charging an electrochemical capacitor from a battery, can be used to provide pulses of energy for low-duty-cycle (1 percent or less) devices without compromising battery capacity. However, if devices like the multifunction laser (estimated at 4 W peak power) are used several times in succession, the local duty cycle will either not allow enough time for the hybrid system to recover or else appear as a higher duty cycle peak demand with adverse affects on capacity, especially if batteries are the main power source.

The committee had additional substantive observations on the length of the LW procurement cycle, incentives for saving power, and the important area of soldier communications.

The time horizon of the LTI contract is probably not long enough to collect effective feedback even though the program has adopted an iterative development and improvement cycle. Further, the relatively short duration of the cycle militates against there being time to bring energy-efficient system-on-a-chip (SoC) technology into play and significantly reduce power demand of one or more of the LW subsystems.

Although SoC technology targeting the OFW application was recommended in Energy-Efficient Technologies (NRC, 1997), OFW-ATD will use off-the-shelf electronics componentry. The Army should begin the development of SoC technology that can evolve with requirements as they are understood and with new developments in algorithms and protocols.

The current approach to designing and procuring Army soldier systems should be contrasted with the approach to designing commercial products such as cell phones. Each generation of an Army system starts with a new contractor and a clean sheet of paper, allowing only an after-the-fact, lessons-learned critique of the previous generation. There is not a lot of learning transferred from one generation to the next, leading to a lack of continuity in design concepts. In the commercial world, by contrast, there is continuity between products over multiple generations. Commercial electronics developers aim for progressive improvements to design, with successive generations of SoCs containing capabilities better than those of the previous generation. By building on earlier SoC designs, the cost and risk of the later generations are substantially less than the cost and risk of the first generation.

Another cost of the standards-based plug-and-play strategy of the OFW is that standardized USB and Ethernet hubs for the wired soldier body LAN use considerably more energy and do not directly enhance the effectiveness of the soldier. There should be investments in developing low-power interconnect technology. For example, a fundamentally different approach would use a high-speed, short-range, wireless body LAN that has an undetectable emission signature. One approach to this goal would use ultrawideband (UWB) radio transmission, which is being developed commercially to transmit in the 3 to 5 GHz range and (from the 802.11.3a proposed standards) at a rate of 100 Mbits per second at less than 100 mW total power demand; receive at 200 mW; and, most important, have sleep modes that are three orders of magnitude lower (Batra et al., 2003). The very low transmit power and secure characteristics of the transmission signal would provide a radio frequency (RF) signature that would not be detectable beyond 10 m (or even less if the transmit power is constrained further). Chip sets for this network approach are projected to be available from Motorola, Intel, and other vendors for home video networks in the next 3 to 4 years at a cost of less than $5 per node. Assuming that internal or local operational interference is not a problem, such wireless technology could obviate the tethering of data buses on a soldier’s system.

A lesson from the original LW integration program is that there was not enough time or money to fully optimize energy efficiency. Due consideration must be given not only to the various power sources and sinks, but also to designs for electronics integration and power management.

The OFW LTI will propose systems for integration, but neither the LTI nor the Army PEO have enough influence over concurrent acquisition efforts to effectively reduce power demand in the main electronics subsystems. An incentive structure would be one way to achieve innovation at the subsystem level. The shipping cost of batteries in the first Iraq conflict is estimated at more than $500 million, an indication of the savings that are possible in logistics alone. This includes only the cost of the logistical support, not of the batteries themselves. By reducing the average power demand by only 10 percent, a saving of $50 million could have been realized. This would be enough to develop five chips at $10 million apiece. The cost per soldier of providing batteries and related power source hardware, such as chargers, will be substantially higher as the OFW electronics suite is introduced. It is also possible to have reductions of much more than 10 percent. Finally, if the power requirements are reduced, the type of energy sources can be changed, which could also save costs. The committee therefore recommends that the Army should undertake a complete life-cycle cost analysis to determine the overall savings achievable by a substantial increase in development activity solely targeting power reductions (such as SoC design).

OFW is assuming the JTRS radio. Little information was available about the progress of JTRS design, but committee members familiar with software radio research suggested several areas for the Army to investigate for possible improvements in energy efficiency.