Full spectrum

Full spectrum

Published: MEA

The challenge with large-scale wireless systems is that unless carefully planned, interference and intermodulation can cause huge problems. When you are working in the finite space of the RF spectrum you have to be incredibly careful how many channels you use and which frequency range they operate in, particularly when the channel count numbers in the hundreds and the solution is being installed into a prestigious location.

The newly renovated Sheraton hotel in Doha is exactly this kind of environment. As a popular venue for meetings and congresses of all sizes in Qatar, it required the scale of wireless conference and translation installation that would test any system to its limits. Approximately 80 per cent of the rooms and meeting spaces in the hotel needed to be covered by wireless systems. Add to this the pressures of a short project timeframe with a very high-profile event to complete by and the task becomes even greater.

‘When Q2 approached us with the project, I think we had about 24 hours to put together a design and a BOQ,’ recalls Ryan Burr, technical sales manager for Sennheiser Middle East. ‘We worked through the night to put everything together. It’s around 200 RF channels just on wireless microphones. That’s not taking into account the RF required for the interpretation system and the RF required for the conference system.’

‘There are nearly 400 wireless delegate units spread over five different conference systems, 4,000 wireless receivers for the translation system plus nearly 200 channels of wireless mics,’ adds Sennheiser Middle East director of sales and marketing, Mig Cardamone. ‘It was our biggest ADNw sale globally and a huge translation system of 4,000 pieces, but we also had 120 channels of 3000/5000 Series which is our top of the range analogue wireless system. Every single handheld had Neumann KK-105 capsules on. The specification of the equipment was absolutely first class.’

Obviously, with this number of wireless channels required for the hotel, the RF spectrum very quickly became a key concern. ‘Everybody was concerned about the RF, if there would be interference and if it would work,’ recalls Esber Nasrallah, operations manager for Doummar – Q2 Advanced Technology Contracting, the company responsible for the whole A/V installation. ‘They didn’t know about the product, so we had some problems approving it because they are not used to such systems. Sometimes I would put Sennheiser in direct touch with the regulator over the phone to solve some technical issues.’

‘I remember a couple of phone calls of us having to communicate directly with the authorities in Doha to make assurances to them that we wouldn’t encroach on frequencies that are being used for telecommunications purposes, particularly with the ADN-W,’ furthers Mr Burr. ‘It uses 2.4GHz, 5GHz and 5.5GHz and they didn’t want us to use the 5GHz range. We had to have a special preset written by Germany that we could install into the system with a firmware upgrade to give the authorities the assurance that we weren’t going to use that part of the spectrum, and that had to be done quickly. A project and a customer like this warrants that kind of attention.’

The task of avoiding interference was a much more challenging one, and the team from Sennheiser and Q2 had to be careful about how it used the frequency spectrum. ‘There’s a process of dealing with intermodulation so this can all be formulised on what channels you can’t use and which ones you can use and how to distribute the RF spectrum that you’ve got to work with,’ explains Mr Burr, who achieved the manufacturer’s RF Expert certification during the project. ‘In Qatar we’re quite fortunate in the sense that there’s not a lot of TV channels that are transmitting in the air. In fact, we only had two blocks where we had some digital TV and that we had to avoid. That then left us with all of the remaining spectrum from 470MHz right up to 800MHz practically. So taking out the DTV, then coming up with a configuration across multiple ranges of our wireless microphones, I think I used two ranges starting at 470MHz going up to 690MHz and I managed to squeeze 203 channels into that.

‘We have a custom piece of software called SIFM, which is a frequency management program that you can configure seeing which parts of the spectrum you have to work with and how many channels you want to fit into that,’ he continues. ‘It uses an algorithm to come up with channels that are intermodulation free and will cover that whole amount of spectrum.’

With a project of this scale, there are several different ways the team could have configured the RF setup. A simple route would have been to repeat the frequency spread in several rooms that are distributed a long distance apart within the hotel. But this was not the route Mr Burr wished to take.

‘I did it as a complete system over the whole site,’ he explains. ‘You’ve got rooms that are probably a kilometre away from other rooms so you could have used the same frequencies within those – because of the transmission power you’re working with they wouldn’t have interfered. I didn’t want to do that just in case. You never know what may happen.’

‘It gives flexibility,’ adds Mr Cardamone. ‘It means they can move transmitters around without having to worry if it will interfere with a room. It’s absolutely intermodulation free and interference free.’

With such a busy spectrum, avoiding interference from companies coming in with their own equipment was also a key element of the RF design. ‘When I designed the RF part of it, I made sure that the guys on site had spare channels that they could say to people who were bringing RF equipment, “please use these frequencies”. They were built into the whole plan,’ explains Mr Burr.

A separate area of the installation, and the spectrum, was dedicated to the translation portion of the project. ‘It was a little bit of a challenge with the translation system,’ recalls Mr Burr. ‘The requirement was for six languages. Instead of using traditional infrared systems, we used digital RF systems. We went with digital RF because it’s more stable. IR requires considerably more installation. You need to have radiators everywhere particularly in areas where you have lots of natural light. Then you can suffer from interference from all sorts of other sources.

