Frequently asked Questions
What is the purpose of the LTE signal measurement?
The reality is that an abundance of leaks exist in the LTE band, and some strategy needs to be employed in order to prioritize which ones should be fixed. In order to assure egress is not disruptive to wireless carriers, it makes sense to focus on locations where LTE signal strength is the strongest, and not just focus on leak level. The first level of prioritization should be large leaks in areas with strong signal level. Many years ago when we first raised this issue, we recommended adding a database of tower locations and using this as an area of focus. Further testing and the realities of cell networks have proven that this approach will not work. As an alternative, we integrated a much better process into our system. LTE signal strength at any location is not dependent on proximity to a tower – the reality is much more complex. Geography, tower height, beam focus (MIMO), antenna characteristics, nearby building and obstructions, and many other factors are all at play. Additionally, given the new, smaller cells that the wireless industry is moving towards, we really have no idea where the towers are located. So we simply jump to the LTE downlink and public safety frequencies during portions of seconds when we are not detecting, and we measure LTE signal strength. We include this as a critical parameter in our leakage database used for prioritization. It takes the guessing and estimation out of the process.
Why do you reference LTE leakage and not UHF leakage?
We think that UHF leakage only tells part of the story and can leave the operator vulnerable if leakage detection is solely done at lower UHF frequencies instead of at the LTE band. Testing has repeatedly proven that the higher you go in frequency, the more leaks you have. In every system there are simply more leaks in the LTE band than at lower UHF frequencies. 612MHz is not ‘near LTE’ and is too distant from the LTE band to provide meaningful results.
Do you need a data plan to use QAM Snare?
Data connectivity is required for QAM Snare field devices when operating in QAM detector mode. Analog, analog tag, and OFDM detector modes do not require continuous connectivity – but do require occasional communication in order to report drive routes, detected leaks, and LTE signal level to the server. GSM and WiFi versions of the product are available. Of the two, WiFi is the recommended implementation, as it allows existing connectivity from trucks or technician laptops and iPads to be leveraged. If connectivity exists, then no additional data plan is required. The GSM version does require a data plan for each device. QS Isolator sets do not require any type of data plan, as data is sent from the transmitter to the detector over an ISM chip-set.
Can QAM Snare operate on public WiFi networks?
No, public WiFi is not intended for or capable of operating with any sort of mobile connectivity.
How does QAM Snare perform in a Multi-Hub environment?
QAM Snare was designed specifically to operate in these environments. The hub boundary coordinates are overlaid onto the QAM Snare maps. As the units in the field travel throughout the network, information on their current GPS coordinates is provided to the server connected to all the hubs. The server uses this information and sends samples to the field device that corresponds to the hub in which the device is currently located. When the field device is at a location bordering multiple hubs, it simply sends data to both.
How does Time Difference of Arrival (TDOA) algorithm work?
Because QAM Snare inherently utilizes time delay, we are uniquely able to leverage this towards the most advanced and accurate leak location technique in the industry. QS Technology utilizes differences in time delay at multiple detection points to calculate the exact GPS coordinates of the leak.
How accurate is the QS TDOA algorithm?
The accuracy of the location is dependent upon the number of detection points and their relative location. A radius number is retained in the database. This number is an indication of how accurate the flag location is – usually within 3–10 meters. Typically, when you reach a flag location, a pole or pedestal is obvious and will be the most likely source of the egress. The impaired device, cable, or connector can quickly and easily be troubleshot by using a companion Isolator to move in the direction of increasing signal level.
Are multiple vehicle passes used to continuously refine
the QS technology and leak location?
Yes. As leak detection vehicles drive by existing open leak locations, the additional information on level and location is added to the existing database, providing more data with which to refine the QS Technology GPS location and radius. This is all done in real time and the information is updated immediately.
How is the QS Technology calculation performed?
The correlation detection is performed in the field unit. This data, along with the GPS location, is transmitted to the server. The server performs the calculation to determine the QS Technology GPS leak location, which is immediately sent back to the Navigator or Navigator Plus field unit. A flag showing the location is then displayed, allowing for immediate repair.
How prevalent are leaks in the LTE band?
In the years we have been working with QAM Snare, many thousands of leaks have been detected. When looking at summary data for all systems, the average number for every system is an abundant one LTE leak per mile driven.
Would detection at 612MHZ provide the same result as working within the actual LTE band?
Absolutely not. 612MHz is 170MHz away from parts of the LTE band. Given the significant frequency response variation of leaks we have seen, it is clear that egress at 612Hz is not indicative of egress within the LTE band. For the very first device that we measured the frequency response using a GTEM chamber, we measured an 18dB difference in shielding effectiveness between the two frequencies. Accounting for 2dB of tilt, there was a total of 20dB difference. To put that in more meaningful terms, a 100μV leak at one frequency would be measured as a 10μV leak at the other. Given the vast number of LTE leaks, it is operationally important to ensure repair support is working on the right problems, and this cannot be done while detecting at 612MHz. It is essential to measure LTE egress within the LTE band.
Can QAM Snare detect leakage on any channel?
QAM Snare is frequency agile and is capable of detecting leakage on any suitable channel. QAM Snare can detect leakage on Analog channels, QAM channels, and OFDM channels. For QAM detection the channel needs to be configured as a broadcast and not a narrowcast channel, so all content is the same on all nodes. DOCSIS QAMs are inherently narrowcast and are not suitable. However, the channel does need to be free from strong co-channel interference.
