Coordinated resource allocation for satellite-terrestrial coexistence based on radio maps

In this letter, we address the problem of energy efficient coordinated power allocation in a multicell distributed antenna system (DAS). Due to the mutual coupling of multiple cells caused by intercell interference (ICI), the problem is nonconvex and, therefore, is difficult to solve. We assume that only the large-scale channel state information at the transmitter (CSIT) is known to reduce the system cost. Using successive Taylor expansion, we formulate the problem as a series of quasi-concave fractional programming subproblems. These subproblems are further solved using an iterative power allocation algorithm. The proposed solution is superior to existing methods, as verified by simulation results.

SummaryThe enormous growth of mobile broadband traffic is a catalyst for expanding terrestrial communication systems and their integration with satellite communication systems. This results in sharing frequencies allocated to satellite communication systems with terrestrial systems. As this can lead to interference between the incumbent and the upcoming service, coexistence studies are conducted. In the case of sharing satellite uplink frequencies with terrestrial communication systems, interference from base stations (BSs) is dominant. While there are methods to estimate the number of BSs that may be deployed, it is unclear where the BSs will be located. The BS locations play a pivotal role in interference calculation, as the values of link budget parameters are highly dependent on the longitude and latitude of interfering transmitters. This article presents an intelligent method which balances network capacity and coverage for simulating base stations (BSs) in coexistence studies. A realistic BS distribution is generated using weighted K‐means clustering (WKMC) algorithm and incorporating population density along with Haversine distance. The paper provides a case study of co‐frequency, co‐coverage interference in the satellite uplink in the C‐band to demonstrate the impact of BS distribution on the results of coexistence studies. This paper will find applications in upcoming frequency sharing and coexistence studies and the design of integrated satellite‐terrestrial communication networks.

In this paper, we have developed a machine learning based adaptive predistorter for high power amplifier linearization approach under dynamically changing environment. In the “bent-pipe” transponder in satellite communication (SATCOM) system, the High Power Amplifiers (HPAs), which are similar to other amplifiers in the communication system, can cause nonlinear distortions to transmitted signals, deteriorating the system transmission performance. The traditional model based processing techniques such as the Extended Saleh's Model (ESM) based predistortion design can be applied to maximize transponder throughput along with HPA power efficiency but sensitive to dynamically changing environment. In this paper, the compensated HPA linearity characterized through Amplitude Modulation-to-Amplitude Modulation (AM-AM) and Amplitude Modulation-to-Phase Modulation (AM-PM) effects is used as the system reward, we leveraged reinforcement learning approach to dynamically optimize the parameter set for the ESM based PD to improve system performance in various environmental conditions. Finally, simulation results are provided to evaluate and verify Bit Error Rate (BER) improvement for the considered SATCOM system by applying our proposed PD technique.

The integration of satellite and terrestrial communication systems has the potential to revolutionize worldwide services, enabling ubiquitous and dependable coverage. However, these systems’ unique complexity and design also present opportunities for cyber attacks. The “new space revolution” makes it possible to launch many commercial satellites at a meager cost equipped with smart phased array beam having electronic steering capabilities. The wide spread use of space technologies creates opportunities for cyber attackers to hijack satellites and direct their beams toward specific geographic areas, posing a threat to ground stations and other terrestrial networks. To counter this problem, we propose a cutting-edge signal processing algorithm that can authenticate signals transmitted by satellites to ground stations. Our innovative algorithm can differentiate between signals originating from different satellites by leveraging the spatio-temporal imprint on the signal as it travels through different atmospheric paths in the channel. Simulation studies show that the algorithm achieves a remarkable authentication rate of more than $$95\%$$ for signals received by a ground station located in Beer Sheva, Israel, based on a control experiment involving two different GEO satellites, AMOS-17 and AsiaSat-7. By enhancing physical layer security, our algorithm can protect satellite and terrestrial communication systems against cyber-attacks, ensuring reliable and secure global communication services.

Multiple antennas can be used for increasing the packet reliability (spatial diversity) or the spectral efficiency (spatial multiplexing) in wireless communication systems with slow fading. Zheng and Tse showed that both types of gains can be simultaneously obtained for a given multiple antenna channel, but there is a fundamental tradeoff between spatial diversity and spatial multiplexing. They considered the case of no CSIT but perfect CSIR. In this paper, we focus on the role of channel state information at the transmitter (CSIT) on the diversity multiplexing tradeoff. When there is perfect CSIT, there is no packet outage in slow fading channels through proper rate adaptation and hence, the diversity order can be regarded as infinity. However, perfect CSIT is not realistic. Thus, we consider the diversity and multiplexing tradeoff with imperfect CSIT for slow fading MIMO channels. The imperfect CSIT is parameterized by the CSIT estimation error sigma2 DeltaH. Hence, the results obtained are the generalizations of the Zheng-Tse results. We show that when SNRsigma2 DeltaH rarr infin as SNR rarr infin, the availability of the imperfect CSIT does not improve the diversity multiplexing tradeoff

