寬帶無線局域網(wǎng)MAC協(xié)議研究
發(fā)布時間：2018-10-23 11:39
【摘要】：隨著無線局域網(wǎng)絡(luò)(WLAN)應(yīng)用的不斷推廣,WLAN在物理層技術(shù)及頻譜利用方面也得到了快速的發(fā)展。WLAN的媒質(zhì)訪問控制(MAC)協(xié)議決定了網(wǎng)絡(luò)系統(tǒng)中各節(jié)點(diǎn)共享接入信道的具體實(shí)現(xiàn)方式,并從根本上決定著WLAN的性能�，F(xiàn)有IEEE 802.11系列的MAC主要采用了基于CSMA/CA協(xié)議的分布式協(xié)調(diào)功能(DCF)以實(shí)現(xiàn)媒體的共享接入。然而,伴隨OFDM調(diào)制技術(shù)在物理層的應(yīng)用而帶來的物理層速率的增加,CSMA/CA的吞吐量性能卻隨之下降。另外,在長時延及相干時間較大的無線信道環(huán)境下,CSMA/CA已經(jīng)不再適應(yīng)用,此時,時隙ALOHA協(xié)議成為一種新的選擇。時隙ALOHA及其改進(jìn)協(xié)議由于簡單而在認(rèn)知無線網(wǎng)絡(luò)、射頻識別(FRID)的標(biāo)簽識別、衛(wèi)星通信及新的無線網(wǎng)絡(luò)技術(shù)研究等方面得到了廣泛應(yīng)用。為提高信道利用率,保證時隙ALOHA的穩(wěn)定性及獲得最大系統(tǒng)吞吐量方面展開了大量相關(guān)研究。本文針對傳統(tǒng)MAC隨機(jī)信道接入機(jī)制CSMA/CA在寬帶WLAN環(huán)境下存在的問題,考慮以時隙ALOHA作為這類應(yīng)用的信道接入控制協(xié)議,并對時隙ALOHA協(xié)議的性能及穩(wěn)定性控制開展了一些具有創(chuàng)新意義的工作。本文的創(chuàng)新點(diǎn)如下:1.與現(xiàn)有文獻(xiàn)主要考慮采用幀匯聚方式來達(dá)到提高寬帶WLAN環(huán)境下DCF吞吐量性能不同,提出采用基于時隙的信道控制協(xié)議作為寬帶WLAN環(huán)境下的MAC協(xié)議。針對高速物理信道環(huán)境下,每個OFDM符號能攜帶更多的數(shù)據(jù)信息,以Bianchi的二維維Markov模型為基礎(chǔ),研究了OFDM攜帶比特數(shù)、OFDM符號持續(xù)時間及數(shù)據(jù)分組長度對信道利用率的影響。數(shù)值分析及仿真結(jié)果表明,當(dāng)物理層速率超過100Mbps,數(shù)據(jù)分組長度小于1000字節(jié)時,無論采用RTS/CTS模式還是Basic模式,也無論系統(tǒng)的節(jié)點(diǎn)數(shù)如何,信道的有效吞吐量均小于0.35,低于時隙ALOHA協(xié)議的吞吐量。當(dāng)物理層速率到達(dá)600Mbps時,每個OFDM符號攜帶信息達(dá)到2400bit,基于RTS/CTS模式的CSMA/CA協(xié)議的信道吞吐量率小于0.16,而Basic模式的信道吞吐量也不足25%�？紤]采用時分多址作為寬帶無線局域網(wǎng)絡(luò)的MAC層協(xié)議,提出了集中調(diào)度與完全自由競爭兩種應(yīng)用場景下MAC設(shè)計方案。2.提出了長時延寬帶WLAN的MAC設(shè)計方案�，F(xiàn)有WLAN主要應(yīng)用于終端節(jié)點(diǎn)近距離范圍內(nèi)無線接入網(wǎng)絡(luò)的場景,而本文研究了長距離范圍內(nèi)WLAN的應(yīng)用問題,在此場景下無線信號傳輸時延增大。針對長時延無線信道網(wǎng)絡(luò)應(yīng)用環(huán)境,受信道特性的影響OFDM符號時間較大,CSMA/CA性能較低,確定采用OFDM符號為單位的時隙ALOHA作為信道控制協(xié)議。提出在集中式網(wǎng)絡(luò)環(huán)境中采用競爭加預(yù)約的時隙ALOHA協(xié)議;而分布式無線網(wǎng)絡(luò)環(huán)境下采用時隙ALOHA的信道控制算法。并進(jìn)一步分析了時隙ALOHA的穩(wěn)定性。3.提出了p堅持控制算法(pPCA),并將二進(jìn)制指數(shù)回退算法(BEBA)應(yīng)用到時隙ALOHA系統(tǒng)中�，F(xiàn)有時隙ALOHA控制算法的研究均基于節(jié)點(diǎn)傳輸后能夠立即獲得信道狀態(tài)信息的假設(shè)條件,但實(shí)現(xiàn)上這種假設(shè)往往是不成立的。本文首先分析了基于傳統(tǒng)假設(shè)的偽貝葉斯控制(PBCA)經(jīng)典控制算法的性能。其次,針對節(jié)點(diǎn)只能檢測到信道空閑狀態(tài)的應(yīng)用環(huán)境,提出了以時間幀為更新單位的p堅持控制算法。系統(tǒng)通過統(tǒng)計某時間窗口內(nèi)空閑時隙的概率,估計出系統(tǒng)節(jié)點(diǎn)數(shù)n,然后調(diào)整節(jié)點(diǎn)的發(fā)送概率為1/n,以獲得系統(tǒng)最大穩(wěn)定吞吐量。并考慮到二進(jìn)制指數(shù)回退算法在CSMA/CA中的應(yīng)用,提出將該算法應(yīng)用到時隙ALOHA中,通過二維Markov模型獲得系統(tǒng)穩(wěn)定吞吐量的數(shù)學(xué)表達(dá)式。仿真結(jié)果表明,三種控制算法均能獲得接近理論最大值的系統(tǒng)穩(wěn)定吞吐量。最后對三種控制算法在調(diào)整過程中的吞吐量,達(dá)到穩(wěn)定最大吞吐量的時間及算法復(fù)雜度三個方面進(jìn)行了比較。仿真結(jié)果顯示,當(dāng)節(jié)點(diǎn)數(shù)較小,PBCA在平均吞吐量和調(diào)節(jié)時間上都優(yōu)于BEB算法和pPCA算法;當(dāng)節(jié)點(diǎn)數(shù)較大時,三種算法的平均吞吐量基本一致,但pPCA調(diào)節(jié)時間較長;在算法復(fù)雜度方面,PBCA最優(yōu)。4.提出了快速自適應(yīng)(FA)時隙ALOHA穩(wěn)定控制算法。針對偽貝葉斯控制算法及p堅持控制算法中,當(dāng)節(jié)點(diǎn)數(shù)目突然發(fā)生急驟變化時,穩(wěn)定調(diào)節(jié)時間較長的問題,提出依據(jù)信道狀態(tài)的游程長度先進(jìn)行快速調(diào)整,將系統(tǒng)實(shí)際節(jié)點(diǎn)數(shù)與估計節(jié)點(diǎn)數(shù)之比調(diào)整到0.5~2的范圍內(nèi),然后再采用pPCA或PBCA進(jìn)行調(diào)整。仿真結(jié)果表明,自適應(yīng)控制算法能很好的適應(yīng)節(jié)點(diǎn)急驟變化的應(yīng)用場景。
[Abstract]:With the continuous popularization of wireless local area network (WLAN) applications, WLAN has developed rapidly in physical layer technology and spectrum utilization. The medium access control (MAC) protocol of WLAN determines the specific implementation mode of the shared access channel of each node in the network system, and decides the performance of WLAN fundamentally. The MAC of IEEE 802. 11 series mainly adopts the distributed coordination function (DCF) based on CSMA/ CA protocol to realize the shared access of the media. However, the throughput performance of CSMA/ CA decreases with the increase of the physical layer rate resulting from the application of the OFDM modulation technique in the physical layer. In addition, CSMA/ CA is no longer suitable for long time delay and large coherence time, at which time slot ALOHA protocol becomes a new choice. The time slot ALOHA and its improved protocols have been widely used in cognitive radio network, radio frequency identification (FRID) tag identification, satellite