L
ite-Fi is the industry’s first product offering ultra-low power draft 802.11n connectivity to handheld devices.
Shown in Figure 1, Lite-Fi, a mixed-signal SoC, includes an analog front-end (AFE), a baseband processor (BBP), a lower MAC in hardware (LMAC), a CPU subsystem built around a Redpine proprietary multi-thread processing system, a choice of host interfaces, a 32kHz oscillator for use during low-power sleep modes, and a power management unit (PMU). The product family has several chip and package variants including a 116-pin WLCSP and LGA, and a 188-pin WFBGA with an external SRAM interface.
RF TRANSCEIVER
The Lite-Fi module for mobile devices contains, in addition to the SoC, an integrated RF transceiver with power amplifier, an EEPROM, and optionally a VCXO.
Redpine’s multi-thread processor is optimized for low-power wireless embedded system applications. The MAC in Lite-Fi is implemented on this processor and is supported by hardware assists in the LMAC. The protocol function distribution between hardware and software is based on minimization of power consumption, governed by silicon area, CPU clock speed, and memory accesses. The LMAC contains, apart from hardware security engines and data buffers, a 16-bit RISC engine —also developed in-house—that is optimized for implementing latency-critical protocol functions in a small silicon area.
Lite-Fi is designed for primary use in handheld devices, and therefore offers the SDIO, SPI, and memory-mapped host interfaces. The SDIO interface in this device, unlike those on products from other sources, supports the full 11n user-level throughput—up to 48Mbps UDP in the single-stream 11n mode. With most of the WLAN and data transfer functionality being taken care of within the device, the host processor is minimally loaded, enabling easy integration of Lite-Fi in a variety of mobile platforms.
Additionally, one thread of the multi-thread processor is made available to user applications; and the chip also provides a hardware security engine for efficiently carrying out application level security processing, further reducing host processor load.
The BBP in Lite-Fi is built upon Redpine’s 802.11abg technology that has been integrated into commercial products by customers. The BBP outperforms most available WLAN solutions, especially in hostile wireless environments. The additional performance helps reduce power con-sumption by enabling transfer of data at higher rates in a given situation, minimizing active, or “on-air” time.
Lite-Fi supports 802.11n modes, including space-time block codes (STBC), that enable transfer of data robustly at higher rates with lower overheads, consuming lesser energy.
The MAC, implemented across the LMAC and the multi-thread processing subsystem, offers all 802.11abgn functionality including advanced QoS and power-save modes. The platform conforms to the WiFi certification requirements of WPA, WPA2, WMM, and WMM-PS.
Redpine has multiple patents pending on the technological innovations incorporated into Lite-Fi. These include innovations in OFDM reception, low-power techniques and architectures, and hardware and software architectures.
Author information
You can reach N. Venkatesh at n.venkatesh@redpinesignals.com
Caption: Figure 1: The Lite-Fi SoC.
