Coded Caching

Cadami offers a software implementation of Coded Caching for commercial applications. Coded Caching uses a combination of caches at the receivers and coded broadcast transmission. The following example illustrates an application.

A video-on-demand service offers a library containing a yellow, an orange, and a blue video. The three users request videos represented by the colors of their screens. Each user has one video in his cache (colored file in the top
row of their user’s cloud) and is missing the other two videos
(gray files in the top row of the user’s cloud). Conventional unicast streaming without caches at the users has to transmit three videos. With caches at the users, the amount of data to transmit is reduced by the cache hit rate. In our example, user 3 has a cache hit for the orange video. Instead of three, only two videos are transmitted. For the remaining two users the cache is missed and thus provides no benefit.

We can further exploit the caches at the users by coding and broadcast transmission. Upon receiving the requests for the yellow and blue video, the server combines both and serves them with one coded broadcast transmission. The server combines the yellow video and the blue video by applying a bit-wise XOR operation to generate a green file X = A ⊕ B. File X has the same size as A and B and not the size of A plus the size of B. The server broadcasts the green file X to both users in a single transmission. The yellow user feeds both its received file X and the blue video from its cache into the decoder. The decoder returns the requested yellow file A by computing B ⊕ X = B ⊕ (A ⊕ B) = A. Similarly, the blue user computes A ⊕ X = A ⊕ (A ⊕ B) = B from its received file X and the yellow video A from its cache. By Coded Caching both users to retrieve their desired content from a single broadcast stream. For this example, we require the transmission of one file, while conventional caching requires two files, and streaming without caches three files.

Generalization

The example illustrates how the combination of caching, broadcast transmission, and coding can save a significant amount of resources for video-on-demand delivery. Coded Caching generalizes these gains to general libraries, user populations, and arbitrary user requests. The video files in the library are chopped up into sufficiently small pieces. Each user stores its unique systematic selection of pieces of each file. The design of the cache is vital for achieving gains in resource reduction. For example, consider a system with five files (A yellow, B blue, C orange, D gray, E red) and four users (left-to-right: S, T, U, V ) where each user stores 50% of each file, as shown in the figure.

As soon as every user requests a file as indicated by the colors of the device screens, that is S → A, T → B, U → C, V → D, only the missing parts of the requested files need to be transmitted. Additionally, the server can code together 3 missing parts in each transmission. That is, it transmits

X1 = A2 ⊕ C3 ⊕ D6
X2 = A4 ⊕ B6 ⊕ C1
X3 = A5 ⊕ B3 ⊕ D1
X4 = B2 ⊕ C5 ⊕ D4

using four broadcast transmissions. For example, user S decodes its missing file part A2 from the received X1 and C1 and D3 from the cache as A2 = X1 ⊕ C3 ⊕ D6. With Coded Caching, we require the transmission of four pieces, while conventional caching requires 12 pieces, and streaming without caches 24 pieces. One can verify, that any user request can be satisfied by transmitting four pieces.

In case you want to learn more about the theory of Coded Caching, we recommend “Fundamental Limits of Caching” by Mohammad Ali Maddah-Ali and Urs Niesen. If you would like an analysis if your application can benefit from Coded Caching, contact us at sales@cadami.net or use the form:

AIX – Media Coverage

We had a great time at AIX 2019. We met old friends and met new ones, and we introduced our technology to some of the journalists there.

click here will take you to the articles so you can see what the experts have been saying about our technology

FIRST VIABLE CABIN WIFI NETWORK LAUNCHED BY CADAMI

Advanced network technology solutions remove barriers to wireless distribution of high-quality IFE content

Aircraft Interiors Expo, Hamburg, 2 April 2019 – Cadami is launching its WiFi cabin technology at Aircraft Interiors. There are significant benefits to using a wireless network. However, current WiFi technology has limited utility because the aircraft cabin is a crowded environment, making it very hard to provide the right bandwidth to transmit high quality content. 

Thomas Kuehn, managing director of Cadami, said, “Wireless transmission of high-quality IFE content has always been just out of reach. Our network technology solutions make it viable.”

Cadami’s network technology solutions give airlines and their IFEC partners all the benefits of using a WiFi network. It is cheaper to install and maintain than a cabled network. Because it uses less cabling, it saves weight. And the network technology solutions make the transmission of a huge library of high-quality content, to both seat back screens and passenger devices, efficient and reliable.

Thomas Kuehn continued, “Our technology is already flying on nearly 200 aircraft, operating over cabled networks and giving passengers around the world access to thousands of films. The next stage is to start WiFi. Using Efficient Coded Caching, we can both overcome the current WiFi limitations while providing the same libraries people are used to with Netflix and Amazon Prime.”

Efficient Coded Caching is a unique, patented combination of the latest coded caching with advanced transmission techniques to make highly efficient use of the network infrastructure and seat-back screens. The result is to effectively increase bandwidth by a factor of between two and five. It means an airline can viably use a WiFi network to make a large library of HD and 4K video content available to every passenger on the biggest aircraft, without jeopardising quality. 

Thomas Kuehn concluded, “We are constantly pushing the boundaries of what technology can do, to provide airlines with more efficient solutions and their passengers with an even better experience.”

Cadami is showing its technology at the Aircraft Interiors Expo at booth 4A04 in the IFEC Zone.

Aircraft Interiors – wireless IFE

Even though there are significant benefits to using a wireless network, the wireless transmission of high-quality IFE content has always been just out of reach. The Cadami network technology solutions make it viable.

We’re going to Aircraft Interiors Expo in Hamburg, from 2-5 April, where we’ll be launching our new WiFi cabin technology.

It is cheaper to install and maintain than a cabled network. Because it uses less cabling, it saves weight. And our Efficient Coded Caching technology solutions make the transmission of a huge library of high-quality content, to both seat back screens and passenger devices, efficient and reliable.

Come and see for yourself on booth 4A04 in the IFEC Zone. We look forward to seeing you there.


CADAMI SUPPORTS IEEE 5G SUMMIT

MUNICH, 25 September 2018– Cadami used the IEEE 5G Summit in Dresden in September both to highlight its highly efficient video distribution technology and secure new cooperative deals with both industrial and academic partners.

At IEEE, Cadami was showing the latest platform, developed with Steinwurf ApS. This new generation platform is easier for network owners to deploy. It also provides improved Video on Demand and video streaming quality. 

Cadami, one of the event’s Silver Patrons, demonstrated its advanced coded caching and media transmission technology. It optimises the use of the network, reducing bandwidth usage by 50 to 80 percent. These efficiency savings enable the transmission of a significantly larger library of video content, as well as increased internet capacity.

Michael Heindlmaier of Cadami said, “The IEEE 5G Summit was a very useful day for us. We started out as academics bringing an industrial idea to market, so having the combination of both worlds under one roof is very important, both for us and for the development of 5G technologies. Apart from anything else, it balances what is technologically doable with what is commercially viable.

“The result is that we were able to strengthen our relationships with the world of academia, ensuring we are fully up-to-date with all the latest developments. We also closed agreements to co-operate with other companies on the development of new products and solutions.”

Steinwurf, a Danish software company, specialises in network coding, complimenting Cadami’s technology.


This screenshot shows four screens, all running over the same network. However, the top two are running Cadami software. Click on the image to see the video.