Mobile Broadband Wireless Access Research Articles

Combined centralised and distributed mechanism for utilisation of node association in broadband wireless network

Mobile broadband wireless access system has the stations that might be fixed, nomadic or mobile. Regarding the mobility, the node association procedure is critical for network entry as well as network re-entry during handover. The flexibility and utilisation of MAC protocols scheduling have an important role. The standard provides the Partition Scheme as the scheduling mechanism which separates the allocation of minislots for scheduling. However, minislots cannot be flexibly reserved for centralised and distributed scheduling. In this paper we analysed the scheduling mechanism to improve the utilisation of minislots allocation during the exchange of MAC massages. The centralised and distributed scheduling is implemented in some topology scenarios. The result shows the proposed mechanism has better performance for node association than partition scheme.

Performance Evaluation of Low Density Parity Check (LDPC) Codes Over Gigabit Ethernet Protocol

Error Correcting Low density Parity Check codes enable the communication systems to have a low-power, reliable transmission over noisy channels and can achieve data rates very close to Shannon limit when iteratively decoded. They are used in many digital communication systems such as digital video broadcasting (DVB-S2), MIMO-WLAN (802.11n), WMAN (802.16e), mobile broadband wireless access (MBW A) (802.20) and have a very good error correcting performance over a variety of channels. In this paper we present a performance platform for simulation studies of of LDPC decoding algorithms. We present the results of the simulation studies of Bit Error Rate (BER) performance for various block length like 64 and 256 bytes frame over Additive White Gaussian Noise (AWGN) channel. The comparative studies are made for Log Domain and Log Doman Simple decoding algorithms.

Joint Timing Synchronization and Channel Estimation Using Perfect Sequence in Uplink Time Domain Synchronous OFDMA

AbstractTime Domain Synchronous Orthogonal Frequency Division Multiple Access (TDS-OFDMA) is used in mobile broadband wireless access scheme in uplink transmission. This leads to multiple user interference due to timing offset and frequency offset. In this paper, the effect of timing offset and channel estimation in mobile broadband system is analysed. Time-space two dimensional structure is used in TDS-OFDMA and perfect sequence is used for guard interval to achieve perfect timing synchronization and channel estimation for each user. Simulations are performed for timing synchronization and channel estimation using perfect sequence under Urban channel, Indoor Office B channel and HIPER LAN-A channel. Simulation results show that the timing synchronization is achieved and channel estimation performance using perfect sequence is better than CAZAC and PN Sequences.

Orthogonal frequency division multiple access downlink physical layer communication for IEEE 802.16‐2009 standard

Worldwide interoperability for microwave access (WiMAX) is a wireless broadband technology, which supports point to multi-point (PMP) broadband wireless access. WiMAX is basically a new shorthand term for IEEE Standard 802.16. This standard determines the air interface, including the medium access control layer and physical layer (PHY), of consolidated fixed and mobile point to-multipoint broadband wireless access frameworks offering numerous services. WiMAX PHY incorporates orthogonal frequency division multiplexing/orthogonal frequency division multiple access (OFDM/OFDMA) as the modulation technique in uplink as well as downlink. Hence, this study addresses OFDMA basics, OFDMA frame structure, OFDMA symbol, OFDMA PHY as per IEEE 802.16e-2009 standard. It also explains OFDMA time-division duplexing frame which consists of partial usage of subchannels and adaptive modulation and coding zones in the downlink from base station to two mobile stations (MS). The author analysed the system performance by reconfiguring different channels such as additive white Gaussian noise (AWGN), flat fading channel and multipath fading or frequency-selective channels. The impact of each channel on received signals (MS 1 and MS 2) is shown in figures and the corresponding values are noted in a table.

