Chiew-Tong Lau

A reconfigurable multi-standard channelizer using QMF trees for software radio receivers

The flexibility of a software-defined radio (SRR) depends on its capability to operate in multi-standard wireless communication environments. The most computationally intensive part of wideband receivers is the channelizer, which extracts multiple narrowband signals from adjacent frequency hands. In an SDR receiver, the compatibility of the channelizer with different communication standards is guaranteed by its reconfigurability. This paper presents an efficient channelizer that has a reconfigurable architecture based on quadrature mirror filter bank (QMF) trees. We show that the channelizer can he efficiently implemented using common subexpression based filter structures. An example of dual-mode global system for mobile communication (GSM)/personal digital cellular (PDC) channelizer is discussed to illustrate the proposed design methodology.

Evaluation of terrain effects on mobile WiMax in a vehicular environment

Mobile WiMax is a suitable wireless technology for networked vehicular applications because of its mobility support at vehicular speeds and its inherent wide coverage, which minimizes the rate of handover and thus data loss due to disrupted communication. Apart from vehicular mobility, the terrain over which the network is deployed will also impact the network due to its effects on wireless signal propagation. In this paper, the performance of a WiMax vehicular network is investigated under different terrain environments, namely flat, urban and rural terrains, with varying building heights and densities, using realistic signal propagation models and vehicle movement patterns.

Error concealment scheme for MPEG-AAC

MPEG-AAC is the state-of-the-art in audio compression technology. Promising CD quality at 64 kbps, AAC is the leading option for low bandwidth audio streaming applications. In spite of the support from channel coding and the error resilience features of AAC itself, handling erroneous transmission requires the decoder to be equipped with error concealment scheme to cater for missing packets. However, complexity is limited by the real time requirement in this application. We present in this paper a novel scheme of error concealment, specifically for AAC. This scheme exploits the time domain aliasing cancellation property of MDCT based codec and the block-switching feature of AAC. Preliminary simulations show significant improvement in both error performance and subjective quality testing compared to general method of concealment. The scheme does not introduce major computational load, and hence suitable for real time low power decoder

Low-complexity filter bank channelizer for wideband receivers using minimum adder multiplier blocks

The computational complexity of linear phase finite impulse response (LPFIR) filters used in the channelizer of a wideband receiver is dominated by the number of adders (subtracters) employed in the multipliers. Common subexpression elimination (CSE) is a well-known technique for minimizing the number of adders in LPFIR filters. An improved CSE method is proposed in this paper, which is used to implement the channel filters of a filter bank channelizer (FBC). In the FBC, each modulated bandpass filter extract one channel from the input wideband signal. The reduction in number of adders is obtained by eliminating redundant multiplications of common subexpressions that exist among the channel filters of the FBC with the input signal. Design example of the channel filters employed in the digital advanced mobile phone system (D-AMPS) show that the proposed method offers considerable reduction in the number of full adders when compared with conventional CSE methods.

Cognitive Radio Network- A Review

As discussed in Chap. 1, the quality of service and energy efficiency of a cognitive radio system depends upon various parameters, including spectrum selection, media access scheme and spectrum sensing order. In this chapter, we provide a review on technologies which facilitates/improves the parameters responsible for QoS and energy management. At the end of this chapter, we will discuss about different cognitive radio platforms and their evolution.

Multiwavelets based multi-user cognitive radio network

Cognitive radio (CR) resolves the problem of spectrum scarcity in the fast growing wireless communication scenario. A multi user CR network using orthogonal compact support multiwavelts is proposed in this work. Multiwavelets are never considered in the field of wireless communication so far. Linear B spline multi wavelets are generated and simulated the performance characteristics. A generalization of the multiwavelet concept combining with wavelet packets is briefly explained.

Optimization method for designing filter bank channelizer of a software defined radio using vertical common subexpression elimination

The most computationally intensive part of wide-band receivers in software defined radios is the channelizer, which extracts individual radio channels from the output of the ADC. The computational complexity of finite impulse response (FIR) filters used in the channelizer is dominated by the number of adders (subtractors) employed in the multipliers. A method for designing channel filters using the minimum number of adders by optimizing vertical common subexpression elimination is presented in this paper. The reduction in number of adders is obtained by eliminating redundant multiplications of common subexpressions that exist among the channel filters of the filter bank channelizer (FBC) with the input signal. Design example of the channel filters employed in the Digital Advanced Mobile Phone System (D-AMPS) show that the proposed method offers considerable reduction in the number of full adders over conventional common subexpression elimination method.

Case Study: Self-coexistence in CRN Framework

The free use of wireless frequency spectrum by cognitive radio network is anticipated to increase its application in a multitude of wireless systems.

QoS Provisioning and Energy Management Framework for CRN

The cognitive radio comprises of the following three important functional components to realize its operation as wireless communication device.

QoS and Energy Management in Cognitive Radio Network

Introduction -- Cognitive Radio Network and QoS provisioning -- QoS Provisioning Framework for Cognitive Radio Network -- Channel Selection Techniques in Cognitive Radio Network -- Energy Management in Cognitive Radio Network -- Media Access Scheme for Cognitive Radio Network -- Self-Coexistence among Cognitive Radio Networks -- Case Studies- QoS Framework for Cognitive radio network.