Spurred by the increasing market needs for big data and cloud services, global server suppliers and hyper- scalers are looking to adopt high-speed and large-capacity memory modules. To fulfill this trend, the brand- new low-voltage operable DDR5 (double data rate 5th generation) memory can be an appropriate solution, with the highest speed of 7.2 Gbps and the largest capacity of 512 GB. However, some critical obstacles, such as increased capacity and high-speed I/O requirements, unstable power noise occurrences, high power consumption, and increase in operating temperature, must be overcome. This poster will cover various technical pathfinding solutions for world's first DDR5 512 GB module with an advanced DRAM process and I/O schemes, package technology, and module architecture regarding improvements in the following four aspects: performance, speed, capacity, and power. This will unveil the industry's first high-performance and large-capacity memory product with 8-stacked DDR5 DRAMs. Samsung believes that this product will pave the way for achieving both higher bandwidth and lower power consumption to inaugurate the era of terabyte DRAM modules for next-gen servers.

In this paper, we extend the construction by Vu and Gong for families of M-ary sequences of period q - 1 from the array structure of an M-ary Sidelnikov sequence of period q2- 1, where q is a prime power and M|q - 1. The construction now applies to the cases of using any period qd-1 for 3 ≤ d27. The proposed construction results in a family of M-ary sequences of period q-1 with: 1) the correlation magnitudes, which are upper bounded by (2d -1)√q +1 and 2) the asymptotic size of (M -1)qd-1/d as q increases. We also characterize some subsets of the above of size ~(r - 1)qd-1/d but with a tighter upper bound (2d - 2)√q + 2 on its correlation magnitude. We discuss reducing both time and memory complexities for the practical implementation of such constructions in some special cases. We further give some approximate size of the newly constructed families in general and an exact count when d is a prime power or a product of two distinct primes. The main results of this paper now give more freedom of tradeoff in the design of M-ary sequence family between the family size and the correlation magnitude of the family.

In this paper, we propose new precoding methods for two-way multiple input multiple output physical network coding (PNC) systems which employ the modulo operation. In our work, the transmit and receive filters are determined to maximize the minimum distance of the received constellations assuming global channel state information. The precoding operations are separately optimized for the multiple access (MA) and the broadcast stages, and the optimal precoding is obtained by applying a semidefinite relaxation method. Especially, we prove that for the system with linear detection the modulo operation for the PNC achieves optimality with the derived precoding for the MA stage in terms of the minimum distance. Also, we present a closed-form solution for the optimal filter designs for two special cases. For computing solutions, we transform our max min problem into a simple maximization problem by imposing additional constraints. Also, we propose a suboptimal non-iterative precoding scheme whose performance is within 1 dB at a bit error rate (BER) of 10-4compared to the optimum iterative method with much reduced complexity. Finally, the simulation results show that the proposed systems achieve 2-3 dB gains at a BER of 10-4compared to the optimal amplify-and-forward systems.

In this paper, we propose a limited feedback system for two-way wireless relaying channels with physical network coding (PNC). The optimal system with full feedback has already been studied when a modulo operation is employed for the PNC. In this case, phase and power of channels of two end nodes are adjusted to maximize the minimum distance. Based on this full feedback system, we design new quantization methods for the phase and the power. From the observation of the minimum distance, we present a codebook design. Especially, for the quantization of power in the system with 16-QAM, a novel power quantization scheme is proposed to maximize the worst minimum distance. Finally, the simulation results confirm that our proposed scheme outperforms conventional limited systems with reduced complexity.

A relay selection method is one of popular approaches to overcome fading effects in wireless relay channel due to its simplicity. However, previous works were concentrated on the case of analog network coding systems. In this paper, we consider a relay selection scheme in two-way relaying systems with physical network coding. Since conventional schemes based on analog network coding does not provide effective performance in physical network coded systems, we propose new selection criteria which maximize the minimum distance at the multiple access phase to achieve full diversity. Moreover, through asymptotic error rate analysis, it is confirmed that the proposed scheme is able to attain full diversity. Simulations results are also provided to verify the analysis of the proposed scheme.

This letter considers a multi-user wireless communication system employing physical network coding (PNC), where a pair of users communicates with each other via a relay. To attain reliable communication over time varying channels, we apply an opportunistic scheduling scheme for the PNC to both the broadcast channel phase and the multiple access channel phase. We propose two criteria for selecting users based on the channel norm and the minimum distance. Also, an efficient method to compute the minimum distance for superposed QPSK signals is introduced. Simulation results show that the proposed scheduling for PNC provides a significant improvement over conventional schemes.

