Time-Scale Domain Characterization of Time-Varying Ultrawideband Infostation Channel

The time-scale domain geometrical-based method for the characterization of the time varying ultrawideband (UWB) channel typical of an infostation channel is presented. Compared to methods that use Doppler shift as a measure of time-variation in the channel this model provides a more reliable measure of frequency dispersion caused by terminal mobility in the UWB infostation channel. Particularly, it offers carrier frequency independent method of computing wideband channel responses and parameters which are important for ultrawideband systems. Results show that the frequency dispersion of the channel depends on the frequency and not on the choice of bandwidth. And time dispersion depends on bandwidth and not on the frequency. It is also shown that for time-varying UWB, frame length defined over the coherence time obtained with reference to the carrier frequency results in an error margin which can be reduced by using the coherence time defined with respect to the maximum frequency in a given frequency band. And the estimation of the frequency offset using the time-scale domain (wideband) model presented here (especially in the case of multiband UWB frequency synchronization) is more accurate than using frequency offset estimate obtained from narrowband models

Resource Management in Delay Tolerant Networks and Smart Grid

In recent years, significant advances have been achieved in communication networks and electric power systems. Communication networks are developed to provide services within not only well-connected network environments such as wireless local area networks, but also challenged network environments where continuous end-to-end connections can hardly be established between information sources and destinations. Delay tolerant network (DTN) is proposed to achieve this objective by utilizing a store-carry-and-forward routing scheme. However, as the network connections in DTNs are intermittent in nature, the management of network resources such as communication bandwidth and buffer storage becomes a challenging issue. On the other hand, the smart grid is to explore information and communication technologies in electric power grids to achieve electricity delivery in a more efficient and reliable way. A high penetration level of electric vehicles and renewable power generation is expected in the future smart grid. However, the randomness of electric vehicle mobility and the intermittency of renewable power generation bring new challenges to the resources management in the smart grid, such as electric power, energy storage, and communication bandwidth management. This thesis consists of two parts. In part I, we focus on the resource management in DTNs. Specifically, we investigate data dissemination and on-demand data delivery which are two of the major data services in DTNs. Two kinds of mobile nodes are considered for the two types of services which correspond to the pedestrians and high-speed train passengers, respectively. For pedestrian nodes, the roadside wireless local area networks are used as an auxiliary communication infrastructure for data service delivery. We consider a cooperative data dissemination approach with a packet pre-downloading mechanism and propose a double-loop receiver-initiated medium access control scheme to resolve the channel contention among multiple direct/relay links and exploit the predictable traffic characteristics as a result of packet pre-downloading. For high-speed train nodes, we investigate on-demand data service delivery via a cellular/infostation integrated network. The optimal resource allocation problem is formulated by taking account of the intermittent network connectivity and multi-service demands. In order to achieve efficient resource allocation with low computational complexity, the original problem is transformed into a single-machine preemptive scheduling problem and an online resource allocation algorithm is proposed. If the link from the backbone network to an infostation is a bottleneck, a service pre-downloading algorithm is also proposed to facilitate the resource allocation. In part II, we focus on resource management in the smart grid. We first investigate the optimal energy delivery for plug-in hybrid electric vehicles via vehicle-to-grid systems. A dynamic programming formulation is established by considering the bidirectional energy flow, non-stationary energy demand, battery characteristics, and time-of-use electricity price. We prove the optimality of a state-dependent double-threshold policy based on the stochastic inventory theory. A modified backward iteration algorithm is devised for practical applications, where an exponentially weighted moving average algorithm is used to estimate the statistics of vehicle mobility and energy demand. Then, we propose a decentralized economic dispatch approach for microgrids such that the optimal decision on power generation is made by each distributed generation unit locally via multiagent coordination. To avoid a slow convergence speed of multiagent coordination, we propose a heterogeneous wireless network architecture for microgrids. Two multiagent coordination schemes are proposed for the single-stage and hierarchical operation modes, respectively. The optimal number of activated cellular communication devices is obtained based on the tradeoff between communication and generation costs

