Broadband Fixed Wireless Access Research Articles

Outage performance of dual branch diversity techniques in broadband fixed wireless access networks

New physical–mathematical models for the calculation of the outage probability of the maximal ratio combining and selection combining dual branch spatial diversity schemes for broadband fixed wireless access networks operating above 10 GHz are presented. At these frequency bands and considering line-of-sight conditions, rain attenuation is the dominant fading mechanism, which should be taken into account in the radio communications system design. The models are based on bivariate inverse Gaussian (IG) distribution and on the adoption of a spatial correlation coefficient for the convergent terrestrial wireless links. IG distribution has been shown that models accurately the rain attenuation fading for both temperate and tropical climatic regions. The models are validated with numerical results and some useful conclusions are drawn.

BIT ERROR RATE ANALYSIS OF WIMAX PHYSICAL LAYER UNDER SUI AND AWGN CHANNEL MODEL WITH VARYING CYCLIC PREFIX, MODULATION TECHNIQUES AND CODING SCHEMES

Requirement of portable, mobile and high speed connectivity for internet access is increasing day by day. WiMAX will be playing an important role in the Broadband Wireless Technology (BWT) sector, since it is more cost-effective and easy to install technology. It is a fixed Broadband Wireless Access (BWA) system based on the IEEE 802.16 standards and will be used to provide “last mile” access to the broadband and Internet access services. The WiMAX technology is based on the IEEE 802.16-2004 Air Interface Standard and is rapidly proving itself as a technology that will play a significant role in fixed broadband wireless metropolitan area networks. It is based on the concept of orthogonal frequency division multiple access technique in wireless communication. This paper investigates the performance of WiMAX network under AWGN and SUI Channel Model by varying physical layer parameter such as higher M-ary modulation, coding scheme and cyclic prefix.

A novel wide band open ended air gap radial line slot array antenna at 5.8-GHz frequency band

This article presents a wide band linearly polarized beam squinted radial line slot array (RLSA) antenna at 5.8-GHz band. The open ended air gap technique was used to broader the bandwidth, reduce the antenna size but maintain the high-performance characteristic. The antenna implemented radiating slot design with diameter of 200 and 1.6 mm hybrid FR4 and 8-mm open ended air gap for dielectric height. The antenna also successfully fabricated and performed a good result. The measured results show a wide 38% of bandwidth with 16 dBi gain at 5.8-GHz frequency. The beamwidth obtained below 15° for E and H plane. The research found a wide band RLSA antenna can be achieved using air gap technique and will be a potential candidate for future point to point application for fixed broadband wireless access. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:938–944, 2014

The Performance Evaluation of IEEE 802.16 Physical Layer in the Basis of Bit Error Rate Considering Reference Channel Models

Fixed Broadband Wireless Access is a promising technology which can offer high speed data rate from transmitting end to customer end which can offer high speed text, voice, and video data. IEEE 802.16 WirelessMAN is a standard that specifies medium access control layer and a set of PHY layer to fixed and mobile BWA in broad range of frequencies and it supports equipment manufacturers due to its robust performance in multipath environment. Consequently WiMAX forum has adopted this version to develop the network world wide. In this paper the performance of IEEE 802.16 OFDM PHY Layer has been investigated by using the simulation model in Matlab. The Stanford University Interim (SUI) channel models are selected for the performance evaluation of this standard. The Ideal Channel estimation is considered in this work and the performance evaluation is observed in the basis of BER.

End-to-End Performance Analysis of Millimeter Wave Triple-Hop Backhaul Transmission Systems

Frequencies above 10 GHz nowadays may be employed either for backhaul networks of mobile communication access networks or for broadband fixed wireless access networks. Millimeter wave networks can afford large bandwidth by carrying the aggregate traffic through different network nodes. Consequently, many line-of-sight multi-hop transmissions may occur. At these frequency bands, rain attenuation is the dominant fading mechanism that aggravates the outage performance of these networks. The objective of this paper is the presentation of analytical models for the calculation of the end-to-end performance analysis of a triple-hop system with non-regenerative and regenerative relays using the trivariate lognormal distribution along with a physical model for the calculation of the correlation coefficients among the rain fading channels. Moreover, an accurate rain attenuation time series synthesizer based on multi-dimensional first order Stochastic Differential eqnarrays is employed in order to validate the analytical results. Finally, extended numerical results investigate the impact of various operational and geographical parameters, as well as the influence of the arbitrary position of the relays on the outage system performance.

