At this stage, there are three mature LAN technologies: Ethernet, Token Ring and Fiber Distributed Data Interface (FDDI), and Ethernet technology has gradually become the mainstream of LAN technology.
The English full name of CSMA/CD is Carrier Sense Multiple Access with Collision Detetion, and Chinese is the carrier sense multiple access technology with collision detection.
Detailed explanation: Ethernet is a kind of local area network technology with shared medium. Multiple stations are connected to a shared medium, and only one station can send data at the same time. This kind of shared medium communication method must have a conflict problem. How to detect whether the link is idle and whether the station can send data is a problem that must be solved by the shared link.
Connecting multiple terminals on the same link is multiple access. Therefore, CSMA/CD provides a method for multiple access control protocols for multiple access links and multiple sites to send data at the same time to avoid conflicts.
The specific working method of CSMA/CD:
(1) Monitor the channel before sending the data frame. If the channel is busy, continue to monitor until the channel
idle. Send immediately when the channel is idle.
(2) Detect conflicts while sending. If no conflict is detected after sending, then send
success.
(3) If a conflict is detected, stop sending and send a 32-bit interference bit to strengthen the conflict
signal. After using the binary exponential backoff algorithm to randomly delay for a period of time, go to (1).
3. Conflict domain and broadcast domain
Conflict domain: In the traditional Ethernet with thick coaxial cable as the transmission medium, multiple nodes on the same medium share the bandwidth of the link and compete for the right to use the link, so there will be conflicts, CSMA/CD In the mechanism, when a conflict occurs, the network will fall back, and no data will be transmitted on the link during this fallback period. And this situation is inevitable. When there are more nodes on the same medium, the probability of collision will be greater. This collection of all nodes connected on the same wire is a collision domain.
The host connected by the coaxial cable and the HUB belongs to a collision domain. Their common feature is that all nodes must share bandwidth, conflicts will occur, and messages sent by one node (whether unicast, multicast, or broadcast) can be received by other nodes.
Therefore, all nodes connected by Hub or Repeater can be considered to be in the same collision domain. The second-tier devices (bridges, switches) and the third-tier devices (routers) can be divided into conflict domains.
Broadcast domain:
We know that broadcasting will take up bandwidth and reduce the processing efficiency of nodes, so broadcasting must be restricted. This kind of collection of nodes that can be received by other nodes when a site sends a broadcast message is a broadcast domain.
All ports of a traditional Layer 2 switch belong to a broadcast domain.
The traditional bridge (Bridge) can forward unicast messages according to the MAC table. Broadcast messages are forwarded to all ports. Therefore, the nodes connected to all ports of the bridge belong to a broadcast domain, but each port belongs to a separate Conflict domain.
4. Ethernet frame format
Currently the most widely used is Ethernet II encapsulation. So we show its Ethernet frame format.
Preamble: Synchronization character (7B) and Start of Frame Delimiter (1B)
When each Ethernet frame is sent, it starts with an 8-byte preamble. The Preamble is a 7-byte data with alternating 1 and 0 (1 0 1 0 1 0…….). The function of this part is to notify the reception. When a data frame arrives, keep it synchronized with the input clock. The 56-bit mode allows the station to discard some bits at the beginning of the frame.
Destination Address DA (Destination Address): 6 bytes, the MAC address of the destination node.
Source Address SA (Source Address): 6 bytes, the MAC address of the source node.
Type/Length field (Type/Length): Specify the upper layer protocol (when >1500) or the length of the payload (when ≤1500).
Payload: User data. Add padding byte (any byte) to 46 bytes when it is less than 46 bytes.
Frame Check Sequence: CRC-32 check the destination address, source address, type/length and payload (plus padding) fields
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How far(long) the transmitter cover?
The transmission range depends on many factors. The true distance is based on the antenna installing height , antenna gain, using environment like building and other obstructions , sensitivity of the receiver, antenna of the receiver . Installing antenna more high and using in the countryside , the distance will much more far.
