Sat, 19 Jul 2008 03:02:44 BST CiteULike: dcastro's Lee http://www.citeulike.org/user/dcastro/author/Lee CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/dcastro/article/3015403 <i>Antennas and Propagation, IEEE Transactions on, Vol. 56, No. 5. (2008), pp. 1236-1241.</i><br /><br />A small-sized active integrated antenna (AIA), consisting of a transmission feedback oscillator loaded with a microstrip antenna is presented in this paper. The oscillator antenna, which consists of a NEC super low noise high frequency field effect transistor (HF FET) integrated into the center of a segmented patch antenna, was designed for X-band at 8.50 GHz, and occupies a 5 times 6 mm² area. The active integrated antenna demonstrates stable oscillations and excellent radiation patterns at X-band design frequencies. When biased using a single 1.5 volt battery connected between the source and drain and with the gate terminal open, the antenna effective isotropic radiated power (EIRP) and direct current (DC)-to-radiated radio frequency (RF) conversion efficiency are +11.2 dBm and 10.5%, respectively. The radiated power level and directivity are +4.5 dBm and 6.7 dBi, respectively. The phase noise at 100 kHz offset from the carrier is -87.5 dBc/Hz, which is a notable improvement over existing AIA designs. The AIA features compact size and simple geometry, yet provides radiated power levels and radiation efficiencies that are comparable to values typically obtained using circuits that occupy larger areas, and use thicker substrates with much lower dielectric constant values. Small-Size X-Band Active Integrated Antenna With Feedback Loop CH Mueller RQ Lee RR Romanofsky CL Kory KM Lambert FW Van Keuls FA Miranda doi:10.1109/TAP.2008.922628 Antennas and Propagation, IEEE Transactions on, Vol. 56, No. 5. (2008), pp. 1236-1241. 2008-07-17T19:46:52-00:00 2008 Antennas and Propagation, IEEE Transactions on 56 5 1236 1241 active antenna small http://www.citeulike.org/user/dcastro/article/3008096 <i>Vehicular Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61st, Vol. 3 (2005), pp. 1763-1767 Vol. 3.</i><br /><br />This paper proposes the novel OFDM transmission scheme that can effectively overcome ISI by adjusting CP length. As a way of combating ISI caused by multipath delay longer than guard interval, interference canceller or powerful channel coding has been proposed. Such approaches may reduce ISI, but it needs much complex computation or considerably decreases transmission efficiency to completely eliminate ISI. In our proposed scheme, CP length can be adaptively controlled by simply adjusting sampling rate. Hence it does neither much increase receiver complexity nor decrease effective data rate, compared to the conventional schemes. Our simulation results show that by employing the proposed OFDM transmission scheme, ISI can be effectively avoided in mobile environment with various multipath delays. Novel OFDM transmission scheme to overcome caused by multipath delay longer than cyclic prefix Chiwoo Lim Youngbin Chang Jaeweon Cho Panyuh Joo Hyeonwoo Lee doi:10.1109/VETECS.2005.1543624 Vehicular Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61st, Vol. 3 (2005), pp. 1763-1767 Vol. 3. 2008-07-16T11:27:19-00:00 2005 Vehicular Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61st 3 1763 1767 Vol. 3 multipath ofdm http://www.citeulike.org/user/dcastro/article/2933575 <i>Communications, IEEE Transactions on, Vol. 54, No. 7. (2006), pp. 1170-1174.</i><br /><br />A multiuser bit-loading problem is investigated in multicarrier communication systems. Assuming knowledge of all the channel gains, we propose a multiuser bit-loading algorithm that attempts to minimize the total power to transmit a target rate-sum of all users. It is shown that this algorithm is optimal when the interference among users is nonexistent or strong. The simulation results show that the proposed algorithm finds a near-optimal solution for very-high-speed digital subscriber line systems. Multiuser bit loading for multicarrier systems Jungwon Lee RV Sonalkar JM Cioffi doi:10.1109/TCOMM.2006.877955 Communications, IEEE Transactions on, Vol. 54, No. 7. (2006), pp. 1170-1174. 2008-06-27T11:08:55-00:00 2006 Communications, IEEE Transactions on 54 7 1170 1174 bit-loading multicarrier multiuser http://www.citeulike.org/user/dcastro/article/1674569 <i>Wireless Communications, IEEE [see also IEEE Personal Communications], Vol. 12, No. 2. (2005), pp. 56-65.</i><br /><br />High peak-to-average power ratio of the transmit signal is a major drawback of multicarrier transmission such as OFDM or DMT. This article describes some of the important PAPR reduction techniques for multicarrier transmission including amplitude clipping and filtering, coding, partial transmit sequence, selected mapping, interleaving, tone reservation, tone injection, and active constellation extension. Also, we make some remarks on the criteria for PAPR reduction technique selection and briefly address the problem of PAPR reduction in OFDMA and MIMO-OFDM. An overview of peak-to-average power ratio reduction techniques for multicarrier transmission Seung Han Jae Lee doi:10.1109/MWC.2005.1421929 Wireless Communications, IEEE [see also IEEE Personal Communications], Vol. 12, No. 2. (2005), pp. 56-65. 2007-09-19T07:04:50-00:00 2005 Wireless Communications, IEEE [see also IEEE Personal Communications] 12 2 56 65 ofdm overview papr http://www.citeulike.org/user/dcastro/article/2923030 <i>Solid-State Circuits, IEEE Journal of, Vol. 35, No. 3. (2000), pp. 326-336.</i><br /><br />Linear time-invariant (LTI) phase noise theories provide important qualitative design insights but are limited in their quantitative predictive power. Part of the difficulty is that device noise undergoes multiple frequency translations to become oscillator phase noise. A quantitative understanding of this process requires abandoning the principle of time invariance assumed in most older theories of phase noise. Fortunately, the noise-to-phase transfer function of oscillators is still linear, despite the existence of the nonlinearities necessary for amplitude stabilization. In addition to providing a quantitative reconciliation between theory and measurement, the time-varying phase noise model presented in this tutorial identifies the importance of symmetry in suppressing the upconversion of 1/f noise into close-in phase noise, and provides an explicit appreciation of cyclostationary effects and AM-PM conversion. These insights allow a reinterpretation of why the Colpitts oscillator exhibits good performance, and suggest new oscillator topologies. Tuned LC and ring oscillator circuit examples are presented to reinforce the theoretical considerations developed. Simulation issues and the accommodation of amplitude noise are considered in appendixes Oscillator phase noise: a tutorial TH Lee A Hajimiri doi:10.1109/4.826814 Solid-State Circuits, IEEE Journal of, Vol. 35, No. 3. (2000), pp. 326-336. 2008-06-24T09:43:22-00:00 2000 Solid-State Circuits, IEEE Journal of 35 3 326 336 noise oscillator phase tutorial http://www.citeulike.org/user/dcastro/article/2896196 <i>Electronics Letters, Vol. 31, No. 16. (1995), pp. 1310-1312.</i><br /><br />A coaxially-fed single-layer single-patch wide-band microstrip antenna in the form of a rectangular patch with a U-shaped slot is discussed. Measurements showed that this antenna can attain 10-40% impedance bandwidth without the need of adding parasitic patches in another layer or in the same layer Single-layer single-patch wideband microstrip antenna T Huynh KF Lee Electronics Letters, Vol. 31, No. 16. (1995), pp. 1310-1312. 