Haut PDF The virtual sub-channel protocol for satellite link communications

The virtual sub-channel protocol for satellite link communications

The virtual sub-channel protocol for satellite link communications

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Phase Noise Model Selection for Sub-THz Communications

Phase Noise Model Selection for Sub-THz Communications

has been confirmed by deriving the closed-form expression of the LLR between the correlated and uncorrelated PN models. Given the number of samples in a frame and the normalized corner frequency, an analytical condition has been proposed to select the best PN model between correlated and uncor- related. Simulation results have shown that an uncorrelated Gaussian process is an appropriate PN model for sub-THz communication systems. Finally, a practical application of model selection has been presented. We have investigated a link adaptation scheme where the transceiver selects the most robust modulation between a coherent and a differential one with regard to the PN performance. Though the results of the paper are presented within the context of sub-THz com- munication, the analysis remain true for other scenarios such as satellite communications or next generation of millimeter- wave communication (5G).
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Cross-Layer Optimization Techniques for Satellite Communications Networks

Cross-Layer Optimization Techniques for Satellite Communications Networks

In the author's opinion, the recently coined term "cross-layer" should not hide the fact that from the beginning of computer communications, engineers have put their energies on creating and main- taining systems that work, rather than on building well-oiled abstractions. Historically, abstraction in layers came later as RFC 1958 points it out: "The Internet and its architecture have grown in evolutionary fashion from modest beginnings, rather than from a Grand Plan" [32]. People behind the ARPANET faced complex engineering problems with specic constraints and resources, and made choices that resulted in having functions and protocols divided in layers as we know today. In a certain sense, they were "cross-layering" without knowing it, and of course, without really using these words. For instance, RFC 4907 [88] recalls that the use of upward link indications within the Internet architecture has a long history. In response to an attempt to send data to a host that was o-line, the ARPANET link layer protocol provided a "Destination Dead" indication, described in RFC 816: "Fault Isolation and Recovery" [91]. Some ARPANET experiments even included link-aware routing metrics calculations.
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On an efficient equalization structure for aeronautical communications via a satellite link

On an efficient equalization structure for aeronautical communications via a satellite link

Fig. 7: Proposed MAP equalizer structure IV. E FFICIENT CHANNEL EQUALIZATION FOR THE AERONAUTICAL CHANNEL A. Existing equalization solutions for sparse channels Sparse channel equalization has been considered in several works [4]–[7] to exploit the sparsity, mainly using parallel trellis based detection algorithm such as Viterbi or MAP algorithms. For equalization of zero padded sparse channels, the parallel MAP receiver is shown to be optimal [5], [6], [8]. For more general sparse channels, interference cancellation has been taken into account by introducing inter-trellis interfer- ence mitigation between parallel trellis. This is done at the expense of additional complexity due to the need for proper scheduling [7], [9]. Several extensions of these works have been considered for application in turbo-equalization [6], [10], [11]. However, in these approaches, there is no consideration for a particular structure of the sparse channel. In our context, we try to take further benefit from the sparse nature of the channel by considering the relative power levels of the different channel taps to have an efficient interference cancellation scheme combined with parallel equalizers.
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On the quality of VoIP with DCCP for satellite communications

On the quality of VoIP with DCCP for satellite communications

To bridge the gap between UDP and TCP, which is a reliable transport protocol and is not suitable for real time traffic, a new transport protocol for multimedia applications, Datagram Congestion Control Protocol (DCCP), has been proposed by IETF [2]. The main driver for having congestion control in an unreliable transport protocol was fairness to TCP traffic, which constitutes majority of the traffic on any Internet link. DCCP includes multiple congestion control algorithms identified by the Congestion Control Identifier (CCID), so that the application not needing reliable transport can select the appropriate congestion control method. CCID3 [3] and it’s small packet variant CCID4 [6] relies on the TCP-Friendly Rate Control (TFRC) algorithm which is suitable for traffic with smooth changes in sending rates, such as telephony or video streaming. TFRC, originally specified in [7] and updated in [37], is based on the TCP throughput equation and is therefore shown to be reasonably fair when competing with TCP flows. CCID3 is more suitable for streaming applications while CCID4 has been designed for applications with small packets like VoIP.
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On the Impact of Link Layer Retransmissions on TCP for Aeronautical Communications

