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PDM-QPSK and PDM-BPSK are compared against PS-QPSK and PQ-16PPM with equal bandwidth expansion factors. The results show that better sensitivity is achieved by using strong FEC codes on standard modulation formats rather than using high-sensitivity modulation formats.
This paper investigates Orthogonal Frequency- Division Multiplexing (OFDM) transmission in intensity modulated, direct-detected (IM/DD) optical systems. Due to the unipolarity of the IM/DD optical channel, DC biasing and associated nonlinear clipping distortion (NLCD) is inevitable, unless an anti-periodic signal is created by limiting bit loading to only half of the available bandwidth. To generalize...
This paper looks at the problem of performance enhancement for orthogonal frequency-division multiplexing (OFDM) transmission in intensity modulated, direct detected (IM/DD) optical systems. Due to the unipolarity of the IM/DD channel, asymmetric clipping and associated biasing is inevitable, which results in a significant signal degradation. ACO-OFDM has been previously proposed to avoid this detrimental...
This paper investigates the effects of nonlinear biasing and clipping (BAC) on a random optical orthogonal frequency-division multiplexing (OFDM) signal with direct detection. We look at the problem of theoretical performance evaluation of such a system. Specifically, we derive an approximation for the symbol error rate (SER). The nonlinear BAC process is modeled as a linear deterministic gain plus...
One of the main problems with orthogonal frequency division multiplexing (OFDM) modulation is the high peak-to-average-ratio (PAR) of the transmitted time-domain signal. Optimally distorting the transmitted constellation for peak reduction in OFDM systems was introduced and shown to be a convex optimization problem. This work advantageously extends this approach to multiple-input multiple-output (MIMO)...
The high peak-to-average-power ratio (PAR) of orthogonal frequency division multiplexing (OFDM) transmission systems significantly reduces the power efficiency or performance of such systems, and many techniques have been proposed to deal with this problem. Recently, the active constellation extension (ACE) algorithm has received much attention, where the main idea is to reduce the PAR by introducing...
The goal of this paper is to consider the impact of tone selection on the performance of PAR reduction in uplink OFDMA systems using tone reservation. Previous work has given an efficient approach and potential results, but in a realistic system, the number of reserved tones and the effect of multi-user interference (from power in these tones) can limit the amount of PAR reduction. In addition to...
Energy usage is one of the most critically important problems in the exploitation of wireless sensor networks. Using the information redundancy typically present in the data streams in sensor networks due to spatial correlation we may address how to optimize the useful life span of a sensor network under energy constraints for each sensor. A new cost criterion for power optimization amongst sensors...
This paper investigates the power minimization problem in OFDMA based wireless multihop systems with the knowledge of channel state information (CSI). The joint allocation problem is divided into two stages: bandwidth allocation and subchannel assignment. Efficient optimal and suboptimal algorithms for both stages are jointed together to provide beneficial and stable improvements by exploiting a form...
The implementation of practical adaptive resource allocation scheme remains a key criterion to be satisfied for realising spectrally efficient multitone wireless communications. The ever-increasing demand for spectrally efficient broadband wireless transmission technologies has spurred intensive research leading towards the implementation of adaptive OFDM and adaptive MIMO systems. Efforts in this...
We extend our previous work on optimal dynamic resource allocation in wireless environments to incorporate prediction of the frequency-selective OFDM channel. We briefly summarize our previous work and its exploitation of convexity for the resource allocation problem in point-to-point digital wireless communication links. We introduce channel prediction to overcome latency associated with symbol recovery,...
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