Channel Characteristics and Transmission Performance for Various Channel Configurations at 60 GHz

Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2007, Article ID 19613, 15 pages doi:10.1155/2007/19613 Research Article Channel Characteristics and Transmission Performance for Various Channel Configurations at 60 GHz Haibing Yang, Peter F. M. Smulders, and Matti H. A. J. Herben Department of Electrical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands Received 13 June 2006; Accepted 20 March 2007 Recommended by Chia-Chin Chong Extensive measurements are conducted in room environments at 60 GHz to analyze the channel characteristics for various channel configurations. Channel parameters retrieved from measurements are presented and analyzed based on generic channel models. Particularly, a simple single-cluster model is applied for the parameter retrieval and performance evaluation. By this model, power delay profiles are simply described by a K-factor, a root-mean-squared delay spread, and a shape parameter. The considered channels are configured with the combination of omnidirectional, fan-beam, and pencil-beam antennas at transmitter and receiver sides. Both line-of-sight (LOS) and non-LOS (NLOS) channels are considered. Further, to evaluate the transmission performance, we analyze the link budget in the considered environments, then design and simulate an OFDM system with a data rate of 2 Gbps to compare the bit-error-rate (BER) performance by using the measured and modeled channels. Both coded and uncoded OFDM systems are simulated. It is observed that the BER performance agrees well for the measured and modeled channels. In addition, directive configurations can provide sufficient link margins and BER performance for high data rate communications. To increase the coverage and performance in the NLOS area, it is preferable to apply directive antennas. Copyright © 2007 Haibing Yang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1. INTRODUCTION In recent years, intensive efforts have been made worldwide for the application of high data rate wireless communication system in the frequency band of 60 GHz [1–5]. Special features of the radio propagation in this frequency band, namely high penetration loss of construction materials and severe oxygen absorption, and broadband spectrum (common bands of 59–62 GHz worldwide) make it suitable for the deployment of high data rate short-distance communications [3, 6]. Recently, the IEEE 802.15.3 Task Group 3c was formed to standardize the 60 GHz wireless personal area network (WPAN) systems, which will allow high data rate up to 3 Gbps [5]. Even higher data rate requirements would be expected in the future. The low-cost and low-complexity implementation of such systems requires a suitable channel model for the characteristics of the 60 GHz radio propagation, which can be used for the codesign of RF front-end and baseband processing. To this end, this paper will focus on channel modelling, model parameter retrieval, and system performance evaluation over 60 GHz channels. One of the biggest challenges for designing a high datarate 60 GHz system is the limited link budget due to high path loss during radio propagation [3, 5–7]. For a fixed separation between transmitter (TX) and receiver (RX), the propagation loss at 60 GHz is about 30 dB higher than at 2 GHz in free space. In this sense, it is preferable to employ high-gain directive antennas, especially for a fixed point-to-point application. Thanks to the relatively small dimensions of 60 GHz antennas, an alternative to high-gain antennas is to use highly flexible antenna arrays for adaptive beamforming. On the other hand, an omnidirectional antenna might be used in some applications where a full coverage is required. For most 60 GHz applications, the transmitter and the receiver will keep stationary, and the time variation of the channel will be introduced by moving objects due to the Doppler effect. In particular, the movements of human bodies within the channel will cause significant temporal fading and shadowing effect, whose level depends on the moving speed, the number of persons, and the propagation environment [8–10]. The remaining significant impact on the system caused by the radio channel is the frequency selectivity due 2 EURASIP Journal on Wireless Communications and Networking to multipath effect, which induces intersymbol interference (ISI) in communication systems [11–14]. Multipath propagation in indoor environments is strongly affected by the dimensions of the environment and the density of furnishings. The influence of the environment on the channel can be noticed in the power delay profile (PDP), which describes the span of the received signal over time delay. In a local area within a range of tens of wavelength, cluster-wise arrival behavior of scattered waves has been observed from measurements and the average PDP is formulated by multicluster models [15–19]. In a global area such as a room environment, the average PDP is exponentially decaying over delay in addition to the direct path [20, 21]. In this single cluster model, a constant-level part might appear before the decaying part caused by the elevation dependence of antenna radiation patterns and the height difference between the transmit antenna and the receive antenna [21]. The impact of various PDP shapes on system performance has been considered in [12, 22, 23]. There they conclude that as long as the root-mean-squared (RMS) delay spread of the PDP is small compared with the symbol duration, the profile shape has a negligible impact on system performance, but the performance is strongly influenced by the RMS delay spread. The purpose of this paper is to analyze the 60 GHz channel characteristics and to evaluate the system performance for various channel configurations. Due to the simplicity and the directness of the relationship between RMS delay spread (RDS) and PDP, the simple single-cluster model is applied to retrieve model parameters from measurements and used to evaluate the system performance. The structure of this paper is as follows. In Section 2, we give an overview of the generic theory for radio channels. In Section 3, channel measurements will be described in indoor environments for various antenna configurations. Then, channel parameters are retrieved and analyzed from the measured data. Particularly, the shape parameters of power delay profiles are retrieved to distinguish the channel characteristics of various configurations. Next in Section 4, we analyze the link budget and then simulate an equivalent baseband OFDM system for 60 GHz radio applications. The coded/uncoded BER performance is evaluated and compared for the measured and modeled channels. The BER performance for various channel configurations is also a (...truncated)