BWA Networks Research Articles

Enhanced Call Admission Control based on History in BWA Networks

WiMAX is a wireless technology that supports many blooming applications. To efficiently assign resources to traffic flows, bandwidth allocation and Connection Admission Control (CAC) modules are included in MAC layer and Burst Allocation (BA) module is added to PHY layer. It is essential to lessen delay and effectively schedule requests for BA. In this paper, CAC-based on History (CACH) and scheduler based on Delay Tolerance (SDT) for BA are proposed for WiMAX networks. CACH accepts/ rejects connections based on values in Contention Window (CW) in former Time Frame (TF). SDT and a Bucket-based BA (BBA) assign resources to flows with least amount of DT. Performance is analyzed based on throughput, Packet Loss Ratio (PLR) and delay. Index Terms: WiMAX, Contention Window, Contention Delay, Delay Tolerance, Traffic Priority, Connection Admission Control, Burst Allocation

Reducing Phase Offset Using Novel Adaptive Cyclic Prefix Based Adaptive Sub Block Correlation for BWA Networks

In this paper, a generic approach has been developed for the reduction of phase offset in BWA networks considering a novel Adaptive Cyclic Prefix (ACP) and Adaptive Sub Block (ASB) correlation computation for both WiMAX and LTE networks. The successive design steps along with practical assumptions and mathematical derivations are incorporated in developing the ACPASB algorithm. In comparison to the conventional Fixed Sub Block (FSB) mechanism, the ACPASB algorithm improves the correlation among the subcarriers by drastic reduction of phase offset, leading to maximum removal of Inter Symbol Interference (ISI). The index for reduction of phase offset is evaluated in terms of increased estimated correlation factor (η) for which the correlation threshold (ηth) has been determined using Pearson Product Moment formula and specific degree of freedom (df). Estimated ηth serves as an indicator of maximum ISI free region. The estimation of phase offset is accomplished by the measurement of Error Vector Magnitude (EVM) and Relative Constellation Error (RCE) with the help of Vector Signal Analyzer (VSA) incorporated in the model of WiMAX/LTE transceiver. The data transmission with such minimum ISI, guarantees the selection of highest order modulation and coding scheme (64-QAM (3/4)) even under severe degradation of the channel in a typical BWA network. It has alsobeen observed that even under severely fading channel, the selection of dynamic sub-block length inherently delivers a substantially good Raw Data Rate (RDR) under 64-QAM (3/4) modulation. Complexity analysis and simulation results show that ACPASB scheme outperforms ACPFSB thereby saving design turnaround time significantly.

QoS Aware Integrated Call Admission and Cognitive Channel Allocation Scheme for A Macro-Femto BWA Network

QoS Aware Integrated Call Admission and Cognitive Channel Allocation Scheme for A Macro-Femto BWA Network

Load Balancing with Reduced Unnecessary Handoff in Energy Efficient Macro/Femto-Cell Based BWA Networks

The hierarchical macro/femto cell based BWA networks are observed to be quite promising for mobile operators as it improves their network coverage and capacity at the outskirt of the macro cell. However, this new technology introduces increased number of macro/femto handoff and wastage of electrical energy which in turn may affect the system performance. Users moving with high velocity or undergoing real-time transmission suffers degraded performance due to huge number of unnecessary macro/femto handoff. On the other hand, huge amount of electrical energy is wasted when a femto BS is active in the network but remains unutilized due to low network load. Our proposed energy efficient handoff decision algorithm eliminates the unnecessary handoff while balancing the load of the macro and femto cells at minimal energy consumption. The performance of the proposed algorithm is analyzed using Continuous Time Markov Chain (CTMC) Model. In addition, we have also contributed a method to determine the balanced threshold level of the received signal strength (RSS) from macro base station (BS). The balanced threshold level provides equal load distribution of the mobile users to the macro and femto BSs. The balanced threshold level is evaluated based on the distant location of the femto cells for small scaled networks. Numerical analysis shows that threshold level above the balanced threshold results in higher load distribution of the mobile users to the femto BSs.

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.

An integrated buffer management strategy for the TDD mode in IEEE 802.16 BWA networks

Considering IEEE 802.16 networks having different types of service flows, in this paper, we propose a rearranging scheme of a two-tier hierarchy for the TDD mode in IEEE 802.16 broadband wireless access networks to dynamically adapt to the traffic burstiness according to the change of instant buffers on buffer management. We demonstrate the performance improvement of the rearranging scheme in terms of accumulated throughput and fairness in the finite buffer case compared with the fixed rule by simulations. The simulation results show that the proposed scheme in the case of finite buffer depth not only can provide much better fairness and achieve higher accumulated throughput but also is less buffer-consuming than that without rearranging, meaning that the hardware cost can be reduced by employing the proposed scheme.