On the Impact of Link Layer Retransmissions on TCP for Aeronautical Communications

(fistname.lastname@thalesaleniaspace.com) Abstract. In this article, we evaluate the impact of link layer retrans- missions on the performance of TCP in the context of aeronautical com- munications. We present the architecture of aeronautical networks, which is manly driven by an important channel access delay, and the various retransmission strategies that can be implemented at both link and trans- port layers. We consider a worst case scenario to illustrate the benefits provided by the ARQ scheme at the link layer in terms of transmission delay. We evaluate the trade-off between allowing a fast data transmission and a low usage of satellite capacity by adjusting link layer parameters.
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Determinism Enhancement of AFDX Networks via Frame Insertion and Sub-Virtual Link Aggregation

Determinism Enhancement of AFDX Networks via Frame Insertion and Sub-Virtual Link Aggregation

Nevertheless, there still exist some sources of non- determinism in AFDX networks. First, being an asynchronous protocol, a global time cannot be defined or used throughout the network. Note that the asynchronism is a feature of this network, which has been chosen in order to provide robustness in communications and to facilitate the design of applications using the network. A second source of non-determinism is related to fault detection in the destination ESs. Indeed, the AFDX standard does not force a VL to transmit frames if there is no data to transmit, even though the VL is available. This means that destination ESs cannot detect one or several consecutive frame losses (due to frame corruptions or device malfunctions on both redundant networks) until a valid frame arrives. For safety-critical applications, this raises a serious issue in terms of determinism and reliability. The motivation of this paper is then to enhance the determinism of AFDX networks by proposing a solution to frame arrival uncertainty. The proposed solution is based on the idea of inserting filler frames in a VL when its source is silent. This allows destination ESs of the VL to detect a fault if a frame is missing from the periodical pattern obtained with filler frames. Obviously, this mechanism does not affect the maximum band- width reserved for a VL and the worst-case performance of a regulated VL. However, inserting filler frames will increase network load and the average bandwidth used by a VL. In order to mitigate the impact on the overall network perfor- mance, we leverage a feature described in the AFDX standard, namely Sub-Virtual Link (Sub-VL) aggregation. We show that Sub-VLs aggregation in source ESs allows optimizing the bandwidth utilization of VLs. A Sub-VL aggregation strategy, formulated as a multi-objective optimization problem aimed at minimizing the overhead due to filler frame insertion and the delay introduced by Sub-VL aggregation, is then presented. It is worth noting that the proposed formulation can be applied to the generic Sub-VL aggregation problem in AFDX network design and to the extent of our knowledge, little work is dedicated to the optimization of Sub-VL aggregation. The
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SatERN: a PEP-less solution for satellite communications

SatERN: a PEP-less solution for satellite communications

based networks, standard TCP is unable to correctly grab the available resources. To overcome this problem, Performance En- hancing Proxies (PEPs), which break the end-to-end connection and simulate a receiver close enough to the sender, can be placed before the links with large delay. Although splitting PEPs does not modify the transport protocol at the end nodes, they prevent the use of security protocols such as IPsec. In this paper, we propose solutions to replace the use of PEPs named SatERN. This proposal, based on Explicit Rate Notification (ERN) protocols over IP, does not split connections and is compliant with IP-in- IP tunneling solutions. Finally, we show that the SatERN solution achieves high satellite link utilization and fairness of the satellite traffic.
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Enhanced HARQ for Delay Tolerant Services in Mobile Satellite Communications

Enhanced HARQ for Delay Tolerant Services in Mobile Satellite Communications

To deal with problems caused by link characteristics in mobile satellite communications, there are many solutions. One of these solutions is to use pure Forward Error Correction (FEC), which can makes the message very robust. However using FEC is not sufficient sometimes, due to the highly varying channel, where its quality changes dramatically. This make it difficult sometimes to decode the message, even if the used code is very robust. Alternatively, Automatic Repeat reQuest (ARQ) can be used as a solution to deal with channel variations, where transmitter attempts many retransmissions in case of unsuccessful decoding. ARQ messages without FEC, are not so robust to ensure a reliable communication.
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A comparison of iterative receivers for the non linear satellite channel

