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This document describes the ability of the InfiNet devices to provide sustainable wireless connectivity with mobile objects in various scenarios. A basic deployment is generally presented along with the features related to its implementation for the mining industry, railway and water transport.
Let's look at the scenario below (Figure 1), which involves the movement of one or more objects throughout the enterprise area along a given path between points A and B. The network control center is located at a certain distance from the area where the moving object can be located.
The project goal is to organize a reliable wireless connectivity between the control center and the mobile objects in order to provide various information services, such as telemetry data gathering, video surveillance, telephony etc.
Figure 1 - Basic scenario for connectivity with mobile objects |
Two categories of tasks must be solved to achieve this goal:
The solution to the tasks described above is shown in Figure 2 and it can be divided into four components:
The backhaul radio network consists of several base stations (BS), joined by a wired infrastructure. Each BS can consist of one or several sectors and the combination of their antenna patterns forms the radio network coverage area. The InfiMAN 2x2 family devices can be used as CPEs and BS sectors. Keep in mind that wireless links as well as combined infrastructure can be used to join several BSs.
The base stations are joined at the aggregation node where the InfiMUX device is installed. As shown below, the InfiMUX simplifies the configuration for the InfiNet devices by joining all the BSs into a single MINT area.
A backbone link is established between the aggregation node and the network control center. The choice of specific devices for the radio link is determined by the transmitted traffic capacity (see Performance of the InfiNet Wireless devices). The following throughput values can be achieved:
A subscriber station (CPE) is installed on each mobile object and its configuration contains radio profiles for each BS sector in its area of motion. The operational principle is that the CPE can switch the connections while moving between the base stations. Since the BS sectors provide coverage for the entire area in which the CPE can be located, the CPE is always in the coverage area of at least one BS. As soon as the radio parameters of the current connection deteriorate, the CPE interrupts the radio link and connects to another sector. So, while the object moves from point A to point B (Figure 2) the CPE is connecting one by one to the sectors of BS1, BS2, BS3 and BS4.
Keep in mind that the CPE cannot be simultaneously connected to two base stations, because the device has one radio module, so the roaming between the base station sectors is accompanied by a short-term connectivity break. Several CPEs can be simultaneously connected to one BS sector.
Figure 2 - Distribution of areas |
In addition to the infrastructure described earlier there is an extended list of requirements, which make the solution fault-tolerant and more efficient:
The implementation of a QoS policy does not require the installation of additional devices and it is solved by configuring the wireless units and the InfiMUX device:
Each implemented solution is unique and requires careful preliminary planning. It is a very important stage, saving resources at the design stage can greatly increase the operational costs. Within this document, the radio frequency planning and placement of the devices will be reviewed.
Frequency planning is a complex, creative process that defines:
The result of the frequency planning is a device allocation map with basic radio settings. A convenient tool for radio planning and potential performance assessment depending on the radio parameters is InfiPLANNER.
The frequency channel selection is determined by the following factors:
Some frequency allocation examples are presented below. Figure 3a illustrates a scheme where each BS sector has it's own frequency channel. This approach requires the allocation of 4 frequency channels.
Let's look at the optimized scheme (Figure 3b). Since the sectors' position is chosen in such a way that the radiation patterns of BS1 and BS3, BS2 and BS4 do not intersect in pairs, they will not interfere with each other. This will optimize the frequency resource utilization, reducing the number of frequency channels from 4 to 2.
a) |
b) Figure 3 - The allocation of frequency channels between BS: a - using four channels, b - using two channels |
The position of the devices in space determines the actual quality indicators of the wireless link. The position of the devices is determined by the:
In projects with mobile objects, the antenna's directional properties should be taken into account. If the BSs are static and the radio coverage area is constant, then the CPE's antenna radiation pattern can greatly affect the link quality. InfiNet's product portfolio includes devices with integrated antennas and the ability to connect external antennas as well. The selection of a specific device is determined by the specific requirements of the project.
The route profile must be evaluated along the entire trajectory of the object. This will allow to find potential "dead zones", with no connectivity with the mobile object. A decision to change the location of several base stations might be necessary in this case. In addition, perform a survey along the enterprise's territory, because the InfiPLANNER link planning tool does not take into account the effects of obstacles such as trees, buildings etc.
The InfiNet product portfolio includes a wide range of accessories, including mounting kits that allow to install devices in various conditions with the possibility of flexible alignment and the CAB-RV1 alignment tool which allows to perform preliminary device diagnostics.
