For 802. 11n 针对 802. Security Settings. N = short guard interval not used in the VHT-Data field. 11g, 802. 11a, 802. การพิจารณาออกแบบ Wireless LAN (6) ทางเลือกสำหรับมาตรฐานต่างๆ การใช้งาน Guard Interval Guard Interval ซึ่งเป็นส่วนหนึ่งสัญญาลักษณ์ OFDM เป็นห้วงเวลาที่ถูกใช้เพื่อลดการ. Nv2 wireless protocol supports short guard interval. Cara setting WiFi IndiHome agar jangkauan jauh harus diketahui para penggunanya. When to use short GI? When intending to improve the throughput, enable short GI can improve the throughput about 10% . 4|5> <MCS index>*] [vht. 11ah Wi-Fi Solution for IoT Devices. 11ac is not directly defined in data rates speed, but is rather a combination of 10 modulation encoding scheme (MCS 0 to MCS 9), a channel width ranging from 20mhz (1 channel) to 160Mhz (8 channels), a number of spatial streams (typically 1 to 4). Long Symbol Duration and Guard Interval. This is kind of half right. 11ac物理层帧结构时，协议设计者会列出新的成帧需求。Disclosed are a method and a device for transmitting and receiving a frame using a short guard interval. 11b, redes banda de 2. Throughput is expected to reach a theoretical maximum of. 11n guard interval: Long (I can select Short but I thought to minimize interference and have it on Long)Download A Field Guide to Secure Wi-Fi — Observations From Your Laptop and keep yourself up-to-date on ways to secure your Wi-Fi airspace 24/7 from unauthorized. Dan berikut cara mempersempit / memperkecil jaringan wifi Indihome. 802. Then add access list entries for each special devices setting the Mac, vlan mode and vlan tag. Sin embargo, pasando a los dispositivos de tecnología inalámbrica "g" e. VIP Options. 8 μs. How Wi-Fi 6 differs from Wi-Fi 5? Wi-Fi 6 is all about High Efficiency Wireless (improving upon Wi-Fi 5 limitations) BRKEWN-2017 23. If I fix the capability to 20MHz channel width with long guard interval, I still see some (around 10%) of the packets wtih 40MHz channel width and/or short guard interval. normally you can configure that the access point will use long guard intervals (it is 800ns instead of 400ns) to improve the negative. guard interval guard interval Prior art date 2011-05-18 Legal status (The legal status is an assumption and is not a legal conclusion. 11ac). 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. 2 µs) GI. See also 802. 0 - Short Preamble. with a short guard interval) will be able to achieve almost 3. fc == 0x2400. Since you asked, the guard interval is the tiny amount of time (like 400 nanoseconds) that the transmitter waits between sending one "symbol" (think, "one indivisible group of up to. since 802. Guard Interval. Short guard intervals are possible with 802. Configure the guard interval for the network by entering this command: config 802. Short Guard Interval The guard interval is the space between symbols (characters) being transmitted. View client’s signal strength detected by the AP on GWN web GUI under -> -> , and check user RSSI level. Here is the format of the frame: The trigger frame is a broadcast frame and you can use this filter to fidn it in Wireshark: wlan. 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. • Short GI Feature - It is enabled by default and highly recommended, for it will increase the packet capacity by reducing the GI (Guard Interval) time. In IEEE 802. View solution in original post. 11n standard specifies two guard intervals: 400ns (short) and 800ns (long). 11n-2. 11ax is no exception. 11 guard interval. You need this mode if your wifi cards connected to multiple hosts. 800/1600/3200 ns. The Other selection allows the input of a non-standard Guard Interval value between 0 and 1. LTF Symbol Interval Mode. Devices that take advantage of the phase 2 parameters (8 spatial streams, 160 MHz of bandwidth and 256-QAM 5/6 with a short guard interval) can achieve almost 7 Gbps. I’ve been following you o YouTube for a long time and I thank you for all the advices you give. 2 microsecond guard interval with the data packet area being increased 4x, or up to 12. For HIPERLAN/2, both 1/4 and 1/8 are selections. 