Full Rate L2-Orthogonal Space-Time CPM for Three Antennas

To combine the power efficiency of Continuous Phase Modulation (CPM) with enhanced performance in fading environments, some authors have suggested to use CPM in combination with Space-Time Codes (STC). Recently, we have proposed a CPM ST-coding scheme based on L2-orthogonality for two transmitting antennas. In this paper we extend this approach to the three antennas case. We analytically derive a family of coding schemes which we call Parallel Code (PC). This code family has full rate and we prove that the proposed coding scheme achieves full diversity as confirmed by accompanying simulations. We detail an example of the proposed ST codes that can be interpreted as a conventional CPM scheme with different alphabet sets for the different transmit antennas which results in a simplified implementation. Thanks to L2-orthogonality, the decoding complexity, usually exponentially proportional to the number of transmitting antennas, is reduced to linear complexity

L2 Orthogonal Space Time Code for Continuous Phase Modulation

To combine the high power efficiency of Continuous Phase Modulation (CPM) with either high spectral efficiency or enhanced performance in low Signal to Noise conditions, some authors have proposed to introduce CPM in a MIMO frame, by using Space Time Codes (STC). In this paper, we address the code design problem of Space Time Block Codes combined with CPM and introduce a new design criterion based on L2 orthogonality. This L2 orthogonality condition, with the help of simplifying assumption, leads, in the 2x2 case, to a new family of codes. These codes generalize the Wang and Xia code, which was based on pointwise orthogonality. Simulations indicate that the new codes achieve full diversity and a slightly better coding gain. Moreover, one of the codes can be interpreted as two antennas fed by two conventional CPMs using the same data but with different alphabet sets. Inspection of these alphabet sets lead also to a simple explanation of the (small) spectrum broadening of Space Time Coded CPM

End-To-End Performance Analysis of Two-Hop Asynchronous Cooperative Diversity

International audienceFor mobile users without antenna arrays, transmission diversity can be achieved with cooperative space-time encoded transmissions. This paper present an end-to-end performance analysis of Two-Hop asynchronous cooperative diversity with regenerative relays over Rayleigh Block-Flat-Fading channel. We present a precoding frame-based scheme with packet-wise encoding which enables best synchronization and channel estimation. We derive the bit-error rate and the end-to-end bit-error rate expressions for binary phase-shift keying. We present the performance of the frame-error rate and the end-to-end frame-error rate. Finally, comparisons between three system configurations are presented. Numerical results show that the simulations coincide with the analytical results

L2 OSTC-CPM: Theory and design

The combination of space-time coding (STC) and continuous phase modulation (CPM) is an attractive field of research because both STC and CPM bring many advantages for wireless communications. Zhang and Fitz [1] were the first to apply this idea by constructing a trellis based scheme. But for these codes the decoding effort grows exponentially with the number of transmitting antennas. This was circumvented by orthogonal codes introduced by Wang and Xia [2]. Unfortunately, based on Alamouti code [3], this design is restricted to two antennas. However, by relaxing the orthogonality condition, we prove here that it is possible to design L2-orthogonal space-time codes which achieve full rate and full diversity with low decoding effort. In part one, we generalize the two-antenna code proposed by Wang and Xia [2] from pointwise to L2-orthogonality and in part two we present the first L2-orthogonal code for CPM with three antennas. In this report, we detail these results and focus on the properties of these codes. Of special interest is the optimization of the bit error rate which depends on the initial phase of the system. Our simulation results illustrate the systemic behavior of these conditions

Optimizing the joint transmit and receive MMSE design using mode selection

International audienceTo approach the potential multiple-input multiple-output (MIMO) capacity while optimizing the system bit-error rate (BER) performance, the joint transmit and receive minimum mean squared error (joint Tx/Rx MMSE) design has been proposed. It is the optimal linear scheme for spatial multiplexing MIMO systems, assuming a fixed number of spatial streams p as well as fixed modulation and coding across these spatial streams. However, the number of spatial streams has been arbitrarily chosen and fixed, which may lead to an inefficient power allocation strategy and a poor BER performance. In this paper, we relax the constraint of fixed number of streams p and optimize this value for the current channel realization, under the constraints of fixed average total transmit power P/sub T/ and fixed rate R, what we refer to as mode selection . Based on the observation of the existence of a dominant optimal number of streams value for the considered Rayleigh flat-fading MIMO channel model, we further propose an "average" mode selection that avoids the per-channel adaptation through using the latter dominant value for all channel realizations. Finally, we exhibit the significant BER improvement provided by our mode selection over the conventional joint Tx/Rx MMSE design. Such significant improvement is due to the better exploitation of the MIMO spatial diversity and the more efficient power allocation enabled by our mode selection

Resource allocation in DMT transmitters with per-tone pulse shaping

International audiencePer-tone pulse shaping has been proposed as an alternative to time domain spectral shaping for DMT transmitters, e.g. VDSL modems. It shapes the spectrum of individual tones such that the stop band energy of each tone can be minimized. This in particular enables transmitter to use more tones without violating the PSD mask constraint for data transmission. In pertone pulse shaping based DMT transmitters a fixed length pulse shaping filter is typically used for every tone. The tones in the middle of the pass band however, contribute less to the overall stop band energy, so that using a high order pulse shaping filter for these tones does not result in a significant reduction of the stop band energy. As a result a significant number of pulse shaping filter taps are wasted on the tones in the middle of the pass band and do not bring any performance gain. Using a variable length pulse shaping filter which is designed such that the PSD mask constraint is not violated can then significantly reduce the total number of pulse shaping filter taps without compromising performance. In this paper, a resource allocation technique is presented for variable length pulse shaping filter design using a dual problem formulation. This optimally solves the problem of pulse shaping filter tap distribution over tones for given PSD mask constraints, with a relatively low complexity

Hybrid Beamforming for dual-polarized antenna

International audienceRecently, dual-polarized antenna has attracted strong attention in Millimeter wave (mmWave) systems. It provides an additional degree-of-freedom in wireless communication, yielding higher throughput. Nowadays, with the development of antenna technology, dual-polarized large scale antenna arrays can be realized inexpensively. However, several challenges must be addressed when using dual-polarized antennas in practical transmission such as mobile phone rotation and non-ideal polarization isolation. We address these challenges in the frame of dual-polarized hybrid beamformers. In this paper, we analyze the performance of dual-polarized beamforming based on two popular techniques: Beam steering and Orthogonal Matching Pursuit. Three categories of dual-polarized beam steering are analyzed : (1) same ray : the two polarizations are sent on the same ray, (2) different ray-same polarization : the two polarizations are sent on different pathes, and the receiver uses the same polarization as the emitter, (3) different ray-different polarization : the receiver uses the orthogonal polarization w.r.t. the emitter. An algorithm to choose the rays and polarizations to use, taking the mobile rotation into account, is also developed. Moreover, we develop a hybrid beamforming algorithm inspired by Orthogonal Matching Pursuit that approaches the fully digital beamforming data-rate and outperforms beam steering. Its developed version-Orthogonal based Matching Pursuit-is also introduced to reduce the computational complexity and overcome the unavailability of the Angle of Arrival

Blind channel identification based on cyclic statistics

International audienceBlind channel identification based on cyclic statistic