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April 21, 2011

Next-generation LTE base stations speed mobile connectivity with SDRs, hard-coded accelerators, and multicore CPUs and smartphones will use integrated processors

DSP chips are powering the race to 4G in next generation base stations Next-generation base stations speed mobile connectivity with SDRs, hard-coded accelerators, and multicore CPUs. EDN covers the DSP, FPGA technology that is going into the new base stations.

To build a 4G modem, you must start with the PHY (physical) layer, Layer 1 or the radio-interface layer. To exploit the high data rate and spectral efficiency of 4G radio technologies, which are similar for LTE and WiMax, designers apply sophisticated DSP for the OFDMA (orthogonal-frequency-division/multiple-access) modulation with as much as 64-QAM (64- state quadrature-amplitude modulation); the interface to MIMO (multiple-input/multiple-output) antennas with adaptive beam forming; and a host of sophisticated techniques for packet processing, error control, and QOS (quality of service).



Alan Taylor, marketing director for wireless-baseband products at Mindspeed, says that a targeted, multicore SOC is the best method of minimizing power and cost and meeting the high-performance DSP requirements of 4G baseband processing. He also notes that scalability is essential as network operators migrate from 3G as 4G standards for LTE continue to evolve. General-purpose DSPs lack the needed precision, Taylor says, and performance requirements drive the need for dedicated fixed-function processors to eliminate the overhead of implementing functions such as FFTs in software. He believes that offloading fixed functions to FPGAs, as has been common in base-station designs, introduces additional power consumption and cost.

The complex, heterogeneous Transcede 4000 SOC integrates 26 programmable processors. The PHY layer includes 10 instances of Ceva’s 1641 DSP-IP core and 10 Mindspeed DSP accelerators in the SPU (signal-processing-unit) cluster. The microcoded processors accelerate fixed functions, and the Ceva cores handle general-purpose programmable-DSP functions. Mindspeed can remap the microcoded accelerators to suit various applications if necessary.



2. Silicon integration will be the key differentiator in smartphones which could grow to 600 million units in 2014, driven by expansion in low-cost handsets. By 2014 nearly 70 percent of all smartphones will use such integrated chips, up from 40 percent in 2010. Such chips will be key as designers try to hit prices as low as $100 for smartphones sold in emerging markets. quad-cores will be more successful in tablets initially because of their better heat dissipation" until 28nm versions for smartphones are available.

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