Multi-frequency Time Division Multiple Access Research Articles

Research on onboard multistage digital demultiplexer for satellite communication based on MF-TDMA system

A new multicarrier multi-rate digital demultiplexer system structure based on MF-TDMA(Multi-Frequency Time Division Multiple Access) in a wideband satellite communication system is described. Compared with the traditional tree multicarrier demultiplexer method, the new structure uses a half-band filter instead of the quadrature mirror filter, which has three advantages: 1) It fully avoids the shortcomings of the traditional method, such as confusion distortion and amplitude distortion. 2) The computation to achieve filtering is reduced by nearly half. 3) It effectively improves the demodulation performance of the system. In this paper, the new structure performs the multistage digital demultiplexer and demodulation of the MF-TDMA signal. The results show no obvious signal distortion, which is demultiplexed by the new structure. The bit error rate of the demodulated signal is better than that of the traditional single carrier demodulator. The bit error rate is very close to the theoretical value of QPSK demodulation.

Multiobjective Anti-Collision for Massive Access Ranging in MF-TDMA Satellite Communication System

The collision of ranging signals in the process of massive concurrent access ranging seriously affects the networking speed of satellite communication networks. Random access schemes are usually used to reduce the collision probability, but their effects are limited due to the limitation of ranging access rules and the network size. To further improve the performance of access ranging, the idea of optimal access ranging parameters is introduced in this article. A multiobjective anti-collision algorithm (MOACA) is proposed to optimize the concurrent access ranging process of high-capacity nodes of Internet of Things (IoT) to multifrequency time-division multiple-access (MF-TDMA) satellite communication systems. The model of the ranging measurement process is put forward and the expressions of ranging measurement time, collision probability, and the number of ranging channels are derived. On this basis, a multiobjective optimization problem (MOP) of the access ranging process is established. In MOACA, an ideal point database is formed based on the solutions of the MOP problem with typical inputs, and the negotiation curves of objectives are introduced to obtain the most appropriate ideal point from the database under certain requirements and system states. Besides, MOACA also contains a single-objective problem (SOP) for achieving the ideal point in the situation where no matching pattern can be found in the database. The simulation result shows that MOACA can improve the performance of the concurrent access ranging process.

A Clock Synchronization Algorithm for the Satellite System Based on MF-TDMA

In order to ensure microsecond slot scheduling, all terminals must maintain high precision of time synchronization in MF-TDMA(Multi-Frequency Time Division Multiple Access) satellite communication system. Due to the different frequency of crystal oscillator at the terminal, the absolute value of the clock deviation is constantly increasing, so a clock synchronization algorithm is required to keep the time synchronization of the satellite system. The traditional satellite clock synchronization algorithm minimizes the clock error through periodic synchronization, but it only considers the phase offset, not the crystal frequency offset, the synchronization accuracy is low and waste of bandwidth resources. Based on the traditional satellite clock synchronization, this paper proposes a gradient descent algorithm for the satellite system based on MF-TDMA(GDAS), adding clock frequency offset prediction and compensation mechanism to improve clock synchronization accuracy and bandwidth resource utilization rate. The simulation results of the proposed algorithm has optimized the precision performance of clock synchronization.

EVALUATION OF INFLUENCE OF UNINTENTIONAL NON-STATIONARY INTERFERENCE ON FUNCTIONING OF SATELLITE COMMUNICATION SYSTEM WITH MULTIFREQUENCY TIME-DIVISION MULTIPLE ACCESS

The article considers the effect of non-Stationary unintentional interference on the earth station of a satellite communications system with Multi-Frequency Time-Division Multiple Access. The influence of non-stationary interference and white Gaussian noise on the earth station reception channel is compared using simulation modeling. The simulation model takes into account the effect of unintentional interference on the synchronization subsystem and the allocation of the boundaries of the transmitted packet of the receiver of the earth station of the satellite communication system. The probability of a bit error was used as a criterion for the quality of the satellite channel operation. The article shows the dependence of the protective ratio on the ratio of the preamble length to the packet length under the influence of pulsed interference. The obtained dependence can be used to assess the noise immunity of an earth station in a satellite communications system under the influence of pulsed interference.