Channel quality map construction scheme using location information for heterogeneous wireless network

Heterogeneous wireless systems, such as a combination of mobile broadband wireless access (MBWA) and wireless local area network (WLAN), are candidates to achieve large capacity in next generation mobile communication systems. For capacity expansion, small cells of multiple wireless networks are deployed densely in these systems. Many cells overlap. Therefore, users must discover many cells at once for cell selection. Consequently, radio resources are used intensively for cell selection. Cell selection errors occur in dense small cell environments. As described herein, a channel quality map construction scheme using multi-Global Navigation Satellite System (GNSS) signals for heterogeneous wireless networks is proposed. The scheme uses positioning information and the average of signal strength for cell selection. Using positioning information, users can select cells which have a better channel quality quickly and easily. The proposed scheme is considered to be useful to optimize data traffic offloading in the heterogeneous wireless network. The 50 % user throughput and system throughput of the proposed scheme by comparison with the conventional scheme which uses measured instantaneous signal strength was studied. Computer simulation results show that the proposed scheme can improve the 50 % user throughput by 68 % in comparison with the conventional scheme. In addition, the system throughput is enhanced by 10 % compared with the conventional scheme. Furthermore, based on measured data, the positioning accuracy with multi-GNSS signals is a realizable level for the channel quality map construction scheme. This report describes the developed channel quality map construction scheme prototype system.

Modulation Aware Connection Admission Control and Uplink Scheduling Algorithm for Wimax Networks

Mobile WiMAX standard defines air interface for mobile broadband wireless access (BWA) systems and aimed to provide high data rate with seamless mobility while maintaining the quality of service (QoS). However, QoS of real-time applications depends on the link quality, which necessitate the channel-aware connection admission control (CAC) and scheduling schemes. In this paper Modulation aware CAC scheme and base station (BS) uplink scheduling algorithm are proposed to improve the system capacity and QoS performance respectively. The proposed CAC scheme aims to increase the admission of higher priority real time services by degrading the bandwidth of admitted lower priority connections on the basis of their channel status without deteriorating their QoS performance much. The performances of proposed algorithms are evaluated through simulation by considering the metrics like throughput, delay and number of connections admitted.

Personal mobile services

Ubiquitous information access through mobile devices has become a typical practice in everyday life. The mobile service paradigm shifts the role of mobile devices from consumers to providers, opening up new opportunities for a multitude of collaborative services and applications ranging from sharing personal information to collaborative participatory sensing. Although many basic principles of the standard Web service approach continue to apply, the inherent constraints of mobile devices and broadband wireless access render the deployment of the standard architecture in mobile environments inefficient. This paper introduced personal services, a user-centric paradigm that enables service-oriented interactions among mobile devices that are controlled via user-specified authorization policies. Personal services exploit the user's contact list (ranging from phonebook to social lists) in order to publish and discover Web services while placing users in full control of their own personal data and privacy. Experimental validation demonstrates the ability of personal services to foster a new generation of collaborative mobile services. Performance evaluation results show that the publication and discovery through contact lists are efficient and that service announcements and discovery requests can reach a huge number of users in a few seconds. Results also support a conclusion that resources-constrained devices can collaborate to carry out functionalities beyond the ability of their resources limitations.

Concurrent Scanning for High Quality Hand Over Support in Mobile WiMAX Networks

Mobile WiMAX is IEEE 802.16e standard established for mobile broadband wireless access (BWA). Mobility in WiMAX system is an important issue when the mobile station (MS) moves and be handover between base stations (BSs). This issue causes an unnecessary neighboring BS scanning and association, handover delay, and MAC overhead which may affect real-time applications.
 The MS movement direction prediction (MMDP) based MS scanning is used to reduce the number of scanning’s required in mobile WiMAX handover process. In this paper with reduction in number of scanning’s we propose to reduce the scanning delay required for evaluated two best target BSs by using concurrent scanning process. Network issues like ideal sectors in WiMAX 2 (IEEE 802.16m), network congestion and fast change in RSS are important parameters which can affect the QoS. With this proposed model we are able to provide the high quality hand over support in mobile WiMAX wherein we are able to solve the above stated network problems. Here on using the concurrent scanning process the authors are able to reduce the scanning delay by 40%. As a part of this paper, network layer parameters called routing protocols are analyzed for hand over support. This analysis shows an efficient routing protocol for real time application and the best effort service. This reviles that fisheye protocol is better to use for smaller network and LANMAR for the larger networks in real time application and IERP protocol is good for best effort services.

