Exponential error bounds achievable by universal coding and decoding are derived for frame-asynchronous discrete memoryless multiple access channels with two senders, via the method of subtypes, a refinement of the method of types. An empirical entropy decoder is employed. A key tool is an improved packing lemma, that overcomes the technical difficulty caused by codeword repetitions via an induction based new argument. The asymptotic form of the bounds admits numerical evaluation. This demonstrates that error exponents achievable by synchronous transmission can be superseded via controlled asynchronism, i.e. a deliberate shift of the codewords.

Abstract This paper is motivated by the need of deadline-bounded applications in live mobile network environments to obtain the guarantee and the appropriate share of an input and output (I/O) data rate. However, data processing frameworks only support the request of memory and the computing capacity at present. In this paper, we propose a solution that allows the control of disk I/O and network I/O for data processing applications in YARN and Mesos frameworks. Experimental results show that our tool can provision the I/O data rate sharing of competing data processing applications.

The following conjectures from previous work of the authors are proven, enhancing the relevance of results there on the subject in the title: (i) The error exponents previously derived assuming that consecutive messages could be encoded using different codebooks, are also achievable with each sender using only one codebook. (ii) In case the senders could be synchronized, controlled asynchronism (a deliberate shift of codewords) may admit to achieve error exponents unachievable by synchronous transmission.

A variant of successive decoding for asynchronous multiple access channel is introduced involving constant composition codebooks and maximal mutual information decoder. This admits to improve known achievability results to universal achievability, complemented by error exponents. A further result is that when synchronization is available, a deliberate shifting of the starting times of codewords (controlled asynchronism) combined with successive decoding offers a substitute for techniques of rate splitting and time sharing.

Csiszár's channel coding theorem for multiple codebooks is generalized allowing the code word lengths differ across codebooks. Also in this case, for each codebook an error exponent can be achieved that equals the random coding exponent for this codebook alone. In addition, when the rate and code word-type of the employed codebook do not admit reliable transmission over the given channel, overload is detected with probability approaching 1. This is proved even for a sender and receiver not knowing the channel beyond the alphabets. A substantial improvement is obtained when the sender knows the channel while the receiver still does not.

Csiszár's channel coding theorem for multiple code-books is generalized allowing the codeword lengths differ across codebooks. Also in this case, for each codebook an error exponent can be achieved that equals the random coding exponent for this codebook alone, in addition, the overload detection failure probability tends to 0. This is proved even for sender and receiver not knowing the channel. As a corollary, a substantial improvement is obtained when the sender knows the channel.

Communication over a discrete memoryless channel is addressed when codewords are transmitted in certain time intervals of arbitrary locations, at other times the channel outputs pure noise. The receiver has to locate and decode the codewords. Exponential error bounds are derived, jointly achievable via a semi-universal or universal decoder. Implications are discussed for the familiar model of communication under strong asynchronism when in exponentially long time only one codeword is transmitted.

Improved exponential error bounds are derived for frame-asynchronous discrete memoryless multiple access channels with two senders. By numerical evaluation for a particular case, it follows that the best error exponent known for synchronous transmission may be beaten if the senders are allowed to transmit with a chosen delay.

A new universal coding/decoding scheme for random access with collision detection is given in case of two senders. The result is used to give achievable joint source-channel coding error exponents for multiple access channel and independent sources. In a modified model admitting zero rate communication between the senders, an improved exponent is derived, of form similar to Csiszár’s joint source-channel exponent for the one-sender case.

Exponential error bounds achievable via universal decoder are derived for frame-asynchronous discrete memoryless multiple access channels with two senders. The exponent is strictly positive inside the capacity region. The method of types and a modified maximal mutual information decoder are used.

A new universal coding/decoding scheme for Random Access with collision detection is given in case of two senders. The result is used to give an achievable source-channel coding error exponent for Multiple-Access channels in case of independent sources.

Frame asynchronous discrete memoryless multiple access channels are analyzed, where some groups of senders are synchronized but the groups are not synchronized with each other. A single-letter characterization of the capacity region is obtained.

Motivated by the importance of asynchronous multiple access channels we give an exact formalization. This formalization admits different distributions on delays. The two classical settings when the delay is uniformly distributed and when it is bounded are discussed as special cases of this model. Our method also allows for the analysis of a so far unexplored class of models, where the known distribution of the delay has a special form, leading to new interesting capacity regions.

To understand the technical feasibility and user perception of mobile video, we conducted a two-week trial where a student community used mobile phone and Web technologies to share the events of a campus festival. The questions we investigated included the capability of contemporary smart phones to capture and share the events via real time and stored video; the usage patterns that arise within mobile video community; and the social connections between shooters and viewers. Outcomes on the technical level indicate that challenges remain. The bandwidth of 3G cellular connections limits the quality of live videos and video transfer via public WLAN networks is unreliable causing lost connections. The best results today can be achieved by sending the captured videos from mobile phones to the server in the background and providing video-on-demand rather than live video service. The observed consumption patterns show that freshness of the videos is the least important selection factor while manual and automatic textual tagging is important. Seamless integration of video sharing to camera application would improve the user experience.

Evolved HSPA is a distributed, packet based radio access system that provides high user data rate and low latency. In our contribution the performance of streaming applications over Evolved HSPA is analyzed in realistic network scenarios. The simulation results indicate that in certain scenarios the adaptation latency experienced in case of applying 3GPP PSS Release 8-compliant streaming adaptation is excessively high, causing stream degradation and thus contributing to an end user experience of lower quality. Possible ways of mitigation are briefly outlined.