Adaptive QoS provision for IEEE 802.16e BWA networks based on cross-layer design

This article proposes an integrated framework for adaptive QoS provision in IEEE 802.16e broadband wireless access networks based on cross-layer design. On one hand, an efficient admission control (AC) algorithm is proposed along with a semi-reservation scheme to guarantee the connection-level QoS. First, to guarantee the service continuity for handoff connections and resource efficiency, our semi-reservation scheme considers both users' handoff probability and average resource consumption together, which effectively avoids resource over-reservation and insufficient reservation. For AC, a new/handoff connection is accepted only when the target cell has enough resource to afford both instantaneous and average resource consumption to meet the average source rate request. On the other hand, a joint resource allocation and packet scheduling scheme is designed to provide packet-level QoS guarantee in term of "QoS rate", which can ensure fairness for the services with identical priority level in case of bandwidth shortage. Particularly, an enhanced bandwidth request scheme is designed to reduce unnecessary BR delay and redundant signaling overhead caused by the existing one in IEEE 802.16e, which further improves the packet-level QoS performance and resource efficiency for uplink transmission. Simulation results show that the proposed approach not only balances the tradeoff among connection blocking rate, connection dropping rate, and connection failure rate, but also achieves low mean packet dropping rate (PDR), small deviation of PDR, and low QoS outage rate. Moreover, high resource efficiency is ensured.

Application-Aware Design to Enhance System Efficiency for VoIP Services in BWA Networks

This paper has designed a cross-layer framework for voice over Internet protocol (VoIP) services in IEEE 802.16 systems. It uses the application session information of the session description protocol to generate the quality of service parameters in IEEE 802.16 systems. This feature allows the system to efficiently allocate the radio resource because it can exactly estimate the properties of VoIP services such as packet-size and packet-generation-interval. In other words, the cross-layer framework is expected to achieve a novel resource request scheme for a VoIP service that dynamically assigns the radio resource. This paper has analyzed the maximum number of supportable VoIP users for the resource request schemes in terms of the packet-generation-interval in the silent-period, the duration of the silent-period, and the major VoIP speech codec. The numerical results show that the proposed scheme can efficiently support the VoIP services for the various communication environments. Particularly, it can improve the maximum number of supportable VoIP users by 14 ~ 93% compared to an extended real-time polling service.

Special Issue on Next Generation Wireless Technologies

The next generation wireless networks are expected to converge into a ubiquitous architecture, which includes high-speed cellular networks, wireless local area networks (WLANs), mobile ad hoc networks, peer-to-peer networks, wireless metropolitan area networks (WMANs), etc. The increasing demand of wireless multimedia services has motivated the development of broad wireless access in the heterogeneous wireless networks. Mobile subscribers can enjoy the high bit rate, low cost, ubiquitous coverage, and secure connection. For the next generation wireless networks, further extensive investigation, experimentation and development are necessary, such as capacity analysis/ enhancement, quality-of-service (QoS) support, power saving, wireless routing, security, and mobility management. This special issue presents recent cutting edge research and state-of-the-art technology. The accepted eight papers are selected from the 2nd International Conference on Broadband Networks (BroadNets’05, held in Boston, MA, Oct. 3–7, 2005), the 2nd International Conference on Quality of Service for Heterogeneous Wired/Wireless Networks (QShine’05, held in Orlando, FL, Aug. 22–24, 2005), and the 11th Mobile Computing Workshop (held in Taiwan, Mar. 31, 2005). These papers are timely and valuable for future analysis, implementation and experiments of heterogeneous broadband wireless networks. In the first paper “Dynamic power saving mechanism for 3G UMTS system,” Yang investigates a power saving mechanism for Universal Mobile Telecommunications System (UMTS). Analytic and simulation models are proposed to study the two control parameters: discontinuous reception (DRX) cycle and the inactivity timer threshold. Optimal values of the two parameters in terms of maximum power saving are obtained. A dynamic algorithm is also proposed to enhance the performance of DRX. In the second paper “Predictive dynamic channel allocation scheme for improving power saving and mobility in BWA networks,” Chen and Tan propose a signal-aware dynamic channel allocation (SDCA) to improve the channel utilization as well as to reduce the probability of out-ofservice for IEEE 802.16 networks. The SDCA not only increases the capacity of the system but saves the overall power consumption of the system well. A location prediction scheme is presented to prevent the out-of-service effect on mobile subscriber stations due to user mobility. In the third paper “Queue analysis and multiplexing of heavy-tailed traffic in wireless packet data networks,” Teymori and Zhuang investigate the queuing behavior of self-similar traffic flows for data applications in a packetswitching single-server wireless network. Close-form expressions are derived for the relation among the traffic parameters, the channel working state probability, the server capacity, and the queue distribution for an infinite Mobile Netw Appl (2007) 12:1–3 DOI 10.1007/s11036-006-0001-1

Smart antennas for broadband wireless access networks

This article is an overview of smart antenna applications in fixed broadband wireless access networks. Different smart antenna techniques are described including advances such as "spatial multiplexing" that can dramatically increase the performance of BWA networks. The impact of SA techniques on capacity and throughput of BWA networks is discussed.