How many channels can QAM Snare process?
Each QAM Snare server can process four channels simultaneously, and can support field devices working on these four frequencies. Each Navigator and Navigator Plus field unit can simultaneously process and detect leaks on one, two, or three channels, providing visibility on plant egress across the entire spectrum – in the aeronautical band, in the middle band in proximity to UHF broadcast signals, and in the LTE band. It is important to note that this is not an either/or option as is the case for other leak detection systems, which require the user to stop driving and look at the meter in order to manually toggle between frequency bands. The QAM Snare Snoop FTM is able to simultaneously detect two channels, one in the lower band and one in the LTE band.
How does multi-channel detection work?
The QAM Snare Server sends a data packet containing a signal sample to each field device twice per second. In one-channel mode, samples are sent once per second. In two-channel mode, samples for the first channel are sent in the first half of the second, while samples for the second are sent in the latter half. In three-channel mode, samples of the first channel are sent in the first half of each second, and the second half of each second alternates between the second and third channel, allowing these channels to be sampled every other second. QS Isolator sends samples for the channel in use, twice per second, closely simulating the behavior of legacy analog equipment.
Is additional equipment required for multiple channel detection?
The only additional item required is an antenna-combining network – either a diplex combiner for use in the two-channel mode with two antennas, or a triplex combiner for use with three antennas. The two or three antenna inputs are combined and connected to the single QAM Snare antenna input. These are readily available for the recommended configuration. Given the wide differences in frequency bands, a separate antenna is required for use in each of the three bands.
Do LTE uplink and downlink signals interfere with QAM Snare? How can these frequencies be used?
LTE downlink frequencies (tower to phone) are definitely not recommended for use due to the presence of very strong signals. However, the LTE uplink frequencies are ideal and actually turn out to be some of the quietest bandwidth available. The QAM Snare utilizes pulse communication of 1msec duration, twice per second – this is only .2% of the time. LTE traffic is also pulse-based in time and frequency, and very rarely does a device use the entire 10MHz spectrum. It uses only a few frequency sectors, as directed by the BTS, at various moments in time. Thus, the potential interference is held to a small frequency band – not enough to overload anything. The uplink pulse would have to happen at the exact moment of our pulse, which is statistically unlikely. Also one 10MHz LTE channel is spread over two QAM channels. The power level of the phone is also typically not very high, especially in environments where there are many towers. Lastly, both the vehicle and the other LTE devices are moving. In order for interference to occur, all of these unlikely events would have to coincide perfectly, and if it does happen during one second, it is extremely unlikely to happen during the next.
What’s the downside to multi-channel detection
and how many channels are recommended?
One downside is the additional amount of leak data that will be generated at the second and third frequency, especially when first using the equipment. The average, one leak per mile quantity of LTE leaks detected, can easily outpace the ability of a system to repair, and since these LTE leaks will likely be more network-affecting than, say, a middle frequency leak, the LTE leaks should always get attention first. Certainly, if you are using the QAM Snare for aeronautical compliance, a second frequency will be necessary. So when starting out, in order not to overwhelm staff, our recommendation is to only use one– or two-channel detection. Secondly, while using three-channel detection, the second and third channel samples are correlated once every other second instead of every second. This could result in slightly less visibility to smaller leaks. However, multiple channel modes compensate for this by automatically increasing the sensitivity by 6dB within a time delay window that corresponds with previously detected data points. This method results in more distant leak visibility and additional acquired data points, so that on the whole there is only minimal difference. Finally, you should note that an additional antenna is required for each frequency.
Will the QAM Snare work-order system work
with my existing system?
Definitely, we have already customized and developed tools to make the process seamless – just ask!
How are work-orders dispatched?
The internal work-order system is extremely flexible and can be configured to automatically dispatch leaks to various levels of technicians according to the needs of your particular operation. Certain high frequency leaks, which are likely hardline problems, can be dispatched to line techs. Different amplitude leaks can be assigned to a certain level of tech, and leaks can be grouped according to proximity to each other. Specific nodes can also be associated to specific technicians, who can be dispatched based on proximity to a technician’s home. They can even be priority dispatched based upon proximity to LTE towers. And if we can’t currently do it like you want, just ask – and we can build in the capability.
Are there limits to the speed a vehicle can travel
while detecting leakage?
In other systems, sensitivity decreases significantly whenever the carrier vehicle travels greater than 30 mph. However, there are no speed-associated Doppler issues with QAM Snare. The technology has even been adapted for use in aircraft flyovers. Unlike aeronautical leakage, which is more often found in soft cable, LTE leakage is primarily hard cable based. Therefore, your detection needs are not limited just to neighborhoods where driving slow is not a problem – you also need to detect along highways and high-speed roads commonly adjacent to hardline with no loss of sensitivity. QAM Snare is the only system that is efficiently able to perform in this environment.
Why is QAM Snare impervious to multipath?
For QAM Snare, multipath issues manifest themselves as multiple attenuated peaks in our correlation function (essentially another smaller leak at a different but close-in time distance). To eliminate the potential for multipath, we simply filter these additional close-in peaks in software and display the maximum amplitude result in the correlation process. No leakage detection method other than QAM Snare has the ability to eliminate multipath, making it the easiest and quickest method for technicians to resolve the final source of impairment.
Will QAM Snare GPS work in urban tunnel environments?
Yes, the product is now available with GLONASS capability in addition to GPS, significantly improving the ability to function in difficult tunnel-type environments.