013, 'Position Accuracy of Time-of-Arrival Based Ranging Using Visible Light With Application in Indoor Localization Systems', JOURNAL OF LIGHTWAVE TECHNOLOGY, vol. 31, no. 20, pp. 3302-3308.View/Download from: UTS OPUS or Publisher's site
Wang, TQ, Sekercioglu, YA & Armstrong, J 2013, 'Analysis of An Optical Wireless Receiver Using a Hemispherical Lens With Application in MIMO Visible Light Communications', JOURNAL OF LIGHTWAVE TECHNOLOGY, vol. 31, no. 11, pp. 1744-1754.View/Download from: UTS OPUS or Publisher's site
Wang, Q, Yue, D-W & Lau, FCM 2012, 'Performance of cooperative spectrum sensing over fading channels with low signal-to-noise ratio', IET COMMUNICATIONS, vol. 6, no. 13, pp. 1988-1999.View/Download from: UTS OPUS or Publisher's site
Wang, Q, Yue, DW & Yan, QN 2012, 'Optimal fusion rule for cooperative spectrum sensing in cognitive radio networks', Journal of China Universities of Posts and Telecommunications, vol. 19, no. 5, pp. 58-65.View/Download from: UTS OPUS or Publisher's site
In this paper, we analyze performance of cooperative spectrum sensing under counting rules when exponential model is utilized to characterize the burst nature of primary user (PU) link. Our objective is to minimize the average error probability (AEP) so that the link utilization in the considered link achieves its maximum. We derive a closed-form expression of AEP as well as the probability of interference (PoI) by classifying cognitive transmission into six events. Then, we consider the minimization of AEP over counting rules under the constraint of interference. As the solution, we develop an efficient algorithm to evaluate the optimal fusion rule. Finally, we verify our analysis in numerical results. © 2012 The Journal of China Universities of Posts and Telecommunications.
Yan, QN, Yue, DW & Wang, Q 2012, 'Analysis of correlated MIMO channel capacity under co-channel interference', Dianbo Kexue Xuebao/Chinese Journal of Radio Science, vol. 27, no. 3, pp. 556-563.View/Download from: UTS OPUS
In Rayleigh fading environments, this paper addresses the issue of multiple-input multiple-output (MIMO) channel capacity under co-channel interference, and focuses on the case with transmit spatial correlation for the desired user. It is assumed that perfect channel state information (CSI) is available to the receiver, but unavailable to the transmitter. Based on theory of matrix variate distributions, this paper first derives an exact closed-form expression of the moment generating function (MGF) of mutual information of MIMO channels with interference, and then obtains an exact expression of the MIMO ergodic capacity by using the MGF formula of mutual information. Finally, numerical results are present to illustrate the mathematical formalism and to show the effect of various parameters on the ergodic capacity. This paper emphasizes applications of matrix variate distribution theory to the study of MIMO channel capacity. Copyright © 2012 by Editorial Department of Chinese Journal of Radio Science.
Wang, Q, Yue, D-W & Lau, FCM 2012, 'Optimisation of throughput in cognitive radio networks: an analysis at the data link layer', IET COMMUNICATIONS, vol. 6, no. 1, pp. 1-12.View/Download from: UTS OPUS or Publisher's site
Wang, Q & Yue, DW 2010, 'Performance analysis of spectrum sensing using diversity technique', Tongxin Xuebao/Journal on Communications, vol. 31, no. 4, pp. 134-140.
Performance of spectrum sensing using energy detection and equal gain combining technique was investigated in the general correlated non-identical Nakagami-m fading channels. Closed-form expression of detection probability was derived, and performance improvement obtained by utilizing equal gain combining was analyzed via the asymptotical analysis. The validity of theoretical results were shown by comparing numerical results with Monte-Carlo simulations. At last, the influence of channel correlation on the detection probability was observed by Monte-Carlo simulation.
This letter presents a new look at the problem of energy detection with and without diversity schemes. The impact of channel fading and/or diversity scheme on the probability of missing detection is quantified and then the definition, sensing gain, is proposed based on the analytical result. The sensing gain proposed in this letter determines the slope of the probability of missing detection versus average signal-to-noise ratio (SNR) curve, at high SNR, in a log-log scale. Our result shows that the sensing gain just has a relationship with the type of channel fading and/or diversity scheme and is totally irrelevant with the false alarm probability which is preset. © 2009 IEEE.
