Wireless

• Infrastructure
  
• Configuration
  

Infrastructure

Table 2-1 Required Wi-Fi Versions

Wi-Fi Version	Description
Wi-Fi 3 IEEE 802.11g	Supports 2.4 GHz and 5 GHz frequency bands
Wi-Fi 4 IEEE 802.11n	Supports 2.4 GHz and 5 GHz frequency bands

Table 2-2 Recommended Wi-Fi Version

Wi-Fi Version	Description
Wi-Fi 5 IEEE 802.11ac	Supports higher bandwidths and Multiple Input, Multiple Output (MIMO)

The rogue detection feature is recommended for all wireless network infrastructures. Rogue or interfering access points (APs) and other devices can potentially disrupt network operations.

Configuration

Can I broadcast POS SSID in 2.4 and 5 GHz band?

Broadcasting the POS SSID on both bands may negatively affect performance due to band steering. Band steering enables dual-band devices to detect the higher-frequency 5 GHz band and automatically connect to it.

POS devices require a stable and constant connection to the wireless network; therefore, any network connection interruptions result in poor service.

The POS SSID should always be broadcast on a single band.

Will my POS devices work well in the 2.4 GHz band?

POS devices connected to the 2.4 GHz band may operate well under certain conditions, provided there is no external interference, access points are correctly positioned with a clear broadcast path, the Wi-Fi network does not experience bottlenecks, and each access point is hosting a low SSID-to-AP ratio.

A single property with three access points placed at appropriate intervals and having a low number of client connections may provide good wireless coverage and performance.

The 2.4 GHz band can experience interference from various devices, such as Bluetooth devices, mobile phones, and microwave ovens.

5 GHz band preference

The 5 GHz band is preferred by most vendors, as it experiences less interference from both internal and external sources.

Common non-Wi-Fi devices such as microwaves and CCTV RF sensors do not interfere with the network broadcast.

The 5 GHz band supports more than 20 non-overlapping channels, depending on the region. The availability of additional non-overlapping channels gives the 5 GHz band a distinct advantage in reducing interference from neighboring Wi-Fi networks.

Table 2-3 Connectivity in 2.4 GHz

Power Level	Description
-30 dBm	Reliable network coverage offering good connection and uninterrupted data flow.
-65 dBm	Good network coverage with reliable data flow.
-70 dBm	Minimal reliable distance and coverage. POS device may start experiencing latency.
-75 dBm	POS devices may experience data flow issues, network timeouts, and latency, which can prevent check functions from working properly.

Table 2-4 Connectivity in 5 GHz 802.11ac

Power Level	Description
-30 dBm	Reliable network coverage offering good connection and uninterrupted data flow.
-65 dBm	Reliable network coverage.
-70 dBm	Good network coverage with reliable data flow.
-75 dBm	At the minimum reliable distance for coverage, POS devices may experience latency.

SSIDs

SSIDs are configured in the wireless network infrastructure to separate internal and external client communications. Some organizations may create multiple SSIDs in the wireless environment to meet various business needs and requirements.

How do I determine the correct number of SSIDs serviced by each AP?

The number of SSIDs per access point depends on the hardware and its manufacturing limitations. Some vendors may support multiple SSIDs to reduce costs; however, this can lead to increased latency and service disruptions.

The allocation of SSIDs across access points should be carefully planned, taking into account network demand and the bandwidth requirements of each SSID. Determining the appropriate number of SSIDs and access points is a critical step in ensuring reliable client communication.

Who is responsible for determining the number of broadcasting SSIDs?

The vendor or internet provider should make an evaluation based on the following factors:

• Property size and coverage area

• Wireless network capacity and demand

• Bandwidth requirement for each SSID

• Hardware manufacturer recommendations and limitations

• Approximate number of concurrent connections per access point

• Maximum connections allowed per radio

Will my wireless network operate efficiently if I have a high number of broadcasting SSIDs?

The wireless network will not operate efficiently if:

• The number of configured and broadcasting SSIDs exceeds the manufacturer’s recommended level

• The number of connected clients in each SSID exceeds the client number threshold

• The number of connected clients to each access point exceeds the recommended threshold

Examples of ratios that may have a detrimental impact on client communication

• Low number of access points with a high number of broadcasted SSIDs

  Depending on the number of connected clients, such an environment may experience a high number of client connections per access point, leading to network failures. Network latency is the most common issue in saturated wireless networks.

• Incorrect bandwidth sizing

  An incorrect bandwidth sizing per SSID may lead to poor client performance and network latency.

• A high number of clients per SSID

  POS devices connected to a congested Wi-Fi network may experience poor performance and connection failures. Such environments can cause data flow disruption and unreliable communication.

