Mobile WiMAX System Research Articles

Optimize Transmission of Image over Integrated Mobile WiMAX and WiLAN Network

The problem of multiuser downlink resource allocation in Mobile WiMAX system was studied. Three different network scenarios considered for the transmission of image data. Resource allocation is done using Active Set Optimization and Genetic Algorithm, for all the three network scenarios. Simulation results show that information fed back and association among subcarriers play vital role to improve system performance. As compared to reduced complexity, resource allocation using Active Set Optimization and Genetic Algorithm seems especially attractive as the number of users increases for Image Data. It is observed through simulation that the System using Genetic Algorithm performs better than Active Set. Linear Resource Allocation in terms of significantly decreasing the computational complexity and achieve higher capacities, while being applicable to a more general class of systems. As Genetic Algorithm follows constraints of Stochastic processes it didn’t give results highest in all Experiment Conducted. It is also observed that for Integer-Binary Objective function Performance of Genetic Algorithm is not that much satisfied because of its stochastic processing. Also processing time required to reach final optimize variables values is too much.

A Review of Physical Layer of Mobile WiMAX System and OFDM

A Review of Physical Layer of Mobile WiMAX System and OFDM

Implementation of a Regional Spectrum Sensing Based Cognitive Radio System for Digital TV White Space

ABSTRACTIt is well-known that cognitive radio (CR) is a fundamental solution to mitigate the spectrum scarcity of today's wireless communication systems. For the realization of CR, there are many obstacles to resolve, including technical and policy perspectives. Since CR is a very sensitive technology, it is particularly important to test the scheme with appropriate operation in a real environment. In this regard, we have developed a testbed of a regional spectrum sensing based CR system for digital TV (DTV) white space. The developed system has a centralized spectrum sensor, and according to the sensing results, mobile WiMAX system provides high quality multimedia service through the spectrum hole in DTV band. There is also a fast frequency hopping capability depending on the sensing results to minimize interference to the actual licensee, the primary DTV system. The performance analysis shows that the developed CR system has excellent performance satisfying the IEEE 802.22 requirements, and is suitable for use in the real environment.

A Review of Physical Layer of Mobile WiMAX System and OFDM

A Review of Physical Layer of Mobile WiMAX System and OFDM

A symmetric key-based pre-authentication protocol for secure handover in mobile WiMAX networks

Providing secured and seamless service is one of the most important aspects of mobile networks, particularly for mobile WiMAX systems. However, the long delay handover schemes brought by the time-consuming EAP-based authentication may cause service disruption when a mobile WiMAX user moves between the coverage areas of different base stations. In this paper, we propose a handover scheme using symmetric key cryptography and pre-authentication approach to shorten the delay while ensuring high security level for Mobile WiMAX handover. The scheme is proven by BAN logic to achieve the security goals of an authentication scheme. A performance analysis is also carried out to show the effectiveness of this scheme in reducing handover delay and saving computational resources.

Computer Simulation and Field Experiment for Downlink Multiuser MIMO in Mobile WiMAX System.

The transmission performance for a downlink mobile WiMAX system with multiuser multiple-input multiple-output (MU-MIMO) systems in a computer simulation and field experiment is described. In computer simulation, a MU-MIMO transmission system can be realized by using the block diagonalization (BD) algorithm, and each user can receive signals without any signal interference from other users. The bit error rate (BER) performance and channel capacity in accordance with modulation schemes and the number of streams were simulated in a spatially correlated multipath fading environment. Furthermore, we propose a method for evaluating the transmission performance for this downlink mobile WiMAX system in this environment by using the computer simulation. In the field experiment, the received power and downlink throughput in the UDP layer were measured on an experimental mobile WiMAX system developed in Azumino City in Japan. In comparison with the simulated and experimented results, the measured maximum throughput performance in the downlink had almost the same performance as the simulated throughput. It was confirmed that the experimental mobile WiMAX system for MU-MIMO transmission successfully increased the total channel capacity of the system.