2008-06-15T13:37:14-00:00 1995 Electronics Letters 31 16 1310 1312 antenna microstrip patch wideband http://www.citeulike.org/user/dcastro/article/2877935 <i>Communications, IEEE Transactions on, Vol. 42, No. 12. (1994), pp. 3073-3079.</i><br /><br />New good rate-P/(P+δ) rate-compatible punctured convolutional (RCPC) codes for 2&les;P&les;7 and 1&les;δ&les;(n-1)P were found and tabulated, These codes have been determined by iterative search based upon a criterion of maximizing the free distance and were generated by periodically puncturing their rate-1/n mother codes of memory 2&les;M&les;6 and n=2. These codes are expected to find their applications in unequal error protection schemes employing Viterbi decoding New rate-compatible punctured convolutional codes for Viterbi decoding LHC Lee doi:10.1109/26.339824 Communications, IEEE Transactions on, Vol. 42, No. 12. (1994), pp. 3073-3079. 2008-06-09T19:24:44-00:00 1994 Communications, IEEE Transactions on 42 12 3073 3079 convolutional puncturing viterbi http://www.citeulike.org/user/dcastro/article/2877933 <i>Vehicular Technology, IEEE Transactions on, Vol. 40, No. 2. (1991), pp. 291-302.</i><br /><br />A general description of code division multiple access (CDMA) is presented. This overview of CDMA highlights the potential for increasing capacity in future cellular communications. The author describes the mobile radio environment and its impact on narrowband and wideband propagation. The advantage of having CDMA in cellular systems is discussed, and the concept of radio capacity in cellular CDMA is introduced. The power control schemes in CDMA are analyzed in detail Overview of cellular CDMA WCY Lee doi:10.1109/25.289410 Vehicular Technology, IEEE Transactions on, Vol. 40, No. 2. (1991), pp. 291-302. 2008-06-09T19:24:40-00:00 1991 Vehicular Technology, IEEE Transactions on 40 2 291 302 cdma cellular overview http://www.citeulike.org/user/dcastro/article/2839848 <i>Antennas and Propagation Society International Symposium, 2005 IEEE, Vol. 2B (2005), pp. 218-221 vol. 2B.</i><br /><br />The paper presents the design of an electrically small antenna employing a composite right/left-handed (CRLH) transmission line. The physical size and operating frequency of the antenna depend on the unit cell size and equivalent transmission line model parameters. Therefore, the small antenna is realized by miniaturizing the unit cell and increasing the shunt inductance and series capacitance. A four unit cell resonant antenna is designed and tested at 1.06 GHz. The length, width and height of the proposed antenna are (1/19)/spl lambda//sub 0/, (1/23)/spl lambda//sub 0/, and (1/83)/spl lambda//sub 0/, respectively. Design of resonant small antenna using composite right/left-handed transmission line Cheng-Jung Lee KMKH Leong T Itoh Antennas and Propagation Society International Symposium, 2005 IEEE, Vol. 2B (2005), pp. 218-221 vol. 2B. 2008-05-28T06:43:43-00:00 2005 Antennas and Propagation Society International Symposium, 2005 IEEE 2B 218 221 vol. 2B antenna crlh resonant small tl http://www.citeulike.org/user/dcastro/article/2839847 <i>Microwave Symposium Digest, 2006. IEEE MTT-S International (2006), pp. 935-938.</i><br /><br />This paper presents a methodology of designing a microwave bandstop filter and a bandpass filter by using a Composite Right/Left Handed transmission line (CRLH-TL) as part of a transversal filter. The CRLH-TL can be engineered to have specific phase slope and phase offset. Connecting the CRLH-TL and the conventional microstrip delay line at both input and output can establish a transversal filter where the signal merging at the output has broadband out of phase characteristics. Therefore, the bandstop filter can be created with signal rejection over a wide frequency range. The measured 3dB bandwidth of the bandstop filter is 130% and the minimum insertion loss at the next passband is ¿1.7dB. In addition, based on the bandstop filter a bandpass filter with a wide signal rejection range is developed by creating a frequency dependent defect in one branch of the bandstop filter. This is implemented by either attaching a microstrip open stub or capacitively coupling a microstrip resonator to the microstrip delay line. The 3dB passband bandwidth and the minimum insertion loss are 18%, ¿1.5dB and 8%, ¿2dB corresponding to the open stub and the resonator scheme, respectively. Metamaterial Transmission Line Based Bandstop and Bandpass Filter Designs Using Broadband Phase Cancellation Cheng-Jung Lee KMKH Leong Tatsuo Itoh doi:10.1109/MWSYM.2006.249870 Microwave Symposium Digest, 2006. IEEE MTT-S International (2006), pp. 935-938. 2008-05-28T06:43:41-00:00 2006 Microwave Symposium Digest, 2006. IEEE MTT-S International 935 938 filter metamaterial tl http://www.citeulike.org/user/dcastro/article/2839827 <i>Microwave Symposium, 2007. IEEE/MTT-S International (2007), pp. 1745-1748.</i><br /><br />This paper presents a broadband quadrature hybrid which makes use of the broadband power division properties of conventional Wilkinson power splitters along with broadband phase difference achieved using metamaterial based delay lines. The bandwidth of the 90degplusmn5deg phase difference and 0.48 dB power difference between the outputs of the Wilkinson power splitter and metamaterial delay line combination is 67%. The full four-port coupler is formed employing an additional combiner. A phase/power difference between the hybrid outputs of 90degplusmn10deg and 1.2 dB, respectively, are observed over the same 67% bandwidth. To demonstrate the applicability of the proposed broadband quadrature hybrid, a continuous phase shifter which is based on the vector sum method is tested. Broadband Quadrature Hybrid Design Using Metamaterial Transmission Line and Its Application in the Broadband Continuous Phase Shifter Cheng-Jung Lee KMKH Leong T Itoh doi:10.1109/MWSYM.2007.380066 Microwave Symposium, 2007. IEEE/MTT-S International (2007), pp. 1745-1748. 2008-05-28T06:41:48-00:00 2007 Microwave Symposium, 2007. IEEE/MTT-S International 1745 1748 broadband crlh metamaterial tl http://www.citeulike.org/user/dcastro/article/2833503 <i>Computers, IEEE Transactions on, Vol. 53, No. 12. (2004), pp. 1523-1534.</i><br /><br />Hardware simulation offers the potential of improving code evaluation speed by orders of magnitude over workstation or PC-based simulation. We describe a hardware-based Gaussian noise generator used as a key component in a hardware simulation system, for exploring channel code behavior at very low bit error rates (BERs) in the range of 10/sup -9/ to 10/sup -10/. The main novelty is the design and use of nonuniform piecewise linear approximations in computing trigonometric and logarithmic functions. The parameters of the approximation are chosen carefully to enable rapid computation of coefficients from the inputs while still retaining high fidelity to the modeled functions. The output of the noise generator accurately models a true Gaussian Probability Density Function (PDF) even at very high /spl sigma/ values. Its properties are explored using: 1) several different statistical tests, including the chi-square test and the Anderson-Darling test, and 2) an application for decoding of low-density parity-check (LDPC) codes. An implementation at 133 MHz on a Xilinx Virtex-II XC2V4000-6 FPGA produces 133 million samples per second, which is seven times faster than a 2.6 GHz Pentium-IV PC; another implementation on a Xilinx Spartan-IIE XC2S300E-7 FPGA at 62 MHz is capable of a three times speedup. The performance can be improved by exploiting parallelism: an XC2V4000-6 FPGA with nine parallel instances of the noise generator at 105 MHz can run 50 times faster than a 2.6 GHz Pentium-IV PC. We illustrate the deterioration of clock speed with the increase in the number of instances. A Gaussian noise generator for hardware-based simulations DU Lee W Luk JD Villasenor PYK Cheung doi:10.1109/TC.2004.106 Computers, IEEE Transactions on, Vol. 53, No. 12. (2004), pp. 1523-1534. 