Distributed Reliable and Energy-Efficient Scheduling for LR-WPANs

Pervasiveness of wireless networks drives the heterogeneity and density of devices in a vast diversity of environments. To achieve high reliability and low energy consumption while enabling pervasiveness is inherently a resource allocation problem. In low-rate wireless personal area networks, multi-frequency time-division multiple access methods are identified as compelling solutions to resource allocation via scheduling transmissions in time and frequency. This work presents the TREE (TRaffic-aware Energy Efficient) algorithm, an adaptive and distributed scheduling algorithm, designed to provide high reliability in terms of packet reception ratio while optimizing the energy consumption of each device. This algorithm schedules communications according to the packets in the queue and short-memory performance. Decisions are made locally, and low-interference scheduling emerges at the network level. TREE is an adaptive threshold-based model that allocates more network resources (e.g., timeslots) when the communication queue size crosses a threshold and frees resources if the resource was underutilized. Implemented over IEEE-802.15.4-TSCH and extensively tested in simulation and on real deployments up to 81 devices, the algorithm is compared to MSF, Alice, and Orchestra, the state of the art in time-slotted channel hopping scheduling. Results highlight a high reliability regarding packet reception ratio and a lower energy consumption compared to the state of the art.

A tradeoff resource allocation based on MF‐TDMA scheme in the multibeam data relay satellite systems

SummaryA tremendous increase in the number of distributed satellite constellations with the unscheduled burst data traffic will impose addition and diverse requirements on the DRS (data relay satellite) systems, which increases the complexity for beam management and affects a real‐time data return and acquisition. In this paper, we suggested that a large capacity can be achieved by a multibeam DRS system based on multifrequency time division multiple access scheme providing multiaccess for the distributed satellite constellations. Because the space‐based information network is characterized by the limited on‐board resources, a highly dynamic topology and time‐varying intersatellite links, we designed a 2‐stage dynamic optimization approach to separate the multiobjective optimization for frequency/time blocks and power, aiming at the rapidly converging to the optimal solution and at the same time meeting the fairness resource allocation. In particular, a capacity‐fairness tradeoff algorithm is proposed based on hybrid the enhanced genetic algorithm and the particle swarm optimization. Simulation results show that the tradeoff between maximizing total capacity and providing proportional fairness allocation is well balanced. The proposed algorithm can rapidly converge to adapt to the highly dynamic topology in data relay satellite systems.

Delay-aware and reliability-aware contention-free MF–TDMA protocol for automated RFID monitoring in industrial IoT

Abstract This paper presents a multi-frequency time division multiple access (MF–TDMA) protocol for Radio Frequency IDentification (RFID) monitoring system in industrial Internet of Things (IoT). Unlike critical industrial control system which requires 1–2 ms response in communication, the monitoring system in industries normally demands a guaranteed delay in hundred-millisecond level. Under the context of IoT, massive items are monitored, the requirements of the monitoring system thus further include reliable communication, low-power low-cost flexible hardware structure, scalable system infrastructure, and quality of service (QoS) on demand. To fulfill these, we employ a flexible hardware infrastructure which uses a centralized coordinator and a set of readers to support multiple frequency channels or technologies to maximize the system capacity. The proposed MF–TDMA protocol provides a scheduled communication both in time and frequency with an optional automatic repeat request (ARQ), independent/uniform synchronization and control mechanism, and an optimization of time slot allocation to increase the transmission reliability while decreasing the latency to a guaranteed bound. The performance evaluation indicates that based on the proposed MF–TDMA protocol, the system can promise more than 95% of the tags to enjoy than 50 ms waiting time. And a delay bound of 100 ms is achieved when a 16-byte packet is transmitted at 256 kbps. Moreover, 100% packet transmission ratio can always be obtained thanks to the schedule and optimization mechanism.

