With the increasing demand of massive/big data applications, nonvolatile memory (NVM), such as phase-change memory (PCM), has become a promising candidate to replace DRAM because of its low leakage power, nonvolatility, and high density. However, most of the existing memory read/write intensive algorithms and data structures are not aware of the PCM write heterogeneity in terms of both energy consumption and latency. In particular, self-balancing binary search trees, which are widely used to manage massive data in the big-data era, were designed without the consideration of PCM characteristics. Thus, the multiple rotations of the tree balancing process would degrade the memory performance. This work explores the relations among nodes and analyzes tree operations, and the node indexing and address mapping are redesigned to reduce the tree management overhead on single-level cell (SLC) PCM by decreasing the number of bit flips of tree rotations. When multilevel cell (MLC) PCM is included, our address mapping algorithm is developed to reduce the total energy consumption and latency with considerations of the heterogeneous write operations of different cell states. Experimental results show that our solution significantly outperforms the original implementation of a self-balancing binary search tree when the amount of data is large.

Phase change memory (PCM) has become a promising candidate to replace DRAM in some massive/big data applications because of its low leakage power, non-volatility, and high density. However, most of the existing memory read/write intensive algorithms/designs are not aware of the endurance and write asymmetry issues of PCM. In particular, self-balancing binary search trees, which are widely used to manage massive data in the big-data era, were designed without the consideration of PCM characteristics and could degrade the memory performance. In this work, we rethink the design of self-balancing binary search trees, and propose a write-asymmetry-aware self-balancing tree to reduce the tree management overhead by decreasing the total/average number of bit flips of tree rotations with the consideration of the endurance and write asymmetry issues of PCM. Experimental results show that our solution significantly outperforms the original implementation of a self-balancing binary search tree, in terms of minimizing the total number of bit flips when the amount of data is large.

In this letter, a novel phase discriminator called digital phase discriminator (DPD) is proposed for 1-bit analog-to-digital-conversion (ADC) software-defined receivers. Using fewer computations, the DPD achieves higher accuracy than that of the typical arctangent phase discriminator (APD). The improvement is up to several orders when the sampling frequency keeps increasing since the accuracy of APD is bounded mainly due to quantization loss. Finally, the simulation results demonstrate the superiority of the proposed approach and the critical uniformity condition is verified.

In this paper, we propose techniques for the construction of frequency-coding sequences that give rise to frequency-coded waveforms having ambiguity functions with a clear area - containing no sidelobes - in a connected region surrounding the main lobe. These constructed sequences are called pushing sequences. First, two important properties of pushing sequences are investigated: the group D/sub 4/ dihedral symmetry property and the frequency omission property. Using the group D/sub 4/ dihedral symmetry property, we show how to construct additional pushing sequences from a given pushing sequence. Using the frequency omission property, we show how to construct pushing sequences of any length N and design proper frequency-coded waveforms that meet specific constraints in the frequency domain. Next, we use the Lempel T/sub 4/ construction of Costas sequences to construct pushing sequences with power 1. Finally, we show how to construct pushing sequences with any desired power using Lee codewords. Because these arbitrary-power pushing sequences constructed using Lee codewords do not have the Costas property, we derive expressions for the pattern of hits in the geometric array. Based on this, the general form of the positions and levels of all the sidelobe peaks are derived.