Wireless AP Capacity and Network Bandwidth Calculation Method

Wireless AP is the access point for users to enter the wired network using wireless devices (mobile devices such as mobile phones and wireless devices such as laptops). It is mainly used in broadband homes, inside buildings, campuses, parks, warehouses, factories and other places that require wireless monitoring. The typical coverage distance is tens of meters to hundreds of meters. It can also be used for long-distance transmission. The farthest can reach about 30KM. The main technology is IEEE802.11 series. Most wireless APs also have access point client mode (AP client), which can connect to other APs wirelessly to extend the coverage of the network.

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When building a wireless network, you will definitely encounter this problem: After investigating the environment, how can you accurately, scientifically, and quickly predict the approximate demand for wireless APs? With this question in mind, let's discuss how to use bandwidth to estimate the deployment volume of wireless APs.

1. Factors Affecting the Number of Wireless APs

When estimating the number of wireless APs, four key points need to be clarified, namely network bandwidth, throughput, AP coverage distance, and number of access users. The following describes how these key points affect the number of wireless APs.

1. Network bandwidth

When discussing link bandwidth, we usually refer to the number of bits that can be transmitted per second on the link, emphasizing the maximum rate that can be achieved. For example, the bandwidth of 100M Ethernet is 100Mbps, and the bandwidth of Gigabit Ethernet is 1000Mbps.

2. Throughput

Throughput and bandwidth are words that are easily confused. When discussing the bandwidth of a communication link, it generally refers to the number of bits that can be transmitted per second on the link. It depends on the link clock rate and channel coding, which is also called line speed in computer networks. In other words, the bandwidth of 100M Ethernet is 100Mbps.

The difference between bandwidth and throughput: bandwidth emphasizes the maximum speed that can be achieved, while throughput emphasizes the speed under actual circumstances. Due to the influence of various inefficiencies in reality, it is usually preferred to use "throughput" to express the performance of the network.

3. Coverage

In non-high-density areas, the number of wireless APs can be roughly determined based on the actual area of ​​the scene and the recommended coverage range. In some cases, the maximum coverage distance can also be calculated, and the coverage range can be appropriately adjusted based on the power.

4. Number of users

In high-density areas, the number of access users also needs to be considered. Different models of wireless APs have different recommended access users in different scenarios. The number of wireless APs can be determined by the number of concurrent access users (there are slight differences between laptops and mobile phones).

2. Bandwidth calculation of wireless AP quantity

Many friends are often asked by customers such questions: In this scenario and this solution, so many APs are deployed. Does the bandwidth support it? If not, will the user's Internet speed become slow? Or how much export bandwidth is needed for the deployed APs?

• The egress bandwidth can be calculated based on the number of APs, the maximum number of concurrent users, and the bandwidth allocated to each user. WLAN capacity bandwidth = maximum number of concurrent users × bandwidth per user.
• ***The number of concurrent users can be estimated at 50%~70% based on the number of people in the coverage scenario.
• In order to allow each wireless terminal to have enough bandwidth available, it is generally recommended that one wireless AP access 10 to 15 wireless devices (taking RD-W2***P as an example, based on the recommended access quantity in the table above).
• Number of APs = ***number of concurrent users ÷ 15 (number of users accommodated by a single AP).
• The bandwidth allocated to each user can generally be set to an intermediate value for calculation and estimation, such as 100kbps. (Common unit conversion: 1TB=1024GB, 1G=1024MB, 1MB=1024KB, 1KB=1024B, 1 byte=8 bits.)

For example: A university has 30,000 on-campus users and 15,000 mobile terminal users. The concurrency ratio is calculated as 50% to 70%, and the bandwidth per user is 512 Kbps. Find the approximate WLAN capacity and number of APs.

answer:

• Number of concurrent users = 15000 x (50%~70%) = 7500~10500;
• Number of APs = *** number of concurrent users ÷ 15 = (7500~10500) ÷ 15 = 500~700;
• WLAN capacity requirement = (7500~10500)×0.512= (3840~5376)M.

3. Calculation of actual Internet application bandwidth

When many people do project demonstrations, they will intuitively test the speed by connecting the device to WiFi. However, the download speed can also be used to simply estimate the theoretical broadband rate of the corresponding application.

Network speed unit:

• bps: bits per second, usually used as the unit for serial bus devices, such as serial ports, USB ports, Ethernet buses, etc.
• Bps: Bytes per second. Usually Bps is used as the unit for parallel bus devices, such as parallel ports, IDE hard drives, etc.
• Conversion relationship: 100M bps ≈ 10M Bps

Generally speaking, if we say that the Internet speed is 100 Mbps, it means 100 Mbps. If you download software from the Internet, the speed unit displayed is Bps, which is the number of bytes downloaded per second. Therefore, it is important to distinguish that the units of Internet speed are different in different situations and cannot be mistaken, because the speed of these two expressions differs by more than 10 times.

In computer networks and IDC rooms, the unit of broadband speed is bps (or b/s); the conversion relationship is: 1 Byte = 8 bits

• 1B=8b ---------- 1B/s=8b/s (or 1Bps=8bps)
• 1KB=1024B ---------- 1KB/s=1024B/s
• 1MB=1024KB ---------- 1MB/s=1024KB/s

Broadband *** download theoretical value:

• 1.5M =169KB/s
• 3M =338KB/s
• 6M =676KB/s
• 10M =1126KB/s

In actual Internet applications, when downloading software, you often see broadband speeds such as 128KB (KB/s), 103KB/s, etc. This is because the line bandwidth provided by the ISP uses bits, while general download software displays bytes (1 byte = 8 bits), so you have to convert to get the actual value. However, we can convert it according to the conversion formula:

128KB/s=128×8(Kb/s)=1024Kb/s=1Mb/s: 128KB/s=1Mb/s

In theory:

• The theoretical rate of 2M (i.e. 2Mb/s) broadband is: 256KB/s (i.e. 2048Kb/s), and the actual rate is about 80--200kB/s; (the reason is that it is affected by many factors such as user computer performance, network equipment quality, resource usage, network peak period, website service capacity, line loss, signal attenuation, etc.).
• The theoretical rate of 4M (i.e. 4Mb/s) broadband is: 512KB/s, and the actual rate is about 200---440kB/s

The uplink rate refers to the data transmission rate when the user's computer sends information to the network, and the downlink rate refers to the data transmission rate when the network sends information to the user's computer. For example, when uploading files to the Internet using FTP, the uplink rate affects the upload speed; and when downloading files from the Internet, the downlink rate affects the download speed. Of course, in the actual uploading and downloading process, the quality of the line, equipment (including computers and other equipment), etc. will also have more or less impact on the speed.

The above data is mainly caused by multiple factors such as user computer performance, network equipment quality, resource usage, network peak period, website service capacity, line loss, signal attenuation, etc.