88 research outputs found
Improving Achievable Rate for the Two-User SISO Interference Channel with Improper Gaussian Signaling
This paper studies the achievable rate region of the two-user
single-input-single-output (SISO) Gaussian interference channel, when the
improper Gaussian signaling is applied. Under the assumption that the
interference is treated as additive Gaussian noise, we show that the user's
achievable rate can be expressed as a summation of the rate achievable by the
conventional proper Gaussian signaling, which depends on the users' input
covariances only, and an additional term, which is a function of both the
users' covariances and pseudo-covariances. The additional degree of freedom
given by the pseudo-covariance, which is conventionally set to be zero for the
case of proper Gaussian signaling, provides an opportunity to improve the
achievable rate by employing the improper Gaussian signaling. Since finding the
optimal solution for the joint covariance and pseudo-covariance optimization is
difficult, we propose a sub-optimal but efficient algorithm by separately
optimizing these two sets of parameters. Numerical results show that the
proposed algorithm provides a close-to-optimal performance as compared to the
exhaustive search method, and significantly outperforms the optimal proper
Gaussian signaling and other existing improper Gaussian signaling schemes.Comment: Version 2, Invited paper, submitted to Asilomar 201
On the superiority of improper Gaussian signaling in wireless interference MIMO scenarios
©2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Recent results have elucidated the benefits of using improper Gaussian signaling (IGS) as compared to conventional proper Gaussian signaling (PGS) in terms of achievable rate for interference-limited conditions. This paper exploits majorization
theory tools to formally quantify the gains of IGS along with widely linear transceivers for MIMO systems in interferencelimited scenarios. The MIMO point-to-point channel with interference (P2P-I) is analyzed, assuming that received interference can be either proper or improper, and we demonstrate that the
use of the optimal IGS when received interference is improper strictly outperforms (in terms of achievable rate and mean square error) the use of the optimal PGS when interference is proper.
Then, these results are extended to two practical situations. First, the MIMO Z-interference channel (Z-IC) is investigated, where a trade-off arises: with IGS we could increase the achievable rate of the interfered user while gracefully degrading the rate of the non-interfered user. Second, these concepts are applied to a
two-tier heterogeneous cellular network (HCN) where macrocells and smallcells coexist and multiple MIMO Z-IC appear.Peer ReviewedPostprint (author's final draft
Optimized Transmission with Improper Gaussian Signaling in the K-User MISO Interference Channel
This paper studies the achievable rate region of the K-user Gaussian
multiple-input single-output interference channel (MISO-IC) with the
interference treated as noise, when improper or circularly asymmetric complex
Gaussian signaling is applied. The transmit optimization with improper Gaussian
signaling involves not only the signal covariance matrix as in the conventional
proper or circularly symmetric Gaussian signaling, but also the signal
pseudo-covariance matrix, which is conventionally set to zero in proper
Gaussian signaling. By exploiting the separable rate expression with improper
Gaussian signaling, we propose a separate transmit covariance and
pseudo-covariance optimization algorithm, which is guaranteed to improve the
users' achievable rates over the conventional proper Gaussian signaling. In
particular, for the pseudo-covariance optimization, we establish the optimality
of rank-1 pseudo-covariance matrices, given the optimal rank-1 transmit
covariance matrices for achieving the Pareto boundary of the rate region. Based
on this result, we are able to greatly reduce the number of variables in the
pseudo-covariance optimization problem and thereby develop an efficient
solution by applying the celebrated semidefinite relaxation (SDR) technique.