Novel MF-TDMA/SCPC switching algorithm for DVB-RCS/RCS2 return link in railway scenario

This work focuses on the return channel resource allocation in the DVB-RCS/RCS2 system for mobile terminals. A continuous carrier (CC) operation mode based on DVB-S2/S2X is considered and investigated. The paper focuses on the possibility of transmitting simultaneously in multifrequency–time division multiple access (MF-TDMA) or single channel per carrier (SCPC) medium access techniques, as suggested by a previous DVB-RCS+M standard. The introduction of this capability has also been analyzed for a new DVB-RCS2 standard that gives the possibility of using both return link (RL) modalities. Moreover, we propose a detailed study of the RL channel in a satellite platform in order to understand the operative range of SCPC and MF-TDMA techniques. The contribution seeks to provide some threshold indications to network operators for dynamically managing satellite resources.We considered the railway market, which is characterized by an N-LOS condition due to blockage caused by tunnels, vegetation, and buildings, as the reference scenario. Furthermore, we introduced a transparent gap filler (GF) solution to overcome this issue. Simulation campaigns are shown, in order to give satellite operators some guidelines, when they want to make use of this hybrid channel modality.

A Multiple Frequency Channels Reserved Timeslots Assignment Algorithm for Real-Time Traffic in MF-TDMA Satellite System

Timeslots assignment can have a great impact on the bandwidth allocation efficiency in multi-frequency time division multiple access (MF-TDMA) satellite system. In this paper a multiple frequency c...

MF-TDMA DAMA 방식 위성 망에서 효율적인 자원할당 시스템 설계

본 논문에서는 MF-TDMA (Multi Frequency-Time Division Multiple Access) DAMA (Demand-Assigned Multiple Access) 방식을 사용하는 위성 망에서 지상 단말이 네트워크 제어기에게 자원을 요청할 때, 자신에게 유입되어지는 트래픽에 대한 이전 정보(History) 즉, 트래픽 발생 패턴이나 트래픽 종류 등을 바탕으로 자원을 요청하고, 네트워크 제어기는 지상 단말들이 이전에 요청했던 정보(History)를 바탕으로 보다 효율적으로 위성 자원을 할당하여 위성 망 자원 할당 시간의 지연으로 인한 다량의 데이터 폐기를 최대한 억제하기 위한 MF-TDMA DAMA 방식 위성 시스템을 설계하였다. 미군의 전략적 군사 정보망 (Warfighter Information Network-Tactical, WIN-T) 커뮤니티에서는 L-3 Linkabit 다중 주파수-시간 분할 다중 접속 (MF-TDMA) 요청에 의해 할당되어지는 다중 접속 (DAMA) 네트워크 중심 파형 (Network Centric Waveform, NCW)을 full-mesh IP over SHF 위성 통신을 위한 네트워크 표준으로 선택하였다. MF-TDMA 위성 망에서는 네트워크 제어기(Network Controller, NC)가 최대 255개의 지상 단말들 (Earth Terminals, ETs)의 주기적인 자원요청에 대하여 동적으로 위성 망 자원을 할당하여 단말들 간의 통신을 가능하도록 한다. In this paper, I designed the satellite system, using the MF-TDMA (Multi Frequency-Time Division Multiple Access) DAMA (Demand-Assigned Multiple Access) method, that allocates the satellite resources more effectively to prevent a large quantity data discard when Earth Terminals (ETs) request their satellite network resource to Network Controller (NC) by using their history information, such as traffic pattern or traffic class which have been receiving, and the network controller allocates the satellite network resource and send to earth terminals by using his history information that earth terminals have been requested already. The U.S. Military Warfighter Information Network-Tactical (WIN-T) community has selected the L-3 Linkabit MF-TDMA DAMA Network Centric Waveform (NCW) as the networking standard for full-mesh IP over SHF satellite communications. In the MF-TDMA DAMA satellite network, network controller allocates the satellite network resources and enables maximum 255 earth terminals to communicate each other for periodic satellite network resource requests of earth terminals.

