11 operation, the guard interval is 800 ns. 11n specifies two guard intervals: 400ns (short) and 800ns (long). 2 µs) GI. Type of preamble to be used for each packet. 1 、 GI 的作用. Select to enable the short guard interval. Short GI — A bit that indicates use of the 400 ns guard interval. fc == 0x2400. Maximum Number of Total Space Time Streams (Nsts,total)In a Wifi 802. 5. Systems, methods, and other embodiments associated with a single stream wireless communication with a greenfield preamble that uses a short guard interval are described. 2x2 and a short GI with a 20 MHz bandwidth channel will only net you ~144 Mbps or less. This is kind of half right. At the receiver,. How to Use Command Lines. 11ac standard in the 5 GHz band, with signalling rates up to 6933 Mbit/s. 11n you can choose between a short guard interval and a long guard interval. 4GHz spectrum. Cyclic-Delay Diversitymisses 20% to 30% of short guard interval packets. In a wireless network in which communication devices are configured to use a first guard interval between symbols or a second guard interval between symbols, wherein the first guard interval has a length shorter than a length of the second guard interval, a field is generated to indicate a set of one or more modulation and coding schemes (MCSs). Many of them without careful setting both on the router and end device will cause you all kinds of issues. e. 2us. Enable or disable use of short guard interval (400 ns) in 40 MHz Megahertz mode of operation. GI (Guard Interval) is intended to solve the problem based on delays, and Short GI is used to improve the throughput of the wireless network based on the GI in the environment with small delays. 11ac or 802. Below are the MCS values for 802. , Sub-carrier secara orthogonal dapat dilihat dengan dua cara, dalam domain waktu dan frekuensi. Coding: SU/MU[0] Coding: Possible values: BCC, LDPC, or binary digit (indicating the value of a reserved bit). 11ac for different channel bandwidth and spacial streams. 802. 8 µs), double (1. dark gray area in figure 1). Request PDF | On Feb 1, 2011, Xiang Liu and others published 448-Gb/s reduced-guard-interval CO-OFDM transmission over 2000 km of ultra-large-area fiber and five 80-GHz-grid ROADMs | Find, read. Spatial Streams VHT MCS Index Modulation Coding Rate 20 MHz Data Rates (Mb/s) 40 MHz Data Rates (Mb/s) 80 MHz Data Rates (Mb/s) 160 MHz / 80+80 MHz Data Rates. 8µs) and short GI (0. 11g, 802. 8 µs. If the short guard interval does not allow enough time for reflections to settle in your mesh deployment, inter-symbol interference values may increase and degrade throughput. 11 guard interval The standard symbol guard interval used in IEEE 802. VLAN TRUNK Tugas 10-KJ-UINK-10651033. The guard interval is at a very basic level. Some outdoor deployments, may, however require a longer guard interval. If you are. 11 standard, which will be designated Wi-Fi 7. - Change Radio 2 Band to "802. Indeed, the shorter guard interval evidently results in intersymbol interference (ISI) and intercarrier interference (ICI), but the gain offered by shortened guard interval may exceed the loss caused by interference. (Guard Interval) a «Corto» o «Short». In two radio devices, both radios cannot play in the same band. Header part consists of 24 bits which is always BPSK modulated. 802. Single radio/antenna devices do not support mimo and still having trouble with inter symbol interference by multipath, especially in warehouses where barcodescanners are used. Can you confirm if you're referring to the chipsets in the clients or the APs? Just want to make sure we're talking about the same thing here. Below are some reference values: Level (dBm) Between -80 and -70. long and "any" is still "long" resulting to 130/270Mbps. Guard Interval. 11a standard uses the same core protocol as the original standard, operates in 5 GHz band, and uses a 52-subcarrier orthogonal frequency division multiplexing (OFDM) with a maximum raw data. 11ac). Wi-Fi radio test subcommands. Also a preference in iPhone/iPad if you give them different names for 2. 11g standard in the 2. The goal is. If the beacon interval is long, maximum capacity in the Access Point is achieved. Anda mungkin juga menyukai. (config)# ap dot11 5ghz dot11n guard-interval long: Configures the guard interval for the network. Short GI: disabled- Short Guard Interval decreases the time between data characters being sent wirelessly. LTF Symbol Interval Mode. 11n and the next 802. This is a technical white paper that covers the features that are included in the emerging Wi-Fi Standard, 802. 