This contribution presents the results of the first digital terrestrial television field trials and coverage measurements in spain. First of all the VIDITER project is presented. The main objective of this work is to ...
详细信息
This contribution presents the results of the first digital terrestrial television field trials and coverage measurements in spain. First of all the VIDITER project is presented. The main objective of this work is to study the behavior of a whole digital terrestrial television network, from source coding up to the final signal reception, At this point, the experimental network installed in Madrid-will be described. Next, the measurement campaign is explained, first, by describing the network configuration used for these first field trials, and then, paying attention to the criteria used to select the measurement points and the parameter set to be tested. Some of the results obtained will be shown as a first approach to the figures needed to develop and plan a fully operational digital terrestrial television service.
Throughout 1998, the TDMA community investigated and defined an enhanced suite of voice and data services for TIA/EIA-136 while also improving its basic system capabilities. These enhancements, collectively named 136+...
详细信息
Throughout 1998, the TDMA community investigated and defined an enhanced suite of voice and data services for TIA/EIA-136 while also improving its basic system capabilities. These enhancements, collectively named 136+, provide improved voice quality, increased capacity, higher data rates, and improved tools for RF system engineering. The enhancements are obtained by introducing a new modulation scheme (8-PSK), new slot formals, and the addition of several new interleaving and coding options. As a result, TIA/EIA-136 now supports a new vocoder mode, the GSM Enhanced Full-Rate (US1) for improved fidelity applications, a robust IS-641 vocoder mode with a 4 dB FER enhancement on the IS136 downlink, and a new packet data service capable of providing usable data rates of 14.4, 28.8, or 43.2 kb/s on a full-rate, double full-rate, or triple full-rate channel, respectively. The packet data service is truly evolutionary in nature, having a new medium access control layer with a network layer very similar to that used for the existing digital control channel. In addition, it maximizes commonalities among TDMA technologies, using identical higher layers and network architecture to the General Packet Radio Service specified in GSM. furthermore, by using a concept known as tunneling to pass TIA/EIA-136 messages through the GPRS network elements, the existing features defined on the DCCH are maintained. This article provides an overview of these 136+-applications, as well as insight into additional near-term improvements, such as the ability to support six voice users per 30 kHz (TDMA6), downlink time diversity, and fast power control.
Block-coded modulation (BCM) combines bandwidth-efficient modulation techniques with error-correction capabilities to allow efficient data transmission over communication channels. The disadvantage of this technique, ...
详细信息
Block-coded modulation (BCM) combines bandwidth-efficient modulation techniques with error-correction capabilities to allow efficient data transmission over communication channels. The disadvantage of this technique, however, is the complexity of the trellis used in the Viterbi decoding, process. The authors address this problem and propose a method for the reduction of decoding complexity. Optimal sectionalisation has been identified as an appropriate technique and it is applied to trellises of BCM schemes based on a set of new objective functions. The resulting sectionalisation algorithm has been applied to various BCM schemes including 4-PSK, 8-PSK and 16-PSK and a complexity reduction of approximately 20% is achieved. Extensive simulation las shown that both original and sectionalised trellises have the same performance: over Rayleigh, K = 6 Rician and K = 10 Rician fading channels. Furthermore, a comparison between the considered BCM schemes and ring-TCM is provided in term of code performance and decoding complexity.
In this paper, transmitter diversity wireless communication systems over Rayleigh fading channels using pilot symbol assisted modulation (PSAM) are studied. Unlike conventional transmitter diversity systems with PSAM ...
详细信息
In this paper, transmitter diversity wireless communication systems over Rayleigh fading channels using pilot symbol assisted modulation (PSAM) are studied. Unlike conventional transmitter diversity systems with PSAM that estimate the superimposed fading process, we are able to estimate each individual fading process corresponding to the multiple transmitters by using appropriately designed pilot symbol sequences. With such sequences, special coded modulation schemes can then be designed to access the diversity provided by the multiple transmitters without having to use an interleaver or expand the signal bandwidth, The notion of code matrix is introduced for the coded modulation scheme, and its design criteria are also established. In addition to the reduction in receiver complexity, simulation results are compared to, and shown to be superior to, that of an intentional frequency offset system over a wide range of system parameters.
Future multimedia services will require the transmission of very high data rates over broad-band radio channels. In order to provide these services to mobile users, anl appropriate transmission technique has to cope w...
