Final Report Summary - NOWIRE (Network Coding for Wireless Networks)
NOWIRE aim is to make wireless networks more reliable, efficient and secure, responding to the crucial demand for more efficient bandwidth use, enhanced security and higher mobile speeds today. As a supporting datapoint, Cisco reports that mobile traffic is projected to increase nearly 11-fold until 2018; during the same period, the mobile speed is only expected to double.
The number of wireless devices has already reached 7 billion, with a host of new applications constantly emerging. Wireless is becoming our defacto mode of connectivity, and we increasingly need to rely on wireless services even for our most security-sensitive data.
NOWIRE developed research along three main axis: packet level cooperation empowered by network coding techniques, physical layer cooperation, and wireless security with unconditional guarantees. Our developed schemes can significantly reduce the operational complexity and battery usage, and multi-fold increase the throughput and reliability of wireless communications.
The common core principle of our work is to leverage the wireless channel properties and exploit user cooperation in uncoventional and novel ways,
in particular through the use of coding techniques. Our results range from theoretical foundations to practical systems implementations over our testbeds, and include:
(1) Network Coding: We have proposed the first deterministic algebraic designs for vector network coding,
that enable benefits in terms of alphabet size and operational complexity. We have presented capacity characterizations of non-coherent network coding as well as coding designs. We have introduced the pliable index coding formulation and proved that it requires (in the worst case) an exponentially smaller number of transmissions than traditional index coding.
We have designed and deployed on our sensor testbed SenseCode, as far as we know the first network-coded protocol deployed on sensor networks. We have contributed to the design and deployment of Microcast, that enables to boost the speed of video downloading by simultaneously expoiting multiple wireless interfaces across proximal devices.
(2) Physical Layer Cooperation:
We have developed the first polynomial time algorithms that generalize the Ford-Fulkerson algorithm from graphs to
arbitrary deterministic networks that capture broadcasting and interference. We have formulated the network simplification paradigm, and shown that in a Gaussian diamond network with n relays we can approximately achieve a fraction k/k+1 of the network capacity by using at most k of the relays. We have translated the Quantize-Map-Forward information theoretical principles to practical relaying schemes that compared favorably with alternatives in our testbed of software radios. We have shown that half-duplex network operation requires a polynomial (as opposed to exponential) number of scheduling states for an optimal operation in a number of cases, and that there exist very simple schedules that achieve at least half of the network capacity.
(3) Wireless Security: We have characterized the secret key generation and secret message capacity, in the presence of an eavesdropping Eve, in a number of small networks that include the parallel-links, triangle and line network. We have developed new outer bounds, as well as new achievability schemes, that rely on Linear Programming (LP) formulations of the secrecy problem over arbitrary graphs. We have deployed protocols for key generation in our software radios testbeds and showed that it is possible to generate tenths of Kbps of group secret keys.