Digital Leakage Today Analog and Digital Leakage LTE interference - PowerPoint PPT Presentation

Digital Leakage Today Analog and Digital Leakage LTE interference Kendall Robinson Regional Account Director Arcom Digital < HOME

Digital Leakage Outline • Digital Leakage • Traditional Leakage • LTE • Ingress and Egress issues • QAM Snare overview • Analysis of results at 3 leakage demo trials < HOME

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Traditional Signal Leakage Today • Most legacy leakage systems are in the aeronautical band from 108 to 137MHz • A common frequency is 133.26MHz (Visual CEA channel) • Max allowed signal strength at 10 feet is 20uV/m • Many operators target to fix all leaks greater than 10uV/m • Some fix above 5uVm • A few have a goal to fix any size leak on their system < HOME

Signal Leakage Regulations Signal leakage regulations in Part 76 of the FCC’s Rules. The following table, taken from § 76.605(a)(12), states the maximum allowable signal leakage field strengths across various frequency ranges: Frequencies Signal leakage Distance in Distance in limit in micro- feet (f) meters (m) volt per meter (uV/m) Less than 15 ~100 30 54MHz 54MHz to 20 ~10 3 216MHz Over 216 MHz 15 ~100 30 < HOME

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Signal Leakage Regulations Distance at 10 feet is 20uV/m larger Frequencies Signal leakage Distance in Distance in limit in micro- feet (f) meters (m) volt per meter (uV/m) Over 216 MHz 15 ~100 30 Over 216 MHz 150 ~10 3 < HOME

LTE Overview • LTE means (Long Term Evolution) • Downlink: OFDM - (QPSK, 16QAM and 64QAM) • Uplink: SC-FDMA (QPSK and 16QAM) • Paired Duplex: FDD (Frequency-division duplex) – paired downlink and uplink • Bandwidth: 5 and 10MHz (typical in the US) < HOME

Orthogonal Frequency Division Multiplexing OFDM is a broadband multicarrier modulation method that offers superior performance and benefits over older, more traditional single-carrier modulation methods because it is a better fit with today’s high-speed data requirements and operation in the UHF and microwave spectrum. < HOME

What makes LTE different to Traditional Cell technology? • LTE in the USA is in the 698-806 MHz band which falls in the CATV frequency band • Compare to traditional cell (CDMS and GSM) at 1.8GHz, 1.9GHz and 2.1GHz. • LTE is of particular concern for Cable systems with 750 MHz, 850 MHz and 1 GHZ systems. • Signals in the 700 MHz band (compared to traditional cell signals) travel further and are less attenuated by structures. • OFDM in the downlink side has a higher potential power spectral density than traditional cell signals. (These change) • When there are fewer resource blocks and the total signal power is divided among fewer subscribers. There is a higher probability of ingress as the energy is concentrated to a smaller allocated bandwidth. Especially an issue in the LTE uplink. < HOME

LTE bandwidth and frequency allocation • LTE bandwidth is allocated in “Resource Blocks” allowing signal sharing by multiple users • “Resource Blocks” are a set of subcarriers and OFDM symbols • For a 10MHz signal there are 50 “Resource Blocks”. (5 per 1MHz) • There are correlations between “Resource Blocks” and Interference • Frequency Allocations: • Band 13 (DL 746-756 MHz, UL 777-787 MHz) for Verizon • Band 17 (DL 734-746 MHz, UL 704-716 MHz) for AT&T. < HOME

US FCC 700MHz LTE Bands < HOME

The potential future of expanded LTE • LTE currently only in the 700MHz spectrum • It is highly likely in the future LTE will be even lower from 570 MHz to 780 MHz. (Currently 730 MHz to 790 MHZ) • Plans are being proposed to vacate Broadcasters from OTA channels 31-51 (572-698 MHz) and auctioning off this valuable spectrum. • In Feb 2013, T-Mobile starts discussion with the FCC to repurpose the entire 600MHz band for LTE since AT&T and Verizon already are using 100MHz of the bandwidth. < HOME

LTE Ingress Interference LTE interfering with the CATV system • LTE can interfere with STB’s, Cable Modems and TV’s at the customer premise • Cable Modems are susceptible to even low LTE emission levels • Most frequent issues to customers devices are direct pickup due to lack of sufficient shielding of the equipment. • This interference has been shown to even be through steel and concrete barriers • Interference also enters on the cable plant where there are areas of damaged cable and connectors (potential leak locations) Ingress: RF signal leaking into the coaxial plant.. < HOME

