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Differential amplitude phase shift keying (DAPSK) is a promising modulation technique for use in high-mobility environments, as it does not require channel estimation. In this paper, a novel reduced complexity soft demodulator for high-order DAPSK constellations is proposed. The main idea relies on a two-step approximation of the sum-log demapper. In the first step, a parallel factor analysis (PARAFAC) decomposition is used to approximate log-likelihood ratios. Next, the basis functions obtained through the first step are approximated by piecewise-linear curves. Numerical optimization techniques are employed for the PARAFAC decomposition and its piecewise-linear approximation whose parameters are then stored in a lookup table. It has been verified through computer simulations that the proposed scheme clearly outperforms the scheme proposed in the paper “Reduced-complexity noncoherent soft-decision-aided DAPSK dispensing with channel estimation,” ( IEEE Trans. Veh. Technol. , vol. 62, pp. 2633–2643, 2013.), while also having lower computational cost. Moreover, it is shown that the performance of the exact sum-log demapper and the proposed demapper is very close for ${\text{2}}\times {\text{4}}$ and ${\text{4}}\times {\text{16}}$ DAPSK constellations.

In this letter, we introduce a novel method for demodulation of general amplitude- and phase-shift keying (APSK) constellations. By noting that the max-log log-likelihood ratio (LLR) is a piecewise linear function of the received signal, we devise a scheme to determine in which linear region that the received signal falls, obtain the linear parameters from a lookup table and compute the LLR. This method is general and works for any APSK (two-dimensional) constellation. By pruning the search tree, it also provides a mechanism for performance-complexity tradeoff and we show that its complexity is much lower than a previously published scheme (which only works for regular APSK constellations).

In this letter, we derive a low-complexity method for demodulating nonuniform PAM signals. With uniform Gray-coded M-PAM constellations, the reflective symmetry can be exploited to demodulate the signals with low complexity. However with nonuniform constellations, this symmetry is lost and more complicated computations are required. We derive an analytic expression for the max-log LLR functions and show that they are piecewise linear functions. Based on this, we devise a demodulation algorithm that has complexity $\mathcal{O} \left(\log_2 M \right)$ as opposed to $\mathcal{O} \left(M \right)$ for the exhaustive search. We also present an approximation with reduced complexity and only modest performance degradation.

A fog radio access network (F-RAN) is studied, in which $K_T$ edge nodes (ENs) connected to a cloud server via orthogonal fronthaul links, serve $K_R$ users through a wireless Gaussian interference channel. Both the ENs and the users have finite-capacity cache memories, which are filled before the user demands are revealed. While a centralized placement phase is used for the ENs, which model static base stations, a decentralized placement is leveraged for the mobile users. An achievable transmission scheme is presented, which employs a combination of interference alignment, zero-forcing and interference cancellation techniques in the delivery phase, and the \textit{normalized delivery time} (NDT), which captures the worst-case latency, is analyzed., Comment: 6 pages, 7 figures

In this letter we consider array codes that are used for erasure protection in, e.g., wireless sensor networks. By treating the network as distributed storage with multiple sources, information can be exchanged between the nodes in the network allowing each node to store parity symbols relating to data from other nodes. We show how these array codes can be reconfigured to minimise the probability that some data symbols are not correctly exchanged (and therefore reducing the erasure correcting capability of the array code). We also present a suboptimal method for a class of array codes which significantly reduces the complexity of the reconfiguration while maintaining almost all of the performance.

In this paper, we introduce a lowest-density maximum-distance separable MDS array code, which is applied to a Smart Meter network to introduce reliability. By treating the network as distributed storage with multiple sources, information can be exchanged between the nodes in the network allowing each node to store parity symbols relating to data from other nodes. A lowest-density MDS array code is then applied to make the network robust against outages, ensuring low overhead and data transfers. We show the minimum amount of overhead required to be able to recover from r node erasures in an n node network and explicitly design an optimal array code with lowest density. In contrast to existing codes, this one has no restrictions on the number of nodes or erasures it can correct. Furthermore, we consider incomplete networks where all nodes are not connected to each other. This limits the exchange of data for purposes of redundancy, and we derive conditions on the minimum node degree that allow lowest-density MDS codes to exist. We also present an explicit code design for incomplete networks that is capable of correcting two node failures. Copyright © 2015 John Wiley & Sons, Ltd.

