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Martin Haardt, Siemens (Germany)
Josef A. Nossek, Technical University of Munich (Germany)
It is essential for an efficient frequency and time slot allocation procedure in future mobile communication systems using space division multiple access (SDMA) to determine the mobiles that are spatially well separated from one another. Thus, once a mobile desires to initiate a call, precise knowledge of the 2-D arrival angles of its dominant wavefronts is required. In this application, 3-D Unitary ESPRIT for joint 2-D angle and carrier estimation offers an efficient way to handle such mobile access requests since it provides efficient high-resolution measurements of the spatial characteristics of the wireless channel, even if only a small number of antennas is available at the base station. Automatic pairing of the 3-D estimates is achieved via a new simultaneous Schur decomposition (SSD) of three real-valued, non-symmetric matrices. In general, the SSD enables an R-dimensional extension of Unitary ESPRIT (R greater-or-equal-to 3) to estimate several undamped R-dimensional modes or frequencies along with their correct pairing in multidimensional harmonic retrieval problems. Here, we present a Jacobi-type method to calculate the SSD. For each of the R dimensions, the corresponding frequency estimates are obtained from the real eigenvalues of a real-valued matrix. The SSD jointly estimates the eigenvalues of all R matrices and, thereby, achieves automatic pairing of the estimated R-dimensional modes via a closed-form procedure that neither requires any search nor any other heuristic pairing strategy.
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Thomas Hindelang, Technical University of Munich (Germany)
Wen Xu, Technical University of Munich (Germany)
Christian Erben, Technical University of Munich (Germany)
There is often residual redundancy remaining in coded speech data, even if a powerful speech codec (e.g. the full rate coder used in GSM mobile communications) is employed. By using such redundancy together with the information provided by the channel decoder, such as soft output (L-value), the number of channel bits inverted by the decoder, or a cyclic redundancy check, the bit error rate can be further reduced and a more graceful degradation of speech quality can be achieved, especially under bad channel conditions. In this paper, we report on the study with regard to this aspect for GSM full rate speech transmission and error concealment. The algorithms developed can be easily implemented with a currently available DSP designed for GSM mobile phones.
ic970259.pdf ic970259.pdf TOPFuyun Ling, Motorola (U.S.A.)
Optimal pilot assisted estimation of communication channels is considered for coherent cellular and PCS CDMA reverse link communications. Both pilot symbol and pilot channel based schemes are described and the optimal estimators for these two schemes are analyzed. Relative mean square estimation error (RMSEE) and optimal power allocation between data and pilot signals are derived based on the analysis. Finally, simulation results are given to show the reverse link performance can be significantly improved by using the pilot assisted coherent communication instead of non-coherent schemes for CDMA reverse link.
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Christian Bergogne, Telecom Paris, Alcatel Telspace (France)
Michel Bousquet, ENSAE (France)
Philippe Sehier, Alcatel Telspace (France)
In TDMA communications systems using all feedforward sychronization techniques, the quality of data decoding strictly depends on the estimation accuracy of the synchronization parameters (timing, carrier phase/frequency and preamble detection) extracted from the received signal. The frequency offset estimation is the most critical point. Indeed, an inaccurate frequency estimation can cause cycle slips and then errors during decoding. In this paper, we propose a new frequency estimator, analytically derived from the Maximum Likelihood principle and optimized thanks to variance simulations. Its performance is compared to the Cramer Rao Bound.
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Thorsten Groetker, ISS, RWTH Aachen (Germany)
Rainer Schoenen, ISS, RWTH Aachen (Germany)
Heinrich Meyr, ISS, RWTH Aachen (Germany)
Many signal processing systems use event driven mechanisms - typically based on finite state machines (FSMs) - to control the operation of computationally intensive (data flow) parts. The state machines in turn are often fueled by external inputs as well as by feedback from the signal processing portions of the system. Packet-based transmission systems are a good example for such a close interaction between data and control flow. For an efficient design flow it is of crucial importance to be able to model and analyze the complete functionality of the system within one single design environment. Therefore, we developed a computational model that integrates the specification of control and data flow by combining the notion of data flow graphs with event driven process activation.
ic970271.pdf ic970271.pdf TOPJan M. Rabaey, University of California at Berkeley (U.S.A.)
