Silex Unwired

Top 5 Things You Should Know About Ultra-Low-Power Wi-Fi Modules for the IoT


The “Internet of things” (IoT) is becoming an increasingly growing topic of conversation in the Wi-Fi industry. It’s a concept that not only has the potential to impact how we live but also how we work. Simply put this is the concept of basically connecting any device with an on and off switch to the Internet (and/or to each other). The Wi-Fi solution providers like us have different products to offer as connectivity options for this new IoT Market. The two most important factors for an IoT Wi-Fi device are low cost and low power.

Silex Technology’s latest module designed for these low cost and power applications for the IoT is the SX-ULPAN. The SX-ULPAN is an ultra-low-power Wi-Fi module with dual-band 802.11 a/b/g/n support with enterprise reliability based on Qualcomm’s 4004 Wi-Fi chipset. It offers a list of features that makes it a viable candidate for the IoT market. A device manufacturer should understand a few things regarding our latest SX-ULPAN and these ultra-low-power Wi-Fi modules in general.

  1. What is the difference between the so-called “Ultra-Low Power Wi-Fi” and traditional Wi-Fi?

The ultra-low power Wi-Fi allows the use of a much smaller and lower power host CPU or even no host CPU, creating an overall smaller power draw for the system. So, ultra-low power Wi-Fi refers to the whole system power, and not just the Wi-Fi.

What makes SX-ULPAN different from "traditional" Wi-Fi is driver, supplicant and protocol (TCP/IP) offload feature. Traditional Wi-Fi requires Linux-class OS and several megabytes of memory on host system to run driver/supplicant. In the case of QCA400x/SX-ULPAN, minimum memory requirement is as low as 128KByte for code and 16KByte for data. Thus, it can reduce power requirement as whole system.

  1. What is GreenTX?

GreenTX is Qualcomm-Atheros proprietary function and only works when connected to a GreenTX capable Access Point. This feature allows the device to save power when communicating with a nearby station or access point when high output power is not required to sustain reliable communications. In such cases, the transmitter will reduce the transmit power to obtain current saving, while maintaining its high uplink throughput.

The QCA400x supports this function, but we at Silex have not tested the SX-ULPAN for this feature. Cannot comment how much power saving is expected with this function.

  1. What is AllJoyn?

AllJoyn is one of proposed standard protocol for IoT, provided from AllSeen Alliance, which is mainly driven by Qualcomm. AllJoyn code for QCA4004 is provided by Qualcomm; however we have not tested this feature and do not claim support.

  1. Do I need an external CPU with the SX-ULPAN?

An external CPU or MCU is needed for the SX-ULPAN hardware with the driver version 3.0.2. However, our next version of the hardware will use v3.2 driver which will support host-less mode which will allow the Wi-Fi module to function as a complete autonomous system, without the need for an external CPU.

  1. Is it easy to port SX-ULPAN driver across different platforms (CPU/RTOS)?

It is not trivial. It depends on a number of factors including:

  • If we previously have ported to that CPU/RTOS or not
  • If not, similarity between existing system and new system
  • Memory capacity and BSP support is another factor

If target system already has running RTOS BSP with working SPI driver, it is definitely easier than porting to a new platform.

Additional Resources

White Paper: Internet-of-Things Wi-Fi® Designs – Hosted & Hostless

Infographic: IoT Wi-Fi Module Selection Guide

White Paper:  Catching the Perfect Wave of 802.11ac