Fundamental limits of communication is studied in a 4 × 4 interference network, in which the transmitters are equipped with cache memories. Each of the receivers requests one file from a library of N equal-size files. The caches at the transmitters are filled without the knowledge of the user demands, such that all possible demand combinations can be satisfied reliably over the interference channel. The achievable normalized delivery time (NDT) is studied under centralized cache placement. By combining the interference alignment (IA) and zero-forcing (ZF) techniques, a novel caching and transmission scheme is presented, and is shown to be optimal for all possible cache sizes; fully characterizing the NDT for the 4× 4 interference network with caches at the transmitter side.

While obtaining the channel state information (CSI) required to perform Interference Alignment (IA) in a centralised MIMO network is a challenge, this is compounded in unplanned wireless networks that may be decentralised - not to mention composed of devices with varying degrees of complexity and capability. This is of particular interest to heterogeneous networks and the Internet of Things (IoT). The disparity in antenna number caused by this variation in capability can be taken advantage of, increasing the sum rate of the network providing the users are aware of the capabilities of their neighbours. This paper presents a method for estimating with a high degree of certainty the number of antennas each user possesses, endowing the receiver with the vital CSI required before channel equalisation or estimation can take place. The method is correlation based and so is not restricted to full rank channels where the receiving device has an equal or greater number of antennas than the transmitter. This permits the use of the method in situations where the rank of the channel is restricted, either by design or by nature (e.g. 'keyhole' channels).

In this paper, we extend the concept of maximum-distance separable (MDS) array codes to a larger class of codes, where the array columns contain a variable number of data and parity symbols and the codewords cannot be arranged, in general, in a regular array structure with equal column length. These new codes, named irregular MDS array codes, find applications in problems of distributed data storage with multiple sources of information generating data at unequal rates. We solve the problem of finding optimal parity symbol allocations that achieve minimum redundancy for a given level of protection against block erasures. We provide a classification of irregular MDS array codes according to the parameters of their parity symbol allocation and we show how regular MDS array codes are a special case of this wider class. We derive necessary and sufficient conditions for such irregular array codes to be MDS and extend the concept of the lowest density generator matrix. Finally, we show how a simple constructive method allows to design irregular lowest density MDS array codes with alphabet size independent of the size of the array columns.

Spectrum handoff is a promising spectrum management approach that enables the secondary user to continue its transmission by switching to a sensed-as-idle channel when the current channel is re-occupied by the primary user. Periodic sensing is commonly employed to facilitate spectrum handoff by improving sensing accuracy so that the secondary user has a better opportunity to avoid transmission collision via switching to a truly idle channel. However, byproducts of spectrum handoff, such as extra energy cost on channel switch, switch delay, and collisions due to excessive switch, have been largely underestimated. These by-products which have significant impacts on the overall performance lead to the questions: Should we switch the channel? How often should we switch? In this article we first review several different periodic sensing and handoff mechanisms. Then we identify the trade-off between the secondary user's energy efficiency and transmission reliability. The proposed switch-stay model is elaborated and studied to balance the aforementioned trade-off in light of sensing accuracy, the probability of collision, throughput and delay constraints. Upper and lower bounds of the stay probability on the current channel are illustrated from these constraints. In addition, we discuss the implementation of an antenna-selection sensing mechanism in order to relax these bounds for a better energy-efficient spectrum management solution. Performance evaluation and some open issues are also discussed in this article.

