针对无线多跳自组织网络中随机网络编码,之前提出了一种网络编码随机优先级检测调度算法(Random early detection with priority,REDP),对两条不同优先级的数据流建立Markov数学模型,推导出了引入REDP算法下数据流的单节点的时延数学表达式,该算法使得数据流能够根据自身优先级和拥塞程度调整丢包概率,从而主动丢弃数据包提前避免拥塞。文中将单节点时延问题拓展到多节点的网络拓扑结构中,提出了动态时延分配算法,该算法能够根据各个节点队列的缓存情况,动态调整各个节点的时延分配,仿真结果表明,动态时延分配算法能够实现实时数据流严格的Qo S时延保障,更利于视频、语音等实时业务流的传输。
In this paper, we propose two novel efficient scheduling schemes with network coding in multi-relay wireless network to maximize the transmission efficiency. The first one uses adaptive forwarding with network coding(AF-NC), in which each relay adaptively calculates the number of packets having innovative information according to the feedback from the sink. With AF-NC, duplicate packets are not sent, and the total number of time slots needed to complete transmission can be significantly reduced. The second scheme, named adaptive forwarding with network coding and retransmission(AFR-NC), combines AF-NC with automatic repeat request(ARQ) to guarantee reliable end-to-end communication with limited resource occupation. Numerical results show that compared with simple forwarding with network coding(F-NC), AF-NC has close successful delivery rate with dramatically less time slots, while AFR-NC achieves strict reliability with limited resource cost.
Since FCC's opening for white space(WS) utilization,database-assisted dynamic spectrum access(DSA) has become the de facto solution for the realization of dynamic spectrum sharing(DSS),due to its simplicity and compatibility with commercial off-the-shelf(COTS) devices.It is envisioned that such technology will strongly support the prosperous wireless multimedia networking(WMN) applications with satisfying QoS guarantees in the future.However,how to counter the time-frequency variant property when exploiting the WS spectrum for the provision of these services to secondary users(SUs) still remains a great challenge.In such context,a dynamic secondary access scheme for database-assisted spectrum sharing networks is proposed in this paper.In the beginning,the spectrum requirements of SUs for diverse services are modeled by considering the minimum required service data-rate and spectrum access duration.Afterwards,the spectrum demand evaluation and bidding policy are formulated based on the service classes of SUs.Furthermore,a doublephase(DP) spectrum allocation scheme,which consists of the initial resource allocation phase and resource allocation adjustment phase,is carefully designed for DSA.Finally,extensive simulations are conducted and the results demonstrate that our scheme can increase the spectrum trading revenue and adapt to varying service requirements.
This letter presents a low cost solution for wavelength division multiplexed orthogonal frequency division multiplexed passive optical network(WDM-OFDM-PON)with widely tunable optical filter and linear small form-factor pluggable(SFP)module.With 9-nm tunable range from 1551 to 1560 nm,the tunable filter can support up to 10-channel 100-GHz spacing WDM PON system.A linear avalanche photodiode(APD)based SFP+module is designed for optical OFDM signal demodulation,which can provide better receiver performance compared with limiting APD module.Experimental results show that～34 dB power budget can be achieved in 4×5-Gbps WDM-OFDM-PON system,which can satisfy the transmission requirements of next generation PON system.