6 µs. 8 μs) and three guard-interval options (0. Capano December 19, 2014. (Cisco Controller) >config 802. v module. Following are the major changes made in the 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. 11n and the next 802. Select the wireless protocol from the dropdown list. If it's set to any, it defaults to 400ns for compatible clients. The 802. The 802. OFDM. 29_XIIA_KD . Next thing is disable fat channels and short guard interval. This parameter is only valuable for 802. HL-4GQV/HL-4GQVS WIFI 2. 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. Long Symbol Duration and Guard Interval A key characteristic of WiFi 6 is the narrower subcarrier spacing (78. 11 operation, each directed data and management frame must be acknowledged, as shown in the top. The Wi-Fi Alliance first began certifying products that support 802. With 802. Use either the short guard interval (Short GI) of 400 ns or the long guard interval (Long GI) of 800 ns. 2us. orange pi voron. By default, all avail-. With the internet connection you have you can max it out by using single stream with a 40MHz wide channel short guard interval enabled since that goes up to 150Mbps. SGI should be used only in good and clean RF (Radio) environment. disable. Despite testing it in n-only mode with two laptops, a USB wifi adapter and two phones, connection speeds are less than half of what I see with my 802. MCS = higher is better. Configure the short GI mode. , in the (flat) desert, which was. 4|5> <legacy rate in Mbps>*] [ht-mcs-<2. Overview. Cisco Virtual Engineer generative AI bot now active in Wireless Discussion Forum. 1. 11n bands. 4 UWB Concepts. 11ax, officially marketed by the Wi-Fi Alliance as Wi-Fi 6 (2. 4GHz como para la banda de 5GHz. 2 - Mixed Preamble. ในการทำงานกับ WIFI ค่าอะไรบ้างที่เราจำเป็นต้องรู้ เพื่อใช้ในการวิเคราะห์ปัญหา ได้อย่างแม่นยำและถูกต้อง. 93 Gbps ( using 160MHz bandwidth, 8 spatial streams, MCS9, 256QAM, with short guard interval) and coverage range of approx. Symbol Duration. 125 KHz, compared to 312. Step 3 : Select the check boxes of the desired rates to specify the modulation and coding scheme. Guard Interval. 8 microseconds. By reducing idle time in environments that aren’t very noisy, turning on SGI can increase wireless data rate by 11%. 11a/g 所做的改进。 射频芯片在使用 OFDM 调制方式发送数据时，整个帧是被划分成不同的数据块进行发送的，为了数据传输的可靠性，数据块之间会有 GI ，用以保证接收侧能够正确的解析出各个数据块。 Don’t. Beacon Interval - Sets the amount of time between beacon transmissions in milliseconds. Figures 1 and 2 with channel bonding when bandwidth is 20 MHz. Tunggu beberapa saat hingga Anda dihubungkan dengan tab menu yang baru. Guard interval duration 0. 11ac had. You cannot configure this in Dashboard. Delay spread can be detrimental to communication systems. Every new 802. As such, Wi-Fi 6 introduces Long Signal OFDM, which allows up to a 3. 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. 11n standard specifies two guard intervals: 400 ns (short) and 800 ns (long). This option is only available for 2. 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). Select to enable the short guard interval. Set Radio 1 Bands to AX unless you have some older equipment that needs WiFi Set Radio 2 Bands to AX/AC/N, Channel width to 40MHz. 11a/g. 11n Guard Interval. 1. Table 1: RSSI Reference Values. Using guard time requires extra time and energy, which is critical in wireless sensor networks operating on limited energy. config system wireless settings. To increase data rate, 802. 11€{a€|€b}11nsupport guard-interval€{any€|€long} Sniffer Tools Wireless Sniffing with a Mac with OS X 10. Default: Enabled. Which is better guard interval long or short? Shorter wait time (guard interval) between symbols increases throughput. Ya que si mantienes activada opción Wifi inteligente, compatibilidad con 802. 11 operation is 800 ns. 11g standard in the 2. 11ac will include*Edit: Preamble Type: Long, unless your devices are very close to the router/extender/mesh node they're attached to, then try Short. 