Layered Multicast Scheme Research Articles

Prioritization-based Layered Multicast for Fixed/Mobile Networks with Fast Convergence and Inter-Session Fairness

Multimedia streaming services are becoming popular in both wired and wireless networks. Layered multicast is a widely accepted approach for streaming multimedia data to a large number of users. Existing layered multicast approaches donot interact well with network dynamics. Indeed, upon a change in network conditions, they require a long time till they can appropriately adjust their data transmission rate. Additionally, they do not achieve fairness when users from different sessions share the bandwidth of a bottleneck link.In this paper, we propose a scheme that allows newly-arriving users to promptly converge their data transmission rates to the most optimal rate that best suit the current conditions of the network without degrading the system fairness. The proposed scheme is based on the fact that layered multicast uses prioritybased packet dropping policies. In the proposed scheme, two newly-defined packet messages are considered: “low priority join” and “normal join” messages. To join a session, a user first subscribes to all corresponding layers by issuing “low priority join” messages. It then computes packet drops experienced oneach layer. If packets of a given layer experience a drop rate higher than a predetermined threshold, the user leaves that layer and all higher layers. The user then “officially” joins the remaining layers by transmitting “normal join” messages. This operation helps users to subscrive to only layers whose aggregate bandwidth fits the current network conditions. The performance of the proposed scheme is evaluated through computer simulations and is compared against the Receiverdriven Layered Multicast (RLM) scheme. The results show that the proposed scheme achieves appropriate bandwidth utilization from the start of the session. The results demonstrate also that the proposed scheme is effective in managing handover in mobile networks and achieves better Quality of Service (QoS) inheterogeneous mobile environments.

Energy-Efficient Layered Video Multicast over OFDM-Based Cognitive Radio Systems

An energy-efficient layered video multicast (LVM) scheme for “bandwidth-hungry” video services is studied in OFDM-based cognitive radio (CR) systems, where the video data is encoded into a base layer and several enhancement layers with the former intended for all subscribers to guarantee the basic quality of reconstructed video and the latter aiming at the quality improvement for the promising users with good channel conditions. Moreover, in order to balance user experience maximization and power consumption minimization, a novel performance metricenergy utility(EU) is proposed to measure the sum achieved quality of reconstructed video at all subscribers when unit transmit power is consumed. Our objective is to maximize the system EU by jointly optimizing the intersession/interlayer subcarrier assignment and subsequent power allocation. For this purpose, we first perform subcarrier assignment for base layer and enhancement layers using greedy algorithm and then present an optimal power allocation algorithm to maximize the achievable EU using fractional programming. Simulation results show that the proposed algorithms can adaptively capture the state variations of licensed spectrum and dynamically adjust the video transmission to exploit the scarce spectrum and energy resources adequately. Meanwhile, the system EU obtained in our algorithms is greatly improved over traditional spectrum efficiency (SE) and energy efficiency (EE) optimization models.

Optimal joint rate and power allocation for layered multicast with superposition coding in cellular systems

We propose a layered multicast transmission scheme with superposition coding for cellular systems, i.e., at a base station a basic multicast stream (BMS) and an enhanced multicast stream (EMS) are superimposed and transmitted, the same BMS is repeatedly transmitted multiple times to ensure most users in the cell receive basic qualities of the service, while in each transmission different EMSs are transmitted to make the users with good channel conditions receive higher qualities of the service. In this paper, the optimal joint rate and power allocation for the layered multicast scheme is studied. Specifically, we first give a proof on the claim that the system delay of a BMS is minimized if the transmission rate of the BMS is set according to a fixed user selection ratio in each transmission. Then subject to fixed transmit power and power allocation, we derive the optimal transmission rate of a BMS that minimizes the system delay of the BMS, and the optimal transmission rate of an EMS that maximizes the average throughput of the EMS. Finally, by balancing the tradeoff between the system delay of a BMS and the average throughput of an EMS, we find the optimal joint rate and power allocation for the layered multicast scheme. Numerical results show that the optimized layered multicast scheme outperforms the conventional schemes in terms of the system delay of a BMS and the average throughput of an EMS.

Optimized layered multicast with superposition coding in cellular systems

ABSTRACTWe consider the problem of optimal power allocation and optimal user selection in a layered multicast transmission over quasi‐static Rayleigh fading channels. A scheme based on superposition coding is proposed in which basic multicast streams and enhanced multicast streams are superimposed and transmitted by a base station, while users with worse channel conditions can only decode basic multicast streams, and users with better channel conditions can decode both basic and enhanced multicast streams. In this paper, subject to fixed user selection ratios, the optimal power allocation for each stream that maximizes average throughput is investigated, and the impact of power allocation on average outage probability is discussed. Finally, subject to fixed transmit power and power allocation, the optimal user selection ratio for enhanced multicast streams is also studied. Numerical results show that the optimized layered multicast scheme outperforms the conventional multicast scheme in terms of average throughput. Copyright © 2010 John Wiley & Sons, Ltd.

Loss differentiated multicast congestion control

A new layered multicast scheme known as loss differentiated multicast congestion control architecture is proposed to provide effective congestion control in heterogeneous multicast networks. It is comprised of two components, the random early detection assisted layered multicast (RALM) and the layer marking discovery protocol (LMDP). The RALM protocol utilises the packet marking and priority dropping mechanisms of the differentiated services architecture to differentiate losses in the layers of a layered multicast session. The LMDP protocol assists in the discovery of the optimal subscription levels to which packets of the layers should be marked. By marking the layers’ packets appropriately and dropping them differently during congestion, the RALM protocol guides receivers to their stable optimal subscription levels that satisfy their bandwidth requirements while providing multirate max–min fairness in the network.

NLM: network-based layered multicast for traffic control of heterogeneous network

Layered multicast has been considered to be an efficient approach for coping with the network heterogeneity. Receiver-driven Layered Multicast (RLM) and its variants suggest that every receiver adjusts the reception level based on the packet loss rate. In this paper we propose a scheme called network-based layered multicast (NLM) scheme, which enhances the packet scoping mechanism employed in current multicast backbone (MBone). It makes use of the TTL bits and TOS bits in IP header, and packets are filtered in the routers using both the measured and predicted traffic condition. This allows the network quickly and efficiently adapts to the traffic condition. We evaluate and compare the scheme with the receiver-driven schemes using Network Simulator for a 33-node network topology with realistic bandwidths. The simulation reveals that the proposed NLM scheme substantially improves the stability and fairness of the RLM scheme for multicast sessions, while it displays comparable performance to the RLM with Priority (RLMP) scheme. For mixed type traffic of multicast and TCP sessions, it outperforms both the schemes.