2008-05-26T10:59:07-00:00 2004 Computers, IEEE Transactions on 53 12 1523 1534 generator hardware noise http://www.citeulike.org/user/dcastro/article/2819371 <i></i><br /><br />In the context of orthogonal frequency division multiplexing (OFDM), most papers define OFDM symbol synchronization as frame synchronization. In this paper, a frame is defined as a block of several OFDM symbols in the time dimension. The main contribution of this work is to propose a novel, lowcomplexity, frame synchronization method for multi-carrier systems that does not require any transmission overhead; this increases the channel capacity, power and bandwidth efficiency. Also, it enables a... New Frame Synchronization Technique For Ofdm/ofdma And Mc-Cdma Systems Lee Darnell 2008-05-21T10:53:17-00:00 cdma frame ofdm ofdma synchronization http://www.citeulike.org/user/dcastro/article/2809089 <i>Communications, 2003. ICC '03. IEEE International Conference on, Vol. 2 (2003), pp. 1196-1200 vol.2.</i><br /><br />In recent years there has been considerable interest in the development of standards for wireless local area networks. In particular, IEEE's 802.11a and 802.11g both employ coded orthogonal frequency division multiplexing (COFDM) but operate in different frequency bands. In this paper, the performance and relative merits of 802.11a and 802.11g are compared for the scenario of a corporate office wireless LAN application. It is shown that for comparable scenarios 802.11g achieves superior range but that 802.11a achieves higher data rates. Thus the two standards are found to have complimentary strengths and weaknesses. An evaluation of the performance of IEEE 802.11a and 802.11g wireless local area networks in a corporate office environment A Doefexi S Armour Beng-Sin Lee A Nix D Bull doi:10.1109/ICC.2003.1204558 Communications, 2003. ICC '03. IEEE International Conference on, Vol. 2 (2003), pp. 1196-1200 vol.2. 2008-05-18T14:14:36-00:00 2003 Communications, 2003. ICC '03. IEEE International Conference on 2 1196 1200 vol.2 80211 performance wireless wlan http://www.citeulike.org/user/dcastro/article/2808917 <i>PROCEEDINGS OF ISAP2005 (2005)</i> A Novel Design of Balun using Left-Handed Transmission Line Seungjun Lee Jong-Sik Lim Hoe-Sung Yang Sangwook Nam PROCEEDINGS OF ISAP2005 (2005) 2008-05-18T12:24:35-00:00 2005 PROCEEDINGS OF ISAP2005 balun crlh metamaterial tl http://www.citeulike.org/user/dcastro/article/2805105 <i>Global Telecommunications Conference, 1998. GLOBECOM 98. The Bridge to Global Integration. IEEE, Vol. 4 (1998), pp. 2168-2173 vol.4.</i><br /><br />A noncoherent sequential PN code acquisition technique is proposed. Noncoherent detection is employed to handle the seriously noisy environments, while the carrier frequency offset and data modulation effects can be simultaneously taken care of. To realize the sequential acquisition, the out-of-phase and in-phase sequences are properly modeled to avoid the significantly high error probabilities caused by the conventional widely used zero sequence model. Extensive computer simulation results indicated that the proposed PN code acquisition outperforms the fixed-dwell-time counterparts by roughly 2-6 dB with much lower false alarm and miss probabilities, and the superiority of the proposed technique becomes more significant at lower SNR conditions A noncoherent sequential PN code acquisition scheme in DS/SS receivers Jia-Chin Lin Lin-Shan Lee doi:10.1109/GLOCOM.1998.775919 Global Telecommunications Conference, 1998. GLOBECOM 98. The Bridge to Global Integration. IEEE, Vol. 4 (1998), pp. 2168-2173 vol.4. 2008-05-16T11:35:46-00:00 1998 Global Telecommunications Conference, 1998. GLOBECOM 98. The Bridge to Global Integration. IEEE 4 2168 2173 vol.4 acquisition code pn receiver sequential spread-spectrum http://www.citeulike.org/user/dcastro/article/2802472 <i>Vehicular Technology, IEEE Transactions on, Vol. 53, No. 1. (2004), pp. 49-60.</i><br /><br />In this paper, a fast acquisition scheme of pseudonoise (PN) sequences for direct-sequence spread-spectrum systems is proposed. The scheme exploits a new decision logic not only to estimate chip values, but also to check the reliability of the chip estimates. As a result, the internal state of a PN sequence generator is estimated more accurately. We derive the probability of finding a correct state estimate and show that the proposed scheme can reduce the average number of chips for acquisition when compared with the conventional scheme. It is also shown that the performance improvement is more noticeable in the moderate signal-to-noise-ratio range. Rapid acquisition of PN sequences with a new decision logic Jung Lee Iickho Song So Park Jumi Lee doi:10.1109/TVT.2003.819813 Vehicular Technology, IEEE Transactions on, Vol. 53, No. 1. (2004), pp. 49-60. 2008-05-15T18:51:28-00:00 2004 Vehicular Technology, IEEE Transactions on 53 1 49 60 acquisition fast pn http://www.citeulike.org/user/dcastro/article/2802464 <i>Personal, Indoor and Mobile Radio Communications, 2001 12th IEEE International Symposium on, Vol. 2 (2001), pp. G-6-G-10 vol.2.</i><br /><br />We propose an improved scheme for parallel acquisition of PN sequences of multi-carrier direct-sequence spread spectrum systems in the Rayleigh fading channel. Unlike conventional parallel acquisition schemes, the search region of each searcher in the proposed scheme is modified so that it is overlapped with that of other searchers. The use of the proposed search scheme enables us to obtain multiple information on the same code phase at different time instants, providing the time diversity effect. This effect results in acquisition performance robust to fading. The performance of the proposed acquisition scheme is analytically evaluated in terms of the detection probability and the mean acquisition time in the Rayleigh fading channel. Numerical results show that the proposed scheme can provide acquisition performance robust to channel conditions, including fading and correlation between the subchannels Parallel acquisition of PN sequences in Rayleigh fading channel and the application to the multi-carrier CDMA systems June Moon Yong-Hwan Lee doi:10.1109/PIMRC.2001.965311 Personal, Indoor and Mobile Radio Communications, 2001 12th IEEE International Symposium on, Vol. 2 (2001), pp. G-6-G-10 vol.2. 2008-05-15T18:49:52-00:00 2001 Personal, Indoor and Mobile Radio Communications, 2001 12th IEEE International Symposium on 2 G-6 G-10 vol.2 acquisition cdma channel fading parallel pn rayleigh http://www.citeulike.org/user/dcastro/article/2802245 <i>Communications, IEEE Transactions on, Vol. 47, No. 8. (1999), pp. 1233-1244.