Efficient resource allocation schemes based on time slot reallocation and region division in CDMA/TDD systems

Abstract

Until now, CDMA/FDD systems are used to serve the voice service in the world. That is, current CDMA(Code Division Multiple Access) systems based on IS-95A support only a voice communication. However, as users of internet service are growing, the multimedia service including data service is required in the third generation CDMA systems such as 3GPP and 3GPP2. This integrated service (voice and data) needs more careful resource allocation and management scheme. The data service properties may be different from voice service in view of delay requirement, FER requirement, activity factor and so on. Thus, many people develop the multimedia CDMA system supporting various services. Because CDMA system uses a wider bandwidth than an original datarate, CDMA system has a disadvantage that it is difficult to support the multimedia service such as web service and video service. Moreover, because FDD(Frequency Division Duplex) systems employ the same bandwidth in uplink and downlink channels, the wireless resource can not be efficiently utilized. That is, when traffic patterns are strongly biased toward downlink channels, there is the bandwidth waste in uplink channels and total capacity might be degraded. To overcome this problem, TDD(Time Division Duplex) system can be used. CDMA/TDD system can use entire wireless resource effectively even with traffic asymmetry. Additionally, TDD system can be used in non-paired frequency allocation. And the other advantage of TDD over FDD is that the same frequency channel is used. From this property, reciprocity between uplink and downlink channels exists and many functions such as power control, signal pre-emphasis, shaping and diversity transmission can be implemented in open-loop fashion. As described in above paragraph, CDMA/TDD system can accommodate multimedia services even with traffic asymmetry. However, because of interference limitations, boundaries between uplink and downlink should be the same in overall cells. This scheme...