Anders A. Hansson

Scalable and Reliable Sensor Network Routing: Performance Study from Field Deployment

Scalable and reliable routing is a critical issue in sensor network deployment. A number of approaches have been proposed for sensor network routing, but sensor field implementation tends to be lacking in the literature. In our study, the problems of scalability and reliability in sensor network routing are addressed through a simple but powerful scheme implemented on Mica2 motes running TinyOS along with other, more widely-used routing protocols. Motes are tested in an outdoor sensor field, and detailed experiments are carried out for performance analysis. This paper presents the implementation details and the results obtained from head-to-head comparison of routing protocols. The proposed protocol delivers 93% of packets injected at a rate of one packet per second in networks with end to end hop distances of over 10 hops-a result which significantly improves upon results from the standard TinyOS routing implementation of MINTRoute. The promising results can be explained by the key protocol properties of reliability (via multi-path redundancy), scalability (with efficiently contained flooding), and flexibility (source-tunable per-packet priority) which are achieved without adding protocol complexity or resource consumption. These strengths enable the protocol to outperform even sophisticated link estimation based protocols especially in adverse outdoor sensor field environments.

Metropolitan road traffic simulation on FPGAs

This work demonstrates that road traffic simulation of entire metropolitan areas is possible with reconfigurable supercomputing that combines 64-bit microprocessors and FPGAs in a high bandwidth, low latency interconnect. Previously, traffic simulation on FPGAs was limited to very-short road segments or required a very large number of FPGAs. Our data streaming approach overcomes scaling issues associated with direct implementations and still allows for high-level parallelism by dividing the data sets between hardware and software across the reconfigurable supercomputer. Using one FPGA on the Cray XD1 supercomputer, we are able to achieve a 34.4/spl times/ speed up over the AMD microprocessor. System integration issues must be optimized to exploit this speedup in the overall simulation.

On forward-adaptive versus forward/backward-adaptive SISO algorithms for Rayleigh fading channels

Two types of soft-input soft-output (SISO) algorithms have previously been proposed for iterative decoding of concatenated codes applied over fading channels; forward-adaptive algorithms exploit the dependency between the present symbol interval and past symbol intervals, while forward/backward-adaptive algorithms take both the past and the future into account. Numerical results presented for interleaved serially concatenated continuous phase modulation (CPM) over the Rayleigh fading channel indicate that the performance of forward-adaptive algorithms approaches the performance of forward/backward-adaptive algorithms when a long channel-memory depth is exploited.

ON ASYNCHRONOUS CELLULAR AUTOMATA

We study asynchronous cellular automata (ACA) induced by symmetric Boolean functions [1]. These systems can be considered as sequential dynamical systems (SDS) over words, a class of dynamical systems that consists of (a) a finite, labeled graph Y with vertex set {v1,…,vn} and where each vertex vi has a state xvi in a finite field K, (b) a sequence of functions (Fvi,Y)i, and (c) a word w = (w1,…,wk), where each wi is a vertex in Y. The function Fvi,Y updates the state of vertex vi as a function of the state of vi and its Y-neighbors and maps all other vertex states identically. The SDS is the composed map

Non-traditional irregular interconnects for massive scale SoC

[\mathfrak{F}_Y,w]=\prod_{i=1}^{k} F_{w_{i}}: K^n\rightarrow K^n

Generalized APP detection of continuous phase modulation over unknown ISI channels

. In the particular case of ACA, the graph is the circle graph on n vertices (Y = Circn), and all the maps Fvi are induced by a common Boolean function. Our main result is the identification of all w-independent ACA, that is, all ACA with periodic points that are independent of the word (update schedule) w. In general, for each w-independent SDS, there is a finite group whose structure contains information about for example SDS with specific phase space properties. We classify and enumerate the set of periodic points for all w-independent ACA, and we also compute their associated groups in the case of Y = Circ4. Finally, we analyze invertible ACA and offer an interpretation of S35 as the group of an SDS over the three-dimensional cube with local functions induced by nor3 + nand3.

On antenna array receiver principles for space-time-selective Rayleigh fading channels

By using self-assembling fabrication techniques at the cellular, molecular, or atomic scale, it is nowadays possible to create functional assemblies in a mainly bottom-up way that involve massive numbers of interconnected components. However, such assemblies are often highly irregular, unreliable, and heterogeneous. A grand challenge for future and emerging electronics is thus to reliably and efficiently compute and communicate in such systems. The goal of this paper is to illustrate why non-traditional network-on-chip paradigms are promising for massive scale systems and what the limits are. We have previously shown that certain irregular 3D assemblies and interconnects have major advantages over regular 2D and 3D mesh fabrics in terms of latency, throughput, scalability, and the robustness against simple link failures. We present these results from a complex network perspective and look into the scaling properties of different interconnect topologies and routing algorithms in an abstract framework. We argue that only small-world topologies will scale up to massive scale systems. The long term goal in using irregular, fabrication-friendly, and non-traditional interconnects is to eventually be able to cheaply and easily assemble massive scale computing devices that are able to solve specific large- scale problems competitively with traditional top-down fabricated silicon technology.

Semantic compression of TCP traces

Techniques for computing soft information in the presence of unknown intersymbol interference are presented, with a particular focus on iterative detection of serially concatenated continuous phase modulation. The techniques are centered around the recursive least-squares algorithm, thus enabling unsupervised detection. In particular, we employ bidirectional estimation.

Low-complexity iterative detection based on bi-directional trellis search

Optimum (in the sense of minimum-error probability) single-symbol diversity detection for fading, noisy channels is too complex for practical implementation. A simplified, near-optimum array receiver is proposed, which is based on the statistics (i.e., the covariance-function matrix) of the fading channel. This detector is then analyzed by calculating the exact error probability. When there is a spread of the direction of arrival of the incident radio waves, the proposed detector significantly gains over an adaptive antenna array (which forms a weighted sum of the received antenna signals). Also, for this adaptive array, a fundamental difference between maximum-likelihood weights and least-mean-square weights is observed.

Iterative diversity detection for correlated continuous-time Rayleigh fading channels

We propose a new methodology, Restored, for model-based storage and regeneration of TCP traces. Restored provides significant data compression by exploiting semantics of TCP. Experiments show that Restored can achieve over 10,000-fold compression ratios for some really large input connections, while still being able to recover several structural and QoS measures.