Coalitions in Cooperative Wireless Networks

Cooperation between rational users in wireless networks is studied using coalitional game theory. Using the rate achieved by a user as its utility, it is shown that the stable coalition structure, i.e., set of coalitions from which users have no incentives to defect, depends on the manner in which the rate gains are apportioned among the cooperating users. Specifically, the stability of the grand coalition (GC), i.e., the coalition of all users, is studied. Transmitter and receiver cooperation in an interference channel (IC) are studied as illustrative cooperative models to determine the stable coalitions for both flexible (transferable) and fixed (non-transferable) apportioning schemes. It is shown that the stable sum-rate optimal coalition when only receivers cooperate by jointly decoding (transferable) is the GC. The stability of the GC depends on the detector when receivers cooperate using linear multiuser detectors (non-transferable). Transmitter cooperation is studied assuming that all receivers cooperate perfectly and that users outside a coalition act as jammers. The stability of the GC is studied for both the case of perfectly cooperating transmitters (transferrable) and under a partial decode-and-forward strategy (non-transferable). In both cases, the stability is shown to depend on the channel gains and the transmitter jamming strengths.Comment: To appear in the IEEE Journal on Selected Areas in Communication, Special Issue on Game Theory in Communication Systems, 200

Emotional responses to Hindustani raga music: the role of musical structure

In Indian classical music, ragas constitute specific combinations of tonic intervals potentially capable of evoking distinct emotions. A raga composition is typically presented in two modes, namely, alaap and gat. Alaap is the note by note delineation of a raga bound by a slow tempo, but not bound by a rhythmic cycle. Gat on the other hand is rendered at a faster tempo and follows a rhythmic cycle. Our primary objective was to (1) discriminate the emotions experienced across alaap and gat of ragas, (2) investigate the association of tonic intervals, tempo and rhythmic regularity with emotional response. 122 participants rated their experienced emotion across alaap and gat of 12 ragas. Analysis of the emotional responses revealed that (1) ragas elicit distinct emotions across the two presentation modes, and (2) specific tonic intervals are robust predictors of emotional response. Specifically, our results showed that the ‘minor second’ is a direct predictor of negative valence. (3) Tonality determines the emotion experienced for a raga where as rhythmic regularity and tempo modulate levels of arousal. Our findings provide new insights into the emotional response to Indian ragas and the impact of tempo, rhythmic regularity and tonality on it

Prevalence of leukoplakia, oral submucous fibrosis, papilloma and its relation with stress among green marbles mine laborers, India

Objectives: To determine the prevalence of leukoplakia, oral submucous fibrosis and papilloma among ?Green Marble Mines? laborer and uncover its relation with occupational stress. Methods: Mines were divided in four geographic zones, and participants were selected by stratified cluster sampling technique. A total of 513 subjects were included in final study which were alienated among the four age cohort 15-24 , 25-34 , 35-44, 45-54 respectively. The study was been conducted following the research methodology recommended by World Health Organization- Oral Health Surveys 1997. A questionnaire from ?Union of Shops, Distribution and Allied Worker (USDAW) Nationwide, Manchester? was used for stress assessment of mine workers and clinical examination for oral mucosa was conducted by one of the three examiner with the aid of an artificial light source. The kappa statistics for diagnosis of leukoplakia, oral submucous fibrosis and papilloma was determined (field teams versus expert) 0.81, 0.92 and 0.89 respectively two days prior to the examination. Data was analyzed using bivariate and multivariate analysis. Results: An overall elevated prevalence of all three oral-mucosal lesion was found among mine workers (36.7%), mainly leukoplakia affecting 171 mine workers (33.3%). The affected workers were having body problems like headache, backache and stressed due to under-payment. Individuals having papilloma have faced problem at work like noise, dust or fumes and poor maintenance of equipment. Multiple logistic regression analysis model of oral-mucosal lesion have shown highly significant relation (p<0.01) with increased stress, age, alcohol habits and malnutrition. Conclusion: The prevalence of oral mucosal lesion is higher, among marble mine laborers, and occupational stress can intensify the disease condition. Curative services along with prevention and stress reduction program, requires primary anticipation