Finally, we extend the result to the Gaussian MISO broadcast channel (MISO-BC)
with improper Gaussian signaling or so-called widely linear transmit precoding.Comment: 27 pages, 5 figures, 2 table
Ergodic rate for fading interference channels with proper and improper Gaussian signaling
This paper studies the performance of improper Gaussian signaling (IGS) over a 2-user Rayleigh single-input single-output (SISO) interference channel, treating interference as noise. We assume that the receivers have perfect channel state information (CSI), while the transmitters have access to only statistical CSI. Under these assumptions, we consider a signaling scheme, which we refer to as proper/improper Gaussian signaling or PGS/IGS, where at most one user may employ IGS. For the Rayleigh fading channel model, we characterize the statistical distribution of the signal-to-interference-plus-noise ratio at each receiver and derive closed-form expressions for the ergodic rates. By adapting the powers, we characterize the Pareto boundary of the ergodic rate region for the 2-user fading IC. The ergodic transmission rates can be attained using fixed-rate codebooks and no optimization is involved. Our results show that, in the moderate and strong interference regimes, the proposed PGS/IGS scheme improves the performance with respect to the PGS scheme. Additionally, we numerically compute the ergodic rate region of the full IGS scheme when both users can employ IGS and their transmission parameters are optimized by an exhaustive search. Our results suggest that most of the Pareto optimal points for the 2-user fading IC channel are attained when either both users transmit PGS or when one transmits PGS and the other transmits maximally improper Gaussian signals and time sharing is allowed.The work of M. Soleymani, C. Lameiro and P. J. Schreier was supported by the German Research Foundation
(DFG) under grants LA 4107/1-1, SCHR 1384/7-1 and SCHR 1384/8-1. The work of I. Santamaria was supported by MINECO of Spain and AEI/FEDER funds of the E.U., under grant TEC2016-75067-C4-4-R (CARMEN)
Robust improper signaling for two-user SISO interference channels
It has been shown that improper Gaussian signaling (IGS) can improve the performance of wireless interference-limited systems when perfect channel-state information (CSI) is available. In this paper, we investigate the robustness of IGS against imperfect CSI on the transmitter side in a two-user single-input single-output (SISO) interference channel (IC) as well as in a SISO Z-IC, when interference is treated as noise. We assume that the true channel coefficients belong to a known region around the channel estimates, which we call the uncertainty region. Following a worst-case robustness approach, we study the rate-region boundary of the IC for the worst channel in the uncertainty region. For the two-user IC, we derive a robust design in closed form, which is independent of the phase of the channels by allowing only one of the users to transmit IGS. For the Z-IC, we provide a closed-form design for the transmission parameters by considering an enlarged uncertainty region and allowing both users to employ IGS. In both cases, the IGS-based designs are ensured to perform no worse than proper Gaussian signaling. Furthermore, we show, through numerical examples, that the proposed robust designs significantly outperform non-robust solutions.The work of M. Soleymani, C. Lameiro and P. J. Schreier was supported by the German Research Foundation (DFG) under grants LA 4107/1-1 and SCHR 1384/8-1. The work of I. Santamaria was supported by MINECO of Spain and AEI/FEDER funds of the E.U., under grant TEC2016-75067-C4-4-R (CARMEN)
Benefits of improper signaling for underlay cognitive radio
In this letter we study the potential benefits of improper signaling for a secondary user (SU) in underlay cognitive radio networks. We consider a basic yet illustrative scenario in which the primary user (PU) always transmit proper Gaussian signals and has a minimum rate constraint. After parameterizing the SU transmit signal in terms of its power and circularity coefficient (which measures the degree of impropriety), we prove that the SU improves its rate by transmitting improper signals only when the ratio of the squared modulus between the SU-PU interference link and the SU direct link exceeds a given threshold. As a by-product of this analysis, we obtain the optimal circularity coefficient that must be used by the SU depending on its power budget. Some simulation results show that the SU benefits from the transmission of improper signals especially when the PU is not highly loaded.C. Lameiro and I. Santamaría have received funding from the Spanish Government (MICINN) under projects CONSOLIDER-INGENIO 2010 CSD2008-00010 (COMONSENS), TEC2013-47141-C4-3-R (RACHEL) and FPU Grant AP2010-2189; and also from the Deutscher Akademischer Austauschdienst (DAAD) under its programm ”Research grants for doctoral candidates and young academics and scientists”. P. Schreier receives financial support from the Alfried Krupp von Bohlen und Halbach foundation, under its program ”Return of German scientists from abroad”
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