WiMAX Base Station Research Articles

Perspectives on quality of experience for video streaming over WiMAX

The advent of broadband wireless networks, such as WiMAX, is paving the way for the widespread deployment of high-bandwidth video streaming services for mobile users. To provide acceptable end-to-end performance in such a network, it is important to monitor the Quality of Experience (QoE) of the user, since the inherent variability in the wireless channel can undermine the video quality significantly. In this context, this paper undertakes a simulation study to evaluate the user's QoE (using PSNR as the representative metric) when video is streamed from a source to a Mobile Station (MS) via a WiMAX Base Station (BS). The WiMAX Forum's ns-2 simulator is used to carry out all the simulations. In particular, we explore the impact of the following parameters, namely, (1) the reserved rate at the BS for the video stream, (2) the Modulation and Coding Scheme employed, (3) the distance between BS and MS, and (4) the tolerable end-to-end delay, on the QoE. Our results point to various trade-offs that exist among these parameters, which can be effectively used to manage the user's viewing experience under varying channel conditions and resource constraints.

Greedy scheduling algorithm (GSA) – Design and evaluation of an efficient and flexible WiMAX OFDMA scheduling solution

WiMAX is one of the most promising technologies to provide broadband wireless access in the near future. In this paper we focus on the study of the combined performance of a WiMAX Base Station MAC downlink scheduler and OFDMA packing algorithm which mainly determine the usage efficiency of the available radio resources. We design and analyze an efficient and flexible solution, greedy scheduling algorithm (GSA), and evaluate its performance as compared to several relevant alternative solutions. Specifically, we analyze performance differences with respect to efficiency, flexibility to provide per subscriber station burst shape preferences, interference mitigation and computational load. Our results show that GSA achieves a performance similar to the one of the competing approaches considered in terms of efficiency, even better in some cases, and significantly outperforms them in flexibility to provide per subscriber station burst shape preferences, interference mitigation and computational load. As a conclusion, the proposed GSA solution is a promising candidate to maximize the utilization of the available WiMAX radio resources at a low computational cost while at the same time being able to fulfill a wide range of requirements based on operators' preferences and/or network environment specifics.

Mobile-Taiwan experience in voice over IP-worldwide interoperability for microwave access trial

Considering voice as a dominant telecommunication service, the performance of Voice over IP (VoIP) plays a critical role in deployment of worldwide interoperability for microwave access (WiMAX) technology providing all-IP network services. To that effect, in this study, the authors investigate the performance of a WiMAX-based VoIP established under the mobile Taiwan (M-Taiwan) field-trial funded program. To achieve the objectives of the trial the measurement results expressed in the form of mean opinion score (MOS), packet loss, packet delay and jitters. For the worst-case scenario, the tests were conducted under a stringent condition of both communicating devices, wirelessly connected to the same WiMAX base station under a heavy background traffic and interference, were experiencing simultaneous handovers during the communication. Upon their analysis, the field measurements confirm an excellent performance when both communicating devices kept stationary and show an acceptable quality for the service when both communicating devices are on the move at a speed of 50 km/h.

Bipolar M-EBG structure for WIMAX base station sectoral antennas

This Letter deals specifically with sectoral antennas and focuses on the ability to design a bipolar structure using a double layer of metallic electromagnetic bandgap (M-EBG) materials working on orthogonal polarisations as a superstrate. This antenna is able to radiate in vertical, horizontal and dual polarisation with a wide radiation pattern form, i.e. presenting at least 60° angular beamwidth in the azimuth plane. A bipolar M-EBG sectoral antenna for WIMAX application [5.15–5.35] GHz is designed and its performances are presented. Finally, a prototype is realised and experimental measurements are compared to simulated ones.

Minimization of outage probability of WiMAX link supported by laser link between a high-altitude platform and a satellite

Various technologies for the implementation of a WiMAX (IEEE802.16) base station on board a high-altitude platform (HAP) are currently being researched. The network configuration under consideration includes a satellite, several HAPs, and subscribers on the ground. The WiMAX base station is positioned on the satellite and connects with the HAP via an analog RF over-laser communication (LC) link. The HAPs house a transparent transponder that converts the optic signal to a WiMAX RF signal and the reverse. The LC system consists of a laser transmitter and an optical receiver that need to be strictly aligned to achieve a line-of-sight link. However, mechanical vibration and electronic noise in the control system challenge the transmitter-receiver alignment and cause pointing errors. The outcome of pointing errors is fading of the received signal, which leads to impaired link performance. In this paper, we derive the value of laser transmitter gain that can minimize the outage probability of the WiMAX link. The results indicate that the optimum value of the laser transmitter gain is not a function of the pointing error statistics.

