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首页> 外文期刊>IEEE transactions on mobile computing >Multicast Scheduling for Relay-Based Heterogeneous Networks Using Rateless Codes
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Multicast Scheduling for Relay-Based Heterogeneous Networks Using Rateless Codes

机译：基于无速率码的基于中继的异构网络的组播调度

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摘要

We consider the multicast scheduling problem in the heterogeneous network using a half-duplex relay station (RS). Our goal is to minimize the delay of transmitting a block of packets to users over time-varying channels using rateless codes. Due to half-duplex operation, at each time slot, the RS can choose to either multicast a packet to the users, or fetch a packet from the macro base station. We formulate a fluid relaxation for the optimal decision problem, and reveal that the optimal policy has a threshold-based structure so as to exploit the opportunism of multicast channel: the RS should multicast only when the channel quality is sufficiently “high”. We propose an online policy based on the relaxation which does not require the knowledge of channel distribution. When the channel distribution is symmetric across users, we provide a closed-form expression of the asymptotic performance of our policy. For two-user systems, we prove that our scheme is asymptotically optimal. When the users’ channels are independent, we derive a performance bound based on water-filling rate allocation which approximates the optimal policy well. Simulation results show that our scheme performs close to theoretical bounds, under correlated as well as independent fading channels.
机译：我们考虑使用半双工中继站（RS）的异构网络中的多播调度问题。我们的目标是使使用无速率码在时变信道上向用户传输数据包块的延迟最小化。由于半双工操作，RS在每个时隙都可以选择向用户多播数据包，或者从宏基站获取数据包。我们为最优决策问题制定了一种流体松弛的方法，并揭示了最优策略具有基于阈值的结构，以便利用多播信道的机会：仅当信道质量足够“高”时，RS才应进行多播。我们提出了一种基于放宽的在线政策，该政策不需要了解渠道分配情况。当用户之间的渠道分布对称时，我们将提供政策渐进性能的封闭形式。对于两用户系统，我们证明了我们的方案是渐近最优的。当用户的渠道独立时，我们将根据注水率分配得出性能界限，该界限很好地接近了最佳策略。仿真结果表明，我们的方案在相关衰落信道和独立衰落信道下均接近理论极限。

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