Cobham Wireless’ RF automated test equipment (ATE) system now supports the testing of small cells. The ATE is based on its PXI modular instruments and PXI Maestro test sequencing software and can be used to verify RF alignment and performance of small cells.
Tim Carey, senior product manager for Modular Instruments at Cobham Wireless, told Wireless at the launch of the new product at the Small Cells World Summit last week (9-11 June): ‘The main benefit of our solution is that vendors and end users do not have to build their own test capability.’
Cobham has worked closely with Qualcomm using its reference designs, along with its own to provide a quick, simple test solution for small cells. Integrated device control software for Qualcomm Technologies' FSM99xx based multi-mode enterprise, residential and metro small cells is included.
Carey explained that much of the solution has been adapted from its expertise in user equipment (UE) terminal testing. ‘Macro cells have such a high value in terms of mobile network product capex that test systems of a high order have been developed and the test times are also of a high order because of the critical nature of a macro cell.
‘But as you move into small cells you go into something that is more like the user equipment (UE) terminal type testing world. The variation of each device demands a certain test approach; one more acutely able to deal with those variations.’
Cobham has been able to build on its long relationship with Qualcomm for UE testing to develop its small cell test solution. ‘Mobile infrastructure is still some way behind UE testing in considering the types of test within the product, so we think we are very well placed to bring our UE testing expertise to help develop the features Qualcomm puts in the chip sets,’ said Carey.
He added that as small cells transmit on a very low power, Cobham has been able to adapt its PXI Maestro software previously used for UE testing. ‘We’ve dominated device testing with this solution and so in a way the small cell market is coming to us, as we can use the same test platforms with software variations.’
PXI Maestro test software provides an out-of-the-box solution integrating all the sequencing control necessary to measure multiple devices under test (multi-DUT). This provides the ability to test up to four small cells in parallel using a single RF channel (a single vector signal analyzer and signal generator) by the use of novel RF signal conditioning and intelligent test sequencing, providing for a low cost and fast test solution times.
The customisable components of the PXI Maestro software, such as device control, test plan editing, result formatting, and the PXI Maestro graphical user interface, combine to present an ATE solution that is capable for measurements from benchtop R&D characterisation right through to multi-DUT volume manufacturing. The PXI Maestro small cell capability provides frequency coverage up to 6 GHz for all LTE, LTE-A and HSPA bands.
Carey noted that it can take up to two hours to test a macro cell and the aim is to try and reduce that time to a matter of minutes for small cells by introducing functionality into the Qualcomm chip-based small cell baseband to make it much faster to test. ‘We are taking our UE experience and leveraging that for infrastructure testing,’ he said.
Highlighting an additional benefit, Carey said that new small cell vendors rely on test equipment vendors to handle testing for them, as they do not have the kinds of test facilities available to the large OEMs such as Ericsson or Alcatel-Lucent.
‘Our solution removes the complexity for them as they no longer need to have a test engineering department. Sure, you need someone to be in charge of tests, but they can execute the tests using our software – no one has to write code.’
Carey also pointed that the other big benefit of Maestro is that it can test multiple devices concurrently, thereby saving small cell vendors a lot of time and money.
A base station may be designed to support a number of bands, so the vendor may have to test all those bands and numbers of channels in those bands. The problem is that at the factory stage the vendor does not know which frequencies and SON software will be used.
‘The network operator will define what the test plan is that is executed in manufacturing,’ explained Carey, ‘so the vendor will only test those operator specific test plans. But Maestro makes it very easy to reconfigure the test system to meet different operator test plans; you just programme it in and Maestro generates a test plan automatically.’
Carey added that the likes of Cobham have to work closely with silicon vendors as the functionality it needs to test the processes executed on the small cell needs to be incorporated on the chip. ‘We design for test features which are very mundane. They have no relevance to the services the network and small cell provide the end user, but enormous relevance in terms of what can be achieved in terms of throughput in a manufacturing environment.’
Carey said that Cobham chose to work with Qualcomm first because of its long relationship with the silicon vendor and its dominance in the 4G space. However, he said that the software is such that it is very easy for Cobham to programme in different silicon vendors, such as Intel or Broadcom, or different silicon types.