</i><br /><br />We present two code-acquisition schemes for a multicarrier direct-sequence code-division multiple-access system, one that uses equal gain combining and the other that uses selection combining. The code-acquisition performance of the two multicarrier systems, as well as that of a single-carrier system, are analyzed in both nonfading and Rayleigh fading channels under the assumption that the receiver is chip-synchronized; the effect of partial-band interference (PBI) on the performance is also included. It is demonstrated that in an additive white Gaussian noise channel, the single-carrier system has a better code-acquisition performance than both multicarrier systems. However, in a Rayleigh fading channel, the code-acquisition performance of a multicarrier system with equal gain combining is better than that of the single-carrier system, while a multicarrier system with selection combining has the same performance as the single-carrier system. Further, the presence of PBI more severely affects the code-acquisition performance of the single-carrier system than those of both multicarrier systems. Finally, the code-acquisition performance of a multicarrier system with equal gain combining is always better than that of the selection combining system Analysis of a multicarrier DS-CDMA code-acquisition system Dongwook Lee LB Milstein Hun Lee doi:10.1109/26.780460 Communications, IEEE Transactions on, Vol. 47, No. 8. (1999), pp. 1233-1244. 2008-05-15T17:57:12-00:00 1999 Communications, IEEE Transactions on 47 8 1233 1244 acquisition cdma code http://www.citeulike.org/user/dcastro/article/2802225 <i>Communications, IEEE Transactions on, Vol. 49, No. 4. (2001), pp. 734-743.</i><br /><br />A novel acquisition scheme that utilizes multipaths to improve the acquisition performance is proposed for frequency-selective fading channels. The proposed acquisition scheme employs nonconsecutive search and joint triple-cell detection. The performance is analyzed in frequency-selective Rayleigh fading channels. Equations for the probabilities of detection and false alarm are derived, and an expression for the mean acquisition time is developed. The mean acquisition time performance of the proposed and conventional acquisition schemes is evaluated and compared. It is found that the proposed acquisition scheme significantly outperforms the conventional one. The effects of various channel parameters such as the number of resolvable paths, the shape of the multipath intensity profile (MIP) and the signal-to-interference ratio (SIR) on acquisition performance are also investigated Utilization of multipaths for spread-spectrum code acquisition in frequency-selective Rayleigh fading channels Oh-Soon Shin Kwang Lee doi:10.1109/26.917779 Communications, IEEE Transactions on, Vol. 49, No. 4. (2001), pp. 734-743. 2008-05-15T17:46:43-00:00 2001 Communications, IEEE Transactions on 49 4 734 743 acquisition channel code fading frequency rayleigh selective spread-spectrum http://www.citeulike.org/user/dcastro/article/2802216 <i>Electronics Letters, Vol. 33, No. 16. (1997), pp. 1352-1354.</i><br /><br />An adaptive acquisition scheme of PN sequences is presented for DS/SS communications. The basic idea of the scheme is to apply the radar CFAR technique to the acquisition of PN sequences. The detection performance is analysed and an example of adaptive thresholding for multipath Rayleigh fading channels is given Acquisition of PN code with adaptive threshold for DS/SS communications Chang-Joo Kim Tae-Won Hwang Hyuck-Jae Lee Hwang-Soo Lee Electronics Letters, Vol. 33, No. 16. (1997), pp. 1352-1354. 2008-05-15T17:42:33-00:00 1997 Electronics Letters 33 16 1352 1354 acquisition adaptive code pn spread-spectrum threshold http://www.citeulike.org/user/dcastro/article/2802215 <i>Selected Areas in Communications, IEEE Journal on, Vol. 10, No. 4. (1992), pp. 750-759.</i><br /><br />The performance of sequential acquisition of <e1>m</e1> sequences, based on the sequential probability ratio test (SPRT), is studied. The authors consider a sliding correlator-type structure for the acquisition scheme, which the mean acquisition time is proportional to the average number of samples used for a synchronization test. Sequential acquisition requires the knowledge of the partial correlation of the pseudonoise (PN) sequence, however, as the partial correlation of an <e1>m</e1> sequence is difficult to model the authors propose an approximate upper bound. This is then piecewise linearized and used for designing the SPRT which is then compared to the fixed-dwell time technique, a scheme using the fixed sample size test. Numerical results show that the saving of acquisition time by the SPRT increases as the desired probabilities of errors and/or the input SNR decrease. Analytic results are verified by computer simulation Sequential acquisition of PN sequences for DS/SS communications: design and performance YH Lee S Tantaratana doi:10.1109/49.136070 Selected Areas in Communications, IEEE Journal on, Vol. 10, No. 4. (1992), pp. 750-759. 2008-05-15T17:42:26-00:00 1992 Selected Areas in Communications, IEEE Journal on 10 4 750 759 acquisition pn sequential spread-spectrum http://www.citeulike.org/user/dcastro/article/2802207 <i>Military Communications Conference Proceedings, 1999. MILCOM 1999. IEEE, Vol. 2 (1999), pp. 791-795 vol.2.</i><br /><br />When the code phase offset between two sequences is within one chip duration, the sum of two successive matched filter outputs has a constant value regardless of the residual code phase offset if the noise is absent. Based on this observation, we propose a new code acquisition scheme, which is robust to the variation of the residual code phase offset and outperforms the conventional scheme. Numerical results are also given to show that the proposed scheme is more robust to the variation of the residual code phase offset and has better performance than the conventional scheme on average A code acquisition scheme for DS/CDMA systems Seokho Yoon Iickho Song So Park Sun Kim Jooshik Lee doi:10.1109/MILCOM.1999.821311 Military Communications Conference Proceedings, 1999. MILCOM 1999. IEEE, Vol. 2 (1999), pp. 791-795 vol.2. 2008-05-15T17:42:10-00:00 1999 Military Communications Conference Proceedings, 1999. MILCOM 1999. IEEE 2 791 795 vol.2 acquisition cdma code http://www.citeulike.org/user/dcastro/article/2782058 <i>Antennas and Propagation Society International Symposium, 1999. IEEE, Vol. 2 (1999), pp. 912-915 vol.2.</i><br /><br />Two different types of novel dual band antennas suitable for a data communicator device are reported. The first antenna is a dual frequency, dual polarization microstrip patch antenna, capable of generating two distinct frequencies with different polarization characteristics and radiation patterns. This antenna has been intended for coverage of the GSM/Iridium's satellite frequencies. The second antenna modified bent folded monopole antenna having two resonant frequencies, with a frequency separation of 1.9. This antenna could be used in the GSM/DCS1800 frequencies. The limitations of both antennas are also briefly mentioned Multi-band antennas E Lee PS Hall P Gardner D Kitchener doi:10.1109/APS.1999.789460 Antennas and Propagation Society International Symposium, 1999. IEEE, Vol. 2 (1999), pp. 912-915 vol.2. 2008-05-10T00:00:58-00:00 1999 Antennas and Propagation Society International Symposium, 1999. IEEE 2 912 915 vol.2 antenna multiband http://www.citeulike.org/user/dcastro/article/2782021 <i>Microwave and Wireless Components Letters, IEEE, Vol. 12, No. 11. (2002), pp. 421-423.</i><br /><br />The authors experimentally investigate and discuss the effects of output harmonic termination on power added efficiency (PAE) and output power of an AlGaN/GaN high electron mobility transistor (HEMT) power amplifier (PA). The AlGaN/GaN HEMT PA with gate periphery of 1 mm was built and tested at L-band. Large-signal measurements and comparisons of the PAE and output power were carried out at different DC bias conditions from 50% of saturated drain current (I/sub dss/) to 1% of Id., for the PA with and without output harmonic termination. For class-AB operation at 25% of I/sub dss/, an increase of about 10% in peak PAE and 1 dBm in output power were observed in saturated output power range. Improvements of up to 9% in PAE and 1.2 dBm in output power were achieved over the measured DC bias conditions provided the output harmonics are properly terminated. Effects of output harmonic termination on PAE and output power of AlGaN/GaN HEMT power amplifier Y Chung CY Hang S Cai Y Chen W Lee CP Wen KL Wang T Itoh doi:10.1109/LMWC.2002.805532 Microwave and Wireless Components Letters, IEEE, Vol. 12, No. 11. (2002), pp. 421-423. 