WirelessPulse-Comsearch E-News - September 2005 Comsearch's quarterly e-newsletter for professionals in
the wireless industry. |
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FEATURE ARTICLE CASE CORNER REGULATORY RAP WHAT'S NEW AT COMSEARCH! |
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Editor’s Note: Many Comsearch staff experts are engaged in research and development projects on advanced wireless issues related to our normal business. The following article represents a research project by Dr. Saúl Torrico, our expert on wireless propagation. The full article will appear in an upcoming edition of the IEEE Antenna and Propagation Magazine. The design of wireless communication systems beyond 2G technologies requires a detailed understanding of various radio channel parameters, which is usually cast in terms of their statistical distribution. 1G and 2G system design required knowledge of the mean received signal and its variability. 3G and future digital wireless communication systems additionally require knowledge of the delay spread. Operation of wide band code division multiple access (W-CDMA) technology depends on the statistics of multipath components in terms of their number and lifetime for rake receiver design as shown in Figure 1. Design of smart antennas and other multiple antenna systems, which can improve system capacity or could be used to geolocate mobiles, make use of the distribution in angle-of-arrival of the scattered signal. The foregoing information can be determined from radio surveys, but such surveys are expensive, particularly since they need to be repeated for different antenna heights, and in a number of different propagation environments. It is advantageous for the system designer to have available a computer-based tool that can be used to predict area coverage, delay spread, angle-of-arrival, etc. The basis of this tool is a reliable propagation model that accounts for buildings and terrain. The ray representation of radio propagation in the UHF band and above provides a physical basis for the multipath description of the received signal used by system designers. By tracing the rays and accounting for reflections from buildings and the ground, diffraction at building edges, and non-specular scattering at building surfaces, it is possible to make statistically meaningful predictions of radio channel characteristics. A number of ray tracing models have been developed for the special conditions of radio propagation in cities, where the building walls are vertical and multiple events (reflections, diffraction or scattering) must be accounted for. Comparison of the predictions generated by one of these models with measurements show that the small area average power over a region can be computed with mean error of less than 1 dB and standard deviation of about 8 dB, or even less as shown in Figure 2 above. Because the models give all the physical parameters of the ray paths, they can be used to simulate other properties of interest to system designers, such as the spread in the time delay and angle-of-arrival of the individual rays as shown in Figures 3 to 5. The statistical distributions of these quantities that are obtained from simulations are found to compare well with those obtained from measurements. Ray models are at the point where inexpensive simulations can be used to test radio system concepts before more expensive field trials are run. Simulations can help select system parameters, such as the required bandwidth, the number and location of antennas and their directivity, as well as evaluate the effectiveness of signal processing algorithms. Unlike field trials where the entire system is tested with a pass/fail outcome, simulations allow each system feature to be varied in order to see its effect on overall system performance. Another potential benefit is locating mobiles from their signals arriving at a single base station for applications such as E911 geolocation or location-based services. Presently there are several geolocation techniques used to locate mobiles (i.e. Uplink Time Difference of Arrival (U-TDOA), Cell ID, Assisted-GPS, etc.). As another complementary alternative to improve the accuracy of locating mobiles, we could use an array of antennas and space-time processing to extract the individual ray arrivals. Ray models could trace the rays back to find the common intersection point, which is the location of the mobile. This application still remains to be evaluated. Running time of the ray models remains a barrier to their use for practical cell system layout, which requires the evaluation of coverage and interference at many locations from several base stations. However, running time limitations may be less severe for the small cells of 3G and 4G networks, and as computers become faster and less expensive. To date, the approaches taken to improve computation time have been to limit the type of rays considered, and to use ideas taken from computer science. The advent of inexpensive multiprocessor systems has also reduced the simulation times through the application of parallel processing techniques. Regarding errors, over distances on the order of 1 km, the errors for ray predictions have standard deviation of 6 - 8 dB, while for shorter distances the error is less. This behavior may be related to the fact that ray paths, like the path of a billiard ball, are chaotic in that the small change in the initial ray direction eventually causes the ray to miss a reflecting wall and subsequently travel along a totally different path (the electromagnetic fields however are not chaotic). It may be that for travel beyond some distance from the base station, the rays become chaotic and give only a statistical measure of the fields. This conjecture remains to be examined. In conclusion, the design of future wireless communication
systems may benefit from a robust computer ray model that could more precisely
predict the propagation loss between the transmitter and the receiver.
