Mobile Broadband Wireless Access Systems 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.

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.

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).

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.

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.

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.

A low complexity two dimensional differential demodulation for OFDM systems

Abstract A novel two dimensional differential demodulation (2D DD) is investigated, which exploits both the time and the frequency dimensions using the orthogonal frequency division multiplexing (OFDM) frame structure. Without changing the transmitter, the proposed 2D DD based on graph attempts to search for a more confident bypass, probably containing multiple DD operations. Simplified soft decision metrics of the amplitude ratio and phase difference are derived by making use of a Gaussian approximation. Two optimal path searching algorithms, based on depth-first search (DFS) and breadth-first search (BFS) respectively, are brought up and analyzed in details. Moreover, a random access memory (RAM) method is combined with DFS and BFS to further simplify the optimal path searching algorithms for a small maximum path length. Taking the 64-differential amplitude and phase shift keying (64-DAPSK) modulation scheme for example, simulation results show that the proposed 2D DD can obtain substantial performance gains with reasonable computational complexity. Among the four optimal path searching algorithms, BFS-RAM algorithm is the most potential one for practical applications with its ability of parallel computation. In addition, 2D DD is advantageous to withstand the Doppler effect, which is hence suitable for high mobile broadband wireless access systems.

End-to-End Security Protection

The IEEE 802.16 standard (mobile broadband wireless access system), which is also known as worldwide interoperability for microwave access (WiMAX), is one of the latest technologies in the wireless world. The main goal of WiMAX is to deliver wireless communications with quality of service (QoS) guarantees, security, and mobility. In this article, we have evaluated the performance of the Internet Protocol security (IPSec) over WiMAX networks. We have also illustrated the results of the simulations. We have also depicted the processing time and the throughput introduced when IPSec is applied over WiMAX technology (IEEE 802.16).

Opportunistic packet scheduling algorithm for non-real-time service with a soft QoS requirement in a mobile broadband wireless access system

In this paper, we present a packet scheduling algorithm for a non-real-time service, with soft QoS requirements, which allows for degrading the QoS level, e.g., typically the packet delay, whenever necessary, in mobile broadband wireless Internet access systems. This algorithm is designed to properly trade off system throughput and delay performance, which can improve the system capacity by relaxing the delay constraint with respect to the underlying soft QoS requirement. This is as opposed to most of the existing packet scheduling algorithms for non-real-time service which are simply designed to maximize the system throughput without a delay constraint. The proposed adaptive exponential scheduling algorithm intentionally introduces additional delay to some users, especially under bad channel conditions, opportunistically allowing for serving users only under good channel conditions, as long as the resulting QoS degradation is acceptable for non-real-time service users. The results from a system-level simulation demonstrate that the system capacity can be significantly increased over existing algorithms, by as much as 65%, using the adaptive exponential scheduling algorithm while satisfying the given QoS-level requirements.

Adaptive delay threshold-based priority queuing scheme with opportunistic packet scheduling for integrated service in mobile broadband wireless access systems

In this letter, we propose a novel method of implementing an opportunistic priority queuing scheme that supports both latency-sensitive real-time (RT) and best-effort non-realtime (NRT) service classes in mobile broadband wireless (MBWA) systems. It employs an adaptive delay threshold as a dynamic reference of prioritizing the urgent RT service users over others, which allows for fully leveraging the multiuser diversity gain of NRT service users under the varying system conditions. It is shown that the overall system capacity can be further increased by the proposed adaptation rule, as compared with the existing opportunistic priority queuing scheme with the fixed delay threshold.

QoS Management and Control for an All‐IP WiMAX Network Architecture: Design, Implementation and Evaluation

The IEEE 802.16 standard provides a specification for a fixed and mobile broadband wireless access system, offering high data rate transmission of multimedia services with different Quality‐of‐Service (QoS) requirements through the air interface. The WiMAX Forum, going beyond the air interface, defined an end‐to‐end WiMAX network architecture, based on an all‐IP platform in order to complete the standards required for a commercial rollout of WiMAX as broadband wireless access solution. As the WiMAX network architecture is only a functional specification, this paper focuses on an innovative solution for an end‐to‐end WiMAX network architecture offering in compliance with the WiMAX Forum specification. To our best knowledge, this is the first WiMAX architecture built by a research consortium globally and was performed within the framework of the European IST project WEIRD (WiMAX Extension to Isolated Research Data networks). One of the principal features of our architecture is support for end‐to‐end QoS achieved by the integration of resource control in the WiMAX wireless link and the resource management in the wired domains in the network core. In this paper we present the architectural design of these QoS features in the overall WiMAX all‐IP framework and their functional as well as performance evaluation. The presented results can safely be considered as unique and timely for any WiMAX system integrator.

Packet Scheduling Algorithm Considering a Minimum Bit Rate for Non-realtime Traffic in an OFDMA/FDD-Based Mobile Internet Access System

In this letter, we consider a new packet scheduling algorithm for an orthogonal frequency division multiplexing access/frequency division duplex (OFDMA/FDD)-based system, e.g., mobile broadband wireless access or high-speed portable internet systems, in which the radio resources of both time and frequency slots are dynamically shared by all users under a proper scheduling policy. Our design objective is to increase the number of non-realtime service (e.g., WWW) users that can be supported in the system, especially when the minimum bit rate requirement is imposed on them. The simulation results show that our proposed algorithm can provide a significant improvement in the average outage probability performance for the NRT service, i.e., significantly increasing the number of NRT users without much compromising of the cell throughput.