Satellite communication (SATCOM) system is to be applied in the communication, oceanographic, and meteorological satellite (COMS). ETRI has completed the preliminary design effort for the SATCOM project - an effort which included clarifying requirements, refining mission description and operation, determining the configuration of the payload, and anticipating subsystem performances, schedules, costs, and so on. This paper includes an overview of the project work, and the preliminary design of the Ka-band on-board switching transponder in point of RF performances. A recommendation for future work is also included to aid subsequent projects associated with SATCOM system

In this letter, a multi-cell distributed antenna system (DAS) with multiple users served via linear beamforming in each cell is considered. We focus on joint beamformer optimization (JBO) with the target of system weighted sum capacity maximization based on only partial channel state information at the transmitter (CSIT), which includes instantaneous intra-cell and large-scale inter-cell CSIT. After the formulation of a non-convex JBO problem, an algorithm is proposed to find the globally optimal beamformers based on monotonic optimization and the bisection method. Simulation results are provided to show the superiority of the proposed algorithm and the noticeable performance gain of the JBO based on partial CSIT. The proposed algorithm can be used as a benchmark for low-complexity JBO scheme design for practical applications.

The virtual multiple input multiple output (MIMO) technique can dramatically improve the performance of a multi-cell distributed antenna system (DAS), thanks to its great potentials for inter-cell interference mitigation. One of the most challenging issues for virtual MIMO is the acquisition of channel state information at the transmitter (CSIT), which usually leads to an overwhelming amount of system overhead. In this work, we focus on the case that only the slowly-varying large-scale channel state is required at the transmitter, and explore the performance gain that can be achieved by coordinated transmissions for virtual MIMO with large-scale CSIT. Aiming at maximizing the achievable ergodic sum rate, the input covariances for all the mobile terminals (MTs) are jointly optimized, which turns out to be a complicated non-convex problem with a non-closed-form objective function. Further analysis reveals that the coordinated transmission problem can be recast as a Max-Min problem with a closed-form objective function and linear constraints. Then, by appealing to the successive approximation method and the saddle-point theory of concave-convex functions, we propose an iterative algorithm for coordinated transmissions with large-scale CSIT and establish its convergence. Simulation results corroborate that the proposed scheme converges quickly, and it yields significant performance gains compared to the existing schemes. Moreover, it is observed that the proposed scheme can achieve a nearly globally-optimal point under the diagonal input covariance constraint. Since the acquisition of large-scale CSIT is far less demanding than that of full CSIT, we believe that the proposed coordinated transmissions with large-scale CSIT in DASs shed some light on virtual MIMO in the making.

In this paper, we propose the handover decision method for inter-system handover between satellite communication system and terrestrial communication system. The characteristics of signal of satellite communication system are not different from those of terrestrial communication system. Therefore, we analyze the characteristics of satellite signal, and we design the handover decision method to reflect those characteristics. The performance of proposed method is validated through simulations. The proposed method decreases the unnecessary handovers more than that of existing handover method which considers only hysteresis margin.

Rainfall rate is the main cause of fades in the frequency bands above 10 GHz. To optimize the planning of satellite and terrestrial radio communication systems operating on these frequency bands, it is essential to have a detailed knowledge of the temporal and spatial distributions of the rainfall rate. For this reason, it is necessary to develop experimental networks, which provide adequate data to study, prevent, and compensate the rain fade. In this paper, an experimental instrumentation network is presented. This network comprises weather stations that are capable of measuring rainfall rate, temperature, and humidity; a weather radar; and three radio links. This paper first introduces the rationale and the state of the art in meteorological sensors and describes the experimental network for automatic data acquisition as a distributed process system. The design of the experimental network is explained in detail. Finally, the interest in millimeter wavelength for broadband applications is outlined, and some research lines from the collected data are presented.

To accommodate multimedia, wide-band operations at Ka-band (e.g., 30 GHz) are attracting much attention in both wireless terrestrial and satellite communication systems. With handset antennas operating at these frequencies, significantly high-peak specific absorption rate (SAR) may occur in the skin region of the human head. It has been found that the popular numerical techniques have severe computational limitations in dealing with thin layers and high frequencies. In order to critically assess human-antenna interactions at Ka-band, an efficient hybridization of the eigenfunction expansion method (EEM) and the method of moments (MoM) has been utilized. At this frequency band, most power absorption of the antenna-radiated power occurs within the thin layer of skin. With a half-wave dipole antenna separated at 2 cm from the head, it is found that the unaveraged peak SAR can become extremely high in the skin tissue (/spl sim/450 W/kg) with 1 W of the delivered power, while the l-g averaged peak SAR is /spl sim/10 W/kg. However, the use of a directional two-element end-fire antenna can significantly reduce the unaveraged peak SAR (/spl sim/3 W/kg), 1-g averaged peak SAR (/spl sim/0.1 W/kg), and power absorption in the head.