2008-05-09T23:49:18-00:00 2002 Microwave and Wireless Components Letters, IEEE 12 11 421 423 amplifier power http://www.citeulike.org/user/dcastro/article/2782004 <i>Microwave Conference, 2006. 36th European (2006), pp. 1044-1047.</i><br /><br />This paper presents a resonant type dual-band antenna with compact size which is realized by using an anisotropic metamaterial. The artificial anisotropic medium is implemented by employing a composite right/left-handed transmission line. The dispersion relation and the antenna physical size only depend on the composition of the unit cell and the number of cells used. By engineering the characteristics of the unit cells to be different in two orthogonal directions, the corresponding propagation constants can be controlled, thus enabling dual-band antenna resonances. In addition, the antenna dimensions can be markedly minimized by maximally reducing the unit cell size. The proposed antenna is designed at frequencies for PCS/Bluetooth applications. The physical size of the proposed dual-band antenna is 1/17lambda₀x1/17lambda₀x1/19lambda₀ where lambda₀ is the free space wavelength at 2.37GHz Compact Dual-Band Antenna Using an Anisotropic Metamaterial Cheng-Jung Lee KMKH Leong Tatsuo Itoh doi:10.1109/EUMC.2006.281112 Microwave Conference, 2006. 36th European (2006), pp. 1044-1047. 2008-05-09T23:43:04-00:00 2006 Microwave Conference, 2006. 36th European 1044 1047 antenna compact dual-band metamaterial http://www.citeulike.org/user/dcastro/article/2764007 <i>Selected Areas in Communications, IEEE Journal on, Vol. 19, No. 6. (2001), pp. 1128-1137.</i><br /><br />We propose a new scheme for rapid acquisition of PN signals in direct-sequence spread spectrum (DS/SS) systems by estimating the phase of the received PN signal with the use of an auxiliary signal. The auxiliary signal can be generated by a sum of the phase shifted PN signals. The phase of the incoming PN signal is estimated using the properties of cross correlation between the PN signal and the auxiliary signal. True phase alignment is detected using a conventional serial search scheme, where the initial phase of the local PN generators is set to a value obtained by the phase estimator. The performance of the proposed acquisition scheme is analytically evaluated in terms of the mean acquisition time. Numerical results show that the proposed scheme can achieve acquisition at least two times faster than the conventional scheme in the nominal operating condition Rapid acquisition of PN signals for DS/SS systems using a phase estimator Suwon Kang Yong-Hwan Lee doi:10.1109/49.926368 Selected Areas in Communications, IEEE Journal on, Vol. 19, No. 6. (2001), pp. 1128-1137. 2008-05-07T06:42:44-00:00 2001 Selected Areas in Communications, IEEE Journal on 19 6 1128 1137 acquisition pn pn-sequence spread-spectrum http://www.citeulike.org/user/dcastro/article/2762226 <i>Microwave Symposium Digest, 1998 IEEE MTT-S International, Vol. 1 (1998), pp. 327-330 vol.1.</i><br /><br />This paper presents several power amplifier approaches that promise to significantly improve efficiency, while meeting the linearity requirements of advanced, spectrally efficient wireless systems. The approaches include: a) use of active integrated antenna structures that provide harmonic terminations for high efficiency Class F amplifiers; b) integrated dc-dc converters for power conditioning and envelope restoration; c) switching mode amplifiers based on bipolar transistors with controlled saturation; and d) the use of band-pass delta-sigma modulators to tailor input signals Device and circuit approaches for improved linearity and efficiency in microwave transmitters PM Asbeck T Itoh Y Qian MF Chang L Milstein G Hanington PF Chen V Schultz DW Lee DW Lee J Arun A10 doi:10.1109/MWSYM.1998.689385 Microwave Symposium Digest, 1998 IEEE MTT-S International, Vol. 1 (1998), pp. 327-330 vol.1. 2008-05-06T18:30:58-00:00 1998 Microwave Symposium Digest, 1998 IEEE MTT-S International 1 327 330 vol.1 efficiency microwave transmitter http://www.citeulike.org/user/dcastro/article/2762091 <i>Electronics Letters, Vol. 34, No. 15. (1998), pp. 1442-1443.</i><br /><br />The characteristics of a rectangular microstrip antenna with an L-shaped probe are investigated. A foam layer with a thickness of around 10% of the wavelength is used as the supporting substrate. An impedance bandwidth of 35% and an average gain of 7.5 dBi can be achieved. The radiation pattern is stable across the passband Broadband microstrip patch antenna KM Luk CL Mak YL Chow KF Lee Electronics Letters, Vol. 34, No. 15. (1998), pp. 1442-1443. 2008-05-06T17:16:02-00:00 1998 Electronics Letters 34 15 1442 1443 antenna broadband microstrip patch http://www.citeulike.org/user/dcastro/article/2712323 <i>Wireless Personal Communications, Vol. 25, No. 2. (1 May 2003), pp. 163-176.</i><br /><br />This paper compares parallel acquisition with hybrid acquisition in terms of mean acquisition time in code acquisition system of forward link and reverse link of direct sequence code division multiple access (DS-CDMA) system. The mean acquisition time of the hybrid and parallel acquisitions is derived from the distribution of the multiple correct code-phase offsets. Especially, the mean acquisition time of the hybrid acquisition scheme is derived by considering both case 1 (the correct code-phase offsets are included in one subset) and case 2 (the correct code-phase offsets exist at the boundary of two subsets), which are caused by the distribution of the correct code-phase offsets in the subset. Results are provided for the performance comparison between hybrid acquisition and parallel acquisition under the same hardware complexity in the forward and reverse links. In our performance evaluation of code acquisition in DS-CDMA system, the hybrid acquisition shows a better performance than the parallel acquisition in terms of mean acquisition time of the both links in the frequency-selective Rayleigh fading channel. A Performance Comparison of Code Acquisition Techniques in DS-CDMA System Bub-Joo Kang Il-Kyoo Lee doi:10.1023/A:1023619426148 Wireless Personal Communications, Vol. 25, No. 2. (1 May 2003), pp. 163-176. 2008-04-24T08:48:30-00:00 2003 Wireless Personal Communications 25 2 163 176 acquisition cdma code http://www.citeulike.org/user/dcastro/article/2693241 <i>Communications Magazine, IEEE, Vol. 35, No. 1. (1997), pp. 20-26.</i><br /><br />This article reviews the technologies and potential markets, applications, and architectures for broadband wireless access. The emergence of wireless communications for cellular systems is presented, together with its projected future evolution to mobile wideband systems. The field of broadband access systems, services, and network architectures is also covered, and then systems for broadband wireless communications for indoor local area networks and outdoor public fixed access networks are discussed. Broadband wireless access systems are emerging as a new and growing area of telecommunications, since the ability to provide access without extensive installation of copper or fiber infrastructures make wireless technology well suited for broadband services. Finally, some of the key enabling technologies, such as adaptive antennas and video compression, and the future architectural directions of broadband wireless networks are presented Broadband wireless access W Honcharenko JP Kruys DY Lee NJ Shah doi:10.1109/35.568192 Communications Magazine, IEEE, Vol. 35, No. 1. (1997), pp. 20-26. 