INTRODUCTION: Barrett esophagus (BE) is a complication of gastroesophageal reflux disease. We wish to determine the effects of surgery on the histology of the esophageal mucosa and evaluate Quality of Life. MATERIALS AND METHODS: Twenty-seven patients with columnar-lined esophagus (CLE) metaplasia underwent laparoscopic Nissen-Rossetti fundoplication. Patients were submitted to close follow-up. RESULTS: One patient voluntarily left follow-up after surgery. CLE was still present in 18 patients (66.6%); no patient developed dysplasia or esophageal adenocarcinoma. Two patients with gastric metaplasia and 1 patient with intestinal metaplasia had regression at 12 and 24 months after surgery (11.1%). DeMeester and Johnson score decreased from 38.69 (SD ± 51.44) to 11.99 (SD ± 18.08) at 6 months, 12.69 (SD ± 12.91) at 12 months, and it was 11.38 (SD ± 6.43) at 24 months. Preoperative gastroesophageal reflux disease-health related quality of life was 19.90 (SD ± 18.54), 9.80 (SD ± 8.77) at 6 months, 9.57 (SD ± 9.14) at 12 months, and 11.53 (SD ± 6.48) at 24 months. Short form-36 measurement showed significant improvement. CONCLUSIONS: Management of CLE requires multidisciplinary approach. Medical therapy does not prevent biliary reflux into the esophagus. Surgical therapy is effective and long lasting. It should be performed by experienced surgical teams.

A $K_T \times K_R$ cache-aided wireless interference network, in which both the transmitters and the receivers are equipped with cache memories is studied. Each user requests one file from a library of $N$ popular files. The goal is to design the cache contents without the knowledge of the particular user demands, such that all possible demand combinations can be satisfied reliably over the interference channel. The achievable sum degrees-of-freedom ($\mathrm{sDoF}$) and the normalized delivery time (NDT) are studied for centralized and decentralized network architectures, respectively. First, using a combination of interference alignment (IA), zero-forcing (ZF) and interference cancellation (IC) techniques, a novel caching and transmission scheme for centralized networks is introduced, and it is shown to improve the $\mathrm{sDoF}$ upon the state-of-the-art. Then, the NDT is studied when the content placement at the receiver caches is carried out in a decentralized manner. Our results indicate that, for this particular network architecture, caches located at the receiver side are more effective than those at the transmitter side in order to reduce the NDT., Comment: 6 pages, 4 figures, conference

The paper focuses on the performance analysis of channel assignment algorithms for peer to peer wireless ad hoc network by means of realistic channel model. The channel assignment is modeled as an edge colouring problem and two colouring algorithms including random and greedy colouring have been studied using the realistic 3D ray tracing based path loss model and its performance is compared with the theoretical model. The simulation study shows that the algorithms perform better with the ray tracer model with around 10 dB improvement in SINR as compared to the theoretical model.

Multiple-input multiple-output (MIMO) techniques are now being commonplace in wireless communication systems as they provide diversity and spatial multiplexing gains compared to single-input single-output (SISO) systems. Due to the induced high complexity of maximum likelihood (ML) detection for MIMO systems, suboptimal detection is usually employed but at a performance loss. This loss has been fully characterized for linear receivers, namely, zero-forcing (ZF) and minimum mean square error (MMSE) detectors. Interestingly, it has been noticed that in case of coding across transmit antennas, the MMSE receiver showed significant improvement over ZF in terms of outage probability at low spectral efficiencies, whereas for high spectral efficiencies, both receivers showed similar behaviour. We fill the gap between the two extreme cases (i.e., ML and linear receivers) through relaxing the linearity constraint by considering group receivers (viz. group zero-forcing (GZF) and group minimum mean square error (GMMSE) detectors) with coding across transmit antennas. We first derive the diversity-multiplexing tradeoff (DMT) for those group detectors. Next, we characterize the peculiar rate-dependent outage behaviour of the GMMSE, where it is found that tolerating additional detection complexity provides performance advantage w.r.t the MMSE at specific ranges of spectral efficiency. We corroborate our theoretical analysis via numerical simulations.

Tone reservation (TR) is a well-known and practical strategy to reduce peak-to-average power ratio (PAPR) in OFDM signals. In TR some unused or reserved subcarriers are used to accommodate a peak-cancelling signal that lowers the PAPR of the time domain OFDM signal. Several methods have been proposed to optimise the peak-cancelling signal, amongst which the so called active-set method has been shown to converge very quickly to a minimum PAPR solution for a real baseband signal with no additional power constraints. However, for a general complex baseband signal and/or when the peak-cancelling signal has to be power limited, there is no guarantee of optimality. Moreover, in the complex baseband model, the TR optimisation problem is a quadratically constrained quadratic program (QCQP), which has a prohibitive computational cost. In this paper we introduce a tree-search approach to designing the TR signal based on the sphere decoding/encoding principle. The method is proved to provide the minimum PAPR solution in the limit of fine lattice quantisation. Simulation results show a significant margin of improvement over the best known active-set method.