Yue, DW & Wang, Q 2009, 'Capacity of orthogonal space-time block codes in MISO fading channels with co-channel interference and noise', Science in China, Series F: Information Sciences, vol. 52, no. 9, pp. 1697-1703.View/Download from: Publisher's site
Orthogonal space-time block codes (OSTBCs) are an efficient mean in order to exploit the diversity offered by the wireless multiple-input multiple-output (MIMO) channel. This paper considers capacity problems of OSTBCs over spatially correlated multiple-input single-out (MISO) Rayleigh fading channels in the presence of spatially correlated Rayleigh co-channel interference and additive Gaussian noise, and derives exact expressions of the ergodic capacity and outage probability (capacity distribution) for such OSTBCs. Some numerical examples are given to illustrate the effect of co-channel interference on the ergodic and outage capacity of OSTBCs. © 2009 Science in China Press and Springer Berlin Heidelberg.
Wang, Y, Yue, DW, Wang, Q & He, RX 2009, 'Channel statistics based cooperative spectrum sensing for cognitive radios', Dianbo Kexue Xuebao/Chinese Journal of Radio Science, vol. 24, no. 6, pp. 1049-1054.
Cooperative spectrum sensing for cognitive radios was studied with the assumption that the control channels between cognitive radios and the fusion center are Nakagami-m fading channels. The likelihood ratio test equation with the knowledge of the channel statistics was derived. With this method, the fusion center can perform cooperative spectrum sensing without the instantaneous channel state information, and the spectrum sensing process is simplified and more suitable for practical applications. The performance of the proposed cooperative spectrum sensing was analyzed through simulation, the results of which show that the performance of the proposed channel statistics based spectrum sensing method degrades performance slightly compared with the channel state information based likelihood ratio test, but when the average receive SNR is high or the fading effect is weak, the performance of the proposed method can approach that of the channel state information based likelihood ratio test. In addition, the number of cognitive radios has almost no influence on the performance difference between the two methods.
Li, H, Wang, Q, Huang, X & Guo, YJ 2018, 'Matrix Normalization Based ZF Hybrid Precoded Multi-User MIMO mmWave Systems with Massive Array', IEEE Vehicular Technology Conference, IEEE, Chicago, USA.View/Download from: UTS OPUS or Publisher's site
Steendam, H, Wang, TQ & Armstrong, J 2017, 'Cramer-Rao bound for AOA-based VLP with an aperture-based receiver', IEEE International Conference on Communications, IEEE International Conference on Communications (ICC), IEEE, Paris, France.View/Download from: UTS OPUS or Publisher's site
© 2017 IEEE. Visible light positioning (VLP) for indoor applications has recently received considerable attention. In this paper, an aperture based receiver is considered and the position is estimated based on the angle-of-arrival (AOA), because the AOA can be determined by comparing the relative differences in the received signal strengths (RSS) in the different photodiodes (PDs) of the receiver. Hence, in contrast to RSS based positioning solutions, knowledge of the transmitted signal strengths is not required. The performance of the proposed approach depends on the transmitted signal strength only through the dependency on the signal-to-noise ratio. To evaluate the accuracy of the estimates of the AOA, we derive the Cramer-Rao lower bound, and show that the expected error on the AOA is very small. Applying triangulation to determine the position of the receiver, it follows that centimetre accuracy can be obtained with the aperture-based receiver.
