FEC Code Rate Research Articles

An ANALYSIS OF DVB-T2 TV BROADCAST TESTING DRIVE TEST AND FIELD STRENGTH METHODS IN THE JAKARTA SERVICE AREA

Indonesia has adopted DVB-T2 as the technology standard for terrestrial digital television broadcasting. This research aims to test and analyze the reception quality of DVB-T2 TV broadcasts in the DKI Jakarta service area. The research was conducted using drive test and field strength methods to test and evaluate the quality of digital television broadcasts. Tests were conducted in various locations in the DKI Jakarta service area using the Gsertel Hexylon TV Analyzer technical device to test DVB-T2 TV broadcast signals. The field strength test results were more accurate and higher values were generated than the drive test. Several parameters such as signal level and MER are evaluated and analyzed to find out what affects their values. The transmitter parameter settings such as modulation, FEC code rate, FFT Mode, Guard Interval, and Pilot Pattern greatly affect the signal level and MER values. The optimization performed on CH 24 also managed to maintain its signal level value of 18.19 dB and its MER of 55.01 dBµV to maintain broadcast stability during a technical failure of the transmitter on CH 1.

Performance evaluation of free space optics communication system in the scenario of triple play service using probabilistic shaping scheme

An advanced triple-play-services (TPS) system based on probabilistic shaping (PS) scheme for free- space-optical (FSO) communication network is proposed and experimentally demonstrated for the first time. In this paper, the PS-32-quadrature amplitude modulation (QAM) 10 Gb/s data, PS-32-QAM 10 Gb/s voice and PS based 2.5 Gb/s HDTV signal are successfully transmitted over 600-m FSO link employing doublet lens scheme. The PS and polarization multiplexing technique both are helped to upgrade the spectral efficiency and improve the system performance. Normalized-generalized-mutual-information (NGMI) threshold is 0.92 at FEC code rate 9/10 for voice/data and 0.82 at FEC code rate 4/5 for video signal are selected to successfully execute the experiment. The spectral efficiency of our system is achieved by calculating the NGMI and shaping parameter (α), 13.6 bits/s/Hz (voice and data) and 10.41 bits/s/Hz (video) spectral efficiency are obtained at maximum α. Experimental results prove that PS based FSO communication system provides flexible data rate and greater spectrum efficiency and also be a powerful candidate to alleviate pressure on modern optical transport system.

Demonstration of flexible access in a rate-adaptive visible light communication system with constellation probabilistic shaping.

In this paper, we propose and experimentally demonstrate a distance-based rate-adaptive visible light communication (VLC) system based on constellation probabilistic shaping (PS) for a multiple-user access network. For users with different access distance, we optimize the transmission data rate close to the channel capacity by applying PS combined with code-rate adaptive FEC at the transmitter side according to the per-user signal-to-noise ratio (SNR) budget. This is also proved to be a convenient way to ensure fine granularity of information rate per user with wider flexibility compared with non-PS modulation formats. We also investigate the performances of different PS-QAM modulation formats under different SNR level when considering peak-to-average power ratio (PAPR) in the VLC system. Optimal PS-QAM and FEC code-rate are also studied in the flexible VLC access system. In addition, in order to overcome the nonlinear distortion in the system, a neural network (NN) is used as the post-equalization. Finally, we demonstrate the flexible access with the net data-rate from 1.84 to 3.37 Gbps for 20 and 1-meter distance, with a maximum 28% overall capacity improvement compared with regular non-PS modulations.

Rate Redundancy and Entropy Allocation for PAS-OFDM Based Mobile Fronthaul

From the perspective of an experimentalist, we discuss the comparison framework that ensures the same information rate in probabilistic shaping (PS) signals. Theoretically, the information rate can be tuned by adjusting the target entropy, scaling the signal bandwidth and adjusting FEC code rate. In practice, the information rate tuning should be based on the hardware feasibility (e.g., DAC resolution, available analog bandwidth, cost of rate adaptation). Adjusting a constellation entropy rate without considering FEC redundancy will cause an over-estimation of the PS system performance gain. To avoid the over-estimation issue, the modified pre-FEC threshold for PS signal is also proposed to estimate the system performance accurately. The modified pre-FEC threshold is obtained from the FEC code rate of PS signal. Moreover, we experimentally investigated the adaptive entropy allocation scheme in a millimeter-wave analog radio over fiber fronthaul using the modified pre-FEC threshold. By grouping the subcarriers into PS units and using the same QAM order, the proposed scheme can reduce the required data frame length as well as the processing complexity. Notably, this method requires neither dynamic FEC coding rate nor bandwidth adjusting method. Up to 2.5-dB power margins and a smoother pre-FEC performance among PS units are achieved in a frequency selective fading channel. If the modified FEC threshold were not used, it would induce up to 0.7-dB over-estimation in the received sensitivity. This indicates the importance of employing the proposed methods for comparison when FEC is used in combination with PS.