Engineering analysis and economic evaluation of broadband fixed wireless access in developing country: wireless city in Thailand

The emergence of advanced broadband wireless access technologies has significantly increased choices, putting pressures on network operators to obtain the necessary information on which to base their investment decisions. This research focuses on the technological and economical assessments of WiMAX, in a specific developing telecommunications market. The study examines the economic feasibility, and presents a discussion of planning and characteristics of WiMAX technology. The study also explores a new engineering-economic analytical model for evaluating a WiMAX system in a prospective wireless city and demonstrates its real-world applicability using Bangkok as the case study. The results show that the service area, quality of network planning and amount of frequency bandwidth allocated to WiMAX technology strongly influence the network’s economic merit, making investment decisions in BFWA network highly dependent on them.

Experimental distribution functions for analysis of coherence bandwidth fluctuations for a fixed broadband wireless access system

In this study the authors propose three methods of analysis in order to develop an in-depth study of the temporal or spatial coherence bandwidth fluctuations in a real environment. Firstly, the authors review the classical coherence bandwidth (CB) estimation that offers constant single values under the assumption of an ergodic radio channel model. Secondly, the authors introduce the estimation of the experimental cumulative distribution function for CB as a method to characterise and parameterise the fluctuations that this frequency channel parameter can undergo in real environments where the ergodicity condition cannot be fully ensured. Finally, the authors estimate the probability distribution functions regarding the correlation level α in order to determine the operations quality to be expected of a specific channel bandwidth. The CB trial values are the result of experimental measurements conducted in diverse scenarios which used different antenna pattern and polarisations within the frequency band of 40 GHz. The proposed statistical analysis reveals important information about this channel parameter that can determine the accurate design and performance of a broadband system operating within this spectrum region; besides, this method can also be extrapolated to other frequencies.

Climate-Driven Fuzzy Inference System for Downlink Power Control in CDMA Millimeter Wireless Access Networks

Broadband Fixed Wireless Access (BFWA) systems operating at millimeter frequencies and using orthogonal direct sequence code division multiple access (DS-CDMA) have been proposed as an alternative technology for the enhancement of the network capacity. The major limiting factors of the capacity are the propagation phenomena (rain attenuation for frequencies above 10GHz) and intercell interference. Several power control schemes have been proposed to mitigate these factors and decrease the outage time. In this Letter we propose a new Climate-Driven Fuzzy Inference System for downlink power control with engineering inputs such as the rain induced attenuation on the wanted and the interfering links, the deterministic path loss and the clear-sky carrier-to-interference ratio. The proposed FIS scheme has different parameters based on the statistics of rain rate and is more energy efficient. Numerical calculations highlight the superiority of the proposed downlink power control compared to existing schemes.

Bit-Error Outage over SIMO Spatially Correlated Rain-Fading Channels [Wireless Corner

In this paper, a propagation model is presented for the bit-error outage probability (BEOP) in distributed single-input multiple-output (SIMO) correlated rain-fading channels. The general case of unbalanced spatial-diversity reception is considered. Such rain-fading channels usually represent terrestrial millimeter-wave line-of-sight (LOS) broadband fixed-wireless-access (BFWA) channels, operating at frequencies above 10 GHz. Useful numerical results regarding the validity of the proposed model are obtained to investigate the effects of spatial correlation and unequal diversity branch gains on the bit-error outage. The flexibility and global-scale applicability of the proposed propagation model for BEOP is also numerically demonstrated.

Equalization of rotationally variant signals

Several equalization algorithms utilizing the rotationally variant nature of the received signals are presented in this paper to combat the detrimental effect of intersymbol interference (ISI) introduced by frequency selective channels. Their adaptive implementations and application to a time-reversal space-time block coded (TR-STBC) system are also considered. In addition, a turbo equalization algorithm is derived for systems employing the error correction code. The proposed equalizers and turbo equalizer are evaluated over broadband fixed wireless access channels, and are shown to yield superior performance compared to the conventional equalization schemes.