The designer could actually understand the spreading of the signal in
time and space (angle of arrival) and obtain the number and the life time
of the multipath signal. This will allow the designer to improve capacity
and efficiency of these advanced digital systems. The basis of this robust
model is a more reliable propagation model that can account for buildings
and terrain. The full article will appear in the IEEE-Antenna Propagation Magazine, authored by CASE CORNER Automating Spectrum Management Introduction The Objective Frequency Planning Automatic Frequency
Planning Automatic Frequency Planning has the potential to significantly
improve the efficiency of network rollout and optimization. It allows
network designers to consider multiple scenarios, rapidly analyzing the
interference impact of an entire design rather than by one link at a time.
It can also be very useful for planning upgrades to existing networks
to increase capacity or improve efficiencies.
The answers to these questions had to satisfy the requirements of multiple operators with varying priorities. Therefore, the user interfaces addressing these issues had to be flexible. For prioritizing links, an Automatic Frequency Planning tool provides a list of every link that is being analyzed. The user has several options to specify priority:
Once the list of links is identified and the method of priority is chosen, it’s time to run them through a detailed interference analysis. At this point, it’s necessary to define the user’s idea of the “Best Frequency”. For some, it might be the frequency with the least total interfering level. For others, it’s the frequency that can be reused the most, pushing the interference objective to its limits. And still others, it might be one of three, off-the-shelf radios that are pre-tuned to a specific frequency. AFP provides the user with the options to accommodate these varying requirements. Following the analysis, AFP provides a report of the links that had frequencies assigned and those that could not meet the objectives. Before making any permanent changes to the network design, the user can decide what to accept and what needs further investigation. Any change accepted by the user becomes part of the master database and will be considered as part of any future analysis. Conclusions This type of interference mitigation software is also finding its way off the desktop and into the field. In the not-so-distant future, software-defined radios, with built-in Automatic Frequency Planning, will play a large role in facilitating rapid rollout of new technologies, while continuing to make the best use of the available spectrum. REGULATORY
RAP MICROWAVE Canada and U.S. to Facilitate Deployment of Border Public Safety Services in the 764-776 and 794-806 MHz Bands - DOC-259427A1.pdf FCC Delays Effective Date for Rules Concerning Unsolicited Fax Advertisements - New Implementation Date is January 9, 2006. (Dkt No 02-278, FCC No. 05-132) DOC-259689A1.pdf FCC-05-132A1.pdf Licensing Procedures Announced to Facilitate the Transition of BAS, CARS, and LTTS Licenses to the 2025-2110 MHz Band - (DA No. 05-2223) DA-05-2223A1.pdf Universal Licensing System Changed to Implement the Immediate Approval Procedures for Wireless License Assignments and Transfers - (DA No. 05-2226) DA-05-2226A1.pdf FCC Adopts Policy Statement
- New Principles to Preserve and Promote the Open and Interconnected Nature
of Public Internet. DOC-260435A1.pdf FCC Requires Certain Broadband and VOIP Providers to Accommodate Wiretaps - DOC-260434A1.pdf DOC-260434A2.pdf DOC-260434A3.pdf Biennial Regulatory Review - Amendment of Parts 1, 22, 24, 27, and 90 to Streamline and Harmonize Various Rules Affecting Wireless Radio Services - (Dkt No. 03-264, FCC No. 05-144) FCC-05-144A1.pdf FCC-05-144A2.pdf Service Rules For Advanced Wireless Services in the 1.7 and 2.1 GHz Bands - The FCC moved to make spectrum available for an array of innovative wireless services and technologies, including voice, data, video, and other wireless broadband services offered over Third Generation ("3G") mobile networks. (Dkt No. 02-353, FCC No. 05-149) FCC-05-149A1.pdf FCC-05-149A2.pdf FCC-05-149A3.pdf FCC-05-149A4.pdf DOC-260432A1.pdf DOC-260432A2.pdf DOC-260432A3.pdf FCC Releases
"Trends In The International Telecommunications Industry" Report
- DOC-261024A1.pdf
DOC-261024A2.pdf SATELLITE International Bureau Extends Comment Period in Satellite Space and Earth Station Licensing Reform Proceeding (IB Docket No. 00-248) for Interested Parties Impacted by Hurricane Katrina On March 10, 2005, the Commission adopted a Third Notice of Proposed Rulemaking in its ongoing efforts to modernize and reform space station and earth station licensing. Specifically, the Commission sought comment on proposed revisions to Part 25 of the Commission’s rules that should give earth station operators in the fixed-satellite service more flexibility in implementing state-of-the-art earth stations in the Fixed Satellite Service (FSS) in the conventional C-band and Ku-band. Currently, comments in this proceeding are due on September 6, 2005, and reply comments are due October 6, 2005. As a result of the devastation