Tag: wifi

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Does wifi extender affect speed?

Thanks for asking this question.

In a wifi setup the internet speed depends on

  1. The main connection speed. How fast the line at your place actually is?

  2. The speed of devices. Do they support the latest standard? Are they capable of processing max throughput?

  3. How many devices are accessing the medium at once? Wifi is a shared access protocol. For small number of devices the waiting time is negligible and can be safely ignored. But as the devices increase the channel may get congested and you may feel the speed going down even though max amount of time is spent waiting to get the access of the network.

Now with these points in mind it’s easy to see that wifi can’t possibly increase the line speed. Assuming that you have the best client as well as access point hardware, wifi extender will increase the perceived speed by decongesting the channel.

Think of it as increasing the number of queues at a ticket counter. A single queue will have the longest waiting time. 2 queues will halve the waiting time and so on.

With an extender your client devices will have more communication paths to talk with your main line internet.

In the best case you want your extender to be connected via a cable to your modem. Although it can also be connected wirelessly (provided that the wireless connection does not use the same channel as used by other client devices)

On the flip side if you extended your WiFi with the same channel that other client devices are using then you simply add a bottleneck. Instead of adding 2 queues you double the length of your first queue.

Workrock Enterprise

WRE

workrockin@gmail.com

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What does the gigahertz band (like 2.4 GHz, 5 GHz) in a WiFi router mean?

It represents the frequency of the carrier wave.

In communication systems a carrier wave is the medium on which the message is transferred.

Wifi and Bluetooth have no wires (unlike Ethernet). So they emit a signal that acts as a communication channel. This channel is shared among all the connecting devices.

2.4Ghz means that the electromagnetic signal oscillates 2.4 billion times per second (giga is billion or 10^9) 5Ghz is an electromagnetic wave oscillating 5 billion times per second.

These signals are created by chips inside your router and radiated with the help of an antenna.

Before a carrier wave is generated information is encoded on it with the help of a process known as modulation.

[Modulation is the process of altering some aspect of the carrier that can be reliably detected by the receiver]

At the receiver antenna will “catch” the wave and then extract information from it. This is the reverse of modulation and is called demodulation.

Some Notes

  1. The frequency of information signal is less than the carrier frequency. The reason is simple: if the frequency is greater the carrier won’t be able to carry it. Like, for example, a bag the carries 1L of milk has slightly greater capacity than 1L.

  2. Carrier waves represent the Physical layer in the OSI model. You can think of them as invisible wires. It is in this foundation other layers are built. For internet communication the entire TCP IP stack is built on a wireless router.

  3. Any application that is running on a wireless router can then be accessed by simply connecting to the wifi. This is the foundation for the beacon technology that is promising a physical internet. A world where you can interact with physical devices by simply connecting to WiFi signals.

workrockin@gmail.com

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Why is LiFi not being used in place of wifi?

In my view there are a few reasons why LiFi is experiencing slower adoption

  1. People underestimate sheer momentum of an existing technology. All the effort that has been put by wifi into educating the customers, building a supply chain and creating an ecosystem is not easy to change. Definitely not by any technological invention/scientific discovery. It requires more than that. Wifi is used in billions of devices. It has been in operation for decades. No matter how good a replacement is, it will not make things that already work obsolete. If we look past that LiFi also has to overcome the chicken and egg problem. It needs special devices to function for transmitting as well as receiving signals. New investment to deliver the same result?

  2. Rather than disrupting an existing market the goal of a new technology should be to create something new. Something that does not yet exist. LiFi has that potential to do that but it insists on going after existing wifi markets and it runs against difficulties described point #1.

  3. Wifi works everywhere. It does not need any special conditions to be satisfied before it can be set up. LiFi on the other hand can only be successful in places where there is no interference to it’s light signals. These places are hard to discover. Sunlight, tubes, bulbs, flashlights all seem to be working against LIFI. It is true that LiFi signals are modulated (as opposed to natural light) but even then the signals get weaker as they interact with light from other sources. Reducing the distance of communication. Something similar to what happens when wifi signals are within range of electronic appliances like microwave ovens [3]. Use of optical filters can filter out data signal just as easily as it does light noise. LiFi’s carrier signal deals with much higher environmental noise than WiFi’s carrier wave.

Does this mean LiFi has no future?

On the contrary I think that LiFi has very bright future. I don’t think that it’s going to be in consumer grade communication equipment though. I believe that the real application of LiFi would be in photonic computing [1]. More specially in specialized wireless computing chips.