A Comparison Study for the BER in Broadband Fixed Wireless Access Systems Based on Using M-QAM

An analytical model for the bit error rate with different values of M-ary quadrature amplitude modulation (M-QAM) for broadband fixed wireless access (BFWA) is presented. The expressions/relations are derived and investigated for different values of M: 4, 8, 16, 32, 64, 128, and 256 to evaluate conditional probability of error, bit error probability and average of the probability of error. The analyses are presented for coherent and non-coherent detection schemes and comparisons between their performances are given. The achieved results show that with keeping a fixed amount of symbols energy for all considered levels/symbols the degradation in BER is remarkable with low SNR with using non-coherent detection compared with utilizing coherent one for all M-ary values. Also, less power is needed in order to achieve the same BER with utilizing non-coherent detection method.

Computation of Bit-Error Rate of Coherent and Non-Coherent Detection M-Ary PSK With Gray Code in BFWA Systems

In this paper we examined the broadband fixed wireless access (BFWA) systems by coherent and non-coherent detection using M-ary PSK with Gray code. A closed form for the exact symbol error rate and bit error rate (BER) of M-ary PSK is presented. We show through analysis the physical limitations of the BFWA channels over different values of M (2,4,8,16,32) and the performance difference between the two type of detection (coherent and non-coherent).

Combined Dynamic Channel Simulator for High Capacity Broadband Fixed Wireless Access Systems

We present a time dynamic channel simulator for broadband fixed wireless access systems which properly combines earlier reported models for single degradation effects. The wideband model combines the effect of rain, scintillation, vegetation and multipath propagation. The objective is to specify the relationship between propagation effects and combine them to construct a comprehensive channel model suitable for designing fade mitigation techniques and evaluating system performance. The dynamics of rain attenuation is done using the Maseng-Bakken model. The multipath propagation is modeled using the geometrical based single bounce elliptical channel model. The spatial correlation between multipath taps during rain is incorporated using a space-time rain attenuation model. A lowpass filter which models the power spectral density of scintillation is used to describe the dynamic characteristics of scintillation. The signal fading due to swaying vegetation is described by utilizing a multiple mass-spring system to represent a tree and a turbulent wind model. In addition, numerical results under different combinations of propagation impairments are presented.

A FMIPv6 Based Handover Scheme for Real-Time Applications in Mobile WiMAX

The IEEE 802.16 standard was designed to provide rapid deployment, high bandwidth, and low-cost fixed broadband wireless access (BWA). As an enhancement, IEEE 802.16e standard was developed for further supporting mobility. As media streaming services are extending to mobile stations, it is crucial to minimize the handover delay and service disruption time so as to maintain the sustained connection of IP sessions. In this work, we propose a cross-layer IPv6 fast handover scheme which features integrated layer 2/layer 3 messages and fast network re-entry methods. Compared with the fast mobile IPv6 over 802.16e network scheme in predictive mode, our proposed scheme can reduce the service disruption time by more than 90% and 85% for downlink and uplink, respectively so that the quality of service (QoS) for real-time applications can be improved significantly.

Performance Evaluation of TV Over Broadband Wireless Access Networks

Worldwide Interoperability for Microwave Access is an emerging wireless access networks offering high data rates and good range. These features, in addition to moderate installation and maintenance costs, make it an appealing last-mile delivery network for IPTV and video applications, especially, in rural regions. However, TV/video delivery must be designed with respect to network characteristics in different environmental conditions. This paper studies the possibility of providing TV and video over the downlink and uplink of this fixed broadband wireless access network without compromising the video quality. The downlink scenario typically corresponds to offering high and standard definition IPTV to customer set-top box, whereas the uplink scenario can be for video surveillance or camera live broadcast. Measurements were taken using professional IPTV and video streaming equipments on commercial IEEE 802.16d system. Analysis was done for different video settings and network configurations in order to characterize network performance and identify video quality in different attenuation and interference conditions. A key outcome of this analysis was the feasibility of TV/video delivery over broadband wireless access networks with good quality of experience provided that system limitations are respected.

Planning of Efficient Wireless Access with IEEE 802.16 for Connecting Home Network to the Internet

