To efficiently support mobility of users on transportation systems, we propose a distributed group location tracking (DGLT) scheme based on several virtual visitor location registers (VVLRs) and representative identities. We analyze the DGLT scheme in view of the database (DB) access cost and the signaling cost under a one-dimensional network architecture. Compared with the IS-41 scheme, the DGLT scheme using distributed group management has a lower signaling cost as well as a lower DB access cost. As the user mobility-increases or the number of users on a TS increases, the outperformance of the DGLT scheme increases. Generally, the DGLT scheme in which a corresponding home location register selects an optimum VVLR among several VVLRs has a lower signaling cost, although a DB access cost is increased slightly compared with the GLT scheme.

A new resource allocation scheme is proposed for data services in an integrated voice/data CDMA system. After delay-sensitive voice users are first allocated, residual resources are then allocated to data users. To allocate data users fairly, we apply WFQ (weighted fair queueing) to a CDMA system with consideration of a generalized processor sharing (GPS) fluid-flow model. In order to implement this fair resource allocation scheme, a virtual clock and a credit table method are used. The throughput and delay of the data service under burst error conditions are shown. Numerical results show that the throughput of each data user has the same characteristics under burst error conditions.

A location tracking scheme called as a group location tracking (GLT) is proposed to reduce the location update cost for terrestrial transportation systems (TSs) in personal communication networks. To provide user mobility in a TS, we introduce two new concepts, virtual visitor location register (VVLR) and representative identity (RID). A VVLR is used to provide current location of a TS and an RID of a TS is used to represent a TS and the group of all users on the TS. When a TS moves into a new registration area, the GLT scheme based on an RID of the TS and a VVLR updates location information by a group location update request message instead of individual location update request messages generated by each user in the TS. We analyze the performance of our proposed scheme in view of the signaling load and call delivery failure. Compared with the IS-41 location tracking scheme, the GLT scheme significantly reduces frequent location updates caused by the high mobility of a TS and a large number of users in a TS.

We analyze the throughput of a direct-sequence spread spectrum multiple access (DS/SSMA) unslotted ALOHA system with variable length data traffic. The system is analyzed for two cases: (1) systems without a channel load sensing protocol (CLSP) and (2) systems with a CLSP. The bit-error probability and the throughput are obtained as a function of the signal-to-noise ratio (SNR) during message transmission, considering the number of overlapped messages and the amount of time overlap. We assume that the generation of data messages is Poisson distributed and that the messages are divided into packets before transmission. The system is modeled as a Markov chain under the assumption that the number of packets in a message is geometrically distributed with a constant packet length. The throughput variance of the DS/SSMA unslotted ALOHA system with variable length data traffic is obtained as the Reed-Solomon code rate varies. Results show that a significant throughput improvement can be obtained by using an error-correcting code.