Next generation testing technology
The emerging CDMA-based 3G systems bring with them a new set of requirements for channel simulators employed in R&D, validation and type approval tests. While unified and standardized channel models for 3G have yet to be defined, some general requirements can be inferred from 3G system characteristics. The most significant factor is the wide bandwidth of the radio signal. In addition to wide simulation bandwidth, this implies a high number of resolvable multipath components and improved delay resolution. Receiver architectures will experience a significant change in 3G systems. Rake receivers will be widely applied and thorough testing of the acquisition and tracking capabilities requires a dynamic channel model, where the propagation path delays vary in time. Fixed path delays have been utilized in the testing of 2G radios.

WCDMA systems, to choose one 3G example, exhibit non-constant envelope characteristics in RF modulation and closed loop power control, where base stations are controlling the transmit powers of the mobiles and vice versa. These features increase the input signal power variation considerably, which sets increased demands on the simulator linearity.

The increased complexity of wireless communications environments and test scenarios necessitate more realistic channel simulation beyond standard channel models. To reach the ultimate degree of reality, the simulator should be able to import measured channel responses and then reproduce the measured channel as accurately as possible. The range of physical environments in which the 3G radios will be used—from high mobility outdoor macro cells to indoor static terminal scenarios—introduces a new range of propagation phenomena. This makes the role of radio channel simulators increasingly critical in making 3G radios work.

Thanks to a solid background in wideband spread spectrum systems, Elektrobit of Finland has been able to develop advanced test equipment that fit into CDMA-based 3G systems and experimental 4G systems.

Among these is PROPSim+, a Wideband Radio Channel Simulator that enables the wireless systems developers to simulate complex, realistic environments and propagation phenomena real-time in the laboratory.

Smart answers
Metawave Communications Corp. has announced that its CDMA smart antenna system, SpotLight 2000, has demonstrated a 50 percent capacity increase at a CDMA cell site in a Phoenix, Ariz. cellular network. Simulations conducted before the first field deployments of SpotLight 2000 suggested that the smart antenna system could provide CDMA capacity increases of up to 40 percent. The 50 percent capacity gains in the Phoenix deployment topped initial estimates by 25 percent, though achievable capacity gains vary by cell site. SpotLight 2000 increases the capacity of CDMA cell sites by balancing sector traffic loads, reducing handoff overhead and controlling pilot pollution.

Good timing
DSP Communications, Inc has commenced delivery of its new WorldCDMA ARM integrated multi-mode baseband chipset, the D5421, said by the company to be the only cdmaOne chipset available today that enables handset manufactures to achieve standby times of up to 350 hours. The D5421, DSPC’s second generation chipset, provides PowerSmart management for minimizing power consumption, while adding functionality such as voice recognition.

With an integrated ARM7 TDMI(TM) MCU and OAK(TM) DSP core, DSPC’s CDMA chipset provides a compact solution for satisfying cdmaOne baseband processing requirements. The D5421 WorldCDMA chipset is based on 0.25 micron CMOS technology featuring high speed and 2.5V operation. The D5421 is available in low footprint FPBGA packaging.

The WorldCDMA chipset family offers a worldwide cdmaOne-compliant solution for complete baseband processing for dual mode cellular, PCS, and WLL handsets. Implementing three vocoders, including the 8 Kbps and 13 Kbps QCELP(R) and EVRC, the WorldCDMA family offers high voice quality to end-users together with compliance with worldwide standards’ requirements. With built-in flexibility for software modifications, WorldCDMA chipsets can be easily customized, giving handset manufacturers the ability to differentiate their products.