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Articles 1 - 16 of 16
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On Some Antenna Selection Techniques For Wireless Channels Utilizing Differential Space-Time Modulation, Le Chung Tran, Tadeusz A. Wysocki
On Some Antenna Selection Techniques For Wireless Channels Utilizing Differential Space-Time Modulation, Le Chung Tran, Tadeusz A. Wysocki
Tadeusz Wysocki
The paper deals with antenna selection techniques for wireless channels utilizing differential space-time modulation. We propose here the restricted N-out-of-M antenna selection technique providing relatively good bit error performance, while using only one feedback bit for transmit diversity purpose. In addition, we also present an improved N-out-of-(N+1) antenna selection technique, which shortens the time required for processing feedback information. These techniques remarkably improve performance of wireless channels using differential detection.
Performance Investigation On Three-Classes Of Manet Routing Protocols, Mehran Abolhasan, Tadeusz A. Wysocki, Justin Lipman
Performance Investigation On Three-Classes Of Manet Routing Protocols, Mehran Abolhasan, Tadeusz A. Wysocki, Justin Lipman
Tadeusz Wysocki
Routing in Ad-hoc Networks has received significant attention with a number of different routing protocols proposed in recent years. These routing protocols may be classified into three main categories: proactive, reactive and hybrid. Prior work aimed at comparing the performance of routing protocols has mainly fo cused on comparing reactive and proactive protocols [6] [4] [1]. In this paper, we present a simulation study of different routing protocols from all three categories. We also explore the benefits and performance of each routing category. Further, we present a discussion of future research directions for routing in Ad-hoc Networks.
Fading Characteristics For Indoor Wireless Channels At 5 Ghz Unlicensed Bands, M. Carroll, Tadeusz A. Wysocki
Fading Characteristics For Indoor Wireless Channels At 5 Ghz Unlicensed Bands, M. Carroll, Tadeusz A. Wysocki
Tadeusz Wysocki
The paper reports on experiments undertaken at the University of Wollongong to characterise fading profiles of indoor wireless channels at the 5 GHz bands. The measurements were undertaken at different locations around the campus with results recorded for post-processing to calculate the Rician k-factor, the level crossing rate and the average fade duration.
On The Performance Of Turbo Codes With Convolutional Interleavers, Sina Vafi, Tadeusz A. Wysocki
On The Performance Of Turbo Codes With Convolutional Interleavers, Sina Vafi, Tadeusz A. Wysocki
Tadeusz Wysocki
In this paper, some issues governing the block-wise performance of convolutional interleavers used in turbo codes are presented. Two different constructions of convolutional interleaver differing by the position of stuff bits in the interleaved data block are considered here. The performance assessment is based on the contribution of each weight to the overall code performance. For the given turbo code and each utilized interleaver, weight contribution is computed to finalize the code behavior in different signal to noise ratios. Simulations have been performed to verify the conducted analysis.
Amicable Orthogonal Designs Of Order 8 For Complex Space-Time Block Codes, Y. Zhao, Jennifer Seberry, Tianbing Xia, Y. Wang, Beata J. Wysocki, Tadeusz A. Wysocki, Le Chung Tran
Amicable Orthogonal Designs Of Order 8 For Complex Space-Time Block Codes, Y. Zhao, Jennifer Seberry, Tianbing Xia, Y. Wang, Beata J. Wysocki, Tadeusz A. Wysocki, Le Chung Tran
Tadeusz Wysocki
New amicable orthogonal designs AODs(8; 1; 1; 1; 2; 2; 2), AODs(8; 1; 1; 4; 1; 2; 2), AODs(8; 1; 2;2; 2; 2; 4), AODs(8; 1; 2; 2; 1; 2; 4), AODs(8; 1; 1; 2; 1; 2; 4), AODs(8; 1; 2; 4; 2; 2; 2), AODs(8; 1; 1; 4; 1; 1; 2; 2), AODs(8; 2; 2; 2; 2; 2; 2; 2; 2) and AODs(8; 1; 1; 1; 2; 1; 2; 2; 2) are found by applying a new theorem or by an exhaustive search. Also some previously undecided cases of amicable pairs are demonstrated to be non-existent after a complete …
Complex Orthogonal Sequences From Amicable Hadamard Matrices, Le Chung Tran, Jennifer Seberry, Beata J. Wysocki, Tadeusz A. Wysocki, Tianbing Xia, Y. Zhao
Complex Orthogonal Sequences From Amicable Hadamard Matrices, Le Chung Tran, Jennifer Seberry, Beata J. Wysocki, Tadeusz A. Wysocki, Tianbing Xia, Y. Zhao
Tadeusz Wysocki
The paper deals with the novel technique of designing complex spreading sequences with only four phases (0.257/spl pi/, 0.75/spl pi/, 1.25/spl pi/, 1.75/spl pi/). The interesting feature of those new sequences is the fact that not only the complex sequences are orthogonal but the real parts and imaginary parts are independently orthogonal. This can be utilized for spreading of complex constellation signals where the independent spreading using bipolar sequences (real part for in-phase component and imaginary part for quadrature component) can be applied. The paper introduces the theoretical background, and some example constructions of the amicable Hadamard matrices and the …
Inequivalence Of Nega-Cyclic ±1 Matrices, R. Ang, Jennifer Seberry, Tadeusz A. Wysocki
Inequivalence Of Nega-Cyclic ±1 Matrices, R. Ang, Jennifer Seberry, Tadeusz A. Wysocki
Tadeusz Wysocki
We study nega-cyclic ±1 matrices. We obtain preliminary results which are then used to decrease the search space. We find that there are 2, 4, 9, 23, 63, and 187 ip-equivalence classes for lengths 3, 5, 7, 9, 11, and 13 respectively. The matrices we find are used in a variant given here of the Goethals-Seidel array to form Hadamard matrices, the aim being to later check them for suitability for CDMA schemes.
