The Direct-Sequence Code Division Multiple Access (DS-CDMA) is one of the most likely candidates for the 3rd generation mobile communication systems. On the other hand, a network supporting integrated data transfer and providing predictable qualities of service (QoS) to such application is an attractive issue. This paper proposes several schemes based on the majority rule concerned with resource reservation to investigate the performance of a CDMA cellular system. The admission control is based on the residue capacity and required signal-to-noise ratio (SNR) for multimedia traffic including voice, data and video. The system performance is explored with variable spreading gain and multi-code CDMA systems under the proposed schemes. Moreover, several system parameters including the handoff probability (lifetime in a cell) and the traffic load are investigated to study the impact to system performance. The results show the trade-off between the blocking probability of new calls and dropping probability of handoff calls under diversified situations. However, it is inefficient under resource reservation due to unused capacity. In this paper, we also propose a resource-borrowing scheme to improve system performance. Simulation results show that our proposed algorithm really improves the system performance in a multimedia CDMA cellular system with resource reservation.

The CDMA system can provide more capacity than other systems and the hierarchical layer of cells is required for system design to provide a balance between maximizing the number of users perfrequency band and minimizing the network control associated with handoff. However, the co-channel interference from microcell to macrocell and vice versa in such a two-tier structure is different from that in a homogeneous structure. In order to avoid the serious interference, different RF channels should be used in microcell and macrocell in hierarchical structure. The efficient usage of multi-channels for macrocell and microcell is of primary concern herein. In this study, we investigate the channel segregation in a two-tier cellular system. Moreover, we intentionally arrange the procedures for the MS in macrocell and microcell to choose the channel. The macrocell's (resp., microcell's ) channels to be accessed are sorted into three priority groups. In order to justify the merits of the proposed channel segregation method, we define the following three performance measures including capacity gain, response to the variation of traffic loading and system stability. Under the condition of steady-state traffic load, capacity gain is 10% on the average. If the traffic load vary, the system can respond quickly and retrieve the borrowed channels with 2tp time interval as long as appropriate system parameters are chosen.

The next generation of wireless networks must provide sufficient resources to support a broader range of services beyond the traditional voice-only services provided in current wireless systems. For this, packet scheduling is the most critical function involved in the provision of individual bandwidth, and delay guarantee to meet the required qualities of service (QoS) for the switched sessions. In this paper we introduce the concept of system capacity in the multi-code CDMA system and evaluate the system performance constrained by the required SNRth and other QoS factors. The CAC algorithm is proposed to administer the requests. Moreover, the enforcer, scheduler and shaper are proposed to maintain the required QoS. The system performance including blocking probability, mean delay and bandwidth utilization in the BS egress are evaluated and compared under different traffic loadings.

Emerging requirement for higher rate data services and better spectrum efficiency is the main driving force identified for the third generation mobile radio systems. Moreover, it needs the capability of providing predictable qualities of service (QoS) for different applications. To maintain different QoS requirements, mechanisms such as call admission control (CAC) and load control, etc. are needed to achieve the required services. In this paper, we propose a CAC algorithm based on channel assignment in a multi-chip rate direct-sequence CDMA (MCR-DS-CDMA) cellular system supporting multi-rate services. Five multi-MBC (mapping of information bit rates to chip rates) channel assignment schemes and corresponding channel selection rules are proposed herein. Computer simulation, where multimedia applications are considered, is used to evaluate the system performance (e.g., blocking probability and system capacity) with different channel assignment schemes. Numerical results demonstrate that scheme 5 (i.e., Minimum-influence scheme) performs better because it provides the highest system capacity and least blocking probability.