Giải pháp sử dụng bộ lọc thích nghi Kalman cho hệ thống ước lượng kênh truyền WiMAX di động

Mobile WiMAX (Worldwide Interoperability for Microwave Access) system has been recently applied widely in wireless communication systems [1]. WiMAX uses OFDM (Orthogonal Frequency Division Multiplexing) as a technical platform because of high spectral efficiency [2]. In this paper, the channelestimation algorithms were studied for OFDM system for mobile WiMAX. The comb-pilot structure was usedfor channel estimation algorithms. We proposed algorithms of channel estimation based on two adaptive filters: Kalman and Extended Kalman, Thesealgorithms were compared with popular LS (Least Square) estimator. The simulation results showed that Estimators based on Kalman Filters had performance improvement in slow fading condition with low Doppler shift and limited quality in fast fading condition with high Doppler shift.

A testbed‐based framework for performance evaluation of multicast broadcast systems in OFDMA networks

AbstractMulticast Broadcast Service (MBS) applications can efficiently reduce the usage of network resources, still providing mobile users with real‐time high‐quality content. MBS capabilities are usually implemented by using a single frequency network; moreover, new features, such as connection identifier for broadcast/multicast messages and other MBS‐enabled descriptors, are added to cope with already existent entities and services. With the intention to optimize performances and verify the on‐field feasibility, we propose an MBS approach to Orthogonal Frequency Division Multiple Access systems based on superposition coding (SPC). Because MBS features have a large impact in the architectural design of the network protocols, an integrated framework is mandatory to speed up the system simulation, verification, and redesign steps. This paper shows the design of an experimental testbed for performance evaluation of SPC‐enabled physical (PHY) and medium access control (MAC) layers over Mobile WiMAX systems. In addition, it proposes some architectural modifications of the WiMAX protocols, by exploiting its core network capabilities. The experimental results obtained from the testbed confirm that augmented throughput capabilities can be achieved by SPC‐enabled PHY/MAC layers. However, to fully exploit the additional available throughput, an integrated framework must be adopted to evaluate the protocol modifications for the MBS‐enabled entities. Copyright © 2014 John Wiley & Sons, Ltd.

Performance Evaluation of Physical Layer of Mobile WiMAX System by Implementing Hybrid Channel Coding Scheme

The demand of wireless communication is high data rate along with error free communication. An error in communication can be reduced by employing proper channel coding techniques. In this paper, authors have proposed the hybrid channel coding scheme in which convolution codes and turbo codes are combined to perform together. This scheme helps to provide smooth communication with high data rate even under different channel conditions. The SNR is the threshold parameter for adaptive encoding which can be measured by the channel estimation techniques for mobile WiMAX system. Authors have also taken efforts for adding adaptive code rate and modulation schemes for optimizing the mobile WiMAX system. Use of proper adaptive coding for optimizing the performance of mobile WiMAX system can be achieved. For this newly introduced hybrid scheme, the analysis and simulation are carried out with respective to standard AWGN channel which shows improved Bit Error Rate performance and also overcomes the drawbacks such as high complexity, decoding delay and power requirement.

Mobile WiMAX Network Planning and Optimization

 Abstract—Software suitable for estimating Mobile WiMAX capacity in network planning and optimization is presented. The implementation of the software is based on analytical method to evaluate IEEE 802.16e Mobile WiMAX system's capacity, throughput and a traffic model for mixed application users. Various Overheads that impact the capacity of the system are analyzed. A step by step description of the analysis is made and a flow chart for the determination of available bandwidth and maximum number of users supported is presented. Based on the description of the flow chart, a program in java language that implemented the entire analysis is written. A simulation of the software is used for the determination of the maximum number of subscribers that each specific Mobile WiMAX sector can support. This would help service providers to plan and implement a wide coverage network in a city. The proposed analytical method and software program will enable service providers to estimate the number of base stations that can be deployed in a given area. Thus the network investment, profitability and avoidance of future network congestion can be evaluated and estimated.

