A Study on Development of Path loss Modelling Schemes and Coverage Analysis for a Broadband Wireless Access Network

Abstract

Worldwide interoperability for Microwave Access (WiMAX) recognized as a 4G wireless broadband access technology enables ubiquitous delivery of services such as voice, data and multimedia for fixed and mobile users. High data rate, simple network architecture, ease of installation, low cost, reliability etc., are the major advantages of this technology. Accurate planning as well as the proper deployment of this network is quite challenging and also link budget analysis is a prerequisite. Moreover precise path loss (PL) models are essential for coverage analysis study and accurate estimation of outage probability such that a trade-off between transmission power and adjacent frequency blocks interference can be possible. Hence frequency band has a major significance on the dimension and planning of the wireless network. So in consideration of above factors, this research study attempts on development of some empirical path loss models based on regression analysis for specific 2.63GHz and 2.65GHz WiMAX networks deployed in LOS and NLOS environments of nearby rural and suburban locations respectively. Several measurement campaigns are carried out for collecting appropriate received signal strength indicator (RSSI) as well as carrier to interference plus noise ratio (CINR) data in such network environments through experimental setups. Further, the link budget analysis and statistical characterization of proposed path loss are undertaken and compared with standard models. In order to enhance the accuracy of the predicted path loss models, the outlier removal algorithm is combined with regression technique. The efficiency of the proposed empirical path loss models is compared with the standard path loss models on the basis of goodness of fit parameters. Further, the coverage analysis of the WiMAX network employed in the considered measurement scenario is studied using the proposed path loss models. It is observed that due to overall path loss, shadowing and fading effects, the received signal strength at the cell edge is far more inferior compared to the threshold signal to noise ratio (SNR) required for establishing a reliable communication link. As the application of cooperative relaying are already being established by various researchers, this research work has suggested an improvised WiMAX framework incorporating cooperative relaying schemes. The standard amplify-forward (AF) relay protocol is incorporated to ensure the coverage extension for such network. Further, the impact of varying base station (BS) transmit power and height of receiver on cell coverage area are
discussed in detail. It has been observed that though the multirelay architecture improves the performance of wireless network by exploiting the diversity gain and has improved SNR at receiver, it suffers some key limitations like increased computational complexities at the BS, the requirement of precise time and frequency synchronization etc. So, this research work has further studied various effective relay selection algorithms in an IEEE 802.16j mobile multihop relay (MMR) WiMAX framework which outperform the existing schemes on the basis of symbol error rate (SER) and channel capacity. Detail analysis of both AF and decode forward (DF) relaying are carried out along with the standard diversity combining techniques such as maximal ratio combining (MRC) and selection combining (SC) etc. Further, this research work proposes modified relay selection schemes such as threshold based max-min and threshold based harmonic mean of SNR which have been employed for various combinations of relay-diversity combining techniques (i.e. AF-SC, AF-MRC, DF-SC and DF-MRC). The performance of this network utilizing the proposed relay selection algorithms is analysed for these hybrid schemes. In addition, the impacts of varying the relay locations on the performance metrics are demonstrated through MATLAB based simulation study. Reliable communication with peak data rate in high mobility scenarios such as high speed railway (HSR) and vehicles are expected to be the major challenges for upcoming 5G wireless network. So, this research work has attempted to verify the suitability of this broadband access technology for HSR communication with enhanced network coverage in diverse terrain scenarios. It is observed through performance analysis that the proposed relay reinforced WiMAX network has the potential to be utilized for improving the proficiency of HSR communication service.