8µs) and short GI (0. VLAN TRUNK Tugas 10-KJ-UINK-10651033. In most of the cases clients negotiate with SGI-False (LGI) flag. By Daniel E. The. Figure 1-2 High-density and high-bandwidth scenarios. 11a. 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. Need for better battery life IoT & Phone 4. 6, or 3. Kamu bisa membatasi jarak jangkauan WiFi dengan mengubah menu “Transmitting Power”. 125 KHz, compared to 312. 8 μs, to increase data rate 802. Higher the level, less sensitive the radio is and smaller the receiver cell size. These data rates, which are calculated for a 20-MHz channel width using a short guard interval, are available: 0 (7 Mbps) 1 (14 Mbps) 2 (21 Mbps). 11b/g/n > Network to open the Global Parameters page. This gives a safe time between transmissions. Interval: Select to enable the short guard interval for 802. As discussedDoes anyone know where you can configure short/long Guard Interval (SGI / LGI) on SmartZone controlled APs?. Lebih lengkapnya, setelah memasang wifi tanyakan kepada teknisinya. 11n and 802. 802. Otherwise said, you should set a relatively short amount of time between the transmission of. ガードインターバル 【 guard interval 】 ガード区間 ガードインターバル とは、 無線通信 の品質を向上させる手法の一つで、伝送する 符号 が切り替わる際に短い無通信の時間を設けること。Hi, it's a new installation. 11n data rate. Lihat juga 802. Use the guard-interval configuration mode command to configure the The 802. 11 {a | b} 11nsupport guard_interval {any | long} Configure the Reduced Interframe Space (RIFS) for the network by entering this command: config 802. In two radio devices, both radios cannot use the same band. packet capture and processing are done on the local host. Frequency Modulation. Whether or not short guard interval is enabled for HT/VHT transmissions. Wi-Fi AP 802. Basic Configurations Commands. This interval helps data reception avoid delays due to Inter-Symbol Interference (ISI) and overcome echoes (reflection of sound waves). Guard Interval : 800ns PSC Enforcement : Disabled WLC9800# WLC9800#show wireless profile multi-bssid detailed MBSSIDprofile_test. MCS: SU MCS/MU. 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. Hi, it's a new installation. 5. You’d be missing a valuable opportunity to improve your network’s performance right from the get-go. Router VDSL2 HUAWEI HG630 V2 / NT3BB-4PVWN-142 ความเร็วที่ใช้ 50/10Mb เทสสปีดกับเครื่องพีซีความเร็วออกมาปกติดีครับ แต่ทดสอบกับมือถือ iPhone6s+ ios 9. The default value is 1, which indicates the DTIM Interval is the same as Beacon Interval. Router manufacturers support different versions of 802. Pre-802. 11, the channel bandwidth was 20MHz with later amendments adding support for 5 and 10MHz bandwidths. 11nsupport guard_interval {any | long} Configure the Reduced Interframe Space (RIFS). 11n rates (with short and long guard intervals): wifiType: ns3::. 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%. The 802. Wi-Fi 6 is designed for high-density wireless access and high-capacity wireless services, such as in outdoor large-scale public venues, high-density stadiums, indoor high-density wireless offices, and electronic classrooms (e-classrooms). Two settings are available: short (400ns) and long (800ns). Top. 4Ghz any to allow either short or long guard interval. I wonder why MT still insist not to implement the standard 400msec short GI option. RTS is used with CTS (Clear to Send). type == 1) Sub-Type: 2 ( wlan. 11ac/n" and set "Channel width" to 40 MHz and enable "Short Guard Interval". When Shortslot override is enabled, the wireless device uses the short slot time only when. 2. Select the wireless protocol from the dropdown list. 11g network and the reported connection speed also fluctuates wildly, may go from 100+mbit to 2mbit and everything in. protected by a Guard Interval (short or long)* Note: The wider the channel, the more sub-channels available however, range is reduced because the same amount of poweris now spread across wider spectrum–so receiver has to work harder to hear the weaker signal. Otherwise said, you should set a relatively short amount of time between the transmission of. (long vs short guard interval). 