Adaptive algorithms for improving the throughput in an indoor mobile s-aloha ds-cdma system

This paper presents a novel Adaptive DSCDMA Slotted-ALOHA packet random access scheme with transmitter-based spreading codes for mobiles. It is aimed at improving the throughput and message delay delivery when traffic load values below the saturation point of the conventional DS-CDMA Slotted-ALOHA system are sensed in the channel. For this purpose, one Mobile and two Base Station assisted algorithms are envisaged to control the change of the transmission rate according to the traffic load. These algorithms revealed that the optimum behavior, obtained using a Markov Chain model, may be almost reached at a low complexity cost.Peer ReviewedPostprint (published version

A mobile controlled algorithm for improving the throughput in a s-aloha ds-cdma system

This paper presents a novel adaptive DS-CDMA slotted-ALOHA packet random access scheme with transmitter-based spreading codes for mobiles. It is aimed at improving the throughput and message delay delivery when traffic load values below the saturation point of the conventional DS-CDMA slotted-ALOHA system are sensed in the channel. For this purpose a mobile assisted algorithm is envisaged to control the change of the transmission rate according to the traffic load. This algorithm revealed that the optimum behavior, obtained using a Markov chain model, may be almost reached at a low complexity cost. Moreover, priorities between mobiles could be easily established. Finally, a traffic model based on a realistic statistical length distribution of the messages illustrates how the delay delivery can be greatly reduced.Peer ReviewedPostprint (published version

Adaptive schemes for packet data in a ds-cdma environment

This paper presents a novel adaptive DS-CDMA slotted-ALOHA packet random access scheme for improving the throughput of the conventional DS-CDMA slotted-ALOHA system. For this purpose a mobile-assisted algorithm is envisaged to control the change of the transmission rate according to the traffic load. This algorithm revealed that the optimum behavior may be almost reached at a low complexity cost. Moreover, the proposed algorithm was found to be robust to intercell interferencePeer ReviewedPostprint (published version

Dect architecture proposal for a construction site

A construction site is an specific environment where important propagation related issues have to be considered. In particular an important problem concerns the coverage of buildings under construction and therefore continuously changing. The deployment of a DECT system in such scenarios can not be carried out as usually, by means of DECT base stations linked by cables. Another specific problem is that no measures can be done prior to decide the best place for the antennas since initially the building does not exist. In this paper a way to solve both problems is proposed through a specific system architecture, a propagation model and a combination of software with a CAD tool.Peer ReviewedPostprint (published version

An efficient data transmission policy in an integrated voice-data ds-cdma network

CDMA schemes appear to be promising access techniques for coping with the requirements of third-generation mobile systems, mainly because of their flexibility. This paper proposes an adaptive S-ALOHA DS-CDMA access scheme as a method for integrating non-real time (i.e. Internet applications) and real-time (i.e. voice) services, by exploiting the potentials of CDMA under time-varying conditions. The adaptive component terminals autonomously change their transmission rate according to the total (voice+data) channel occupancy, so that the minimum possible data delay is almost always achieved.Peer ReviewedPostprint (published version

Performance analysis of a second order delay-lock loop with application to a CDMA system with multipath propagation

CDMA systems require synchronization between the received sequence and the locally generated sequence. This is done by means of a delay-lock loop (DLL). The differential equation of an incoherent second-order DLL has been programmed. The mean time to lose lock (MTLL) of the DLL is a very important design parameter. The authors have obtained this parameter by computer simulation and are able to plot the MTLL as a function of the signal to noise ratio in the data bandwidth. In a narrow-band system, the simulation shows that the effect of the fast Rayleigh fading is a performance degradation even with high mean signal to noise ratio. Assuming a wide-band system, so that the receiver has enough bandwidth to resolve the different propagation paths, the authors propose a modified DLL scheme. The MTLL of the proposed DLL is evaluated using a dynamic simulation of the multipath channel. The results show an improvement with respect to the conventional DLL.Peer ReviewedPostprint (published version

Performance of a linear interference canceller for a ds/cdma synchronous system based on the ekf delay estimator

