Cellular system information capacity change at higher frequencies due to propagation loss and system parameters

In this paper, mathematical analysis supported by computer simulation is used to study cellular system information capacity change due to propagation loss and system parameters (such as path loss exponent, shadowing and antenna height) at microwave carrier frequencies greater than 2 GHz and smaller cell size radius. An improved co-channel interference model, which includes the second tier co-channel interfering cells is used for the analysis. The system performance is measured in terms of the uplink information capacity of a time-division multiple access (TDMA) based cellular wireless system. The analysis and simulation results show that the second tier co-channel interfering cells become active at higher microwave carrier frequencies and smaller cell size radius. The results show that for both distance-dependent: path loss, shadowing and effective road height the uplink information capacity of the cellular wireless system decreases as carrier frequency increases and cell size radius R decreases. For example at a carrier frequency fc = 15.75 GHz, basic path loss exponent α = 2 and cell size radius R = 100, 500 and 1000m the decrease in information capacity was 20, 5.29 and 2.68%

Sensitivity of cellular wireless network performance to system & propagation parameters at carrier frequencies greater than 2 GHz

In this paper, mathematical analysis supported by computer simulation is used to investigate the impact of both system and propagation loss parameters on the performance of cellular wireless network operating at microwave carrier frequencies greater than 2 GHz, where multiple tier of co-channel interfering cells are considered to be active. The two-slope path loss model and the uplink information capacity of the cellular network is used for the performance analysis. Results show that for carrier frequencies greater than 2 GHz and smaller cell radius multiple tier of co-channel interfering cells become active as compared to carrier frequencies lesser than 2 GHz. The multiple tier of co-channel interfering cells, leads to a decrease in the information capacity of the cellular wireless network. The results also show that the system performance is sensitive to most of the propagation model parameters such as the basic and extra path loss exponent

Communication system model for information rate evaluation of differential detection over time-varying channels

A communication system model for mutual information performance analysis of multiple-symbol differential M-phase shift keying over time-correlated, time-varying flat-fading communication channels is developed. This model is a finite-state Markov (FSM) equivalent channel representing the cascade of the differential encoder, FSM channel model and differential decoder. A state-space approach is used to model channel phase time correlations. The equivalent model falls in a class that facilitates the use of the forward backward algorithm, enabling the important information theoretic results to be evaluated. Using such a model, one is able to calculate mutual information for differential detection over time-varying fading channels with an essentially finite time set of correlations, including the Clarke fading channel. Using the equivalent channel, it is proved and corroborated by simulations that multiple-symbol differential detection preserves the channel information capacity when the observation interval approaches infinity

Sensitivity of information capacity of land mobile cellular system to the base station antenna height at higher microwave frequencies

In this paper, mathematical analysis, supported by simulations is used to study the impact of base station antenna height on the performance of land mobile cellular network. The performance is evaluated in terms of the uplink information capacity of the cellular wireless network, when both the first six co-channel interfering cells (first tier) and those beyond it are considered to be dominant. It is shown that at microwave frequencies beyond 2 GHZ as the antenna height increases the area spectrum efficiency of the land mobile cellular network decreases

Mobile Telemedicine for Accident and Emergency Scenes in Tropical Regions

A wireless communication system utilizing wideband point-to-point link is proposed in this paper. The system provides transmission of telemedicine information for an ambulance attending an accident or emergency scene where different types of information related to the patient can be received by the hospital prior to the patient's arrival so that necessary preparations can be made. The system's reliability is evaluated for operation in tropical regions where persistent heavy rainfall can severely affect availability of radio links at microwave frequencies

A Continuous Phase Modulation Scheme for Telemedicine Systems

We study the use a continuous phase modulation (CPM) system providing mobile data service with QPSK transmission for a telemedicine system. The results of using an I/Q modulation and CPM schemes with their BER performance are compared. The system provides direct symbol-by-symbol detection with no special decoding mechanism necessary. We have compared the performance in bit error rate (BER) with coherent detection of CPM and I/Q modulation. The scheme offers high bandwidth and power efficiency making it particularly suitable for telemedicine applications

The effect of rain attenuation on orthogonally polarized LMDS systems in tropical rain regions

The effect of rainfall is to reduce the link reliability of local multipoint distribution service (LMDS) systems. We study the effects of rain attenuation on the microwave channel in two heavy rainfall tropical cites in Asia for wideband signals using a line-of-sight LMDS link with orthogonal polarizations. This is performed by transmitting signals with horizontal and vertical polarizations with carrier frequencies commonly used in LMDS systems. It is noted that the effect of depolarization due to rain is minimal at around 10 GHz; it is also observed that the rainfall rate has little effect on the difference in attenuation with different polarizations

Vector precoding scheme for multi-user MIMO systems

In this paper, the performance of vector precoding in multiple input multiple output broadcast channels (MIMO BC) is investigated and compared with other channel decomposition techniques utilized for implementing zero forcing (ZF) preceding. It is a known result that ZF precoding requires pseudo inversion of the channel matrix, where this operation is only optimum when the transmitter power is unconstrained. The problem when the transmitter is subject to average or maximum power constraints is well known, where results published have indicated that ZF precoding approaches the maximum capacity bound if the dimensionality of the system is greater than the number of transmitter antennas. A vector precoding technique for MIMO BC channels is investigated in this paper where pseudo inversion is circumvented by employing joint co-operation between transmitter and receiver for all users. This technique adopts a time scheduling approach to service the users which facilitates decentralized multi-user detection at the receiver. This approach yields an improvement to the bit error rate probability by approximately an order of magnitude as compared to the ZF approach utilizing other channel decomposition techniques. The scheme also enables an increase in the capacity of the MIMO BC, with less computational complexity as compared to the techniques employing Moore-Penrose pseudo inverse

Geometry-based statistical model for radio propagation in rectangular office buildings

We present a new approach to the modeling of angle and time of arrival statistics for radio propagation in typical office buildings, in which the majority of interior scattering objects are either parallel or perpendicular to the exterior walls. We first describe the reradiating elements in office buildings as randomly distributed arrays of thin strips. The amount of clutter and the amount of transmission/reflection loss are then accounted for through several key parameters of the site-specific features of indoor environment, such as the layout and materials of the building under consideration. Subsequently, the important channel parameters including power azimuthal spectrum (PAS) and power delay spectrum (PDS) are derived. An appealing observation is that when the path angles from multiple channel trials are measured and collectively analyzed, deterministic angle clustering becomes evident. This phenomenon agrees well with the existing ray-tracing (RT) results reported by Jo et al. in buildings of this type and cannot be explained by other geometric channel models (GCMs). Furthermore, the proposed model predicts an asymmetric cluster PAS for a single-channel-trial scenario, which yields an excellent fit to the experimental data presented by Poon and Ho. Finally, we have also investigated the behaviors of the superimposed PAS and PDS under various channel conditions

Polarization of received signals for wideband wireless communications in a heavy rainfall region

Wireless fixed network access offers many advantages such as scalability and ease of deployment in low population density areas. However, its coverage is greatly affected by rainfall. In this letter, we study the effects of rain attenuation on the radio channel in a heavy rainfall region for wideband signals in the 10-40-GHz frequency range. We conclude that although a lower frequency of <10 GHz is more affected by multipath due to a longer wavelength, it is still optimal in a heavy rainfall region due to high losses associated with higher frequency signals. In addition, for a path of over 1.5 km, the difference in horizontal and vertical polarization becomes significant