| Higher requirements are put forward for the future 5G network: 1000 x mobile data volume, 10-100 x connected devices, 5x lower latency, 10-100 x end–user data rate, etc. To meet the exponential growth of wireless communication capacity, cooperative transmission has been studied in many papers as an effective approach to improve the wireless transmission capacity and reliability in the fifth generation(5G) small cell networks. Heterogeneous with dense deployed small cell network which can enhance the system capacity but also brings the challenges. The more complicated interference, the more frequently handoff and larger overhead because of user mobility, all these problems required to be solved.First, this paper introduced in a new network structure with C/U split. And deploy small cells on the cover area of macrocell, the small cell is PPP(Poisson Point Process). Then we propose a cooperative scheme which is based on the distance between user and the small cell bases. With a cooperative threshold the user chooses the suitable small cell base station to cooperate. We derive the distribution of the distance and further derive the cooperation probability.Based on the cooperative model, we analyze the coverage probability of SISO(single input single output) scenario. And then that of MIMO(Multiple Input Multiple Output), the simulation results indicates that compared with no cooperation and cooperation with single antenna, the multi-cell cooperative scheme has a better coverage performance.Finally, with the cooperative probability and coverage probability we derived from above, we propose an overhead rate to evaluate the performance. We evaluate the handoff rate of user. The simulation results show that there is a minimum overhead rate with different cooperative threshold, which means we can find a compromise between overhead and the capacity gain. This can be instructive to evaluate the overhead and help to choose the small cell’s radius of network deployment. |
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