A modified proportional fairness (PF) scheduling scheme for OFDMA systems with imperfect channel quality indicator is suggested. It is based on user grouping, and in system level simulations, the proposed scheme improves average user throughput considerably when compared to conventional PF scheduling without grouping.

In mobile computing environments, cache invalidation techiniques are widely used. However, theses techniques require a large-sized invalidation report and show low cache utilization under high server update rate. In this paper, we propose a new cache-level cache invalidation technique called TTCI (Timestamp Tree-based Cache Invalidation technique) to overcome the above two problems. TTCI also supports selective tuning for a cache-level cache invalidation. We show in our experiment that our technique requires much smaller size of cache invalidation report and improves cache utilization.

Periodic reservation allows periodic and random packets to share the same satellite random access channel efficiently. The periodic reservation protocol is particularly suitable for mobile satellite position reporting services, where some of the information messages, such as dispatch function, are classified as "periodic" and others, such as signaling, are classified as "random." When a new mobile terminal logs on to the system, Network Management Center (NMC) reserves subsequent time slots for transmitting periodic packets without contention. A mobile terminal recognizes each time slot as "reserved" or "unreserved (available)" according to the broadcast message received from NMC. Other random packets use the slotted ALOHA protocol to contend with other mobile terminals for an unreserved time slot. The performance results suggest that the use of the periodic reservation protocol can be regarded as a viable solution for mobile satellite position reporting services such as automatic dependent surveillance (ADS).

The problem of presentation view generation over external/conceptual view is discussed for database systems. The presentation view is expressed by a format of a report which is generated as the result of a database query. A new presentation format generation scheme for composite reports is proposed for object-oriented databae systems. The reports can have nested (extended non-first-normal-form) formats. The presentation format should vary at run time, depending on repeating groups and data arrangement. The proposed scheme is based on the idea of dynamic co-referring objects, which uses an object-oriented data model extended to the presentation layer. As important features, various composite reports can be easily derived from databases, and dynamic format modification is possible interactively, even after retrieving the data. The scheme is useful for database applications which require a wide variety of formats for casual queries, where the report generation programming cost will be greatly reduced.