• The following SSIDs may have a negative impact on the POS network:

  Voice over IP (VoIP) solutions provide real-time audio and video services to devices within the organization; however, they can be resource intensive.

  Guests can benefit from free internal guest Wi-Fi when using designated apps; however, a large number of connected clients may cause network latency.

Note:

In some environments, it may be necessary to create a dedicated POS Wi-Fi network within the existing infrastructure by disabling the broadcast of high-demand SSIDs to reduce the number of client connections.

Channels

What is channel overlapping?

Channel overlapping occurs when two or more access points are positioned too close to each other. The degree of overlap is influenced by the access point’s proximity, broadcast channel, and power output. When two wireless devices transmit simultaneously, their radio signals collide and become distorted.

Channel management may not function properly when the number of access points exceeds the recommended number of radios in an area, as the 2.4 GHz frequency band offers only three non-overlapping channels.

How do I prevent channel overlapping?

The 5 GHz band offers more non-overlapping channels and should generally be the preferred choice.

When the 2.4 GHz band is required, access points should be configured to channels 1, 6, and 11, as these are the non-overlapping channels.

A stable network is essential for POS devices to operate properly, and to use Simphony functions, such as:

• Check Creation

• Check Access

• Check Sharing

• Tender Media

• Service Total

• Remote Printing

• Fiscal Operations

• Credit Card Payments

• POS API functions

Roaming

Roaming occurs when a POS device moves between access points, typically triggered by reaching a specific signal strength threshold. When the signal from the current access point drops below a certain threshold, the POS device connects to a stronger access point in the area that broadcasts the designated POS SSID. During access point roaming, POS devices may experience brief network connection disruptions, which can negatively impact performance. In some cases, this disruption can render POS devices unusable, resulting in complete network connection failure.

Seamless roaming among dedicated POS access points and coverage areas is essential to maintain reliable communication within the system.

Roaming should be tested in all areas where POS devices operate and across all access points to which they connect.

Important:

Perform roaming tests using a POS device, not a third-party device, because wireless hardware components can respond differently. Testing with other Wi-Fi devices may yield different results, as wireless devices can behave uniquely under specific circumstances and conditions.

Communication disruption during roaming

A common symptom of poor roaming is prolonged loss of communication with POS devices. During connection blackouts, POS devices cannot support online Simphony functions and may be considered offline. The time required for POS devices to reconnect between access points should be minimized.

A higher number of lost pings increases the likelihood of operational disruptions, which can cause problems with data sharing between POS devices and the system. Ping data loss should be minimal, with no more than three lost pings while roaming between access points. Excessive ping loss may result in service interruptions.

Note:

The ping command can be used to verify the number of lost pings.

Design factors that may impede seamless roaming

• High number of access points installed in the area

  Too many access points can hinder POS device roaming if the minimum RSSI advertised by each access point exceeds the required signal strength.

  POS devices will not roam between access points unless the signal strength drops below a certain threshold, regardless of other available access points in the area. POS devices may roam excessively if the roaming threshold is frequently reached.

  The power output of each access point should be limited to the required coverage area to prevent signal overlap.

• Authentication issues

  Network authentication issues can prevent POS devices from authenticating seamlessly when roaming between access points.

  Authentication issues can lead to network communication failures and prolonged connection times to access points.

Roaming Aggressiveness POS Configuration

This setting alters the signal strength threshold at which the Wi-Fi adapter starts scanning for another candidate access point. The default value is Medium. Depending on the environment, one option may work better than another.

• Lowest: The Wi-Fi adapter will trigger a scan for another candidate access point when the signal strength with the current access point is very low.

• Medium-Low

• Medium (default): Recommended value.

• Medium-High

• Highest: The Wi-Fi adapter triggers a scan for another candidate access point when the signal strength with the current access point remains good.

Encryption

Wired Equivalent Privacy (WEP)

WEP is highly vulnerable and should not be used. The Wi-Fi Alliance officially abandoned WEP in 2004.

Wi-Fi Protected Access (WPA)

WPA applications use a Pre-Shared Key PSK, known as WPA Personal, and the Temporal Key Integrity Protocol (TKIP).

WPA Enterprise uses an authentication server to manage keys and certificates.

WPA, like WEP, is vulnerable to intrusion and is not recommended.

Expected Encryption

Wi-Fi Protected Access (WPA2)

WPA2 uses Advanced Encryption Standard AES.

WPA2-Enterprise requires a RADIUS server for authentication. A RADIUS server handles authentication tasks for all network users. The authentication process is based on the 802.1X standard.