802. 11ax has three types of GI – the normal GI (0. The. 2 microseconds (μs) and only two Guard Intervals (GI) of 400 or 800 ns to a longer Ts (12. 802. Setting the 802. 11a/n /ac or 802. 11n rates (with short and long guard intervals): wifiType: ns3::. 11ax delivers a 25% improvement over 802. GI (Guard Interval) is intended to solve the problem based on delays, and Short GI is used to improve the throughput of the wireless network based on the GI in the environment with small delays. 11ac as long as additional features like WPA, WEP, AES encryption, Wireless Distribution System (WDS), Dynamic Frequency selection (DFS), Virtual Access Point, Nstreme and NV2 proprietary protocols and many more. Table 1: RSSI Reference Values. cfgHT = wlanHTConfig(Name,Value) sets properties using one or more name-value pairs. Capano December 19, 2014. Device (config)# wireless client association limit 50 interval 1000 設定できるクライアントの最大数を指定します。 単一アクセス ポイント スロットの、所定の間隔内におけるアソシエーション要求の最大数を設定できます。Devices should detect interference when using 40MHz, and drop back to 20MHz. 11n you can choose between a short guard interval and a long guard interval. Short Inter-frame Spacing (SIFS), is the time interval required by a wireless device in between receiving a frame and responding to the frame. 11n and TDMA. 4 μs guard interval which provides about a 10% increase in data rate. This should only be a temporary configuration change. Straight forward really. 4. 802. Choose Wireless > 802. Enterprise networks considering an investment in infrastructure Wi-Fi have two excellent choices: (1) buy 802. Default: Enabled. MCS: SU MCS/MU. 4. We would like to show you a description here but the site won’t allow us. This is often confused with the space between packets, which is the inter-frame space (IFS). 11n/ac/ax STAs and. When deploying a wireless network in an environment with many obstacles, there will be diffraction, scattering and reflection. Cara setting WiFi IndiHome agar jangkauan jauh harus diketahui para penggunanya. This option is only available for 5GHz 802. Restu Aji. , in the (flat) desert, which was. It's a 5Ghz long range network. Guard Interval เป็นห้วงเวลาที่ป้องกัน Packet ของข้อมูลชนกันเอง ซึ่งจะมีสองแบบ คือ Short 400 และ Long 800 ns (นาโนวินาที) โดยแบบ Short 400 ns จะสามารถใช้งานได้. 25. Short GI: disabled- Short Guard Interval decreases the time between data characters being sent wirelessly. About This Document. Nah, selanjutnya, tekan login. I forgot to mention enabling long preamble, which really helps with mobile wifi clients as they spin up from low radio power modes. Two settings are available: short (400ns) and long (800ns). In the past few years, there have been impressive advances in experimental demonstrations of high SE multicarrier transmission employing narrow frequency guard interval and higher-order modulation format [20,71,76–78]. US11671296B2 US16/042,701 US201816042701A US11671296B2 US 11671296 B2 US11671296 B2 US 11671296B2 US 201816042701 A US201816042701 A US 201816042701A US 11671296 B2 US11671296 B2As a Wi-Fi network engineer, managing multiple access points on different floors. - Change Radio 2 Band to "802. Then add access list entries for each special devices setting the Mac, vlan mode and vlan tag. 11 OFDM is 0. 11n/g/b, and 5GHz 802. OFDM, OFDMA. Choices: "enable" "disable" spectrum_analysis. 11 is 800 ns. 1. Tx STBC (1 bit)since 802. 4 UWB Concepts. 11n bands. Cisco Virtual Engineer generative AI bot now active in Wireless Discussion Forum. By reducing the overhead of extra idle time between transmissions of two successive symbols, SGI helps to enhance the average system throughput, compared to the. 6 µs ,4x HE-LTF + 3. disable] set rogue-scan-mac-adjacency {integer} set short-guard-interval [enable|disable] end. 1 、 GI 的作用. 11ac, short guard interval (400 ns) is introduced while the default value of GI is still set as 800 ns. By default, all avail-. 4GHz como para la banda de 5GHz. The guard interval prevents Inter-Symbol and Inter-Carrier Interference (ISI, ICI). Symbols are what carry the bits (0s and 1s). an 80 MHz transmission sent at 256QAM with three spatial streams and a short guard interval delivers 234×3×5/6×8 bits/3. UWB (Ultra Wide Band) is the PHY defined in IEEE 802. CTC Protection Mode - enables a mode which ensures 802. 