One of the most compelling issues in the design of wireless commu- nication components is to keep power dissipation between bounds. While low-power solutions are readily achieved in an application- specific approach, doing so in a programmable environment is a sub- stantially harder problem. This paper presents an approach to low- power programmable DSP that is based on the dynamic reconfigura- tion of hardware modules. This technique has shown to yield at least an order of magnitude of power reduction compared to traditional instruction-based engines for problems in the area of wireless com- munication.
ic970275.pdf ic970275.pdf TOPGerhard P. Fettweis, Technical University of Dresden (Germany)
Digital signal processors (DSPs) have become a key component for the design of communications ICs. Application customization leads to key market advantages but also to enormous problems of having too many different DSPs and their software development tools. First, by analysis of the problem open issues are pointed out. Then, a possible solution named CATS is presented, which allows for customization without the generation of too much heterogeneity in hardware and tools.
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Sanjay Kasturia, Bell Labs, Lucent Technologies (U.S.A.)
Colin Warwick, Bell Labs, Lucent Technologies (U.S.A.)
The mobile communication industry in the United States is undergoing major changes. Auctioning of additional spectrum will lead to more service providers and will significantly increase competition. Service providers are likely to customize the services they offer to differentiate themselves from others. We will discuss possible technologies for differentiation of services and the implications of these on the requirements for embedded DSPs. In the US, supporting the customization in the absence of a single industry wide standard, and the high likelihood of at least three widely used air interfaces will significantly challenge the ability of the industry to serve the phone needs of all service providers. The need for customization in the context of multiple standards, will create strong pressure to significantly improve the code development environment for DSPs. This also implies evolution to architectures that are more friendly to developers.
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Markus Willems, ISS, RWTH Aachen (Germany)
Volker Bürsgens, ISS, RWTH Aachen (Germany)
Thorsten Grötker, ISS, RWTH Aachen (Germany)
Heinrich Meyr, ISS, RWTH Aachen (Germany)
Digital mobile systems are sensitive to power consumption, chip size and costs. Therefore they are realized using fixed-point architectures, either dedicated HW or fixed-point processors. On the other hand, system design starts from a floating-point description. These requirements have been the motivation for FRIDGE, a design environment for the specification, evaluation and implementation of fixed-point systems. FRIDGE offers a seamless design flow from a floating-point description to a fixed-point implementation. Within this paper we focus on the FRIDGE-concept of an interactive, automated transformation of floating-point programs written in ANSI-C into fixed-point specifications, based on an interpolative approach. Since HW and SW implementations of the same functionality in general require different fixed-point specifications, the design time reductions that can be achieved by using FRIDGE make it a key component for an efficient HW/SW-CoDesign.
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Ravi Subramanian, Synopsys Inc. (U.S.A.)
Marc Barberis, Synopsys Inc. (U.S.A.)
Herbert Dawid, Synopsys GmbH (Germany)
While the mobile communication electronics industry's appetite grows for ever more functions and ever higher levels of integration, the complexity of these large designs is creating a discontinuity in the method by which these systems are designed. In this paper, we will take a close look at what is causing the design discontinuity, and how new design technologies are being used to design advanced digital communications systems for portable and wireless communication applications. We will examine how system-level design tools closely tied to silicon design implementation and verification technologies are enabling the creation of digital communications ICs in record time. We take several examples of commercially available silicon solutions designed using these methodologies- a G.721 ADPCM speech codec for cordless telephony and a complete variable-rate digital-video broadcast receiver for the DVB-S broadcast standard.
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