[Data in computers is moved along electrical paths connected by wires. In optical computing it’s not the electrons that move but the photons. Minimizing the heat loss and in reading the data width. And when you talk about microchip level movement why do you need wires at all?]

At the moment (going by expert opinion) most computer chip manufacturers are facing issues with power management.Technology that replaces electronic communication with photonic communication is going to win big time. Right now fiber optic interconnects are being investigated. [2] But LiFi maybe the alternative.

However that’s just my layman opinion. Smarter, more knowledgeable people are working on the technology and I’m sure they’d have already considered and overcome these objections. Maybe we’ll see something unexpected from them. I feel that LiFi is in capable hands. And it will surely make it’s impact.

workrockin@gmail.com

Footnotes

  1. https://en.m.wikipedia.org/wiki/Optical_computing

  2. https://www.electronicdesign.com/power/prize-winning-fiber-optic-chip-solution-knocks-out-copper-wires

  3. https://io9.gizmodo.com/why-does-your-microwave-oven-mess-with-the-wi-fi-connec-1666117933/amp

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How can li-fi be better than wifi?

Any communication technology provides a communication channel and a means to access that channel.

You may pick any wired or wireless standard and you’ll find this statement to be true. Ethernet, wifi, 4g and lifi they all work the same way.

For any technology to be better than the other in terms of speed it needs to provide a faster access to the channel as well as faster data rate on that channel.

Ethernet is faster than wifi over short range because it allows for bidirectional data transfer. Upload and download at the same time. Point to point connections mean that each participant on the network has their own dedicated channel which implies that the channel does not have to be multiplexed or shared.

On the other hand wifi has to share the channel and divide the bandwidth on uploads and downloads.

If Li-Fi wants to be better than wifi then it can

  1. Use visible light to offer separate channels for each connected user. If primary colors are exhausted secondary colors may be used. There are infinite combinations available so channels will never run out. However since visible light consists of 7 colors, using map theorem only 4 colors may be needed to provide distinct communication channels to participants. Greatly reducing the complexity of channel allocation but increasing the complexity of service area division. This will not increase the per user speed but will allow more users access to the same speed.

  2. Use more efficient modulation to offer higher speed over channel. Wifi uses QAM modulation to encode bits over the air. By using higher bandwidth of the visible light same modulation technique can be used to encode more bits of data.

The challenge faced by Li-Fi is interference from existing light sources. Outdoor connectivity is doubtful because of sunlight. Indoor would also suffer from in house lightning.

However Li-Fi can find great use in photonics. It’s an upcoming technology that looks to use photons for computing instead of electrons. Fiber optic connectors have been demonstrated to work in a few experiments.

If Li-FI can develop efficient light based communication it can be used inside chips. But that’s just the beginning. In the future colors of light may even be used for representing information rather than 1s and 0s that we use today.

Further Reading

Bit Depth — https://www.cambridgeincolour.com/tutorials/bit-depth.htm

workrockin@gmail.com

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Is wifi as reliable as Ethernet?

  1. Both wifi and Ethernet provide physical and data link layers of the communication stack. In OSI model this is called layer 1 and layer 2.

  2. Both Ethernet and wifi are shared access mediums. They both work on CSMA. Or carrier sense multiple access. That is before transmission can happen it is verified that no other node is using the carrier signal.

  3. Ethernet uses Collision Detection or CD to stop transmission as soon as packets collide . Wifi uses Collision avoidance or CA to stop collision from happening in the first place. This way single transmission medium is used by many nodes. Or it’s multiplexed.

  4. Ethernet is best for point to point and fixed multipoint connections. Since wifi communication is over the air it’s best for mobile point to multipoint as well as mobile point to point connections.

  5. In terms of speed Ethernet is faster than wifi with speeds touching 100 Gbps.

  6. Because Ethernet uses a wire for transmission it does not have to deal with interference. Wifi signals on the other hand suffer reflection,interference, diffusion etc.

Layer 2 offloading with Network switch

An Ethernet works in a full duplex mode when separate wires are used for transmission and reception. Lan cables like cat 5 or cat 6 are twisted pair. Pair refers to two set of wires. One set for transmission and the other set for reception.

As such when there is no longer a shared medium it can upload and download at the same time.

This is achieved with the help of a network switch. A separate hardware that takes care of medium access control. It provides the layer 2 functionality that was previously handled by CSMA/CD.

Since the medium is no longer shared ,due to separate wires being used, you can have full duplex high speed connection. No multiplexing is required since each device has a different communication channel.

Summary

On paper both WiFi and Ethernet are equally reliable. In the real world, nothing can beat a fixed wire connection. But that reliability is of little use if it can’t be distributed efficiently. Or require fixed devices for access.