Measured Downlink Throughput Performance of MBWA System in Urban Area

This paper describes downlink throughput performances measured in a mobile broadband wireless access (MBWA) system field trial with Fast Low-latency Access with Seamless Handoff Orthogonal Frequency Division Multiplexing (FLASH-OFDM). The field trial results show that the downlink cell sizes are 0.4km2, 0.6km2, and 1.7km2 when the sector antenna heights are 19m, 58m, and 84m, respectively, assuming the following items. (1) The cell shape is circular. (2) The cell edge is defined as the location where the average downlink throughput is 1.5Mbit/s.

Simulation of IEEE 802.16e Physical Layer

Growth in technology has led to unprecedented demand for high speed Internet access. IEEE 802.16e (Mobile WiMAX) is a wireless communication standard with high data transfer rates and good performance. It not only is efficient as compared to its counterpart technologies today (Wi-Fi and 3G), but also lays the foundation for 4G mobile communication. In 4G wireless communication systems, bandwidth is a precious resource, and service providers are continuously met with the challenge of accommodating more users within a limited allocated bandwidth. To increase data rate of wireless medium with higher performance, Mobile WiMAX uses Orthogonal Frequency Division Multiple Access (OFDMA). This paper describes the simulation of the physical layer of IEEE 802.16e using Simulink in Matlab 7.0 (R2010a). The system performance is evaluated considering the Signal to noise ratio (SNR) and Bit error rate (BER) parameters. I. INTRODUCTION The world is passionately accepting the new wireless communication methods and services. The global demand for multimedia data services has grown at a remarkable pace which has led to the expansion of system capacity in terms of the number of subscribers supported, higher data rate and ubiquitous coverage with high mobility. Broadband wireless access (BWA) systems have evolved as the solution for the persistent demand of these multimedia services. The IEEE 802.16e air interface standard extends its fixed wireless access predecessor, IEEE 802.16-2004, to support mobile broadband wireless access systems. Mobile WiMAX (Worldwide Interoperability for Microwave Access), is a broadband wireless solution that enables wireless data over long distances in a variety of ways, from point-to-point links to full mobile cellular type access. It is a wireless digital communications system that is intended for wireless metropolitan area networks. This technology can provide broadband wireless access (BWA) up to 30 miles (50 km) for fixed stations, and 3 - 10 miles (5 - 15 km) for mobile stations upto 75mph. With WiMAX, WiFi-like data rates are easily supported, but the issue of interference is reduced. WiMAX operates on both licensed and non-licensed frequencies, providing a regulated environment and viable economic model for wireless carriers. IEEE 802.16e can operate in both Line-Of-Sight (LOS) and Non-Line-Of-Sight (NLOS) environments. In NLOS, the PHY specification is extended to 2-11 GHz frequency band which aims to fight with fading and multipath propagation. Mobile WiMAX physical layer is based on Scalable OFDMA technology to support variable channel bandwidth demand (1)-(5).

Performance of Turbo Product Code in Wimax

IEEE 802.16 is a standard for Broadband Wireless Access (BWA) air interface. 802.16e supports mobile broadband wireless access, which is an additional feature over its predecessors, which support fixed wireless access. Binary Convolutional Turbo Coding (CTC) is used as mandatory Forward Error Correction method in 802.16e. In this paper the performance of a simple and efficient optional coding scheme namely Turbo Product Code (TPC) is proposed for 802.16e system and is compared with CTC.

