International communications satellite systems

Ten satellite systems for international communication are briefly described. Modulation and coding schemes on some of these systems are highlighted

Iterative carrier synchronization in the absence of distributed pilots for low SNR applications

We consider the advanced modulation and coding schemes used in CCSDS (Consultative Committee for Space Data Systems) standards for deep space telemetry and telecommand. They are based on a powerful turbo or low-density parity check (LDPC) outer code and binary modulation formats that, for those schemes foreseen to be employed at the lowest baud rates, may contain an unsuppressed carrier to help synchronization. In this paper, we face the problem of carrier phase synchronization for these modulation and coding schemes

A LTE MIMO OTA Test System Using Vector Signal Transceivers

A 2 × 2 multiple-input-multiple-output over-the-air (MIMO OTA) test system based on four field-programmable Vector-Signal-Transceiver (VST) modules is presented. The system enables 2 x 2 MIMO OTA testing by assembling of a twochannel Evolved Node B (eNodeB) LTE base station emulator, a 2x2 channel emulator, and a two-channel user equipment (UE) simulator. A two-stage MIMO OTA test method has been demonstrated with downlink Long-Term Evolution Time-Division Duplex (LTE-TDD) mode using different modulation and coding schemes (MCSs). Test results and analysis are shown. This system will allow a systematic study of MIMO OTA metrology needs

Low energy indoor network : deployment optimisation

This article considers what the minimum energy indoor access point deployment is in order to achieve a certain downlink quality-of-service. The article investigates two conventional multiple-access technologies, namely: LTE-femtocells and 802.11n Wi-Fi. This is done in a dynamic multi-user and multi-cell interference network. Our baseline results are reinforced by novel theoretical expressions. Furthermore, the work underlines the importance of considering optimisation when accounting for the capacity saturation of realistic modulation and coding schemes. The results in this article show that optimising the location of access points both within a building and within the individual rooms is critical to minimise the energy consumption

Current optical technologies for wireless access

The objective of this paper is to describe recent activities and investigations on free-space optics (FSO) or optical wireless and the excellent results achieved within SatNEx an EU-framework 6th programme and IC 0802 a COST action. In a first part, the FSO technology is briefly discussed. In a second part, we mention some performance evaluation criterions for the FSO. In third part, we briefly discuss some optical signal propagation experiments through the atmosphere by mentioning network architectures for FSO and then discuss the recent investigations in airborne and satellite application experiments for FSO. In part four, we mention some recent investigation results on modelling the FSO channel under fog conditions and atmospheric turbulence. Additionally, some recent major performance improvement results obtained by employing hybrid systems and using some specific modulation and coding schemes are presented

Improving the system capacity of broadband services using multiple high-altitude platforms

A method of significantly improving the capacity of high-altitude platform (HAP) communications networks operating in the millimeter-wave bands is presented. It is shown how constellations of HAPs can share a common frequency allocation by exploiting the directionality of the user antenna. The system capacity of such constellations is critically affected by the minimum angular separation of the HAPs and the sidelobe level of the user antenna. For typical antenna beamwidths of approximately 5/spl deg/ an inter-HAP spacing of 4 km is sufficient to deliver optimum performance. The aggregate bandwidth efficiency is evaluated, both theoretically using the Shannon equation, and using practical modulation and coding schemes, for multiple HAP configurations delivering either single or multiple cells. For the user antenna beamwidths used, it is shown that capacity increases are commensurate with the increase in the number of platforms, up to 10 HAPs. For increases beyond this the choice of constellation strategy becomes increasingly important

Effect of Adaptive Modulation and Coding Schemes on Scheduling Algorithms for LTE Downlink

Long Term Evolution (LTE) network uses Radio Resource Management (RRM) mechanisms such as Scheduling and Adaptive Modulation and Coding (AMC) for realizing Quality of Service (QoS) requirements and optimizing system performance. Scheduling is the process of dynamically allocating physical resources to User Equipments (UEs) based on scheduling algorithms implemented at MAC sublayer of the LTE base station. Whereas AMC is Link Adaptation functionality of LTE Physical layer to enhance higher system performance. AMC scheme adopted in LTE Downlink depends on the channel quality Index (CQI) feedback from User Equipments. Hence in this paper, an attempt has been made to study and compare the performance of Blind Equal Throughput (BET), Maximum Throughput (MT) and Proportional Fair (PF) scheduling algorithms for Downlink connections with AMC (64 QAM, 16 QAM and QPSK regions) for Constant Bit Rate (CBR) traffic scenario. Performance metrics considered for simulation studies are throughput, delay, jitter and fairness. From the simulation results it is evident that the throughput, delay, jitter and fairness performances of the considered scheduling algorithms are better in 64QAM region. Also, MT scheduling algorithm achieves better throughput and BET scheduling algorithm achieves better fairness