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The magic of WiMAX silicon

A major driver of growth in the WiMAX industry relies on the availability of WiMAX semiconductors to enable the connectivity of everything from CPEs to mobile devices. However, exactly what the magic produced by the slivers of silicon remain unknown to many industry participants. Below is a brief summary of the various chipsets that will help propel the WiMAX industry forward in the next few years.

Integrated circuits (IC) have fueled the growth of the PC, mobile telephone and Wi-Fi industries. Also known as semiconductors, or simply “chipsets”, integrated circuits are the heart of any WiMAX device. There are several key chipsets that deliver functionality to current and future WiMAX devices, each with its own particular focus.

The antenna of a WiMAX device (such as a laptop computer, a CPE modem, or other handheld device) receives a signal transmitted from a WiMAX base station. Along with various filters and power amplifier (PA), the antenna delivers the digital signal to a specialised chip inside the device called the Radio Frequency Integrated Circuit (RFIC). An RFIC chip contains a wireless transceiver constructed as an integrated circuit. The RFIC receives the signal at the transmitted frequency (e.g., 700MHz, 2.5GHz, 3.5GHz) and converts the signal down to a lower frequency called “baseband.” RFICs can cover a narrow range of frequencies, and more elegant designs can have a single RFIC support multi-band WiMAX products.

The second key WiMAX chip is the baseband device, the “brains” of the system. The baseband chip receives the down-converted signal from the RFIC. The baseband chip demodulates the signal and resolves what’s received to extract information bits from the noise bits. Each wireless technology (Wi-Fi, WiMAX, GSM, CDMA) has its own PHY (physical layer) and MAC (media access controller) modes. A mobile WiMAX baseband chip, for example, is optimised for the 802.16e PHY/MAC and takes the received information bits and turns these into data and applications (like voice, video, text).

When a wireless device transmits, the applications are turned into information bits in the baseband chip, processed by the PHY/MAC, delivered at baseband frequency to the RFIC which up-converts the signal, and in turn, is passed through the PA and filters to the device’s antenna.

Matching the performance of RFICs and BB chips, as well as IC design and packaging is an art that must balance performance, power draw, size and cost. SOC or “system on a chip” designs integrate RF and baseband silicon and packaging to create optimised products.

Wireless devices can have additional integrated circuits including application processors, memory, video and power management chips.