This paper discusses various challenges to realize a fixed wireless ATM network and provides solutions to these challenges. The capacity allocation in wireless ATM, wireless link impact on ATM traffic, and optimum utilisation of the wireless network resources for a LOS wireless ATM link are studied. An adaptive MQAM modulator is introduced to provide an optimum solution to these problems. The modulator level is adjusted using a unique QoS metric in a wireless ATM network. The metric, termed modified effective bandwidth, takes into account the bandwidth demand, QoS requirements, and outage conditions of the wireless ATM link. A performance study using VBR MPEG-1 video traffic in a fixed wireless channel (Ricean channel) demonstrates the advantages of the proposed system.

A phase locked loop based architecture is proposed for generation and frequency stabilization of direct Gaussian minimum shift keying (GMSK) at microwave and millimeterwave frequencies. A continuous phase frequency shift keyed (CPFSK) signal with a modulation index of 0.5 is produced at the desired output frequency using a full 360 degree linear continuous phase modulator that is controlled by the integrated baseband information signal. This modulated signal is used as the reference signal for a phase locked high power voltage controlled oscillator. The phase locked loop facilitates reference signal frequency tracking and provides Gaussian spectral shaping to the modulated output signal. Phase locked loop imperfections and their effect on the modulated output signal are considered and simulation results are presented.

The concept of effective bandwidth has been recently introduced to analyze the call admission, congestion control, and resource management in ATM networks. In this paper, the effective bandwidth is proposed as a metric of quality of service for wired and radio ATM. Using traditional and self-similar models of traffic sources, the effective bandwidth for an ideal channel is computed. The results are extended to random error and burst error channels by computing cell loss ratio. Using a modified fluid flow model, analytical approaches are examined using an ATM-simulator with different buffer sizes and Hurst parameters. The results can be used by the ATM system designer when dealing with bandwidth restricted channels, e.g., radio ATM.

A new Z search method is proposed which can significantly improve mean acquisition time when compared with the best previous Z search strategy. The codephase search starts from a position offset from centre of a range which has been determined from a priori information. The proposed search method includes previous Z search strategies as special cases. The distribution and mean of acquisition time have been developed for the proposed search strategies. With minimum mean acquisition time as objective, optimization of the starting position offset has been investigated.

Direct-sequence spread spectrum systems utilizing RAKE receivers provide inherent diversity for in-building mobile CDMA radio. A new compact expression for the SNR of the decision variable of a RAKE receiver is derived for generalized offset quadrature carrier modulation in this multipath environment. This expression also applies to BPSK, QPSK, and MSK modulation. The novelty of the derived expression is that it includes the effects of filtering. Filtering must be used to eliminate out-of band radiation and can also be used to shape the in-band spectrum, It is shown that bandlimiting filters have a significant effect on the SNR. A comparison of bandlimited O-QPSK and MSK reveals that, under the same co-user load, MSK has a lower SNR-0.917 times that of O-QPSK. However, MSK has an offsetting advantage of being a constant envelope-type modulation that can be very efficiently generated using direct modulation of a power RF oscillator. It is further shown that the O-QPSK SNR can be increased by a factor of 1.63 by whitening the in-band spectrum.>

Battery power efficiency of the portable unit is a major issue in the design of indoor radio telecommunication systems. The efficiency of the portables depends on the modulation method employed. Digital modulation methods with constant envelope signals are more battery efficient than those with modulated envelope signals since the latter require inefficient linear radio frequency amplifiers. The improvement in efficiency is very significant when the constant envelope modulation method is minimum shift keying and a directly modulated power radio frequency oscillator is used to generate the modulated signal. This paper compares the performance of binary phase shift keying (BPSK) and minimum frequency shift keying (MSK) in a spread spectrum code division multiple access setting. The BPSK system can support about 8 percent plus 0.5 more simultaneous users for a given carrier to interference ratio but the MSK system has the advantage of being more power efficient.>

Serial search spread-spectrum code acquisition is analyzed. A modified flow graph is presented. It permits the use of a generalized lock strategy and allows the false alarm time to be treated as a random variable. The distribution of acquisition time is obtained directly by using an extended generalization of Bernoulli trials. Compared to recent work which uses a fixed penalty false alarm time, the analysis is more general and requires fewer assumptions and approximations. The analysis is suitable for both single dwell and multidwell systems. Examples are presented to show the effect on the acquisition time distribution of sequence length and normalized detection threshold.>