Time division multiplexing for Infostations

In ATSC 3.0 physical layer standard, a layered division multiplexing (LDM) scheme has newly accepted as one of the multiplexing schemes in order to improve the reception performance when multiple broadcasting contents are simultaneously delivered through a single RF channel. This paper presents comparison results of LDM and time division multiplexing (TDM) schemes under fixed reception environments, and analyzes the performance gain of LDM over TDM. From the field test results, it was confirmed that the LDM gain in the theoretical analysis is still maintained in the actual field.

In recent years, most of the research about distributed video coding focus on how to get the exact side-information and virtual channel estimation parameters in order to achieve better rate-distortion performance. However, there is quite few research about the practical transmission issue, i.e., no practical and effective transmission scheme has been proposed yet for distributed video coding (DVC). Feedback channel based DVC can usually achieve better rate-distortion performance, while leading to long delay because of feed-backs. The traditional video transmission scheme, which doesn't consider the characteristics of DVC, will introduce long delay since the encoder needs to wait until receiving the feedback information. As a result, the effective bandwidth of the network will be reduced greatly. In this paper, we have proposed an adaptive time division multiplexing video transmission scheme for the DVC which can reduce the delay due to waiting feed-backs. Experimental results show that our method can reduce transmission time effectively. And as a result, it can improve the effective bandwidth and the buffer utilization rate, thus higher transmission efficiency can be achieved.

The present paper deals with bandwidth allocation and congestion avoidance in a broadband satellite with on-board switching, oriented towards guaranteeing the Quality of Service (QoS) associated with various traffic/service classes as defined by ATM forum. At the core of the bandwidth allocation a novel uplink (UL) access protocol is proposed, based on a Multi-Frequency Time Division Multiple Access (MF-TDMA) primary access scheme, in conjunction with a downlink (DL) access protocol based on a more traditional Time Division Multiplex (TDM) scheme. This UL access protocol is complemented by a rate-based congestion control protocol (consistent with ATM Forum recommendations), which is an adaptation to GEO satellites environment of the Explicit Rate Indication for Congestion Avoidance (ERICA) algorithm developed for terrestrial networks. The performance of both UL access and congestion avoidance schemes has been evaluated through extensive simulations and the results compared with those obtained with other protocols or by analytical approximations.

We have devised a digital time-division multiplexing (TDM) scheme for minimizing the circuit complexity required for an array of sensors. As a proof-of-concept, we have designed, fabricated, and tested a four-channel digital TDM readout circuit. The proposed scheme can be generalized for a larger number of channels. The readout circuit comprises an array of ADCs to digitize sensor outputs, a multiplexing unit, a clock controller, and a counter with parallel-to-serial output interface. For demonstration purposes, we employed low-pass phase modulation–demodulation ADCs running in a synchronous mode of operation. To facilitate an independent verification of circuit operation, we also placed an on-chip pattern generator to apply a unique pattern to each channel. The multiplexing unit is based on an array of sequentially triggered switches, each controlling the flow of data from a single ADC to a common output bus. In our scheme, the switches are realized using RS-flip-flops with nondestructive (RSN) readout cells with only one RSN cell turned on at a time. Multiplexed output data were stored in ripple counter based on T-flip-flops and read out to room temperature electronics using a serial interface. The chip was immersed in liquid helium at 4.2-K temperature and extensively evaluated at sampling frequencies up to 12.8 GHz. By means of embedded pattern generators, we proved the correct operation of each channel and of all four channels combined. We also were able to perform reconstruction of a signal applied to individual ADC. The chip was fabricated using HYPRES’ 4.5-kA/cm2 process with four Nb metal layers. We briefly discuss the proposed scheme's scalability for higher current density and smaller feature size fab processes.

In this article, we adopt outage probability (λ-capacity) in fast-fading channels as a pay-off function in a zero-sum game between a legitimate transceiver pair and an uncorrelated Gaussian jammer. The transmitter aims at minimising the outage probability, while the jammer attempts to maximise the outage probability. We consider both peak (over each codeword) and average (over all codewords) power constraints. For peak power constraints, a transmission rate is either supported by the system, or if too large, causes the whole transmission to fail. By imposing average power constraints, large rates can be supported at the cost of positive probability of codeword error. Maxmin (where the jammer is assumed to play first) and minimax (where the transmitter is assumed to play first) power control strategies are developed under each power constraint, which show that no Nash equilibrium of pure strategies exists under the average power constraint when the follower has perfect knowledge about the randomisation outcome of the first player.

