| Heterogeneous networks and cooperative communications are two of important aspects of research on 5G mobile communications. In this paper, we investigate the cooperative communications in heterogeneous networks that support two kinds of transmission technologies, namely, short-distance network transmission and conventional cellular networks transmission. A mobile station(MS) equipped with both short-distance transport interface and cellular network interface can choose one of them to transmit data in heterogeneous network can. MSs choose access ports for optimizing the usage of the network resources and deceasing the load of base stations(BSs). There are many technologies are employed for user cooperation, including multiplexing technology and relay coordination which we focus on.In this paper, we analyze the uplink communication performance in the heterogeneous network scenario consisting of some BSs and MSs whose locations follow Poisson point processes(PPPs), respectively. The MSs are equipped with multiple radio access interfaces including a cellular access interface and at least one short-range communication interface. We mainly analyze two kinds of cooperation technology(relay technology and multiplexing technology) and their impacts on connectivity and energy efficiency of the network and get close-formed mathematical expressions about them.First of all, we analyze relay technologies in uplink transmission, and propose a nearest free MS cooperation scheme considering free MSs as relay nodes and study this scheme and its impact on network connectivity and energy consumption. Then we present a nearest active MS cooperation scheme considering multiplexing technology, in which the cooperation occurs between a MS and its recent active neighbor MS for the uplink transmission. Specifically, the MS and its nearest neighbor first exchange data by the short-range communication. Upon successful decoding of the data from each other, theyproceed to send their own data, as well as the data received from the other, to the BS. At this time MS can use a variety of multiplexing techniques, e.g., OFDM technology and time-division multiplexing technology, etc. Considering that the homogeneous PPP distribution of MSs and the Rayleigh fading channel, we derive close-formed mathematical solution of the outage probability and the energy consumption.Numerical results show that employing the nearest free MS cooperative transmission scheme leads to a great improvement of network connectivity. When using the nearest active MS cooperative transmission scheme, we can see not only the greatly improved connectivity, but also sharply declined energy consumption. These two schemes, which can improve the system performance effectively, are of significant technical feasibility, so they can be easily used in 5G heterogeneous mobile communication. |
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