10,105 research outputs found
On the Computation of 16-QAM and 64-QAM Performance in Rayleigh-Fading Channels
No full textSUMMARY Quadrature Amplitude Modulation (QAM) schemes are attractive in terms of bandwidth efficiency and offer a number of subchannels with different integrities via both Gaussian and Rayleigh-fading channels, Specifically, the 16-QAM phasor constellation has two, while the 64-QAM possesses three such subchannels, which become dramatically different via Rayleigh-fading channels. The analytically derived bit error rate (BER) formulae yield virtually identical curves with simulation results, exhibiting adequate BERs for the highest integrity subchannels of both 16-QAM and 64-QAM to be further reduced by forward error correction coding (FEC). However, the BERs of the lower integrity subchannels require fading compensation to reduce their values for FEC techniques to become effective. This property creates ground for a variety of carefully matched, embedded mobile transmission schemes of different complexities. The practical implementation of such an embedded scheme is demonstrated by a low-cost, low-complexity and low consumption 50 kBd mobile video telephone scheme offering adequate speech and image quality for channel SNRs in excess of about 20 dB via Rayleigh-fading channels. key words: QAM theory; modulation for microcellular fading channels
Effect of Soft and Softer Handoffs on CDMA System Capacity
No full textAbstract? The effect of soft and softer handoffs on code-division multiple-access (CDMA) system capacity is evaluated for unsectorized and sectorized hexagonal cells according to an average bit energy-to-interference power spectral density, which corresponds to a bit-error rate (BER) of 10-3. The effect of imperfect sectorization on sectorization efficiency is also considered. On the reverse link, there is no capacity loss as no extra channels are needed to perform soft handoff, while the macrodiversity provided by soft handoff can improve the reverse-link quality and extend the cell coverage. On the forward link, when soft handoff is employed in unsectorized cells, the capacity loss due to two traffic channels assigned to a user in the handoff zone is 0.2% or 1.1% for a voice activity factor of 3/8 or 1/2, respectively. As the forward-link capacity is higher than that of the reverse link, this small capacity loss does not affect the system capacity. For sectorized cells having three sectors per cell, there are overlapping coverage areas between sectors, where mobiles in these areas are subjected to an increase in cochannel iterference. For an overlapping angle of 5°, the sectorization efficiency is 0.96 and 0.7 for the reverse-link and forward-link systems, respectively. When soft and softer handoffs are employed, the forward-link sectorization efficiency is improved to 0.97. We find the application of soft and softer handoff improves not only the forward-link capacity, but also the signal-to-interference ratio (SIR) for mobiles near the cell and sector boundaries. Index Terms?CDMA, macrodiversity, sectorization efficiency, soft handoff, softer handoff
Fashion Culture: Constance White in conversation with Valerie Steele
No full textOn February 27, 2018, author Constance White joined Dr. Valerie Steele to discuss the influence of black style on today’s fashion vernacular, drawing on striking images of trendsetters from Josephine Baker to Michelle Obama, Rihanna, and Pharrell Williams. White’s book, How to Slay, is one of the few surveys of black style and fashion ever published
Introducing Microcells into Macrocellular Networks: A Case Study
No full textAbstract?The performance in terms of signal-to-interference ratio (SIR), teletraffic, and spectral efficiency of a combined macrocellular and microcellular network is investigated when either both types of cells share the same channel set, or when the channel set is partitioned between the macrocells and the microcells. The analysis is for time-division multiple access (TDMA) with frequency hopping, power control, and discontinuous transmission, and the radio channel is composed of an inverse fourth-power path loss law with log-normal fading. We commence by introducing a single microcell into a hexagonal cluster of macrocells before considering clustered microcells. Both omni-directional and sectorized cells are examined. We find that high reuse factors are required when channel sharing is employed. When channel partitioning is used, no co-channel interference occurs between the microcells and the macrocells allowing them to be planned independently. The reuse factors in the microcells and macrocells therefore do not need to be increased beyond conventional values. The outcome is that by opting for channel partitioning, the improvement in spectral efficiency compared to channel sharing is two to three times greater. Index Terms?Co-channel interference, land mobile radio cel-lular systems, time division multiaccess
Cellular Communications Using Aerial Platforms
No full textThis paper is devoted to the study of cellular communications using aerial platforms (APs). A set of key equations is derived that quantify the coverage area on the ground as a function of AP elevation, the operation of the adaptive multibeam antenna on the AP, and the formulation of contiguous terrestrial cells and their shapes. Specifically, we consider the deployment of an AP to provide terrestrial mobile radio communications using the universal mobile telecommunication system operating in its wide-band code-division multiple-access mode. Calculations are made of the number of users versus Eb/No for different service rates. Multi-tiered cellular structures having cells of different size that are steerable with the offered teletraffic are examined. The array structure to achieve this is identified. The preliminary results shows that an AP at a height of 21 km covers an area of radius 517 km. Up to 21 users per cell with a service rate of 8 kb/s can be accommodated in the 2.2-GHz band. These services can be provided within an area of radius 70 km with transmitted powers of less than 1 W. High system capacity is proved to be possible by constructing cells of radius as small as 100 m using square planar arrays with dimensions of less than 12 m x 12 m. The AP system provides high capacity and Doppler frequency shifts that only originate from roving mobiles
The drummer, or, The haunted-house : a comedy with a preface by Sir Richard Steele, & his letter to Mr. Congreve, concerning the author of this play, &c
No full text[Joseph Addison]Verfasser ist Joseph Addison - siehe Nicol
Charles K. Steele, Sr., circa 1979
No full textCharles K. Steele, Sr. poses for a photo holding his cane and a Bible, sitting in a pulpit chair in a church.The Atlanta University Center Robert W. Woodruff Library acknowledges the generous support of the Joseph & Evelyn Lowery Institute for Justice and Human Rights, the Joseph Echols Lowery Irrevocable Trust, and other donors in supporting the processing and digitization of Morehouse College's Joseph Echols and Evelyn Gibson Lowery Collection
Fashion Culture: Misty Copeland in conversation with Valerie Steele
No full textMisty Copeland is a soloist with American Ballet Theatre. In 2007 she made history by becoming their second African American Female Soloist and the first in two decades. In September 2014, she was the first black woman to perform the lead role of Odette/Odile in American Ballet Theatre’s production of Swan Lake during the company’s first ever tour to Australia. Misty is the author of the New York Times bestselling memoir, Life in Motion (2014), co-written with Charisse Jones, and of the picture book Firebird (2014) in collaboration with Christopher Myers.Misty Copeland was in conversation with Valerie Steele at The Museum at FIT on Tuesday, November 4, 2014
Indrani Waltzes.
No full textintroduction, three sectional waltzes, and codapianoTo the Gallant Vessel Whose Name it Bears, and to Capt. W.B. Webb R.N.R. her Genial Commander, This is Most Respectfully Dedicated by the Author, R. Steele.--GlasgowJohns Hopkins University, Levy Sheet Music Collection, Box
181, Item 146R. Steele
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