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Combined Multicast and Unicast Scheduling for Multicast Applications

IP.com Disclosure Number: IPCOM000169158D
Original Publication Date: 2008-Apr-24
Included in the Prior Art Database: 2008-Apr-24
Document File: 2 page(s) / 58K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

The distribution of multimedia content in mobile cellular systems usually involves the transmission of the same information to many users. For this purpose, common multicast links are established, so that the information is not transmitted several times on individual links. The established multicast links are designed in respect of the user with the worst channel conditions. This assures that the weakest client still achieves the specified performance. Due to this design, the channel capacity for all other users is greater than required and the scheme is not optimal in terms of its spectral efficiency. Furthermore, multi-user diversity, i.e. performance enhancement by scheduling users with favorable channel conditions, is not possible. In this context, a novel scheduling method can enhance the spectral efficiency: the combined use of multicast links and unicast links for users with good channel conditions. First, the multicast link is designed according to the optimal n-th lowest average Signal-to-Noise Ratio (SNR) which has to be separately calculated. Then individual unicast links are additionally established for the users with lower SNRs in order to fill the gap between the required data rate and their achieved rate over the multicast link. The precondition to profit from this multi-user diversity is that the unicast links are scheduled on resources, e.g. time slots or frequency chunks, on which the channel resources are in good fading conditions. Also, two possible scheduling strategies exist: Either the unicast links are optimally scheduled for every recipient or the unicast links are decoded by multiple users. Another option is to allocate different or common resource blocks for the multicast and unicast links.

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Combined Multicast and Unicast Scheduling for Multicast Applications

Idea: Michael Faerber, DE-Munich; Martin Senst, DE-Aachen; Markus Jordan, DE-Aachen; Meik

Doerpinghaus, DE-Aachen

The distribution of multimedia content in mobile cellular systems usually involves the transmission of the same information to many users. For this purpose, common multicast links are established, so that the information is not transmitted several times on individual links. The established multicast links are designed in respect of the user with the worst channel conditions. This assures that the weakest client still achieves the specified performance. Due to this design, the channel capacity for all other users is greater than required and the scheme is not optimal in terms of its spectral efficiency. Furthermore, multi-user diversity, i.e. performance enhancement by scheduling users with favorable channel conditions, is not possible.

In this context, a novel scheduling method can enhance the spectral efficiency: the combined use of multicast links and unicast links for users with good channel conditions. First, the multicast link is designed according to the optimal n-th lowest average Signal-to-Noise Ratio (SNR) which has to be separately calculated. Then individual unicast links are additionally established for the users with lower SNRs in order to fill the gap between the required data rate and their achieved rate over the multicast link. The precondition to profit from this multi-user diversity is that the unicast links are scheduled on resources, e.g. time slots or frequency chunks, on which the channel resources are in good fading conditions. Also, two possible scheduling strategies exist: Either the unicast links are optimally scheduled for every recipient or the unicast links are decoded by multiple users. Another option is to allocate different or common resource blocks for the multicast and unicast links.

The evaluations concerning the overall resource requirements are carried out with an information theoretic approach. Generally, the distribution of the average SNR of the users...