Impact of diversity on mobile radio systems with coded modulation, fading, and co-channel interference

We study the impact of diversity on coded digital communication systems operating over channels affected by co-channel interference and by independent flat Rayleigh fading. We provide bounds on error probability, an error floor analysis, simulation results, and an asymptotic analysis of the diversity channel as the diversity order increases. Our results show the effectiveness of diversity as a way to combat the irreducible error floor due to co-channel interference in fading channels. Calculation of the channel cut-off rate provides guidelines for the design of coded systems in such an environment

Impact of diversity reception on fading channels with coded modulation. Part I: Coherent detection

We address the problem of designing and analyzing the performance of a coded modulation scheme for the fading channel when space diversity is used. Under fairly general conditions, a channel affected by fading can be turned into an additive white Gaussian noise (AWGN) channel by increasing the number of diversity branches. Consequently, it can be expected (and is indeed verified by our analyses and simulations) that a coded modulation scheme designed to be optimal for the AWGN channel also will perform asymptotically well on a fading channel with diversity. This paper presents bounds on the bit-error probability of a system with coded modulation and diversity for space- and time-correlated Rician flat fading. Specifically, we derive a new method which allows evaluation of the pairwise error probability extremely easily, as well as accurately and computationally fast. The accuracy achieved improves considerably on the widely used, but rather loose Chernoff bound. Starting from this analysis, we study the asymptotic behavior of the fading channel with diversity as the number of diversity branches increases, and we address the effects of diversity on coded modulation performance and design criteria, including the effect on interleaver depth (which affects the total delay of the system

Impact of diversity reception on fading channels with coded modulation. Part III: Co-channel interference

For pt.II see ibid., vol.45, no.6, p.55-67, 1997. In previous work, we have studied the impact of diversity on coded digital communication systems operating over fading channels. In particular, we have shown that diversity may be thought of as a way of making the channel more similar to a Gaussian one. The present paper extends this analysis to fading channels affected by co-channel interference (CCI). Three receiver models are examined, namely, with coherent detection and perfect channel-state information (CSI), with differential; and with pilot-tone detection. We study the effect of diversity on the irreducible error floor caused by CCI and fading, and the asymptotic behavior of the channel as the diversity order increases. Our results show that, when perfect CSI is available, diversity is able to turn asymptotically the channel into a CCI-free additive white Gaussian noise (AWGN) channel with the same signal-to-noise ratio (SNR). On the other hand, differential and pilot-tone detection do not remove interference in the limit. Nevertheless, also with these detection schemes, diversity achieves significant gains when the SNR is large enough. Calculation of the channel cutoff rate provides guidelines for the design of coded systems with CCI in fading environments. A wide range of examples, validated by computer simulation, illustrates our conclusion

Impact of diversity reception on fading channels with coded modulation. Part II: Differential block detection

For pt. I see ibid., vol.45, no.6, p.563-572, 1997. We study coded modulation with block differential detection in an arbitrarily correlated Rician fading channel with space diversity. Coded differential q-PSK is included in our analysis as a special case. A metric is chosen that is optimum for perfect interleaving, slow fading, and independent diversity branches. For slow fading, we compare the the cutoff rates of the channels resulting from different choices of block length N and diversity index M. Specifically, we show that block detection with diversity may or may not generate a better coding channel than usual differential detection, according to the code selected and the combination of values of M and N. In particular, for low-diversity orders (M=1,2) and for low-to-medium code rates, differential detection is still an optimal or near-optimal solution, while for high-diversity orders (M⩾2) and medium-to-high code rates (up to uncoded modulation) block detection with N>2 can provide a significant gain. An error floor always exists when fading is fast. It decreases exponentially with the product of code diversity and space diversity, so that the latter emerges as a very effective technique for lowering the error floor of a system affected by fast fading. Performance examples based on actual coding schemes are also show

Impact of diversity reception on fading channels with coded modulation. Part III: Co-channel interference

In previous work we have studied the impact of diversity on coded digital communication systems operating over fading channels. In particular, we have shown that diversity may be thought of as a way of making the channel more similar to a Gaussian one. The present paper extends this analysis to fading channels affected by co-channel interference (CCI). Several receiver models are examined, namely, with ideal coherent detection and perfect channel-state information (CSI), and with differential and pilottone detection. We study the effect of diversity on the irreducible error floor caused by CCI and fading, and the asymptotic behavior of the channel as the diversity order increases. Our results show that, when perfect CSI is available, diversity is able to turn asymptotically the channel into a CCI-free additive white Gaussian noise (AWGN) channel with the same signal-to-noise ratio (SNR). On the other hand, for differential and pilot-tone detection, diversity achieves significant gains ..

GENESIS-1 mission for improved reference frames and Earth science applications

Improving and homogenizing time and space references on Earth and, more directly, realizing the terrestrial reference system with an accuracy of 1 mm and a long-term stability of 0.1 mm/yr are relevant for many scientific and societal endeavours. The knowledge of the terrestrial reference frame (TRF) is fundamental for Earth system monitoring and related applications. For instance, quantifying sea level change strongly depends on an accurate determination of the geocenter motion but also of the position of continental or island reference stations, such as those located at tide gauges, as well as the ground stations of the tracking networks. Also, numerous applications in geophysics require absolute millimetre precision from the reference frame, as for example monitoring tectonic motion or crustal deformation for predicting natural hazards. The TRF accuracy to be achieved (mentioned above) represents the consensus of various authorities, including the International Association of Geodesy, which has enunciated geodesy requirements for Earth science (see GGOS-2020). Moreover, as stated in the A/RES/69/266 United Nations Resolution: “A global geodetic reference frame for sustainable development”, the UN recognizes the importance of “the investments of Member States in developing satellite missions for positioning and remote sensing of the Earth, supporting a range of scientific endeavours that improve our understanding of the Earth system and underpin decision-making, and… that the full societal benefits of these investments are realized only if they are referenced to a common global geodetic reference frame at the national, regional and global levels”. These strong statements by international bodies underline that a dedicated mission is highly needed and timely. Today we are still far away from this ambitious goal. It can be achieved by combining and co-locating, on one satellite platform, the full set of fundamental space-time geodetic systems, namely GNSS and DORIS radio satellite tracking systems, the satellite laser ranging (SLR) technique, and the very long baseline interferometry (VLBI) technique, that currently operates by recording the signals from quasars. This platform can then be considered as a dynamic space geodetic observatory carrying all these geodetic instruments referenced to one another on a unique well-calibrated platform through carefully measured space ties and a very precise atomic clock. It is necessary to set up a co-location of the techniques in space to resolve the inconsistencies and biases between them. Such a mission will be proposed as the first one of a series of missions in the GNSS/NAV Science Programme. The purpose of this abstract/talk is to revive the support of the scientific community for this mission