As 4G networks rise from infancy and become the cool kids of the wireless playground, network operators and device manufacturers make big promises about blazing multimedia performance, zero-lag voice communications and enough apps to guarantee a varsity-caliber revenue boost.
In reality, though, basic wireless channel physics tell a different story – essentially changing the rules of the game. What good is a 4G network if devices can barely “see” it? What good is a sleek handset if it only works with a huge bumper on it? By investing in technologies that enhance overall receiver performance, network operators and device manufacturers stand a vastly improved chance of delivering the functionality they promise. In fact, there are emerging solutions that can boost spectral efficiencies up to 60 percent, regardless of the antenna configuration of choice.
Proponents of WiMAX and LTE claim theoretical 4G data rates in excess of 100 Mbps. The fact is that these numbers are difficult to achieve. Wireless channels impose fundamental range and data rate limits, and OFDM is inherently vulnerable to Doppler frequency shifts that result from high mobility speeds. OFDM is also sensitive to interference caused by other base station transmissions, which, in dense urban deployments, becomes increasingly problematic.
Radio spectrum is scarce and expensive. Although significant new blocks of spectrum are being made available as military and analog TV bands are released, wireless operators and device manufacturers must always manage the trade-off between data speeds and system cost. Since the effective capacity of any given bandwidth allocation is degraded by multiple sources of interference, there are several approaches on the market to preserve as much performance as possible, mainly through significantly higher handset costs for additional antennas. In the wireless broadband space, for example, the current approach to counteracting interference is multiple in, multiple out (MIMO) antenna on base stations and handsets. But like other solutions, MIMO is complicated and the hardware is expensive.
Where there’s trouble, there’s also a market opportunity. Technology now exists in the form of chip-level, IP core receiver solutions for OFDM-based 4G wireless networks that offer more than 60 percent gain in spectral efficiency. With the resulting increase in capacity and bandwidth efficiency, mobile operators can deliver higher data rates and wider coverage to end-users, greatly improving the business case for deploying LTE or WiMAX networks.
Advanced PHY, or innovation at the physical layer, mitigates noise and interference by using an extremely evolved algorithm derived from mathematics pioneered in the 1950s for physics applications. With far lower complexity and occupying less than one-half of a square millimeter of chip space, these algorithms have been demonstrated both in simulations and in commercial hardware to offer upwards of 10dB Packet Error Rate (PER) improvement under certain conditions and environments. It is also particularly effective at reducing Doppler-related performance degradation.
Increasing overall receiver performance provides capacity improvements under challenging mobile channel conditions: Co-channel interference, inter-carrier interference and multi-path interference no longer have to be the monsters they are today. Compared to other solutions, the advanced PHY provides some of the highest spectral gain per dollar while retaining critically low implementation complexity. Moreover, it can be easily integrated into a 4G chipset solution with minimal impact. Perhaps best of all, the advanced PHY can work with a single antenna or as an improvement to MIMO receivers. All things considered, service providers can deploy fewer base stations and still deliver a better user experience.
Advanced PHY has multiple potential applications. The technology can boost existing MIMO performance and potentially eliminate the need for advanced MIMO in some instances that may be significantly cost sensitive. In fact, simulations have shown the advanced PHY, in a single antenna (SISO) configuration, to perform above certain MIMO implementations specified in current standards. This advanced PHY also helps in DSL fixed-wire and HD digital TV broadcast applications. Simulations suggest that the algorithm can potentially double effective spectrum capacity at significantly lower cost to proposed alternatives.
The race to 4G is currently a consumer-driven competition. Growth in data consumption necessitates higher connection speeds. Since devices are battery-driven and battery-limited, network infrastructure must be equipped for tremendous bandwidth and relentless traffic. Much as Internet providers had to address “the last 10 feet” of connectivity between the wall and connected home devices, wireless operators and device manufacturers must look for effective and cost-sensitive methods for consumers to get the most out of 4G networks. Simply put, advanced PHY rises to the 4G occasion and gives operators and manufacturers explosive return on investment.
Steve Caliguri is vice president of Business Development at Acorn Technologies.