2008-04-20T16:24:02-00:00 1997 Communications Magazine, IEEE 35 1 20 26 access broadband wireless http://www.citeulike.org/user/dcastro/article/2682293 <i>Advanced Information Networking and Applications, 2005. AINA 2005. 19th International Conference on, Vol. 1 (2005), pp. 781-785 vol.1.</i><br /><br />The forward error correction (FEC) code in IEEE 802.16a OFDM mode deals with six mandatory options for different data rates. Different from WLAN systems, IEEE 802.16a OFDM system incorporates Reed-Solomon (RS) encoder of (255,239,8) with convolutional encoder as a concatenated code. This paper presents the performances of the six mandatory options with concatenated code under fading channel. The RS encoder only and convolutional encoder only for FEC in the wireless-MAN OFDM system is also simulated to figure out the performance given by the concatenated code. As a more practical work, the packet detection, frequency offset estimation, frame synchronization, cyclic prefix estimation, and channel estimation of inner loop procedures, which deal with channel effects are already put into this design. Performance of concatenated FEC under fading channel in wireless-MAN OFDM system Shuenn Lee doi:10.1109/AINA.2005.277 Advanced Information Networking and Applications, 2005. AINA 2005. 19th International Conference on, Vol. 1 (2005), pp. 781-785 vol.1. 2008-04-17T15:04:18-00:00 2005 Advanced Information Networking and Applications, 2005. AINA 2005. 19th International Conference on 1 781 785 vol.1 8016 channel coding error fading ofdm wimax http://www.citeulike.org/user/dcastro/article/2674709 <i>Microwave Conference, 2007. European (2007), pp. 400-403.</i><br /><br />In this paper, metamaterial-based transmission lines will be discussed, with a focus placed on how these structures can be utilized in microwave systems. The different devices necessary for a basic dual-band receiver will be discussed and it will be shown how these dual-band components can be realized using metamaterial-based structure. Also, two different types of two-dimensional beam scanning systems will be introduced that utilize both one and two dimensional metamaterial-based structures. Practical applications of metamaterial-based structures in microwave systems CA Allen A Lai Cheng-Jung Lee T Itoh doi:10.1109/EUMC.2007.4405211 Microwave Conference, 2007. European (2007), pp. 400-403. 2008-04-15T18:08:16-00:00 2007 Microwave Conference, 2007. European 400 403 metamaterial microwave structure http://www.citeulike.org/user/dcastro/article/2674551 <i>Information Technology and Applications, 2005. ICITA 2005. Third International Conference on, Vol. 2 (2005), pp. 295-298 vol.2.</i><br /><br />Wideband mobile radio channel characteristics were measured in various environments in Korea. SKT conducted impulse response measurements at 2.3 GHz with a commercial channel sounder and presents multipath channel models for wireless local and metropolitan area networks. In this paper, we describe the process to analyze the measured data and build tapped delay line channel models. The whole measurements were conducted throughout more than 25 sites around Seoul city and various channel models that represents rural, suburban, suburban alternative, micro-cell hilly, urban high-rise and urban rooftop environments are presented. Multipath channel models for wireless local and metropolitan area networks K Jeong SH Kim KM Chung JC Kim JH Yu JS Lee SH Seo doi:10.1109/ICITA.2005.187 Information Technology and Applications, 2005. ICITA 2005. Third International Conference on, Vol. 2 (2005), pp. 295-298 vol.2. 2008-04-15T17:51:06-00:00 2005 Information Technology and Applications, 2005. ICITA 2005. Third International Conference on 2 295 298 vol.2 channel model multipath network wireless http://www.citeulike.org/user/dcastro/article/2500350 <i>Selected Areas in Communications, IEEE Journal on, Vol. 20, No. 9. (2002), pp. 1677-1683.</i><br /><br />A time-of-arrival (ToA)-based ranging scheme using an ultra-wideband (UWB) radio link is proposed. This ranging scheme implements a search algorithm for the detection of a direct path signal in the presence of dense multipath, utilizing generalized maximum-likelihood (GML) estimation. Models for critical parameters in the algorithm are based on statistical analysis of propagation data and the algorithm is tested on another independent set of propagation measurements. The proposed UWB ranging system uses a correlator and a parallel sampler with a high-speed measurement capability in each transceiver to accomplish two-way ranging between them in the absence of a common clock. Ranging in a dense multipath environment using an UWB radio link Joon-Yong Lee RA Scholtz doi:10.1109/JSAC.2002.805060 Selected Areas in Communications, IEEE Journal on, Vol. 20, No. 9. (2002), pp. 1677-1683. 2008-03-10T12:32:33-00:00 2002 Selected Areas in Communications, IEEE Journal on 20 9 1677 1683 environment multipath radio ranging uwb http://www.citeulike.org/user/dcastro/article/2619473 <i>Antennas and Propagation Society International Symposium, 1983, Vol. 21 (1983), pp. 55-58.</i> Mode characteristics of annular-ring and cirular-disc microstrip antennas with and without airgaps Kai Lee J Dahele Antennas and Propagation Society International Symposium, 1983, Vol. 21 (1983), pp. 55-58. 2008-04-01T11:16:22-00:00 1983 Antennas and Propagation Society International Symposium, 1983 21 55 58 antenna microstrip patch ring shorted http://www.citeulike.org/user/dcastro/article/2431136 <i>Acoustics, Speech, and Signal Processing, 2001. Proceedings. (ICASSP '01). 2001 IEEE International Conference on, Vol. 4 (2001), pp. 2329-2332 vol.4.</i><br /><br />In the context of orthogonal frequency division multiplexing (OFDM), most papers define OFDM symbol synchronization as frame synchronization. In this paper, a frame is defined as a block of several OFDM symbols in the time dimension. The main contribution of this work is to propose a novel, low-complexity, frame synchronization method for multi-carrier systems that does not require any transmission overhead; this increases the channel capacity, power and bandwidth efficiency. Also, it enables a flexible multiple-access scheme to be implemented in OFDM, whereby each user can have different frame size. The proposed frame synchronization method is compared with a conventional method using a preamble. Power compensation and frame averaging techniques are proposed to improve the performance of the frame synchronizer. The performance of the proposed frame synchronizer is evaluated over a Rayleigh fading channel for orthogonal frequency division multiple-access (OFDMA) and multi-carrier code-division multiple-access (MC-CDMA) systems New frame synchronization technique for OFDM/OFDMA and MC-CDMA systems CD Lee M Darnell doi:10.1109/ICASSP.2001.940466 Acoustics, Speech, and Signal Processing, 2001. Proceedings. (ICASSP '01). 2001 IEEE International Conference on, Vol. 4 (2001), pp. 2329-2332 vol.4. 2008-02-26T19:34:43-00:00 2001 Acoustics, Speech, and Signal Processing, 2001. Proceedings. (ICASSP '01). 2001 IEEE International Conference on 4 2329 2332 vol.4 cdma frame ofdm ofdma synchronization http://www.citeulike.org/user/dcastro/article/2425791 <i>Communications, IEEE Transactions on, Vol. 46, No. 8. (1998), pp. 993-996.