The problem of designing optimal quantizers for distributed source coding is addressed. The generality of this formulation includes both the symmetric and asymmetric scenarios, together with a number of coding schemes, such as ideal coding achieving a rate equal to the joint conditional entropy of the quantized sources given the side information. The paper shows the optimality conditions that quantizers must satisfy, and generalizes the Lloyd algorithm for their design. Experimental results are shown for the Gaussian scalar asymmetric case.
This letter advances the non-orthogonal multiple access (NOMA) technique for cellular downlink co-channel interference mitigation, via exploiting the (limited) cooperation among base stations (BSs). Specifically, we consider a simplified but practically relevant scenario of two co-channel cells with asymmetric interference, i.e., only the user in one cell receives the strong interference from the BS in the other cell. To mitigate such interference, we propose a new cooperative NOMA scheme, where the interfered user's serving BS sends a superposed signal comprising both the desired message and the co-channel user's message (shared by the interfering BS). The co-channel user's signal is aimed to add constructively with the interfering BS's signal at the interfered user's receiver so that the combined interference with enhanced power can be effectively decoded and cancelled. This thus leads to a new problem on how to optimally allocate the transmit power for the two superposed messages. We provide the closed-form solution to this problem and investigate the conditions under which the performance of the proposed scheme is superior over the existing schemes.
This letter studies a K-link interference channel (IFC) with simultaneous wireless information and power transfer (SWIPT). Our objective is to maximize the minimum signal to interference plus noise ratio (SINR) of the K links by jointly designing the power allocations at all transmitters and the power splitting (PS) ratios at their receivers under both the individual minimum energy harvesting (EH) constraints and maximum transmit power constraints. We propose a centralized algorithm to optimally solve the nonconvex problem. A distributed algorithm is further designed where each link updates its transmit power and PS ratio through an iterative process. Numerical results show that the proposed algorithms provide improved tradeoffs in the achievable max-min SINR versus harvested energy compared against other existing algorithms.
Factory systems often include many field units that speak different message formats such as OPC-UA and MQTT. Many software bridges can link these units, but they often add long wait time, extra link steps, or slow return after faults. We built a small Go-based gateway that joins both formats and uses short worker groups to handle tasks at the same time. Tests on 102 devices with mixed data show that round-trip delay fell by about 21%, bridging cost dropped by about 35%, and link recovery time improved from 290 ms to about 170 ms. The gateway kept steady message flow during brief bursts and did not require changes to field units, which helps when old and new devices must work together. These results show that placing a compact tool near edge nodes can improve message time and lower setup work in plant networks. Limits came from small boards, where heavy traffic raised CPU use. Future work will test larger setups and add timing support such as TSN or QUIC.
Block diagonalization (BD) is a practical linear precoding technique that eliminates the inter-user interference in downlink multiuser multiple-input multiple-output (MIMO) systems. In this paper, we apply BD to the downlink transmission in a cooperative multi-cell MIMO system, where the signals from different base stations (BSs) to all the mobile stations (MSs) are jointly designed with the perfect knowledge of the downlink channels and transmit messages. Specifically, we study the optimal BD precoder design to maximize the weighted sum-rate of all the MSs subject to a set of per-BS power constraints. This design problem is formulated in an auxiliary MIMO broadcast channel (BC) with a set of transmit power constraints corresponding to those for individual BSs in the multi-cell system. By applying convex optimization techniques, this paper develops an efficient algorithm to solve this problem, and derives the closed-form expression for the optimal BD precoding matrix. It is revealed that the optimal BD precoding vectors for each MS in the per-BS power constraint case are in general non-orthogonal, which differs from the conventional orthogonal BD precoder design for the MIMO-BC under one single sum-power constraint. Moreover, for the special case of single-antenna BSs and MSs, the proposed solution reduces to the optimal zero-forcing beamforming (ZF-BF) precoder design for the weighted sum-rate maximization in the multiple-input single-output (MISO) BC with per-antenna power constraints. Suboptimal and low-complexity BD/ZF-BF precoding schemes are also presented, and their achievable rates are compared against those with the optimal schemes.
