Mobile WiMAX (IEEE 802.16e-2005)

Mobile WiMAX (IEEE 802.16e-2005)

Perhaps the biggest shortcoming of 802.16-2004 is the lack of support for mobility. IEEE addressed this issue by developing specifications for a separate version of the standard, the 802.16e, which was approved on December 7, 2005 (IEEE 2005).

Also known as mobile WiMAX, the standard is seen to be in competition with 3G cellular technologies. Its radio access method is even more sophisticated than that of fixed WiMAX, utilizing scalable OFDMA and thus achieving an even better link budget. The tradeoff is increased complexity in physical layer processing.

Fast handover signaling is supported, e.g., to allow users in moving vehicles to seamlessly switch between base stations. (Baines 2005) Mobile WiMAX operates in the 2 to 6 GHz range that mainly consists of licensed bands. Mobile applications are likely to operate in frequencies below 3 GHz, while even some fixed applications are expected to use 802.16e due to its better characteristics.

However, it should be noted that there is no backward compatibility with fixed WiMAX. Cell radiuses are expected to be typically 2 to 5 km, and user data rates up to 30 Mbit/s are achievable in theory with full 10 MHz channels. The first certified 802.16e products are expected to be available by late 2006, though wide scale commercial deployments are expected not earlier than 2008.

On a further note, South Korea has its own variant of mobile WiMAX called WiBro which is standardized by TTA. It uses 10 MHz channels in the 2.3 GHz band in Korea, and aims for interoperability with official 802.16e equipment. According to a recent performance analysis, WiBro performs favorably in comparison with 3G High-Speed Downlink Packet Access (HSDPA) in multipath fading channels (Shin et al. 2005).