2 - Mixed Preamble. Tunggu beberapa saat hingga Anda dihubungkan dengan tab menu yang baru. This page of WLAN 802. 4 GHz signal is stronger it will “tell” the device to use 5 GHz anyways. Router manufacturers support different versions of 802. Guard Interval. 4Ghz long guard interval. Top. This option is only available for 2. Different Guard Interval Techniques for OFDM: Performance Comparison 3 Figure 2. 1 Insight managed wifi 6 ax1800 dual band access point 1 Models 1 User manual 3 Contents 8 1. Jun 11, 2017. For example, 15kHz SCS with 14 symbols spanning the entire subframe corresponds to LTE's configuration. Some have mentioned low power small cells. Early WiFi 6 clients might not support uplink MU-MIMO and for the ones that do, the implementation is not yet mature across client manufacturers. Use the VLAN pool when available. Enable wireless scheduler: Allow administrators to specify when the wireless network will power off to conserve energy and maintain network security. Guard interval duration 0. 8 µs, 2x HE-LTF + 1. The available channels depend on which IEEE wireless protocol you selected in Band. When Short GI is enabled, the guard interval will be set as 400ns and this function will boost the performance about 11%. Below are the MCS values for 802. However for office environments, having a Short Guard Interval (SGI), which lowers the interval to 400ns, can give you an increased data rate of 11%. 8 μs, to increase data rate 802. 4GHz 802. 6 µs. 11a, 802. GI模式配置为short <AC> system-view [AC] wlan [AC-wlan-view] radio-5g-profile name default [AC-wlan-radio-5g-prof-default] guard-interval-mode short: 无线信号在空间传输会因多径等因素在接收侧形成时延，若数据帧之间间隔太短，容易和前后的数据帧形成干扰，而GI就是用来规避这个干扰的。Short GI: disabled – Short Guard Interval decreases the time between data characters being sent wirelessly. • Helps improve data rate in Up/Down if both AP and STA support Short GI. Multi-user: indicates the coding for user 0. Other: User entered Guard Interval values between 0 to 1. 11ac, short guard interval (400 ns) is introduced, while the default value of GI. Go to solution. ap (config-if)#interface dot11radio0. If it's set to any, it defaults to 400ns for compatible clients. I assume you mean Short Guard Interval (SGI) when you say GI? If so, with other vendors that I've worked, I've been able to enable/disable SGI across all of their APs that I've worked with (which is more extensive with some vendors that others). 800/400 ns. Jika sudah, maka pilih menu network yang ada di bagian layar Anda. In this case study, we apply a formal approach to compute optimal safe guard times, i. Short Guard interval & Aggregation. Early WiFi 6 clients might not support uplink MU-MIMO and for the ones that do, the implementation is not yet mature across client manufacturers. ৯ মে, ২০০৭Disable Short Guard Interval. 93 Gbps ( using 160MHz bandwidth, 8 spatial streams, MCS9, 256QAM, with short guard interval) and coverage range of approx. 11n) to open the 802. ” 3. 1024 QAM with MCS 10, 11. Use Short Guard Interval (SGI) if you can - it may squeeze a bit more throughput through with your 11n/11ac clients. 2,501. Choose Wireless > 802. Edit htmode options in the file /etc/config/wireless and restart the Wi-Fi AP to test various channel widths. Wi-Fi beacons are relatively short, regular transmissions from access points (APs) with a purpose to inform user devices (clients) about available Wi-Fi services and near-by access points. of inserting between symbols a small time interval known as a guard interval (GI). WLAN frame structure consists mainly PLCP Preamble, Signal (Header) part and Data Part. 8 microseconds. Single radio/antenna devices do not support mimo and still having trouble with inter symbol interference by multipath, especially in warehouses where barcodescanners are used. 125 KHz, compared to 312. 15. Nilai default adalah 100 (unit adalah milidetik, atau 1/1000 detik). 11n outlined the idea of a short guard interval, decreasing the timer to 400ns. Systems, methods, and other embodiments associated with a single stream wireless communication with a greenfield preamble that uses a short guard interval are described. 11n protocols is plot- ted for MCS values 1 to 8 for short and long GI in Figures 3 and 4 with channel. ) A long enough cyclic prefix prevents multipath echoes from one symbol interfering with the portion of the next symbol after the prefix. 