In this letter, we study multiple-input single-output joint processing (JP) systems with limited feedback where base stations exchange both channel state information and their data via ideal backhaul links. In order to optimize the sum-rate performance of the JP system, we propose a new feedback bit allocation scheme which maximizes quantization accuracy in the presence of pathloss. The quantization accuracy is formulated by the expectation of the inner product between the actual channel vector and the quantized channel vector. First, we derive the quantization accuracy as a closed form, which compensates the phase difference of two channels. Then, the maximum quantization accuracy is achieved by searching possible bit combinations. Simulation results show that the sum rate of our proposed feedback bit allocation strategy is more than twice compared to the conventional equal bit allocation method in the three cell case.

In this paper, we propose precoding methods for multiple input multiple output physical network coding systems, which employ the modulo operation. In our work, the transmit and receive filters are determined to maximize the minimum distance on the received constellations. Especially, to address non-concavity of the given problems, we change our problem into a concave one which can be optimized by an iterative method. Also, we propose a suboptimal non-iterative scheme whose performance is very close to the optimum iterative method. In our derivations, we prove that the modulo operation achieves the optimality in terms of the minimum distance. Finally, it is confirmed from the simulation results that the proposed systems outperform conventional schemes in terms of the error performance.

In this paper, we study multiple-input single-output joint processing (JP) systems with limited feedback where two adjacent base stations exchange both channel state information and their data. To optimize the sum-rate performance of the JP system, we propose a new feedback bit allocation method which maximizes quantization accuracy in the presence of pathloss. The quantization accuracy is formulated by the expectation of the inner product between the actual channel vector and the quantized channel vector. In order to maximize the quantization accuracy, we employ a new method which compensates the phase difference of the two channels. Through numerical evaluations, we show that our proposed feedback bit allocation strategies provide about 50% performance gain in terms of the sum rate performance compared to the conventional method with the equal bit allocation scheme.

This paper considers a three-way wireless communication system employing physical layer network coding (PNC), where each user desires to transmit independent data to the other users via relay. However, one difficulty with this system is that the performance is limited by worst channel. To overcome this problem, we adopt a scheduling system. Since channel characteristics vary over time in wireless communications, a scheduling technique employing network coding where users are selected based on the instantaneous signal-to-noise ratio was proposed for the broadcast channel (BC) phase. In this paper, we extend the scheduling technique to the multiple access channel phase as well as the BC phase. We propose two criteria for selecting users based on the channel norm and the minimum distance criterion. Also, an efficient method to compute the minimum distance is introduced. The proposed scheduling for PNC provides a significant improvement over the conventional scheme.

Orthogonalized spatial multiplexing (OSM) systems with optimal precoding, denoted by POSM, was recently proposed which allows a single-symbol decodable maximum likelihood receiver in closed-loop multiple-input multiple-output (MIMO) systems. It was shown that the performance of the POSM is identical to that of the optimal closed-loop MIMO system in terms of the minimum distance. In this letter, we derive an exact symbol error rate (SER) expression of the POSM for 4-QAM and 16-QAM in Rayleigh fading channels. By using polar coordinates and the singular value distributions, the final expression of the SER can be evaluated with a single-integral form. Also, in the high SNR regime, we obtain a simple average SER expression of the POSM which shows that the POSM with two transmitting antennas achieves full diversity. Simulation results confirm the accuracy of our derived analysis.

We consider the downlink of a cellular network with multiple cells and multi-antenna base stations. Our model includes distance-dependent pathloss, arbitrary clusters of cooperating cells, and general “fairness” requirements. Beyond Monte Carlo simulation, no efficient computation method to evaluate the ergodic throughput of such systems has been presented, yet. Furthermore, for systems of practical size with tens of cells and hundreds of users per cell, even simulation becomes challenging. We develop an analytic framework based on the combination of results from large random matrix theory and convex optimization. This allows computationally efficient calculation of the system performance in the so-called “large system limit”, i.e., in the limit of a large number of antennas per base station and a large number of users per cell, while the ratio of antennas per user is kept constant. In particular, the system ergodic throughput, subject to per-base station power constraints and to general fairness criteria, is obtained via the iterative solution of a system of fixed-point equations. Comparisons with finite-dimensional simulation results show that the large-system analysis provides remarkably accurate approximations for the actual finite-dimensional systems, even for a small number of users and base station antennas.

