Pedestrians effects on indoor MIMO-OFDM channel capacity

Temporal variations caused by pedestrian movement can significantly affect the channel capacity of indoor MIMOOFDM wireless systems. This paper compares systematic measurements of MIMO-OFDM channel capacity in presence of pedestrians with predicted MIMO-OFDM channel capacity values using geometric optics-based ray tracing techniques. Capacity results are presented for a single room environment using 5.2 GHz with 2x2, 3x3 and 4x4 arrays as well as a 2.45 GHz narrowband 8x8 MIMO array. The analysis shows an increase of up to 2 b/s/Hz on instant channel capacity with up to 3 pedestrians. There is an increase of up to 1 b/s/Hz in the average capacity of the 4x4 MIMO-OFDM channel when the number of pedestrians goes from 1 to 3. Additionally, an increment of up to 2.5 b/s/Hz in MIMO-OFDM channel capacity was measured for a 4x4 array compared to a 2x2 array in presence of pedestrians. Channel capacity values derived from this analysis are important in terms of understanding the limitations and possibilities for MIMO-OFDM systems in indoor populated environments

Advanced space system concepts and their orbital support needs (1980 - 2000). Volume 2: Final report

The results are presented of a study which identifies over 100 new and highly capable space systems for the 1980-2000 time period: civilian systems which could bring benefits to large numbers of average citizens in everyday life, much enhance the kinds and levels of public services, increase the economic motivation for industrial investment in space, expand scientific horizons; and, in the military area, systems which could materially alter current concepts of tactical and strategic engagements. The requirements for space transportation, orbital support, and technology for these systems are derived, and those requirements likely to be shared between NASA and the DoD in the time period identified. The high leverage technologies for the time period are identified as very large microwave antennas and optics, high energy power subsystems, high precision and high power lasers, microelectronic circuit complexes and data processors, mosaic solid state sensing devices, and long-life cryogenic refrigerators

Predicting the statistics of wave transport through chaotic cavities by the Random Coupling Model: a review and recent progress

In this review, a model (the Random Coupling Model) that gives a statistical description of the coupling of radiation into and out of large enclosures through localized and/or distributed channels is presented. The Random Coupling Model combines both deterministic and statistical phenomena. The model makes use of wave chaos theory to extend the classical modal description of the cavity fields in the presence of boundaries that lead to chaotic ray trajectories. The model is based on a clear separation between the universal statistical behavior of the isolated chaotic system, and the deterministic coupling channel characteristics. Moreover, the ability of the random coupling model to describe interconnected cavities, aperture coupling, and the effects of short ray trajectories is discussed. A relation between the random coupling model and other formulations adopted in acoustics, optics, and statistical electromagnetics, is examined. In particular, a rigorous analogy of the random coupling model with the Statistical Energy Analysis used in acoustics is presented.Comment: 32 pages, 9 figures, submitted to 'Wave Motion', special issue 'Innovations in Wave Model

Advanced space system concepts and their orbital support needs (1980 - 2000). Volume 1: Executive summary

The likely system concepts which might be representative of NASA and DoD space programs in the 1980-2000 time period were studied along with the programs' likely needs for major space transportation vehicles, orbital support vehicles, and technology developments which could be shared by the military and civilian space establishments in that time period. Such needs could then be used by NASA as an input in determining the nature of its long-range development plan. The approach used was to develop a list of possible space system concepts (initiatives) in parallel with a list of needs based on consideration of the likely environments and goals of the future. The two lists thus obtained represented what could be done, regardless of need; and what should be done, regardless of capability, respectively. A set of development program plans for space application concepts was then assembled, matching needs against capabilities, and the requirements of the space concepts for support vehicles, transportation, and technology were extracted. The process was pursued in parallel for likely military and civilian programs, and the common support needs thus identified

