Coordinated multi-point transmission (CoMP) with the joint transmission (JT) scheme is employed in cellular networks to improve the data rate, the cell-edge throughput and/or to increase the system throughput. In CoMP-JT, since the user equipment (UE) is capable of receiving the desired signal from an adjacent cell as well as from its serving cell, it can achieve an improved signal to interference ratio. However, this scheme entails exhaustion of resources in serving base station (BS). In this paper, we propose a call admission control scheme (CAC) to improve the performance of CoMP-JT based cellular systems. In this CAC scheme, CoMP-JT technique is applied to UEs located near the edge of a cell. In order to establish an analytical model for CoMP-JT based cellular systems, we introduce a model for traffic analysis using a two-dimensional Markov chain and approximate the computation of the power sum of multiple log-normal random components in a multi-cell environment. Performances of CoMP-JT based cellular systems are evaluated with respect to two quality of service (QoS) constraints pertaining to call-blocking and outage probabilities, respectively from the network-layer and the physical-layer perspectives. We first measure the resource utilization and call blocking probability for the downlink resources for various offered loads in the cell. Based on that, we obtain the outage probability and effective throughput of the system. The analytical results are compared with computer simulations. Finally, we consider the dynamic point selection (DPS) scheme that is a modified version of the JT scheme, in which some resources of adjacent cells are muted.

In this paper, we investigate the performance of IEEE802.16d random access protocol based on orthogonal code-division-multiple-access and frequency-division-multiple-access in time division duplexing mode using equilibrium point analysis. The random access protocol of IEEE802.16d is similar to demand-assigned multiple access with piggyback, in which bandwidth request is allowed at the end of data transmission. In the analysis, we consider the retransmission probability derived from a binary exponential backoff algorithm. The performance is presented in terms of initial access delay, its throughput, message transmission delay and the system throughput with piggyback by varying number of subscriber stations, number of PN codes for bandwidth request ranging, number of slot-subchannel and the parameters of the binary exponential backoff algorithm.

Virtual simulation technology has been considered as a highly efficient and cost-effective solution for a soldier training system, and evolved into diverse combinations of hardware and software. To maximize the virtual reality effect within a restricted space, a locomotion interface such as an omni-directional treadmill is introduced as a major component of a virtual simulator, therefore real time interaction between human and the virtual simulator becomes very important. Displacement and heading changes of the trainee are crucial information to control the virtual simulator when we implement highly reactive motion control for the omni-directional treadmill and interaction control of the virtual contents. This paper proposes a control parameter estimation algorithm for the virtual training simulator by using two types of motion capture sensors and presents the experimental results. Kinematic joint positions are analyzed to estimate the trainee’s location and velocity for feedback and feedforward control of the omni-directional treadmill. The accuracy of two approaches is evaluated by comparing with the reference system, which gives a ground truth value.

The IEEE802.16j standard uses non-transparent relay stations to extend coverage. There are two types of non-transparent relay modes, that is, the time-division transmit and receive (TTR) relay mode which can operate with one of two types of frame structures, a single-frame and multiframe structure, and the simultaneous transmit and receive (STR) relay mode. In this paper, we analyze the relay performance of TTR and STR relay modes in IEEE 802.16j MMR system. We also propose a fair resource allocation scheme for the downlink relay frame. Numerical results show that relay performance of the TTR with a single-frame or a multiframe structure and that of the STR relay modes are almost the same in a two-hop system. However, in a three-hop system, the TTR mode with a single-frame structure outperforms other relay modes.