Seven Castles

Sino-Telecom- -

                                      

Part of the English version required by a foreign agency.

 

3.3 System design
The satellite-based voice communication network by Sino-Telecom uses SCPC DAMA system, operating in C band. It consists of a host station of satellite network management system and a number of remote earth stations. The satellite network system sets up SCPC satellite links on demand and provide the customer voice communications.
The while network consists of host station, 30-channel station, 8-channel station, 2-channel station and transportable station. The specific configuration of antennas and power amplifiers will be examined in 6.2.
Outdoor units and indoor units are connected with IFL cables of L band, transmitting signals and messages on monitoring and controlling. In one rack of RF channel unit, an RF indoor unit board and three voice and data channel unit boards are inserted. With cascading of multiple racks, and configuration of the corresponding number of voice and data channel unit boards, the requirements for voice or data channels can be met.
That allows users to perform real-time monitor and control over all the equipment, through GUI on the management and maintenance terminals of the network management system. All the channel transmission parameters can be randomly defined and modified at the host station. Meanwhile, users can run and set software on the site of a remote station, and monitor and control all the equipment of the current station and set parameters via PC serial ports.
The network management system of the host station can automatically generate communication records, which include information such as caller, the called, and duration of communication. Off-line billing system is available to customers. Remote interface functions can be used as well, so that customers can get access to communication records in a real-time manner and put them into use of online real-time billing system.
Voice/data channel unit board in the existing system can support compressed encoded voice via satellite at the rates of 8kbps or 16kbps. Connection with PSTN is through Chinese One signaling system or SS7, providing long-distance trunk gateway for the whole satellite network. It is also possible to use E&M signaling to connect the existing PBX or directly connect a telephone set.
4. Connection with PSTN
This satellite network system supports various telephone signaling systems. The system supports the following signaling systems via software settings: POTS, PLAR, FXS/FXO, Cat.1-5 E&M, DTMF subscriber lines and trunks, pulse dial-up, R1, R2, ITU#5, SS7 and Chinese One signaling, etc.
Voice/data channel unit boards are directly inserted to the channel unit rack in the existing system, supporting compressed encoded voice via satellite at the rates of 8kb/s or 16 kb/s. Connection with PSTN is through PDH, using Chinese One signaling system or SS7, providing long-distance trunk gateway for the whole satellite network. It is also possible to use E&M signaling to connect the existing PBX or directly connect a telephone set. If CCMT is purchased for the network management system, the multi-party teleconferences with one chair can be held by all the above mentioned VES.
The followings are sketches showing how the whole system, and small stations of 2-channel, 8-channel,30-channel connect telephone terminals, and PBX or PSTN:
6. Environment requirements for use of satellite earth stations
The operating environment for satellite communication earth stations should be assured with its main technical requirements as follows:
6.1 Electromagnetic interference
Permitted value of interference: the interference signal peak level at the input of earth station receiver should be 30dB lower than the normal receive signal level.
Currently, there are four methods to eliminate or alleviate interference for a few areas with serious interference or complicated electromagnetic interference:
(1) Site selection
The position of antenna for the earth station should be far away or isolated from TV station and microwave towers, due to electromagnetic interference in urban area caused by microwave communications and radio and TV broadcasting.
(2) Frequency selection
Operating frequencies that are free of interference will be selected to eliminate interference for a number of small stations. However, frequency change as required will sometimes be impossible, due to restrictions by systems.
(3) Shielding network deployment
Deployment of shielding network around antenna can attenuate interference signals (good shielding network can attenuate interference signals up to 15dB).
6.2 Antenna position and base
The position of antenna should meet the requirements of no blockade in the range with an azimuth of 120-240 degrees and an angle of elevation over 5 degrees. For those sites that do not meet the requirements, the minimum requirements of antenna pipe type spot protection angle in the direction to the satellite should be met, as shown in the Figure 1. The position of antenna should be far away from TV towers and microwave towers or off the sight of TV towers and microwave towers, to prevent from electromagnetic interference.
Antenna base should be constructed as strictly defined by the drawings to ensure the security and precision of direction-pointing. To avoid possible equipment damage caused by electric potential difference between indoor unit and outdoor unit of VSAT station, antenna base is not connected with the steel bars of buildings, as building structure and thunder-proof design allows, for those antennas on the top of the buildings. Antenna base of reinforce concrete should be constructed one month prior to antenna installation. During the construction, the direction of antenna base should be in the due south, to ensure the rotating mechanism of the antenna can be rotated in the range of +90 degrees, meeting the requirements of adjustment for the satellite. The distance of cables between antenna and IDU in satellite equipment room should be no longer than 100 meters.
6.3 Outdoor environment requirements
Outdoor environment requirements for VSAT stations mainly mean antenna feeders and RF terminal systems. See the equipment performance criteria for the environment requirements of RF terminal systems. The following environment conditions should meet the requirements for use.
Temperature: -40-+50oC
Humidity: 0%-100%
Salt fog: 810/Method 509.2
Outdoor units are usually installed on the pole of antenna. The lower part of the equipment should be more than 50 cm distant from the ground. When the pole is shorter, fixed stand should be made for the equipment. And the installation should be close to the antenna. In places with higher temperature outdoors, sunshade measures should be taken for the equipment.  
