Titolo: Resource Allocation in Adaptive Parallel ...
Casa editrice: Shaker Verlag Dez 2013
Data di pubblicazione: 2013
Condizione libro: Neu
Neuware - In order to successfully transmit a message from a source to a receiver without the cooperation of other nodes over a long distance results in a high energy consumption. Cooperative relaying protocols have the potential to save energy and enhance the throughput by utilizing the broadcast nature of the wireless medium. Therefore, it is believed that cooperative relaying strategies will play a crucial role in future wireless communication systems. In an orthogonal multiple access scheme, the relays use exclusive time-slots or frequency-bands. Thus, efficient resource allocation is critical for the enhancement of throughput in a relay network with orthogonal multiple access scheme. The present thesis addresses the issue of resource allocation in a parallel relay network. These resources include time-slots or frequency-bands, power (energy), and the code rate. Moreover, the main consideration of this thesis is a network with adaptive relays, i.e., the relays change their processing behavior w.r.t. the reliability of the received signal from the source. Allocation of channel resources such as number of time-slots or frequency-bands is dealt by proposing different optimal and sub-optimal solutions in Chapter 3. A novel allocation scheme termed as marginal returns based resource allocation is introduced to allocate the number of time-slots or frequency-bands. The computational complexity of these algorithms is determined using simulations. The results show that the suboptimal solution has very small computational complexity as compared to the optimal solution, nevertheless the performance of the proposed sub-optimal solution is similar to the optimal solution. Furthermore, results show that though efficient resource allocation requires channel state information it can significantly improve the performance of the considered cooperative relay network as compared to the fixed time-slots allocation. It is also observed that the allocation of the optimal number of time-slots to the source is necessary for better performance. For power allocation, the convex optimization technique the method of Lagrangian multipliers is used in Chapter 4. In the context of power allocation, the impact of power minimization on the throughput and vice versa are also discussed. These results also show that the proposed technique significantly save more energy as compared to a strategy with uniform power allocation and non-cooperative case. Furthermore, it is shown that the throughput maximization has deep impact on the sum power minimization and vice versa. The concept of resource allocation with marginal returns is extended and applied to the rate allocation for relaying protocols with repetition coding and coded cooperation in Chapter 5. It is evident from the simulation results that though coded cooperation requires the activated relays to decode successfully, still its performance is much better than that of the relaying protocols based on repetition coding and non-cooperative case. Moreover, it is found in Chapter 3 that for channel resources allocation it is important to optimize the number of time-slots (frequency-bands) allocated to the source. However, for rate optimization, it is optimal to allocate only a single time-slot or frequency-band to the source. Furthermore, it is found that most of the times only relays with decode-and-forward are activated and relays with amplify-and-forward are used rarely in conjunction with rate optimization. The devised resource allocation solutions assume perfect channel state information and Shannon's capacity achieving codes. Both of these suppositions are not possible in practice. Therefore, strategies for power allocation with imperfect channel knowledge and practical codes are also proposed in Chapter 6. 230 pp. Englisch. Codice inventario libreria 9783844024036
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