Precoding is a common technique used in wireless transmissions where multiple data streams are spatially multiplexed by an access point or base station to a number of receiving stations by using multiple transmit antennas. The design of the precoder can be divided into two separate functional blocks: 1) the transmit filters, for example zero-forcing or minimum mean-square error, with unit norm columns and 2) the power loading. In a conventional system the transmit filters and power loading strategy are applied on individual OFDM subcarriers or groups of subcarriers. In this paper we study a codeword based power loading strategy combined with precoding. In this new technique the power allocation is done jointly across the subcarriers spanned by the encoded transmissions to optimise some codeword-related performance requirement. Simulations show that this strategy offers performance gain in terms of both packet error rate and throughput over conventional per-subcarrier power loading. The saving in computational complexity can also be significant, particularly for the MMSE precoder design.

We study the effect on diversity of using the sphere encoder-based vector perturbation (VP) technique of Peel and the lattice reduction-aided techniques (Babai approximations) of Windpassinger on a subset of the transmitted symbols. For a system with n diversity channels, we prove that the diversity order gap between the maximum diversity of n achieved by the full-size VP and the minimum diversity of 1 provided by linear precoding can be bridged by applying VP to a group of transmitted symbols. In particular, we prove that the diversity order is n-l , where l is the number of symbols that are not vector-perturbed. We show that this result holds true for lattice-reduction with both the rounding-off and nearest plane Babai approximations. The result shows that in terms of diversity, the group of vector-perturbed users counts as a single user. In fact, in a multiple-input and multiple-output Gaussian broadcast channel with l linearly precoded users, we can add up to n-l VP users and the diversity order for all users will decrease only by one, irrespective of how many VP users are added.

In this paper we derive a novel method for encoding the MIMO channel state information (CSI) for frequency selective channels and limited feedback. The technique is based on the decomposition of the directional information of a MIMO channel in a two-coordinate system formed by the tangent space of a Grassmann manifold and the tangent space of a unitary group. The first component provides a non-redundant description of the subspace spanned by a set of channel eigenvectors, while the second component provides a non-redundant addendum of information to identify the strongest channel vector directions within that subspace. One advantage of this feedback representation is that it allows to exploit the correlation of MIMO channels by applying standard source coding techniques to the two coordinate components. We also provide simulation results of an LTE downlink system, which show that the proposed CSI feedback description offers dramatic throughput improvement over the existing feedback scheme for MU-MIMO transmission.

This paper presents a novel method for overlaying an analogue value on top of a digital signal. By adding a phase rotation and a signature sequence to a block of digitally modulated data symbols, this analogue value can be conveyed to a receiver without significant degradation to the underlying digital data. A near-ML estimator is derived which is non-data driven and hence independent of the digital data sequence. It is shown that this method of signalling a value is superior to quantising it and adding it to the digital data stream. We analyse the performance of the analogue and digital methods and also compare them using simulations.

Laparoscopic Nissen fundoplication is currently the gold standard for surgical treatment of gastroesophageal reflux disease. The aim of this study was to present our experience with this procedure at 1 year of follow-up. Forty patients were operated on between January 2006 and July 2007, and 30 underwent a 24-hour postoperative pH-metry study. Ninety-two percent of the patients were asymptomatic at a follow-up of 12 months. All pH-metric parameters improved. DeMeester and Johnson's score was reduced from 44.7 to 7.75; endoscopy with histologic samples revealed the healing of esophagitis in all patients; 4 (13%) patients complained of dysphagia, which resolved within 1 month after surgery. Twenty-seven (90%) patients were completely satisfied by their surgical results. One year after surgery, 24-hour ph-metric results show that laparoscopic Nissen fundoplication can completely control acid reflux with relatively few complications and a high degree of patient satisfaction.

