Admission control is an important strategy for Quality of Service (QoS) provisioning in Asynchro- nous Transfer Mode (ATM) networks. Based on a control-theory model of resources on-Demand Allocation (DA) protocol, the paper studies the effect of the protocol on the statistical characteristics of network traffic, and proposes a combined connection admission control algorithm with the DA protocol to achieve full utiliza- tion of link resources in satellite communication systems. The proposed algorithm is based on the cross-layer-design approach. Theoretical analysis and system simulation results show that the proposed algo- rithm can admit more connections within certain admission thresholds than one that does not take into account the DA protocol. Thus, the proposed algorithm can increase admission ratio of traffic sources for satellite ATM networks and improve satellite link utilization.
为提高基于星上ATM(asynchronous transfer mode)交换的宽带卫星通信网络的星上缓存资源的利用率,针对非实时数据业务,提出了一种跨层星上缓存管理策略——错误信元尾丢弃ECTD(erroneouscell tail drop)。该策略把由信道引起的错误信元及后续的属于同一协议数据单元的无效信元丢弃。基于系统仿真,采用Goodput和有效吞吐量两种性能评估指标分析了ECTD的性能。结果表明,ECTD提高了星上交换机的业务传递效率以及下行链路的利用率,其对有效吞吐量性能的提高大于Goodput性能的提高。
研究3GPP(third generation partnership project)蜂窝网络与WLAN(wireless local area network)融合的无线异构网络中WLAN发现机制的能耗问题,提出一种终端能耗分析模型,分析了基于寻呼的WLAN发现机制以及其他4种WLAN发现机制的能耗。理论分析和仿真结果表明:基于寻呼的WLAN发现机制能耗最小,终端始终处于扫描状态的机制能耗最大。结果还表明:终端仅在与WLAN重叠的蜂窝小区内进行周期扫描的机制,与终端在所有的区域中进行周期扫描的机制比较,二者能耗相当。
为了对无线异构网络中多模终端的能耗分析问题进行研究,通过考察终端的工作机理,利用半马尔科夫链描述终端的通信状态,从而得到终端的能耗分析方程.相比已有的工作,提出的模型更全面地考虑了终端的工作状态,还考虑了终端发现wireless local area network(WLAN)的概率和业务类别等因素的影响.分析结果表明,终端能耗随呼叫到达强度和呼叫持续时间增大而增大;终端能耗与话音业务的比例和发现WLAN的概率均成近似线性关系;使WLAN模块进入低能耗的等待状态并不会节省终端能耗.
ECTD (erroneous cell tail drop), a buffer management optimization strategy is suggested which can improve the utilization of buffer resources in satellite ATM (asynchronous transfer mode) networks. The strategy, in which erroneous cells caused by satellite channel and the following cells that belong to the same PDU (protocol data Unit ) are discarded, concerns non-real-time data services that use higher layer protocol for retransmission. Based on EPD (early packet drop) policy, mathematical models are established with and without ECTD. The numerical results show that ECTD would optimize buffer management and improve effective throughput (goodput), and the increment of goodput is relative to the CER (cell error ratio) and the PDU length. The higher their values are, the greater the increment. For example, when the average PDU length values are 30 and 90, the improvement of goodput are respectively about 4% and 10%.