communication and new wireless network technology research. In order to improve the channel utilization rate, the stability of slotted ALOHA and the maximum system throughput have been studied. Aiming at the existing problems of CSMA/ CA in the broadband WLAN environment, this paper considers the channel access control protocol which takes the time slot ALOHA as the class application, and carries out some innovative work on the performance and stability control of the slotted ALOHA protocol. The innovation points in this paper are as follows: 1. Compared with the existing literatures, we mainly consider adopting the frame convergence method to improve the DCF throughput performance in the broadband WLAN environment, and propose a channel control protocol based on time slot as the MAC protocol in the broadband WLAN environment. For high-speed physical channel environment, each OFDM symbol can carry more data information, based on Bianchi's two-dimensional Markov model, the effect of OFDM carrying bit number, OFDM symbol duration and data packet length on channel utilization rate is studied. Numerical analysis and simulation results show that when the physical layer rate exceeds 100Mbps, the data packet length is less than 1000 bytes, whether the RTS/ CTS mode or the basic mode is adopted, regardless of the number of nodes in the system, the effective throughput of the channel is less than 0. 35, which is lower than the throughput of the time slot ALOHA protocol. When the physical layer rate reaches 600Mbps, each OFDM symbol carries information up to 2400bit, the channel throughput rate of CSMA/ CA protocol based on RTS/ CTS mode is less than 0.016, and the channel throughput of Basic mode is less than 25%. Considering the adoption of time division multiple access (TDMA) as the MAC layer protocol of the broadband wireless local area network, the MAC design scheme in two application scenarios of centralized scheduling and full free competition is proposed. The MAC design scheme of long-delay broadband WLAN is proposed. The existing WLAN mainly applies to the scene of the wireless access network in the short range of the terminal node, and the application problem of WLAN in long-distance range is studied, and the transmission time delay of the wireless signal is increased in this scenario. Aiming at the long-delay wireless channel network application environment, the OFDM symbol time is greatly influenced by the channel characteristics, the CSMA/ CA performance is low, and the time slot ALOHA with the OFDM symbol as the unit is determined as the channel control protocol. This paper proposes a time slot ALOHA protocol which uses contention plus reservation in a centralized network environment, and a channel control algorithm with time slot ALOHA is adopted in the distributed wireless network environment. The stability of time slot ALOHA was further analyzed. The p persistence control algorithm (pPCA) is proposed and the binary exponential backoff algorithm (BEBA) is applied to the slotted ALOHA system. The existing time slot ALOHA control algorithm is based on the assumption that the channel state information can be obtained immediately after the node transmission, but this assumption is often not established. In this paper, we first analyze the performance of pseudo-Bayesian control (PBCA) classical control algorithm based on traditional hypothesis. Secondly, aiming at the application environment that the node can only detect the idle state of the channel, the p persistence control algorithm based on the time frame as the update unit is proposed. The system estimates the system node number n by counting the probability of the idle time slot in a certain time window, and then adjusts the transmission probability of the node to 1/ n to obtain the maximum stable throughput of the system. Taking into account the application of binary exponential backoff algorithm in CSMA/ CA, this paper proposes the application of the algorithm into the slot ALOHA, and obtains the mathematical expression of the system's stable throughput through the