Dynamic Service Selection and Bandwidth Allocation in IEEE 802.16m Mobile Relay Networks

Cooperative relay network will be supported in IEEE 802.16m to improve the coverage and performance of mobile broadband wireless access service. In this paper, we jointly consider the problem of dynamic service selection and bandwidth allocation in IEEE 802.16m mobile relay networks. Specifically, the advanced mobile stations (AMSs) perform the selection of advanced base station (ABS) and transmission mode (i.e., direct transmission or relay-cooperation transmission) for a better service quality. The ABSs allocate the bandwidth for different transmission modes to maintain the desired queue level at base stations and user distribution for satisfying performance requirements. This problem is challenging when the strategies of both ABSs and AMSs influence each other and the decisions are made dynamically. To address this problem, a two-level dynamic game framework based on an evolutionary game and a differential game is developed. Since the mobile stations can adapt their strategies according to the received service quality, the dynamic service selection is modeled as an evolutionary game at the lower level. At the upper level, a differential game is formulated for a dynamic bandwidth allocation of base stations and a closed-loop Nash equilibrium is obtained as the solution. Viewing the fluctuation of traffic flow rate as disturbance, the robust bandwidth allocation strategy design is performed. Both stochastic optimal control and H_∞ optimal control approaches are adopted for average performance and worst-case performance design, respectively.

Dynamic radio resource and interference management for MIMO–OFDMA mobile broadband wireless access systems

A multi-user multi-cell Multiple-Input Multiple Output/Orthogonal Frequency Division Multiple Access (MIMO/OFDMA) system for next generation Broadband Wireless Access (BWA) networks is studied, in which the Base Station (BS) or evolved Node B (eNB) has only knowledge of the statistics of the channel. A combination of MIMO and OFDMA could increase the spectral efficiency in a high speed network. We investigate methods with scalable channel feedback and we analyze the trade off between the amount of Channel State Information (CSI) to the transmitter and the system performance. The proposed schemes with limited feedback are combined with other cell interference reduction strategies based on cooperation for improving the performance of a coordinated multi-cell system under very dynamic conditions like high velocity and fast fading. Simulation results demonstrate that substantial gain is obtained by the proposed schemes which take advantage of the statistical information of the highly dynamic channel.

Dynamically alternating power saving scheme for IEEE 802.16e mobile broadband wireless access systems

Power saving is one of the most important features that extends the lifetime of portable devices in mobile wireless networks. The IEEE 802.16e mobile broadband wireless access system adopts a power saving mechanism with a binary truncated exponent algorithm for determining sleep intervals. When using this standard power saving scheme, there is often a delay before data packets are received at the mobile subscriber station (MSS). In order to extend the lifetime of a MSS, the battery energy must be used efficiently. This paper presents a dynamically alternating sleep interval scheduling algorithm as a solution to deal with the power consumption problem. We take into account different traffic classes and schedule a proper sequence of power saving classes. The window size of the sleep interval is calculated dynamically according to the packet arrival rate. We make a tradeoff between the power consumption and packet delay. The method achieves the goal of efficiently reducing the listening window size, which leads to increased power saving. The performance of our proposed scheme is compared to that of the standard power saving scheme. Simulation results demonstrate the superior performance of our power saving scheme and its ability to strike the appropriate performance balance between power saving and packet delay for a MSS in an IEEE 802.16e mobile broadband wireless access system.

System modeling and performance analysis of the power saving class type II in BWA networks

For reducing the energy consumption of the Mobile Station in mobile Broadband Wireless Access networks, IEEE 802.16 offers three kinds of sleep mode operations called power saving classes type I, type II and type III. In order to investigate mathematically the inherent relationships between the performance measures and the system parameters, we propose in this paper a novel method for modeling the sleep mode with the power saving class type II in IEEE 802.16 and analyzing the performance of this sleep mode. Considering the attractive feature that some data frames can be transmitted during the listening state, we present a queueing model with two kinds of busy mechanisms to capture the working principle of the sleep mode operations with the power saving class type II. With the first and higher derivatives of the probability generating functions, we can give the averages and the standard deviations for the system performance using the diffusion approximation for the operating process of the system. We also propose methods for measuring the system performance in terms of the switching ratio, the energy saving ratio, and the average response time of data frames, as well as giving the expressions for these performance measures. Numerical results are provided with analysis and simulation to show the average performance measures, standard deviations and the cost function with different system loads. Moreover, we construct a cost function with the aim of determining the optimal time length of the sleep window to minimize the cost function.

