Statistical Interference Modeling and Performance Analysis for Synchronous Frequency-Hopping Spread-Spectrum Multiple-Access Networks

DoctorIn this thesis, we analyze the performance of synchronous fast frequencyhopping spread-spectrum multiple-access (FHSS-MA) networks using M-ary frequency shift keying (MFSK) modulation under Rayleigh fading. First, we analyze the performance of binary soft decision decoded, synchronous, fast FHSSMA networks with MFSK and noncoherent detection in Rayleigh fading channels. The joint probability density function (pdf) of the absolute values of the correlator outputs is derived to compute the bit interleaved coded modulation (BICM) channel capacity and evaluate the soft decision decoding performance of the binary 3GPP Turbo and convolutional codes. Results indicate that soft decision decoding based on the derived pdf drastically outperforms traditional decoders based on the Gaussian approximation of the effect of the multipleaccess interference (MAI). The sensitivity of the derived soft decision decoder to estimation errors in system parameters and the required computational complexities of the derived soft decision decoding metrics are also investigated.We also analyze the performance of M-ary Turbo coded, synchronous, fast FHSS-MA networks with MFSK and noncoherent detection under Rayleigh fading channels based on the joint pdf of the absolute values of the correlator outputs. The coded modulation (CM) channel capacity along with the associated normalized network throughput are computed and the frame error rate (FER) performance of M-ary Turbo codes designed in [27] are evaluated. Numerical results show that M-ary coded FHSS-MA networks dramatically outperform binary coded FHSS-MA networks, resulting in excess of three-fold increase in the network capacity.Finally, we analyze the performance of both binary and M-ary Turbo coded, synchronous, fast FHSS-MA networks using coherent MFSK and quadrature amplitude modulation (QAM) under Rayleigh fading channels. The joint pdf of the correlator outputs is derived to compute the BICM and CM channel capacity along with the associated normalized network throughput. We also evaluate the FER performance of practical binary 3GPP Turbo codes [28] and M-ary Turbo codes designed in [27]. Numerical results show that M-ary Turbo coded FHSS-MA networks using coherent MFSK significantly outperform binary andM-ary Turbo coded FHSS-MA networks using QAM. Moreover, for the cases using QAM and coherent MFSK, we observe that the derived maximum likelihood (ML) soft decision decoders are quite insensitive to estimation errors in system parameters such as the number of active users in the network and the received signal to noise ratio (SNR) which are required to compute the ML soft metric at the receiver

Study of continuous-phase four-state modulation for cordless telecommunications. Assessment by simulation of CP-QFSK as an alternative modulation scheme for TDMA digital cordless telecommunications systems operating in indoor applications

One of the major driving elements behind the explosive boom in wireless revolution is the advances in the field of modulation which plays a fundamental role in any communication system, and especially in cellular radio systems. Hence, the elaborate choice of an efficient modulation scheme is of paramount importance in the design and employment of any communications system. Work presented in this thesis is an investigation (study) of the feasibility of whether multilevel FSK modulation scheme would provide a viable alternative modem that can be employed in TDMA cordless communications systems. In the thesis the design and performance analysis of a non-coherent multi-level modem that offers a great deal of bandwidth efficiency and hardware simplicity is studied in detail. Simulation results demonstrate that 2RC pre-modulation filter pulse shaping with a modulation index of 0.3, and pre-detection filter normalized equivalent noise bandwidth of 1.5 are optimum system parameter values. Results reported in chapter 5 signify that an adjacent channel rejection factor of around 40 dB has been achieved at channel spacing of 1.5 times the symbol rate while the DECT system standards stipulated a much lower rejection limit criterion (25-30dB), implying that CP-QFSK modulation out-performs the conventional GMSK as it causes significantly less ACI, thus it is more spectrally efficient in a multi-channel system. However, measured system performance in terms of BER indicates that this system does not coexist well with other interferers as at delay spreads between 100ns to 200ns, which are commonly encountered in such indoor environment, a severe degradation in system performance apparently caused by multi-path fading has been noticed, and there exists a noise floor of about 40 dB, i.e. high irreducible error rate of less than 5.10-3. Implementing MRC diversity combiner and BCH codec has brought in a good gain.Higher Education Ministr

Advanced Trends in Wireless Communications

Physical limitations on wireless communication channels impose huge challenges to reliable communication. Bandwidth limitations, propagation loss, noise and interference make the wireless channel a narrow pipe that does not readily accommodate rapid flow of data. Thus, researches aim to design systems that are suitable to operate in such channels, in order to have high performance quality of service. Also, the mobility of the communication systems requires further investigations to reduce the complexity and the power consumption of the receiver. This book aims to provide highlights of the current research in the field of wireless communications. The subjects discussed are very valuable to communication researchers rather than researchers in the wireless related areas. The book chapters cover a wide range of wireless communication topics

Performance of soft decision decoded synchronous FHSS multiple access networks using MFSK modulation under Rayleigh fading

In this paper, we analyze the performance of soft decision decoded, synchronous, fast frequency-hopping spread-spectrum multiple-access networks using M-ary frequency shift keying in Rayleigh fading channels under the assumption that the number of frequency hopping slots is sufficiently large. The joint probability density function (pdf) of the absolute values of the correlator outputs is derived to compute the channel capacity and evaluate the soft decision decoding performance of the 3GPP Turbo and convolutional codes. Results indicate that soft decision decoding based on the derived pdf drastically outperforms traditional decoders based on the Gaussian approximation of the effect of the multiple access interference (MAI). The sensitivity of the derived soft decision decoder to estimation errors in system parameters and the required computational complexities of the derived soft decision decoding metrics are also investigated.X1179sciescopu