Design Article
Handheld receiver provides aerial downlink in mission-critical applications
Stephen Shpock, IMT
7/18/2011 9:36 PM EDT
The need for mission-critical microwave video solutions for defense, security and law enforcement applications has never been greater. IMT's MobilCMDR (COFDM Mobile Diversity Receiver) was designed for enhanced reception for situational awareness in tactical and strategic settings. The main application of the handheld MobilCMDR is for video downlinking for tactical applications, including airborne, ground, and remote surveillance.
In situations that require field deployment and mobility in uncertain conditions, coded orthogonal frequency division multiplexing (COFDM) microwave links provide an alternative to IP wireless or SATCOM technologies. These non line-of-sight links can deliver range lengths from several 100 meters (low power) to 50 miles or more (for airborne systems). Range is dependent on power, antenna placement, path, and more.
Older, conventional, single-carrier microwave transmission is susceptible to signal fading caused by multipath reflections when a line-of-sight path is not available. Fading can cause picture distortion in analog receivers, and loss of demodulator lock in digital receivers.
COFDM modulation can overcome these impairments by using multiple carriers rather than single carrier transmission schemes. Even if multiple carriers are lost due to fading, additional error correction techniques enable a receiver to recover the intended video data.
COFDM offers significant advantages when using microwave links to transport video in portable, field-deployable, or non-engineered situations. COFDM systems:
Advancements in COFDM technologies have resulted in microwave systems that are ideal for a growing range of video surveillance applications, minimizing operational failures and maximizing success rates in covert and situational awareness/surveillance.
An airborne tracking operation is one application where the COFDM and the MobilCMDR excels. By having a law enforcement helicopter or airplane follow a suspect from above, it allows ground officers to stay well behind the suspect while being able to watch the aerial video on the ground at a safe distance. Tailing a vehicle (subject) also allows the arresting crew to remain well out of vision so the perpetrator does not think (or know) that he or she is being followed. By keeping the element of surprise, the police are afforded the upper hand, which can prove critical in keeping everyone involved safe.
Another application where the MobilCMDR works well is firefighting. Having the ability to fly above a fire and downlink the thermal video down to the firefighters is a major breakthrough in this field. The firefighters on the ground are now able to use the MobilCMDR to see where the infrared hotspots are and can ultimately direct their efforts for quicker and faster results.
In the past, a helicopter crew would have to explain to the hose crew on the ground (if communication was even possible) whether or not the hose crew’s aim was on target. The MobilCMDR provides a much more efficient way of getting information to the ground team. This not only saves critical time and resources, it can also significantly impact a department’s budget.
In a hostage situation, MobilCMDR can be used on the receiving end with a body worn camera/transmitter by a member of the SWAT team. The SWAT team member can transmit video from his location whether it be perimeter surveillance or inside a building. Thus, the MobilCMDR is used as a force multiplier in creating a vision not normally used in these tactical operations. When used in this way, someone in tactical command can give directions and intelligence to the team to efficiently ensure operation success.
In addition, bomb squads can also use the MobilCMDR in robotic video applications for bomb disposal, monitoring or detection. The use of an EOD robot and the small handheld receiver are viewing the robot visual area of action. They can also transmit the video to more than just one person in the command and control group. As a result, numerous members of the squad can examine the video and get an idea of just how serious the situation is without having to get too close. This outlook enables the team to ascertain the best scenarios to diffuse the situation.
Next: How it Works
In situations that require field deployment and mobility in uncertain conditions, coded orthogonal frequency division multiplexing (COFDM) microwave links provide an alternative to IP wireless or SATCOM technologies. These non line-of-sight links can deliver range lengths from several 100 meters (low power) to 50 miles or more (for airborne systems). Range is dependent on power, antenna placement, path, and more.
Older, conventional, single-carrier microwave transmission is susceptible to signal fading caused by multipath reflections when a line-of-sight path is not available. Fading can cause picture distortion in analog receivers, and loss of demodulator lock in digital receivers.
COFDM modulation can overcome these impairments by using multiple carriers rather than single carrier transmission schemes. Even if multiple carriers are lost due to fading, additional error correction techniques enable a receiver to recover the intended video data.