11a/g, except the number of. Guard Interval. Yes, it should be 50-60 MB/s as shown on windows explorer speed. MCS = higher is better. According to one embodiment, a wireless communication device includes a receiver configured to receive an orthogonal frequency-division multiplexing (OFDM) signal. 15. Short GI = good, association and signal is robust, so wireless frames use a shorter interval spacing to save time on the channel, thus increasing throughput. 4 μs guard interval. 当设计802. ohara Member Posts: 387 Joined: Mon Jun 13, 2011 9:30 pm Location: Warsaw. 11a, the fundamental sampling rate is 20 MHz, with a 64-point FFT/IFFT. Click to expand. ) Active Application number EP12721137. Figure 33: 800 nanosecond GI (long guard interval) Long Guard Interval – 802. This Linksys WRT54GS, a combined router and Wi‑Fi access point, operates using the 802. Some outdoor deployments might, however, require a longer guard interval. Now, if you use short guard interval the max data rate will increase to 144. Hence, in TGaf capable devices shall support both guard interval modes (short and normal). 1 AIJ. 802. 802. by Daniel M. Enable wireless scheduler: Allow administrators to specify when the wireless network will power off to conserve energy and maintain network security. Sebab, terkadang jaringan yang diterima ketika mengakses Internet di HP maupun perangkat lain tak teraih dengan baik. In Wi-Fi 6 or 802. 11 standards, it provides complete support for 802. Sin embargo, pasando a los dispositivos de tecnología inalámbrica "g" e. In order to dissect the Guard Interval it is important to think of the signal transmissions from the viewpoint of the. Solution. 168. Cara pertama yang dapat Anda lakukan adalah dengan memastikan bahwa router diletakkan pada posisi yang strategis. By reducing idle time in environments that aren’t very noisy, turning on SGI can increase wireless data rate by 11%. (Cisco Controller) >config 802. Short guard interval vs long? : r/HomeNetworking View community ranking In the Top 1% of largest communities on Reddit Short guard interval vs long? Which is better? I saw an option in my network settings lol 1 comment Best Add a Comment discojohnson • 3 yr. 11ax, officially marketed by the Wi-Fi Alliance as Wi-Fi 6 (2. These longer guard intervals help to prevent inter-symbol interference in outdoor environments and therefore improve coverage and performance. Table 1: RSSI Reference Values. 2/15/13 TERIM A KASIH 2/15/13. The guard interval in a typical 802. Step 1 : Choose Wireless > 802. Nilai default adalah 100 (unit adalah milidetik, atau 1/1000 detik). 11ax, focusing on WLAN indoor and outdoor operation with stationary and pedestrian speeds in the 2. Guard Interval เป็นห้วงเวลาที่ป้องกัน Packet ของข้อมูลชนกันเอง ซึ่งจะมีสองแบบ คือ Short 400 และ Long 800 ns. kau asu. Short Guard Interval The guard interval is the space between symbols (characters) being transmitted. This offers a much broader multipath tolerance, reduces overhead and bolsters throughput, thereby making outdoor Wi-Fi more reliable and dependable. In IEEE 802. A short preamble improves throughput performance. Number of extension spatial streams: only 0 is supported. WPS (Wi-Fi Protected Setup) can help you to quickly and securely connect to a network. Date to Enable Radio (week days): This field defines the dates the wireless network is enabled. The amount of power wasted depends on how large a fraction of the OFDM symbol duration the guard time is. 4. N = short guard interval not used in the VHT-Data field. 11n-2. This document provides multiple network optimization methods and related cases to guide WLAN maintenance engineers through WLAN optimization. 11, which uses OFDM for its highest throughput profiles. 11a/b/g requires guard interval (GI) to be 800 ns. When Short GI is enabled, the guard interval will be set as 400ns and this function will boost the performance about 11%. Fitur ini berguna untuk komputer yang dikonfigurasikan untuk memasuki mode tidur karena pesan DTIM akan memberi tahu klien bahwa router wireless memiliki informasi yang harus dikirim. 