Coding and modulation for LMDS and analysis of the LMDS channel

Abstract

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.

Rigorous nonlinearity analysis of multicarrier wireless systems

“…On the other hand, real experiments of the radar systems in the abovementioned ground-penetrating applications show a stable antenna performance that is not significantly affected by the ground type being observed. As compared to the corner reflector or the horn antenna employed in previous versions of the radar system [1,2], the proposed antenna's performance proved to be much better. Thus, it is obvious that the back-scattered field that appears in the simulation results is due to some program restrictions concerning the antenna's structural model used during the simulation procedure.…”

“…This explicit relationship between BER and SNR is directly related to the modulation scheme and coding of the systems [1,2]. Here, modulation schemes of QAM64, QAM16, and QPSK with ReedSolomon coding RS (204, 188) are considered.…”

“…One involves the system performance requirements, which are necessary for the system to (1,1) parameters for the proposed antenna, taking the surrounding metallic box into consideration achieve the desired performance and meet the quality of service (QoS) requirements of end users. One explicit example is the customer requirement of bit error ratio (BER).…”

Symbol rate and signal capture in LMDS systems

“…Photonic crystals or electromagnetic band gap (EBG) structures are periodic metallic or dielectric materials [1]. They can control the propagation of electromagnetic waves, irregardless of their direction of propagation.…”

“…Fixed wireless LMDS networks [1] provide a broadband access "last mail" solution for communication services. As compared with cable, ADSL, and other wireless data services such as wireless LAN [2], EDGE/GPRS [3], 3G [4] and CDMA 1 ϫ RTT [5], the high-speed connection of LMDS systems would provide a privilege.…”