Huamin Zhu

Performance analysis of an adaptive handoff algorithm based on distance information

Mobility is the most important feature of a wireless cellular communication system. Handoff, the process of changing the channel associated with the current connection while a call is in progress, is a key concept in providing this mobility. Continuation of an active call is one of the most important quality measurements in the cellular systems. Handoff makes it possible for a user to travel from one cell to another while having a seamless connection. In this study, an adaptive handoff algorithm with a dynamic hysteresis value, based on the distance between the mobile station and the serving base station, is proposed for cellular communications. Handoff probability is calculated to evaluate handoff algorithms analytically. The proposed handoff algorithm is compared with an algorithm with a fixed hysteresis value, algorithm based on absolute and relative signal strength measurements and algorithm based on distance and relative signal strength measurements. Performance is evaluated in terms of the average number of handoffs, average handoff delay, standard deviation of handoff location, average signal strength during handoff, and probability of link degradation. Numerical results and simulations demonstrate that the proposed algorithm outperforms the handoff algorithm with fixed hysteresis level, handoff algorithm using both threshold and hysteresis, and handoff algorithm based on distance and hysteresis. The effect of distance error is also discussed.

Performance analysis of fast handoff with mobility prediction

A location-aided handoff reservation scheme with mobility prediction for wireless cellular networks is proposed in this study. We analyze the performance of the proposed handoff reservation scheme and propose a two-dimensional (2-D) random walk model for simulation to show its effectiveness. The influences of the threshold distance and mean value of the distance that the mobile station moves in a straight line are also investigated.

Improving handoff performance by using distance-based dynamic hysteresis value

In this study, an adaptive handoff algorithm with a dynamic hysteresis value, based on the distance between the mobile station and the serving base station, is proposed for cellular communications. Handoff probability is calculated to evaluate handoff algorithms analytically. The proposed handoff algorithm is compared with an algorithm with fixed hysteresis, an algorithm using both threshold and hysteresis, and a handoff algorithm based on distance and hysteresis. Performance is evaluated in terms of the average number of handoffs, average handoff delay, standard deviation of handoff location, average signal strength during handoff, and probability of link degradation. Numerical results and simulations demonstrate that the proposed algorithm outperforms other handoff algorithms. The effect of distance error is also discussed.

SUPERIMPOSED TRAINING-BASED CHANNEL ESTIMATION FOR MIMO-MB-OFDM UWB SYSTEMS

A novel channel estimation scheme based on superimposed training is proposed for multiple-input multiple-output multi-band orthogonal frequency division multiplexing ultra-wideband systems. The optimal training symbols are derived with respect to the least-square channel estimate mean square error. Simulation shows that the proposed scheme benefits much higher effective data throughput over the conventional method.

Adaptive Handoff Using Distance Information

In this study, we propose an adaptive handoff scheme with dynamic hysteresis value for cellular communications, which is based on distance between the mobile station and the serving base station. Performance is evaluated in terms of the expected number of handoffs, the expected handoff delay, standard deviation of handoff location, and the expected link degradation probability as well. Numerical results and simulations show that the proposed scheme outperforms the handoff schemes with static hysteresis levels. The effect of distance error is also discussed

Resource Reservation for Handoff Using Location-Aided Mobility Prediction

In this paper, a resource reservation scheme for handoff using location-aided mobility prediction is proposed for wireless cellular networks. We analyze the performance of the proposed scheme and propose a two-dimensional random walk model for performance evaluation. The influences of threshold distance, average distance where the mobile station moves along a straight line and location error are investigated. The effectiveness of mobility prediction is also evaluated. Performance comparison reveals that the proposed scheme performs better than the solely distance-based scheme without mobility prediction

LOCATION-AIDED RESOURCE RESERVATION FOR HANDOFF BASED ON MOBILITY PREDICTION

In this paper, a location-aided resource reservation scheme for handoff based on mobility prediction is proposed for wireless cellular networks. We analyze the performance of the proposed scheme and propose a two-dimensional random walk model for simulation. Performance evaluation is done by computing several key performance criteria, i.e., prediction accuracy, average number of reservation per call, reservation efficiency, and reservation time overhead. The influences of threshold distance, average distance where the mobile station moves along a straight line, location error and sample time are investigated, and the effectiveness of mobility prediction is also evaluated. Performance comparison reveals that the proposed scheme performs better than a solely distance-based scheme without mobility prediction.

Performance analysis of an adaptive soft handoff algorithm for mobile cellular systems

In this paper, an adaptive soft handoff algorithm, which dynamically calculates the threshold values for soft handoff based on the received signal strength, is proposed for mobile cellular communication systems. An analytical model is developed to study the performance of soft handoff algorithms. Performance is evaluated in terms of the average number active set updates, the mean size of the active set, the mean time of soft handoff, the average signal quality and link degradation probability, where a link degradation is defined to be the event that the signal strength falls below a level required for satisfactory communication. The adaptive soft handoff is shown to yield a significantly better tradeoff than the handoff algorithm with static thresholds.

Centralized and Decentralized Channel Estimation for Multiuser MIMO-OFDM Systems

This paper addresses pilot-aided multiuser least square (LS) channel estimation for the uplink of MIMO-OFDM systems. The systems under consideration allow all users use all available subcarriers independently and thus involve multiuser interference in the frequency domain. We develop the decentralized and centralized channel estimation algorithms according to different multiuser scenarios. Optimal multiuser pilots are proposed specially for centralized estimation methods with respect to the mean square error (MSE) of LS channel estimate

Adaptive Handoff with Dynamic Hysteresis Value Using Distance Information in Cellular Communications

In this study, we propose an adaptive handoff scheme with dynamic hysteresis value for cellular communications, which is based on distance between the mobile station and the serving base station. Performance is evaluated in terms of the expected number of handoffs, the expected handoff delay, standard deviation of handoff location, and the expected link degradation probability as well. Numerical results and simulations show that the proposed scheme outperforms the handoff schemes with static hysteresis levels. The effect of distance error is also discussed.