This paper describes the design of reliable wireless Asynchronous Transfer Mode (ATM) System to be used by the U.S. military and the commercial marketplace. This system, called Survivable ATM, consists of three main components: (1) Transmission Error Control System (TECS), (2) Reliable ATM Adaptation Layer (AAL), (3) Network Management System. These three components deliver a set of previously unavailable capabilities to achieve and maintain reliable performance of commercial ATM technology in wireless environments. These components collectively provide reliable end-to-end operation of ATM communication systems in deployed wireless terrestrial and satellite networks. At the data link layer, the TECS dynamically selects data link packet length and the strength of Forward Error Correction (FEC) coding. The result of this adaptive error control mechanism allows for the maximum utilization of bandwidth for wireless terrestrial and satellite communication systems. Higher performance can be achieved by pushing down the error correction lower on the protocol stack. The Reliable AAL, referred to as AAL X, provides for residual error recovery during cases of ATM congestion, where the TECS cannot detect this type of condition. Environments with limited bandwidth capabilities, such as the U.S. military, can truly benefit from the Survivable ATM System.

An information system formed by high altitude platform (HAP) will be a new generation-system for the wireless communications and HAP station (HAPS) communication system combines the advantages of both terrestrial and satellite communication systems and avoids, to different extents, their disadvantages. The link simulation scenarios and results have been given for vehicular mobiles in 3.84 Mcps TDD systems in three different kinds of channels: case 3 in 3GPP. It is shown that the maximum performance degradation due to high mobility in 'case 3' and 'vehicular A' channel is about 3 dB while only less than 1 dB performance loss is observed in 'Rician' channel. Simulations show that no significant performance impact is introduced by high speed mobility. Even in the worst channel conditions, only extra 3 dB margin is required to deliver the high speed data service.

Multiple-input multiple-output (MIMO) systems can be leveraged to increase capacity in fading channels. Especially in multiuser downlink communication systems, it has been shown that knowledge of channel state information at the transmitter (CSIT) is critical to leverage the capacity gain available from multiple antennas. When duplexing is performed using time division, CSIT can often be successfully obtained when channel reciprocity is available. CSIT acquisition, however, is much more difficult in frequency division duplexing. Sending feedback on the uplink has been shown to be a powerful technique to improve downlink performance in single user MIMO systems. The basic idea is to restrict the CSIT to a B bit codebook so that the mobiles can easily transmit these bits on the uplink. In this paper, we consider the multiuser downlink model with unitary precoding when there is a codebook consisting of 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</sup> unitary matrices that the precoder is restricted to lie in. This codebook is designed offline and known to both the base-station and all users. Each user sends back signal-to-interference plus noise ratio (SINR) information along with binary feedback about the unitary precoder. Based on the CSIT received on the uplink, the base-station selects one of the unitary matrices in the codebook to maximize the sum-rate. For this set-up, we first analyze the sum-rate performance of the unitary precoding scheme. We then show that the codebook of unitary pre-coders represents a collection of points in a special kind of manifold and show how the achievable sum-rate performance relates to the minimum distance of the codebook points in this space. Finally, we present a framework for constructing the codebook to maximize this minimum distance. Monte Carlo simulation results are presented to show the sum-rate performance of the proposed codebook design.

Application of multiple-input and multiple-output (MIMO) technology in wireless systems not only provides high spectral efficiency by the deployment of many number of antennas at both sides of a communication system for a given total transmit power, but it also enhances physical- layer security. Given the need for evaluation of realistic systems, this works studies the total information flow during multicast transmission in a region $\mathcal{R}$, accounting for the unavoidable statistical spatial randomness of users locations, both in absence or presence of eavesdroppers under conditions of imperfect channel state information at the transmitter (CSIT) due to users' mobility. In particular, we first introduce a lower-bound of the space-time mutual information without any eavesdropping, and then we proceed with the derivation for both finite and infinitely large number of antennas. Moreover, in case that eavesdropping is present, we determine a metric, called space-time secrecy rate with imperfect CSIT, which characterizes the total amount of common confidential information flow per receive antenna, and we obtain it with asymptotic arguments in terms of the numbers of antennas at each side. Numerical results, validated by simulations, shed light on how the imperfect conditions affect the performance. Remarkably, imperfect CSIT may present benefits, since it engenders degradation in eavesdropper's performance.