Local Multipoint Distribution Service Systems Research Articles

Bandwidth Overlap Factor for Feasible Coexistence of LTE-A and Point to Multipoint LMDS Systems

The necessity to share the radio spectrum becomes highly significant in the recent time due to emerging new wireless technologies and, the cost and difficulty in attaining new frequency spectrum licenses. However, spectrum sharing leads to substantial interference between the close systems especially in the same frequency band. In this paper, we present a spectrum sharing scheme to investigate coexistence feasibility results in interference from orthogonal frequency division multiplexing (OFDM)-based Long Term Evolution-Advanced (LTE-A) into point to multipoint (P-MP) local multipoint distribution service (LMDS). This method proposes a spectrum frequency mask for the OFDM-based LTE-A according to bandwidth overlapping method with the P-MP LMDS system. The relative power spectral density of the proposed spectrum emission mask due to bandwidth overlap has been mathematically derived in a more compact closed-form. It shows smoother and 1.7 dB less than that of traditional OFDM mask in the main spectrum bandwidth which in turn leads to reduce the interference effects to LMDS system. The coexistence coordination studies are made at the frequency of 3500 MHz, on the base of co-primary operation and co-located systems. The numerical results demonstrate that the difference in amount of the required carrier frequency for safe coexistence increases as LMDS sector size increases. In addition, OFDM system with small channel bandwidth is much more affected than the wider channel bandwidth in terms of the necessary minimum guard bandwidth for harmless coexistence when the LMDS cell size changes from 0.5 to 3 km2.

Intercell Radio Interference Studies in Broadband Wireless Access Networks

Capacity has become of primary importance in broadband wireless access (BWA) networks due to the ever-increasing demand for multimedia services and the possibility of providing wireless Internet, leading to their standardization by IEEE (802.16 WirelessMAN) and ETSI (BRAN HIPERACCESS). The major factor limiting capacity in such systems is interference originating from adjacent cells, namely intercell interference. This paper presents a general analysis of intercell interference for a spectrally efficient BWA cellular configuration. It examines the statistical properties of the carrier-to-interference ratio in both downstream and upstream channels. The focus is on the spatial inhomogeneity of rain attenuation over multiple paths, which is the dominant fading mechanism in the frequency range above 20 GHz, especially when two-layered [i.e., line-of-sight (LOS) and non-LOS] architectures are involved. Besides attenuation from precipitation, various architectural and propagation aspects of local multipoint distribution service systems are investigated through simulations, and worst-case interference scenarios are identified

LMDS diversity systems: a new performance model incorporating stratified rain

Cell-site diversity may prove an efficient fade mitigation technique to increase the availability of local multipoint distribution service systems, in this Letter, a recently suggested physical model for the prediction of cell-site diversity performance is properly modified to include stratified rain. The model-obtained is satisfactorily verified using radar derived data from UK and Canada. Simulated BEP results concerning LMDS diversity systems are also presented.

Symbol rate and signal capture in LMDS systems

AbstractBased on the Monte‐Carlo simulation of frequency tolerance and drift parameters in the microwave local multipoint distribution service (LMDS) systems, the relationships among symbol rate, temperature variation, and signal capture probability are investigated. To guarantee 100% probability of signal capture, symbol rate limitations are presented. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 418–420, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11397

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.

K-band and millimeter-wave MMICs for emerging commercial wireless applications

The recent K-band monolithic-microwave integrated-circuit (MMIC) technologies for the local multipoint distribution service systems and novel MMIC technologies for potential low-cost millimeter-wave MMICs are presented in this paper via a review of Fujitsu Quantum Devices Limited technology. The devices being demonstrated are a 23-26-GHz 2-W power amplifier module with a broad-band driver amplifier, a 19-33-GHz miniature low-noise amplifier, a frequency multiplier by four for K-band local oscillators, a flip-chip MMIC module for radar application, and three-dimensional MMIC image-rejection harmonic mixers. Through these devices, the recent trend of design and fabrication methodologies for the K-band and millimeter-wave devices will be described.

Coding and Modulation for LMDS and Analysis of the LMDS Channel.

Local Multipoint Distribution Service (LMDS) has the potential to become a viable alternative to coaxial cable, fiber and other wired and wireless technologies providing “last mile” communication services. A major obstacle, however, is the high equipment cost. While for example cable modems supporting two-way services are available for $200 to $300, LMDS modem providing similar services will cost over $1000. The major cost driver of LMDS equipment is the radio frequency (RF) unit, as Ka-band technology still is quite expensive. The modem design must minimize the overall architecture cost, and low-cost modems requiring an expensive architecture should not be used. The channel characteristics of LMDS systems are very different from those of fiber, coaxial cable, and lower frequency wireless links, major channel impairments being non-linear high power amplifier (HPA), high phase noise and high co-channel interference. Modems should therefore be developed specifically for LMDS systems. This report deals with the choice of coding and modulation schemes, the LMDS channel, and how the channel impairments should be overcome by digital signal processing algorithms.