When it comes to 3G and 4G infrastructure, speed is a double-edged sword. On the one hand, multi-megabit data rates let operators support a wider range of applications, which means more revenue opportunities. On the other hand, these rates require much more processing power at the basestation. Simply increasing the megahertz of a single processor core to meet the demanding performance requirements of technologies such as HSPA, Long-Term Evolution (LTE), and WiMAX may not be the best solution.

Digital signal processors (DSPs) are at the heart of most basestations. The faster the DSP runs, the more power it consumes, the more heat it generates, and the more cooling it requires—which all increase operating expenses and erode the operator’s margins. Hot-running DSPs have a ripple effect. They create hotspots on the board, which then has to be designed larger to create more breathing room between the DSP and neighboring components.

The cabinet ultimately dictates the board’s size, though, so excessive heat limits the number of DSPs that can be put on each board. The generated heat has to be removed as well. At the very least, this means more and more powerful fans, which means additional power consumption—a huge downside at a time when electric rates keep increasing in both developed and developing markets.

The boards themselves also may need to be spaced farther apart to allow more air to circulate. All of this means the basestation cannot be as compact as one would prefer, potentially triggering additional lease fees if it takes up too much space in the cell hut. Those fees, along with larger cabinets, also reduce the operator’s margins.

Heat also can limit the ability to change channel cards in a basestation to support more bandwidth and more customers. That’s because most racks have a fixed cooling system, which may not be able to adequately cool upgraded channel cards using more power than originally designed. If that’s the case, the operator may not be able to meet market demand, or it may have to complete a larger-scale upgrade. Both undermine its competitive position and margins.

Multiple Cores, Multiple Benefits

A smarter alternative is to design basestations around multicore DSPs, which spread the workload over multiple cores. If the system requires a DSP with 3 GHz worth of performance, a multicore design could have three cores running at 1 GHz each, all in a single DSP package.

This design is highly efficient, particularly in terms of power consumption. With each multicore DSP running cooler than an equivalent single-core processor, less heat is generated, so there is less heat to remove. This means fewer fans drawing less power, reducing the operator’s electric bill. A slower-running DSP also consumes less electricity.

Furthermore, multicore DSPs are efficient in terms of space. Less heat generation means the boards can be more compact and spaced closer to one another in the rack. This enables compact basestations, which are particularly valuable in urban areas, where real estate leases are expensive. To fully appreciate the benefits of multicore DSPs, it helps to look at the devices available today.

One example is Texas Instruments’ TCI6488, which features three DSP cores, each running at 1 GHz (figure). The multicore design runs cooler than equivalent single-core DSP devices, so basestations that use the TCI6488 have lower air-conditioning requirements—a major plus in the eyes of service providers, which are always looking to reduce costs to help price their services competitively yet profitably.

Designed to support all of the necessary baseband functions required for a macro basestation on a single chip, the TCI6488 eliminates the need for devices such as field-programmable gate arrays (FPGAs) and application-specific integrated circuits (ASICs). That all-in-one performance reduces the basestation vendor’s bill of materials by up to a factor of five. That’s a major asset, given the enormous, continued pricing pressure in today’s basestation market.

The TCI6488 supports a variety of existing and forthcoming 3G and 4G standards, including HSPA, LTE, TD-SCDMA, and mobile WiMAX (IEEE 802.16e Wave 2). This flexibility, a byproduct of the DSP’s inherent advantages as a programmable device, allows systems designers to meet the demands of the highly fragmented cellular marketplace, including the trend toward orthogonal frequency-division multiple access (OFDMA). That in turn reduces both their development costs and time-to-market, allowing them to capitalize on marketplace changes quickly and cost-effectively.