作者:
Turletti, TTennenhouse, DINRIA
High Speed Networking Res Grp Sophia Antipolis France MIT
Comp Sci Lab Cambridge MA 02139 USA MIT
Alfred P Sloan Sch Management Cambridge MA 02139 USA
There is increasing interest in developing radio-based applications in software. The new architecture for implementing mobile telephony base stations has the potential of offering many benefits: great cost savings by ...
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There is increasing interest in developing radio-based applications in software. The new architecture for implementing mobile telephony base stations has the potential of offering many benefits: great cost savings by using one transceiver per BTS instead of one per channel, tremendous flexibility by moving system-specific parameters to the digital part, and allowing the support of a wide range of modulation and coding schemes. A very important problem in designing software radio applications is the need to estimate the required complexity of processing to dimension systems. For example, with a software GSM BTS it is critical to estimate the number of channels that can be supported by a given processor configuration, and to predict the impact of future processor enhancements on its capacity. This article is a short version of one which appeared in the IEEE Journal on Selected Areas in Communications Special Issue on Software Radios [1]. It focuses on the design of a software implementation of a GSM BTS and proposes a platform-independent evaluation of its computational requirements based on SPEC benchmarks [2].
We study the synergy between coded modulation and antenna-diversity reception on channels affected by slow Rician fading, Specifically, we assess the impact of channel-state information (CSI) on error probability. We ...
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We study the synergy between coded modulation and antenna-diversity reception on channels affected by slow Rician fading, Specifically, we assess the impact of channel-state information (CSI) on error probability. We show that with a good coding and constant envelope modulations (for example, phase-shift keying) scheme the loss in performance when CSI is not available is moderate (around 1.5 dB). Moreover, as the diversity order grows, the channel tends to become Gaussian.
Multilevel coding and bit-interleaved coded modulation employing differential encoding and non-coherent reception over flat fading channels are assessed. To achieve high bandwidth efliciencies mixed amplitude/phase mo...
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Multilevel coding and bit-interleaved coded modulation employing differential encoding and non-coherent reception over flat fading channels are assessed. To achieve high bandwidth efliciencies mixed amplitude/phase modulation is performed. It is shown that multiple symbol detection only provides gains for multilevel coding as Gray labelling of the differential symbols is not possible.
A set of code sequences is proposed for radar applications in which all phase steps are equal and the time duration of each phase state is varied in order to properly approximate either a stepped-RE waveform or a line...
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A set of code sequences is proposed for radar applications in which all phase steps are equal and the time duration of each phase state is varied in order to properly approximate either a stepped-RE waveform or a linear FM waveform, Since these proposed waveforms have varying time durations at each phase state, they are referred to as "Polytime" codes. Polytime code sequences have the advantage that arbitrary time-bandwidth waveforms can be generated with a few phase states. Of particular interest are cases where phase is quantized into two states (i.e., 0 degrees and 180 degrees).
This paper compares the performances of ATSC 8-VSB and DVB-T COFDM transmission systems for Digital Television Terrestrial Broadcasting. The comparison is based on the most recent laboratory test results and theoretic...
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This paper compares the performances of ATSC 8-VSB and DVB-T COFDM transmission systems for Digital Television Terrestrial Broadcasting. The comparison is based on the most recent laboratory test results and theoretical analysis.
UCSD's Center for Wireless Communications was founded in March 1995 as a partnership between the University and the wireless communications industry. Its goals include the definition and pursuit of a cutting-edge ...
