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Employing multiple channels to improve the multi-hop wireless network performance has recently attracted a lot of attention. Given that hidden node collision is a key cause of the performance degradation in multi-hop wireless networks, we propose a solution to minimize the hidden node collision probability. It involves the use of a coordination mechanism, which tries to assign different frequency...
This paper presents an adaptive combined correction and compensation (ACCC) scheme to mitigate the distortion caused by I/Q imbalance and multipath channel, for OFDM receivers. For the proposed scheme, the estimation of the I/Q and channel parameters have been performed in the frequency domain. By the help of the estimated values, a nominal I/Q gain and phase has been obtained which has been fed back...
Multi-hop wireless sensor networks (WSN) have many applications in nowadays' environment monitoring. However, it is very challenging to predict the throughput for an arbitrary multi-hop wireless sensor network with different source data rates. In this paper, we propose an iterative decomposition method for this purpose. We first identify a limited number of basic network configuration of chain topology...
This paper presents an adaptive scheme in overcoming signal distortion, caused by I/Q imbalance and multipath propagation, in an OFDM receiver. Estimation of I/Q imbalance and channel parameters is performed in the frequency domain with the aid of pilot tones. These estimated values are then used to adjust the gain and phase to reduce the distortion caused by I/Q imbalance. The resulting less distorted...
The presence of in-phase/quadrature (I/Q) imbalance in a dual branch receiver gives rise to signal distortion. If the incoming signal is also corrupted by multipath fading, then the task of correcting or compensating for these two forms of distortion becomes technically very challenging. This paper proposes an adaptive approach which involves first correcting for the I/Q imbalance before the signal...
It is well known that dual-branch receivers suffer from in-phase (I) and quadrature (Q) imbalance problems resulting in distortion and poor signal quality. This paper presents a novel technique, incorporating adaptive estimation and compensation, to mitigate the combined effects of I/Q imbalance and multipath channel on the received signal. Estimation of the channel and I/Q imbalance parameters is...
An IEEE 802.16 wireless backhaul network is a cost effective, easier to deploy, and readily scalable solution to deliver broadband communication services from gateway nodes located in regional or metropolitan centres to less densely populated remote rural communities. In order to ensure the network remains operational even under a node or link failure, extra nodes and links are incorporated to provide...
This paper studies the influence of tolerances in inter-element spacing and element gain on the operation of the LLMS adaptive beamforming algorithm. Both random and worst case scenarios of inter-element spacing and element gain variations have been considered. Computer simulations show that these practical tolerances have greater influence on the beam pattern than the error vector magnitude (EVM)...
A wireless backhaul network is used to interconnect intermediate nodes to gateway nodes. As it is designed to serve a large population of broadband users, failure sustainability becomes an essential requirement to ensure uninterrupted telecommunication services even in the presence of occasional node or link failures. In this paper, the performance of a failure sustainable wireless backhaul, based...
This paper studies the influence of the use of finite wordlength on the operation of the RLMS adaptive beamforming algorithm. The convergence behavior of RLMS, based on the minimum mean square error (MSE), is analyzed for operation with finite precision. Computer simulation results verify that a wordlength of nine bits is sufficient for the RLMS algorithm to achieve performance close to that provided...
A new adaptive algorithm, called LLMS, which employs an array image factor, AI, sandwiched in between two Least Mean Square (LMS) sections, is proposed for different applications of array beamforming. The convergence of LLMS algorithm is analyzed, in terms of mean square error, in the presence of Additive White Gaussian Noise (AWGN) for two different modes of operation; namely with either an external...
A new adaptive algorithm, called LLMS, which employs two Least Mean Square (LMS) sections in tandem, is proposed for different applications of array beamforming. The convergence of the LLMS algorithm is analyzed, in terms of mean square error, in the presence of Additive White Gaussian Noise (AWGN) for two different operation modes; normal referencing and self-referencing. Computer simulation results...
A new adaptive algorithm, called least mean square- least mean square (LLMS) algorithm, which employs an array image factor, , sandwiched in between two least mean square (LMS) algorithm sections, is proposed for different applications of array beamforming. It can operate with either prescribed or adaptive . The convergence of LLMS algorithm is analyzed for two different operation modes; namely with...
This paper describes a flexible way of evaluating the power line (PL) channel frequency response, H(f), and input impedance, in the frequency range of 0-30 MHz, by means of a two port network (TPN) methodology. As an example, the method is applied to investigate the power line channel variability under various practical load conditions in a typical modern Australian two bedroom apartment. In order...
This paper presents a flexible method of achieving either fixed or self-adaptive antenna beamforming. It involves the use of the array image factor A??d, which interfaces the Recursive Least Squares (RLS) and Least Mean Squares (LMS) sections in cascade to form the RLMS beamforming algorithm. It is shown that an accurate fixed beam can be obtained by simply setting the elements of A??d A with prescribed...
This paper presents a flexible method of achieving either fixed or self-adaptive antenna beamforming. It involves the use of an array image factor ??d, which interfaces an RLS and LMS sections in cascade to form the RLMS beamforming algorithm. It is shown that an accurate fixed beam can be obtained by prior setting the elements of ??d with prescribed values for the required direction. Moreover, the...
The IEEE 802.16(d) mesh mode is proposed for the next generation wireless mesh network. It specifies two mechanisms to schedule data transmission, namely centralized scheduling and distributed scheduling. In this paper, we evaluate the performance of VoIP traffic over an IEEE 802.16(d) mesh network using the distributed scheduling. The problems of the system in supporting voice traffic are identified...
Backhaul network plays a significant role to interconnect access points and further connect them to gateway nodes. A failure sustainable wireless backhaul topology is proposed to ensure undisrupted telecommunication services even in the presence of occasional node or link failures. Furthermore, a new control message, called reverse notification, is proposed to improve the performance of coordinated...
In this paper, the performance of a wireless mesh network (WMN) is improved by introducing a number of long links at strategic locations, based on the small world network concept, to shorten transmission delay. A genetic algorithm (GA) is used to determine the minimum number of long links and their locations such that the maximum number of hops of a given WMN with n nodes is minimized. In the optimization...
This paper examines the performance of an adaptive linear array employing the new RLMS algorithm, which consists of a recursive least square (RLS) section followed by a least mean square (LMS) section. The performance measures used are output and input signal-to-interference plus noise ratios (SINR), side lobe level (SLL), and ??SINR0 as a function of the direction of arrival of the interfering signal...
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