Simulation Of Capture Behaviour In Ieee 802.11 Radio Modems, C. Ware, Joe F. Chicharo, Tadeusz A. Wysocki
Simulation Of Capture Behaviour In Ieee 802.11 Radio Modems, C. Ware, Joe F. Chicharo, Tadeusz A. Wysocki
Tadeusz Wysocki
In this paper we investigate the performance of common capture models in terms of the fairness properties they reflect across contenting hidden connections. We propose a new capture model, Message Retraining,as a means of providing an accurate description of experimental data. Using two fairness indices we undertake a quantitative study of the accuracy with which each capture model is able to reflect experimental data. Standard capture models are shown to be unable to accurately reflect the fairness properties of empirical data. The Message Retraining capture model is shown to provide a good estimate of actual system performance in varying signal …
Golay Sequences For Ds Cdma Applications, Jennifer Seberry, Beata J. Wysocki, Tadeusz A. Wysocki
Golay Sequences For Ds Cdma Applications, Jennifer Seberry, Beata J. Wysocki, Tadeusz A. Wysocki
Tadeusz Wysocki
Golay complementary sequences, often referred to as Golay pairs, are characterised by the property that the sum of their aperiodic autocorrelation functions equals to zero, except for the zero shift. Because of this property, Golay complementary sequences can be utilised to construct Hadamard matrices defining sets of orthogonal spreading sequences for DS CDMA systems of the lengths not necessary being a power of 2. In the paper, we present an evaluation, from the viewpoint of DS CDMA applications of some sets of spreading sequences based on Golay complementary sequences. We then modify those sets of sequences to enhance their correlation …
Performance Comparison Of Uwb Hopping Codes In A Multi-User Rich Scattering Environment, K. Popovski, Beata J. Wysocki, Tadeusz A. Wysocki
Performance Comparison Of Uwb Hopping Codes In A Multi-User Rich Scattering Environment, K. Popovski, Beata J. Wysocki, Tadeusz A. Wysocki
Tadeusz Wysocki
Ultra Wideband is a short-range wireless communication technique which has seen increased interest over the past decade. Having several methods of implementation, a key issue will always be the avoidance of multi-user interference. For time-hopped Ultra Wideband, this is achieved through the use of different codes assigned to each user, performing time-hopped code division multiple access. This paper presents a performance comparison of several time hopping sequence construction methods. It presents correlation results between sequences, and simulation results in a Gaussian noise degraded, scattering rich multi-user environment. Simulations are based on the IEEE channel model for UWB communications.