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UCSD's Center for Wireless Communications was founded in March 1995 as a partnership between the University and the wireless communications industry. Its goals include the definition and pursuit of a cutting-edge program of precompetitive, multidisciplinary research focused on wireless access systems, technologies, and applications;the creation of a relevant base of new knowledge with high commercial impact potential;and the production of graduates at all degree levels trained to meet industrial human resources needs. Of paramount importance to the achievement of these goals are the involvement, collaboration, and financial support of the CWC's Industrial Participants. Working in close cooperation with its Industrial Participants, the theme of broadband wireless access to the Internet was chosen as the unifying focus for the Center's programs, and five thrust areas have been defined: circuits, signal processing (smart antennas and compression), communication theory, networks, and software to wirelessly support multimedia applications. Seven specific goal-oriented projects are currently underway, each intended to meet the long-term interests of a subset of our Industrial Participants. These seven projects focus, respectively, on ad hoc home networks, universal wide-area wireless service. space-time processing, modulation/coding for enhanced coverage, linear power amplifiers, RF receivers, and changes to the Internet infrastructure needed to support ubiquitous broadband wireless access. Among the many issues being addressed are agent-based computing, division of responsibilities between the tetherless information portal and the infrastructure-based agents, battery-conserving protocols for the air interface, quality of service at the wireless networking layer? capacity enhancement and interference suppression on the radio air interface, modulation and coding, image and video compression, and low-power RF and integrated circuits for the handheld device.
A random array exclusive OR modulation (REOM) channel coding technique is proposed for digital holographic data storage. The effect of channel coding on the system performance is analyzed through simulations. The perf...
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A random array exclusive OR modulation (REOM) channel coding technique is proposed for digital holographic data storage. The effect of channel coding on the system performance is analyzed through simulations. The performance of REOM is compared with that of other coding methods in terms of system raw bit error rate (BER) and signal-to-noise ratio (SNR). It is shown that REOM provides relatively uniform intensity distribution on the recording plane and therefore gives an improved performance.
Trellis coded modulation was designed to improve error performance of synchronous data links without sacrificing data rate, or expanding bandwidth. The codes are interpreted as binary convolutional codes with a mappin...
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Trellis coded modulation was designed to improve error performance of synchronous data links without sacrificing data rate, or expanding bandwidth. The codes are interpreted as binary convolutional codes with a mapping of coded bits into multilevel/phase signals to increase free Euclidean distance. The technique referred to as "mapping by set partitioning" is claimed as an optimal assignment. The rules for assigning channel signals first proposed by Ungerboeck assure maximum free Euclidean distance. However, by taking advantage of a butterfly structure in the trellis and modifying Ungerboeck's rules, the multiplicity of error events with free Euclidean distance can be minimized. In this paper, the relationship between butterfly and signal assignment is revealed and a modified rule is proposed for optimality of the trellis assignment.
In this paper, the performance of trellis coded M-PSK systems in the fading environment is investigated. The combined effects of the fading and the non-ideal coherent receiver on the phase of the received signal are t...
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In this paper, the performance of trellis coded M-PSK systems in the fading environment is investigated. The combined effects of the fading and the non-ideal coherent receiver on the phase of the received signal are taken into account. Thus, performance analysis results will reflect the degradations both due to the effects of the fading on the amplitude of the received signal and of a noisy carrier reference, each modeled by the Rician and Tikhonov distributions, respectively.
Communication over the discrete time memoryless Rayleigh fading channel is investigated. Codes achieving bit error rate (BER) lower than 10/sup -4/ at bit energy over the noise spectral density ratio (E/sub b//N/sub o...
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Communication over the discrete time memoryless Rayleigh fading channel is investigated. Codes achieving bit error rate (BER) lower than 10/sup -4/ at bit energy over the noise spectral density ratio (E/sub b//N/sub o/) of 1 to 2 dB from the channel capacity limit were found with a coding rate of 0.05 to 0.36 bits per channel use. Similar codes with rates of up to 0.57 also performed reasonably close to the capacity limit. The codes are serial concatenation of turbo code and a modulation code such as pulse position modulation (PPM). The receiver is based on joint iterative decoding of the turbo code and the modulation code. The results are applicable also to fast frequency hopping spread spectrum and to a certain multiuser communication scenario over a rapidly varying fading channel.
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