Capacity Analysis and Simulation for Mobile WiMAX System in Distributed Subcarrier Permutation Modes in a Proposed Channel

In this paper, capacity analysis for mobile WiMAX working in distributed subcarrier permutation modes is investigated mathematically depending on the physical layer simulation results. These simulation results of physical layerdispose exact values for the number of best burst profiles that candidate to carry Medium Access Control (MAC) payload in a proposed ITU-R mixed user channel. The complete simulation model for physical and MAC layers has been made using OPNET 14.5 to validate the analytical resultsof the obtained capacity. This approach for capacity analysis based on simulation results is proposed to overcome the lack of interests by other researches in the significant influence of the physical layer constraints on the MAC layer capacity calculations. As well as in this paper,a proposed ITU-R mixed user channelis performed to suit the high mobility users involved under distributed subcarrier permutation modes. Moreover, this paper focused on the exact overhead calculations by taking into account all the significant overhead parameters in the MAC layer frame structure that affects the overall system capacity. Keywords IEEE802.16e-2005, OFDMA, PUSC, FUSC, QoS, proposed ITU-R mixed user channel model, PER.

The Analysis of Mobile WiMAX and LTE using MIMO technique

A quality of service is a fundamental component of the 4G broadband network for satisfactory service delivery by evolving internet application to end user, and managing the network resources. The 4G technology has emerged one of the most fruitful technologies as it supports large number of applications including VOIP, video conferencing, file transfer, video streaming and web browsing. IEEE 802.16E, IEEE 802.16M and LTE along with various application and QoS requirement also support Multiple-Input-multiple-output (MIMO) techniques including Spatial Multiplexing (SM), Space Time Block Coding(STBC) and Eigen Beam-forming (BM).In the paper we will study Physical, MAC layer of WiMAX and LTE. We will also study MIMO techniques. In this paper  the detailed study of the throughput for a MIMO mobile WiMAX system and LTE under two different PHY PER QoS threshold. Various modulation and channel coding techniques have been applied.

Mobile Station Movement Direction Prediction (MMDP) Based Handover Scanning for Mobile WiMAX System

Mobile WiMAX is a broadband technology that is capable of delivering triple play services (voice, data, and video). However, mobility in mobile WiMAX system is still an issue when the mobile station (MS) moves and its connection is handed over between base stations (BSs). In the handover process, scanning is one of the required phases to find the target BS. During the handover scanning process, the MS must synchronize with all the advertised neighbour BSs (nBSs) to select the best BS candidate for the incoming handover action. Without terminating the connection between the SBS and MS, the SBS will schedule the scanning intervals and sleep-intervals (also called interleaving interval) to MS for the handover scanning. However, during the scanning interval period, all the coming transmissions will be paused. Therefore, the redundant or unnecessary scanning of neighbouring BS cause delay and MAC overhead which may affect real-time applications. In this paper, the MS movement direction prediction (MMDP) based handover scanning scheme is introduced to overcome the mobile WiMAX handover scanning issue. It based on dividing the BS coverage area is into zones and sectors. According to the signal quality; there are three zones, no handover (No-HO), low handover (Low-HO) and high handover (High-HO) zones respectively and six sectors. In this scheme, only two BSs can become candidates; the two that the MS moves toward them will be chosen as the candidate for the handover scanning purpose. Hence, the handover scanning process repetition will be reduced with these two shortlisted BS candidates instead of scanning all nBSs. Thus, MMDP will reduce scanning delay and the number of exchange messages during the handover scanning comparing to the conventional scanning scheme. Although, the MMDP may need an extra computational time, the prediction and scanning process will be finished before the MS reach the High-HO zone, which mean the end-user's running application will be affected. Simulation results show that the proposed MMDP scheme reduces the total handover scanning delay and scanning interval duration by 25 and 50 % respectively. Also, the size of scanning message is reduced, which leads to reduced signalling overhead.

