Performance Analysis And Resource Allocation Of LoRa Modulation-aided Cooperation Communication Networks

With the explosive growth of Internet of Things（Io T）technologies,large-scale Io T deployments like smart transportation and smart city demand for low-power,wide-area and low-cost solutions,which are not fulfilled by conventional wireless communication technologies.In order to meet the requirements,low power wide area network（LPWAN）technology has been proposed.As an outstanding candidate in LPWAN technologies,LoRa technology has many unique advantages,which are robust to interference,multi-path fading and Doppler effect.Hence LoRa technology has appeared to be a competitive and promising alternative in LPWAN technologies.In conventional star-topology LoRa networks,long-range information transmission is inevitable among LoRa devices.Hence,a major challenge for the conventional LoRa system is the performance degradation due to the long-range communication over fading channels.Since cooperative communication has the inherent advantage of mitigating wireless channel fading,which it helps to improve the reliability of the wireless networks by allowing the nodes to collaborate with each other.To resolve the challenging issue,this thesis integrates the relaying techniques with LoRa networks,gives the performance analysis of the proposed system,and proposes a resource allocation optimization scheme for the system.The system performance is also investigated when interference is considered.The main contributions of the dissertation lie in:（1）This thesis investigates a two-hop amplify-and-forward relaying LoRa network in a two-dimension plane,where random nodal distances are considered.Moreover,since the relay selection is crucial for the whole network in cooperative communication,a relay-selection mechanism is developed for the proposed system.It has talented portability since the nodes operate with different modes specified in LoRaWAN protocol and hence can be applied to the conventional LoRa system conveniently.（2）With the best relay-selection protocol,the analytical bit-error-rate（BER）and asymptotic BER expressions are derived over the Nakagami-m fading channel.Based on the asymptotic results,the achievable diversity order,coverage probability,and throughput of the proposed system are carefully derived.Simulation and numerical results show that although the proposed system reduces the throughput compared to the conventional LoRa system,it significantly improves the BER and coverage probability.（3）Based on the proposed relay-selection mechanism,to maximize the throughput of the proposed system,a two-dimensional resource allocation optimization problem（i.e.,the spread factor selection and power allocation optimization）is formulated and investigated.In the spread factor selection phase,the proposed selection algorithm can select the best spread factor under the throughput threshold constraint.In the power allocation optimization phase,the optimal allocation factor is calculated by convex optimization and numerical optimization methods under the symmetric and asymmetric Nakagami-m fading channel,respectively.Analyses and simulations have demonstrated that,the proposed joint spread factor and power allocation optimization scheme achieves the significant BER and throughput performance improvement in the proposed system,which outperforms the two baseline schemes.