6.4 Lightening arresting device for systems
Satellite equipment is costly. Antenna of satellite earth station and buildings should be under protection of lightening rods. Equipment should be installed with the protection of lightening rod. Lightening arresting device should have good independent grounding. Power supplies should be protected with lightening arresting device. A complete lightning arresting device is shown in the following figure.
6.6 Requirements for satellite equipment rooms
Equipment rooms mainly mean rooms for communication equipment, operation, generators, UPS, and distributing devices. Requirements for rooms and restrooms for people on duty, and places for living and activities, etc. will be defined by customers as they like. In principle, they should be separated from the equipment rooms with isolating walls.
(1) Requirements of building
 Satellite communication equipment can share the same equipment room with switches and other computers. However, adequate room should be left for equipment and their installation. There should be at least a room of 60cm in front of and at the back of the place where equipment rack is, for the sake of operation. The height of equipment rooms should be over 3 meters. Good ventilation is needed for equipment cabinets.
 The ground load of equipment room should be over 1,000 kg/square meter.
 Cables can go over or under the cabinets. Anyhow, it is better to go under the cabinets. There should be slots for the cables no matter they go over or under the cabinets.
 Movable floors that prevent from electrostatic induction are recommended for the equipment rooms, 10cm higher from the ground.
 Cable paths should be prepared between equipment rooms and antennas. Bore holes with a diameter of 5-10 cm for the walls and roofs that cables will go through. For exterior walls and roofs, anti-rain measures should be taken.
 It is recommended that the interior surface of equipment rooms are with concrete, lime, and whitewashed, painted by light colors. If possible, wallpapers can be used.
 Gas with corrosive effects are not allowed to enter equipment rooms, for fear of equipment damage.
 Good and effective fire-proof measures and units should be available in equipment rooms.    
 Double windows are required for equipment rooms. There should be a filtering passageway at the entrance of main equipment room.
(2) Environment requirements in equipment rooms
 Operating temperature for equipment in equipment rooms ranges 10-40oC. Air-conditioning equipment with sufficient refrigeration capabilities should be equipped according to the power consumption of the equipment, maintaining the room temperature as 25oC. No coagulation of water. Air-conditioners are usually available in equipment rooms. Air-conditioners should be with medium capacity, ventilation and refrigeration ratio is 1:2 or 2:3. To keep the equipment room clean, filters with rough effects or medium effects are usually equipped. The relative humidity for operation of the equipment in equipment rooms is 0%-95%.
 Dust-proof criterion for equipment rooms is under 10g/square meter, every year.
 Anti-shock criterion for equipment rooms is under 0.035 mm.
 Lighting in equipment rooms should avoid direct lights from the sun. 150LX for both horizontal and vertical planes.
 In any case, equipment rooms should be water-proof and moisture-proof, for fear of equipment damage.
7. Power supplies for systems
Power supplies are 220V, 47-63Hz, two phases and three wires, e.g. live wire, zero wire and ground wire. Required voltage is 220+10%V. Power lines and sockets should be with enough power capacity. Zero should be at left, while fire right.
Continuity of power supply should be assured in use of equipment. UPS should be used, and 50% of its power capacity should larger than the total load power of the equipment.
The resistance between zero and ground should be less than 2 ohm, voltage less than 2V. User's equipment and satellite data receiver are required to use the same zero and ground wires. The power supply offered should be clean power supply, not sharing the same power supply with large electric systems, air-conditioners, welding systems, etc. Alternating zero wire should be isolated from the steel frame of the building. Ground wire system should not use steel doors and windows, or steel bar and water pipes of buildings. When power supplies are not good, clean power supplies should be used for isolation.
To ensure smooth communications in the case with abnormal power supply or power failure, i.e. set-up of satellite earth stations in areas without power supplies, other alternatives of power supplies are required. Single-phase gas generators are the first choice. If possible, solar energy can be used. Main requirements for single-phase gas generators are:
Small stations       Host stations
Power
Specified voltage
Specified frequency
When using stand-by power supplies, minimize the use of supplementary equipment to reduce power consumption.
Power supply requirements for solar energy (only limited to small stations):
Operating voltage: 48V
Load power consumption: 500Watt/1000Watt
Duration of load working: 24 hours
Average duration of lighting: 4.8 hours
Transformation efficiency of storage batteries:85%
Continual overcast and rain: 2 days
8.1 Requirements for transponder bandwidth
The network is mainly for transmission of voice, adopting voice compression technique currently available, with bandwidth of one voice channel as 8kbps. Assume the traffic for each channel is 0.35Erl. If the project is conducted in three phases. The bandwidth for the fast initiation phase is 0.349Mhz, the latter part of the first phase needs bandwidth of 0.920MHz. The second phase needs bandwidth of 2.509MHz, while the third phase needs 3.546MHz. The total bandwidth required is 7.342MHz.
The details from calculation:
A1. Fast initiation phase (the first part of the first phase)
a. One 30-channel voice hub station;
b. 3 30-channel transportable stations (8 channels are opened);
c. One 8-channel fixed station;  
d. One 2-channel fixed station;
e. One 8-channel international gateway;
Total voice channels=30+8X3+8X1+2X1+8=72 channels
Bandwidth for data=8kbpsX72X0.35=201.6kbps
Satellite resources taken=201.6kbpsX1.73=0.349MHz

A.2 The latter part of the first phase
a. Additional 60 voice channels for the hub station;
b. One 8-channel fixed station;
c. One 2-channel fixed station;
d. 3 30-channel transportable stations, 22 voice channels more for each station;
e. 4 30-chanel fixed stations;
Total voice channels=60+8X1+8X1+2X1+22X3+30X4=256 channels
Bandwidth for data=8kbpsX150X0.35=420kbps
Satellite resources taken=(420kbps+16kbpsX7)X1.73=0.92MHz 

- 作者： zhangliping 访问统计：　2005年02月8日, 星期二 18:14 加入博采