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Personal Communications, IEEE

Issue 4 • Date Aug. 1999

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Displaying Results 1 - 9 of 9
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  • The software radio development system

    Page(s): 20 - 24
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    This article focuses on the effort to advance the field of software reprogrammable radios and the building of a software radio testbed to develop advanced radio waveforms and techniques. The Air Force Research Laboratory has performed research on software reprogrammable radios since 1990 when the SPEAKeasy program was begun to determine if a multiband, multimode software radio was technically feasible. The AFRL testbed aids in the development of advanced waveforms and radio techniques regardless of the processor or system architecture used by the intended software radio platform View full abstract»

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  • Cognitive radio: making software radios more personal

    Page(s): 13 - 18
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    Software radios are emerging as platforms for multiband multimode personal communications systems. Radio etiquette is the set of RF bands, air interfaces, protocols, and spatial and temporal patterns that moderate the use of the radio spectrum. Cognitive radio extends the software radio with radio-domain model-based reasoning about such etiquettes. Cognitive radio enhances the flexibility of personal services through a radio knowledge representation language. This language represents knowledge of radio etiquette, devices, software modules, propagation, networks, user needs, and application scenarios in a way that supports automated reasoning about the needs of the user. This empowers software radios to conduct expressive negotiations among peers about the use of radio spectrum across fluents of space, time, and user context. With RKRL, cognitive radio agents may actively manipulate the protocol stack to adapt known etiquettes to better satisfy the user's needs. This transforms radio nodes from blind executors of predefined protocols to radio-domain-aware intelligent agents that search out ways to deliver the services the user wants even if that user does not know how to obtain them. Software radio provides an ideal platform for the realization of cognitive radio View full abstract»

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  • Software-defined radio architectures for interference cancellation in DS-CDMA systems

    Page(s): 26 - 34
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    Third-generation wireless systems call for strategies that can improve achievable performance and data rates while providing flexibility and affordability. Software-defined radio technology is promising to provide the required flexibility in radio frequency, intermediate frequency, and baseband signal processing stages. Baseband signal processing techniques such as interference cancellation for direct-sequence code-division multiple access systems have the potential to provide the higher performance requirements of 3G systems. With advances in digital signal processor technology, the gap between the complexity of interference cancellation algorithms and available processing speeds is narrowing. However, 3G system requirements are ever pushing the envelope of signal processing algorithms required, including multi-user detection schemes, that are considered to be attractive and viable candidates. WINLAB has been working on an attractive SDR solution, to provide flexibility and handle the processing speeds required of 3G radio receivers. The approach is based on SDR architectures that partition radio receiver processing into two core technologies (field programmable gate arrays and DSP devices). We present a summary of the SDR work at WINLAB that is based on using this mixed signal processing approach for implementation of nonlinear interference cancellation and linear multi-user detection algorithms View full abstract»

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  • On the impact of burst errors on wireless ATM

    Page(s): 65 - 76
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    There has been an emerging interest in using ATM for wireless transmissions. Because ATM is primarily designed for an essentially error-free environment, in the wireless context the sources of errors and their consequences must be thoroughly understood. While this concern is valid in any network, it takes on a new, more central role in the wireless environment, where error bursts as expected to be a very significant source of degradation. In this article we examine the impact of burst errors on the direct transfer of ATM cells over a wireless channel, taking into account the cell framing format as well as the cell delineation and synchronization mechanism. We also investigate the consequences of interleaving. We find that fragmenting the data in cells could result in a much higher error rate as seen by the higher layers relative to the bit error rate on the raw channel. We assess the adequacy of HEC-based cell delineation and deduce the most appropriate values of the parameters of the cell delineation algorithm for the wireless channel View full abstract»

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  • The digital front-end of software radio terminals

    Page(s): 40 - 46
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    When expanding digital signal processing of mobile communications terminals toward the antenna while making the terminal more wideband in order to be able to cope with different mobile communications standards in a software radio based terminal, the designer is faced with strong requirements such as bandwidth and dynamic range. Many publications claim that only reconfigurable hardware such as FPGAs can simultaneously cope with such diversity and requirements. Starting with considerations of the receiver architecture, we describe key functionalities of the digital front-end and highlight how the signal characteristics of mobile communications signals and commonalities among different signal processing operations can be exploited to great advantage, eventually enabling implementations on an ASIC that, although not reconfigurable, would empower the software radio concept View full abstract»

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  • Error control coding in software radios: an FPGA approach

    Page(s): 35 - 39
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    Among the various tasks performed by software radios is the reconfiguration of the error control coding algorithm to match the requirement of the radio personality. In the digital radio processor, proper assignment of tasks between DSPs and FPGAs provides performance improvements over the use of DSPs alone. Error control coding functions are good candidates to reside on the FPGA side of this functional partition. Unfortunately, good VLSI designs for codes using BCH or Reed-Solomon codes do not map well to FPGAs. Good FPGA designs must parallelize at every opportunity, minimize timing delays through intelligent floor planning, and use each logic block to its fullest. We demonstrate the merits of these concepts by comparing the performance of popular finite field multiplier designs View full abstract»

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  • Receiver dimensioning in a hybrid multicarrier GSM base station

    Page(s): 56 - 64
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    Wideband multicarrier receivers are an interesting technology for software-defined radios. When combined with suitable digital signal processing hardware and software, they enable flexible adjustment of the number of carriers as well as provide the capability of simultaneous reception of signals with differing bandwidths and modulation formats. Due to technological limitations, the required dynamic range may not be available in the near future, however. For this reason, it has been proposed to install two separate receivers in a base station: a high gain receiver for serving distant terminals and a low gain receiver for nearby terminals. In GSM base stations, it is also necessary to include a narrowband receiver with large dynamic range to enable random access capture. Since the low and high receivers will have only partly overlapping coverage areas, it is interesting to study what the relative traffic through each receiver would be. This will affect the number of carriers to be supported by each receiver. In GSM base stations, it is also important to consider the narrowband receiver, which can serve terminals anywhere within the cell. A series of simulations was performed in order to define the respective traffic capacity requirements in a suburban macrocellular and urban microcellular environment. The number of high input levels in a base station was found to be rather small. Therefore, in base stations of small or moderate capacity, the narrowband receiver can apparently serve those terminals which cannot be supported by the high gain receiver. Consequently, no low gain wideband receiver is needed, and the base station architecture can be simplified. The novel base station architecture brings about the need for a level-based intracell handover. Parameterization of this handover as well as the strategy of allocating channels in the different receivers should be done with care, in order to avoid loss of traffic capacity View full abstract»

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  • ADC and DSP challenges in the development of software radio base stations

    Page(s): 47 - 55
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    The need for software-defined radios raises a number of technical challenges, which play a significant role in the development of third-generation personal communications systems (PCS). Some of the most important technical challenges deal with analog-to-digital conversion and digital signal processing technologies, which, in many cases, cannot provide the advanced hardware needed to support the demanding PCS telecommunications services. We discuss these two technical challenges, focusing primarily on base station radio systems. We first identify the most important requirements for ADC and DSP technologies, and we then extensively discuss and/or propose enabling schemes that could relax these requirements and aid the implementation of software radio base stations. Furthermore, we discuss new structures that can support the development of physically distributed base stations View full abstract»

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Aims & Scope

This Magazine ceased publication in 2001. The current retitled publication is IEEE Wireless Communications.

Full Aims & Scope