Multiuser MIMO vector perturbation precoding facilitates multiple representations of the transmit symbols in order to improve transmit power normalisation of the transmitted signal. All the receiver needs to do is to apply a modulo operation to undo the perturbation. However existing system with multiuser MIMO support, such as LTE, employ linear precoding. This means that these legacy users will not be able to operate together with new users with vector perturbation capabilities, reducing the system throughput and flexibility in resource allocation. In this paper we present a novel precoding technique which allows the joint precoding of legacy and new users. The precoding ensures that no perturbations are made to linearly precoded users, while minimising the power normalisation using a modified sphere encoder. We also show that the diversity order of the joint precoding scheme is the difference between the number of transmit antennas and the number of legacy users, regardless of the number of new users.

In this paper we introduce the concept of lowest density MDS array codes on incomplete graphs. Array codes are used to protect against erasures by adding redundancy. Application examples are networks of wireless sensors or smart meters, where nodes can exchange data between themselves and store parity information for protection against multiple node failures. Array codes can ensure that the data generated by the whole network can be reconstructed when only a subset of nodes are accessible. However, conventional array codes assume that all nodes can communicate with one another to exchange information; in a practical network, some nodes may not be connected between them. Such a network can be described by an incomplete graph and in this paper we discuss the conditions on the minimum node degree that allow lowest density MDS array codes to exist on such graphs. We also present an explicit design for network configurations with minimum node degree. The code is capable of correcting up to two erased nodes for any incomplete graph with an even number of nodes. It can also recover any r node failures for one nonisomorphic class of regular incomplete graphs with a number of nodes that is multiple of r.

In this paper a switch-stay model is proposed for spectrum access by a secondary user in the presence of a primary user, which considers the impact of spectrum handoff delay. This model is then studied to balance the trade-off between the secondary user's energy efficiency and transmission reliability in light of the probability of collision, throughput and delay constraints. Bounds on the probability of stay on the current channel are derived from multiple constraints. An antenna selection sensing mechanism is then proposed to relax these bounds by enhancing the sensing performance. The advantages of the proposed antenna selection sensing are verified by numerical results.

This article presents a distributed antenna system (DAS) architecture for small-cell base stations (BTSs), whereby cooperation between the DAS infrastructure and the BTS allows for an increase in performance compared to conventional systems, while at the same time keeping complexity and cost at low levels. Specifically, the article investigates the improvements in uplink physical layer performance achieved by adding an initial antenna combining step in the DAS system before conventional combining and equalization at the BTS. This initial step can be implemented in a very low-complexity fashion by performing all operations in the time domain and using channel state information calculated at the BTS itself. The article presents this technique in the context of an LTE DAS system. Results from both a software simulator and a custom-made hardware prototype are presented, establishing the feasibility of the proposed architecture.

In this paper† we consider a recently proposed quantise-forward network coding strategy, whereby a relay is used to help resolve the interference caused by independently transmitting source nodes. The relay listens to the interfering signals and performs a course lattice-based quantisation of the observations without decoding the information messages. The quantised observations are forwarded to the destination nodes on an interference-free channel and help the receivers improve the decoding process. We generalise the optimisation of the nested lattice construction to any number of quantisation bits and evaluate the strategy on the turbo codes used in the 3GPP long term evolution (LTE) to assess the viability of the strategy in LTE-based small cell deployments.

Background: We investigated Quality of Life (QoL) and Johnsson & DeMeester score of patients after Nissen-Rossetti fundoplication. Materials and Methods: From January 2007 to June 2008, 43 patients with chronic gastroesophageal reflux underwent laparoscopic Nissen-Rossetti fundoplication; 7 were lost during the follow-up. Patients underwent endoscopy, 24-hour pH-metry, Gastroesophageal Reflux Disease-Health-Related Quality-of-Life (GERD-HRQL), and Short Form 36 (SF-36) questionnaires preoperatively, 6 months, and 12 months after surgery. Results: Endoscopic findings revealed complete healing of esophagitis in all patients. Barrett esophagus was still present. Six patients reported persistence of symptoms but postoperative pH-metry and endoscopy showed the absence of reflux; 2 patients (5.5%) were still on proton pump inhibitor therapy at 12 months. Seven patients (19.4%) reported dysphagia for solids for at least 3 months. Readmission for dysphagia was required for 2 (5.5%) and 1 patient underwent endoscopic dilatation. At 6 and 12 months, no dysphagia was reported. During the follow-up, no gas-bloat syndrome was reported. The Johnsson & DeMeester score and QoL measurement obtained from GERD-HRQL and SF-36 revealed a significant improvement in the related domain. At 6 months, 23 patients (63.8%) were completely satisfied and after 12 months, 30 patients (83.3%) were satisfied. Conclusions: Nissen-Rossetti fundoplication is safe and effective for the treatment of GERD, improving QoL.