Reference

How gigabit ethernet works

https://www.hardwaresecrets.com/how-gigabit-ethernet-works/

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Airport wifi

Today airports are more than just transit hubs. They are community and business centers. They are malls. They are the first point of contact for an international tourist.

Most airports around the world want to provide services beyond just air mobility. That is why we can see restaurants, work desks and even hotels inside the building.

At any point in time there may be thousands of guests at an airport and such a huge volume of people need to say connected at all times.

Airport wifi plays a crucial role in meeting the connectivity requirements

  1. Since wifi uses unliscensed spectrum no additional permission needs to be taken by the management. They are free to deploy as many hotspots as they want.

  2. WiFi is one of the most widely supported protocols. It is guaranteed to work across all client devices regardless of what SIM they use.

  3. As a universal connectivity platform wifi can be used to deliver not just the internet but also other services crucial to the co-ordination of ground staff and partner airlines.

Wifi at an airport needs to provide end to end connectivity. It should be a universal and consistent experience for the visitors. It should be inclusive. It must not rely on authentication methods like OTP codes over SMS that require cellular connectivity and become inaccessible to foreign tourists. The very people.who may need connectivity most.

A reliable wifi leads to a better visitor experience. People will spend more time at airports and therefore create possibilities for alternative sources of income for the operators and partners. Through advertisements, value added services like meeting spaces or maybe even entertainment and shopping.

workrockin@gmail.com

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Do we need free wifi hotspots in the cities?

I’ll try to answer this from a technical perspective not from a political one.

Wifi has traditionally been better suited for internet data. It was built from ground up to do that. It is low powered. It works on open frequency that any one can use. Its cheap. It’s well understood. Every house that has internet has wifi.

Cellular networks were traditionally designed for voice and messages. From the 3rd generation we’ve started seeing the shift towards data. Today even voice and messages are based on internet protocol.

A phone network today provides voice, message and internet. Unfortunately satisfying all there consumer needs have stressed the networks. The solution proposed is to install even more towers. A brute force method of increasing the number of access points to improve connectivity.

However there are a few points that must be considered before such a step is taken

1. Telephone networks are power intensive. Most of them are run on diesel.
2. They require a lot of space to install. Real estate is premium in big cities. And this makes setting up new towers too costly.
3. The mobile networks are segregated. Although there are roaming arrangements between the providers the quality of service varies wildly between networks even in the same region. This often results on poor quality of service for users.

Internet today has become a necessity. Not only does it help people stay connected but also provides critical services like banking, education etc. As more people are coming online we want better connectivity. At the same time we’ve also got to keep the costs low.

Wifi hotspots offer a solution.

– Wifi can be deployed by any one. It does not require any license fee for spectrum usage. Trained professionals for wifi would be easier to find. Unlike telephone network the skill set required to maintain wifi is lower. Maintainence can be done by more people.
– Wifi routers can be customized to offer over the top services like messaging, e-commerce , social networks to communities to help with the efforts of digtization. The open nature of wifi and it’s components make it more flexible. Although such things would be possible on mobile radios it would be much harder.
– Wifi can offload the congestion on mobile networks [2] making them more responsive for critical voice and messaging applications. It will ease the pressure on mobile networks and give them more breathing room.

Additionally they can help make the city more firendly to foreign tourists. Tourists won’t have to shop around for a SIM card before they can get connected. Wifi is universal so anyone can use it from any smart phone.

I welcome the effort to install city wide hotspots but I’m a bit hesitant about the free part. As it is unsustainable. Internet costs money. And the operator must find a way to monetize it.

There are other technical challenges as well. Such as roaming between hotspots and managing user identity. But none of them are major roadblocks. With tweaks these problems can be solved.

I’m excited to see how people react to the initiative.

**Footnotes**

1. When you walk around just try to count the number of telephone towers you see. Notice where they are installed. Try to guess how much the operator would have paid for the spot.

2.https://www.cisco.com/c/en/us/solutions/collateral/service-provider/visual-networking-index-vni/white-paper-c11-738429.html

Simple Wave , an inexpensive last mile connectivity platform

https://workrockin.github.io/simple-wave

workrockin@gmail.com

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What are spatial streams? What is link aggregation?

Spatial streams are separately encoded,independent data signals used for spatial multiplexing.

[Spatial multiplexing is a transmission technique in MIMO(Multi Input Multi Output)]

Spatial streams enable independent transmission and reception of data on a device. The goal is to increase the efficiency of the channel by enabling simultaneous transmission and reception.