</i><br /><br />Since the received signal levels in mobile communications are unknown and the location is varying, acquisition schemes for pseudonoise (PN) sequences with fixed thresholds cannot provide satisfactory performance. This fixed-threshold scheme may cause too many false alarms or result in a low detection probability for a selected threshold value. We present an adaptive acquisition scheme for PN sequences which estimate the background power level, multiply it with a threshold coefficient to keep the false alarms constant, and use it as a threshold Adaptive acquisition of PN sequences for DSSS communications Chang-Joo Kim Hyuck-Jae Lee Hwang-Soo Lee doi:10.1109/26.705393 Communications, IEEE Transactions on, Vol. 46, No. 8. (1998), pp. 993-996. 2008-02-25T15:12:20-00:00 1998 Communications, IEEE Transactions on 46 8 993 996 acquisition adaptive cdma pn-sequence http://www.citeulike.org/user/dcastro/article/2421339 <i>Information Theory, IEEE Transactions on, Vol. 49, No. 10. (2003), pp. 2636-2647.</i><br /><br />The capacity of multiple-input multiple-output (MIMO) wireless channels is limited by both the spatial fading correlation and rank deficiency of the channel. While spatial fading correlation reduces the diversity gains, rank deficiency due to double scattering or keyhole effects decreases the spatial multiplexing gains of multiple-antenna channels. In this paper, taking into account realistic propagation environments in the presence of spatial fading correlation, double scattering, and keyhole effects, we analyze the ergodic (or mean) MIMO capacity for an arbitrary finite number of transmit and receive antennas. We assume that the channel is unknown at the transmitter and perfectly known at the receiver so that equal power is allocated to each of the transmit antennas. Using some statistical properties of complex random matrices such as Gaussian matrices, Wishart (1928) matrices, and quadratic forms in the Gaussian matrix, we present a closed-form expression for the ergodic capacity of independent Rayleigh-fading MIMO channels and a tight upper bound for spatially correlated/double scattering MIMO channels. We also derive a closed-form capacity formula for keyhole MIMO channels. This analytic formula explicitly shows that the use of multiple antennas in keyhole channels only offers the diversity advantage, but provides no spatial multiplexing gains. Numerical results demonstrate the accuracy of our analytical expressions and the tightness of upper bounds. Capacity of multiple-antenna fading channels: spatial fading correlation, double scattering, and keyhole Hyundong Shin Jae Lee doi:10.1109/TIT.2003.817439 Information Theory, IEEE Transactions on, Vol. 49, No. 10. (2003), pp. 2636-2647. 2008-02-24T12:58:16-00:00 2003 Information Theory, IEEE Transactions on 49 10 2636 2647 antenna capacity channel correlation fading multi spatial http://www.citeulike.org/user/dcastro/article/2373847 <i>Wireless Communications, IEEE Transactions on, Vol. 6, No. 4. (2007), pp. 1176-1181.</i> Time and Frequency Synchronization for OFDMA Uplink System using the SAGE Algorithm Jong-Ho Lee Seong-Cheol Kim doi:10.1109/TWC.2007.348309 Wireless Communications, IEEE Transactions on, Vol. 6, No. 4. (2007), pp. 1176-1181. 2008-02-14T13:55:58-00:00 2007 Wireless Communications, IEEE Transactions on 6 4 1176 1181 algorithm frequency ofdma sage synchronization time uplink http://www.citeulike.org/user/dcastro/article/2182162 <i>Antennas and Propagation, IEEE Transactions on [legacy, pre - 1988], Vol. 35, No. 11. (1987), pp. 1281-1285.</i><br /><br />Experimental results of a dual-frequency microstrip antenna consisting of two stacked annular rings of outer radii 5 cm and inner radii 2.5 cm are presented. Fabricated on a Duroid substrate with relative permittivity 2.32 and thickness 0.159 cm, the separations of the two resonant frequencies range from 6.30-9.36 percent for the first three modes. The frequency separations can be altered by means of an adjustable air gap between the lower ring and the upper substrate. Dual-frequency stacked annular-ring microstrip antenna J Dahele K Lee D Wong Antennas and Propagation, IEEE Transactions on [legacy, pre - 1988], Vol. 35, No. 11. (1987), pp. 1281-1285. 2007-12-30T21:31:54-00:00 1987 Antennas and Propagation, IEEE Transactions on [legacy, pre - 1988] 35 11 1281 1285 antenna dual-band microstrip http://www.citeulike.org/user/dcastro/article/2135059 <i>Signals, Systems and Computers, 2003. Conference Record of the Thirty-Seventh Asilomar Conference on, Vol. 1 (2003), pp. 693-697 Vol.1.</i><br /><br />In this paper, we propose new channel estimation and equalization techniques for OFDM (orthogonal frequency division multiplexing) systems in mobile environment. In the mobile OFDM system, the estimation of time varying channel is the most important issue. In the proposed method, we assume that wireless channels are varying in the linear fusion during a certain internal, and estimate the initial channel coefficients and their corresponding slopes. After such estimation, we compensate the estimated channel and ICI (inter-carrier interference) effect due to time selectivity. We verify that this scheme shows better performance than conventional methods using computer simulations. Channel estimation and equalization for high speed mobile OFDM systems Heejung Yu Myung-Soon Kim Sok-Kyu Lee Signals, Systems and Computers, 2003. Conference Record of the Thirty-Seventh Asilomar Conference on, Vol. 1 (2003), pp. 693-697 Vol.1. 2007-12-17T06:51:10-00:00 2003 Signals, Systems and Computers, 2003. Conference Record of the Thirty-Seventh Asilomar Conference on 1 693 697 Vol.1 channel equalization estimation high mobile ofdm http://www.citeulike.org/user/dcastro/article/2085917 <i>Antenna Technology: Small and Smart Antennas Metamaterials and Applications, 2007. IWAT '07. International Workshop on (2007), pp. 435-438.</i><br /><br />This paper presents a design for circular patch antenna with single feed for circular polarization. As an example, patch antenna is designed to operate CP in the ISM band (2.4-2.483 GHz) for WLAN and satellite communication application. CP of the proposed structure can be achieved by embedding two circular slots in the patch resonator. By changing the size and position of the slots, two orthogonal modes with equal amplitude and 90deg out of phase are simultaneously excited. The proposed CP antennas are excited by only single feed without using 90deg phase shifter. By proper arrangement of two circular slots, dual band antenna for WLAN and DMB application can also be successfully excited Small Single Band Circular Polarization and Dual Band Circular Patch Antenna Tzong-Chee Yo Chien-Ming Lee Ching-Hsing Luo Antenna Technology: Small and Smart Antennas Metamaterials and Applications, 2007. IWAT '07. International Workshop on (2007), pp. 435-438. 2007-12-10T14:44:37-00:00 2007 Antenna Technology: Small and Smart Antennas Metamaterials and Applications, 2007. IWAT '07. International Workshop on 435 438 antenna circularly dual-band patch polarisation http://www.citeulike.org/user/dcastro/article/2072422 <i>Vehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th, Vol. 2 (2004), pp. 989-993 Vol. 2.</i><br /><br />An increasing number of systems are adopting orthogonal frequency division multiple access (OFDMA) as their high-speed wireless transmission method supporting multiple users, and impacts on performance of OFDMA systems under mobile cellular environments are currently being investigated. In this paper, channel state and quality estimation performance issues are addressed for varying types of pilot structures in the transmitted burst. It is demonstrated that significant performance variations can occur in estimation of the state and quality of the wireless link depending on the pilot pattern used in the preamble symbol. In particular, advantages of using disjoint patterns for downlink transmission from adjacent cells are quantitatively presented, by evaluating the bit error rate and the carrier-to-interference ratio (CIR) estimation performance. Performance improvement of channel estimation based on pilot structure variations for cellular OFDMA systems Junghoon Lee Jaewon Chang Wonjin Sung Vehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th, Vol. 2 (2004), pp. 989-993 Vol. 2. 