two-dimensional Markov model. The simulation results show that the three control algorithms can obtain the system stable throughput close to the theoretical maximum. Finally, the throughput of three control algorithms is compared in three aspects: the throughput of the three control algorithms during the adjustment process, the time to reach the stable maximum throughput and the complexity of the algorithm. Simulation results show that when the number of nodes is small, PBCA is better than BEB algorithm and pPCA algorithm on average throughput and adjustment time; when the number of nodes is large, the average throughput of the three algorithms is basically the same, but the pPCA adjustment time is longer; in terms of algorithm complexity, PBCA is the best. A fast adaptive (FA) slot ALOHA stabilization control algorithm is presented. aiming at the pseudo-Bayesian control algorithm and the p-persistence control algorithm, when the number of nodes suddenly changes abruptly, the problem of longer stable adjustment time is solved, and the run length according to the channel state is firstly adjusted quickly, the ratio of the actual number of nodes of the system to the number of estimated nodes is adjusted to a range of 0.5 to 2, and then the pPCA or PBCA is used for adjustment. The simulation results show that the adaptive control algorithm can adapt to the application scenarios of sudden change of nodes.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TN925.93
，
本文編號：2289122
[Abstract]:With the continuous popularization of wireless local area network (WLAN) applications, WLAN has developed rapidly in physical layer technology and spectrum utilization. The medium access control (MAC) protocol of WLAN determines the specific implementation mode of the shared access channel of each node in the network system, and decides the performance of WLAN fundamentally. The MAC of IEEE 802. 11 series mainly adopts the distributed coordination function (DCF) based on CSMA/ CA protocol to realize the shared access of the media. However, the throughput performance of CSMA/ CA decreases with the increase of the physical layer rate resulting from the application of the OFDM modulation technique in the physical layer. In addition, CSMA/ CA is no longer suitable for long time delay and large coherence time, at which time slot ALOHA protocol becomes a new choice. The time slot ALOHA and its improved protocols have been widely used in cognitive radio network, radio frequency identification (FRID) tag identification, satellite communication and new wireless network technology research. In order to improve the channel utilization rate, the stability of slotted ALOHA and the maximum system throughput have been studied. Aiming at the existing problems of CSMA/ CA in the broadband WLAN environment, this paper considers the channel access control protocol which takes the time slot ALOHA as the class application, and carries out some innovative work on the performance and stability control of the slotted ALOHA protocol. The innovation points in this paper are as follows: 1. Compared with the existing literatures, we mainly consider adopting the frame convergence method to improve the DCF throughput performance in the broadband WLAN environment, and propose a channel control protocol based on time slot as the MAC protocol in the broadband WLAN environment. For high-speed physical channel environment, each OFDM symbol can carry more data information, based on Bianchi's two-dimensional Markov model, the effect of OFDM carrying bit number, OFDM symbol duration and data packet length on channel utilization rate is studied. Numerical analysis and simulation results show that when the physical layer rate exceeds 100Mbps, the data packet length is less than 1000 bytes, whether the RTS/ CTS mode or the basic mode is adopted, regardless of the number of nodes in the system, the effective throughput of the channel is less than 0. 