Influences of digital leaks on communication systems • Ingress from LTE can be a big issue when leakage affects QAM and Broadcast channels. • Of course cellular transmission can also affect these channels. < HOME

What ATT and Verizon are finding • Leaking CATV devices using a portable spectrum analyzer and directional antennas. • R&S < HOME

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Here the measurement was made at a distance of ≈ 10 ft with an 11dBi Yagi at 780 MHz. The signal level at the top of the QAM at the input of the SA is ≈ -25dBmV for the 30kHz ResBW. The field strength calculation at 10 ft comes out to a substantial 2200µV/m. Courtesy Verizon < HOME

Courtesy Verizon < HOME

Courtesy Verizon < HOME

Courtesy Verizon < HOME

Courtesy Verizon < HOME

Courtesy Verizon < HOME

Courtesy Verizon < HOME

Courtesy Verizon < HOME

Courtesy Verizon < HOME

What CATV operators are finding – causes of high frequency leakage • Holes in Cable • Thin Cracks / ring cracks in Cable • Leaking Tap Face Plates / Bad fitting of the metallic gasket • Broken connectors • Loose Connectors • Illegal connections < HOME

LTE Egress Interference The CATV system interfering with LTE • We will look at multiple examples of this. • Typical locations that cause these issue are: Loose or damaged hardline connectors, insufficiently shielded splitters, switches, amplifiers, as well as unterminated outlets which are common egress sources. Keep in mind that any egress locations are potential ingress locations for the CATV system as well. • In addition, common physical defects responsible for egress include ring cracks in the coaxial cables, damage from chewing/gnawing by animals, loose covers, loose hardline connectors, faulty AGC, etc. • Illegals: Connections and alterations made by persons engaged in cable theft have also been reported as a serious source of problems: improperly spliced cables, poor-quality materials, etc. • Adding a Digital Leakage program in the upper band frequencies can ensure a much tighter plant. Egress: RF signal leaking out of the coaxial plant. < HOME

What we have discovered about Leaks at higher frequencies • No real correlation or reason why some leaks are higher at low or high frequencies • In many cases a very high leak in the 700MHz band will show no leak in the VHF frequency band • These higher frequency leaks are typically at higher levels • Possible reason are: • In some part due to the tilt on outside plant • Also higher frequencies travel more efficiently • Mostly due to the component that is leaking • Eg: cracks in the cable, leaking RF tap gasket, hole in cable < HOME

Digital Leakage Detection > This is a location where a tree grew through a cable on a busy thoroughfare a few blocks from a hub. > Hundreds of service vehicles drove past this location every day. It was a small analog leak that wasn’t worth stopping for. (8uV/m – low) > No correlation between low and high frequency. (We show this in the next few slides) > Very High leakage at 735MHz Monitoring at just one frequency will not > allow you to detect all leaks. > QAM Snare simultaneously detect leaks at Multiple Frequencies < HOME

The technology > The process whereby QAM Snare detects and pinpoints leaks is fairly straightforward to explain: 1. Samples of the QAM channel are taken at the headend and transmitted to the field unit over a wireless network. * 2. The field unit compares these samples with signals pulled off of its antenna – when there is correlation and the two signals are the same – a leak has been detected. 3. After detection the next step is resolving the exact GPS coordinates of the leak, which is accomplished through an advanced technique called TDOA – time difference of arrival. * With the QAM Snare Isolator used in the home, samples are acquired locally < HOME

Advanced location methodology •Because of the employed Time difference of correlation detection process arrival (TDOA) – and inherent time delay hyperbolic location output – we have a unique opportunity to make use of this data and employ the most accurate location methodology called Time Difference of Arrival (TDOA) to resolve the GPS location of the leak. •QAM Snare is impervious to multipath/standing wave type issues that are prevalent with analog detectors – thereby making the final isolation process significantly easier. < HOME

Simultaneous three channel detection • QAM Snare is designed to detect and record leakage from any three digital channels simultaneously • Typical choices are Aeronautical (130 -200MHz) , Mid-band (550MHz) and LTE (750MHz) 729MHz 567MHz 579MHz < HOME