In this paper, we propose a new handover algorithm to guarantee handover quality in 4G mobile systems. The proposed algorithm limits the handover interruption time by improving the HARQ retransmission latency of the first packet transmitted from new serving cell. Through the simulations, we proved that our algorithm meets the requirement of handover interruption time for TCP services with high rate.

Wireless content sharing where peers share content and services via wireless access networks requires user contributions, as in fixed P2P content sharing. However, in wireless access environments, since the resources of mobile terminals are strictly limited, mobile users are not as likely to contribute as ones in fixed environments. Therefore, incentives to encourage user contributions are more significant in wireless access environments. Although an incentive service differentiation architecture where the content transfer rate is adjusted according to the contributions of each downloading user has been already proposed for fixed P2P, it may not work well in wireless access environments because several factors effect wireless throughput. In this paper, we propose a novel architecture for contribution-based transfer-rate differentiation using wireless quality of service (QoS) techniques that motivates users to contribute their resources for wireless content sharing. We also propose a radio resource assignment method for our architecture. Computer simulations and game-theoretic calculations validate our architecture.

Supporting diversified rates for real-time communications will become possible and essential with the rapidly increasing transmission rates provided by the 4th generation (4G) mobile communication systems. In this paper, a novel wireless Quality of Service (QoS) scheme suitable for broadband CDMA packet cellular systems with adaptive modulation coding is proposed and its characteristics are described. The proposed QoS scheme comprises several control factors laid on the MAC and RRC layers, and can be harmonized with IP-QoS. Two important control factors are proposed: radio-condition-aware admission control and resource allocation reflected multistage scheduling. Computer simulations and testbed experiments indicate that by using the radio-condition-aware admission control, stable and guaranteed service can be provided to real-time users regardless of the interference and the variation in the location of the mobile station. Moreover, resource allocation reflected multistage scheduling maintains guaranteed rates for real-time users and provides high resource utilization efficiency for best-effort users. Consequently, by using the proposed wireless QoS scheme, it is possible to provide users with high quality and diversified real-time services, on a packet based radio network for enhanced 3G and beyond.

In this letter, we propose an efficient transmission slot selection scheme for Band Division Multi-Carrier-CDMA (BD-MC-CDMA) systems under the constraints of packet loss and delay bound for each individual session. By utilizing channel dynamics together with the delay deadline and loss history, one can determine whether to transmit or not during each time slot, based on the prediction of future channel variations. To validate the efficiency of the proposed algorithm, we model each sub-band as a discrete time Markov Chain using a finite state Markov channel (FSMC) and derive the criteria required for transmission decision. Simulation results show that our proposed scheme can satisfy quality of service (QoS) requirements for real-time traffic with minimum use of resources, while increasing throughput of non-real-time traffic with the resources saved from real-time traffic.

The emerging multimedia applications for future mobile communication systems typically require highly diversified Quality of Service (QoS). However, due to the time and location dependent fluctuating nature of radio resources in the radio link, it is very difficult to maintain a constant level of QoS with the current end-to-end QoS control only. Therefore, wireless-aware QoS is the key issue for achieving better end-end QoS. In this paper, a new wireless QoS scheme for a joint CDMA/NC-PRMA cellular system are proposed considering QoS prioritization mechanism, users' diversified requirements and the harmonization with IP-QoS. Two wireless QoS-aware resource allocation algorithms are proposed to support QoS prioritization while achieving high radio resource utilization. By introducing a set of new QoS resource request parameters (minimum, average and maximum requirements), the algorithms can assign radio resource in a more flexible way than the conventional fixed resource allocation. Computer simulations indicate that the proposed QoS algorithms exhibit superior performance with respect to packet dropping probability for realtime application users, and improve transmission rate for non-realtime application users, which evince the effectiveness of the proposed wireless QoS algorithms.