Proposal of Heterogeneous Wireless Network with Handover in Application Layer: Feasibility Study Based on Field Trial Results

This paper proposes a heterogeneous wireless network with handover in the application layer. The proposed network requires no upgrade of wireless infrastructure and mobile terminals to convert the present homogeneous networks to the proposed heterogeneous network. Only installing application programs on the content server side and the mobile terminal side is required. The performance of the proposed network has been evaluated in a field trial using a mobile broadband wireless access (MBWA) air interface with wide coverage and a wireless local area network (WLAN) air interface with high throughput. The field trial results show that the maximum value of the handover outage time is only 170ms. The proposed heterogeneous wireless network is promising since both high throughput and wide coverage area are attained by a combination of the proposed handover scheme with the present homogeneous wireless networks.

Ultra-wideband planar inverted-F antennas with cut-etched ground plane

Improved bandwidth property of the planar inverted-F antenna (PIFA) is presented by using a cut-etcheded ground plane. A demonstration PIFA exhibits more than 100% bandwidth with resonance covering all wireless local area network frequencies and 2-6 GHz mobile broadband wireless access applications. It is shown that such an ultra-wideband PIFA will achieve nearly omnidirectional radiation pattern at 2.4/2.5 GHz, and mainly backward radiation at 3.8 GHz and 5.1-5.8 GHz.

A fast and efficient algorithm to exploit multi-user diversity in IEEE 802.16 BandAMC

Mobile broadband wireless access systems like IEEE 802.16/WiMAX use Orthogonal Frequency Division Multiple Access (OFDMA) in order to exploit frequency and multi-user diversity for improving the spectral efficiency. We assume in this work a two-stage approach for resource allocation, whereby scheduling of packets in a given time frame, and their allocation across different subcarriers and time slots, are carried out separately one after the other. We specifically focus on the allocation problem in the second stage. Our first contribution is a problem formulation which is based on a detailed system model close to a practical IEEE 802.16/WiMAX system using BandAMC. The problem is proved to be NP -complete. Secondly, we propose a heuristic allocation algorithm, called Maximum Regret Band Allocation, and show through an extensive numerical analysis that it is very effective in realistic scenarios, as well as so computationally efficient to be executed in times in the order of one millisecond.

Preamble design, system acquisition, and determination in modern OFDMA cellular communications: an overview

The wide choices of deployment parameters in next generation wireless communication systems, such as flexible bandwidth allocation, synchronous/ asynchronous modes, FDD/TDD, full/half duplex, and configurable cyclic prefix duration, etc., present significant challenges in preamble and system acquisition design. This article addresses these challenges, as well as the solutions provided by the next generation wireless standards, such as the IEEE 802.20 Mobile Broadband Wireless Access (MBWA) standard and the 3GPP LTE standard. The design facilitates the maximal flexibility of the system configuration and yet has low overhead, low acquisition latency, and low complexity. System acquisition and determination techniques are also discussed in detail.

Power-aware opportunistic downlink scheduling in IEEE 802.16 wireless networks

The IEEE 802.16 is a standard for fixed and mobile Broadband Wireless Access (BWA). In this paper, we deal with two key challenges of 802.16-based networks. First, terminals close to cell edge experience poor channel quality, due to severe path-loss and high interference from concurrent transmissions in nearby cells. To address this issue, we propose a framework based on a static partitioning of bandwidth into chunks with different transmission power levels. Terminals with impaired channel conditions can then benefit from being allocated a higher amount of transmission power than the others. Secondly, transmissions should be scheduled according to Quality of Service (QoS) requirements to keep users with real-time video or voice calls satisfied, while best-effort connections should fairly share the remaining capacity. To this aim, we propose a scheduling algorithm, called Power-aware Opportunistic Downlink Scheduling (PODS), that aims at meeting both the QoS and fairness requirements, while taking into account the different power levels of the bandwidth chunks. The performance of the proposed scheduler is assessed through detailed packet-level simulation in realistic scenarios and compared with well-known scheduling algorithms. Results confirm that PODS is able to exploit power boosting to provide real-time connections with the desired level of QoS, irrespectively of their MSs’ channel quality.