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1

ALGORITHM OF HIGH-PRECISION TRACKING OF SECONDARY SOURCES OPTICAL RADIATION AND ITS EFfi CIENCY

Автор: Dontsov

With use of methods of the theory of a fi ltration of existential signals the algorithm of highprecision tracking of moving object according to the image of its secondary source of optical radiation (an engine torch) is synthesized. It is shown that due to introduction of procedure of an assessment of equivalent radius of the image of a torch of the engine the algorithm provides steady tracking coordinates of moving object with a mistake no more than two elements of permission

2

AN EFFICIENT CROSS-LAYER AWARE MAPPING OF VOIP CALLS IN WIRELESS OFDMA SYSTEMS Part II. Mapping Algorithms and their Performance

Purpose: This work address and solve the problem of efficient broadcasting of resource allocations descriptors for VoIP traffic in mobile OFDMA-based wireless systems. Methods: We show that the mapping overhead is substantially reduced by using semi-persistent allocations and that by taking advantage of the periodicity of VoIP frames, generated by a multiphase vocoder. To handle the impact of mobility on the characteristics of the wireless channel we utilize a cross-layer decision approach to track the channel conditions and predict the expected mobile user behavior such that the system may under-react to channel changes in some cases. Results: The development efforts in this paper were directed towards developing efficient heuristic solutions since the problem is NP hard. Two heuristic algorithms with low computational complexity of O(n2) are presented and their performance gains are compared against a simple persistent allocation approach. Extensive simulations show that these mapping algorithms reduce the allocation overhead substantially in OFDMA-based systems such as WiMAX and LTE. The main advantage of the proposed algorithms is their ability to support multiple codecs, or a single codec with different operational modes, that result in different packet sizes and different periods. In addition, our proposed algorithms cluster the assignments together hence enabling the BS to allocate unused resources to other traffic types. Practical relevance: The proposed algorithmic solutions are simple enough to be implemented in practical OFDMA systems such as WiMAX and LTE to allow an efficient use of bandwidth for high quality VoIP sessions in of mobile users.

3

AN EFFICIENT CROSS-LAYER AWARE MAPPING OF VOIP CALLS IN WIRELESS OFDMA SYSTEMS Part I. Problem description and channel tracking

Purpose: This work addresses the problem of efficient broadcasting of resource allocations descriptors for VoIP traffic in mobile OFDMA-based wireless systems. Methods: We present the problem of mapping overhead and show that it can be substantially reduced by using semi-persistent allocations and by taking advantage of the periodicity of VoIP frames, generated by a multi-phase vocoder. To handle the impact of mobility on the characteristics of the wireless channel we utilize a cross-layer decision approach that tracks the channel quality and predicts the expected mobile user behavior such that the system may under-react to channel changes in some cases. Results: We explicitly show how the variability of the wireless channel can be tracked by using a Markovian model with a set of discrete states. By estimating both state- and transition probabilities of the multi-state Markovian model, we underline the foundations for a cross-layer decision algorithm that is able to overlook short transitions in channel states, without changing the modulation and/or the coding schemes. The main advantage of this approach is the ability to support multiple codecs, or a single codec with different operational modes, both result in different packet sizes and different periods. Practical relevance: The proposed channel tracking mechanism is simple enough to be implemented in the base station of any practical OFDMA-based system using the WiMAX or LTE technology