Modified SNR gap approximation for resource allocation in LDPC-coded multicarrier systems

The signal-to-noise ratio (SNR) gap approximation provides a closed-form expression for the SNR required for a coded modulation system to achieve a given target error performance for a given constellation size. This approximation has been widely used for resource allocation in the context of trellis-coded multicarrier systems (e.g., for digital subscriber line communication). In this contribution, we show that the SNR gap approximation does not accurately model the relation between constellation size and required SNR in low-density parity-check (LDPC) coded multicarrier systems. We solve this problem by using a simple modification of the SNR gap approximation instead, which fully retains the analytical convenience of the former approximation. The performance advantage resulting from the proposed modification is illustrated for single-user digital subscriber line transmission

Error performance prediction of randomly shortened and punctured LDPC codes

In this contribution, we show that the word error rate (WER) performance in the waterfall region of a randomly shortened and punctured low density parity check code can be accurately predicted from the WER performance of its finitelength mother code. We derive an approximate analytical expression for the mutual information (MI) required by a daughter code to achieve a given WER, based on the MI required by the mother code, which shows that the gap to the capacity of the daughter code grows the more the code is punctured or shortened. The theoretical results are confirmed by simulations (where the random shortening and puncturing pattern is either selected independently per codeword or kept the same for all codewords) for practical codes on both the binary erasure channel and the binary-input additive white Gaussian noise channel

Tenogenically induced allogeneic mesenchymal stem cells for the treatment of proximal suspensory ligament desmitis in a horse

Suspensory ligament injuries are a common injury in sport horses, especially in competing dressage horses. Because of the poor healing of chronic recalcitrant tendon injuries, this represents a major problem in the rehabilitation of sport horses and often compromises the return to the initial performance level. Stem cells are considered as a novel treatment for different pathologies in horses and humans. Autologous mesenchymal stem cells (MSCs) are well known for their use in the treatment of tendinopathies; however, recent studies report a safe use of allogeneic MSCs for different orthopedic applications in horses. Moreover, it has been reported that pre-differentiation of MSCs prior to injection might result in improved clinical outcomes. For all these reasons, the present case report describes the use of allogeneic tenogenically induced peripheral blood-derived MSCs for the treatment of a proximal suspensory ligament injury. During conservative management for 4 months, the horse demonstrated no improvement of a right front lameness with a Grade 2/5 on the American Association of Equine Practitioners (AAEP) scale and a clear hypo-echoic area detectable in 30% of the cross sectional area. From 4 weeks after treatment, the lameness reduced to an AAEP Grade 1/5 and a clear filling of the lesion could be noticed on ultrasound. At 12 weeks (T-4) after the first injection, a second intra-lesional injection with allogeneic tenogenically induced MSCs and platelet rich plasma was given and at 4 weeks after the second injection (T-5), the horse trotted sound under all circumstances with a close to total fiber alignment. The horse went back to previous performance level at 32 weeks after the first regenerative therapy and is currently still doing so (i.e., 20 weeks later or 1 year after the first stem cell treatment). In conclusion, the present case report demonstrated a positive evolution of proximal suspensory ligament desmitis after treatment with allogeneic tenogenically induced MSCs

Equine allogeneic chondrogenic induced mesenchymal stem cells are an effective treatment for degenerative joint disease in horses

Degenerative joint disease is one of the main causes of equine early retirement from pleasure riding or a performance career. The disease is initially triggered by an abnormal loading of normal cartilage or a normal loading of abnormal cartilage. This primary insult is accompanied with joint inflammation, which leads to further progressive degeneration of the articular cartilage and changes in the surrounding tissues. Therefore, in search for an effective treatment, 75 adult horses with early signs of degenerative fetlock joint disease were enrolled in a randomized, multicenter, double-blinded, and placebo-controlled study. Fifty animals were injected intra-articularly with the investigational veterinary product (IVP) consisting of allogeneic chondrogenic induced mesenchymal stem cells (ciMSCs) with equine allogeneic plasma, and 25 horses were injected with 0.9% NaCl (saline) control product. From week 3 to 18 after treatment, lameness scores (P<0.001), flexion test responses (P<0.034), and joint effusion scores (P<0.001) were remarkably superior in IVP-treated horses. Besides nasal discharge in both treatment groups, no adverse events were observed during the entire study period. On long-term follow-up (1 year), significantly more investigational product-treated horses were working at training level or were returned to their previous level of work (P<0.001)

Modulo loss reduction in spatial multiplexing systems with Tomlinson-Harashima precoding

When a multi-user communication system over a block-fading MIMO channel utilizes Tomlinson-Harashima precoding in the downstream direction, to eliminate the interference between the spatially multiplexed data streams, the conventional detection, involving a modulo operation at the receiving terminals, is known to yield a performance degradation that becomes considerable at low SNR. In this contribution, we propose a novel detection method that exploits sending one bit of extra information per user and per frame to the receiver, which indicates whether or not the considered user can detect all its data within the frame without performing a modulo operation. Moreover, in the case of M-PAM transmission it is possible to optimize the rotation of the constellations at the transmitter, maximizing for each frame the number of users for which no modulo operation is required. Numerical results show that in the case of 2-PAM the novel detection algorithm is able to completely recover the modulo loss experienced by the conventional detection method without an increase in transmit power, and to outperform 4-QAM (with conventional or novel detection) in terms of mutual information at low SNR

Modulo loss reduction for Tomlinson-Harashima precoding in a multi-beam satellite forward link

Full frequency reuse in multi-beam satellite communication systems allows to achieve a high capacity, provided that the inter-beam co-channel interference (CCI) can be properly dealt with. Tomlinson-Harashima precoding (THP) is a popular technique applied at the basestation transmitter to cancel the interference in the forward link. However, the conventional detection of THP, involving a modulo operation at the receiver terminals, is known to suffer from modulo loss, which becomes considerable at low SNR. This contribution explores alternative detection techniques to reduce the modulo loss. We point out that by applying proper signal rotations at the basestation transmitter, these alternative detectors almost completely recover the modulo loss for 2-PAM, achieving a higher mutual information (MI) than 4-QAM at low SNR

Semi-analytical evaluation of concatenated RS/LDPC coding performance with finite block interleaving against impulsive noise

This contribution considers the word error rate (WER) performance of a concatenated coding scheme in the presence of impulsive noise (IN), which is modeled as gated white Gaussian noise, with on-and off-times governed by a 2-state Markov model. The scheme consists of a Reed-Solomon (RS) outer code and a low-density parity-check (LDPC) inner code, which are separated by a block interleaver with finite depth. The Monte Carlo (MC) simulation of the WER of such communication systems is time-consuming, especially when targeting low error rates and examining several interleaver settings. We present a semi-analytical evaluation of the WER, which relies on a simple semi-analytical statistical model for the number of byte errors in a segment of the information word after LDPC decoding. To compute the error performance of the concatenated code corresponding to different parameters of the RS code and the interleaver, we require only the WER and byte error rate (ByteER) of the inner subsystem, determined by the LDPC code and the considered constellation, in the presence of stationary white noise. We show that the semi-analytical WER of the concatenated system closely matches the WER resulting from MC simulations and use the proposed model to investigate the effect of the interleaver depth on the WER performance