Can a New Approach to Wireless Beat Shannon’s Law?

Steve Wildstrom / July 28th, 2011

For the past 60 years, electrical engineers have understood the hard limits that physics imposes on the data capacity of any channel. The law, formulated by Claude Shannon of Bell Telephone Labs, says that the data capacity, in bits per second, is a function of the bandwidth, the signal strength, and the noise in the channel.

Shannon's law formula

Shannon's Law (Wikipedia)

No one has yet found a way to break Shannon’s law, but Rearden Companies, the brainchild of Steve Perlman, who is behind the bandwidth-bending OnLive online games service, claims to have found a way to cheat significantly. A paper by Perlman and Rearden Principal Scientist Antonio Forenza, describes a technology called Distributed-Input-Distributed-Output (DIDO).

Normally, when a wireless channel, such as a connection to a Wi-Fi access point, is shared by two or more users, each user can only get a fraction of the channel’s capacity. But DIDO allows each user to communicate, in theory, up to the full Shannon limit of the channel.

The explanation for just how this works is complicated, but the technology uses array of antennas to create a non-interfering path between an access point and a user. Shannon’s law applies not to a particular piece of bandwidth but to each channel. Traditionally, we have thought of the two as the same, but DIDO spearates the concept and allows the link between the access point and each user to function as an independent channel within the dame physical bandwidth.

Normally, I am deeply skeptical about claims of fundamental scientific breakthroughs. My skepticism is mitigated by what Perlman has already accomplished with OnLive, which moves gaming data across internet connections with an efficiency that no one thought possible. Clearly, this guy knows how to move bits.

Don’t expect to see DIDO deployed anytime in the very near future. It requires significant changes to network design.. including interposing a DIDO data center between an internet source and an access point to encode data as well as sophisticated new antennas.  But it does hold real promise to to reduce the growing crunch on our wireless airspace.

Steve Wildstrom

Steve Wildstrom is veteran technology reporter, writer, and analyst based in the Washington, D.C. area. He created and wrote BusinessWeek’s Technology & You column for 15 years. Since leaving BusinessWeek in the fall of 2009, he has written his own blog, Wildstrom on Tech and has contributed to corporate blogs, including those of Cisco and AMD and also consults for major technology companies.
  • Dan Boschen

    How is this any different from MIMO being deployed in LTE and 802.11.ac systems? (Multi-Input Multi-Output system that uses non-interfering paths to optimally increase data capacity beyond Shannon’s Capacitiy limit)

    • Ben Thornton

      I would just like to say that repeatedly I have seen reputable news outlets and blogs mistakenly report that Steve Perlman or his respective companies claim to have broken the Shannon Hartley theorem. The claim is only to have side stepped its limitations by challenging the assumptions that the theorem is based on. Specifically they separate the limitation imposed by “Shannon’s Law” from relating to wireless spectrum as opposed to wireless channels, the assumption in every other wireless technology is that these are the same. DIDO overcomes the problem by separating each user with their own Shannon limited channel while sharing the same wireless spectrum, this is how the claim, “all users get 100% of the bandwidth” is reportedly realised. It is important to get this right because there are so many commenters responding to articles on the subject and even articles themselves that have said for example, “well violating Shannon’s law is impossible so therefore this is no more than snake oil and Steve Perlman is a liar” There is no doubt in my mind that Steve Perlman is not a liar and the claims are if exaggerated non the less true. The question most important then is not, “is this going to work” but how and when the hell can I get it?

  • Selvan999uk

    “No one has yet found a way to break Shannon’s law, but Rearden Companies…….”
    What a stupid statement!

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