Young-uk Chung

Macrocell/microcell selection schemes based on a new velocity estimation in multitier cellular system

The International Mobile Telecommunications IMT-2000 system uses a microcell concept to provide multimedia services and to support an increasing number of users. However, in a microcell system, the number of handoffs is greatly increased. To solve this problem, a multitier cellular structure is proposed, in which high-speed mobile terminals (MTs) are serviced in macrocells and low-speed MTs are serviced in microcells to minimize the number of handoffs. It is important to estimate precisely the speed of the MT for the correct selection of the macrocell/microcell. We propose two macrocell/microcell selection schemes based on a new velocity estimation method in a multitier cellular system which uses the sojourn time in a microcell overlapping region. The proposed schemes have various advantages such as good performance when the MTs direction is varying, efficient user allocation to cells, quick velocity estimation capability, easy implementation, and low power consumption. We analyze and simulate conventional schemes and our proposed schemes in the Manhattan cell model, and show that the proposed schemes have better performance.

Velocity estimation using adaptive array antennas

Estimation of user velocity is important for efficient system management in mobile cellular systems. A velocity estimation scheme using adaptive array antennas is proposed. The proposed scheme estimates user velocity based on moving distance information and sojourn time information. This scheme can estimate real velocity accurately with low cost. We analyzed and simulated our proposed scheme, and it is shown that the proposed schemes can estimates user velocity accurately.

A new macrocell/microcell selection method in multitier cellular system

In this paper, we propose a new macrocell/microcell selection scheme in a multitier cellular system using sojourn time of microcell overlapped region. The proposed scheme has many advantages such as good performance when the direction of the mobile terminal is varying, efficient user allocation to cells, capability of relatively accurate velocity estimation, easy implementation and low power consumption. Also, comparing the analysis and simulation results with conventional methods, we found that the proposed scheme has better performance than conventional schemes.

A novel transmission procedure for throughput maximization in 1xEV-DV reverse link

In this paper, we propose an enhanced reverse link transmission procedure for 1xEV-DV which is an evolution of the cdma2000 1x for the support of circuit-switched voice and data as well as packet-switched high speed data on the same spectrum. The proposed scenario controls all mobile terminals separately. To dedicate control of each user, this scenario induces rate control (RC), MT status indication (MSI), and rate variation indication (RVI). It supports a large variance of the data rate due to the estimation of the mobile location and speed. To verify the performance of the proposed scenario, we investigated a portion of overshoot, goodput and delay. The results shows that the proposed scenario can utilize the reverse link resource efficiently by providing a rapid adaptation and accurate control of the data rate.

A resource allocation algorithm using frequency borrowing in hierarchical CDMA cellular systems

The great increase of the number of users requires efficient management of the spectrum. In hierarchical cellular systems based on CDMA, the frequency borrowing resource allocation (FBRA) algorithm is proposed to allocate frequency spectrum more efficiently. This algorithm lends frequency spectrum of macrocell to microcells when mass hot spot occurred. We analyze the interference to signal ratio and reverse link capacity in case of using the proposed algorithm. Based on the result, the algorithm performance is evaluated in view of blocking, the handoff refused probability, and the spectrum efficiency. The numerical result shows that the proposed algorithm can increase the capacity and solve the mass hot spot problem.

Performance analysis of handoff algorithm in fiber-optic microcell/picocell radio system

The fiber-optic radio system was proposed to solve the cost problem of micro/picocell system. In this system, all channel elements in a system can be dynamically assigned when the SDS is used. We analyzed the performance of soft handoff used as intergroup handoff in the CDMA based fiber-optic cellular system with a spectrum delivery switch (SDS). Performance is evaluated in view of blocking and handoff refused probability. The numerical results show that the smaller the handoff region or the more the channel, the larger the system capacity. We can also see that the larger queue makes the handoff refused probability lower.

General modeling of radio resource management scheme for multimedia data packet transmission in wireless forward channel

Up to now, much portion of studies for mobile communication is focused on reverse link because the current mobile communication is adapted to voice traffic. But as data traffic increases, research on using forward link resource efficiently providing the QoS becomes important. In this paper, a general model of resource management schemes that provide the QoS is proposed and its characteristics are also shown. The proposed general model is verified through numerical examples for a system that provide voice and Web service.

A traffic dispersion strategy in fiber-optic multitier cellular system

Using frequency borrowing, we propose a channel allocation scheme in a hierarchical cell structure. The proposed scheme is suitable for a downtown environment in which bulky hot spot cells occur periodically at specific times. The performance is evaluated in view of blocking, handoff dropping probability and FA efficiency.

Performance analysis of group handoff in fiber-optic cellular system

The simulcast technique is used to diminish handoff rate and share resources among multiple cells. Using dynamic grouping, the simulcast technique can also rearrange traffic load. In the fiber-optic cellular system, this technique can be implemented easily. In this paper, we analyze group handoff generated by dynamic grouping in the fiber-optic cellular system. Performance is evaluated in view of blocking and handoff call dropping probability. It is shown that the larger the difference of call arrival rate in each group, the better the performance of dynamic grouping. Numerical results also show that simulcast technique using dynamic grouping provides better performance than that using fixed grouping.