In this paper, we consider an optimal power allocation problem that maximizes the sum-rate of a single-cell MISO broadcast channel with regularized channel inversion (RCI) beamforming at the base station (BS). Unlike the channel inversion or zero forcing beamforming, the optimal power allocation with RCI precoding at the base station is a nonlinear non-convex optimization problem with many local optima. Here, we investigate this problem in the large system limit, i.e., when the number of users K and antennas at the base station N tend to infinity with their ratio β = K/N being held constant. We assume each user has data symbol with power p k , and slow-varying path-loss a k . In this setting, we first derive the expression for the signal to interference plus noise ratio (SINR). Then, we divide all K users into L groups where all users in each group are assumed to be co-located or to have approximately the same distance from the BS. In other words, the users in each group have the same path-loss which is distance dependent. Moreover, in each group, we assume that the power allocated to each user is the same. Based on this system model, we investigate optimal power allocation schemes that maximize the sum-rate per antenna, firstly under average power constraint, and then under both average and per-user power constraints. We show that both problems are convex and the power allocation mainly follows the well-known water-filling strategy.

Layered Division Multiplexing (LDM) has demonstrated increased data rate capacity for wireless applications where the service bitrates being multiplexed are unbalanced. Current Direct-To-Home (DTH) broadcasting satellite standards (DVB-S2 and DVB-S2X) include Variable Coding and Modulation (VCM) mode. VCM provides the opportunity to deliver different services on a Time Division Multiplexing (TDM) basis and in consequence target different reception conditions with a single carrier. This article proposes the combination of the tools provided by DVB-S2X with LDM for satellite broadcast and communication systems. This article describes use cases where multiplexing schemes can be beneficial in comparison with VCM (TDM) approach. The use cases include the delivery of High Definition (HD) and Ultra High Definition (UHD) TV services to customers as well as additional communication services. The performance of the proposal is evaluated with simulations under different channels, including the impact of satellite equipment non-linearities. Analysis shows that LDM provides considerable gain in comparison with VCM in both AWGN and non-linear satellite channels.

SummaryThis article is aimed at designing positioning system using visible light communication technology by incorporating three different diversity schemes, namely, transmit diversity (TD), receive diversity (RD), and angle diversity. For the TD, multiple transmitters with single receiver (MISO) is used to obtain the target location using frequency division multiplexing (FDM) and variable phase approach. To deploy RD, the proposed system comprises multiple receivers and single transmitter (SIMO). Only one transmitter's absolute coordinates are required to obtain the location coordinates of optical receivers. FDM and time division multiplexing access schemes have been utilized to transmit the unique signals by light‐emitting diodes (LEDs). To implement angle diversity, orientation of transmitter and receiver is considered for positioning purposes. Under this environment, there is no constraint for the LEDs to be installed on ceiling; they can be at any point within the room or at different heights. The information regarding spherical coordinates (representing the orientation) of LEDs (single or multiple) is used to determine the coordinates or the orientation of receiver having multiple or single photodiodes, respectively. Under multiple orientations, this system is analyzed with both scenarios, that is, MISO and SIMO.

In this work, we consider delay-constrained systems in cooperative relay networks, and derive methods to maximize the throughput when a limited feedback link to the transmitter nodes exist. We derive the optimal rate control policy, and show that with just a few hits of feedback, most of the gains of the perfect feedback rate control policy are achievable. We maximize the throughput for popular methods of transmission in a network such as relaying, routing, and direct transmission. It is observed that for a finite rate of feedback, the throughput maximizing outage probability can be relatively high. This suggests using higher rate codes, and allowing some outages in an effort to increase the overall throughput. Interestingly, for large average power constraints, power control is unnecessary to maximize the throughput. On the other hand, for small average power constraints, we show that power control is more important than rate control.

