We propose a formal model for non-interactive message authentication protocols (NIMAPs) using two channels and analyze all the attacks that can occur in this model. Further, we introduce the notion of hybrid-collision resistant (HCR) hash functions. This leads to a new proposal for a NIMAP based on HCR hash functions. This protocol is as efficient as the best previous NIMAP while having a very simple structure and not requiring any long strings to be authenticated ahead of time. We investigate interactive message authentication protocols (IMAPs) and propose a new IMAP, based on the existence of interactive-collision resistant (ICR) hash functions, a new notion of hash function security. The efficient and easy-to-use structure of our IMAP makes it very practical in real world ad hoc network scenarios. We also look at message recognition protocols (MRPs) and prove that there is a one-to-one correspondence between non-interactive MRPs and digital signature schemes with message recovery. Further, we look at an existing recognition protocol and point out its inability to recover in case of a specific adversarial disruption. We improve this protocol by suggesting a variant which is equipped with a resynchronization process. Moreover, another variant of the protocol is proposed which self-recovers in case of an intrusion. Finally, we propose a new design for message recognition in ad hoc networks which does not make use of hash chains. This new design uses random passwords that are being refreshed in each session, as opposed to precomputed elements of a hash chain.

In this thesis, we study a three-node full-duplex network, where the infrastructure node has simultaneous up- and downlink communication in the same frequency band with two half-duplex nodes. In addition to self-interference at the full-duplex infrastructure node, the three-node network has to contend with the inter-node interference between the two half-duplex nodes. The two forms of interferences differ in one important aspect that the self-interference is known at the interfered receiver. Therefore, we propose to leverage a wireless side-channel to manage the inter-node interference. We characterize the impact of inter-node interference on the network achievable rate region with and without a side-channel between the nodes. We present four distributed full-duplex inter-node interference cancellation schemes, which leverage the device-to-device wireless side-channel for improved interference cancellation. Of the four, bin-and-cancel is asymptotically optimal in high signal-to-noise ratio limit which uses Han-Kobayashi common-private message splitting and achieves within 1 bits/s/Hz of the capacity region for all values of channel parameters. The other three schemes are simpler compared to bin-and-cancel but achieve the near-optimal performance only in certain regimes of channel values. Asymptotic multiplexing gains of all proposed schemes are derived to show analytically that leveraging the side channel can be highly beneficial in increasing the multiplexing gain of the system exactly in those regimes where inter-node interference has the highest impact.

This master thesis investigates the uplink transmition from User Equipment (UE) to base station in LET (Long Term Evolution) and channel estimation using pilot symbols with parameter defined in 3GPP (3rd Generation Partnership Project) specifications. The purpose of the thesis was to implement a simulator which can generate uplink signal as it is generated by UE. The Third Generation (3G) mobile system was given the name LTE. This thesis focus on the uplink of LTE where single carrier frequency division multiple access (SC-FDMA) is utilized as a multiple access technique. The advantage over the orthogonal frequency division multiple access (OFDMA), which is used in downlink is to get better peak power characteristics. Because in uplink communication better peak power characteristic is necessary for better power efficiency in mobile terminals. To access the performance of uplink transmition realistic channel model for wireless communication system is essential. Channel models used are proposed by International Telecommunication Union (ITU) and the correct knowledge of these models is important for testing, optimization and performance improvements of signal processing algorithms. The channel estimation techniques used are Least Square (LS) and Least Minimum Mean Square Error (LMMSE) for different channel models. Performance of these algorithms has been measured in term of Bit Error Rate (BER) and Signal to Noise Ratio (SNR).

The role of branding in building distribution relationships has attained increased attention in the marketing literature lately and several studies have shown that branding is an effective tool for building stronger relationships between manufacturers and their distribution partners. Unfortunately these findings fail to explain how channel push strategies work independently of consumer pull strategies when it comes to building strong manufacturer brands. On one hand, it is asserted that close interaction between brand representatives and distribution channel members is a prerequisite for success, while it on the other hand is asserted that direct communication to end users is just as important. In terms of managerial implications this has often led to vague recommendations in crafting a "perfect blend" between push and pull strategies.These recommendations constitute a status quo, where marketing managers in manufacturing firms have been placed in between two strategies without clear recommendations on how they work independently of each other. This status quo is a problem in both academic research and managerial practice since distribution channel relationships are seen as an increasingly important source of competitive advantage. As a result, the theoretical foundation of a blended strategy might be reprioritized in advantage for better relationships with distribution channel members, which in effect make push efforts the prioritized channel for manufacturer brand management.This master thesis gives all its attention to channel push branding and provides essential insights into how a brand is built in the minds of distributors, resellers and end-users, through a channel-push strategy. A single case study design is used, investigating a telecom-brand focused solely on a channel push strategy. The investigation concerns the brand identity as well as interviews with distributors, resellers and end-users. The studied brand is analyzed through Aaker's (2002) conceptualization of consumer based brand equity, consisting of brand awareness, brand associations, perceived quality and brand loyalty. Although an equity model is used, the goal is not to assess brand value, rather to investigate how brand equity is built through a strict channel push strategy.Although this case illustrates both challenges and limitations, I strongly argue against the assertion that strict push strategies are something of the past. The studied brand is filled with relevant associations and functional attributes and has only suffered minor diversities between different intermediaries and regions. However, this case also shows that channel push branding is a complex procedure that requires careful and specific considerations. Main areas which should be considered are; limitations in awareness creation, difficulties in building brand associations, dependence of interpersonal relations and the activity of the end-user-brand relationship. My main contribution with this case study is a rich description of the underlying phenomena which constitute these considerations. Distribution channel relationships are an increasingly important source of competitive advantage, and I believe that this case provides a new perspective on channel push branding, both to practitioners and to researchers.