COFDM offers significant advantages when using microwave links to transport video in portable, field-deployable, or non-engineered situations. COFDM systems:
- Deliver robust signals even when analog paths don’t work.
- Can be used in remote monitoring, mobile command or airborne applications.
- Can provide received video signals that are equal to the field inputs. After compression, the video signals retain their carrier-to-noise ratio even as the transmitted signal approaches the threshold of the microwave receiver.
- Can use less bandwidth than analog techniques.
- Provide extremely effective adjacent channel and co-channel interference rejection—reducing interference with the transmission.
- Can achieve transmission distances equal or greater than analog techniques.
- Enable the application of small format, low-profile, covert systems.
Advancements in COFDM technologies have resulted in microwave systems that are ideal for a growing range of video surveillance applications, minimizing operational failures and maximizing success rates in covert and situational awareness/surveillance.
An airborne tracking operation is one application where the COFDM and the MobilCMDR excels. By having a law enforcement helicopter or airplane follow a suspect from above, it allows ground officers to stay well behind the suspect while being able to watch the aerial video on the ground at a safe distance. Tailing a vehicle (subject) also allows the arresting crew to remain well out of vision so the perpetrator does not think (or know) that he or she is being followed. By keeping the element of surprise, the police are afforded the upper hand, which can prove critical in keeping everyone involved safe.
Another application where the MobilCMDR works well is firefighting. Having the ability to fly above a fire and downlink the thermal video down to the firefighters is a major breakthrough in this field. The firefighters on the ground are now able to use the MobilCMDR to see where the infrared hotspots are and can ultimately direct their efforts for quicker and faster results.
In the past, a helicopter crew would have to explain to the hose crew on the ground (if communication was even possible) whether or not the hose crew’s aim was on target. The MobilCMDR provides a much more efficient way of getting information to the ground team. This not only saves critical time and resources, it can also significantly impact a department’s budget.
In a hostage situation, MobilCMDR can be used on the receiving end with a body worn camera/transmitter by a member of the SWAT team. The SWAT team member can transmit video from his location whether it be perimeter surveillance or inside a building. Thus, the MobilCMDR is used as a force multiplier in creating a vision not normally used in these tactical operations. When used in this way, someone in tactical command can give directions and intelligence to the team to efficiently ensure operation success.
In addition, bomb squads can also use the MobilCMDR in robotic video applications for bomb disposal, monitoring or detection. The use of an EOD robot and the small handheld receiver are viewing the robot visual area of action. They can also transmit the video to more than just one person in the command and control group. As a result, numerous members of the squad can examine the video and get an idea of just how serious the situation is without having to get too close. This outlook enables the team to ascertain the best scenarios to diffuse the situation.
Next: How it Works
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kinnar
7/18/2011 11:58 PM EDT
OFDM is the technique being used in most of the sophisticated wireless applications, and it have prove itself.
Now there will be so many applications like this coming up in line as the world is changing towards wireless links and each application is trying to make use of wireless technologies for betterment.
There is no doubt about it that OFDM will be the underlying technology for all of these applications.
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Darius Pl.
7/25/2011 5:18 PM EDT
This is a good "sales flier". It's a shame that it does not include more technical details about RF and other technologies included in this product as I guess the audience of this portal is particularity interested in such details. On the other hand, I doubt very much that the potential customers are reading these pages...
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janine.love
7/25/2011 5:30 PM EDT
Hi, Yes the readers are interested in those details. This is an application based piece. Readers asked for more of them when I asked, so this is part of what I call "RF in Action." I invite you to look around the site http://www.eetimes.com/design/microwave-rf-design and sign up for the newsletters to get a better idea of what we do.
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WKetel
7/30/2011 8:05 PM EDT
Yes, readers are indeed interested in a lot more of the technical details. Of course, it would be over some heads, but how better to learn? I was reading "electronics" magazine very shortly after I learned to read. Did I understand much of it? No, but I certainly found it interesting. On the other side, I was not one who would be purchasing any of the materials advertised at the time.
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