ieee_80211基礎(chǔ)-文庫吧資料
2025-02-21 12:00本頁面
【正文】 arrow beam width, might not a issue for backhaul, but it will be a tradeoff for coverage – 加高性能的低噪聲放大器 ? Example: add a booster after antenna 2023114 36 AZC/STR2023:0002, Commercial in confidential – 無線射頻 ? RSSI – Received signal strength indication: ? Defined by standard as a relative number, implementation is depended on each vendor ? Atheros (our chip vendor) uses it the same way as SNR: received power – radio noise floor – Noise floor = 174 dBm (thermal noise in 1 Hz) + 10*log (20 MHz) + system noise figure (dB), ? typically number around 92dBm – Most important parameter, throughput will be determined by RSSI under AWGN (additive white Gaussian noise) condition – Record this number first when trouble shooting 2023114 37 AZC/STR2023:0002, Commercial in confidential – 無線射頻 ? Adjacent/alternate channel rejection Table 91—Receiver performance requirements Data rate (Mbits/s) Minimum sensitivity (dBm) Adjacent channel rejection (dB) Alternate adjacent channel rejection (dB) 6 –82 16 32 9 –81 15 31 12 –79 13 29 18 –77 11 27 24 –74 8 24 36 –70 4 20 48 –66 0 16 54 –65 –1 15 2023114 38 AZC/STR2023:0002, Commercial in confidential – 無線射頻 ? Throughput – One of those most important numbers to users – TX rate is not throughput, need subtract MAC overhead – Application type will affect throughput ? Example: small packet size will reduce throughput Rate (Mb/s) 1 2 11 6 9 12 18 24 36 48 54 TCP (Mb/s) 8 5.6 4.3 6.2 8 14.2 18.6 21.7 UDP (Mb/s) 8 7.1 5.1 7.4 9.6 17 23.1 27.4 2023114 39 AZC/STR2023:0002, Commercial in confidential – 無 線射頻 ? 多用戶流量 – Useractivityfactor = 2023114 40 AZC/STR2023:0002, Commercial in confidential – 無 線射頻 ? Radio Propagation model – Free space: Loss (dB) = 20*log(4*pi*d/λ) – Two lines: Loss (dB) = Ld0 + 20*n*log(d/d0) ? Ld0 is break point loss, usually use free space loss at 1m or 10m as break point loss. ? n is depended on the environment – Extra margin needs to add to the loss ? Free space: 18dB ? Two lines: 810dB – Link budget: ? TX power (dBm) + Gtx + Grx – Loss ≥ Rx sensitivity (dBm) ? Rx sensitivity is rate depended. 2023114 41 AZC/STR2023:0002, Commercial in confidential QA 2023114 42 AZC/STR2023:0002, Commercial in confidential 謝謝！ 2023114 43 AZC/STR2023:0002, Commercial in confidential ? 靜夜四無鄰，荒居舊業(yè)貧。 2023114 20 AZC/STR2023:0002, Commercial in confidential 安全 WPA ? WPA 利用 TKIP(Temporal Key Integrity Protocol) 來代替 WEP ? TKIP 仍用 RC4加密算法 , 但是每個包的 RC4 key是不同的 ? 利用兩種方法管理關(guān)鍵字 – 外部認(rèn)證服務(wù)器 (Radius) and EAP – Preshared keys 沒有附加的服務(wù)器 ? WPA 引入 4個新算法 – 48位初始化向量 (IV) – IV順序規(guī)則 (IV Sequencing Rules)、
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