A Rapidly Deployable Communications Network Architecture for Disaster Management

It is amply clear from the recent unfortunate events of September 11, 2001 and the South-Asian tsunami disaster that there exists a strong need for a rapidly deployable communications network that would serve to provide much needed connectivity and communications capabilities to rescue workers and survivors. Disaster sites are often located in geographical areas with little or no infrastructure [1] and often cause existing communications infrastructure to saturate or become unavailable. The present document analyses the requirements of such a network and proposes a suitable architecture. Further it details an appropriate case study and a performance evaluation of the system based on expected average and peak loads. I

Building information-theoretic confidentiality and traffic privacy into wireless networks

This dissertation studies how information-theoretically secure mechanisms for confidentiality and data-traffic privacy can be incorporated into existing and emerging wireless systems. The dissertation consists of three parts. In the first two parts, we study how certain properties of wireless channels can be employed to enhance confidentiality services that have traditionally been the responsibility of higher layers. We first explore the use of the wireless medium for the extraction of secret keys at the two ends of a wireless link, wherein the transceivers at either end are separated by a rich multipath scattering environment. We build a low complexity algorithm that allows two wireless devices to extract a common sequence of random secret bits, by repeatedly probing and estimating a time-varying channel between themselves. Further, we report on an implementation and evaluation of our algorithm on a modified 802.11a system. Next, we study the problem of securely pairing wireless devices in proximity of one another by establishing a shared secret key using a public source of RF transmissions. We employ measurement data to characterize the rate at which bits can be extracted and explore the simultaneous use of multiple transmitters to increase rate. Finally, we study the case when the public transmitter itself is under the arbitrary control of an adversary and we demonstrate a method that can allow successful key-extraction even with such an active adversary. In the final part of this dissertation, we introduce the problem of an unintended information-leakage channel in data traffic consisting of varying packet sizes. Packet sizes convey semantic information that can be related to their con- tent, which can be used as a fingerprint for classification. We formally study the packet-size side channel and explore obfuscation approaches to prevent infor- mation leakage, while considering padded dummy traffic and delay as bounded resources. We show that randomized algorithms for obfuscation can be studied as well known information-theoretic constructs, such as discrete channels with and without memory, and often lead to efficiently solvable constrained optimization problems.Ph.D.Includes bibliographical referencesIncludes vitaby Suhas Mathu

Coalitional games in Gaussian interference channels

Abstract — The formation of coalitions in a Gaussian interference channel comprised of M transmit-receive links where the receivers are allowed to cooperate is studied under the framework of coalitional game theory. Allowing any arbitrary sharing of the total rate achieved by a coalition between its member links, it is shown that the grand coalition (coalition of all links) maximizes spectrum utilization and is also stable, that is, the links in this coalition have no incentives to leave and form other coalitions. The issue of fairness in allocating rates to members of a grand coalition is addressed via a Nash bargaining solution where each link utility is modeled as the rate gained by being in a coalition relative to the rate achieved in the interference channel. Further, a rate allocation solution using proportional fairness is also presented and the results are illustrated with examples. I

Coalitional games in receiver cooperation for spectrum sharing

Abstract — The issue of sharing spectrum through receiver cooperation in wireless networks is studied under the framework of coalitional game theory. In particular, we consider two illustrative network models: (1) a Gaussian interference channel with receiver cooperation and (2) a multiple access channel (MAC) with linear multiuser detection. Allowing any arbitrary sharing of the sum-rate achieved by a coalition between member links in a Gaussian interference channel, it is shown that the grand coalition (coalition of all receivers) maximizes spectrum utilization and is also stable. For the linear MMSE multiuser detector, it is shown that the grand coalition is always stable and sum-rate maximizing, while for the decorrelating multiuser detector, the above observation is shown to be true only in the high SNR regime. Finally, transmitter cooperation in the context of a Gaussian interference channel is discussed, with focus on some open problems and a simplified framework for the resulting coalitional game is proposed. I