WiMAX Location Update for Vehicle Applications

In IEEE 802.16e mobile Worldwide Interoperability for Microwave Access (WiMAX), paging groups (PGs; groups of base stations) are used to identify the locations of mobile stations (MSs). An anchor paging controller (APC) is assigned to an MS to handle location tracking for the MS. During location update, the WiMAX network may or may not relocate the APC. This paper considers a linear WiMAX base station layout for vehicle applications, where a base station serves as a roadside unit, and a WiMAX MS installed in a vehicle serves as an onboard unit. In these vehicle applications, APC relocation may significantly affect the network traffic. This paper proposes an analytic model to study the performance of the location update with/without APC relocation. Our study provides guidelines to utilize the APC relocation for vehicles with various moving behaviors.

The Accuracy of Location Prediction Algorithms Based on Markovian Mobility Models

The efficient dimensioning of cellular wireless access networks depends highly on the accuracy of the underlying mathematical models of user distribution and traffic estimations. The optimal placement/deployment of e.g. UMTS, IEEE 802.16 WiMAX base stations or IEEE 802.11 WLAN access points is based on user distribution and traffic characteristics in the service area. In this paper we focus on the tradeoff between the accuracy and the complexity of the mathematical models used to describe user movements in the network. We propose a novel Markov chain based model capable of utilizing user’s movement history thus providing more accurate results than other models in the literature. The new model is applicable in real-life scenarios, because it relies on information effectively available in cellular networks (e.g. handover history). The complexity of the proposed model is analyzed, and the accuracy is justified by means of simulation.

Municipalities as a Driver for Wireless Broadband Access

Municipalities can form a driving force behind the deployment of new telecom infrastructure. While a telecom operator focuses on direct (financial) profits, a municipality is mainly interested in the social benefits for its inhabitants. In this paper, we evaluate a wireless municipality network from both a technical and an economic point of view. WiFi and WiMAX are considered as the most suited technologies for this purpose. A detailed techno-economic study has been performed including forecasting of the user adoption, dimensioning of the wireless network and modelling the related costs and revenues. The trade-off between installing a high number of relatively cheap WiFi access points, and a smaller number of more expensive WiMAX base stations for delivering full coverage is investigated in several scenarios.

Sectorial-Beam Dielectric Resonator Antenna for WiMAX With Bent Ground Plane

A dielectric resonator (DR) antenna with a well is proposed, of which the beamwidth is increased to more than 120deg by bending the ground plane. This DR antenna has its 10 dB return-loss band in 3.4-3.8 GHz, thus can be used as a sectorial antenna in WiMAX (3.4-3.7 GHz) base station.

Planar C-Band Antenna with Electronically Controllable Switched Beams

The design, manufacturing, and measurements of a switchable-beam antenna at 3.5 GHz for WLL or Wimax base station antennas in planar technology are presented. This antenna performs a discrete beam scan of a60∘sector in azimuth and can be easily upgraded to 5 or more steps. The switching capabilities have been implemented by the inclusion of phase shifters based on PIN diodes in the feed network following a strategy that allows the reduction of the number of switches compared to a classic design. The measurements show that the design objectives have been achieved and encourage the application of the acquired experience in antennas for space applications, such as X-band SAR and Ku-band DBS.

Highest Urgency First (HUF): A latency and modulation aware bandwidth allocation algorithm for WiMAX base stations

The mobile WiMAX systems based on IEEE 802.16e-2005 provide high data rate for mobile wireless networks. However, the link quality is frequently unstable owing to mobility and air interference and therefore impacts the latency requirement of real-time applications. In the WiMAX standard, the modulation/coding scheme and the boundary of uplink/downlink sub-frames could be adjusted subject to channel quality and the traffic volume, respectively. This provides us a chance to design a MAC-layer uplink/downlink bandwidth allocation algorithm that is QoS/PHY-aware. This work takes into account the adaptive modulation and coding scheme (MCS), uplink and downlink traffic volume, and QoS parameters of all five defined service classes to design a bandwidth allocation algorithm that calculates the slot allocation in two phases. The first phase decides the boundary of uplink and downlink sub-frames by satisfying requests with pending latency violation and proportionating according to traffic volume, while the second phase allocates slots to mobile stations considering urgency, priority and fairness. Simulation results show our algorithm achieves zero latency violation and higher system throughput compared to existing non-QoS/PHY-aware or less-QoS/PHY-aware approaches.

Performance Evaluation of WiMAX Broadband from High Altitude Platform Cellular System and Terrestrial Coexistence Capability

The performance obtained from providing worldwide interoperability for microwave access (WiMAX) from high altitude platforms (HAPs) with multiple antenna payloads is investigated, and the coexistence capability with multiple-operator terrestrial WiMAX deployments is examined. A scenario composed of a single HAP and coexisting multiple terrestrial WiMAX base stations deployed inside the HAP coverage area (with radius of 30 km) to provide services to fixed users with the antenna mounted on the roof with a directive antenna to receive signals from HAPs is proposed. A HAP cellular configuration with different possible reuse patterns is established. The coexistence performance is assessed in terms of HAP downlink and uplink performance, interfered by terrestrial WiMAX deployment. Simulation results show that it is effective to deliver WiMAX via HAPs and share the spectrum with terrestrial systems.