The Ethernet link layer protocol was developed for the wired networks and does not take into account the specifics of the wireless environment. Wireless device manufacturers can use standard wireless protocols, such as Wi-Fi, or use their self-developed protocols. InfiNet Wireless has developed a proprietary data transfer protocol called MINT, especially designed for data exchange in a wireless environment.
MINT (Mesh Interconnection Network Technolohy) - InfiNet's proprietary technology used by the InfiLINK 2x2 and InfiMAN 2x2 family devices, provides data transfer between devices via wireless and wired links.
One of the MINT protocol's main concepts is the MINT area. A MINT area consist of many neighboring devices and data exchange between them is carried out using MINT frames (check the "MINT protocol" lesson of the InfiLINK 2x2 and InfiMAN 2x2: Switching online course).
Let's look at the solution described below, that implements the MINT areas concept (see Figure 4). A radio link is installed between the Master and Slave devices, they form MINT 5 area. Each of the BS1, BS2, BS3, and BS4 sectors is potentially ready to establish a radio link with the CPE installed on the mobile object and form a separate MINT area with the corresponding identifier.
Figure 4 - Multiple MINT areas in the mobility scenario |
Note that the MINT protocol is intended for data exchange within the MINT area. Data outside the MINT area can be transmitted using other protocols, such as Ethernet, i.e. the CPEs and each of the base stations are the gateway between the MINT and Ethernet networks. In our scheme, data is exchanged between a mobile object and a control center, i.e. the frame will go through several Ethernet segments and MINT areas in the forward and backward directions. Thus, switch group configuration on each device is a prerequisite for data transfer:
switch group 1 add eth0 rf5.0 switch group 1 start switch start |
In addition to encapsulating the Ethernet frames during the transmission through the MINT area, the MINT protocol performs an exchange of service messages to fill in the frame redirection table. The frame redirection table allows to select the frame transmission route (see video 5) through the MINT area in accordance with the radio parameters and the link load. This mechanism guarantees the selection of the route with the optimal radio parameters and prevents loops.
Video 1 - An example of route selection between nodes J and F in MINT |
If necessary, you can influence the path selection algorithm by setting the link metric value manually. This can be done by summing the calculated and additional costs or by fixing a certain value (switching in InfiNet devices is described in the online course InfiLINK 2x2 and InfiMAN 2x2: Switching)
mint rf5.0 -extracost 1000 |
mint rf5.0 -fixedcost 1000 |
Data transfer and QoS configuration on each wireless device is a time-consuming task that can be simplified by extending the MINT area. The schemes intended to simplify the configuration of the wireless devices by joining them into a single MINT area, are shown below.
The main disadvantage of the solution above is the necessity to configure switch groups on all wireless devices. Since the switch group is a gateway between MINT and Ethernet, it is possible to combine all the BSs of the radio network into a single MINT area, transferring the gateway role to the InfiMUX switch (see Figure 5). In this case, a switch group has to be configured only on the InfiMUX. Joining devices into a single MINT area and the advantages of such a scheme are described in the InfiLINK 2x2 and InfiMAN 2x2: Switching online course.
Figure 5 - Joining the backhaul radio network into a single MINT area |
Using the MINT protocol in a wired infrastructure is possible with the help of the PRF (pseudo radio) interface. It is a virtual interface that has a wired interface as parent and it encapsulates Ethernet frames into MINT frames. Configuration via CLI:
Create a PRF interface on a wireless device or on the InfiMUX:
ifc prf0 mtu 1500 up prf 0 parent eth0 hwmtu 1514 mint prf0 start |
Join RF and PRF interfaces on the wireless device:
mint join rf5.0 prf0 |
Join two PRF interfaces on the InfiMUX:
mint join prf0 prf1 |
The advantages of such a solution is the simplification of the QoS configuration, as traffic processing rules for different service classes are configured only on the InfiMUX.
The disadvantage of the scheme having the backhaul radio network devices joined into a single MINT area is the quality of service policy that needs to be implemented at the backbone devices as well: the traffic classification rules must be duplicated on the InfiMUX and on the Master and Slave devices. If these rules are not duplicated, the effect of the QoS policy implementation can be significantly reduced.
One of the solutions is to combine the devices of the backbone link into a single area with all the other devices (see Figure 6). This solution is possible only when using InfiLINK 2x2 family devices for the backbone link. In this case, the unified traffic classification rules configured on the Master device will be valid in the entire MINT area. In addition, the gateway functions between MINT and Ethernet can be transferred to the Master device, while any switch can be used instead of InfiMUX.