Effect of Physical Layer Limitations on the MAC Layer Capacity of Mobile WiMAX System, Analysis and Simulation

this paper, the effect of physical layer limitations on the MAC layer capacity of mobile WiMAX system is analyzed mathematically. The downlink physical layer simulation results show the best burst profiles for a mobile WiMAX system working in a multipath fading channel under the Quality of Service (QoS) requirements for video streaming applications. The capacity mathematical results are obtained based on the physical layer constraints after discarding the MAC layer overheads. Then, a complete simulation model for physical and MAC layers are built to validate the capacity analytical results. The simulation results show a good degree of convergence between the analytical and simulation capacity results. Also, the results show that the maximum number of users that can be served instantaneously by the BS are different depends on the used distributed subcarrier permutation mode. KeywordsWiMAX, physical layer, MAC layer, PUSC, FUSC, ITU-R mixed users channel model, QoS.

A Combined Algorithm of Kalman Estimator and Guard Interval Optimization for Mobile WiMAX

Mobile WiMAX (Worldwide Interoperability for Microwave Access) system has been recently applied widely in wireless communication systems. In this paper, the channel estimation algorithms were studied for the mobile WiMAX system. The comb-type pilot was used for channel estimation algorithms. The authors proposed an adaptive algorithm of channel estimation based on Kalman filter which had good performance in fading channels. Then, based on the result of channel estimation, we proposed an advanced algorithm of GI (Guard Interval) optimization. The results showed that the Kalman estimator combined with GI optimization algorithm showed the best performance in this paper. This algorithm was verified by computer simulation.

Performance analysis of VoIP services in mobile WiMAX systems with a hybrid ARQ scheme

This paper analyzes the performance of voice-over-Internet protocol (VoIP) services in terms of the system throughput, the packet delay, and the signaling overhead in a mobile WiMAX system with a hybrid automatic repeat request (HARQ) mechanism. Furthermore, a queueing analytical model is developed with due consideration of adaptive modulation and coding, the signaling overhead, and the retransmissions of erroneous packets. The arrival process is modeled as the sum of the arrival rate at the initial transmission queue and the retransmission queue, respectively. The service rate is calculated by taking the HARQ retransmissions into consideration. This paper also evaluates the performance of VoIP services in a mobile WiMAX system with and without persistent allocation; persistent allocation is a technique used to reduce the signaling overhead for connections with a periodic traffic pattern and a relatively fixed payload. As shown in the simulation results, the HARQ mechanism increases the system throughput as well as the signaling overhead and the packet delay.

Impact of Downlink Distributed and Adjacent Subcarrier Permutation Modes on the Performance of Mobile WiMAX System in ITU-R Ped. B Channel with Obtaining Optimum Cyclic Prefix

Mobile WiMAX is one of the candidate technologies for 4G wireless systems, promising high data rates and affluent multimedia services. The mobile WiMAX standard (IEEE802.16e-2005)is based on Orthogonal Frequency Division Multiple Access (OFDMA), which allows a very efficient use of bandwidth in a wide frequency range, this is due to the fact that OFDMA uses multi-channel OFDM approach and provides subcarrier access in the time and the frequency domains. In this paper the impact of downlink distributed (FUSC, PUSC) and adjacent (AMC) subcarrier permutation modes used in mobile WiMAX system are investigated using simulation under various modulation and coding schemes (link speeds)with the support of optimum value of the Cyclic Prefix (CP) for the OFDMA symbol duration. The results are expressed in terms of the maximum achievable throughput and operating distance from base station in pedestrian multipath fading channel (ITU-R Ped. B at 3Km/h speed) under a UDP-based application (video streaming), which is the proper application for multimedia services. The results show the optimum cyclic prefix valve for the FUSC, PUSC and AMC subcarrier permutation modes to achieve the best system performance, also the results show differences in PER performance atvarious modulation and coding schemes for the three subcarrier permutation modes (FUSC, PUSC and AMC). These differences in performance are exploited in the present work to show the best threshold SNR to switch from link speed to another link speed in terms of throughput and operating distance. Key words: IEEE802.16e-2005, OFDMA, FUSC, PUSC, AMC, ITU-R Ped. B channel, PER.