Computer-network Solutions for Pervasive Computing

Lo scenario delle reti di comunicazione di tipo wireless sta rapidamente evolvendo verso i sistemi pervasivi in cui i dispositivi wireless, di diversi tipi e grandezze, costituiscono parte integrante dell’ambiente in cui sono immersi, ed interagiscono continuamente ed in maniera trasparente con gli utenti che vi vivono o che lo attraversano. Si parla a tal proposito anche di ambienti intelligenti. Seguendo l’evoluzione dai sistemi mobili a quelli pervasivi, questa tesi rivisita diversi tipi di ambienti wireless che si sono sviluppati e diffusi negli ultimi 20 anni: a partire dalle wireless LANs, proseguendo con le reti ad hoc, per finire con le reti opportunistiche. Sebbene molte problematiche delle reti wireless si ripropongano in quasi tutti gli scenari (ad esempio il risparmio energetico), a scenari wireless diversi corrispondono in genere utilizzi differenti e diversi fabbisogni degli utenti, come pure problemi specifici che richiedono soluzioni dedicate. Alcune soluzioni specifiche sono analizzate e proposte in questa tesi. Le reti WLANs basate su infrastruttura sono usate generalmente per fornire accesso alla rete Internet ed infatti lo scenario che le comprende è solitamente riferito come Wireless Internet. Nonostante la presenza dell’infrastruttuta fissa garantisca in generale una trasmissione di dati affidabile, l’utilizzo di questo tipo di reti per fornire esattamente gli stessi tipi di servizi delle reti fisse provoca un elevato consumo di risorse che all’interno delle WLANs sono invece limitate. Inoltre l’utilizzo dei protocolli dello stack TCP/IP sui link wireless è di solito fonte di inefficienze viste le profonde differenze esistenti fra i link wireless e quelli fissi. La progettazione di servizi in uno scenario di wireless Internet ha come primario obiettivo quello di garantire la fruizione da parte degli utenti mobili senza soluzione di continuità, mascherando così la presenza del link wireless che ha banda nominale inferiore rispetto ai link fissi ed è soggetto a maggiori perdite, e supportando la mobilità degli utenti all’interno delle zone di copertura (handoff). La gestione dei servizi di wireless Internet deve sempre essere integrata con soluzioni di risparmio energetico tese ad allungare il più possibile l’autonomia energetica dei dispositivi degli utenti (alimentati a batteria) garantendo così loro un servizio duraturo nel tempo. Abbiamo studiato una soluzione per servizi di streaming audio-video verso terminali mobili in un ambiente di wireless LAN. Oltre a garantire la continuità della riproduzione multimediale con buona qualità, questa soluzione ottimizza il consumo energetico del terminale wireless agendo sulla scheda di rete wireless. Durante lo streaming infatti, la scheda di rete viene periodicamente messa in uno stato a basso consumo energetico (sleep). I periodi di sleep della scheda vengono calcolati adattivamente in funzione dello stato di avanzamento della riproduzione multimediale e della banda disponibile istantaneamente sul canale wireless opportunamente monitorato. Il riposo della scheda di rete non incide sul processo di riproduzione e quindi sulla qualità del servizio percepita dall’utente mobile. A differenza delle WLANs, le reti MANETs sono prive di infrastruttura fissa ed i nodi che vi partecipano si autoconfigurano ed autoorganizzano tra di loro. Le MANETs si mostrano particolarmente adatte ad esigenze temporanee di gruppi di utenti che vogliano condividere dati, scambiarsi messaggi, o altro. Uno dei principali interessi di ricerca nell’ambito delle reti MANETs ha riguardato storicamente lo studio dei protocolli di routing per l’instradamento delle informazioni fra nodi sorgente e nodi destinatari. In una rete MANET infatti, vista l’assenza di infrastruttura, ogni nodo è coinvolto nella funzione di instradamento. Negli ultimi anni tuttavia, un nuovo aspetto di ricerca sta acquistando sempre maggiore attenzione e riguarda la sperimentazione su testbed reali. Le poche esperienze sperimentali eseguite su MANETs hanno dimostrato l’inadeguatezza degli studi di tipo analitico-simulativo nel giudicare l’efficacia delle soluzioni progettate per reti MANETs. Questo è principalmente dovuto al fatto che gli scenari wireless sono estremamente complessi e soggetti a fenomeni di diversa natura che influiscono sulle comunicazioni ma che sono difficilmente condensabili in un modello analitico completo. I modelli esistenti nei simulatori attualmente diffusi sono spesso causa di errori nel validare o al contrario bocciare le soluzioni ed i protocolli testati. Le attività di sperimentazione su testbed reali hanno dunque un duplice scopo: i) validare protocolli e soluzioni proposte attualmente, e ii) gettare le basi per la costruizione di nuovi modelli analitici e simulativi che siano maggiormente attendibili di quelli attuali. L’esperienza condotta su di un testbed reale per reti ad hoc comprendente portatili e palmari fino ad un totale di 12 nodi, ha dimostrato l’efficacia delle implementazioni di due protocolli di routing: AODV (Ad hoc On demand Distance Vector) ed OLSR (Optimized Link State Routing). Tuttavia, benchè entrambi siano funzionalmente corretti, mostrano comportamenti differenti quando usati per supportare servizi di livello middleware ed applicativi (vedi ad esempio file sharing o trasferimenti ftp). In particolare, i ritardi causati dalla scoperta delle rotte in AODV sono spesso causa di inefficienze o addirittura di interruzione del servizio. OLSR invece, seppure responsabile di un overhead di traffico maggiore, si mostra maggiormente adatto alle interazioni con i servizi dei livelli superiori. Infine, l’esperienza ha dimostrato la necessità di ripensare molti dei servizi disponibili su rete fissa per adeguarli alle caratteristiche delle reti wireless e particolarmente di quelle ad hoc. Una nuova tipologia di reti wireless sta emergendo attualmente e si sta rivelando di particolare interesse: quella delle reti opportunistiche. Le reti opportunistiche non si appoggiano su alcuna infrastruttura fissa, né cercano di autoconfigurarsi in una infrastruttura wireless temporanea costituita da nodi vicini. Sfruttano le opportunità di contatto che si verificano fra i nodi (dispositivi wireless di piccola taglia) trasportati dagli utenti nelle loro attività quotidiane (ad esempio a lavoro, sugli autobus, a scuola o all’università, ecc.). I messaggi sono scambiati ogni qualvolta si renda possibile, ovunque sia possibile ed il successo della loro trasmissione è strettamente legato alle dinamiche sociali in cui sono coinvolti gli utenti che trasportano i dispositivi ed alla storia degli incontri tra individui. Data la mobilità estremamente elevata che caratterizza questo nuovo scenario di reti, e la nota rumorosità delle comunicazioni wireless, l’affidabilità delle trasmissioni emerge come uno dei fattori di principale interesse. Infatti, le comunicazioni possono aver luogo soltanto durante i periodi di contatto tra i nodi e devono essere estremamente veloci ed efficaci. Questo porta a dover fare uno sforzo di progettazione per nuovi protocolli di comunicazione che si diversifichino da quelli oggi più diffusi e basati sulla ritrasmissione dei dati mancanti. Le ritrasmissioni infatti, nella maggior parte dei casi potrebbero non poter essere eseguite per mancanza di tempo. Una strategia valida per gestire l’affidabilità delle comunicazioni opportunistiche in simili scenari estremi (caratterizzati cioè da scarse risorse e scarsa connettività) prevede l’utilizzo combinato di tecniche di codifica dei dati e strategie di instradamento di tipo epidemico. Questo approccio sfrutta la ridondanza sia delle informazioni, sia dei percorsi. La ridondanza delle informazioni dà robustezza a fronte della perdita dei dati in rete poiché è necessario che soltanto un sottoinsieme dei codici generati arrivi a destinazione per consentire al ricostruzione corretta delle informazioni. La ridondanza dei percorsi invece è necessaria poichè non è possibile predirre in anticipo la sequenza dei contatti che può portare i dati a destinazione e pertanto è necessario distribuire l’informazione in più direzioni. Le reti opportunistiche caratterizzate dalla presenza di dispositivi con limitata autonomia energetica e risorse limitate, offrono attualmente lo scenario che meglio traduce il concetto di sistemi pervasivi. Di particolare interesse è il caso delle reti di sensori sparse in cui i sensori sono disposti nell’ambiente con funzione di monitoraggio ed i dati che collezionano vengono raccolti da degli agenti mobili che passano nelle vicinanze e che sono noti come data MULEs. I data MULEs possono utilizzare le informazioni acquisite dai sensori per eseguire applicazioni dipendenti dal contesto o possono semplicemente inoltrarle fino a quando raggiungono l’infrastruttura dove vengono elaborati e memorizzati. Le interazioni fra i sensori immersi nell’ambiente ed i data MULEs sono soltanto un primo passo di un sistema di comunicazione globale completamente opportunistico in cui i data MULEs scambiano l’un l’altro le informazioni che trasportano fino a quando infine, i dati pervengono alle destinazioni più lontane. In questo scenario, le comunicazioni wireless completano naturalmente le interazioni fra gli utenti e si verificano ogni qualvolta gli utenti si incontrano oppure si avvicinano casualmente l’un l’altro, dovunque questa interazione avvenga. Per supportare un simile framework, è necessario sviluppare nuovi paradigmi di comunicazione che tengano in considerazione l’assenza di link stabili tra i nodi che comunicano (connettività intermittente) e che assumano quindi la disponibilità di brevi periodi di contatto per comunicare. Inoltre i nuovi paradigmi di comunicazione devono generalmente assumere l’assenza di un percorso completo fra i nodi sorgente e destinatario e sfruttare invece forme di instradamento delle informazioni che sono simili al modo in cui avvengono le interazioni sociali fra le persone. Strategie di instradamento basate su codifica dei dati offrono una valida soluzione per supportare il framework emergente dei sistemi pervasivi

