A. Wiesler

A software radio for second- and third-generation mobile systems

This paper picks up the interesting technology of software radio. An explanation of the term software radio is given and differences between civilian and military applications are described. For the frequency region of second- and third-generation mobile cellular systems, the construction of a software radio terminal is investigated. Radiofrequency as well as intermediate-frequency processing and complex base-band processing are discussed. It is shown that all important mobile radio interfaces can be described by parameter lists and that a software radio can be reconfigured by using these parameter lists. With this strategy, interstandard handover becomes feasible. At the same time, the hardware effort is minimized.

Comparison of GMSK and linear approximated GMSK for use in software radio

In Wiesler and Jondral (1998) a common software radio structure for second generation mobile systems has been introduced. This SWRADIO combines different standards of mobile communication systems like GSM, DECT, IS-54 and PDC. All baseband functions like channel coding, modulation and equalisation are implemented in a general, parametrized way, so that all of them can be used for the selected standards. This structure has several advantages like a reduced size of the hardware platform, fast performance by changing the air interface for a system handover and the possibility of global roaming. The linear approximated GMSK is used in the SWRADIO because this enables a common I/Q-modulator for all second generation systems. In this paper it is proved, that with the usual receiver (Viterbi equalizer with least square channel estimate) there is no performance loss by using the approximated GMSK instead of the original GMSK.

Software radio structure for second generation mobile communication systems

Third generation mobile communication systems like the European UMTS will enable a flexible communication, free from standard specific regulation of modulation, channel coding, baud rate and multiple access schemes. This flexibility can only be reached by a radio structure which performs all baseband functions in software and is therefore totally software programmable. To ensure that different software configurations can be understood and supported by all mobile terminal architectures a general programming language is required to describe the used air interface components. By the example of the second generation mobile communication systems like the European GSM, the Japanese PDC, the American IS-54 (respectively IS-136) and the European wireless communications system DECT, a common description and implementation of the transceiver functions like channel coding, modulation and equalisation have been developed.

Software radio structure for UMTS and second generation mobile communication systems

The third generation mobile communication system UMTS will enable a very flexible communication technology which means variable data rates from 8 kbit/s speech up to 2 Mbit/s data transmission. But the new standard cannot replace established systems like the European GSM and DECT, instead it is planed as an expansion of the second generation systems. That means future UMTS handhelds must be able to perform second and third generation communication technologies and also seamless system handover. To enable small handhelds and fast system handover an UMTS mobile station can only be realized with a transmitter structure which is totally software programmable, a so called software radio. All baseband functions are implemented in a general, parametrized way, so that all of them can be used for the selected standards by using different parameter sets. The air interfaces of DECT, GSM and WBCDMA have been analysed and common baseband functions have been developed and implemented.

A software defined radio structure for 2nd and 3rd generation mobile communications standards

The international standard for third generation (3G) mobile communications IMT-2000 includes five different air interfaces. It is desirable that all interfaces can operate everywhere in order to reach a global roaming. Furthermore a backward compatibility to the second generation (2G) mobile systems such as GSM, IS-136 and IS-95 is required. As IMT-2000 will be introduced in Europe in 2001/2002, a pragmatic solution for the problem of interoperability must be found. To guarantee small handsets, the possibility of updating and of seamless system handover, e.g., between UTRA and GSM, a common frontend and a parametrized structure for the base band processing are proposed. As one hand-held should be able to perform the different aforementioned air interfaces and since the baseband functions are going to be implemented on reconfigurable hardware like DSPs and FPGAs, it can be seen as a software radio or software defined radio.

MAP-algorithm with fixed-point representation for software radios

The international mobile communication system IMT2000 will enable very flexible communication, which means variable data rates from 8 kbit/s speech up to 2 Mbit/s for data transmission. In November 1999 five modes of IMT2000 have been specified. In several modes turbo codes are proposed to enable bit error rates (BER) as low as 10/sup -6/ for high quality data services. Usually for this type of channel coding two MAP-algorithms, based on the maximum a posteriori criterion, are used for decoding. The MAP-algorithm utilizes soft input information and produces soft output information. The practical implementation of the MAP-algorithm, respectively its computational reduced version log-MAP and max-log-MAP, is investigated.

Comparison of UTRA-FDD and cdma2000 with intra- and intercell interference

The international standards for mobile communications IMT-2000 include amongst others the European UTRA-FDD and the American cdma2000 proposal, which both are in principle wideband CDMA (WB-CDMA) systems. In the year 2000 many countries will award licenses for the frequency bands of IMT-2000. Operators will be free to choose one or more air interfaces of the IMT-2000 family. As frequency packages of 10 MHz will be given to one operator, intercell interference will occur, especially for WB-CDMA. The interference between users in one cell and neighboring cells (i.e. intra- and intercell interference) is of major impact for the system capacity. These are examined for both UTRA-FDD and cdma2000. Another important aspect is to merge the various different modes of IMT-2000 to one general software defined core. In this paper common structures of the two wideband CDMA systems are pointed out for further use in software radios.

Parameter representations for baseband processing of 2G and 3G mobile communications systems

The international Standard for third generation (3G) mobile communications IMT-2000 includes five different air interfaces. It is desirable that all interfaces can operate everywhere in order to reach a global roaming, however this may be not feasible. Furthermore a backward compatibility to the second generation (2G) mobile systems such as GSM, IS-136 and IS-95 is required. So at least the hand-helds should be able to perform the main 2G and 3G air interfaces to operate in the available systems. A parametrized structure for the base band processing is proposed in this paper, which guarantees small handsets, the possibility of updating and of seamless system handover, e.g. between UTRA and GSM. Since the baseband functions will be implemented on reconfigurable hardware like DSPs and FPGAs, it can bee viewed as a software radio or software defined radio. The way of parameterization is explained in detail by the example of a common modulator in this paper. Also some implementation aspects of the MAP-algorithm used for channel decoding and equalization are discussed.

Spezielle stochastische Prozesse

Im letzten Kapitel dieses Buches wollen wir uns mit speziellen stochastischen Prozessen beschaftigen. Die fur die Anwendung uberaus wichtige Klasse der normalen oder Gausprozesse haben wir bereits in Abschnitt 8.2 (Definition 8.2-5) kennengelernt. Wir werden uns hier zunachst einem Spezialfall aus dieser Klasse zuwenden.

Kennwerte von Zufallsvariablen

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