Low-PowerWireless Sensor Network Platforms - Signal Processing Systems - page 384

Tabl e 3 Radio features, current consumptions, and energy efficiencies

Data rate

Band Buffer Sleep RX TX RX TX

Radio A) (mA) (mA) (nJ/b) (nJ/b)

MC MRF24J40 250 2,400 128 2 18 22 264 216
NS nRF2401A 1,000 2,400 32 0.9 19.0 13.0 39 57
NS nRF24L01 2,000 2,400 32 0.9 12.3 11.3 17 18
NS nRF905 50 433-915 32 2.5 14.0 12.5 750 840
RFM TR1001 115.2 868 no 0.7 3.8 12 313 99
RFM TR3100 576 433 no 0.7 7.0 10 52 36
SE XE1201A 64 433 no 0.2 6.0 11.0 516 281
SE XE1203F 152.3 433-915 no 0.2 14.0 33.0 650 276
TI CC2420 250 2,400 128 1 18.8 17.4 209 226
TI CC2500 500 2,400 64 0.4 17.0 21.2 127 102
TI CC1000 76.8 433-915 no 0.2 9.3 10.4 406 363
TI CC1100 500 433-915 64 0.4 16.5 15.5 93 99
Manufacturers: Microchip (MC), Nordic Semiconductor (NS), sRF Monolithics (RFM), Semtech
(SE), Texas Instruments (TI)

(kbps) (MHz) ( B ) ( μ

on-chip buffers for the adaptation of a high-speed radio with a low-speed MCU.
Current consumptions are specified at the lowest band and 0 dBm transmission
power. The table indicates that data rate and frequency band has only a low effect
on current consumption. The last two columns present the energy consumption with
3.0 V supply voltage, indicating that the radios operating at the 2.4 GHz frequency
band are the most energy-efficient, which is mostly caused by their high data rates.

4.2 Computing Subsystem

The central component of a platform is processor unit that forms the computing
subsystem. The processor unit is typically implemented by a MCU, which inte-
grates a processor core with program and data memories, timers, configurable I/O
ports, Analog-to-Digital Converter (ADC) and other peripherals. Flash memory is
typically used as a program memory, while data memory consists of Static Random
Access Memory (SRAM) and Electronically Erasable Programmable Read-Only
Memory (EEPROM). WSN nodes utilize typically 1-10 Million Instructions Per
Second (MIPS) processing speed. Memory resources typically consists of 1-10 kB
of data memory and 16-128 kB of program memory.
The characteristics of potential MCUs from different manufacturers are com-
pared in Table 4 . The energy-efficiencies of MCUs can be compared according to
their current consumption at one MIPS processing speed. The comparison indicates
that Semtech XE8802 and Texas Instruments MSP430F1611 MCUs are the most
energy-efficient [ 25 ] .