Figure 6 - Joining all wireless devices into a single MINT area |
The movement of the mobile object, with the CPE installed on top, within the access radio network is accompanied by a transition from the coverage area of one BS sector to another sector's coverage area of the same or of another BS. The transition process of the CPE between the BS sectors is called roaming. Roaming implies the disconnection of the radio link with the first sector and the connection establishment with the second sector.
Let's look at the roaming mechanism (see video 2):#min_max
Video 2 - Roaming mechanism |
A radio link can be established between two devices if the following requirements are met:
On Master devices, only one set of radio parameters can be configured, which will be used to establish the links. On Slave devices, several radio profiles can be created, or only one, but with the ability to automatically select a frequency. Configuration via CLI:
Configure the radio parameters on the Master device:
rf rf5.0 band 20 rf rf5.0 mimo greenfield rf rf5.0 freq 5510 bitr 130000 sid 10101010 burst rf rf5.0 txpwr auto pwrctl distance auto |
Create a radio profile on the Slave device with a fixed frequency value:
mint rf5.0 prof 1 -band 20 -freq 5510 -sid 10101010 \ -nodeid 60755 -type slave \ -autobitr -mimo greenfield |
Create a radio profile on the Slave device with automatic frequency selection (if a profile with a fixed frequency value is used, the command below will not be executed):
mint rf5.0 prof 1 -band 20 -freq auto -sid 10101010 \ -nodeid 60755 -type slave \ -autobitr -mimo greenfield |
When the Slave device tries to establish a connection, it cyclicaly looks over the radio profiles added to its configuration. As soon as one of the profiles becomes suitable for link establishment with the Master device, it initiates the connection and the profile search is stopped. In case that a profile with automatic frequency selection is used, the Slave device tries to establish a connection with the Master by searching through the frequencies supported by the radio module. The list of frequencies to search through may be limited by the configuration of the user frequency grid.
Example of a custom frequency grid configuration via CLI (for the rf5.0 interface, the frequency range from 5000 MHz to 5100 MHz with a step of 10 MHz is set, when using a channel width of 20 MHz):
rf rf5.0 grid 20 5000-5100/10 |
Obviously, link establishing can be a longtime operation when the automatic frequency selection mode is used due to the wide range of frequencies supported by the radio module. It is unacceptable in scenarios with roaming, therefore, we recommend to create on the CPE separate radio profiles for each BS sector of the backhauling radio network.
Master devices as well as Slave devices, support the dynamic frequency selection (DFS) mode. Before selecting a frequency, the devices with DFS support scan the available frequency range, evaluate the interference level and the presence of radar. The operational channel is selected among the channels free of radar, having a minimum interference level.
DFS is a standard technology for wireless devices, but the disadvantage is that the assessment of the radio environment is performed only in the beginning and no updates are performed during operation. Using an additional radio module, on some models of InfiNet devices, allows to implement the proprietary Instant DFS technology. An additional radio module constantly scans the air, performing a swap between frequency channels in accordance with the interference levels in real time. The DFS, Radar detection and Instant DFS technologies are described in the Dynamic Frequency Selection document.
DFS configuration via CLI:
Enable DFS on the Master device:
dfs rf5.0 dfsonly dfs rf5.0 freq auto |
Enable DFS and Radar detection on the Master device:
dfs rf5.0 dfsradar dfs rf5.0 freq auto |
Enable the iDFS support on the Master and Slave devices:
mint rf5.0 -idfs |
In this document frequency roaming represents a change in the operating frequency of the link, i.e. the frequency change is performed on both devices.
The frequency roaming mechanism operation is closely related to the Instant DFS function. When a frequency channel with a lower interference level is detected, the BS sector in PtMP mode or the Master in PtP mode must change the operating frequency. At the same time, the devices connected to them must also change the frequency channel. The behavior during frequency roaming is determined by the "roaming" parameter value:
This solution does not use the DFS technology, however, in projects where the use of DFS / iDFS is necessary, it is advisable to configure the BS sectors as "roaming leader" and the CPEs as "roaming enable".
Configuration via CLI:
Enable roaming on the Master device:
mint rf5.0 roaming leader |
Enable roaming on the Slave device:
mint rf5.0 roaming enable |
Restart the rf5.0 interface on both devices
mint rf5.0 restart |
Note that a Slave device with "roaming enable", having received a command to change the operating frequency from the "roaming leader", will switch to another frequency channel even if there is no corresponding radio profile in the Slave device configuration. In this case, after a reboot, the slave will not be able to establish a link, because it will still be guided by the set of radio profiles added to the configuration.
The main disadvantage of the roaming mechanism is that the CPE, after breaking the link with BS1, tries to restore this connection and only after several unsuccessful attempts, searches for other BSs to establish a new connection. InfiNet devices support the proprietary MultiBS function, which speeds up this process.