Wang, Q & Huang, X 2017, 'Dimming Compatible Optical OFDM for High Speed Visible Light Communications', Proceedings of the 85th IEEE Vehicular Technology Conference, IEEE Vehicular Technology Conference, IEEE, Sydney, Australia, pp. 1-4.View/Download from: UTS OPUS or Publisher's site
In this paper, we study a novel optical orthogonal frequency division multiplexing (OFDM) scheme, fractional reversed polarity optical OFDM (FRPO- OFDM), which enables dimmable visible light communications. The scheme combines an asymmetrically clipped optical OFDM (ACO-OFDM) sequence with an information-carrying brightness control sequence (BCS). We show that the new scheme can create a wide range of brightness levels whilst transmitting extra information using the BCS to enhance the spectral efficiency. The detector which can recover information from both sequences is derived based on maximum likelihood (ML) detection and estimation. It is shown that the information carried by the BCS using variable on-off keying (VOOK) can be detected with extremely low bit error rate (BER) and that the resulting overall BER of FRPO-OFDM is constant over a wide dimming range
LI, H, Wang, Q, Huang, X & Zhang, JA 2017, 'Low-Complexity Uplink Multiuser Receivers for MIMO System with Massive Hybrid Array', Proceedings of the 2017 IEEE 85th Vehicular Technology Conference (VTC Spring), IEEE Vehicular Technology Conference, IEEE, Sydney, Australia, pp. 1-5.View/Download from: UTS OPUS or Publisher's site
Due to the enormous needs for signal processing and hardware constraints, the full digital implementation for a large antenna array at mmWave frequencies becomes intractable. Hence, receiver design for MIMO system with massive hybrid array is very demanding, particularly for subarray structure. In this paper, we propose two low- complexity uplink multiuser receiver design schemes (single-beam and multi-beam) under the circumstances of only users' angles of arrival (AOAs) available at base station, which greatly simplify the analog beamforming structure and reduce the complexity of channel estimation especially when the number of antenna elements is considerably large. In the single-beam scheme, subarrays are mapped to different users one by one such that each subarray serves a specific user. In the multibeam scheme, all subarrays use the same analog beamforming and any subarray's beamforming signal potentially points at all users. Digital beamforming is then employed to combine all subarray signals followed by equalization. Simulations are performed to compare the proposed schemes with other schemes that need channel information available at the subarray output. Since only AOAs are required for analog and digital beamformings, the proposed schemes are more suitable for mmWave MIMO system with massive hybrid array in spite of slight sum-rate loss.
He, C, Wang, TQ & Armstrong, J 2016, 'Performance comparison between spatial multiplexing and spatial modulation in indoor MIMO visible light communication systems', 2016 IEEE International Conference on Communications, ICC 2016, IEEE International Conference on Communications, IEEE, Kuala Lumpur, Malaysia, pp. 1-6.View/Download from: UTS OPUS or Publisher's site
© 2016 IEEE.Spatial multiplexing (SMP) and optical spatial modulation (OSM) are two important technologies for indoor multiple-input multiple-output (MIMO) visible light communications (VLC). In this paper, we compare the performance of SMP and OSM systems which are operated with typical configurations in an indoor scenario. Both systems transmit data using asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) as the modulation scheme. It is shown that in order to achieve the same data rate with the SMP, the OSM has to employ large constellations which become impractical when either the number of luminaires or the constellation size of the SMP is greater than four. Simulation results are presented for both MIMO systems using four luminaires as transmitters and a receiver configured with three different front-ends. These receivers include a conventional non-imaging receiver, a prism-based receiver and an aperture-based receiver. The BER results demonstrate that SMP outperforms OSM in terms of both the size of the region in which a receiver can achieve low BER and the BER at typical receiver positions.
Steendam, H, Wang, TQ & Armstrong, J 2016, 'Cramer-Rao bound for indoor visible light positioning using an aperture-based angular-diversity receiver', 2016 IEEE International Conference on Communications, ICC 2016, IEEE International Conference on Communications, IEEE, Kuala Lumpur, Malaysia.View/Download from: Publisher's site
© 2016 IEEE.In this paper, we investigate the problem of indoor positioning using visible light systems. The directional detector array we use is comprised of a number of receiving elements, each consisting of an aperture and a photo diode, which are arranged to offer good angular diversity, and can be implemented within a compact receiver structure . The receiving elements receive the light from a number of white LEDs, which are typically attached to the ceiling, and which act as anchors. In order to get an indication of the received signal strengths of the different LEDs, we average the received signals over time. The relative signal strengths in the different receiving elements do not only provide information on the distance between the LEDs and the detector array, but also about the angle-of-arrival of the light. By combining the information of the receiving elements, the position of the detector can be estimated. In order to assess the accuracy of positioning algorithms based on this approach, we derive the Cramer-Rao lower bound on the position accuracy. Assuming the white LEDs transmit an optical power of 1 W, and the time averaging is done over 1 millisecond, an accuracy of the order of a centimetre can be achieved.