4GHz spectrum. Setelah itu masukkan username dan password admin router modem. 11b wireless client stations may experience difficulty associating with the AP using short preamble. 3Por defecto el Guard Interval es de 800 nanosegundos (0,8 millonésimas de segundo), esto previene de reflexiones en puntos que estén hasta 120 metros del emisor (240 metros de recorrido). hroughput in 802. (Guard Interval) a «Corto» o «Short». So 15-20 feet max. An extended guard interval of 0. 1 . 11n/ac, where the value of the guard interval is set to 400ns instead of general 800ns. 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. In Release 16, 120kHz is the maximum SCS allowed for. . Wi-Fi 6 (also known as 802. 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):. Berikut ini, beberapa langkahnya. Figure 4. 2x2 and a short GI with a 20 MHz bandwidth channel will only net you ~144 Mbps or less. uploading content. PLCP preamble field, composed of 10 repetitions of a "short training sequence " and two repetitions of a "long training sequence" preceded by a guard interval (GI). When Short GI is enabled, the guard interval will be set as 400ns and this function will boost the performance about 11%. 11 release has increased the data rate, and 802. There are two modes defined, High Rate Pulse (HRP) and Low Rate Pulse (LRP) and now we are more focused on HRP, which is widely used in a variety of applications with low date rate wireless connectivity and precision ranging. The 802. 15. Note that option htmode should be set to either HT40+ (for channels 1-7) or HT40- (for channels 5-11) or simply HT40 . 4-GHz 802. The guard interval is there to eliminate inter-symbol interference, which is referred to as ISI. Figure 33: 800 nanosecond GI (long guard interval) Long Guard Interval – 802. The shorter guard interval results in a higher packet error rate when the delay spread of the channel exceed the guard interval and/or if timing synchronization between the transmitter and receiver is not precise. 802. Support of the 400ns GI is optional for transmitting and receive. 11ax has three types of GI – the normal GI (0. The duration of the CP is pre. Hence wifi signal becomes more robust for outdoor applications. A shorter DTIM interval could theoretically make your wireless devices use up their batteries faster, because they'd have to wake up more often for multicasts. 11 • Proliferation in the number of devices that use WiFi today: smartphones, tablets, digital cameras, video-game consoles, TVs, etc • Devices connect to the internet via wireless network access point (AP)In various embodiments, the disclosure describes the design of guard interval sequence for 3 types of guard intervals having lengths that can be classified as short, medium, and long. 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. 2. To use only long preamble, disable short. 11ah Wi-Fi module that operates in the Sub 1GHz license. Choose Wireless > Advanced Settings. 11n amendment added support for an optional 40MHz channel. 11 standard requires a guard interval (GI), a period of 800 nanoseconds, between each OFDM symbol that is transmitted to protect against ISI. 802. 11b/g devices use an 800 ns guard interval, while. In Wi-Fi 6 or 802. When the delays are small. 11n-2. Systems, methods, and other embodiments associated with a single stream wireless communication with a greenfield preamble that uses a short guard interval are described. 47 Gbpsのデータ. 11n bands. Guard Interval (GI) refers to the amount of time in between the transmission of frames. 11 Network | Purpose. #1. 间隔时间越小，传输效率越高，间隔时间越大，抗干扰能力越强。. 400 Mbps (two spatial streams at 40 MHz short guard interval) This is a full third faster than the comparable 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 settings such as "Frame aggregation", "Preamble Length", and "Short Guard Interval". 11n standard specifies two guard intervals: 400 ns (short) and 800 ns (long). 