An Effective Approach to Contention Based Bandwidth Request Mechanism in WiMAX Networks

In this paper the IEEE 802.16 standard based Mobile WiMAX (Worldwide Interoperability for Microwave Access) system is investigated for the purpose of Quality of Service provisioning. As a potential solution, scheduling algorithms have been taken into major concern. Within the pool of scheduling algorithms and for the purpose Contention based bandwidth request resolution, the Modified Contention Based BW Resolution algorithm (MCB-BWR-Scheme) is proposed. Supported by the fact that the standard does not emphasize a specific scheduling algorithm for contention period based services, therefore, the choice of the scheduling algorithm for the WiMAX systems is very important. There are several scheduling algorithms for WiMAX in the literature, however, studies show that an efficient, fair and robust scheduling algorithm for WiMAX systems is still an open research area and hence a well thought out algorithm will be of great contribution to the area under investigation. Results from the OPNET Modeler simulation program show that the adjusted algorithm works well with delay and throughput constraints. It is also in consistent with the quality of service demands of the video and voice traffic.

On the peak-to-average power ratio reduction in mobile WiMAX: A discrete cosine transform matrix precoding based random-interleaved orthogonal frequency division multiple access uplink system

Mobile worldwide interoperability for microwave access (Mobile WiMAX) is a broadband wireless solution that enables the convergence of mobile and fixed broadband networks through a common wide area radio-access (RA) technology and flexible network architecture. Since January 2007, the IEEE 802.16 working group (WG) has been developing a new amendment of the IEEE 802.16 standard i.e. IEEE 802.16m as an advanced air interface to meet the requirements of ITU-R/IMT-Advanced for 4G systems. The mobile WiMAX air interface adopts orthogonal frequency division multiple access (OFDMA) as multiple access technique for its uplink (UL) and downlink (DL) to improve the multipath performance. All OFDMA based networks, including mobile WiMAX experiences the problem of high peak-to-average power ratio (PAPR). This paper presents: Discrete-Cosine transform matrix (DCTM) precoding based random-interleaved OFDMA uplink system and selecting mapping (SLM) based DCTM precoded random-interleaved OFDMA uplink system respectively, for PAPR reduction in mobile WiMAX systems. PAPR of the proposed systems is analyzed with the root-raised-cosine (RRC) pulse shaping to keep out of band radiation low and to meet the transmission spectrum mask requirement. Simulation results show that, the proposed systems have low PAPR than the Walsh-Hadamard transform (WHT) precoded random-interleaved OFDMA uplink systems and the conventional random-interleaved OFDMA uplink systems. Symbol-error-rate (SER) performance of the proposed system is also better than the conventional random-interleaved OFDMA uplink systems and at par with WHT based random-interleaved OFDMA uplink systems. Good improvement in PAPR and SER offered by the proposed systems can notably reduce the cost and complexity of the transmitter.

간섭 상쇄 기법과 장기 누적 기법을 이용한 WiBro 지상파 측위 시스템의 가청성 향상

Abstract: Together with the GPS-based approach, geolocation through mobile communication networks is a key technology for location-based service. Since the Mobile WiMAX system is considered as a candidate for fourth-generation mobile systems, it is important to investigate its location capability. The geolocation of Mobile WiMAX can be realized when the preamble symbols in the down-link channel are appropriately used for a TDOA (Time-Difference-of-Arrival) approach. However, the cellular structure of Mobile WiMAX inevitably generates co-channel interference, and it is difficult for the mobile terminal to acquire distance measurements from multiple base stations. Therefore, for geolocation via multilateration using the Mobile WiMAX network, it is very important to increase hearability. This paper proposes a geolocation method for Mobile WiMAX which employs interference cancellation and preamble signal overlapping for the enhancement of hearability. A novel interference cancellation strategy for complex-valued Mobile WiMAX signals is presented which has an iterative structure. Simulation results show that the proposed geolocation method provides the user’s position with an accuracy of less than 20 m through the Mobile WiMAX cellular network if there is no multi-path or NLOS (None-Line-of-Sight).Keywords: WiBro, geo-location, interference cancelation