DIPOL Weekly Review - TV and SAT TV, CCTV, WLAN

It is easier to flow with the current - a new networking standard.

On October 18, 2010, IEEE announced the ratification of the IEEE 1901 (TM) standard.
The new standard, Broadband over Power Line (BPL), applies to equipment for data transmission via electricity networks. According to the specified solutions, transfers between devices will exceed speeds of 500 Mb/s, over distances up to 1500 m. Special modulation techniques will allow to transmit the data over standard AC power lines, using carrier frequencies below 100 MHz.

Are there any cons of BPL?

With BPL devices we will be able to use Internet access points integrated into the AC power sockets. Given the universal power supply of electronic devices through the AC power network, it will eliminate any additional installation work.

The requirements of modern televisions may be the best example of the need to integrate power supply and data transmission. Another examples, outside buildings, may be BPL applications on means of transport such as a train, a subway or an airplane, where the technology will support transmitters allowing passengers to connect to the network while traveling, without a risk of unstable transmission.

An important functionality of BPL equipment is the possibility of building hybrid structures - WLAN plus BPL. WLAN enables wireless transmission on each story/level, and BPL network carries the signals through the ceilings which significantly attenuate electromagnetic waves.

The first hybrid devices are already under construction - Atheros company announced their market launch later this year. Atheros will offer not only the equipment, but also dedicated software to manage the entire network created by the transmitters.

Currently there are many devices that enable data transmission via electric cables. However, widespread adoption of the standard will help to standardize the technology and will ensure compatibility of all products. It will result in greater consumer interest, further increasing with inevitable decline in prices.

Antennas on a volcano - which one?

It is the largest volcanic cone on the continent - with 145 km circumference of the foot and the height of 3340 meters above sea level.
The last eruption took place on November 6, 2009, so, because of continuous threat, it requires constant monitoring. The volcano observatory is located at an altitude of 2942 meters above sea level.
For monitoring of more than 270 craters that are located on the slopes of the mountain and transmitting the data, the most convenient technology is wireless transmission.
What is the name of the volcano and where it is - you'll find the answer at the end of this issue.

Power supply of multiswitch systems.

Multiswitch systems for hundreds of users are becoming increasingly common these days. The manufactures of the multiswitches have to provide means for effective power supply of such large systems. The multiswitches from reputable manufacturers often have two ways of power supply.
TERRA multiswitches of MSR series are powered from built-in AC/DC adapters, whereas cascadable multiswitches and those of MSV series can be powered from external power supply R71465 or from multichannel amplifiers SA-x01 ( R70501, R70901 ). The AC/DC adapter integrated with SA-501 R70501 amplifier can power multiswitches of MSV-5x series, and that integrated with SA-901 R70901 - of MSV-9xx series. In both cases the multiswitches are powered through H lines.

Each power source has a current capacity that cannot be exceeded. For example, SA-901 amplifier or R71465 power supply has capacity of 2 A. Taking into account typical current consumption of two LNBs (2 x 300 mA), there is 1.4 A left (2 A - 2 x 0.3 A = 1.4 A). So, each of the devices can power up to 14 cascadable or MSV multiswitches (each consuming 100 mA).

Example of installation with two power supplies: that built into R70901 amplifier and the R71465. TERRA taps can permit (ON) or block (OFF) power transmission via H lines.

Is there a need to measure digital TV signals? - MER parameter.

It is well known that DVB-T signals in identical propagation conditions can be received with satisfactory quality in a wider area than analog signals. This translates into generally easier reception of digital channels, with much lower requirements for the antennas.

However, in analog TV the decline of the carrier to noise parameter (C/N) caused proportional decrease of image quality, and the picture was still visible even in the case of the lowest C/N values that allowed any reception. The difference in the C/N ratio could be as much as 25 dB, and the installer and/or the user could see directly on the screen the actual image quality and decide on its approval or taking further steps to improve the signal.

In the case of a digital signal, the boundary between an ideal image quality and loss of reception is very sharp. In DVB-T, similarly to other digital broadcasting, we have to cope with "digital cliff" effect. This means a sudden jump from a normal reception to a complete lack of content.

The cliff effect in digital DVB-T. The quality of analog TV picture decreases gradually.
(source: en.wikipedia.org/wiki/Digital_cliff)

This feature creates a substantial risk in areas with unstable transmission conditions. Having a perfect picture on the TV screen we don't know how far we are from the effect of the complete loss of reception. The instability can be caused by changeable weather conditions, installation faults, interferences, trees, passing cars etc.

To avoid such problems, professional antenna installers should measure MER (Modulation Error Ratio). In some sense, it is an equivalent of C/N ratio of analog signal. Its value tells us how far we actually are from the boundary of the "digital cliff".
Different types of modulation and variants of FEC error correction require suitable minimum and "safe" values of MER. Generally, the MER value for DVB-T with COFDM modulation should be at least 26 dB.

