The purpose of this thesis work is to examine the possibility of building a software-defined radio (SDR) for the VHF-band. The goal is to accomplish this with as few components as possible, thus cutting down the size and the production cost. An SDR solution means that the sampling of the signal is done as close to the antenna as possible. The wide bandwidth needed in such a product is achieved by using SP Devices algorithm for time-interleaved ADCs. Two hardware prototypes and two versions of the software were designed and implemented using this technology. They were also analyzed within this thesis work. The results proved to be good, and the possibilities to produce a commercial software-defined radio receiver for the VHF-band are good. / Syftet med det här examensarbetet är att utreda möjligheten att bygga en mjukvarustyrd radiomottagare (SDR) för VHF-bandet. Målet är att göra detta genom att använda så få komponenter som möjligt, och därigenom minska storleken och produktionskostnaden. En SDR lösning ger att samplingen kommer att ske så nära antennen som möjligt. Den stora bandbredd som behövs för en sådan produkt uppnås genom att använda SP Devices algoritm för att ''tidsinterleava'' höghastighets ADC:er. Två hårdvaruprototyper och två versioner av mjukvaran har designats och implementerats. Analyserna har visat bra resultat, och möjligheterna att bygga en komersiell mjukvarudefinierade radiomottagare för VHF-bandet ses som goda.

Rutiner skrivna i Verilog har utvecklats för avkodning av en frekvensmodulerad signal givet ett Analog Devices AD9874-chip. Olika metoder för I/Q-demodulation har utvärderats och av dessa har CORDIC valts och implementerats i Verilog. Koden har till viss del testats på en IGLOO nano-FPGA men framförallt simulerats och verifierats i ModelSim. / Routines written in Verilog have been developed to perform I/Q-demodulation of a frequency modulated signal given valuesfrom a Analog Devices AD9874 chip. Different methods for I/Q-demodulation have been evaluated and among theseCORDIC has been chosen and implemented in Verilog. The code has to some extent been tested on a IGLOO nano FPGA but foremost been simulated and verified in ModelSim.

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This research investigates robust demodulation of Gaussian Minimum Shift Keying (GMSK) signals, using demodulator diversity and real-time bit-error-rate (BER) estimation. GMSK is particularly important because of its use in promi- nent wireless standards around the world (GSM, DECT, CDPD, DCS1800, and PCS1900). The dissertation begins with a literature review of GMSK demodu- lation techniques (coherent and noncoherent) and includes an overview of single- channel interference rejection techniques in digital wireless communications. Vari- ous forms of GMSK demodulation are simulated, including the limiter discrimina- tor and di erential demodulator (i.e., twenty-five variations in all). Ten represent new structures and variations. The demodulator performances are evaluated in realistic wireless environments, such as additive white Gaussian noise, co-channel interference, and multipath environments modeled by COST207 and SMRCIM. Certain demodulators are superior to others for particular channel impairments, so that no demodulator is necessarily the best in every channel impairment. This research formally introduces the concept of demodulator diversity, a new idea which consists of a bank of demodulators which simultaneously demodulate the same signal and take advantage of the redundancy in the similar signals. The dissertation also proposes practical real-time BER estimation techniques which have tremendous ramifications for communications. Using Parzen's estimator for probability density functions (pdfs) and Gram-Charlier series approximation for pdfs, BER can be estimated using short observation intervals (10 to 500 training symbols) and, in some cases, without any training sequence. We also introduce new variations of Gram-Charlier estimation using robust estimators. BER (in place of MSE) can now drive adaptive signal processing. Using a cost function and gradient for Parzen's estimator (derived in this paper), BER estimation is applied to demodulator diversity with substantial gains of 1-10 dB in carrier- to-interference ratio over individual receivers in realistic channels (with adaptive selection and weighting). With such gains, a BER-based demodulator diversity scheme can allow the employment of a frequency reuse factor of N = 4, instead of N = 7, with no degradation in performance. A lower reuse factor means more channels are available in a cell, thus increasing overall capacity. The resulting techniques are simple and easily implemented at the mobile. BER estimation techniques can also be used in BER-based equalization and dynamic allocation of resources. / Ph. D.

