Carrier Aggregation in Satellite Communications: Impact and Performance Study

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.

Carrier aggregation (CA) is a technology first introduced in LTE-Advanced (LTE-A) to increase the peak data rate of 4G networks (for example, the maximum available speed) [1]. The mobile network operator can increase the total available bandwidth for a single user by aggregating multiple channels together, thereby increasing the user data rate as well as the spectrum utilization efficiency and resource allocation flexibility of the entire network. Before LTE-A, mobile network operators could allocate the spectral resource only to a particular user within a single designated frequency band, limiting the maximum channel capacity. The realization of CA allows network operators to create larger channels from nonadjacent spectrum blocks. For example, operators can use a 10-MHz carrier from the 2,100-MHz band and combine it with another 5-MHz carrier from the 700-MHz band to create a 15-MHz LTE channel. The LTE-A standard specifies that each of the component carriers (CCs) of the communication signal is limited to 20 MHz of bandwidth. Aggregation of up to five CCs allows a maximum of 100 MHz of total signal bandwidth, as depicted in Figure 1. This leads to a fivefold increase in channel capacity and data speed [2]. It is projected that CA technology will continue to be widely and intensively used in future-generation communications, such as 5G.

Coexistence of satellite and terrestrial wireless communication systems in the same frequency band is quite promising for addressing the challenge of spectrum scarcity. To cope with the inevitable inter-system interference, radio resource allocation at both sides should be carefully re-optimized. In this paper, we focus on a scenario where a satellite communication system and a terrestrial distributed antenna system (DAS) coexist via spectrum sharing. We particularly utilize the radio map (RM) to reduce the system overhead for channel acquisition. Based on the large-scale channel state information at the transmitter (CSIT), which is derived from the RM, we propose an optimized power allocation scheme to improve the achievable sum rate of the terrestrial system. For the satellite side, an opportunistic user scheduling scheme is presented, to reduce the harmful leakage interference to the terrestrial mobile users. Simulation results demonstrate that the proposed RM-based coordination scheme can significantly promote the performance of satellite terrestrial coexistence, although the small-scale channel fading has been ignored in the formulated optimization.

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

With the increasing popularity of social media, artificial intelligence (AI) and mobile computing, higher data-rate wireless communication is required. In the existing limited 4G spectrum, 3GPP standards have defined several methods to increase the data-rate, e.g., carrier aggregation (CA), high-order modulation (HOM) and MIMO technique; however this comes at the cost of extra power consumption and potential sensitivity degradation due to the spurious components generated by CA. In addition, high-power user equipment (HPUE) extends the coverage range and uplink throughput, but introduces more stringent linearity requirements for transmitter design. In this work, we present a 28nm CMOS LTE-A transceiver, capable of supporting up to 4 inter-band downlink (or 2-carrier $4 \times 4$ downlink MIMO) and 2 inter-band uplink CA concurrently while adopting ADPLLs for RX and TX with 256-QAM capability. The techniques adopted to achieve these features are described in this paper.

The deployment of small cells with carrier aggregation (CA) technique is a significant feature of next-generation cellular networks. The potential benefits of dense base stations (BSs) deployment are provided by using proper interference management mechanisms. Meanwhile, the user equipments (UEs) can simultaneously access multiple component carriers (CCs) to meet the dramatically increased traffic demand by means of CA. In this paper, an optimization problem consists of UE-BS association, CC configuration, frequency resources scheduling, and power allocation with adaptive modulation schemes is investigated to enhance energy efficiency, focusing on the quality of service (QoS)-aware CA. To obtain the near optimal solutions as well as the consideration of computational complexity, a cross entropy- based algorithm (CEA) is proposed to jointly solve the combinatorial problem. Compared to the traditional heuristic algorithms, the merits of proposed scheme can be observed via simulation results.

This paper presented a strategy which is based on carrier aggregation and frequency hopping technology. In the strategy, carrier frequency is introduced by Scheduling the allocation of spectrum resources, and furthermore, the carrier frequency will change during a call. The strategy is introduced in the short wave communications system. The simulation model of communication reconnaissance system is established, and then the interception time of radio signal is simulated. The results of simulation show that the anti- reconnaissance performance which adopts the carrier aggregation is much higher than that common system which adopt single carrier. Furthermore, the technology of carrier aggregation which is introduced in frequency hopping system could reduce the hopping rate. It is proved that the frequency-hopping system which adopts the carrier aggregation technology could achieve high level security classification in the case of low hop rate.

The spread spectrum technology has been widely used in ground communication systems. With the development of global satellite communication, spread spectrum communication has also been widely used in satellite communication system. However, spread spectrum communication has many challenges to address, such as multi-user interference, near-far effect, random phase, delay and so on. Multi-user detection technology makes use of spreading sequence, delay, amplitude and phase information of each user for joint detection, which can effectively suppress multiple access interference, make full use of the frequency spectrum resources at the uplink and improve system capacity. Thus, the multiple user detection is one of the key technologies in CDMA communication systems. This paper adopts the multiple user detection scheme that is based on convolution coding block parallel iteration interference cancellation and conducts MATLAB simulation on multiple user detection algorithms. Though the study of three different data rate scenarios, this paper verifies that the multiple user detection algorithm can reduce the bit error rate of the reference user and improve system capacity.

