【摘要】：隨著無線局域網(wǎng)技術(shù)的快速發(fā)展,2.4GHz、5GHz頻段已不能滿足高速率無線傳輸對頻譜資源的需求,60GHz毫米波頻段WLAN關(guān)鍵技術(shù)成為未來5G通信的研究熱點(diǎn)之一。與2.4GHz、5GHz頻段相比,60GHz頻段具有更寬的信道和更高的傳輸速率,但同時也帶來了路徑損耗大和穿透性差的問題,具有傳輸距離短、定向傳輸?shù)奶攸c(diǎn)。由于60GHz毫米波鏈路傳輸?shù)姆较蛐?使得全向傳輸下隱藏終端和暴露終端問題面臨新的挑戰(zhàn)。此外,IEEE標(biāo)準(zhǔn)組目前正在推進(jìn)下一代毫米波60GHz頻段無線局域網(wǎng)傳輸標(biāo)準(zhǔn)IEEE 802.11ay,作為2013年訂立的IEEE 802.11ad標(biāo)準(zhǔn)的演進(jìn)。與IEEE802.11ad標(biāo)準(zhǔn)相比,IEEE802.11ay標(biāo)準(zhǔn)具有更高的傳輸率、支持多用戶和一定的移動性,其關(guān)鍵技術(shù)包括MU-MIMO和信道綁定。通過采用信道綁定技術(shù),802.11ay中同一對STA和AP節(jié)點(diǎn)間可能采用不同帶寬的波束賦形(beamformed)鏈路進(jìn)行傳輸。IEEE802.11 ad中定義的單鏈路有效性維護(hù)和指示機(jī)制不能滿足802.11ay的需求。在IEEE 802.11ad標(biāo)準(zhǔn)定義的鏈路維護(hù)機(jī)制基礎(chǔ)上,本文進(jìn)行了改進(jìn),提出了一種適用于IEEE 802.11ay的信道綁定機(jī)制下同一對節(jié)點(diǎn)多條鏈路有效性指示和維護(hù)的方案。具體改進(jìn)工作包括:首先定義了一種新的beamlinkmaintenance element,以標(biāo)識及區(qū)分不同帶寬綁定鏈路的Timer。其次,針對不同的幾種信道綁定鏈路的建立方式,給出了各個Timer的具體啟動時機(jī)。此外,針對同一 STA/AP中不同鏈路的有效性時長的差異性,將802.11ad標(biāo)準(zhǔn)中以節(jié)點(diǎn)為單位的Timer凍結(jié)和遞減原則修改為以鏈路為單位進(jìn)行凍結(jié)和遞減,從而避免由于一條鏈路的失效而導(dǎo)致所有鏈路都需要進(jìn)行重新訓(xùn)練的操作,減少了不必要的訓(xùn)練開銷。性能分析及仿真實驗驗證了本文所提多Timer機(jī)制的有效性。針對60GHz毫米波頻段WLAN定向傳輸場景下的隱藏終端和暴露終端的問題,本文提出了一種定向傳輸下緩解隱藏終端和暴露終端的E-CCA(Enhanced CCA)方案。該方案的主要思路是全向CCA檢測和定向CCA檢測相結(jié)合、發(fā)送節(jié)點(diǎn)和接收節(jié)點(diǎn)都進(jìn)行CCA檢測。將CCA配置與波束方向相關(guān)聯(lián),使一個CCA配置與節(jié)點(diǎn)對數(shù)無關(guān),在一個波速方向上只對應(yīng)一個NAV,以減少NAV設(shè)置的冗余,提高效率。并根據(jù)信道狀態(tài)對全向CCA和定向CCA的閾值進(jìn)行動態(tài)設(shè)置,來緩解定向隱藏終端和暴露終端問題。性能仿真實驗證明E-CCA方案可以在一定程度上降低丟包率,提高網(wǎng)絡(luò)的平均吞吐量。
[Abstract]:With the rapid development of wireless local area network (WLAN) technology, the 2.4GHz / 5GHz band can no longer meet the demand of high rate wireless transmission for spectrum resources. The key technology of 60GHz millimeter-wave band WLAN has become one of the research hotspots of 5G communication in the future. Compared with 2.4GHz / 5GHz band, the 60GHz band has wider channel and higher transmission rate, but it also brings the problems of high path loss and poor penetration. It has the characteristics of short transmission distance and directional transmission. Due to the directionality of 60GHz millimeter-wave link transmission, hidden terminals and exposed terminals in omnidirectional transmission are facing new challenges. In addition, the IEEE Standard Group is currently promoting the next generation of millimeter-wave 60GHz band WLAN transmission standard IEEE 802.11ayas the evolution of the IEEE 802.11ad standard established in 2013. Compared with the IEEE802.11ad standard, the IEEE 802.11ay standard has higher transmission rate, multi-user support and mobility. Its key technologies include MU-MIMO and channel binding. The single link validity maintenance and indication mechanism defined in IEEE 802.11ad can not meet the requirements of 802.11ay by adopting the channel binding technique and the beamforming (beamformed) link with different bandwidth between the same pair of STA and AP nodes in 802.11ay. Based on the link maintenance mechanism defined by IEEE 802.11ad standard, this paper proposes a scheme for indicating and maintaining the validity of multiple links of the same pair of nodes under the channel binding mechanism suitable for IEEE 802.11ay. The specific improvements include: firstly, a new beamlinkmaintenance element is defined to identify and distinguish timers for different bandwidth-bound links. Secondly, the starting time of each Timer is given according to the different channel binding links. In addition, in view of the difference of the validity time of different links in the same STA/AP, the principle of freezing and decreasing Timer in the 802.11ad standard is modified to freeze and decrease in the unit of link. Therefore, it can avoid the operation that all links need to be retrained because of the failure of one link, thus reducing the unnecessary training cost. Performance analysis and simulation results verify the effectiveness of the proposed multiple Timer mechanism. Aiming at the problem of hidden terminal and exposed terminal in WLAN directional transmission scene of 60GHz millimeter wave band, this paper proposes a E-CCA (Enhanced CCA) scheme to alleviate hidden terminal and exposed terminal under directional transmission. The main idea of this scheme is to combine omnidirectional CCA detection with directional CCA detection, and both sending and receiving nodes perform CCA detection. The CCA configuration is associated with the beam direction, which makes a CCA configuration independent of the node logarithm, and only corresponds to one CCA in the direction of the wave velocity, so as to reduce the redundancy of the NAV configuration and improve the efficiency. The threshold of omnidirectional CCA and directional CCA is set dynamically according to the channel state to alleviate the problem of directional hidden terminal and exposed terminal. The simulation results show that the E-CCA scheme can reduce the packet loss rate to some extent and improve the average throughput of the network.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN925.93

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