This paper studies the decoding of traceability codes though the lens of the Koetter- Vardy algebraic soft-decision decoding algorithm. Our focus is on the multiplicity assignment step. Previous works assumed that the cost of the multiplicity matrix had to approach infinity. We show that the cost of the multiplicity matrix can be polynomial in the code length in order to find identifiable traitors.

Approaches based on signal-strength measurements are at present the most popular on indoor location due to their reasonable accuracy and cost effective deployment. In this paper, we present an outlook of our research on different alternatives to implement an indoor location approach based on signal-strength measurements for an uncoordinated environment, an environment where we do not have any control on the number of access points, their location, availability or transmitted power.

A fingerprinting code is a set of codewords that are embedded in each copy of a digital object with the purpose of making each copy unique. If the fingerprinting code is$c$-secure with$\epsilon $error, then the decoding of a pirate word created by a coalition of at most$c$dishonest users, will expose at least one of the guilty parties with probability$1-\epsilon $. The Boneh–Shaw fingerprinting codes are$n$-secure codes with$\epsilon _{B}$error, where$n$also denotes the number of authorized users. Unfortunately, the length the Boneh–Shaw codes should be of order$O(n^{3}\log (n/\epsilon _{B}))$, which is prohibitive for practical applications. In this paper, we prove that the Boneh–Shaw codes are ($c< n$)-secure for lengths of order$O(nc^{2}\log (n/\epsilon _{B}))$. Moreover, in this paper it is also shown how to use these codes to construct binary fingerprinting codes of length$L=O(c^{6}\log (c/\epsilon ) \log n)$, with probability of error$\epsilon < \epsilon _{B}$and an identification algorithm of complexity$poly(\log n)=poly(L)$. These results improve in some aspects the best known schemes and with a much more simple construction.

In a fingerprinting scheme, a distributor places marks in each copy of a digital object. Placing different marks in different copies uniquely identifies the recipient of each copy, and therefore allows tracing of the source of an unauthorised redistribution. A widely used approach to the fingerprinting problem is the use of error correcting codes with a suitable large minimum distance. With this approach, the set of embedded marks in a given copy is precisely a code word of the error correcting code. We present two different approaches that use side information for the tracing process. The first approach deals uses the Guruswami–Sudan errors-and-erasures list decoding algorithm whereas the second approach shows the use of a full side information matrix.

In this paper we present constructions of traceability codes based on the Chinese Remainder Theorem. Taking into account the non-uniformity of the alphabet of the code, we derive a new expression for the minimum distance that allows us to provide a criterion to obtain traceability codes with the maximum number of code words. In order to make the traceability conditions as independent as possible of the code parameters, we also present a new family of non-uniform alphabet codes whose tracing capabilities only depend on the code length.

Up to the present, several studies have been performed in order to provide prioritization of stations or classes of service for WLAN IEEE 802.11. The IEEE 802.11e draft specification aims to extend the original IEEE 802.11 MAC protocol to support QoS. One of the mechanisms for prioritizing traffic is the assignment of different AIFS times to each priority level. Nevertheless, the AIFSs employed are separated by values that are multiples of the slot time. Therefore, due to the fact that the backoff time counter is slotted, the different priority levels can attempt for transmission simultaneously. In this paper, we evaluate the performance of the IEEE 802.11e when its working procedure is desynchronized: we avoid that stations belonging to different priority levels attempt for transmission at the same time. We assign AIFS times that are separated by values that are not multiples of the slot time, in order to avoid collisions between the different priority levels. We present a mathematical model and simulation results for analyzing the performance of the differentiation mechanism proposed. The results show that it solves the strangulation of low priority traffic, fact that occurs in IEEE 802.11e EDCA. Moreover, this proposal leads to a significant increase in the performance of the system as a whole

Most studies about the performance of IEEE 802.11 consider scenarios of ad-hoc topology and networks where all stations have the same traffic load (symmetric traffic conditions). This paper presents a study of performance parameters of more realistic networks. We focus the attention on WLAN with infrastructure networks, where the traffic distribution is asymmetric. In this case, the traffic load at the access point is much heavier than that at user stations. These studies are more realistic because most nowadays installed WLAN are infrastructure topology type, due to the fact that they are used as access networks. In this case, the access point has to retransmit all incoming traffic to the basic service set and therefore its traffic load is higher. Finally, the paper presents the tuning of the contention window, taken from IEEE 802.11e, used to increase the system performance under asymmetric traffic conditions, and the proposal of an adaptive algorithm to adapt the MAC layer settings to the system traffic load

Most studies about the performance of IEEE 802.11 are limited to a single cell environment. Nevertheless, the idea of designing an outdoor cellular network based on WLAN IEEE 802.11 is very attractive, due to the several advantages that this technology presents: the low cost of the equipment, its operation in unlicensed spectrum and its higher data rates. In this paper, we study the possibility of designing an outdoor cellular network based on the IEEE 802.11g standard. We present its performance under different load conditions and compare this behavior with the results obtained in an isolated single cell environment, without co-channel interference. Finally, going a step further, this paper explores the IEEE 802.11g cellular network performance for different cluster sizes, as a method to reduce the interference influence on network's performance.

This paper is focused on the study of WLAN performance in IEEE 802.11 networks that are in a situation of asymmetric traffic, where the access point (AP) transmits much more than the user stations (US). This situation is very different from the symmetric one, wherein all the stations have the same traffic load. The paper also presents a discussion of the different mechanisms in order to increase AP priority under the asymmetric traffic situation.

Most studies of the performance of IEEE 802.11 consider scenarios of ad-hoc topology networks and do not contemplate the network broadcast information contained in beacon frames. The paper presents a study of the performance of a WLAN whose infrastructure's topology is such that the access point is in charge of broadcasting the beacon frames. Thus, it is more realistic than previous studies, because beacon frames are usually transmitted in order to announce control information and network identity. Furthermore, in the coverage area, user stations are likely to be working at different data rates, depending on their signal quality. Because beacon frames must be received by all stations, they are transmitted at the lowest data rate operating in the coverage area. The article introduces a mathematical method to calculate the influence of beacon frames on the total throughput, collision probability and delays of the IEEE 802.11g protocol. The model is validated by simulation analysis.