Sean McGrath

The common RRM approach to admission control for converged heterogeneous wireless networks

As the wireless environment becomes ever more populated and complex, individual networks offering single or restricted services will become ever more uncompetitive. Common radio resource management algorithms and strategies are used in heterogeneous or converged wireless networks to integrate multiple physical radio interfaces to support different levels of data rates, mobility, and traffic. Admission control in a common RRM environment is used to select the most appropriate wireless access based on service type, user preference, and network load. This is used to provide a balance between real-time and non-real-time traffic across the available access technologies. The development of common radio resource management strategies requires a suitable platform of coupled access networks and is the motivation behind the development of a converged wireless test platform. The tightly coupled platform supports voice and data call setup and delivery over UMTS and WLAN

Spectrum efficiency optimization in multiuser Ultra Wideband cognitive radio networks

In this paper, we present a new dynamic spectrum access algorithm in multiuser Ultra Wideband cognitive radio networks for spectrum efficiency optimization. The proposed optimization algorithm can optimally distribute the radio spectrum, transmitted power and data bits among different UWB nodes while guaranteeing the aggregate interference power to the primary wireless systems is below a certain threshold. The aggregate interference power in the UWB fading channel environment is computed by using Fenton-Wilkinson method. We analyze the performance of the proposed algorithm over different UWB channel models. The results illustrate that the new dynamic spectrum access algorithm can maximize the spectrum efficiency with a low complexity.

Low complexity GMSK modulator and demodulator for integrated circuit implementation

The design of a reduced-complexity modulator and demodulator using Gaussian minimum shift keying (GMSK) is presented. Both modulator and demodulator follow the European Conference of Postal and Telecommunications Administrations (CEPT), Group Special Mobile (GSM) recommendations. A single ROM modulator circuit and a coherent demodulator using De Buda (1972) clock and carrier techniques are used to give reduced complexity designs. The demodulator is a coherent receiver that uses phase-locked loops in the clock and carrier recovery circuits. Both the modulator and demodulator designs give satisfactory performance at reduced complexity, and are suitable for implementation on silicon.<<ETX>>

Characteristics, Results and Findings of IEEE 802.11 in an RF Isolated Testbed

Simulation has been one of the most important methods for evaluating the characteristics of network protocols and applications before deployment in wireless communication networks. This paper presents the findings of a controlled and automated experimental IEEE 802.11 testbed and compares them to results of popular network simulators. The comparison shows the differences and similarities of three network simulators with the testbed using identical test scenarios. The comparison has shown that some simulators can produce misleading results under certain conditions. The discrepancy can be caused by simulators using simple and invalid models. Without realistic modelling in simulations, the evaluation of performance of mobile networks may not correlate well with performance in reality.

Cognitive ultra wideband radio spectrum sensing window length optimization algorithm

A critical objective of cognitive radio (CR) system is to enhance the spectrum efficiency, and one of the key factors that can determine the spectrum efficiency is the system spectrum sensing performance with respect to sensing window length. For non-coherent detection-based sensing technique, the length of the sensing window required to meet the detection criteria is inversely proportional to the detected signal-to-noise ratio (SNR) of the primary users (PUs). This fact may result in an inadequate use of the white or gray space for the conventional CR system whose transmission and sensing window length are both fixed because a high detected PUs SNR can lead to an excessive long fixed sensing window which occupies the potential CR transmission opportunities while a low received PUs SNR can result in an insufficient sensing window length which degrades the CR detection criteria. In this paper, to improve the spectrum efficiency compared with the fixed sensing/transmission window length-based CR system, we propose an adaptive spectrum sensing window length optimization algorithm. We design the algorithm based on the ultra wideband (UWB) system which is an ideal candidate for the implementation of the CR technology. Based on the analysis of the CR-UWB’s spectrum sensing technique in terms of the factors such as spectrum efficiency, spectrum sensing length, PUs SNR, detection criteria etc., we formulate the optimization problem into a convex problem, which enables the proposed algorithm to find the optimal trade-off with low computational complexity between the sensing window length and the desired detection probabilities for the CR-UWB system. Compared with the conventional fixed length spectrum sensing techniques, the proposed algorithm is verified to be able to adapt the length of the CR-UWB’s transmission window according to the PUs SNR to optimize the use of the available spectrum while guaranteeing the PUs from being interfered.