caused by Hurricane Katrina in certain areas within the states of Louisiana, Mississippi, and Alabama, the International Bureau is extending the comment date for interested parties and/or their counsel located in the affected areas from September 6, 2005 to September 28, 2005. Replies responsive to issues raised in late-filed comments may be filed on October 14, 2005. Intelsat Set To Become Largest Satellite Operator With Acquisition Of Panamsat Intelsat Ltd. has agreed to acquire Panamsat for $3.2 billion to create the world's largest Fixed Satellite Services company. The combined company, which will retain the name Intelsat, will operate a fleet of 53 satellites and generate more than $1.9 billion in annual revenue. Under the agreement, announced Aug. 29, shareholders of Panamsat Holding Corp. will receive $25 per share, nearly 40 percent above the company's March initial public offering price. Intelsat also will assume $3.2 billion in debt held by Panamsat and its subsidiaries. Intelsat's deal with Panamsat trumps a reported combination with New Skies Satellites. The deal is expected to close by August 2006, dependent on U.S. government approval. Chief of Satellite Division, FCC’s International Bureau Retires Goldberg, Godles, Wiener & Wright announced that Thomas Tycz would become the firm's senior policy advisor, effective Sept. 19. Tycz recently retired from the U.S. Federal Communications Commission (FCC) from his position as chief of the satellite division in the FCC's International Bureau. He spent more than 30 years at the FCC in various executive positions. Satellite Operators Contribute to Katrina Disaster Relief Numerous Satellite Operators have joined forces and have been involved in the relief effort following the aftermath of hurricane Katrina. They have been able to provide rapid data management collection capabilities and mobile satellite communications to elements of the 2nd U.S. Marine Expeditionary Force and the Federal Emergency Management Agency (FEMA), which currently are assisting victims of Hurricane Katrina. Globalstar announced Sept. 6 it has deployed more than 10,000 handheld satellite phones to customers in the Gulf region, primarily to government agencies and relief workers, within the first week following the Aug. 29 landfall of Hurricane Katrina. Globalstar said it increased the capacity of its satellite network to ensure continued communications service to the region. Federal Geographic Data Committee Issues Guidelines On Offering Satellite Imagery The Federal Geographic Data Committee of the U.S. Geological Survey (USGS) published guidelines intended to set standard procedures for governing the dissemination of geospatial imagery. The guidelines "are directed at organizations that originate geospatial data and are interested in disseminating data publicly but are concerned that such actions may pose a risk to security." Services such as Google Earth, which offers free satellite imagery, among other things, via the Web, would fall under these guidelines. According to the committee document, "dissemination is essential to the mission of many organizations and the majority of these data are appropriate for public release. However a small portion of these data could pose risks to security and may therefore require safeguarding." A copy of the guidelines can be found on the committee's Web site at http://www.fgdc.gov/fgdc/homeland/access_guidelines.pdf What's New at Comsearch! Comsearch Supports Microwave Licensees
Impacted by Hurricane Katrina "We understand the importance of this massive recovery effort," said Chris Hardy, Vice President and General Manager for Comsearch. "The severity of Hurricane Katrina lead to significant disruption of wireless services and Comsearch will continue to do its part to help wireless operators quickly restore services to the devastated gulf region." For more information on Comsearch’s microwave services, please contact us at customersupport@comsearch.com. Comsearch Releases iQ·link®
Version 8.3.07 The Comsearch iQ·link®
User Conference is Scheduled for December 1 – 2 For more information on the SBE 2005 Annual Expo, visit www.sbe.org and click on Conferences & Conventions in the left menu. Comsearch Article on 71-95 GHz Registration Gets
Published in Mission Critical Communications, September 2005
Issue Comsearch Selected, for the 8th Year in a Row,
to Serve as the Official Frequency Coordinator for CTIA Wireless I.T.
and Entertainment 2005 in San Francisco, CA, September 27-29, 2005 Comsearch Offers Protection Services to 6.1 GHz
Terrestrial Microwave Facilities Operating Near the Coast, a Waterway,
or Harbor! Comsearch’s 6.1 GHz Terrestrial Microwave Protection Services help ensure that your systems are free of interference and any potential problems with other systems are identified during the coordination process. To find out more about Comsearch’s Coordination and Frequency Protection Services or about the FCCs ESV rulemaking contact Denise Finney at customersupport@comsearch.com or at 800-318-1234. If you have been forwarded WirelessPulse by a friend
or colleague and wish to subscribe
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