Performance evaluation of broadband fixed wireless system based on IEEE 802.16

Fixed Wireless Access systems operating below 11 GHz have the potential to provide broadband wireless access for non line-of-sight operation. In this paper the performance of a typical broadband fixed wireless system based on the IEEE 802.16-2004 specifications is determined. A scenario for business applications with outdoor customer premises equipment is investigated in the 3.5 GHz frequency band. Different path loss models and terrain types are considered. Coverage and throughput in a sector are determined for this business scenario

Caracterización y modelado de canales BFWA en entornos OUTDOOR – INDOOR

This paper presents the experimental characterization of the radio channel for outdoor-indoor communications, within the frame of Fixed Wireless Access systems. The obtained results show that the presence of line of sight minimizes the influence of the scatters that surrounds the receiver, contributing to delay spread values lower than in the non line of sigth situations. In order to reproduce the behavior of these kind of channels several models based on tapped delay lines have been developed. These models provide a good fit of the temporal channel parameters and can be useful to complete the channel collections of current and future standards

Broadband business and residential radio access

This paper discusses some of the issues associated with broadband wireless access particularly directed at the non Line-of-Sight (nLoS) paths necessary for large scale deployment of Point to Multipoint networks. The paper discusses the modulation choices that can be made and how they affect the deployability of the systems. The au-thor recommends the use of Orthogonal Frequency Divi-sion Multiplex (OFDM). Proprietary and competing sys-tems have held back the promise of wireless access sys-tems, as they become more complex providing greater bandwidths and services, success will only be achieved by standardisation.

On the problems of symbol-spaced tapped-delay-line models for WSSUS channels

Article from the journal: Wireless Communications and Mobile Computing The deposited fulltext is a preprint of the definitive article at Wiley Interscience http://dx.doi.org/10.1002/wcm.683This paper analyzes the validity and statistical behavior of symbol-spaced tapped-delay-line (SSTDL) models for wide-sense stationary uncorrelated scattering (WSSUS) mobile radio channels. SSTDL models are obtained by sampling the channel impulse response (CIR) in delay domain at a rate equal to the reciprocal of the symbol duration. They were proposed more than four decades ago as canonical channel models for band-limited timevariant linear (TVL) systems, and are nowadays widely in use for assessing the performance of several wireless communication systems. The applicability of these tapped-delay-line (TDL) models seems to be unquestionable, as they were developed in the framework of the sampling theorem. Nonetheless, we show here that SSTDL models should be used with care to model WSSUS channels, because the channel's uncorrelated scattering (US) condition might easily be violated. Furthermore, we show that SSTDL models suffer from strong limitations in emulating the channel frequency correlation funcion (FCF). This drawback leads to an inaccurate performance evaluation of wireless communication systems sensitive to the FCF. To cope with this problem, we present a simple solution by doubling the channel's sampling rate. The benefits of this solution are demonstrated with some exemplary simulation results. © 2008 John Wiley & Sons, Ltd

Interactive Data Services in Wireless Access Networks: Capacity Planning and Protocols

In this paper, we study the capacity planning in wireless access network for interactive data services such as web browsing. A closed queuing model has been developed which can capture the bottleneck effects in both the forward and the reverse channels. The model can be used to calculate the average throughput, the average response time and the number of users the system can support. We evaluate the performance of several MAC protocols such as slotted Aloha, static TDMA, Aloha/periodic stream and combined free demand assignment multiple access (CFDAMA) using realistic web traffic models. Based on the performance evaluation, we propose a new MAC protocol and a new transport layer protocol. Our new MAC protocol called combined polling free demand assignment multiple access (CPFDAMA) explores the correlation between forward channel data packets and reverse channel acknowledgement packets. Our new transport layer protocol called RWBP uses per-flow queuing, round robin scheduling and receiver window backpressure for congestion management. RWBP can eliminate congestion losses inside the wireless networks. Our protocol suite outperforms the proposed protocols in term of both channel utilization and response time. Our results can be used for service providers to dimension their networks and provide quality of service to a certain number of users

A statistical ultra wideband indoor channel model and the effects of antenna directivity on multipath delay spread and path loss in ultra wideband indoor channels

Ultra-wideband (UWB) indoor frequency domain channel measurements have been performed in the 2 GHz to 6 GHz frequency band using three different transmitter/receiver (Tx/Rx) antenna combination pairs. The effects of antenna directivity on path loss and multipath propagation in the channel were analyzed extensively for various omni-directional and directional antenna combinations. A statistical model of the path loss in the channel is presented, where the parameters in the model (i.e., path loss exponent and shadow fading statistics) are dependent on the particular Tx/Rx antenna combination. Time domain statistics of the channel (i.e., mean delay spread and RMS delay spread) are analyzed thoroughly for each antenna combination. Results show that RMS delay spread increases over distance for all three antenna combinations, but at a greater rate when directional antennas are used in the channel. There is a significant reduction in RMS delay spread when directional antennas are used at the transmitter and receiver or solely at the receiver with respect to an omni-directional/omni-directional antenna pair. Results show that directional antennas can be used as an effective way of mitigating the effects of multipath propagation in UWB indoor channels. A distance dependent statistical impulse response model of the channel is also presented, which statistically reproduces the impulse response of the channel with high fidelity