We present a range of coding schemes for OFDM transmission using binary, quaternary, octary, and higher order modulation that give high code rates for moderate numbers of carriers. These schemes have tightly bounded peak-to-mean envelope power ratio (PMEPR) and simultaneously have good error correction capability. The key theoretical result is a previously unrecognized connection between Golay complementary sequences and second-order Reed-Muller codes over alphabets Z/sub 2/h. We obtain additional flexibility in trading off code rate, PMEPR, and error correction capability by partitioning the second-order Reed-Muller code into cosets such that codewords with large values of PMEPR are isolated. For all the proposed schemes we show that encoding is straightforward and give an efficient decoding algorithm involving multiple fast Hadamard transforms. Since the coding schemes are all based on the same formal generator matrix we can deal adaptively with varying channel constraints and evolving system requirements.

/pdf/peak-to-mean-power-control-in-ofdm-golay-complementary-384pix8yoa.pdf

Peak-to-mean power control in OFDM, Golay complementary sequences and Reed-Muller codes

Controlling the peak-to-mean envelope power ratio (PMEPR) of orthogonal frequency-division multiplexed (OFDM) transmissions is a notoriously difficult problem, though one which is of vital importance for the practical application of OFDM in low-cost applications The utility of Golay complementary sequences in solving this problem has been recognized for some time In this paper, a powerful theory linking Golay complementary sets of polyphase sequences and Reed-Muller codes is developed Our main result shows that any second-order coset of a q-ary generalization of the first order Reed-Muller code can be partitioned into Golay complementary sets whose size depends only on a single parameter that is easily computed from a graph associated with the coset As a first consequence, recent results of Davis and Jedwab (see Electron Lett, vol33, p267-8, 1997) on Golay pairs, as well as earlier constructions of Golay (1949, 1951, 1961), Budisin (1990) and Sivaswamy (1978) are shown to arise as special cases of a unified theory for Golay complementary sets As a second consequence, the main result directly yields bounds on the PMEPRs of codes formed from selected cosets of the generalized first order Reed-Muller code These codes enjoy efficient encoding, good error-correcting capability, and tightly controlled PMEPR, and significantly extend the range of coding options for applications of OFDM using small numbers of carriers

https://www.hpl.hp.com/techreports/98/HPL-98-57R1.pdf

Generalised Reed-Muller codes and power control in OFDM modulation

Fiber-optic distributed sensing, employing the Brillouin effect, is already a commercially available measurement technique for the accurate estimation of the static strain/temperature fields along tens of kilometers with a spatial resolution of the order of a meter. Furthermore, relentless research efforts are paving the way to even much wider usability of the technique through recently achieved enhanced performance in each of its critical dimensions: measurement range has been extended to hundreds of kilometers; spatial resolution is of the order of a centimeter or less, signal to noise ratio has been significantly improved; fast dynamic events can be captured at kHz’s sampling rates; and a much better understanding of the underlying physics has been obtained, along with the formulation of figures of merit, and the preparation and early adoption of appropriate standards and guidelines. This paper describes the basics, as well as the state of the art, of the leading Brillouin interrogation methods, with emphasis on the significant progress made in the last 3 years. It also includes a short introduction to coding, which has proven instrumental in many of the recently obtained performance records.

[INVITED] State of the art of Brillouin fiber-optic distributed sensing

Optical fiber sensors offer unprecedented features, the most unique of which is the ability of monitoring varia- tions of the observed physical field with spatial continuity along the fiber. These distributed optical fiber sensors are based on the scattering processes that originate from the interaction between light and matter. Among the three different scatter- ing processes that may take place in a fiber—namely Rayleigh, Raman and Brillouin scattering, this paper focuses on Rayleigh-based distributed optical fiber sensors. For a given optical frequency, Rayleigh-based sensors exploit the three main properties of light: intensity, phase and polarization. All these sensing mechanisms are reviewed, along with basic principles, main acquisition techniques and fields of application. Emphasis, however, will be put on polarization-based distributed optical fiber sensors. While they currently represent a niche, they offer promising unique features worth being considered in greater detail.

/pdf/distributed-optical-fiber-sensing-based-on-rayleigh-1s5pjkfra2.pdf

Distributed Optical Fiber Sensing Based on Rayleigh Scattering

Raman-based fibre sensors: Trends and applications

The improved performance of an optical time-domain reflectometer (OTDR) through the application of a correlation technique using codes with complementary autocorrelation properties is discussed. The theoretical foundations of the method are presented along with experimental results exhibiting the best one-way range reported to date for a practical long-haul, long-wavelength OTDR system. >

Real-time long range complementary correlation optical time domain reflectometer

In this paper, we validate the industry standard ASM-HEMT model for non-linear large-signal modeling of 140 nm GaN HEMT at X-band. An accurate model has been developed for fundamental, second-, and third-order harmonic frequency. Time-domain waveforms and dynamic load-line simulations from ASM-HEMT model are also validated against non-linear vector analyzer measurements. This is the first validation of ASM-HEMT model for harmonics and NVNA data. A good model agreement with measurements has been obtained.

Accurate non-linear harmonic simulations at X-band using the ASM-HEMT model validated with NVNA measurements

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Real-time long range complementary correlation optical time domain reflectometer

Accurate non-linear harmonic simulations at X-band using the ASM-HEMT model validated with NVNA measurements