Radio over Fiber (RoF) is a promising solution for providing wireless access services. Heterogeneous radio signals are transferred via an optical fiber link using an analog transmission technique. When the RoF and the radio frequency (RF) devices have a nonlinear characteristic, these will create the intermodulation products (IMPs) in the system and generate the intermodulation distortion (IMD). In this paper, the IMD interference in the uplink RF signals from the coupling effect between the downlink and the uplink antennas has been addressed. We propose a method using the dynamic channel allocation (DCA) algorithm with the predistortion (PD) technique to improve the throughput performance of the multi-channel RoF system. The carrier to distortion plus noise power ratio (CDNR) is evaluated for all channel allocation combinations; then the best channel combination is assigned as a set of active channels to minimize the effect of IMD. The results show that the DCA with PD has the lowest IMD and obtains a better throughput performance.

The dynamic channel allocation (DCA) scheme in multi-cell systems causes serious inter-cell interference (ICI) problem to some existing calls when channels for new calls are allocated. Such a problem can be addressed by advanced centralized DCA design that is able to minimize ICI. Thus, in this paper, a centralized DCA is developed for the downlink of multi-cell orthogonal frequency division multiple access (OFDMA) systems with full spectral reuse. However, in practice, as the search space of channel assignment for centralized DCA scheme in multi-cell systems grows exponentially with the increase of the number of required calls, channels, and cells, it becomes an NP-hard problem and is currently too complicated to find an optimum channel allocation. In this paper, we propose an ant colony optimization (ACO) based DCA scheme using a low-complexity ACO algorithm which is a kind of heuristic algorithm in order to solve the aforementioned problem. Simulation results demonstrate significant performance improvements compared to the existing schemes in terms of the grade of service (GoS) performance and the forced termination probability of existing calls without degrading the system performance of the average throughput.

In this paper a multi-channel MAC protocol with dynamic channel allocation (MMAC-DCA) in CDMA Ad Hoc networks is proposed. Under MMAC-DCA, the service sub-channels are dynamically allocated by the RTS/CTS dialogue on the common sub-channel, only when a node has a packet to transmit. In addition, a Markov mode is presented to analyze the performance of MMAC-DCA.

It is well known that the diversity gain attained by DCA (Dynamic Channel Allocation) is generally very high over OFDM (Orthogonal Frequency Division Multiplexing)-based broadband networks. This paper introduces a numerical approach for measuring the performance gain afforded by DCA. In the mathematical analysis, the property of order statistics is adopted to derive the upper bound of the expected throughput via the use of DCA. In the simulation, it was possible to achieve a gain of 5 dB by exploiting multi-user and spectral diversities when the number of users is 16 and the total number of subcarriers is 256.

Our investigation is presented into analysis of the co-channel interference (CCI) statistic in orthogonal frequency-division multiple access (OFDMA) uplink systems. The derived statistic is then used to analyze the performance of reuse partitioning (RP)-based dynamic channel allocation (DCA). Analysis and simulation results show that the performance of DCA in multi-cell environments is noticeably dependent on the CCI. Finally, the results of the analysis yield the optimum RP area for achieving the maximum spectral efficiency.

In designing a video-on-demand system, one of the major challenges is how to reduce the client's waiting time maintaining the concurrently used channels. For this reason, the hybrid architectures which integrate the multicast streams with the unicast streams were suggested in order to improve channel efficiency in recent years. In combining multicast with unicast, the ways to group the channels together are important so that more clients can share the multicast transmission channels. This paper proposes a hybrid video-on-demand system which gathers the unicast and multicast transmission channels efficiently by using dynamic channel allocation architecture. The newly proposed architecture can reduce the average client's waiting time significantly. The numerical results demonstrate that the dynamic channel allocation architecture in some case (e.g., 100-channel and 10-video system at 0.5 requests/second) achieves performance gain of 551% compared to existing architecture. This paper presents procedure of channel release and reuse, performance analysis, and simulation results of the dynamic channel allocation architecture.

The umbrella cell system, where the same radio system is used for microcells and overlaying macrocells, is a promising strategy for deploying microcell service to cope with the locally increased radio traffic. The interference at microcells due to macrocells can be compensated by increasing the transmit power of microcell. In this paper, a practical method to implementing a microcell system overlaid with an existing macrocell system is proposed. In order to engineer the radio resource planning for the underlaid microcells, transmit power design and application of Channel Segregation, a self-organized dynamic channel assignment, are proposed. By these techniques, the system channels are reused automatically while minimizing interference between macrocell and microcell systems, thereby communication quality of umbrella cell system can be improved. Furthermore, the prime advantage of the proposed method is that locally increased traffic is handled by the underlaid microcells without any extra effort for channel management.

This paper reviews Dynamic Channel Allocation (DCA) in TDMA cellular systems. The emphasis is on distributed DCA, which features decentralized control and adaptability to interference. Performance measures are discussed not only from a theoretical viewpoint but also from a practical viewpoint. Major techniques to enhance the capacity of cellular systems are channel segregation, reuse-partitioning, and transmitter power control. In addition to the performance of conventional cellular systems, differing performance in microcellular systems and multi-layer cellular systems is also discussed.

A new dynamic channel allocation algorithm which is integrated with transmitting power control is proposed. By introducing a new threshold, referred to as TPC threshold (Transmitting Power Control threshold), which is added some margin to the threshold of channel allocation, the subsequent transmitting power control can be performed effectively. This DCA algorithm can achieve a cellular system with both high traffic capacity and high service quality such as interference frequency performance simultaneously. The computer simulation shows that this DCA algorithm improves blocking probability performance 4 times better than that of DECT system at 14 Erlang, while keeping the same interference frequency and forced termination performances.

Fiber-optic passive double star (PDS) network is described as an access network for microcellular radio communication systems. The intrinsic characteristics of the PDS network, reduction in the optical fiber count and flexible access capability, are examined. A unit cell structure is introduced which enables the PDS network to be effectively incorporated into the access portion of microcellular radio communication systems. The reduced total fiber length in the unit cell structure based on the PDS network is discussed in comparison with the conventional architecture. Calculations show that there is an optimum splitting ratio that minimizes the total fiber length. When the microcell radius and service area radius are 100m and 10km, respectively, the total fiber length of the PDS network is reduced to only about 9% of that of the conventional single star (SS) network for a splitting ratio of 34. Resource sharing and handover between microcells in a unit cell are performed by using the dynamic channel allocation function of the PDS system. Substantial performance improvement for loaded traffic can be obtained by resource sharing. When the splitting ratio is 32, the available traffic of a base station (BS) increases from 0.9 [erl/BS] to 3.4 [erl/BS] by adopting dynamic channel allocation for the lost call probability of 0.01.