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

Microsoft is preparing a revolution of the Windows caliber.

During the mid-January conference on a new operating system, Windows 10, Microsoft for the first time revealed the fact of working on a virtual reality system. The necessary gadget is Microsoft HoloLens, the glasses in which the real world is seen in conjunction with the virtual world. Using gestures recognized by sensors embedded in the glasses, the user can manipulate virtual objects. For example, it is possible to place a virtual vase on a real desk.

The virtual objects are sort of holograms that can be seen only through the HoloLens glasses. Technical details have not been revealed, but the results are amazing - the virtual objects fuse with the environment and look very natural and sharp. The position of the user is continuously tracked and the view of the holograms is suitably adapted.
The glasses are completely autonomous - they do not need any additional hardware or support from a smartphone and are equipped with their own operating system. The construction is based on a new processor - HPU (Holographic Processing Unit) and specially designed GPU. HoloLens also contain numerous sensors to analyze gestures and voice of the user, and provide spatial sounds allowing to "hear holograms wherever they are in the room with pinpoint precision".

Video footage from the Microsoft conference
- presentation of the idea and capabilities of HoloLens

The device can have very interesting applications. One can imagine the ease of designing three-dimensional objects with the use of gestures and words. Another promising perspective is application of this Microsoft's product for learning new things, gaming, communicating. The new Windows 10 operating system will be equipped with Windows Holographic platform providing developers with the tools needed to create a variety of virtual worlds. Every developer can "help shape the future of holographic computing".

Multiswitch system in star topology for 8 receivers.

Below we present SMATV solution implemented in a private house. The installation is responsible for the distribution of satellite signals from Hellas-Sat-2 on the 39° E orbital position, and DVB-T broadcasts received by Dipol 44/21-60 Tri Digit A2675 UHF antenna with LNA-177 B4009 preamplifier. The system was installed and configured by ALARMS-GDS in Romania.

The TERRA MR-508 R70608 multiswitch has a switch used for optional supplying (12 VDC) of an preamplifier in the terrestrial TV path. In the presented case, it has been set to the ON position in order to power the B4009 preamplifier.

An important advantage of MR-5XX multiswitches is diversification of signal levels at different groups of outputs. It allows to compensate the differences in attenuation of various lengths of cables that have to be used in the installation - we can get similar levels in all outlets. Additionally, the multiswitches compensate cable characteristics (provide higher levels for higher frequencies).

WLAN network in large facilities.

The implementation of an efficient WLAN network in such a facility (hall, covered market, assembly room etc) depends on the architecture (structure, layout, materials used) and the way of using the room (machines, racks etc). The actual situation inside a facility is always somewhere between a free space (the signal propagates nearly uniformly) and a highly dense environment with walls, production equipment, stored goods etc (the propagation of the signal is heavily distorted).

When the characteristic of a facility is similar to the first situation, the suitable solution is to mount the Ubiquiti UniFi AP Outdoor N2576 access point in the geometric center of the facility. However, the AP should not be mounted too high due to a relatively small radiation angle in the vertical plane (half-power angle of 9⁰).

If the characteristic is closer to the second case, it is necessary to take into account the layout of objects that act as an obstacle to the signal. An appropriate signal coverage can be achieved using multiple access points, for example Ubiquiti UniFi UAP-LR N2574. Their number and location are mostly determined through practical experiments. Because they form a single network, the users of mobile devices do not have to repeat the logon procedures to the individuals APs. A distinguishing feature of the solution is advanced management by the UNIFI WiFi Enterprise System. Using the software, the administrator can configure and manage wireless network composed of UniFi devices directly from a web browser. The app enables the administrator to view the status of devices and operation parameters in real time. Additionally, the software also allows for import of premises maps to display the signal range of each device.

The use of the N2574 APs in a warehouse

Optical power budget in practice.

An important task in the design of a fiber optic link is to determine the maximum range of the optical transmission path, resulting from the balance of optical power in the link. The power balance is a comparison of the power at the input of the optical link with the losses in fiber optic cables and other path components. This will help to find the optimal parameters of transmitting and receiving devices in order to ensure proper signal transmission.