A comparison of iterative receivers for the non linear satellite channel

transmit signal x(t). This signal is sent to a satellite transpon- der which amplifies and redirects the uplink sub-band signal to the corresponding downlink channel and is thus composed of three processing stages. The Input MultipleXer (IMUX) is a band-pass filter which filters out the undesired adjacent channels, the power amplifier amplifies the input signal to a desired output power following the requirements of the link budget, and finally an Output MultipleXer (OMUX) mitigates out-of-band spectral regrowth in order not to interfere on adjacent channels at the downlink. The uplink noise and adjacent channels interferences are neglected. The satellite power amplifier is typically a Travelling Wave-Tube Amplifier the response of which is characterised by two memoryless functions relating the amplitude of the input signal to both the amplitude (AM/AM) and phase (AM/PM) of the output signal. The complex envelope of the signal at the output of the amplifier writes as follows:
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Extended interface ID for virtual link selection in GeoNetworking to IPv6 Adaptation Sub-layer (GN6ASL)

Extended interface ID for virtual link selection in GeoNetworking to IPv6 Adaptation Sub-layer (GN6ASL)

In order to allow for the resolution of a GeoUnicast destination GN_ADDR from an IPv6 destination address using virtual interfaces of type Ethernet V2.0/IEEE 802.3 LAN, the GeoNetworking address space shall remain 48-bit wide (size of the MID field in the GeoNetworking address). In particular, as described in TS 102 636-6-1 [6], table 1, note 1, the GN6ASL resolves an MID from a unicast destination IPv6 address and passes it to GeoNetworking via the GN-DATA.request primitive (clause H.2). Then, the GeoNetworking protocol entity is responsible for deriving a full GN_ADDR from the MID. This full GN_ADDR shall be derived from a LocTE (if it exists) or by executing the Location Service with Request GN_ADDR field containing only the MID part and the other bits set to 0.
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Effect of residual channel estimation errors in random access methods for satellite communications

Effect of residual channel estimation errors in random access methods for satellite communications

The problem to be addressed in this paper is the impact of residual channel estimation errors on recent TDMA based RA methods. The main issue is to be able to estimate the channel parameters in the case of multiple superimposed signals and to achieve performance close to the perfect knowledge case. This challenge has already been addressed in part in the existing literature. In [5] a method based on the Expectation- Maximization (EM) algorithm is presented to estimate channel parameters simultaneously. In [6], another approach uses the autocorrelation to derive channel amplitude and frequency offsets from packets that did not experience collision. In [7], channel estimation using EM is evaluated for a network coded diversity protocol (NDCP). We have also presented a first con- tribution of our work in [8], where we have used an EM based channel estimation method and evaluated experimentally the effect of imperfect interference cancellation on the decoding of the remaining packet.
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Constant Delivery Delay Protocol Sequences for the Collision Channel Without Feedback

Constant Delivery Delay Protocol Sequences for the Collision Channel Without Feedback

Keywords—Collision channel without feedback, protocol se- quences, wireless ad-hoc networks, multiple access. I. I NTRODUCTION Many research activities have been conducted in the context of multiple access communications in which several users access a shared channel. Without synchronization, users might transmit packets at the same time causing collisions and the loss of packets. A possible solution is to use protocol that achieves collision-free transmission such as the well known time division multiple access (TDMA). However, in commu- nication systems such as impulse radio [1], wireless sensor networks [2] and ad hoc mobile networks [3], devices have constrained resource, limited communication power and need a flexible transmission scheme. Collision-free protocols such as TDMA may not be practical for these systems, since it requires stringent time synchronization. Other contention based random access protocols such as IEEE 802.11 CSMA/CA [4] can provide a more flexible transmission scheme. However, they still require some backoff algorithms and a feedback link which may not be practical for these low resource devices. These systems require simple multiple access protocol with no stringent time synchronization, frequent channel monitoring and feedback link.
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Random access techniques for satellite communications

