In order to improve performance while keeping high spectrum efficiency of analog signal transmission, we recently proposed an analog single-carrier transmission with frequency-domain equalization (analog SC-FDE). In this paper, in order to improve the spectrum efficiency, analog SC-FDE using single sideband (SSB) technique is proposed. A theoretical analysis of normalized mean square error (NMSE) performance is carried out and confirmed by computer simulation. We show that analog SC-FDE using SSB technique achieves better NMSE performance than both conventional SSB transmission and analog SC-FDE while doubling spectrum efficiency of analog SC-FDE.
This paper addresses an approach to the conflict avoidance between Mobility Load Balancing (MLB) and Mobility Robustness Optimization (MRO) in the self-organizing networks. Conflict avoided methods have been proposed in the existing schemes. However, they cannot get the optimum values. Moreover, the distribution of the neighbor cell load is neglected, which has a great impact on the network performance. To this end, an effective scheme based on cell load has been presented. The objectives for MLB are designed and the MLB problem is formulated as a linear programming problem. Moreover, considering the cell load, the appropriate value of handover parameters for MLB can be obtained. The simulation results demonstrate the performance of the proposed method outperforms the exiting methods.
Bit Error Rate (BER) is a significant metric extensively used in the performance evaluation of digital communication systems. Although BER can always be estimated through computer simulation, closed form expressions are often desirable in many scenarios. In this paper we propose an approximate formula for the BER of Turbo codes. With the proposed approximation, BER of Turbo codes under additive white Gaussian noise (AWGN) channel can be expressed as a product of two Gaussian Q functions with a scaling factor only depends on the signal-to-noise ratio (SNR). Simulation results show that the approximation error of the proposed formula is less than 0.3 dB both in AWGN and block Rayleigh fading channel.
Estimation methods based on two-frequency continuous wave modulation (2FCW) for the train speed which are not affected by idling and slide of wheels are presented. The initial experimental results on the railway environments are also shown. The proposed methods obtained stable estimation results even in the situation where there exists shielding objects. The nonlinear least square method with an unknown quantity had the smallest standard deviation in the environment where the height of ballast track bed was not changed. The nonlinear least square method with two unknowns had the smallest bias errors between the estimation results and GPS speedometer.
We proposed an analog eigenmode transmission technique, that realizes multi-stream parallel transmission in a short-range multiple-input multiple-output (SR-MIMO) communication using only 180-degree hybrid couplers. Provided the MIMO array is symmetric, this technique can orthogonalize MIMO channels independently of antenna spacing and Tx-Rx distance. Furthermore, due to wideband characteristics of a hybrid, the channel orthogonalization effect can hold over a broad band of frequencies. In this letter, its array parameter independency and wideband characteristics are quantitatively evaluated in term of channel capacity. It has been experimentally clarified that this technique achieves approximately 90-% performance of ideal eigenbeam space division multiplexing (E-SDM) by digital-beamforming despite the deviations of the above factors.
In a 16QAM communication system, its carrier frequency offset (CFO) can be estimated by employing 4th power method if the 16QAM has 90-degree rotational invariance and the phase ambiguity can be removed by differential encoding. In this letter, we propose a new two-level differentially encoded 16QAM (TD16QAM) design which is suitable for tackling the CFO problem. The proposed TD16QAM is superior to the previously known TD16QAM in the bit-interleaved coded modulation (BICM) system corrupted by CFO.
Out-of-order packet problem incurs severe degradation of throughput performance of Multipath TCP (MPTCP) with heterogeneous communication links. In this paper, we propose an extended version of MPTCP to solve the out-of-order packet problem. The proposed method defines two types of ACK: Regular ACK and Extended ACK. When a receiver receives a data packet, the receiver sends a Regular ACK to the original path through which the data is transmitted, and Extended ACKs to all the other paths. If the Extended ACK arrives earlier than the Regular ACK, the proposed method solves the out-of-order packet problem. We evaluate the performance of the proposed method via NS-3 computer simulations, and show that the proposed method can improve the throughput performance when RTT of paths is heterogeneous.
Active Optical Network (ActiON) using a conventional slot allocation method in Plumbum Lanthanum Zirconate Titanate (PLZT) optical switches was proposed. The conventional slot allocation method shortens the switching idle time, which is a product of the switching guard time and the number of switching times. However, the transmission waiting time could exceed a user’s allowable delay. This paper proposes a delay-sensitive slot allocation method, which minimizes the switching idle time while considering the user’s allowable delay. Numerical results show that the proposed method reduces the number of switching times by up to 88 percent when compared to the conventional method.