My research interests mainly lie in the areas of information and coding theory, especially from the perspective of understanding the design principles of data transmission and storage systems. Thus far, much of my research has gravitated towards the study of * distributed * communication and storage systems. I provide here high-level summaries of some facets of my research. For a list of my publications, click here.

## Wireless Communications

It is well known that interference between devices that communicate over the same spectrum is the primary bottleneck of data speeds in modern wireless communication systems. Much of my research in wireless communications has involved the study of *interference alignment** - *a promising technique to manages interference in wireless communication systems. In my doctoral work, I developed and studied interference alignment for various communication scenarios. In my postdoctoral stint, I am exploring the use of lattice codes for wireless systems, in particular, their usefulness for interference alignment. To learn more about interference alignment, click here. Some sample publications are listed below.

Viveck R Cadambe, Syed A Jafar, Interference Alignment on the Degrees of Freedom of the K user Interference Channel, IEEE Transactions on Information Theory, Aug 2008.

Krishna Gomadam, Viveck R Cadambe, Syed A Jafar, A Distributed Numerical Approach to Interference Alignment and Applications to Wireless Interference Networks, IEEE Transactions on Information Theory, Jun, 2011 Vasilis Ntranos, Viveck R. Cadambe, Bobak Nazer, Giuseppe Caire Integer-Forcing Interference Alignment, IEEE International Symposium on Information Theory (ISIT), Jun, 2013

## Distributed Storage Systems

In modern data storage systems such as data centers, the data is stored in a distributed storage system with multiple servers. In such systems, it is important that the data is available to the user, even though the system components could be unreliable, specifically that the servers could fail. Classical coding theory provides several powerful techniques to design such failure tolerance with a small overhead in terms of storage footprint. In modern data storage systems, there are often additional requirements in several applications that lead to interesting research problems. I have done some work in this domain that I summarize below.

### Repair Efficient Erasure Codes

It is of interest in storage systems that when a server has failed, or is unavailable for some other reason (e.g., when it is away for an upgrade), the data be reconstructed as efficiently as possible from the other available servers. In my research, I have studied code design for reconstruction of data by incurring a small cost of repair, both in terms of access and bandwidth. Some related publications are listed.

Viveck R. Cadambe, Syed A. Jafar, Cheng Huang, Jin Li, Optimal Repair of MDS Codes in Distributed Storage via Subspace Interference Alignment, Available on arxiv:1106.1250

Viveck R. Cadambe, Syed A. Jafar, Hamed Maleki, Kannan Ramchandran, Changho Suh, Asymptotic Interference Alignment for Optimal Repair of MDS Codes in Distributed Data Storage, IEEE Transactions on Information Theory, May 2013

Viveck R. Cadambe, Arya Mazumdar An Upper Bound on the Size of Locally Recoverable Codes, IEEE International Symposium on Network Coding (Netcod), Jun, 2013. ### Coding for Distributed Computing Theory

Recently, I have studied a problem that lies in the intersection of erasure coding and distributed computing theory. When a distributed storage system is used as a shared memory for applications of distributed computing, it is important that the data should appear to the users as if stored on a single centralized system even though the data is stored in distributed servers, i.e., the storage system should be

*atomic*. I have recently designed efficient atomic shared memory algorithms that are based on erasure coding, and incur relatively smaller communication and storage costs than their replication based counterparts. The following technical report provides details.

Viveck R. Cadambe, Nancy Lynch, Muriel Medard, Peter Musial, Coded Atomic Shared Memory Emulation for Message Passing Architectures, CSAIL Technical Report, MIT-CSAIL-TR-2013-016,3 ## Other Topics

I have also studied other problems, some of which are related to the above areas. For instance, I have worked on the index coding problem, an open problem with a simple description that arose in theoretical computer science literature, with surprising connections to network coding theory. In my postdoctoral stint, I am exploring the multiple unicast problem, a challenging problem that is aims to generalize the classical max-flow-min-cut theorem I am also exploring applications of signal processing and statistical inference to computational forensics, in particular, for person identification using Short-Tandem-Repeat (STR) alleles.