Everything is Duplexing

Fiber optic wires spread apart and sending out light.

When you talk to someone on the phone typically someone makes a statement or asks a question then the other party responds. We take turns. You talk then I talk, then you talk then I talk – back and forth. That is also how many internet services and wireless communications work as well — they either take turns sending then receiving data (time division duplex or TDD) or will use separate frequencies for transmitting and receiving (frequency division duplex or FDD).

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Google’s Cell Service Play

Google Project fi logo - a green and blue lower-case "f" and yellow "i". The dot above the "i" is white and overlaps the cross of the "f".

Google likes to jump into a number of businesses that involve technology. They are heavily involved in robotics and are developing a self-driving car, conduct a number of research projects, jumped into the cloud computing ring, more recently became an ISP (Internet Service Provider) by rolling out fiber-optic internet to a number of cities across the United States, and develop the Andorid OS (operating system) that runs roughly half of the world’s cell phones. Now they are looking to take over your cell phone service as well. Google just announced Project Fi, their new mobile phone service.

Google Project fi logo - a green and blue lower-case "f" and yellow "i". The dot above the "i" is white and overlaps the cross of the "f".
Google’s Project fi Logo

The new service — currently only open to a few who request an invite — offers mobile phone service for $20 per month with data starting at $30 per month for 3 GB (gigabytes) — total of $50 per month. That is a little underwhelming given that other wireless carriers offer similarly-priced plans. It is not until you add in the discounts and features they it becomes mildly intriguing. First of all they refund you for the data you did not use. So you get refunded for the amount of data you don’t use under $3. So if you only use 1 GB in a month they will refund you $20 (data is charged at $10 per GB). There are no contracts.

One of the major drawbacks of this service is the phone selection. There is none. Currently you can only use the Motorola-produced Google Nexus 6. Sorry, no Apple iPhones here.

Where this show gets somewhat more interesting is how the service works: It uses 2 networks. Google partnered with Sprint and T-Mobile — both providers use similar technology in their networks — and the phone can simply hop onto the network that has the strongest signal. This probably increases the signal strength mildly since Sprint and T-Mobile are the smaller networks operating in the U.S. The other way to make calls is over a Wi-Fi network (including the many open networks available at restaurants, coffee shops, airports, and other offices and retail stores nationwide). However, even that is not new: T-Mobile already offers a service that allows for calls over a Wi-Fi connection.

On the plus side if you travel a lot it could be a sigh of relef. Some other mobile service providers make you jump through hoops, pay a little to a lot more for service and/or data, or simply don’t offer service in other countries. This new plan from Google works in more than 120 countries (since Sprint and T-Mobile use the same wireless technology the majority of service providers outside the U.S. use it is more compatible) though data speed is limited since only 3G connections will work. They also do not charge any more for data when traveling. It’s still the same $10 per GB. International calling rate of $0.20 per minute apply. No extra charges for texting internationally.

It’s an modest start — it’s not likely to cause a mass-exodus from other cell service providers — but will be interesting to see how their service evolves.

WiFi Traffic Management Algorithm

Visual representation of the 2.4 GHz WiFi frequency channels. Each channel is represented by a dotted half-circle representing 22 MHz of bandwidth. The half-circles representing the 3 front channels (1, 6, and 11) have solid outlines. The others overlap behind and between the front 3 channels except for channel 14 which only overlaps the edges of the 12th and 13th channels.

Phys.org reports on a new algorithm developed by a doctoral student at École polytechnique fédérale de Lausanne (EPFL) that changes frequencies and bandwidth usage based on the type of data packets being sent and received. Many routers today are set by default to use channel 6 of the 2.4 GHz frequency which causes a build-up of WiFi traffic on that channel. The problem is that many other channels overlap and use much of the same frequencies. In fact, while there are 14 total channels made available in the 2.4 GHz range, many countries ban the use of some of those frequencies. In the United States (US) channels 12 through 14 are not able to be used yet are the ones with the greatest frequency gap between channels. In effect, because the frequency bands overlap you can argue that there are really only 3 available spaces to transmit data in the 2.4 GHz WiFi band.

Visual representation of the 2.4 GHz WiFi frequency channels. Each channel is represented by a dotted half-circle representing 22 MHz of bandwidth. The half-circles representing the 3 front channels (1, 6, and 11) have solid outlines. The others overlap behind and between the front 3 channels except for channel 14 which only overlaps the edges of the 12th and 13th channels.
Visual representation of the 2.4 GHz WiFi frequency channels and how they overlap (22 MHz channels). Creative commons licensed image by Michael Gauthier on Wikimedia Commons.

The graph above shows the frequency channels for the 2.4 GHz WiFi range and how the channels overlap. Most routers are set to channel 6 by default and while they may change channels depending on availability they generally pick a channel and stick with it. In addition, many routers will use up to 8 of these channels at the same time. The problem is that this rather small range gets filled up in areas where many routers are being run and essentially cause a traffic jam of data. The other problem is that because routers will often stick with a set channel other may actually be open and unused.

The new algorithm would determine the bandwidth requirements of the data being sent and received and would select an appropriate channel and width. It essentially removed the idea of “channels” and instead divvies up the available frequency range into “lanes.” Some of the lanes are specialized similar to having a carpool or bike lane. As an example, if all you did was check your e-mail and browse a few websites you don’t need much bandwidth. The new algorithm would utilize a small amount of bandwidth – say within channels 1 and 2 – for just website browsing and email. Videos such as Vimeo and YouTube, which require much more bandwidth, may get a large chunk of channels 6 through 10 to use, and the remaining could be used for various other purposes such as websites with larger images, chat programs, and cell-phone updates. It spreads out the use over the available bandwidth and specialized certain areas for things like low-bandwidth data such as web and email, cell-phone updates, and high-bandwidth videos. The developer claims that it could increase typical router throughput by up to seven times (7X).