Optical-path difference (OPD) is a key parameter for the fiber-optic interferometer, especially for the large-scale multiplexing of fiber-optic interferometric sensors (FOIS) array. Due to the OPD directly affects the background noise of the system and the performance consistency among different array elements. Most of the time, the latter is very critical for the FOIS array. Several methods have been adopted for the OPD measurement of the fiber-optic interferometer, including the white-light interferometry, the optical-time-domain reflectometry (OTDR), the optical-frequency-domain reflectometry (OFDR). Unfortunately, none of the methods mentioned above can directly realize OPD on-line measurement of FOIS, which is multiplexed with the time division multiplexing (TDM) and the wavelength division multiplexing (WDM). In this paper, an OPD measurement method for multiplexing FOIS using TDM and WDM based on the improved OFDR has been present. The most distinguishing feature of this method is that it transformed the FOIS array under tested into a part of the OFDR system. The modulated linear sweep light directly injected into the FOIS array under tested and traversed every array element through array network. Thus every interferometer of FOIS became the interferometric structure of the improved OFDR, and the OPD measurement of complexity multiplexing FOIS array has been vastly simplified into the fiber length measurement of interferometer in proper order. Results show that the measurement accuracy of this approach can achieve millimeter level and the measurement range up to hundred meters for FOIS using TDM and WDM through a single measurement.

MIMO radar systems create a large virtual aperture to enhance the angular resolution. As a multiplexing scheme often the time-division multiplexing (TDM) procedure is chosen. The drawbacks are a reduced maximal unambiguously detectable Doppler frequency and the need to correct a phase error in angle estimation for relative radial velocities. To overcome these disadvantages a multiplexing scheme is proposed which uses different chirp rates. Every transmitting antenna is active at the same time but can be distinguished due to the different slopes of the frequency ramps.

For the high-resolution DoA (Direction of Arrival) estimation, various multiplexing schemes are considered for the multi-input multi-output (MIMO) fast chirp frequency-modulated continuous-wave (FMCW) radar. However, current schemes such as time-division multiplexing (TDM) and binary-phase modulation (BPM) may reduce the maximum detectable velocity, which causes the velocity ambiguity problem. As an extension of the BPM scheme to mitigate this issue, we propose a novel multiplexing scheme using M phase-shift keying (MPSK) code which duplicates shifted target peaks at unequal intervals over the velocity domain. The proposed scheme finds the true peaks to resolve the velocity ambiguity problem by the inversion of the circulant matrix with low additional computation. In addition, the successful implementation of the proposed scheme is conducted with 4 by 8 MIMO uniform linear array (ULA) antennas through the state-of-the-art FMCW radar. Finally, the proposed scheme is compared to the conventional TDM based MIMO scheme regarding signal to noise ratio (SNR) and phase calibration issues for moving targets. The proposed scheme is to estimate the accurate 4D information of targets while resolving the velocity ambiguity problem in the MIMO FMCW radar systems.

We present an upper bound on the probability of error of a signaling scheme that achieves the capacity of the multipath fading channel under an average power constraint in the limit of infinite bandwidth. The bound is derived under the assumption of Rayleigh block fading. We are therefore able to determine the performance of the scheme when a given finite bandwidth Is available. We evaluate the bound numerically for some reasonable parameters and study its interplay with other parameters of interest.

Polar codes are designed for parallel binary-input additive white Gaussian noise (BiAWGN) channels with an average power constraint. The two main design choices are: the mapping between codeword bits and channels of different quality, and the power allocation under the average power constraint. Information theory suggests to allocate power such that the sum of mutual information (MI) terms is maximized. However, a power allocation specific to polar codes shows significant gains.

This paper considers a multiple-input multiple-output (MIMO) Gaussian wiretap channel, where there exists a transmitter, a legitimate receiver and an eavesdropper, each equipped with multiple antennas. In particular, we study the rank of the optimal input covariance matrix that achieves the secrecy capacity of the multiple antenna MIMO Gaussian wiretap channel under an average power constraint. The rank and other properties of the optimal solution are derived based on certain relationships between the channel matrices for the legitimate receiver and eavesdropper. Such properties are useful steps towards characterizing the general solution to the MIMO wiretap problem with an average power constraint.