Angle of arrival (AoA) and angle of departure (AoD) are introduced in Bluetooth 5 to better support indoor localization and tracking. However, the performance of AoA estimation using Bluetooth 5 is not thoroughly understood at present. In this paper, a Cramér-Rao lower bound (CRLB) model, taking into account Constant Tone Extension (CTE) signals firstly adopted by Bluethooth 5, is proposed to theoretically analyze its performance given different uniform antenna arrays, such as linear, rectangular and circular arrays, and on these grounds, the effects of the number of antennas, inter antenna distance, incident angle, and CTE parameters on AoA estimation are carefully investigated. A simulation analysis is carried out and a comparison between different types of antenna arrays is reported as well.

Dual connectivity (DC) is regarded as a promising technology to increase users’ throughput, provide radio link robustness, and improve load-balancing among base stations (BSs). However, since the introduction of DC makes the mobility of network more complex and diversified, especially the mobility management of heterogeneous networks (HetNets) based on DC faces great challenges. Taking event-A3-based measurement report as the trigger condition for handover (HO), this paper compares and evaluates the influences of HO of master nodes (MNs) and secondary nodes (SNs) on link reliability in different bearing modes. Particularly, hybrid automatic repeat request (HARQ), throughput, channel quality indicators (CQIs), and data packets queuing time are taken as link reliability analysis indicators. Besides, we study how DC utilizes the traffic split ratio between MNs and SNs to maximize the superiority of throughput. Simulation results show that DC can effectively reduce the impact of HO on the number of HARQ and increase the throughput of users. When the data traffic is tilted to the secondary nodes, the superiority of throughput is more obvious.

The reform of any course cannot be accomplished in one move and needs to be improved continuously for a long time.The scheme of blended learning reforms was shown from selecting online learning resources, dividing curriculum content, the problem of Blending learning hours and the implementation of discussion and cooperative learning in this paper.We also discussed some problems faced by Fundamentals of Circuit Analysis course in the Blending learning reform, and shared some of the accumulated experience and relevant suggestions.After 4 years' blended learning reforms, the class based on Fundamentals of Circuit Analysis has effectively improved the dull state, and enhanced students' interest in learning, which has also significantly improved the teaching effect.At the same time, this "student-centered" teaching design plays a great role in cultivating students' innovation ability.

In this paper, we analyze the performance of outage probability for downlink transmission in two-tier heterogeneous cellular networks. In order to save spectrum resources, we adopt frequency reuse scheme, which will result in cross-tier interferences. The macro base station (MBS) provides useful signal for macro user equipment (MUE), in contrast, the signals provided by small base stations (SBSs) around MUE becoming the interferences. We use Fenton-Wilkinson method and Farley method to approximate the sum of multiple interferences, these two methods can simplify the calculation of outage probability and then we compare the approximation results. The derived expressions are validated by the Monte Carlo simulations and simulation results are generated to assess the feasibility of two methods' accuracy and the circumstance of applications.

In this paper, we consider a system where a secondary base station (SBS) with K antennas utilizes the licensed spectrum of a single primary user (PU) to send information to N secondary users (SUs). Each SU and PU is equipped with one antenna, respectively. The SBS selects only one antenna out of the K antennas by using maximum signal power to leak interference power ratio strategy (SLIR). Using asymptotic analysis, we first derive the average capacity of the best user scheme, with perfect channel state information from the SBS to the PU (interference CSI) available at the SBS. Due to limited cooperation between the SBS and the PU, perfect interference CSI is not always available at the SBS. Then, we characterize their capacity loss in the case that perfect interference CSI is not always available at the SBS.

This paper first introduces the performance analysis of two classical channel quality indicator (CQI) feedback schemes which are best-n feedback and the threshold based feedback and derives the mathematical expressions of average capacity which is described by Theorem 1 and 2. Then, a reduced feedback scheme is designed for multiple traffics and multi-channel. The novel scheme combines the best-n feedback and the threshold based feedback together to reduce the feedback overhead. The proposed scheme can not only guarantee the quality of service (QoS) requirement of real time (RT) traffic but also reduce feedback overhead at the cost of a marginal increased downlink overhead. Simulation results demonstrated the good performance of the proposed feedback scheme.

In this paper, a novel semi-static inter-cell interference coordination scheme based on spectrum pool is proposed for cellular OFDMA systems. In the proposed scheme, the spectrum is divided into three partitions, called major subbands group, minor subbands group and spectrum pool group. The major subbands and the spectrum pool are used by all users in a cell and the minor subbands only can be used by cell center users. The proposed scheme consists of two stages, i.e. at the frequency planning stage, the eNB allocates the major subbands and the spectrum pool to cell edge users and the minor subbands to the cell center users according to variation of the cell edge traffic load; at the intra-cell scheduling stage, the cell edge users are scheduled based on the major subbands and the spectrum pool first, and then the cell center users are scheduled on the remaining resources. The proposed scheme not only enhances the cell edge throughput but also reduces the inter-cell signaling overhead and complexity. Simulation results and performance analysis validate the effectiveness and good performance of the proposed scheme.

Impact of the channel estimation error and feedback delay on the throughput of multi-input and multi-output (MIMO) downlink systems is investigated. The dynamic transmission schemes based on TDMA and SDMA with zero-forcing beamforming (ZFBF) are described and their associated system throughput are compared. It is shown that the system performance is sensitive to the channel estimation error, and degrades significantly as variance of estimation error increases.

The downlink zero-forcing beamforming strategy in the case of random packet arrivals is investigated. Under this setting, the relevant fairness criterion is the stabilization of all buffer queues which guarantees a bounded average delay for all users. It has been shown that allocating resources to maximize a queue-length-weighted sum of the rates is a stabilizing policy. However, the high complexity of user selection and the feasible rates determination for optimal scheme may prevent the real-time scheduling operation. Two low complexity algorithms are provided taking the channel state, queue state and orthogonality into account. In particular, the authors pick the first user with the largest product between channel gain and queuing length, and select the remaining users to construct candidate user set based on the greedy user selection method or channel orthogonal user selection method. Then, the power and rate allocation for the selected users are implemented based on the modified water-filling method. The complexity of the proposed algorithms is analyzed. The average delay and average throughput are studied in homogeneous scenarios and heterogeneous scenarios, respectively. Simulation results show that the proposed algorithms can take full advantage of the multi-user diversity gain and provide average delay (or throughput) and fairness improvement compared with channel-aware-only schemes.

A new and efficient radio resource allocation and scheduling algorithm for SDMA/OFDMA systems with downlink zero-forcing beamforming is proposed to support the diverse quality of service (QoS) requirements of heterogeneous services. In particular, a unified urgent weight is given by taking into account QoS requirements (i.e., delay deadline, minimum data rate), queue length and user fairness. The subcarrier is dynamically allocated to the user with the highest priority. Then the remaining users on the same carrier are selected based on the semi-orthogonal user selection scheme. Finally, allocating the transmit power with a greedy method to the spatial subchannels; is implemented. The goal of the algorithm is to maximize the system throughput by fully exploiting multiuser diversity gain in space, time, and frequency domain while guaranteeing the QoS for real time (NT) services with delay deadline requirement and non-real time (NRT) services with minimum data rate requirement.