CHANNEL MODELING FOR FIFTH GENERATION CELLULAR NETWORKS AND WIRELESS SENSOR NETWORKS

In view of exponential growth in data traffic demand, the wireless communications industry has aimed to increase the capacity of existing networks by 1000 times over the next 20 years. A combination of extreme cell densification, more bandwidth, and higher spectral efficiency is needed to support the data traffic requirements for fifth generation (5G) cellular communications. In this research, the potential improvements achieved by using three major 5G enabling technologies (i.e., small cells, millimeter-wave spectrum, and massive MIMO) in rural and urban environments are investigated. This work develops SPM and KA-based ray models to investigate the impact of geometrical parameters on terrain-based multiuser MIMO channel characteristic. Moreover, a new directional 3D channel model is developed for urban millimeter-wave (mmW) small cells. Path-loss, spatial correlation, coverage distance, and coherence length are studied in urban areas. Exploiting physical optics (PO) and geometric optics (GO) solutions, closed form expressions are derived for spatial correlation. Achievable spatial diversity is evaluated using horizontal and vertical linear arrays as well as planar 2D arrays. In another study, a versatile near-ground field prediction model is proposed to facilitate accurate wireless sensor network (WSN) simulations. Monte Carlo simulations are used to investigate the effects of antenna height, frequency of operation, polarization, and terrain dielectric and roughness properties on WSNs performance

Application of advanced technology to space automation

Automated operations in space provide the key to optimized mission design and data acquisition at minimum cost for the future. The results of this study strongly accentuate this statement and should provide further incentive for immediate development of specific automtion technology as defined herein. Essential automation technology requirements were identified for future programs. The study was undertaken to address the future role of automation in the space program, the potential benefits to be derived, and the technology efforts that should be directed toward obtaining these benefits

Performance characterisation of MIMO-UWB systems for indoor environments

Although recent advances in wireless system technologies have provided ever increasing throughputs, end user demand continues to increase unabated. The research investigates the performance of a system harnessing two relatively new but powerful technologies, Multiple-Input and Multiple-Output (MIMO) and Ultra Wideband (UWB) transmission as a possible solution to meet the growing demand for capacity. Each of these technologies in its own right has been subject to a large volume of research and has been proven to bring an increase in throughput. Nevertheless the predicted future demand will outstrip what each strategy can provide individually. MIMO-UWB systems are thus an emerging wireless solution with, in particular, the potential to satisfy short distance, high speed transmission requirements within indoor environments. Before any system is deployed it is important to characterise performance within representative operating environments. The study therefore emulates appropriate indoor environments, defines an experimental protocol to execute a range of measurements that provide robust evidence of the behaviour of the combined system within indoor scenarios. The application scenario dictates that the transmitter represents a gateway device attached to the ceiling and the receiver, a user device set on a table. The sequence of measurements relate to different positioning of the user device, with different angles and ranges to the gateway device, the layout of antenna placements being important. The output of the study is an accurate model for engineers and, the foundation for the design of MIMO-UWB systems for indoor services.Although recent advances in wireless system technologies have provided ever increasing throughputs, end user demand continues to increase unabated. The research investigates the performance of a system harnessing two relatively new but powerful technologies, Multiple-Input and Multiple-Output (MIMO) and Ultra Wideband (UWB) transmission as a possible solution to meet the growing demand for capacity. Each of these technologies in its own right has been subject to a large volume of research and has been proven to bring an increase in throughput. Nevertheless the predicted future demand will outstrip what each strategy can provide individually. MIMO-UWB systems are thus an emerging wireless solution with, in particular, the potential to satisfy short distance, high speed transmission requirements within indoor environments. Before any system is deployed it is important to characterise performance within representative operating environments. The study therefore emulates appropriate indoor environments, defines an experimental protocol to execute a range of measurements that provide robust evidence of the behaviour of the combined system within indoor scenarios. The application scenario dictates that the transmitter represents a gateway device attached to the ceiling and the receiver, a user device set on a table. The sequence of measurements relate to different positioning of the user device, with different angles and ranges to the gateway device, the layout of antenna placements being important. The output of the study is an accurate model for engineers and, the foundation for the design of MIMO-UWB systems for indoor services