Kiattisak Maichalernnukul

On the performance of coherent and noncoherent UWB detection systems using a relay with multiple antennas

In this paper, we present detect-and-forward relaying approaches for a coherent ultra-wideband (UWB) detection (specifically selective-Rake reception) system and for a noncoherent UWB detection (specifically differential transmittedreference, DTR) system in order to achieve greater coverage in multipath fading channels. Multiple-antenna relay system are also proposed to further enhance the overall system performance. The corresponding bit error rate (BER) performance is evaluated theoretically and via simulations. The effect of some design factors on this performance is investigated. Analytical and simulation results verify the performance improvement of the proposed relay systems over the direct transmission systems.

Design and Performance of Dual-Hop MIMO UWB Transmissions

To coexist with existing legacy wireless systems, the transmit power spectral density of ultrawideband (UWB) impulse radio systems is limited. The coverage range of UWB systems is then confined to within a few meters. Dual-hop relaying or multiple-input-multiple-output (MIMO) technology is one possible way of achieving greater UWB system coverage. This paper presents the design of dual-hop UWB MIMO relay systems (in which a source, relay, and destination have multiple antennas) according to the availability of channel state information (CSI) and their performance analysis over a UWB multipath fading channel. In particular, the decouple-and-forward and decode-and-forward relay systems are proposed when partial CSI is only available at the receiver side. On the other hand, with partial CSI being available at the transmitter side, we propose the amplify-and-forward and detect-and-forward relay systems. The exact formulas for the outage probabilities of those systems are derived. Furthermore, we evaluate, in closed form, the amount of fading and bit error rate expressions under sufficiently high signal-to-noise ratio and verify them through comparison with the simulation results. The effect of spatial correlation on the performance of our proposed systems is also studied. Numerical examples of the results provide valuable insights into the design of UWB MIMO relay systems.

Performance Investigation of a UWB Relay System using Multiple Relays with Multiple Antennas in IEEE 802.15.3a Channel

In order to coexist with existing legacy wireless systems, the transmit power spectral density (PSD) of ultra-wideband (UWB) impulse radio systems is limited. The coverage range of the UWB systems is then confined within a few meters. One possible way to achieve a greater coverage is a short-range multihop relaying strategy. This paper proposes a two-hop UWB relay system using multiple detect-and-forward relays, each of which is equipped with multiple antennas. Each multiple-antenna relay performs spatial diversity reception with partial-Rake scheme in the first hop, and decides whether or not to perform spatial transmit diversity with partial-pre-Rake scheme in the second hop. This leads not only to low complexity at the receiver, but also to reduced error propagation. Moreover, we derive the outage probability of the proposed relay system based on the IEEE 802.15.3a channel model. The effects of using multiple relay antennas, relays, and Rake/pre-Rake fingers on the outage performance are demonstrated. The tradeoffs among the numbers of relay antennas, relays, and Rake/pre-Rake fingers are also investigated. Numerical results show that it is best to use multiple relay antennas to improve the outage performance of the proposed system. Furthermore, in general, increasing the number of relays is more beneficial than increasing the number of Rake/pre-Rake fingers.

UWB MIMO cooperative relay systems: BER analysis and relay regions

In this paper, bit error rate (BER) analysis is presented for ultra-wideband (UWB) multiple-input multiple-output (MIMO) cooperative relay systems, where partial channel state information (CSI) is only available at the receiver side. In the analysis, decouple-and-forward (DCF) and decode-and-forward (DF) relaying schemes are considered. For these schemes, the relay regions, in which cooperative relaying outperforms direct transmission, and the effects of power optimization are studied through numerical results.

Performance of dual-hop MIMO ultra-wideband transmissions: Preliminary results

In this paper, a dual-hop multiple-input multiple-output (MIMO) ultra-wideband (UWB) communication system in a frequency-selective fading environment is presented for the first time. The focus is on the case that partial channel state information (CSI) is only available at the receiver side. The relaying schemes associated with this case are proposed, and the exact outage probability analysis of the dual-hop MIMO UWB system using such relaying schemes is provided.

Rake fingers versus multiple antennas for UWB relay systems - which one is better?

In order to coexist with existing legacy wireless systems, the transmit power spectral density (PSD) of ultra-wideband (UWB) impulse radio systems is limited. The coverage range of the UWB systems is then confined within a few meters. One possible way to achieve a greater coverage is a short-range multihop relaying strategy. A one-hop relay node can be either an amplify-and-forward (AF) or decode-and-forward (DF) relay. This paper analyzes the bit error rate (BER) performance of a selective-Rake system using an uncoded DF relay under imperfect channel estimation in UWB multipath fading channels. A multiple-antenna relay system is proposed to further enhance the overall system performance. The influence of the number of selective-Rake fingers, the number of relay antennas, and channel estimation errors on the performance of the single- and multiple-antenna relay systems is investigated. Analytical and simulation results verify the performance improvement of the relay systems over the direct transmission system.

Classification via k-means clustering and distance-based outlier detection

We propose a two-phase classification method. Specifically, in the first phase, a set of patterns (data) are clustered by the k-means algorithm. In the second phase, outliers are constructed by a distance-based technique and a class label is assigned to each pattern. The Knowledge Discovery Databases (KDD) Cup 1999 data set, which has been utilized extensively for development of intrusion detection systems, is used in our experiment. The results show that the proposed method is effective in intrusion detection.

On the Performance of the Time Reversal SM-MIMO-UWB System on Correlated Channels

The impact of spatial correlation on the multi-input multi-output ultrawide band (MIMO-UWB) system using the time reversal (TR) technique is investigated. Thanks to TR, several data streams can be transmitted by using only one antenna in a system named virtual MIMO-TRUWB. Since the virtual MIMO-TR-UWB system is not affected by the transmit correlation, under the condition of the high spatial correlation, it outperforms the true MIMO-UWB system with multiple transmit antennas. The channel measurements are performed in short-range indoor environment, both line-of-sight and non-line-of-sight to verify the adopted correlated channel model.

Performance of ultrawideband cooperative relay systems in the presence of narrowband interference

In this paper, the performance of ultrawideband (UWB) cooperative relay systems in the presence of narrowband (NB) interference is evaluated for the first time. Specifically, we consider UWB cooperative amplify-and-forward and UWB cooperative detect-and-forward systems where a single-tone NB interferer exists, and present their bit-error-rate analysis. Simulation results based on such analysis demonstrate how the NB interference impacts on the system performance.

Performance of UWB MIMO relay systems in real UWB channels

In this paper, the performance of various ultra-wideband (UWB) multiple-input multiple-output (MIMO) relay systems is evaluated for the first time based on UWB channel measurements. In particular, the measurement results for UWB relay channels in line-of-sight as well as non-line-of-sight indoor environments are presented. The average bit error rates of dual-hop MIMO relay systems and cooperative MIMO relay systems are examined and compared in the measured channels.