Gastroesphageal reflux disease (GERD) is a common condition in the general population, affecting patients' quality of life and predisposing to Barrett's esophagus and its most fearsome complication, esophageal adenocarcinoma. The aim of this study is to compare objective and subjective outcomes of laparoscopic Nissen-Rossetti fundoplication after 2 years of follow-up.Seventy-six GERD patients underwent laparoscopic Nissen-Rossetti fundoplication. Patients were subjected to close follow-up.The DeMeester and Johnson score average decreased from a mean preoperative value of 35.48 (SD±40.24) to 9.83 (SD±6.40) at 6 months; at 12 months it was 11.44 (SD±10.28), and at 24 months it was 10.25 (SD±5.61). GERD Health-Related Quality of Life decreased from a preoperative value of 23.04 (SD±11.59) to 9.84 (SD±8.98) at 6 months, 8.34 (SD±8.98) at 12 months, and 6.8 (SD±6.46) at 24 months. The Short Form-36 measurement showed significant improvement.GERD patients need adequate reflux control. Successful antireflux surgery is more effective than medical therapy in preventing both acid and bile reflux. Surgical therapy is effective in terms of reflux control and improvement in quality of life. Strict and rigorous follow-up with both subjective and objective tests is important in order to identify asymptomatic recurrence of reflux after surgery.

Gastro-esophageal reflux disease (GERD) is “a condition which develops when the reflux of stomach contents causes troublesome symptoms (i.e., at least two heartburn episodes per week) and/or complications” (Vakil et al 2006) and represents one of the fastest growing disease affecting the alimentary tract. Recently studies on the epidemiology of GERD demonstrating that GERD is a highly prevalent disorder with 10-20% of individuals affected in western civilization (Dent et al 2005). When GERD is defined as twice weekly reflux over several months, 10-20% of individuals in Western civilization are affected, which is significantly higher than in Asian population (5%) (Bonatti et al 2008). In a large prospective American cohort study is reported that 25% of investigated individuals experienced nocturnal reflux symptoms (Fass et al 2005). A recent population-based study demonstrated the prevalence of reflux symptoms to be 44% with 24% of individuals experiencing symptoms for two days or more per week. The prevalence of oesophagitis and Barrett’s oesophagus was 12% and 1.3% respectively, irrespective of symptoms (Zagari et al 2008).Thirty-three per cent of individuals with oesophagitis and 46% with Barrett’s oesophagus were asymptomatic. Severe GERD can lead to potentially avoidable complications including severe oesophagitis with scarring and stricture formation, Barrett’s esophagus and adenocarcinoma.When symptoms become frequent and severe enough to require regular medication, there is a significant impact on quality of life (Ware et al 1992).(QOL)

BACKGROUND Gastroesophageal reflux disease (GERD) has emerged as one of the most common diseases in the modern civilization.The immense success of laparoscopic surgery as an effective treatment of GERD has established the minimally invasive surgery as the gold standard for this condition with lower morbidity and mortality, shorter hospital stay, faster recovery, and reduced postoperative pain. METHODS Articles were sourced from PubMed and Medline, using the MeSH terms "gastroesophageal reflux disease" and "laparoscopic surgery" and "fundoplication technique." The selection of articles was based on peer review, journal, relevance, and English language. RESULTS AND CONCLUSIONS There are some controversies with regard to the technique. First, whether total or partial fundoplication is the more appropriate treatment for GERD; second, if a total fundoplication (360 degrees) is performed, what is the effect of fundic mobilization and the division of short gastric vessels. In this review article the authors evaluate the most recent articles to establish the parameters for a "gold standard technique" in antireflux surgery.