Energy Optimization For Wireless Video Transmission Employing Hybrid ARQ

In this paper we investigate energy-optimized wireless video transmission employing a hybrid automatic repeat request. We formulate the problem as maximizing the video quality, subject to a constraint on the wireless transmission energy consumption. We consider multiple parameters in multiple layers in a wireless video transmission system: transmit power, alphabet size, FEC code rate, maximum number of transmissions, and unequal video data importance. An analytical framework is proposed to include these parameters, which allows us to divide this problem into two sub-problems: data transmission and unequal error protection. The problem is tackled by solving the two sub-problems, which are done by exhaustive search and convex optimization, respectively. Simulations of different videos show that the proposed scheme outperforms methods using conventional data transmission and/or unequal error protection.

Adaptive-Truncated-HARQ-Aided Layered Video Streaming Relying on Interlayer FEC Coding

Interlayer forward error correction (IL-FEC) coding constitutes an effective unequal error protection (UEP) scheme conceived for transmitting layered video over wireless channels. In contrast to traditional UEP schemes, it operates by embedding extra information concerning the base layer (BL) into the enhancement layers (ELs) without requiring extra transmission resources. The received EL packets assist in the decoding of the BL to reduce the distortion of the reconstructed video. The optimum scheduling of the IL-FEC coded layered video streaming in a truncated hybrid automatic repeat request (THARQ)-aided system is an open problem. Hence, in this paper, we conceive an adaptive THARQ (ATHARQ) algorithm for finding the most appropriate scheduling of the IL-FEC coded layered video packets for the sake of minimizing the video distortion under the constraint of a given total number of transmission time slots (TSs). Furthermore, we develop a method of online coding-rate optimization algorithm for our IL-ATHARQ transmission scheme to find the best FEC code rate distribution among the video layers that results in the lowest possible video distortion. When using a recursive systematic convolutional (RSC) code, our simulation results show that the proposed rate-optimized (RO) IL-ATHARQ system outperforms the traditional THARQ transmission scheme by about 5.3 dB of $E_{b}/N_{0}$ at a peak signal-to-noise ratio (PSNR) of 38.5 dB. Viewing the improvements in terms of the video quality, 2.5 dB of PSNR improvement is attained at an $E_{b}/N_{0}$ of 15 dB.

Robust video broadcasting over 802.11a/g in time-correlated fading channels

In order to deliver video streams efficiently over WiFi to many thousands of consumer handheld devices, broadcast protocols must be employed. In this mode of operation the received video quality can deteriorate rapidly as a result of high application layer packet loss which occurs because MAC frame retransmission cannot be used. In this paper we develop a robust video delivery solution for broadcast transmission over 802.11a/g. Using a cross-layer WiFi simulator in combination with an accurate time-correlated fading channel, the received video quality is evaluated for broadcast H.264 video sequences. Application layer cross-packet forward error correction is then used together with error concealment at the video client. Furthermore, the application of an external packet interleaver is considered. Combining a block size of two hundred packets (which introduces a 4.8 second delay) and an application layer FEC code rate of 0.75 our results demonstrate that video can be successfully broadcast over WiFi to many thousands of handheld terminals at large-scale spectator events.

Throughput-Energy Efficiency Performance of TCP with Link Layer FEC/ARQ on Wireless Links

In this paper, we investigate the throughput-energy efficiency performance of TCP Tahoe and Reno on wireless links using a FEC/ARQ protocol at the link layer. The effect of link layer (LL) parameters like the LL packet size, number of LL retransmission attempts, and FEC code rate on the TCP performance is evaluated. It is shown that the retransmissions at the link layer must persist long enough to outlast the average bad state duration of the multipath Rayleigh fading process in order to achieve throughput performance better than TCP without ARQ at the link layer. We also evaluate the energy consumption performance of TCP Tahoe and Reno with and without LL FEC/ARQ by defining energy efficiency as the average number of successful TCP packet transmissions per unit energy consumed. It is shown that without LL ARQ, using TCP Reno instead of TCP Tahoe leads to some degradation in throughput and a much more significant degradation in energy efficiency. However, with a suitable LL ARQ in place, TCP Reno performs as good as TCP Tahoe.

An adaptive resource sharing strategy for TDMA

AbstractA satellite‐based TDMA network consisting of four stations within different rain climatic zones has been operated in the 20/30 GHz frequency range using a recently developed flexible TDMA system allowing for FEC code rate and transmission bit rate variation.In this paper a strategy is presented to counteract overall link degradations due to atmospheric attenuation by dynamic allocation of resources. A spare time slot within the TDMA frame as a ‘common resource’ for bit rate and code rate switching offers up to 12 dB gain, whereas up‐link power control, as it is implemented in this configuration, can cope with fades of 8 dB at maximum.For an experimental network configuration the expected long‐term performance in terms of system availability is estimated for a viable version of the resource sharing strategy. Thereby, a model to calculate the probability of concurrent attenuation at the individual earth‐station sites (‘satellite based diversity’) has been applied and the resulting probability to exhaust the resources is considered as a function of the degrading correlation between attenuations.Simulations with measured data via a ‘channel simulator’ and satellite measurements during the summer months of 1994 with the adaptive TDMA system are planned to test the functionality of the fade countermeasure strategy. Long‐term propagation measurements on large‐scale site diversity are required to verify predictions on the effective utilization of common resources.