MSR and multimeasurement needs pose wireless test challenges

As cellular systems transition from 2G to 3G to 4G, and as WLAN  systems undergo similar rapid evolution, wireless products must incorporate multistandard radios (MSRs), and designers find themselves needing to simultaneously make multiple measurements. In a recent conference call, Liz Ruetsch, applications marketing and planning manager in the Microwave & Communications Division of Agilent Technologies, and Ken Voelker, senior product planner for 89600 VSA and 89600 WLA products in the same division, explained how Agilent is addressing the challenges designers are facing.

Ruetsch began the conversation by noting that new broadband applications are fueling the drive for next-generation wireless devices that will deliver more functionality at lower cost. Agilent is positioned to respond, she said, through its participation in wireless standards bodies and industry forums and through its work with industry-leading customers to bring new technologies to market fast. In particular, she noted, the smart-phone market is evolving rapidly, with smart-phone shipments growing 40% in 2010 and expected to double by 2014. In addition, she noted, mobile traffic is growing exponentially, and she traced data rates from 384 kbps for W-CDMA on to 14 Mbps for HSPA, 21 to 168 Mbps for HSPA+, and on to 150 to 300 Mbps for LTE and 1 Gbps for LTE-Advanced.

She traced a similar growth in performance in Wi-Fi, noting that the WLAN retail and enterprise market grew 23% in 2010. She traced Wi-Fi performance from 11 Mbps for 802.11b through 54 Mbps for 802.11a/g, 600 Mbps for 802.11n, 1 Gbps to 6.93 Gbps for 802.11ac, and 7 Gbps for 802.11ad.

This rapid evolution in cellular and WLAN technologies is driving the need for multimeasurement capabilities in support of multistandard radios, and Ruetsch and Voelker described Agilent's response.

Ruetsch began by noting that seamless transition in the cellular space requires support for different RATs within a single base station and within the same spectrum band. A key technology enabler, she said, is the combined innovations in RF and software-defined radio technologies. By 2013, she said, MSR-BTS technology will represent more than 50% of base-station shipments.

The test challenge, she said, is to determine how a multistandard signal affects a base-station power amplifier. Agilent's solution is to use Signal Studio software (N7624B) to create any combination of LTE-FDD, W-CDMA/HSPA/HSPA+, and GSM/EDGE/EDGE Evolution waveforms using a single signal generator. The software includes built in tools to analyze amplifier compression for different signal configurations.

Other challenges include determining whether MSR base station transmitters must the RF requirements defined in 3GPP Rel 9. Ruetsch said Agilent offers test equipment covering GSM, W-CDMA, LTE-FDD as defined by 3GPP Rel 9, including the MSR X-Series measurement application (N9083A), which provides fast one-button measurement per 3GPP Rel 9 to analyze GSM/EDGE/EDGE Evolution, W-CDMA/ HSPA/ HSPA+, and LTE-FDD in a single application while not requiring a wide analysis bandwidth option, coupled with X-Series signal analyzers, including the PXA, MXA, EXA, and CXA.

Voelker then commented on multimeasurement capability, calling it a departure from traditional one-at-a-time measurements. It involves users predefining a collection of VSA measurements, with the measurement parameters residing in memory and instantly ready to run. Execution styles range from true simultaneous to fast-sequencing, he said, with display tools supporting correlation of multiple results.

He described an example in which a DUT delivers multiple signals acquired by wide-bandwidth hardware. Agilent's 89600 VSA software then simultaneously processes multiple measurements, such as LTE EVM, GSM modulation quality, and composite CCDF. He noted that when a single acquisition instrument can't handle the necessary bandwidth, users can simple add another instrument.

The multimeasurement technique, he said, can help simultaneously verity all carriers in a multicarrier power amplifier, simultaneously verity all signals on a multistandard device, explore interactions between multiple transmitters within one device, analyze uplink and downlink signals within a single frame, compare signals at different test points within the same signal path, and perform several measurements at once, such as measuring in-channel modulation quality while testing for spurious or harmonic emissions.

Other recent, related introductions from Agilent include the combination of 89600 VSA software and the new 89600 WLA (wireless link analysis) software, with the latter being a protocol-layer complement to the former. In the WLAN space, Agilent has introduced Signal Studio for WLAN (N7617B) and the SystemVue WLAN baseband verification library (W1917). In addition, the PXA signal analyzer has a new 160-MHz bandwidth which can combine with the VSA software for making measurements on 256-QAM-modulated 802.11ac signals.

Ruetsch concluded by noting that for 802.11ac test applications, the 89600 VSA software can work with various hardware platforms, including Infiniium and Infiniivision oscilloscopes (offering 1-GHz or wider bandwidths), PXI microwave signal analyzers (offering bandwidths to 250 MHz), PXI digitizers, and quad microwave downconverters.

Posted 11/21/2011 8:03 AM. Go to top of the “Rick's Blog” main page.

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