Since the conventional detector often fails to produce reliable decisions for a CDMA channel, several new multiuser detectors have previously proposed. In the present paper, the authors propose both a simple linear scheme for interference cancellation, which exhibits good performance, and a synchronism scheme based on the extended Kalman filter (EKF) to achieve synchronization among the different users at the base station, for a direct-sequence code-division multiple-access (DS/CDMA) synchronous system. The influence of the synchronism scheme on the performance of the interference canceller is analyzed under Rayleigh multipath fading.Peer ReviewedPostprint (published version

Seguretat, qualitat i higiene a la venda de carn a Barcelona durant el segle XIV

El present estudi analitza el consum de carn a la Barcelona del segle XIV a través de les «ordinacions» municipals. Al llarg del text s'intenta observar la mentalitat amb què s'enfronten els consellers als problemes que generen l'entrada d'animals destinats a carn a la ciutat, el seu escorxament i, finalment, la seva venda. Problemes que vénen donats per diversos factors: d'una banda, per les diferències que s'estableixen, segons la mentalitat dels metges i dels consellers, entre les diferents carns des d'un punt de vista nutritiu i de salut; cosa que genera tota una legislació concreta que intenta separar les diferents carns per categories. D'altra banda, pels perills que certes carns, pel seu origen o per defectes de manipulació o conservació, poden provocar a la salut humana. Es pot concloure que els consellers a través de les «ordinacions» van intentar conciliar el bon abastament càrnic de la ciutat amb la correcta identificació de les carns, i van aconseguir, així, que tothom sabés en tot moment la qualitat o perillositat de la carn que estava comprant.The present study analyzes the consumption of meat in Barcelona during the 14century through city ordinations. Along the text we try to observe the mentality that the consellers took to face the problems generated by the entrance of food-production animals in the city, its sacrifice and, finally, its sale. Problems that are given by diverse factors: on the one hand, the difference between the doctors and the consellers mentality among the different meats from a nutritional and health point of view, factor that generates the whole legislation to separate the different meats in categories; on the other hand, the dangers that certain meats, because of its origin or the faults on their manipulation or conservation, can produce in human health. It is possible to conclude that the consellers tried to get a good meat supply to the city with a correct identification of meats, in order that everyone knew at all time the quality or the harmfulness of meat they were buying

L'Aprovisionament de carn a Barcelona durant els segles XIV i XV

L'objectiu d'aquesta tesi era analitzar tot el procés de comercialització de la carn en una gran ciutat baixmedieval com Barcelona. Per aconseguir aquest objectiu s'ha buidat de manera sistemàtica tota la documentació de l'Arxiu Històric de la Ciutat de Barcelona (AHCB). El fet de triar la documentació d'aquest arxiu de manera preferent es deu a l'important paper que va tenir el Consell de Cent en el mercat de la carn. Al llarg de la recerca s'ha pogut comprovar que els carnissers monopolitzaven tot el procés comercial de la carn, des de la compra del bestiar a les fires i mercats ramaders fins a la venda al detall a la taula. Aquest monopoli del mercat per part dels carnissers fins a finals del segle XV ens ha permès delimitar clarament els dos actors principals en aquest comerç: els carnissers i els consellers de la ciutat. Dos actors amb interessos contraposats o coincidents segons el moment del procés mercantil del qual parlem; així, eren coincidents en la defensa dels privilegis de pas i pastura de la ciutat contra els senyors feudals de Catalunya, però eren absolutament divergents a l'hora de fixar els preus i les imposicions que gravaven la carn, o a l'hora de crear les mesures higièniques que regulaven la venda de carn.The aim of this thesis was analyze the whole process of meat trade in a great city of Late Middle Ages like Barcelona. To obtain this aim the whole documentation of the AHCB (Historical Archive of the City of Barcelona) has been analyzed in a systematic way.We chose the documentation of this archive because the Consell de Cent played an important role on the meat market. Along the research we verify that the butchers were monopolizing the whole commercial process of the meat, they bought the cattle in the fairs and cattle markets and they sold the meat in their stalls. The monopoly of the market by the butchers until ends of the 15th century has allowed us to delimit clearly the both principal actors in this trade: the butchers and the city ministers. This two actors had opposite or coincidental interests in the different moments of the mercantile process; so, they were coincidental in the defense of the tolls and pasture city privileges against the Catalonias feudal Lords, but they were absolutely divergent in the moment to fix the meat prices and taxes, or in the moment to create the hygiene legislation of the meat