‘We operate our digital RF systems in a part of the spectrum – 863-865MHz – which is supposedly licence-free. But within that range you can only fit eight channels,’ continues Mr Burr. ‘The rooms are so large, we had to use special boosters to increase the signal of the transmitters for the translation system up to 100mW from 10mW. But also within that we had to taper it off to make sure that it didn’t spill out into other rooms, because each space is using the same frequency ranges for translation.

‘We tested all this. In Majlis, which is one of the rooms, we had a 100mW booster but found that when we were walking out of the room and into the corridor spaces that it was still receiving,’ recalls the technical sales manager. ‘So we put in attenuators and attenuated that down to 50mW so the minute you walked out of the room then, you lost the signal.’

With the RF challenges covered, the biggest issue for the whole project was delivering it on time prior to the GCC Summit which was scheduled to take place in the hotel. Q2 was responsible for the whole A/V setup in the hotel, including the BGM system using products from Bose, Biamp and Apart, Christie projection with Orray and Gerriets screens and the Meyer Sound Mica and Melodie main sound systems with their Midas Pro1 and Pro2 consoles. Added to this was a broadcast system calling on equipment from Sony, Multidyne and Miranda, lighting from Phillips and A/V control from Extron and Crestron.

With such a large volume of equipment being delivered and installed, it was key that strict timescales would be met. ‘The big challenge for everyone was the delivery of this project,’ says Mr Nasrallah. ‘Everything was planned to be delivered for the end of November. We all knew that we had to finish because the GCC Summit was taking place in early December. When we came to see Sennheiser for the delivery of this project they assured us they would deliver on time, and this is what happened.’

As Sennheiser was the largest single supplier for the project, hitting this deadline required a great deal of coordination with its factory in Germany. ‘In terms of the supply challenges, we had a short timescale that we had to work to once the order was confirmed,’ recalls Mr Burr. ‘We were already working on a large-scale project where we had to supply 7,100 receivers, so already production was going around the clock to be able to fulfil that.’

‘The two orders came at around the same time,’ furthers Mr Cardamone. ‘The summer is not a traditionally busy time here and not a particularly busy time for our production colleagues in Germany and it coincided with our two biggest projects.

‘The first challenge was meeting the delivery date for a project in Turkmenistan which was 7,100 of these headsets – by far the largest order we’ve had for this particular product. So we were in constant dialogue with Germany about getting production ramped up, getting the supply of the materials, making sure we met what was a really challenging delivery deadline,’ he continues. ‘Whilst we were in the throws of these discussions and still had the challenges of meeting this deadline, we landed with another order for 4,000 pieces of HDE-2020, which was the second biggest order they’d ever had.

‘We were in communication with them from the start. We were talking to product planning, materials control, literally everybody at every stage was involved in meeting the deadline,’ recalls Mr Cardamone. ‘We understood how important it was that the delivery deadline had to be met because they had incredible timescales to meet.’

With the equipment built and shipped to the Middle East, everything was looking on schedule for the installation. However, there were some unexpected regulatory issues which delayed the arrival of the equipment into the country. ‘The cables and the racks were already there, we were just waiting for the rack equipment and the termination,’ recalls Mr Nasrallah. ‘All of this happened in fewer than 10 days, we were working around the clock.’

While this created obvious challenges, it also brought everyone together to make sure the installation was completed on schedule. ‘Even during the final days of the installation, we felt that we were really one team,’ says Mr Nasrallah. ‘You would see Ryan opening boxes and putting 4,000 batteries in. We were like one team, we were there just to deliver on time.’

‘When we first went onto site, fortunately I had the support of both the UK and Germany,’ adds Mr Burr. ‘I called on Jens Werner who is portfolio manager for conference and translation systems so he came over and assisted. ADN had never been tested to this capacity before. Its capacity is 400 units and we were having 392 on site. It was pretty much imperative that he was here on site. I also brought across Sam Davison from the UK who is head of our service department and a very well-qualified engineer just in case something went wrong and we had to pull equipment apart. I knew that he would know what he was looking at a lot more than I would.

‘I was glad we did, because on a couple of the rooms we had to help with terminations and getting things cabled up,’ he continues. ‘It would have taken these guys another couple of days had we not been there to do that.’

With everything installed, commissioning the system was the final stage. As part of this, the Sennheiser team ensured they tested the solution to its full capacity. ‘When we were on site during the last few days of commissioning, we tested everything to the max. We had everything running in every room all at the same time and we went round the different rooms doing RF scanning just to make sure that everything was stable,’ says Mr Burr. ‘We had confidence that even if they were using everything at the same time it would work.’

The end result is something that everyone involved is rightly proud of. ‘Q2 did a fantastic job in getting everything in,’ says Mr Cardamone. ‘This site was just a hive of activity, everyone was really busy and Q2 were right in the thick of it, making sure they delivered this project. It was a phenomenal achievement. They did a first-rate job, really fantastic.’

As for the client, its use of the system speaks volumes. ‘They have a lot of events on a daily basis and they have been using the system since mid-December,’ says Mr Nasrallah. ‘We have received no negative feedback on the installation and no calls to assist or remedy any defect in the installation.’ This is the best kind of praise any system can receive, particularly one with as many channels and as many variables as the Sheraton Doha.


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