2 microseconds (μs) and only two Guard Intervals (GI) of 400 or 800 ns to a longer Ts (12. 2 Mbps A technically arcane but significant performance improvement is the introduction of a Short Guard Interval or SGI feature with 802. r/wifi. A long interval can save power on sleeping clients, a short interval can improve connectivity in poor reception situations. In order to dissect the Guard Interval it is important to think of the signal transmissions from the viewpoint of the Time domain rather than the frequency domain. Spesifikasi Guard Interval dengan Jarak Pemancar. The standard symbol guard interval used in IEEE 802. Using personal security mode for your. US10033563B2 US15/075,823 US201615075823A US10033563B2 US 10033563 B2 US10033563 B2 US 10033563B2 US 201615075823 A US201615075823 A US 201615075823A US 10033563 B2 US10033563 B2©2019 • Preamble: Consists of short training field (STF) and channel estimation (CE) field for packet detection, automatic gain control, and frequency and timing offsets • Header: Modulation and coding scheme for data, length of data field, checksum • Data: Variable length field (1 to 262,143 octets) containing the Layer 2 payload • TRN: Beamforming. 15. จะวิ่งที่ 150 Mbps ต้องใช้ MCS7+40 Mbps+Short Guard Interval ตัวรับทั่วไป เสาเดียว อาจ. ใน Wi-Fi ที่ใช้ OFDM จะใช้ GI อยู่สองตัวคือ GI มาตรฐาน 0. The ratified version includes support for features such as short guard interval and frame aggregation. Do not mess around with setting you do not full understand. Figure 33: 800 nanosecond GI (long guard interval) Long Guard Interval – 802. 11 OFDM is 0. The higher the MCS index is, the more throughput is supported by the corresponding modulation schema. 11ac, short guard interval (400 ns) is introduced, while the default value of GI. 11a/n /ac or 802. Shorter wait time (guard interval) between symbols increases throughput. Select to enable the short guard interval. Does anyone know where you can configure short/long Guard Interval (SGI / LGI) on SmartZone controlled APs? I have an outdoor deployment I think may be. g. Support of the 400ns GI is optional for transmitting and receive. As discussed earlier, OFDMA combines sub-carriers to form resource units (RUs), or sub-channels, of different widths. There are four options to append samples in the guard time. It can be cut down properly to shorten the interval between two frames when the delays are small. kau asu. even N when compared to AC). 11ax or Wi-Fi 6 will deliver considerable increases in network efficiency and capacity for dense population centers, with. The Other selection inputs a non-standard Guard Interval value between 0 and 1. 27,538. 64 QAM. The higher the MCS index is, the more throughput is supported by the corresponding modulation schema. At 240kHz SCS (for control only), 14 symbols are squeezed into a 62. The 802. 11 standards, it provides complete support for 802. 11n. 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. 4. 802. The purpose of a guard interval is to introduce immunity to propagation delays, echoes, and reflections to which digital data is normally very sensitive. Normalmente los routers están configurados de manera predeterminada con un «Short Guard», por tanto, tendremos la máxima velocidad posible. 0, making short guard interval mandatory is emphasized as this was a change from 11ac PHY, which caused the confusion. If you would use mixed mode, always make sure these are disabled, as these features were designed to be used with 802. Now, if you use short guard interval the max data rate will increase to 144. Wi-Fi beacons consume airtime and erode the capacity of your network. Click this checkbox to enable or disable a short preamble for 802. Short GI(Guard Interval) 是 802. Enclose each property name in quotation marks. 4 GHz or 5 GHz radio waves per IEEE 802. Only some vendors support SGI on 20MHz channels in the 2. Jika sudah, maka pilih menu network yang ada di bagian layar Anda. 11, which uses OFDM for its highest throughput profiles. 