Accurate Determination of the Electromagnetic Field Due to WiMAX Base Station Antennas

A method for accurate determination of electromagnetic fields around the Worldwide Interoperability for Microwave Access (WiMAX) base stations (BSs) is developed in this paper. The influence of the characteristics of the WiMAX signal on the settings and parameters of the spectrum analyzer (SA) used for exposure assessment is investigated. Optimal settings of the SA are proposed, and the results obtained using simulations and measurements agree very well. A practical application in the neighborhood of a WiMAX BS is performed. The obtained electric field values correspond very well for the different settings and are compared with the reference levels for the general public and those for occupational exposure. The results of this paper can be used for practical measurement procedures of the exposure due to WiMAX signals.

Cross-layer mobile WiMAX MAC designs for the H.264/AVC scalable video coding

To effectively provide the QoS of streaming services in mobile WiMAX systems, this paper proposes a cross-layer design between the streaming server and mobile WiMAX base stations. We will show that for each user the implementation of multiple connections with feedback information of the available transmission bandwidth is critical for supporting H.264/AVC-based scalable video coding in which the transmission packets can be further separated into multiple levels of importance. To quantify the performance, a mobile WiMAX simulation platform including both the video encoder/decoder and IEEE 802.16e MAC controls is developed.

A hybrid-mesh solution for coverage issues in WiMAX metropolitan area networks

The new WiMAX technology offers several advantages over the currently available (GSMor UMTS-based) solutions. It is a cost effective, evolving, and robust technology providing quality of service guarantees, high reliability, wide cov- erage and non-line-of-sight (NLOS) transmission capabilities. All these features make it particularly suitable for densely populated urban environments. In this paper we discuss the design and implementation difficulties concerning network coverage discovered in a test-bed implementation of WiMAX. We point out the presence of unexpected “white spots” in the coverage, which are not inherently characteristic of the WiMAX concept. As a possible remedy to this significant drawback of the otherwise very promising technology, we consider reconfigurable mesh organization of WiMAX base stations. We also suggest directions for further development of this kind of network operation, partly based on our practical experience. Despite the clear advantages of the mesh mode in WiMAX networks, its development is currently at an early stage, due to the high complexity of the necessary mechanisms. In this situation, we propose an original, much simpler solution: the so-called support-mesh mode.

Accurate Assessment of Electromagnetic Exposure From WiMAX Signals Using a Spectrum Analyzer

The influence of the characteristics of the WiMAX signal on the settings and parameters of the spectrum analyzer used for exposure assessment is investigated in this paper. Optimal settings of the spectrum analyzer are proposed for accurate determination of electromagnetic exposure around WiMAX base stations.

Interoperability between WiMAXand broadband mobile space networks [topics in radio communications

In several countries manufacturers, operators, and public authorities look at WiMAX system as a viable technology to fill the digital divide, providing broadband services mainly in suburban and rural areas, but also in densely populated areas. Nevertheless, as a standalone system it will never offer global services, and to complement its capabilities, the utilization of broadband space-based access shared among users represents a scalable and cost-effective solution to offer wider area coverage, improved performance in terms of QoS, service continuity in case of terrestrial network failure, and long-range user mobility. Integration between WiMAX and a space-based infrastructure, composed of a combination of satellites and high altitude platforms, can be pursued in several ways. The simplest solution is based on connecting a WiMAX network by means of a terrestrial network terminating at a hub station connected to the space infrastructure. A more flexible solution should allow the WiMAX subscriber station or base station to directly access the space infrastructure. This article addresses the identification of suitable scenarios and a feasibility analysis presenting link budget results related to a subset of the identified solutions.

Fixed Mobile Convergence Architectures for Broadband Access: Integration of EPON and WiMAX [Topics in Optical Communications

EPON and WiMAX are two promising broadband access technologies for new-generation wired and wireless access. Their complementary features motivate interest in using EPON as a backhaul to connect multiple dispersed WiMAX base stations. In this article we propose four broadband access architectures to integrate EPON and WiMAX technologies. The integrated architectures can take advantage of the bandwidth benefit of fiber communications, and the mobile and non-line-of-sight features of wireless communications. Based on these integrated architectures, we elaborate on related control and operation issues to address the benefits gained by this integration. Integration of EPON and WiMAX enables fixed mobile convergence, and is expected to significantly reduce overall design and operational costs for new-generation broadband access networks.