On Network Performance Of Wireless Heterogeneous Network With Cooperation

With the burgeoning development of mobile Internet, the proliferated data requirement of mobile communications has been increasingly apparent. The wireless heterogeneous network with cooperation, which is capable of providing services on demand for users by taking full advantages of abundant stations, has been considered as one of the most promising architectures for the 5th generation mobile network. With the existence of more complicated wireless environment and more diverse network elements, there are the challenges for wireless heterogeneous network with cooperation in network strategy design, performance analysis and promotion, and radio resource management, etc. In order to meet these challenges, this dissertation makes an exploratory study on analyzing and promoting the performances of wireless heterogeneous networks with coordinated transmission. The main contributions of this dissertation are summarized as follows.(1)Performance analysis of wireless heterogeneous networks with dynamic cooperative clusters: To analize and promote the networking performances of general users in wireless heterogeneous networks, a K-tier network model is established utilizing stochastic geometry, and a dynamic selection strategy for station clusters to perform CoMP (Coordinated Multipoint) transmission based on average long-term received signal power is proposed. The expressions for coverage probability, average data rate and power efficiency are derived for a typical user based on the proposed model and strategy. With proper cooperation threshold selection,the proposed strategy outperforms the scheme of fixed number of stations both in coverage probability (41.1% increase on average based on simulations) and power efficiency (87.1% increase on average based on simulations), due to its design in dynamic decision of serving cluster according to current user requirements and network status. A trade-off between coverage probability and power efficiency is discovered and evaluated by proposing the new index "revenue efficiency". The impacts of network parameters including cooperation threshold on performances are also studied and discussed by analysis and simulations.(2)Performance analysis of cell-edge users with location-based cooperation: To analize and promote the performances of cell-edge users in wireless heterogeneous networks, a location-based CoMP strategy is proposed with 2-tier stochastic geometry model. The expressions for coverage probability, average data rate, power efficiency and revenue efficiency are derived for a typical user based on the proposed strategy. The proposed strategy significantly increases the coverage probability of cell-edge users comparing with no-cooperation scheme, due to its design in dynamic decision on serving mode according to current user location and network capability. It is discovered that the macro and micro stations have equivalent contributions in promoting coverage performance in cooperation. Besides, it is more effective for cooperation in promoting coverage performance if the coverage threshold or path loss factor is lower.(3)Physical layer security performance analysis of wireless heterogeneous networks with cooperation: To analyze the impact on physical layer security performance of introducing CoMP, the expressions of secured coverage probability for a typical user with non-colluding or colluding eavesdroppers are derived based on K-tier stochastic geometry model and dynamic cooperative clusters. It is proved that, introducing CoMP will increase secured coverage probability and the gain is negatively related to cooperation threshold with non-colluding eavesdroppers, while a maximum limitation for cooperation threshold exists in promoting secured coverage performance (23.5% increase on average based on simulations) with colluding eavesdroppers.(4)Joint allocation of bandwidth and power for wireless heterogeneous networks with cooperation: To reduce the complexity of radio resource management in wireless heterogeneous networks with cooperation, the optimization problem of bandwidth and power for cooperative networks with M stations and N users in no-interference scenario is established, and a low-complexity optimal allocation algorithm is designed both for cooperative diversity and multiplex modes based on the optimal solution conditions. This algorithm simplifies the allocation solutions in cooperative diversity mode, and reduces the computational complexity in cooperative multiplex mode from O[f(M,N)] to O[f(2,N)]. Considering game-based allocation in interference scenario,the gaming time is reduced as well by utilizing results from the proposed algorithm as the initial values.Thus, the above research can provid a theoretic guide for the sustainable operation and promote networking performances of wireless heterogeneous networks with cooperation, in terms of coverage probability,average rate, power efficiency and physical layer security. Moreover, the proposed allocation algorithm gives new simplification approaches and solutions in reducing the complexity in radio resource management.