[Spatial streams can be visualized as separate radios (and antennas) one handling transmission and the other reception for a device]

Why is it needed?

Traditionally a wifi channel can communicate with one device at a time. Sequentially. When communication is happening all the other devices have to wait in queue[1].

Moreover when a channel is being used by a device it can either transmit or receive but not do both. Spatial streams allow a single device to transmit and receive at the same time. All the other devices however are still waiting in queue.

Thus it can be said that in wireless communication spatial streams are meant for single devices. Client devices receive from and transmit to multiple antennas but still only one at a time.

The parlellism that spatial streams introduce is single device parlellism.This technology is called SU-MIMO where SU stands for single user.

[MU or multi user MIMO extends this parellism to multiple users. Enabling several devices to transmit and receive at the same time. ]

Application

In practical world, available bandwidth is rarely distributed by a single station. A network with its collection of access points is able to serve multiple users simultaneously.

Now while the devices still use channel sequentially, multiple access points mean that there are multiple queues of devices.This technique is the foundation for MU-MIMO which makes a single network capable of serving multiple users at once using streams.

Improvements in Wireless services not only mean a greater throughput to a device but also total increase in network capacity.Where we lack is in distribution of this speed equally among devices. We need to focus more on distribution than throughput.

Aggregation

Link aggregation allows us to introduce network redundancy. Multiple data lines are accessed from a single point. So that a user has a singular view of the network. For them its as if the data was available from a single provider. Although it may be that the data is infact being served by several different service providers.

The real benefit of aggregation is to provide network redundancy so that even if one provider goes down we can use others to keep the system online. Traffic may be distributed across different networks but that is only effective if all the networks are guaranteed to work at all times.

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How to choose a wifi router that can connect to 50 or more devices?

Before I can answer this it is important to understand how the data is transmitted over wifi.

Wifi uses what is known as CSMA/CA as medium access control.

CSMA stands for carrier sense multiple access. It means that a single wifi channel is shared among multiple devices but transmission occurs only when the channel is completely free. In other words only one device can use a channel at a time.

CA stands for collision avoidence. This is the part that is responsible for implemting the channel integrity that is the requirement of CSMA. It makes sure that the channel is completely free before allocating to a wifi device.

Wifi devices that remain unconnected have a cool down period during which they do nothing and after which they try again.

When you have a large number of devices that are doing nothing then almost any router can keep them happily “connected”. They’ll just sit and wait untill they want something to be transmitted.

In a more dynamic system where multiple devices are sending and receiving data the demands on the wireless router increases. Then it needs to have

  1. Good Radios.
  2. Adequate RAM.
  3. A good processor.

Absent any one of these things the router itself becomes a bottleneck.

However higer end router become dramatically more expensive. So much so that it’s way better to have multiple cheap routers providing wireless access than a single more expensive one.

Depending upon your budget I’d say buy a couple of entry level AC wifi routers and have them operate on different channels.

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What is the difference between wifi adapter with and without antenna? Which one is better?

All wifi devices have antennas. That is how they are able to transmit wifi signals. Without antenna there can be no wifi.

Portable devices like mobile phone, chip based wifi adapters, laptop and computers have PIFA (planar inverted-F antenna). They are used because:-

“PIFAs can be printed using the microstrip format, a widely used technology that allows printed RF components to be manufactured as part of the same printed circuit board used to mount other components. ” [1] [2]

“A: printed inverted-F antenna, B: meandered printed inverted-F antenna: C: patch antenna: D: Planar inverted-F antenna (PIFA) ”

In case there is no visible antenna in a Wifi device it is most probably using PIFA.

Visible antennas are of various types [3] depending upon the requirement. Most commonly, though you’ll find dipole antennas on wifi device that are omni directional. That is they can radiate signals in all directions.

An external antenna is better in the sense that it does allow you to have better transmission and reception capabilities. So it will most likely outperform a device that has no external antennas.

The newer wifi devices these days,with external antennas, come with MU-MIMO support (do check the specifications though before buying!) which allow them to introduce parallelism in data transfer. That is transmitting and receiving data from multiple devices at once.

So yes, an adapter with an external antenna is an indication of a better performing (in terms of transmission and reception quality) than a similar device with no external antenna.

[1]https://en.wikipedia.org/wiki/Inverted-F_antenna

[2]https://en.wikipedia.org/wiki/Patch_antenna

[3]https://www.accessagility.com/blog/wifi-antenna-types

Simple Wave, an inexpensive last mile communication technology.

https://www.reddit.com/user/workrockin/comments/cj9p7b/simple_wave_an_inexpensive_last_mile/

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