Wang, TQ, He, C & Armstrong, J 2015, 'Angular diversity for indoor MIMO optical wireless communications', IEEE International Conference on Communications, IEEE International Conference on Communications, IEEE, UK, pp. 5066-5071.View/Download from: Publisher's site
© 2015 IEEE. In this paper, we present a new type of receiver for MIMO optical wireless communications. The new receiver consists of multiple receiving elements (REs), each made up of a photodetector (PD) placed under an aperture. The directionality of each RE is shown to depend on the relative position of the PD and the aperture. Receiving patterns are calculated for various MIMO receiver designs, demonstrating that significant angular diversity can be achieved within a compact receiver structure. Simulation results are presented for a number of typical indoor scenarios when the transmitted signals are modulated using asymmetrically clipped optical OFDM (ACO-OFDM). For the scenarios considered, the bit error rate is lowest in the middle of the room and highest in the corners. The results indicate that for typical parameter values, reliable communication can be achieved throughout the room.
He, C, Wang, TQ & Armstrong, J 2015, 'MIMO optical wireless receiver using photodetectors with different fields of view', IEEE Vehicular Technology Conference, IEEE Vehicular Technology Conference, IEEE, UK.View/Download from: Publisher's site
© 2015 IEEE. This paper describes a new form of receiver for multiple-input multiple-output (MIMO) optical wireless communications. The new receiver uses a number of photodetectors (PDs), all facing in the same direction but with different fields of view (FOVs). This enables a compact planar receiver structure. The performance of the receiver is analyzed for an indoor visible light communications system where LED lights are used as data transmitters. It is shown that the MIMO channel matrix has full rank for typical receiver positions and that for a given number of PDs, the new receiver provides much greater diversity than a conventional receiver of the same overall dimensions in which all of the PDs have the same FOV. Finally the overall bit error rate (BER) is presented for systems using asymmetrically clipped optical OFDM (ACO-OFDM) as the modulation scheme. Results are presented for both zero forcing (ZF) and minimum mean square error (MMSE) equalization in the receiver. It is shown that the BER varies with receiver position, with relatively high values in the center and the corners of the room.
He, C, Wang, TQ, Abdullah Masum, M & Armstrong, J 2015, 'Performance of optical receivers using photodetectors with different fields of view in an indoor cellular communication system', 25th International Telecommunication Networks and Applications Conference, ITNAC 2015, Australasian Telecommunication Networks and Applications Conference, IEEE, Sydney, Australia, pp. 77-82.View/Download from: Publisher's site
© 2015 IEEE. This paper describes the use of an optical receiver which has photodiodes (PDs) with two different fields of view (2-FOV) in an indoor visible light communications (VLC) system. Data is transmitted using asymmetrically clipped optical OFDM (ACO-OFDM) from white light emitting diodes (LEDs) which are also used for illumination. A cellular configuration is considered where each transmitter transmits data to receivers within its cell. A minimum mean square error (MMSE) combiner is used in the receiver to separate the wanted signal from the interference. Results are calculated for the signal to interference plus noise ratio (SINR) as a function of the transmitter and receiver characteristics and the relative positions of the transmitters and receiver. It is shown that for most receiver positions the 2-FOV receiver outperforms a conventional receiver in which all of the PDs have the same FOV. It is also shown that increasing the number of PDs in the 2-FOV receiver from two to eight gives negligible improvement in performance. Bit error rate (BER) results are presented for a number of receiver positions showing that at some positions the 2-FOV receiver gives a significant improvement in performance but that at others no improvement is observed.
Wang, TQ, Green, RJ & Armstrong, J 2014, 'Prism array-based receiver with application in MIMO indoor optical wireless communications', International Conference on Transparent Optical Networks, 2014 16th International Conference on Transparent Optical Networks (ICTON).View/Download from: UTS OPUS or Publisher's site
In this paper, a prism array-based receiver for intensity-modulated direct-detection (IM/DD) optical wireless systems has been investigated. The receiver uses an array of prisms to achieve angular diversity within a compact receiver structure. The transmission of light through a prism onto a photodetecting surface is presented, showing the power loss of the light. The resulting channel gains are determined and show that the new receiver has a wide field of view (FOV). This receiver is then applied in a typical room using lighting light emitting diodes (LEDs) as transmitters. It is shown that there is relatively little variation in performance as a function of the position of the receiver within the room. This means that the new structure can form the basis of robust optical wireless MIMO systems. © 2014 IEEE.