Random access techniques for satellite communications

Initially, a consortium called Digital Video Broadcasting (DVB) was created to offer a world- wide digital television service through an international open standard. Satellite television was standardized in the DVB-S (DVB-Satellite) [42197], which has been later improved in the DVB-S2 (Second Generation) [V1.15a] through coding (low-density parity-check LDPC codes) and enhanced modulation schemes, VCM (Variable Coding and Modulation) and ACM (Adaptive Coding and Modulation). DVB-S2X (Extension) [V1.15b] extended the DVB-S2 towards more flexibility in the modulation schemes, better filtering ...etc. Also DVB-SH (Satellite services to Handhelds) [V1.11] introduced advanced service delivery based on In- ternet Protocol (IP) for small size terminals like mobile phones. Most of these standards operate on the forward link for broadcasting services that reach the user terminals. However, advanced applications that require bi-directional systems made it necessary to define the re- turn link. DVB-RCS [79003] that stands for Return Channel Link via Satellite, and later its corresponding Second Generation (DVB-RCS2) [A1511] are hence the leading standards for a variety of interactive applications. IP based services are covered by the DVB-RCS2. Information are carried in MF-TDMA frames organized in time slots. Many waveform char- acteristics of reference are defined. They list the modulation, its order and the coding rate to use, the length of the useful information in bytes and symbols, and the total burst length in symbols in addition to its type as well. For example, the third waveform, in the DVB-RCS2, whose IDentifier (ID) is 3 uses QPSK (Quadrature Phase Shift Keying) modulation with a code rate of 1/3. The useful information length is 456 symbols and the total burst length is 664 symbols whose type is TRF1. The latter means that the time slot in the MF-TDMA frame occupies two BTU (Bandwidth-Time Unit).
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Effect of residual channel estimation errors in random access methods for satellite communications

Effect of residual channel estimation errors in random access methods for satellite communications

The problem to be addressed in this paper is the impact of residual channel estimation errors on recent TDMA based RA methods. The main issue is to be able to estimate the channel parameters in the case of multiple superimposed signals and to achieve performance close to the perfect knowledge case. This challenge has already been addressed in part in the existing literature. In [5] a method based on the Expectation- Maximization (EM) algorithm is presented to estimate channel parameters simultaneously. In [6], another approach uses the autocorrelation to derive channel amplitude and frequency offsets from packets that did not experience collision. In [7], channel estimation using EM is evaluated for a network coded diversity protocol (NDCP). We have also presented a first con- tribution of our work in [8], where we have used an EM based channel estimation method and evaluated experimentally the effect of imperfect interference cancellation on the decoding of the remaining packet.
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Channel estimation with a priori position for aeronautical communications via a satellite link

Channel estimation with a priori position for aeronautical communications via a satellite link

I. I NTRODUCTION In wireless communication systems, the estimate of the channel impulse response is necessary for the coherent demod- ulation. For this, it is common to introduce training sequences in the transmitted signal [1]. If the channel varies over time and if one knows the coherence time, one can then define the frames so that the channel can be assumed to be stationary on each. When estimating directly the equivalent discrete baseband channel impulse response, the use of the maximum likelihood (ML) criterion leads to an optimal solution. How- ever, this estimation process can be very complex due to the memory channel which is generally long. In the presence of Gaussian noise, ML estimation becomes equivalent to the least square criterion (LS)[2] and reaches the Cramer- Rao bound (CRB).Under some considerations, improvements can be achieved if one is able to perform joint estimation of both attenuations and delays of the continuous impulse response which is generally practically achieved through an iterative estimation procedure [2]. These methods are based on a explicit multipath parametric model. However, in some transmission systems, such as aeronautical communication systems, some parameters for the continuous channel can be determined in a very accurate manner, such as the delays of the different paths, based on some geometrical considerations from geolocation techniques [3]. This extra a priori allows us to further reduce the unknowns of our system and leads to more efficient multipath parametric based estimation methods. Only the attenuation coefficients of the multipath channel will be estimated. This has to be compared with the classical estimation of all taps of the discrete equivalent channel as usually done. Other features could be exploited such as the sparsity of the channel [4].
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On an efficient equalization structure for aeronautical communications via a satellite link