35, which is lower than the throughput of the time slot ALOHA protocol. When the physical layer rate reaches 600Mbps, each OFDM symbol carries information up to 2400bit, the channel throughput rate of CSMA/ CA protocol based on RTS/ CTS mode is less than 0.016, and the channel throughput of Basic mode is less than 25%. Considering the adoption of time division multiple access (TDMA) as the MAC layer protocol of the broadband wireless local area network, the MAC design scheme in two application scenarios of centralized scheduling and full free competition is proposed. The MAC design scheme of long-delay broadband WLAN is proposed. The existing WLAN mainly applies to the scene of the wireless access network in the short range of the terminal node, and the application problem of WLAN in long-distance range is studied, and the transmission time delay of the wireless signal is increased in this scenario. Aiming at the long-delay wireless channel network application environment, the OFDM symbol time is greatly influenced by the channel characteristics, the CSMA/ CA performance is low, and the time slot ALOHA with the OFDM symbol as the unit is determined as the channel control protocol. This paper proposes a time slot ALOHA protocol which uses contention plus reservation in a centralized network environment, and a channel control algorithm with time slot ALOHA is adopted in the distributed wireless network environment. The stability of time slot ALOHA was further analyzed. The p persistence control algorithm (pPCA) is proposed and the binary exponential backoff algorithm (BEBA) is applied to the slotted ALOHA system. The existing time slot ALOHA control algorithm is based on the assumption that the channel state information can be obtained immediately after the node transmission, but this assumption is often not established. In this paper, we first analyze the performance of pseudo-Bayesian control (PBCA) classical control algorithm based on traditional hypothesis. Secondly, aiming at the application environment that the node can only detect the idle state of the channel, the p persistence control algorithm based on the time frame as the update unit is proposed. The system estimates the system node number n by counting the probability of the idle time slot in a certain time window, and then adjusts the transmission probability of the node to 1/ n to obtain the maximum stable throughput of the system. Taking into account the application of binary exponential backoff algorithm in CSMA/ CA, this paper proposes the application of the algorithm into the slot ALOHA, and obtains the mathematical expression of the system's stable throughput through the two-dimensional Markov model. The simulation results show that the three control algorithms can obtain the system stable throughput close to the theoretical maximum. Finally, the throughput of three control algorithms is compared in three aspects: the throughput of the three control algorithms during the adjustment process, the time to reach the stable maximum throughput and the complexity of the algorithm. Simulation results show that when the number of nodes is small, PBCA is better than BEB algorithm and pPCA algorithm on average throughput and adjustment time; when the number of nodes is large, the average throughput of the three algorithms is basically the same, but the pPCA adjustment time is longer; in terms of algorithm complexity, PBCA is the best. A fast adaptive (FA) slot ALOHA stabilization control algorithm is presented. aiming at the pseudo-Bayesian control algorithm and the p-persistence control algorithm, when the number of nodes suddenly changes abruptly, the problem of longer stable adjustment time is solved, and the run length according to the channel state is firstly adjusted quickly, the ratio of the actual number of nodes of the system to the number of estimated nodes is adjusted to a range of 0.5 to 2, and then the pPCA or PBCA is used for adjustment. The simulation results show that the adaptive control algorithm can adapt to the application scenarios of sudden change of nodes.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TN925.93
，
本文編號：2289122
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