This article puts forward a new solution to the bound of the outage probability and transmission capacity of Ad-hoc networks. For the proofs of the upper and lower bounds are too complex, a much easier way is introduced to get the same results, and by using Taylor series, the asymptotic bound is derived. By comparing with the simulation results, we found that the asymptotic bound is sufficient accurate when the network parameters are selected properly, and is tighter than the upper and lower bounds.
The Internet of Things （loT） is called the world＇ s third wave of the information industry. As the core technology of IoT, Cognitive Radio Sensor Networks （CRSN） technology can improve spectrum utilization efficiency and lay a sofid foundation for large-scale application of IoT. Reliable spectrum sensing is a crucial task of the CR. For energy de- tection, threshold will determine the probability of detection （Pd） and the probability of false alarm Pf at the same time. While the threshold increases, Pd and Pf will both decrease. In this paper we focus on the maximum of the difference of Pd and Pf, and try to find out how to determine the threshold with this precondition. Simulation results show that the proposed method can effectively approach the ideal optimal result.
IEEE 802.11p has been proposed to extend the application of IEEE 802.11 to Wireless Access fast fading Vehicular Environments (WAVE).Due to the high velocities of vehicles and thus the inconstant topology of networks,it is extremely difficult to maintain communications without handoff in an Internet of Vehicles (IoV).Hence,fast handoff from one roadside unit (RSU) to another is necessary.Although some solutions have been given in IEEE 802.11r and 802.11f standards,the handoff latency is still as high as about 50 ms when adopting them.To address this issue in WAVE systems,a novel position-based handoff (PHO) scheme is proposed in this paper.In PHO scheme,the triggering of the handoff is accomplished by the location information of a vehicle instead of the power level of the received signal.Both the handoff process and latency of PHO scheme are analyzed.Finally,to verify the analytical results,simulations were conducted to date the effectiveness of the proposed PHO scheme.
In this paper, a cluster-based virtual multiple-input multiple-output （MIMO） transmission architecture is proposed for energy-constrained wireless sensor networks. In the proposed architecture, instead of using cluster members as cooperative nodes, multiple cluster heads cooperate to form virtual antenna array so that MIMO transmission can be implemented. According to the MIMO techniques used in this architecture, two different schemes, vertical Bell Laboratories layered space-time （V-BLAST） based cluster heads cooperative transmission （VCHCT） and space time block code （STBC） based cluster heads cooperative transmission （SCHCT）, are developed. Based on the communication energy consumption model, theoverall energy consumption model for both VCHCT and SCHCT are derived. Detailed comparison between these two schemes and the original low-energy adaptive clustering hierarchy （LEACH） is performed to investigate the performance of these two schemes. Simulation results not only verify the theoretical analysis but also show that the two schemes have their specific application scenarios. When the sink is far from the sensor area, SCHCT scheme is much more energy efficient than LEACH and VCHCT scheme even if it consumes additional inter-cluster communication energy. When the distance to sink is near the sensor area, VCHCT is preferable.
In order to improve the efficiency and fairness of radio resource utilization,a scheme of dynamic cooperative subcarrier and power allocation based on Nash bargaining solution（NBS-DCSPA） is proposed in the uplink of a three-node symmetric cooperative orthogonal frequency division multiple access（OFDMA） system.In the proposed NBS-DCSPA scheme,resource allocation problem is formulated as a two-person subcarrier and power allocation bargaining game（SPABG） to maximize the system utility,under the constraints of each user＇s maximal power and minimal rate,while considering the fairness between the two users.Firstly,the equivalent direct channel gain of the relay link is introduced to decide the transmission mode of each subcarrier.Then,all subcarriers can be dynamically allocated to the two users in terms of their selected transmission mode.After that,the adaptive power allocation scheme combined with dynamic subcarrier allocation is optimized according to NBS.Finally,computer simulation is conducted to show the efficiency and fairness performance of the proposed NBS-DCSPA scheme.