The roaming mechanism with the MultiBS function is presented below (see video 3):
Video 3 - Roaming mechanism with MultiBS function |
Run the following command to enable the MultiBS function:
mint rf5.0 roaming enable multiBS |
Let's look at a scenario in which the wired connection between the InfiMUX and the power injector of BS1 is damaged (see Figure 7), i.e. power is supplied to BS1 and the device is ready to establish radio connections, but data can not be transmitted to the control center.
The vehicle with the CPE installed starts moving along the trajectory, from point A to point B. Being in the BS1 coverage area, the CPE establishes a radio link with it. Since the wired connection is damaged, no data is transmitted between the moving object and the control center. Moving along the trajectory, the mobile object gets in the area where it is possible to connect to BS2, but the connection parameters with BS1 are satisfactory and the CPE does not perform roaming between the BSs. Without the MultiBS function, the CPE will keep the connection with BS1 until it leaves its radio coverage area.
The "Global" proprietary feature avoids this situation. If the Global function is activated on the CPE, it will only establish a radio link with the devices on which the Global function is also enabled. In addition, devices in the same MINT area can perform a proxy function for devices with the Global function enabled. Thus, if the Global function is enabled on the InfiMUX and on the CPE, then all the BSs will inform the CPE that they have a connection with the InfiMUX with the Global function activated at the time the radio connection is established. If a wired connection is damaged between BS1 and the InfiMUX, BS1 will not inform the CPE about the availability of the InfiMUX, i.e. the CPE will not establish a radio link with BS1.
Using the Global function allows to increase the fault tolerance of the backhaul radio network, however, it will have a positive effect only with an appropriate radio frequency planning since the coverage areas of the sectors must overlap.
Figure 7 - Global function usage |
Device configuration via CLI:
Enable the Global function on the CPE:
mint rf5.0 roaming enable global |
Enable the Global function on the InfiMUX:
mint prf0 roaming enable global |
One of the mechanisms to determine the moment of disconnection from one sector and the establishment of a connection with another, is the assessment of the SNR threshold values. Two thresholds are used in a wireless device configuration:
Thus, the thresholds values' configuration on the BS or on the CPE is the mechanism for controlling the roaming process.
The SNR level configuration for establishing a radio link on wireless devices is performed using the following commands:
mint rf5.0 -hiamp 2 |
mint rf5.0 -loamp 0 |
One of the factors affecting the link parameters for a moving object is the relevance of the MINT frame redirection table. The below configuration can only be applied on the InfiLINK 2x2 and InfiMAN 2x2 families devices. The device configuration allows to set the update interval for the MINT redirection table entries by choosing one of the three "mode" parameter values:
As shown above, a CPE with the MultiBS function activated, compares the current radio link performance with the maximum achieved. There is a possible scenario in which the radio link parameters deteriorate sharply due to the short-term influence of the interference and also recovers sharply afterwards. The CPE will break the connection with the BS in accordance with the MultiBS algorithm, despite the fact that the radio link deterioration had a short-term occurrence. The “mode” parameter selection affects the radio parameters' analysis when the MultiBS function is enabled, by setting the evaluation time interval. Thus, a device in a fixed mode evaluates the radio parameters over a three seconds interval and it is more resistant to link disconnection under short-term interference, than a device in a mobile mode, that evaluates the parameters more often.
The "mode" parameter can be configured by using the following commands:
Set the fixed mode on the Master and Slave devices:
mint rf5.0 -mode fixed |
Set the nomadic mode on the Master and Slave devices:
mint rf5.0 -mode nomadic |
Set the mobile mode on the Master and Slave devices:
mint rf5.0 -mode mobile |
As shown above, the MultiBS function speeds up the CPE roaming between the BSs, however, roaming is still accompanied by a short break in the connection. Link interruption avoidance can be achieved by using two CPEs on the moving object, combined with the functionalities of the InfiMUX. In this case, each CPE will independently establish a radio link with the BS and the InfiMUX will route the data traffic by choosing one of those links.
Let's look at the roaming algorithm with two CPEs (see Figure 8):
FIgure 8 - Roaming with two CPEs on a mobile object |
To perform the configuration, PRF interfaces should be created on the CPE1 and CPE2 devices towards the InfiMUX. PRF interfaces should also be created on the InfiMUX towards the wireless devices. In addition, the switch groups configuration must be performed on the InfiMUX, not on the CPEs.
Keep in mind that any changes in the configuration from the command line, should be saved. The command to save configuration:
config save |