We propose a novel differential amplitude pulse-position modulation (DAPPM) for indoor optical wireless communications. DAPPM yields advantages over PPM, DPPM, and DH-PIMα 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-PIMα 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 dB and 1.5 dB more power than PPM and DPPM, respectively, at high bit rates over a dispersive channel. Conversely, DAPPM requires less power than DH-PIM2. When the number of bits per symbol is the same, PAM requires more power, and DH-PIM2 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.

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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. We present the symbol structure and the properties of DAPPM. The power spectral density of DAPPM is also derived and compared to other modulation schemes. DAPPM yields advantages over PPM and DPPM in terms of bandwidth efficiency, capacity and peak-to-average power ratio (PAPR). The power efficiency is also examined. Over a non-dispersive channel, DAPPM gives better bandwidth and/or power efficiency depending on the number of amplitude levels (A) and the maximum length (L) of a symbol. We also show that, over a dispersive channel, DAPPM has better bandwidth efficiency but requires more power than PPM and DPPM for the same value of L.

Differential amplitude pulse-position modulation for indoor wireless optical channels

An optical Amplitude and Pulse Position Modulation (APPM) mapping scheme for strong turbulent atmospheric channel is proposed to optimize Bit Error Rate (BER) performance. In this scheme, a non-equidifferent amplitude series is designed based on quantitative BER analysis of the specific A×M APPM demapping procedures containing time slot selection and amplitude decision in selected time slot, which are different from traditional ones. Simulation results of 4×4, 4×8 and 4×16 APPM show 4, 3.4 and 6.9 dB SNR gain against traditional APPM scheme respectively. Thus significant BER performance improvement is achieved which helps to enhance reliability of free-space optical communication systems.

A novel non-equidifferent optical APPM mapping scheme for strong turbulent atmospheric channel

This paper presents a constructive discussion and inclusive review on advancements in the coded modulation free-space optical (FSO) communication system and corresponding techniques. These techniques mainly include channel model, forward error correction (FEC) and modulation schemes. Firstly, a complete view of FSO system is presented which contains the description, the current research situation along with the advantages over the traditional radio frequency (RF) wireless communication and fiber optical communications. Then, the channel model, FEC, modulation schemes and complete system of coded modulation FSO are analyzed successively. At last, the review work of coded modulation FSO system is summarized and further improvements are prospected.

Review of coded modulation free space optical communication system

In this communication we consider the use of PPM based modulation methods, such as the hybrid modulation method called amplitude and pulse-position modulation (APPM) and overlapping pulse-position modulation (OPPM), to improve the performance of infrared WLANs. The bandwidth efficiency expressions of these modulation schemes are presented and compared against the one of pulse-position modulation (PPM), which allows to conclude that both APPM and OPPM can be used to improve the performance of PPM without significant bandwidth expansion, using trellis-coded modulation (TCM) codes. We also derive the best codes for some APPM and OPPM schemes, and the results show that non-negligible coding gains without bandwidth expansion can be obtained with trellis codes of moderate complexity.

/pdf/coding-of-ppm-based-modulation-techniques-to-improve-the-1e7tmqnhtm.pdf

Coding of PPM based modulation techniques to improve the performance of infrared WLANs

In this communication we consider the use of an hybrid modulation method called amplitude and pulse-position modulation (APPM) in infrared WLAN. In this hybrid method the information is conveyed both in the position and amplitude of a pulse. The bandwidth efficiency and the capacity of this new modulation scheme are derived and compared against pulse-position modulation (PPM), which allows us to conclude that APPM can be used to improve the performance of PPM without bandwidth expansion, using trellis-coded modulation (TCM) codes. We also derive the best trellis codes for some A/spl times/2-APPM, and the results show that non-negligible coding gains can be obtained with trellis codes of moderate complexity.

R. Alves

Papers

Trellis codes based on amplitude and position modulation for infrared WLANs