Joint Spectrum Sensing and Power Allocation Algorithm for Spectrum Efficiency Optimization in Ultra Wideband Cognitive Radio Networks

Ultra Wideband (UWB) system uses extremely low signal power to coexist with other primary users (PUs), which limits the use of the UWBs wide spectrum band. Cognitive Radio (CR) enables UWB systems to efficiently use the overlapped spectrum without causing interference to other wireless systems. In this paper, we focuses on the low-complexity joint optimization algorithm design with respect to transmit power allocation and spectrum sensing time (SST) for maximizing the spectrum efficiency of the Orthogonal Frequency Division Multiplexing based CR-UWB system. The SST optimization algorithm minimizes the spectrum sensing time in order to maximize the time length of applying the power allocation algorithm for data transmission. The proposed group power allocation algorithm adaptively assigns the transmit power to the subcarrier groups according to the effective signal-to-noise ratio (SNR) of each subcarrier group based on greedy algorithm. The proposed joint optimization algorithm can maximize the CR-UWB systems spectrum efficiency at a extremely low primary user SNR regime with low complexity.

A Novel Indoor Navigation Approach Employing Motion Statistics

In this paper, we devised a novel indoor navigation system based on a probabilistic approach that employs data from the wireless adapter, accelerometer, and compass of the mobile device in order to determine user position. A routing algorithm employed by the device calculates the optimal path between user position and its destination. Experimental results verified that two meter accuracy was achieved by the proposed design. This technique shows promise for future handheld indoor navigation systems that can be used in malls, museums, hospitals, and college campuses.

An energy spreading technique for cognitive radio networks

This paper presents a novel cognitive radio network architecture that optimizes information routing to preserve battery capacity while maintaining an acceptable signal quality. This is implemented via the monitoring of current link quality and battery levels of the nodes within the network and by performing a routing algorithm to optimize the signal quality of the links and the battery life of the nodes. A weight-based modification of Dijkstras algorithm and a rank-based routing algorithm that calculated and maximized the nodes battery lives were implemented. Experimental results show that the network performs the entire optimization process successfully 87.5% of 40 test trials.

Saturation throughput analysis of Multiband-OFDM ultra wideband networks

The saturation throughput analysis of the prioritized contention access (PCA) of the WiMedia Ultra Wideband (UWB) standard is presented in this paper. In the WiMedia standard, the Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) is used as the basic physical scheme. An in-depth Bit Error Rate (BER) performance analysis of the MB-OFDM UWB system using IEEE 802.15.3a channel models is conducted to aid the throughput analysis. The PCA throughput performance analysis is carried out by extending an original Enhanced Distributed Contention Access (EDCA) model for 802.11e into the MB-OFDM UWB protocol. The extended model considers the effects of the bit error rate, the transmission opportunity limits, and the uniqueness of WiMedia MAC timing structure. The results illustrate that the station saturation throughput of the PCA scheme is sensitive to the frame payload length, and there exists an optimal frame payload length that maximizes the saturation throughput. The results also show that the saturation throughput of the Access Category (AC) with higher priority outperforms the lower prioritized AC under all types of BER conditions.

TH-UWB and DS-UWB in lognormal fading channel and 802.11a interference

Ultra wideband communication systems provide high data rate transmission at low power. The transmission of narrow pulses can be implemented using time hopping or direct sequence techniques. This work deals with the comparison of TH-BPSK and DS-BPSK systems in lognormal fading channel with 802.11a interference. DS-BPSK presents slightly better bit error rate performance than TH-BPSK when line-of-sight multipath channel, and high multi user interference. When high dense NLOS channel is considered both systems shows similar behaviour.