In standard predictive video coders, intra-mode coding of macroblocks (MBs) provides packet loss resilience, at the cost of reduced compression efficiency. Conventional mode selection algorithms are "greedy" as they focus on minimization of distortion of current MB, while ignoring the effect of this selection on subsequent frames. This paper proposes an algorithm for prescient mode selection: the coding modes of MBs are chosen while taking into account the distortion of subsequent frames. The problem is formulated as one of joint selection of MB coding modes, for a group of pictures, so as to minimize the rate-distortion cost. The straightforward solution based on dynamic programming requires enormous computational complexity. We propose an iterative algorithm which obtains a locally optimal solution at feasible complexity. The total decoder distortion is computed using recursive optimal per-pixel estimate (ROPE) which accurately accounts for the effects of quantization, packet loss, error propagation, and error concealment. Simulation results show consistent improvement over our previous "greedy" ROPE-RD mode selection, and substantial gains over other (non-ROPE) mode selection schemes.
Prior study on the cognitive radio (CR) has mostly adopted the passive sensing protocol, where the CR keeps monitoring the spectrum of interest, and decides to transmit when the sensing result indicates that the primary radio (PR) is inactive. In this paper, we propose an alternative active sensing protocol where, prior to the sensing, the CR generates a temporary jamming signal to deliberately interfere with the PR. The jamming signal is aimed to trigger an interesting interaction between the CR and PR, named as the hidden power-feedback loop: If the PR is indeed active and reacts upon receiving the jamming signal by increasing its transmit power, the CR will receive a power-boosted PR signal that is more easily detectable. Moreover, this paper demonstrates the usefulness of exploiting the power-feedback loop for the CR to effectively estimate the channel from the CR to the PR. This is well-known as a crucial task to implement for the CR operating under the so-called interference temperature constraint, where the CR is allowed to transmit regardless of the PR's on/off status, provided that the resultant interference power level at the PR is kept below some predefined threshold.
Ambiguity performances of reference signal patterns for integrated communication and sensing are studied via time delay and Doppler shift detection. A reference signal pattern with a staggering offset of a linear slope relatively prime to the transmission comb is suggested for low-complexity, standard-resolution sensing algorithms. We also propose an extended guard interval design to extend the maximum time delay for post-FFT sensing algorithms.
This paper presents TIGHT, a geographic routing protocol for cognitive radio mobile ad hoc networks. TIGHT offers three routing modes and allows secondary users to fully explore the transmission opportunities over a primary channel without affecting primary users (PUs). The greedy mode routes a packet via greedy geographic forwarding until a PU region is encountered and then further routes the packet around the PU region to where greedy forwarding can resume. It works best when the PUs are only occasionally active. In contrast, the optimal and suboptimal modes route a packet along optimal and suboptimal trajectories to the destination, respectively. They work best when the PUs are active most of the time. The suboptimal mode is computationally more efficient than the optimal mode at the cost of using suboptimal trajectories in rare cases. The efficacy of TIGHT is confirmed by extensive simulations.
Conventional beamforming with fixed-position antenna (FPA) arrays has a fundamental trade-off between maximizing the signal power (array gain) over a desired direction and simultaneously minimizing the interference power over undesired directions. To overcome this limitation, this letter investigates the movable antenna (MA) array enhanced beamforming by exploiting the new degree of freedom (DoF) via antenna position optimization, in addition to the design of antenna weights. We show that by jointly optimizing the antenna positions vector (APV) and antenna weights vector (AWV) of a linear MA array, the full array gain can be achieved over the desired direction while null steering can be realized over all undesired directions, under certain numbers of MAs and null-steering directions. The optimal solutions for AWV and APV are derived in closed form, which reveal that the optimal AWV for MA arrays requires only the signal phase adjustment with a fixed amplitude. Numerical results validate our analytical solutions for MA array beamforming and show their superior performance to the conventional beamforming techniques with FPA arrays.
No abstract is provided for this article.
In response to the development of future remote sensing satellites transmission, the parallel structure of the digital receiver should be adopted under the current hardware limitation of the-state of art of the FPGA. A parallel timing recovery algorithm and a parallel carrier recovery algorithm are proposed in this paper. The simulation and implementation results show that the proposed parallel digital receiver is capable for the Gbps demodulation. The structure has lower complexity for implementation compared to the PRX and APRX.
