A. Nordbotten

Bio: A. Nordbotten is an academic researcher from Telenor. The author has contributed to research in topics: Broadband networks & Local Multipoint Distribution Service. The author has an hindex of 1, co-authored 1 publications receiving 86 citations.

LMDS systems and their application

Abstract: Local multipoint distribution systems (LMDS) represent a new radio-based access technology with cellular architecture offering flexible high-capacity connections to private users and organizations. The systems employ a point-to-multipoint broadcast downlink with a total capacity of 36-38 Mb/s per transport stream, giving high flexibility for inclusion of any type of data. The interactive channel, being a point-to-point connection, may employ different technologies depending on availability and user demand for capacity. This capacity may basically range from a few kilobits per second up to at least 25.6 Mb/s. LMDS performance relative to other broadband access technologies is discussed. A major remaining development task is the establishment and verification of methods for coverage of normally shielded areas. The availability of cheap repeaters and possibly reflectors for increased coverage is a must, which will significantly improve coverage. The LMDS technology, now in its first stage of implementation, is expected to enhance development of broadband services such as e-commerce and tele-teaching.

Design of compact stacked-patch antennas in LTCC multilayer packaging modules for wireless applications

Abstract: A simple procedure for the design of compact stacked-patch antennas is presented based on LTCC multilayer packaging technology. The advantage of this topology is that only one parameter, i.e., the substrate thickness (or equivalently the number of LTCC layers), needs to be adjusted in order to achieve an optimized bandwidth performance. The validity of the new design strategy is verified through applying it to practical compact antenna design for several wireless communication bands, including ISM 2.4-GHz band, IEEE 802.11a 5.8-GHz, and LMDS 28-GHz band. It is shown that a 10-dB return-loss bandwidth of 7% can be achieved for the LTCC (/spl epsiv//sub r/=5.6) multilayer structure with a thickness of less than 0.03 wavelengths, which can be realized using a different number of laminated layers for different frequencies (e.g., three layers for the 28-GHz band).

Subcarrier intensity modulated free-space optical communication systems

Abstract: This thesis investigates and analyses the performance of terrestrial free-space optical communication (FSO) system based on the phase shift keying pre-modulated subcarrier intensity modulation (SIM) The results are theoretically and experimentally compared with the classical On-Off keying (OOK) modulated FSO system in the presence of atmospheric turbulence The performance analysis is based on the bit error rate (BER) and outage probability metrics Optical signal traversing the atmospheric channel suffers attenuation due to scattering and absorption of the signal by aerosols, fog, atmospheric gases and precipitation In the event of thick fog, the atmospheric attenuation coefficient exceeds 100 dB/km, this potentially limits the achievable FSO link length to less than 1 kilometre But even in clear atmospheric conditions when signal absorption and scattering are less severe with a combined attenuation coefficient of less than 1 dB/km, the atmospheric turbulence significantly impairs the achievable error rate, the outage probability and the available link margin of a terrestrial FSO communication system The effect of atmospheric turbulence on the symbol detection of an OOK based terrestrial FSO system is presented analytically and experimentally verified It was found that atmospheric turbulence induced channel fading will require the OOK threshold detector to have the knowledge of the channel fading strength and noise levels if the detection error is to be reduced to its barest minimum This poses a serious design difficulty that can be circumvented by employing phase shift keying (PSK) pre-modulated SIM The results of the analysis and experiments showed that for a binary PSK-SIM based FSO system, the symbol detection threshold level does not require the knowledge of the channel fading strength or noise level As such, the threshold level is fixed at the zero mark in the presence or absence of atmospheric turbulence Also for the full and seamless integration of FSO into the access network, a study of SIM-FSO performance becomes compelling because existing networks already contain subcarrier-like signals such as radio over fibre and cable television signals The use of multiple subcarrier signals as a means of increasing the throughput/capacity is also investigated and the effect of optical source nonlinearity is found to result in intermodulation distortion The intermodulation distortion can impose a BER floor of up to 10-4 on the system error performance In addition, spatial diversity and subcarrier delay diversity techniques are studied as means of ameliorating the effect of atmospheric turbulence on the error and outage performance of SIM-FSO systems The three spatial diversity linear combining techniques analysed are maximum ratio combining, equal gain combining and selection combining The system performance based on each of these combining techniques is presented and compared under different strengths of atmospheric turbulence The results predicted that achieving a 4 km SIM-FSO link length with no diversity technique will require about 12 dB of power more than using a 4 × 4 transmitter/receiver array system with the same data rate in a weak turbulent atmospheric channel On the other hand, retransmitting the delayed copy of the data once on a different subcarrier frequency was found to result in a gain of up to 45 dB in weak atmospheric turbulence channel

Performance analysis of optimized millimeter-wave fiber radio links

Abstract: We present a comprehensive performance analysis of several optimized fiber radio distribution schemes for millimeter-wave radio services. The analysis includes the noise and nonlinear characteristics of the transmitter (Tx)-receiver (Rx) pair integrated with the analog optical link in the downlink transmission of a given wavelength without optical amplification. Investigations are focused on four configurations of optimized fiber radio links, which were derived by considering the best performing possible Tx-Rx configuration and specifications of commercially available devices to support multichannel subcarrier multiplexed transmission. It was found that the nonlinear characteristics of the Mach-Zehnder modulator are the major source of performance degradation of the fiber radio links. A comparison of RF-over-fiber and IF-over-fiber transport schemes also shows that RF-over-fiber can yield 3-dB improvement in performance compared to IF-over-fiber techniques.

On the scalability of fixed broadband wireless access network deployment

Abstract: Fixed broadband wireless access systems, such as the local multipoint distribution service, use an open system architecture that supports a scalable solution for the Internet services over IEEE 802.16 wireless networks. This article presents an overview of various features of BWA systems toward realizing a high level of scalability to support a potentially fast expanding network. This is achieved by optimizing various network resources, which include utilizing the available bandwidth efficiency, making a minor enhancement to an existing system that minimizes the disruption to network services during the network expansion process, and combining the benefits of different features to increase network capacity.