Introduction
As WiMAX projects develop it becomes clear that licensed spectrum implementations are calling for Time Division Duplexing WiMAX (TDD WiMAX) to optimize their efficiency and usage of a limited spectrum. TDD WiMAX, WiBRO and the soon available IEEE 802.16e (mobile WiMAX) put stringent phase timing constraints to the synchronization of base stations.

The solution is to phase synchronize all base stations with highly accurate and perfectly phase aligned GPS receivers clocks. Oscilloquartz developed a specific series of WiMAX GPS receiver clocks based on a highly stable Double Oven Crystal Oscillator (OCXO). The product known as OSA WiMAX series exceeds TDD WiMAX requirements especially in the domain of phase alignment and low phase noise. OSA WiMAX series is a versatile solution that can be integrated in several ways to better accommodate the different type of Base Stations: Outdoor versus Indoor, Macro versus Micro, FDD versus TDD, single versus multiple RF modules.

The precise and stable frequency and Phase Time of OSA WiMAX Series allows the WiMAX Base Station:

• Frequency optimization with minimal frequency guard-bands
• Minimal Transmit and Receive Transition gaps
• Faster BTS/CPE synchronization
• Fully reliable hand-over of voice and data sessions (mobility IEEE 802.16-e)
• Manageable coexistence of FDD and TDD
• Multiple output for multiple RF modules (multi-sector antennas)

Beyond the several limited field trials, the OSA WiMAX series was chosen for the synchronization of the largest WiMAX Metropolitan Area Network in TOKYO where more than 1200 base stations are being deployed. Higher grade Base Station synchronization is required where operators do not compromise between Quality Of Service, Speed of transmission and optimal usage of the too limited bandwidth.  

Features
All OSA WiMAX Series products provide standard 1 PPS, low noise 10 MHz and TOD (Time Of Day) outputs referenced to UTC1.  They all include a highly accurate oven controlled oscillator which filters the reference signal and provides a holdover quality comparable to that of an SSU in case of loss of external GPS reference. Multiple 1PPS and 10 MHz outputs provided on request.

Control Software and Manageability
The OSA WiMAX Series products are fully manageable by the Base Station through a comprehensive and intuitive set of commands over serial data link. 
Additionally they are locally manageable via the OSA Control and Monitoring software (CMSW.NET) that gives full control of the units through an intuitive MS-Windows based graphical user interface.