A Generalized Algorithm For The Generation Of Correlated Rayleigh Fading Envelopes In Radio Channels, Le Chung Tran, Tadeusz A. Wysocki, Jennifer Seberry, Alfred Mertins
A Generalized Algorithm For The Generation Of Correlated Rayleigh Fading Envelopes In Radio Channels, Le Chung Tran, Tadeusz A. Wysocki, Jennifer Seberry, Alfred Mertins
Tadeusz Wysocki
Although generation of correlated Rayleigh fading envelopes has been intensively considered in the literature, all conventional methods have their own shortcomings, which seriously impede their applicability. In this paper, a very general, straightforward algorithm for generation of an arbitrary number of Rayleigh envelopes with any desired, equal or unequal power, in wireless channels either with or without Doppler frequency shifts, is proposed. The proposed algorithm can be applied in case of spatial correlation, such as with antenna arrays in Multiple Input Multiple Output (MIMO) systems, or spectral correlation between the random processes like in Orthogonal Frequency Division Multiplexing (OFDM) systems. …
Combinatorial Constructions Of 3- And 4-Secure Codes, Y. Wang, Jennifer Seberry, Beata J. Wysocki, Tadeusz A. Wysocki, Willy Susilo, Tianbing Xia, Y. Zhao, Le Chung Tran
Combinatorial Constructions Of 3- And 4-Secure Codes, Y. Wang, Jennifer Seberry, Beata J. Wysocki, Tadeusz A. Wysocki, Willy Susilo, Tianbing Xia, Y. Zhao, Le Chung Tran
Tadeusz Wysocki
In this paper, 3- and 4-secure codes are constructed from combinatorial designs. Both constant weight and non-constant weight codes are shown.
Multi-Modulation Schemes To Increase The Rate Space-Time Block Codes In Rayleigh Fading Channels, Le Chung Tran, Tadeusz A. Wysocki, Alfred Mertins
Multi-Modulation Schemes To Increase The Rate Space-Time Block Codes In Rayleigh Fading Channels, Le Chung Tran, Tadeusz A. Wysocki, Alfred Mertins
Tadeusz Wysocki
The paper examines multimodulation schemes (MMSs) to increase the rate of our two new complex orthogonal designs (CODs) proposed for eight transmit antennas, namely C/sub 1/ and C/sub 2/, corresponding to the Amicable Orthogonal Designs (AODs) (8;1,1,2,2;1,1,2,2) and (8;1,1,1,4;1,1,1,4), respectively. In addition, the optimal intersymbol power allocation in the proposed codes in single modulation as well as in MMSs in flat Rayleigh fading channels is considered. It turns out that, in some modulation schemes, equal power transmission per each symbol time slot is not only optimal from the technical point of view, but also optimal in terms of achieving the …
A Generalized Algorithm For The Generation Of Correlated Rayleigh Fading Envelopes, Le Chung Tran, Tadeusz A. Wysocki, Jennifer Seberry, Alfred Mertins
A Generalized Algorithm For The Generation Of Correlated Rayleigh Fading Envelopes, Le Chung Tran, Tadeusz A. Wysocki, Jennifer Seberry, Alfred Mertins
Tadeusz Wysocki
Although the generation of correlated Rayleigh fading envelopes has been intensively considered in the literature, all conventional methods have their own particular shortcomings, which seriously impedes their applicability. A very general, straightforward algorithm is proposed for the generation of an arbitrary number of Rayleigh envelopes with any desired, equal or unequal power in wireless channels, either with or without Doppler frequency shifts. The proposed algorithm can be applied in the case of spatial correlation, such as with antenna arrays in multiple input multiple output (MIMO) systems, or spectral correlation between random processes, as in orthogonal frequency division multiplexing (OFDM) systems. …
Secure Authorization, Access Control And Data Integrity In Bluetooth, L. Nguyen, R. Safavi-Naini, Willy Susilo, Tadeusz A. Wysocki
Secure Authorization, Access Control And Data Integrity In Bluetooth, L. Nguyen, R. Safavi-Naini, Willy Susilo, Tadeusz A. Wysocki
Tadeusz Wysocki
The Bluetooth standard has a provision for mutual authentication of connecting devices but not their actual users and allows access control during connection setup only. We propose a user authorization and pairing (UAP) application, that has the ability to perform authentication and authorization of users using role based model. The pairing procedure, which exchanges link key between devices, is also performed as a part of the user authorization process. The integrity of the message is guaranteed by using message authentication codes. We also extend an attack on a short PIN during the pairing procedure for devices compliant with the Bluetooth …
Complex Orthogonal Spreading Sequences Using Mutually Orthogonal Complementary Sets, Y. Zhao, Jennifer Seberry, Beata J. Wysocki, Tadeusz A. Wysocki
Complex Orthogonal Spreading Sequences Using Mutually Orthogonal Complementary Sets, Y. Zhao, Jennifer Seberry, Beata J. Wysocki, Tadeusz A. Wysocki
Tadeusz Wysocki
This paper presents a new family of complex spreading sequences designed using mutually orthogonal(MO) complementary sets. Based on the technique described in this paper, the correlation properties of sets of sequences are compared to well-known Walsh-Hadamard sequence sets. Further improvement of correlation qualities can be achieved by employing a diagonal modification method. We also present simulation results of an asynchronous multiuser CDMA system using the modified sequences.