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DESIGNER'S TOOLKIT
As Devices Like Wireless-Entertainment Consoles Enter The Scene, System Design Methods Must Face The Test of 3G.
THIRD-generation (3G) wireless access will soon make its way into products like portable game consoles. This evolution will enable users to play interactively with friends anywhere and anytime. Compared to previous-generation wireless systems, however, 3G raises multifold design obstacles. With dynamically changing parameters and closed-loop operation between the transmitter and receiver, 3G modems demand diligence in system design.
To help meet third-generation wireless standards and optimize performance, designers of 3G wireless-handset digital-baseband receivers must plan carefully. They must prepare to deal with the project's complexity and optimization requirements from the beginning. Meeting this goal requires a seamless design and verification flow. This flow must start with a high-level, floatingpoint representation for algorithm optimization. A refining of the implementation for hardware, software, and their interfaces will follow. By adhering to this methodology and taking advantage of available standards-based models, hardware and software developers can accelerate the design process.
This article describes some of the FUNCtions and requirements for a modem that complies with the frequency-divisionduplex (FDD) UMTS wideband CDMA (WCDMA) wireless-system standard. This information stems from the work of a design team within Synopsys Professional Services. This group created a UMTS-FDD digital-baseband receiver and transmitter for use in 3G-handset applications. The modem was developed from high-level product requirements. It was implemented as part of a complete 3G-handset prototype that was successfully tested with commercial testers. Speech calls and video transmissions to a UMTS-FDD base station have been conducted successfully.
The modem contains a significant amount of control flow functionality. This characteristic facilitates dynamic Layer 1 (L1) configuration changes, as well as closed-loop operation between base transceiver stations and user equipment. These functions have high computational requirements. In addition, they must support user bit rates as high as 2 Mbps. A significant part of the hardware is thus dedicated to basebanddataflow signal-processing tasks with a sophisticated interface to the LI software.
Much of the design information presented here concerns the operation of the random-access channel. Among other things, this channel is used by a handset to initiate connections with a base station. Because this channel involves many of the modem's hardware units and software functions,...