Cellular Digital Packet Data (CDPD) is a new wireless packet data communications system which was developed by a consortium of U.S. cellular service providers to augment their voice communications systems. The main goal of the CDPD system design was to provide wireless packet data connectivity to mobile data communications customers. This thesis presents fundamental information required to successfully implement CDPD base station or mobile equipment. This information includes an introduction to the operation of data networks, a discussion of Gaussian Filtered Minimum Shift Keying (GMSK), and a detailed analysis of Reed-Solomon error correction codes. / Master of Science

Cellular digital packet data (CDPD) is a new service for wide-area data communication with wireless mobile users. CDPD system uses the existing infrastructure of the analog Advanced Mobile Phone Service (AMPS) cellular telephone network to transmit data with a channel hopping technique. The CDPD system employs Gaussian minimum shift keying (GMSK) as a modulation scheme and a Reed-Solomon code for error control to transmit high-quality data in the mobile and wireless environment. Most current CDPD receivers use errors only decoding of the Reed-Solomon code, although an improved errors and erasures decoding technique would also be possible. This thesis undertakes a performance evaluation of the CDPD system with an errors and erasures decoder for the Reed-Solomon coding. A thorough system simulation is conducted for both white Gaussian noise and flat Rayleigh fading channel environments. Results show that improved coding gains of 0.5 ~ 1 dB are possible for the additive white Gaussian noise channel and improved coding gains of 1.9 ~ 2.7 dB are possible for the fading channel. / Master of Science

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Most traditional approaches to TT&C have employed waveforms that are neither very power nor bandwidth efficient. A new approach to TT&C waveforms greatly improves these efficiencies. Binary Gaussian Minimum Shift Keying (GMSK) provides a constant envelope bandwidth efficient signal for applications above about 10 Kbps. The constant envelope preserves the spectrum through saturated amplifiers. It provides the best power efficiency when used with turbo coding. For protection against various kinds of burst errors it includes the hybrid interleaving for memory and delay efficiency and packet compatible operations in Time Division Multiple Access (TDMA) environments. Commanding, telemetry, mission data transmission, and tracking are multiplexed in TDMA format.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Gaussian Minimum Shift Keying (GMSK) is a form of Continuous Phase Modulation (CPM) whose spectral occupancy can be easily tailored to the available channel bandwidth by a suitable choice of signal parameters. The constant envelope of the GMSK signal enables it to corporate with saturated power amplifier without the spectral re-growth problem. This paper provides a quantitative synopsis of binary GMSK signals in terms of their bandwidth occupancy and coherent demodulation performance. A detailed account of how to demodulate such signals using the Viterbi Algorithm (VA) is given, along with analytical power spectral density (PSD) and computer simulated bit-error-rate (BER) results for various signal BT products. The effect of adjacent channel interference (ACI) is also quantified. Ideal synchronization for both symbol time and carrier phase is assumed.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / A data-aided approach to symbol time and carrier phase synchronization applicable to general continuous phase modulation (CPM) signals with modulation index 0.5 is described. Simulated BER performance of two receivers equipped with these synchronizers is presented for a GMSK BT=1/5 signal received in noise with constant and dynamic synchronization errors. Results demonstrate that these synchronizers provide a very promising and yet simple solution to the tracking problem in the design of coherent CPM receivers.

<p>This thesis deals with output power calibration of a mobile platform that supports EGPRS.Two different topics are examined. First some different measurement methods are compared concerning cost efficiency, accuracy, and speed and later measurements are carried out on a mobile platform. </p><p>The output power from the mobile platform is controlled by three parameters and the influence on the output power when varying those parameters is investigated and presented. Furthermore, two methods of improving the speed of the calibration are presented. </p><p>The first one aims to decrease the number of bursts to average over as much as possible. The conclusion is that 10-20 bursts are enough for GMSK modulation and about five bursts for 8PSK modulation. The purpose of the second investigation is to examine the possibility to measure the output power in one modulation and frequency band, and then calculate the output power in the other bands. The conclusion in this case is that, based on the units investigated, it is possible for some values of the parameters and in some frequency bands. However, more units need to be included in the basic data for decision-making and it is possible that the hardware variation is too large.</p>