Improving TCP behaviour to non-invasively share spectrum with safety messages in VANET

There is a broad range of technologies available for wireless communications for moving vehicles, such as Worldwide Interoperability for Microwave Access (WiMax), 3G, Dedicated Short Range Communication (DSRC)/ Wireless Access for Vehicular Environment (WAVE) and Mobile Broadband Wireless Access (MBWA). These technologies are needed to support delay-sensitive safety related applications such as collision avoidance and emergency breaking. Among them, the IEEE802.11p standard (aka DSRC/WAVE), a Wi-Fi based medium RF range technology, is considered to be one of the best suited draft architectures for time-sensitive safety applications. In addition to safety applications, however, services of non-safety nature like electronic toll tax collection, infotainment and traffic control are also becoming important these days. To support delay-insensitive infotainment applications, the DSRC protocol suite also provides facilities to use Internet Protocols. The DSRC architecture actually consists of WAVE Short Messaging Protocol (WSMP) specifically formulated for realtime safety applications as well as the conventional transport layer protocols TCP/UDP for non-safety purposes. But the layer four protocol TCP was originally designed for reliable data delivery only over wired networks, and so the performance quality was not guaranteed for the wireless medium, especially in the highly unstable network topology engendered by fast moving vehicles. The vehicular wireless medium is inherently unreliable because of intermittent disconnections caused by moving vehicles, and in addition, it suffers from multi-path and fading phenomena (and a host of others) that greatly degrade the network performance. One of the TCP problems in the context of vehicular wireless network is that it interprets transmission errors as symptomatic of an incipient congestion situation and as a result, reduces the throughput deliberately by frequently invoking slow-start congestion control algorithms. Despite the availability of many congestion control mechanisms to address this problem, the conventional TCP continues to suffer from poor performance when deployed in the Vehicular Ad-hoc Network (VANET) environment. Moreover, the way non-safety applications, when pressed into service, will treat the existing delay-sensitive safety messaging applications and the way these two types of applications interact between them are not (well) understood, and therefore, in order for them to coexist, the implication and repercussion need to be examined closely. This is especially important as IEEE 802.11p standards are not designed keeping in view the issues TCP raises in relation to safety messages. This dissertation addresses the issues arising out of this situation and in particular confronts the congestion challenges thrown up in the context of heterogenous communication in VANET environment by proposing an innovative solution with two optimized congestion control algorithms. Extensive simulation studies conducted by the author shows that both these algorithms have improved TCP performance in terms of metrics like Packet Delivery Fraction (PDF), Packet Loss and End-to-End Delay (E2ED), and at the same time they encourage the non-safety TCP application to behave unobtrusively and cooperatively to a large extent with DSRC’s safety applications. The first algorithm, called vScalable-TCP – a modification of the existing TCPScalable variant – introduces a reliable transport protocol suitable for DSRC. In the proposed approach, whenever packets are discarded excessively due to congestion, the slow-start mechanism is purposely suppressed temporarily to avoid further congestion and packet loss. The crucial idea here is how to adjust and regulate the behaviour of vScalable-TCP in a way that the existing safety message flows are least disturbed. The simulation results confirm that the new vScalable-TCP provides better performance for real-time safety applications than TCP-Reno and other TCP variants considered in this thesis in terms of standard performance metrics. The second algorithm, named vLP-TCP – a modification of the existing TCP-LP variant – is designed to test and demonstrate that the strategy developed for vScalable-TCP is also compatible with another congestion control mechanism and achieves the same purpose. This expectation is borne out well by the simulation results. The same slow-start congestion management strategy has been employed but with only a few amendments. This modified algorithm also improves substantially the performance of basic safety management applications. The present work thus clearly confirms that both vScalable-TCP and vLP-TCP algorithms – the prefix ‘v’ to the names standing for ‘vehicular’ – outperform the existing unadorned TCP-Scalable and TCP-LP algorithms, in terms of standard performance metrics, while at the same time behaving in a friendly manner, by way of sharing bandwidth non-intrusively with DSRC safety applications. This paves the way for the smooth and harmonious coexistence of these two broad, clearly incompatible or complementary categories of applications – viz. time-sensitive safety applications and delay-tolerant infotainment applications – by narrowing down their apparent impedance or behavioural mismatch, when they are coerced to go hand in hand in a DSRC environment