详细信息
Future multimedia services will require the transmission of very high data rates over broad-band radio channels. In order to provide these services to mobile users, anl appropriate transmission technique has to cope with frequency-selective and time-variant radio channels. The computation complexity for an equalizer increases in a frequency-selective radio channel for high data-rate applications. Furthermore, the overhead for channel estimation procedures increases in time-variant channels. To overcome these drawbacks orthogonal frequency division multiplexing (OFDM) has been considered for broad-band applications in many publications. The objective of this paper is to describe the large potential, the flexibility and adaptivity of the OFDM transmission technique in frequency-selective and time-variant radio channels. In this paper several technical aspects of OFDM transmission systems are discussed, especially the topics of differential modulation for which we compare different demodulation methods and channel coding with soft decision decoding. For higher level differential modulation, multilevel coding is taken into consideration.
In this paper, we propose several modulation techniques for use in military avionics optical fiber data buses, namely, Extended Manchester II Pi-Phase coding with Beginning-Stopping Flags, Partial Trilevel Manchester ...
详细信息
In this paper, we propose several modulation techniques for use in military avionics optical fiber data buses, namely, Extended Manchester II Pi-Phase coding with Beginning-Stopping Flags, Partial Trilevel Manchester II Bi-Phase coding, Four-ary Pulse Width modulation, Two-ary Pulse Width modulation with Amplitude-Distinguished Syne Field, Two-ary Message Pulse Width modulation and Two-ary Syne Pulse Amplitude modulation, respectively. Compared with an existing modulation scheme of MIL-STD-1773 avionics data buses, the proposed techniques can be effectively used to overcome the difficulty in recognizing the correct operation states of an active transmitter at the output of optical receivers. The feasibility of proposed modulation schemes are discussed, and their performance is also evaluated.
modulation codes with d>0 are essential in optical recording to enable useful densities, since the minimum mark size achievable is limited by the diffraction-limited spot size. The EFMPLus modulation code is a codi...
详细信息
modulation codes with d>0 are essential in optical recording to enable useful densities, since the minimum mark size achievable is limited by the diffraction-limited spot size. The EFMPLus modulation code is a coding scheme adopted for the digital video disk (DVD). This is a run-length limited code with constraints d=2 and k=10. It is appropriate to exploit this knowledge of the coding scheme in the detection strategies, to sustain high performance at higher densities and data rates. This paper presents the performance of two simple equalizers, one of which uses decision feedback, to achieve a target response that enables optimal detection by simple thresholding. The evaluations are done using a channel model. Equalization strategies that exploit the d=2 RLL constraint in the DVD channel provide improved performance of about 2 to 4 db for the DVD specifications.
We present a trellis code which reduces the probability that transition jitter will cause one allowed sequence to be decoded as another allowed sequence. This code requires that transition times mod 4 be in the code o...
详细信息
We present a trellis code which reduces the probability that transition jitter will cause one allowed sequence to be decoded as another allowed sequence. This code requires that transition times mod 4 be in the code of a 4-state convolutional encoder. We also exclude adjacent transitions (d = 1). Sequences satisfying this constraint have capacity of approx. 4/9. This code can be implemented using a finite state encoder, Viterbi detector and sliding-block decoder. Tn the presence of pure jitter noise this code realizes a gain of approximately 3 dB over uncoded recording at the same user density.
Iterative demodulation and decoding of convolutionally encoded data is treated as a special case of the recently proposed serial concatenation of interleaved codes. It is shown that by exploiting the recursive nature ...
详细信息
Iterative demodulation and decoding of convolutionally encoded data is treated as a special case of the recently proposed serial concatenation of interleaved codes. It is shown that by exploiting the recursive nature of the differential modulation schemes (for example, DBPSK, DQPSK, CPM, etc.), large interleaving gains tan be achieved similar to serial concatenation schemes. We also show that when memoryless modulation is used, preceding can be used to create a rate-1 recursive inner code in order to obtain interleaving gains without adding redundancy from the inner code.
The celebration and highlights of 50 years of signal processing technology as it is applied to communication systems are presented. Some of the numerous opportunities this exciting area opens up for signal processing ...
详细信息
The celebration and highlights of 50 years of signal processing technology as it is applied to communication systems are presented. Some of the numerous opportunities this exciting area opens up for signal processing research and development are discussed. This celebration came at a time when a dramatic upswing in modern telecommunications worldwide is witnessed.
暂无评论