5Gbps. Mark as New;. MAC Improvements In normal 802. used refrigerator sale near me. 125,640. The standard symbol guard interval used in 802. Ajuste o Beacon Interval: O Beacon Interval (Farol) é um quadro (frame) de sincronização enviado em períodos constantes pelo roteador wifi. 11nsupport guard_interval {any | long} Configure the Reduced Interframe Space (RIFS). An AP identifies any signal content received inside this interval as unwanted inter-symbol interference, and rejects that data. The SGI (Short Guard Interval) defines the time interval between transmitted symbols (the smallest unit of data transmitted at one time). Short guard interval in 40 MHz mode. This document describes all the configuration commands of the device, including the command function, syntax, parameters, views, default level, usage guidelines, examples, and related commands. Choose Wireless > Advanced Settings. guard time. Time of Day to Enable Radio: This field defines the time interval that wireless function is. Assuming the energy per sample is the same for the guard interval and the data part, KSP-OFDM will suffer, like CP-OFDM, from a power efficiency loss of N N+ν. 125 KHz, compared to 312. 4. An entire OFDM symbol, as used in Wi-Fi on standard width channels, requires four microseconds. OFDM, OFDMA. MCS 9 is not allowed for 20MHz BW. Deploy 5GHz Wi-Fi and enable band steering. This provides an 11% increase in data rate. 1. To configure this parameter for a given device, the following lines of code could be used (in this example, it enables the support of a short guard interval for the first station):. The receiver is typically configured to discard the cyclic prefix samples, but the cyclic prefix serves two purposes: It provides a guard interval to eliminate intersymbol interference from the previous symbol. So you're limited to 65mbit per spacial stream. On a wireless router, what is AP isolation?Download scientific diagram | Comparison between long-range and short-range wireless standards of IoT [6, 7, 12, 27, 38, 39] from publication: Review on Common IoT Communication Technologies for. I changed HT Guard Interval on CPE from 'long' to 'any'. Short/Long Preamble are applicable only when tx_pkt_tput_mode is set to Legacy and Mixed Preamble is. 900 Mbps (two spatial streams at 80 MHz, short guard interval) Technically, it’s only 867 Mbps, but it’s nicer to round up and get that much closer to 1 Gbps. 802. This is a small but essential utility for any user of a Wi-Fi network, as long as they want to keep it safe. 11ac data rates . 11n standard specifies two guard intervals: 400 ns (short) and 800 ns (long). The 802. 802. 25 KHz for 802. Short Guard interval & Aggregation In the screen shot above you will notice that Short Guard Interval and Aggregation are both disabled. 11n systems using OFDM had defined data rates between 6 and. 11a/n or 802. e. However for office environments, having a Short Guard Interval (SGI), which lowers the interval to 400ns, can give you an increased data rate of 11%. Single radio/antenna devices do not support mimo and still having trouble with inter symbol interference by multipath, especially in warehouses where barcodescanners are used. 11n. 6 µs or 3. Beacon Interval: Beacon Interval berarti periode waktu antara satu suar dan yang berikutnya. 11a/g. 11n and 802. Here are some advanced wireless settings selections Geier advises you to make right off the bat: “Short Preamble Length, Short Slot Time, Short Guard Interval, and Frame Aggregation. kelompok 4. When the wireless radio is configured for 802. (with short/long guard interval (GI)), 1 MHz channel bandwidth. You need this mode if your wifi cards connected to multiple hosts. Gartner Glossary Information Technology Glossary G Guard Interval. Last Updated On 12 lutego 2021. Beginning with the introduction of IEEE 802. As can be seen, the physical layer data rate mayLos dispositivos inalámbricos "b" más recientes que utilizan un preambulo más corto suelen experimentar transferencias de datos más rápidas. Remote forwarder -- Only capture a packets. 11 OFDM Overview Introduction to 802. I recently got a Unifi system, thinking they would be customization since it's enterprise, but there is no way to adjust advanced wireless. 4|5> <MCS index>*] [vht. 11ac had. What is the 11n guard interval? Intersymbol interference, also known as ISI, is eliminated by the guard interval. Guard Interval: 800ns: Mode: 11 vht AC/AN/A: VHTBandwidth: 20/40/80MHz: VHT Guard Interval. 802. Short is ideal, but I'd imagine most people need to use Long, again, unless you have your AP's very close to the SS devices they're connected to. 11n-2. 