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We investigate and analyze the asymmetrically clipped and direct-current-biased optical orthogonal frequency division multiplexing (ADO-OFDM) in visible light communication (VLC) system. Then we propose two modified channel equalization algorithms of ADO-OFDM in VLC systems. It is shown that the algorithm combined with channel estimation for interference cancellation to recover ADO-OFDM signal is...
Visible light communication (VLC) has been a research hotspot for broad bandwidth, high speed, and anti-interference. Power line communication (PLC) has the advantages of low cost and flexible access, which is connected and combined with VLC to be a hybrid communication system. We set up a communication system model of PLC&VLC based on orthogonal frequency division multiplexing (OFDM) modulation,...
With the wide application of OFDM technology, the security of OFDM system is becoming more and more important. In this paper, we propose a secrecy transmission scheme with phase rotation and sub-carrier mapping based on chaos sequences. The scheme employs the characteristics of pseudorandom and sensitivity to initial conditions of chaos sequences. We have studied on the observed signal features, computational...
At present, the user experience provided by smart mobile terminals is limited to the battery capacity. This paper focuses on how to improve the energy efficiency of terminals in OFDMA-based wireless multicast systems with frequency-selective channels. We assume that multicast terminals can switch to sleep mode during the transmission of some OFDM symbols according to their OFDMA frame-level quality...
Performance analysis of a bandlimited nonorthogonal waveform transmission (NOWT) scheme for high data rate wireless communications is presented. The technique is a potential alternative to classic orthogonal multiplexing techniques such as OFDM and QAM. It shows faster data transmission rate than Nyquist rate, and considerable performance gain compared with orthogonal techniques, as well as much lower...
As an extension of IEEE 802.11 standards, IEEE 802.11p is specially developed for vehicular wireless communications. Routing plays a very important role in VANETs for packet delivery to mobile vehicles. To evaluate scalability and efficiency of routing protocols in VANETs, it is a critical need to simulate routing protocols with realistic mobility models. In this paper, we mainly focus on modeling...
This paper investigates coordinated resource allocation for cell-center and cell-edge users in multicell orthogonal frequency division multiple-access (OFDMA) wireless networks. Here, we assume the data symbols of each user is only known by one base station (BS). Referring to the fractional frequency reuse (FFR) scheme, the resources for cell-center and cell-edge users are partitioned. Based on such...
In long term evolution (LTE) downlink indoor scenarios, we study an inter-cell interference coordination (ICIC) by interacting the relative narrow-band transmit power (RNTP) indicators among evolved NodeBs (eNBs). Assuming the data symbols of each user is only known by one eNB, a novel RNTP-based resource block (RB) allocation scheme is presented and carried out in two steps: 1) Each eNB partitions...
This paper analyzes the performance of a novel time domain pilot scheme using least square channel estimation in convolutional multiplexed multicarrier (CMM) systems. To reduce decoding complexity and achieve higher spectral efficiency, data symbols are encoded through serial concatenated structure of convolutional multiplexing technique, while simultaneously pilot sequences are generated and multiplexed...
In this paper, we study the cross-layer resource allocation for the secondary users (SUs) supporting heterogeneous services in interference-limited spectrum sharing system. Two classes of SUs are considered: delay-tolerant SUs (DT-SUs) and delay- sensitive SUs (DS-SUs). With the queue theory, the delay requirements of DS-SUs are transformed into constant rate requirements. Unlike most previous works,...
A novel intra-cell frequency planning scheme based on interference coordination is exploited for cellular Orthogonal Frequency Division Multiplexing (OFDM)-Relay systems. In this strategy, a factor RI is introduced to model the interference in the 2nd slot. According to RI and the signal-to-interference-plus-noise ratio, the scheduler groups all the users into three sets. Furthermore, the total spectrum...
Record wireless data transmission of 31.4 Gbps within 7 GHz license-free band at 60 GHz is experimentally demonstrated using adaptive bit-loading OFDM modulation. Adaptive bit-loading OFDM also enables extended fiber transmission distances beyond 5km.
This paper reviews 60-GHz radio-over-fiber systems employing optical frequency multiplication and adaptive OFDM signals with multi-level modulation formats to achieve an ultra-high data rate of up to 32.65 Gbps within the 7-GHz license-free band.
By using frequency-domain oversampling at the receiver, we propose a novel blind channel estimation scheme for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. Specifically, a subspace blind channel estimation approach is developed, based only on second-order statistics of the received signal. The estimated MIMO channel is nicely determined by Nt minimum...
We experimentally demonstrated an adaptive I/Q imbalance correction scheme to compensate I/Q-imbalance. With I/Q correction, a 32.65-Gbps OFDM signal at 60 GHz within 7-GHz license-free band is successfully generated and, following 25km SMF transmission, negligible power penalty is observed.
With only second-order statistical information, subspace based blind channel estimation has received considerable attention. To make subspace based blind channel estimation methods feasible, signal redundancy is necessary, which is usually acquired by time-domain oversampling or using multiple receive antennas. In this paper, a new perspective, frequency-domain oversampling, is taken to develop a...
This paper studies the power allocation (PA) and distributed antenna (DA) selection in the downlink orthogonal frequency division multiplexing distributed antenna systems (OFDM-DAS). Two schemes are analyzed, with the objective of maximizing the downlink received signal power. In the first scheme, the DA selection is based on large-scale fading only and the related PA is simple. It is proved that...
We present a compressive wide-band spectrum sensing scheme for cognitive radios. The received analog signal at the cognitive radio sensing receiver is transformed in to a digital signal using an analog-to-information converter. The autocorrelation of this compressed signal is then used to reconstruct an estimate of the signal spectrum. We evaluate the performance of this scheme in terms of the mean...
For the evolved UTRA (EUTRA), cell edge bit-rate and system throughput become important criteria for the evaluation of the system proposals and requirements on the system performance. Inter-cell interference is the main source of performance degradation for OFDM, especially the data rate of cell edge UEs is severely limited. Many inter-cell interference mitigation schemes are proposed to improve the...
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