EXAMPLE 5W FM Transmitter use in the city and hometown:
I have a USA customer use 5W fm transmitter with GP antenna in his hometown ,and he test it with a car, it cover 10km(6.21mile).
I test the 5W fm transmitter with GP antenna in my hometown ,it cover about 2km(1.24mile).
I test the 5W fm transmitter with GP antenna in Guangzhou city ,it cover about only 300meter(984ft).
Below are the approximate range of different power FM Transmitters. ( The range is diameter )
0.1W ~ 5W FM Transmitter ：100M ~1KM
5W ~15W FM Ttransmitter : 1KM ~ 3KM
15W ~ 80W FM Transmitter : 3KM ~10KM
80W ~500W FM Transmitter : 10KM ~30KM
500W ~1000W FM Transmitter : 30KM ~ 50KM
1KW ~ 2KW FM Transmitter : 50KM ~100KM
2KW ~5KW FM Transmitter : 100KM ~150KM
5KW ~10KW FM Transmitter : 150KM ~200KM
How to contact us for the transmitter?
Call me +8618078869184 OR
Email me [email protected]
1.How far you want to cover in diameter ?
2.How tall of you tower ?
3.Where are you from ?
And we will give you more professional advice.
About Us
FMUSER.ORG is a system integration company focusing on RF wireless transmission / studio video audio equipment / streaming and data processing .We are providing everything from advice and consultancy through rack integration to installation, commissioning and training.
We offer FM Transmitter, Analog TV Transmitter, Digital TV transmitter, VHF UHF Transmitter, Antennas, Coaxial Cable Connectors, STL, On Air Processing, Broadcast Products for the Studio, RF Signal Monitoring, RDS Encoders, Audio Processors and Remote Site Control Units, IPTV Products, Video / Audio Encoder / Decoder, designed to meet the needs of both large international broadcast networks and small private stations alike.
Our solution has FM Radio Station / Analog TV Station / Digital TV Station / Audio Video Studio Equipment / Studio Transmitter Link / Transmitter Telemetry System / Hotel TV System / IPTV Live Broadcasting / Streaming Live Broadcast / Video Conference / CATV Broadcasting system.
We are using advanced technology products for all the systems, because we know the high reliability and high performance are so important for the system and solution . At the same time we also have to make sure our products system with a very reasonable price.
We have customers of public and commercial broadcasters, telecom operators and regulation authorities , and we also offer solution and products to many hundreds of smaller, local and community broadcasters .
FMUSER.ORG has been exporting more than 15 years and have clients all over the world. With 13 years experience in this field ,we have a professional team to solve customer's all kinds of problems. We dedicated in supplying the extremely reasonable pricing of professional products & services. Contact email : [email protected]
Our Factory
We have modernization of the factory . You are welcome to visit our factory when you come to China.
At present , there are already 1095 customers around the world visited our Guangzhou Tianhe office . If you come to China , you are welcome to visit us .
At Fair
This is our participation in 2012 Global Sources Hong Kong Electronics Fair . Customers from all over the world finally have a chance to get together.
Where is Fmuser ?
You can search this numbers " 23.127460034623816,113.33224654197693 " in google map , then you can find our fmuser office .
FMUSER Guangzhou office is in Tianhe District which is the center of the Canton . Very near to the Canton Fair , guangzhou railway station, xiaobei road and dashatou , only need 10 minutes if take TAXI . Welcome friends around the world to visit and negotiate .
Contact: Sky Blue
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E-mail: [email protected]
QQ: 727926717
Skype: sky198710021
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English: We accept all payments , such as PayPal, Credit Card, Western Union, Alipay, Money Bookers, T/T, LC, DP, DA, OA, Payoneer, If you have any question , please contact me [email protected] or WhatsApp +8618078869184
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Pay by Western Union to me :
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First BANK INFORMATION (COMPANY ACCOUNT):
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For Warranty .
Contact US--->>Return the item to us--->>Receive and send another replace .
Name: Liu xiaoxia
Address: 305Fang HuiLanGe HuangPuDaDaoXi 273Hao TianHeQu Guangzhou China.
ZIP:510620
Phone: +8618078869184
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