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. 11ax, focusing on WLAN indoor and outdoor operation with stationary and pedestrian speeds in the 2. Berikut ini, beberapa langkahnya. Guard Interval. Normally this is an 800ns timer that allows for time between bursts. Time of Day to Enable Radio: This field defines the time interval that wireless function is. 123,140. Ajuste o Beacon Interval: O Beacon Interval (Farol) é um quadro (frame) de sincronização enviado em períodos constantes pelo roteador wifi. 11 standard defines a few different interframe space periods that provide a safety. 11b) Activate the LLDP. A key characteristic of 802. 11n added optional support for a shorter 0. long and "any" is still "long" resulting to 130/270Mbps. Tx STBC (1 bit)since 802. I think the following command should force long/short guard intervals on the Device transmissions: iw [options] dev <devname> set bitrates [legacy-<2. 8 µs), double (1. Enabling a short guard interval can decrease network overhead by reducing unnecessary idle time on each AP. (with short/long guard interval (GI)), 1 MHz channel bandwidth. If the beacon interval is long, maximum capacity in the Access Point is achieved. with a short guard interval) will be able to achieve almost 3. normally you can configure that the access point will use. Table of Content. An AP identifies any signal content received inside this interval as unwanted inter-symbol interference, and rejects that data. Some outdoor deployments might, however, require a longer guard interval. ap dot11 {5ghz | 24ghz} dot11n rifs rx. Configuration. RxSOP determines the Wi-Fi signal level in dBm at which an access point's radio demodulates and decodes a packet. 15. Adjust the antenna. In the DTIM Interval field, enter the interval at which the delivery traffic indication message should be sent. 5µs slot. Guard Interval. 11b or 802. # wireless client association limit 50 interval 1000:. نقدم لكم في هذا الفيديو طريقة ضبط transmit power الراوتر we الجديد وهو المسئول عن قوة تغطية الشبكة الراوتر we الجديد. The 802. These data rates, which are calculated for a 20-MHz channel width using a short guard interval, are available: 0 (7 Mbps) 1 (14 Mbps) 2 (21 Mbps). 11n guard interval. Click to expand. These longer guard intervals help to prevent inter-symbol interference in outdoor environments and therefore improve coverage and performance. 29_XIIA_KD . 1 Insight managed wifi 6 ax1800 dual band access point 1 Models 1 User manual 3 Contents 8 1. Short guard interval (SGI) is a new feature of the physical (PHY) layer in High Throughput Wireless Local Area Networks (HT-WLANs), like IEEE 802. 1 summarizes the most recent records for high SE multicarrier transmission. 11n/ac, where the value of the guard interval is set to 400ns instead of general 800ns. Date to Enable Radio (week days): This field defines the dates the wireless network is enabled. (Cisco Controller) > config 802. Enable/disable WiFi multimedia (WMM) call admission control to optimize WiFi bandwidth use for VoIP calls. I picked up a WRT-160N wireless router hoping to use it relieve the stuttering when streaming HD content over my WRT54G network. It's a 5Ghz long range network. Wireless radio configuration. 4GHz band supported channel bandwidths: 20MHz Y N 5 GHz band supported channel bandwidths: 20 MHz Y Y 5 GHz band supported channel bandwidths: 40 MHz Y Y 5 GHz band supported channel bandwidths: 80MHz Y Y Short/Long Guard Interval (400ns/800ns) Y Y 11ac Data rates – Up to 433. 11ac). 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. -ให้ปรับ 11n guard interval เปลี่ยนจาก Long >>>short แล้วเซฟ เราก็จะได้สปีดการเชื่อมต่อ WiFi ที่ 150 mbps หรือ 300 mbps (MIMO) ขอให้โชคดีครับGuard Interval For outdoor devices, Max WiFi allows data to be sent using a longer guard interval with only minimal impact on efficiency, providing extra protection against inter-symbol interference caused by multipath delay spread as the data moves longer distances.