In this brief summary we show an alternate prove for the fundamental theorem of quantum channel coding. This new prove is stronger then the previously known results because it is used von Neumann measurement. Moreover, the compound quantum channel is defined, and its capacity deduced, with the help of this new measurement.

This paper targets mobile streaming in which Series 60 smart phones are the stream creators and PC-s are the stream consumers. The aim is to provide experimental data reflecting under which conditions video streaming from smart phones is feasible and whether duplex interactive video between a phone and a PC can be achieved or not. Phones used corporate WiFi and UMTS, PC-s were on the corporate Intranet and respectively on an ADSL connection. The outcomes of the experiments indicate that using the considered technologies and experimental setups in most scenarios video streaming from smart phones over WiFi and UMTS is feasible today, for about an hour. However, providing the level of interactivity needed for video calls is challenging, requiring additional measures. As for the extension of the streaming duration to several hours a technological breakthrough would be required.

A powerful use case for voice recording is the case of meetings and other social events. A single recorder is a point device which has a local perspective of the event, meaning that it can record the voice of people nearby but cannot accurately record audio events that happen further away. By letting smart phones record audio content point-wise and exchange the locally recorded content to other smart phones over ad-hoc proximity connections, each smart phone will gain a broader perspective and a consistent audio representation of the entire event. In this paper we analyze such a scenario in which Symbian S60 platforms with Bluetooth version 1.2 stack were used. A distributed recording and content delivery framework is proposed and its performance analyzed by means of simulation and measurements. The validation of our algorithm has been performed using a prototype implementation over these platforms.

In this paper a local connectivity solution is presented in which smart phones and PDA-s can connect to the enterprise intranet using either Bluetooth or Wi-Fi proximity networking via access points. The contribution highlights the differences at various levels of the implementation between the Bluetooth-based and Wi-Fi based components in our attempt to create a unified service level for Bluetooth-based, Wi-Fi based and both Bluetooth- and Wi-Fi based terminals (newer generation smart phones). Finally use cases and a list of applications are presented that can benefit from our solution in the enterprise segment.

In this paper we describe four P2P applications developed for smart phones, ranging from distributed computing to content sharing and search in closed and open user groups. Their common feature relies in the communication interface which has been cellular data transmission (SMS, HSCSD, respectively GPRS). Through our examples we highlight various aspects that application development on smart phones has to take into account, such as traffic efficiency, CPU load and social awareness. We discuss our main observations related to the experiments and highlight some promising directions for future mobile P2P applications. The discussed set of applications developed by us in the period between 2001-2005 cover the areas of distributed computing, large-scale content sharing in open communities, content sharing in closed groups, respectively keyword search in a social network of phones

This work studies a special multicasting problem in Bluetooth networks supporting point-to-point connections and piconets. The reason for the topic choice relies in the fact that Bluetooth, a de-facto proximity communication technique widely available in smart phones today, supports piconets, but sending content to more than 7 nodes is cumbersome. It turns out that by using a non-standard approach, that of parallel piconets of two nodes each, we can obtain a more efficient multicasting than through the legacy multicasting approach

A very efficient peer-to-peer application layer architecture is analyzed as a potential candidate for wireless peer-to-peer applications. Its performance in terms of generated traffic and load balance are simulated for different network sizes. A number of candidate cluster topologies are proposed. Based on the simulation results, the optimal cluster topology and cluster size are identified. We conclude that cluster sizes that are the square root of the number of nodes generate uniform traffic. The cluster topology should be star, ring or a compromise between the two, 'planned N'. We show that, for these topologies, the traffic increases less than linearly with the number of nodes in the network, making it highly scalable. Our conclusions are valid for uniform query and update distributions. In addition to the approach from earlier work (Csucs, G. et al., 2002), maintenance aspects are also dealt with; we briefly describe the basic link management procedures that make such networks feasible, but we do not cover their performance analysis. Neither do we treat query topologies.

During the planning of an UMTS radio network, there is a natural need for a base station positioning procedure. Good coverage at an acceptable level of network installation and maintaining costs, low interference and uniform interface load are the main requirements. In this paper we present an approach based on simulated annealing.

We present a point-multipoint system optimisation based on simulated annealing heuristics. The system is intended to operate in the 3.5 GHz frequency band mainly in densely built-up environments.

We have proposed to simulate the propagation characteristics of the satellite-to-indoor propagation channel. Our first goal has been to find a proper description of the polarization state of the received indoor wave. As far as our first investigations lead us, the polarization state of the indoor wave basically changes as we move further away from the windows, i.e. the secondary source of radiation. First we investigate how the polarization state of a complex harmonic field can be described, then results regarding our first simulations of the polarization state are presented. A modified 3D ray-launching tool has been utilized for the coverage prediction. Further work will include an exhaustive analysis of the dependence of the indoor wave on the elevation angle of the satellite, and the wideband characteristics of the channel: delay spread characteristics and Doppler spread, caused by satellite motion.

There is a growing interest in providing and improving radio coverage for mobile phones and wireless LANs inside buildings. The need of such coverage appears mainly in office buildings, shopping malls, train stations where many subscribers are placed. The cost of cellular systems and also the one of indoor wireless systems depend highly on the number of base stations required to achieve the desired coverage for a given level of field strength.