Connectivity and Data Transmission over Wireless Mobile Systems

We live in a world where wireless connectivity is pervasive and becomes ubiquitous. Numerous devices with varying capabilities and multiple interfaces are surrounding us. Most home users use Wi-Fi routers, whereas a large portion of human inhabited land is covered by cellular networks. As the number of these devices, and the services they provide, increase, our needs in bandwidth and interoperability are also augmented. Although deploying additional infrastructure and future protocols may alleviate these problems, efficient use of the available resources is important. We are interested in the problem of identifying the properties of a system able to operate using multiple interfaces, take advantage of user locations, identify the users that should be involved in the routing, and setup a mechanism for information dissemination. The challenges we need to overcome arise from network complexity and heterogeneousness, as well as the fact that they have no single owner or manager. In this thesis I focus on two cases, namely that of utilizing "in-situ" WiFi Access Points to enhance the connections of mobile users, and that of establishing "Virtual Access Points" in locations where there is no fixed roadside equipment available. Both environments have attracted interest for numerous related works. In the first case the main effort is to take advantage of the available bandwidth, while in the second to provide delay tolerant connectivity, possibly in the face of disasters. Our main contribution is to utilize a database to store user locations in the system, and to provide ways to use that information to improve system effectiveness. This feature allows our system to remain effective in specific scenarios and tests, where other approaches fail

Design and Performance Analysis of Opportunistic Routing Protocols for Delay Tolerant Networks

