The performance of a non-coherent delay-locked loop (DLL) in the presence of multiple-access interference (MAI) is presented. The effect of the MAI on performance is evaluated in terms of two performance criteria: the...
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The performance of a non-coherent delay-locked loop (DLL) in the presence of multiple-access interference (MAI) is presented. The effect of the MAI on performance is evaluated in terms of two performance criteria: the mean-time-to-loss-lock (MTLL) and the root-mean-square (rms) tracking error. It is shown that the performance of the non-coherent DLL is drastically effected as the number of users in a system is increased. The effect of the near-far ratio, PN code sequence length, and loop signal-to-noise ratio (SNR) on the DLL's performance in MAI are also examined.
In most of the prevalent low-bit-rate speech coding schemes, lossy speech models are used, which makes the perfect reconstruction of speech impossible even at higher bit rates. In this paper, a lossless model of speec...
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In most of the prevalent low-bit-rate speech coding schemes, lossy speech models are used, which makes the perfect reconstruction of speech impossible even at higher bit rates. In this paper, a lossless model of speech is presented. It performs a pitch synchronous modulated lapped transform (MLT) on the linear prediction residual of speech. The residual signal can be reconstructed without distortion from its transform when the quantization error is neglected. The pitch synchronous process exploits the quasi-periodicity of the speech. The MLT converts the 'periodic' signal into the frequency domain. Efficient coding similar to that used in the waveform interpolation speech coder can be achieved on the transform result. The combination of pitch synchronization and MLT provides a promising basic model for speech coding and processing.
A new approach to reliable image and video transmission over a noisy channel is proposed. The proposed subband modulation scheme combines source coding and a channel modulation scheme to achieve high compression effic...
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A new approach to reliable image and video transmission over a noisy channel is proposed. The proposed subband modulation scheme combines source coding and a channel modulation scheme to achieve high compression efficiency and preferable quality. Further performance gain is obtained by multiresolution modulation and bits re-mapping scheme that assign efficient mapping from source codeword to channel modulation points. The bits re-mapping scheme performs nearly the same as the optimal mapping design scheme (Lervik and Ramstad, 1996) but with much lower complexity. The simulation is carried out on an additive white Gaussian noise (AWGN) channel, and extended to the slow Rayleigh fading channel.
We introduce a class of encoders, called bit geometrically uniform (BGU) encoders, for which the bit error probability does not depend on the transmitted sequence. Strong connections between the symmetry groups of geo...
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We introduce a class of encoders, called bit geometrically uniform (BGU) encoders, for which the bit error probability does not depend on the transmitted sequence. Strong connections between the symmetry groups of geometrically uniform signal constellations and those of the binary Hamming spaces are involved. Both uncoded modulation and infinitely long trellis codes are considered, and connections with the code linearity discussed. The theory of BGU encoders proves very useful for the analysis and design of codes aimed at minimizing the bit, rather than symbol, or sequence error probability. We apply the theory to the design of good serially concatenated trellis-coded modulation schemes.
This paper investigates the performance of handover algorithms, used in microcellular urban mobile systems, by means of an analytical model able to take frequency hopping, modulation and coding schemes, fading and int...
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This paper investigates the performance of handover algorithms, used in microcellular urban mobile systems, by means of an analytical model able to take frequency hopping, modulation and coding schemes, fading and interference due to a multicell environment into account. We investigate the performance of handover algorithms based on hysteresis and quality-driven, emphasizing the role played by interference and cellular traffic load. The results apply to F-TDMA networks, such as GSM.
In order to combat transmission errors in digital communication systems, forward error protection based on convolutional codes and interleaving in conjunction with soft decision maximum-likelihood decoding through the...
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In order to combat transmission errors in digital communication systems, forward error protection based on convolutional codes and interleaving in conjunction with soft decision maximum-likelihood decoding through the Viterbi (193) algorithm is often applied. The expected bit error rate for a given signal-to-noise ratio is generally difficult to foresee for a certain system. In this paper, we introduce a method which vividly treats the error behaviour on particular stages of the receiver, hereby allowing a coarse estimate of the overall bit error rate. Although no close mathematical results are given, several astonishing effects can easily be explained thus providing a better understanding of concatenated systems.
Self-concatenated trellis coded modulation with b(g-1) interleavers is a concatenated coded scheme based on only one rate bq/n convolutional code. The b input information sequences and their permuted versions are conn...
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Self-concatenated trellis coded modulation with b(g-1) interleavers is a concatenated coded scheme based on only one rate bq/n convolutional code. The b input information sequences and their permuted versions are connected through b(q-1) interleavers to the bq inputs of the convolutional encoder. A subset of the output, including the b information bits and parity bits, is mapped to modulation signals, e.g., MPSK, MQAM. First we obtain an upper bound to the average maximum-likelihood bit error probability of the self-concatenated convolutional coding scheme for binary modulation which also applies to QPSK modulation. Design rules for the single convolutional code, that maximize the interleavers gain and the asymptotic slope of the error probability curves are presented. The asymptotic error performance and design rules for binary modulation are extended to non-binary modulations for the design of self-concatenated trellis coded modulation. A low complexity self-iterative decoding algorithm for self-concatenated trellis coded modulation is proposed. Examples of self-concatenated coding/decoding are given for binary modulation with q=2, b=1, and 8-PSK modulation with q=2, b=2. Finally, simulation results for the examples are given for short and long interleavers, using the self iterative decoder.
This paper studies a modulation method for a wideband code division multiple access (W-CDMA) system in order to enhance its performance. The modulation method studied here introduce bi-orthogonal modulation instead of...
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This paper studies a modulation method for a wideband code division multiple access (W-CDMA) system in order to enhance its performance. The modulation method studied here introduce bi-orthogonal modulation instead of multicode transmission in order to suppress the envelope variation which comes from code division multiplexing in multicode transmission. Bi-orthogonal modulation studied here selects a single code in both in-phase and quadrature components, and leads to relaxation of the requirement of HPA linearity. This relaxation enhances the implementation of the mobile station (MS) with smaller size or lower power consumption. Computer simulation results show that the power level of spurious emission in the adjacent channel is reduced by approximately 8 dB with use of bi-orthogonal modulation, while keeping the required E/sub b//I/sub o/ almost the same as multicode transmission.
Low complexity maximum-likelihood and bounded-distance soft decoding algorithms are presented for several block and lattice codes. The bounded-distance algorithms are based upon multilevel constructions of the codes. ...
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Low complexity maximum-likelihood and bounded-distance soft decoding algorithms are presented for several block and lattice codes. The bounded-distance algorithms are based upon multilevel constructions of the codes. To demonstrate the approach, maximum-likelihood and bounded-distance decoders are devised for several well known codes and sphere packings in 8, 12 and 16 dimensions.
The results on the design and the measurement of a 5.8 GHz GaAs transmitter MMIC for electronic toll collection (ETC) system on-board equipment are presented. The MMIC of single chip and single supply without any exte...
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The results on the design and the measurement of a 5.8 GHz GaAs transmitter MMIC for electronic toll collection (ETC) system on-board equipment are presented. The MMIC of single chip and single supply without any external element is assembled into a 16-pin SSOP package. A novel drain-controlling modulation circuit is invented as a modulator to provide linear modulation. The measured adjacent channel power (ACP) is lower than -47 dBc. The on/off ratio of modulation is above 40 dB at 5.8 GHz under a random data modulation of 1.024 Mbps with Manchester coding.
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