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【正文】 2023/2/2 16:23:2116:23:2102 February 2023n 1一個(gè)人即使已登上頂峰，也仍要自強(qiáng)不息。勝人者有力，自勝者強(qiáng)。 二月 21二月 21Tuesday, February 02, 2023n 閱讀一切好書如同和過去最杰出的人談話。 。 二月 2116:23:2116:23Feb2102Feb21n 1世間成事，不求其絕對圓滿，留一份不足，可得無限完美。 2023/2/2 16:23:2116:23:2102 February 2023n 1做前，能夠環(huán)視四周；做時(shí)，你只能或者最好沿著以腳為起點(diǎn)的射線向前。 二月 21二月 2116:23:2116:23:21February 02, 2023n 1他鄉(xiāng)生白發(fā)，舊國見青山。 二月 21二月 21Tuesday, February 02, 2023n 雨中黃葉樹，燈下白頭人。2/2/2023 11成大資訊 鄭憲宗直接序列展頻（ DSSS）2/2/2023 12成大資訊 鄭憲宗跳頻展頻（ FHSS）2/2/2023 13成大資訊 鄭憲宗IEEE TGan The TGa is working on the high datarate extension in the 5 GHz band, project , was able to produce a new draft standard that has the support of at least 80 % of the members.n TGa is looking at a candidate for worldwide standardization! 2/2/2023 14成大資訊 鄭憲宗IEEE TGa (cont.)n The specifications of the Physical Layer enpass data rates from 6 Mbit/s up to 54 Mbit/s, with 20 MHz spacing between adjacent channels. n All implementations are required to support 6, 12 and 24 Mbit/s. Optional extensions are for 9, 18, 36, 48 and 54Mbit/s. n The multirate mechanism of the MAC protocol ensures that all devices municate with each other at the best data rate in the present channel. 2/2/2023 15成大資訊 鄭憲宗IEEE TGbn The TGb is working on the extension of the 1 and 2 Mbit/s data rates in the GHz band with and 11 Mbit/s has reached a technical promise solution to improve the coexistence and interoperability characteristics between options. n The multirate mechanism warrants that the 11 Mbit/s operation can switch back to Stations that are even further could switch back to the 2 and 1 Mbit/s capabilities of the DSSS modulation. 2/2/2023 16成大資訊 鄭憲宗CSMA/CD (LAN)1. Send data if the medium is sensed “idle”2. If collides with other host(s),3. then backoff for a random number of times3. Resend data later2/2/2023 17成大資訊 鄭憲宗Hidden Terminal Problem BA Cdata data2/2/2023 18成大資訊 鄭憲宗Solution to HTPBA CRequestGrant2/2/2023 19成大資訊 鄭憲宗Detection of CollisionBA CRequest Request2/2/2023 20成大資訊 鄭憲宗BA CRequestA is Grant A is GrantDCollision Avoidance2/2/2023 21成大資訊 鄭憲宗RTS/CTS/data/ACK and NAV setting2/2/2023 22成大資訊 鄭憲宗Some IFS relationships and basic access method2/2/2023 23成大資訊 鄭憲宗Random backoff timen Backoff time = INT(CW * Random())*aSlotTimen INT(x) : 小於或等於 x的最大整數(shù)n CW(contention window parameter ) : 介於CWmin和 Cwmax間的整數(shù) , CW依序遞增的順序?yàn)?(7,15,31,63,127,255,255,255……)n Random() : 介於 0到 1間的實(shí)數(shù)n aSlotTime : 傳送器開啟延遲 + 媒介傳遞延遲 + 媒介忙碌偵測反應(yīng)時(shí)間2/2/2023 24成大資訊 鄭憲宗An example of exponential increase of CW2/2/2023 25成大資訊 鄭憲宗Backoff procedure2/2/2023 26成大資訊 鄭憲宗Transmission of a multifragment MPDU using SIFS 2/2/2023 27成大資訊 鄭憲宗RTS/CTS with fragmented MSDU2/2/2023 28成大資訊 鄭憲宗RTS/CTS with transmitter priority and missed acknowledgment2/2/2023 29成大資訊 鄭憲宗Direct data/ACK MPDU
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