The necessary condition for appropriate optical transmission via an optical link is a state in which the cumulative attenuation of passive components (fibers, splices, connectors, adapters, splitters - in the case of PON solutions) is less than the optical power budget offered by active devices. Any transmitter has a maximum transmission power (usually expressed in dBm), while each receiver the minimum optical power that is required for a specified level of performance. The difference of these two values is called the power budget.

When defining:
Bt-Br = Bp - power budget (Bt - output power of the transmitter, Br - sensitivity of the receiver)
Tl - loses in fiber(s),
Pl - losses in other passive components (splices, connectors, adapters, splitters),
G - total gain of all intermediate active devices (amplifiers),
Pm (3 dB) - a margin due to the expected reduction in laser efficiency during use

The output power of a transmitter and the sensitivity of a receiver are provided in the data sheets of these devices. For example, the Ultimode M-203G L11025 media converter has maximum output power at the level of -3 dBm, while its rated sensitivity is at least -22 dBm. This means that the power budget is 19 dB. Theoretically, without any losses other than in the fiber (0.4 dB/km), the maximum range of such a set amounts to 47 km. In practice, the 19 dB budget must cover all other losses in the link (connectors etc) plus safety margin 3 to 5 dB, so the real range is considerably lower and must be calculated taking into account all components of the real link.

More on optical power budget and other examples.

Use of two streams in HIKVISION NVRs.

After connecting IP cameras to an NVR and appropriate configuration, there can be a problem with simultaneous displaying their images via the NVR. The cause of this problem may be an improper configuration of secondary streams (sub-streams) in the NVR. In the case of Hikvision NVRs, the existence of such a problem can be verified by the network or on the NVR.

View of the configuration menu of a Hikvision NVR after logging in via a web browser

Using a browser, the user should log on to the NVR and select Configuration -> Camera Settings -> Video settings page, then select the number of the camera for verification and choose Stream Type. In the case of using the NVR menu, it is necessary to select Recording -> Parameters window and then Video Stream.
If there are two options: Main Stream (Normal) and Sub Stream, it means that the NVR properly identifies the secondary stream. Otherwise (there is only Main Stream (Normal)), the second stream is not detected and the simultaneous preview of multiple cameras is based on the main stream, which results in excessive load on the NVR. To get rid of this problem, the user should upgrade the DVR and cameras to the latest firmware and check again the recognition of the auxiliary streams. In the case of using the same type of IP cameras, all should be upgraded to the the same firmware version.

Stream bit rate and the number of clients of Sunell IP cameras.

A single data stream from any Sunell IP camera can reach 12 Mbps (in practice it is usually set to 4-5 Mbps). The total data rate from the camera can amount to 24 Mbps (for all connected clients). So, the total stream is divided among all clients, such as NVRs, PCs equipped with client software, smartphones etc. The maximum number of clients is limited by the firmware to 10. If the bit rate value for a single client is set too high, the number of the clients will be lower (it is impossible to connect new clients due to the fact that the maximum bit rate cannot be exceeded). In the case of an request from a client "out of band", the image will not be displayed. However, it will not affect in any way the video transmission to the clients that have already been connected.

In systems with multiple clients the total bandwidth from a single Sunnell IP camera can reach 24 Mbps, which should be taken into consideration at the system designing stage.

The Sunell SN-IPR54/14APDN K1685 IP camera can generate data stream up to 24 Mbps for up to 10 clients

PoE compatibility issues. The 802.3af standard defines two types of PoE implementation:

• option A - power is sent together with the data on pairs 1/2 and 3/6
• option B - power is sent on pairs 4/5 and 7/8 (unused in Fast Ethernet networks, in the case of Gigabit Ethernet the pairs are used both for data and power transmission)...
more

Connections in a switch with PoE (endspan) and in the powered device (802.3af); type A - violet, type B - yellow

Technical drawings of devices in DWG and PDF formats