The emergence of IEEE802.16 wireless standard technology (WiMAX) has significantly increased the choice to operators for the provisioning of wireless broadband access network. WiMAX is being deployed to compliment with xDSL in underserved or lack of the broadband network area, in both developed and developing countries. Many incumbent operators in developing countries are considering the deployment of WiMAX as part of their broadband access strategy. This paper presents an efficient and simple method for planning of broadband fixed wireless access (BFWA) with IEEE802.16 standard to support home connection to Internet. The study formulates the framework for planning both coverage and capacity designs. The relationship between coverage area and access rate from subscriber in each environment area is presented. The study also presents the throughput and channel capacity of IEEE802.16 in different access rates. An extensive analysis is performed and the results are applied to the real case study to demonstrate the practicality of using IEEE 802.16 for connecting home to Internet. Using empirical data and original subscriber traffic from measurement, it is shown that the BFWA with IEEE802.16 standard is a capacity limited system. The capacity of IEEE802.16 is related to different factors including frequency bandwidth, spectrum allocation, estimation of traffic per subscriber, and choice of adaptive modulation from subscriber terminal. The wireless access methods and procedures evolved in this research work and set out in this paper are shown to be well suited for planning BFWA system based on IEEE802.16 which supports broadband home to Internet connections.

Performance-complexity tradeoff of convolutional codes for broadband fixed wireless access systems

In this study, the authors investigate the performance-complexity tradeoff of convolutional codes for broadband fixed wireless access systems by considering the effects of quantisation and path metric memory in practical Viterbi decoding implementations. They show that in systems with limited antenna diversity, low-memory codes achieve a better error-rate performance compared to that of high-memory codes. Only in systems with considerable antenna diversity, can the performance of a convolutional code be improved by increasing its memory size. Nevertheless, the authors demonstrate that the coding advantage offered by the high-memory codes is not large enough to justify the significant increase in implementation complexity. In particular, memory-2 convolutional codes achieve a coding gain of up to 1.2 dB over their memory-8 counterparts in single-input single-output fixed wireless access systems. The situation is reversed when multiple antennas are used, but the decoder of memory-8 codes occupies at least 130 times more silicon area than that of memory-2 codes.

Adaptive terminal to base station assignment in BFWA systems

In point-multipoint systems the signal to interference plus noise ratio highly depends on the assignment of terminal stations (TS) to base stations (BS). The Broadband Fixed Wireless Access (BFWA) systems operate at high carrier frequencies. In this frequency range wave propagation is highly influenced by precipitation. Applying site diversity can mitigate rain attenuation effects. Present contribution provides a special site diversity method adopting genetic algorithm to adaptively optimize TS-BS assignments from point of view of the interference in BFWA service area. Rain events are generated with a Markov modeled simulation of the rain cell translations.

Controlling Intercell Interference in CDMA-based Fixed Wireless Networks Through Multirate Techniques

A number of research works have suggested a possible capacity advantage when employing direct sequence-code division multiple access (DS-CDMA) instead of the more common time division multiple access option for fixed broadband wireless access networks operating at millimeter-waves. The choice of this multiple access scheme, which, up to now, has not been foreseen by recent WiMax (worldwide interoperability for microwave access) standards, exhibits an improved performance in terms of cochannel interference in the upstream, even though it experiences higher interference in the downstream. The present paper focuses on enhancing the bottleneck downstream performance of fixed wireless networks by proposing a methodology for controlling the signal-to-interference ratio throughout the cell, so that all subscribers meet the given interference quality-of-service specifications. This is accomplished by exploiting the properties of a combination of multirate CDMA techniques. The paper describes a simple policy for code assignment, which is proved to be optimal, incorporating the effect of rain fading over multiple paths. The performance of the algorithm is tested against single code DS-CDMA both under long term channel statistics (static code assignment) and under dynamic channel effects (dynamic code assignment). The first test verifies the compliance of all sector subscribers with more demanding SIR specifications, while the second yields a significant improvement in terms of resource utilization.

Propagation Issues for Cognitive Radio

Cognitive radios are expected to work in bands below about 3.5 GHz and may be used for a variety of applications, e.g., broadband fixed wireless access, mobile and nomadic access, etc. Cognitive radio system designers must have access to a wide range of channel models covering a wide span of operating frequencies, carrier bandwidths, deployment conditions, and environments. This paper provides a comprehensive overview of the propagation channel models that will be used for the design of cognitive radio systems. We start with classical models for signal loss versus distance and discuss their dependence on the physical properties of the environment and operating frequency. Here we also introduce the concept of log-normal shadowing resulting from signal blockage by man-made and natural features. Next, we discuss the time-varying nature of the wireless channel, introduced as a result of the motion of objects in the channel. This is followed by a discussion on the dispersion of the signal caused by various effects of propagation, especially in the time and frequency domains. Angular dispersion, which is discussed next, is important because cognitive radios may be based on modems that exploit the spatial domain. Lastly, we summarize channel models that have been standardized for fixed and mobile systems.