摘要：
Under the decoding and forwarding mode,traditional differential network coding schemes involve complicated procedures of detection and re-coding at relay nodes.To solve this issue,a differential network coding scheme with symbol multiplying in complex field is presented.Consequently,two relay detection meth-ods are proposed,w hich can reduce the detection and recoding complexity significantly at relay nodes.In order to achieve the high order diversity gain,the proposed differential network coding is extended to multi-relay set-ting.As a result,a differential random space-time network coding scheme is presented,where the cooperative diversity order that can be achieved is equal to the activated relay number.The analysis and simulation results validate the proposed differential network coding schemes in both single-and multi-relay settings.%傳統(tǒng)差分網(wǎng)絡(luò)編碼在解碼轉(zhuǎn)發(fā)方式下編碼環(huán)節(jié)繁雜、中繼檢測復雜度高.基于此,文中提出復數(shù)域符號相乘的差分網(wǎng)絡(luò)編碼,并構(gòu)建了中繼檢測方法一和中繼檢測方法二,能顯著降低中繼的檢測和編解碼復雜度.同時,將提出的編碼方法拓展到多中繼協(xié)作方式以獲取高階協(xié)作分集增益,并得到隨機差分空時網(wǎng)絡(luò)編碼,其能獲得的分集增益階數(shù)為解碼正確的中繼個數(shù).仿真實驗和理論分析均驗證了提出的復數(shù)域符號相乘的差分網(wǎng)絡(luò)編碼方法在單中繼和多中繼協(xié)作方式下的有效性.
摘要：
A joint subcarrier and power allocation scheme based on limited feedback for cooperative multicast network was proposed to minimize the consumed power under constrain of QoS requirement.The new scheme worked in two steps.Firstly,subcarriers were distributed to different multicast groups with equal rate assumption according to limited feedback information,where fair subcarrier allocation scheme was used to achieve a tradeoff between power and fairness.Then,a cooperative power iterative scheme was adopted to allocate power effectively,where target rate on each subcarrier was computed by water-filling algorithm in the first place and then a power iterate process was implemented to optimize power allocation.Simulation and comparison results show that the new scheme significantly reduces uplink feedback overhear and the required power and the multicast service outage of cooperative scheme is much less than those of the direct scheme.Besides,cooperative power iterative scheme has lower computational complexity and therefore is suitable for practical system.%提出了協(xié)作多播網(wǎng)絡(luò)中基于有限反饋的聯(lián)合子載波和功率分配策略,在滿足QoS需求的條件下使功率消耗最小化.該策略首先利用有限的反饋信息在等速率分配下將子載波分給不同的多播組,并提出“公平子載波分配”策略,達到了功率消耗和公平性的折中.然后利用提出的“協(xié)作功率迭代”策略完成有效的功率分配,該策略利用注水定理確定每個子載波的目標速率后,又通過一個功率迭代過程實現(xiàn)功率最佳化.仿真結(jié)果顯示,新的協(xié)作策略大大降低了上行反饋開銷,且所需功率和多播業(yè)務(wù)中斷概率遠遠小于直傳策略.此外,協(xié)作功率迭代策略由于有較低的計算復雜度,因此更適合于實際系統(tǒng).
摘要：
To solve the issue of handoff management of WLAN in CBTC systems for urban rail transit ,a hand‐off algorithm using cooperative diversity technology for trains has been proposed , w hich has been combined with Stackelberg game model with competitive mechanism , to meet the needs for continuous communications for CBTC systems with high reliability . After the analysis of relay triggering and the handoff process of a run‐ning train under the WLAN environment , the price strategy has been determined by relay nodes in the light of the bandwidth requested by the train . Then ,a utility function of train ,based on price and revenue ,has been designed , and the existence of Nash equilibrium has been proved . In order to achieve the optimized bandwidth strategy of train and network revenue ,a distributed iterative learning method has been proposed to figure out the Nash equilibrium and the handoff process of train has been further analyzed . The simulation experiments show that the game strategy proposed in this paper can motivate relay nodes to participate in the cooperation for reasonable resource allocation of networks , the dynamic handoff time of the train is less than 50 ms and the handoff success probability is significantly higher than that of the traditional method .%針對城市軌道交通CBTC系統(tǒng)無線局域網(wǎng)越區(qū)切換問題，結(jié)合具有競爭機制的Stackelberg博弈模型，提出一種采用協(xié)作分集技術(shù)的列車越區(qū)切換算法，滿足CBTC系統(tǒng)可靠連續(xù)通信的要求。本文分析列車在無線局域網(wǎng)環(huán)境下的中繼觸發(fā)和越區(qū)切換過程，中繼節(jié)點根據(jù)列車請求的帶寬確定價格策略，設(shè)計一種基于價格和收益的列車效用函數(shù)，證明納什均衡的存在性。為獲取列車的最優(yōu)帶寬策略和網(wǎng)絡(luò)收益，提出一種分布式迭代學習法求解納什均衡，并進一步分析列車越區(qū)切換過程。仿真結(jié)果表明，本文提出的博弈策略能夠激勵中繼節(jié)點參與協(xié)作，合理分配網(wǎng)絡(luò)資源；列車動態(tài)越區(qū)切換時間小于50ms，切換成功概率明顯高于傳統(tǒng)切換方法。
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