Wang, TQ & Armstrong, J 2014, 'Performance of indoor MIMO optical wireless system using linear receiver with prism array', 2014 Australian Communications Theory Workshop, AusCTW 2014, Australian Communications Theory Workshop, IEEE, Sydney, NSW, Australia, pp. 51-56.View/Download from: UTS OPUS or Publisher's site
In this paper, we analyze the performance of an indoor MIMO optical wireless system with a linear receiver. The receiver uses an array of prisms to form channel matrices that can achieve angular diversity within a compact receiver structure. The transmission of light through a prism onto a photodetecting surface is analyzed showing that the channel gain depends on the orientation of the prisms. Thus, by arranging the prisms carefully, channel matrices with full rank can be formed in a multiple LED scenario, which facilitates the use of low complexity linear de-multiplexing algorithms, including zero-forcing (ZF) and minimum mean square error (MMSE). We present bit error rate (BER) results in a typical indoor scenario. It is shown that the BER varies with the position of the receiver, with relatively high values for the receiver located at the center and near the corners of the room. © 2014 IEEE.
Wang, TQ, Sekercioglu, YA & Armstrong, J 2012, 'Hemispherical lens based imaging receiver for MIMO optical wireless communications', 2012 IEEE Globecom Workshops, GC Wkshps 2012, IEEE Globecom Workshops (Gc Workshops), IEEE, Institute of Electrical and Electronics Engineers, Anaheim, CA, USA, pp. 1239-1243.View/Download from: UTS OPUS or Publisher's site
White lighting LED based systems are emerging as an important form of high data rate communications, especially for indoor applications. Two limitations of existing systems are the small field of view of typical receivers and the poor performance of optical wireless MIMO due to lack of spatial diversity. In this paper we describe a novel design which overcomes these problems by using a hemispherical lens in the receiver. We show that the new system has a wide field of view and also provides significant spatial diversity for typical MIMO visible light scenarios. Numerical results are provided for a range of LED transmitters with different half power semi-angles. Our analysis shows that systems can be designed with adequate channel gain for angles of incidence as large as 70 degrees. The optical power density is also calculated to show the received optical power distributions for the case of four LED transmitters. The results indicate that the images of the LEDs are clearly separated. This reduces the channel correlations between individual transmitters and receivers and thus promises a significant diversity order for MIMO optical wireless systems. © 2012 IEEE.
Wang, Q, Yue, DW & Wang, Y 2010, 'Throughput maximization in cognitive radio networks', 2010 6th International Conference on Wireless Communications, Networking and Mobile Computing, WiCOM 2010.View/Download from: Publisher's site
In this paper, we present a new look at the sensing-throughput tradeoff problem. Distinguishing with the previous work, the throughput in our paper is defined as the number of data bits per second received correctly rather than the achievable rate. This choice facilitates the investigation on optimizing throughput for a frame based wireless data transmission scheme from a general point of view. Our objective is to maximize the cognitive radio (CR) throughput under the constraint of the preset detection probability threshold. We investigate the behaviors of the throughput under the situations with and without cooperative spectrum sensing and propose efficient algorithms in both cases for the throughput maximization. Numerical results show that the throughput obtained by our proposed algorithms achieve the optimal performance. © 2010 IEEE.
Yue, DW, Wang, Q & Lau, FCM 2010, 'Spectrum sensing gain analysis in cooperative cognitive radio networks', 2010 6th International Conference on Wireless Communications, Networking and Mobile Computing, WiCOM 2010.View/Download from: Publisher's site
In order to quantify the impact of channel and/or diversity scheme on the probability of mission detection, a concept of sensing gain was defined recently by us, very similar to diversity gain, which determines the slope of probability of missing detection versus average signal-to-noise ratio (SNR) curve. The sensing gain is an important performance target, and very useful in the performance analysis of spectrum sensing in cognitive radio (CR) networks. In this paper, we analyze spectrum sensing performance in cooperative CR networks with N CR nodes and a fusion center, and focus on the problem of determining their sensing gain. It is assumed that all channel links from the primary user to the CR nodes and from the CR nodes to the fusion center are flat Rayleigh fading, and the fusion center utilizes the K out of N rule (such as the Majority rule) as its fusion rule. It is shown that (1) the sensing gain can be designed to be equal to N-K+1 for the K out of N rule; and (2) the sensing gain can become N/2 for the Majority rule by setting an appropriate SNR threshold for the fusion center. © 2010 IEEE.