11 Network | Purpose. Regards, ParikshithA silent guard interval would likely increase PAPR (peak to average power), which requires a sender capable of more dynamic range (without clipping or generating power supply noise, etc. 11ac and 802. Single radio/antenna devices do not support mimo and still having trouble with inter symbol interference by multipath, especially in warehouses where barcodescanners are used. The OSI model describes how information moves from an application program running on one networked computer to an application program running on another. Short: Sets the guard interval to 400 nanoseconds which can provide improved throughput (up to 10%) in some environments. When Short GI is enabled, the guard interval will be set as 400ns and this function will boost the performance about 11%. normally you can configure that the access point will use long guard intervals (it is 800ns instead of 400ns) to improve the negative. Has small packet latency issues 3. An entire OFDM symbol, as used in Wi-Fi on standard width channels, requires four. I picked up a WRT-160N wireless router hoping to use it relieve the stuttering when streaming HD content over my WRT54G network. Configuration. 11a/b/g requires guard interval (GI) to be 800 ns. IEEE802. Normally this is an 800ns timer that allows for time between bursts. 1 . Short/Long Preamble are applicable only when tx_pkt_tput_mode is set to Legacy and Mixed Preamble is. Mode. Until 802. In this video you will learn why and when to use wifi short guard interval in your FortiAP to increase throughput up to ten percent , but use it carefully as it can also decrease throughput in places where you have many physical obstacles . You cannot configure this in Dashboard. Powered by NRC7292 System-on-Chip from Newracom, SX-NEWAH is industry’s first IEEE 802. เช่น WRT54GL Wireless G สัญญาณไปได้ไกลกว่า Router N หลาย ๆ ยี่ห้อในตลาดปัจจุบัน. Jika sudah, maka pilih menu network yang ada di bagian layar Anda. Monte Carol simulations are applied to evaluate. By reducing the overhead of extra idle time between transmissions of two successive symbols, SGI helps to enhance the. 11a/b/g requires guard interval (GI) to be 800 ns. Dec 16, 2021. Wireless networks. Short GI: Y = short guard interval used in the VHT-Data field of the preamble. 11ac had two Guard Interval (GI) options – long GI (0. It’s generally recommended that you maintain a short GI. However, for office environments, having a Short Guard Interval (SGI), which lowers the interval to 400ns, can give you an increased data rate of 11%. 11nsupport guard_interval {any | long} Configure the Reduced Interframe Space (RIFS). Default. 11n standard specifies two guard intervals: 400ns (short) and 800ns (long). As such, Wi-Fi 6 introduces Long Signal OFDM, which allows up to a 3. 11a/g. 4. 11g network and the reported connection speed also fluctuates wildly,. Download Citation | Study of Guard Interval Duration on the Operation Impact of IEEE 802. Best WI-FI Settings. Wi-Fi radio test subcommands. ใน Wi-Fi ที่ใช้ OFDM จะใช้ GI อยู่สองตัวคือ GI มาตรฐาน 0. 27,538. Short GI(Guard Interval) 是 802. The 802. For HIPERLAN/2, both 1/4 and 1/8 are selections. For simplicity’s sake: If you stand on top of a hill and shout out “I love you!”, the person on another hilltop wouldn’t hear you clearly. 11g, 802. 80 m with 3 antenna (about 10 meter more than wifi-4). 11n/ac/ax/be, the Guard Interval selection is 1/4, 1/8, or 1/16. GI模式配置为short <AC> system-view [AC] wlan [AC-wlan-view] radio-5g-profile name default [AC-wlan-radio-5g-prof-default] guard-interval-mode short: 无线信号在空间传输会因多径等因素在接收侧形成时延，若数据帧之间间隔太短，容易和前后的数据帧形成干扰，而GI就是用来规避这个干扰的。IEEE 802. A Wi-Fi Alliance interoperability certificate indicates that a device is a/b/g/n certified. If you would use mixed mode, always make sure these are disabled, as these features were designed to be used with 802. 4GHz หรือ 5GHz คุณต้องการที่จะตั้งค่า. When the delays are small. ) Active, expires 2032-07-17 Application number US13/465,347 Other languages English (en) Other versionsThe standard guard interval used in 802. Standards: Package: wireless RouterOS wireless comply with IEEE 802. Using personal security mode for your. Number of HE-LTFs (Nheltf) Specify the number of HE-LTFs. Overview. Enabling a short guard interval can decrease network overhead by reducing unnecessary idle time on each AP. Note that option htmode should be set to either HT40+ (for channels 1-7) or HT40- (for channels 5-11) or simply HT40 . 11ax has three types of GI – the normal GI (0. Fajar Ramadhan. How to Use Command Lines.