Delay Tolerant Networks (DTNs) are characterized by the lack of continuous end-to-end connections because of node mobility, constrained power sources, and limited data storage space of some or all of its nodes. Applications of DTNs include vehicular networks and sensor networks in suburban and rural areas. The intermittent connection in DTNs creates a new and challenging environment that has not been tackled before in wireless and wired networks. Traditional routing protocols fail to deliver data packets because they assume the existence of continuous end-to-end connections. To overcome the frequent disconnections, a DTN node is required to store data packets for long periods of time until it becomes in the communication range of other nodes. In addition, to increase the delivery probability, a DTN node spreads multiple copies of the same packet on the network so that one of the copies reaches the destination. Given the limited storage and energy resources of DTN nodes, there is a trade off between maximizing delivery and minimizing storage and energy consumption. DTN routing protocols can be classified as either blind routing, in which no information is provided to select the next node in the path, or guided routing, in which some network information is used to guide data packets to their destinations. In addition they differ in the amount of overhead they impose on the network and its nodes. The objective of DTN routing protocols is to deliver as many packets as possible. Acquiring network information helps in maximizing packet delivery probability and minimizing the network overhead resulting from replicating many packet copies. Network information could be node contact times and durations, node buffer capacities, packet lifetimes, and many others. The more information acquired, the higher performance could be achieved. However, the cost of acquiring the network information in terms of delay and storage could be high to the degree that render the protocol impractical. In designing a DTN routing protocol, the trade-off between the benefits of acquiring information and its costs should be considered. In this thesis, we study the routing problem in DTN with limited resources. Our objective is to design and implement routing protocols that effectively handles the intermittent connection in DTNs to achieve high packet delivery ratios with lower delivery cost. Delivery cost is represented in terms of number of transmissions per delivered packet. Decreasing the delivery cost means less network overhead and less energy consumption per node. In order to achieve that objective, we first target the optimal results that could be achieved in an ideal scenario. We formulate a mathematical model for optimal routing, assuming the presence of a global observer that can collect information about all the nodes in the network. The optimal results provide us with bounds on the performance metrics, and show the room for improvement that should be worked on. However, optimal routing with a global observer is just a theoretical model, and cannot be implemented practically. In DTNs, there is a need for a distributed routing protocol which utilizes local and easily-collectable data. Therefore, We investigate the different types of heuristic (non-optimal) distributed routing protocols, showing their strengths and weaknesses. Out of the large collection of protocols, we select four protocols that represent different routing classes and are well-known and highly referred by others working in the same area. We implement the protocols using a DTN simulator, and compare their performance under different network and node conditions. We study the impact of changing the node buffer capacities, packet lifetimes, number of nodes, and traffic load on their performance metrics, which are the delivery ratio, delivery cost, and packet average delay. Based on these comparisons, we draw conclusions and guidelines to design an efficient DTN routing protocol. Given the protocol design guidelines, we develop our first DTN routing protocol, Eco-Friendly Routing for DTN (EFR-DTN), which combines the strengths of two of the previously proposed protocols to provide better delivery ratio with low network overhead (less power consumption). The protocol utilizes node encounters to estimate the route to destination, while minimizing the number of packet copies throughout the network. All current DTN routing protocols strive to estimate the route from source to destination, which requires collecting information about node encounters. In addition to the overhead it imposes on the network to collect this information, the time to collect this information could render the data worthless to propagate through the network. Our next proposal is a routing protocol, Social Groups Based Routing (SGBR), which uses social relations among network nodes to exclude the nodes that are not expected to significantly increase the probability of delivering the packet to its destination. Using social relations among nodes, detected from node encounters, every group of nodes can form a social group. Nodes belonging to the same social group are expected to meet each other frequently, and meet nodes from other groups less frequently. Spreading packet copies inside the same social group is found to be of low-added value to the carrying node in delivering a packet to its destination. Therefore, our proposed routing protocol spreads the packet copies to other social groups, which decreases the number of copies throughout the network. We compare the new protocol with the optimal results and the existing well-known routing protocols using real-life simulations. Results show that the proposed protocol achieves higher delivery ratio and less average delay compared to other protocols with significant reduction in network overhead. Finally, we discuss the willingness of DTN nodes to cooperate in routing services. From a network perspective, all nodes are required to participate in delivering packets of each other. From a node perspective, minimizing resource consumption is a critical requirement. We investigate the degree of fair cooperation where all nodes are satisfied with their participation in the network routing services. A new credit-based system is implemented to keep track of and reward node participation in packet routing. Results show that the proposed system improves the fairness among nodes and increases their satisfaction

Practical mobile ad hoc networks for large scale cattle monitoring

This thesis is concerned with identification of realistic requirements for the cattle monitoring system and design of the practical architecture addressing these requirements. Automated monitoring of cattle with wireless monitoring devices mounted on the animals can increase efficiency of cattle production, decrease its reliance on human labour and thus increase its profitability. Multi-hop ad hoc wireless communication has the potential to increase battery life of the animal mounted devices, decrease their size and combat disconnections. This thesis reveals that no current approach sufficiently addresses energy constrains of the animal mounted devices and potential disconnections. We propose a delay tolerant store and forward architecture that provides data retention, detecting custom events, issues notifications, answers remote and in-situ queries, based on requirements identified during field experiments we conducted. This architecture utilizes fixed infrastructure but also works in ad hoc infrastructureless conditions. The core of the proposed architecture, Mobile Ad Hoc Network (MANET) communication, provides offloading data for long term storage by sending data to farm servers via sinks that are a part of MANET and handles in-situ queries issued by users collocated with the animals. The proposed MANET routing algorithm addresses high mobility of nodes and disconnections. It provides lower and more balanced energy usage, shorter delays and increased success ratio of delivering answers to in-situ queries than more generic existing approaches. Problems of large scale deployment of the envisaged system are also addressed. We discuss the necessary configuration process performed during the system installation as well as pervasive mobile and home access to the target system. We propose cost efficient strategies for sinks installation and connecting sinks to farm servers, adaptive to different requirements, estates layout, available infrastructure and existing human and vehicle mobility. We also propose a cost efficient security model for the target system based on public key cryptography