In order to take full advantage of the discontinuous and irregular frequency in complex electromagnetic environment, an irregular carrier aggregation method is proposed. In the proposed method, several frequency bands from 1 MHz to 20 MHz can be combined to a wideband channel, witch can transmit HD image etc. The process and the key technologies are introduced, including channelized spectrum, resource allocation, synchronization and channel estimation. Analysis shows that the proposed carrier aggregation method has effective anti-jamming ability and the spectrum resources can be utilized efficiently.

Satellite communication technology has become a research hotspot in today's society because of its important significance to the development of modern society. However, the realization of satellite communication is a big project with high difficulty and high cost. Therefore, it is necessary to use computer software to model the satellite communication system and further understand the satellite communication scenarios and communication links. Based on the basic theory of LEO communication satellite, this paper uses STK software to complete the modeling of traditional satellite communication system, and realizes the visual simulation of LEO satellite communication. Finally, through the analysis of the simulation process and simulation results, the connection rate of normal communication between ground stations is calculated.

LTE-based mobile satellite communication system is a combination of terrestrial LTE system and satellite communication techniques, which aims at improving the current LTE system's technical specifications for better service quality. AMC (Adaptive Modulation and Coding) technique is applied in current LTE system to improve system capacity and data transmission efficiency. CQI (Channel Quality Indicator), which is measured by UE, is an essential indicator for AMC process. However in satellite system, the said data received by eNodeB are all outdated due to the long delay caused by satellite link. So there exists need for predicting CQI data in advance. ARIMA (Autoregressive Integrated Moving Average Model) is a good choice for predicting CQI in terrestrial system, but its prediction ability is limited when prediction length is too long in satellite communication system. To solve this problem, a prediction scheme is proposed in this paper. This method predicts CQI states, instead of predicting the specific CQI values, and provides the reference CQI for AMC. A modified ARIMA model is applied for reducing the prediction complexity and delay. Simulation shows that the proposed method can realize CQI prediction with acceptable RMSE performance.

To satisfy the ever increasing demand for higher throughput and data rates, wireless communication systems need to operate in wider bandwidths. 3GPP LTE-Advanced with carrier aggregation enables operators to maximally and optimally utilize their available spectrum resources for increased data rates and user experience while reducing their incurred OPEX and CAPEX. This article provides a tutorial overview of 3GPP LTE-Advanced with carrier aggregation as specified in Rel-10 including deployment scenarios of interest, main design features, PHY/MAC procedures, and potential enhancements for future standard releases.

In the past few years, non-geostationary orbit (NGSO) satellite communication constellations have regained popularity due to their conspicuous advantages. Nevertheless, with more NGSO satellites getting involved in communications, the spectrum resources should become much more scarce. Multi-beam high throughput satellite and spectrum sharing are two major techniques in communication design. The two techniques can significantly mitigate interference and highly augment the capacity of the communication system. Thus, they are commonly used in satellite communication systems nowadays. With a massive number of NGSO satellites comprising the communication system and moving in their orbits, interference scenarios are pretty complex. In this article, the relationship between the level of interference and the beam distance is deduced. Moreover, for beams with different tilting angles, the different off-axis angles may correspond to the same beam distance, which is directly related to the interference level. Through the interference analysis, we propose a channel allocation method that uses a beam search algorithm to optimize the channel allocation problem and achieves outstanding time efficiency. The performance of the proposed method is validated by a coexisting scenario of the geostationary orbit and NGSO satellite communication systems. The results show that the level of interference can be largely mitigated, and the capacity of communication systems is significantly augmented.

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.

Cognitive radio has attracted considerable attention because of its ability to make full use of the available spectrum resources for wireless terrestrial communication networks. In addition, the satellite communication scenario, which requires a transparent air interface to integrated/hybrid Satellite–Terrestrial communication systems and provides a supplement for other multimedia services, will cause frequency scarcity. Satellite communication systems based on cognitive radio are available under scenarios that involve transmission with changing communications. In this paper, a cooperative spectrum-sensing algorithm based on a time or bandwidth-based cooperative spectrum-sensing model of an integrated/hybrid cooperative satellite communication system is proposed. Moreover, the concept of weighted cooperative spectrum sensing is introduced. Compared with the traditional single-user spectrum-sensing algorithm, the cooperative spectrum sensing is able to cope with the interference to the primary user caused by a secondary user better. In addition, multiple earth stations that use some part of the bandwidth cooperatively to perform spectrum sensing throughout the whole frame can detect the presence of primary user in time. The satellite component combines the sensing results from earth stations to reach a final decision, and the optimal combination weights to maximize the detection probability of the secondary user are obtained. Numerical results that demonstrate the performance of the proposed algorithm are presented. Copyright © 2015 John Wiley & Sons, Ltd.