Why is the bitrate of infrared smaller than the bitrate of WiFi?

Question

Infrared has a frequency of 300 GHz – 430 THz, while WiFi has a frequency of 2.4 GHz or 5 GHz.

As the frequency of infrared is greater than the frequency of WiFi, the transfer rate (bitrate) of IR should be greater than WiFi.

In reality, IR transmission is in Kbps, while WiFi for WLAN is about 100 Mbps.

We know that a greater frequency wave can carry more bit data, but it is difficult to handle interference such as thick wall obstacles, therefore lower coverage range, and vice versa for lower frequency.

That statement only applies between mobile cellular band LTE (2.3 GHz) and WiFi (2.4 GHz) where WiFi bitrate is higher than LTE, but not between IR and WiFi.

Edit: I said Kbps after I read random article about IR Remote.

Answer 1

The premise is false. Infrared communication can be much higher bandwidth than wifi; just look at modern fiber-optic communications.

It looks like you're really asking why wifi is faster than the protocol used by infrared remote controls, though. The reason for that is quite simple: the remote control doesn't need to transmit quickly. It only needs to send a tiny amount of data intermittently. Designing a high-bandwidth communications protocol simply to let your TV know that you hit the power button is completely unnecessary. Remote controls are also designed to last a long time on small batteries, so simpler protocols are better--complicated modulation schemes require more electronics and more power consumption. And on top of that, the system used by remote controls was designed in the 1970s! Not exactly what you'd call modern communications systems.

Answer 2

Even free-space IR connections can be quicker than you think - or at least they were 20 years ago.

Consider some of the IrDA standards for line-of-sight IR. They can get into the hundreds of Mbit or even Gbit range.

When IrDA ports were first common, they had rates comparable to the high end of RS232, which was good for the time (late 90s). By the time I last made good use of IrDA, overlapping with early bluetooth, IR connections were often quicker in prcatice - but you needed a continuous line of sight between devices, for a beam you couldn't see, which was inconvenient for large file transfers (I used to sync MP3s onto a PDA over IR from my desktop).

Answer 3

You are comparing apples to oranges, when considering the bitrate of the communications channel you not only need to consider the frequency of the medium that's traveling in but also the bandwidth (the amount of spectrum), the bitrate and the modulation scheme.

So the properly make a comparison between Wi-Fi and infrared you'd also need to consider the fiber optic line or laser system.

Answer 4

The bitrate of an IR optically based communication system functionally similar to a WiFi connection is limited by multipath interference - the light propagating directly to the receiver takes less time than light scattering off a wall or ceiling. If the bit rate is on the same order of time as the difference in time of propagation there is interference and this limits the bit rate.

Answer 5

WiFi uses extensive negotiation and handshaking processes to maximize channel efficiency. This makes it possible to achieve very high data rates, but at the expense of increasing the time required to establish a connection.

Further, WiFi expects that while a channel is being used for transmission, the signal received from the transmitter on that channel will be stronger than any signals from any other sources that might simultaneously be received on that channel.

Infrared remotes need to be able to send data almost instantly, even when incandescent within the sensor's field of view are brighter than the remote control.

Typical remote control designs prioritize cost, robustness, and "instant" operation, over communications bandwidth. RF remote controls for things like garage door openers often have designs that are much closer to those of infrared remote controllers than to those of WiFi systems, and have communications rates which are likewise closer to those of infrared remotes than to WiFi. On the flip side, infrared communications can be very fast when using bidirectional communications links that allow receivers to continuously recalibrate themselves to recognize more complex forms of modulation.

Answer 6

Because WiFi can go through walls.

Yes, WiFi does get blocked, or significantly degraded, by some types of walls and other objects. But infrared can be blocked by almost any solid object except clear glass or clear plastic. The usefulness of WiFi isn't just the raw speed, it is that it can be easily used in multiple rooms and without a direct (or near direct, such as a mirror) line of transmission. As others have pointed out, where infrared can be used at high speed and long distances is through optical fiber. But if you could connect some "thing" between your computer and router, you could use optical fiber or perhaps copper wires (like ethernet...) and wouldn't need WiFi.

As a result, infrared through the air for consumer use is generally limited to remote controls and other low-bandwidth devices, with WiFi or copper wires or fiber used for higher speed where needed.