With the increasing demand of higher data rate for telecommunication, the IEEE802.11n standard was constituted in 2009. Themost important character of the standard is MIMO-OFDM, which not only improves the throughput but also the spectrumefficiency and channel capacity. This report focuses on the physical layer IEEE802.11n model. By utilizing an existingSimulink based IEEE802.11n system, functionalities like MIMO (up to 4*4), OFDM, STBC, Beamforming, and MMSEdetector are simulated. The results such as bit error rate, packet error rate and bit rate with different system settings are given.Furthermore, the channel estimation process is clarified, and a DSP builder based MMSE detector is realized, which can fulfillexactly the same function as the Simulink model.

This thesis work carries out a study of IEEE 802.16 standards and mainly concentrates on the 802.16a OFDM PHY layer. A Simulink model based on 802.16a OFDM PHY baseband is built for simulation and performance evaluation. All mandatory blocks in the 802.16a OFDM-PHY specification are included: Randomization, FEC,adaptive modulation, and IFFT/FFT. A multipath Rayleigh fading channel is implemented and frequency domain channel estimation is selected for this model. Perfect synchronization is assumed.

In an optimal power control scheme for a Code Division Multiple Access (CDMA) system all mobile stations signals should arrive to the base station at equal power. If not, stronger singals may cause too much interference and block out weaker ones. Commonly used power control schemes utilizes the Signal to Interference Ratio (SIR) to design a Power Control Command (PCC) to adjust the transmit power of the mobile station. A significant problem within the conventional methods is the slow SIR recovery due to deep channel fades. Conventional methods base the PCC on the previous channel state when in fact, the channel state may have significantly changed when transmission occurs. These channel changes may cause the SIR to drop or rise drastically and lead to uncontrollable Multi Access Interference (MAI) resulting in power escalation and making the system unstable. In order to overcome power escalation and improve the recovery from deep fades a novel power control method has been developed. Based on Linear Quadratic Control and Kalman filtering for channel prediction this method designs the PCC based on the coming channel state instead of the current. This optimizes the PCC for the channel state where transmission occurs. Simulations show that this control scheme outperforms previous methods by making the impacts of the deep fades less severe on the SIR and also improves the overall SIR behaviour.

In this thesis we propose a multi-channel wireless network based on nodes that use multiple 802. 11 radio interfaces. The proposed system is singular, as it does not require new hardware or a new MAC, but instead leverages commodity 802. 11-based products. With this system, we target scenarios where the nodes are stationary and where their location can often be controlled. We evaluate the performance in this setup using an ad-hoc network approach whereby nodes generate as well as forward data. We also present and appraise a purely-wireless multi-channel infrastructure, which operates like the WLAN infrastructure-based networks in existence today, but without any fixed-line support. In such an infrastructure nodes dedicated for routing purposes provide wireless connectivity to users. We show that a multi-interface system provide significantly higher capacity in many scenarios. Our work puts forward various challenges, points to various anomalies in the operation of the 802. 11 MAC protocol, and shows the need to tackle unfairness issues. Our experiments demonstrate that the mere use of more dual-interface nodes does not necessarily create higher capacity. We also show that traffic differentiation significantly increases aggregate throughput in realistic scenarios. Finally, we provide an example of how simple channel-allocation algorithms in controlled random topologies can allow us to take advantage of a multi-interface system.

The traditional model of cryptography examines the security of cryptographic primitives as mathematical functions. This approach does not account for the physical side effects of using these primitives in the real world. A more realistic model employs the concept of a <I>side channel</I>. A side channel is a source of information that is inherent to a physical implementation of a primitive. Research done in the last half of the 1990s has shown that the information transmitted by side channels, such as execution time, computational faults and power consumption, can be detrimental to the security of ciphers like DES and RSA. This thesis surveys the techniques of side channel cryptanalysis presented in [Kocher1996], [Boneh1997], and [Kocher1998] and shows how side channel information can be used to break implementations of DES and RSA. Some specific techniques covered include the timing attack, differential fault analysis, simple power analysis and differential power analysis. Possible defenses against each of these side channel attacks are also discussed.

In the first part of the thesis, we study the trade-off between the transmission reliability and data rate in high signal-to-noise ratio regime in ad-hoc wireless networks. Bandwidth allocation plays a significant role in this trade-off, since dividing bandwidth reduces the number of users on each band and consequently decreases the interference level, however it also decreases the data rate. Noting that the interference power is substantially influenced by the network density, this trade-off introduces a measure for appropriate bandwidth allocation among users considering the network density. The diversity-multiplexing trade-off is derived for a one-dimensional regular ad-hoc network. In the second part of the thesis, we study the performance of point-to-point and broadcast systems with partial channel state information at the transmitter in a time-varying environment. First, the capacity of time-varying channels with periodic feedback at the transmitter is evaluated. It is assumed that the channel state information is perfectly known at the receiver and is fed back to the transmitter at the regular time-intervals. The system capacity is investigated in two cases: i) finite state Markov channel, and ii) additive white Gaussian noise channel with time-correlated fading. In a multiuser scenario, we consider a downlink system in which a single-antenna base station communicates with single antenna users, over a time-correlated fading channel. It is assumed that channel state information is perfectly known at each receiver, while the rate of channel variations and the fading gain at the beginning of each frame are known to the transmitter. The asymptotic throughput of the scheduling that transmits to the user with the maximum signal to noise ratio is examined applying variable code rate and/or variable codeword length signaling. It is shown that by selecting a fixed codeword length for all users, the order of the maximum possible throughput (corresponding to quasi-static fading) is achieved.