Units RAy3-17 and RAy3-24 must be mounted with opposite polarization; one with TX horizontal polarization (horizontal arrow) and the second with TX vertical polarization (vertical arrow). See Cross polarization for more info.
Install the unit with the correct horizontal or vertical polarization: The arrow mark indicates the unit TX polarization. When the arrows heading perpendicular to the earth, the unit transmits a signal in vertical polarization. When the arrow is heading parallel to the earth, the unit transmits a signal in horizontal polarization. The connectors must point downward at an angle.
The link cannot be established
Double check the correct polarization (see above) of both units on the link.
Double check the correct compatibility settings for both units on the link. For more info see the section called “Radio adaptation” and Troubleshooting topic Setting up a link between RAy3-24S and other hardware variant of RAy3-24 (see below in this chapter).
Start with the most “resilient” configuration. This configuration depends on the variant of unit. We recommend using the narrowest available bandwidth (e.g. 3.5 MHz), the lowest modulation level (QPSK_S) and maximum available output power. TX and RX channels must be the same as the RX and TX channels in the remote unit. When the connection has been established and the antennas have been directed, proceed with operation parameters.
RSS and Antenna alignment
To configure the link and monitor its state, several menus display the RSS signal strength (most interactive are pages Live Data / Bar indicators or Antenna Alignment Tool). Additionally RSS can be monitored by a voltmeter connected to RSS voltage contacts or by RAy Tools on a mobile phone connected to RAy WiFi. smartphone application
Please keep in mind, that RAy is not a measuring instrument, hence the precision of the RSS reading is limited. Though, in most situations the RSS reading accuracy is better than ± 2dB, the absolute RSS value should not be used for accurate comparisons e.g. between two links.
Ethernet Buffers are small
To optimize the total buffer size of RAy radio (by optimizing a cooperation between Ethernet switch buffer and a buffer inside modem chip) it is required to set ‘Flow Control receive’ for port ‘Air (p9)’ (in menu Switch settings / Interface / Port) on both units to be ‘on’. With latest FW versions this parameter cannot be edited in web interface (CLI still allows that), so the change to the proper state can be achieved in web interface only by applying unit defaults (followed by manual settings of other parameters in this page, if needed). See Chapter 6, Command Line Interface.
Correct Flow Control setting typically increases operational speed of the link for mixed traffic, where bigger capacity of buffers helps to optimize the link performance.
Additional link performance and better utilization of all available buffers in transmitting network could be typically achieved by configuring Flow Control also between each MW unit and the nearest switch feeding the link by data. For more info see Port setup in Section 5.5.2, “Interface”.
Ethernet throughput far below published RFC2544 numbers
In the case when Ethernet throughput of the link is far below expectations based on published Ethernet speeds measured according RFC2544, one of the reasons may be wrong settings for a cooperation between Ethernet buffers inside RAy unit and between RAy unit (Ethernet switch inside the unit) and outside network (Ethernet switches and routers RAy is connected to).
To ensure buffers inside RAy unit are cooperating optimally please double-check ‘Flow Control Receive’ parameter for port ‘Air (p9)’ (in menu Switch settings / Interface / Port) – it should be ‘on’ for both units. (Units produced with initial FW 188.8.131.52 and later solve that automatically, so there is no need to manually set the parameter).
Access to the Local unit is blocked
Access to the Local unit may be accidentally blocked, for instance by disabling HTTPS access. If you can access the Remote unit over HTTPS, type its address in your web browser’s address field. The link will transfer the packet over the Local unit with blocked service access all the way to the Remote unit, which will give you access to the control menus of both units. Warning, the Remote unit will report as Local.
A unit accessed via service access always reports as Local. If you connect through another (peer) unit and radio channel, a certain amount of caution is necessary. For example, do not reduce the transmission power so that the link interrupts accidentally. Errors of this type should be fixed by the rollback function within approx. 1 minute.
Resolution can be done by comparing the length of ping on Local and Remote. Pinging the unit behind the radio channel is slower. The difference is more pronounced in the case of a long packet and the low speed of the radio channel.
For better protection against unauthorised access to configuration you should only allow as few kinds of access as possible. The most secure type is SSH with key – leave only SSH active with “only key” choice.
Problem with HTTPS certificate
First login into the unit management typically requires to accept web browser warning about self-signed HTTPS certificate. The issue may occur if a list of trusted HTTPS certificates stored by your web browser already contains a record for a network element with identical IP address or network name as the current unit management interface. In this case, the trusted HTTPS certificates for the particular network element in your web browser needs to be manually erased. After that self-signed certificate of the unit can be accepted.
Fast workaround: Try to use a different web browser or use HTTP connection instead (should be no issue in private network).
A natural property of each radio receiver is to compress the signal in one of the functional blocks, when the signal level gets out of the AGC (automatic gain control) dynamic range. The result of this effect is non-linear distortion of the received signal which is observed as decrease in the signal to noise ratio, i.e. in case of digital modulations increase of the Mean Square Error (MSE).
Limit for guaranteed functionality of RAy3 radio receiver is -15 dBm (measured on the waveguide input). This limit applies for all channel bandwidths and all modulations.
Beyond this limit the distortion of linearity appears and signal quality is depreciated. In extreme cases, this can lead to the disintegration of the radio link due to reduced signal to noise ratio (as a result of signal distortion).
Sometime it is necessary to set up a link from a legacy unit RAy3-24S and some newly deployed hardware variant of RAy3-24 unit (like RAy3-24X) – for example after exchange of failed unit on one end of the link (for an explanation of hardware variants ’24S’, ’24X’, ’24E’ and other see Section 1.7, “Ordering codes”).
Then it is necessary to configure newly deployed unit to behave like unit variant ‘S’ (legacy model). To achieve that the parameter ‘Unit 24S compatibility’ (in menu Tools / Maintenance / Radio adaptation) has to be set to ‘active’.
Wrong setting of compatibility causes the link is not established (both units remain in status ‘Connecting’).
Unit with FW version 184.108.40.206 with activated ‘Unit S mode’ (identical with ‘Unit 24S compatibility’ in later FW versions) requires to manually set RX FlowControl for port ‘Air (p9)’ (in menu Switch settings / Interface / Port) to the value ‘auto’. On FW version 220.127.116.11 it is recommended to set this parameter to ‘on’. In later FW versions it is enough to manually apply default values of FlowControl parameters.