فهرست مطالب

Journal of Communication Engineering
Volume:2 Issue: 1, Winter 2013

  • تاریخ انتشار: 1392/02/04
  • تعداد عناوین: 6
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  • H. Samimi Pages 1-12
    In this paper, the performance analysis of an energy detector is exploited over composite multipath/shadowing fading channels, which is modeled by Rayleigh-lognormal (RL) distribution. Based on an approximate channel model which was recently proposed by the author, the RL envelope probability density function (pdf) is approximated by a finite sum of weighted Rayleigh pdfs. Relying on this interesting feature, the performance of energy detector over RL fading channel is investigated and approximate closed-form expression is derived for the detection probability (). Further, results are extended to diversity reception case, where selection diversity (SC) technique is adopted to improve the detection performance. Selection Diversity is one of the most simplest diversity techniques, in which, the receiver simply picks the signal with the largest SNR among the received signals. In this regard, an approximate closed-form expression is derived for the pdf of the resulting signal-to-noise ratio (SNR) of SC receiver. Using this approximated pdf, an analytical closed-form expression is derived for the of energy detector with SC diversity. The presented analysis is validated by numerical and simulation results.
    Keywords: Energy detection, Rayleigh, lognormal distribution, Selection combining, composite fading channel
  • V. Golzadeh, S. Akhlaghi, M. Baghani Pages 13-21
    This paper concerns two-hop communication over relay-assisted Block fading channel. It is assumed there is not a direct link between the transmitter and the affiliated destination and the communication occurs in two hops through the use of a relay, where the amplify and forward (AF) strategy is employed at this node. In this case, in a Rayleigh block fading channel, the optimal weight function at the relay in terms of maximizing the received signal to noise ratio (SNR) at the destination is derived, assuming the relay is aware of channel gains associated with both hops and that the relay is subject to an average power constraint. Finally, the resulting SNR is compared to the case of having a peak power constraint at the relay which is served as a benchmark throughout the simulations.
    Keywords: amplify, forward relay, peak power constraint, average power constraint
  • . Osmani-Bojd, A. Sahebalam, Gh. Abed Hodtani Pages 22-42
    In this paper, Ultra-wideband (UWB) multiple access relay channel with correlated noises at the relay and receiver is investigated. We obtain outer and inner bounds for the IEEE 802.15.3a UWB multiple access relay channel, and also, a diversity gain bound. Finally, we evaluate some results numerically and show that noise correlation coefficients play important role in determining relay position.
    Keywords: Ultra wideband, multiple access relay channel, diversity gain, outage probability
  • M. Darvish, H. R. Hassani Pages 43-53
    This paper presents a new approach for the design of a multiband uniplanar CPW-fed monopole antenna. The antenna consists of a fork like monopole strip to which is added an inverted U-shaped strip. The three branch fork like strip can create three resonant bands within the WLAN range while the placement of the inverted U-shaped strip provides a better impedance matching for the lowest resonant frequency band. Loading slot on the top of the U-shaped strip with asymmetric arms can add two further resonant frequency bands. This antenna can cover the frequencies of PCS, WiMAX and WLAN applications along with the major part of the C band. A prototype of the antenna is fabricated and tested. A good agreement is found between simulated and measured results.
    Keywords: Multiband Slot Loaded CPW, fed Monopole Antenna
  • Hamid G. Bafghi, Babak Seyfe Pages 54-63
    In this paper the secrecy problem in the cognitive state-dependent interference channel is considered. In this scenario we have a primary and a cognitive transmitter-receiver pairs. The cognitive transmitter has the message of the primary sender as side information. In addition, the state of the channel is known at the cognitive encoder. Hence, the cognitive encoder uses this side information to cooperate with the primary transmitter. The message of the cognitive encoder must be secret at the primary receiver, i.e., the primary receiver act as an eavesdropper for the cognitive transmitter. An achievable rate region and an outer bound on the rate region in this channel are derived. The results are extended to the previous works as special cases.
    Keywords: Cognitive radio, secrecy capacity, side information, perfect secrecy
  • Maryam Majidzadeh, Changiz Ghobadi, Javad Nourinia Pages 64-73
    In this paper, a novel CPW-fed antenna is presented for UWB applications. The antenna mainly comprises of a simple circular patch and a modified ground plane. The inclusion of two novel symmetrical rectangular slots with inner area of 3×2.8 mm2 to the top corners of the antenna creates a new path for the current and consequently leads to the bandwidth enhancement. A rectangular stub is also adopted to further broaden the antenna impedance bandwidth. The proposed antenna has a compact size of 20×20×1.6 mm3 and covers the wide frequency band of 3-23.5 GHz (154%). Constant gain and suitable radiation patterns are observed for the presented antenna. Good agreement between the simulated and measured results clearly shows the validity of the proposed structure. The design steps and bandwidth enhancement process are discussed in detail.
    Keywords: CPW feed line, UWB antenna, Wide frequency band