International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / This paper uses ARTM channel sounding data collected at Edwards Air Force Base to investigate the dependency between the characteristics of frequency selective multipath fading and carrier frequency and ground based received antenna diameter. Channel model parameters are obtained from data sets measured at different frequencies and various ground based antenna diameters. The analysis shows that the multipath characteristics do not statistically change between the L-band and S-band carrier frequencies, but do change with antenna diameter. Furthermore, Flight 18 data shows that antenna diversity may be a useful technique to reduce data loss from multipath fading.

An analytically tractable model for Gaussian multiuser channels with fading is studied, and the capacity region of this model is found to be a good approximation of the capacity region of the original Gaussian network. This work extends the existing body of work on deterministic models for Gaussian multiuser channels to include the physical phenomenon of fading. In particular, it generalizes these results to a unicast, multiple node network setting with fading. / text

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Zugl.: Aachen, Techn. Hochsch., Diss., 2007.

This work examines error rate performance of Multi-Hop communication systems, employing Single Input Single Output (SISO) transmissions over Nakagami-m fading channel. Mobile multi-hop relaying (MMR) system has been adopted in several Broadband Wireless Access Networks (BWAN) as a cost-effective means of extending the coverage and improving the capacity of these wireless networks. In a MMR system, communication between the source node and destination node is achieved through an intermediate node (i.e., Relay Station). It is widely accepted that multi-hop relaying communication can provide higher capacity and can reduce the interference in BWANs. Such claims though have not been quantified. Quantification of such claims is an essential step to justify a better opportunity for wide deployment of relay stations.In this thesis, Bit Error Rate (BER) of multi-hop communication systems has been analysed. Different kinds of fading channels have been used to estimate the error rate performance for wireless transmission. Binary Phase Shift Keying (BPSK) has been employed as the modulation technique and Additive White Gaussian Noise (AWGN) has been used as the channel noise. The same Signal to Noise Ratio (SNR) was used to estimate the channel performance. Three channels were compared by simulating their BER, namely, Rayleigh, Rician and Nakagami. Matlab has been used for simulation.

In this thesis, the blind phase estimator algorithms are studied, including Histogram Algorithm (HA), Modified Histogram Algorithm (MHA), Maximum Likelihood (ML), 4th power-law and modified 4th power-law to compare their performance under quadrature amplitude modulation and additive white gaussian noise(AWGN) channel. Owing to the development of wireless communication, I used the fading channel of wireless communication and studied the performance of all algorithms again. After differential encoding and quadrature amplitude modulation, signals enter additive white gaussian noise(AWGN), constant phase offset and fading channel. At receiver, I use the above estimator to find the phase offset. If there is not line of sight under fading channel, all estimators performance are not good from simulation results, if there is a strong line of sight, all estimators performance are good and approximate to the AWGN channel.

We propose and analyze new finger assignment/management techniques that are applicable for RAKE receivers when they operate in the soft handover region. Two main criteria are considered: minimum use of additional network resources and minimum call drops. For the schemes minimizing the use of network resources, basic principles are to use the network resources only if necessary while minimum call drop schemes rely on balancing or distributing the signal strength/paths among as many base stations as possible. The analyses of these schemes require us to consider joint microscopic/macroscopic diversity techniques which have seldom been considered before and as such, we tackle the statistics of several correlated generalized selection combining output signal-to-noise ratios in order to obtain closed-form expressions for the statistics of interest. To provide a general comprehensive framework for the assessment of the proposed schemes, we investigate not only the complexity in terms of the average number of required path estimations/comparisons, the average number of combined paths, and the soft handover overhead but also the error performance of the proposed schemes over independent and identically distributed fading channels. We also examine via computer simulations the effect of path unbalance/correlation as well as outdated/imperfect channel estimations. We show through numerical exam ples that the proposed schemes which are designed for the minimum use of network resources can save a certain amount of complexity load and soft handover overhead with a very slight performance loss compared to the conventional generalized selection combining-based diversity systems. For the minimum call drop schemes, by accurately quantifying the average error rate, we show that in comparison to the conventional schemes, the proposed distributed schemes offer the better error performance when there is a considerable chance of loosing the signals from one of the active base stations.

First, we proved that the - Columnwise Complementary codes is better than - Columnwise Complementary code in time selective channel by explaining the probability of happening MAI elimination in frequency domain and proposing a method to use - Columnwise Complementary codes in one cell. Furthermore, we proposed the method to increase the capability of resisting of frequency selective fading channel without decreasing the capability of resisting of time selective fading channel. Finally, we showed some simulation results about receiver velocity and MAI elimination in frequency domain.

In mobile radio systems, the bandwidth of spread spectrum signals for CDMA system is very wide. If the bandwidth exceeds the coherence bandwidth of the channel, the signal is transmitted in the frequency-selective channel, and the signal is severely distorted by the multiple propagation paths. Each bandwidth of the signals for Multi-Carrier CDMA system is smaller. If the bandwidth is smaller than the coherence bandwidth of the channel, the channel is said to be frequency-nonselective. Besides, the data rate of Multi-carrier-CDMA is higher than the data rate of CDMA. If the traditional combing detector is used for Multi-Carrier CDMA system, the channel coefficients have to be estimated first. The error of the estimated channel coefficients will result in the performance of detector degrade. The blind adaptive algorithm doesn