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In case of serial communications, the gross bit rate is related to the bit transmission time as: R b = 1 T b , {\displaystyle R_{\text{b}}={1 \over T_{\text{b}}},} The gross bit rate is related to the symbol rate or modulation rate, which is expressed in bauds or symbols per second.
- Overview
- Sending streams of 1s and 0s
- Bit rate
- Bandwidth
- Latency
- Internet speed
All of the computing devices on the Internet are communicating in binary. Whether they are connected via wired or wireless, they are sending electromagnetic signals that represent streams of 1s and 0s.
Let's explore how those bits are sent and how quickly they can be sent.
When computers need to internally represent the number 5 (101 in binary), they can use three wires to represent the three bits: one wire on, one wire off, one wire on.
If a computer wants to send the number 5 to another computer, they can't use as many wires as they want. In fact, they may only have a single wire to send information over. Instead, they can send the number 5 over three time periods: first sending an on pulse (and waiting), then sending nothing (and waiting), then sending an on pulse.
As long as the two computers agree on the time period, then they can transfer information to each other, turning binary data into signals and turning the signals back to binary data.
In an electrical connection (such as Ethernet), the signal would be a voltage or current. In an optical connection (such as a fiber-optic cable), the signal would be the intensity of light.
Network connections can send bits very fast. We measure that speed using the bit rate, the number of bits of data that are sent each second.
The earliest Internet connections were just 75 bps (bits per second). These days, connections are more often measured in Mbps (megabits per second).
A megabit is huge: 1 million bits! A 10 Mbps connection transfers data at 10 million bits per second.
That's one bit every 100 nanoseconds (0.0000001 seconds).
We use the term bandwidth to describe the maximum bit rate of a system. If a network connection has a bandwidth of 100 Mbps, that means it can't transfer more than 100 megabits per second. Fortunately, that's still a lot!
Ever heard the term "broadband Internet"? That refers to a connection with a minimum bandwidth of 256 Kbps. That's enough bandwidth for basic Internet use like checking emails and reading websites, but not quite enough for watching online videos. As of 2016, only 40% of people in developing nations have access to even broadband Internet.
your understanding
When I was a kid, our Internet connection had a bandwidth of 56 Kbps (kilobits per second). How many bits per second could that transfer?
Choose 1 answer:
Choose 1 answer:
Another way to measure the speed of a computer network is latency. You might guess what that means from the word itself: latency measures how late the bits arrive. To put it in more formal terms: latency is the time between the sending of a data message and the receiving of that message, measured in milliseconds.
We typically measure the "round-trip" latency of a request. Let's walk through a real example to see what that means.
My computer sends a message to the Google server. 30 milliseconds later, Google receives the message. 40 milliseconds later, my computer gets an acknowledgement from Google that it received the message.
That's a total round-trip latency of 70 ms. The latency depends on a number of physical factors: the type of connection from my computer to Google, the distance from my computer to the Google servers, and the congestion in the network (which may mean my request has to wait in line).
Speed is a combination of bandwidth and latency. Computers split up messages into packets, and they can't send another message until the first packet is received. Even if a computer is on a connection with high bandwidth, its speed of sending and receiving messages will still be limited by the latency of the connection.
You can measure the current speed of a network using an Internet speed test: a website that downloads and uploads data while tracking how quickly the data is transferred.
Here are the results from an Internet speed test from my home laptop:
The latency (also called the ping rate) was just 18 ms. That's fast enough for most multi-player online games.
The download bit rate is 39 Mbps and the upload bit rate is 5.85 Mbps, significantly less. Actually, that's expected. Internet providers often support a much faster download speed than upload speed, because Internet users spend much more time downloading data (reading articles, watching movies) than uploading data (writing blog posts, submitting forms).
🔍 What's the speed of your Internet connection? What bandwidth does your Internet provider promise? What type of physical connection are you using? This is a great opportunity to get a deeper understanding of the physical infrastructure you use every day.
The packet transmission time in seconds can be obtained from the packet size in bit and the bit rate in bit/s as: Packet transmission time = Packet size / Bit rate. Example: Assuming 100 Mbit/s Ethernet, and the maximum packet size of 1526 bytes, results in Maximum packet transmission time = 1526×8 bit / (100 × 10 6 bit/s) ≈ 122 μs
Gross bit rate - also called the digital signalling rate, this is the total number of bits transmitted per second including overhead. Net bit rate - the total number of bits transmitted per second excluding overhead.
In telecommunications, data signaling rate (DSR), also known as gross bit rate, is the aggregate rate at which data passes a point in the transmission path of a data transmission system.
Data RateStandard1.5 Mbit/s1.544 Mbit/s12 Mbit/s155 Mbit/sIn case of serial communications, the gross bit rate is related to the bit transmission time as: The gross bit rate is related to the symbol rate or modulation rate, which is expressed in bauds or symbols per second.
The gross bit rate is related to the symbol rate or modulation rate, which is expressed in bauds or symbols per second.