2007-12-07T10:20:40-00:00 2004 Vehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th 2 989 993 Vol. 2 channel estimation mobile ofdma performance pilot http://www.citeulike.org/user/dcastro/article/797825 <i>Wireless Communications, IEEE [see also IEEE Personal Communications], Vol. 13, No. 2. (2006), pp. 56-63.</i><br /><br />Wireless mesh networking is a promising technology for numerous applications which appeals especially to those applications that cannot be directly supported by other wireless technologies. The commercial success of Wi-Fi and the advances in many wireless technologies have in part stimulated the development of wireless mesh networks. The persistent driving force, however, comes from the envisioned advantages of wireless mesh techniques themselves, including extended coverage, robustness, self-configuration, easy maintenance, and low cost. This article presents an overview of this emerging technology, focusing on the technical merits and related standards activities of IEEE and ZigBee that are actively applying the concept of multi-hop mesh techniques in the field of wireless networking technologies, ranging from personal area networks (PANs) to metropolitan area networks (MANs). Emerging standards for wireless mesh technology MJ Lee Jianliang Zheng Young-Bae Ko DM Shrestha Wireless Communications, IEEE [see also IEEE Personal Communications], Vol. 13, No. 2. (2006), pp. 56-63. 2006-08-11T20:59:57-00:00 2006 Wireless Communications, IEEE [see also IEEE Personal Communications] 13 2 56 63 mesh wireless http://www.citeulike.org/user/dcastro/article/2072362 <i>Vehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59th, Vol. 3 (2004), pp. 1816-1820 Vol.3.</i><br /><br />This paper investigates the adaptive subcarrier and bit allocation algorithm for OFDMA systems. To minimize overall transmit power, we propose a novel adaptive subcarrier and bit allocation algorithm based on channel state information, Moreover, the block-wise method is considered based on channel variation for adaptive subcarrier and bit allocation. It is shown that a near optimal solution is obtained by the proposed algorithm which has low complexity compared to that of other conventional algorithms. Also, it is shown that the block-wise method significantly reduces the complexity and the feedback or side information though has a slight transmit power increase. Efficient subcarrier and bit allocation algorithm for OFDMA system with adaptive modulation Ho Kim JS Kwak Jung Choi Jae Lee Vehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59th, Vol. 3 (2004), pp. 1816-1820 Vol.3. 2007-12-07T09:53:34-00:00 2004 Vehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59th 3 1816 1820 Vol.3 adaptive algorithm carrier modulation ofdma http://www.citeulike.org/user/dcastro/article/2060698 <i>Wireless Communication Technology, 2003. IEEE Topical Conference on (2003), pp. 273-274.</i><br /><br />In this paper we present two novel multiband antenna designs for multiple frequency applications. The first of these, which is based on fractal concepts, is a Sierpinski gasket type of fractal configuration, printed on a dielectric substrate backed by a ground plane. We propose a novel approach to enhancing its multiband performance, in terms of impedance matching characteristics as well as radiation patterns, at three operating frequencies. The second design combines a rectangular microstrip patch with a cylindrical dielectric resonator, and operates at multiple frequencies. Specifically, we describe a stacked configuration of a dielectric resonator antenna on a microstrip patch for three frequency bands. Circular polarization is obtained by utilizing four coaxial feeds in phase quadrature. This configuration is found to exhibit good cross-polarisation rejection characteristics. Fractal and multiband communication antennas Y Lee J Yeo R Mittra S Ganguly J Tenbarge Wireless Communication Technology, 2003. IEEE Topical Conference on (2003), pp. 273-274. 2007-12-05T12:09:54-00:00 2003 Wireless Communication Technology, 2003. IEEE Topical Conference on 273 274 antenna fractal http://www.citeulike.org/user/dcastro/article/2060666 <i>Solid-State Circuits, IEEE Journal of, Vol. 33, No. 12. (1998), pp. 2035-2041.</i><br /><br />A linear capacitor structure using fractal geometries is described. This capacitor exploits both lateral and vertical electric fields to increase the capacitance per unit area. Compared to standard parallel-plate capacitors, the parasitic bottom-plate capacitance is reduced. Unlike conventional metal-to-metal capacitors, the capacitance density increases with technology scaling. A classic fractal structure is implemented with 0.6-μm metal spacing, and a factor of 2.3 increase in the capacitance per unit area is observed. It is shown that capacitance boost factors in excess of ten may be possible as technology continues to scale. A computer-aided-design tool to automatically generate and analyze custom fractal layouts has been developed Fractal capacitors H Samavati A Hajimiri AR Shahani GN Nasserbakht TH Lee Solid-State Circuits, IEEE Journal of, Vol. 33, No. 12. (1998), pp. 2035-2041. 2007-12-05T11:56:24-00:00 1998 Solid-State Circuits, IEEE Journal of 33 12 2035 2041 capacitor fractal http://www.citeulike.org/user/dcastro/article/2060611 <i>(1998)</i><br /><br />A linear capacitor structure using fractal geometries is described. This capacitor exploits both lateral and vertical electric fields to increase the capacitance per unit area. Compared to standard parallel-plate capacitors, the parasitic bottomplate capacitance is reduced. Unlike conventional metal-to-metal capacitors, the capacitance density increases with technology scaling. A classic fractal structure is implemented with 0.6-m metal spacing, and a factor of 2.3 increase in the capacitance... Fractal Capacitors H Samavati A Hajimiri A Shahani G Nasserbakht T Lee (1998) 2007-12-05T11:31:07-00:00 1998 capacitor fractal http://www.citeulike.org/user/dcastro/article/1026660 <i>Communications, 2006 IEEE International Conference on, Vol. 12 (2006), pp. 5595-5599.</i><br /><br />In the IEEE 802.16 network the SINR per subcarrier, the average SINR, and the SINR RMS are stochastic processes. In this paper, we analyze the statistical properties of these stochastic processes using system level simulation. We present the probability density functions for the SINR per subcarrier and the average SINR stochastic processes expressed in both logarithmic and linear scales. We also present the probability density function for the SINR RMS stochastic process, expressed in the logarithmic scale. The results, obtained in this paper, allow using the statistical approach while developing the adaptive transmission algorithms for the IEEE 802.16 network. Analysis of the Statistical Properties of the SINR in the IEEE 802.16 OFDMA Network SN Moiseev SA Filin MS Kondakov AV Garmonov Do Yim Jaeho Lee Sunny Chang Communications, 2006 IEEE International Conference on, Vol. 12 (2006), pp. 5595-5599. 2007-01-05T13:38:36-00:00 2006 Communications, 2006 IEEE International Conference on 12 5595 5599 80216 network ofdm sinr statistical