DVB-T meter Digiair Pro R10510

The Digiair Pro R10510 meter is an inexpensive professional instrument for antenna technicians who don't like nasty surprises. In addition to the MER parameter, it can measure bit error rate (BER) and several other parameters specific to digital and analog television signals.

Remote monitoring of construction site - TREND DVRs and cellular phones.

A customer of a Slovak company dealing with the implementation of CCTV systems asked for installation of video surveillance system on one of its construction sites. The requirements included remote access to the images via cellular phones.

The optimal choice has been application of modern DVR TREND 250X04 M72504.
TREND 250X04 is a four-channel DVR that provides recording capabilities of 4CIF (704 x 576) images at 6 frames per second or 2CIF (704 x 288) images at 12 fps (in each channel). The DVR can be operated locally, using the included USB mouse, remote control, or the keys on the front panel, as well as remotely via the Internet (Internet Explorer). The device is supplied with free utility for remote monitoring via mobile phones and free software for installing on PC computers running Windows(R) OS.
The option to set parameters of additional stream ensures smooth flow of transmitted images, even if the users are connected over slower network links. H.264 compression with the ability to support up to 2 TB hard drives allows to record large amounts of video footage.

Online preview of images from a CCTV camera on cellular phone.
The menu available through the phone allows to select the camera and perform PTZ and digital zoom functions.

Block diagram of the CCTV system supporting access through a cellular network

According to the investor, "... due to high quality and functionality, the DVRs can be recommended to anyone seeking modern and economical solutions ... the images from the cameras are incomparably better than from other devices in this price range".

A functional breakthrough in video surveillance systems - no need for a monitoring center.

In a typical CCTV system the images from cameras are recorded by DVR recorders, servers or network recorders (NVR). The devices run intelligent software that supports the surveillance staff. The disadvantages of such a system include the need to transmit large amounts of data and necessity of employing a group of people who monitor the images and provide information to intervention groups.
Along with higher capabilities of processors, allowing image analysis directly in cameras, the alarm signals can be directed straight to the intervention groups, without any intermediate organizational unit. The critical information can be recorded on memory cards in the cameras. The cameras equipped with motion detection software send images from the areas with detected motion directly to the cellular phones of patrol groups, allowing them better orientation and quicker response.

An example of such a camera is Aviosys 9070 CS K1161, allowing to record video or JPEG images on the included 2 GB SD card. The recording can be triggered by:

This solution can be very convenient for homeowners, who usually don't need continuous recording of the surveillance video. The local recording can be activated by an intruder crossing the fence of the property. In such a case, the owner gets instant information on the event along with a photo and possibility to remotely view the recorded video through a web browser.
The recordings can be played on a laptop or PC and copied onto the hard drive and/or a DVD-ROM .

Overvoltage protection of overhead lines - AXON AIR NetProtector.

AXON AIR NetProtector J2835 is designed for surge protection of devices connected to Ethernet 10/100/1000 Mb/s networks via an overhead UTP/FTP cable.
AXON AIR AIR NET Protector should be used as the first level of protection when employing overhead transmission cables. The signal circuits are protected by elements that carry excessive charges to the ground, as well as eliminate overvoltages between the wires of each pair. The basic condition for an effective operation of the device is to connect the green&yellow cable to the ground (no to a lightning conductor) or to the protective earth/ground conductor (PE) of the AC power network.

Computer network protectors

Overvoltage protection of overhead lines
AXON AIR NetProtector J2835

Example of application of the J2835 protection of overhead lines
and AXON PoE NetProtector J2836

Mount Etna volcano - Sicily.

Since the fifth century, there had been recorded 80 large explosions, of which the strongest one took place in 1669, destroying Catania city. The eruption of Mount Etna in 1971 destroyed a cable railway and astronomical observatory. On July 13, 2001, the volcanic lava destroyed the upper cable car station.
In winter the craters and slopes of Mount Etna are used by skiers.

The map of Mount Etna and the currently existing infrastructure

We have written about:

Multiswitch system with 700 outlets in a 35-story building. The design and implementation of such an installation is a major challenge for the designer and installation company.
The job can be properly done only when the designer and the contractor employ first-class equipment. The project uses MSV-932 R70882, MSV-924 R70874, and MSV-912 R70862 multiswitches from TERRA...

The design of the multiswitch system for 700 outlets

Megapixel Aviosys cameras - a milestone in the presentation of live video on the Web. Many people want to create their own website which will be streaming live video from a camera, at the lowest possible cost. However, such a service typically involves a monthly subscription for video streaming, a cost of renting space on a server, and a quite extensive knowledge of programming....

Example website with live video from Aviosys camera

Power over Ethernet (PoE) adapter. The PoE adapter N9206 allows to power LAN devices through typical transmission cable (FTP/UTP etc.)... It is very useful solution in the case of Access Points, where the AP can be placed in a hermetic box just by the antenna (to lower the loss in the RF cable) and supplied via transmission cable from power source located inside a building...

Index of published issues