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New HSPA+ Features Add to Test Complexity
Latest surveys show close to 300 live or committed HSPA+ deployments and a majority of current HSPA installations delivering up to 7.2 Mbps downlink and 5.8 Mbps uplink. For those whose networks are based on 3GPP specifications, most of whom have already deployed HSPA, HSPA+ is a software upgrade – ideal in these days of tight budgets. HSPA+ delivers high enough speeds to compare with most home broadband systems, so the user experience will adequately meet customer expectations.
What’s new in HSPA+
The major goals of HSPA+, as defined by the 3GPP standards organization are:
- To exploit the full potential of the CDMA physical layer before moving to OFDM
- To achieve performance comparable with LTE in a 5 MHz channel bandwidth
- To provide smooth interworking between HSPA+ and LTE
- To achieve co-existence of both technologies in one network
- To allow operation in a packet-only mode for both voice and data
- To be backward compatible with earlier user devices
Current WCDMA systems are all based on a 5 MHz channel bandwidth, of which 3.84 MHz is used and the remainder acts as a guard band between channels. New in release 8 is the option for dual-carrier HSDPA; that is to have the system aggregate the content of 2 contiguous carriers – doubling downlink data rates at a stroke, and further enabling HSPA to maintain its place in the high-speed world. It’s important to recognise that improving uplink performance also helps the downlink. By providing faster acknowledgement, downlink capacity and latency both benefit. The option to have the HSPA+ network operate fully in packet mode for both voice and data updates the backhaul network to make future LTE deployment simpler: only the physical (base station radio) layer would need major upgrade.
Dual carrier or dual cell high-speed downlink packet access (DC-HSDPA) is a W-CDMA feature defined in 3GPP Release 8 that allows the network to transmit HSDPA data to a mobile device from two cells simultaneously. A theoretical maximum throughput of 42 Mbps in the downlink can be achieved with this configuration. Dual carrier operation is characterized as simultaneous reception of more than one HS-DSCH transport channel. Certain categories of user equipment (UEs) may be configured into dual cell operation.
New test requirements for HSPA+ (3GPP Release 7 and 8) and Agilent design and test solutions
Today’s handsets, be they low-cost feature phones, smartphones, tablets or laptop data cards, typically already support legacy 2 and 2.5G as well as standard and enhanced 3G functionality: GSM, GPRS, EGPRS, W-CDMA and HSPA. In adding Release 7 and 8 HSPA+ capability, developers must ensure they correctly interpret and implement the required new features, and at the same time make sure they don’t cause failures in the existing base product. With DC-HSDPA, this will focus particularly on the additional receiver capability, and on ensuring there are no adverse interactions.
The final arbiter of product success is the court of public opinion – is the user experience a delight, or a focus of customer complaint?
Agilent representatives have been involved in developing new specifications and test methods for the new capabilities, and they can be found in 3GPP TS 34.121-1 V10.1.0 (2011-12) UE Conformance Specification; Radio Transmission and Reception (FDD), at http://www.3gpp.org/ftp/Specs/archive/34_series/34.121-1/34121-1-a10.zip
SystemVue design libraries
There are two SystemVue design libraries that are useful for HSPA+ design work. They both include functional TX and RX models, so it is possible to make a system-level closed-loop BER/PER measurement. Features specific to DC-HSDPA will be added to the May 2012 release, which is available as a pre-release through SystemVue’s Early Access program. See http://www.agilent.com/find/eesof-systemvue-earlyaccess.
SystemVue’s W1916 3G library is an algorithmic reference for Baseband PHY design, which also interacts with Agilent signal generation and analysis test equipment and RF EDA platforms. It already includes CDMA, CDMA2000, W-CDMA and HSPA.
The W2364 2G/3G Cellular Library is a component of the Agilent Advanced Design System, used for simulation-based pre-compliance/verification of RF/analog designs. It can be used to measure DC-RF efficiency, spectral re-growth of power amplifiers, receiver characteristics and generally to speed the design verification process.
Signal generation and Signal Studio waveform creation software
N7600B Signal Studio for 3GPP W-CDMA FDD is PC-based software that simplifies creation of standard-compliant 3GPP W-CDMA ARB test signals. It is compatible with Agilent’s ESG, PSG and PXG Vector Signal Generators and PXB Baseband Generator and Channel Emulator.
For component testing, N7600B generates uplink and downlink W-CDMA, HSPA, and HSPA+ signals with standard-compliant physical layer configurations.
For BTS receiver testing, N7600B generates transport-channel coded W-CDMA, HSPA, and HSPA+ uplink signals, including flexible HARQ and CQI patterns for dual-cell and MIMO testing and FRC configurations for conformance testing.
For UE receiver testing, N7600B generates transport-channel-coded W-CDMA and HSDPA downlink signals and includes pre-defined RMC and H-Set 1-5 configurations.
Vector Signal Analysis
On the signal analysis side, the 89600B VSA supports the new Release 7 and 8 features, including MIMO and the analysis of the uplink transmission to the serving cell of the dual-cell HS-DPCCH Ack/Nack and CQI report decodes.
8960 Wireless Communications Test Set
The updated 8960 (E5515E) supports DC-HSDPA connections for all defined HS-DSCH categories that support DC-HSDPA: 21, 22, 23 and 24. Both FDD test mode (non-signaling) and active cell DC-HSDPA connections are supported. In active cell, both RB test mode (with signaling) and PS data DC-HSDPA connections are supported. The maximum data rates for DC-HSDPA connections are 42 Mbps in the downlink and 11 Mbps in the uplink. The serving cell and secondary serving cell are generated on adjacent 5 MHz channels in any band supported by the 8960, Bands I through XIV and XIX through XXI. The data throughput monitor and HSDPA BLER measurement report results for the serving cell, the secondary serving cell and the combination of both cells. For testing 3GPP TS 34.121-1 test cases, all of the new H-Sets defined for use with DC-HSDPA are supported.
For more on these and other products, see http://www.agilent.com/find/HSPA