The optimization of the weighted ergodic sum rate is considered for the downlink of a cellular networks with multiple cells and multi-antenna base stations. We focus on the large system limit where the number of base station antennas and the number of users per cell go to infinity with a fixed ratio. We consider two extreme cases of full inter-cell cooperation (network MIMO) and no inter-cell cooperation (single-cell multiuser MIMO). Using the large random matrix theory and Lagrangian optimization, we obtain a numerical algorithm that exactly computes the maximum weighted sum rate in this asymptotic regime. Numerical results are presented for a simple case of two interfering cells in a linear arrangement.

Recently an orthogonalized spatial multiplexing scheme with optimal precoding, referred to as POSM, has been proposed. The POSM achieves optimal performance in terms of maximizing the received minimum Euclidean distance dmin,Rin closed-loop multiple-input multiple-output (MIMO) systems. In this paper, we derive exact closed-form expressions of the symbol error rate (SER) for the POSM with 4-QAM and 16-QAM in Rayleigh fading channels. We first introduce a new system model for the given channel. Based on this system model and a unique feature of the POSM effective constellations, the final expression of the SER using polar coordinates can be evaluated with a single-integral form. Simulation results confirm the accuracy of our derived analysis.

This paper proposes a new precoding algorithm for orthogonalized spatial multiplexing (OSM) systems over flat-fading multiple-input multiple-output (MIMO) channels. The OSM scheme was recently introduced for closed-loop MIMO systems which allows single symbol decodability for maximum likelihood detection. To further improve the performance in OSM systems, we propose a new precoding method. For identifying the parameters of a precoder, we introduce a partitioning approach on the minimum Euclidean distance between constellation points in the effective channel. Also, it is shown that two real value parameters and one bit are required for feedback information in 4-QAM systems. Simulation results demonstrate that our precoding algorithm allows us to significantly improve the system performance with small increase of feedback values. We also confirm through simulations that the performance of the proposed scheme is the same as the optimum closed-loop MIMO systems.

This paper introduces a new efficient design scheme for spatial multiplexing (SM) systems over closed loop multiple- input multiple-output (MIMO) wireless channels. Extending the orthogonalized spatial multiplexing (OSM) scheme which was developed recently for transmitting two data streams, we propose a new SM scheme where a larger number of data streams can be supported. To achieve this goal, we partition the data streams into several subblocks and execute the block-diagonalization process at the receiver. The proposed scheme still guarantees single- symbol maximum likelihood (ML) detection with small feedback information. Simulation results verify that the proposed scheme achieves a huge performance gain at a bit error rate (BER) of 10-4over conventional closed-loop schemes based on minimum mean-square error (MSE) or bit error rate (BER) criterion. We also show that an additional 2.5 dB gain can be obtained by optimizing the group selection with extra feedback information.

In this paper, we propose a new precoding algorithm for orthogonalized spatial multiplexing (OSM) systems over flat-fading multiple-input multiple-output (MIMO) channels. The OSM scheme was recently introduced for closed-loop MIMO systems which allows single symbol decodable maximum likelihood detection. To further improve the performance of the OSM system, we propose a new precoding method by maximizing the minimum Euclidean distance between constellation points in the effective channel. In order to efficiently identify the parameters of a precoder which maximizes the minimum distance, we introduce a partitioning approach. Through analysis, it is shown that one real value parameter and two bits are required for feedback information for precoding in 16-QAM systems. Simulation results demonstrate that our algorithm provides 9 dB and 7.5 dB gains at a bit error rate (BER) of 10-4over the conventional OSM systems for 4-QAM and 16-QAM, respectively. We also confirm that the performance of the proposed scheme is the same as that of the optimum closed-loop MIMO systems in terms of the minimum distance. Consequently, our precoding algorithm significantly improves the system performance with a small increase of feedback amount.

In this paper, we propose a new power allocation algorithm for orthogonalized spatial multiplexing (OSM) systems over flat-fading multiple-input multiple-output (MIMO) channels. Compared to SVD-based transmission scheme, the OSM scheme exhibits a good system performance with lower complexity and feedback overhead. To further improve the performance in OSM systems with power allocation, we introduce a geometric approach on the Euclidean distance between the constellation points in the effective channel. Using this approach, we show that the optimal power allocation parameters in terms of the minimum distance can be obtained. Simulation results demonstrate that our algorithm provides a 5 dB gain at a bit error rate (BER) of 10-4over that of no power allocation case with both QPSK and 16-QAM.