Convolutional coded dual header pulse interval modulation for line of sight photonic wireless links.

The analysis and simulation for convolutional coded dual header pulse interval modulation (CC-DH-PIM) scheme using a rate ½ convolutional code with the constraint length of 3 is presented. Decoding is implemented using the Viterbi algorithm with a hard decision. Mathematical analysis for the slot error rate (SER) upper bounds is presented and results are compared with the simulated data for a number of different modulation techniques. The authors show that the coded DH-PIM outperforms the pulse position modulation (PPM) scheme and offers >4 dB code gain at the SER of 10?4 compared to the standard DH-PIM. Results presented show that the CC-DH-PIM with a higher constraint length of 7 offers a code gain of 2 dB at SER of 10?5 compared to the CC-DH-PIM with a constraint length of 3. However, in CC-DH-PIM the improvement in the error performance is achieved at the cost of reduced transmission throughput compared to the standard DH-PIM

Slot error rate performance of DH-PIM with symbol retransmission for optical wireless links

In this paper we introduce the dual-header pulse interval modulation (DH-PIM) technique employing a simple retransmission coupled with a majority decision detection scheme at the receiver. We analytically investigate the slot error rate (SER) performance and compare results with simulated data for the symbol retransmissions rates of three, four and five, showing a good agreement. We demonstrate that the proposed scheme significantly reduces the SER compared with the standard single symbol transmission system, with retransmission rate of five offering the highest code gain of 5 dB

Channel equalization for indoor lighting communications networks

We consider indoors communications networks using modulated LEDs to transmit the information packets. A generic indoor channel equalization formulation is proposed assuming the existence of both line of sight and diffuse emitters. The proposed approach is of relevance to emergent indoors distributed sensing modalities for which various lighting based network communications protocols are considered

Constrained pre-equalization accounting for multi-path fading emulated using large RC networks: applications to wireless and photonics communications

Multi-path propagation is modelled assuming a multi-layer RC network with randomly allocated resistors and capacitors to represent the transmission medium. Due to frequency-selective attenuation, the waveforms associated with each propagation path incur path-dependent distortion. A pre-equalization procedure that takes into account the capabilities of the transmission source as well as the transmission properties of the medium is developed. The problem is cast within a Mixed Integer Linear Programming optimization framework that uses the developed nominal RC network model, with the excitation waveform customized to optimize signal fidelity from the transmitter to the receiver. The objective is to match a Gaussian pulse input accounting for frequency regions where there would be pronounced fading. Simulations are carried out with different network realizations in order to evaluate the sensitivity of the solution with respect to changes in the transmission medium mimicking the multi-path propagation. The proposed approach is of relevance where equalization techniques are difficult to implement. Applications are discussed within the context of emergent communication modalities across the EM spectrum such as light percolation as well as emergent indoor communications assuming various modulation protocols or UWB schemes as well as within the context of space division multiplexing

The Application of Human Resource Management in Thai SMEs – A Case Study of Albatross Company Limited

Date June 04, 2008 Level Master Thesis EFO705, 10 points (15 credits) Authors Pornratchanee Sethakaset Tanawan Santimataneedol Bangkok, Thailand Bangkok Thailand Date of Birth: 28 October 1982 Date of Birth: 5 March 1984 Title The Application of Human Resource Management in Thai SMEs – A Case Study of Albatross Company Limited Supervisor Mona Andersson Problems : How can the entrepreneur of SMEs manage their human resources? Can previous research and studies about HRM in SMEs be applied in the Thai entrepreneurial SME? Does the HRM in the company change and transform over time? Purposes : The purposes of this study are to review the relevant studies and research about HRM in SMEs in order to investigate how human resources are managed in SMEs and to determine if the previous studies are applicable to Thai entrepreneurial SMEs. Methodology : This master’s thesis is based on a qualitative approach in order to investigate HRM in SMEs and easier to understand the behavior in a certain case. The main secondary data is also collected from website which is the utilizing material for this thesis. Conclusion : In this study, it was concluded that this Thai SME manages its human resource in a mixture between informal and formal way. HRM is used and practiced more as the company grows which the entrepreneur plays a central role in the Human Resource Management in SMEs

Differential Amplitude Pulse-Position Modulation for Indoor Wireless Optical Communications

We propose a novel differential amplitude pulse-position modulation (DAPPM) for indoor optical wireless communications. DAPPM yields advantages over PPM, DPPM, and DH-PIM &alpha; in terms of bandwidth requirements, capacity, and peak-to-average power ratio (PAPR). The performance of a DAPPM system with an unequalized receiver is examined over nondispersive and dispersive channels. DAPPM can provide better bandwidth and/or power efficiency than PAM, PPM, DPPM, and DH-PIM &alpha; depending on the number of amplitude levels A and the maximum length L of a symbol. We also show that, given the same maximum length, DAPPM has better bandwidth efficiency but requires about 1&thinsp;dB and 1.5&thinsp;dB more power than PPM and DPPM, respectively, at high bit rates over a dispersive channel. Conversely, DAPPM requires less power than DH-PIM 2 . When the number of bits per symbol is the same, PAM requires more power, and DH-PIM 2 less power, than DAPPM. Finally, it is shown that the performance of DAPPM can be improved with MLSD, chip-rate DFE, and multichip-rate DFE.</p

Using full duplex relaying in device-to-device (D2D) based wireless multicast services: a two-user case

D2D communication has been proposed as an important supplement to the existing centralized cellular networks which allows two physically adjacent cellular user equipments (UEs) to communicate directly. This paper concerns using D2D to improve wireless multicast services in cellular networks. Specially, we consider a D2D transmitter UE can act as a full-duplex (FD) relay to assist a cellular multicast from a base station (BS) to a group of two UEs. And a new scheme which allows an intra-cell D2D retransmission to underlay a cellular multicast is proposed. Under the constraint of the minimum signal-to-interference-and-noise ratio (SINR) required by each of the receiver UEs, the aim of the scheme is to select the best UE in a multicast group to perform the D2D retransmission with the serving BS. Thus, the aggregate transmit power consumed at the BS and at the selected UE can be minimized. The numerical results show that the proposed scheme outperforms traditional cellular multicast scheme as it consumes less transmit power to achieve the same SINR target at the receiver UEs