On an efficient equalization structure for aeronautical communications via a satellite link

Fig. 10: Coded BPSK, C/M = 6 dB Fig. 11: Coded 8-PSK, C/M = 6 dB VI. C ONCLUSION In this paper, we have investigated an efficient imple- mentation of channel equalization for aeronautical channels using a satellite link. The discrete equivalent channel can be decomposed in a strong sparse channel component with additional low power interference residual terms. Based on this model, an efficient equalizer structure can be derived that considers independent parallel MAP equalizers with proper it- erative interference cancellation. The proposed scheme exhibits interesting performance. Further investigations will consider turbo-equalization based on this structure.
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Channel Estimation and Equalization for CPM with Application for Aeronautical Communications via a Satellite Link

Channel Estimation and Equalization for CPM with Application for Aeronautical Communications via a Satellite Link

N X T −1 n=0 b p,n l p (t − nT s ) (4) It will be useful to derive a model that allows frequency domain equalization, enabling significant gain in complexity at the receiver. To perform frequency domain equalization, we first need to circularize the channel, as for linear modulation, enabling the efficient use of FFT operators at the receiver. To do so, we can use several methods such as a Cyclic Prefix (CP) or a known Unique Word (UW) (also called Training Sequence). We suppose the use of UW despite its loss of spectral efficiency compared to CP. This is mainly motivated by the fact that UW can be used to perform parameters estimation as carrier and phase frequency, channel estimation... [12]. It seems important to recall that, due to the CPM memory, some termination symbols must be added at the end of the data block in order to ensure the phase continuity and
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Channel estimation with a priori position for aeronautical communications via a satellite link

Channel estimation with a priori position for aeronautical communications via a satellite link

I. I NTRODUCTION In wireless communication systems, the estimate of the channel impulse response is necessary for the coherent demod- ulation. For this, it is common to introduce training sequences in the transmitted signal [1]. If the channel varies over time and if one knows the coherence time, one can then define the frames so that the channel can be assumed to be stationary on each. When estimating directly the equivalent discrete baseband channel impulse response, the use of the maximum likelihood (ML) criterion leads to an optimal solution. How- ever, this estimation process can be very complex due to the memory channel which is generally long. In the presence of Gaussian noise, ML estimation becomes equivalent to the least square criterion (LS)[2] and reaches the Cramer- Rao bound (CRB).Under some considerations, improvements can be achieved if one is able to perform joint estimation of both attenuations and delays of the continuous impulse response which is generally practically achieved through an iterative estimation procedure [2]. These methods are based on a explicit multipath parametric model. However, in some transmission systems, such as aeronautical communication systems, some parameters for the continuous channel can be determined in a very accurate manner, such as the delays of the different paths, based on some geometrical considerations from geolocation techniques [3]. This extra a priori allows us to further reduce the unknowns of our system and leads to more efficient multipath parametric based estimation methods. Only the attenuation coefficients of the multipath channel will be estimated. This has to be compared with the classical estimation of all taps of the discrete equivalent channel as usually done. Other features could be exploited such as the sparsity of the channel [4].
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A comparison of iterative receivers for the non linear satellite channel

A comparison of iterative receivers for the non linear satellite channel

transmit signal x(t). This signal is sent to a satellite transpon- der which amplifies and redirects the uplink sub-band signal to the corresponding downlink channel and is thus composed of three processing stages. The Input MultipleXer (IMUX) is a band-pass filter which filters out the undesired adjacent channels, the power amplifier amplifies the input signal to a desired output power following the requirements of the link budget, and finally an Output MultipleXer (OMUX) mitigates out-of-band spectral regrowth in order not to interfere on adjacent channels at the downlink. The uplink noise and adjacent channels interferences are neglected. The satellite power amplifier is typically a Travelling Wave-Tube Amplifier the response of which is characterised by two memoryless functions relating the amplitude of the input signal to both the amplitude (AM/AM) and phase (AM/PM) of the output signal. The complex envelope of the signal at the output of the amplifier writes as follows:
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