A MF-TDMA Signal Monitoring Receiver Based on Polyphase Filter

Concerning on the need of Multi-frequency Time Division Multiple Access (MF-TDMA) signal monitoring system, this paper investigates the relevant receiver architecture: the innate defect of the traditional sweep receiver is expounded, and after that we introduce the channelized receiver based on polyphase filter which is suitable for demultiplexing uniform-band signals as MF-TDMA. Simulation and experimental results show that the proposed receiver structure is less computational intensive, easier to implement, and hence more efficient for the monitoring system.

Delivery of triple-play services over broadband satellite networks

Digital video broadcast return channel via satellite system (RCS) is a key European standard that specifies a broadband satellite system using dynamic capacity assignment and multi-frequency time-division multiple access. This study introduces new architectural components for an RCS system to support advanced Internet protocol (IP)-oriented multimedia. This will allow closer integration of satellite networks with the next generation of multimedia-enabled networks enabling operators to offer triple-play services that simultaneously support voice over IP, television-over IP and other services. These types of services are particularly suited to next generation satellite systems that combine transparent and multi-spot beam satellites with on-board regenerative signal processing, and can evolve to use adaptive coding and modulation.

Suitability of DAMA and Contention-Based Satellite Access Schemes for TCP Traffic in Mobile DVB-RCS

The problem of optimizing access and bandwidth sharing among transmission control protocol (TCP) connections in the mobile digital video broadcasting return channel via satellite (DVB-RCS) is tackled in this paper. After sketching the general system architecture, we explicitly deal with the dynamic assignment of bandwidth to TCP connections on the return link, which is accomplished by a network control center (NCC) placed onboard the satellite. Mobile users access the satellite in multifrequency time-division multiple access (MF-TDMA), whereas they receive data from the NCC in time-division multiplexing (TDM). Two different techniques, based on deterministic and random access, are compared in terms of bandwidth usage and average completion time per connection, when the mobile user acts as both server and client. In the server case, to increase the TCP throughput, both packet-level forward error correction (FEC) on data sent by mobile users and a duplicated and delayed acknowledgment technique for TCP acknowledgment traffic from the NCC to the mobile users are applied. An analysis of the packet losses and a simulation campaign of file transfers by employing a realistic channel model has been carried out. The results of the analysis show the convenience of adopting a technique, in addition to the optimal data redundancy in different cases, such as the server or client role of users, their willingness to pay, the file size, and the environment type.

Timing Synchronization in MF-TDMA Systems for Geostationary Satellites[Topics in Radio Communications

The most expensive costs in satellite communication are incurred by the space segment. Therefore, effort should be focused on the efficient use of this resource. One aspect is the optimization of the physical layer, to approach the Shannon limit of channel capacity. In IP-based networks, communication between arbitrary terminals can be established, which must hold for IP-based satellite networks as well. A commonly used topology is the star network, where data are routed via the master station, which in case of satellite communications introduces a double hop for terminal-to-terminal connections [1]. A double hop requires twice the bandwidth and twice the response time, which is very unattractive for interactive services. This drawback is avoided with a fully meshed topology, where terminals can communicate directly. Of course, an appropriately designed access system is required in this context. The well-known multi-frequency, time-division multiple access (MF-TDMA) scheme slices the channel capacity along both time and frequency axes. Each fragment (slot) can be used by any station for direct communication [2, 3]. This article describes the method on an abstraction layer, starting with the high-level timing that copes with frame numbers; the low-level timing that maps the frame numbers to time instants of the local time scale; and ends with the time stamp handled in the hardware, where calculation delays and filter flushing affect the received time stamp. Compared to commercial systems, the method described in this article uses differential time stamps, which reduces the effort of the synchronization procedure.

Joint Channel Synchronization under Interference Limited Conditions

Spectral efficiency is of great concern in the return channel of satellite based broadband systems. In (Beidas, 2002) the feasibility of increased efficiency by reducing channel spacing below the symbol rate was demonstrated using joint detection and decoding for a synchronized system. We extend this work by addressing the critical synchronization problem in the presence of adjacent channel interference (ACI) which limits performance as carrier spacing is reduced. A pilot sequence aided joint synchronization scheme for a multi-frequency time division multiple access (MF-TDMA) system is proposed. Based on a maximum likelihood (ML) criterion, the channel parameters, including frequency, time and phase are jointly estimated for the channel of interest and the adjacent channels. The impact of ACI on the synchronization and detection performance is investigated. It is shown that joint channel parameter estimation outperforms single carrier synchronization with reasonable additional computational complexity in the receiver. Based on the proposed synchronization scheme in conjunction with an appropriate joint detection mechanism, see (Beidas, 2002), carrier spacing can be reduced significantly compared to current systems providing a substantial increase in spectral efficiency.

