| WiMAX as a new technology got the attention of researchers and wireless companies. This new wireless technology promises to deliver both high data rates and long-range coverage areas. With the approval of the new mobile WiMAX standard (IEEE802.16e-2005) at the beginning of the year 2006, this technology became even more exciting. Unlike WiFi which was originally designed for indoor applications and local area networks (LAN), WiMAX is optimized for outdoor applications and Metropolitan area networks (MAN). It has been even anticipated that WiMAX will replace city-wide WiFi projects.
One of the exciting aspects of WiMAX is the orthogonal frequency multiple access (OFDMA) physical layer mode. OFDMA PHY mode enables a WiMAX base station (BS) to support multiple users at the same time. In this mode, the used subcarriers are divided into subchannels that can be assigned by the BS to multiple users in a sophisticated and adaptive manner. Actually, users can be assigned different bandwidths, different time durations, and different modulation orders based on various parameters such as the user carrier-to-interference-and-noise ratio (CINR) and the available bandwidth.
However, with these advantages the complexity increases and new problems that need to be addressed will appear. One of these problems is timing and synchronization between the BS and the subscriber stations (SS). For OFDMA PHY mode to work correctly, all users should arrive at the BS at the same time with a considerably high accuracy. This process is called Ranging, and it’s mandated for all SS that desire to synchronize to the channel initially.
In this paper, we propose a new ranging detection algorithm as well as discuss other existing algorithms in the literature. A performance and complexity comparisons between the proposed algorithm and the current algorithms will be presented.
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