Codebook-based limited feedback precoded MIMO systems involve vector quantization, which may require intensive computations, especially for large codebooks. In this paper we show how the complexity and codebook storage can be significantly reduced by using a special alphabet to generate the codebook. Simulation results show that the performance with the generated codebook is comparable with other codebooks which have higher complexity.

In this paperwe look at the problem of successively refining the description of a Gaussian i.i.d. source in a Grassmannian space. This problem is relevant, for example, in the encoding of channel state information for the limited feedback MIMO broadcast channel. We show how it is possible to achieve an isotropic distribution of the error vector by applying unitary transformations, which simplifies the problem of finding optimal codebooks for the error quantisation. Reconstruction error analysis and numerical tests show how the proposed technique can, in practice, perform very close to the distortion-rate bound and suggest that, in some cases, these successive error descriptions can be optimal refinements of one another.

We introduce a scheme for overlaying an analogue phase signal on digitally modulated symbol sequences. The scheme applies phase rotations to generic PSK or QAM constellations that are rotationally invariant by multiples of an angle, and uses phase signatures to spread the phase signal over a block of symbols in order to resolve any ambiguity in the rotated constellations. A near maximumlikelihood estimator for reconstructing the analog signal is derived as well as conditions for the design of the signature sequences. The proposed scheme may be used as an alternative to quantisation and digital transmission in control channels of mobile or WLAN standards, where one or more phase references have to be provided to the terminals and where other existing digitally-modulated control information can serve as host. Analysis and simulations show that the analogue overlaying scheme can offer better performance than a digital scheme with the same spectral efficiency for the host signal, in terms of both mean square error of the reconstructed phase information and bit error rate of the underlying digital stream.

Dirty-paper coding (DPC) is a well-known construction capable of achieving the ultimate capacity limit of the MIMO broadcast channel (MIMO-BC). One recently proposed DPC scheme is based on Voronoi codes, minimum mean-square error generalised decision-feedback equaliser (MMSE-GDFE), dither and lattice decoding. Building on this approach, in this paper we introduce a linear pre-coder for the MIMO-BC, which, although sub-optimal compared to the original DPC construction, may be regarded as a valuable option for practical applications because of its simplicity and its close-to-capacity achievable rates. We provide a theoretical analysis as well as numerical results which show the achievable rates of our linear pre-processing scheme compared to the DPC construction and to another recently proposed linear technique for throughput maximisation, based on gradient nulling.

Between January 1, 1971, and December 31, 1978, 73 patients with adenocarcinoma of the cardia were treated by total gastrectomy with distal esophagectomy. The continuity of the alimentary tract was restored by esophagojejunostomy using a Roux-Y procedure in 32 patients and jejunal loop interposition in 41 patients. The early postoperative mortality rate was 18 percent. The overall 5 year survival rate was 26.7 percent, and the 5 year survival rate for stage I and II disease was 91.6 percent and 25 percent, respectively, whereas none of the stage III and IV patients survived more than 4 years. Fifty-eight percent of the patients without nodal involvement lived more than 5 years. The 5 year survival rate was only 9.3 percent in the presence of nodal metastases. Our 5 year survival rates suggest the value of elective total gastrectomy for stage I or II adenocarcinoma of the cardia. Jejunal loop interposition is a time-consuming but functionally superior procedure in comparison to other reconstructive procedures after total gastrectomy.

The therapy of esophageal diverticula has not yet been defined, even if our knowledge of the functional alterations involved seems to have clarified the pathogenesis of this disease. The objective of this study was to verify the results of surgical therapy carried out following physiopathological criteria.

Compressive sensing (CS) is a new signal acquisition framework, which allows for a signal recovery from far fewer samples than what is required by traditional sampling methods. In this paper we propose new strategies for adaptively adjusting the number of CS samples in wireless sensor networks (WSNs). Additionally, in the signal reconstruction procedure we apply homotopy algorithm to update the reconstructed signals. The reduction of CS samples and the homotopy update reduce the computational complexity and save processing time and energy for both the fusion centre and wireless sensors. The proposed techniques are investigated numerically in various WSN scenarios.