Joint Frequency Offset and Carrier Phase Estimation for the Return Channel for Digital Video Broadcasting

This paper investigates the design of joint frequency offset and carrier phase estimation of a multi-frequency time division multiple access (MF-TDMA) demodulator that is applied to a digital video broadcasting-return channel system via satellite (DVB-RCS). The proposed joint estimation algorithm is based on the interpolation technique for two correlation values in the frequency and phase domains. This simple interpolation technique can significantly improve frequency and phase resolution capabilities of the proposed technique without increasing the number of the correlation values. In addition, the overall block diagram of a digital communications receiver for DVB-RCS is presented, which was designed using the proposed estimation algorithms.

Allocation of QoS Connections in MF-TDMA Satellite Systems: A Two-Phase Approach

We address the problem of providing guaranteed quality-of-service (QoS) connections over a multifrequency time-division multiple-access (MF-TDMA) system that employs differential phase-shift keying (DPSK) with various modulation modes. The problem can be divided into two parts-resource calculation and resource allocation. We present algorithms for performing these two tasks and evaluate their performance in the case of a Milstar extremely high frequency satellite communication (EHF-SATCOM) system. In the resource-calculation phase, we calculate the minimum number of timeslots required to provide the desired level of bit-error rate (BER) and data rate. The BER is directly affected by the disturbance in the link parameters. We use a Markov modeling technique to predict the worst case disturbance over the connection duration. The Markov model is trained offline to generate a transition-probability matrix, which is then used for predicting the worst case disturbance level. We provide simulation results to demonstrate that our scheme outperforms the scheme currently implemented in the EHF-SATCOM system. The resource-allocation phase addresses the problem of allocating actual timeslots in the MF-TDMA channel structure (MTCS). If we view the MTCS as a collection of bins, then the allocation of the timeslots can be considered as a variant of the dynamic bin-packing problem. Because the this problem is known to be NP-complete, obtaining an optimal packing scheme requires a prohibitive amount of computation. We propose a novel packing heuristic called reserve channel with priority (RCP) fit and show that it outperforms two common bin-packing heuristics.

A low overhead encapsulation method for MF-TDMA

Modern radio systems have to meet demanding criteria, like availability of multicast, broadcast and point-to-point transmission, support of Quality of Service (QoS) and fairness, but also low overhead and low error multiplication. These criteria should all be combined for a successful technology. In this paper we explain the benefits of Low Overhead Encapsulation (LOE) and how it can be properly tailored for a Multi-Frequency-Time Division Multiple Access (MF-TDMA) access scheme.

Improving Efficiency of Timeslot Assignment for Non-realtime Data in a DVB-RCS Return Link: Modeling and Algorithm

This paper presents a dynamic resource allocation algorithm with multi-frequency time-division multiple access for the return link of interactive satellite multimedia networks such as digital video broadcasting return channel via satellite systems. The proposed timeslot assignment algorithm, called the very efficient dynamic timeslot assignment (VEDTA) algorithm, gives an optimal assignment plan within a very short period. The optimality and computational efficiency of this algorithm demonstrate that it will be useful in field applications.

Optimal Design of Superframe Pattern for DVB-RCS Return Link

We developed a method for optimal superframe design in the multi-frequency time division multiple access (MF-TDMA) return-link of a satellite multimedia interactive network called a digital video broadcasting return channel over satellite (DVB-RCS) sub-network. To find the optimal superframe pattern with the maximum data throughput, we formulated the design problem as a non-linear combinatorial optimization problem. We also devised the proposed simple method so that it would have field applicability for improving radio resource utilization in the MF-TDMA return link.